Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ACCLIMATIZATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,369 records · Page 76Linked to original sources
PubMed2001

Utilization of stress in the development of an equine model for equine protozoal myeloencephalitis.

Neurologic disease in horses caused by Sarcocystis neurona is difficult to diagnose, treat, or prevent, due to the lack of knowledge about the pathogenesis of the disease. This in turn is confounded by the lack of a reliable equine model of equine protozoal myeloencephalitis (EPM). Epidemiologic studies have implicated stress as a risk factor for this disease, thus, the role of transport stress was evaluated for incorporation into an equine model for EPM. Sporocysts from feral opossums were bioassayed in interferon-gamma gene knockout (KO) mice to determine minimum number of viable S. neurona sporocysts in the inoculum. A minimum of 80,000 viable S. neurona sporocysts were fed to each of the nine horses. A total of 12 S. neurona antibody negative horses were divided into four groups (1-4). Three horses (group 1) were fed sporocysts on the day of arrival at the study site, three horses were fed sporocysts 14 days after acclimatization (group 2), three horses were given sporocysts and dexamethasone 14 days after acclimatization (group 3) and three horses were controls (group 4). All horses fed sporocysts in the study developed antibodies to S. neurona in serum and cerebrospinal fluid (CSF) and developed clinical signs of neurologic disease. The most severe clinical signs were in horses in group 1 subjected to transport stress. The least severe neurologic signs were in horses treated with dexamethasone (group 3). Clinical signs improved in four horses from two treatment groups by the time of euthanasia (group 1, day 44; group 3, day 47). Post-mortem examinations, and tissues that were collected for light microscopy, immunohistochemistry, tissue cultures, and bioassay in KO mice, revealed no direct evidence of S. neurona infection. However, there were lesions compatible with S. neurona infection in horses. The results of this investigation suggest that stress can play a role in the pathogenesis of EPM. There is also evidence to suggest that horses in nature may clear the organism routinely, which may explain the relatively high number of normal horses with CSF antibodies to S. neurona compared to the prevalence of EPM.

Animals↗
PubMed1999

Lack of effects of moderate-high altitude upon lung function in healthy middle-aged volunteers.

This study investigates the effects of moderate-high altitude on lung function and exercise performance in 46 volunteers (19 females, 27 males), with a mean age of 42.4 +/- 1.4 years (+/- SEM) and varying smoking and exercise habits, who were not previously acclimatized. Measures obtained in the base camp (1140 m) and at altitude (2630 m), in random order, included forced spirometry, maximal voluntary ventilation, maximal inspiratory and expiratory pressures, arterial oxygen saturation and capillary lactate concentration after a standardized exercise test. The smoking history, Fagerström test and degree of habitual physical activity were also recorded for each participant. The percentage of smokers was similar in males (19%) and females (21%) (P = n.s.). Mean habitual physical activity index was 8.2 +/- 0.2 (range, 5.88-11.63). At the base camp, all lung function variables were within the normal range. Lactate concentration after exercise averaged 3.7 +/- 0.3 mm l-1. No significant change was observed at altitude, except for a higher heart rate and a lower arterial oxygen saturation (SaO2) (both at rest and after inspiratory manoeuvres). The smoking history and the degree of physical activity did not influence lung function or exercise performance at altitude. The results of this study show that in middle-aged, healthy, not particularly well-trained individuals, lung function is not significantly altered by moderate-high altitude, despite the absence of any acclimatization period and independent of their smoking history and previous exercise habits.

Altitude↗
PubMed2000

The Irving-Scholander legacy in polar physiology.

The pioneer arctic and cold environment studies of Laurence Irving and Per Scholander, undertaken during the middle decades of the 20th century, have had a wide ranging and major influence on the direction and character of experimental research on polar species. Their investigations included comparative studies of metabolism, insulation, and acclimatization of mammals and birds in arctic Alaska and the tropics. Freezing, supercooling, and antifreeze research included fishes, insects, and plants. They examined the special problems of cooling in appendages of mammals and birds and the potential for acclimatization of these structures by repeated cold exposure. Studies of cold exposure in human populations considered possible adaptive reactions. Their research on diving mammals opened a vast new area for studies with attention to asphyxial tolerance and temperature regulation. A lesser-known accomplishment was an innovative approach to recovery of ancient atmospheric gases from polar ice fields, an approach that was stimulated by original investigations of frozen insect larvae and gas permeability through ice.

Adaptation, Physiological↗
PubMed2003

Hydrostatic pressure and cellular respiration: are the values observed post-decompression representative of the reality under pressure?

The goal of this article was to assess whether a pressure change can constitute a bias of interpretation of pressure effects on pressure-acclimatized fishes. This work consisted first in a study of the recompression effects of mitochondrial extracts from eels pressure-acclimatized; and then in a study of red muscle fibre compression/decompression. The first experimental series shows a decrease of mitochondrial performances after recompression when compared with the decompressed group. It is concluded that recompression does not allow to get rid of decompression effects. This is confirmed by the second experimental series which show that a decompression induces a stronger reduction of MO2 than the previous compression.

Journal Article↗
PubMed1997

Prevalence and correlates of susceptibility to motion sickness.

Data on susceptibility to motion sickness were collected on a sample of 535 individuals divided into eight groups. The prevalence of motion sickness among Tibetans and Northeast Indians (28%) was slightly higher than Northwest Indians (26%). Generally speaking, females (27.3%) were more susceptible than males (16.8%). Among different groups, the highest incidence of susceptibility to motion sickness (SMS) was recorded in schizophrenic patients (30%), while the lowest in rowers (zero percent). Ears and eyes are the most potent receptors of provocative motion that causes sickness. Individuals with greater spatial and motor control, reflected in sports like rowing, athletics and professions like armed and paramilitary forces, were less susceptible to motion sickness. The SMS was significantly higher in individuals who suffered from spatial disorientation (35.05%), migraine (26.31%), gastrointestinal disorders (26.82%) and those who were more sensitive to unpleasant odours (24.64%) and preferred sweet flavours (24.48%) than their counterparts. These correlates have been utilized to explain the genesis of sickness using threshold model. Genetic and environmental pathways are strongly advocated. Past episodes of motion sickness acted as a strong psychological attribute in determining further episodes. The roadway buses and trucks proved more effective passive transportation types that caused sickness. The voluntary stabilization of the head and neck movements and gaze control proved very effective natural measures adopted by 38% subjects to avoid or limit motion sickness. About 50% of susceptible individuals became less susceptible or fully acclimatized to motion sickness due to habituation. The mean age at acclimatization was 21.98 +/- 5.93 years.

Adaptation, Physiological↗
PubMed1981

The effect of temperature on the behaviour of the infective larvae of Trichostrongylus colubriformis.

The effect of temperature on the behaviour of the infective larvae of Trichostrongylus colubriformis has been investigated. Larvae acclimatized at 3 degrees C or 20 degrees C respond to sudden or gradual increases in temperature by coiling. Increased temperature may indicate a risk of exposure to desiccation and elicits a behavioural response which optimizes survival. Larvae are straight when inactive; coiling is an active response to specific stimuli. Larval activity is initiated by exogenous stimuli. Mechanical disturbance is a major stimulus, the response being affected by changes in temperature. Larvae acclimatized at 3 degrees C or 20 degrees C show a peak of activity at temperatures between 15 and 25 degrees C.

Larva↗
PubMed1996

The course of Plasmodium berghei, P. chabaudi and P. yoelii infections in beta-thalassaemic mice.

In order to study the effects of acclimatization of Plasmodium in beta-thalassaemic mice, we used a mouse model of beta-thalassaemia (DBA/2J/beta-thal/beta-thal), similar to that observed in humans. We acclimatized 3 rodent malarias (P. berghei, P. chabaudi and P. yoelii) in DBA/2J and DBA/2J/beta-thal mice lines, by 4 intraperitoneal serial transfers. All 3 rodent malarias developed in red blood cells of beta-thalassaemic mice without losing their virulence. There was no delay in infection and peaks of parasitaemia were similar in beta-thalassaemic and normal mice. The mortality occurred earlier in beta-thalassaemic mice than in control mice for P. berghei and P. chabaudi. The difference was more pronounced for P. yoelii NS where normal mice did not die. These results could be explained by a failure of erythropoiesis in beta-thalassaemic mice, which are unable to compensate for the destruction of red blood cells by the parasites, and the mice died of anaemia. Ultrastructural examination of the rodent malaria parasites in beta-thalassaemic RBC showed a normal development even in the presence of Heinz bodies. In conclusion, no effective protection against malaria was provided by the beta-thalassaemia in this mouse model.

Animals↗
PubMed2002

Reduced heat stress in offices in the tropics using solar powered drying of the supply air.

Many solutions to indoor climate problems known from developed countries may have prohibitive installation and running costs in developing countries. The purpose was to develop a low-cost solution to heat stress in a hot and humid environment based on solar powered drying of supply air. Dry supply air may facilitate personal cooling by increased evaporation of sweat. Heat acclimatized people with efficient sweating may in particular benefit from this cooling. A prototype solar powered supply system for dried-only air was made. Air from the system was mixed with room air, heated to six different combinations of temperature and humidity and led to Personal Units for Ventilation and Cooling (PUVAC) in six cubicles simulating office workplaces. A total of 123 heat acclimatized subjects were exposed 45 min in each of the cubicles. A model for the combined effect of operative temperature of room, moisture content of room air, temperature of supply air and moisture content of supply air was developed based on the experiments. Reduction of moisture content in the supply air by 1.6 g/kg had the same effect as lowering the operative temperature by 1 degree C. The solar-powered system for supplying dry air is a low-cost alternative to traditional air conditioning in hot and humid regions.

Air Movements↗
PubMed1985

Cigarette smoking as a risk for cardiovascular disease. Part VI. Compensation with nicotine availability as a single variable.

In a biochemical investigation of human smoking behavior with filter cigarettes with high draw resistance that varied only in nicotine yield, we attempted to determine which nicotine levels provide desired nicotine intake with a minimum of physiologic and biochemical consequences. Twelve prescreened subjects were divided into two study groups and supplied with cigarettes that varied in nicotine delivery. Both groups were initially monitored while smoking their usual cigarette. At the following visit, smokers in group 1 received incremental increases and smokers in group 2 received incremental decreases in nicotine levels in assigned cigarettes. All subjects were monitored upon first exposure, after 1 week of acclimatization to each experimental cigarette, and upon return to their usual brands. Subjects in both groups were unable to compensate fully for their nicotine uptake from the lowest nicotine cigarette. In subjects in group 1, new nicotine baselines began to develop after 1 week of acclimatization to cigarettes containing 0.9 and 1.3 mg nicotine. New baseline nicotine levels were also noted in subjects receiving decreases in nicotine (group 2) after smoking the cigarette containing 1.3 mg nicotine for 1 week. Carboxyhemoglobin concentrations did not differ from those measured after the usual-brand cigarettes. Plasma cotinine concentrations increased as nicotine content per cigarette increased, except when subjects smoked a 1.3 mg nicotine cigarette. Plasma thiocyanate levels did not vary in either group. Systolic and diastolic blood pressures were generally not different from control values.

Adult↗
PubMed1971

Temperature and the regulation of enzyme activity in poikilotherms. Regulatory properties of fructose diphosphatase from muscle of the Alaskan king-crab.

1. The properties of fructose diphosphatase from skeletal muscle of the Alaskan king-crab (Paralithodes camtschatica) were examined over the physiological temperature range of the animal. 2. King-crab muscle fructose diphosphatase is first activated by Na(+) and NH(4) (+) and is then partially inhibited by these cations at concentrations higher than 10mm at 0 degrees , 8 degrees and 15 degrees C. Enzyme activity is stimulated by K(+) at 0 degrees C, but is curtailed at 8 degrees C and 15 degrees C, an effect that could render rate independent of temperature. 3. Affinity for substrate increases with decreasing temperature; below the temperature of acclimatization, K(m) for fructose 1,6-diphosphate increases, resulting in a complex U-shaped temperature-K(m) curve. 4. King-crab muscle fructose diphosphatase is inhibited by low concentrations of AMP. As with enzymes of other poikilotherms, inhibition by AMP is sensitive to temperature; the enzyme is least sensitive to inhibition by AMP near the temperature of acclimatization. 5. The affinity of fructose diphosphatase for fructose 1,6-diphosphate is enhanced by phosphoenolpyruvate, and this activation is temperature-sensitive; 0.5mm-phosphoenolpyruvate causes a sevenfold decrease in K(m) for fructose 1,6-diphosphate at 15 degrees C but a 25-fold decrease at 0 degrees C. 6. Phosphoenolpyruvate appears to decrease the affinity of king-crab muscle fructose diphosphatase for AMP at low temperature, whereas at the higher temperature it appears to enhance inhibition by AMP. Phosphoenolpyruvate was not observed to cause a reversal of inhibition of fructose diphosphatase activity by AMP. The identification of phosphoenolpyruvate as an activator of a rate-limiting step in gluconeogenesis permits the suggestion of a coupling of the controlling mechanisms of several steps in the glycolytic and gluconeogenic chains. 7. These findings suggest mechanisms for the maintenance and regulation of control of fructose diphosphatase activity in king-crab skeletal muscle at low temperature and under conditions that favour concomitant activity of phosphofructokinase.

Adenine Nucleotides↗
PubMed2004

Comparison of speech perception in background noise with acceptance of background noise in aided and unaided conditions.

Background noise is a significant factor influencing hearing-aid satisfaction and is a major reason for rejection of hearing aids. Attempts have been made by previous researchers to relate the use of hearing aids to speech perception in noise (SPIN), with an expectation of improved speech perception followed by an increased acceptance of hearing aids. Unfortunately, SPIN was not related to hearing-aid use or satisfaction. A new measure of listener reaction to background noise has been proposed. The acceptable noise level (ANL), expressed in decibels, is defined as a difference between the most comfortable listening level for speech and the highest background noise level that is acceptable when listening to and following a story. The ANL measure assumes that speech understanding in noise may not be as important as is the willingness to listen in the presence of noise. It has been established that people who accept background noise have smaller ANLs and tend to be "good" users of hearing aids. Conversely, people who cannot accept background noise have larger ANLs and may only use hearing aids occasionally or reject them altogether. Because this is a new measure, it was important to determine the reliability of the ANL over time with and without hearing aids, to determine the effect of acclimatization to hearing aids, and to compare the ANL to well-established measures such as speech perception scores collected with the SPIN test. Results from 50 listeners indicate that for both good and occasional hearing aid users, the ANL is comparable in reliability to the SPIN test and that both measures do not change with acclimatization. The ANLs and SPIN scores are unrelated. Although the SPIN scores improve with amplification, the ANLs are unaffected by amplification, suggesting that the ANL is inherent to an individual and can be established prior to hearing aid fitting as a possible predictor of hearing-aid use.

Adaptation, Physiological↗
PubMed2000

O2-sensing after carotid chemodenervation: hypoxic ventilatory responsiveness and upregulation of tyrosine hydroxylase mRNA in brainstem catecholaminergic cells.

Ventilatory responses to acute and long-term hypoxia are classically triggered by carotid chemoreceptors. The chemosensory inputs are carried within the carotid sinus nerve to the nucleus tractus solitarius and the brainstem respiratory centres. To investigate whether hypoxia acts directly on brainstem neurons or secondarily via carotid body inputs, we tested the ventilatory responses to acute and long-term hypoxia in rats with bilaterally transected carotid sinus nerves and in sham-operated rats. Because brainstem catecholaminergic neurons are part of the chemoreflex pathway, the ventilatory response to hypoxia was studied in association with the expression of tyrosine hydroxylase (TH). TH mRNA levels were assessed in the brainstem by in situ hybridization and hypoxic ventilatory responses were measured in vivo by plethysmography. After long-term hypoxia, TH mRNA levels in the nucleus tractus solitarius and ventrolateral medulla increased similarly in chemodenervated and sham-operated rats. Ventilatory acclimatization to hypoxia developed in chemodenervated rats, but to a lesser extent than in sham-operated rats. Ventilatory response to acute hypoxia, which was initially low in chemodenervated rats, was fully restored within 21 days in long-term hypoxic rats, as well as in normoxic animals which do not overexpress TH. Therefore, activation of brainstem catecholaminergic neurons and ventilatory adjustments to hypoxia occurred independently of carotid chemosensory inputs. O2-sensing mechanisms unmasked by carotid chemodenervation triggered two ventilatory adjustments: (i) a partial acclimatization to long-term hypoxia associated with TH upregulation; (ii) a complete restoration of acute hypoxic responsivity independent of TH upregulation.

Adaptation, Physiological↗
PubMed2002

Oxygen saturation course and altitude symptomatology during an expedition to broad peak (8047 m).

Thirteen healthy European mountaineers (11 male, 2 female) participated in the 62-day German-Pakistani Research Expedition to Broad Peak (8047 m) in the Karakorum, Pakistan. During ascent, base camp stay and approach to the summit, oxygen saturation was measured by pulse oximetry at rest, during exercise and during sleep; in addition, questionnaires on high altitude symptomatic had to be answered. We found a dramatic decrease in oxygen saturation especially at extreme altitudes (7100 m: Median 63%, Min 59%, Max 65%) and a long time required for real acclimatization. The lowest figures at 4850 m were found during maximal exercise, 77.5% (69 - 85%) and during sleep, 81% (73 - 88%), the highest ones at rest, 86.5% (77 - 89%). There was a significant correlation (Spearman rank correlation coefficient with ties) between measured oxygen saturation during the ascent to/stay at base camp and high altitude illness (p = 0.005 - 0.05), as well as with high altitude performance (p = 0.025 - 0.01). The limiting values of "no high altitude symptomatic", "high altitude discomfort", AMS and the malignant forms could be estimated for acclimatized (>90%/>80%/>70%/<70%) and unacclimatized (>80%/>70%/>65%/<65%) condition. Pulse oximetry is an objective non-invasive method of measurement that is easy to handle. It is a suitable device besides clinical examination and questionnaire-test in the diagnosis of high altitude illness even in the hands of non-professionals. The measurement at sleep can possibly explain present high altitude symptomatic despite of (nearly) normal oxygen saturation values at rest.

Adult↗
PubMed1993

Body composition and maximum alactic anaerobic performance during a one month stay at high altitude.

Prolonged altitude exposure usually leads to considerable weight loss of which a large part is from muscle tissue. This loss reduces maximum alactic anaerobic muscle power. It was hypothesized that most of the weight loss may simply be the result of malnutrition due to lack of palatable food in an uncomfortable environment. To test this hypothesis eight healthy male subjects (age 33.7 +/- 4.6 S.C. yr), well acclimatized to prevent symptoms of acute mountain sickness, were exposed for 4 weeks to an altitude of 5050 m with access to a large choice of palatable food in comfortable conditions. Body weight (with a scale), body composition (from skinfolds), arm muscle plus bone cross-sectional area (Am + b) and muscle plus bone leg volume (Vm+b) (from skinfolds and circumferences), maximum voluntary contraction force of the elbow flexors (MVC, with a load cell) and maximum jumping height (Hmax, on a platform) were measured before departure (SL) and in the first (ALT1), second (ALT2) and fourth week (ALT4) of their altitude sojourn. Three-day dietary records were obtained at SL and at ALT4. Body mass had decreased significantly at ALT2 (-3.8%) and at ALT4 (-4.6%) likely reflecting changes in body water homeostasis. No changes were found in %fat, Am+b, Vm+b, MVC or Hmax. Average dietary intake at SL was 8.96 +/- 1.45 MJ and had increased to 13.59 +/- 3.07 MJ at ALT4. In conclusion, up to an altitude of 5050 m loss of body mass from fat and muscle tissue, and hence impairment of maximum anaerobic muscle power (alactic) appears to be avoidable by food intake matched to energy expenditure. The latter may be achieved simply by proper acclimatization, sufficient comfort and availability of palatable food.

Adipose Tissue↗
PubMed1988

Hypoxic ventilatory response of rats born at simulated altitude.

Steady-state ventilatory response to isocapnic hypoxia was measured in awake rats: a) resident at sea level (Control); b) born at sea level and acclimatized to a simulated altitude of 3500 m (Newcomers); c) born and raised for two generations at a simulated altitude of 3500 m (HA-II Generation). Arterial PO2, PCO2, and pH were measured at the same time as ventilation. Resting ventilation (mean +/- SE) on room air in Control, Newcomers, and HA-II Generation was 707 +/- 25, 811 +/- 28 and 878 +/- 21 ml.min-1.kg-1, respectively. The ratios of ventilations measured at PaO2 55 and 100 Torr were 1.61 for Control, 1.52 for Newcomers, and 1.60 for HA-II Generation and were not significantly different from one another. The ventilatory response to 5% CO2 in air was also similar in all three groups. After four days at sea level, ventilatory responses of HA-II Generation to normoxia or isocapnic hypoxia were the same as those of sea level control. We conclude that the HA-II Generation groups had ventilatory responses to hypoxia that did not differ from those of Newcomers acclimatized to the same altitude. Unlike man, rats that were born and raised at altitude for two generations did not show any "blunting" of the ventilatory response to hypoxia.

Altitude↗
PubMed1976

Sherpas living permanently at high altitutde: a new pattern of adaptation.

Adaptation of Sherpas to high altitude has been studied and compared with that of Caucasians acclimatized to high altitude. Sherpas living permanently at 4000 m above sea level do not have increased hematological parameters (i.e., red cell number, hematocrit, hemoglobin content, and 2,3-diphosphoglycerate/hemoglobin ratio) and have a higher affinity of blood for oxygen as compared with acclimatized Caucasians. Sherpas permanently living at low altitude, on the contrary, have lower affinity of blood for oxygen than do Caucasians living at comparable altitude and are mildly "anemic,". Various other red cell biochemical parameters (possibly related to adaptation to altitude) have also been studied in the same population. We suggest that Sherpas are genetically better adapted to high altitude than are Amerindians living on the Peruvian highlands, possibly as a consequence of a much more prolonged exposure to such an ecological factor of selection as high altitude.

Adaptation, Physiological↗
PubMed2001

Effect of copper sulfate addition on nitrous-oxide emission in high speed dentrification process using macro-porous cellulose carrier.

Nitrous oxide emission from the immobilized denitrification process was investigated under copper-added and copper-free conditions to realize high-speed denitrification with minimum nitrous oxide emission. Nitrous oxide emission was found to be smaller in culture using immobilized cells acclimatized under copper-added condition. Transient phenomena of nitrous oxide emission, nitrate reduction and nitrite accumulation were then investigated in repeated batch experiments by transferring immobilized cells acclimatized in copper-free conditions into copper-added medium. Nitrous oxide emission obviously decreased, and maximum nitrous oxide concentration of seventh batch culture was about 1/40,000 of that of first batch culture. Nitrate reduction gradually decreased from second batch to fourth batch culture and it turned to increase from fifth batch culture to seventh batch culture. At seventh batch culture, nitrate reduction rate was restored up to 80% of the initial speed. This repeated batch experiment clarified that nitrous oxide emission was repressed by copper sulfate addition. The effect of pH and temperature on nitrous oxide emission were also investigated in a continuous denitrification experiment under copper added conditions. Nitrous oxide emission was increased by lowering pH and lowering temperature. At optimum operating condition (pH8.0, 30 degrees C), nitrogen removal efficiency of 99.9%, nitrous-oxide concentration in the emitted gas of 3.1ppm(v/v) and conversion ratio to nitrous oxide of 0.000316% were obtained when 280mg-Nl(-1) nitrate containing medium was treated at 6 hours of hydraulic retention time.

Cells, Cultured↗
PubMed2005

Application of aerobic granular sludge in polishing the UASB effluent.

Stable aerobic granules were successfully developed in a sequencing batch reactor (SBR) fed with glucose and sodium acetate as the main carbon sources, and then they were acclimatized to polish the effluent from an up-flow anaerobic sludge blanket (UASB) reactor. It was found that more than 95% chemical oxygen demand (COD) and 85% suspended solids (SS) in the UASB effluent could be removed by an aerobic granular SBR as a post treatment unit. The performance of the SBR was stable over the whole experimental period. At an organic loading rate (OLR) of 4.5 to 5.4 g l(-1) d(-1), the acclimatized aerobic granules had an average diameter of 3.5 to 6.0 mm and a minimal settling velocity of 72 m h(-1). The biomass concentration in the SBR was as high as 8.4 g (dry weight) l(-1). This study showed for the first time that aerobic granular sludge in SBR would be an effective means to polish the effluent from UASB reactor.

Aerobiosis↗