Tohru Ishigaki

Role of xanthine oxidase in delayed lipid peroxidation in rat liver induced by acute exhausting exercise

Abstract The aim of this study was to examine whether xanthine oxidase (XOD)-derived hepatic oxidative damage occurs in the main not during but following strenuous exercise. The degree of damage to hepatic tissue catalyzed by XOD was investigated immediately and 3 h after a single bout of exhausting exercise, in allopurinol and saline injected female Wistar rats. Allopurinol treatment resulted in increased hypoxanthine and decreased uric acid contents in the liver compared with the saline treated group, immediately and 3 h after the exercise. Analysis immediately after the exercise showed no changes in hepatic hypoxanthine, uric acid, and thiobarbituric acid-reactive substance (TBARS) contents in the saline treated group, when compared with the resting controls. However, significant increases in uric acid contents in the saline treated livers were observed 3 h after the exercise, relative to the controls. Hepatic TBARS content in the saline treated group were markedly greater than those in both the control and allopurinol treated groups after 3 h of recovery following the exercise. It was concluded that a single bout of exhausting exercise may impose XOD-derived hepatic oxidative damage, primarily during the recovery phase after acute severe exercise.

Effect of serotonin on ouabain-sensitive, K+-dependent, p-nitrophenylphosphatase activity in strial marginal cells of normal and reserpinized guinea pigs

Na+,K+-ATPase activity is abundant on the basolateral infoldings of the strial marginal cells and contributes to the maintenance of the characteristic electrolyte composition of the endolymph. However, the stria vascularis of the cochlea is known not to be innervated. In order to clarify its humoral regulation by serotonin, the K+-p-nitrophenylphosphatase activity of strial marginal cells was investigated with a cerium-based method in normal guinea pigs and in guinea pigs treated with reserpine, 5-hydroxytryptamine or reserpine plus 5-hydroxytryptamine. K+-p-nitrophenylphosphatase activity was almost completely depressed 3--20 days after reserpine administration. Ten days after reserpinization, followed by repeated 5-hydroxytryptamine treatment, the enzyme activity was detectable. These results suggest that 5-hydroxytryptamine increases the phosphatase activity. Thus, the function of the stria vascularis in producing cochlear endolymph may be regulated by 5-hydroxytrypt amine.

Zucker obese rats are sensitive to weight-reducing effect and insensitive to orexigenic effect by cold exposure

Abstract Male Wistar and Zucker (lean and obese) rats at 7 weeks of age were divided into three groups: warm-acclimated (25°C for 11 weeks), cold-acclimated (10°C for 11 weeks), and deacclimated (10°C for 9 weeks and 25°C for 2 weeks) groups. The rate of increase in body mass (BM) was lower in obese rats as compared to lean rats. Cold-acclimated Wistar and Zucker lean rats exhibited greater food intake, compared to warm-acclimated rats. Food intake did not increase in obese rats exposed to cold. Obese rats are sensitive to weight-reducing effect and insensitive to the orexigenic effect by cold exposure.

Adaptive changes in brown adipose tissue in Wistar rats, Zucker lean and obese rats

Abstract (1) Male Wistar, and Zucker (lean and obese) rats aged 7 weeks of age were divided into three groups; warm acclimated (25°C for 11 weeks), cold acclimated (10°C for 11 weeks), and deacclimated (10°C for 9 weeks and 25°C for 2 weeks) groups. (2) Density of lipid droplet in brown adipose tissue (BAT) of obese rats was the greatest and that in lean rats was less than that in Wistar rats. (3) Mass of brown adipose tissues (BATM) per body mass (BM) was greater in obese rats than lean rats. (4) Marked weight-reducing effect observed in obese rats during cold acclimation is partly resulted from greater BATM/BM.

Comparison of tympanic membrane temperatures measured by contact and noncontact tympanic thermometers during prolonged exercise in the heat

Abstract We examined the agreement between the tympanic membrane temperature (Tty) measured by a contact tympanic thermometer (Contact-Tty) and the Tty measured by a noncontact tympanic thermometer (Infrared-Tty). In addition, we also evaluated the usefulness of an assessment of core body temperature using a noncontact tympanic thermometer during prolonged exercise in the heat. Seven healthy male subjects cycled for the same four experimental trials at 50% peak oxygen uptake for 90 min in the heat (32°C ambient temperature, 50% relative humidity and 26.6°C wet bulb globe temeprature). The correlation coefficient between both temperatures was strong, 0.89 ( p