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Biomedical subjects

R E SMITH

Publications and source records attributed to R E SMITH.

At least 19 recordsLinked to original sources
PubMed1964

THERMOREGULATORY AND ADAPTIVE BEHAVIOR OF BROWN ADIPOSE TISSUE.

Brown adipose tissue has been shown to be a strongly thermogenic effector organ in homeothermic animals exposed to cold and in hibernators during cold-induced arousal from deep hibernation. Because of the anatomical distribution of brown fat and the utilization of vascular countercurrent heat exchange, this cold-induced thermogenic response protects the animal by contributing heat to the vital organs of the thorax, the cervical and thoracic segments of the spinal cord, and the sympathetic chain. Evidence indicates that control of thermogenic activity of brown fat is mediated by the sympathetic nervous system.

Acclimatization↗
PubMed1964

CYTOLOGICAL RESPONSES OF BROWN FAT TISSUE IN COLD-EXPOSED RATS.

In young adult laboratory rats exposed to cold (6 degrees C) the brown adipose tissue undergoes time-dependent increases in cellularity, vascular supply, and total mass. These changes are largely complete after 16 days in the cold and concurrent generally with the development of a thermoregulatory state not greatly dependent upon shivering. Histologically the brown fat changes from a tissue having both unilocular and multilocular fat cell types to one having almost exclusively the latter. During the first 6 to 12 hours in cold, the multilocular cells lose their lipid vacuoles and decrease in size, but these features are restored to normal by 24 hours. Cell proliferation, as estimated by the DNA synthetic index method (using tritiated thymidine autoradiography), appears in the reticuloendothelial cells of the brown fat at 1 day of cold exposure, becomes maximal at 4 days, and returns to the control level by 16 days. In animals injected with tritiated thymidine on the 3rd day of cold exposure and then maintained for 1 or more additional days in the cold, autoradiographs indicate that new brown fat (multilocular) cells arise by cytogenesis from reticuloendothelial progenitor cells and not by proliferation of existing brown fat cells. Throughout this and subsequent periods, cells of the epididymal white adipose tissue slowly decrease in size. Because a thermogenic role in cold acclimation has been established for the brown fat, the reported changes are regarded as adaptive responses to a cold environment.

Adipose Tissue↗
PubMed1963

Brown fat: thermogenic effector of arousal in hibernators.

Earlier indications that brown fat has a thermogenic role in rats exposed to cold suggested that certain comparable functions in hibernating marmots be investigated. From the results it appears that arousal of the animal by cold is induced by sympathetically activated thermogenesis in areas of brown fat so located, relative to the vasculature, that heat is transferred to the thoracic structures and cervical spinal regions.

Adipose Tissue↗