Variation in the susceptibility to cold injury in Indians

The peripheral vascular responses during local cold stress, (heat output from the hands and cold induced vasodilatation-CIVD response) were studied on 4 groups (10 each) of Indian population, viz., South-Indians, North-Indians, Gurkhas and High Altitude Natives (HAN) of 3,500m. The parameters were recorded at Delhi, and at 3,500 m in thermoneutral laboratory (25–28°C). The sea level readings of HAN were taken after 3 weeks of their stay at Delhi; and that of lowlanders at 3,500 m were taken after 3 weeks of their sojourn. The results show that the heat output and CIVD were highest in HAN, and lowest in the South-Indians. The responses of the other two groups were similar in nature and were better than that of South-Indians. Based on an earlier study which has shown that individuals with higher heat output and CIVD are better protected against the occurrence of cold injuries, it can be suggested that HAN are most resistant and the South-Indians are highly susceptible to the occurrence of cold injuries.     

Respiration of juvenile Arctic cod (Boreogadus saida): effects of acclimation,temperature, and food intake

Oxygen consumption (VO₂) of juvenile Arctic cod (Boreogadus saida) was investigated at low tempera tures (six temperatures; range -0.5 to 2.7°C). Small (mean wt. 6–8 g) and large (mean wt. 14 g) fish were acclimated, or adjusted to a constant temperature (0.4°C), for 5 months and then tested for metabolic cold adaptation (elevated metabolic rates in polar fishes). Short-term (2 weeks) acclimated fish showed elevated VO₂ similar to previously established values for polar fishes, but there was no such evidence after longterm acclimation. Long-term acclimation caused VO₂ values to drop significantly (from 86.0 to 46.5 mg O₂·kg^–1·h^–1, at 0.4°C), which showed that metabolic cold adaptation was a phenomenon caused by insufficien: acclimation time for fish in respiration experiments. We also measured the effects of temperature and feeding on VO₂. A temperature increase of 2.3°C resulted in relatively large increases in VO₂ for both longand short-term acclimated fish (Q₁₀ = 6.7 and 7.1, respectively), which suggests that metabolic processes are strongly influenced by temperature when it is close to zero. Feeding individuals to satiation caused significant increases in VO₂ above pre-fed values (34–60% within 1–2 days after feeding). Respiration budgets of starved and fed Arctic cod at ambient temperatures in Resolute Bay N.W.T., Canada, were used to model annual respiration costs and potential weight loss. Low respiration costs for Arctic cod at ambient temperatures result in high growth efficiency during periods of feeding and low weight loss during periods of starvation.     

Effects of cold adaptation and noradrenaline on thermosensitivity of rat hypothalamic neurons studiedin vitro

The experiments performed on rat brain slices have shown that cold adaptation of an animal influences the thermosensitivity of hypothalamic medial preoptical neurons. The adaptation is followed by an increase in the proportion of 38–41°C-thermoresponsive neurons and by a decrease in the proportion of 35–38°C-thermoresponsive units. In control animals, noradrenaline (NA) increased the responses of hypothalamic neurons to the action of 35–38°C temperature and decreased them to the action of 38–41°C temperature. Cold adaptation prevented the effects of NA on neuronal thermosensitivity, which suggests that their NA sensitivity is modified by cold adaptation.Neirofiziologiya/Neurophysiology, Vol. 26, No. 3, pp. 171–176, May–June, 1994.     

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° 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.     

The effect of repeated mild cold water immersions on the adaptation of the vasomotor responses

There are several types of cold adaptation based on the alteration of thermoregulatory response. It has been thought that the temperature of repeated cold exposures during the adaptation period is one of the factors affecting the type of cold adaptation developed. This study tested the hypothesis that repeated mild cold immersions would induce an insulative cold adaptation but would not alter the metabolic response. Seven healthy male participants were immersed to their xiphoid process level repeatedly in 26°C water for 60 min, 3 days every week, for 4 weeks. During the first and last exposure of this cold acclimation period, the participants underwent body immersion tests measuring their thermoregulatory responses to cold. Separately, they conducted finger immersion into 5°C water for 30 min to assess their cold-induced vasodilation (CIVD) response before and after cold acclimation. During the immersion to xiphoid process, participants showed significantly lower mean skin temperature and skin blood flow in the forearm post-acclimation, while no adaptation was observed in the metabolic response. Additionally, blunted CIVD responses were observed after cold acclimation. From these results, it was considered that the participants showed an insulative-type of cold acclimation after the repeated mild cold immersions. The major finding of this study was the acceptance of the hypothesis that repeated mild cold immersion was sufficient to induce insulative cold adaptation but did not alter the metabolic response. It is suggested that the adaptation in the thermoregulatory response is specific to the response which is repeatedly stimulated during the adaptation process.     

EEG patterns and body temperatures in man during sleep in arctic winter nights

Two Caucasian males, aged 19 and 22, slept at night in sleeping bags (9.0 clo) in an unheated tent at ambient temperatures between –25 and –35°C in the Arctic. Electroencephalographic (EEG) sleep studies were conducted for two baseline nights (19–21°C), 10 cold exposure nights and 2 recovery nights (19–21°C). Rectal and skin temperatures, and heart rates were also recorded. The subjects suffered disturbances in sleep patterns involving an insomnia composed of an increased wakefulness, a decrease in slow wave sleep and a deprivation in rapid eye movement (REM) sleep. Dissimilarities appeared between the subjects which may be related to differences in thermoregulatory responses.     

Seasonal changes in sea-water tolerance of Arctic charr (Salvelinus alpinus)

Summary Groups of Arctic charr,Salvelinus alpinus, which had been acclimated to water with a salinity of 7 g·l^–1 and natural temperature and photoperiod, were exposed to water with different salinities and temperatures in June, September and February. At a salinity of 15 g·l^–1, plasma osmolality, plasma Na⁺, Cl^–, Mg²⁺ concentrations and the activity of gill Na-K-ATPase were stable, irrespective of temperature and season. In June, the charr were able to regulate blood plasma ionic levels within narrow limits when exposed to a salinity of 34 g·l^–1 (sea water) and a temperature of 8°C. The hypo-osmoregulatory capacity was less, but sufficient if the temperature was only 1°C during the seawater exposure. At the start of the experiment, the gill Na-K-ATPase activity was significantly higher in June than corresponding enzyme activities in September and February. Furthermore, an increase in gill Na-K-ATPase activity during the seawater exposure (8°C) was seen in June. Irrespective of ambient temperature and salinity, no fish died during the June experiments. In September and February, exposure to sea water produced marked increases in plasma osmolality and plasma ion concentrations. There were no changes in gill Na-K-ATPase activity. Consequently, the fish became dehydrated and were moribund after a short period of seawater exposure. Highest mortality was recorded when charr were exposed to winter sea conditions (34 g·l^–1 and 1°C) in February. The results indicate that an increase in daylength induce a hypo-osmoregulatory capacity in the Arctic charr during summer. In fall and winter, however, reduced daylength are accompanied by poor hypo-osmoregulatory capacity. This leads to high mortality as a result of increased electrolyte levels and dehydration.     

Induction of freezing tolerance in alfalfa cell suspension cultures

The effects of ABA, 2,4-D, kinetin and cold exposure on the cold hardiness of Medicago sativa L. cell suspensions were investigated. Cultures treated with 5×10^–5 M ABA at 2°C for 4 weeks in the absence of kinetin showed a 50% survival after freezing to –12.5°C, whereas cultures grown at 25°C under normal conditions tolerated freezing to only –3°C. The optimum ABA treatment of 5×10^–5 M for 4 weeks was effective only in combination with cold exposure. Of six cell lines tested, all showed different degrees of induced cold hardiness. The results suggest that ABA alone cannot induce freezing tolerance on alfalfa cell suspension cultures and that the deletion of kinetin and combination of low temperature and ABA is critical for the induction of cold hardiness in alfalfa cell suspension cultures.Abbreviations ABA abscisic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - LT₅₀ 50% killing temperature     

Circadian and circannual variations in growth and cold resistance of warm acclimated rats and their relationship with the geomagnetic activity

In winter, summer, spring and fall, groups of 200 g Sprague Dawley male rats were kept for 14 days at constant Ta 28°C±°C and LD 12:12(07:00–19:00 h). They were fed a laboratory chow (P) or a semi-purified diet (H). They were weighed at 0, 7 and 14 days. Cold resistance was determined by the fall in rectal temperature during 4 hours of restrained exposure to +1°C either in the morning (09:00 – 13:00 h) or in the afternoon (14:00 – 18:00 h). Rats fed the H diet could better tolerate cold exposure in the morning than in the afternoon, whereas the chow-fed rats were more vulnerable and became severely hypothermic both in morning and afternoon. The greater morning resistance provided by the H diet was evident in summer and winter but not in spring or fall. With both diets, cold resistance as well as growth decreased during spring and fall. Frozen storage of the diets and the water for use during other seasons showed that the nutrients per se were not a factor in the observed seasonal cycle. Although humidity in the 28°C room varied between a minimum of 26.5% in April to a maximum of 44.3% in August, it was not a statistically significant factor in the growth cycle. Arguments are presented to rule out relative humidity as a significant factor in the seasonal variation in the degree of cold resistance. A significant correlation was found for growth and cold resistance with geomagnetic activity.NRCC # 17310     

Cold-induced vasodilation and vasoconstriction in the finger of tropical and temperate indigenes

While heat acclimatization reflects the development of heat tolerance, it may weaken an ability to tolerate cold. The purpose of this study was to explore cold-induced vasodilation (CIVD) responses in the finger of tropical indigenes during finger cold immersion, along with temperate indigenes. Thirteen tropical male indigenes (subjects born and raised in the tropics) and 11 temperate male indigenes (subjects born and raised in Japan and China) participated. Subjects immersed their middle finger at 4.3±0.8 °C water for 30 min. Rectal temperature, skin temperatures, finger skin blood flow, blood pressure and subjective sensations were recorded during the test. The results showed that: (1) the tropical group demonstrated a lower minimum (T_min), maximum (T_max) and mean finger temperature (T_mean) compared to those of the temperate group (P<0.05); (2) seven tropical indigenes demonstrated a late-plateau type of CIVD pattern, which is characterized by a pronounced 1st vasoconstriction and a single CIVD with a faint and weak 2nd vasoconstriction, whereas no temperate indigene demonstrated the late-plateau type; and (3) the hand temperature at the end of finger immersion was 3 °C lower in the tropical than the temperate group (P<0.05). These results indicate that tropical indigenes have less active responses of arterio-venous anastomoses in the finger and weaker vasoconstrictions after the first CIVD response during finger cold immersion, which can be considered as being more vulnerable to cold injury of the periphery in severe cold.     

Rapid cold hardening in the olive fruit fly Bactrocera oleae under laboratory and field conditions

A rapid cold hardening response was studied in females and males of the olive fruit fly Bactrocera (Dacus) oleae. When laboratory-reared females and males were transferred and maintained from the rearing temperature of 24 °C for 2 h to –6.5 °C approximately 5% survived. However, conditioning of both females and males for 2 h at various temperatures from 0 to 10 °C before their exposure for 2 h to –6.5 °C increased survival to 80 to 92%. A similar rapid cold hardening response in both females and males was also induced through gradual cooling of the flies at a rate of approximately 0.4 °C per min. The rapid increase in cold tolerance after prior conditioning of the flies to low temperatures, was rapidly lost when they returned to a higher temperature of 24 °C. In the field, in late February and early March, females and males were capable of a rapid cold hardening response. After exposure to the critical temperature they suffered a high mortality when tested in the afternoon and low mortality early in the morning on consecutive days, probably because of differences in the prevailing field temperatures a few hours before testing. This plasticity of cold tolerance gained through rapid cold hardening may allow the flies to survive during periods of the year with great fluctuation in circadian temperatures.     

Induction of adult diapause in Pyrrhocoris apterus L. by short cold exposure

Summary The ripening of ovaries in the females of Pyrrhocoris apterus can be inhibited not only by short-day photoperiod but also by cold shocks during the first week of the adult life.Ovaries in a part of the females are prevented from ripening by transferring the bugs from 25° C and long-day photoperiod to substantially lower temperatures for 2 (or 4) days. The oviposition is inhibited at least for 3 weeks after the return to original conditions favourable for reproduction. This effect is achieved when cold treatment is combined either with darkness or with long day. A difference between 2 and 4 days of chilling was not recorded. The effect of cold exposure (evaluated in our experiments by the proportion of mature and immature females) depends on the temperature of the cold exposure and on the age of females at the time of transfer to cold. The incidence of immature females was higher when lower temperatures (+2 to +6° C) were used and when females were transferred to cold early (0–2 days) after the adult moult.     

Changes in leaf ultrastructure and carbohydrates inArabidopsis thaliana L. (Heyn) cv. Columbia during rapid cold acclimation

Summary We studied cell ultrastructure and carbohydrate levels in the leaf tissue ofArabidopsis thaliana L. (Heyn) cv. Columbia during rapid cold acclimation. Freezing tolerance of the leaves from 26 day old plants was determined after 48 h and 10 days at 4°C. Acclimation treatment of 48 h decreased the lethal freezing temperature from –5.7°C to –9.4°C. Freezing tolerance was not altered further by acclimation at 4 °C for 10 days. Ultrastructural changes in the parenchyma cells were evident after 6 to 24 h of cold acclimation. The plasma membrane showed signs of extensive turnover. Evidence of membrane invaginations and sequestering of membrane material was observed. In addition, numerous microvesicles, paramural bodies, and fragments of endoplasmic reticulum were noticed in the vicinity of plasma membrane. Modifications in the structure of cell membranes were evident after 5 days of exposure to low temperature. Small, darkly stained globules were seen on the plasma membrane, tonoplast, chloroplast envelope membrane, mitochondrion outer membrane, dictyosome cisternae membrane, and microvesicle membrane. As far as we are aware, this type of membrane modification has not been described previously in plant cells exposed to low temperature. We propose to call these structures membraglobuli. Acclimation treatment also increased the concentrations of soluble sugars and starch. These observations suggest that cold acclimation inA. thaliana induces changes in both plasma membrane properties and carbohydrate composition.     

Cold tolerance in rats following administration of streptozotocin,glucose, insulin and glucose plus insulin

Fall in rectal temperature (T_re) and survival time was determined on exposure to–20°C in adult normoglycemic and diabetic (streptozotocin treated) rats and 1 h following glucose feeding or insulin administration or both and on exposure to–10°C in young rats with and without glucose feeding. The susceptibility to frostbite was determined by exposure of the limbs to freezing mixture of–19°C or–23°C. The rate of fall of T_re was less and the survival time more in glucose and insulin plus glucose treated animals. On the other hand, the rate of fall of T_re was more and the survival time less, in dia betic and insulin-treated animals. The rectal temperature at which the animal died was the same in the control and the treated animals. The susceptibility to frost bite was more in insulin treated and diabetic animals and less in glucose-fed animals. Exposure to cold during the second h after glucose or glucose plus insulin injection did not alter the blood glucose from that obtained at room temperature. In insulin-treated animals the rate of rise of blood glucose during the second h was much higher at low temperature than at room temperature. The rise in blood glucose in diabetic animals was much higher than in normoglycemic animals exposed to cold.     

Metabolomic Analysis of Cold Acclimation of Arctic Mesorhizobium sp. Strain N33

Arctic Mesorhizobium sp. N₃₃ isolated from nodules of Oxytropis arctobia in Canada’s eastern Arctic has a growth temperature range from 0°C to 30°C and is a well-known cold-adapted rhizobia. The key molecular mechanisms underlying cold adaptation in Arctic rhizobia remains totally unknown. Since the concentration and contents of metabolites are closely related to stress adaptation, we applied GC-MS and NMR to identify and quantify fatty acids and water soluble compounds possibly related to low temperature acclimation in strain N₃₃. Bacterial cells were grown at three different growing temperatures (4°C, 10°C and 21°C). Cells from 21°C were also cold-exposed to 4°C for different times (2, 4, 8, 60 and 240 minutes). We identified that poly-unsaturated linoleic acids 18∶2 (9, 12) & 18∶2 (6, 9) were more abundant in cells growing at 4 or 10°C, than in cells cultivated at 21°C. The mono-unsaturated phospho/neutral fatty acids myristoleic acid 14∶1(11) were the most significantly overexpressed (45-fold) after 1hour of exposure to 4°C. As reported in the literature, these fatty acids play important roles in cold adaptability by supplying cell membrane fluidity, and by providing energy to cells. Analysis of water-soluble compounds revealed that isobutyrate, sarcosine, threonine and valine were more accumulated during exposure to 4°C. These metabolites might play a role in conferring cold acclimation to strain N₃₃ at 4°C, probably by acting as cryoprotectants. Isobutyrate was highly upregulated (19.4-fold) during growth at 4°C, thus suggesting that this compound is a precursor for the cold-regulated fatty acids modification to low temperature adaptation.     

Alteration of Ion Channels in the Plasmalemma of Nitella flexilisCells during Long-Term Hyperthermia

The conventional microelectrode technique was applied to study changes in conductance and activation characteristics of potassium and chloride channels in the plasmalemma of characean alga Nitella flexilis(L.) Agardz. during long-term heat treatment. Measurements were conducted at 18–20°C after preliminary exposure of cells to 33°C for 1–25 days. The conductance of outward- and inward-rectifying potassium channels, as well as the currents of excitable chloride channels, decreased after 2–3 days of heat treatment. By the 15th–17th days, the conductance of potassium channels was reduced by a factor of 3–5, whereas the peak values of the chloride current, associated with the action potential, was reduced by a factor of 8–10. These heat-induced changes were long lasting: the restoration of the initial parameters of transport systems after transferring cells to chilling or room temperature occurred within several days. Moreover, the recovery at chilling temperatures (8–10°C) proceeded nearly two times longer than at room temperature. Prolonged hyperthermia accelerated activation and deactivation of outward-rectifying potassium channels and caused the shift of their activation curve towards positive potentials by 35–40 mV. Analysis of current–voltage relations showed that the inward current in inward- and outward-rectifying potassium channels was reduced to a greater extent than the outward current. At the same time, both inward and outward currents of chloride channels were reduced to an equal extent. It is assumed that the changes observed are involved in thermal adaptation and account for the decrease in the intracellular concentrations of potassium and other cations and anions, which represents a nonspecific response of plant cells to stress.     

The Effect of Acute Stress and Temperature on Plasma Cortisol and ion Concentrations and Growth of Lake Inari Arctic Charr, Salvelinus Alpinus

One year old, individually tagged Lake Inari Arctic charr, Salvelinus alpinus, were reared at three constant temperatures, 10.3°C, 14.1°C and 18.1°C, over four weeks. Blood samples were collected from a group of unstressed fish after the cultivation period at the same time as another group of fish were subjected to acute handling stress treatment (2min netting in air and 40min (± 20min) recovery period in water). Plasma cortisol, calcium, sodium, potassium and chloride concentrations were measured on both groups. To study the effect of minor daily temperature fluctuations on the stress response of Arctic charr, two additional daily fluctuating temperature (14 ± 1°C, 18 ± 1°C) treatments were established. The samples were taken in the same manner as those in the constant temperature treatments. Growth was fastest at 10.3–14.1°C and clearly lower at 18.1°C. Pre-stress plasma cortisol levels were low but increased slightly with increasing temperature. After stressor treatment, the cortisol concentrations of Arctic charr were clearly higher in all temperature treatments but there were no significant differences in plasma cortisol concentrations among temperatures. Plasma calcium levels increased during the stress treatment but temperature did not modulate this effect. The plasma potassium concentrations declined at 14.1–18.1°C after acute stress but the response was not affected by temperature within this range. The concentrations of sodium and chloride were unaffected by acute stress. Temperatures of 10.3–18.1°C and fluctuating temperature treatments had no influence on any plasma ion concentrations. Arctic charr were able to maintain the plasma ion concentrations in fresh water at 10.3–18.1°C and after acute stress treatment. Results indicate that the optimum temperature for growth of Arctic charr has little to do with the plasma ion concentrations or the ability to maintain those concentrations after short-term stress. The plasma cortisol responses further indicate that the optimum temperature for growth of Arctic charr is not related to the suppressed ability to react to an acute handling stressor. Temperature fluctuations did not cause significant differences in cortisol levels when compared with constant temperatures.     

Molecular evolution of haemoglobins of polar fishes

The Arctic and the Antarctic differ by age and isolation of the respective marine faunas. Antarctic fish are highly stenothermal, in response to stable water temperatures, whereas the Arctic ones are exposed to seasonal and latitudinal temperature variations. The knowledge of the mechanisms of phenotypic response to cold exposure in species of both polar habitats offers fundamental insights into the nature of environmental adaptation. In the process of cold adaptation, the evolutionary trend of Antarctic fish has led to unique specialisations, including modification of haematological characteristics, e.g. decreased amounts and multiplicity of haemoglobins.Unlike Antarctic Notothenioidei, Arctic teleosts have high haemoglobin multiplicity. Although the presence of functionally and structurally distinct haemoglobins is a plesiomorphic condition for many perciform-like fishes, it seems that the oxygen-transport system of teleost fish in the Arctic region has been adjusted to temperature differences and fluctuations of Arctic waters, much larger than in the Antarctic. The amino-acid sequences used to gain insight into the evolution history of α and β globins of polar fish have clearly shown that Antarctic and Arctic globins have different phylogenies, leading to the hypothesis that the selective pressure of environment stability allows the phylogenetic signal to be maintained in the Antarctic sequences, whereas environmental variability would tend to disrupt this signal in Arctic sequences.     

Physiological characteristics of cold acclimatization in man

Studies were conducted on 15 healthy young soldiers to evaluate the effect of a cold acclimatization schedule on the thermoregulatory and metabolic activity on exposure to acute cold stress. These men were exposed to cold (10C) for 4 h daily wearing only shorts for 21 days, in a cold chamber. They were subjected to a standard cold test at 10 ± 1C the day 1, 6, 11 and 21. The subjects were made to relax in a thermoneutral room (26–28C) for 1 h and their heart rate, blood pressure, oxygen consumption, oral temperature, mean skin temperature, mean body temperature, peripheral temperatures, and shivering activity were recorded. Then they were exposed to 10C and measurements were repeated at 30 min intervals, for 2 h. The cold induced vasodilatation (CIVD), cold pressor response and thermoregulatory efficiency tests were measured initially and at the end of acclimatization schedule. The data show that the procedure resulted in elevated resting metabolism, less fall in body temperature during acute cold stress, reduction in shivering, improvement in CIVD and thermoregulatory efficiency and less rise in BP and HR during cold pressor response. The data suggest the possibility of cold acclimatization in man by repeated exposure to moderately severe cold stress.