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Biomedical subjects

S Robinson

Publications and source records attributed to S Robinson.

At least 343 records · Page 19Linked to original sources
PubMed1976

Physiological aging of champion runners.

The physiological adjustments to aerobic work (5.6 km/h, up a 9% grade) and to exhausting treadmill work of former champion middle-distance runners were determined in 1971, at ages 47-68 yr, 25-43 yr after their competitive careers in track. In the resting state the former athletes as a group are very much like nonathletes of the same ages. Efficiency in the aerobic walk was the same in both groups and did not change with age in either, but the former athletes on the average performed the walk with less strain as indicated by lower blood lactates, "ventilatory equivalents," and heart rates than nonathletes at corresponding ages. Mean VO2max of the runners declined from 71.4 ml/min-kg-1 in youth to 41.8 at a mean age of 56.6 yr, as compared with mean values of 50.6 and 36.5 ml/min-kg-1 in nonathletes at corresponding ages. VO2max had declined below the average of nonathletic men in only two of the former runners. Mean maximal heart rate declined with age from 186 to 180 in the runners, and from 199 to 186 in nonathletes at corresponding ages. Ventilatory responses of men in both groups were closely related to the increases of blood lactate in both aerobic and maximal work.

Aged↗
PubMed1976

Drug modification of hypothermia induced by CNS glucopenia in the mouse.

2-Deoxy-D-glucose (2-DG), insulin, or norepinephrine (NE), when injected into the cerebral ventricles of conscious mice, produce decreased rates of O2 consumption and hypothermia. These changes are accompanied by hyperglycemia with 2-DG, hypoglycemia with insulin, and normoglycemia with NE. Desipramine blocks the reduction in body temperature and O2 consumption produced by each of these agents, but does not modify significantly their effects on plasma glucose. The latter suggests that the thermal and oxidative responses to central glucopenia can be dissociated from concurrent alterations in circulating glucose. Propranolol enhances the hypothermic response produced by administered 2-DG, insulin, or NE. Phentolamine, however, antagonizes the hypothermia only with NE, indicating the 2-DG and insulin are probably not acting through the release of endogenous NE.

Animals↗
PubMed1976

Lifelong alterations in endocrine function resulting from brief perinatal hypothyroidism in the rat.

The late consequences of a brief period of perinatal hypothyroidism were studied in the rat by giving propylthiouracil (PTU) prenatally to the mothers and/or neonatally for 5 days to the pups. Perinatal hypothyroidism produced a delay in eye opening, a diminution in weaning weight, a delay in puberty and first estrus, and a prolongation of estrus cycles. The neo-PTU rats usually had a persistently enlarged thyroid gland associated with an elevated pituitary, hypothalamic, and serum thyroid-stimulating hormone (TSH) concentration. The metabolic clearance rate of TSH and response to luteinizing hormone-releasing hormone (LH-RH) were normal. The response to thyrotropin-releasing hormone (TRH) stimulation was significantly blunted in adult neo-PUT males, suggesting secondary or tertiary hypothyroidism. As a result of these studies, serious thought should be given to the possible consequences of antithyroid drug therapy of pregnant women, and certainly all pregnant hypothyroid women should receive full replacement therapy.

Animals↗
PubMed1975

Longitudinal studies of aging in 37 men.

The physiological adjustments of the men to both aerobic (5.6 km/h, up 9% grade), and maximal treadmill work were first determined when they were healthy college students, ages 18-22 yr. They were restudied at ages 40-44, and again at ages 49-53 yr. In the aerobic walk VO2 increased in proportion to weight gain, but efficiency did not change with age. The men who had gained most weight showed the greatest elevations of heart rate, blood lactate and "ventilatory equivalent," and reductions of the "O2 pulse" in the walk. At age 50 mean "O2 pulse" in exhausting work had declined 13%, even though mean maximal heart rate had declined 15 beats/min from values observed in youth. At ages 40-44 yr mean VO2 max had declined 25% to values 12% lower than mean values reported in 1938 for men of this age. Eight of the men imporved an average of 11% in VO2 max between ages 40-44 and 49-53 yr; mean VO2 max of the others continued to decline with age. The five men who improved most had increased their participation in vigorous activities (tennis, squash, skiing, jogging, etc.) and had quit or reduced their smoking.

Adolescent↗
PubMed1975

A design improvement in continuous blood sampling and analysis for glucose in rest and exercise.

In the past 15 yr attempts to sample blood continuously for glucose analysis with the AutoAnalyzer (Technicon Corp.) have been reasonably successful in resting subjects. However, they have sometimes required heparinization of the subjects so as to avoid clotting in the tubes of the system. To avoid the hazards of heparinization during exercise, a method is described for sampling and analyzing blood glucose continuously with the AutoAnalyzer, using a specially designed male Luer adaptor which fits into disposable Teflon catheters.

Blood Glucose↗
PubMed1975

Late effects of neonatal undernutrition and overnutrition on pituitary-thyroidal and gonadal function.

Neonatal rats were underfed or overfed and then, at weaning, placed on a normal diet and allowed to mature. Although overfed rats were obese at weaning, they were of normal weight when mature. The underfed rats remained smaller all their lives. The endocrine organs did not share in this retardation, and were actually larger in several instances when expressed per 100 g body weight. Underfed rats also had delayed eye-opening, normal puberty and normal estrous cycles. Pituitary, hypothalamic and serum TSH concentrations were normal, or even increased (in the underfed females). The responses to propylthiouracil and to thyrotropin-releasing hormone (TRH) were both normal. Thus the tertiary hypothyroidism reported in underfed rats 16 days old did not persist into adult life. In all comparisons the males had higher serum TSH concentrations than females and usually had a greater response to TRH stimulation. The various persistent endocrine abnormalities resulting from neonatal thyrotoxicosis differ from those seen after neonatal caloric deprivation in all pertinent regards except that both have reduced body weights.

Animal Nutritional Physiological Phenomena↗
PubMed1975

Endocrine studies of the untreated progeny of thyroidectomized rats.

Experiments were conducted to assess late and persistent endocrine changes in the progeny of rats born and/or nursed by thyroidectomized (Tx) dams. Forty-five female rats were radiothyroidectomized several weeks before mating with normal males, and compared with the progeny of 26 control females. In all, 248 progeny were studied when adult. Tx dams had significantly reduced fertility (87% of controls), increased pup (11% versus 0) and maternal mortality (27% versus 0), and smaller litters (6.5 versus 11.8 pups/litter). It was shown that the offspring of thyroidectomized female rats had delayed eye opening (15.3 versus 14.3 days), smaller weaning (40.4 versus 54.4 g) and adult body weight (230 versus 260 g), smaller pituitary glands (12.2 versus 14.0 mg), and enlarged thyroid gland (14.2 versus 12.4 mg). Ovarian and testicular weight were decreased (73.9 versus 83.7 mg and 3.2 versus 3.6 g, respectively). The serum thyroid stimulating hormone (TSH) concentrations were increased from 53.8 to 84.4 muU/ml in the males. The pituitary TSH contents were not significantly altered, and the serum TSH response to thyrotropin releasing hormone (TRH) was normal. These persistent effects differed from the late effects of both fetal and neonatal hypothyroidism and neonatal underfeeding. Cross-fostering experiments showed that the diminished weaning weights were the result of the pups being nursed by the hypothyroid dams. The increased nursing mortality and the pituitary and thyroidal changes were the result of prenatal influences produced by the hypothyroid dams, since being nursed by a normal foster dam did not prevent them. The persistently enlarged thyroid glands and the elevated serum TSH in the male offspring of thyroidectomized dams suggested a permanent alteration in the set point of pituitary-thyroid regulation as the consequence of maternal hypothyroidism.

Adrenal Glands↗
PubMed1975

The late effects of neonatal hyperthyroidism upon the feedback regulation of TSH secretion in rats.

Rats made thyrotoxic with large doses of thyroxine (T4) during the neonatal period (neo-T4) show many abnormalities as adults. These usually include impaired body, pituitary and thyroid growth, diminished pituitary and serum TSH concentrations, a diminished serum T4 and a diminished response to PTU challenge and to thyrotropin-releasing hormone (TRH) stimulation. Experiments are presented which show that these rats are hypersensitive to feedback regulation by T4 in a manner similar to that seen after bilateral anterior hypothalamic lesions. They show a subnormal response to PTU challenge and an excessive suppression of serum TSH and goiter growth after T4. Pituitary TSH was less depleted in neo-T4 rats when a small dose of T4 was given daily with PTU and pituitary TSH was more sensitive to suppression by a larger dose of T4 in the neo-T4 group. There was an impaired rebound increase in pituitary TSH following a single inhibitory dose of T4 injected into the adult hypothyroid rat. Although the hypothalamic TRH content is increased in the neo-T4 rat, the circulating concentration of TRH was found to be significantly decreased, supporting the theory that the defects observed in the neo-T4 rat may be the consequence of an impaired hypothalamic secretion of TRH.

Animals↗
PubMed1975

Effect of warm-up on metabolic responses to strenuous exercise.

Aerobic and anaerobic energy transformations were measured in two trained runners during 90-sec treadmill runs at 23.6 km/hr (2% grade). The runs were preceded by rest or either of two warm-ups: 1) 15-min run at 10 km/hr, or 2) 15-min run at 10 km/hr followed by 3-min standing. Compared with runs without warm-up, during the third half minute of runs following both types of warm-up 11% greater heart rates (HR), 8% greater oxygen consumption (Vo2), and unchanged ventilation were recorded. The rate constant of the approach of Vo2 to O2 in the first minute of work was unaffected by warm-up. Runs following either warm-up resulted in 25% lower lactate production; during these runs 3 to 4 degrees C higher gastrocnemius muscle temperatures (Tm) were maintained. The differences in HR, Vo2, and Tm continued throughout exhausting 5-min runs at 20.9 km/hr (2% grade). An elevated muscle temperature may therefore be requisite for the maximal aerobic response to a short exhausting run.

Adaptation, Physiological↗