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Results for “Temperature environment”

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PubMed2000

[Male infertility. Current life style could be responsible for infertility].

Optimal spermatogenesis requires the testicles to be at a lower temperature than the body core. This is achieved by the following factors:--Blood in the testicular artery is precooled by the surrounding veins of the plexus pampiniformis; nevertheless, high fever results in substantial warming of the testicles;--Heat loss via the scrotal skin, with tight-fitting, thermally insulating clothing or obesity having an unfavorable effect;--increased circulation of air around the genitals on physical activity;--High temperature gradient to the environment when ambient temperatures are low. If the combination of these factors is unfavorable, disturbed spermatogenesis and fertility may result, which, however, is usually reversible. Likewise, electromagnetic waves may impair spermatogenesis by heat induction in the testicles, but only when exposure is excessive.

Body Temperature↗
PubMed1982

Head-temperature effects on physiology, comfort, and performance during hyperthermia.

This study assessed the effects of head temperature on subjects under hyperthermic conditions. Six volunteers were trained to plateau on a manikin task that tested cognitive performance and reaction time. A subject's core temperature was driven with a full-length, liquid-conditioned garment perfused with water at 30 degrees or 43 degrees C, and head temperature was controlled by a cap with an inlet temperature of 8 degrees or 43 degrees C. Heavy insulation was worn overall; ambient temperature was 30 degrees C. Subjects were heated and cooled twice during each experiment to include all possible cap/suit temperature combinations. Each subject did one control and four stress experiments. Comfort and performance were measured as the subject's esophageal temperature (Tes) rose and fell through the range 37.5-39.0 degrees C. Cap temperature did not affect rectal temperature (Tre) but significantly altered the Tes rate of change; a cool head sometimes truncated the peak Tes value. Although the cap covered only 3-4% of the body surface, the head was a major determinant of subjective comfort. Body heating tended to shorten reaction time and diminish performance accuracy, while head cooling largely reversed these trends. Possible mechanisms include 1) change in overall heat balance; 2) countercurrent exchanges in the neck, and 3) change in sensory output. Head cooling deserves serious consideration for machinery operators where whole-body thermoneutrality is impractical.

Adult↗
PubMed1966

Observations on temperature distribution in the cardiovascular system, thorax and abdomen of monkeys in relation to environment.

1. Thermo-electric observations of temperature distribution in the ;core' area of monkeys and baboons are reported.2. Temperature gradients were shown to exist in the inferior vena cava, temperatures rising by a mean value of 0.2 degrees C at the entry of the renal veins and again by a further 0.2 degrees C at the level of the hepatic veins.3. Temperatures in the right atrium were on average 0.1 degrees C lower than in the inferior vena cava due to the return of relatively cooler blood from the superior vena cava.4. Net heat exchanges in the thorax were small. Right atrial and aortic blood temperatures were not significantly different and it was concluded that heat losses in the thorax were balanced by heat production in lungs and heart.5. The mean liver temperature was 0.1 degrees C higher than that of the aortic blood irrespective of the environment.6. The mean temperature recorded from the lumen of the jejunum was 0.2 degrees C warmer than the aorta in the ;warm' environment and 0.4 degrees C hotter than the aorta in the ;cool' environment. In both environments intrajejunal temperature was higher than the liver but the differential was increased by exposure to a ;cool' environment.7. Evidence is adduced to suggest that the gastro-intestinal tract in the body at rest is a major heat producer contributing about double the amount of heat generated by the liver.8. It is suggested that blood flow redistribution in the splanchnic area on exposure of the body to cold is the main cause of the change in aortic-jejunal and jejunal-liver differentials. Metabolic factors have, however, not been excluded.

Animals↗
PubMed2005

Influence of in-tunnel environment to in-bus air quality and thermal condition in Hong Kong.

In this study, the potential exposure of bus commuters to significant air parameters (CO(2), CO and RSP) and thermal environment (air temperature and relative humidity) when buses traveled through tunnels in Hong Kong was investigated. It was found that air-conditioned buses provided a better commuting environment than non-air-conditioned buses. The blate increasing trend was found on air-conditioned buses as the in-bus air parameters concentration levels rose slowly throughout the traveling process. In contrast, the in-bus environment varied rapidly on non-air-conditioned buses as it depended on the out-bus environment. The measured in-bus CO concentration was 2.9 ppm on air-conditioned buses, while it was 4.6 ppm (even reaching the highest level at 12.0 ppm) on non-air-conditioned buses. Considering the in-bus thermal environment, air-conditioned buses provided thermally comfortable cabins (about 24 degrees C and 59% of relative humidity). However, on non-air-conditioned buses, the thermal environment varied with the out-bus environment. The mean in-bus air temperature was about 34 degrees C and 66% of relative humidity, and the in-bus air temperature varied between 29 and 38 degrees C. Also, the lower-deck to upper-deck air parameters concentration ratios indicated that the vertical dispersion of air pollutants in tunnels influenced non-air-conditioned buses as higher air parameters concentration levels were obtained on the lower-deck cabins.

Air Conditioning↗
PubMed2005

Factors affecting elimination of polycyclic aromatic hydrocarbons from smoked meat foods and liquid smoke flavorings.

This review deals with effects of environmental and physicochemical factors affecting polyaromatic hydrocarbon (PAH) elimination from smoked meat products and liquid smoke flavoring (LSF). In the introductory part, some essential information are aimed at principles of food smoking and PAH formation during smoke generation as a result of incomplete wood combustion. Also, an application of alternative technology for food aromatization using LSF is briefly mentioned. Similarly, latest European legislation, biological effects, and analytical aspects of PAHs are mentioned concisely. The main part is devoted to physicochemical factors affecting the PAH content in smoked meat products, such as light, additional cooking, and packaging, which are able to decrease considerably PAH content in some meat products. The most important effect on PAH concentration decrease in LSF has low-density polyethylene (LDPE) package due to sorption processes on a surface of the plastic with subsequent diffusion into the plastic bulk. A less effective material is polyethylene terephthalate (PET), when only a surface adsorption process comes into account. Moreover, this process is affected also by other compounds presented in liquid media able to compete for the adsorption center on the PET surface.

Animals↗
PubMed2006

Temperature acclimation alters cardiac performance in the lobster Homarus americanus.

The American lobster is a poikilotherm that inhabits a marine environment where temperature varies over a 25 degrees C range and depends on the winds, the tides and the seasons. To determine how cardiac performance depends on the water temperature to which the lobsters are acclimated we measured lobster heart rates in vivo. The upper limit for cardiac function in lobsters acclimated to 20 degrees C is approximately 29 degrees C, 5 degrees C warmer than that measured in lobsters acclimated to 4 degrees C. Warm acclimation also slows the lobster heart rate within the temperature range from 4 to 12 degrees C. Both effects are apparent after relatively short periods of warm acclimation (3-14 days). However, warm acclimation impairs cardiac function at cold temperatures: following several hours exposure to frigid (<5 degrees C) temperatures heart rates become slow and arrhythmic in warm acclimated, but not cold acclimated, lobsters. Thus, acclimation temperature determines the thermal limits for cardiac function at both extremes of the 25 degrees C temperature range lobsters inhabit in the wild. These observations suggest that regulation of cardiac thermal tolerance by the prevailing environmental temperature protects against the possibility of cardiac failure due to thermal stress.

Acclimatization↗
PubMed2005

Moderate hypoxia does not affect the zone of thermal comfort in humans.

The zone of thermal comfort was determined during normoxia and hypoxia in 15 healthy normothermic young subjects. Subjects dressed only in shorts/shorts and bikini top donned a water-perfused suit and assumed a supine position on a bench. The ambient temperature was maintained at a mean (SD) of 25.7 (0.3) degrees C. The thermal comfort zone was determined by increasing the temperature of the water perfusing the suit from cool to warm. During the heating process, subjects were instructed to report when their perception of the thermal stimulus provided by the suit changed from unpleasant to pleasant, and again from pleasant to unpleasant. The boundaries of the thermal comfort zone were assumed to be the temperatures of the water perfusing the suit at the time the subjects reported a change in the affective component of their thermal perception. In normoxia, subjects inspired room air and in hypoxia a gas mixture containing 10% O(2) in N(2). Tympanic temperature was similar in the normoxia and hypoxia conditions (P>0.05). The average (SD) lower and upper limits of the thermal comfort zone were 30.5 (1.5) and 34.7 (3.3) degrees C, respectively, during normoxia, and 30.5 (1.7) and 35.1 (3.4) degrees C, respectively, during hypoxia. No significant differences were observed between the normoxia and hypoxia conditions (P>0.05). Also, no gender-related differences were observed in the characteristics of the thermal comfort zone. The results of the present study indicate that acute hypoxic exposure simulated in the present study does not affect the zone of thermal comfort in humans.

Adult↗
PubMed1995

Expression of stress proteins in cultured HT29 human cell-line; a model for studying environmental aggression.

The current study was undertaken to investigate the expression of stress proteins (HSP) in cultured human HT29 cells submitted to stressing events under in vitro conditions. Heat shocks (45 degrees C, for 15-60 min) or cold shocks (+ 1 degree C for 4 hr) were found to modify cell growth (growth curves) and to enhance HSP expression. In most cases, changes in HSP expression are much more pronounced than changes in cell growth. Exposure to 8% ethanol for 15 min resulted in both growth inhibition and HSP overexpression. Propanol-1 was found to be more toxic since 5% concentration given for 15 min stops cell growth. 2.5% propanol-1 for 15 min induces a slight reduction of cell growth but a clear-cut overexpression of stress proteins. We conclude that expression of stress proteins, especially those of the HSP68/70 family, constitutes a more sensitive response than changes in growth rate in case of external aggression. This could make our model an interesting biological sensor to environmental physical or chemical pollutants.

1-Propanol↗
PubMed2000

Measurement of porcine heart temperatures.

During cardiac surgery local hypothermia of the heart is used to slow down cellular metabolism. It has been shown by computer simulation that heart muscle is not uniformly cooled to the desired temperatures. The aim of our work was to find out a way for measuring the temperatures of the ventricular wall and the septum with +/-0.1 degrees C accuracy. The measurement protocol should be applicable during operations on the human heart, during which disturbing factors should be minimized. We have tested the protocol and the equipment on porcine hearts. Two types of probes were tested, the contact-probe, which can be attached to the heart-wall surface, and the needle-probe, which can be inserted into the heart tissue. Before experiments the probes were calibrated and their heat transfer characteristics determined. We conclude that the probes and the protocol are suitable for studying the effects of cardioplegia, and for checking the results previously obtained by computer simulation.

Animals↗
PubMed1997

[Physiological effects of cabin temperature decrease on human].

To study effects of cabin temperature on human body, changes in rectal temperature, local skin temperature, local skin heat fluxes and skin infrared thermogram were observed in 5 male subjects dressed in different thermal insulation clothings under 20 degrees C, 15 degrees C and 10 degrees C cabin temperatures. The results showed that, average skin temperature and tip temperature obviously dropped, and skin heat fluxes increased with falling of cabin temperature, and changes of local skin infrared thermogram were significant. Subjective feeling were comfortable and cool at cabin temperature of 20 degrees C and 15 degrees C respectively. While subjective feeling was cold and there was a thermal debt of body 144 kJ/m2 at 10 degrees C which indicated that it was slightly cold but tolerable. The results may be valuable in determining the lowest tolerable limit of cabin temperature.

Acclimatization↗