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PubMed1995

Auditory evoked responses in tropical men during sojourn over the arctic region.

The influence of an arctic environment on auditory evoked responses, both brainstem and cognitive, were evaluated in 10 Indian soldiers. They were first tested in Delhi and then flown to an arctic region where they were tested in the first week and again in the eighth week of their stay. Two migrants from Moscow, their usual place of residence, and six natives, born and brought up in the arctic, were also tested for comparison. The Indians, on their return to India, were tested again. The auditory evoked responses were recorded using the Nicolet (USA) Compact 4 Instrument. The Indians showed a delay in all the waves of the auditory brainstem response (ABR) during their induction in the arctic and these persisted even on their return to India whereas the migrants and the natives had relatively higher ABR latency values.

Acclimatization↗
PubMed1993

Changes in immunohistochemical distribution of cytochrome MC-P-448 in the rat liver during acclimation to cold.

Immunohistochemical localization of cytochrome MC-P-448 (form of cytochrome P-450 induced by methylcholanthrene) in rat hepatic lobule and the changes in their distribution pattern in response to cold exposure at 4 degrees C were investigated. The distribution of hepatocytes expressing immunoreactivity to cytochrome MC-P-448 was demonstrated with rabbit anti-MC-P-448 serum using a microphotomeasurment system P1 (Nikon). A duration of cold exposure for 1, 2, 3 or 4 weeks at 4 degrees C was applied to study the effect of cold adaptation of cytochrome MC-P-448. In control rats housed at 24 degrees C, hepatocytes showing high immunoreactivity to cytochrome MC-P-448 were located in the centrilobular areas of the hepatic lobules, whereas they disappeared markedly in the 4-week cold-exposed rats. In 1-week and 2-week cold-exposed rats, only a slight decrease in the expression of MC-P-448 positive hepatocytes was observed. These changes were clearly seen by visual inspection of the distribution topography as determined by a microphotomeasurement technique. In conclusion, cytochrome MC-P-448 forms which were predominantly located in centrilobular areas in the hepatic lobule decreased in 4-week cold-exposed rats. This was in contrast to our early report which showed an increasing tendency of cytochrome PB-P-450 forms in 4-week cold-exposed rats.

Acclimatization↗
PubMed1993

Effect of local cooling on skin temperature and blood flow of men in Antarctica.

Alterations to the finger skin temperature (Tsk) and blood flow (FBF) before and after cold immersion on exposure to an Antarctic environment for 8 weeks were studied in 64 subjects. There was a significant fall in Tsk and increase in finger blood flow after 1 week of Antarctic exposure. The Tsk did not further change even after 8 weeks of stay in Antarctica but a significant increase in FBF was obtained after 8 weeks. The cold immersion test was performed at non-Antarctic and Antarctic conditions by immersing the hand for 2 min in 0-4 degrees C cold water. In the non-Antarctic environment the Tsk and FBF dropped significantly (P < 0.001) indicating a vasoconstriction response. Interestingly after 8 weeks of stay in Antarctic conditions, the skin temperature dropped (P < 0.001) but the cold induced fall in FBF was inhibited. Based on these observations it may be hypothesized that continuous cold exposure in Antarctica results in vasodilatation, which overrides the stronger vasoactive response of acute cold exposure and thus prevents cold injuries.

Acclimatization↗
PubMed1994

Different stability of posttranslationally modified brain microtubules isolated from cold-temperate fish.

Microtubule proteins were isolated by a temperature-dependent assembly-disassembly method from brain tissue of for cold-temperature fish; one fresh water fish (Oncorhynchus mykiss), and three marine fish (Labrus berggylta, Zoarces viviparus and Gadus morhua). The alpha-tubulins from all four fish species were acetylated. The alpha-tubulins from the marine fish were composed of a mixture of tyrosinated and detyrosinated tubulin, while the fresh water fish tubulin only reacted with an antibody against detyrosinated tubulin. The isolated microtubules had a similar MAP composition. A 400 kD protein and a MAP2-like protein were found, but MAP1 was missing. All microtubules disassembled upon cooling to 0 degrees C. In spite of these common characteristics, the assembly of microtubules from Labrus berggylta was inhibited by colchicine and calcium, in contrast to the assembly of microtubules from Oncorhynchus mykiss and Zoarces viviparus. For the latter, colchicine was not completely inhibitory even at a concentration as high as 1 mM, and calcium induced the formation of both loosely and densely coiled ribbons. The effects of calcium and colchicine on microtubules from Oncorhynchus mykiss and Zoarces viviparus were modulated by either fish or cow MAPs, indicating that the effects are due to intrinsic properties of the fish tubulins and not the MAPs. In view of these findings, our results suggest that there is no correlation between colchicine sensitivity, inability of calcium to inhibit microtubule assembly, and acetylation and detyrosination.

Acetylation↗
PubMed1993

Cryoprotective properties of water in the Earth cryolithosphere and its role in exobiology.

In permanently frozen rocks, water occurs in all the three phases and plays a dual role from the biological point of view. About 93-98% of it is in the solid state. This, alongside with negative temperatures, contributes to cell cryoconservation. The remaining 2-7% is in the unfrozen state and represents thin films enveloping organic-mineral particles. These films play the role of cryoprotectors against cell damage by ice crystals during geologically significant time. Electron microscope examinations of prokaryotes revealed the well preserved outer cell structures, specifically strong envelopes and capsules. The cells are resistant to water phase transitions through 0 degrees C, i.e. to the freezing-thawing stress. The exobiological implication of this phenomenon is determined by the fact that the Earth permafrost at first approximation can he considered as a model of e.g. the Mars one. The latter protects the cells against radiation and simultaneously serves as a cryoconservant. However, most important is the possible presence of unfrozen (= liquid) water as prerequisite for the development of microbial life forms.

Cold Climate↗
PubMed1993

The iceman.

Explore the source record for details and available documents.

Adult↗
PubMed1989

Changes in seasonal mortalities with improvement in home heating in England and Wales from 1964 to 1984.

Changes in summer (July-September) and winter (January-March) mortalities of people aged 70-74 in England and Wales from 1964 to 1984 were compared with possible causal factors. Summer mortalities were little affected by annual temperature or influenza epidemics and fell from 1972-1975 for all causes, coronary and respiratory causes, while cerebrovascular mortality fell more rapidly from that time. Cigarette consumption also fell from 1972-1975; falling consumptions of total fat from 1970 and saturated fat from 1972-1975 probably also contributed to the fall in arterial deaths, and likewise falls in prescription rates for tranquillisers and sedatives from 1976-1978 to the fall in respiratory deaths. From 1964 to 1984 use of central heating increased from 13% to 69% of households, domestic fuel consumption increased, and excess mortality in winter from respiratory disease declined by 69%, even relative to summer mortality and when adjusted for varying coldness of winters. The improvement was partly explained by a decline in influenza epidemics. By contrast, excess mortalities in winter from coronary and cerebrovascular disease, although rising in some early influenza epidemics, did not fall significantly as home heating improved. These thrombotic deaths together accounted for 56% of the total excess winter mortality by 1984. The findings support other indications that most of the excess mortality from arterial thrombosis in winter in England and Wales is due to brief excursions outdoors rather than to low indoor temperatures.

Aged↗
PubMed1989

Effects of cold exposure on cyclic AMP concentration in plasma, liver, and brown and white adipose tissues in cold-acclimated rats.

Effects of acute cold exposure on plasma energy substrates and tissue 3',5'-adenosine monophosphate (cAMP) were analyzed in intact rats, to define an involvement of the nucleotide in nonshivering thermogenesis (NST) and resultant cold acclimation. After an acute cold exposure to -5 degrees C, the plasma glucose level increased gradually in warm-kept control rats (C) while it decreased significantly in cold-acclimated rats (CA). However, it was increased considerably by an extreme cold exposure to -15 degrees C in both C and CA. By contrast, plasma levels of free fatty acids (FFA) increased immediately after cold exposure and the release lasted during the period of exposure especially in C. The cold exposure also increased plasma cAMP concentration but no concomitant increase was found in the liver. In both brown (IBAT) and white (WAT) adipose tissues the nucleotide concentration showed a stepwise decrease. The observed correlation between lipolysis and plasma cAMP response after cold exposure suggests an involvement of the adenylate cyclase-cAMP system in NST via lipid metabolism, at least, in the early stages of cold acclimation.

Acclimatization↗
PubMed1979

Amino acids in a carbonaceous chondrite from Antarctica.

A carbonaceous chondrite from the Antarctic, referred to as the Allan Hills meteorite 77306, appears to be free from terrestrial organic contamination. The presence of both protein and non-protein amino acids and an equal abundance of D- and L-enantiomers of amino acids, is testimony to the extraterrestrial nature of these compounds.

Amino Acids↗
PubMed1986

Temperature dependence of neurotransmitter release in the antarctic fish Pagothenia borchgrevinki.

The quantal contents of endplate potentials from extraocular muscles of an antarctic fish Pagothenia borchgrevinki were measured over a range of temperatures. Quantal release was maximal at about 5 degrees C but showed little dependence on temperature between -2 degrees C and 10 degrees C. Above 10 degrees C quantal content declined until release ceased about 18 degrees C. In view of the fact that the ambient temperature at which these fish live is constant at -1.9 degrees C, the results suggest that Pagothenia borchgrevinki is only partially adapted to its environment despite 25 million years acclimatization.

Animals↗
PubMed1985

Physiological adaptations and activity recorded at a polar base.

Physiological parameters and activity were recorded monthly on 19 men wintering at a polar base. A comparison was made between those in their first Antarctic winter (Group A, n = 13) and those in their second consecutive Antarctic winter (Group B, n = 6). Group A were more active (p less than 0.001) and spent more time outside (p less than 0.001) during the summer months than during the darker and colder winter period. Combined data showed no correlation between total activity and meteorological conditions, but a clear (p less than 0.001) negative correlation with time spent outside and wind speed. In the first part of the year group A became fitter (as shown by a lower heart rate at a VO2 1.51 min-1), increased basal oxygen uptake under standard conditions and put on body and fat mass. These changes were not demonstrated in group B living and working under identical conditions. Lean body mass of both groups rose throughout the year (A, p less than 0.001; B, p less than 0.05). These data suggested that the changes in physiological parameters in group A were in response to the life style and activity of a polar base, rather than to the Antarctic climate per se.

Adaptation, Physiological↗
PubMed1996

Energy intake and utilisation by nursing bearded seal (Erignathus barbatus) pups from Svalbard, Norway.

In this study we measure energy intake via milk in nursing bearded seal (Erignathus barbatus) pups and determine how this energy is allocated into metabolism and storage of new tissues. This was accomplished using longitudinal mass gain records and the doubly labelled water technique on nursing pups in combination with cross-sectional data on changes in milk composition from bearded seal mothers. The pups (n = 3) were all less than a week old at the start of the experiments. Pups gained 3.3 +/- 0.4 kg.day-1 of which 50% was fat, 14% protein and 36% water. Average daily water influx for the pups was 69.5 +/- 9.0 ml.kg-1. day-1. Average CO2 production during the study period was 0.99 +/- 0.10 ml.g-1.h-1, which corresponds to a field metabolic rate of 642 +/- 67 kJ.kg-1. day-1, or 6.0 +/- 0.5 times the predicted basal metabolic rate according to Kleiber (1975). The pups drank an average of 7.6 +/- 0.5 kg of milk daily. This corresponds to a daily energy intake of 154 +/- 8 MJ, 47 +/- 14% of which was stored as new body tissue. Despite this high energy intake bearded seal pups do not get as fat as do other nursing phocids. This is in part due to their larger body size but also due to their very active aquatic lifestyle and the lower and more consistent fat content of the milk compared to other phocid species. Bearded seal mothers forage during lactation and may also be involved in teaching their pups to feed independently. All these data suggest that the lactation strategy of bearded seals differs from the phocid norm.

Animals↗