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PubMed1976

Parietalectomy and thermal selection in the lizard Sceloporus magister.

Lizards were acclimatized to various regimes of temperature (15 degrees, 35 degrees C) and photoperiod (LD 08:16, 16:8). Parietalectomized, sham operated, and control animals were placed in thermal gradients and their body temperatures monitored for periods of up to 15 days. Daily rhythms of thermal selection were evident with higher temperatures selected in late photophase and lower temperatures selected in scotophase. Thermal selection was more variable in scotophase than in photophase. Parietalectomized lizards chose significantly higher body temperatures than did shams or controls. Acclimatization to temperature and photoperiod had little or no effect on the thermal preferendum. The preferred body temperature of controls was 33.2 degrees C +/- 3.59. Length of time in the gradient tended to change thermal preference, especially in lizards acclimated to 15 degrees C. Through interactions with the pineal gland the parietal eye is probably important in synchronizing many bodily functions with photoperiod.

Acclimatization↗
PubMed1988

Renal structural flexibility in response to environmental water stress in feral hogs.

Several morphological characteristics of the kidney were studied to determine the degree of acclimatization that may occur in three groups of feral hogs raised under different environmental conditions. Two groups of hogs were living in the wild, while another was raised in captivity for three generations and was directly descended from one of the wild-living groups. The two groups of wild hogs were living under two different types of water stress conditions. One group experienced periodic drought, and the other ate a high salt diet. The captive hogs were given food and water ad libitum. The captive-raised hogs had significantly lower relative medullary thickness (RMT) and relative medullary area (RMA) values (RMT of 2.35; RMA of 0.35) than either group of hogs living in the wild (RMT of 2.70 and 2.69; RMA of 0.41 and 0.44). Since the feral hogs living in the wild were exposed to a higher degree of water stress than the captive-raised hogs, it was concluded that the differences in observed kidney structure were due to acclimatization.

Acclimatization↗
PubMed2001

Stress response to cold in Trichinella species.

Trichinella-type larvae (L(1)) are found in the muscles of infected wild animals and domestic pigs and are the cause of trichinosis in man and other animals throughout the world. These parasites are exposed to low temperatures during their life cycle. On this premise, three Trichinella species of different types of habitat (the arctic T. nativa, the cosmopolitan T. spiralis, and the tropical T. nelsoni) were selected to examine the effect of a shift in temperature, from 37 to 4 degrees C, on long-term survival. Evaluation was then made of whether these effects were related to differential protein synthesis and/or heat shock protein (Hsp) expression. Test samples at 0, 2, 4, or 8 h and 1, 5, or 9 days after the temperature shift were obtained and subjected to Hsp determination by Western blotting. Total protein changes were explored by SDS-PAGE followed by densitometric analysis of the gels. During the "acclimatization phase" (at 2, 4, and 8 h), a different total protein and a depressed Hsp expression pattern were shown in each Trichinella species. Following acclimatization, Hsp70, but not Hsp60 or Hsp90, markedly increased above control levels in the three species, indicating a role for this Hsp as a classic stress protein. The synthesis of a 50-kDa Hsp was significantly induced in T. spiralis larvae, suggesting its potential function as a cold shock protein in this species.

Acclimatization↗
PubMed2006

Lake Louise consensus methods for measuring the hypoxic ventilatory response.

The hypoxic ventilatory response (HVR) is the body's first line of defense against environmental hypoxia, for example, at high altitude. In acute hypoxia, the HVR is a reflex increase in ventilation in response to decreased arterial PO2, which is rapidly sensed by arterial chemoreceptors primarily in the carotid bodies. With sustained exposure to hypoxia, the HVR changes (8). For example, after 5 to 20 minutes of hypoxia, ventilation "rolls off' relative to the acute hypoxic response and this is called hypoxic ventilatory decline (HVD). With continuous hypoxia, for example during acclimatization to high altitude, ventilation increases above the level of the acute HVR with ventilatory acclimatization to hypoxia (VAH). The different time domains of the HVR raise many questions about the physiological mechanisms of oxygen sensing and the control of breathing. They also raise many issues about experimental methods to measure the HVR and comparing results between laboratories. At the 13th International Hypoxia Symposium, John Severinghaus proposed consensus methods for measuring the HVR in humans, and the discussion continued at the 14th International Hypoxia Symposium in Lake Louise. The goal of this report is to stimulate further discussion and experiments so we can adopt a "Lake Louise Consensus for Measuring the HVR" at the 15th International Hypoxia Symposium in 2007.

Acclimatization↗
PubMed1988

Physiological adaptations to thermal stress in tropical Asians.

Young sedentary adult males of Malay, Indian, and Chinese origin who had established continuous residence in tropical Malaysia and presumed to be naturally acclimatized to heat, were studied to evaluate their physiological responses to a standard heat stress test. The Malay and Indian races have evolved in hot and humid geographical zones, whereas the Chinese originated from a temperate area. Subjects exercised at 50% VO2max alternating 18 minutes walking and 2 min rest during a 2-h exposure to an ambient of 34.9 degrees C dry bulb and 32.1 degrees C wet bulb. Heart rates, core and skin temperatures, sweat rates, and oxygen uptakes were measured during the heat exposure. The subjects of Malay origin exhibited the least circulatory stress of the three ethnic groups. The data obtained on these long-term residents of a hot-wet climate and who were considered acclimatized to this environment were compared to experimental data obtained by other investigators and other ethnic groups.

Acclimatization↗
PubMed1986

Behavioural temperature regulation during a motor-toboggan traverse in Antarctica.

Ten men, members of the International Biomedical Expedition to the Antarctic (IBEA), regularly recorded their thermal comfort, clothing, and activity for 60 days while travelling by motor toboggan and living in tents on the Antarctic plateau. Air temperature averaged -14 degrees C (range +2 degrees to -29 degrees C) and wind speed 11 m s-1 (range 0 to 22 m s-1); on half the days there was wind-blown ("drift") snow. Almost 2,000 sets of observations, evenly distributed throughout the 12 h sampling period 0700 h to 1900 h, were made. Daily (24 h) energy expenditure averaged 14.6 MJ on travelling days, 12.7 MJ on days when men worked in camp, and 13.3 MJ for the whole traverse. Men were outdoors for 7.6 h of the 12 h sampling period on travel days and for 3.6 h on camp days. Bulky down-filled clothing, typical of that used by present-day polar expeditions, adequately protected the trunk from cold at the cost of overheating during exercise. Face, hands, and feet were less well protected, and they experienced cold-induced numbness and pain in 33%, 19%, and 12%, respectively, of the observations made in the coldest weather. Because men could not conveniently reduce clothing insulation to the extent required, sweating and discomfort from warmth increased with energy expenditure and were present in 60% of the observations made during heavy work. The results suggest that there is a need for improvements in clothing design which will permit a more complete adjustment to changes in activity. The residual cold stress might possibly have been enough to induce cold acclimatization, although the accompanying heat stress was probably insufficient to induce acclimatization to heat.

Acclimatization↗
PubMed1994

Physiological changes induced by pre-adaptation to high altitude.

To study the physiological effects of pre-adaptation to high altitude, seven subjects were submitted to acclimatization at 4350 m followed by intermittent acclimation in a low barometric pressure chamber (5000 m to 8500 m). The subjects then spent 25 days in the Himalayas. Ventilatory and cardiac responses were studied during a hypobaric poikilocapnic hypoxic test performed both at rest and during exercise (100 W) in normoxia and in hypoxia (barometric pressure: 589 hPa, altitude: 4500 m). Haemoglobin, erythrocytes, reticulocytes, packed cell volume, 2,3-diphosphoglycerate (2,3-DPG) and erythropoietin (EPO) were measured. All variables were studied before pre-adaptation to high altitude (A), after the acclimatization period (B), after the acclimation period (C) and after the expedition (D). The ventilatory and cardiac responses were characterized by an increased tidal volume in hypoxia (+33% during exercise in B, P < 0.05; +100% at rest and +33% during exercise in C, P < 0.05) without any change in respiratory frequency, whereas an increased systolic blood pressure was only observed in C during exercise in hypoxia [+23 mmHg (3.07 kPa), P < 0.01]. Arterial O2 saturation was higher in hypoxia in C and D, both at rest (+8.2% and +4.7%, P < 0.01, respectively), and during exercise (+6.3% and +6.3%, P < 0.01, respectively). Erythrocytes, haemoglobin and packed cell volume did not vary significantly. The number of reticulocytes was higher in B (+172%, P < 0.05) and in C (+249%, P < 0.05). EPO and 2,3-DPG increased only in C (+770%, P < 0.01 and +23%, P < 0.05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1993

The effects of acute altitude exposure in Swiss highlanders and lowlanders.

The functional characteristics at rest in responding to stepwise acute exposure to simulated altitude (6000 m) were compared in 10 acclimatized mountaineers (highlanders), residents of Zermatt (1616 m) working at an altitude up to about 4000 m, and in 11 nonacclimatized control subjects (lowlanders) living and working in Zurich (450 m). In comparison with the lowlanders, the highlanders showed at altitude significantly greater hyperventilation, lower heart rate and systolic blood pressure, smaller haemoconcentration, lower urodilatin secretion and natriuresis, and a preserved neuropsychological ability (attentiveness) and vasomotor tone (diastolic blood pressure); the critical altitude at which hypoxic short-term adaptation became insufficient was 6000 m. The lowlanders, however, manifested reduced tolerance of hypoxia, i.e. insufficient short-term adjustment with subjective and objective distress coinciding with the first signs of hypoxia of the central nervous system, already apparent at and above 4000 m. It was concluded that the functional differences between highlanders and lowlanders in responding to acute gradual hypoxia indicated factors contributing to altitude acclimatization.

Acclimatization↗
PubMed1996

Hypoxic ventilatory response during rest and exercise after a Himalayan expedition.

Hypoxic ventilatory response (HVR) was examined before and after acclimatization to high altitude. Transient hyperoxic switches according to Dejours's technique were used to examine the contribution of HVR to the hyperpnoea of increasing exercise intensities. Ten mountaineers were exposed to hypoxia (oxygen fraction in inspired gas. F1O2 = 0.11, 79 mmHg) before the expedition and after return from altitude (56 days, 30 days at 4900 m or higher). After 25-min breathing hypoxic gas, the subjects performed a maximal cycle ergometer test (increments 50 W per 5 min). Respired gases and ventilation (VE) were analysed breath-by-breath, partial pressure of oxygen (PO2) and oxygen saturation (SO2) were measured in capillary blood. The HVR was tested by switching two breaths to an F1O2 of 1.0. The nadir of VE after the switch was measured (decrease in ventilation, DVE). The HVR was expressed as the DVE at a PO2 of 40 mmHg (DVE40) and the DVE versus decrease of SO2 (DVE/[100-SO2]). The HVR estimated by DVE40 increased from 19.9 to 28.0 l.min-1 (median, P = 0.013). The HVR expressed as DVE (100-SO2) at rest was no different before and after acclimatization (0.89 and 0.86 l.min-1.%-1 respectively) and during exercise it did not change before the expedition (0.83 l.min-1. %-1). However, DVE/(100-SO2) increased significantly with exercise intensity after the expedition (1.61 l.min-1.% at 200 W). The changes of DVE versus SO2 as well as of DVE versus VE were steeper after the expedition than before. In summary, after return from 30 day at high altitude, an increased HVR was observed. The augmentation of HVR was evident at higher exercise intensities and we suggest that this reflects a change in sensitivity of the peripheral chemoreflex loop.

Acclimatization↗
PubMed2005

Seasonal modulation of growth hormone mRNA and protein levels in carp pituitary: evidence for two expressed genes.

Adaptation of eurythermal fish to naturally varying environmental conditions involves modulation of expressions of various factors in the hypothalamo-hypophyseal axis. Here we used three complementary approaches to assess the seasonal variation of growth hormone (GH) protein and mRNA levels in pituitary glands of acclimatized carp fish. First, a polyclonal antibody raised against an oligopeptide derived from the carp GH sequence was used for immunohistochemistry; second, oligonucleotides specific for GH transcripts were used for in situ hybridization. Specific immunodetection of GH coincides with visualization of GH mRNA in the proximal pars distalis, the specific location of somatotroph cells in carp pituitary gland. Finally, competitive RT-PCR analyses confirmed that GH expression exhibits seasonal cyclical reprogramming with higher levels in summer- than in winter-adapted fish. The expression pattern suggests an important role for GH in the molecular mechanisms underlying the acclimatization process. In parallel, amplification of sequences from the fourth intron and adjacent sites from exons IV and V demonstrates the existence of a new GH gene previously undescribed. The detection of transcripts corresponding to each gene suggests that both GH gene copies are active in the duplicated carp genome and that they are similarly affected by seasonal adaptation.

Acclimatization↗
PubMed1991

Echocardiographic assessment of left ventricular function and wall motion at high altitude in normal subjects.

To understand the effects of high-altitude hypoxia on cardiac function and the change in cardiac function during high-altitude acclimatization, precise studies were first performed at greater than 5,000 m of altitude in Himalaya by 2-dimensional echocardiography. In addition to examining well-known indexes of cardiac function, the centerline method was used to assess regional wall motion, which has not been examined under conditions of high-altitude hypoxia. The subjects were 11 climbing members (aged 21 to 43 years) of the Kyoto University Medical Research Expedition of Xixabangma (8,027 m) in 1990. Examinations were performed at sea level, at the base camp (5,020 m), and twice at the advanced base camp (5,650 m). Heart rate, left ventricular (LV) end-diastolic volume, cardiac output, mean rate of circumferential fiber shortening, ejection fraction, % fractional shortening, and regional LV wall motion were measured. At high altitude, heart rate increased to 136% of the sea level value, but gradually decreased in the degree of increment at the early and late advanced base camp measurements. LV end-diastolic volume decreased significantly by 70%. At base camp there were significant increases in ejection fraction, mean rate of circumferential fiber shortening, and % fractional shortening, which showed little change during the long-term stay at high altitude. Regional wall motion at high altitude (measured by the center-line method) decreased at the septal wall and increased at the posterolateral wall. These results demonstrate that: (1) LV cardiac performance at high altitude is enhanced significantly in spite of reduced preload. After good acclimatization, cardiac performance remains augmented, but there is a tendency to decrease the degree of augmentation. (2) In regional LV wall motion, septal wall motion is impaired, but LV posterolateral wall motion shows a compensatory increase.

Acclimatization↗
PubMed1978

Pulmonary gas exchange, diffusing capacity in natives and newcomers at high altitude.

At high altitude, in resting conditions, no differences have been observed between High Altitude Natives (HAN) and acclimatized Sea Level Natives (SLN) in AaDO2, aADCO2 or venous admixture. In acclimatized SLN, AaDO2 is smaller than at sea level because of: (1) The minor effect on arterial oxygenation of the probably constant venous admixture. (2) The reduction of VA/Q inequality as shown by a smaller aADCO2. In HAN, DLCO is greater than in SLN; the contribution of DM or VC in this difference remains unsettled, mainly because of the difficulties of measurement of DM and VC in HAN suddenly exposed to acute hyperoxia. In SLN, in acute hypoxia, DLCO increased transitorily. Asynchronous mechanisms of adaptation to high altitude are evoked.

Acclimatization↗
PubMed1994

Ventilatory responses to brief hypoxic stimuli after simulated altitude exposure in rat.

A blunted ventilatory response to acute hypoxia is described in altitude acclimatized small mammals. The peripheral or central origin of this blunting remains controversial. As the O2 sensitivity is always tested by steady-state steps of progressive hypoxia, an enhanced central inhibiting mechanism similar to those created by sustained hypoxia is suspected to be involved in the blunting. To avoid such central effect, we analyzed the ventilatory responses to very short glomic stimuli such as N2 tests and administration of NaCN by intravenous bolus in chronically hypoxic rats. The blunted ventilatory response was present only for hypoxemic hypoxia. A D2-receptor blockade failed to restore this response to those of littermate controls. We concluded that in rats, after altitude acclimatization, the central transduction of glomic afferences was intact because of the unchanged ventilatory response to cyanide. Reduced glomic sensitivity to low PO2 appeared specifically responsible for the blunted response to N2 tests with a very limited contribution from inhibitory dopaminergic mechanisms.

Acclimatization↗
PubMed1976

Heat illness. I. Epidemiology.

Reliable information on the epidemiology of heat illness has come, until recently, mainly from the armed forces and, to a lesser extent, from some industries and civil communities. Data from the records of the British Army, Royal Navy, Royal Air Force, Indian Armed Forces, U.S. Army and forces engaged in the Arab-Israeli wars, from the South African gold mining corporations and Persian Gulf oil tankers, and from civilian communities, mainly in the U.S.A., are reviewed and discussed with particular reference to the classification of heat illness and definition of the terms used, and the effects on acclimatized and non-acclimatized personnel and on other sections of the civilian communities most at risk, i.e. the old and very young. This section concludes with an outline of the classification of acute heat illnesses from 1899 to the eighth revision of the WHO International Classification of Diseases in 1967.

Acclimatization↗
PubMed1990

Effects of hyperbaric pressure and temperature on atria from ectotherm animals (Rana pipiens and Anguilla anguilla).

1. Spontaneously beating atria from frogs (R. pipiens) and eels (A. anguilla) were compressed hydraulically to 10 MPa. Effects on beating frequency and twitch tension were studied. 2. At low temperatures (8-10 degrees C) compression to 10 MPa caused a slowing of the beat frequency. No effects were noted at higher temperatures (16-24 degrees C). Twitch tension was decreased by pressure at low temperatures and increased at high temperatures. 3. Differences were noted between preparations from cold and warm acclimatized frogs, and from silver and yellow eels, respectively. 4. The effect of temperature acclimatization on pressure and temperature sensitivity is discussed in relation to data on cardiac phospholipid fatty acid composition.

Acclimatization↗
PubMed2004

High-altitude illness.

Travel to a high altitude requires that the human body acclimatize to hypobaric hypoxia. Failure to acclimatize results in three common but preventable maladies known collectively as high-altitude illness: acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE). Capillary leakage in the brain (AMS/HACE) or lungs (HAPE) accounts for these syndromes. The morbidity and mortality associated with high-altitude illness are significant and unfortunate, given they are preventable. Practitioners working in or advising those traveling to a high altitude must be familiar with the early recognition of symptoms, prompt and appropriate therapy, and proper preventative measures for high-altitude illness.

Acclimatization↗
PubMed2005

Seasonal environmental changes regulate the expression of the histone variant macroH2A in an eurythermal fish.

Adaptation to cold and warm conditions requires dramatic change in gene expression. The acclimatization process of the common carp Cyprinus carpio L. in its natural habitat has been used to study how organisms respond to natural environmental changes. At the cellular level, adaptation to cold condition is accompanied by a dramatic alteration in nucleolar structure and a down regulation of the expression of ribosomal genes. We show that the enrichment of condensed chromatin in winter adapted cells is not correlated with an increase of the heterochromatin marker trimethyl and monomethyl K20H4. However, the expression of the tri methyl K4 H3 and of the variant histone macroH2A is significantly increased during the winter season together with a hypermethylation of CpG residues. Taking into account the properties of macroH2A toward chromatin structure and dynamics and its role in gene repression our data suggest that the increased expression of macroH2A and the hypermethylation of DNA which occurs upon winter-acclimatization plays a major role for the reorganization of chromatin structure and the regulation of gene expression during the physiological adaptation to a colder environment.

Acclimatization↗
PubMed2005

Peroxidases, lignin and anatomy during in vitro and ex vitro rooting of gardenia (Gardenia jasminoides Ellis) microshoots.

In vitro and ex vitro rooting of gardenia (Gardenia jasminoides Ellis) microshoots with or without indolic-3-butyric acid (IBA) was studied in order to improve acclimatization of microplants after root formation and transplantation. Peroxidase (POD) activity and isoforms, lignin content and anatomical observations were evaluated in the course of the three interdependent phases (induction, initiation and expression) of microshoot rooting. Microshoots treated or not treated with IBA achieved high rooting percentages both in vitro and ex vitro. At the end of the 2-week acclimatization period, the percentage of surviving microplants ranged from 80% to 100%, for in vitro and ex vitro rooted microshoots, respectively. Microshoots rooted in vitro and ex vitro showed a relationship between rooting and POD activity but in a different time course. It appeared that root formation occurred after the microshoots had reached and passed a peak of maximum enzyme activity. In all treatments, electrophoretic analysis (native PAGE) of PODs revealed the appearance of one anionic and three cationic POD isoforms (C(1), C(3) and C(4)). An additional cationic POD isoform (C(2)) appeared only in the ex vitro rooting. The lignin content was similar in microshoots rooted both in vitro and ex vitro. The sequential anatomical changes during the rooting process were similar in both in vitro and ex vitro rooting treatments. In the case of in vitro rooting, pith cells had vacuoles entirely filled with a dark substance, while in the case of ex vitro rooting, pith cells contained many amyloplasts. The origin of the adventitious roots, in both rooting conditions, was located in the cambial ring. Roots with organized tissue systems emerged from the microshoot stem 10-14 days after the root induction treatments; on day 10 for rooting in vitro, while a 4-day delay was noted in microshoots rooted ex vitro.

Acclimatization↗