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PubMed1980

Psychrophiles, psychrotrophs, and mesophiles in an environment which experiences seasonal temperature fluctuations.

The quantification of psychrophilic/psychrotrophic and mesophilic, heterotrophic bacteria from a lake which experiences seasonal temperature fluctuations showed that the psychrophilic/psychrotrophic population ranged in number from 1212 to 87000/mL, whereas the mesophilic population ranged from 67 to 3783/mL, for sediment-water interface samples over the yearly cycle. The relative abundance of psychrophiles/psychrotrophs and mesophiles varied with season, but psychrophilic/psychrotrophic bacteria were found to predominate on every sampling occasion. A considerable number of the 37 degree C isolates were found to be psychrotrophs having broad temperature ranges for growth. An especially notable result was the isolation os psychrophiles on every sampling occasion, and in such high numbers, from this "nonpermanently cold" environment. A total of 388 isolates were described according to Gram reaction, colony and cell morphology, biochemical activities, and thermal type, and on the basis of similarities they were grouped into 158 "working types" with their frequencies of occurrence, for all four samplings, did not reveal a direct relationship between numerical predominance and growth rate as determined by temperature.

Bacteria↗
PubMed1984

The dynamic properties of trigeminal thermoreceptors following heat-rearing in rats.

Dynamic properties of thermoresponsive units at the caudal trigeminal nucleus are not modified by heat-rearing. The modification of the thermoregulatory system by heat-rearing is unlikely to be a consequence of altered thermoreceptive function at this level. Rats were reared at ambient temperatures of 30 degrees C (heat-reared) and 20 degrees C (controls). Extracellular recordings of thermoresponsive units at the caudal trigeminal nucleus were made while the facial receptive fields of these thermoresponsive units were stimulated with 6 different rates of temperature change (+0.5, +0.1, +0.02, -0.02, -0.1 and -0.5 degrees C/sec). All thermoresponsive units encountered were cold-sensitive. The static maxima were clustered around 13.5 degrees C and did not differ between treatment groups. Dynamic maxima occurred at temperatures around 29-30 degrees C and were not different in thermoresponsive neurones from the two treatment groups. There was no difference between the two treatment groups in the dynamic activity of trigeminal cold-responsive neurones at any of the 42 combinations of temperature and rate of temperature change examined.

Animals↗
PubMed1995

Preferred room temperature of young vs aged males: the influence of thermal sensation, thermal comfort, and affect.

BACKGROUND: While research has demonstrated that aged persons may show impaired thermoregulatory control, we do not know whether dysthermia in the aged results from altered behavioral or autonomic responses. Consequently, we investigated age-related differences concerning the ability to regulate room temperature. METHODS: Two groups of matched healthy males (22.9 yr and 66.9 yr) were subjects of this study. After equilibration at 24 degrees C (rh 50%), chamber temperature controllers were set into cooling mode. Using a dual position switch, subjects adjusted this temperature when air temperature moved outside their preferred range. Switch operation resulted in maximal cooling or heating, without a steady state. Subjective ratings of thermal sensation, discomfort, and affect were provided at each activation. RESULTS: Both groups controlled temperature equivalently: 24.9 degrees C (+/- 1.3, young) and 24.5 degrees C (+/- 1.5, elderly; p > .05). At cold-induced change points, the skin temperatures of the calf, thigh, chest, and hand were significantly lower in the elderly subjects. During the heat-induced changes, chest, hand, upper arm, and mean skin temperatures were also lower (p < .05). At cold-induced change points, the elderly group felt colder (p < .05), were less uncomfortable (p < .05), and felt better than the young subjects (p < .05). During heat-induced changes, thermal sensation was equivalent, the elderly were more comfortable (p < .05), and felt better (p < .05). CONCLUSIONS: Assuming thermal discomforture drives behavior, it is possible that elderly people may require a more intense thermal stimulus to elicit the appropriate behavioral responses in the home. It is also possible that such stimuli will result in a greater heat flow, elevating the risk of dysthermia in the aged.

Adult↗
PubMed1996

Group selection for adaptation to multiple-hen cages: production traits during heat and cold exposures.

A selected line of White Leghorns that has shown improved survivability and productivity and reduced feather loss in multiple-hen cages was evaluated for production traits under both stressed and unstressed conditions. It was hypothesized that hens selected for adaptation to multiple-bird cages would react less intensely to stressors and therefore lay more eggs and have lower mortality under stressed conditions. Three lines of chickens (selected, control, and commercial) were housed in either single-hen (1 hen) or multiple-hen cages (12 hens, social competition) at 16.7 or 17.1 wk of age. They were subsequently subjected to cold exposure at 33 wk of age and heat exposure at 44 wk of age. The selected line of chickens in multiple-hen cages showed an increased resistance to heat exposure, as indicated by lower mortality, when compared to the control and commercial lines housed in multiple-hen cages. Egg production 8 d prior to, during, and 8 d following either cold or heat exposures indicated that the selected line of chickens withstood social, handling, and environmental stressors better than the control line and, in some cases, the commercial line of chickens. It was concluded that the selected line of Leghorns showed evidence of stress resistance through lowered mortality and improved production.

Adaptation, Physiological↗
PubMedDate not supplied

[Adaptive changes of chloroplast membrane lipid components under environmental factors].

Review deals with some modern views of the membrane chloroplast lipid composition role in low-, high temperature and water stress adaptive reactions. It is shown that the transformed changes in membrane lipid composition determined the biochemical adaptive process due homeostasis support and preservation of the lipid bilayer fluidity, being necessary for their normal functioning in the changed environmental conditions. The aspects of long-term and short-term adaptive reactions in protein/lipid membrane complexes is discussed. The lipid sensor functions at genetically regulation of adaptive mechanisms is considered.

Adaptation, Physiological↗