Biomedical subjects

M I Talan

Publications and source records attributed to M I Talan.

57 records · Page 4Linked to original sources

PubMedDate not supplied

Nonshivering thermogenesis in adult and aged C57BL/6J mice housed at 22 degrees C and at 29 degrees C.

Twelve- and 28-month-old C57BL/6J male mice were housed either at room temperature of 22 degrees C or at thermoneutrality (29 degrees C) during the two months prior to experiments. Acute experiments were conducted under anesthesia, myorelaxation, and artificial ventilation. We recorded efferent electrical impulse activity in one of the sympathetic nerves innervating the interscapular brown adipose tissue in response to acute cold stimulation, when body temperature was lowered 7.5 degrees C below control level. In separate experiments we measured O2 consumption and CO2 production and calculated the nonshivering thermogenesis. We also measured the concentration of uncoupling protein in interscapular brown adipose tissue before and after three-hour cold stress. In aged mice, both sympathetic nervous activity and nonshivering thermogenesis were lower in animals housed at thermoneutrality (29 degrees C) than in mice housed at 22 degrees. Among mice maintained at 22 degrees C, but not at thermoneutrality, aged animals had greater nonshivering thermogenesis and greater cold induced concentration of uncoupling protein in the brown adipose tissue than adults. Sympathetic nervous outflow to brown adipose tissue was always greater in aged mice, regardless of the temperature of acclimation. We concluded that aged mice, housed at 22 degrees C, showed the changes in nonshivering thermogenesis associated with cold acclimation. However, an increased sympathetic outflow to brown adipose tissue in aged animals reflects an age-related elevation of the tone and responsiveness of the sympathetic nervous system.

Adipose Tissue, Brown↗

PubMedDate not supplied

Change in heat loss as a part of adaptation to repeated cold exposures in adult and aged male C57BL/6J mice.

Previous studies have shown that adult mice increase cold-induced heat production as a result of repeated exposures to cold, but that aged mice do not. The objective of the present study was to investigate changes in heat loss during repeated cold exposures in adult and aged C57BL/6J mice. Mice were partially restrained for three hours at 6 degrees C, three times at one-week intervals. Dry heat loss was inferred from measurements of differential temperature between the incoming and outgoing air in the experimental chamber. During the first cold exposure, aged mice showed less heat loss (both total and adjusted for body temperature) than adult animals, suggesting greater peripheral vasoconstriction in aged mice. With repeated cold exposures, both age groups showed increased heat loss, but the aged mice showed greater increase of heat loss, so that by the third cold stress test, no significant differences in heat loss between adult and aged mice were observed. The increase of heat loss after repeated cold exposures in aged mice might reflect a lesser peripheral vasoconstriction, serving to reduce the possibility of tissue necrosis in the cold.

Acclimatization↗

PubMedDate not supplied

The effect of exercise training in a cold environment on thermoregulation in adult and aged C57BL/6J mice.

We studied the effect of exercise training in cold environment (six weeks of daily, one-hour runs on a treadmill at ambient temperature of 6 +/- 1 degrees C at 60-65% of VO2max) on cold-induced metabolic heat production, heat loss, and cold tolerance in adult and aged C57BL/6J male mice. In adult mice, exercise training in cold environment resulted in greater cold-induced heat production and cold tolerance without changes in heat loss, similar to the effects of daily cold exposure without exercise. In aged mice, daily cold exposures did not affect cold tolerance and cold-induced heat production, but exercise training in the cold resulted in greater cold-induced heat production and cold tolerance. Heat loss in aged mice increased similarly after both repeated cold exposures and exercise training in the cold. Therefore, mechanisms of effect of exercise training on cold tolerance are different in adult and aged animals. Exercise training in cold environment does not affect cold-induced heat production and cold tolerance in adult mice, but improves them in aged animals.

Acclimatization↗