MASAMOTO KAZUTO
| Department of Mechanical and Intelligent Systems Engineering | Professor |
| Cluster II (Emerging Multi-interdisciplinary Engineering) | Professor |
| Center for Neuroscience and Biomedical Engineering | Professor |
| Public Relations Center | Professor |
Researcher Information
Research Keyword
Research Activity Information
Award
Paper
- Microfluctuations in Capillary Lumens Independent of Pericyte Lining Density in the Anesthetized Mouse Cortex
Hiroki Suzuki; Juri Murata; Miyuki Unekawa; Iwao Kanno; Yoshikane Izawa; Yutaka Tomita; Kenji F. Tanaka; Jin Nakahara; Kazuto Masamoto
Last, Microcirculation, Wiley, 16 Sep. 2024, ABSTRACT
Objective
This study aimed to examine the spatiotemporal coherence of capillary lumen fluctuations in relation to spatial variations in the pericyte lining in the cortex of anesthetized mice.
Methods
Two‐photon microscopic angiography data (previously published) were reanalyzed, and spatial variations in capillary diameter fluctuations at rest and in capillary lining with vascular mural cells were measured along capillary centerlines.
Results
Relatively large diameters of the capillaries (5.5 μm) coincided with a dense pericyte lining, while small capillaries (4.3 μm) had a sparse pericyte lining. Temporal variations had a frequency of about 0.1 Hz with an amplitude of 0.5 μm, which were negatively correlated with pericyte lining density. Spatial frequency analysis further revealed a common pattern of spatial variations in capillary diameter and pericyte lining, but temporal variations differed. The temporal variations in capillary lumens were locally distinct from those in neighboring locations, suggesting intrinsic fluctuations independent of the pericyte lining.
Conclusions
Capillary lumens in the brain exhibit slow microfluctuations that are independent of pericyte lining. These microfluctuations could affect the distribution of flowing blood cells and may be important for homogenizing their distribution in capillary networks.
Scientific journal, English - Effect of Diabetes on Microvascular Morphology and Permeability of Rat Skeletal Muscle: In Vivo Imaging Using Two-Photon Laser Scanning Microscopy
Kazuki Hotta; Rie Shimotsu; Bradley J. Behnke; Kazuto Masamoto; Kazuyoshi Yagishita; David C. Poole; Yutaka Kano
Journal of Applied Physiology, American Physiological Society, 15 Aug. 2024, This investigation evaluated the microvascular permeability and ultrastructure of skeletal muscle capillaries in skeletal muscle of diabetic (DIA) rats using two-photon laser scanning microscopy (TPLSM) and transmission electron microscopy (TEM). Microvascular permeability was assessed in the tibialis anterior muscle of control (CON) and DIA (streptozocin) male Wistar rats (n = 20, 10-14 wk) by in vivo imaging using TPLSM after fluorescent dye intravenous infusion. Fluorescent dye leakage was quantified to determine microvascular permeability. The ultrastructure was imaged by TEM ex vivo to calculate the size and number of intercellular clefts between capillary endothelial cells and also intracellular vesicles. Compared with control, the volumetrically determined interstitial fluorescent dye leakage, the endothelial cell thickness, and the number of intercellular clefts per capillary perimeter were significantly higher, and the cleft width was significantly narrower in TA of DIA (interstitial fluorescent dye leakage, 2.88 ± 1.40 vs. 10.95 ± 1.41 µm3 x min x 106; endothelial thickness 0.28 ± 0.02 vs. 0.45 ± 0.03 µm; number of intercellular clefts per capillary perimeter 6.3 ± 0.80 vs. 13.6 ± 1.7 /100 µm; cleft width 11.92 ± 0.95 vs. 8.40 ± 1.03 nm, CON vs. DIA respectively, all p <0.05). The size of intracellular vesicles in the vascular endothelium showed an increased proportion of large vesicles in the DIA group compared to the CON group (p < 0.05). Diabetes mellitus enhances the microvascular permeability of skeletal muscle microvessels, due, in part, to a higher density and narrowing of the endothelial intercellular clefts, and larger intracellular vesicles.
Scientific journal - Serotonergic regulation of cortical neurovascular coupling and hemodynamics upon awakening from sleep in mice
Akiyo Natsubori; Soojin Kwon; Yoshiko Honda; Takashi Kojima; Akihiro Karashima; Kazuto Masamoto; Makoto Honda
Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, 44, 9, 1591-1607, 13 Mar. 2024, Neurovascular coupling (NVC) is the functional hyperemia of the brain responding to local neuronal activity. It is mediated by astrocytes and affected by subcortical ascending pathways in the cortex that convey information, such as sensory stimuli and the animal condition. Here, we investigate the influence of the raphe serotonergic system, a subcortical ascending arousal system in animals, on the modulation of cortical NVC and cerebral blood flow (CBF). Raphe serotonergic neurons were optogenically activated for 30 s, which immediately awakened the mice from non-rapid eye movement sleep. This caused a biphasic cortical hemodynamic change: a transient increase for a few seconds immediately after photostimulation onset, followed by a large progressive decrease during the stimulation period. Serotonergic neuron activation increased intracellular Ca2+ levels in cortical pyramidal neurons and astrocytes, demonstrating its effect on the NVC components. Pharmacological inhibition of cortical neuronal firing activity and astrocyte metabolic activity had small hypovolemic effects on serotonin-induced biphasic CBF changes, while blocking 5-HT1B receptors expressed primarily in cerebral vasculature attenuated the decreasing CBF phase. This suggests that serotonergic neuron activation leading to animal awakening could allow the NVC to exert a hyperemic function during a biphasic CBF response, with a predominant decrease in the cortex.
Scientific journal, English - Detection of backside coupled propagating surface plasmon resonance on the sidewall of a wafer
M. Oshita; S. Suzuki; K. Masamoto; T. Kan
AIP Advances, AIP Publishing, 13, 11, 01 Nov. 2023, We proposed a surface plasmon resonance (SPR) sensor structure that utilized a glass wafer with a diffraction grating and an n-type silicon piece bonded near the SPR coupling site. This configuration enabled surface plasmon excitation from the back of the substrate without the unwanted interaction between the excitation light and the sample, and electrical detection of the SPR response by a 0.7-eV Schottky barrier at the Au/n-Si interface formed on the sidewall of the silicon piece was achieved. Experimental evaluation of the surface plasmon coupling performance was conducted, showing clear peaks in the photocurrent for various wavelengths in the NIR-II window, ranging from 1100 to 1300 nm. The device’s ability to detect propagating surface plasmons as a photocurrent was confirmed; the results indicated a consistent trend with theoretical and numerical calculations. Since the device was composed of a glass substrate, the use of wavelengths shorter than the near-infrared wavelength was possible, including visible wavelengths where the optical absorption by water is negligible. Thus, our proposed sensor provides a compact and efficient solution for SPR sensing in aqueous solutions.
Scientific journal - Acceleration of the Development of Microcirculation Embolism in the Brain due to Capillary Narrowing
Juri Murata; Miyuki Unekawa; Yuya Kudo; Maho Kotani; Iwao Kanno; Yoshikane Izawa; Yutaka Tomita; Kenji F. Tanaka; Jin Nakahara; Kazuto Masamoto
Last, Stroke, Ovid Technologies (Wolters Kluwer Health), 54, 8, 2135-2144, Aug. 2023, Peer-reviwed, BACKGROUND:
Cerebral microvascular obstruction is critically involved in recurrent stroke and decreased cerebral blood flow with age. The obstruction must occur in the capillary with a greater resistance to perfusion pressure through the microvascular networks. However, little is known about the relationship between capillary size and embolism formation. This study aimed to determine whether the capillary lumen space contributes to the development of microcirculation embolism.
METHODS:
To spatiotemporally manipulate capillary diameters in vivo, transgenic mice expressing the light-gated cation channel protein ChR2 (channelrhodopsin-2) in mural cells were used. The spatiotemporal changes in the regional cerebral blood flow in response to the photoactivation of ChR2 mural cells were first characterized using laser speckle flowgraphy. Capillary responses to optimized photostimulation were then examined in vivo using 2-photon microscopy. Finally, microcirculation embolism due to intravenously injected fluorescent microbeads was compared under conditions with or without photoactivation of ChR2 mural cells.
RESULTS:
Following transcranial photostimulation, the stimulation intensity-dependent decrease in cerebral blood flow centered at the irradiation was observed (14%–49% decreases relative to the baseline). The cerebrovascular response to photostimulation showed significant constriction of the cerebral arteries and capillaries but not of the veins. As a result of vasoconstriction, a temporal stall of red blood cell flow occurred in the capillaries of the venous sides. The 2-photon excitation of a single ChR2 pericyte demonstrated the partial shrinkage of capillaries (7% relative to the baseline) around the stimulated cell. With the intravenous injection of microbeads, the occurrence of microcirculation embolism was significantly enhanced (11% increases compared to the control) with photostimulation.
CONCLUSIONS:
Capillary narrowing increases the risk of developing microcirculation embolism in the venous sides of the cerebral capillaries.
Scientific journal, English - Capillary responses to functional and pathological activations rely on the capillary states at rest
Hiroki Suzuki; Hiroshi Takeda; Hiroyuki Takuwa; Bin Ji; Makoto Higuchi; Iwao Kanno; Kazuto Masamoto
Last, Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, 43, 6, 1010-1024, 08 Feb. 2023, Peer-reviwed, Brain capillaries play a crucial role in maintaining cellular viability and thus preventing neurodegeneration. The aim of this study was to characterize the brain capillary morphology at rest and during neural activation based on a big data analysis from three-dimensional microangiography. Neurovascular responses were measured using a genetic calcium sensor expressed in neurons and microangiography with two-photon microscopy, while neural acivity was modulated by stimulation of contralateral whiskers or by a seizure evoked by kainic acid. For whisker stimulation, 84% of the capillary sites showed no detectable diameter change. The remaining 10% and 6% were dilated and constricted, respectively. Significant differences were observed for capillaries in the diameter at rest between the locations of dilation and constriction. Even the seizures resulted in 44% of the capillaries having no detectable change in diameter, while 56% of the capillaries dilated. The extent of dilation was dependent on the diameter at rest. In conclusion, big data analysis on brain capillary morphology has identified at least two types of capillary states: capillaries with diameters that are relatively large at rest and stable over time regardless of neural activity and capillaries whose diameters are relatively small at rest and vary according to neural activity.
Scientific journal, English - Close association between spreading depolarization and development of infarction under experimental ischemia in anesthetized male mice
Miyuki Unekawa; Yutaka Tomita; Kazuto Masamoto; Iwao Kanno; Jin Nakahara; Yoshikane Izawa
Brain Research, Elsevier BV, 1792, 148023-148023, Oct. 2022, Peer-reviwed
Scientific journal - Spatiotemporal analysis of blood plasma and blood cell flow fluctuations of cerebral microcirculation in anesthetized rats
Tomoya Niizawa; Ruka Sakuraba; Tomoya Kusaka; Yuika Kurihara; Takuma Sugashi; Hiroshi Kawaguchi; Iwao Kanno; Kazuto Masamoto
Last, Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, 43, 1, 138-152, 22 Sep. 2022, Peer-reviwed, Cerebral hemodynamics fluctuates spontaneously over broad frequency ranges. However, its spatiotemporal coherence of flow oscillations in cerebral microcirculation remains incompletely understood. The objective of this study was to characterize the spatiotemporal fluctuations of red blood cells (RBCs) and plasma flow in the rat cerebral microcirculation by simultaneously imaging their dynamic behaviors. Comparisons of changes in cross-section diameters between RBC and plasma flow showed dissociations in penetrating arterioles. The results indicate that vasomotion has the least effect on the lateral movement of circulating RBCs, resulting in variable changes in plasma layer thickness. Parenchymal capillaries exhibited slow fluctuations in RBC velocity (0.1 to 0.3 Hz), regardless of capillary diameter fluctuations (<0.1 Hz). Temporal fluctuations and the velocity of RBCs decreased significantly at divergent capillary bifurcations. The results indicate that a transit of RBCs generates flow resistance in the capillaries and that slow velocity fluctuations of the RBCs are subject to a number of bifurcations. In conclusion, the high-frequency oscillation of the blood flow is filtered at the bifurcation through the capillary networks. Therefore, a number of bifurcations in the cerebral microcirculation may contribute to the power of low-frequency oscillations.
Scientific journal - Automated capillary flow segmentation and mapping for nailfold video capillaroscopy
Tomoya Niizawa; Kota Yokemura; Tomoya Kusaka; Takuma Sugashi; Ichiro Miura; Keiji Kawagoe; Kazuto Masamoto
Last, Microcirculation, Wiley, 29, 3, e12753, Mar. 2022, Peer-reviwed, Abstract
Objective
This study aimed to develop an automated image analysis method for segmentation and mapping of capillary flow dynamics captured using nailfold video capillaroscopy (NVC). Methods were applied to compare capillary flow structures and dynamics between young and middle‐aged healthy controls.
Methods
NVC images were obtained in a resting state, and a region of the vessel in the image was extracted using a conventional U‐Net neural network. The approximate length, diameter, and radius of the curvature were calculated automatically. Flow speed and its fluctuation over time were mapped using the Radon transform and frequency spectrum analysis from the kymograph image created along the vessel's centerline.
Results
The diameter of the curve segment (14.4 μm and 13.0 μm) and the interval of two straight segments (13.7 μm and 32.1 μm) of young and middle‐aged subjects, respectively, were significantly different. Faster flow was observed in older subjects (0.48 mm/s) than in younger subjects (0.26 mm/s). The power spectral analysis revealed a significant correlation between the high‐frequency power spectrum and the flow speed.
Conclusions
The present method allows a spatiotemporal characterization of capillary morphology and flow dynamics with NVC, allowing a wide application such as large‐scale health assessment.
Scientific journal, English - 実験動物の画像情報に基づいた行動評価法の提案:撮像のフレームレートによる影響評価
村田樹里; 濱谷ひかる; 井上幹太; 矢野祐希; 吉田智毅; 新澤智也; 須貸拓馬; 正本和人
Last, 生体医工学, 59, 6, 139-145, Dec. 2021, Peer-reviwed
Scientific journal, Japanese - Three-dimensional microvascular network reconstruction from in vivo images with adaptation of the regional inhomogeneity in the signal-to-noise ratio
Takuma Sugashi; Hiroya Yuki; Tomoya Niizawa; Hiroyuki Takuwa; Iwao Kanno; Kazuto Masamoto
Microcirculation, John Wiley and Sons Inc, 28, 5, 01 Jul. 2021, Objective: Quantification of angiographic images with two-photon laser scanning fluorescence microscopy (2PLSM) relies on proper segmentation of the vascular images. However, the images contain inhomogeneities in the signal-to-noise ratio (SNR) arising from regional effects of light scattering and absorption. The present study developed a semiautomated quantification method for volume images of 2PLSM angiography by adjusting the binarization threshold according to local SNR along the vessel centerlines. Methods: A phantom model made with fluorescent microbeads was used to incorporate a region-dependent binarization threshold. Results: The recommended SNR for imaging was found to be 4.2–10.6 that provide the true size of imaged objects if the binarization threshold was fixed at 50% of SNR. However, angiographic images in the mouse cortex showed variable SNR up to 45 over the depths. To minimize the errors caused by variable SNR and a spatial extent of the imaged objects in an axial direction, the microvascular networks were three-dimensionally reconstructed based on the cross-sectional diameters measured along the vessel centerline from the XY-plane images with adapted binarization threshold. The arterial volume was relatively constant over depths of 0–500 µm, and the capillary volume (1.7% relative to the scanned volume) showed the larger volumes than the artery (0.8%) and vein (0.6%). Conclusions: The present methods allow consistent segmentation of microvasculature by adapting the local inhomogeneity in the SNR, which will be useful for quantitative comparison of the microvascular networks, such as under disease conditions where SNR in the 2PLSM images varies over space and time.
Scientific journal, English - Optical manipulation of local cerebral blood flow in the deep brain of freely moving mice
Yoshifumi Abe; Soojin Kwon; Mitsuhiro Oishi; Miyuki Unekawa; Norio Takata; Fumiko Seki; Ryuta Koyama; Manabu Abe; Kenji Sakimura; Kazuto Masamoto; Yutaka Tomita; Hideyuki Okano; Hajime Mushiake; Kenji F. Tanaka
Cell Reports, Elsevier BV, 36, 4, 109427-109427, Jul. 2021, Peer-reviwed
Scientific journal, English - Vascular permeability of skeletal muscle microvessels in rat arterial ligation model: in vivo analysis using two-photon laser scanning microscopy.
Rie Shimotsu; Kzuki Hotta; Ryo Ikegami; Tomoyo Asamura; Ayaka Tabuchi; Kazuto Masamoto; Kazuyoshi Yagishita; David C Poole; Yutaka Kano
American journal of physiology. Regulatory, integrative and comparative physiology, 320, 6, R972-R983, 01 Jun. 2021, Peer-reviwed, True, Peripheral artery disease (PAD) in the lower limb compromises oxygen supply due to arterial occlusion. Ischemic skeletal muscle is accompanied by capillary structural deformation. Therefore, using novel microscopy techniques, we tested the hypothesis that endothelial cell swelling temporally and quantitatively corresponds to enhanced microvascular permeability. Hindlimb ischemia was created in male Wistar rat's by iliac artery ligation (AL). The tibialis anterior (TA) muscle microcirculation was imaged using intravenously infused rhodamine B isothiocyanate dextran fluorescent dye via two-photon laser scanning microscopy (TPLSM) and dye extravasation at 3 and 7 days post-AL quantified to assess microvascular permeability. The TA microvascular endothelial ultrastructure was analyzed by transmission electron microscopy (TEM). Compared with control (0.40 ± 0.15 μm3 × 106), using TPLSM, the volumetrically determined interstitial leakage of fluorescent dye measured at 3 (3.0 ± 0.40 μm3 × 106) and 7 (2.5 ± 0.8 μm3 × 106) days was increased (both P < 0.05). Capillary wall thickness was also elevated at 3 (0.21 ± 0.06 μm) and 7 (0.21 ± 0.08 μm) days versus control (0.11 ± 0.03 μm, both P < 0.05). Capillary endothelial cell swelling was temporally and quantitatively associated with elevated vascular permeability in the AL model of PAD but these changes occurred in the absence of elevations in protein levels of vascular endothelial growth factor (VEGF) its receptor (VEGFR2 which decreased by AL-7 day) or matrix metalloproteinase. The temporal coherence of endothelial cell swelling and increased vascular permeability supports a common upstream mediator. TPLSM, in combination with TEM, provides a sensitive and spatially discrete technique to assess the mechanistic bases for, and efficacy of, therapeutic countermeasures to the pernicious sequelae of compromised peripheral arterial function.
Scientific journal, English - Error Evaluation for Automated Diameter Measurements of Cerebral Capillaries Captured with Two-Photon Laser Scanning Fluorescence Microscopy
Hiroki Suzuki; Takuma Sugashi; Hiroshi Takeda; Hiroyuki Takuwa; Iwao Kanno; Kazuto Masamoto
Last, Advances in Experimental Medicine and Biology, Springer International Publishing, 241-245, 09 May 2021, Peer-reviwed
In book, English - Time Series Tracking of Cerebral Microvascular Adaptation to Hypoxia and Hyperoxia Imaged with Repeated In Vivo Two-Photon Microscopy
Takuma Sugashi; Tomoya Niizawa; Hiroki Suzuki; Hiroyuki Takuwa; Miyuki Unekawa; Yutaka Tomita; Iwao Kanno; Kazuto Masamoto
Last, Advances in Experimental Medicine and Biology, Springer International Publishing, 323-327, 09 May 2021, Peer-reviwed
In book, English - Differential pial and penetrating arterial responses examined by optogenetic activation of astrocytes and neurons
Nao Hatakeyama; Miyuki Unekawa; Juri Murata; Yutaka Tomita; Norihiro Suzuki; Jin Nakahara; Hiroyuki Takuwa; Iwao Kanno; Ko Matsui; Kenji F Tanaka; Kazuto Masamoto
Last, Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, 41, 10, 2676-2689, 25 Apr. 2021, Peer-reviwed, A variety of brain cells participates in neurovascular coupling by transmitting and modulating vasoactive signals. The present study aimed to probe cell type-dependent cerebrovascular (i.e., pial and penetrating arterial) responses with optogenetics in the cortex of anesthetized mice. Two lines of the transgenic mice expressing a step function type of light-gated cation channel (channelrhodopsine-2; ChR2) in either cortical neurons (muscarinic acetylcholine receptors) or astrocytes (Mlc1-positive) were used in the experiments. Photo-activation of ChR2-expressing astrocytes resulted in a widespread increase in cerebral blood flow (CBF), extending to the nonstimulated periphery. In contrast, photo-activation of ChR2-expressing neurons led to a relatively localized increase in CBF. The differences in the spatial extent of the CBF responses are potentially explained by differences in the involvement of the vascular compartments. In vivo imaging of the cerebrovascular responses revealed that ChR2-expressing astrocyte activation led to the dilation of both pial and penetrating arteries, whereas ChR2-expressing neuron activation predominantly caused dilation of the penetrating arterioles. Pharmacological studies showed that cell type-specific signaling mechanisms participate in the optogenetically induced cerebrovascular responses. In conclusion, pial and penetrating arterial vasodilation were differentially evoked by ChR2-expressing astrocytes and neurons.
Scientific journal, English - Mapping of flow velocity using spatiotemporal changes in time‐intensity curves from indocyanine green videoangiography
Tomoya Niizawa; Ryota Hachiya; Takuma Sugashi; Satoshi Terao; Mutsumi Nagai; Mami Ishikawa; Kazuto Masamoto
Last, Microcirculation, Wiley, 28, 4, e12685, 03 Mar. 2021, Peer-reviwed, Abstract
Objective
The present study developed an image‐based analysis method that uses indocyanine green videoangiography (ICG‐VA) to measure flow velocity in the arteries and veins of the cortical surface in patients undergoing neurosurgery.
Methods
MATLAB‐based code was used to correct motion artifacts in the ICG‐VA and determine the time‐intensity curve of the ICG. The slope of the initial increase in ICG intensity following the bolus injection was measured and normalized using the predicted input function in the imaging field. Flow velocity over a certain distance determined by the user was measured based on a time shift of the time‐intensity curves along the centerline of the vessels.
Results
The normalized slope of ICG intensity represented the expected differences in the flow velocity among the artery (0.67 ± 0.05 s−1), parenchymal tissue (0.49 ± 0.10 s−1), and vein (0.44 ± 0.11 s−1). The flow velocities measured along the vessel centerline were 2.5 ± 1.1 cm/s and 1.1 ± 0.3 cm/s in the arteries (0.5 ± 0.2 mm in diameter) and veins (0.6 ± 0.2 mm in diameter), respectively.
Conclusions
An image‐based analysis method for ICG‐VA was developed to map the expected differences in the flow velocity based on the rising slope of ICG intensity and to measure the absolute flow velocities using the flexible zone and cross‐correlation methods.
Scientific journal, English - Tracking tau fibrillogenesis and consequent primary phagocytosis of neurons mediated by microglia in a living tauopathy model
Hiroyuki Takuwa; Asumi Orihara; Yuhei Takado; Takuya Urushihata; Masafumi Shimojo; Ai Ishikawa; Manami Takahashi; Anna M. Barron; Maiko Ono; Jun Maeda; Kazuto Masamoto; Hiroyasu Akatsu; Aviva M. Tolkovsky; Bin Ji; Yutaka Tomita; Hiroshi Ito; Ming-Rong Zhang; Michel Goedert; Maria Grazia Spillantini; Virginia M. -Y. Lee; John Q. Trojanowski; Taketoshi Maehara; Tetsuya Suhara; Naruhiko Sahara; Makoto Higuchi
Cold Spring Harbor Laboratory, 05 Nov. 2020, ABSTRACT
Fibrillary tau pathologies have been implicated in Alzheimer’s and allied neurodegenerative diseases, while mechanisms by which neurons bearing tau tangles die remain enigmatic. To address this issue, we pursued tau and related key pathologies macroscopically by PET and MRI and microscopically by intravital two-photon laser optics. Time-course macroscopic assays of tau transgenic mice demonstrated intimate associations of tau deposition and increase of an inflammatory microglial marker, translocator protein (TSPO), with regional brain atrophy. Longitudinal microscopy of these mice revealed a rapid turnover of tau lesions resulting from continuous generation of new tau aggregates followed by loss of neurons and their fibrillar contents. This technology also allowed the capturing of the disappearance of tangle-bearing neurons several days after being engulfed by activated microglia. Notably, a therapeutic TSPO ligand profoundly suppressed the mobility and phagocytotic activity of microglia and improved neuronal survival in this model, supporting the involvement of primary phagocytosis of viable neurons by microglia in tau-primed neuronal death. Finally, partial depletion of microglia revealed roles of immune factors, MFG-E8 and C1q, as ‘eat-me’ signals for an immediate attraction of phagocytic microglia towards the elimination of tangle-loaded neurons. - Intracellular ATP levels in mouse cortical excitatory neurons varies with sleep–wake states
Akiyo Natsubori; Tomomi Tsunematsu; Akihiro Karashima; Hiromi Imamura; Naoya Kabe; Andrea Trevisiol; Johannes Hirrlinger; Tohru Kodama; Tomomi Sanagi; Kazuto Masamoto; Norio Takata; Klaus-Armin Nave; Ko Matsui; Kenji F. Tanaka; Makoto Honda
Communications Biology, Springer Science and Business Media LLC, 3, 1, 07 Sep. 2020, Peer-reviwed, Abstract
Whilst the brain is assumed to exert homeostatic functions to keep the cellular energy status constant under physiological conditions, this has not been experimentally proven. Here, we conducted in vivo optical recordings of intracellular concentration of adenosine 5’-triphosphate (ATP), the major cellular energy metabolite, using a genetically encoded sensor in the mouse brain. We demonstrate that intracellular ATP levels in cortical excitatory neurons fluctuate in a cortex-wide manner depending on the sleep-wake states, correlating with arousal. Interestingly, ATP levels profoundly decreased during rapid eye movement sleep, suggesting a negative energy balance in neurons despite a simultaneous increase in cerebral hemodynamics for energy supply. The reduction in intracellular ATP was also observed in response to local electrical stimulation for neuronal activation, whereas the hemodynamics were simultaneously enhanced. These observations indicate that cerebral energy metabolism may not always meet neuronal energy demands, consequently resulting in physiological fluctuations of intracellular ATP levels in neurons.
Scientific journal, English - Neurosurgical intraoperative ultrasonography using contrast enhanced superb microvascular imaging -vessel density and appearance time of the contrast agent-
Mami Ishikawa; Kazuto Masamoto; Ryota Hachiya; Hiroshi Kagami; Makoto Inaba; Heiji Naritaka; Shojiro Katoh
British Journal of Neurosurgery, Informa UK Limited, 37, 3, 485-494, 10 Jul. 2020, Peer-reviwed
Scientific journal, English - Spatiotemporal dynamics of red blood cells in capillaries in layer I of the cerebral cortex and changes in arterial diameter during cortical spreading depression and response to hypercapnia in anesthetized mice
Miyuki Unekawa; Yutaka Tomita; Haruki Toriumi; Takashi Osada; Kazuto Masamoto; Hiroshi Kawaguchi; Yoshikane Izawa; Yoshiaki Itoh; Iwao Kanno; Norihiro Suzuki; Jin Nakahara
Microcirculation, Wiley, 26, 6, e12552, 02 Jun. 2019, Peer-reviwed, Abstract
Objective
Control of red blood cell velocity in capillaries is essential to meet local neuronal metabolic requirements, although changes of capillary diameter are limited. To further understand the microcirculatory response during cortical spreading depression, we analyzed the spatiotemporal changes of red blood cell velocity in intraparenchymal capillaries.
Methods
In urethane‐anesthetized Tie2‐green fluorescent protein transgenic mice, the velocity of fluorescence‐labeled red blood cells flowing in capillaries in layer I of the cerebral cortex was automatically measured with our Matlab domain software (KEIO‐IS2) in sequential images obtained with a high‐speed camera laser‐scanning confocal fluorescence microscope system.
Results
Cortical spreading depression repeatedly increased the red blood cell velocity prior to arterial constriction/dilation. During the first cortical spreading depression, red blood cell velocity significantly decreased, and sluggishly moving or retrograde‐moving red blood cells were observed, concomitantly with marked arterial constriction. The velocity subsequently returned to around the basal level, while oligemia after cortical spreading depression with slight vasoconstriction remained. After several passages of cortical spreading depression, hypercapnia‐induced increase of red blood cell velocity, regional cerebral blood flow and arterial diameter were all significantly reduced, and the correlations among them became extremely weak.
Conclusions
Taken together with our previous findings, these simultaneous measurements of red blood cell velocity in multiple capillaries, arterial diameter and regional cerebral blood flow support the idea that red blood cell flow might be altered independently, at least in part, from arterial regulation, that neuro‐capillary coupling plays a role in rapidly meeting local neural demand.
Scientific journal, English - Vascular Gap Junctions Contribute to Forepaw Stimulation-Induced Vasodilation Differentially in the Pial and Penetrating Arteries in Isoflurane-Anesthetized Rats
Nobuhiro Watanabe; Satoshi Sasaki; Kazuto Masamoto; Harumi Hotta
Frontiers in Molecular Neuroscience, Frontiers Media SA, 11, 446, 03 Dec. 2018, Peer-reviwed
Scientific journal, English - Optical imaging and modulation of neurovascular responses.
Masamoto K; Vazquez A
J Cereb Blood Flow Metab., 38, 12, 2057-2072, Dec. 2018, Peer-reviwed
English - Microvascular permeability of skeletal muscle after eccentric contraction-induced muscle injury: in vivo imaging using two-photon laser scanning microscopy
Kazuki Hotta; Bradley Jon Behnke; Kazuto Masamoto; Rie Shimotsu; Naoya Onodera; Akihiko Yamaguchi; David C. Poole; Yutaka Kano
Journal of Applied Physiology, American Physiological Society, 125, 2, 369-380, 01 Aug. 2018, Peer-reviwed, Via modulation of endothelial integrity and vascular permeability in response to damage, skeletal muscle microvessels play a crucial permissive role in tissue leukocyte invasion. However, direct visual evidence of altered microvascular permeability of skeletal muscle has not been technically feasible, impairing mechanistic understanding of these responses. Two-photon laser scanning microscopy (TPLSM) allows three-dimensional in vivo imaging of skeletal muscle microcirculation. We hypothesized that the regulation of microvascular permeability in vivo is temporally related to acute inflammatory and regenerative processes following muscle injury. To test our hypothesis, tibialis anterior muscles of anesthetized male Wistar rats were subjected to eccentric contractions (ECCs) via electrical stimulation. The skeletal muscle microcirculation was imaged by an intravenously infused fluorescent dye (rhodamine B isothiocyanate-dextran) to assess microvascular permeability via TPLSM 1, 3, and 7 days after ECC. Immunohistochemistry on serial muscle sections was performed to determine the proportion of VEGF-A-positive muscle fibers in the damaged muscle. Compared with control rats, the volumetrically determined interstitial leakage of fluorescent dye (5.1 ± 1.4, 5.3 ± 1.2 vs. 0.51 ± 0.14 μm3 × 106; P < 0.05, days 1 and 3, respectively, vs. control) and percentage of VEGF-A-positive fibers in the damaged muscle (10 ± 0.4%, 22 ± 1.1% vs. 0%; days 1 and 3, respectively, vs. control) were significantly higher on days 1 and 3 after ECC. The interstitial leakage volume returned to control by day 7. These results suggest that microvascular hyperpermeability assessed by in vivo TPLSM imaging is associated with ECC-induced muscle damage and increased VEGF expression.
NEW & NOTEWORTHY This investigation employed a novel in vivo imaging technique for skeletal muscle microcirculation using two-photon laser scanning microscopy that enabled microvascular permeability to be assessed by four-dimensional image analysis. By combining in vivo imaging and histological analysis, we found the temporal profile of microvascular hyperpermeability to be related to that of eccentric contraction-induced skeletal muscle injury and pronounced novel myocyte VEGF expression.
Scientific journal, English - Positron emission tomography of cerebral angiogenesis and TSPO expression in a mouse model of chronic hypoxia
Iwao Kanno; Chie Seki; Hiroyuki Takuwa; Zhao-Hui Jin; Didier Boturyn; Pascal Dumy; Takako Furukawa; Tsuneo Saga; Hiroshi Ito; Kazuto Masamoto
Last, Journal of Cerebral Blood Flow and Metabolism, SAGE Publications Ltd, 38, 4, 687-696, 01 Apr. 2018, Peer-reviwed, The present study aimed to examine whether positron emission tomography (PET) could evaluate cerebral angiogenesis. Mice were housed in a hypoxic chamber with 8–9% oxygen for 4, 7, and 14 days, and the angiogenic responses were evaluated with a radiotracer, 64Cu-cyclam-RAFT-c(-RGDfK-)4, which targeted αVβ3 integrin and was imaged with PET. The PET imaging results showed little uptake during all of the hypoxic periods. Immunofluorescence staining of the β3 integrin, CD61, revealed weak expression, while the microvessel density assessed by CD31 staining increased with the hypoxic duration. These observations suggest that the increased vascular density originated from other types of vascular remodeling, unlike angiogenic sprouting. We then searched for any signs of vascular remodeling that could be detected using PET. PET imaging of 11C-PK11195, a marker of the 18-kDa translocator protein (TSPO), revealed a transient increase at day 4 of hypoxia. Because the immunofluorescence of glial markers showed unchanged staining over the early phase of hypoxia, the observed upregulation of TSPO expression probably originated from non-glial cells (e.g. vascular cells). In conclusion, a transient increase in TSPO probe uptake was detected with PET at only the early phase of hypoxia, which indicates an early sign of vascular remodeling induced by hypoxia.
Scientific journal, English - Changes in effective diffusivity for oxygen during neural activation and deactivation estimated from capillary diameter measured by two-photon laser microscope
Hiroshi Ito; Hiroyuki Takuwa; Yosuke Tajima; Hiroshi Kawaguchi; Takuya Urushihata; Junko Taniguchi; Yoko Ikoma; Chie Seki; Masanobu Ibaraki; Kazuto Masamoto; Iwao Kanno
JOURNAL OF PHYSIOLOGICAL SCIENCES, SPRINGER JAPAN KK, 67, 2, 325-330, Mar. 2017, Peer-reviwed, The relation between cerebral blood flow (CBF) and cerebral oxygen extraction fraction (OEF) can be expressed using the effective diffusivity for oxygen in the capillary bed (D) as OEF = 1 - exp(-D/CBF). The D value is proportional to the microvessel blood volume. In this study, changes in D during neural activation and deactivation were estimated from changes in capillary and arteriole diameter measured by two-photon microscopy in awake mice. Capillary and arteriole vessel diameter in the somatosensory cortex and cerebellum were measured under neural activation (sensory stimulation) and neural deactivation [crossed cerebellar diaschisis (CCD)], respectively. Percentage changes in D during sensory stimulation and CCD were 10.3 +/- 7.3 and -17.5 +/- 5.3 % for capillary diameter of < 6 mu m, respectively. These values were closest to the percentage changes in D calculated from previously reported human positron emission tomography data. This may indicate that thinner capillaries might play the greatest role in oxygen transport from blood to brain tissue.
Scientific journal, English - Dynamic diameter response of intraparenchymal penetrating arteries during cortical spreading depression and elimination of vasoreactivity to hypercapnia in anesthetized mice
Miyuki Unekawa; Yutaka Tomita; Kazuto Masamoto; Haruki Toriumi; Takashi Osada; Iwao Kanno; Norihiro Suzuki
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM, SAGE PUBLICATIONS INC, 37, 2, 657-670, Feb. 2017, Peer-reviwed, Cortical spreading depression (CSD) induces marked hyperemia with a transient decrease of regional cerebral blood flow (rCBF), followed by sustained oligemia. To further understand the microcirculatory mechanisms associated with CSD, we examined the temporal changes of diameter of intraparenchymal penetrating arteries during CSD. In urethane-anesthetized mice, the diameter of single penetrating arteries at three depths was measured using two-photon microscopy during passage of repeated CSD, with continuous recordings of direct current potential and rCBF. The first CSD elicited marked constriction superimposed on the upstrokes of profound dilation throughout each depth of the penetrating artery, and the vasoreaction temporally corresponded to the change of rCBF. Second or later CSD elicited marked dilation with little or no constriction phase throughout each depth, and the vasodilation also temporally corresponded to the increase of rCBF. Furthermore, the peak dilation showed good negative correlations with basal diameter and increase of rCBF. Vasodilation induced by 5% CO2 inhalation was significantly suppressed after CSD passage at any depth as well as hyperperfusion. These results may indicate that CSD-induced rCBF changes mainly reflect the diametric changes of the intraparenchymal arteries, despite the elimination of responsiveness to hypercapnia.
Scientific journal, English - Long-term repeated in vivo real-time analysis of microglia in the mouse cortex with a closed-cranial window by Tomita-Seylaz method
Hiroya Yuki; Kazuto Masamoto; Miyuki Unekawa; Yutaka Tomita; Iwao Kanno; Norihiro Suzuki
Corresponding, Cerebral Blood Flow and Metabolism (Japanese journal of cerebral blood flow and metabolism), The Japanese Society of Cerebral Blood Flow and Metabolism, 28, 2, 249-256, 2017, Peer-reviwed
Scientific journal - Dynamic Flow Velocity Mapping from Fluorescent Dye Transit Times in the Brain Surface Microcirculation of Anesthetized Rats and Mice
Ryo Hoshikawa; Hiroshi Kawaguchi; Hiroyuki Takuwa; Yoko Ikoma; Yutaka Tomita; Miyuki Unekawa; Norihiro Suzuki; Iwao Kanno; Kazuto Masamoto
Last, MICROCIRCULATION, WILEY-BLACKWELL, 23, 6, 416-425, Aug. 2016, Peer-reviwed, ObjectiveThis study aimed to develop a new method for mapping blood flow velocity based on the spatial evolution of fluorescent dye transit times captured with CLSFM in the cerebral microcirculation of anesthetized rodents.
MethodsThe animals were anesthetized with isoflurane, and a small amount of fluorescent dye was intravenously injected to label blood plasma. The CLSFM was conducted through a closed cranial window to capture propagation of the dye in the cortical vessels. The transit time of the dye over a certain distance in a single vessel was determined with automated image analyses, and average flow velocity was mapped in each vessel.
ResultsThe average flow velocity measured in the rat pial artery and vein was 4.41.2 and 2.4 +/- 0.5mm/sec, respectively. A similar range of flow velocity to those of the rats was observed in the mice; 4.9 +/- 1.4 and 2.0 +/- 0.9mm/sec, respectively, although the vessel diameter in the mice was about half of that in the rats.
ConclusionsFlow velocity in the cerebral microcirculation can be mapped based on fluorescent dye transit time measurements with conventional CLSFM in experimental animals.
Scientific journal, English - ASTROCYTIC DEPOLARIZATION INDUCED RAPID AND BROAD INCREASE IN CBF IN IN VIVO MOUSE CORTEX
K. Masamoto; M. Unekawa; T. Watanabe; H. Toriumi; H. Takuwa; H. Kawaguchi; I. Kanno; K. Matsui; K. Tanaka; Y. Tomita; N. Suzuki
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM, SAGE PUBLICATIONS INC, 36, 28-29, Jun. 2016
Scientific journal, English - BEHAVIOR OF RED BLOOD CELLS IN INTRAPARENCHYMAL CAPILLARIES DURING CORTICAL SPREADING DEPRESSION OBSERVED WITH HIGH-SPEED CAMERA CONFOCAL FLUORESCENCE MICROSCOPE IN ANESTHETIZED MICE
Y. Tomita; M. Unekawa; H. Toriumi; T. Osada; K. Masamoto; H. Kawaguchi; Y. Itoh; I. Kanno; N. Suzuki
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM, SAGE PUBLICATIONS INC, 36, 544-545, Jun. 2016
Scientific journal, English - Long-term effects of cerebral hypoperfusion on neural density and function using misery perfusion animal model
Asuka Nishino; Yosuke Tajima; Hiroyuki Takuwa; Kazuto Masamoto; Junko Taniguchi; Hidekatsu Wakizaka; Daisuke Kokuryo; Takuya Urushihata; Ichio Aoki; Iwao Kanno; Yutaka Tomita; Norihiro Suzuki; Yoko Ikoma; Hiroshi Ito
SCIENTIFIC REPORTS, NATURE PUBLISHING GROUP, 6, 25072, Apr. 2016, Peer-reviwed, We investigated the chronic effects of cerebral hypoperfusion on neuronal density and functional hyperemia using our misery perfusion mouse model under unilateral common carotid artery occlusion (UCCAO). Neuronal density evaluated 28 days after UCCAO using [C-11]flumazenil-PET and histology indicated no neurologic deficit in the hippocampus and neocortex. CBF response to sensory stimulation was assessed using laser-Doppler flowmetry. Percentage changes in CBF response of the ipsilateral hemisphere to UCCAO were 18.4 +/- 3.0%, 6.9 +/- 2.8%, 6.8 +/- 2.3% and 4.9 +/- 2.4% before, and 7, 14 and 28 days after UCCAO, respectively. Statistical significance was found at 7, 14 and 28 days after UCCAO (P < 0.01). Contrary to our previous finding (Tajima et al. 2014) showing recovered CBF response to hypercapnia on 28 days after UCCAO using the same model, functional hyperemia was sustained and became worse 28 days after UCCAO.
Scientific journal, English - Establishment and evaluation of a new highly metastatic tumor cell line 5a-D-Luc-ZsGreen expressing both luciferase and green fluorescent protein
Hitomi Sudo; Atsushi B. Tsuji; Aya Sugyo; Hiroyuki Takuwa; Kazuto Masamoto; Yutaka Tomita; Norihiro Suzuki; Takeshi Imamura; Mitsuru Koizumi; Tsuneo Saga
INTERNATIONAL JOURNAL OF ONCOLOGY, SPANDIDOS PUBL LTD, 48, 2, 525-532, Feb. 2016, Peer-reviwed, Breast cancer is the most common cancer in women. Although advances in diagnostic imaging for early detection, surgical techniques and chemotherapy have improved overall survival, the prognosis of patients with metastatic breast cancer remains poor. Understanding cancer cell dynamics in the metastatic process is important to develop new therapeutic strategies. Experimental animal models and imaging would be powerful tools for understanding of the molecular events of multistep process of metastasis. In the present study, to develop a new cancer cell line that is applicable to bioluminescence and fluorescence imaging, we transfected the expression vector of a green fluorescent protein ZsGreen1 into a metastatic cell line 5a-D-Luc, which is a subclone of the MDA-MB-231 breast cancer cell line expressing luciferase, and established a new tumor cell line 5a-D-Luc-ZsGreen expressing both luciferase and ZsGreen1. The 5a-D-Luc-ZsGreen cells proliferate more rapidly and have a more invasive phenotype compared with 5a-D-Luc cells following intracardiac injection. Metastasis sites were easily detected in the whole body by bioluminescence imaging and in excised tissues by ex vivo fluorescence imaging. The fluorescence of 5a-D-Luc-ZsGreen cells was not lost after formalin fixation and decalcification. It enabled us to easily evaluate tumor spread and localization at the cellular level in microscopic analysis. The strong fluorescence of 5a-D-Luc-ZsGreen cells allowed for real-time imaging of circulating tumor cells in cerebral blood vessels of live animals immediately after intracardiac injection of cells using two-photon laser-scanning microscopy. These findings suggest that the 5a-D-Luc-ZsGreen cells would be a useful tool for research on mechanisms of metastatic process in animal models.
Scientific journal, English - Fluorescence Imaging of Blood Flow Velocity in the Rodent Brain
Kazuto Masamoto; Ryo Hoshikawa; Hiroshi Kawaguchi
Lead, CURRENT TOPICS IN MEDICINAL CHEMISTRY, BENTHAM SCIENCE PUBL LTD, 16, 24, 2677-2684, 2016, Peer-reviwed, An adequate supply of blood flow to the brain is critically important to maintain long-term brain function. However, many issues surrounding the regulatory mechanism of the blood flow supply to the brain remain unclear, such as i) the appropriate range of capillary flow velocity to keep neurons healthy, ii) the size of the vascular module to support a functioning neural unit, iii) the sensing mechanism for capillary flow control, and iv) the role of flow regulation in promoting neural plasticity. A fluorescence technique allows for visualization of the dynamic changes between cerebral microcirculation and neural activity concurrently and thus is capable of addressing these questions. Here, we briefly review the methodological aspects of measuring blood flow using fluorescence imaging in rodent brains and introduce a novel approach for mapping the flow velocity in multiple vessels with laser scanning fluorescence microscopy. The flow velocity was imaged by calculating the traveling distance and time of the instantaneously injected fluorescent tags through the vascular networks. Using the present method, we observed that the average flow velocity in the pial artery and vein was 3.0 +/- 1.4 mm/s and 1.6 +/- 0.5 mm/s, respectively (N = 6 mice). A limitation of the method presented is that the quantification is only applicable to the vascular networks laid in two-dimensional planes, such as pial vascular networks. Further technical improvement is needed to quantify three-dimensional flow through parenchymal microcirculation. Furthermore, it is also needed to fill a gap between the microscopically measured flow parameters and the macroscopic feature of the brain blood flow for clinical interpretation.
Scientific journal, English - Unveiling astrocytic control of cerebral blood flow with optogenetics
Kazuto Masamoto; Miyuki Unekawa; Tatsushi Watanabe; Haruki Toriumi; Hiroyuki Takuwa; Hiroshi Kawaguchi; Iwao Kanno; Ko Matsui; Kenji F. Tanaka; Yutaka Tomita; Norihiro Suzuki
Lead, SCIENTIFIC REPORTS, NATURE PUBLISHING GROUP, 5, 11455, Jun. 2015, Peer-reviwed, Cortical neural activities lead to changes in the cerebral blood flow (CBF), which involves astrocytic control of cerebrovascular tone. However, the manner in which astrocytic activity specifically leads to vasodilation or vasoconstriction is difficult to determine. Here, cortical astrocytes genetically expressing a light-sensitive cation channel, channelrhodopsin-2 (ChR2), were transcranially activated with a blue laser while the spatiotemporal changes in CBF were noninvasively monitored with laser speckle flowgraphy in the anesthetised mouse cortex. A brief photostimulation induced a fast transient increase in CBF. The average response onset time was 0.7 +/- 0.7 sec at the activation foci, and this CBF increase spread widely from the irradiation spot with an apparent propagation speed of 0.8-1.1 mm/sec. The broad increase in the CBF could be due to a propagation of diffusible vasoactive signals derived from the stimulated astrocytes. Pharmacological manipulation showed that topical administration of a K+ channel inhibitor (BaCl2; 0.1-0.5 mM) significantly reduced the photostimulation-induced CBF responses, which indicates that the ChR2-evoked astrocytic activity involves K+ signalling to the vascular smooth muscle cells. These findings demonstrate a unique model for exploring the role of the astrocytes in gliovascular coupling using non-invasive, time-controlled, cell-type specific perturbations.
Scientific journal, English - Hyperperfusion counteracted by transient rapid vasoconstriction followed by long-lasting oligemia induced by cortical spreading depression in anesthetized mice
Miyuki Unekawa; Yutaka Tomita; Haruki Toriumi; Takashi Osada; Kazuto Masamoto; Hiroshi Kawaguchi; Yoshiaki Itoh; Iwao Kanno; Norihiro Suzuki
Journal of Cerebral Blood Flow and Metabolism, Nature Publishing Group, 35, 4, 689-698, 31 Mar. 2015, Peer-reviwed, Cortical spreading depression (CSD) involves mass depolarization of neurons and glial cells accompanied with changes in regional cerebral blood flow (rCBF) and energy metabolism. To further understand the mechanisms of CBF response, we examined the temporal diametric changes in pial arteries, pial veins, and cortical capillaries. In urethane-anesthetized mice, the diameters of these vessels were measured while simultaneously recording rCBF with a laser Doppler flowmeter. We observed a considerable increase in rCBF during depolarization in CSD induced by application of KCl, accompanied by a transient dip of rCBF with marked vasoconstriction of pial arteries, which resembled the response to pin-prick-induced CSD. Arterial constriction diminished or disappeared during the second and third passages of CSD, whereas the rCBF increase was maintained without a transient dip. Long-lasting oligemia with a decrease in the reciprocal of mean transit time of injected dye and mild constriction of pial arteries was observed after several passages of the CSD wave. These results indicate that CSD-induced rCBF changes consist of initial hyperemia with a transient dip and followed by a long-lasting oligemia, partially corresponding to the diametric changes of pial arteries, and further suggest that vessels other than pial arteries, such as intracortical vessels, are involved.
Scientific journal, English - Pial arteries respond earlier than penetrating arterioles to neural activation in the somatosensory cortex in awake mice exposed to chronic hypoxia: an additional mechanism to proximal integration signaling?
Yuta Sekiguchi; Hiroyuki Takuwa; Hiroshi Kawaguchi; Takahiro Kikuchi; Eiji Okada; Iwao Kanno; Hiroshi Ito; Yutaka Tomita; Yoshiaki Itoh; Norihiro Suzuki; Ryo Sudo; Kazuo Tanishita; Kazuto Masamoto
Last, JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM, SAGE PUBLICATIONS INC, 34, 11, 1761-1770, Nov. 2014, Peer-reviwed, The pial and penetrating arteries have a crucial role in regulating cerebral blood flow (CBF) to meet neural demand in the cortex. Here, we examined the longitudinal effects of chronic hypoxia on the arterial diameter responses to single whisker stimulation in the awake mouse cortex, where activity-induced responses of CBF were gradually attenuated. The vasodilation responses to whisker stimulation under prehypoxia normal conditions were 8.1% and 12% relative to their baselines in the pial arteries and penetrating arterioles, respectively. After 3 weeks of hypoxia, however, these responses were significantly reduced to 5.5% and 4.1%, respectively. The CBF response, measured using laser-Doppler flowmetry (LDF), induced by the same whisker stimulation was also attenuated (14% to 2.6%). A close linear correlation was found for the responses between the penetrating arteriolar diameter and LDF, and their temporal dynamics. After 3 weeks of chronic hypoxia, the initiation of vasodilation in the penetrating arterioles was significantly extended, but the pial artery responses remained unchanged. These results show that vasodilation of the penetrating arterioles followed the pial artery responses, which are not explainable in terms of proximal integration signaling. The findings therefore indicate an additional mechanism for triggering pial artery dilation in the neurovascular coupling.
Scientific journal, English - Changes in cortical microvasculature during misery perfusion measured by two-photon laser scanning microscopy
Yosuke Tajima; Hiroyuki Takuwa; Daisuke Kokuryo; Hiroshi Kawaguchi; Chie Seki; Kazuto Masamoto; Yoko Ikoma; Junko Taniguchi; Ichio Aoki; Yutaka Tomita; Norihiro Suzuki; Iwao Kanno; Naokatsu Saeki; Hiroshi Ito
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM, NATURE PUBLISHING GROUP, 34, 8, 1363-1372, Aug. 2014, Peer-reviwed, This study aimed to examine the cortical microvessel diameter response to hypercapnia in misery perfusion using two-photon laser scanning microscopy (TPLSM). We evaluated whether the vascular response to hypercapnia could represent the cerebrovascular reserve. Cerebral blood flow (CBF) during normocapnia and hypercapnia was measured by laser-Doppler flowmetry through cranial windows in awake C57/BL6 mice before and at 1, 7, 14, and 28 days after unilateral common carotid artery occlusion (UCCAO). Diameters of the cortical microvessels during normocapnia and hypercapnia were also measured by TPLSM. Cerebral blood flow and the vascular response to hypercapnia were decreased after UCCAO. Before UCCAO, vasodilation during hypercapnia was found primarily in arterioles (22.9%+/- 3.5%). At 14 days after UCCAO, arterioles, capillaries, and venules were autoregulatorily dilated by 79.5%+/- 19.7%, 57.2%+/- 32.3%, and 32.0%+/- 10.8%, respectively. At the same time, the diameter response to hypercapnia in arterioles was significantly decreased to 1.9%+/- 1.5%. A significant negative correlation was observed between autoregulatory vasodilation and the diameter response to hypercapnia in arterioles. Our findings indicate that arterioles play main roles in both autoregulatory vasodilation and hypercapnic vasodilation, and that the vascular response to hypercapnia can be used to estimate the cerebrovascular reserve.
Scientific journal, English - Cerebral hemodynamic response to acute hyperoxia in awake mice
Yosuke Tajima; Hiroyuki Takuwa; Asuka Nishino; Tetsuya Matsuura; Hiroshi Kawaguchi; Yoko Ikoma; Junko Taniguchi; Chie Seki; Kazuto Masamoto; Iwao Kanno; Naokatsu Saeki; Hiroshi Ito
BRAIN RESEARCH, ELSEVIER SCIENCE BV, 1557, 155-163, Apr. 2014, Peer-reviwed, Cerebral hemodynamic response to acute hyperoxia was investigated in awake mice. Using laser-Doppler flowmetry (LDF), baseline cerebral blood flow (CBF) and the cerebrovascular responses to whisker stimulation were measured in awake mice during normoxia and hyperoxia. Using two-photon laser scanning microscopy (TPLSM), the changes in cortical microvasculature were measured during normoxia and hyperoxia. During hyperoatia (PaO2=482.3 +/- 19.7 mmHg), baseline CBF was 6.8% lower than normoxia (PaO2=97.3 +/- 6.0 mmHg). The degree of increase in CBF evoked by whisker stimulation was greater during hyperoxia (18.1 +/- 5.0%) than normoxia (13.1 +/- 3.5%) (P<0.05). TPLSM imaging of the somatosensory cortex showed vasconsttiction in arterioles and capillaries during hyperoxia. Since the effective diffusivity for oxygen in the capillary bed might decrease by hyperoxia due to a decrease in capillary blood volume according to Hyder's model, an increase in the cerebral metabolic rate of oxygen utilization by neural activation during hyperoxia might need a greater increase in CBF as compared with normoxia. The hemodynamic response to neural activation could be modified by acute hyperoxia due to modification of the relation between changes in CBF and oxygen consumption by neural activation. (c) 2014 Elsevier B.V. All rights reserved.
Scientific journal, English - Vessel Specific Imaging of Glucose Transfer with Fluorescent Glucose Analogue in Anesthetized Mouse Cortex
Rei Murata; Yuki Takada; Hiroyuki Takuwa; Hiroshi Kawaguchi; Hiroshi Ito; Iwao Kanno; Naotomo Tottori; Yukio Yamada; Yutaka Tomita; Yoshiaki Itoh; Norihiro Suzuki; Katsuya Yamada; Kazuto Masamoto
Last, Advances in Experimental Medicine and Biology, Springer New York, 241-246, 22 Mar. 2014, Peer-reviwed
In book, English - Automated Image Analysis for Diameters and Branching Points of Cerebral Penetrating Arteries and Veins Captured with Two-Photon Microscopy
Takuma Sugashi; Kouichi Yoshihara; Hiroshi Kawaguchi; Hiroyuki Takuwa; Hiroshi Ito; Iwao Kanno; Yukio Yamada; Kazuto Masamoto
Last, Advances in Experimental Medicine and Biology, Springer New York, 209-215, 22 Mar. 2014, Peer-reviwed
In book, English - Microvascular sprouting, extension, and creation of new capillary connections with adaptation of the neighboring astrocytes in adult mouse cortex under chronic hypoxia
Kazuto Masamoto; Hiroyuki Takuwa; Chie Seki; Junko Taniguchi; Yoshiaki Itoh; Yutaka Tomita; Haruki Toriumi; Miyuki Unekawa; Hiroshi Kawaguchi; Hiroshi Ito; Norihiro Suzuki; Iwao Kanno
Lead, JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM, NATURE PUBLISHING GROUP, 34, 2, 325-331, Feb. 2014, Peer-reviwed, The present study aimed to determine the spatiotemporal dynamics of microvascular and astrocytic adaptation during hypoxia-induced cerebral angiogenesis. Adult C57BL/6J and Tie2-green fluorescent protein (GFP) mice with vascular endothelial cells expressing GFP were exposed to normobaric hypoxia for 3 weeks, whereas the three-dimensional microvessels and astrocytes were imaged repeatedly using two-photon microscopy. After 7 to 14 days of hypoxia, a vessel sprout appeared from the capillaries with a bump-like head shape (mean diameter 14 pm), and stagnant blood cells were seen inside the sprout. However, no detectable changes in the astrocyte morphology were observed for this early phase of the hypoxia adaptation. More than 50% of the sprouts emerged from capillaries 60,mu m away from the center penetrating arteries, which indicates that the capillary distant from the penetrating arteries is a favored site for sprouting. After 14 to 21 days of hypoxia, the sprouting vessels created a new connection with an existing capillary. In this phase, the shape of the new vessel and its blood flow were normalized, and the outside of the vessels were wrapped with numerous processes from the neighboring astrocytes. The findings indicate that hypoxia-induced cerebral angiogenesis provokes the adaptation of neighboring astrocytes, which may stabilize the blood-brain barrier in immature vessels.
Scientific journal, English - Reproducibility of measuring cerebral blood flow by laser-Doppler flowmetry in mice
Tajima Y; Takuwa H; Kawaguchi H; Masamoto K; Ikoma Y; Seki C; Taniguchi J; Kanno I; Saeki N; Ito H
Frontiers in Bioscience, IMR Press, E6, 1, 62-68, 2014, Peer-reviwed
Scientific journal, English - Hemodynamic changes during neural deactivation in awake mice: A measurement by laser-Doppler flowmetry in crossed cerebellar diaschisis
Hiroyuki Takuwa; Yosuke Tajima; Daisuke Kokuryo; Tetsuya Matsuura; Hiroshi Kawaguchi; Kazuto Masamoto; Junko Taniguchi; Yoko Ikoma; Chie Seki; Ichio Aoki; Yutaka Tomita; Norihiro Suzuki; Iwao Kanno; Hiroshi Ito
Brain Research, Elsevier BV, 1537, 350-355, Nov. 2013, Peer-reviwed
Scientific journal, English - Imaging of Tau Pathology in a Tauopathy Mouse Model and in Alzheimer Patients Compared to Normal Controls
Masahiro Maruyama; Hitoshi Shimada; Tetsuya Suhara; Hitoshi Shinotoh; Bin Ji; Jun Maeda; Ming-Rong Zhang; John Q. Trojanowski; Virginia M. -Y. Lee; Maiko Ono; Kazuto Masamoto; Harumasa Takano; Naruhiko Sahara; Nobuhisa Iwata; Nobuyuki Okamura; Shozo Furumoto; Yukitsuka Kudo; Qing Chang; Takaomi C. Saido; Akihiko Takashima; Jada Lewis; Ming-Kuei Jang; Ichio Aoki; Hiroshi Ito; Makoto Higuchi
NEURON, CELL PRESS, 79, 6, 1094-1108, Sep. 2013, Peer-reviwed, Accumulation of intracellular tau fibrils has been the focus of research on the mechanisms of neurodegeneration in Alzheimer's disease (AD) and related tauopathies. Here, we have developed a class of tau ligands, phenyl/pyridinyl-butadienyl-benzothiazoles/benzothiazoliums (PBBs), for visualizing diverse tau inclusions in brains of living patients with AD or non-AD tauopathies and animal models of these disorders. In vivo optical and positron emission tomographic (PET) imaging of a transgenic mouse model demonstrated sensitive detection of tau inclusions by PBBs. A pyridinated PBB, [C-11]PBB3, was next applied in a clinical PET study, and its robust signal in the AD hippocampus wherein tau pathology is enriched contrasted strikingly with that of a senile plaque radioligand, [C-11]Pittsburgh Compound-B ([C-11]PIB. [C-11]PBB3-PET data were also consistent with the spreading of tau pathology with AD progression. Furthermore, increased [C-11]PBB3 signals were found in a corticobasal syndrome patient negative for [C-11]PIB-PET.
Scientific journal, English - Layer-specific dilation of penetrating arteries induced by stimulation of the nucleus basalis of Meynert in the mouse frontal cortex
Harumi Hotta; Kazuto Masamoto; Sae Uchida; Yuta Sekiguchi; Hiroyuki Takuwa; Hiroshi Kawaguchi; Kazuhiro Shigemoto; Ryo Sudo; Kazuo Tanishita; Hiroshi Ito; Iwao Kanno
Journal of Cerebral Blood Flow and Metabolism, 33, 9, 1440-1447, Sep. 2013, Peer-reviwed, To clarify mechanisms through which activation of the nucleus basalis of Meynert (NBM) increases cerebral cortical blood flow, we examined whether cortical parenchymal arteries dilate during NBM stimulation in anesthetized mice. We used two-photon microscopy to measure the diameter of single penetrating arteries at different depths (∼800 μm, layers I to V) of the frontal cortex, and examined changes in the diameter during focal electrical stimulation of the NBM (0.5 ms at 30 to 50 μA and 50 Hz) and hypercapnia (3% CO 2 inhalation). Stimulation of the NBM caused diameter of penetrating arteries to increase by 9% to 13% of the prestimulus diameter throughout the different layers of the cortex, except at the cortical surface and upper part of layer V, where the diameter of penetrating arteries increased only slightly during NBM stimulation. Hypercapnia caused obvious dilation of the penetrating arteries in all cortical layers, including the surface arteries. The diameters began to increase within 1 second after the onset of NBM stimulation in the upper cortical layers, and later in lower layers. Our results indicate that activation of the NBM dilates cortical penetrating arteries in a layer-specific manner in magnitude and latency, presumably related to the density of cholinergic nerve terminals from the NBM. © 2013 ISCBFM.
Scientific journal, English - Hypoxia-Induced Cerebral Angiogenesis in Mouse Cortex with Two-Photon Microscopy
Kazuto Masamoto; Hiroyuki Takuwa; Yutaka Tomita; Haruki Toriumi; Miyuki Unekawa; Junko Taniguchi; Hiroshi Kawaguchi; Yoshiaki Itoh; Norihiro Suzuki; Hiroshi Ito; Iwao Kanno
Lead, Oxygen Transport to Tissue XXXV, Springer New York, 15-20, 04 Jun. 2013, Peer-reviwed
In book, English - Measuring the Vascular Diameter of Brain Surface and Parenchymal Arteries in Awake Mouse
Yuta Sekiguchi; Kazuto Masamoto; Hiroyuki Takuwa; Hiroshi Kawaguchi; Iwao Kanno; Hiroshi Ito; Yutaka Tomita; Yoshiaki Itoh; Norihiro Suzuki; Ryo Sudo; Kazuo Tanishita
Corresponding, Oxygen Transport to Tissue XXXV, Springer New York, 419-425, 04 Jun. 2013, Peer-reviwed
In book, English - Long-term adaptation of cerebral hemodynamic response to somatosensory stimulation during chronic hypoxia in awake mice
Hiroyuki Takuwa; Kazuto Masamoto; Kyoko Yamazaki; Hiroshi Kawaguchi; Yoko Ikoma; Yousuke Tajima; Takayuki Obata; Yutaka Tomita; Norihiro Suzuki; Iwao Kanno; Hiroshi Ito
Journal of Cerebral Blood Flow and Metabolism, 33, 5, 774-779, May 2013, Peer-reviwed, Effects of chronic hypoxia on hemodynamic response to sensory stimulation were investigated. Using laser-Doppler flowmetry, change in cerebral blood flow (CBF) was measured in awake mice, which were housed in a hypoxic chamber (8% O 2) for 1 month. The degree of increase in CBF evoked by sensory stimulation was gradually decreased over 1 month of chronic hypoxia. No significant reduction of increase in CBF induced by hypercapnia was observed during 1 month. Voltage-sensitive dye (VSD) imaging of the somatosensory cortex showed no significant decrease in neural activation over 1 month, indicating that the reduction of increase in CBF to sensory stimulation was not caused by cerebrovascular or neural dysfunction. The simulation study showed that, when effective diffusivity for oxygen in the capillary bed (D) value increases by chronic hypoxia due to an increase in capillary blood volume, an increase in the cerebral metabolic rate of oxygen utilization during neural activation can occur without any increase in CBF. Although previous study showed no direct effects of acute hypoxia on CBF response, our finding showed that hemodynamic response to neural activation could be modified in response to a change in their balance to energy demand using chronic hypoxia experiments. © 2013 ISCBFM All rights reserved.
Scientific journal, English - Phantom and mouse experiments of time-domain fluorescence tomography using total light approach
Shinpei Okawa; Akira Yano; Kazuki Uchida; Yohei Mitsui; Masaki Yoshida; Masashi Takekoshi; Andhi Marjono; Feng Gao; Yoko Hoshi; Ikuhiro Kida; Kazuto Masamoto; Yukio Yamada
BIOMEDICAL OPTICS EXPRESS, OPTICAL SOC AMER, 4, 4, 635-651, Apr. 2013, Peer-reviwed, Phantom and mouse experiments of time-domain fluorescence tomography were conducted to demonstrate the total light approach which was previously proposed by authors. The total light approach reduces the computation time to solve the forward model for light propagation. Time-resolved temporal profiles were acquired for cylindrical phantoms having single or double targets containing indocyanine green (ICG) solutions. The reconstructed images of ICG concentration reflected the true distributions of ICG concentration with a spatial resolution of about 10 mm. In vivo experiments were conducted using a mouse in which an ICG capsule was embedded beneath the skin in the abdomen. The reconstructed image of the ICG concentration again reflected the true distribution of ICG although artifacts due to autofluorescence appeared in the vicinity of the skin. The effectiveness of the total light approach was demonstrated by the phantom and mouse experiments. (C) 2013 Optical Society of America
Scientific journal, English - Potassium-induced cortical spreading depression bilaterally suppresses the electroencephalogram but only ipsilaterally affects red blood cell velocity in intraparenchymal capillaries
Miyuki Unekawa; Yutaka Tomita; Haruki Toriumi; Kazuto Masamoto; Iwao Kanno; Norihiro Suzuki
JOURNAL OF NEUROSCIENCE RESEARCH, WILEY-BLACKWELL, 91, 4, 578-584, Apr. 2013, Peer-reviwed, Cortical spreading depression (CSD) is a repetitive, propagating profile of mass depolarization of neuronal and glial cells, followed by sustained suppression of spontaneous neuronal activity. We have reported a long-lasting suppressive effect on red blood cell (RBC) velocities in intraparenchymal capillaries. Here, to test the hypothesis that the prolonged decrease of RBC velocity in capillaries is due to suppression of neuronal activity, we measured CSD-elicited changes in the electroencephalogram (EEG) as an index of neuronal activity. In isoflurane-anesthetized rats, DC potential, EEG, partial pressure of oxygen (PO2), and cerebral blood flow (CBF) were simultaneously recorded in the temporo-parietal region. The velocities of fluorescently labeled RBCs were evaluated by high-speed camera laser scanning confocal fluorescence microscopy with our original software, KEIO-IS2. Transient deflection of DC potential and PO2 and increase of CBF were repeatedly detected only in the ipsilateral hemisphere following topical KCl application. On the other hand, the relative spectral power of EEG was reduced bilaterally, showing the lowest value at 5 min after KCl application, when the other parameters had already returned to the baseline after the passage of CSD. Mean RBC velocity in capillaries was slightly but significantly reduced during and after passage of CSD in the ipsilateral hemisphere but did not change in the contralateral hemisphere in the same rats. We suggest that mass depolarization of neuronal and glial cells might transiently decelerate RBCs in nearby capillaries, but the sustained reduction of ipsilateral RBC velocity might be a result of the prolonged effect of CSD, not of neuronal suppression alone. (c) 2013 Wiley Periodicals, Inc.
Scientific journal, English - Three-dimensional cortex model including vascular structure for estimation of path length for optical imaging
Takahiro Kikuchi; Hiroyuki Takuwa; Kazuto Masamoto; Hiroshi Ito; Eiji Okada
Optics InfoBase Conference Papers, Optical Society of America, 2013, Optical imaging of hemoglobin concentration changes in the exposed cortex has been used to investigate the functional brain activation. The concentration changes in oxygenated and deoxygenated hemoglobin can be independently obtained from the dual- or multi-wavelength measurements of the change in reflectance of the exposed cortex and wavelengthdependent optical path length in the cortical tissues. In the previous studies, the partial optical path length were generally estimated by homogeneous and layered models. In reality, the concentration changes in the hemoglobin only occurs in the blood vessels. In this study, the partial optical path lengths in the blood vessels were estimated by the heterogeneous model including the blood vessel structure based upon the image acquired by two-photon microscopy. Light propagation in the exposed-cortex model is simulated to estimate the wavelength dependence of the partial optical path length in the blood vessels. The wavelength dependence of the partial optical path length for the heterogeneous model was different from that for the homogeneous model. In the wavelength range from 500 to 580 nm, the partial optical path length in the blood vessels was mainly affected by the structure of the blood vessels in the region shallower than 50 μm. © 2013 OSA-SPIE.
International conference proceedings, English - Image-based vessel-by-vessel analysis for red blood cell and plasma dynamics with automatic segmentation
Hiroshi Kawaguchi; Kazuto Masamoto; Hiroshi Ito; Iwao Kanno
Microvascular Research, Elsevier BV, 84, 2, 178-187, Sep. 2012, Peer-reviwed
Scientific journal, English - Long-term effects of hepatocyte growth factor gene therapy in rat myocardial infarct model
Y-N Jin; M. Inubushi; K. Masamoto; K. Odaka; I. Aoki; A. B. Tsuji; M. Sagara; M. Koizumi; T. Saga
GENE THERAPY, NATURE PUBLISHING GROUP, 19, 8, 836-843, Aug. 2012, Peer-reviwed, We investigated the long-term effects of human hepatocyte growth factor (HGF) gene therapy in a rat myocardial infarct model. Treatment adenovirus coexpressing the HGF therapeutic gene and the human sodium/iodide symporter (NIS) reporter gene or control adenovirus expressing the NIS gene alone were injected directly into the infarct border zone immediately after permanent coronary ligation in rats (n = 6 each). A uniform disease state was confirmed in the acute phase in terms of impaired left ventricular (LV) function by cine magnetic resonance imaging (MRI), large infarct extent by Tc-99m-tetrofosmin single-photon emission computed tomography (SPECT) and successful gene transfer and expression by (TcO4-)-Tc-99m SPECT. After a 10-week follow-up, repeated cine MRI demonstrated no significant difference in the LV ejection fraction between the time points or groups, but a significantly increased end-diastolic volume from the acute to the chronic phase without a significant difference between the groups. Capillary density was significantly higher in the treatment group, whereas arteriole density remained unchanged. Two-photon excitation fluorescence microscopy revealed extremely thin capillaries (2-5 mu m), and their irregular networks increased in the infarct border zone of the treated myocardium. Our results indicated that single HGF gene therapy alone induced an immature and irregular microvasculature.
Scientific journal, English - Dynamic Two-Photon Imaging of Cerebral Microcirculation Using Fluorescently Labeled Red Blood Cells and Plasma
Kazuto Masamoto; Hiroshi Kawaguchi; Hiroshi Ito; Iwao Kanno
Lead, Advances in Experimental Medicine and Biology, Springer New York, 163-168, 21 Jul. 2012, Peer-reviwed
In book, English - 3D Analysis of Intracortical Microvasculature During Chronic Hypoxia in Mouse Brains
Kouichi Yoshihara; Hiroyuki Takuwa; Iwao Kanno; Shinpei Okawa; Yukio Yamada; Kazuto Masamoto
Last, Advances in Experimental Medicine and Biology, Springer New York, 357-363, 21 Jul. 2012, Peer-reviwed
In book, English - Anesthesia and the quantitative evaluation of neurovascular coupling
Kazuto Masamoto; Iwao Kanno
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM, NATURE PUBLISHING GROUP, 32, 7, 1233-1247, Jul. 2012, Peer-reviwed, Anesthesia has broad actions that include changing neuronal excitability, vascular reactivity, and other baseline physiologies and eventually modifies the neurovascular coupling relationship. Here, we review the effects of anesthesia on the spatial propagation, temporal dynamics, and quantitative relationship between the neural and vascular responses to cortical stimulation. Previous studies have shown that the onset latency of evoked cerebral blood flow (CBF) changes is relatively consistent across anesthesia conditions compared with variations in the time-to-peak. This finding indicates that the mechanism of vasodilation onset is less dependent on anesthesia interference, while vasodilation dynamics are subject to this interference. The quantitative coupling relationship is largely influenced by the type and dosage of anesthesia, including the actions on neural processing, vasoactive signal transmission, and vascular reactivity. The effects of anesthesia on the spatial gap between the neural and vascular response regions are not fully understood and require further attention to elucidate the mechanism of vascular control of CBF supply to the underlying focal and surrounding neural activity. The in-depth understanding of the anesthesia actions on neurovascular elements allows for better decision-making regarding the anesthetics used in specific models for neurovascular experiments and may also help elucidate the signal source issues in hemodynamic-based neuroimaging techniques. Journal of Cerebral Blood Flow & Metabolism (2012) 32, 1233-1247; doi: 10.1038/jcbfm.2012.50; published online 18 April 2012
English - Repeated Longitudinal in Vivo Imaging of Neuro-glio-vascular Unit at the Peripheral Boundary of Ischemia in Mouse Cerebral Cortex
K. Masamoto; Y. Tomita; H. Toriumi; I. Aoki; M. Unekawa; H. Takuwa; Y. Itoh; N. Suzuki; I. Kanno
Neuroscience, 212, 190-200, 14 Jun. 2012, Understanding the cellular events evoked at the peripheral boundary of cerebral ischemia is critical for therapeutic outcome against the insult of cerebral ischemia. The present study reports a repeated longitudinal imaging for cellular-scale changes of neuro-glia-vascular unit at the boundary of cerebral ischemia in mouse cerebral cortex in vivo. Two-photon microscopy was used to trace the longitudinal changes of cortical microvasculature and astroglia following permanent middle cerebral artery occlusion (MCAO). We found that sulforhodamine 101 (SR101), a previously-known marker of astroglia, provide a bright signal in the vessels soon after the intraperitoneal injection, and that intensity was sufficient to detect the microvasculature up to a depth of 0.8. mm. After 5-8. h from the injection of SR101, cortical astroglia was also imaged up to a depth of 0.4. mm. After 1. day from MCAO, some microvessels showed a closure of the lumen space in the occluded MCA territory, leading to a restructuring of microvascular networks up to 7. days after MCAO. At the regions of the distorted microvasculature, an increase in the number of cells labeled with SR101 was detected, which was found as due to labeled neurons. Immunohistochemical results further showed that ischemia provokes neuronal uptake of SR101, which delineate a boundary between dying and surviving cells at the peripheral zone of ischemia in vivo. Finally, reproducibility of the MCAO model was evaluated with magnetic resonance imaging (MRI) in a different animal group, which showed the consistent infarct volume at the MCA territory over the subjects. © 2012 IBRO.
Scientific journal, English - Early and progressive impairment of spinal blood flow-glucose metabolism coupling in motor neuron degeneration of ALS model mice
Kazunori Miyazaki; Kazuto Masamoto; Nobutoshi Morimoto; Tomoko Kurata; Takahumi Mimoto; Takayuki Obata; Iwao Kanno; Koji Abe
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM, NATURE PUBLISHING GROUP, 32, 3, 456-467, Mar. 2012, Peer-reviwed, The exact mechanism of selective motor neuron death in amyotrophic lateral sclerosis (ALS) remains still unclear. In the present study, we performed in vivo capillary imaging, directly measured spinal blood flow (SBF) and glucose metabolism, and analyzed whether if a possible flow-metabolism coupling is disturbed in motor neuron degeneration of ALS model mice. In vivo capillary imaging showed progressive decrease of capillary diameter, capillary density, and red blood cell speed during the disease course. Spinal blood flow was progressively decreased in the anterior gray matter (GM) from presymptomatic stage to 0.80-fold of wild-type (WT) mice, 0.61 at early-symptomatic, and 0.49 at end stage of the disease. Local spinal glucose utilization (LSGU) was transiently increased to 1.19-fold in anterior GM at presymptomatic stage, which in turn progressively decreased to 0.84 and 0.60 at early-symptomatic and end stage of the disease. The LSGU/SBF ratio representing flow-metabolism uncoupling (FMU) preceded the sequential pathological changes in the spinal cord of ALS mice and was preferentially found in the affected region of ALS. The present study suggests that this early and progressive FMU could profoundly involve in the whole disease process as a vascular factor of ALS pathology, and could also be a potential target for therapeutic intervention of ALS. Journal of Cerebral Blood Flow & Metabolism (2012) 32, 456-467; doi: 10.1038/jcbfm.2011.155; published online 9 November 2011
Scientific journal, English - Spatial Frequency-Based Analysis of Mean Red Blood Cell Speed in Single Microvessels: Investigation of Microvascular Perfusion in Rat Cerebral Cortex
Joonas Autio; Hiroshi Kawaguchi; Shigeyoshi Saito; Ichio Aoki; Takayuki Obata; Kazuto Masamoto; Iwao Kanno
PLOS ONE, PUBLIC LIBRARY SCIENCE, 6, 8, e24056, Aug. 2011, Peer-reviwed, Background: Our previous study has shown that prenatal exposure to X-ray irradiation causes cerebral hypo-perfusion during the postnatal development of central nervous system (CNS). However, the source of the hypo-perfusion and its impact on the CNS development remains unclear. The present study developed an automatic analysis method to determine the mean red blood cell (RBC) speed through single microvessels imaged with two-photon microscopy in the cerebral cortex of rats prenatally exposed to X-ray irradiation (1.5 Gy).
Methodology/Principal Findings: We obtained a mean RBC speed (0.9 +/- 0.6 mm/sec) that ranged from 0.2 to 4.4 mm/sec from 121 vessels in the radiation-exposed rats, which was about 40% lower than that of normal rats that were not exposed. These results were then compared with the conventional method for monitoring microvascular perfusion using the arteriovenous transit time (AVTT) determined by tracking fluorescent markers. A significant increase in the AVTT was observed in the exposed rats (1.9 +/- 0.6 sec) as compared to the age-matched non-exposed rats (1.2 +/- 0.3 sec). The results indicate that parenchyma capillary blood velocity in the exposed rats was approximately 37% lower than in non-exposed rats.
Conclusions/Significance: The algorithm presented is simple and robust relative to monitoring individual RBC speeds, which is superior in terms of noise tolerance and computation time. The demonstrative results show that the method developed in this study for determining the mean RBC speed in the spatial frequency domain was consistent with the conventional transit time method.
Scientific journal, English - Comparison of Temporal Response to Cerebral Blood Flow Measured by Laser Speckle Flowgraphy and Laser Doppler Flowmetry
Masashi Kusano; Haruka Nakayama; Hiroyuki Takuwa; Kazuto Masamoto; Iwao Kanno; Eiji Okada
Optics InfoBase Conference Papers, Optical Society of America (OSA), 2011, Cerebral blood flow (CBF) change of mice during whisker stimulation is measured by laser speckle flowgraphy (LSFG) and laser Doppler flowmetry (LDF). Laser speckle flowgraphy (LSFG) has been used to obtain the two-dimensional distribution of the blood flow in tissue as well as scanning laser Doppler flowmetry (LDF). There are several parameters of LSFG to obtain the blood flow maps and the distribution change of blood flow. In this study, we calculate four parameters from the speckle pattern to measure CBF in awake mice. The temporal resolution of LSFG is likely to be less than that of LDF. The temporal changes in CBF obtained from the four parameters calculated from the speckle pattern detected by a common CCD camera are compared with those measured by LDF. The time courses of CBF change measured by LSFG highly correlate with those by LDF. The results indicate that the temporal response of LSFG is sufficient to measure CBF change evoked by brain activations. © 2011 SPIE-OSA.
International conference proceedings, English - Reproducibility and variance of a stimulation-induced hemodynamic response in barrel cortex of awake behaving mice
Hiroyuki Takuwa; Joonas Autio; Haruka Nakayama; Tetsuya Matsuura; Takayuki Obata; Eiji Okada; Kazuto Masamoto; Iwao Kanno
Corresponding, BRAIN RESEARCH, ELSEVIER SCIENCE BV, 1369, 103-111, Jan. 2011, Peer-reviwed, The present work evaluated the reproducibility and variance of the cerebral blood flow (CBF) response to natural whisker stimulation in the barrel cortex of awake behaving mice. The animal was placed on an air float ball that allowed the animal to walk, while the head of the animal was fixed in a custom-made stereotactic apparatus. Dynamic CBF changes in the barrel cortex and animal locomotion were simultaneously monitored with laser Doppler flowmetry (LDF) and an optical motion sensor that detected the rotation distance of the ball, respectively. Whisker stimulation-induced CBF measured under daytime and nighttime conditions showed consistent responses (24% and 23% of the pre-stimulus baseline, respectively), whereas the amount of locomotion was 1.4 times higher during nighttime relative to daytime. Repeated longitudinal experiments over 7 days showed a reproducible, evoked CBF (13-26% relative to the baseline among 7 animals). The mean of the variance coefficient (i.e., standard deviation divided by mean) across multiple days was 0.11 and 0.75 for evoked CBF and locomotion, respectively. These results showed reproducible and reliable measurements of longitudinal CBF response in behaving mice regardless of day-to-day variations in locomotion. Furthermore, we confirmed that the CBF response to whisker stimulation was well localized and reproducible, measured with laser speckle imaging under awake condition. The results further show the capability of long-term hemodynamic imaging in normal and disease-model mice, which is of particular importance for understanding the longitudinal changes and plasticity of neurovascular coupling and behavioral performances such as during growth, development and aging. (C) 2010 Elsevier B.V. All rights reserved.
Scientific journal, English - Frequency-dependent neural activity, CBF, and BOLD fMRI to somatosensory stimuli in isoflurane-anesthetized rats
Tae Kim; Kazuto Masamoto; Mitsuhiro Fukuda; Alberto Vazquez; Seong-Gi Kim
NEUROIMAGE, ACADEMIC PRESS INC ELSEVIER SCIENCE, 52, 1, 224-233, Aug. 2010, Peer-reviwed, Inhalation anesthetics (e g isoflurane) are preferable for longitudinal fMRI experiments in the same animals. We previously implemented isoflurane anesthesia for rodent forepaw stimulation studies, and optimized the stimulus parameters with short stimuli (1-3-s long stimulation with ten electric pulses). These parameters, however, may not be applicable for long periods of stimulation because repetitive stimuli induce neural adaptation. Here we evaluated frequency-dependent responses (pulse width of 1 0 ms and current of 1.5 mA) for 30-s long stimulation under 1.3-1.5% isoflurane anesthesia. The cerebral blood flow (CBF) response (using laser Doppler flowmetry CBF(LDF)) and field potential (FP) changes were simultaneously measured for nine stimulus frequencies (1-24 Hz). CBF (using arterial spin labeling CBF(ASL)) and blood oxygenation level dependent (BOLD) fMRI responses were measured at 9.4 T for four stimulus frequencies (1 5-12 Hz) Higher stimulus frequencies (12-24 Hz) produced a larger FP per unit time initially, but decreased more rapidly later due to neural adaptation effects On the other hand, lower stimulus frequencies (1-3 Hz) induced smaller, but sustained FP activities over the entire stimulus period Similar frequency-dependencies were observed in CBF(LDF). CBF(ASL) and BOLD responses. A linear relationship between FP and CBF(LDF) was observed for all stimulus frequencies Stimulation frequency for the maximal cumulative neural and hemodynamic changes is dependent on stimulus duration, 8-12 Hz for short stimulus durations (<10 s) and 6-8 Hz for 30-s stimulation Our findings suggest that neural adaptation should be considered in determining the somatosensory stimulation frequency and duration under isoflurane anesthesia (C) 2010 Elsevier Inc All rights reserved
Scientific journal, English - Cerebrovascular dynamics in response to neural stimulation
Kazuto Masamoto; Takayuki Obata; Iwao Kanno
Hirosaki Medical Journal, 61, SUPPL., S181-S186, 08 Jul. 2010, Peer-reviwed, Cerebral blood flow is tightly regulated, and local metabolic demands are met by adjustments to the regional density of microvascular networks and by temporal and spatial changes in microvascular blood flow. Cerebral blood flow regulation may involve communication between and across the vascular cells and neural or glial cells in either rapid or slow conduits. In the present study, we report distinct differences between the dynamic reactions of cerebral arterial networks in cortical surface and in intracortical tissue regions in response to sensory stimulation. Using confocal and multi-photon excitation laser scanning fluorescence microscopy, we imaged the cortical surface and subsurface vascular networks in the somatosensory cortex of isoflurane-anesthetized rats. Changes in lumen diameter were imaged at a rate of 13 frames per second with a field of view of 512 by 512 pixels. We consistently observed a stimulus-dependent increase in the lumen diameter of arterial networks in both cortical surface and subsurface regions. The onset time of vasodilation was observed to be-0.8 sec for the subsurface arterioles (<40 nm), which was significantly shorter than the-1.1 sec vasodilation onset time of the surface arteries (20-120 urn). The peak dilation accounted for 10% of the pre-stimulus baseline diameter. Further, the propagation of surface arterial vasodilation increased in a stimulus-dependent manner. The results indicate that global vasodilation of upstream parent arteries may be necessary to prevent "blood steal" by inactive regions nearby. Further studies are needed to elucidate the physiological mechanisms underlying the propagation of vasodilation induced by neural stimulation.
International conference proceedings, English - Changes in cerebral arterial, tissue and venous oxygenation with evoked neural stimulation: implications for hemoglobin-based functional neuroimaging
Alberto L. Vazquez; Mitsuhiro Fukuda; Michelle L. Tasker; Kazuto Masamoto; Seong-Gi Kim
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM, NATURE PUBLISHING GROUP, 30, 2, 428-439, Feb. 2010, Peer-reviwed, Little is known regarding the changes in blood oxygen tension (P(O2)) with changes in brain function. This work aimed to measure the blood P(O2) in surface arteries and veins as well as tissue with evoked somato-sensory stimulation in the anesthetized rat. Electrical stimulation of the forepaw induced average increases in blood flow of 44% as well as increases in the tissue P(O2) of 28%. More importantly, increases in P(O2) throughout pial arteries (resting diameters = 59 to 129 mu m) and pial veins (resting diameters = 62 to 361 lm) were observed. The largest increases in vascular P(O2) were observed in the small veins (from 33 to 40mmHg) and small arteries (from 78 to 88mmHg). The changes in oxygen saturation (S(O2)) were calculated and the largest increases were observed in small veins (Delta = + 11%) while its increase in small arteries was small (Delta = + 4%). The average diameter of arterial vessels was observed to increase by 4 to 6% while that of veins was not observed to change with evoked stimulation. These findings show that the increases in arterial P(O2) contribute to the hyper-oxygenation of tissue and, mostly likely, also to the signal changes in hemoglobin-based functional imaging methods (e.g. BOLD fMRI). Journal of Cerebral Blood Flow & Metabolism (2010) 30, 428-439; doi: 10.1038/jcbfm.2009.213; published online 21 October 2009
Scientific journal, English - Cerebral oxygen delivery and consumption during evoked neural activity
Vazquez AL; Masamoto K; Fukuda M; Kim SG
Frontiers in Neuroenergetics, Frontiers Media SA, 2, 11, 2010, Peer-reviwed
Scientific journal, English - Dose‐dependent effect of isoflurane on neurovascular coupling in rat cerebral cortex
Kazuto Masamoto; Mitsuhiro Fukuda; Alberto Vazquez; Seong‐Gi Kim
Lead, European Journal of Neuroscience, Wiley, 30, 2, 242-250, 20 Jul. 2009, Peer-reviwed, Abstract
Neurovascular coupling studies are widely conducted in anesthetized animals using functional magnetic resonance imaging (fMRI). In this study, the dose‐dependent effects of isoflurane on neurovascular coupling were examined with concurrent recordings of the local field potential (FP) and cerebral blood flow (CBF) in the rat somatosensory cortex. Electrical forepaw stimulation was used, and consisted of either a single pulse or 10 pulses at various frequencies. We observed that the FP response to single‐pulse stimulation remained unaffected across the different levels of isoflurane tested (1.1–2.1%), whereas the CBF response to single‐pulse stimulation increased dose‐dependently (7 ± 3% to 17 ± 4%). The isoflurane dose did not affect the vascular reactivity induced by a hypercapnic challenge. These findings suggest that the action of isoflurane affects the neurovascular mechanisms. For 10‐pulse stimulation, the summation of the evoked FP responses monotonically decreased with an increase in the isoflurane dose, possibly due to enhancement of the neural adaptation. In contrast, the dose‐dependent effect on the CBF response varied with the stimulus frequency; a dose‐dependent decrease in the CBF response was observed for high‐frequency stimulation, whereas a dose‐dependent increase was observed for low‐frequency stimulation. Furthermore, a linear time‐invariant model consisting of the single‐pulse hemodynamic impulse response convoluted with 10‐pulse FP recordings showed that the neurovascular transfer function was altered by the isoflurane dose for high‐frequency stimulation. These results indicate that careful and consistent maintenance of the depth of anesthesia is required when comparing fMRI data obtained from different animals or physiological and pharmacological manipulations.
Scientific journal, English - Neurovascular coupling in primary auditory cortex investigated with voltage-sensitive dye imaging and laser-Doppler flowmetry
Hiroshi Kameyama; Kazuto Masamoto; Yoichi Imaizumi; Tetsuro Omura; Takusige Katura; Atsushi Maki; Kazuo Tanishita
Corresponding, Brain Research, Elsevier BV, 1244, 82-88, Dec. 2008, Peer-reviwed
Scientific journal, English - Dynamics of oxygen delivery and consumption during stimulation using a compartment model and CBF and tissue P-O2 measurements
Alberto L. Vazquez; Kazuto Masamoto; Seong-Gi Kim
NEUROIMAGE, ACADEMIC PRESS INC ELSEVIER SCIENCE, 42, 1, 49-59, Aug. 2008, Peer-reviwed, The dynamics of blood oxygen delivery and tissue consumption produced by evoked stimulation of the rat somato-sensory cortex were investigated. Tissue oxygen tension (P-O2) and laser Doppler flowmetry (LDF) measurements were recorded under two experimental conditions: normal, which represented both oxygen delivery and consumption, and suppressed CBF (achieved using a vasodilator), which only represented tissue oxygen consumption. Forepaw stimulation for 10 s produced increases of 27.7% and 48.8% in tissue P-O2 and LDF signal under normal conditions, respectively. The tissue P-O2 response peaked 9.8 s after stimulation onset and did not show any early transient decreases indicating that measurable oxygen deficits are not required to increase the delivery of oxygen by blood flow. Under suppressed CBF conditions, the LDF signal was mostly suppressed while the tissue P-O2 decreased by 11.7% and reached a minimum 10.8 s after stimulation onset. These data were analyzed using a dynamic model that described the transport of oxygen from blood to tissue. In order to explain the differences between the model prediction of the tissue P-O2 changes and the experimental data, several hypothetical scenarios were considered, such as changes in the vascular volume, perineability-surface area or arterial oxygenation. The increase in tissue P-O2 was found to probably require the recruitment of upstream oxygen from larger arteries as well as increases in the vascular volume at the oxygen exchange sites. The amplitude of the estimated tissue tension of oxygen delivered was about 2.7x larger than the estimated consumption under normal conditions (45.7% vs. 17.1%, respectively). (C) 2008 Elsevier Inc. All rights reserved.
Scientific journal, English - Multimodal Silica-Shelled Quantum Dots: Direct Intracellular Delivery, Photosensitization, Toxic, and Microcirculation Effects
Rumiana Bakalova; Zhivko Zhelev; Ichio Aoki; Kazuto Masamoto; Milka Mileva; Takayuki Obata; Makoto Higuchi; Veselina Gadjeva; Iwao Kanno
Bioconjugate Chemistry, American Chemical Society (ACS), 19, 6, 1135-1142, 22 May 2008, Peer-reviwed
Scientific journal, English - Trial-by-trial relationship between neural activity, oxygen consumption, and blood flow responses
Kazuto Masamoto; Alberto Vazquez; Ping Wang; Seong-Gi Kim
Lead, NEUROIMAGE, ACADEMIC PRESS INC ELSEVIER SCIENCE, 40, 2, 442-450, Apr. 2008, Peer-reviwed, Trial-by-trial variability in local field potential (LFP), tissue partial pressure Of Oxygen (PO2), cerebral blood flow (CBF), and deoxyhemoglobin-weighted optical imaging of intrinsic signals (OIS) were tested in the rat somatosensory cortex while fixed electrical forepaw stimulation (1.0-ms pulses with amplitude of 1.2 mA at a frequency of 6 Hz) was repeatedly applied. The changes in the cerebral metabolic rate of oxygen (CMRO2) were also evaluated using a hypotension condition established by our group based on the administration of a vasodilator. Under normal conditions, CBF, PO2, and OIS showed positive signal changes (48%, 32%, and 0.42%, respectively) following stimulation. Over multiple trials, the CBF responses were well correlated with the integral of the LFP amplitudes (Sigma LFP) (R-mean=0.78), whereas a lower correlation was found between PO2 and Sigma LFP (R-mean=0.60) and between OIS and Sigma LFP (R-mean=0.54). Under the hypotension condition the LFP responses were preserved, but the CBF responses were suppressed and the PO2 and OIS changes were negative (-12% and -0.28%, respectively). In this condition, the trial-by-trial variations in PO2 and OIS were well correlated with the variability in Sigma LFPs (R-mean=-0.77 and -0.76, respectively), indicating a single trial coupling between CMRO2 changes and Sigma LFP. These findings show that CBF and CMRO2 signals are more directly correlated with neural activity compared to blood oxygen-sensitive methods such as OIS and BOLD fMRI. (C) 2007 Elsevier Inc. All rights reserved.
Scientific journal, English - Imaging brain vasculature with BOLD microscopy: MR detection limits determined by in vivo two-photon microscopy
Sung-Hong Park; Kazuto Masamoto; Kristy Hendrich; Twao Kanno; Seong-Gi Kim
MAGNETIC RESONANCE IN MEDICINE, JOHN WILEY & SONS INC, 59, 4, 855-865, Apr. 2008, Peer-reviwed, Rat brain vasculature was imaged at 9.4T with blood oxygenation level-dependent (BOLD) microscopy. Data were acquired without exogenous contrast agent in <35 min using 3D gradient-echo imaging with 78-mu m isotropic resolution. Detailed vascular patterns including intracortical veins and some branches were observed in simple magnitude-contrast data acquired at an experimentally optimized echo time. The venous origin of the dark patterns was confirmed by oxygenation-dependent studies, and when the systemic arterial oxygen saturation level was <80% BOLD microscopy revealed additional intracortical vessels presumed to be of arterial origin. Quantification shows a decrease of intracortical venous density with depth. The full width at half-minimum intensity was 90-190 mu m for most intracortical venous vessels identifiable by BOLD venography. Since actual diameters are not directly quantifiable by BOLD, we also measured diameter-dependent intracortical venous density in vivo by two-photon excitation fluorescent microscopy. Density comparisons between the two modalities, along with computer simulations, show that venous vessels as small as similar to 16-30 mu m diameter are detectable with 9.4T BOLD microscopy under our experimental conditions.
Scientific journal, English - Apparent diffusion time of oxygen from blood to tissue in rat cerebral cortex: implication for tissue oxygen dynamics during brain functions
Kazuto Masamoto; Jeff Kershaw; Masakatsu Ureshi; Naosada Takizawa; Hirosuke Kobayashi; Kazuo Tanishita; Iwao Kanno
Lead, Journal of Applied Physiology, American Physiological Society, 103, 4, 1352-1358, Oct. 2007, Peer-reviwed, To investigate the dynamics of tissue oxygen demand and supply during brain functions, we simultaneously recorded Po2 and local cerebral blood flow (LCBF) with an oxygen microelectrode and laser Doppler flowmetry, respectively, in rat somatosensory cortex. Electrical hindlimb stimuli were applied for 1, 2, and 5 s to vary the duration of evoked cerebral metabolic rate of oxygen (CMRO2). The electrical stimulation induced a robust increase in Po2 (4–9 Torr at peak) after an increase in LCBF (14–26% at peak). A consistent lag of ∼1.2 s (0.6–2.3 s for individual animals) in the Po2 relative to LCBF was found, irrespective of stimulus length. It is argued that the lag in Po2 was predominantly caused by the time required for oxygen to diffuse through tissue. During brain functions, the supply of fresh oxygen further lagged because of the latency of LCBF onset (∼0.4 s). The results indicate that the tissue oxygen supports excess demand until the arrival of fresh oxygen. However, a large drop in Po2 was not observed, indicating that the evoked neural activity demands little extra oxygen or that the time course of excess demand is as slow as the increase in supply. Thus the dynamics of Po2 during brain functions predominantly depend on the time course of LCBF. Possible factors influencing the lag between demand and supply are discussed, including vascular spacing, reactivity of the vessels, and diffusivity of oxygen.
Scientific journal, English - Arterial versus Total Blood Volume Changes during Neural Activity-Induced Cerebral Blood Flow Change: Implication for BOLD fMRI
Tae Kim; Kristy S Hendrich; Kazuto Masamoto; Seong-Gi Kim
Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, 27, 6, 1235-1247, 20 Dec. 2006, Peer-reviwed, Quantifying both arterial cerebral blood volume ( CBVa) changes and total cerebral blood volume ( CBVt) changes during neural activation can provide critical information about vascular control mechanisms, and help to identify the origins of neurovascular responses in conventional blood oxygenation level dependent (BOLD) magnetic resonance imaging (MRI). Cerebral blood flow ( CBF), CBVa, and CBVt were quantified by MRI at 9.4T in isoflurane-anesthetized rats during 15-s duration forepaw stimulation. Cerebral blood flow and CBVa were simultaneously determined by modulation of tissue and vessel signals using arterial spin labeling, while CBVt was measured with a susceptibility-based contrast agent. Baseline versus stimulation values in a region centered over the somatosensory cortex were: CBF = 150 ± 18 versus 182 ± 20 mL/100 g/min, CBVa = 0.83 ± 0.21 versus 1.17 ± 0.30 mL/100 g, CBVt = 3.10 ± 0.55 versus 3.41 ± 0.61 mL/100 g, and CBVa/ CBVt = 0.27 ± 0.05 versus 0.34 ± 0.06 ( n = 7, mean ± s.d.). Neural activity-induced absolute changes in CBVa and CBVt are statistically equivalent and independent of the spatial extent of regional analysis. Under our conditions, increased CBVt during neural activation originates mainly from arterial rather than venous blood volume changes, and therefore a critical implication is that venous blood volume changes may be negligible in BOLD fMRI.
Scientific journal, English - Successive depth variations in microvascular distribution of rat somatosensory cortex
K Masamoto; T Kurachi; N Takizawa; H Kobayashi; K Tanishita
Lead, BRAIN RESEARCH, ELSEVIER SCIENCE BV, 995, 1, 66-75, Jan. 2004, Peer-reviwed, Although hemodynamic-based functional brain imaging techniques are powerful tools to explore the brain functions noninvasively, hemodynamic-based signal is strongly affected by spatial configuration of microvessels. Understanding the quantitative relations between microvascular structure and functional activity is therefore significant to make a valid signal interpretation for the imaging techniques. In the present study, we evaluated depth profiles of microvascular distributions in rat somatosensory subfields (barrel field, forelimb region, trunk region and hindlimb region) and characterized depth variations in microvascular structures, such as locations, lengths and directions of microvessels, throughout the cortical layers (I-VI). To obtain the accurate microvascular structure, we made a customized casting method by using confocal laser scanning microscope. We observed that microvascular distribution successively varied throughout the cortical layers (I-VI) and that the maximum number density of microvessels was consistently found in middle layers (III-V). In addition, superficial layers had relatively long microvessels, almost perpendicular to the cortical surface, whereas middle layers had short microvessels propagating in all directions. These regional differences in microvascular structures were closely related to the somatosensory subfields, e.g., barrel field was the greatest number density of microvessels among the investigated subfields. Based on these observations, we compared microvascular profiles with previously reported distribution patterns of tissue partial pressure of oxygen (pO(2)). The results showed that tissue pO(2) was correlated with microvascular distribution in some but not all of the subfields. This finding shows that detailed microvascular profiles are helpful to investigate causal relationships between microvascular structure and functional activities in cerebral cortex. (C) 2003 Elsevier B.V. All rights reserved.
Scientific journal, English - Biphasic Changes in Tissue Partial Pressure of Oxygen Closely Related to Localized Neural Activity in Guinea Pig Auditory Cortex
Kazuto Masamoto; Tetsuro Omura; Naosada Takizawa; Hirosuke Kobayashi; Takusige Katura; Atsushi Maki; Hideo Kawaguchi; Kazuo Tanishita
Lead, Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, 23, 9, 1075-1084, Sep. 2003, Peer-reviwed, An understanding of the local changes in cerebral oxygen content accompanying functional brain activation is critical for making a valid signal interpretation of hemodynamic-based functional brain imaging. However, spatiotemporal relations between changes in tissue partial pressure of oxygen (Po2) and induced neural activity remain incompletely understood. To characterize the local Po2 response to the given neural activity, the authors simultaneously measured tissue Po2 and neural activity in the identical region of guinea pig auditory cortex with an oxygen microelectrode (tip < 10 μm) and optical recording with voltage-sensitive dye (RH 795). In addition, a laser displacement gauge and a laser-Doppler flowmeter were used to monitor the spatial displacement and regional cerebral blood flow, respectively, in the Po2 measurement region. In the activated region, tissue Po2 initially decreased during the ∼3seconds after the onset of acoustic stimuli, and then increased during the next ∼5 seconds. Such biphasic changes are consistently found in cortical layers I to IV. In addition, amplitude of the biphasic change was closely related to detected peak height of the optical signal changes. The results suggest that the initial decrease in tissue Po2 is coupled to the induced neural activity and depends on response time of local increase in cerebral blood flow.
Scientific journal, English - Dual responses of tissue partial pressure of oxygen after functional stimulation in rat somatosensory cortex
Kazuto Masamoto; Naosada Takizawa; Hirosuke Kobayashi; Kotaro Oka; Kazuo Tanishita
Lead, Brain Research, Elsevier BV, 979, 1-2, 104-113, Jul. 2003, Peer-reviwed
Scientific journal, English
MISC
- 脳微小循環ダイナミクスの可視化と制御に関する研究動向
正本和人
2021, 脳血管攣縮, 37, 6-11, Japanese, Invited, Introduction scientific journal - in vivoマウス大脳微小血管の４Dイメージング
正本和人; 須貸拓馬; 畝川美悠紀; 冨田裕; 菅野巖
メディカ出版, 10 Jun. 2019, 脳神経外科速報, 29, 6, 622-628, Japanese, Introduction commerce magazine - 光イメージングによる脳卒中の研究
正本和人
(株)中外医学社, 01 Aug. 2018, Clinical Neuroscience, 36, 8, 963-966, Japanese, Introduction commerce magazine - アストロサイトによる脳血流調節
正本和人; 畝川美悠紀; 冨田裕; 菅野巖; 鈴木則宏
先端医学社, Jan. 2016, 分子精神医学, 16, 1, 17-24, Japanese, Introduction commerce magazine, 1345-9082, 40020718101, AA11500190 - In vivo optical imaging of structural and functional plasticity of neurovascular unit
Kazuto Masamoto; Iwao Kanno
Lead, The Japanese Society of Cerebral Blood Flow and Metabolism, 2015, Cerebral Blood Flow and Metabolism (Japanese journal of cerebral blood flow and metabolism), 26, 2, 99-105, Invited, 0915-9401, 2188-7519 - 光遺伝学による脳血流の操作
正本和人; 畝川美悠紀; 渡辺竜志; 結城浩弥; 田桑弘之; 川口拓之; 菅野巖; 松井広; 田中謙二; 冨田裕; 鈴木則宏
Lead, 07 Nov. 2014, レーザー学会研究会報告, 467th, 43-47, Japanese, 201402287202175286 - 脳表血管・細胞光イメージング
正本和人; 菅野巖
先端医学社, Jul. 2014, 分子脳血管病, 13, 2, 18-23, Japanese, Introduction commerce magazine - Hypoxia-induced adaptation of cerebral microvasculature.
Kazuto Masamoto; Hiroyuki Takuwa; Hiroshi Ito; Iwao Kanno
Feb. 2014, Microvascular Reviews and Communications, 6, 1, 13-18, English - ニューロサイエンスの最新情報 二光子顕微鏡法による脳の微小循環の測定・観察
正本和人; 菅野巖
(株)中外医学社, Nov. 2013, Clinical Neuroscience, 13, 11, 1340-1341, Japanese, Introduction commerce magazine, 0289-0585 - 前脳基底部の刺激で誘発される大脳皮質の層特異的な血管拡張反応
堀田晴美; 内田さえ; 正本和人; 菅野巖
31 Aug. 2013, 日本脳循環代謝学会機関誌, 24, supplement, 95-101, Japanese, Peer-reviwed, Invited, Introduction other - 脳賦活および脳機能抑制による局所脳有効酸素拡散能の変化ー毛細血管径の変化からの推定ー
伊藤浩; 田桑弘之; 川口拓之; 正本和人; 田島洋佑; 茨木正信; 菅野巖
31 Jul. 2013, 日本脳循環代謝学会機関誌, 24, 2, 25-28, Japanese, Peer-reviwed - マイネルト核刺激による大脳皮質層特異的な動脈拡張反応
堀田晴美; 正本和人; 内田さえ; 関口優太; 田桑弘之; 川口拓之; 重本和宏; 須藤亮; 谷下一夫; 伊藤浩; 菅野巌
12 May 2013, 基礎老化研究, 37, 2, 39, Japanese, 0912-8921, 201302201156077119 - Microscopic Optical Imaging of Neurovascular Coupling
MASAMOTO K.; KANNO I.
07 Dec. 2012, レーザー学会研究会報告 = Reports on the Topical meeting of the Laser Society of Japan, 437, (1)-(5), Japanese, 10031140326, AA11604414 - 脳虚血・低酸素モデルマウスにおける血管新生ライブイメージング
正本和人; 冨田裕; 鳥海春樹; 畝川美悠紀; 田桑弘之; 谷口順子; 川口拓之; 伊藤義彰; 鈴木則宏; 伊藤浩; 菅野巖
Sep. 2012, 日本脳循環代謝学会機関誌, 23, 2, 84-89, Japanese, Peer-reviwed, Invited - In Vivo imaging of neurovascular coupling with two-photon excitation laser scanning microscopy
Kazuto Masamoto; Iwao Kanno
社団法人 レーザー学会, Apr. 2012, The Review of Laser Engineering, 40, 4, 230-235, Japanese, Peer-reviwed, Invited, 0387-0200 - 脳機能賦活に起因するマウス皮質組織血流のレーザー計測
草野将史; 中山遙; 正本和人; 菅野巖; 岡田英史
一般社団法人 レーザー学会, Apr. 2012, The Review of Laser Engineering, 40, 4, 274-279, Japanese, Peer-reviwed, 0387-0200 - 脳微小血管と４Ｄイメージング
正本和人; 冨田裕; 菅野巖
メディカルレビュー社, 2012, Vascular Biology and Medicine, 13, 2, 53-60, Japanese, Introduction commerce magazine - 生物発光・蛍光と生体イメージング
山田幸生; 大川晋平; 正本和人
日本伝熱学会, 2011, 伝熱, 50, 210, 25-30, Japanese, Introduction other, 1344-8692, 10027724559, AA11315621 - 生体二光子顕微鏡による脳内微小循環径路の三次元追跡
正本和人; 川口拓之; 菅野巖
2011, 基礎老化研究, 35, 1, 25-28, Japanese, Introduction scientific journal - 光で探る神経血管カップリング
正本和人; 川口拓之; 田桑弘之; 山崎享子; 小畠隆行; 菅野巖
2010, 生体イメージングの未来, 230, 10-13, Japanese, Introduction other - Neurovascular coupling and its molecular mechanism
正本和人; 小畠隆行; 菅野巖
電気学会, 08 Feb. 2008, 光・量子デバイス研究会資料, OQD08, 1, 33-38, Japanese, 10025660720, AN00140211 - Oxygen transport in the microvessel network
K Tanishita; K Masamoto; T Negishi; N Takizawa; H Kobayashi
Oxygen delivery in the brain tissue is carried out by a diffusion process principally determined by spatial differences of partial pressure of oxygen (pO(2)). Previous studies identified inhomogeneous distribution of cerebral tissue pO(2). This inhomogeneous pO(2) distribution might be related to spatial variations in microvascular structure, because a large amount of oxygen is supplied from microvascular network. In this study, to evaluate the oxygen transport in the cerebral cortex, we focused on regional structure of microvascular network and pO(2) distribution in the rat somatosensory cortex. To this end, firstly, we characterized local tissue pO(2) distribution by using an oxygen microelectrode. Secondly, we quantified three-dimensional microvascular structure by combining a traditional method for casting blood capillaries with quantitative analysis by using confocal laser-scanning microscope. Finally, the regional variations in oxygen transport were estimated by using numerical simulation of oxygen transport based on these experimental data (i.e., pO(2) distribution and microvascular structure)., SPRINGER-VERLAG TOKYO, 2005, ORGAN MICROCIRCULATION: A GATEWAY TO DIAGNOSITC AND THERAPEUTIC INTERVENTIONS, 13, 13-20, English, Peer-reviwed, WOS:000226302200002
Books and other publications
- 最新臨床脳卒中学（第２版）下ー最新の診断と治療ー
正本和人; 菅野
Textbook, Japanese, Contributor, XXVI.基礎研究の動向 脳微小循環制御, 日本臨牀社, 28 Feb. 2022 - 実験医学増刊 脳の半分を占めるグリア細胞 脳と心と体をつなぐ”膠”
正本和人
Scholarly book, Japanese, Contributor, 第２章 グリア細胞と神経免疫・臓器連関 グリアの光刺激による脳血流の操作, 羊土社, 01 Nov. 2019, 9784758103824 - 血流改善成分の開発と応用
Scholarly book, Japanese, Contributor, 第３章 血流障害と脳機能, シーエムシー出版, 30 Jul. 2018, 9784781313412 - 脳卒中病態学のススメ
Textbook, Japanese, Contributor, 9章 急性期脳梗塞モデル 4. 評価の方法（顕微鏡画像）, 南山堂, Feb. 2018 - Vascular remodeling after cerebral ischemia. (In: Primer on Cerebrovascular Diseases, Second Edition)
Nishijima Y; Akamatsu Y; Masamoto K; Liu J
Scholarly book, English, Joint work, Chapter 19, San Diego: Academic Press, 18 Mar. 2017 - New Horizons in Neurovascular Coupling : A Bridge between Brain Circulation and Neural Plasticity
Masamoto, Kazuto; Hirase, Hajime; Yamada, Katsuya
Scholarly book, English, Joint editor, Elsevier Science Serials, Apr. 2016 - Bridging macroscopic and microscopic methods for the measurements of cerebral blood flow: Toward finding the determinants in maintaining the CBF homeostasis
I. Kanno; K. Masamoto
English, ELSEVIER SCIENCE BV, 2016, Methods exist to evaluate the cerebral blood flow(CBF) at both the macroscopic and microscopic spatial scales. These methods provide complementary information for understanding the mechanism in maintaining an adequate blood supply in response to neural demand. The macroscopic CBF assesses perfusion flow, which is usually measured using radioactive tracers, such as diffusible, nondiffusible, or microsphere. Each of them determines CBF based on indicator dilution principle or particle fraction principle under the assumption that CBF is steady state during the measurement. Macroscopic CBF therefore represents averaged CBF over a certain space and time domains. On the other hand, the microscopic CBF assesses bulk flow, usually measures using real-time microscopy. The method assesses hemodynamics of microvessels, ie, vascular dimensions and flow velocities of fluorescently labeled or nonlabeled RBC and plasma markers. The microscopic CBF continuously fluctuates in time and space. Smoothing out this heterogeneity may lead to underestimation in the macroscopic CBF. To link the two measurements, it is needed to introduce a common parameter which is measurable for the both methods, such as mean transit time. Additionally, applying the defined physiological and/or pharmacological perturbation may provide a good exercise to determine how the specific perturbations interfere the quantitative relationships between the macroscopic and microscopic CBF. Finally, bridging these two-scale methods potentially gives a further indication how the absolute CBF is regulated with respect to a specific type of the cerebrovascular tones or capillary flow velocities in the brain. - ユニーク&エキサイティングサイエンスIII (総合コミュニケーション科学シリーズ)
正本和人
Scholarly book, Japanese, Contributor, 「呼吸する脳」への招待ー脳の機能を支える血液の流れと物質交換, 近代科学社, 26 Nov. 2014, 9784764904729 - シミュレーション辞典
日本シミュレーション学会
Dictionary or encycropedia, Japanese, Contributor, 分野：生命・医療・福祉 部門：医療「V-4］神経-血管相互作用, コロナ社, 27 Feb. 2012, 9784339024586 - からだと酸素の事典
酸素ダイナミクス研究会
Dictionary or encycropedia, Japanese, Contributor, 微小酸素電極の作製と測定の実際, 朝倉書店, 05 Sep. 2009, 9784254300987 - CBF and pO2 dynamics in rat cortex during neuronal activation by hind paw stimulation
K. Masamoto; J. Kershaw; M. Ureshi; N. Takizawa; H. Kobayashi; K. Tanishita; I. Kanno
English, Medpharm Scientific Publishers, 2004
Lectures, oral presentations, etc.
- 微小循環: 最も細い血管を見て知る体の健康
正本和人
Public discourse, Japanese, 2024年度矢上賞受賞記念講演, Invited
26 Oct. 2024 - Capillary flow imbalances under dehydration in the brain.
Kazuto Masamoto
Invited oral presentation, English, Joint Congress for the 3rd International Qi-Blood Conference and The 8th Chinese Microcirculation Week, Invited
07 Sep. 2024 - 脳における赤血球動態の解析
正本和人
Nominated symposium, Japanese, 日本機械学会 第 36回バイオエンジニアリング講演会 脳の循環と機能のバイオメカニクス（OS4-2）, Invited
11 May 2024 - 認知学習実験における温度環境の影響
井上幹太; 矢野祐希; 和田悠佑; 吉田智毅; 大下雅昭; 正本和人
Oral presentation, 第28回医用近赤外線分光法研究会・第26回酸素ダイナミクス研究会 合同研究会, 酸素ダイナミクス研究会, 鹿児島大学医学部 鶴陵会館（鹿児島）, https://kadaiqqicuhp.org/, Domestic conference
2022
01 Oct. 2022- 02 Oct. 2022
Research Themes
Media Coverage
- 脳の血流増加メカニズムの分離に成功
ニュースリリース 電気通信大学, 脳が活動すると活動部位の血液の流れが増えます。血液の流れを可視化することにより、脳のどこが活動したのかを計測することができます。従来、脳の活動によって生じる脳血管の反応については、ニューロンによる"直接の作用"と神経活動に付随して生じるグリア細胞の活動による"間接の作用"という、二つの経路によって脳の血流が増加することが分かっていました。しかし、二つの作用が独立に生じるのか、あるいは連結して生じるのかは不明でした。
脳血管の拡張機能が衰えると、認知症をはじめとした様々な脳の病気の発症につながるリスクが高まります。本成果によって、脳血管の機能の低下がニューロンの活動に由来するのか、あるいはグリア細胞の活動に由来するのかを病態に応じて明らかにすることが可能になり、将来的には原因となる細胞に特化した脳血管機能の回復、治療、機能低下の予防を行うことができると期待されます。
本研究は、慶應義塾大学医学部、東北大学大学院生命科学研究科、ならびに放射線医学総合研究所（現・量子医科学研究所）と共同で行いました。
15 Jun. 2021
