the minimum number of calories needed for basal metabolism is basal body temperature.
the minimum number of calories needed for basal metabolism is?
basal body temperature
ever since pearl proposed the rate of living theory of aging, numerous studies have demonstrated its validity in poikilotherms. in mammals, however, satisfactory experimental demonstration is still lacking because an externally imposed increase of basal metabolic rate of these animals (e.g. by placement in the cold) is usually accompanied by general homeostatic disturbance and stress. the present study was based on the finding that rats exposed to slightly increased gravity are able to adapt with little chronic stress but at a higher level of basal metabolic expenditure (increased 'rate of living'). the rate of aging of 17-month-old rats that had been exposed to 3.14 "g" in an animal centrifuge for 8 months was larger than of controls as shown by apparently elevated lipofuscin content in heart and kidney, reduced numbers and increased size of mitochondria of heart tissue, and inferior liver mitochondria respiration (reduced 'efficiency': 20% larger adp: 0 ratio, p less than 0.01; reduced 'speed': 8% lower respiratory control ratio, p less than 0.05). steady-state food intake per day per kg body weight, which is presumably proportional to 'rate of living' or specific basal metabolic expenditure, was about 18% higher than in controls (p less than 0.01) after an initial 2-month adaptation period. finally, though half of the centrifuged animals lived only a little shorter than controls (average about 343 vs. 364 days on the centrifuge, difference statistically nonsignificant), the remaining half (longest survivors) lived on the centrifuge an average of 520 days (range 483–572) compared to an average of 574 days (range 502–615) for controls, computed from onset of centrifugation, or 11% shorter (p less than 0.01). therefore, these results show that a moderate increase of the level of basal metabolism of young adult rats adapted to hypergravity compared to controls in normal gravity is accompanied by a roughly similar increase in the rate of organ aging and reduction of survival, in agreement with pearl's rate of living theory of aging, previously experimentally demonstrated only in poikilotherms.
hypergravity
some of aschoff's later work also integrated his initial interest in thermoregulation with his work on circadian rhythm. he found a circadian rhythm in thermal conductance, a measurement of heat transfer from the body. minimal conductance in mammals and birds oscillates with circadian phase, with a wide range of conductance values. this allows animals to release heat during their activity period, when they have higher basal metabolism, as well as conserve heat during their rest period, when they have lower basal metabolism. in birds, the circadian rhythm in conductance results mostly from circadian rates of evaporative heat loss. in mammals, the conductance oscillates with circadian rhythms in the body's heat resistance and blood flow rate.
jürgen aschoff