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PubMed1996

Report of the Eriksholm Workshop on auditory deprivation and acclimatization.

The terminology used in studies documenting changes in auditory performance following fitting of hearing aids has been diverse. Definitions for the auditory deprivation effect and auditory acclimatization are offered as a first step in rationalization. Two statements summarize current knowledge concerning auditory deprivation effects and auditory acclimatization, as well as considering the potential implications for research, field trial and clinical practice applications. Potential areas for future research are identified.

Auditory Perception↗

PubMed1984

Failure of long-term acclimatization in smokers moving to high altitude.

It was found that several foreign experts recruited for an irrigation project in southern Peru could not cope with their work at an altitude of 3 200 m. When we analyzed the haematological acclimatization to high altitude in 109 adult males, we found that the moderate differences in haematocrit level (0.9) and haemoglobin concentration (0.2 g/100 ml) between male smokers and non-smokers at low altitude were almost quadrupled at 3 200 m height. The haemoglobin concentration increased in both groups during the first month, after which it remained constant. Of 51 Swedish employees, 25 smokers and 26 non-smokers, 14 were obliged to terminate their contracts. All 10 who had failed to cope with their work for other than purely medical reasons were smokers. This group of smoking men also had an overconsumption of alcohol. We therefore conclude that life style determines long-term acclimatization to high altitude.

Adaptation, Physiological↗

PubMed2000

PDGF-beta receptor expression and ventilatory acclimatization to hypoxia in the rat.

Activation of platelet-derived growth factor-beta (PDGF-beta) receptors in the nucleus of the solitary tract (nTS) modulates the late phase of the acute hypoxic ventilatory response (HVR) in the rat. We hypothesized that temporal changes in PDGF-beta receptor expression could underlie the ventilatory acclimatization to hypoxia (VAH). Normoxic ventilation was examined in adult Sprague-Dawley rats chronically exposed to 10% O(2), and at 0, 1, 2, 7, and 14 days, Northern and Western blots of the dorsocaudal brain stem were performed for assessment of PDGF-beta receptor expression. Although no significant changes in PDGF-beta receptor mRNA occurred over time, marked attenuation of PDGF-beta receptor protein became apparent after day 7 of hypoxic exposure. Such changes were significantly correlated with concomitant increases in normoxic ventilation, i.e., with VAH (r: -0.56, P < 0.005). In addition, long-term administration of PDGF-BB in the nTS via osmotic pumps loaded with either PDGF-BB (n = 8) or vehicle (Veh; n = 8) showed that although no significant changes in the magnitude of acute HVR occurred in Veh over time, the typical attenuation of HVR by PDGF-BB decreased over time. Furthermore, PDGF-BB microinjections did not attenuate HVR in acclimatized rats at 7 and 14 days of hypoxia (n = 10). We conclude that decreased expression of PDGF-beta receptors in the dorsocaudal brain stem correlates with the magnitude of VAH. We speculate that the decreased expression of PDGF-beta receptors is mediated via internalization and degradation of the receptor rather than by transcriptional regulation.

Adaptation, Physiological↗

PubMed1983

Metabolic acids and [H+] regulation in brain tissue during acclimatization to chronic hypoxia.

Ventilatory acclimatization, arterial acid-base status, brain stem and cortex metabolic acids, and high-energy phosphates were determined in rats during 2-h to 7-days exposure to two levels of hypoxia (O2 inspiratory pressure 75 and 58 Torr), and upon acute restoration of normoxia. Brain lactate concentrations increased during acute exposure to both moderate hypoxia (+52% in cortex and +61% in stem) and severe hypoxia (+211% in cortex and +163% in stem), and during chronic hypoxia remained unchanged or decreased, respectively, as hyperventilation progressed and arterial O2 content rose. Restoration of normoxia after chronic hypoxic exposure resulted in continued hyperventilation and elevated lactate concentrations. Brain intracellular pH was unchanged throughout moderate hypoxia and during severe hypoxia, became acid during acute exposure, but was completely compensated after 72 h of continued hypoxia. Preventing the hypocapnia (via increased inspiratory fraction of CO2) during acute hypoxia or restoring normocapnia during posthypoxic normoxia revealed the effects of hypocapnia independently of hypoxemia. Hypocapnia accounted for all of the changes in brain lactate concentration during moderate hypoxia but only 40-60% of the lactate changes during severe hypoxia. We speculate that the observed changes in plasma and brain tissue metabolic acids and in plasma [HCO-3] would acidify cerebral interstitial fluid (ISF) in chronic hypoxia; however, the time course of this change in ISF acid-base status would be quite different between the two levels of hypoxia and uncorrelated with the patterns of ventilatory acclimatization.

Acid-Base Equilibrium↗

PubMed2006

Heat acclimatization and hydration status of American football players during initial summer workouts.

This investigation evaluated the new National Collegiate Athletic Association model of heat acclimatization for football players using physiological, psychological, fluid balance, anthropometric, and nutritional variables. Eleven football players (20 +/- 1 year, 1.88 +/- 0.05 m, and 115.36 +/- 18.85 kg) from a Division I football team were observed for the first 8 days of preseason practices. Measurements such as heart rate and gastrointestinal temperature (T(GI)) via telemetric sensor were taken before, 3 times during, and after practice daily. An average 1.39-kg (1.2%) decrease of body mass occurred from prepractice to postpractice (p < 0.01). Consistent with mild body mass losses, urinary indices of hydration status (i.e., color, specific gravity, and osmolality) indicated mild fluid deficits. A significant increase (p < 0.05) from pre- to postpractice was observed in urine color and urine specific gravity, but chronic hypohydration over the 8 days was not noted. The Environmental Symptoms Questionnaire (ESQ) postpractice score was significantly higher (p < 0.05) than the prepractice score was, but averages did not differ across practice days. There was no difference in postpractice T(GI) measurements across days (p < 0.05). Heart rate, T(GI), and ESQ measurements indicated that football players experienced gradual heat acclimatization and enhanced heat tolerance, despite progressive increases of exercise variables, clothing, and environmental stressors.

Adaptation, Physiological↗

PubMedDate not supplied

[Acclimatization: speech recognition in hearing aid users].

BACKGROUND: acclimatization is the period that succeeds the fitting of hearing aids, when a progressive improvement of the hearing and speech recognition abilities is observed due to the new speech cues that are available to the hearing aid user. AIM: to verify acclimatization after the fitting of hearing aids through objective (speech tests) and subjective (Questionnaire) evaluations. METHOD: 16 hearing impaired individuals were evaluated on the first day of hearing aid fitting and were monthly reassessed for three months. In all three months the following speech tests were used: PISR - percentage index of speech recognition through monosyllabic words and SRT--speech recognition threshold through sentences, determining the speech/ noise ratio (S/N). The International Outcome Inventory of Hearing Aid (IOI-HA) was also applied in the first and third months after the hearing aids were fitted. RESULTS: the comparison between the first day, first, second and third months after the hearing aids were fitted revealed a statistically significant improvement (p<0.001) between the results, not only for the PISR but also for the S/N ratio. No statistically significant difference was found for the results obtained through the questionnaire applied in the first and third months. CONCLUSION: the objective evaluation, using speech recognition tests, presents better results in the months following the hearing aids fitting indicating a progressive improvement in the speech abilities from the first month onwards. The subjective evaluation does not reveal an improvement when comparing the first and third moths after the hearing aids were fitted.

Adaptation, Physiological↗

PubMed1980

[Survival of acclimatized and hypothyroid rats at 40 degrees C (author's transl)].

The survival of rats acclimatized to either 5 degrees C or 30 degrees C, treated or not with propylthiouracil (P.T.U.), was determined at 40 degrees C. Changes in metabolic rate and rectal temperature were followed throughout exposure. Total water loss was estimated at the end of the experiment. The survival time of rats accclimatized to 5 degrees C was less than that of rats acclimatized to 30 degrees C, and that of controls was less than that of treated animals. The differences reported seem to be independent of heat transfer capacities, which are similar in all treatment conditions and possibly limited by the experimental set up. A high thermogenic rate would appear to limit resistance to heat under conditions where external heat stress approaches heat transferability, such that the animal's temperature overcomes the lethal threshold, and leads to heat stroke. Results of P.T.U. treatment suggest the involvement of thyroid hormones in heat stress-induced thermogenesis and in cellular lability to elevated internal temperatures.

Adaptation, Physiological↗

PubMed1960

Behavior in the cold after acclimatization.

Experimentally naive albino rats begin to press a lever for short bursts of radiant heat earlier in a 16-hour session at 2 degrees C than rats that have been living at this temperature for about a month. This difference reflects the different rates at which body temperature in the cold falls in acclimatized and nonacclimatized animals.

Acclimatization↗

PubMed1984

Fish liver protein synthesis during cold acclimatization: seasonal changes of the ultrastructure of the carp hepatocyte.

A cell-free system, active in protein synthesis, was constructed using ribosomes and supernatant factors isolated from the livers of winter-acclimatized carps. Upon seasonal adaptation, the hepatocytes of these fishes exhibited distinctive morphological features that were not sex dependent. The cytoarchitecture of the liver cell from summer carps is consistent with the cellular arrangements found when the rate of gene expression is high. During winter, several morphological features reveal that macromolecular synthetic activity may be clearly diminished.

Acclimatization↗

PubMed1990

The relative influence of physical fitness, acclimatization state, anthropometric measures and gender on individual reactions to heat stress.

An experiment was set up to quantify the relative influence of fitness, acclimatization, gender and anthropometric measures on physiological responses to heat stress. For this purpose, 12 male and 12 female subjects were exposed to a neutral [ambient temperature (Ta) 21 degrees C, relative humidity (r.h. 50%)], a warm, humid (Ta 34 degrees C, r.h. 80%) and a hot, dry (Ta 45 degrees C, r.h. 20%) climate at rest and at two exercise intensities [25%, and 45% maximal O2 intake (VO2max)], seated seminude in a net chair behind a cycle ergometer. Their physiological responses were recorded and the data submitted to a multiple regression analysis. It was shown that for the variance in heat storage, the percentage of body fat and the surface to mass ratio had relatively the largest influence of all the individual parameters, followed by VO2max and the sweat rate versus increase in core temperature (total r2 = 92%). For the skin temperature variation, the relative influence of individual parameters (sweat gain, VO2max) was small. For body core temperatures, individual parameters had a large influence. The largest effect was due to the percentage of fat and the surface to mass ratio, followed by the sweating setpoint and, finally, VO2max (total r2 = 54%-70%). For the variance in heart rate the VO2max was the most relevant parameter, followed by the setpoint of the sweat rate:rectal temperature relationship (total r2 = 88%). Blood pressure and skin blood flow predictions were also shown to improve by the addition of individual characteristics to the model.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗

PubMed1996

Effects of high altitude acclimatization on heart rate variability in resting humans.

The sympatho-vagal nerve interaction at the heart was studied by means of power spectrum analysis of heart rate variability in seven Caucasians (aged 27-35 years) in resting supine and sitting positions before and during 35 days of a sojourn at 5050 m above sea level (asl) and in six Sherpas (aged 22-30 years) at high altitude only. A high frequency peak (HF)-central frequency between 0.20 and 0.33 Hz, a low frequency peak (LF)-central frequency between 0.08 and 0.14 Hz, and a very low frequency component (< 0.05 Hz), no peak observed, were found in the power spectrum in both positions and independent of altitude. The peak powers, as a percentage of the total power, were affected by both body position and altitude. At sea level the change from a supine to a sitting position yielded a decrease in percentage HF from 25 (SEM 1.9)% to 6.2 (SEM 1.5)% (P < 0.05) and a significant increase in the ratio between LF and HF powers (LF:HF) from 1.7 (SEM 0.4) to 6.9 (SEM 1.6). At altitude compared to sea level in the supine position, percentage HF decreased from 25% to 10.9 (SEM 1.0)% (P < 0.05) and the LF:HF ratio increased from 1.7 to 4.8 (SEM 0.7) (P < 0.05). No changes occurred at altitude in the sitting position either in the peak powers or in the LF:HF ratio, but the central frequency of HF peak increased significantly from 0.25 (SEM 0.02) Hz to 0.32 (SEM 0.01) Hz. In the Sherpas comparable results to the Caucasians were found in both body positions. The high LF:HF ratios observed at altitude in both body positions and groups would suggest that hypoxia caused a shift of sympatho-vagal nerve interaction at rest toward a dominance of the sympathetic system, which was found at sea level only in the sitting position. An acclimatization period of 10 days higher than 2850 m asl and 1 month at 5050 m asl did not modify the interactions of the autonomic systems.

Acclimatization↗

PubMed1975

Ventilatory acclimatization and csf acid-base balance in carotid chemodenervated dogs at 3550 m.

In three awake dogs in a hypobaric chamber at 140 m and at 3550 m, resting ventilation, pulmonary gas exchanges, respiratory gases and pH of the arterial blood, acid-base status in the cerebrospinal fluid (csf), and ventilatory responses to transient O2-inhalation were studied before (intact) and after chronic bilateral carotid body denervation (cbd). 1. The hypoxic chemoreflex drive of ventilation was reduced by about half in cbd dogs. 2. At low altitude, sino-carotid body denervation resulted in hypoventilation and respiratory acidosis in the arterial blood and csf. 3. At high altitude, initial hypoxic hyperventilation, and the related alkalosis in blood and csf, occurred within 30 min in intact dogs, but was not observed in cbd ones. 4. Further increase in ventilation was achieved upon 3 hrs of altitude exposure in intact animals, while a delayed hyperventilation occurred after 24 hrs in cbd ones. 5. Neither in intact nor in cbd dogs, the ventilatory changes at altitude were related to the changes in csf pH. It is concluded that the rate of ventilatory acclimatization to altitude is dependent upon the strength of the arterial chemoreceptor drive. Integrity of this chemoreflex drive of breathing is essential in determining the eupneic level of ventilation and normal acid-base status of the blood and csf at low altitude and at high altitude.

Acclimatization↗

PubMed1976

Is glucagon involved in cold acclimatization?

Cold acclimatization in rats at 5 degrees C for 2 weeks caused a significant elevation of plasma glucagon concentration, accompanied by increased plasma FFA and glucose levels. Acute cold exposure at 5 degrees C for 5 or 60 min did not affect these parameters in plasma.

Acclimatization↗

PubMed1979

Cellularity and composition of epididymal adipose tissue from cold-acclimatized rats.

Cold acclimatization induces morphological and compositional modifications of rat epididymal adipose tissue: a decrease in fat cell size, an increase of fat cell number per g of tissue, but no significant increase in total fat cell number in the tissue; finally, an increase in protein content and a decrease in triglyceride content.

Acclimatization↗

PubMed2003

Sciatic nerve monoaminergic system response to cold acclimatization in Muscovy duckling.

The effect of cold acclimatization on the monoamines in duckling sciatic nerve was studied. In thermoneutral (TN) ducklings, the high dopamine (DA) to norepinephrine (NE) ratios in the right (R, 0.14) or in the left (L, 0.20) sciatic nerves at 6 weeks of age suggests the presence of non-precursor specific dopaminergic pools. DA, DOPAC (3, 4-dihydroxyphenylacetic acid) levels and the ratio DA to NE were similar in cold-acclimated (CA) and TN ducklings sciatic nerves. Moreover, serotonin and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) remained unchanged in the sciatic nerve, indicating that this system is not affected with cold exposure. The contents of NE were higher (R = +44.46%; L = +43.73%) in sciatic nerve of CA than in TN ducklings. The results indicate that noradrenergic systems in the ducklings sciatic nerve are markedly affected by cold exposure. Interestingly, chronic exposure to cold failed to alter the dopaminergic and the serotonergic system in duckling sciatic nerve.

Acclimatization↗

PubMed2000

Spinal cord monoaminergic system response to age and cold-acclimatization in muscovy duckling.

The effect of age and cold acclimatization on the regional distribution of monoamines in duckling spinal cord was studied. In thermoneutral controls (TN), the high dopamine (DA) to norepinephrine (NE) ratios (0.25 at 4 weeks of age and 0.15 at 6 weeks of age) suggest the presence of specific (non precursor) dopaminergic pools in cervical spinal cord. DA levels and the ratio of DA to NE were lowered by age and cold exposure in the cervical cord. In TN ducklings, serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) showed a decline with age in the spinal cord, indicating that this system is affected with development, whereas cold exposure prevents this decrease. The contents of 5-HT (+58%), 5-HIAA (+93%) and the ratio of 5-HIAA to 5-HT (+50%) are higher in the cervical spinal cord of cold acclimated than in TN ducklings. These results indicate that central monoaminergic systems are markedly affected by age and cold exposure.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1985

Biochemical effects of mild iron deficiency and cold acclimatization on rat skeletal muscle.

Most of the previous studies on the effects of iron deficiency on skeletal muscle respiratory capacity and work performance have been investigated in severe or moderate iron-deficiency anemia. We report here that even in mild iron deficiency where the hemoglobin concentration was 10 g/dl and the iron stores in livers and spleen were not completely depleted, a marked reduction in succinate dehydrogenase was observed in skeletal muscles but not in heart. Similarly, cytochrome oxidase activities were reduced. Although no significant change in glycerophosphate dehydrogenase was detected in the iron-deficient rats, exposure to cold in this group greatly reduced this enzyme activity. As cold acclimatization accelerates marrow erythropoiesis (20) which in turn, demands more iron, it seems that in the iron-insufficient state, this iron demand for marrow activity may persist at the expense of the tissue iron pool, resulting in a marked reduction in glycerophosphate dehydrogenase activities. Since succinate dehydrogenase plays a significant role in the impairment of mitochondrial function and early fatigue of iron-deficient muscle (11), the present study shows that even in mild iron deficiency, some loss of muscle functions could result as succinate dehydrogenase activities were greatly reduced.

Acclimatization↗

PubMed1977

The kidney and aldosterone in acclimatization at altitude.

Five climbers were studied during an ascent of a 7500 m mountain in the Hindu Kush. Representiative samples from 24-hour urines were preserved from five subjects at 5400 m and 6600 m and from two at 7000 m. Sodium and cortisol excretion was normal, but that of potassium and especially aldosterone was low, especially in two climbers who had episodes of peripheral oedema. Hypoaldosteronism is a feature of high altitude acclimatization but its cause and significance have still to be elucidated.

Acclimatization↗