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

Age-related alterations in homeostatic mechanisms, as measured by changes in circadian rhythms, have been reported in the literature. The purpose of the present study was to determine if changes in the circadian rhythms of motor activity, body temperature, and body weight occur with age in the long-lived mouse, Peromyscus leucopus, and to determine if the incidence of torpor (hypothermia) was age-dependent. Young and old mice were entrained to an LD 12:12 cycle, and then physiological and behavioral performance was monitored by a data-acquisition system. The major differences between the 6-month and 60-72-month age groups were the following. Significant episodes of torpor occurred in a high percentage of old mice at 0600 hr on consecutive days, but young mice showed no evidence of torpor when food was provided ab libitum. Torpor in young mice was found to occur only during starvation conditions. Old animals phase in and out of torpor over an interval of several days; high-amplitude rhythms and good synchronization of activity and temperature occurred when torpor was expressed, and low-amplitude rhythms, poor synchronization between temperature and activity, and a phase shift of body-weight acrophase occurred on days when torpor was not expressed. Significant changes in acrophase and amplitude occurred between individual animals and days in the old group; no significant change in acrophase and amplitude was observed in the young group. Population-mean cosinor analysis revealed a significant age-related decrease in amplitude and mesor, but no significant change in acrophase was found.
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PMID:Effect of age and torpor on the circadian rhythms of body temperature, activity, and body weight in the mouse (Peromyscus leucopus). 362 26

Prenatal starvation causes pulmonary hypoplasia in newborn guinea pigs, and is associated with postnatal cyanosis, hypothermia, and respiratory failure. To determine the effects of such starvation on ventilation, neonates from litters either fed ad libitum throughout gestation (control) or given 50% rations in the last trimester of pregnancy (starved) were studied at 29 degrees C by plethysmography in 21, 11, and 5% O2. After 15 min (steady-state) in 11% and then 5% O2, 13 of 14 controls (mean = 95 g) sustained increases in weight-specific minute ventilation of 46 and 75% compared to values in air (p less than 0.01), due to increases in respiratory frequency. Seven of 11 starved neonates (mean = 76 g) also sustained increases in respiratory frequency and weight-specific minute ventilation in 11 and 5% O2 similar in magnitude to those of the normal controls, although at higher weight-specific tidal volumes. One abnormal control (85 g) and four starved neonates (mean = 70 g) hyperventilated in air, did not respond to 11% O2, and then hypoventilated in 5% O2 due to a reduced weight-specific tidal volume. Neonates with normal ventilatory patterns did not alter weight-specific minute ventilation in 100% O2 and did not show a biphasic response in acute (1-5 min) exposures to moderate hypoxia, as noted for newborn of other species. Thus, hypoxia identified those starved neonates in which pulmonary immaturity or other starvation-induced pathologies necessitated a maximal ventilatory effect in air. The sustainable hyperventilation among normal guinea pigs during hypoxia emphasizes the precocial development in this species at birth, which may be compromised by intrauterine starvation.
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PMID:Prenatal starvation retards development of the ventilatory response to hypoxia in newborn guinea pigs. 377 4

The overt activity of hepatic carnitine palmitoyltransferase (CPT1) increased during the last day of gestation in the foetus and after prolonged starvation in the newborn kept at 37 degrees C. Its sensitivity to inhibition by malonyl-CoA decreased during the perinatal period studied. Brown fat CPT1 increased under the same experimental conditions. However, its sensitivity to malonyl-CoA remains unchanged. Hypothermia at 24 degrees C decreased in the liver and increased in brown adipose tissue CPT1 activity in response to fasting. Glucose injection at birth decreased CPT1 activity in the liver but did not have any effect in the presence of mannoheptulose. This effect of glucose was non-significant in brown adipose tissue.
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PMID:Regulation of carnitine palmitoyltransferase activity in the liver and brown adipose tissue in the newborn rat: effect of starvation and hypothermia. 396 61

The Eastern pipistrelle (Pipistrellus subflavus) is typical of exceptionally small bats capable of a 30-fold range in aerobic metabolism as they arouse from hypothermia and sustain foraging flight. This report describes their basic lung structure and the extent to which this organ is protected from protein depletion during hibernation. Bats were collected at the beginning (Fall), middle (Winter), and end (Spring) of hibernation from a permanent overwintering cave, and analyzed within several days of capture. Regardless of whether bats were examined in the Fall (average body weight = 6.22 g) or in the Spring (4.58 g) no significant differences existed for total lung volume (237 microliter), alveolar surface area (338 cm2), harmonic mean septal thickness, tau ht (0.221 micron), or membrane diffusing capacity (4.13 microliter O2/sec/mbar). These parameters exceed predictions based on body weights for either season, and resemble published data for another highly active mammalian group, the insectivorous shrews. Both tau ht and the minimal septal thickness of 0.083 micron approach the anatomical limits for thinning of alveolar septa without loss of epithelial continuity. Although both the heart and lungs lost 13% of their fresh weights during hibernation, compared to 25% for the liver, the lung contents of DNA (0.14 mg) and blood-free protein (7.38 mg) were not altered significantly. These small bats possess lungs which are well suited for the high aerobic cost of flight. Those lungs are resistant to hibernation-induced proteolysis, and also resistant to the deterioration of alveolar membranes which occurs in nonhibernators subjected to starvation-induced weight losses of similar magnitude.
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PMID:Pulmonary design in a microchiropteran bat (Pipistrellus subflavus) during hibernation. 399 64

The body temperatures of mature lean and obese C57BL/6J mice were measured just after feeding, during ad libitum access to food, or every 24 h throughout a 3-day fast. Obese mice had body temperatures 1.0-1.4 degrees C lower than lean mice in the postprandial state and during ad libitum feeding. During food deprivation, obese mice became more hypothermic than lean sex-matched controls. A 5 degrees C fall in body temperature was observed in mutant females in the first 24 h of starvation, about twice that seen in any other experimental group. Over the same period the temperature changes of obese males and lean females were similar and both groups had larger hypothermic responses than lean males. The present results indicate that both genotype and gender affect thermoregulation in these mice. Under normal colony room conditions (ad libitum feeding, 23 degrees C) the ob/ob mutation is expressed by lower body temperatures which along with hypoactivity and hyperphagia account for the high rates of energy storage. When food availability is limited, females of both phenotypes display an increased capacity to reduce their maintenance energy requirements by lowering body temperatures. This hypothermia may be responsible for both the increased conservation of body mass seen during starvation and the slightly greater (5%) fat stores observed in female mice.
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PMID:Fed and fasting thermoregulation in ob/ob mice. 406 46

Urinary excretion of the post-translationally modified amino-acid 3-methylhistidine, derived from the contractile proteins actin and myosin, was measured in patients with conditions associated with nitrogen loss. The ratio of 3-methylhistidine:creatinine excretion, a measure of the fractional catabolic rate of myofibrillar protein was increased in severe injury, thyrotoxicosis, neoplastic disease, prednisolone administration, and sometimes Duchenne muscular dystrophy. In myxoedema, osteomalacia, and hypothermia the ratio was decreased; and starvation, elective operations, and rheumatoid arthritis had little effect. Provided that the diet is meat free, measurement of urinary 3-methylhistidine may provide useful information on the cause of protein loss.
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PMID:Clinical usefulness of urinary 3-methylhistidine excretion in indicating muscle protein breakdown. 678 20

The causes of hypothermia in 89 lambs were identified on the basis of history and clinical biochemistry. Excessive heat loss accounted for 24 per cent of the cases, and depressed heat production because of either severe hypoxia during birth, immaturity or starvation accounted for 72 per cent. Exhaustion of energy reserves and hypoglycaemia were marked characteristics of lambs which became hypothermic after 12 hours of age. Most of the lambs were either twins or triplets. The implications of the findings for both the treatment and prevention of hypothermia in newborn lambs are discussed.
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PMID:Causes of hypothermia in 89 lambs. 689 65

The influence of two antidepressants, iproniazid and imipramine, was examined on the antileukemic combination effect of reserpine with 1-gamma-chloropropyl-2-chloromethylpiperidine hydrobromide (CAP-2), mitomycin C, or vinblastine on L1210. While reserpine synergistically increased the life span at the dose of 2.5 mg/kg in combination with these antitumor agents, the mice given reserpine showed considerable reduction of food intake and hypothermia. Iproniazid reduced all these effects of reserpine, while imipramine slightly potentiated hypothermia among these effects of reserpine. Starvation scarcely influenced the effect of the antitumor agents. On the other hand, reserpine also enhanced the antiproliferating effect of CAP-2 against L1210 cells in vitro. Iproniazid did not influence the combined antiproliferating effect of these agents in vitro. These results indicate that iproniazid reduced the antileukemic combination effect of reserpine with antitumor agents through an antireserpic effect such as inhibition of hypothermia. Therefore, it seems likely that the antileukemic combination effect of reserpine is closely related to the marked hypothermia, and only partially related to the direct effect on L1210 cells.
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PMID:Influence of iproniazid on the combination effect of reserpine with antitumor agents on l1210. 715 99

Chickens dying from Eimeria tenella infection revealed four major physiological stresses before death: (1) hypothermia, (2) depletion of carbohydrate stores, (3) metabolic acidosis, and (4) renal tubule-cell dysfunction. These stresses were less pronounced in chickens surviving the infection. Similar stresses could not be demonstrated in pair-feeding trials, in which uninfected chickens were fed only the amount consumed by infected chickens. Prolonged starvation of uninfected chickens only slightly altered the indicators used in assessing the stresses. The variability of previously reported plasma glucose values, in part, may be due to whether the birds tested were those on the verge of death or those that, ultimately, would survive the infection.
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PMID:Physiological basis of Eimeria tenella-induced mortality in individual chickens. 722 21

Hypoglycemia is but one of a number of causes of hypothermia, but is important to keep in mind as a possible precipitating or concurrent event even in those cases in which there are other obvious explanations for decreased body temperature (exposure, alcoholism, starvation, sepsis or hypothyroidism). Hypoglycemia may occur in as many as 40 percent of very cold patients, and be clinically unrecognized because symptoms are masked by the hypothermia itself. Although serum glucose levels are depressed, a cold-induced renal tubular glycosuria may occur. Glucose in the urine, therefore, cannot be used as assurance of hyperglycemia in a hypothermic patient. And, although cold protects against serious end organ damage from hypoglycemia by decreasing tissue metabolic need for glucose, a serum specimen should be drawn for glucose determination in all hypothermic patients and a 50 percent glucose solution immediately given intravenously. If this is not done, serum glucose levels may plummet as the patient is rewarmed and begins to shiver.
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PMID:Hypoglycemia and accidental hypothermia in an alcoholic population. 723 90


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