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Tatsuo Togawa

Publications and source records attributed to Tatsuo Togawa.

6 recordsLinked to original sources
PubMed2006

Arterioles' contribution to oxygen supply to the skeletal muscles at rest.

We tested the hypothesis that oxygen is supplied to the resting skeletal muscle by arterioles rather than by capillaries. This hypothesis was evaluated in rats and rabbits by combining different approaches (1) determination of the intravascular oxygen tension (PO2) in arterioles of different diameters, (2) measurement of the perfused capillary number in response to changes in tissue PO2, and (3) estimation of the optimum capillary number to provide oxygen efficiently to the surrounding tissue. The intravascular PO2 values of arterioles along the vessels decreased downstream, suggesting that a significant amount of oxygen diffuses from the arterioles to the surrounding tissue. The perfused capillary number decreased as the tissue PO2 level was elevated, and this mutual relationship displayed a nonlinear correlation. The results suggest that a boundary PO2 level affecting the capillary recruitment exists for tissue PO2 of less than 40 mmHg with the capillary blood-flow stops above that PO2 level. At a high PO2 level, therefore, the oxygen is supplied from the arterioles. Furthermore, an estimation of optimum capillary number reveals that the capillary arrangement is constructed to achieve sufficient oxygen supply to the muscle during exercise, rather than at rest. These results suggest that oxygen is supplied from arterioles to the resting skeletal muscle, whereas the oxygen is supplied from the capillaries during exercise.

Animals↗
PubMed2005

Nonlinear regulation of capillary perfusion in relation to ambient pO(2) changes in skeletal muscle.

To study the process of O(2) transport to tissue, we investigated how capillary perfusion is controlled in response to changes in tissue O(2) levels in skeletal muscle. Capillary red blood cell (RBC) velocity and perfused capillary recruitment were measured in rabbit tenuissimus muscle at various ambient oxygen tensions (pO(2)) by intravital microscopy. Both RBC velocity and capillary recruitment significantly decreased as the pO(2) level of the suffusate was increased, and the relationship between capillary perfusion, calculated from the velocity and recruitment data, and the pO(2) level of the suffusate clearly yielded a nonlinear correlation that fitted a sigmoidal curve. Capillary perfusion dramatically decreases or increases above or below a suffusate pO(2) level of around 40 Torr, where the O(2) dissociation curve of hemoglobin changes slope. These findings support the hypothesis that microvasculature possesses an intrinsic, effective flow-control mechanism by sensing the metabolic demands of tissue, intimately related to the O(2) saturation of hemoglobin.

Animals↗
PubMed2002

Effect of mineralocorticoid deficiency on ion and urea transporters and aquaporin water channels in the rat.

Mineralocorticoid deficiency is associated with impaired urinary concentration and dilution. The present investigation was undertaken to determine the effects of selective mineralocorticoid deficiency on renal sodium and urea transporters and aquaporin water channels and whether these perturbations can be reversed by maintenance of extracellular fluid volume. Mineralocorticoid deficiency was induced by bilateral adrenalectomies with glucocorticoid replacement. Mineralocorticoid deficient rats receiving plain drinking water (MDW) were compared with mineralocorticoid deficient rats receiving saline-drinking water (MDS) in order to maintain extracellular fluid volume, and with controls (CTL). In MDW rats, there was a significant decrease in renal outer medulla Na-K-2Cl co-transporter and outer medulla Na-K-ATPase as well as an increase in inner medulla aquaporins 2 and 3. There were no significant changes in aquaporin-1, aquaporin-4, or urea transporters. These alterations were reversed with maintenance of extracellular fluid volume in MDS rats. Our findings indicate that mineralocorticoid deficiency in the rat is associated with alterations in factors involved in the countercurrent concentrating mechanism (Na-K-2Cl, Na-K-ATPase) and osmotic water equilibration in the collecting duct (AQP2, AQP3). Maintenance of sodium balance and extracellular fluid volume is associated with normalization of these perturbations.

Adrenalectomy↗
PubMed2002

Discrimination of walking patterns using wavelet-based fractal analysis.

In this paper, we attempted to classify the acceleration signals for walking along a corridor and on stairs by using the wavelet-based fractal analysis method. In addition, the wavelet-based fractal analysis method was used to evaluate the gait of elderly subjects and patients with Parkinson's disease. The triaxial acceleration signals were measured close to the center of gravity of the body while the subject walked along a corridor and up and down stairs continuously. Signal measurements were recorded from 10 healthy young subjects and 11 elderly subjects. For comparison, two patients with Parkinson's disease participated in the level walking. The acceleration signal in each direction was decomposed to seven detailed signals at different wavelet scales by using the discrete wavelet transform. The variances of detailed signals at scales 7 to 1 were calculated. The fractal dimension of the acceleration signal was then estimated from the slope of the variance progression. The fractal dimensions were significantly different among the three types of walking for individual subjects (p < 0.01) and showed a high reproducibility. Our results suggest that the fractal dimensions are effective for classifying the walking types. Moreover, the fractal dimensions were significantly higher for the elderly subjects than for the young subjects (p < 0.01). For the patients with Parkinson's disease, the fractal dimensions tended to be higher than those of healthy subjects. These results suggest that the acceleration signals change into a more complex pattern with aging and with Parkinson's disease, and the fractal dimension can be used to evaluate the gait of elderly subjects and patients with Parkinson's disease.

Acceleration↗
PubMedDate not supplied

Experimental study of decubitus ulcer formation in the rabbit ear lobe.

An animal model of decubitus ulcer was created with the use of ear lobes of Japanese white rabbits. When the strength of the cyclic compressions and the duration of the cycles of compression and release are adjusted, the model successfully reproduced the four grades used to characterize decubitus ulcer. Compressions were recorded with video microscopy to continuously monitor the changes in tissue blood flow, in both the compressed and surrounding regions. This model is unique insofar as the blood-flow characteristics are clearly visible before, during, and after compression. Because long-term observation is possible in a living-body model, our study can easily be extended.

Animals↗