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 1,099 records · Page 61Linked to original sources
PubMed1996

Autonomic regulation of heart rate and peripheral circulation: comparison of high altitude and sea level residents.

1. To evaluate the activity of the autonomic nervous system on the heart and peripheral circulation in native high-altitude residents, during a Himalayan expedition we studied 12 men (age: 48 +/- 4, mean +/- SEM), life-long resident in a village at 4800 m (Sumdo village, Zanskar, India) and 7 healthy sea-level residents (age: 37 +/- 4) after 7 days of acclimatization (acclimatized lowlanders) at the same altitude. Furthermore 25 sea level residents (age: 46 +/- 2) underwent the same protocol at sea level. 2. R-R interval (RR), respiratory signal, non-invasive blood pressure, and skin arteriolar blood flow were evaluated in three different conditions: during free breathing in supine position and during controlled breathing (at 0.15 Hz), in supine and upright position, and analysed by autoregressive spectral analysis [low- (around 0.1 Hz) and high-frequency (respiratory) fluctuations, LF and HF, markers of sympathetic and vagal activity, respectively]. 3. High-altitude residents showed in supine position a higher RR than acclimatized lowlanders, similar to sea-level residents. RR variability was reduced in acclimatized lowlanders compared to both high-altitude residents and sea level residents. Systolic blood pressure (SBP) did not show significant differences between the three groups. High altitude residents showed in supine lower LF in RR signal compared to sea-level residents, and, compared to acclimatized lowlanders, higher HF and lower LF/HF ratio; high-altitude residents showed a reduction in skin microcirculation variability compared to sea-level residents, but this was eight fold greater than in acclimatized lowlander, thus indicating a much greater vasoconstriction in acclimatized lowlanders than in high-altitude residents. 4. In upright position, high-altitude residents showed the same behaviour as sea-level residents, with increase in LF-RR, and decrease in HF and LF-SBP. Acclimatized lowlanders showed similar directional trends though not significant changes for RR-LF. 5. After one week of acclimatization, lowlanders still manifested sympathetic activation and skin vasoconstriction; high-altitude residents did not show reduced vagal tone compared to sea-level residents, but a mild vasoconstriction appeared to be present. In conclusion, normal or enhanced vagal tone and preserved vasomotion are probably evidence of adaptation at high altitude hypoxia.

Adaptation, Physiological↗
PubMed2006

Temperature- and exercise-induced gene expression and metabolic enzyme changes in skeletal muscle of adult zebrafish (Danio rerio).

Both exercise training and cold acclimatization induce muscle remodelling in vertebrates, producing a more aerobic phenotype. In ectothermic species exercise training and cold-acclimatization represent distinct stimuli. It is currently unclear if these stimuli act through a common mechanism or if different mechanisms lead to a common phenotype. The goal of this study was to survey responses that represent potential mechanisms responsible for contraction- and temperature-induced muscle remodelling, using an ectothermic vertebrate. Separate groups of adult zebrafish (Danio rerio) were either swim trained or cold acclimatized for 4 weeks. We found that the mitochondrial marker enzyme citrate synthase (CS) was increased by 1.5x in cold and by 1.3x with exercise (P<0.05). Cytochrome c oxidase (COx) was increased by 1.2x following exercise training (P<0.05) and 1.2x (P=0.07) with cold acclimatization. However, only cold acclimatization increased beta-hydroxyacyl-CoA dehydrogenase (HOAD) compared to exercise-trained (by 1.3x) and pyruvate kinase (PK) relative to control zebrafish. We assessed the whole-animal performance outcomes of these treatments. Maximum absolute sustained swimming speed (Ucrit) was increased in the exercise trained group but not in the cold acclimatized group. Real-time PCR analysis indicated that increases in CS are primarily transcriptionally regulated with exercise but not with cold treatments. Both treatments showed increases in nuclear respiratory factor (NRF)-1 mRNA which was increased by 2.3x in cold-acclimatized and 4x in exercise-trained zebrafish above controls. In contrast, peroxisome proliferator-activated receptor (PPAR)-alpha mRNA levels were decreased in both experimental groups while PPAR-beta1 declined in exercise training only. Moreover, PPAR-gamma coactivator (PGC)-1alpha mRNA was not changed by either treatment. In zebrafish, both temperature and exercise produce a more aerobic phenotype, but there are stimulus-dependent responses (i.e. HOAD and PK activities). While similar changes in NRF-1 mRNA suggest that common responses might underlie aerobic muscle remodelling there are distinct changes (i.e. CS and PPAR-beta1 mRNA) that contribute to specific temperature- and exercise-induced phenotypes.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed2003

Process control and design considerations for methanol-induced denitrification in a sequencing batch reactor.

The primary goal of this research was to determine the effect of methanol-induced denitrification on volatile suspended solids production, settleability, and oxidation-reduction potential in a full-scale sequencing batch reactor. Batch tests were also conducted to determine the influence of mixing and acclimatization on the denitrification of wastewater with methanol. The observed sludge production in the full-scale sequencing batch reactor with methanol addition was 0.21 kg volatile suspended solids l(-1) methanol, versus the calculated stoichiometric sludge production of 0.17 kg volatile suspended solids l(-1) methanol. The settleability in the full-scale sequencing batch reactor, measured by the sludge volume index, increases linearly with increasing denitrification rate. The total change in the oxidation-reduction potential magnitude during a sequencing batch reactor cycle increased linearly with increasing denitrification rate. A minimum of 55% increase in the denitrification rate was observed in a batch reactor with methanol addition and a sludge acclimatized to methanol addition, compared to a batch reactor with methanol addition and a non-acclimatized sludge. The non-acclimatized batch reactor had a negligible denitrification rate without methanol addition. However, significant denitrification rates were observed in the acclimatized batch reactors without methanol addition, potentially caused by microbial storage or an increased population of denitrifiers that scavenge any available carbon. A completely mixed batch reactor, with sludge acclimatized to methanol addition during the anoxic cycle, had an increase in the denitrification rate ranging from 660%, without methanol addition, to 200%, with a methanol dosage of 12.7 mg l(-1), compared to the unmixed batch reactor with an acclimatized sludge. Therefore, mixing appears to be critical to the denitrification process, to realize the best kinetic performance.

Bioreactors↗
PubMed1980

Deposition and clearance of 14C-labelled cigarette smoke particles in Syrian hamster respiratory and digestive tract.

Eight week old male and female Syrian golden hamsters inhaled smoke of Dotriacontane-16, 17- 14C-labelled research cigarettes. The investigation consisted of 4 experiments and each experiment involved 4 groups of 10 animals each. Eighty of the animals (40 males: 40 females) were killed immediately after exposure to the 14C-labelled smoke of 30 cigarettes (10 uCi/cigarette) and the organs of the respiratory and digestive tract were measured for their 14C-activity. Non-acclimatized Syrian golden hamsters inhaled quantitatively more condensate/g organ weight than acclimatized animals. There was no difference between males and females. Nearly 50% of the retained 14C-activity was found in the digestive tract, half of the amount was in the forestomach. The distribution in the respiratory tract showed no difference between acclimatized and nonacclimatized animals. More than 75% of the measured activity in the total respiratory tract was found in the lung. The highest concentration was measured in the lobus dexter caudalis and lobus sinister. The clearance of the lung was slower in acclimatized hamsters than in non-acclimatized animals. When animals inhaled the smoke of labelled cigarettes for five days the clearance of the lung was slower in acclimatized hamsters than in non-acclimatized animals.

Animals↗
PubMed1996

The effects of two types of clothing on seasonal heat tolerance.

The aim of this study was to look at changes in seasonal heat tolerance due to acclimatization produced by different types of clothing. A group of 12 female adults served as subjects in the study which lasted for 3 months from April to June during which the ambient temperature gradually rose. Of the group 6 of them (skirt group) wore knee-length skirts daily, and the others (trouser group) were dressed in full trousers during this acclimatization period. The heat tolerance before and after the acclimatization period was compared between the two groups under conditions in which relative humidity was 30% and ambient temperature was raised to 37 degrees C. Rectal temperature, mean skin temperature and the loss of body mass caused by sweating were measured in the two groups. Before the acclimatization period, no significant differences were found between the two groups. However, observations after the acclimatization period showed higher rectal temperatures in control conditions (ambient air temperature 28 degrees C, relative humidity 60%) in the skirt group. A lower increment of rectal temperature during heat exposure (ambient air temperature 37 degrees C, relative humidity 30%) was also found in this group. Finally, the subjects in the skirt group lost less body mass due to sweating during heat exposure. Consequently, the overall index of physiological strain in the skirt group tended to show a lower value after the period of warm acclimatization. It was concluded that the subjects wearing knee-length skirts improved their heat tolerance with the advance of the seasons.

Acclimatization↗
PubMedDate not supplied

Digitized infrared segmental thermometry: time requirements for stable recordings.

OBJECTIVES: Digitized infrared segmental thermometry (DIST) is a method for measuring and recording skin surface body temperatures. The project evaluated the required length of time for patients to acclimatize their core body temperature to ambient conditions to obtain stable DIST readings. METHODS: Seventeen subjects were allowed a 20-minute acclimatizing period in a temperature-controlled room. The bilateral DIST temperature was measured with thermistors in combination with infrared cameras (IRCs) at the C4 and L4 levels. All IRC temperatures were recorded after a 20-minute stabilization period. The room temperature and relative humidity were recorded throughout all trials. The acclimatization trend was computed from the 20- to 24-minute period for the IRCs, and the acclimatization trend was computed continuously for a total of 30 minutes (at 2-minute intervals) for 5 days. RESULTS: We discovered a stabilization trend in the early trial stages, with the thermistor recordings between 8 and 16 minutes. The IRC trend was also conclusive for the core temperature requirements. CONCLUSIONS: This study determined a core body temperature acclimatization trend tested among patients using thermistor recordings in a controlled environment. Based on these findings, we recommend acclimatization in a temperature- and humidity-controlled environment for a minimum 8-minute period, followed by an 8-minute maximum recording period with the patient in a prone position to obtain accurate DIST recordings.

Acclimatization↗
PubMed2000

Human skeletal muscle exercise metabolism following an expedition to mount denali.

Chronic exposure to high altitude is known to result in changes in the mechanisms regulating O(2) delivery to the contracting muscle. However, the effects of acclimatization on metabolism in the contracting muscle cell remain unclear. In this study, we have investigated the hypothesis that acclimatization would result in a closer coupling between ATP utilization and ATP production and that the improved energy state would be accompanied by a reorganization of the metabolic pathways consisting of an increased oxidative and decreased glycolytic potential. Five men, mean age of 28 +/- 2 (SE) yr, performed a standardized, two-stage submaximal cycling task in normoxia for 20 min at each of 59 and 74% peak O(2) consumption before and 3-4 days after returning from a 21-day expedition to Mount Denali (6,194 m). Acclimatization was without effect in altering the resting values of the adenine nucleotides (ATP, ADP, AMP), inosine monophosphate (IMP), or phosphocreatine (PCr) in the vastus lateralis. During exercise (40 min) after acclimatization compared with preacclimatization, PCr was not as depressed (33.2 +/- 7.1 vs. 40.6 +/- 5.4 mmol/kg dry wt) and IMP (0.289 +/- 0.11 vs. 0. 131 +/- 0.03 mmol/kg dry wt) and lactate (26.1 +/- 6.2 vs. 18.6 +/- 8.8 mmol/kg dry wt) in contracting muscle were not as elevated (P < 0.05). Although no effect of acclimatization was observed for the maximal activity (mol. kg protein(-1). h(-1)) of citrate synthase (4. 76 +/- 0.44 vs. 4.94 +/- 0.45), lactate dehydrogenase was increased by 13% (36.5 +/- 2.6 vs. 41.2 +/- 3.1, P < 0.05). It is concluded that acclimatization results in an improved energy state in the contracting muscle when tested under normoxic conditions; however, these effects are not associated with a higher oxidative potential or a lower glycolytic potential as hypothesized.

Acclimatization↗
PubMed1988

Oxygen transport to exercising leg in chronic hypoxia.

Residence at high altitude could be accompanied by adaptations that alter the mechanisms of O2 delivery to exercising muscle. Seven sea level resident males, aged 22 +/- 1 yr, performed moderate to near-maximal steady-state cycle exercise at sea level in normoxia [inspired PO2 (PIO2) 150 Torr] and acute hypobaric hypoxia (barometric pressure, 445 Torr; PIO2, 83 Torr), and after 18 days' residence on Pikes Peak (4,300 m) while breathing ambient air (PIO2, 86 Torr) and air similar to that at sea level (35% O2, PIO2, 144 Torr). In both hypoxia and normoxia, after acclimatization the femoral arterial-iliac venous O2 content difference, hemoglobin concentration, and arterial O2 content, were higher than before acclimatization, but the venous PO2 (PVO2) was unchanged. Thermodilution leg blood flow was lower but calculated arterial O2 delivery and leg VO2 similar in hypoxia after vs. before acclimatization. Mean arterial pressure (MAP) and total peripheral resistance in hypoxia were greater after, than before, acclimatization. We concluded that acclimatization did not increase O2 delivery but rather maintained delivery via increased arterial oxygenation and decreased leg blood flow. The maintenance of PVO2 and the higher MAP after acclimatization suggested matching of O2 delivery to tissue O2 demands, with vasoconstriction possibly contributing to the decreased flow.

Acclimatization↗
PubMed1991

Oxygen transport during steady-state submaximal exercise in chronic hypoxia.

Arterial O2 delivery during short-term submaximal exercise falls on arrival at high altitude but thereafter remains constant. As arterial O2 content increases with acclimatization, blood flow falls. We evaluated several factors that could influence O2 delivery during more prolonged submaximal exercise after acclimatization at 4,300 m. Seven men (23 +/- 2 yr) performed 45 min of steady-state submaximal exercise at sea level (barometric pressure 751 Torr), on acute ascent to 4,300 m (barometric pressure 463 Torr), and after 21 days of residence at altitude. The O2 uptake (VO2) was constant during exercise, 51 +/- 1% of maximal VO2 at sea level, and 65 +/- 2% VO2 at 4,300 m. After acclimatization, exercise cardiac output decreased 25 +/- 3% compared with arrival and leg blood flow decreased 18 +/- 3% (P less than 0.05), with no change in the percentage of cardiac output to the leg. Hemoglobin concentration and arterial O2 saturation increased, but total body and leg O2 delivery remained unchanged. After acclimatization, a reduction in plasma volume was offset by an increase in erythrocyte volume, and total blood volume did not change. Mean systemic arterial pressure, systemic vascular resistance, and leg vascular resistance were all greater after acclimatization (P less than 0.05). Mean plasma norepinephrine levels also increased during exercise in a parallel fashion with increased vascular resistance. Thus we conclude that both total body and leg O2 delivery decrease after arrival at 4,300 m and remain unchanged with acclimatization as a result of a parallel fall in both cardiac output and leg blood flow and an increase in arterial O2 content.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed2002

Cardiovascular responses to adrenergic agents in different acclimation states in the rock pigeon (Columba livia).

The effect of propranolol on heart rate (fH) was measured in season-acclimatized pigeons. Propranolol treatment decreased fH in winter-acclimatized pigeons, accelerated fH in summer-acclimatized pigeons, but had no effect on fH in spring-acclimatized pigeons. The effect of propranolol in summer-acclimatized pigeons is opposite to that observed in mammals. Interestingly, isoproterenol produced a propranolol-like cardioacceleration in heat-acclimated pigeons. We suggest that propranolol affects fH in summer-acclimatized pigeons via two opposing routes-a direct and a peripheral indirect route. We also suggest that the cardiovascular effects of propranolol are involved in the capacity of the pigeon to evaporate water from its skin.

Acclimatization↗
PubMed1966

Time course and nature of temperature-induced changes in sodium-glucose interactions of the goldfish intestine.

1. Glucose-evoked potentials measured at low incubation temperatures were found to be highly temperature dependent (phase 1), but less so at high incubation temperatures (phase 2) and acclimatization of an 8 degrees C fish to 25 degrees C resulted in the extension of phase 1 up to the environmental temperature of the fish. This change was only part of the mechanism controlling the acclimatization of sodium transport across the intestine.2. The temperature at which the glucose-evoked potential changed from phase 1 to phase 2 was approximately equal to the temperature at which glucose began to raise the steady transmural potential of the intestine.3. No changes in intestinal electrical parameters could be detected when fish, acclimatized to 8 degrees C, were heated at 25 degrees C for 15 hr, but after 20 hr at the higher temperature, acclimatization to the new temperature was complete.4. Intestines from fish acclimatized to 8 degrees C, but which had first spent 15 hr at 25 degrees C and then 10 hr at 8 degrees C, still behaved qualitatively like 8 degrees C - intestines but the magnitude of the glucose-evoked potentials was slightly reduced.5. It is suggested as a working hypothesis that acclimatization of the sodium-glucose interaction to different environmental temperatures involves the synthesis of new carrier molecules, qualitatively different from the old ones.

Animals↗
PubMed1999

Chronic hypercapnia resets CO2 sensitivity of avian intrapulmonary chemoreceptors.

Avian intrapulmonary chemoreceptors (IPC) are vagal sensory neurons that participate in the control of breathing. IPC action potential frequency is inversely proportional to PCO2, but it is unclear whether low PCO2 or high pH is the immediate stimulus for signal transduction in IPC. To address this question, comparisons were made between single cell neural responses of 34 IPC recorded in 6 anesthetized ducks (Anas platyrhynchos) acclimatized 12 days to 7.5% inspired CO2 and 22 IPC recorded in 9 normal anesthetized ducks. We hypothesized that if respiratory-linked pH changes determine IPC activity, action potential frequency as a function of inspiratory PCO2 (PICO2) should be greater after acclimatization due to metabolic acid-base compensation and higher pH. Conversely, if PCO2 alone determines IPC discharge, action potential frequency vs. PCO2 should be unchanged by acclimatization. Results indicate that after acclimatization ventilation was depressed at 28 and 42 Torr PICO2 (P < 0.05) and mean plasma pH at 40 Torr PCO2 increased from 7.38 +/- 0. 03 to 7.56 +/- 0.02 (P < 0.05), indicating significant metabolic acid-base compensation and HCO-3 retention. Mean IPC discharge rate was elevated by CO2 acclimatization at all PCO2 studied. In acclimatized vs. normal animals, regression analysis of IPC discharge as a function of lnPCO2 showed increased mean intercepts of 81.1 +/- 4.0 vs. 48.4 +/- 3.6 impulses/s (P < 0.05) and increased mean slopes of -19.0 +/- 1.0 vs. -12.0 +/- 1.1 impulses. s-1. lnPCO2-1 (P < 0.05). Results indicate that IPC response to CO2 is mediated by H+ from CO2 hydration and not by CO2 directly.

Adaptation, Physiological↗
PubMed2005

Effects of chronic hypoxia on MK-801-induced changes in the acute hypoxic ventilatory response.

Chronic hypoxia increases the sensitivity of the central nervous system to afferent input from carotid body chemoreceptors. We hypothesized that this process involves N-methyl-D-aspartate (NMDA) receptor-mediated mechanisms and predicted that chronic hypoxia would change the effect of the NMDA receptor blocker dizocilpine (MK-801) on the poikilocapnic hypoxic ventilatory response (HVR). Male Sprague-Dawley rats were studied before and after acclimatization to hypoxia (70 Torr inspiratory Po(2) for 9 days). We measured ventilation (VI) and the HVR before and after systemic MK-801 treatment (3 mg/kg ip). MK-801 resulted in a constant respiratory frequency (approximately 175 min(-1)) during acute exposure to 10% and 30% O(2) before and after acclimatization. MK-801 had no effect on tidal volume (VT) before acclimatization, but it significantly decreased Vt when the animals were breathing 10% O(2) after acclimatization. The net effect of MK-801 was to eliminate the O(2) sensitivity of Vi before (via changes in respiratory frequency) and after (via changes in VT) acclimatization. Hence, chronic hypoxia altered the effect of MK-801 on the acute HVR, primarily because of increased effects on Vt. This indicates that changes in NMDA receptor-mediated neurotransmission may be involved in ventilatory acclimatization to hypoxia. However, further experiments are necessary to determine the precise location of such plasticity in the central nervous system.

Acetamides↗
PubMed1996

Lactate during exercise at high altitude.

In acclimatized humans at high altitude the reduction, compared to acute hypoxia, of the blood lactate concentration (la) at any absolute oxygen uptake (VO2), as well as the reduction of maximum la (lamax) after exhaustive exercise, compared to both acute hypoxia or normoxia, have been considered paradoxical, and these phenomena have therefore become known as the "lactate paradox". Since, at any given power output and VO2, mass oxygen transport to the contracting locomotor muscles is not altered by the process of acclimatization to high altitude, the gradual reduction in [la-]max in lowlanders exposed to chronic hypoxia seems not to be due to changes in oxygen availability at the tissue level. At present, it appears that the acclimatization-induced changes in [la-] during exercise are the result of at least two mechanisms: (1) a decrease in maximum substrate flux through aerobic glycolysis due to the reduced VO2max in hypoxia; and (2) alterations in the metabolic control of glycogenolysis and glycolysis at the cellular level, largely because of the changes in adrenergic drive of glycogenolysis that ensue during acclimatization, although effects of changes in peripheral oxygen transfer and the cellular redox state cannot be ruled out. With regard to the differences in lactate accumulation during exercise that have been reported to occur between lowlanders and highlanders, both groups either being acclimatized or not, these do not seem to be based upon fundamentally different metabolic features. Instead, they seem merely to reflect points along the same continuum of phenotypic adaptation of which the location depends on the time spent at high altitude.

Acclimatization↗
PubMed2000

Comparative human ventilatory adaptation to high altitude.

Studies of ventilatory response to high altitudes have occupied an important position in respiratory physiology. This review summarizes recent studies in Tibetan high-altitude residents that collectively challenge the prior consensus that lifelong high-altitude residents ventilate less than acclimatized newcomers do as the result of acquired 'blunting' of hypoxic ventilatory responsiveness. These studies indicate that Tibetans ventilate more than Andean high-altitude natives residing at the same or similar altitudes (PET[CO(2)]) in Tibetans=29.6+/-0.8 vs. Andeans=31.0+/-1.0, P<0.0002 at approximately 4200 m), a difference which approximates the change that occurs between the time of acute hypoxic exposure to once ventilatory acclimatization has been achieved. Tibetans ventilate as much as acclimatized newcomers whereas Andeans ventilate less. However, the extent to which differences in hypoxic ventilatory response (HVR) are responsible is uncertain from existing data. Tibetans have an HVR as high as those of acclimatized newcomers whereas Andeans generally do not, but HVR is not consistently greater in comparisons of Tibetan versus Andean highland residents. Human and experimental animal studies demonstrate that inter-individual and genetic factors affect acute HVR and likely modify acclimatization and hyperventilatory response to high altitude. But the mechanisms responsible for ventilatory roll-off, hyperoxic hyperventilation, and acquired blunting of HVR are poorly understood, especially as they pertain to high-altitude residents. Developmental factors affecting neonatal arterial oxygenation are likely important and may vary between populations. Functional significance has been investigated with respect to the occurrence of chronic mountain sickness and intrauterine growth restriction for which, in both cases, low HVR seems disadvantageous. Additional studies are needed to address the various components of ventilatory control in native Tibetan, Andean and other lifelong high-altitude residents to decide the factors responsible for blunting HVR and diminishing ventilation in some native high-altitude residents.

Acclimatization↗
PubMed2003

Dopaminergic mechanisms of neural plasticity in respiratory control: transgenic approaches.

Data supporting the hypothesis that dopamine-2 receptors (D(2)-R) contribute to time-dependent changes in the hypoxic ventilatory response (HVR) during acclimatization to hypoxia are briefly reviewed. Previous experiments with transgenic animals (D(2)-R 'knockout' mice) support this hypothesis (J. Appl. Physiol. 89 (2000) 1142). However, those experiments could not determine (1) if D(2)-R in the carotid body, the CNS, or both were involved, or (2) if D(2)-R were necessary during the acclimatization to hypoxia versus some time prior to chronic hypoxia, e.g. during a critical period of development. Additional experiments on C57BL/6J mice support the idea that D(2)-R are critical during the period of exposure to hypoxia for normal ventilatory acclimatization. D(2)-R in carotid body chemoreceptors predominate under control conditions to inhibit normoxic ventilation, but excitatory effects of D(2)-R, presumably in the CNS, predominate after acclimatization to hypoxia. The inhibitory effects of D(2)-R in the carotid body are reset to operate primarily under hypoxic conditions in acclimatized rats, thereby optimizing O(2)-sensitivity.

Acclimatization↗
PubMed1992

Morphological and physiological correlates with swimming performance in juvenile largemouth bass.

Winter- and summer-acclimatized largemouth bass (Micropterus salmoides) were collected from hatchery ponds in eastern Colorado during late winter and midsummer, then challenged with two prolonged swimming performances (step test and constant-velocity endurance). Variation in the step test performances was significantly correlated with variation in the endurance performances in the winter-acclimatized but not in the summer-acclimatized fish. Fourteen physiological and morphological traits were measured on each fish, and correlations among these traits and swimming performance were tested. None of the traits measured were correlated with performance variation in both the winter- and summer-acclimatized fish. The only significant correlate with swimming performance in the summer-acclimatized fish was white muscle lactate dehydrogenase activity (n = 19). Six of the seven factors correlating with winter swimming performance (n = 18-19) could be divided into two categories: traits associated with fasting (condition factor and liver enzymatic activity) and those associated with oxygen delivery (heart mass, heart and red muscle cytochrome oxidase activity). The results of this study suggest that morphological and physiological correlates of swimming performance in juvenile largemouth bass are profoundly influenced by seasonal variation.

Acclimatization↗
PubMedDate not supplied

Multifocal electroretinography changes in the macula at high altitude: a report of three cases.

BACKGROUND: To evaluate the short- and long-term effects of high-altitude hypobaric hypoxia on macula morphology and function during ascents, acclimatizations, and descents between 500 m and 5,650 m, macula function was evaluated in three healthy climbers of a trekking expedition. METHODS: Macula physiology was tested with multifocal electroretinography (MF ERG), near and farvisual acuity, and Amsler grid tests. Macula morphology was tested with optical coherence tomography (OCT) and with stereoscopic fundoscopy obtained 1 week before ascent, as well as 1 week and 2 weeks after high-altitude exposure. The following physiological parameters indicative of acclimatization were compared daily during the expedition at altitudes between 500 m and 5,050 m: hemoglobin, oxygen saturation, resting heart rate, retinal findings, and the Lake Louise score of acclimatization. RESULTS: The central macula MF ERG responses were significantly reduced 1 week after high-altitude exposure, and had recovered by the follow-up examination performed during the following week. Near visual acuity and Amsler grid tests remained unaffected at both follow-up examinations. No significant changes were found in the follow-up OCT and daily fundoscopy examinations in all three well-acclimatized climbers. CONCLUSIONS: High-altitude hypobaric hypoxia affects the function of the highly sensitive macula region. This suggests that the exposure of persons with macula diseases such as age-related macula degeneration, tapetoretinal degeneration, or diabetic retinopathy to high altitudes may influence the disease progression. For this reason, this population should avoid prolonged and unnecessary high-altitude exposure without proper acclimatization.

Acclimatization↗