Thermogenesis in normal rabbits and rats: no role for brown adipose tissue?

Thermogenesis and the effect of injected catecholamines on the oxygen consumption of cafeteria-fed rats

1. The oxygen consumption (VO2) of unrestrained rats given a 'cafeteria' (high energy, high fat) or control diet was studied. The resting values of VO2 were the same in each dietary group, whether maintained at 26 degrees C or 6 degrees C. This negative finding suggests that cafeteria feeding is not an important cause of diet-induced thermogenesis (DIT). 2. The response of each group of rats to injected noradrenaline or dopamine was also studied. Each catecholamine could increase VO2 values but the response was much less in cold-adapted rats measured at 6 degrees C. In all experimental circumstances the dopamine response exceeded that of noradrenaline. There was no evidence that the cafeteria diet consistently increased the response to either catecholamine. 3. These results suggest that DIT cannot be equated with non-shivering thermogenesis (NST). Furthermore, it is suggested that dopamine would be a better agent for measuring the oxygen equivalent of NST, since it would stimulate the dopamine receptors as well as the alpha- and beta-adrenoreceptors of brown fat.

The histopathology of enterovirus infections of new-born mice

For 32 years we have provided a routine histopathological service on animals for the Regional Virus Laboratory, Ruchill Hospital, Glasgow. This article concerns mainly experimental coxsackievirus A, coxsackievirus B and echovirus infections in new-born mice. In addition to previously reported findings, we have sometimes observed degenerative and inflammatory changes in neurons related to the Gasserian, posterior root or autonomic ganglia. Not all deposits of brown fat are simultaneously the seat of inflammatory changes; rarely, inflammation of brown fat spills over into the adjacent yellow adipose or connective tissues. Brown fat may occasionally show hyperplasia. Ballooning of the tips of small intestinal villi with interstitial oedema and/or necrosis of villous tips may indicate enanthemata associated with coxsackievirus A2,5,7,8,10,23 as well as with coxsackievirus B1 and B4 infections. Similar appearances were seldom seen with echovirus infections. Focal bone-marrow necrosis and necrosis of cartilage were associated with one coxsackievirus A10 infection, and osteitis with one coxsackievirus B3 infection. The implications of these uncommon observations for human pathology remain to be determined.

Changes in body temperature after administration of adrenergic and serotonergic agents and related drugs including antidepressants: II

This survey continues a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published from 1980 to 1984 but data from many earlier papers are also tabulated.

Effect of dietary protein concentration and ambient temperature on the energy, protein and water metabolism of the rat

Groups of rats (n 8) were offered, to appetite, diets containing 10 (LP), 25 (MP) and 45 (HP)% of gross energy as protein energy from 45 d of age to slaughter 50 d later. At 53 d of age, half the rats on each diet were left at 22 degrees while the other half were transferred to 6 degrees. Water balances were measured daily, and digestibilities of energy and nitrogen and the metabolizability of the diets were measured for each rat over a 7 d period at some stage between the age of 74 and 95 d. The rats were slaughtered at day 95 and their carcasses were analysed for protein, lipid, energy and ash contents. Energy expenditure was calculated as the difference between metabolizable energy intake and energy retained. Growth performance was best on the MP diet at both temperatures. At 22 degrees the rate of gain of body-weight and of energy retention, although not of protein, were slightly reduced on the HP diet while overall performance was markedly inferior on the LP diet. At 6 degrees the LP diet, while not so good as the MP diet, led to significantly better all-round growth performance than did the HP diet. Cold increased the energy expenditure of the rats by 50% (109-138 kJ/d); the increase was greater for the LP group than for the HP group. Intrascapular brown adipose tissue hypertrophied in response to cold and to the LP diet. Adrenal gland size was significantly increased by cold exposure and by increasing level of dietary protein concentration. Urine volume was more closely related to the intake of protein than to that of energy. Urinary N concentration for the HP rats was approximately double that for those on the LP diet. Cold-exposed rats had a high water content in their fat-free carcasses, but there were no differences between the dietary treatments.