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PubMed2000

Operation Everest III: energy and water balance.

We hypothesized that hypoxia decreases energy intake and increases total energy requirement and, additionally, that decreased barometric pressure increases total water requirement. Energy and water balance was studied over 31 days in a hypobaric chamber at 452-253 Torr (corresponding to 4,500-8,848 m altitude), after 7 days acclimatization at 4,350 m. Subjects were eight men, age 27+/-4 years (mean+/-SD), body mass index 22.9+/-1.5 kg/m2. Food and water intake was measured with weighed dietary records, energy expenditure and water loss with labelled water. Insensible water loss was calculated as total water loss minus urinary and faecal water loss. Energy intake at normoxia was 13.6+/-1.8 MJ/d. Energy intake decreased from 10.4+/-2.1 to 8.3+/-1.9 MJ/d (P<0.001) and energy expenditure from 13.3+/-1.6 to 12.1+/-1.8 MJ/d (P<0.001) over the first and second 15-day intervals of progressive hypoxia. Absolute insensible water loss did not change (1.67+/-0.26 and 1.66+/-0.37 l/d), however, adjusted for energy expenditure it increased with ambient pressure reduction (P<0.05). In conclusion, hypoxia induced a negative energy balance, mainly by a reduction of energy intake. Overall insensible water loss was unchanged because the increase in respiratory evaporative water loss was counterbalanced by a decrease in metabolic rate that probably limited the hypoxia-induced increase in ventilation.

Acclimatization↗
PubMed2006

Characterization of LF9, an octoploid strawberry genotype selected for rapid regeneration and transformation.

Cultivated strawberry (Fragaria xananassa) is a valuable crop, yet the absence of a rapid, high-throughput transgenic system has precluded meaningful application of biotechnology and translation of information from plant models to this crop. A new octoploid strawberry genetic line Laboratory Festival #9 has been identified, selected solely for its rapid regeneration and efficient transformation. Direct organogenesis has been achieved from all tissues tested, with rapidly-growing shoot initials visible in as few as 13 days. The conditions for optimal shoot regeneration, transformant selection, root generation, and plant acclimatization are presented. The progression from explant to plant in soil can be achieved in about 60 days. The development of transformation protocols in this rapid-cycling genotype allows high-throughput studies of gene function in the octoploid strawberry genetic background.

Acclimatization↗
PubMed2006

Seasonal thermogenesis and body mass regulation in plateau pikas (Ochotona curzoniae).

Changes in photoperiod, ambient temperature and food availability trigger seasonal acclimatization in physiology and behavior of many animals. In the present study, seasonal adjustments in body mass and in several physiological, hormonal, and biochemical markers were examined in wild-captured plateau pikas (Ochotona curzoniae) from the Qinghai-Tibetan plateau. Our results showed that plateau pikas maintained a relatively constant body mass throughout the year and showed no seasonal changes in body fat mass and circulating levels of serum leptin. However, nonshivering thermogenesis, cytochrome c oxidase activity, and mitochondrial uncoupling protein 1 (UCP1) contents in brown adipose tissues were significantly enhanced in winter. Further, serum leptin levels were positively correlated with body mass and body fat mass while negatively correlated with UCP1 contents. Together, these data suggest that plateau pikas mainly depend on increasing thermogenic capacities, rather than decreasing body mass, to cope with cold, and leptin may play a potential role in their thermogenesis and body mass regulation.

Acclimatization↗
PubMed2006

Role of glucagon in the control of heat production in ducklings.

Glucagon is known to be a central modulator of neural activity and a peripheral thermogenic effect. The purpose of this study was to better understand the role of glucagon in the control of heat production, shivering and particularly as a mediator of nonshivering thermogenesis (NST) in ducklings. In order to study the mechanism of NST, an intracerebroventricular (i.c.v.) injection of glucagon (10(-7) M) in to thermoneutral (TN), chronically glucagon treated (GT) and cold acclimatized (CA) ducklings exposed to acute cold (4 degrees C) or a thermoneutrality (25 degrees C), was performed. At 25 degrees C ambient temperature (Ta), the metabolic rate (MR) remained unchanged after glucagon injection. At 4 degrees C Ta i.c.v. glucagon injection, no significant change in MR was observed in GT and CA ducklings during 160 min of cold exposure, whereas there was 63% decrease in MR in (TN) ducklings (5.02 +/- 0.1 2 vs 7.91 +/- 0.1 4 W/kg(-1) p < 0.05). Shivering activity was completely suppressed in TN and GT ducklings after glucagon administration. The NST was estimated to be 3.26 W/kg. This findings suggest that glucagon administered into the brain has no thermogenic effect but could be involved in the central control of somatic motricity, and here we demonstrated for the first time, of our knowledge, that central glucagon have a role in the development of nonshivering thermogenesis during prolonged cold via an inhibition of shivering in birds.

Acclimatization↗
PubMed2005

[Concept for a bioclimatic evaluation of an expedition and trekking area at moderate and high altitudes].

This paper presents a concept which is built up on climate data with a long period of observation (temperature, wind conditions, precipitation, irradiation, and the frequency of low pressure weather situations with unfavorable biotropy stages). It therefore allows an evaluation of the bioclimate of a high mountain area. With the help of this relatively simple method, the risk of problems like AMS can be better estimated. Latest comparisons between different agencies of expeditions show that often the time schedule for climbing to the summit is too short and allows too little time for acclimatization; furthermore the number of days allowed for recreation is too small. A comparison of selected alpine regions shows better conditions in, for example, the Mount Kenia/Kilimandjaro region and parts of the western Andes in Chile, whereas the Himalaya and the Karakorum group can be problematic.

Acclimatization↗
PubMed1987

Enhanced left ventricular systolic performance at high altitude during Operation Everest II.

Serial rest and upright cycle exercise 2-dimensional echocardiographic studies were performed in 7 healthy young men during acclimatization to a simulated altitude of 29,000 feet (barometric pressure [PB] 240 torr) in a chamber for 40 days. In all subjects left ventricular (LV) end-diastolic, end-systolic and stroke volumes progressively decreased, with mean reductions of 21%, 40% and 14%, respectively, on ascent to 25,000 feet (PB 282 torr) at rest, and reductions of 23%, 43% and 14% during 60-W exercise. At PB 282 torr, mean arterial blood O2 partial pressures were 37 torr (rest) and 32 torr (exercise), with corresponding O2 saturations of 68% and 59%. All 3 indexes of LV systolic function examined--ejection fraction, ratio of peak systolic pressure to end-systolic volume and mean normalized systolic ejection rate at rest--were sustained in all subjects at high altitude despite reduced preload, pulmonary hypertension and severe hypoxemia. Increases in ejection fraction of 6% at rest and 10% during exercise developed at PB 282 torr and a higher mean normalized systolic ejection rate in association with elevated circulating catecholamines reflecting enhanced sympathetic activity. LV systolic function is not a limiting factor in compromising the exercise capacity of normal humans on ascent to high altitude, even to the peak of Mt. Everest.

Acclimatization↗
PubMed1992

The acute-phase response to turpentine-induced abscesses in malnourished rats at different environmental temperatures.

An assessment was made of the independent effect environmental temperature (13, 21, and 30 degrees C) and either protein deficiency or energy deficiency on the metabolic response of rats that had aseptic abscesses induced by subcutaneous injections of turpentine. Measurements of food intake, alpha 2-macroglobulin (alpha 2-M; a major acute-phase protein in the rat), albumin, and various circulating metabolites were made 48 hours after turpentine injection in animals acclimatized at 13, 21, and 30 degrees C and compared with pair-fed controls. Despite differences in basal circulating albumin concentrations between controls and protein deficient rats (P less than .001), turpentine produced a similar reduction in all groups of animals (approximately 10 g/L), independent of environmental temperature. The alpha 2-M response to turpentine was attenuated in all protein-deficient animals and also in the energy-restricted animals at 13 degrees C. The increase in circulating 3-hydroxybutyrate (BOH) and nonesterified fatty acid (NEFA) concentrations, which normally occur with reduced dietary intake, was reduced in the turpentine-injected animals to an extent that depended on prior dietary intake. It is concluded that the metabolic response, particularly the acute-phase protein response, to a standard form of "injury" is affected by protein deficiency and possibly by energy restriction under adverse environmental temperature.

Abscess↗
PubMed1995

Oxygen consumption and body temperature rhythms in the golden spiny mouse: responses to changes in day length.

The golden spiny mouse Acomys russatus is a rock dwelling rodent which lives in extremely arid and hot habitats. In Israel it is nocturnal except in areas in which it coexists with the common spiny mouse A. cahirinus. In such places it is diurnal. The daily rhythms of body temperature (Tb) and oxygen consumption (VO2) were compared in mice acclimated to two different photoperiod regimes in the laboratory: 8L:16D (short day) and 16L:8D (long day) at a constant ambient temperature. The daily rhythms of VO2 and of Tb in A. russatus were found to differ greatly under long and short photoperiod. Both parameters peaked at lights-out under both photoperiod regimes. In short day acclimated mice the effect of transmitter implantation was also studied. VO2 values at night were lower after implanting. The results of this study show that Tb and VO2 rhythms are altered by the lighting regimes. Seasonal acclimatization of thermoregulatory mechanisms in the golden spiny mouse are partly induced by changes in photoperiodicity.

Acclimatization↗
PubMed1975

Breath holding and rebreathing at low and high altitude.

Breath holding and rebreathing have been carried out at sea level in lowlanders and at high altitude in acclimatized lowlanders and in highlanders. It has been shown that the values of gasping time, breath-holding time, rebreathing time and the composition of the alveolar gases at the breaking point are modified by chronic hypoxia, especially in highlanders. The modifications observed can be explained by different sensitivities to humoral stimuli of the different groups of subjects. The importance of nonhumoral factors, as studied by comparing apnea and rebreathing, seems modified at altitude, especially in highlanders, although the mechanism of this change is unknown.

Acclimatization↗
PubMed1977

Temperature-induced variations of blood acid-base status in the lugworm, Arenicola marina (L.): II. In vivo study.

Lugworms, Arenicola marina (L.), acclimatized at 16-17 degrees C, were acclimated at temperatures between 5.3 and 25.7 degrees C for 96 h. Whereas in vitro Arenicola blood behaves like a Rosenthal system, in vivo prebranchial blood does not: the higher the acclimation temperature, the lower the pHv and [HCO3]V, PVCO2, remaining practically constant. Nevertheless, the very low relative alkalinity of the blood in vivo ([OH-]/[H+] is less than 3), and the degree of dissociation of extra- and intracellular proteins, remain practically constant whatever the temperature. From examples in the literature together with these results, it is concluded that poikilothermic air-breathers and poikilothermic water-breathers regulate their blood pH in the face of temperature changes by contrasting mechanisms. In the first, regulation is almost instantaneous and takes place at the pulmonary level through adjustment of CO2 exchanges. In the second this regulation is slow and mainly extraventilatory, occurring through ionic exchanges. This contrast must be considered in relation with differences in blood PCO2 values, caused by the much higher O2 capacitance of air compared to water.

Acclimatization↗
PubMed1983

The effects of unilateral carotid body excision on ventilatory control in goats.

The purpose of this study was to determine whether or not unilateral carotid body excision (UCBE) alters normal respiratory control in awake and otherwise intact goats. We measured resting VE and blood gas tensions and pH and ventilatory responses (VR) to NaCN, dopamine and Doxapram in awake goats before and after UCBE. Resting ventilation, blood gas tensions and pH, and the VR to the above stimuli were not altered by UCBE. During exposure to hypoxia in a hypobaric chamber (PB = 450 torr), PaCO2 decreased in UCBE goats over the first hour, indicating acute hypoxic hyperventilation. During the subsequent 8 h, PaCO2 decreased an additional 5-6 torr, suggesting ventilatory acclimatization to chronic hypoxia (VACH). The response was similar to that observed in intact goats. Acute normoxia following 6 and 8 hr did not completely alleviate the hypocapnia of prolonged hypoxia, further suggesting VACH. We conclude that sufficient redundancy exists in the inputs from the paired carotid body chemoreceptors so that normal ventilatory responsiveness to acute and chronic stimuli is present in goats possessing only a single carotid body.

Acclimatization↗
PubMed1985

Ventilatory control in normal man following five minutes' exposure to hypoxia.

Ventilatory control was studied in normal subjects following brief (5 min) exposure to hypoxia (inhalation 7-8% O2). The ventilatory response to rebreathing CO2 (hyperoxic) was assessed 20 min before and after 5 min exposure to (a) 7-8% O2, (b) 7-8% O2 rebreathing CO2, (c) rebreathing CO2 during hyperoxia, and (d) 10% O2, normocapnic. The slope of the V-PCO2 response (S) was increased for up to 40 min following (a) and (b) by 25-34%, but was unchanged following (c) and (d). Resting ventilation was unchanged throughout. The ventilatory response to normocapnic progressive hypoxia was measured as the slope of the V-Hb% SaO2 relationship (H); this was increased by 26%. The mechanism underlying this change in ventilatory control in man is unknown; it may relate to the process of acclimatization to hypoxia whereby chronic hypoxia is a greater stimulus to ventilation than acute hypoxia.

Acclimatization↗
PubMed1990

Greater maximal O2 uptakes and vital capacities in Tibetan than Han residents of Lhasa.

Maximal O2 uptake provides an index of the integrated functioning of the O2 transport system. Whether lifelong high altitude residents have greater maximal exercise capacities than acclimatized newcomers is of interest for determining whether years to generations of high altitude exposure influence maximal O2 uptake and, if so, what components of O2 transport are involved. We studied 16 Tibetan lifelong residents of Lhasa, Tibet, China (3658 m) and 20 Han ("Chinese") 8 +/- 1 year residents of the same altitude who were matched for age, height, weight and lack of exercise training. At maximal effort, the Tibetans compared to the Hans had greater O2 uptakes (51 +/- 1 vs 46 +/- 1 ml STPD.min-1.(kg bw)-1, P less than 0.05), exercise workloads (177 +/- 5 vs 155 +/- 6 watts, P less than 0.05), minute ventilations (149 +/- 6 vs 126 +/- 4 IBTPS/min, P less than 0.01) and O2 pulse (15.2 +/- 0.4 vs 13.3 +/- 0.5 ml O2 consumption/heart beat, P less than 0.05). Equally high heart rates were present at maximal effort (191 +/- 3 vs 187 +/- 3 beats/min, P = NS), supporting the likelihood that true maxima were achieved in both groups. The greater minute ventilation in the Tibetans resulted from greater tidal volume and the greater maximal tidal volume correlated positively with the resting vital capacity. We concluded that the Tibetans achieved a higher maximal O2 uptake than the Hans, implying an increased capacity for O2 transport to the working muscle.

Acclimatization↗
PubMed1994

Pulmonary gas exchange during hypoxic exercise in the rat.

Pulmonary gas exchange and O2 transport were studied at rest and during maximal treadmill exercise in rats in acute hypoxia (PIO2 approximately 71 Torr), and in littermates acclimatized to PB = 380 Torr (PIO2 approximately 71 Torr) for 3 weeks (chronic hypoxia). To obtain valid estimates of blood gas partial pressures, particularly during exercise, the temperature coefficients of blood pH, PO2 and PCO2 were determined (Appendix). In both acute and chronic hypoxia, the following changes were observed: alveolar and arterial PO2 increased considerably, but the difference, A-aPO2, did not change significantly; arterial O2 concentration (CaO2) decreased, and apparent pulmonary diffusing capacity for O2, Dapp, increased. The increase in Dapp, together with hyperventilation, may prevent further drop in CaO2 due to a large rightward shift in the blood-O2 equilibrium curve caused by lactic acidosis in conjunction with a large Bohr coefficient characteristic of this species. Comparison with corresponding results obtained in man reveals that during hypoxic exercise, the rat shows a larger increase in PAO2, an increase, instead of a decrease, in PaO2, and a larger increase in Dapp.

Acclimatization↗
PubMed1984

Erythrocytic organic phosphates: diel and seasonal cycles in the frog, Rana berlandieri.

Hemoglobin (Hb) concentration, hematocrit (Hct), total organic phosphates (Ptot), nucleoside triphosphates (NTP), 2,3-diphosphoglycerate (DPG), and "inositol polyphosphates" (IPP) were measured in the erythrocytes of adult frogs at different times of day in winter and summer after acclimatization to 15 degrees C and an LD 12:12 photoperiod. The same measurements were also made on animals acclimated to LD 16:8 in summer. All of the measured parameters varied significantly at different times of the day and between seasons in animals acclimated to an LD 12:12 photoperiod. Summer animals acclimated to LD 16:8 showed significant diel cycles only in Hct and Hb.

2,3-Diphosphoglycerate↗
PubMed1985

Seasonal variations in hematocrit, red cell hemoglobin and nucleoside triphosphate concentrations, in the European eel Anguilla anguilla.

Eels acclimatized in nature show a significant annual variation in erythrocytic guanosine triphosphate (GTP) concentration, temperature range 0.5-17 degrees C. A similar but smaller annual variation is also present in eels acclimated in the laboratory at constant temperature, 17 degrees C. Hematocrit and blood oxygen capacity showed no seasonal variation. Natural minimal and maximal red cell GTP concentrations were found at the end of the dormancy period (March) and in the late summer, respectively. Furthermore, a chronological connection of the erythrocytic GTP values versus ambient temperature, in the natural environment, demonstrates a hysteresis. This allows for a prediction of a slowly progressing enhancement of the temperature effect on Hb-O2 binding throughout autumn, whereas a relatively fast and pronounced enhancement predictably takes place in spring (April-May) coincident with the "awakening" of the eels.

Acclimatization↗
PubMed1986

Environmentally-related changes in red cell levels of ionic modulators of hemoglobin-O2 affinity in rainbow trout, Salmo gairdneri.

Hemoglobin content, plasma and red cell levels of chloride and magnesium and molar ion:hemoglobin ratios were examined in trout acclimatized to eight combinations of two treatment levels of temperature (5, 20 degrees C), O2 availability (less than or equal to 30%, greater than or equal to 75% saturation) and photoperiod (16L:8D, 8L:16D). Increases in hemoglobin content were associated with exposure to higher temperature, abbreviated daylength and hypoxia, with hypoxia greater than photoperiod greater than temperature. Under nominal "summer" conditions (20 degrees C, hypoxia, 16L:8D) photoperiodic influence was apparently masked by hypoxic and thermal effects. Temperature was the principal determinant of plasma and cellular chloride levels as well as [Cl:Hb]. O2 availability and photoperiod had little effect. Temperature was also the primary factor influencing magnesium, with hypoxia exerting a lesser influence. Photoperiod effects were negligible. With increased temperature and reduced O2 availability, plasma magnesium increased white cell magnesium levels and [Mg:Hb] declined. These observations suggest that with normal seasonal changes in environmental conditions, temperature-induced increases in the O2 requirements of summer trout are probably accompanied by increases in blood O2-carrying capacity and reductions in hemoglobin-O2 affinity with consequent increases in O2 delivery to tissues.

Acclimatization↗
PubMed1993

Standard and pH-affected hemoglobin-O2 binding curves of Sprague-Dawley rats under normal and shifted P50 conditions.

1. The oxygen saturation (SO2) was determined of Sprague-Dawley rat blood having increased hemoglobin (Hb)-O2 affinity (P50 < 37 mmHg) or capacity (Cmax) over a range of pH's. 2. Rats were untreated (K), or had passed 14 d drinking 0.5% saline (C; ctrl) or NaOCN (N; chronically low P50, high Cmax), 5000 m altitude acclimatization (H; high Cmax), or exchange transfusion with OCN(-)-Hb red cell blood (X; acutely low P50). 3. The P50 [mmHg], Hill's "n", and Cmax [ml O2/100 ml], measured after tonometry, were 36.0, 2.60 and 20.6 (K), 32.6, 2.50 and 21.8 (C), 18.3, 2.35 and 23.9 (N), 36.0, 2.60 and 29.4 (H), and 24.9, 2.73 and 22.3 (X). 4. Oxygen dissociation curves (ODC's), derived from simultaneous SO2 and PO2 measurements during deoxygenation (PO2: 100-0 mmHg) of blood (normal and acidified with CO2 or lactic acid), delivered Bohr coefficients (BCCO2, BCLac) each differing between groups (C vs N) above SO2 50%; within groups BCCO2 vs BCLac differed at SO2 10-90% (P < 0.05). 5. Group-specific ODC's and pH-shifted curves (+/- 0.05, +/- 0.10 and +/- 0.15 units from 7.4, relying on BCCO2) are plotted for direct reading of SO2 and, with Cmax, accurate data on blood O2 content are obtained; corrections for lactic acidosis are discussed.

Acclimatization↗