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PubMed1987

Heat acclimatization during summer running in the northeastern United States.

Five highly trained distance runners (DR) were observed during controlled 90-min thermoregulation trials in spring (T1) and late summer (T2) to document the nature of heat acclimatization in the northeastern United States. These trials simulated environmental (30.3 +/- 0.1 degrees C dry bulb, 34.9 +/- 0.5% relative humidity, 4.47 m X s-1 wind speed) and exercise (treadmill running at 80, 120, 160, and 200 m X min-1) stresses encountered by DR during summer training in the northeastern United States. Between T1 and T2, DR trained outdoors for 14.5 +/- 0.4 wk, but consequently exhibited few physiological adaptations classically associated with heat acclimatization. Statistical comparison of T1 and T2 indicated no significant differences in mean heart rate, rectal temperature, sweat Na+ and K+, plasma Na+ and K+, or change in plasma volume during exercise. Mean weighted skin temperature was unchanged except at 50 min of exercise, and sweat rate was also unchanged except during the initial 30 min segment: 73 +/- 6 vs 93 +/- 8 ml X m-2 X h-1. Significant decreases (P less than 0.05) in submaximal VO2 were observed: T1 vs T2 values were 13.97 +/- 0.27 vs 10.19 +/- 1.19, 31.38 +/- 1.15 vs 27.91 +/- 1.45, and 44.97 +/- 0.85 vs 41.24 +/- 0.97 ml X kg-1 X min-1, at treadmill speeds of 80, 120, and 200 m X min-1, respectively. We conclude that DR did not require 14.5 wk of summer training to maintain safe rectal temperatures (less than or equal to 38.4 degrees C) during T1, which simulated the hottest days of summer in the northeastern United States.

Acclimatization↗
PubMed1981

[In vivo protein synthesis in rainbow trout (Salmo gairdneri R.) muscle. Effect of temperature acclimatization].

Protein synthesis was measured in the muscle of trout acclimatized to 10 and 18 degrees C and weighing about 100 g. Fractional synthesis rate was calculated after a pulse injection of L-leucine U14C by fitting the specific radioactivity of the protein to the computed values obtained with the specific radioactivity of the precursor, according to a precursor product relationship (Martin et al., 1977). At 10 and 18 degrees C, fractional synthesis rate values were 0.9 and 1.2 p. 100/d (plasma as the precursor pool) and 1.9 and 1.8 p. 100/d (intracellular pool as the precursor), respectively. Muscle protein synthesis rates in young trout are lower than in young mammals (rat, rabbit, lamb), and temperature acclimatization had no influence on muscle protein synthesis in trout.

Acclimatization↗
PubMed1993

Acclimatization to altitude: effects on arterial oxygen saturation and pulse rate during prolonged exercise at altitude.

Changes in the arterial haemoglobin-oxygen saturation (SaO2) of the blood, in the blood pressure and in the heart rate, were monitored in subjects performing static exercise at an altitude of 3,600 metres before and after an acclimatization period of 28 days during an expedition to the Bolivian Andes. It was found that acclimatised subjects could maintain their SaO2 during prolonged exercise better than non-acclimatised subjects. The pulse rate of acclimatised subjects was consistently lower at the same work level than that of non-acclimatised subjects. Acclimatised subjects were able to reach higher levels of exercise than when they had first arrived at altitude. These data imply that acclimatization to altitude improves the delivery of oxygen to the tissues. The mechanism of this is not certain, but it may be concerned with a reduction in the degree of ventilation-perfusion inequality of the lung which occurs on exposure to high altitude.

Acclimatization↗
PubMed1996

Changes in plasma electrolytes during acclimatization at high altitude.

The effects on plasma electrolytes and related hormones were determined in non-acclimatized low lander males, exposed for 96 hours to an altitude of 4424 meters. Twenty healthy soldiers aged 18-34 years travelled by road from an altitude of 2303 meters to 4424 meters over a period of 10 hours. Plasma sodium levels (142.09 +/- 1.14 mmol/1) and aldosterone (16.61 +/- 5.70 ng/ml) decreased to 139.69 mmol/1 and 11.6 +/- 4.60 ug/ml respectively after 96 hours of acute exposure to high altitude (p < 0.05). The plasma potassium and chloride levels did not show significant change, while, plasma HCO3 decreased gradually from 21.06 +/- 1.38 mmol/1 to 18.55 +/- 0.82 mmol/1 after 96 hours exposure to this altitude (p < 0.01). The plasma ionized calcium and plasma phosphate concentration decreased from 1.32 +/- 0.11 mmol/1 and 1.58 +/- 1.3 mmol/1 to 1.20 +/- 0.05 mmol/1 and 1.47 +/- 0.99 mmol/1 respectively (p < 0.05). Plasma parathyroid hormone (PTH) level increased from 4.54 +/- 2.1 ng/ml to 11.19 +/- 4.31 ng/ml after 48 hours with subsequent decline to 2.52 +/- 1.7 ng/ml after 96 hours exposure to high altitude. It may be concluded that the process of acclimatization to sudden exposure to high altitude is characterised by fall in plasma aldosterone and PTH with subsequent decrease of related electrolytes.

Acclimatization↗
PubMed1976

Responses of the autonomic nervous system during acclimatization tp high altitude in man.

A study has been conducted on 20 sojourners, between the ages of 20-30 years, to evaluate responses of the autonomic nervous system during acclimatization to high altitude. The responses measured consisted of heart rate (HR), blood pressure (BP), oral temperature (Tor), mean skin temperature (Tsk), cold pressor response (CPR), orthostatic tolerance to tilt, and urinary catecholamines. The subjects were tested initially at Delhi (altitude 260 m) and thereafter, on acute induction to an altitude of 3500 m periodically for 3 weeks. For comparison, the same responses were studied on 10 acclimatized lowlanders (AL) who had been staying at the same altitude for more than a year and on 10 high-altitude natives (HAN). The studies showed a rise in HR, BP, Tor, and urinary catecholamines, and a fall in Tsk, CPR, and orthostatic tolerance immediately on arrival at HA, indicating a relative hyperactivity of the sympathetic system. After a stay of 1 week, there was a gradual recovery in all the responses, though sympathetic hyperactivity was still maintained throughout the 3 weeks of stay. In AL also there was a preponderance of sympathetic activity, though of relatively lesser magnitude than that seen in sojourners. In HAN, on the other hand, there was a relative parasympathetic predomination. It has been concluded that in lowlanders it takes more than a year of stay at altitude for complete recovery of autonomic balance.

Acclimatization↗
PubMed2000

Environmental acclimatization of the carp modulates the transcription of beta-actin.

A cascade of mechanisms involving changes in gene expression are substantial to shape the adaptive responses that a eurythermal fish requires upon environmental changes in its habitat. We have previously shown that the cyclical reprogramming of rRNA transcription is a remarkable feature in carp under seasonal acclimatization. Using in situ hybridization and competitive RT-PCR we found significant differences in beta-actin transcripts, generally accepted to be coded by a typical housekeeping gene, in tissues from summer- and winter-acclimatized carp. The physiological differential beta-actin transcription herein reported places us on the alert for the reference genes estimated to be constitutive to quantitatively assess gene transcripts.

Actins↗
PubMed2001

BTEX catabolism interactions in a toluene-acclimatized biofilter.

BTEX substrate interactions for a toluene-acclimatized biofilter consortium were investigated. Benzene, ethylbenzene, o-xylene, m-xylene and p-xylene removal efficiencies were determined at a loading rate of 18.07 g m(-3) h(-1) and retention times of 0.5-3.0 min. This was also repeated for toluene in a 1:1 (m/m) ratio mixture (toluene: benzene, ethylbenzene, or xylene ) with each of the other compounds individually to obtain a final total loading of 18.07 g m(-3) h(-1). The results obtained were modelled using Michaelis-Menten kinetics and an explicit finite difference scheme to generate vmax and Km parameters. The Vmax/Km ratio (a measure of the catalytic efficiency, or biodegradation capacity, of the reactor) was used to quantify substrate interactions occurring within the biofilter reactor without the need for free-cell suspended and monoculture experimentation. Toluene was found to enhance the catalytic efficiency of the reactor for p-xylene, while catabolism of all the other compounds was inhibited competitively by the presence of toluene. The toluene-acclimatized biofilter was also able to degrade all of the other BTEX compounds, even in the absence of toluene. The catalytic efficiency of the reactor for compounds other than toluene was in the order: ethylbenzene > benzene > o-xylene > m-xylene>p-xylene. The catalytic efficiency for toluene was reduced by the presence of all other tested BTEX compounds, with the greatest inhibitory effect being caused by the presence of benzene, while o-xylene and p-xylene caused the least inhibitory effect. This work illustrated that substrate interactions can be determined directly from biofilter reactor results without the need for free-cell and monoculture experimentation.

Bacteria↗
PubMed1987

Naloxone accelerates the rate of ventilatory acclimatization to hypoxia in awake rats.

During ventilatory acclimatization to hypoxia in rats, PaCO2 progressively falls from about 40 torr in normoxia (PIO2 approximately equal to 150 torr) to a new steady-state at about 23 torr in chronic hypoxia (24 or more hours at PIO2 approximately equal to 90 torr). In acute (20 or 60 minutes) hypoxia naloxone treatment caused a hyperventilation greater than that caused by acute hypoxia alone. Following 20 minutes hypoxia, naloxone treated rats had a PaCO2 = 28.6 +/- 0.7 torr (mean +/- 95% confidence limits) which was significantly lower (P less than .001) than the saline treated PaCO2 = 31.0 +/- 0.6 torr. In contrast, in normoxia and at 24 hour hypoxia and at 20 minute return to normoxia following 24 hours hypoxia, naloxone treatment had no effect on PaCO2. We conclude that in the rat about one third of the ventilatory acclimatization to hypoxia is due to a progressively decreasing endogenous opioid-like inhibition of ventilation.

Adaptation, Physiological↗
PubMed1983

Monoamine neurotransmitter metabolism during acclimatization to hypoxia in rats.

The levels and turnovers of NE, DA and 5HT were determined in whole brain, brain stem, cervical and thoracic spinal cord and carotid bodies (CB) of rats exposed to from 1 h to 7 days of hypobaric hypoxia (PB = 450 torr). Monoamine levels decreased only transiently upon acute exposure to hypoxia. Monoamine turnover in the CNS was estimated from the average of (a) monoamine buildup following inhibition of catabolism, and (b) monoamine breakdown following inhibition of synthesis. Hypoxic effects on CNS monoamine turnover showed that: (a) NE was not affected; (b) DA was not affected in acute hypoxia, but was reduced to about 40% of normoxia control after 1-7 days hypoxia; (c) 5HT fell 50-60% during acute hypoxia but returned to and was maintained at control over 1-7 days of hypoxia; (d) acute restoration of normoxia following acute hypoxia restored 5HT and DA to control or above and in the acclimatized animal acute normoxia increased DA and 5HT turnover to about 1.4 and 1.8 X control. In the CB, DA levels gradually increased to 4 X control after 7 days of hypoxia and further increased to 6 X control upon acute restoration of normoxia. Changes in the metabolism of both central 5HT and CB DA may be related to the mechanisms mediating ventilatory acclimatization to chronic hypoxia.

Adaptation, Physiological↗
PubMed1996

Plasticity of tyrosine hydroxylase gene expression in the rat nucleus tractus solitarius after ventilatory acclimatization to hypoxia.

The aim of this study was to define the influence of long-term hypoxia on gene expression of tyrosine hydroxylase (TH) in the rat nucleus tractus solitarius (NTS). Animals were exposed to normobaric hypoxia (10% O2 in nitrogen) for 2 weeks. At this time, the hypoxia-induced hyperventilation reached a plateau, indicating ventilatory acclimatization. In horizontal brainstem sections, hypoxia-induced changes in TH protein and TH mRNA were assessed by immunocytochemistry and in-situ hybridization, respectively. Long-term hypoxia increased TH mRNA levels seen as both an increase in the number of grains per cell and an extension of the labeled area. The highest degree of labeling was found selectively located in caudal NTS. Hypoxia also enhanced TH immunoreactivity in the caudal NTS but this labeling extended more rostrally than that of TH mRNA. The data suggest that there is an hypoxia-induced plasticity of gene expression at the gene level in the NTS, which is associated with ventilatory acclimatization. The hypoxia model described in this study may serve as a framework for future regulatory studies.

Animals↗
PubMed2005

Acclimatization in first-time hearing aid users using three different fitting protocols.

OBJECTIVE: To study auditory acclimatization and outcome in first time hearing aid users fitted with state of the art hearing aids as a function of different hearing aid fitting protocols. METHODS: Twenty-eight adult subjects participated in the study. Each subject was assigned to one of three study groups (named audiologist driven, AD; patient driven, PD; set-to-target, STT according to the fitting protocol used) and fitted with digital hearing aids (Bernafon Symbio). Speech recognition scores were measured in aided and unaided conditions over a 6-month period. RESULTS: Five subjects (three from the PD-group, two from the STT group) decided to withdraw from the study during the 6-month-study period, leaving a total of 23 complete data sets for analysis. Aided speech understanding increased significantly over this time period in all three groups. However, average hearing aid insertion gain changes were small over the same period. There were no statistically significant differences in aided or unaided speech recognition scores between the three groups after 2 weeks or after 6 months. On average, twice as many fine tunings of the hearing aids were requested by the patients in the AD and the STT group than in the PD group and subjects in the AD and STT group used their hearing aids approximately twice as much as subjects in the PD group. CONCLUSIONS: The substantial increase in speech intelligibility without significant changes of the insertion gain of the hearing aids over a 6-month period in all three groups suggests a significant acclimatization effect. Although the speech recognition with hearing aids did not differ significantly among the three study groups after 6 months, the lower average wearing time and the higher number of withdrawals from the study in the PD group suggest that the patients' needs are not adequately met. In terms of aided speech recognition scores and hearing aid wearing time the STT group and the AD group were very similar. However, comments of the patients and the higher rate of withdrawals in the STT group suggest an over-all advantage for the AD fitting protocol.

Adaptation, Psychological↗
PubMed2004

The filtration-acclimatization method for isolation of an important fraction of the not readily cultivable bacteria.

We developed a novel method, the filtration-acclimatization method (FAM), which enables the isolation and cultivation of an important fraction of the bacterial diversity, which is not cultivable by standard methods. The method consists of a filtration step, which removes most of the readily cultivable bacteria able to overgrow slowly growing bacteria, and an acclimatization procedure that provides a slow transition from the low environmental substrate concentrations to the high concentration of standard microbial media. So far, we isolated in total 65 strains from surface freshwater habitats by utilizing FAM. The isolates are affiliated with Actinobacteria, Alpha-, Betaproteobacteria, Bacteroidetes, and Spirochaeta. All isolates are pure cultures and form visible colonies on agar plates with high substrate concentrations. For further analysis, strains sharing more than a 97% 16S rRNA gene sequence similarity were grouped into one taxon. Based on sequence similarities, 88% of the obtained taxa can be considered to be undescribed species (<97% similarity to closest species). The highest similarity value of the taxa to the respective closest related species ranged from 87.7% to 99.8%, and was on average 94.5%. For comparison we isolated, by direct plating of water samples on a rich agar medium, a similar number of taxa. Amongst these taxa the percentage of taxa, which can be considered to be undescribed species, was only half of the percentage found for the taxa isolated by FAM. More importantly, it was amongst the taxa obtained by the standard method no taxon that was closer related to an uncultured bacterium than to an isolate, while 56% of the taxa isolated by FAM were closely related to uncultured bacteria.

Bacteria↗
PubMed2001

Effect of 8-OH DPAT and ketanserin on the ventilatory acclimatization to hypoxia in awake goats.

We have previously reported that broad-spectrum serotonergic blockade increased the acute hypoxic ventilatory response in awake goats. The purpose of the present study was to examine the putative serotonin (5-HT) receptor subtype(s) that may have contributed to this response. Following the administration of the selective 5-HT(1A)-receptor agonist, 8-hydroxy-(2-di-n-propylamino) tetralin (8-OH DPAT, 0.1 mg x kg(-1)i.v.), there was an increase in normoxic expired minute ventilation (V(E)) that was due to an increased breathing frequency. V(E) increased during hypoxia but the change in V(E) (Delta V(E)) associated with hypoxic exposure was not different from the Delta V(E) of saline treated goats. The combination of 8-OH DPAT and a selective 5-HT(2A/2C) receptor antagonist, ketanserin (0.1 and 1.0 mg x kg(-1)i.v., respectively), also increased normoxic V(E) but did not alter the hypoxia induced Delta V(E). Both 8-OH DPAT alone and in combination with ketanserin attenuated the change in V(E) associated with sustained hypoxia but neither was able to attenuate the increased hypoxic ventilatory response that occurs following acclimatization. The augmented acute hypoxic ventilatory response that we previously reported does not appear to be mediated via the activation of the 5-HT(1A) receptor or through the combination of 5-HT(1A) activation and 5-HT(2A/2C) blockade. The results of this study further suggest that while 5-HT may modulate hypoxic ventilation it does not appear to be necessary for the development of ventilatory acclimatization to hypoxia.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2000

Ecological adaptation and acclimatization of natural freshwater phytoplankters with a nutrient gradient.

Ecological adaptation and acclimatization of natural phytoplankters within a nutrient gradient were studied in an oligotrophic pond with special reference to the diel fluctuations of cell volumes and frequency of dividing cells (FDC) at each season using an in situ gradostat. The predominant phytoplankters (Cryptomonas ovata in spring and autumn, Crucigenia rectangularis in summer and Chlamydomonas elongus in winter) exhibited moderately phased division during each season. These diel cycles could be regressed onto a sine curve to give a highly significant fit. The diel patterns in all gradostat chambers and periods were almost the same except for slight variations in the FDC. This shows that the diel pattern of cell division was governed mainly by the light:dark cycle during the 24 h, without regard to trophic differences of the aquatic environment. The mean growth rates of most phytoplankters were higher in the mesotrophic zone than in the eutrophic zone during each season. In winter, the growth rate of Chlamydomonas elongus was evidently greater during the seventh day of the experiment (Period III) than during the first day (Period I) in the mesotrophic chamber. As Chlamydomonas species occur as mesotrophic species in natural waters, Chlamydomonas elongus must acclimatize easily from the oligotrophic habitat to the mesotrophic environmental condition.

Journal Article↗
PubMed2003

Changes in Escherichia coli transcriptome during acclimatization at low temperature.

Upon cold shock Escherichia coli transiently stops growing and adapts to the new temperature (acclimatization phase). The major physiological effects of cold temperature are a decrease in membrane fluidity and the stabilization of secondary structures of RNA and DNA, which may affect the efficiencies of translation, transcription, and replication. Specific proteins are transiently induced in the acclimatization phase. mRNA stabilization and increased translatability play a major role in this phenomenon. Polynucleotide phosphorylase (PNPase) is one of the cold-induced proteins and is essential for E. coli growth at low temperatures. We investigated the global changes in mRNA abundance during cold adaptation both in wild type E. coli MG1655 and in a PNPase-deficient mutant. We observed a twofold or greater variation in the relative mRNA abundance of 20 genes upon cold shock, notably the cold-inducible subset of csp genes and genes not previously associated with cold shock response, among these, the extracytoplasmic stress response regulators rpoE and rseA, and eight genes with unknown function. Interestingly, we found that PNPase both negatively and positively modulated the transcript abundance of some of these genes, thus suggesting a complex role of PNPase in controlling cold adaptation.

Adaptation, Physiological↗
PubMed2006

Effects of short-term acclimatization to altitude (3200 m) on aerobic and anaerobic exercise performance.

Aerobic exercise performance decreases upon ascent to altitude whereas anaerobic performance remains unchanged. Although the effects of 1 - 3 wk of altitude acclimatization on both aerobic and anaerobic exercise performance have been well studied, the effects of short-term altitude acclimatization (i.e., 45 h) on these parameters have not been well defined. Therefore, both aerobic and anaerobic exercise performance was evaluated in five healthy men (51.4 +/- 7.7 years, 175 +/- 4.2 cm, and 73.8 +/- 6.1 kg) at low altitude (LA, 600 m), upon acute exposure (approximately 1 - 3 h) to 3200 m (HA1) and on the third day of altitude exposure (HA3, 3200 m). Subjects performed three consecutive exercise tests, separated by approximately 1 - 3 h of rest, of various durations (i.e., 30 s, 5 min, and 50 min) on a cycle ergometer in each environmental condition. Anaerobic cycling performance (i. e., 30 s) was the same at LA, HA1, and HA3. Aerobic cycling performance (i. e., 5 min and 50 min) was reduced by 12.0 and 11.3 %, respectively, upon acute exposure to altitude. There was no change in the 5-min cycling performance but the 50-min cycling performance improved by 5.7 % from HA1 to HA3 which implies a 50 % recovery of the initial loss. These findings are important for individuals going to high altitude for work, for athletic competition, or recreation.

Adaptation, Physiological↗
PubMed2004

Biodegradation of phenol by acclimatized Pseudomonas putida cells using glucose as an added growth substrate.

Biodegradation of phenol, a pollutant derived from many industrial processes, was achieved through acclimatized Pseudomonas putida cells. The strategy to overcome the inhibitory effect of phenol on microbial growth involved the addition of glucose, a conventional carbon source. A factorial experimental design was employed in order to optimize the initial phenol and glucose concentrations. The optimum conditions found were applied in 2-lt bioreactors. The development of acclimatized cells and the use of glucose as an added growth substrate resulted in a significant phenol degradation rate of 60.7 mg L(-1) h(-1) with a complete removal of 1200 mg L(-1) phenol.

Biodegradation, Environmental↗
PubMed1996

Cochlear implantation: relationships with research on auditory deprivation and acclimatization.

This paper reviews research on cochlear implantation relevant to deprivation and acclimatization with acoustical hearing aids. The term "deprivation" is used in its everyday sense to refer to the bilateral absence of acoustic stimulation. Results are reviewed from several sources, with detailed evidence presented from three groups of postlingually deafened adult patients and one group of prelingually deafened child patients, all implanted at the University of Iowa. Outcomes from implantation reveal consistent effects of deprivation, evidenced by significant negative correlations between accuracy of speech perception and the duration of profound/total deafness before implantation. Outcomes also show acclimatization in the form of significant improvements in performance over time after implantation. For adult patients, the level of performance measured shortly after implantation on average is about half the level measured eventually. Individually, 80% of the adult patients implanted in Iowa show significant performance improvements with time. On average, performance reached asymptote after 30 to 40 mo of implant use, although individual differences in the rate and amount of improvement are large. Absolute accuracy of speech perception with implants by adults is believed to be related to preoperative measures in three domains: 1) the number and physiological responsiveness of auditory ganglion cells and nerve fibers, indexed by measures of hearing sensitivity, duration of deafness, and age; 2) the responsiveness of the central nervous system, indexed by measures of cognitive and linguistic ability, and possibly also by age and duration of deafness; and 3) the motivation to learn to use the implant. Preliminary analyses suggest that the measures in the first domain are more strongly associated with the immediate benefit from implantation than with the subsequent improvement in performance over time.

Adolescent↗