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PubMed2003

Cognitive effects of dexamethasone at high altitude.

OBJECTIVE: The major therapeutic effect of dexamethasone on persons affected by high-altitude illness may be upon vascular leakiness with a consequent decrease in cerebral edema. We set out to determine if dexamethasone ameliorates the cognitive/psychomotor effects of acute exposure to high altitude on asymptomatic subjects. METHODS: Six adult subjects were tested at baseline (2500 m) with standard, computerized cognitive and psychomotor tests. Over the next 4 days, subjects were acclimatized to an altitude of 3700 m. On the fifth day, subjects ascended to 4800 m where predexamethasone testing was administered. No subject had symptoms of frank altitude illness at 4800 m. To limit acclimatization, subjects descended to 3700 m within 4 hours. The first 4-mg dose of oral dexamethasone was given in the evening of day 5. A second 4-mg dose of dexamethasone was given the following morning, and subjects reascended to 4800 m where postdexamethasone testing was performed. RESULTS: All cognitive and psychomotor tests showed improved reaction times in subjects who were given dexamethasone. Mean reaction time (+/- SD) for shape recognition went from 1.20 +/- 0.36 seconds at 2500 m to 1.40 +/- 0.37 seconds at 4800 m. After dexamethasone administration, mean shape recognition time declined to 1.26 +/- 0.32 seconds (P = .052). CONCLUSION: These data show a trend toward decreased cognitive deficits in subjects pretreated with dexamethasone. One possibility for this trend is that cognitive deficits in otherwise asymptomatic subjects exposed to high altitude are caused by subclinical cerebral edema.

Administration, Oral↗
PubMedDate not supplied

Heat and exercise. Effects on blood volume.

The ability of the cardiovascular system to meet the competing demands of skin and muscle for blood flow without compromising regulation of blood pressure is a critical factor influencing the capacity for prolonged work in hot environments. Unfortunately, this competition is exacerbated by the progressive reduction in blood volume (haemoconcentration) which can occur during exercise in the heat. Thermal stress alone induces haemoconcentration only above the upper limit of the prescriptive zone. Exercise performed in a supine or seated position is associated with an initial rapid haemoconcentration, which, if the environmental temperature is high, is followed by a slower, secondary haemoconcentration. Exercise performed in a standing position is associated with variable changes in blood volume, and effects of a superimposed thermal stress are small unless dehydration supervenes. The magnitude of exercise-induced primary haemoconcentration is limited, probably by oedema-preventing mechanisms, and is inversely related to the magnitude of any preceding postural haemoconcentration. Dehydration reduces absolute blood volume (induces hypovolaemia), and accentuates exercise haemoconcentration. Heat acclimatization attenuates dehydration by inducing hypervolaemia, but still appears to accentuate exercise haemoconcentration. During exercise in the heat haemoconcentration represents an undesirable response, the effects of which can be mitigated by heat acclimatization, endurance training, and preventing dehydration.

Blood Volume↗
PubMed1982

Effects of sweat gland training by repeated local heating.

Effects of sweat gland training by daily local heating were examined and its significance in heat acclimatization was evaluated. Training by 2-hr immersion of an arm in hot water of 43 degrees C caused distinct augmentation of sweat gland activity in the trained area, with reduction in the degree of hidromeiosis, when tested by an arm bag collection of sweat. Concentrations of sweat electrolytes also showed definite decreases. The general tendency that Na and Cl concentrations in sweat rise in the course of hidromeiosis was attenuated or even reversed after the training. The sweat test using resistance hygrometry failed to show a marked or consistent increase in sweat rate of the trained area, although an increase was the common case on the dorsum of the hand and the extensor aspect of the forearm. The effect of training appeared in a few days of training, developed progressively with training days and showed a tendency to develop even after 3 weeks of training. The same training in midsummer failed to exert significant effects on sweat gland activity, suggesting that the sweat gland had been naturally trained to a considerable degree by then. On the other hand, training by repeated radiant heating of a local area caused only obscure changes in the activity of sweat glands. The present results reveal that sweat glands can be trained to be resistant to hidromeiosis in a hot-humid environment and that such peripheral changes appear to play a predominant role in augmentation of sweating capacity in the early stage of heat acclimatization.

Adult↗
PubMed1995

Long-term non-invasive measurement of intraocular pressure in the rat eye.

To study the optic neuropathy associated with glaucoma, a system for accurate, reliable, and non-invasive monitoring of intraocular pressure (IOP) is required. Of particular interest is the effect of sampling frequency on IOP. To address this issue, ten adult male brown Norway rats (group 1) were acclimatized to a 12-h/12-h light/dark cycle. On 20 days over a 30-day period, rats were anesthetized with short-acting isoflurane (Forane) inhalant anesthesia and IOP for each eye was determined by averaging 15 valid individual readings obtained with a TonoPen 2 tonometer. The last 12 measurement sessions were performed on a daily basis. To determine the minimum tolerable interval between IOP measurement sessions, a second group of 10 animals (group 2) was acclimatized in the same manner as group 1, and IOP was measured every 4 days over a period of 80 days. Next, IOP was measured every 4 days over a period of 28 days, and finally, every 2 days over a period of 19 days. For all group 1 measurements, there was no statistically significant difference between the right and left eye IOP, 14.75 +/- 1.08 (SEM) and 14.90 +/- 1.09 mm Hg, respectively. However, daily measurements produced a steady decrease in IOP and gradual weight loss. For group 2, overall mean right and left eye IOPs were 15.24 +/- 1.28 (SEM) and 15.12 +/- 1.26, respectively and were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthetics, Inhalation↗
PubMed1991

Effectiveness of zinc bacitracin on production traits and energy metabolism of heat-stressed hens compared with hens kept under moderate temperature.

Two experiments with a total of 100 White Leghorn hens (26 to 59 wk of age) and 120 Rhode Island Red chickens (4 to 12 wk of age) were conducted to study the effect of 100 mg zinc bacitracin (ZBA)/kg of feed on hens and chickens acclimatized to 20 or 34 C environments. Layers were provided ad libitum access to a diet containing 11.12 MJ ME/kg (1 MJ = .239 Mcal) and 174 g CP/kg supplemented with 0 and 100 mg ZBA/kg. Body weight gain, egg number, total egg mass, and feed efficiency of ZBA-treated hens kept at a moderate temperature (20 C) were not significantly improved by 3.5, 2.6, 3.3, and 3.1%, respectively. However ZBA supplementation induced a more pronounced increase in performance in heat-stressed hens. The respective traits were significantly improved by 66.3, 15.4, 16.9, and 5.9%. Additionally, treated hens maintained at 34 C consumed significantly more feed than untreated hens. Eggshell breaking strength of treated hens held under normal conditions was not significantly improved. Feeding ZBA to heat-stressed hens led to a statistically higher breaking strength. Supplementation with ZBA for hens acclimatized to 20 and 34 C reduced fasting heat production by 4.1 and 7.6%, respectively. However, in the 20 C environment the differences were significant at only one of seven ages. The upper critical temperature (UCT) of ZBA-treated hens increased significantly at both temperatures from 34 to 42 wk of age relative to the control group. No significant effects of ZBA on UCT were observed at 24 to 32 wk and 40 to 52 wk of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

A digital processing strategy to optimize hearing aid outputs directly.

A new amplification strategy (ADRO), based on 64 independently operating channels, was compared with a nine-channel wide dynamic range compression strategy (WDRC). Open-platform in-the-ear hearing instruments were configured either with ADRO or the manufacturer's WDRC strategy. Twenty-two subjects with mild to moderate hearing loss took home the ADRO or WDRC hearing aids. After three weeks' acclimatization, the aids were evaluated using monosyllables in quiet at 50 to 65 dB SPL and sentences in eight-talker babble. The acclimatization and evaluation were repeated in the second phase of the balanced reverse-block blind experimental design. The ADRO program showed a statistically significant mean advantage of 7.85% word score (95% confidence interval 3.19% to 12.51%; p = 0.002) and 6.41% phoneme score for the monosyllables in quiet (95% confidence interval 2.03% to 10.79%; p = 0.006). A statistically significant advantage of 7.25% was also found for the ADRO program in background noise (95% confidence interval 1.95% to 12.55%; p = 0.010). The results are consistent with earlier data for listeners with moderate to severe hearing loss.

Acoustic Stimulation↗
PubMed1976

Physiological performance and work capacity of Sudanese cane cutters with Schistosoma mansoni infection.

Physiological tests of work performance and measurement of field productivity were made in 194 Sudanese cane cutters in order to study the effect of Schistosoma mansoni infection. The cane cutters were selected from two age ranges (16-24 and 25-45 years) and subdivided into three clinical groups: not infected, infected with, and infected without clinical signs of hepatosplenomegaly. Men infected with Schistosoma haemotobium, malaria (blood film), or with hemoglobin levels less than 10 g/100 ml were excluded. There was a statistically significant (P less than 0.002) higher mean hemoglobin concentration in those not infected but the mean difference was less than 1 g/100 ml. Submaximal responses to exercise on a stationary bicycle ergometer, oxygen intake, ventilation, tidal volume, cardiac frequency and estimated maximal aerobic power output calculated both in absolute terms and relative to lean body mass and leg volume were similar in the six groups of cane cutters. No significant differences were found in physique, body composition or in thermoregulatory function tests. The cane cutters were found to have little natural acclimatization to heat in terms of sweating capacity when compared with a group of fully acclimatized Sudanese soldiers. The mean productivity (mean daily weight of cane cut per man) was significantly correlated with the individual's estimated maximum aerobic capacity determined in the laboratory, but not with the degree of S. mansoni infection. The noninfected group was less "efficient" (mean productivity:oxygen intake) during cutting than the infected groups but a larger proportion of the noninfected were in their first season of cutting. There was a positive correlation between the number of seasons' cutting experience and the individual's age, degree of infection and mean productivity. Cane cutters studied in this investigation were a relatively fit, active population from whom the more seriously ill were excluded. These results do not, therefore necessarily reflect the effects of S. mansoni on physiological work capacity and productivity of more static populations in areas of high endemicity.

Adolescent↗
PubMed2004

Experimental infection of house finches with Mycoplasma gallisepticum.

Mycoplasma gallisepticum (MG) has caused an endemic upper respiratory and ocular infection in the eastern house finch (Carpodacus mexicanus) after the epidemic first described in 1994. The disease has been studied by a number of investigators at a population level and reports describe experimental infection in group-housed MG-free house finches. Because detailed observation and evaluation of individual birds in group-housed passerines is problematic, we studied individually housed house finches that were experimentally inoculated with the finch strain of MG in a controlled environment. To accomplish this, a study was conducted spanning the period of November 2001-April 2002 with 20 MG-free (confirmed by the rapid plate agglutination assay and polymerase chain reaction [PCR] assay) eastern house finches captured in the Cayuga Basin area of central New York (USA) in the summer of 2001. After a period of acclimatization and observation (12 wk), 20 finches were inoculated with a 0.05-ml aliquot of MG (3.24 x 10(5) colony-forming units/ml) via bilateral conjunctival sac instillations. Two additional finches acted as controls and were inoculated in the same manner with preservative-free sterile saline solution. After inoculation, all finches except the controls exhibited clinical signs of conjunctivitis within 2-6 days. The progression of the disease was evaluated by several methods, including PCR, behavioral observations, and physical examination including eye scoring, body weight, and body condition index. Over a period of 21 wk, MG-infected finches developed signs of disease and recovered (80%), developed signs of disease and progressed to become chronically infected (15%), or died (5%). We hypothesize that the high survival rate and recovery of these finches after infection was associated with the use of controlled environmental conditions, acclimatization, a high plane of nutrition, and low stocking (housing) density, all of which are factors documented to be important in the outcome of MG infections in domestic poultry and other species.

Animals↗
PubMed2000

Improving athletic performance: is altitude residence or altitude training helpful?

Exercise training studies conducted at different altitudes (1250-5700 m) of varying durations (30 min to 19 wk) are critically reviewed to determine the efficacy of using altitude as a training stimulus to enhance sea level and altitude exercise performance. Four strategies are discussed: a) exercise training while residing at the same altitude; b) exercise training at altitude but residing at sea level; c) exercise training at low altitude but residing at a higher altitude; and d) exercise training under sea level and altitude conditions but only after altitude acclimatization has occurred. Residing at altitude causes a multitude of potentially beneficial physiological, ventilatory, hematological and metabolic changes that theoretically should induce a potentiating effect on endurance exercise performance. While it is accepted that endurance performance is greatly enhanced at altitude, there is less support for the view that altitude training while residing at altitude improves subsequent sea level endurance performance. There is some evidence, though also not universally accepted, that training at altitude but residing at sea level may benefit sea level endurance performance. Most recently, the combination of "living high" (e.g., at 2500 m) to obtain beneficial physiological changes associated with altitude acclimatization and "training low" (e.g., at 1250 m) to allow maintenance of high-intensity training is accumulating scientific and popular support as the most advantageous strategy to improve subsequent sea level exercise performance in well-trained, competitive runners.

Altitude↗
PubMed1999

Cold shock response in Bacillus subtilis.

Following a rapid decrease in temperature, the physiology of Bacillus subtilis cells changes profoundly. Cold shock adaptation has been monitored at the level of membrane composition, adjustment in DNA topology, and change in cytosolic protein synthesis/composition. Some major players in these processes (cold-stress induced proteins and cold acclimatization proteins, CIPs and CAPs) have been identified and mechanisms in cold shock acclimatization begin to emerge; however, important questions regarding their cellular function still need to be answered.

Bacillus↗
PubMed2000

[Research on the relationship between expression of VEGF and high altitude pulmonary edema].

OBJECTIVE: To investigate the relationship between the expression of VEGF and the incidence of high altitude pulmonary edema (HAPE) and the mechanism of high altitude acclimatization-adaptation. METHODS: Pulmonary artery endothelial cells (PAEC) of rat were cultured. The expression of VEGF in PAEC was detected using RT-PCR and ELISA. Rats were divided randomly into five groups by weight: control, acute hypoxia (exposed to a simulated 8,000 m altitude for 4 hours), and three intermittent hypoxia groups (exposed to a simulated 3,000 m or 5,000 m altitude for 2 weeks, 4 hours a day, then to a simulated 8,000 m altitude for 4 hours). VEGF in the lung was detected using immunohis to chemistry and slot hybridization, and the changes of pathology in the lung were observed. VEGF in the blood plasma of rats, in men who immigrated to high altitude at different times, and in those who suffered from high altitude pulmonary edema were measured using ELISA. RESULTS: The expression of VEGF in PAEC was increased under hypoxia condition (1% O2) (P < 0.01). In the blood plasma and lung of rats during hypoxia, levels of VEGF and VEGF mRNA were higher than that in the control group. VEGF in acute hypoxia group was increased significantly compared with that in the intermittent hypoxia groups. Leakage of fluid in the lung of rats was observed in the acute hypoxia group. The longer the rats acclimatized, the lower the level of VEGF expressed, and the less the fluid leaked in the lung. The same tendency could be seen in humans. The level of VEGF in patients with high altitude pulmonary edema pre-therapy was higher than that measured post-therapy. CONCLUSIONS: Hypoxia could stimulate the expression of VEGF, and the upregulated expression of VEGF is one of the most important factors of incidence of high altitude pulmonary edema.

Altitude Sickness↗
PubMed2001

Environmental reprogramming of the expression of protein kinase CK2beta subunit in fish.

The dramatic segregation of the nucleolar components in winter-acclimatized carp is the most striking cellular-phenotypical feature observed during the seasonal adaptation of this fish toward the circannual changes in its habitat. Our studies also show that the carp habitat temperature and photoperiod winter conditions provoke a remarkable reduction of both rRNA transcription and the processing of their precursors. To gain knowledge on the mechanisms involved in the regulation of nucleolar activity during the seasonal adaptation process, we studied the behavior of some genes, specifically snoRNA U3 and protein kinase CK2. Consistent with the reduction in the synthesis and processing of pre-rRNA observed during the cold season, the level of CK2beta expression decreases in winter when compared to that attained in summer. Similarly, in winter, liver and kidney cells contain lower levels of CK2beta subunit protein compared to summer. CK2 is associated with or modifies different factors and enzymes involved in the nucleolar activity; therefore, its higher or lower content could be part of the molecular mechanisms underlying the nucleolar seasonal changes that occur during the compensatory acclimatization process.

Animals↗
PubMed2002

[Dynamic changes of SOD and MDA in canine limbs with gunshot wound in hot and humid environment: an experimental study].

OBJECTIVE: To study the dynamic changes in lipid peroxidation and the activity of antioxidative enzyme in canine limbs with gunshot wound in hot and humid environment. METHODS: Eighteen dogs with gunshot wound were randomly assigned into 3 groups with equal numbers. Dogs observed after injury in normal environment was designated as NE group, those in hot and humid environment as HHE group and those in hot and humid environment with preceding heat acclimatization training as HA group. Contents of superoxide dismutase (SOD) and malonaldehyde (MDA) in both the peripheral blood and muscular tissues from gunshot wound tract were measured at 0, 1, 3, 4, 6, 8, 10, 14, 18 and 24 h respectively after the dogs had been wounded. RESULTS: Positive correlation between SOD and MDA contents was observed in each group. Three hours after injury, MDA level in HHE group began to ascend, reaching the peak level at 6 h that was significantly higher than those in the other 2 groups (P<0.05); SOD level underwent a reverse change, which was significantly lower in HHE group than in the other groups with that in HA group being the highest. Comparable SOD levels in the groups occurred at the time of 14 h, which happened to MDA levels 4 h later. CONCLUSION: Gunshot injuries in the limbs of dogs exposed to hot and humid environment induces increased free oxygen and aggravated the lipid peroxidation, which can be alleviated by heat acclimatization.

Animals↗
PubMedDate not supplied

[The effect of moderate altitude on the maintenance of a good health status and high physical work capacity in cosmonauts over the course of a long period of time].

The development of the methods to maintain good health and high performance and occupational longevity of cosmonauts is an urgent problem. For this end, an effect of periodic (1-2 times a year) training in mid-lands on working and functional capacities of cosmonauts being members of cosmonauts corps for extended periods of time (20 years) was studied; the results of 40 trainings in mid-lands at 1,600 to 2,400 m above sea level are summarized. Before, during and after training, the physiological and physical parameters of the body (BP after Korotkoff, HR, VO2max) during exercise bicycle ergometer tests as well as the time of running on treadmill at a rate of 4.5 m/s to failure have been examined. The experimental findings indicated that after terminating physical training in mid-lands the major group of test subjects exhibited a significant decrease in HR as compared to the control value. During acclimatization, the arterial pressure (systolic and diastolic) measured when exercising on bicycle ergometer at 600 and 1000 kgm/min also reduced. As a result of improving the measured parameters after acclimatization to mountain environments the total body tolerance increased. A cumulative effect of the regular stay in mid-lands appears to change VO2max which did not decrease in man with age and the performance value (after i.v. Aulik classification) in the 40-49 age group subjects became very high.

Adaptation, Physiological↗
PubMedDate not supplied

[Long-term changes in the parasitic fauna of fishes in the Aral Sea].

In the period of 1967--1971 investigations were carried out of the fishes from the Aral Sea. 65 species of parasites have been first recorded from the above fishes, their total list includes 215 species. 23 of them were introduced during the acclimatization of fishes. Progressive salinity growth of this water body has caused the reduction of the distribution area and the decrease in the number of the Aral population of many species. Under changing conditions many species of monogenne and some members of other classes have preserved a wide distribution and in some places a high quantity. The cases of morbidity and mortality of fishes are reported. Materials on the parasite fauna of fishes enabled the author to establish their food relations which are affected by modern hydroregime of the Aral Sea as well as by the acclimatization of the Caspian gobiids.

Animals↗
PubMed1992

The effect of intermediate altitude on the Army Physical Fitness Test.

Official physical training records of personnel stationed at intermediate altitude (elevation 5,280 feet) for at least 1 year were reviewed to gauge the effect of altitude on 2-mile running performance. An average of 48 additional seconds (a 5% increase in time) was required to complete the run compared to sea-level values in the same subjects. Run times gradually diminished during the first 9 months of assignment to altitude before stability was established. These data indicate that acclimatization occurs over several months. Even with acclimatization, substantial loss of performance is associated with habitation at intermediate altitude.

Adult↗
PubMedDate not supplied

Low delta sleep predicted a good clinical response to olanzapine administration in schizophrenic patients.

INTRODUCTION: Schizophrenic patients show sleep abnormalities, consisting mainly of decreased delta sleep time, short rapid eye movement (REM) sleep latency, and a reduction in sleep continuity variables. Olanzapine is a novel antipsychotic drug with an atypical profile. The goals of the present study were to determine if pre-treatment sleep variables and the initial response to olanzapine administration on the sleep variables can predict the clinical improvement after eight weeks of treatment. MATERIAL AND METHODS: Twenty-one schizophrenic (DSM-IV) patients were studied. They were clinically evaluated using the positive and negative syndrome scale (PANSS), and the Calgary Depression Scale for Schizophrenia. Sleep recordings were as follows: one acclimatization nigh, one night of baseline recordings, and two nights in which the patients receives olanzapine 10 mg, one hour before bedtime. For sleep-comparison purposes, a group of normal volunteers were also studied with acclimatization and baseline nights. After the sleep recordings ended patients continued with the administration of 10 mg/d of olanzapine, that was titrated as needed up to 20 mg/d or down to 5 mg/d. Evaluations were conducted weekly. RESULTS: Awakening and sleep latency variables were significantly higher in schizophrenic patients compared to normal volunteers. Delta sleep was lower in patients than in normal subjects, with no detectable values in some of the schizophrenics. There was not correlation at baseline, between psychopathological scores and delta sleep or other sleep variables. The acute administration of olanzapine 10 mg produced an improvement in continuity sleep variables as well as increase in deltas sleep percentage. Having less than 10% of delta sleep at baseline predicted a good clinical outcome. Eleven of 18 patients showed good clinical improvement after eight weeks of treatment with olanzapine, those were the subjects that had an augmentation of delta sleep above 10% with the first two doses of olanzapine, with minimal side effects. CONCLUSIONS: To have low delta sleep at baseline and the effect of the augmentation of this variable in schizophrenic patients seems to predict a good response to olanzapine. Olanzapine was therapeutically useful, well-tolerated medication, with a favorable safety profile.

Adult↗
PubMed2004

Residence at moderate altitude improves ventilatory response to high altitude.

BACKGROUND: This study compared the distribution of arterial oxygen saturation (SaO2) and susceptibility to Acute Mountain Sickness (AMS) in moderate altitude residents (MAR) and low altitude residents (LAR) following rapid ascent to 4056 m. METHODS: Resting PETCO2 and SaO2 were measured in 38 subjects residing for > 3 mo near Colorado Springs, CO (MAR group), at 1940 m (USAF Academy), and after approximately 1 h at 4056 m on the summit of Pikes Peak, CO, following ascent by car. SaO2 was also measured at 610-m elevation intervals during the ascent. Of the LAR (50 m) group, 39 subjects were exposed to a similar ascent profile in a hypobaric chamber. RESULTS: At 1940 m the MAR SaO2 and PETCO2 were 94 +/- 1% (X +/- SD) and 33.6 +/- 2.8 mmHg, respectively. At 3048 m and higher, MAR SaO2 decreased, reaching 86 +/- 2% (p < 0.001) at 4056 m, and PETCO2 (32.1 +/- 4.5 mmHg) decreased (p < 0.05). At 50 m the LAR SaO2 and PETCO2 were 98 +/- 1% and 38.7 +/- 2.7 mmHg, respectively. At 1940 m and higher, LAR SaO2 decreased (p < 0.001), reaching 82 +/- 5% at 4056 m, and PETCO2 (36.4 +/- 3.5 mmHg) decreased (p < 0.05). Above 2438 m, the MAR SaO2 was higher (p < 0.001) than the LAR. Only one MAR subject, but nine LAR subjects reported AMS symptoms. CONCLUSIONS: Ventilatory acclimatization developed during moderate altitude residence substantially enhances arterial oxygenation during rapid ascents to higher altitudes. Compared with prior studies, the level of ventilatory acclimatization achieved at moderate altitude is similar to residing at 4056 m for approximately 5-9 d.

Adaptation, Physiological↗