Biomedical subjects

J Oyama

Publications and source records attributed to J Oyama.

49 records · Page 3Linked to original sources

PubMed1975

Regulation of body mass in rats exposed to chronic acceleration.

Female rats approximately 6 mo old were chronically centrifuged for up to 30 days at 2.76 G or 3.18 G and sacrificed at intervals for body-composition study. Both fat and the fat-free body mass (FFBM) were reduced during the 1st wk of centrifugation, with the fat showing considerably more variation both within and between groups. The FFBM was reduced below control level to the same extent in rats fed commercial chow, a high-fat diet, or a high-protein diet or in rats prefasted to produce a body-mass deficit at the start of centrifugation. There were no centrifugation-associated changes in body water content. It was concluded that body fat showed no evidence of regulation, FFBM is regulated at any constant level of acceleration between 1 and 4.15 G, and the change in FFBM induced by a change in acceleration is probably not regulated.

Acceleration↗

PubMed1975

Increased uptake and utilization of glucose by diaphragms of rats exposed to chronic centrifugation.

Weaning female Sprague-Dawley rats were exposed to 2.76 or 4.15 G for periods ranging from 2 to 20 wk. The isolated diaphragm tissues from these rats were studied in vitro to determine the uptake of glucose and its utilization to CO2 and glycogen. The diaphragm muscle tissues obtained from centrifuged rats showed higher rates of glucose uptake and 14CO2 production from [U-14C]glucose than those obtained from noncentrifuged controls, but no significant differences in the rate of incorporation of [U-14C]glucose into glycogen were observed. Rats centrifuged for 12 wk at 4.15 G continued to show an increase in diaphragm tissue glucose uptake for periods up to 2 wk after return to normal gravity. The stimulating effect of insulin on the uptake of glucose and its incorporation into glycogen was much higher in the diaphragms of centrifuged rats. From the results of this study, it is concluded that one of the adaptive responses of rats to chronic centrifugation is an increase in glucose metabolism of their muscle tissues.

Adaptation, Physiological↗

PubMed1975

Response and adaptation of beagle dogs to hypergravity.

Eight male Beagle dogs, five months old, were centrifuged for three months at progressively increasing loads ranging from 1.5 g to 2.5 g on a 7.9 m radius centrifuge. Dogs were maintained on the centrifuge, which was run almost continuously, by employing a special designed automated waste disposal and life support system. Heart rate and deep body temperature were monitored continuously by implant biotelemetry. Initially, centrifuged dogs showed transient decreases in heart rate and body temperature along with changes in their diurnal rhythm patterns. Compared with normal gravity controls, exposed dogs showed a slower growth rate and a reduced amount of body fat. Blood protein, total lipids, cholesterol, calcium, packed cell volume, red blood cell count, and hemoglobin were also decreased significantly. Absolute weights of the leg bones of centrifuged dogs were significantly greater than controls. Photon absorptiometry revealed significant density increases in selective regions of the femur and humerus of centrifuged dogs. In spite of the various changes noted, results from this and other studies affirm the view that dogs can tolerate and adapt to sustained loads as high as 2.5 g without serious impairment of their body structure and function.

Adaptation, Physiological↗

PubMed1974