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At least 343 records · Page 19Linked to original sources
PubMed1986

Temperature regulation in the mouse and hamster exposed to microwaves in hot environments.

Colonic temperature was measured in naive BALB/c mice and golden hamsters immediately following 90-min exposures to 2450-MHz radiofrequency (RF) radiation at an ambient temperature (Ta) of 32.2 or 35 degrees C (dry air). Exposures were performed in a temperature-controlled waveguide which permitted continuous monitoring of the specific absorption rate (SAR) of RF energy. At a Ta of 32.2 degrees C the threshold SAR for elevating colonic temperature and the SAR resulting in a 0.5 degree C elevation in colonic temperature were, respectively, 4.3 and 6.5 W/kg for the mouse and 0.68 and 1.1 W/kg for the hamster. At a Ta of 35 degrees C these values were 0.12 and 0.63 W/kg for the mouse and 0.46 and 0.8 W/kg for the hamster. The SARs required to elevate body temperature in the mouse and hamster at these relatively warm Ta's are considerably lower than those required at cooler Ta's of 20 to 30 degrees C. Overall, the hamster became hyperthermic at lower SARs than the mouse. Ta's of 35 degrees C and greater are frequently encountered during heat waves in the summer months. Under such stressful environmental conditions where heat loss is impaired, absorption of RF radiation at relatively low SARs may lead to significant hyperthermia which would otherwise be readily dissipated at lower Ta's.

Animals↗
PubMed1984

[Hourly variations in rectal temperature and prolactinemia in the creole goat kept outside in a tropical environment].

Rectal temperature and plasma prolactin level were measured hourly in "creole goats" during 27 consecutive hours in March, July and November. Simultaneously, air, "black-globe" temperature and relative humidity were measured at the height of the animals. Rectal temperature and plasma prolactin level varied according to hour and season and were always higher during the day than during the night. Plasma prolactin level increased dramatically for 3 h after dusk only in March. Rectal temperature showed a significantly higher correlation with air temperature than with "black-globe" temperature. On the contrary, plasma prolactin level was more significantly correlated with "black-globe" temperature than with air temperature. When all seasons and hours were pooled, "black-globe" temperature showed a threshold (32-34 degrees C), beyond which prolactin reached values higher than 100 ng/ml. Rectal temperature was always significantly correlated with plasma prolactin level. Plasma prolactin level as an index of thermal stress and the role of prolactin in thermoregulation have been discussed.

Animals↗
PubMed1984

Respiratory activity and oxidative phosphorylation in mitochondria of the rat brain and liver under conditions of elevated temperature of the environment.

The rate of oxygen consumption by mitochondrial fractions of the brain and liver of rats under elevated ambient temperature was investigated. The animals were placed in a thermostatized chamber for 6 hours at 21 degrees, 28 degrees or 37 degrees C. During the experiment, relative humidity in the chamber was controlled. After exposure, the animals were decapitated, mitochondrial fractions isolated and oxygen consumption measured with the Clark electrode. Respiratory substrates of succinate and glutaminate with malate were used. The analysis of the obtained results was based on the t-Student test, assuming the values obtained for the animals staying at 21 degrees as the control values. It was found that the 6 hrs stay under the ambient hyperthermy conditions did not induce any disturbances in the respiratory processes and oxidative phosphorylation in rat's brain and liver mitochondria.

Animals↗
PubMed1994

Estimates of components of variance of the rectal temperature in clinically healthy dogs in a hospital environment.

The rectal temperature is frequently measured in the morning on a daily basis in hospitalized dogs. Besides comparing the measured temperature to a population-based reference interval, it may also be of interest to evaluate the differences between consecutive measurements in order to follow the health status of a particular dog. In veterinary clinical chemistry, a parameter referred to as the critical difference, which can be used to judge if the difference between two consecutive measurements may be safely ascribed to random variation or not, has recently been introduced. The purpose of the present study was to obtain an estimate of the critical difference of the rectal temperature based on measurements of the rectal temperature in clinically healthy dogs in a hospital environment. The rectal temperature was measured in a standardized manner on 6 different days in 7 dogs. The total variance was estimated as 0.1015. The inter-individual variance was 0.0428, and the intra-analytical variance including the analytical variance was 0.0587. From these components of variance, the critical difference was calculated as 0.69 degrees C. Thus, the rectal temperature measured in the morning in hospitalized dogs can be expected to fluctuate about 0.7 degrees C from day to day due to random variation alone.

Analysis of Variance↗
PubMed1980

Temperature dependence of blood viscosity in frogs and turtles: effect on heat exchange with environment.

The temperature dependence of the viscosity of blood from frogs and turtles has been assessed for temperatures between 5 and 40 degrees C. Viscosity of turtles' blood was, on average, reduced from 3.50 +/- 0.16 to 2.13 +/- 0.10 cP between 10 and 30 degrees C, a decline of 39%. Even larger changes in viscosity were observed for frogs' blood with viscosity falling from 4.55 +/- 0.32 to 2.55 +/- 0.25 cP over the same temperature range, a change of 44%. Blood viscosity was highly correlated with hematocrit in both species at all temperatures. Viscosity of blood from both frogs and turtles showed a large standard deviation at all temperatures and this was attributed to large individual-to-individual variations in hematocrit. Turtles heat faster than they cool, regardless of whether tests are performed at temperatures above or below the range of thermal preference. The effect of temperature dependence of blood viscosity on heating and cooling rates is demonstrated.

Animals↗
PubMed2004

Stable carbon isotopic composition of tree rings from a pine tree from Augustów Wilderness, Poland, as a temperature and local environment conditions indicator.

Tree rings can be used as archives of climatic and environmental data with annual resolution. Tree rings widths, maximum late wood density and other parameters as stable composition in tree rings can be used for the reconstruction of past climatic and environmental changes. Stable carbon isotope ratios in tree rings may provide valuable information on past climatic conditions. 13C/12C ratios of plant organic matter can reflect corresponding 13C/12C ratio of atmospheric CO2 during formation of the rings. Investigations of isotopic carbon composition in tree rings from in the ecologically clean the Augustów Wilderness region in the north-eastern part of Poland (22 degrees 58'E, 53 degrees 51'N) (nowadays a sanctuary) were undertaken. Series of delta13C in alpha-cellulose and in wholewood were acquired. Those measurements constituted a part of more complex investigations of carbon isotope composition in tree rings including the measurements of radiocarbon concentration and tree ring widths. This article presents preliminary results. It is argued that contrary to the tree ring widths and delta13C in wholewood that do not reveal significant correlation with temperature, the variation of delta13C in the latewood alpha-cellulose is correlated with combined July and August temperatures.

Carbon Isotopes↗
PubMed1984

Changes in site specificity of single-strand-specific endonucleases on supercoiled PM2 DNA with temperature and ionic environment.

Mung bean nuclease sites in supercoiled PM2 DNA at neutral pH were located by linearizing the singly-nicked circular DNA product with venom phosphodiesterase followed by restriction endonuclease mapping. The locations of the sites varied with small changes in temperature and in concentration of NaC1 or magnesium ion. Different environmental changes which affect duplex stability in the same direction showed similar effects on the number of sites and in some cases resulted in identical cleavage patterns. Venom phosphodiesterase and P1 nuclease showed cleavage patterns similar to mung bean nuclease under the same environmental conditions and showed similar variations in cleavage patterns when environmental conditions were changed. Relaxed, closed-circular DNA was slowly cleaved at numerous sites whose locations did not vary with environment. Changes in site specificity are likely the result of environmental effects on the conformation of supercoiled DNA as opposed to effects on the single-strand-specific endonucleases themselves.

Bacteriophages↗