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At least 739 records · Page 41Linked to original sources
PubMed1998

Sleep and stress in man: an approach through exercise and exposure to extreme environments.

In this paper, the effects of exercise on human sleep (in temperate, cold, and hot climates) are compared with those of exposure to extreme environments (tropical, polar climates). Exercise has two effect: (i) when the exercise load is too heavy or if the subject is not trained to the exercise conditions, the hypothalamo-pituitary-adrenocortical axis (HPA) is strongly activated (somatic stress reaction), and a diachronic (delayed) decrease in total sleep time and slow-wave sleep (SWS) occurs with a synchronic (concomitant) sleep disruption (such as a decrease in REM sleep); (ii) a diachronic enhancement of SWS and (or) REM sleep occurs during moderate training and in athletes, with a moderate HPA activation (neurogenic stress reaction). Heat acclimatization (neurogenic stress response) results in a diachronic increase in SWS, contrary to acute heat exposure (somatic stress) which leads to a diachronic decrease in SWS. Nocturnal cold exposure (somatic and (or) neurogenic stress) provokes a synchronic decrease in REM sleep with an activation of stress hormones, which are reduced by previous acclimation (neurogenic pathway); SWS remains undisturbed in the cold, as it occurs at the beginning of the night before body cooling. In conclusion, when the brain can deal with the stressor (neurogenic stress), diachronic increases in SWS and (or) REM sleep occur. When these "central" mechanisms are overloaded, the classical "somatic" stress reaction occurs with diachronic and synchronic disruptions of the sleep structure.

Acclimatization↗
PubMed2004

Influence of climate on radial growth of Pinus cembra within the alpine timberline ecotone.

Radial growth variability and response to interannual climate variation of Cembran pine (Pinus cembra L.) were studied in the timberline ecotone on Mt. Patscherkofel (2246 m a.s.l.). The study area, which is in the inner alpine dry region of the Central Austrian Alps, is characterized by a continental climate with minimum precipitation in winter (about 150 mm during December-February) and frequent occurrence of warm dry winds (Föhn) in early spring. The hypothesis that spatial and temporal variability of radial growth is caused by site-related differences in sensitivity to winter stress (i.e., desiccation) was examined by applying dendroclimatological techniques. Ordination methods applied to tree ring time series revealed that spatial variability in radial growth is influenced by the local site factors elevation and slope aspect. Growth-climate relationships were explored using Pearson product-moment correlation coefficients and multiple regression analysis. Radial growth at the timberline was positively correlated with temperature in July and was also strongly correlated with mild temperatures in the previous autumn and high precipitation in winter (January-March). At the tree line, temperatures in the previous autumn and precipitation in late winter (March) also controlled radial growth, whereas July temperature was not significantly correlated with ring width. Because previous autumn temperature and winter precipitation were the main growth-determining factors at the timberline and the tree line, and both of these climate variables are known to influence susceptibility of trees to winter stress, the results support the working hypothesis. Analysis of climatic conditions in extreme growth years confirmed the high sensitivity of tree ring growth to precipitation in late winter (March) at the tree line plots. Furthermore, extent of growth reduction and release varied spatially and temporarily, with south- and west-facing stands showing a higher sensitivity to climate variation in the most recent decade (1990s) than the north-facing stand. This aspect-related change in sensitivity to climate may be associated with effects of climate warming on cambial activity.

Austria↗
PubMed1995

Effects of temperature and host cell growth phase on replication of F-specific RNA coliphage Q beta.

Human enteric viruses have been found in groundwater in the absence of fecal coliforms. Because detection of human enteric viruses is costly, time-consuming, and lacking in sensitivity, F-specific RNA (FRNA) coliphages, which infect Escherichia coli by attachment to F pili, are being examined for suitability as indicators of human enteric viruses in groundwater. Temperatures and host cell growth conditions that constrain F-pilus expression will limit FRNA coliphage replication in groundwater and wastewater, as is desirable in an indicator. Below 25 degrees C F-pilus synthesis ceases; FRNA coliphage Qbeta did not replicate below this temperature in batch cultures. One-step replication studies indicated that the replicative cycle is prolonged and that fewer progeny are released as the temperature decreases. The decreases in phage replication observed in the one-step replication studies were a consequence of fewer cells infected as the temperature was lowered or as host cells entered stationary phase. The numbers of phage particles released from infected cells did not change. The minimum temperature for replication of Qbeta, 25 degrees C, is not maintained in wastewater and does not occur in Wisconsin groundwater. On the basis of temperature and host cell growth phase, we have concluded that extensive replication of FRNA coliphages does not occur in wastewater and groundwater in Wisconsin and areas with similar cool climates.

Anaerobiosis↗
PubMedDate not supplied

[The role of antarctica in formation of the cenozoic climate and contemporary open sea abyssal fauna].

The key role of the Antarctic continent in the formation of the contemporary (Cenozoic) zonal-contrast climate and related geologically "young" (Postmesozoic) contemporary abyssal fauna of the World Ocean is discussed on the basis of the current concepts of pleitectonics, history of planetary climates, paleobiooceanology, and bioevolution. It has been shown that the flows of cold aerated near-Antarctic waters that started to descend in the open sea abyssal in the middle of Cenozoic were capable of substituting for previously (in Mesozoic) heated (up to 15-20 degrees C) abyssal waters within only 1500-2000 years. Following the descending near-Antarctic waters, the shallow and cold water oxyphilic fauna assimilated the abyssal zone that had been warm water and weakly populated.

Animals↗
PubMed1993

Sensitization to domestic mites in a cold temperate region.

Factors favoring sensitization to house dust mites (HDM) were studied in a cold, temperate climate in northern Sweden. Sixty-five children previously found to react positively to a skin prick test (SPT) to HDM were included. The SPT to HDM was repeated, and serum IgE antibodies to D. pteronyssinus and D. farinae were determined. HDM, Euroglyphus maynei, Tarsonemus, or storage mites occurred in mattress dust samples from 23 of the 65 homes, and in 10 homes more than 100 HDM/g of mattress dust were found. Mites were more prevalent in mattress dust from the basement and ground levels than from the upper floors. Sensitization to HDM was strongly with the presence of domestic mites in mattress and floor dust. Previous longer stays in southern Sweden or Europe were also associated with present sensitization to HDM, and this was independent of occurrence of mites in the residence. The results indicate that HDM growth and potential for sensitization in cold, temperate regions is highly dependent on the microhabitat, and that sensitization to HDM should be possible to prevent in such climatic regions.

Adolescent↗