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Hiroyuki Takuwa,
Kazuto Masamoto,
Kyoko Yamazaki,
Hiroshi Kawaguchi,
Yoko Ikoma,
Yousuke Tajima,
Takayuki Obata,
Yutaka Tomita,
Norihiro Suzuki, Iwao Kanno,
Hiroshi Ito
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ABSTRACT: 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.Journal of Cerebral Blood Flow & Metabolism advance online publication, 13 February 2013; doi:10.1038/jcbfm.2013.16.
Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism 02/2013; · 5.46 Impact Factor
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ABSTRACT: The purpose of this study is to determine when and where the brain microvasculature changes its network in response to chronic hypoxia. To identify the hypoxia-induced structural adaptation, we longitudinally imaged cortical microvasculature at the same location within a mouse somatosensory cortex with two-photon microscopy repeatedly for up to 1 month during continuous exposure to hypoxia (either 8 or 10% oxygen conditions). The two-photon microscopy approach made it possible to track a 3D pathway from a cortical surface arteriole to a venule up to a depth of 0.8 mm from the cortical surface. The network pathway was then divided into individual vessel segments at the branches, and their diameters and lengths were measured. We observed 3-11 vessel segments between the penetrating arteriole and the emerging vein over the depths of 20-460 μm within the 3D reconstructed image (0.46 × 0.46 × 0.80 mm(3)). The average length of the individual capillaries (<7 μm in diameter) was 67 ± 46 μm, which was not influenced by hypoxia. In contrast, 1.4 ± 0.3 and 1.2 ± 0.2 fold increases of the capillary diameter were observed 1 week after exposure to 8 % and 10% hypoxia, respectively. At 3 weeks from the exposure, the capillary diameter reached 8.5 ± 1.9 and 6.7 ± 1.8 μm in 8% and 10 % hypoxic conditions, respectively, which accounted for the 1.8 ± 0.5 and 1.4 ± 0.3 fold increases relative to those of the prehypoxic condition. The vasodilation of penetrating arterioles (1.4 ± 0.2 and 1.2 ± 0.2 fold increases) and emerging veins (1.3 ± 0.2 and 1.3 ± 0.2 fold increases) showed relatively small diameter changes compared with the parenchymal capillaries. These findings indicate that parenchymal capillaries are the major site responding to the oxygen environment during chronic hypoxia.
Advances in experimental medicine and biology 01/2013; 765:357-63. · 1.09 Impact Factor
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ABSTRACT: To explore the spatiotemporal dynamics of red blood cells (RBCs) and plasma flow in three-dimensional (3D) microvascular networks of the cerebral cortex, we performed two-photon microscopic imaging of the cortical microvasculature in genetically engineered rats in which the RBCs endogenously express green fluorescent protein (GFP). Water-soluble quantum dots (Qdots) were injected intravenously into the animals to label the plasma, and concurrent imaging was performed for GFP-RBCs and Qdot plasma. The RBC and plasma distributions were compared between resting state and forepaw stimulation-induced neural activation. The RBC and plasma images showed detectable signals up to a depth of 0.4 and 0.6 mm from the cortical surface, respectively. A thicker plasma layer (2-5 μm) was seen in venous vessels relative to the arterial vessels. In response to neural activation, the RBCs were redistributed among the parenchymal capillary networks. In addition, individual capillaries showed a variable ratio of RBC and plasma distributions before and after activation, indicative of dynamic changes of hematocrit in single capillaries. These results demonstrate that this transgenic animal model may be useful in further investigating the mechanism that controls dynamic RBC flow in single capillaries and among multiple capillary networks of the cerebral microcirculation.
Advances in experimental medicine and biology 01/2013; 765:163-8. · 1.09 Impact Factor
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ABSTRACT: As the oscillating gradient spin-echo sequence has shown promise as a means to probe tissue microstructure, it was applied here to diffusion-tensor imaging of in vivo rat brain. The apparent diffusion tensor (ADT) was estimated for motion-probing gradient (MPG) frequencies in the range 33.3-133.3 Hz, and regions-of-interest (ROIs) in the corpus callosum (CC), visual cortex (VC), cerebellar white matter (CBWM) and cerebellar grey matter (CBGM) were selected for detailed analysis. There were substantial, approximately linear changes to the ADT with increasing MPG frequency for all four ROIs. All ROIs showed clear increases in mean diffusivity. CBWM had a substantial decrease in fractional anisotropy, whereas the CC and VC had minor increases of the same parameter. All eigenvalues of the ADT tended to increase with frequency for the CBWM, CBGM and VC, but only the principal eigenvalue increased strongly for the CC. On the other hand, there was no evidence that the orientation of the principal eigenvector varied systematically with MPG frequency for any of the ROIs. The relationship between the behaviour of the eigenvalues and the behaviours of the mean diffusivity and fractional anisotropy is investigated in detail. Pixelwise linear fits to the MD from individual animals found elevated changes across the cerebellum. The data acquired for this work encompassed a range of effective diffusion-times from 7.5 ms down to 1.875 ms, and some ideas on how the results might be used to extract quantitative information about brain tissue microstructure are discussed.
NeuroImage 12/2012; · 5.89 Impact Factor
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ABSTRACT: Elucidating the mechanisms underlying the regulation of cerebral blood flow (CBF) is important to understanding the hemodynamic changes measured by positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) signals. The purpose of this study was to explore changes in hemodynamic characteristics during resting and sensory stimulation in awake animals as compared with those in anesthetized animals. Changes in CBF, red blood cell (RBC) velocity and concentration in the somatosensory cortex to whisker stimulation were measured using laser-Doppler flowmetry in awake and anesthetized mice. The increase in the rate of RBC velocity change observed during whisker stimulation was far greater than the increase in the rate of RBC concentration change under the awake condition. During the resting condition, significant differences in baseline CBF, RBC velocity and concentration between awake and anesthesia mice were not observed. Isoflurane-induced anesthesia attenuated the increase in RBC velocity and concentration during stimulation, with the attenuation of the RBC velocity increase being greater than that of RBC concentration. The RBC measurement techniques in awake animals should lead to much better understanding of the hemodynamic system evoked by neural activity.
Brain research 07/2012; 1472:107-12. · 2.46 Impact Factor
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ABSTRACT: The aim of the present study was to test the hypothesis that vascular tones of cortical surface and parenchymal blood flow can be dissociated depending on the perturbation. To this end, a novel image-based analytical method for quantitatively measuring vessel diameters and flow dynamics was developed. The algorithm relies on the spatiotemporal coherence of the pixel intensity changes induced by the transit of the fluorescent signals measured using confocal laser scanning fluorescent microscopy in the rat cerebral cortex. A cocktail of fluorescently labeled red blood cell (RBC) and plasma agents was administered to simultaneously compare RBC and plasma dynamics in the same vascular networks. The time to fluorescent signal appearance and the width of the fluorescent signal were measured in each segment and compared between sodium nitroprusside-induced global and sensory stimulation-induced local perturbation conditions. We observed that infusion of sodium nitroprusside induced significant vasodilation in the surface artery, particularly in the small arteries (1.8-fold increase). Vasodilation induced by sensory stimulation was observed to depend on vessel size, but significant changes were only detected for the small arteries and veins. Measurements of the time to venous appearance revealed that appearance time was extended by sodium nitroprusside, but shortened during forepaw stimulation, relative to the control condition. Both perturbations provoked the largest changes between the small artery and vein segments, indicating that the changes in the appearance time originate from blood passage through parenchymal microcirculation. These findings support the hypothesis that cortical surface vascular tone and parenchymal blood flow are individually coordinated.
Microvascular Research 05/2012; 84(2):178-87. · 2.83 Impact Factor
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ABSTRACT: 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 and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism 04/2012; 32(7):1233-47. · 5.46 Impact Factor
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ABSTRACT: 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.
Neuroscience 04/2012; 212:190-200. · 3.38 Impact Factor
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ABSTRACT: PurposeWe evaluated the noise reduction capability of wavelet denoising for estimated binding potential (BP) images (k
3/k
4) of the peripheral benzodiazepine receptor using 18F-FEDAA1106 and nonlinear least-square fitting.
MethodsWavelet denoising within a three-dimensional discrete dual-tree complex wavelet transform was applied to simulate data and
clinical dynamic positron emission tomography images of 18F-FEDAA1106. To eliminate noise components in wavelet coefficients, real and imaginary coefficients for each subband were
thresholded individually using NormalShrink. A simulated dynamic brain image of 18F-FEDAA1106 was generated and Gaussian noise was added to mimic PET dynamic scan. The derived BP images were compared with
true images using 156 rectangular regions of interest. Wavelet denoising was also applied to data derived from seven young
normal volunteers.
ResultsIn the simulations, estimated BP by denoised image showed better correlation with the true BP values (Y = 0.83X + 0.94, r = 0.80), although no correlation was observed in the estimates between noise-added and true images (Y = 1.2X + 0.78, r = 0.49). For clinical data, there were visual improvements in the signal-to-noise ratio for estimated BP images.
ConclusionsWavelet denoising improved the bias and reduced the variation of pharmacokinetic parameters for BP.
European journal of nuclear medicine and molecular imaging 04/2012; 35(2):416-423. · 4.99 Impact Factor
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ABSTRACT: We reviewed the literature on human cerebral circulation and oxygen metabolism, as measured by positron emission tomography
(PET), with respect to normal values and of regulation of cerebral circulation. A multicenter study in Japan showed that between-center
variations in cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral oxygen extraction fraction (OEF) and cerebral
metabolic rate of oxygen (CMRO2) values were not considerably larger than the corresponding within-center variations. Overall
mean ± SD values in cerebral cortical regions of normal human subjects were as follows: CBF = 44.4 ± 6.5 m//100 m//min; CBV
= 3.8 ± 0.7 m//100ml; OEF = 0.44 ± 0.06; CMRO2 = 3.3 ± 0.5 m//100 m//min (11 PET centers, 70 subjects). Intrinsic regulation of cerebral circulation involves several factors.
Autoregulation maintains CBF in response to changes in cerebral perfusion pressure; chemical factors such as PaCO2 affect cerebral vascular tone and alter CBF; changes in neural activity cause changes in cerebral energy metabolism and CBF;
neurogenic control of CBF occurs by sympathetic innervation. Regional differences in vascular response to changes in PaCO2 have been reported, indicating regional differences in cerebral vascular tone. Relations between CBF and CBV during changes
in PaCO2 and during changes in neural activity were in good agreement with Poiseuille’s law. The mechanisms of vascular response to
neural activation and deactivation were independent on those of responses to PaCO2 changes. CBV in a brain region is the sum of three components: arterial, capillary and venous blood volumes. It has been
reported that the arterial blood volume fraction is approximately 30% in humans and that changes in human CBV during changes
in PaCO2 are caused by changes in arterial blood volume without changes in venous blood volume. These findings should be considered
in future studies of the pathophysiology of cerebrovascular diseases.
Annals of Nuclear Medicine 04/2012; 19(2):65-74. · 1.50 Impact Factor
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ABSTRACT: 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 and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism 11/2011; 32(3):456-67. · 5.46 Impact Factor
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ABSTRACT: Spin-echo diffusion-weighted functional MRI (DW-fMRI) was performed on a rat forepaw electrostimulation model at 7 T. This small animal model used electric (rather than visual) stimulation and allowed DW-fMRI experiments to be performed over a broader range of acquisition parameters than previous work on humans and cats. Resting state experiments with injections of ultra-small superparamagnetic iron oxide (USPIO) were also used to investigate the effects of gradient coupling on the signal change. The experiments were performed over five b-values (0, 200, 800, 1400 and 2000s/mm(2)) and three echo-times (30, 60 and 90 ms). Alterations to the stimulation-induced response with respect to TE and b-value were evaluated in two intervals: the positive stimulus-correlated response (5-20s after stimulus onset) and the post-stimulus undershoot (27-40s). There was no strong dependence of the signal change on b-value for any of the intervals or TEs. Similarly, changes to the apparent transverse relaxation rate showed no clear dependence on b-value. In contrast to previous DW-fMRI studies, the simplest explanation for the observed data is a single-compartment signal model with the functional signal changes probably corresponding to extravascular SE-BOLD. Experiments with USPIO suggested that at 7 T and within the range of parameters used, the influence of gradient coupling may be sufficient to explain minor DW-fMRI signal changes.
NeuroImage 07/2011; 57(1):140-8. · 5.89 Impact Factor
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ABSTRACT: 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).
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.
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.
PLoS ONE 01/2011; 6(8):e24056. · 4.09 Impact Factor
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ABSTRACT: Our purpose was to noninvasively assess formation of the microvasculature, blood-brain barrier (BBB) and blood-CSF barrier formation of prenatal X-ray-induced CNS abnormalities using quantitative MRI. Eight pregnant female Sprague-Dawley rats were divided into two groups consisting of control and X-irradiated animals. After birth, 20 neonatal male rats were divided into four groups of five rats. To evaluate the development of the BBB, changes in T(1) induced by Gd-DTPA were compared quantitatively in normal and prenatally irradiated animals in the formative period 1 to 2 weeks after birth. To assess the abnormalities of the microvasculature, quantitative perfusion MRI and MR angiography were also used. Histology was also performed to evaluate the BBB (albumin) and vascular endothelial cells (laminin). Decreased cerebral blood flow (CBF) and angioarchitectonic abnormalities were observed in the prenatally irradiated rats. However, abnormalities of the BBB and blood-CSF barrier were not observed using Gd-enhanced MRI and albumin staining. Quantitative perfusion MRI, MR angiography and Gd-enhanced T(1) mapping are useful for assessing CNS disturbance after prenatal exposure to radiation. These techniques provide important diagnostic information for assessing the condition of patients during the early stages of life after accidental or unavoidable prenatal exposure to radiation.
Radiation Research 01/2011; 175(1):1-9. · 2.68 Impact Factor
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ABSTRACT: 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.
Brain research 11/2010; 1369:103-11. · 2.46 Impact Factor
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ABSTRACT: The internal capsule (IC) includes various fiber tracts supporting sensory, motor and cognitive abilities. Diffusion tensor imaging (DTI) is useful for the diagnosis of brain diseases related to IC. However, there is some risk of misdiagnosis when measuring diffusion parameters throughout the whole IC without knowledge of age-related changes, as the thin structure and branching in multiple directions must be expected to produce sub-regional differences. In this study, regional heterogeneity and age-related changes in water diffusion parameters were evaluated in sub-regions of IC. The IC region-of-interest (ROI) was first thinned to reduce contamination from surrounding tissues and then morphologically divided into three regions: anterior limb (AL), genu and posterior limb (PL). To address the branching of PL, a procedure was applied to divide the thinned PL ROI into 10 equally-spaced positions. Estimates of fractional anisotropy (FA), mean diffusivity (MD), and longitudinal (lambda(L)) and transversal (lambda(T)) eigenvalues showed age-related and location-dependent variation in AL, genu and PL ROIs and at the 10 equally-spaced positions of PL. Simultaneous decrease of lambda(L) and increase of lambda(T) resulting in decrease of FA and steady MD with aging were observed. This might be caused by age-related atrophy of main fibers such as the pyramidal tract, possibly resulting in an increase in the relative signal contribution of some crossing fibers in each pixel. Evaluation using eigenvalues (lambda(L) and lambda(T)), as well as FA and MD, may provide important information towards understanding age-related changes and may also be useful for clinical diagnosis of diseased IC.
Brain research 10/2010; 1354:30-9. · 2.46 Impact Factor
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ABSTRACT: This study was designed to clarify whether nitric oxide (NO) participates in the regulation of local cerebral blood flow (CBF) during hypoxia (inhalation of 15% O(2) in N(2)). The CBF response to hind-paw stimulation (evoked CBF) of Sprague-Dawley (SD) rats was measured by laser-Doppler flowmetry. Physiological variables, such as heart rate, mean blood pressure, and PaCO(2) during hypoxia, were identical to those under normoxic conditions. Hypoxia increased the baseline CBF (17.5 ± 14.3%) and the normalized peak amplitude of evoked CBF (31.1 ± 18.5%) relative to those during normoxia. When an NOS inhibitor was infused intravenously, these differences were abolished in both the baseline CBF or evoked CBF between normoxic and hypoxic conditions, whereas the heart rate decreased and the mean blood pressure increased during hypoxia in comparison with these during normoxia. The field potential was constant under all experimental conditions. These results suggest that NO plays a major role in the regulation of baseline and evoked CBF during hypoxia.
The Journal of Physiological Sciences 10/2010; 60(6):399-406. · 1.61 Impact Factor
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ABSTRACT: The present study describes a new diagnostic approach for carcinogenesis based on the different tissue redox activity of normal and cancer-bearing mammalians and its visualization and estimation by cell permeable and DNA annealing probe (nitroxide-labeled nitrosourea) and magnetic resonance imaging.
Molecular BioSystems 10/2010; 6(12):2386-8. · 3.53 Impact Factor
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ABSTRACT: This study presents a combined small animal holding fixture system, termed a 'bridge capsule', which provides for small animal re-fixation with positional reproducibility. This system comprises separate holding fixtures for the head and lower body and a connecting part to a gas anesthesia system. A mouse is fixed in place by the combination of a head fixture with a movable part made from polyacetal resin, a lower body fixture made from vinyl-silicone and a holder for the legs and tail. For re-fixation, a similar posture could be maintained by the same holding fixtures and a constant distance between the head and lower body fixtures is maintained. Artifacts caused by the bridge capsule system were not observed on magnetic resonance (MRI) and positron emission tomography (PET) images. The average position differences of the spinal column and the iliac body before and after re-fixation for the same modality were approximately 1.1 mm. The difference between the MRI and PET images was approximately 1.8 mm for the lower body fixture after image registration using fiducial markers. This system would be useful for longitudinal, repeated and multimodal imaging experiments requiring similar animal postures.
Physics in Medicine and Biology 07/2010; 55(14):4119-30. · 2.83 Impact Factor
