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Biomedical subjects

F E South

Publications and source records attributed to F E South.

At least 19 recordsLinked to original sources
PubMed1986

Vascular smooth muscle responsiveness in a hibernator: effects of season and temperature.

To determine the effects of season, acclimation state, and hibernation on the reactivity of vascular smooth muscle from a hibernant species, strips of thoracic aorta, renal and femoral arteries, and portal vein obtained from adult woodchucks, Marmota monax, were suspended for isometric tension measurements in physiological salt solution. These blood vessels exhibited no seasonal variation in resting tension, connective tissue content, or maximum tension developed to norepinephrine. However, the concentration-response curves to norepinephrine in both aortic and portal vein strips from animals tested in May and June were shifted to the left of those from animals tested in either August or November through February. This increased sensitivity to the catecholamine was seen also in renal vessels from hibernating compared with nonhibernating animals. Decreasing organ bath temperature from 37 to 28 degrees C increased tension developed in response to norepinephrine in aortic and renal strips, whereas that of the femoral artery was unchanged. With further cooling to 17 degrees C, the responses to norepinephrine in aortic and renal strips were similar to the responses at 37 degrees C. The contraction developed to 40 mM KCl was diminished in all tissues at 28 degrees C. Blockade of beta-adrenergic receptors did not augment the response to norepinephrine at 37 degrees C. Contractions of the woodchuck aorta in calcium-free medium were sustained longer than comparable tissue obtained from a rabbit. These data suggest that receptor-mediated processes are modulated in hibernating animals. This modulation varies among vascular beds and may act to maintain or divert perfusion of the tissue through entry, during, and arousal from hibernation.

Acclimatization↗
PubMed1981

Circannual renal function and plasma electrolytes of the marmot.

Studies with unanesthetized active (non-lethargic) marmots demonstrated circannual rhythms of renal function (clearances of p-aminohippurate, creatinine, and inulin), plasma osmolality, and plasma sodium and potassium concentrations. Effective renal plasma flow, glomerular filtration rate, the clearance of creatinine, and plasma potassium were highest in spring and lowest in the fall and winter. Plasma osmolality and plasma sodium concentrations tended to be highest during the winter months and lowest in the spring and summer. p-Aminohippurate excretion was shown to be a Tm-limited system.

Animals↗
PubMed1979

Maintenance of ion concentration gradients in the cold in aorta from rat and ground squirrel.

Cell water and ionic content were measured in aortic smooth muscle from rats and ground squirrels during 48 h of incubation in oxygenated Krebs solution held at low temperatures. Cells from the ground squirrel, a hibernator, maintained sodium and potassium contents near normal levels during incubation at 7 degrees C. In sharp contrast, cells from the rat lost potassium and gained sodium with half times of 14 and 11 h, respectively. The [K] in cell water for the rat decreased 138 mM while [Na] in cell water increased about 148 mM. Cells from the hibernator tended to lose 10 mM K and gain 13 mM Na. Vascular smooth muscle of both the rat and squirrel was able to maintain K content at 17 degrees C. Tissue content of the divalent cations Ca and Mg did not change in vessels from either animal. The present findings suggest that aortic smooth muscle cells from a hibernator have adapted in such a way as to maintain ionic gradients upon prolonged exposure to low temperatures.

Animals↗
PubMed1979

Spinal cord, hypothalamic, and air temperature: interaction with arousal states in the marmot.

Yellow-bellied marmots, Marmota flaviventris, prepared with U-shaped thermodes in the epidural space of the thoracic vertebral canal, a thermode in the preoptic hypothalamus, and cortical surface and hippocampal electrodes, were used to investigate the interaction of arousal states with temperature regulation. It was found that arousal state of the animal influences the thermoregulatory responses initiated in either the spinal cord or hypothalamus. Further, changes in ambient temperature affected both the gain and the threshold of these responses. The interaction of the hypothalamus and spinal cord was not an additive function, however the threshold for shivering of each could be altered by temperature manipulation of the other. Future studies in modeling of temperature regulation should consider the contributions of temperature receptors of the spinal cord and the arousal state of the animal during the stimulation period.

Animals↗
PubMed1977

Renin-angiotensin-aldosterone system of the normothermic marmot.

Adrenal steroid secretion rates and the renin-angiotensin-aldosterone (RAA) system were studied in the normothermic marmot. Adrenal secretion by the anesthetized, laparotomized marmot was (mean +/- SEM); aldosterone 1.2 +/- 0.3 ng/min, deoxycorticosterone 16.7 +/- 11.5 ng/min, corticosterone 15.2 +/- 7.8 ng/min, and cortisol 554 +/- 108 ng/min. Four forcings were investigated that affect feedback control at different sites: adrenocorticotropic hormone (ACTH) and angiotensin II (AII) infusion, sodium (Na) depletion, and Na loading. Plasma aldosterone, cortisol, Na, and potassium (K) concentrations as well as plasma renin activity (PRA) hematocrit (Hct), and in some studies, blood pressure were measured. ACTH infusion increased the plasma concentrations of aldosterone and cortisol. AII infusion increased aldosterone concentration, blood pressure, and Hct. Na depletion increased aldosterone, Hct, and PRA; plasma Na and K were decreased. Aldosterone concentration, Hct, and PRA decreased after salt loading. Normothermic, salt-depleted marmots demonstrated a pronounced fall in blood pressure following infusion of the AII analog, 1-sarcosine-8-alanine AII. The average plasma values for aldosterone, PRA, and cortisol found in 44 control animals were: aldosterone 3.8 +/- 0.3 ng/100 ml, PRA 1.9 +/- 0.2 ng AI-ml-1-h-1, and cortisol 54 +/- 4 ng/ml. It was concluded that normothermic marmots have a RAA system comparable to other mammalian species.

Adrenal Cortex Hormones↗
PubMed1976

Effects of temperature on cardiac transmembrane potentials in hibernation.

Resting and action potential parameters were measured from papillary muscle isolated from hibernating and control hamsters and from rats. The temperature range of the study was 12-38 degrees C. The decrease in resting membrane potential (Em) with decreasing temperature was significantly less in the hibernation preparations (HH), down to 20 degrees C, than in either the control hamsters or rats. Below 20 degrees C the declines in Em of all preparations were indistinguishable. Action potential magnitude was adequately maintained in HH to 12 degrees C while both control hamster and rat action potentials declined markedly as temperatures were reduced. Both types of hamster preparations showed greatly prolonged action potentials with reduced temperatures as contrasted to a limited prolongation of rat action potentials. The data are suggestive of a membrane modication in hibernation.

Action Potentials↗
PubMed1975

Concentration of urine by the hibernating marmot.

Studies wer performed with marmots (Marmota flaviventris) of both sexes that had chronic arterial, venous, and bladder catheters. Urine collection was performed during hibernation and urine osmolalities (611.6 not equal to 166.1 SD) were found to be lower than those of aroused animals (1264 not equal to 472.9 SD), but hypertonic to plasma. Peak osmolality of meduallary slices was found to be in the range of osmotic pressures of urine obtained from hibernating or aroused animals. After single injections of a mixture of rho-aminohippurate and inulin, or during constant infusion of inulin, steady-state excretion by hibernators was not achieved for several days. Indirect evidence indicateds that the hibernating marmot is capable of PAH secretion.

Aminohippuric Acids↗
PubMed1975

Responses to preoptic temperature manipulation in the awake and hibernating marmot.

Responses of normothermic and hibernating marmots to manipulations of the preoptic-hypothalamic temperature (TPO) were studied. Independent variables included alteration of TPO and, during normothermia, room temperature. Hibernation occurred at an ambient of 6 degrees C. Dependent variables include brain, subdermal, and surface temperatures, heart rate, and behavioral, electromyographic cortical, and hippocampal responses. Although normothermic autumn marmots displayed most of the usual mammalian responses to alterations of the TPO, evidence of effective dermal vasomotion was not obtained. Single episodes of water drinking accompanied prolonged raising of the TPO; sleep was not elicited. During hibernation, effective central thermoregulation was not apparent until 3 or 4 days had elapsed. After this, thermoregulation was readily demonstrable in response to both raising and lowering the TPO. The apparent open-loop gains (OLG) for rise in body temperature after lowering of the TPO showed an exponential increase in value at lower prestimulus body temperatures. It was postulated that this could be explained on the basis of the recruitment of cold-sensitive neurones, which in turn would provide an explanation for the hypothesized "alarm temperature."

Animals↗