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Query: UMLS:C0020672 (hypothermia)
 17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Body temperature is maintained by a balance between heat production and heat loss. Temperature regulation consequent to exposure to a cold environment appears to be modified in elderly persons. An evaluation of the physiological adjustments made by older individuals is presented. It is apparent that hypothermia can develop in the older population as a consequence of modifications in both behavioral and physiological responses to cold exposure. With the growing awareness of an energy shortage with consequent lower ambient temperatures in homes, there is a need to obtain adequate information as to the physiological capabilities and adaptive potential of elderly individuals to a cold stress.
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PMID:Hypothermia in the aged. 59 44

The thermal responses produced by both systemic and central administration of prostaglandin E1 (PGE1) at the three different ambient temperatures (Ta) of 2, 22 and 32 degrees C were measured to assess the possible involvement of PGE1 in temperature regulation. The body temperatures, metabolic rate, respiratory evaporative heat loss and vasomotor activity in response to PGE1 were measured. Intravenous administration of PGE1 produced dose-dependent hypothermia at Ta's of both 2 and 22 degrees C. The PGE1 hypothermia was due to cutaneous vasodilation. However, at a Ta of 32 degrees C, intravenous PGE1 produced no changes in rectal temperature and ear blood flow. On the other hand, the direct injection of PGE1 into the third ventricle produced dose-dependent hyperthermia. At a Ta of 22 degrees C, PGE1 fever was due to decreased heat loss along with a small increase in heat production. In the cold, PGE1 fever was due to increased heat production while in the heat heat losses were decreased. The data suggest that elevating PGE1 levels in the periphery causes a hypothermia, while elevating PGE1 levels in the central nervous system causes a hyperthermia at Ta's of both 2 and 22 degrees C.
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PMID:Effects of intravenous and intraventricular prostaglandin E1 on thermoregulatory responses in rabbits. 61 34

The effects of hypothermia (4 degrees C) on the components of the cholinergic system of the ileal longitudinal muscle and the adherent Auerbach's plexus of the guinea pig ileum have been investigated. Acetylcholine (ACh) content of the muscle was determined by pyrolysis-gas chromatography. It decreased from 119 to a fairly steady level of 16 nmol/g of wet tissue during the first 72 h of cold storage at 4 degrees C under anoxic conditions. Concomitantly, responsiveness to intramural electrical stimulation decreased by 72%. Cholinesterase (ChE) and choline acetyltransferase (ChA) activities each dropped by 40% during this period. However, the de novo synthesis of ACh over the period of study did not change significantly. The response of the preparation to the exogenously applied ACh remained fairly constant suggesting that the changes in the cholinergic receptor are not accountable for the decrease in responsiveness to intramural stimulation. From the results of this study, it has been concluded that cold storage for 5 days leads to: (1) a significant decline in ACh content within 72 h of storage; (2) a decrease in ChE and ChA activities; (3) no significant effect on the cholinergic receptor; and (4) a decrease in responsiveness to intramural electrical stimulation which is probably due to a malfunction of the ACh-releasing mechanism.
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PMID:Effects of cooling on the levels of acetylcholine, cholinesterase, choline acetyltransferase and the intramural electrical stimulation on the guinea pig ileum. 62 70

Profound hypothermia (6 degrees C) was induced in cold exposed golden hamsters (Mesocricetus auratus) by a combination of drugs that potentiate brain serotonergic activity (fluoxetine and pargyline) and inhibit noradrenergic activity (alpha-methyl-p-tyrosine). Individual drugs and combinations of 2 were ineffective.
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PMID:Profound hypothermia in golden hamsters (Mesocricetus auratus) induced by serotonergic potentiating and noradrenergic inhibiting drugs. 65 38

Bilateral microinjections of 6-hydroxydopamine (6-OHDA) were made in a volume of 0.5--0.75 microliter through chronically implanted cannulae into anterior hypothalamic, preoptic loci. Sites were selected at which 1.0 to 12.5 microgram of norepinephrine (NE) had previously elicited a fall in the rat's body temperature. After 2.0 to 6.0 microgram of 6-OHDA were injected in the same volume at the same loci, a comparable hypothermia ensued. When the rats were exposed repeatedly for one-hour intervals to an environmental temperature of either 35.0 degrees C or 8.0 degrees C, they were unable to thermoregulate against the heat and their colonic temperature rose. In some experiments, the rats also failed to defend adequately against the cold ambient temperature, but mainly following the microinjection of the higher doses of 6-OHDA . The intakes of food and water were generally suppressed; this was accompanied by a transient decline in body weight. Overall, the severity, duration and direction of the thermoregulatory impairment depended upon the anatomical site of injection and the dose regimen of the neurotoxin employed. These results offer further evidence that an intact catecholaminergic pathway within the anterior hypothalamus is required for the rat's physiological control of heat loss in a warm environmental temperature.
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PMID:Thermoregulation in the rat: deficits following 6-OHDA injections in the hypothalamus. 67 50

Shaven and unshaven rats were exposed to a cold stress at 4 degrees C for 6 hr (SE and UE). Control animals remained at room temperature (SC and UC). Hypothermia was induced in group SE, with mean rectal temperature of 22.0 +/- 2.0 degrees C (+/- S.E.M.). All other groups were normothermic, had similar arterial pO2 and hepatic tryptophan oxygenase levels. Acute hypothermia induced a sloughing of cells from the villi into the lumen of the gut, as indicated by an increased DNA in luminal washings. However, there was an unimpaired 3H-thymidine incorporation into the DNA of the intestinal mucosal cells and those present in lumina washes. Intestinal disaccharidases and alkaline phosphatase were not altered. This suggests that more severe cellular alterations reported earlier in hypothermia may have been caused by associated factors other than a decreased body temperature.
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PMID:Experimental acute hypothermia and intestinal cellular integrity. 67 37

The measurement of lactate dehydrogenase (LDH) release into perfusates after hypothermic storage was found to be a reliable index of ischemic injury of rabbit kidneys. Kidneys were exposed to warm and cold ischemia for varying periods. Each kidney was perfused before and after storage at simple hypothermia with 25 ml of a modified Collins solution. The venous effuent was collected in 5 ml fractions. Total LDH activity was measured in the first fraction after storage and used as a measure of ischemic tissue damage. It was confirmed that increasing the period of cold ischemia result in significant increases in LDH activity. The release of LDH into perfusates was then used to compare kidney damage after preservation with various fluids. With this method, it was not possible to demonstrate any difference in the extent of tissue damage after preservation with sodium-rich vs. potassium-rich perfusion fluid. Addition of steroids, vitamins and essential amino acids did not prevent or reduce tissue damage, estimated in this way. The effects of adding cryoprotectants to the perfusion fluid varied; LDH release following addition of 5% DMSO was significantly greater, and after addition of 5% glycerol smaller than the release after perfusion with a modified Collins solution alone. Stepwise addition of DMSO up to 20% resulted in serious tissue damage with a large LDH release into the perfusate.
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PMID:LDH release into perfusates of preserved kidneys. 78 32

To determine whether perfusion preservation affected the structure and survival of kidney transplants, we correlated clinical and histologic data in 77 kidneys biopsied one hour after transplantation. Twenty-one of 36 perfusion-preserved kidneys had a glomerular capillary lesion suggestive of intravascular coagulation. None of 41 kidneys preserved by hypothermia alone had this lesion. Presence of the lesion did not correlate with donor or recipient characteristics, warm or cold ischemia time, HLA match, percentage of preformed lymphocytotoxic antibody titers or perfusion characteristics. Of 21 transplants with the lesion, nine required nephrectomy by one month, and one-month serum creatinine was less than 2.0 mg per deciliter in only three of the remaining 12 transplants. We conclude that perfusion preservation may cause pathologic changes that may adversely affect kidney-transplant function. The causes of the pathologic process remain unclear.
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PMID:Perfusion nephropathy in human transplants. 79 Jan 84

Renal preservation has contributed to improvements in human cadaver kidney transplantation in terms of viability testing and logistics. Unfortunately, the antigenicity of a kidney has not been reduced by our present preservation methods; consequently, immunologic problems in cadaver kidney transplantation still remain. Simple cold storage is an acceptable method for kidneys subjected to minimal warm ischemia. It can be used where anticipated storage time will not exceed 10 to 15 hours. Pulsatile or nonpulsatile machine perfusion will give better results especially when kidneys have sustained up to 60 minutes warm ischemia. Where there is also a need for storage time longer than 15 hours, perfusion should be used. Cryoprecipitated millipore-filtered plasma remains the most commonly used perfusate. Preservation really begins before the harvesting. Present preservation techniques cannot revive a dying kidney. No single test will determine the degree of viability of a kidney. A systematic multidisciplinary effort is needed to augment our understanding and knowlege about the effect of hypothermia on organs. Hopefully these efforts will result in the development of an organ bank whereby many more kidneys will be available for transplantation.
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PMID:Controversy in organ preservation. 79 Jul 30

Forty infant albino rats were divided into four groups. Group I was exposed 15 minutes daily for one month to a dry ambient temperature of +40 degrees C +/- 1 degree C and group II was exposed to 10 - 20 minutes daily to an ambient temperature of - 10 degrees C +/- 2 degrees C. Groups III and IV served as controls. When they had grown adult the animals of the experimental groups were exposed once to the temperature to which they had been trained. Basal temperature was measured and the temperature curve was recorded for 30 - 60 minutes after removing the animals from the hot or cold environment. Values were compared with those found in the control groups. The statistically processed results show that daily exposure to heat and cold does not influence the basal temperature of adult animals but impairs functional tests and resistance to limit temperature exposure. Thus, compared with controls, animals trained to cold developed a significantly lower hypothermia, whereas the animals trained to heat responded by a temperature rise equalling in height and duration that of controls when they were exposed to +40 degrees C, but displayed a significantly poorer resistance to lethal hyperthermic shock. The paper ends with a discussion of the mechanisms involved in these late effects, which are probably due to the impaired maturation of the pituitary-adrenal system in the neonatal period.
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PMID:Effects of training to heat and cold in the neonatal period on the body temperature response of adult rats. 82 50


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