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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mean skin temperature (Tsk) calculated from seven sites and rectal temperature (Tre) were recorded every minute for a total of 88 man-nights in eight young men sleeping at night in both cold (during the Artic winter) and neutral (laboratory) environments, and were related to the EEG stages of sleep, especially to paradoxical sleep (PS). In the neutral environment, Tre was always above 36 degrees C and Tsk increased during PS. In the cold conditions, during PS, Tsk increased when Tre was high, and decreased when Tre was below 36 degrees C. It was concluded that, although it is not known why a core temperature of about 36 degrees C is the critical point of change in the direction of Tsk variations during PS, the direction in which Tsk will vary during PS is dependent on the core temperature at the time.
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PMID:Skin temperature changes in paradoxical sleep in man in the cold. 22 54

Thermoregulatory responses of six trained swimmers and five runners to cold and heat were evaluated during 30 min of exercise (60% VO2max) while immersed to the neck in 20, 25, 30, and 35 degrees C water. Mean oxygen uptake was similar for both groups during all four trials. Changes in metabolic rate during the 8th to 28th min were significantly greater for the runners in 20 degrees C water, and swimmers in 30 and 35 degrees C water. Heart rates, Tsk, delta Tre, Tb, body heat content, and heat storage were dependent on water temperature. Runners were able to attain higher sweat rates than swimmers in 35 degrees C water. Swimmers had significantly greater tissue conductance values in the 35 degrees C exposure. Swimmers thermoregulated better in 20 degrees C water than runners, possibly due to a larger surface area-to-volume ratio, percentage body fat, subcutaneous fat, or improved vasomotor control. Exercise in the heat was better tolerated by runners. Physical training in water does not improve heat acclimatization to the extent of training in air, but does improve cold tolerance.
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PMID:Thermoregulation in swimmers and runners. 46 28

To determine whether the voluntary contractions of exercise interfere with involuntary shivering contractions, four male subjects were each exposed to a 10 degrees C environment for 60 min of rest followed by either another rest period or 30 min of cycleergometer exercise. On different days exercise was performed at zero load, light load, and moderate load. Each experiment was performed twice, resulting in a minimum of eight experiments for each subject. Esophageal temperature (Tes), eight skin temperatures (Tsk), oxygen uptake (VO2), and the integrated electrical activity from a neck muscle (EMG) were continuously monitored. Pedaling flushed cold blood into the body core, causing Tes to fall. The rate and absolute magnitude of the decrease in Tes was proportional to the intensity of exercise. Thermoregulatory VO2 (attributable to shivering) and EMG were inversely related both to Tsk during rest, prior to any changes in Tes, and to Tes during exercise, when Tsk was constant, once shivering thresholds were surpassed. The slope of the thermoregulatory VO2-to-Tes relation was significantly suppressed by increasing exercise intensity. The slope of the EMG-to-Tes relation was similarly suppressed; since the neck muscles are not involved in the additional acitivity of exercise, we concluded that the graded inhibition of shivering during exercise was of central origin rather than from the rhythmic contractions required to sustain exercise.
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PMID:Thermogenic control during exercise in a cold environment. 51 10

The effect of ambient temperature on the thermosensitivity of preoptic neurones was studied in euthermic golden hamsters. At skin temperatures (Tsk) of 20 degrees C, preoptic units were still responsive to hypothalamic temperatures (Thy) below 10 degrees C, while at Tsk = 36 degrees C these neurones became inactive at Thy = 15 degrees C on the average. These studies suggest that thermoreceptive preoptic neurones, influenced by a high activity of cutaneous cold-receptors, are capable of sensing core temperatures even in deep hibernation.
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PMID:Thermosensitivity of preoptic neurones in a hibernator at high and low ambient temperatures. 56 78

The cutaneous blood flow (mbl), rate of oxygen consumption (Vo2), rectal (Tre) and cutaneous (Tsk) temperatures, and shivering activity were measured in unanthetized male rats during a 2-h exposure to 26, 33, or 5 degrees C 2 wk after selective bilateral hypothalamic microknife cuts. Animals with preoptic-anterior hypothalamic (PO/AH) junction cuts 1.5 or 3.0 mm lateral to the midline, as well as parasagittal cuts which separated connections between the PO/AH and medial forebrain bundle exhibited a higher mbl at 26 degrees C than did sham-operated rats. At 5 degrees C the extended (3.0 mm) PO/AH cuts as well as the parasagittal cuts prevented cutaneous vasoconstriction but had no effect on shivering activity; hence Tre was not maintained. None of the cuts demonstrably impaired thermoregulation in the 33 degrees C environment. These results suggest that different sites in the hypothalamus may separately control cold-induced skin vasoconstriction and shivering activity, as well as heat-induced skin vasodilation. It would seem therefore that the integrity of the PO/AH is indispensable in rats for cold-induced cutaneous vasoconstriction but not for cold thermogenesis, and also not for heat-induced cutaneous vasodilation.
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PMID:Hypothalamic thermoregulatory pathways in the rat. 59 68

The response to local cooling was estimated by the cold hand test (5 degrees C for 2 min) and the cold face test (0 degrees C with 66 km.h-1 wind for 2 min). Heart rate, blood pressure, and skin temperature were measured before, during, and after the tests. The increase in blood pressure (cold hand test) and the fall in Tsk (cold face test) were reduced in trained subjects. Similarly older subjects (53-60 yr of age) responded less to a cold hand test than younger subjects aged 20-40. However, the bradycardia caused by the cold face test was more pronounced in the older subjects. The responses to the cold hand and cold face tests were the same for male and female subjects. During the 2 min after the test, blood pressure and heart rate fell below initial values in the female group but not in the male. It is concluded that, besides adaptation to cold, individual factors such as age, sex, and physical fitness also have a relative importance in the responses to local cooling.
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PMID:Effects of age, sex, and physical fitness on responses to local cooling. 64 81

A study has been conducted on 20 sojourners (SJs) at a high altitude (HA) of 3500 m to evaluate the changes in thermoregulation efficiency (ThE) during acclimatization for 3 weeks, by observing the rate and pattern of rewarming of palm skin temperature (Tsk) after dipping the hand in water of 10 +/- 1 degrees C for 2 min (Tromp's water bath test). The ThE of the SJs was compared to that of 10 acclimatized lowlanders (ALs) staying at the same altitude for about 1 year and 10 high-altitude natives (HANs). In SJ, at sea level (SL), the effect of seasonal variation and ambient temperature on ThE was also studied. The initial Tsk of the palm (29.9 degrees C) was lower at altitude as compared to SL value (32.2 degrees C) in SJs inspite of similar ambient temperature (21 +/- 1 degrees C). There was a prolongation of rewarming time in all the subjects during stay at altitude. The rewarming curve showed a shift towards the right, indicating slower rewarming. The rewarming response of ALs and SJs was comparable at altitude. In HANs, the rewarming at altitude was faster and resembled those of SJs at SL. The rewarming improved in the season following cold months, and at higher ambient temperature in the same season, on the plains. It may be concluded that thermoregulation efficiency of man deteriorates at high altitude, and the peripheral vascular responses to local cold stress do not reach the level attained by natives even after 1 year of acclimatization. General cold acclimatization improves the rewarming response.
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PMID:Effect of altitude acclimatization on thermoregulation efficiency of man. 65 93

Squirrel monkeys (Saimiri sciureus) in a cold environment (10, 0, or -5 degrees C) learned to partially control their chamber air temperature by pulling a chain for 10-s reinforcements of 30 degrees C air. A maximal response rate of 5/min produced an average air temperature (24-27 degrees C), well below their preferred 35 degrees C. Metabolic heat production was elebtaed 0.3-1.0 W/kg. Preoptic cooling (via stereotaxically implanted thermodes) stimulated increased metabolic heat production, with a resultant rise in core temperature. Preoptic warming stimulated reduced heat production and some peripheral vasodilation, resulting in a fall in core tenperature. The metabolic response of all animals was directly related to the skin-to-air temperature difference (Tsk - TA). Usually, mean skin temperature remained essentially unchanges as a result of a steady behavioral response rate. An increase in metabolic heat production was observed in one monkey during preoptic warming. The study demonstrated that even when behavioral thermoregulation is inefficient, it is generally sustained with maximal vigor over long periods. This behavior is then supplemented by appropriate autonomic adjustments when necessary to achieve full regulation of the body temperature.
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PMID:Autonomic thermoregulation in squirrel monkey when behavioral regulation is limited. 81 17

A mathematical model has been developed to anticipate the physiological responses and the thermal state of a naked human under exposure to cold, taking into account his morphological characteristics (skinfold, size, weight) and the environmental conditions (air or water temperature and velocity, barometric pressure and hygrometry). The skinfold conditions the body's thermal conductance and the metabolism depends both on rectal (Tre) and mean skin (Tsk) temperatures. After being tested, this model was used to study the evolution of Tre. It shows the influence of the skinfold which accounts for most of the inter-individual differences. It also permits discussion of survival possibilities during immersion and completes data provided by previously established curves.
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PMID:Mathematical model of man's tolerance to cold using morphological factors. 97 Nov 75

A study has been conducted on 20 sojourners, between the ages of 20-30 years, to evaluate responses of the autonomic nervous system during acclimatization to high altitude. The responses measured consisted of heart rate (HR), blood pressure (BP), oral temperature (Tor), mean skin temperature (Tsk), cold pressor response (CPR), orthostatic tolerance to tilt, and urinary catecholamines. The subjects were tested initially at Delhi (altitude 260 m) and thereafter, on acute induction to an altitude of 3500 m periodically for 3 weeks. For comparison, the same responses were studied on 10 acclimatized lowlanders (AL) who had been staying at the same altitude for more than a year and on 10 high-altitude natives (HAN). The studies showed a rise in HR, BP, Tor, and urinary catecholamines, and a fall in Tsk, CPR, and orthostatic tolerance immediately on arrival at HA, indicating a relative hyperactivity of the sympathetic system. After a stay of 1 week, there was a gradual recovery in all the responses, though sympathetic hyperactivity was still maintained throughout the 3 weeks of stay. In AL also there was a preponderance of sympathetic activity, though of relatively lesser magnitude than that seen in sojourners. In HAN, on the other hand, there was a relative parasympathetic predomination. It has been concluded that in lowlanders it takes more than a year of stay at altitude for complete recovery of autonomic balance.
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PMID:Responses of the autonomic nervous system during acclimatization tp high altitude in man. 98 81


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