Biomedical subjects

S W Corbett

Publications and source records attributed to S W Corbett.

23 records · Page 2Linked to original sources

PubMed1984

Metabolic defense of the body weight set-point.

The energy needs of an organism are a function of the tissue mass it maintains. Interspecific comparisons indicate that energy needs are a power function of body weight (12). Much of the work described here represents an effort to ascertain whether the function relating intraspecific energy expenditure to maintained body weight takes a similar form. The evidence to date from various rat preparations suggests that although some differences may exist, the form of the function for rats is not likely to differ substantially from the interspecific function derived by Kleiber (12). What has also emerged from this work, however is evidence that both the inter- and intraspecific functions accurately predict energy needs only when the organism is at the particular body weight it normally maintains and defends. This is because a rise in weight from the normal level causes energy needs to increase at a faster rate than the relationship would predict, whereas declines in weight from this level produce greater than predicted decreases in energy expenditure. We thus propose that an animal's body weight set-point be taken as the weight at which its daily energy needs can be accurately predicted from its metabolic body size. It is only at this one body weight that the animal is normometabolic. It can then be asked whether organisms maintaining abnormally high or low body weights are suffering from regulatory dysfunctions or regulating normally but at elevated or depressed set-points. We have seen that obese Zucker rats display the same adaptive metabolic adjustments to weight loss as normal weight rats. Since the exact form of the intraspecific body weight-metabolic needs relationship has not yet been determined, we must withhold judgment as to whether Zucker fatty rats are normometabolic at their elevated body weights. Since they display an effective metabolic defense of their obesity, however, an elevated set-point, rather than regulatory failure, seems to be the more probable cause of the Zucker fatty's condition. More compelling evidence of regulation at an altered body weight set-point is provided by the LH-lesioned rat. This preparation is normometabolic at the reduced body weight it maintains, and it becomes hypermetabolic when its weight is elevated to the level of nonlesioned littermates. The obesity of the VMH-lesioned rat, on the other hand, may well stem from primary regulatory impairments.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1983

Effects of beta-adrenergic blockade on lateral hypothalamic lesion-induced thermogenesis.

Oxygen consumption is markedly elevated in rats with lesions of the lateral hypothalamus (LH), a response typically associated with hyperactivity. To test for involvement of adrenergic systems in this hypermetabolic state, propranolol was administered before and immediately after LH lesions. Propranolol attenuated both the lesion-induced rise in oxygen consumption and activity in the 12 h after surgery. A second experiment evaluated the contribution of activity to this thermic response by lesioning rats immobilized by a continuous barbiturate infusion. The persistence of lesion-induced increases in oxygen consumption in the absence of activity and the attenuation of this response by propranolol demonstrated that 1) LH lesions directly alter metabolic heat production, and 2) this effect is at least partly mediated by beta-adrenergic systems. The functional significance of increased energy expenditure after LH lesions is discussed in light of the known effects of this lesion on the level of regulated body weight.

Animals↗

PubMed1982

Energy balance of rats with lateral hypothalamic lesions.

Rats with lateral hypothalamic (LH) lesions maintain body weight at a chronically reduced percentage of nonlesioned controls. An assessment of how they achieve energy balance at subnormal weight levels entailed a determination of both their energy intake and their energy expended or lost in processing ingested food, on basal heat production, on activity, and in feces or urine. It was found that the caloric intake and expenditure of LH-lesioned animals, though significantly lower than those of controls, were appropriate to the reduced metabolic body size (BW0.75) that they maintained. Likewise, energy expenditure in the LH-lesioned animals was normal in that the proportion of their ingested energy relegated to 1) basal metabolism, 2) the processing food, and 3) activity was the same as that of nonlesioned controls. Thus, unlike nonlesioned rats, which at lowered body weights both decrease their energy needs and reorder the pattern of energy expenditure, LH-lesioned animals display a normal pattern of energy utilization at reduced weight levels. These findings provide further evidence that lateral hypothalamic mechanisms play an important role in setting the level at which body weight is regulated.

Animals↗

PubMed1980

Digestibility in male rats with lateral hypothalamic lesions.

The body weight of male rats with lateral hypothalamic lesions remained approximately 20% below that maintained by nonlesioned controls. One month following surgery, both food intake and energy losses in feces and urine were measured in all animals for five days. The percentage of ingested food absorbed by the gut ("digestibility") was determined from calorimetric analysis of the feces to be slightly, though significantly, higher for the lesioned animals (79.7% vs 77.4%). Resorptive capacity, as indicated by the percentage of absorbed energy lost in the urine, was determined to be the same for the lesioned and control animals (4.8% vs 4.5%). These results indicate that the digestive, absorptive, and resorptive processes of LH-lesioned animals are at least as efficient as those of nonlesioned animals maintaining normal body weights. Thus, though LH-lesioned animals are reported to display various gastrointestinal dysfunctions, alterations in digestive or resorptive efficiency are apparently not responsible for their chronically-reduced body weights.

Animals↗

PubMedDate not supplied

Exposure of prehospital care providers to violence.

OBJECTIVE: To evaluate the experience of prehospital care providers with violence. METHODS: A survey addressing experiences with prehospital violence was administered to a convenience sample of emergency medical services (EMS) providers in a southern California metropolitan area. Descriptive statistics are reported. RESULTS: Of 774 EMS providers surveyed, 522 (67%) returned the questionnaire. Members of law enforcement were excluded because their experience with violence, weapons, and tactics is not typical of most paramedics. This left a sample of 490 for further analysis. These prehospital care providers had a median of ten years' experience on the job. They tended to be male (93%) and white (80%). All together, 61% recounted assault on the job, with 25% reporting injury from the assault. Respondents reported a median of three episodes, and the number of assaults for each individual was unrelated to the number of years of experience on the job (r = 0.068). Of those injured, 37% required medical attention. On the other hand, 35% reported that their company had a specific protocol for managing violent situations and 28% stated ever having received formal training in the management of violent encounters. This limited training notwithstanding, nearly all (95%) providers described restraining patients. Use of protective gear was reported (73%), and some (19%) admitted to ever carrying a weapon on the job. CONCLUSIONS: By their own report, EMS providers encounter a substantial amount of violence and injury due to assault on the job. Formal training and protocols to provide a standardized safe approach for such encounters are lacking. Although the limitations of survey data are recognized, further research characterizing the level of violence and potential interventions seems warranted.

Adult↗