Human physiological responses to cold exposure: Acute responses and acclimatization to prolonged exposure

This experiment investigated the physiological responses of Merino wethers (n = 12) to prolonged high heat and humidity similar to that experienced during long haul, live export voyages from Australia to the Middle East. Merino wethers were randomly assigned to individual pens in rooms with a controlled environment, and exposed to gradually increasing temperatures, and two exposures of 3–4 days of sustained high heat and humidity, up to a maximum of 31°C wet bulb temperature (37°C dry bulb and 67% relative humidity). There was 1 day at thermoneutral temperatures separating the heat exposures. The core temperatures and respiratory rates of Merino wethers increased during both heat exposures, with open-mouthed panting observed during both exposures. Plasma partial pressure carbon dioxide (pCO2) and bicarbonate concentration (HCO3–) decreased, and plasma pH increased during the second heat exposure. Both pCO2 and HCO3– returned to normal immediately following the heat exposures. Feed intake was maintained during the heat exposures. There were no large alterations in blood electrolyte concentrations attributable to the effects of the heat. The results show that Merino wethers experienced significant physiological changes during exposure to prolonged and continuous high heat and humidity, but maintained most aspects of homeostasis despite being hyperthermic and recovered quickly when conditions returned to thermoneutral.

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Physiological Responses of Rainbow Trout (Oncorhynchus mykiss) to Prolonged Exposure to Soft Water

Physiological Zoology ◽

10.1086/physzool.69.6.30164267 ◽

1996 ◽

Vol 69 (6) ◽

pp. 1419-1441 ◽

Cited By ~ 16

Author(s):

S. F. Perry ◽

S. G. Reid ◽

E. Wankiewicz ◽

V. Iyer ◽

K. M. Gilmour

Keyword(s):

Rainbow Trout ◽

Oncorhynchus Mykiss ◽

Prolonged Exposure ◽

Physiological Responses ◽

Soft Water ◽

Rainbow Trout Oncorhynchus Mykiss

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Acclimatization of Scottish Blackface sheep to cold. 2. Skin temperature, heart rate, respiration rate, shivering intensity and skinfold thickness

Animal Production ◽

10.1017/s0003356100025903 ◽

1968 ◽

Vol 10 (1) ◽

pp. 17-35 ◽

Cited By ~ 20

Author(s):

A. R. Sykes ◽

J. Slee

Keyword(s):

Heart Rate ◽

Skin Temperature ◽

Cold Exposure ◽

Chronic Exposure ◽

Physiological Responses ◽

Skinfold Thickness ◽

Acute Exposure ◽

Heart Rates ◽

Ambient Temperatures ◽

Acute Cold Exposure

Closely shorn Scottish Blackface female sheep aged 9–14 months, half on high plane and half on low plane nutrition, were subjected, in climate chambers, to two short acute cold exposures down to −20°C. The acute exposures were separated by two weeks chronic exposure to a moderately subcriticai temperature (+8°C) or to a thermoneutral temperature (+30°C). Most of the sheep showed a greater resistance to body cooling at the second acute exposure (Slee and Sykes, 1967). This increased resistance to hypothermia, defined as acclimatization, was apparently influenced more by acute than by chronic cold exposure. The present paper deals with changes in skin temperature, heart rate, shivering intensity and skinfold thickness which also resulted from cold exposure, and accompanied acclimatization.After acute cold exposure followed by chronic exposure to +8°C the following changes in these parameters were observed:1. Extremity skin temperatures and heart rates were consistently increased at thermoneutral ambient temperatures.2. Vasoconstriction of the extremities and increased heart rate, both of which normally occur during the early stages of cold exposure, were delayed.3. Heart rates at sub-zero ambient temperatures were increased.4. Cold-induced vasodilatation at sub-zero ambient temperatures was increased.After acute cold treatment alone the intensity of shivering during the second acute exposure was reduced. Also the onset of foot vasoconstriction was slightly delayed.A highly significant relationship was observed between shivering intensity and heart rate during cold exposure.Plane of nutrition had less effect on the physiological responses to cooling than did previous cold experience.It was suggested in discussion that the physiological responses associated with acclimatization were: elevated basal metabolic rate, delayed onset of vasoconstriction and delayed metabolic response to cold, and consequent lowering of the critical temperature. Summit metabolism was also increased and shivering intensity reduced during acute cold exposure. Some of these responses could have resulted from either acute or chronic moderate cold exposure. However their persistence, once induced, appeared to depend upon continued exposure to moderate cold.

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A methyltransferase required for proper timing of the vernalization response in Arabidopsis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1423585112 ◽

2015 ◽

Vol 112 (7) ◽

pp. 2269-2274 ◽

Cited By ~ 14

Author(s):

Joohyun Lee ◽

Jae-Young Yun ◽

Wei Zhao ◽

Wen-Hui Shen ◽

Richard M. Amasino

Keyword(s):

Cold Exposure ◽

Prolonged Exposure ◽

Cold Treatment ◽

Epigenetic Silencing ◽

Negative Regulator ◽

Gene Encoding ◽

Polycomb Repressive Complex 2 ◽

Proper Timing ◽

Process Loss ◽

Epigenetic Repression

Prolonged exposure to winter cold enables flowering in many plant species through a process called vernalization. In Arabidopsis, vernalization results from the epigenetic silencing of the floral repressor FLOWERING LOCUS C (FLC) via a Polycomb Repressive Complex 2 (PRC2)-mediated increase in the density of the epigenetic silencing mark H3K27me3 at FLC chromatin. During cold exposure, a gene encoding a unique, cold-specific PRC2 component, VERNALIZATION INSENSITIVE 3 (VIN3), which is necessary for PRC2-mediated silencing of FLC, is induced. Here we show that SET DOMAIN GROUP 7 (SDG7) is required for proper timing of VIN3 induction and of the vernalization process. Loss of SDG7 results in a vernalization-hypersensitive phenotype, as well as more rapid cold-mediated up-regulation of VIN3. In the absence of cold, loss of SDG7 results in elevated levels of long noncoding RNAs, which are thought to participate in epigenetic repression of FLC. Furthermore, loss of SDG7 results in increased H3K27me3 deposition on FLC chromatin in the absence of cold exposure and enhanced H3K27me3 spreading during cold treatment. Thus, SDG7 is a negative regulator of vernalization, and loss of SDG7 creates a partially vernalized state without cold exposure.

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Correction: Physiological responses to acute cold exposure in young lean men

PLoS ONE ◽

10.1371/journal.pone.0200865 ◽

2018 ◽

Vol 13 (7) ◽

pp. e0200865 ◽

Cited By ~ 3

Author(s):

Francisco M. Acosta ◽

Borja Martinez-Tellez ◽

Guillermo Sanchez-Delgado ◽

Juan M. A. Alcantara ◽

Pedro Acosta-Manzano ◽

...

Keyword(s):

Cold Exposure ◽

Physiological Responses ◽

Acute Cold Exposure

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Survival of Clinical and Poultry-Derived Isolates of Campylobacter jejuni at a Low Temperature (4°C)

Applied and Environmental Microbiology ◽

10.1128/aem.67.9.4186-4191.2001 ◽

2001 ◽

Vol 67 (9) ◽

pp. 4186-4191 ◽

Cited By ~ 87

Author(s):

Kam Fai Chan ◽

Huyen Le Tran ◽

R. Y. Kanenaka ◽

S. Kathariou

Keyword(s):

Low Temperature ◽

Campylobacter Jejuni ◽

Cold Exposure ◽

Low Temperatures ◽

Prolonged Exposure ◽

Dependent Manner ◽

Temperature Requirements ◽

Bacterial Gastroenteritis ◽

Different Strains ◽

Strain Dependent

ABSTRACT Campylobacter jejuni is a leading cause of bacterial gastroenteritis in humans, and contamination of poultry has been implicated in illness. The bacteria are fastidious in terms of their temperature requirements, being unable to grow below ca. 31°C, but have been found to be physiologically active at lower temperatures and to tolerate exposure to low temperatures in a strain-dependent manner. In this study, 19 field isolates of C. jejuni (10 of clinical and 9 of poultry origin) were studied for their ability to tolerate prolonged exposure to low temperature (4°C). Although substantial variability was found among different strains, clinical isolates tended to be significantly more likely to remain viable following cold exposure than poultry-derived strains. In contrast, the relative degree of tolerance of the bacteria to freezing at −20°C and freeze-thawing was strain specific but independent of strain source (poultry versus clinical) and degree of cold (4°C) tolerance.

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Exertional fatigue and cold exposure: mechanisms of hiker's hypothermia

Applied Physiology Nutrition and Metabolism ◽

10.1139/h07-041 ◽

2007 ◽

Vol 32 (4) ◽

pp. 793-798 ◽

Cited By ~ 7

Author(s):

Andrew J. Young ◽

John W. Castellani

Keyword(s):

Heat Loss ◽

Cold Exposure ◽

Physiological Responses ◽

Physical Exertion ◽

The Body ◽

Cold Weather ◽

Behavioral Strategies ◽

Peripheral Vasoconstriction ◽

Vasoconstrictor Response ◽

Body Heat

Participants in prolonged, physically demanding activities in cold weather are at risk of a condition known as “hiker's hypothermia”. During exposure to cold weather, the increased gradient favoring body heat loss to the environment must be balanced by physiological responses, clothing, and behavioral strategies that conserve body heat stores, or else body temperature will decline. The primary human physiological responses elicited by cold exposure are shivering and peripheral vasoconstriction. Shivering increases thermogenesis and replaces body heat losses, while peripheral vasoconstriction improves thermal insulation of the body and retards the rate of heat loss. A body of scientific literature supports the concept that prolonged and (or) repeated cold exposure, fatigue induced by sustained physical exertion, or both together can impair shivering and vasoconstrictor response to cold. The mechanisms accounting for this thermoregulatory impairment are not clear, but the possibility that changes in blood glucose availability or sympathetic responsiveness to cold due to exertion and fatigue merit further research.

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Influences of age and gender on human thermoregulatory responses to cold exposures

Journal of Applied Physiology ◽

10.1152/jappl.1985.58.1.180 ◽

1985 ◽

Vol 58 (1) ◽

pp. 180-186 ◽

Cited By ~ 63

Author(s):

J. A. Wagner ◽

S. M. Horvath

Keyword(s):

Older Women ◽

Body Fat ◽

Young Women ◽

Cold Exposure ◽

Physiological Responses ◽

Metabolic Cost ◽

Older Men ◽

Age And Gender ◽

Younger Women ◽

And Gender

To delineate age- and gender-related differences in physiological responses to cold exposure, men and women between the ages of 20 and 29 yr and 51 and 72 yr, wearing minimal clothing, were exposed at rest for 2 h to 28, 20, 15, and 10 degrees C room temperatures with 40% relative humidity. During the coldest exposure, the rates of increase in metabolic rate (W X m-2 or ml X kg lean body mass-1 X min-1 were similar for all groups. However, older women (n = 7) may have benefited from a larger (P less than 0.05) early metabolic (M) increase (40% within 15 min) than young men (18%) (n = 10), young women (5%) (n = 10), or older men (5%) (n = 10). A similar rapid M response in older women occurred during the 15 degrees C exposure. During all cold exposures, older women maintained constant rectal temperature (Tre) and young women maintained Tre only during the 20 degrees C exposures, whereas Tre of the men declined during all cold exposures (P less than 0.01). Changes in Tre and mean skin temperature (Ts) during cold exposure were largely related to body fat, although age and surface area/mass modified the changes in men. The data suggest that older men are more susceptible to cold ambients than younger people, since they did not prevent a further decline in their initially relatively low Tre. Despite greater insulation from body fat, the older women maintained a constant Tre at greater metabolic cost than men or younger women.

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