Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Temperature environment”

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 829 records · Page 46Linked to original sources
PubMed1984

Heat exchange following atropine injection before and after heat acclimation.

The effect of saline and atropine injection (2 mg, im) on eight healthy male subjects before and after heat acclimation was studied while each subject walked on a treadmill (1.34 m X s-1) in a hot-dry environment (ambient temperature = 48.4 degrees C, dew-point temperature = 20.5 degrees C). Partitional calorimetric analysis was done for the periods in which maximum sweat inhibition occurred (30 min). Mean skin temperature, rectal temperature, and heart rate were continuously observed. Evaporative loss from the skin was calculated by changes in body weight (Sauter balance); heat transfer coefficients were defined by Nishi equations. A prediction of sweat inhibition based on an analysis of heat storage and its effect on a theoretical temperature, which can be graphed on a psychrometric chart, was developed. A rational effective temperature (ET) defined as the operative temperature at the intersection of the 50% rh, which encompasses total heat exchange, was used to compare the effects of atropine before and after heat acclimation. The results show that heat acclimation reduced ET by approximately 2.5 degrees C when compared with the unacclimated state after atropine injection. Thus heat acclimation reduces the hazards of heatstroke caused by exercise in the heat with atropine injection.

Acclimatization↗
PubMed1987

Cooling different body surfaces during upper and lower body exercise.

The effect of varying the body surface area being cooled by a liquid microclimate system was evaluated during exercise heat-stress conditions. Six male subjects performed a total of six exercise (O2 uptake = 1.2 l/min) tests in a hot environment (ambient temperature = 38 degrees C, relative humidity = 30%) while dressed in clothing having low moisture permeability and high insulation. Each subject completed two upper body exercise (U; arm crank) tests: 1) with only the torso surface (T) cooled; and 2) with the surfaces of both the torso and upper arms (TA) cooled [coolant temperature at the inlet (Ti) was 20 degrees C for all upper body tests]. Each subject also completed four lower body exercise (L; walking) tests: 1) with only the T cooled (Ti = 20 degrees C); 2) with only the T cooled (Ti = 26 degrees C); 3) with torso, upper arm, and thigh surface (TAT) cooled (Ti = 20 degrees C); and 4) with TAT cooled (Ti = 26 degrees C). During U exercise, TA cooling had no effects compared with cooling only T. During L exercise, sweat rates, heart rates, and rectal temperature (Tre) changes were less with TAT cooling compared with cooling only the T. Altering Ti had no effect on Tre changes, but higher heart rates were observed with 26 than with 20 degrees C. These data indicate that cooling arms during upper body exercise provides no thermoregulatory advantage, although cooling the thigh surfaces during lower body exercise does provide an advantage.

Adult↗
PubMed1998

Effect of continuous negative-pressure breathing on skin blood flow during exercise in a hot environment.

To assess the impact of continuous negative-pressure breathing (CNPB) on the regulation of skin blood flow, we measured forearm blood flow (FBF) by venous-occlusion plethysmography and laser-Doppler flow (LDF) at the anterior chest during exercise in a hot environment (ambient temperature = 30 degreesC, relative humidity = approximately 30%). Seven male subjects exercised in the upright position at an intensity of 60% peak oxygen consumption rate for 40 min with and without CNPB after 20 min of exercise. The esophageal temperature (Tes) in both conditions increased to 38.1 degreesC by the end of exercise, without any significant differences between the two trials. Mean arterial pressure (MAP) increased by approximately 15 mmHg by 8 min of exercise, without any significant difference between the two trials before CNPB. However, CNPB reduced MAP by approximately 10 mmHg after 24 min of exercise (P < 0.05). The increase in FBF and LDF in the control condition leveled off after 18 min of exercise above a Tes of 37.7 degreesC, whereas in the CNPB trial the increase continued, with a rise in Tes despite the decrease in MAP. These results suggest that CNPB enhances vasodilation of skin above a Tes of approximately 38 degrees C by stretching intrathoracic baroreceptors such as cardiopulmonary baroreceptors.

Adult↗
PubMed2000

Antibiotic susceptibility and resistance testing: an overview.

The results of in vitro antibiotic susceptibility testing can predict the clinical response to treatment and guide the selection of antibiotics. The minimum inhibitory concentration (MIC) of an organism is the lowest concentration of an antibiotic that will inhibit its growth. Bacteria are classified as sensitive, intermediate or resistant based on breakpoint MIC values that are arbitrarily defined and reflect the achievable levels of the antibiotic, the distribution of MICs for the organism and their correlation with clinical outcome. Broth dilution, agar dilution and gradient diffusion (the 'E test'), where twofold serial dilutions of antibiotic are incorporated into tubes of broth, agar plates or on a paper strip, respectively, are different methods to measure the MIC of an organism. The disk diffusion method defines an organism as sensitive or resistant based on the extent of its growth around an antibiotic-containing disk. MIC values are influenced by several laboratory factors. To ensure reproducible results, the laboratory must closely follow methods developed by the National Committee for Clinical Laboratory Standards, which defines standard growth media, incubation temperature and environment, the inoculum and quality control parameters.

Anti-Bacterial Agents↗
PubMed2004

Context-dependent deactivation of the amygdala during pain.

The amygdala has been implicated in fundamental functions for the survival of the organism, such as fear and pain. In accord with this, several studies have shown increased amygdala activity during fear conditioning and the processing of fear-relevant material in human subjects. In contrast, functional neuroimaging studies of pain have shown a decreased amygdala activity. It has previously been proposed that the observed deactivations of the amygdala in these studies indicate a cognitive strategy to adapt to a distressful but in the experimental setting unavoidable painful event. In this positron emission tomography study, we show that a simple contextual manipulation, immediately preceding a painful stimulation, that increases the anticipated duration of the painful event leads to a decrease in amygdala activity and modulates the autonomic response during the noxious stimulation. On a behavioral level, 7 of the 10 subjects reported that they used coping strategies more intensely in this context. We suggest that the altered activity in the amygdala may be part of a mechanism to attenuate pain-related stress responses in a context that is perceived as being more aversive. The study also showed an increased activity in the rostral part of anterior cingulate cortex in the same context in which the amygdala activity decreased, further supporting the idea that this part of the cingulate cortex is involved in the modulation of emotional and pain networks.

Adaptation, Psychological↗
PubMed2005

Metabolic responses to cold in subterranean crustaceans.

Changes in polyol, sugar and free amino acid (FAA) body contents were investigated in the aquatic, subterranean (i.e. hypogean) crustaceans Niphargus rhenorhodanensis and Niphargus virei and in a morphologically close aquatic, surface-dwelling (i.e. epigean) crustacean Gammarus fossarum acclimated to 12 degrees C, 3 degrees C and -2 degrees C. With decreasing temperature, G. fossarum significantly increased its alanine and glutamine levels, while trehalose body content was found to increase above control levels only at -2 degrees C. N. virei showed moderate increases of alanine and glycine, and no change in trehalose level was observed in this species. By contrast, N. rhenorhodanensis was the only species showing a significant rise in its total FAA pool, mainly explained by alanine, glycine, arginine and glutamine accumulations. This species also gradually increased its trehalose body content with decreasing temperature. Several cold-hardy ectotherms show metabolic responses to cold that are identical to those observed in N. rhenorhodanensis. A previous comparative study showed that the hypogean N. rhenorhodanensis exhibited a survival time (Lt50) at -2 degrees C that was 26.3 times and 2.6 times higher than the hypogean N. virei and the epigean G. fossarum, respectively. Thus, crustacean levels of FAA and trehalose were correlated with their respective cold tolerances. Such differences in metabolic responses to cold in both hypogean organisms were unexpected since they both live in thermally buffered biotopes. Considering the current distribution areas of the two subterranean crustaceans studied, we assume that the cold hardiness found in the hypogean N. rhenorhodanensis could be correlated with its biogeography history during the quaternary glaciations.

Acclimatization↗
PubMed1990

[A study on the effect of water intake of umpires during a baseball game in a summer-heat environment].

The purpose of this study was to examine the effect of umpires' intake of water during a summertime baseball game, on serum and urinary biochemical elements, body weight and physiological factors. Twenty-eight umpires were classified into two groups. Group W was composed of 14 umpires who had water while those who did not were group C. Group W had 250 ml of water that was cooled to about 5 degrees C after the 5th inning of the game. The game was played in the following environment: atmosphere temperature was 31 degrees C; wet-bulb temperature was 26 degrees C; blackglove temperature was 40 degrees C; the velocity of the wind was 1.18 m/sec in bright sunshine on a hot and moist day. The results obtained were as follows. In group W, more body weight was lost than in group C, but statistically there was no significant difference. Urinary volume in group W became smaller than in group C, but statistically there was no significant difference. Water in blood increased in group W and decreased in group C but statistically there was significant difference. In both groups, oral temperature decreased, but only in group C was there a statistically significant difference. Although the intake of water increased the volume of perspiration, it did not dilute the concentrated blood, suppress the rise of body temperature, or result in a rise of low blood pressure.

Adult↗
PubMed1986

Some aspects of the problem of individual predisposition to silicosis.

Based on experimental and epidemiological data findings presented here, as well as on data of other investigators, the authors conclude that a wide interindividual variability of susceptibility to silicosis is a real phenomenon. This susceptibility depends on both intrinsic features of the host and the influence of many environmental factors. The effect of any such factor is realized at different stages of silicosis pathogenesis and in close interrelation with the influence of other factors. The necessity of multifactorial analysis is stressed, and an example of such analysis is presented.

Acclimatization↗
PubMed2004

Assisted reproductive research: laser assisted hatching and spindle detection (spindle view technique).

Animal experiments are very important for the development of new assisted reproductive techniques (ART) for use in human and animal reproductive medicine. Most technical aspects of reproductive manipulation of humans and animals are very similar, and many components of successful human ART used nowadays have been derived from animal studies. In this study we examined (1) the use of 'non-contact' laser for assisted hatching, (2) whether spindles in living mouse oocytes could safely be imaged/examined by polarisation microscope (polscope) and (3) the influence of environment (e.g. temperature, in vitro culture, etc.) on spindle detection/visualisation. The data of the study presented here show that (1) laser assisted hatching (AH) is a fast, very accurate and safe procedure without any harmful effect on embryo development and it can support very effectively the implantation of embryos, (2) the use of polscope facilitates the evaluation of oocyte quality and the selection of oocytes with spindle, (3) by monitoring the spindle position during intracytoplasmic sperm injection (ICSI), we can reduce spindle damage and increase the chance of fertilisation. Further studies are underway to test the hypothesised connection between spindle birefringence and developmental capacity of oocytes/embryos.

Animals↗
PubMed2004

Elevated ultraviolet-B radiation induces cross-protection to cold in leaves of Rhododendron under field conditions.

Previously, we have shown a cold-hardening response in Rhododendron 'English Roseum' exposed to elevated ultraviolet-B radiation (UV-B, 280-320 nm) under growth chamber conditions. We have conducted the present study under field conditions to provide for a higher ratio of photosynthetically active radiation to UV-B (PAR:UV-B) than is possible in the laboratory and to more accurately reflect natural conditions of solar irradiance. Leaf disks taken after 3 months from UV-B-exposed plants exhibited a greater tolerance to freezing temperatures than those from control plants that received no supplemental UV-B exposure during this time. Leaf disks taken from UV-B-irradiated plants survived temperatures below -8 degrees C, whereas control disks were killed at -6 degrees C. Cold hardiness did not significantly increase until September, when environmental cues such as decreasing day length and night temperatures also may have enhanced hardening. Our field findings confirm our previous laboratory study, demonstrating that elevated UV-B induces cross-protection to cold in Rhododendron leaf tissues.

Acclimatization↗
PubMed1996

Control of liquid cooling garments: technical control of body heat storage.

This paper describes a concept of how liquid cooling garments (LCG) can be automatically controlled by the objective physiological state. The technically controlled parameter was mean body temperature which was calculated from the measured rectal and mean skin temperature. This was motivated by the fact that mean body temperature is the basis for estimating body heat storage, a commonly used measure of thermal strain. Here the setpoint of mean body temperature was the individual value taken in a preceeding resting period and it was the task of the technical controller to keep the actual value of mean body temperature as close as possible to the setpoint. The most important tuning parameters of the controller were the weighting coefficients for rectal and mean skin temperature in the calculation for mean body temperature. The ratio of these two coefficients determined the degree of compensation for any rectal temperature shift by changing mean skin temperature. Test experiments were carried out (n = 5) in which the controller was able to clamp mean body temperature to the setpoint thereby preventing heat storage. Although exercise rate (75 W) was the same, sweating and warm discomfort occurred in some cases due to the individual rectal temperature rise. Another source of discomfort were delays or paradoxical time courses of rectal temperature at the start or end of exercise which were responsible for a delayed onset of cooling or heating. To avoid these effects, the oxygen consumption signal, which is very fast and directly correlated to the exercise rate, was added to the control loop. Each increase of this parameter above its resting level lowered suit temperature. As heat storage should not be completely rejected by this new signal pathway, the controller for mean body temperature still remained active. The repetition of the experiments showed that the load error in the control loop was smaller and the comfort level in transient phases higher. For a further improvement of this concept it is recommended that the weighting coefficients be tuned to the individual requirements.

Adult↗
PubMed2005

Thermal comfort: multisensory interactions?

Experimentally, the effects of environmental conditions upon human capabilities have been studied most often through the imposition of a single stressor in isolation. Although it seems to be a common belief that thermal comfort can be influenced by concomitant stimulation of non-tactile sensorial modalities, few studies have succeeded in delineating non-tactile stimulations, which interact with thermal sensation and thermal comfort. Here we briefly overview neurophysiological and behavioural findings in multisensory influences on thermal sensation and thermal comfort.

Body Temperature↗
PubMed2000

Drafts in cold environments--the significance of air temperature and direction.

This paper concerns the influence of air temperature and of the direction of drafts on subjective and physiological responses. In three experimental series 58 healthy persons (50 men, 8 women, 20-29 yrs) were exposed to drafts in overall 446 experimental sessions. Drafts were applied either horizontally or vertically with mean air velocities of 0.1 to 0.3 m/s and a turbulence intensity of 50%. Air temperature was varied between 11 and 23 degrees C and metabolic rates between < 70 and 156 W/m2. These parameters were kept constant during the single one-hour sessions. The subjects were dressed for thermal neutrality. Draft-induced annoyance was registered every 5 minutes using a list of prescribed body parts and skin temperature was measured at the forearm and at the neck. Subjective and physiological responses were systematically related to air temperature. Draft-induced general annoyance, draft-induced local annoyance (neck, forearm) and the drop of the corresponding skin temperature were inversely related to air temperature. Concerning the direction horizontal drafts seem to cause somewhat stronger reactions. The predictive model developed by Toftum underestimates the percentage of persons annoyed. A modified version increases the predictive power significantly.

Adult↗