PubMed Health⌕ Search

Biomedical subjects

X J Musacchia

Publications and source records attributed to X J Musacchia.

At least 55 records · Page 3Linked to original sources
PubMed1980

Model for antiorthostatic hypokinesia: head-down tilt effects on water and salt excretion.

Water and electrolyte excretion was investigated in antiorthostatic hypokinetic and orthostatic hypokinetic and control rats in metabolic cages. Significant (t test, P < 0.05), diuresis, natriuresis, and kaliuresis occurred in the antiorthostatic hypokinetic subjects but did not occur in either the orthostatic hypokinetic or controls. Recovery from antiorthostatic hypokinesia was characterized by retention of water, sodium, and potassium. Patterns of changes in body weight and food and water orthostatic hypokinetic rats and thus could not account for the differences in renal handling of water and electrolytes. Also, differences in ingestion of food and water in controls could not account for differences in excretion of water and electrolytes between these and antiorthostatic hypokinetic rats. It was concluded that the antiorthostatic position was responsible for the diuresis and natriuresis and that the antiorthostatic hypokinetic rat appears to be a good model for the study of water and electrolyte excretion during conditions such as bed rest, water immersion, and exposure to weightlessness.

Animals↗
PubMed1980

Water metabolism and renal function during hibernation and hypothermia.

Total water turnover in normothermic, cold-exposed 13-lined ground squirrels was about half that predicted from allometric relationships of water loss and body weight. During hibernation pulmocutaneous water loss and oxygen consumption were 1/77th and 1/52nd of values during normothermia, respectively, in this species. Renal function during deep torpor with body temperatures of 8 C or lower has also been assessed in ground squirrels and hamsters. The weight of evidence suggests that glomerular filtration and urine formation are absent of undetectable in these animals. We feel that the reduction in arterial blood pressure may be the primary adaptation for eliminating filtration. If filtration (which is not thermally vulnerable, being dependent on hydrostatic pressure) occurred, it is difficult to imagine how reabsorption (which has critical metabolic steps such as ion transport that would be thermally vulnerable) could keep pace. Filtration and hypertonic urine formation occur at body temperatures of 20 to 30 C during the arousal process. Marmots differ from other hibernating rodents in that measurable filtration and hypertonic urine formation occurs during hibernation.

Animals↗
PubMed1979

Intestinal transport of hexoses in the rat following chronic heat exposure.

The effect of 3 wk heat exposure (Ta 34 degrees C) on intestinal weight and intestinal absorption of D-glucose and D-galactose in vitro was examined in the rat. Intestinal dry weight was reduced with heat exposure compared to both ad libitum and pair-fed animals at Ta 22 degrees C. Intestinal tissue water was elevated after pair feeding but not heat exposure; extracellular (inulin) space was similar in the three groups. Mucosal uptake of glucose per gram wet weight in an everted sac preparation was unchanged compared to pair-fed animals, but serosal transfer was increased. Intestinal metabolism of glucose was decreased with heat exposure. Galactose accumulation with 30 min incubation was increased in intestinal rings from both heat-exposed and pair-fed animals. This increase is likely to be related to the reduction in ring size present in the groups with reduced food intake. Vmax and apparent Km for galactose transport were unchanged. Our results indicate that despite a reduction in intestinal weight following heat exposure, the ability of the intestine to transport hexoses per gram remains relatively stable. Alterations of hexose transport appear to be related to altered glucose metabolism and not altered transport capacity. Differences in intestinal weight and glucose utilization between pair-fed and heat-exposed animals suggest that the intestinal response to chronic heat exposure is not solely a function at the amount of food consumed. However, the alteration of more than one variable in pair feeding makes interpretation complex.

Adaptation, Physiological↗
PubMed1979

The function of glucocorticoids in thermogenesis.

Studies both in vivo and in vitro implicate glucocorticoids in various aspects of thermogenesis and prevention of heat loss. Many or most of these effects are probably permissive. Adrenalectomized, cold-exposed rats require glucocorticoids for catecholamine-mediated mobilization of free fatty acids, for shivering responses, and for vasoconstriction and piloerection. Glucocorticoid pretreatment of hypothermic hamsters results in a physiological state more similar bioenergetically to hibernation than to hypothermia. For example, such hamsters can arouse to normothermia from a body temperature of 8 C in a 7--8 C cold room. Lipolytic, gluconeogenic, glycogenolic, and pressor actions resulting from several hormone interactions that require glucocorticoids for optimum responses may account for the enhanced thermogenic ability shown by glucocorticoid-pretreated hamsters. Glucocorticoid treatment also results in enhanced blood and liver carbohydrate levels during hypothermia, a condition similar to that occurring in naturally hibernating animals as opposed to the depleted carbohydrate reserves generally seen in hypothermic animals.

Adipose Tissue↗
PubMed1978

Glucocorticoids and carbohydrate metabolism in hypothermic and hibernating hamsters.

In hibernating hamsters carbohydrate reserves are regulated and are in dynamic equilibrium. During "deep" hypothermia (Tb 7-8 degrees C) hamsters undergo a progressive hypoglycemia, depletion of liver glycogen, and death within 24 hours. Glucocorticoid treatment results in enhanced blood and liver carbohydrates, prolonged survival at Tb 7-8 degrees C, and enhanced thermogenic capacity leading to arousal.

Animals↗
PubMed1977

Mechanisms responsible for decreased glomerular filtration in hibernation and hypothermia.

Mechanisms underlying the elimination or marked depression of renal function in hibernation and hypothermia were investigated through measurements of blood pressure, heart rate, red blood cell and plasma volumes, and relative distribution of cardiac output. Hamsters (Mesocricetus auratus) were made hypothermic (rectal temperature (Tre), 7 degrees C) by exposure to helox and cold, or permitted to hibernate with several weeks of cold exposure (Ta approximately 5 degrees C). Mean arterial pressure, 120 Torr in normothermic control animals, demonstrated a 55% and 60% decrease during hibernation and hypothermia, respectively. As the animals rewarmed from hypothermia or aroused from hibernation, blood pressure increased rapidly at 8-12 degrees C, more gradually at 12-17 degrees C, and plateaued thereafter. Blood pressure rapidly returned to near control levels whereas heart rate remained at less than one-half control value at the highest temperature examined. Red blood cell volume, 26.2 +/- 0.6 ml/kg body wt in the control animals appeared unaffected by hypothermia. Plasma volume, by contrast, decreased from control values of 33.0 +/- 0.8 to 21.3 +/- 0.6 ml/kg body wt in hypothermia, a decrease of approximately 35%. Distribution of cardiac output to various organs in hibernation and hypothermia followed a similar pattern. Relative flow to the heart, lung, diaphragm, and brown fat increased while the fraction distributed to the visceral organs appeared to decrease. The normothermic control kidney received approximately 16% of the cardiac output while the hibernating and hypothermic kidneys received approximately 10% and 6%, respectively. The data are discussed in terms of the determinants of glomarular filtration rate and explain, in part, the elimination or marked reduction in renal function observed in depressed metabolic states.

Animals↗
PubMed1977

Diabetes mellitus in the 13-lined ground squirrel (Citellus tridecemlineatus).

Spontaneous diabetes mellitus was diagnosed in six of 126, 13-lined ground squirrels, Citellus tridecemlineatus. Serum glucose values were significantly higher in the diabetic ground squirrels than in the non-diabetic ground squirrels, while serum insulin values of fasted diabetic squirrels were significantly lower than fasted nondiabetic ground squirrels. In addition, the classic diabetic signs of poly-dipsia, polyuria, glycosuria, ketonuria, polyphasia, and weight loss were present. The proportion of islet tissue to total pancreatic area in diabetic ground squirrels was less than 25% of that in the nondiabetic ground squirrels. Both the number and size of the islets of Langerhans in diabetic ground squirrels were less than those in nondiabetic ground squirrels.

Animals↗
PubMed1976

Norepinephrine turnover in heart and spleen of 7-, 22-, and 34 degree C-acclimated hamsters.

Norepinephrine (NE) turnover rates were measured in hamster (Mesocricetus auratus) heart and spleen tissues after 7-10 wk exposure to 7, 22, and 34 degrees C. The competitive inhibitor of NE synthesis, alpha-methyl-p-tyrosine methyl ester, was injected (200 mg/kg, ip) into acclimated animals. At sequential periods after drug treatment, hamsters were sacrificied by cervical transection, and tissues were removed and frozen. Rate constants, turnover time, and turnover rates were determined from regression analysis of NE tissue decay. Heart NE turnover was highest in cold-acclimated and lowest in heat-exposed animals (.111 and .047 mug/g per h, respectively), control values being intermediate (.081 mug/g per h). NE turnover is inversely related to tissue levels in the myocardium of temperature-acclimated hamsters. Spleen NE turnover was lowest with heat exposure, but spleen tissue levels of NE with heat or cold exposure were not different from control (22 degrees C) measurements. Heat-acclimated hamsters are slightly hyperthermic (Tre, 37.24 +/- .18 C; P, .032) compared to 22 degrees C-maintained controls (Tre, 36.85 +/- .07), but body temperature were unchanged with 7 degrees C exposure. The implication of altered NE synthesis is that sympathetic nerve activity is decreased with heat acclimation and increased with cold acclimation.

Acclimatization↗
PubMed1976

Mechanisms of temperature regulation in heat-acclimated hamsters.

Mechanisms of temperature regulation were assessed by measurements of oxygen consumption (VO2), body temperature (Rre = rectal, Tsk = skin), evaporative water loss (EWL), regional distribution of blood flow, and blood volume. Hamsters (Mesocricetus auratus) were acclimated to ambient temperatures of 34 or 22 degrees C. VO2 of 34 degrees C-exposed animals was reduced to 50% of that of controls at 22 degrees C, whereas EWL with heat exposure was almost double that of controls. Heat-acclimated animals had a slightly elevated Tre in comparison to 22 degrees C-acclimated animals, whereas there was a marked elevation in Tsk with heat exposure, in contrast to control animals at 22 degrees C. Blood flow distribution measurements indicated that with 34 degrees C exposure there was a decreased flow in liver, kidney, and intestine, whereas there was an increase to the carcass. Red cell and plasma volumes in heat-acclimated hamsters were decreased belwo the values of the 22 degrees C controls. Heat acclimation of the fhamster appears to involve reduced VO2 and increased WEL. Convective and radiative heat loss appear to be maintained by increased Tsk with heat exposure. Nonevaporative heat dissipation mechanisms are of primary importance in thermoregulation of the heat-acclimated hamster, and it is suggested that this is mediated by increased peripheral blood flow with reduced flow to the viscera.

Acclimatization↗
PubMed1976

A role for glucose in hypothermic hamsters.

Hamsters undergo hypothermia when exposed to a mixture of 80% helium and 20% oxygen at low ambient temperatures. The hypothermic hamster, rectal temperature (Tre) 7 degrees C, becomes hypoglycemic, and reversal of hypoglycemia is effected with glucose infusion. Hypothermic hamsters at Tre 7 degrees C showed a fivefold increase in survival times from 20 to 100.5 h when infused with glucose which maintained a blood level at about 45 mg/100 ml. A potential role for osmotic effects of the infusion was tested and eliminated. There was no improvement in survival of 3-O-methylglucose or dextran 40-infused animals. The fact that death eventually occurs even in the glucose-infused animal after about 4 days and that VO2 undergoes a slow decrement in that period suggests that hypothermic survival is not wholly substrate limited. Radioactive tracer, [U-14C]glucose, showed that localization of the 14C, was greatest in brain tissue and diaphragm, intermediate in heart and kidney, and lowest in skeletal muscle and liver. The significance of the label at sites important to respiration and circulation was presented.

Animals↗