[The systems-forming role of antihypoxic mechanisms in body adaptation to extreme environmental conditions].
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Adaptation, Physiological↗
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Structure-function relationships in the four repeats of human interphotoreceptor retinoid-binding protein (IRBP).
PURPOSE: Interphotoreceptor retinoid-binding protein (IRBP) binds hydrophobic ligands in the interphotoreceptor space. Human IRBP consists of 1230 amino acids in four 300 amino acid long repeats. We asked: 1. Whether each of the four repeats can bind retinoids or fatty acids, 2. Whether each repeat can prevent retinol degradation in aqueous solutions, 3. Whether a ligand can stabilize the protein from thermal denaturation, 4. Whether the four repeats can be further classified into two groups. Our rationale was to make each repeat from the human cDNA and then examine structural and functional characteristics. METHODS: Individual repeats were produced in E. coli and the whole protein was expressed in baculovirus. Binding properties with all-trans-retinol were characterized by ligand fluorescence enhancement. The quenching of protein fluorescence by retinol, 9-cis-retinal, all-trans-retinoic acid, beta-ionine, alpha-ionine, trans-parinaric acid, and DHA was also examined. Binding curves were analyzed by nonlinear regression. Prevention of retinol decomposition was measured by absorption spectroscopy. Circular dichroism was examined in the far UV range to study protein secondary structure and the near UV range to study ligand binding effects on the tryptophan environment. RESULTS: Temperature dependent denaturation suggests that EcR1 is the most stable of the four repeats. Each repeat possesses the capability of binding 9-cis-retinal, all-trans-retinol, all-trans retinoic acid, docosahexaenoic acid, alpha- and beta-ionine, and trans-parinaric acid. Protein fluorescence quenching by retinol and retinol fluorescence enhancement assays yielded similar binding parameters for each repeat. Each expressed repeat prevents the degradation of retinol in aqueous solutions. CONCLUSIONS: The data contrast with the idea that two or more repeats are needed to bind one molecule of ligand. Each repeat binds both retinoids and analogs, suggesting that each has multiple ligand binding sites or one binding site with affinity for different ligands. Together, the results suggest that each repeat retains all functions of the whole protein. However, there are distinguishing characteristics among the repeats in their ligand binding properties, though the four repeats cannot be classified into just two distinctive groups. Last, these data fit well with the current model of multiple binding sites in IRBP derived from quadruplication of an ancestral monomeric binding protein.
Circular Dichroism↗
[Functional state of the adrenal cortex of rats following cooling in a hermetically sealed chamber and in the process of their adaptation to it].
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Adaptation, Physiological↗
What is known about temperature and complaints in the upper extremity? A systematic review in the VDU work environment.
UNLABELLED: Upper extremity musculoskeletal complaints and disorders are frequently reported among visual display units (VDU) workers. These complaints include cold forearms, hands or fingers. OBJECTIVE: The aim of this systematic review was to gain an insight into the relationship between objective and subjective temperature decrease and musculoskeletal disorders (MSDs) in the upper extremity in a VDU work environment by (internal or external) cooling of the arm and hand. Two questions were formulated: (1) Is a VDU work environment (temperature between 15 and 25 degrees C) associated with temperature decrease of the arm, hand or fingers in healthy subjects? (2) Is there a difference in arm, hand and finger temperature between patients with upper extremity MSDs and healthy subjects in a VDU work environment? METHODS: Through a systematic literature search in six databases between 1989 and October 2005, 327 articles were retrieved and 17 included. RESULTS: Forearm, hand and finger temperature significantly decreases when the ambient temperature (between 15 and 25 degrees C) decreases. The skin temperature in the hand that uses a computer mouse is lower than the other hand in the same ambient temperature. At baseline, no objective temperature differences are found between patient groups and controls, whereas in patients with cold hand complaints, lower skin temperatures are found compared to controls. The association between temperature (changes) in the forearm, hand or fingers during VDU work, and MSDs in the upper extremity is not clear. CONCLUSION: There is no consistent evidence available for the association between upper extremity MSDs and temperature changes in forearm, hand or fingers in an office work environment.
Computer Terminals↗
Effects of hyperbaric helium-oxygen on the antipyretic actions of aspirin and acetaminophen in rats.
The effects of two antipyretics, aspirin and acetaminophen, were studied under hyperbaric helium-oxygen conditions. Groups of yeast-fevered rats were given three different doses of each antipyretic in 1-ATA air and 31-ATA helium-oxygen. Neither agent was as effective an antipyretic in hyperbaric helium as it was in 1-ATA air. Responses to acetaminophen were reduced an average of 73%, and those to the two lower doses of aspirin by 56%; the highest dose of aspirin (135 mg/kg) caused a significant elevation of temperatures in the hyperbaric environment. A similar increase in temperatures was observed in rats treated with 135 mg/kg of aspirin and exposed to hot (30--31 degrees C) air at 1 ATA. It is concluded that the decreased efficacy of antipyretics in hyperbaric helium environments is caused by the high ambient temperatures maintained in helium (34--35 degrees C) to compensate for the greater thermal conductivity of helium compared to nitrogen, which may limit the heat-dissipating abilities of rats in the hyperbaric environment.
Acetaminophen↗
Changes in the hypothalamic mechanisms involved in the control of body temperature induced by the early thermal environment.
The experiments reported in this study were designed to investigate the influence of the early thermal environment on the functional properties of certain putative thermoregulatory neurotransmitters within the hypothalamus of the Sprague-Dawley rat. The effects on body temperature of serotonin, dopamine, carbachol, PGE2 and endotoxin when microinjected into the anterior hypothalamic/preoptic region of the brain have been examined in warm-reared, control and warm-acclimated animals. Serotonin and PGE2 are shown to have different effects on body temperature in warm-reared as compared to warm-acclimated and control animals. The thermoregulatory effects of intrahypothalamic dopamine are shown to be changed by the normal acclimation process, while carbachol and endotoxin have similar effects on the body temperature of all 3 groups of animals. These data suggest that the thermal environment may significantly affect the roles which specific neurotransmitters play in the control of body temperature.
Acclimatization↗
Variations in 6-sulphatoxymelatonin excretion and oral temperature under a 12-hour shiftwork environment.
The aim of the present study was to follow the time-of-day variations in oral temperature and the excretion of a melatonin metabolite, 6-sulphatoxymelatonin (aMT6s), in individuals working fast-rotating, 12-h day and night shifts in a thermoelectric power station. Twenty-three male operators working on a 12-h-shift system (two successive days of the same shift: 0700-1900; 1900-0700, followed by two days off) were investigated. Oral temperature and aMT6s were measured at 4-h intervals on the second day shift and on the first and second night shifts. Clearly expressed "peaks" and "troughs" in aMT6s excretion and in oral temperature were found, indicating that a typical diurnal pattern of variation was preserved during fast-rotating, 12-h-shift work. The differences between the first and the second night shift in the examined parameters, particularly in aMT6s, can be attributed to the changes in sleep time between the two work shifts.
Adult↗
Effect of temperature on hemolysin production in Aeromonas spp. isolated from warm and cold environments.
The effect of growth temperature on the hemolysin production in 97 Aeromonas isolates was studied. Only 9% of the isolates obtained from low-temperature sources such as refrigerated foods, drinking water and trout aquaculture were able to produce high hemolysin titers (titer greater than 128) at 37 degrees C compared with 65% of the isolates from warm sources such as human clinical cases and warm water aquaculture (p less than 0.001). In contrast, 61% of the low-temperature isolates were producing high hemolysin titers at 10 degrees C while only 24% of the isolates from high temperature sources produced high titers at this temperature (p less than 0.05). Hemolytic activity could decrease markedly during longer (48 h) incubation at 37 degrees C. Some of the filtrates from growth at 37 degrees C and 10 degrees C were tested for enterotoxin-like activity in the suckling mice test. Of the culture filtrates produced at 37 degrees C, 40% of A. hydrophila were positive for enterotoxin-like activity, irrespective of hemolysin titer. Of A. sobria 88% of the filtrates with high hemolytin titers and none of the low-titer filtrates were enterotoxigenic. Due to a high mortality rate of mice injected with filtrates produced at 10 degrees C the enterotoxic effect of these filtrates could not be established. Autoagglutination after boiling was observed in 31% of the clinical isolates and 2% of the strains of environmental origin.
Aeromonas↗
Radiant heat loss versus radiant heat gain in premature neonates under radiant warmers.
Premature infants nursed on open radiant warmer beds are exposed to short-wavelength infrared power density distributed evenly over the bed surface. Additionally, infants' sides are exposed to relatively cooler nursery walls, and to the radiant warmer bed platform which may heat and reradiate to the baby. Therefore, infants may not only gain heat from the warmer (Q radiant warmer) but lose or gain radiant heat to the sides as well (+/- Q radiant loss). In order to quantitate these parameters, ten premature newborn infants nursed under radiant warmers servocontrolled to 36.5 degrees C skin temperature (weight 1.27 +/- 0.24 SD kg, gestation 31 +/- 3 weeks) were investigated, and partitional calorimetry previously reported. In the present study, calculation of net rate of radiant heat transfer (Q net radiant) was made from these data (-2.63 +/- -1.52 kcal/kg/h), and compared to direct measurements of Q radiant warmer (-2.49 +/- -0.90 kcal/kg/h). The present report further partitions net radiant heat transfer to evaluate Q radiant loss: -0.13 +/- 1.82 kcal/kg/h (range -3.16 to 1.93). From these calculations mean radiant temperature of this environment was estimated (45.3 +/- 4.3 degrees C) and compared to the radiant warmer temperature received (45.0 +/- 2.9 degrees C). This information suggests other strategies to reduce radiant heat loss as well as convective and evaporative losses in premature neonates nursed on open radiant warmer beds.
Body Temperature Regulation↗
Challenges to temperature regulation when working in hot environments.
The focus of this review is upon acute exposure to hot environments and the accompanying physiological changes. The target audience includes physiologists, physicians and occupational health and safety practitioners. Using the principles of thermodynamics, the avenues for human heat exchange are explored, leading to an evaluation of some methods used to assess thermally-stressful environments. In particular, there is a critique of the wet-bulb globe temperature (WBGT) index, and an overview of an alternative means by which such assessments may be undertaken (the heat stress index). These principles and methods are combined to illustrate how one may evaluate the risk of heat illness. Three general areas of research are briefly reviewed: the physiological impact of wearing thermal protective clothing, heat adaptation (acclimation) and whole-body pre-cooling. These topics are considered as potential pre-exposure techniques that may be used to reduce the threat of hyperthermia, or to enhance work performance in the heat.
Fever↗
[A survey of body temperatures in the elderly and the thermal environment in nursing homes].
In order to understand the relation between body temperatures and activities in the elderly, sublingual temperatures and activities of daily living (ADL) of 92 elderly people living in nursing homes were measured in the winter of 1989 and 1990. Thermal conditions in the three nursing homes were also measured simultaneously. In two nursing homes, where most of the people of low ADL lived, room temperatures were usually kept above 20 degrees C during most of the day, while in the remaining home, where many of the people of high ADL lived, room temperatures in the morning decreased to 8 degrees C. In spite of the better thermal conditions, mean sublingual temperatures, measured in the morning, of the low ADL group were significantly lower than that of middle and the high ADL groups. Moreover, the prevalence of low body temperatures (< 35.5 degrees C) was higher in the low ADL group than in the other two groups. From these results it appears that investigations of the living environment for older people should be widened.
Activities of Daily Living↗
Standard metabolism and body temperature of perameloid marsupials from different environments.
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Adaptation, Physiological↗
The cryptoendolithic microbial environment in the Antarctic cold desert: temperature variations in nature.
In the Antarctic cold desert, cryptoendolithic microorganisms live under the surface of porous sandstone rocks. During the austral summer, the environment of the near-surface rock layers colonized by organisms is characterized by two kinds of temperature oscillations, both occurring across the freezing point. Low-frequency (diurnal) and large-amplitude (up to about 20 degrees C) oscillations on the sunlit surface of rocks result in a daily freeze-thaw cycle. This is a result of the diurnal changes in the sun altitude and angle with respect to the rock surface. The biological effect of this oscillation is the regulation of the onset and cessation of metabolic activity. The high-frequency (few minutes) oscillations occur only under certain weather conditions (sunny days with light winds) and are superimposed on the low-frequency oscillations. They are caused by the cooling effect of wind gusts on rock surfaces that are much warmer than ambient air temperatures. High-frequency oscillations result in a rapid freeze-thaw cycle on the surface, which, however, does not reach the microbial zone. These high-frequency freeze-thaw oscillations are probably the cause of the abiotic nature of the rock surface. Both oscillations seem to have an effect on rock weathering.
Air↗
Adaptation of photosynthesis in marama bean Tylosema esculentum (Burchell A. Schreiber) to a high temperature, high radiation, drought-prone environment.
Marama bean, Tylosema esculentum, is a tuberous legume native to the Kalahari region of Southern Africa where it grows under high temperatures (typical daily max 37 degrees C during growing season) and radiation (frequently in excess of 2000 micromol m(-2) s(-1)) in sandy soils with low rainfall. These conditions might be expected to select for increased water-use efficiency of photosynthesis. However, marama was found to give similar leaf photosynthetic rates to other C3 plants for a given internal leaf CO2 concentration and Rubisco content. Under conditions of increasing drought, no increase in water-use efficiency of photosynthesis was observed, but stomata closed early and preceded any change in leaf water potential. The possibility of subtle adaptations of photosynthetic characteristics to its natural environment were investigated at the level of Rubisco kinetics. The specificity factor of marama Rubisco was slightly lower than that of wheat, but the apparent Km for CO2 in air (Km') was about 20% lower than that of wheat. This is consistent with better adaptation for efficient photosynthesis at high temperatures in marama compared to wheat, although the net benefit is predicted to be very small (<0.5% at 35 degrees C). The sequence of marama rbcL gene shows 27 deduced amino acid residue differences from that for wheat, and the possibility that one or more of these cause the difference in Rubisco Km' is discussed.
Adaptation, Physiological↗
Effects of brainstem lesions on temperature regulation in hot and cold environments.
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Animals↗
[Microbial diversity of deep-sea extremophiles--Piezophiles, Hyperthermophiles, and subsurface microorganisms].
Knowledge of our Planet's biosphere has increased tremendously during the last 10 to 20 years. In the field of Microbiology in particular, scientists have discovered novel "extremophiles", microorganisms capable of living in extreme environments such as highly acidic or alkaline conditions, at high salt concentration, with no oxygen, extreme temperatures (as low as -20 degrees C and as high as 300 degrees C), at high concentrations of heavy metals and in high pressure environments such as the deep-sea. It is apparent that microorganisms can exist in any extreme environment of the Earth, yet already scientists have started to look for life on other planets; the so-called "Exobiology" project. But as yet we have little knowledge of the deep-sea and subsurface biosphere of our own planet. We believe that we should elucidate the Biodiversity of Earth more thoroughly before exploring life on other planets, and these attempts would provide deeper insight into clarifying the existence of extraterrestrial life. We focused on two deep-sea extremophiles in this article; one is "Piezophiles", and another is "Hyperthermophiles". Piezophiles are typical microorganisms adapted to high-pressure and cold temperature environments, and located in deep-sea bottom. Otherwise, hyperthermophiles are living in high temperature environment, and located at around the hydrothermal vent systems in deep-sea. They are not typical deep-sea microorganisms, but they can grow well at high-pressure condition, just like piezophiles. Deming and Baross mentioned that most of the hyperthermophilic archaea isolated from deep-sea hydrothermal vents are able to grow under conditions of high temperature and pressure, and in most cases their optimal pressure for growth was greater than the environmental pressure they were isolated from. It is possible that originally their native environment may have been deeper than the sea floor and that there had to be a deeper biosphere. This implication suggests that the deep-sea hydrothermal vents are the windows to a deep subsurface biosphere. A vast array of chemoautotrophic deep-sea animal communities have been found to exist in cold seep environments, and most of these animals are common with those found in hydrothermal vent environments. Thus, it is possible to consider that the cold seeps are also one of slit windows to a deep subsurface biosphere. We conclude that the deep-sea extremophiles are very closely related into the unseen majority in subsurface biosphere, and the subsurface biosphere probably concerns to consider the "exobiology".
Archaea↗
The influence of environment, sex, and innate timing mechanisms on body temperature patterns of free-ranging black-tailed prairie dogs (Cynomys ludovicianus).
Mechanisms that influence body temperature patterns in black-tailed prairie dogs are not well understood. Previous research on both free-ranging and laboratory populations of black-tailed prairie dogs (Cynomys ludovicianus) has suggested that reductions in ambient temperature and food and water deprivation are the primary factors that stimulate torpor in this species. In other species, however, torpor has been shown to be influenced by a multitude of factors, including innate circadian and circannual timing mechanisms, energy status, and reproductive behaviors. Our objective was to clarify the influence of weather, sex, and intrinsic timing mechanisms on the body temperature patterns of free-ranging black-tailed prairie dogs. We monitored body temperatures of eight adult (>1 yr) prairie dogs from November 1999 to June 2000. Prairie dogs showed distinct daily and seasonal body temperature patterns, which reflected changes in ambient temperatures that occurred during these periods. These patterns of daily and seasonal heterothermy suggest that body temperature patterns of black-tailed prairie dogs may be driven by an innate timing mechanism. All prairie dogs entered torpor intermittently throughout winter and spring. Torpor bouts appeared to be influenced by precipitation and reductions in ambient temperature. Our results also suggest that reproductive behaviors and circadian timing may influence torpor in this species.
Animals↗
Thermal regulation in the heat during exercise after caffeine and ephedrine ingestion.
BACKGROUND: Ingesting a combination of caffeine and ephedrine (C+E) has been shown to raise metabolic heat production and body temperature. This side effect of C+E ingestion may be positive during a cold stress scenario, however, during heat stress it could prove to be detrimental. Thus, the purpose of this study was to clarify the effect of C+E ingestion on body temperature regulation during moderate exercise in a hot dry environment. METHODS: Ten, healthy, non heat acclimated, males exercised at 50% VO2peak in a 40 degrees C and 30% RH environment until rectal temperature reached 39.3 degrees C; heart rate (HR) remained at 95% of peak value or greater for 3 min, dizziness or nausea precluded further exercise, or 3 h had elapsed. They did this four times at weekly intervals: familiarization (Fam), control (Cont), placebo, and C+E (5 mg . kg(-1) caffeine + 1 mg . kg(-1) ephedrine) trials. The Fam and Cont treatments were done first and sequentially while the placebo and C+E treatments were balanced and double-blind. Tolerance times, mean skin temperature (Tsk), rectal temperature (Tre), Vo2, Vco2, VE, sweat rate (SR), HR, and sensation of thermal comfort were measured. RESULTS: Tolerance times (mean+/-SD in minutes) were similar for the placebo (120.0+/-28.4) and C+E (121.3+/-33.9) trials and both times were significantly longer than Cont (106.6+/-24.0) trial. C+E did not affect Tsk, initial TrC, delta Tre, SR or the sensation of thermal comfort. VO2 and VF, were significantly increased by C+E. HR was elevated by C+E compared with the other trials, but only during the initial 20 min of exercise. CONCLUSION: Although the metabolic rate was slightly increased with C+E treatment, it was sufficiently offset by increased heat loss mechanisms so that internal body temperature was not increased during moderate exercise in a hot, dry environment.
Adult↗