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PubMed1975

Variation in the metabolizable energy values of diets and dietary components fed to adult roosters.

Two experiments were conducted to measure the variability of the M.E. values of diets and dietary ingredients fed to adult S.C.W.L. roosters. The first experiment was concerned with the variability between birds and days, the acclimatization to dietary change and the effect of the nitrogen correction. The standard error of the mean dietary M.E. value appropriate to an individual bird on one day was found to be 0.073 kcal./g. Increasing the number of days of excreta collection reduced this value slightly faster than did increasing the number of birds. The results suggest that the dietary acclimatization period should be at least 48 hr. The nitrogen correction was very small and of doubtful value. The second experiment comprised 5 bioassays in each of which 6 different samples of grain were fed at 3 levels of dietary inclusion (25, 50 and 75%) to birds drawn from the population used in the first experiment. The standard error of the mean dietary M.E. value was in agreement with the earlier value. The variance of ingredient M.E. values increased as the level of dietary inclusion decreased. Standard deviations of the mean M.E. value of an ingredient predicted from the data of the first experiment were in agreement with actual values observed in the second experiment. It is concluded that the adult rooster is suitable for use in bioassays designed to measure the M.E. values of diets and ingredients.

Acclimatization↗
PubMed2000

Physiological and cognitive performance of soldiers conducting routine patrol and reconnaissance operations in the tropics.

The physiological and cognitive performance of acclimatized soldiers undertaking routine patrol and reconnaissance activities in the tropics was investigated. Data were obtained during a patrol and a reconnaissance exercise followed by a short assault. Ambient conditions were characterized by temperatures of 30 to 33 degrees C, low humidity (52-59%), and moderate to high solar radiation. Maximum metabolic rates during patrol were high, although the equipment carried was modest and the terrain was not severe. Rectal temperatures peaked at 38.2 and 38.4 degrees C for patrol and assault activities, respectively; peak heart rates were 160 beats min-1 for each activity. Sweat rates of approximately 9 and 14 g kg-1 body weight h-1 were recorded for patrol and assault activities, respectively. The soldiers maintained adequate hydration levels and displayed no evidence of deterioration in cognitive performance. The data show that routine operational activities in tropical conditions induced physiological strain in acclimatized soldiers. However, this strain was not maintained at hazardous levels for lengthy periods.

Acclimatization↗
PubMed1975

[Certain hemodynamic indicators during rest and after intensive physical exercise at high altitude].

For 5 years 364 normal males, aged 19--25, were studied at the altitude of 3800--4200 m, along with local inhabitants of the mountain region; the hemodynamic shifts and arterial blood oxygenation were studied with the base metabolism conditions preserved both at rest, and after intensive physical exercises performed according to the step-test method with the maximum tempo of the work (cardiological motion test, WHO, 1967). The initial reaction of the cardiovascular system to the high altitude conditions manifested itself in an increased stroke volume and cardiac output, of the volume speed of blood ejection, of the cardiac index in a decrease of the total peripheral resistance and oxygen saturation of the arterial blood. This reaction was interpreted as a compensatory one. In the course of acclimatizing, the cardiac output and the pulse amplitude of the arterial pressure gradually decreased, and the total peripheral resistance increased. These hemodynamic changes must be of an adaptative nature. The maximum physical workload caused a distinct intensification of the circulatory reactions, especially in those living for considerable periods of time at high altitude and in local inhabitants. The general state of the examined remained good. Hence, these persons have a considerable reserve of functional capacities of their cardiovascular system, and can perform hard muscle work at high altitude. Individuals staying at high altitude for only short periods of time react to intensive physical workloads by a less distinct intensification of the contractile capacity of the heart and by a sharp decrease of blood oxygenation, considerable acceleration of the heart rate and respiration rate, as well as by a deterioriation of their general state. Such muscular efforts cause overloading of the heart only in persons with a short-term acclimatizing.

Acclimatization↗
PubMedDate not supplied

[Adaptation times of flight-technical personnel to work in subtropical climate conditions].

The results of studying the process and time of adaptation of two groups of the flying personnel who arrived from moderate climate to the subtropic climate show that the early stage of acclimatization lasts from two to four weeks, depending on the season. From the physiological point of view the best season is spring-summer. During this period the time of acclimatization is two times shorter than in winter.

Acclimatization↗
PubMed1976

Potassium losses in sweat under heat stress.

Six healthy, heat-acclimatized subjects were exposed to different hot and humid environments in a climatic chamber and sodium, potassium, and chloride concentrations in their sweat, urine, and blood were determined. The concentration of potassium in sweat was found to be considerably higher than that in the plasma, whereas that of sodium and chloride was very much lower. The concentration of potassium in urine was also 8-12 times higher than that in the plasma as compared to 0.5 to 1.5 times higher for sodium and chloride. The total daily computed losses of potassium in sweat and urine, of a person working in severe heat in the tropics, can be about 116 mEq as against a dietary intake of 97 mEq/d, thereby resulting in negative potassium balance. The potassium depletion in sweat, even in acclimatized Indians, is thus heavy and is likely to play an important role in the causation of heat-illness.

Acclimatization↗
PubMed2004

[A study of high altitude environment affecting on worker's health during the constructing Qinghai-Xizang railway].

OBJECTIVE: To study high altitude environment affecting on worker's health METHODS: Using the cohort study, the altitude reaction was investigated and the WBC, RBC, Hb and oxygenation indexes were measured on workers in several periods, namely, acclimatization period, initially arrived high altitude and resident 90 days. RESULTS: The 83.3% of men had altitude reactions with different kinds at initially arrived high altitude. The headache was the most. The rate of abnormal blood pressure increased with altitude and resident time (P < 0.01). The rate of 90 day's group was 41.7%. The rise of diastole pressure was obvious (P < 0.01). As the beginning of arrived highland, the increase of WBC, RBC were significant (P < 0.01). The increase of Hb appeared only in 90 day's group. The level of malondialdehyde (MDA) obviously increased during acclimatization period and increased with altitude and resident time (P < 0.01). The activity of catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) increased significantly in 90 day's group [(222.36 +/- 36.52) x 10(3) U/L, (158.49 +/- 14.42) U/L, (45.74 +/- 8.31) NU/ml respectively] (P < 0.01). CONCLUSION: The high altitude environment may result in the abnormal blood pressure, the rise of diastolic pressure was important. It lead to the increase of WBC, RBC, Hb. It initiated activity of oxygenation reaction. The symptoms of headache, dizziness, loss of appetite and insomnia appeared as working in high altitude environment.

Acclimatization↗
PubMed2000

[Effects of acclimation temperature on the growth of Perna viridis (Bivalvia: Mytilidae), using the RNA/DNA ratio].

Temperature affects growth rate in aquatic organisms. This can be evaluated in short term using biochemical indexes (RNA/DNA and Protein/DNA). The effect of acclimatization temperature on the instantaneous growth and physiological condition of Perna viridis was studied in organisms collected in La Esmeralda, Sucre State (Venezuela) and taken to the laboratory, where groups of 100 organisms (size 3.0 - 3.5 cm, anteroposterior measurement) were acclimatized at 15, 20, 26 or 28 degrees C during four weeks. Later they were kept in a 60 liters aquarium for another six weeks under the same conditions. Each week, ten organisms per group were extracted to measure concentrations of RNA, DNA (by a fluorometric method with ethidium bromide) and proteins (by a colorimetric method), in tissues (digestive gland, adductor muscle and gills). Protein concentration was greater and highly significant at 15 degrees C for all studied tissues. The opposite was obtained with the RNA/DNA and Protein/DNA ratios: the greatest increase was observed at the highest temperature (28 degrees C) for all tissues. At the lowest temperature there was a tendency to reduce both indexes with time. Greater instantaneous growth can be expected at higher temperatures and 28 degrees C was optimal for growth in these specimens.

Acclimatization↗
PubMed1992

Oxygen transport during exercise at altitude and the lactate paradox: lessons from Operation Everest II and Pikes Peak.

It seems unlikely that oxygen-limited metabolism explains the increased lactate concentrations in blood or muscle during exercise at high altitude compared with sea level values because: 1. Even marked hypoxia equivalent to that at the summit of Mt. Everest may not be sufficiently severe to impair function or to impair muscle oxidative metabolism markedly during exercise; 2. At this very high altitude, muscle hypoxemia is probably not the limiting factor for exercise performance; other systems, i.e., the cerebral cortex [24, 33], probably fail before hypoxemia impairs muscle metabolism; 3. The traditional view of oxygen-limited aerobic metabolism during exercise at high altitude does not explain a long-standing dilemma in altitude physiology, the lactate paradox (in which blood lactate accumulation during exercise is increased on arrival at high altitude but falls with acclimatization), because the lactate fall is independent of muscle oxygenation; 4. Net lactate release by the leg during exercise is independent of oxygenation; 5. Kinetic studies show that lactate appearance and disappearance are closely linked and both increase with acute altitude exposure and decrease with acclimatization; 6. Lactate appearance rate is strongly correlated with, and may be influenced by, the extent of beta-adrenergic stimulation; 7. The beta-adrenergic stimulation may be, in part, determined by the degree of arterial oxygenation.

Acclimatization↗
PubMedDate not supplied

Does hydrostatic pressure have an effect on reactive oxygen species in the eel?

Eels are submitted to hydrostatic pressure (HP) during their spawning migration (about 6000 Km). Before migration, they change from the yellow to the silver stage (silvering process). The effects of HP in relation to the silvering process have been studied on aerobic metabolism and more precisely on reactive oxygen species (ROS) metabolism. HP acclimatization of yellow eels improves oxidative phosphorylation together with supposed concomitant changes in electron leak and ROS production. Therefore hydroxyl radical (OH*) production, superoxyde dismutase and catalase activities, malondialdehyde content and in parallel oxygen consumption were measured in the red muscle of long-term pressure exposed and control group yellow and silver eels. At atmospheric pressure, yellow eels exhibited significantly higher oxygen consumption and OH* production than silver eels; and significantly lower malondialdehyde content. This could be due to the increase in membrane fluidity induced by the silvering process. Long-term HP exposure decreases yellow eel oxygen consumption which becomes similar to that of the silver stage. In parallel there is a decrease in OH* production and concomitantly antioxidant enzyme activities follow the same tendency. Thus the respiratory chain improvement in pressure acclimatized yellow eels is accompanied by a ROS production decrease which could mean an electron leak decrease.

Acclimatization↗
PubMedDate not supplied

Effect of simulated ascent to 3500 meter on neuro-endocrine functions.

Ascent to extreme High Altitude (HA) is in steps and it entails acclimatization at moderately HA locations. In terms of acclimatization, it is pertinent to understand the physiological changes, which occur on immediate ascent to moderate HA. The study aimed to evaluate the effect of ascent to 3500 m on neuro-endocrine responses in the first hour of induction. The plasma levels of catecholamines and cortisol were measured before and after one hour of ascent to high altitude. The peripheral oxygen saturation (SpO2), Galvanic Skin Resistance (GSR), Heart Rate (HR) and Blood Pressure (BP) were simultaneously monitored. The plasma epinephrine, norepinephrine, dopamine and cortisol were increased after one-hour exposure to 3500 m altitude as compared to before exposure. The SpO2 showed a significant decrease during and after high altitude induction. The heart rate and diastolic BP increased at 3500 m whereas the GSR did not show significant changes. There are changes in neuroendocrine responses, which reflect a sympathetic over activity in the first hour of exposure to 3500 m.

Acclimatization↗
PubMed1988

[Periodic respiration during sleep at high altitude. Effects of a hypnotic benzodiazepine, loprazolam].

Sleep and respiration studies were carried out in 12 subjects (9 males, 3 females) at an altitude of 4,800 metres, during effect of a French expedition in the Himalayas. The effect of loprazolam, a hypnotic benzodiazepine, was investigated in a double-blind, 2 parallel group, 1 mg loprazolam versus placebo trial. Sleep was evaluated by means of electroencephalographic recordings and questionnaires. The effects of altitude in each subject were intercurrent wakefulness increase, slow wave sleep and paradoxical sleep decrease and nocturnal periodic breathing. The mean duration of sleep apnea episodes was 12 seconds with a maximum of 24 seconds. These episodes occurred during stages 1 or 2 of sleep and during paradoxical sleep. Female subjects exhibited less periodic breathing than males. Acclimatization to high altitude increased total sleep time, stage 3 duration and percentage of paradoxical sleep. Loprazolam tended to decrease stage 2 latency and did not worsen slow wave sleep depression or episodes of apnea. Normal amounts of slow wave sleep and intrasleep wakefulness appeared in the loprazolam group after acclimatization.

Acclimatization↗
PubMed1988

Age-dependent influence of a moderate altitude (1,350 m) on the rat cardiopulmonary system.

The aim of the study was to determine whether a moderate altitude (1,350 m, Strbské Pleso, High Tatras) would act as a hypoxic stimulus on the cardiopulmonary system of young and adult rats. We used three experimental groups of animals differing in the duration of time for which they were kept at the given altitude (60 and 120 days) and the age at which they were acclimatized (from the 5th and the 60th day of life). The controls were kept at an altitude of 200 m (Prague). We found that an altitude of 1,350 m produced a significant increase in blood pressure in the lesser circulation; this response did not depend on the animals' age. Right ventricular enlargement occurred at the same time and was more pronounced in rats which had been acclimatized from infancy. The systemic blood pressure fell mildly, but significantly, only in animals exposed to altitude from adulthood; elevation of the haematocrit was likewise recorded only in this group. The results show that even a moderate altitude influences the cardiopulmonary system of the rat in a manner characteristic of the effect of chronic hypoxic hypoxia.

Acclimatization↗
PubMed1986

Lactate during exercise at extreme altitude.

Maximal exercise at extreme altitude results in profound arterial hypoxemia and, presumably, extreme tissue hypoxia. The best evidence available indicates that the resting arterial PO2 on the summit of Mount Everest is about 28 torr and that it falls even further during exercise. Nevertheless, some 10 climbers have now reached the summit without supplementary oxygen. Paradoxically, blood lactate for a given work rate at high altitude in acclimatized subjects is essentially the same as at sea level. Because work capacity decreases markedly with increasing altitude, maximal blood lactate also falls. Extrapolation of available data up to 6300 m indicates that a climber who reaches the Everest summit will have no increase in blood lactate. The cause of the low blood lactate during exercise at extreme altitude is not fully understood. One possibility is depletion of plasma bicarbonate in acclimatized subjects, which reduces buffering and results in large increases in H+ concentration for a given release of lactate. The consequent local fall in pH may inhibit enzymes, e.g., phosphofructokinase (EC 2.7.1.56), in the glycolytic pathway.

Acclimatization↗
PubMed1986

Effects of salt loading during exercise in a hot dry climate.

Strenuous work or sports activities in a hot environment can cause significant fluid and salt losses due to excessive sweating. Fluid replacement is commonly accepted to be beneficial, but controversy surrounds the necessity of adding salt to the dietary intake in hot climates. Five healthy young men participated in a self-controlled experiment designed to investigate the effects of salt loading on acclimatized people exercising under controlled laboratory conditions. The additional salt ingestion was found to cause an increase in body weight, rectal temperature, heart rate, urinary sodium and potassium concentrations and in the total amounts of sodium and chloride excreted in urine during the exercise. Furthermore, it decreased plasma aldosterone level and sweat chloride excretion, but did not affect fluid intake, urine output, sweat rate, skin temperature, excretion of sodium and potassium in sweat or urinary potassium content and chloride concentration. Neither did the additional salt intake affect plasma electrolyte levels, renin activity or acid base balance. It is concluded that acclimatized people living in a hot dry climate need no supplementary salt to their daily dietary intake while engaging in physical exercise or sports activities up to two hours a day. Salt loading has no beneficial effects in these conditions and may even be hazardous.

Acclimatization↗
PubMedDate not supplied

The lung at high altitude.

Men and mammals (excluding the indigenous mountain species) who are born at high altitude, or who ascend to live there for a long period, have to undergo acclimatization which affects virtually every system in the body. Since chronic hypoxia is the most important adverse factor in the mountain environment, the lung plays a major part in the process and shows many alterations in structure and function. However, we remain ignorant about many aspects of acclimatization of the lung to hypoxia especially at the ultrastructural level with respect to those cells whose normal function is not yet established. An account of what is known is given in this paper.

Acclimatization↗
PubMed1993

Effects of prolonged head-down bed rest on physiological responses to moderate hypoxia.

To determine the effects of hypoxia on physiological responses to simulated zero-gravity, cardiopulmonary and fluid balance measurements were made in 6 subjects (acclimatized to 5,400 ft) before and during 5 degrees head-down bed rest (HDBR) over 8 d at 10,678 ft and a second time at this altitude as controls (CON). The VO2max increased by 9% after CON, but fell 3% after HDBR (p < 0.05). This reduction in work capacity during HDBR could be accounted for by inactivity. The heart rate response to a head-up tilt was greatly enhanced following HDBR, while mean blood pressure was lower. No significant negative impact of HDBR was noted on the ability to acclimatize to hypoxia in terms of pulmonary mechanics, gas exchange, circulatory or mental function measurements. No evidence of pulmonary interstitial edema or congestion was noted during HDBR at the lower PIO2 and blood rheology properties were not negatively altered. Symptoms of altitude illness were more prevalent, but not marked, during HDBR and arterial blood gases and oxygenation were not seriously effected by simulated microgravity. Declines in base excess with altitude were similar in both conditions. The study demonstrated a minimal effect of HDBR on the ability to adjust to this level of hypoxia.

Acclimatization↗
PubMed1977

Recurrent heat exposure: effects on levels of plasma and urinary sodium and potassium in resting and exercising men.

Heat acclimatization was induced in a group of healthy young men by walking on a treadmill (5.6 km/h, 49 degrees C/27 degrees C dry/wet bulb, 90 min/day, 7 d) and confirmed by observing significantly reduced final rectal temperatures and heart rates on the seventh day of exercise in the heat. A second group of men, paired for maximal oxygen consumption and body weight, remained sedentary under identical environmental conditions. While the mild exercise combined with the severe heat conditions induced significant hyperkalemia (p less than 0.02, minimal significance) on both the first and final days, there did occur an attenuated response with significantly (p less than 0.01) reduced plasma K+ after 45 min on the seventh day when compared with first day levels. No significant inter- or intragroup differences in plasma Na+ content of 24-h urine samples showed that men exercising in the heat retained an increased ability to conserve Na+, while sedentary individuals consistently displayed increased excretion of Na+. Thus, we concluded that even the mild exercise described herein effected hyperkalemia at each sampling time, but the level of hyperkalemia was attenuated after acclimatization, and while Na+ was conserved in the exercising men, no such adaptive processes occurred in sedentary individuals.

Acclimatization↗
PubMed1977

Effect of sojourn at 3200-m altitude on spinal reflexes in young adult males.

Studies of the H reflex and the Achilles tendon reflex (ATR) were performed in 12 healthy males under six conditions: 1) sea level control, 2) during the first 1-3 h at altitude while normoxic conditions were maintained, 3-5) at 6, 24 and 72 h of hypoxia, and 6) after Ve acclimatization at altitude in 5-14 d. After altitude acclimatization, the peak-to-peak amplitude of the H reflex and the ATR response was significantly elevated over control. A trend toward decreased amplitudes of both the ATR and the H reflex was observed at 6 h after the onset of hypoxia. There was no significant alteration in latency of the H reflex under any test condition. These findings suggest that sojourn at altitude by sea level residents induces changes in spinal motor reflexes. These changes are most probably mediated by altered high central modulation of the cord.

Acclimatization↗