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PubMedDate not supplied

[Parameters adaptation in the populations models].

Ecology-evolutionary models of low dimensions were developed on the basis of competitive selection criteria. Dynamics of variables (number of individuals) and the search of evolutionary-stable values of parameters (biological characterictics of populations) were monitored in the suggested models. If the environmental temperature is changing periodically, the average (a) and width (d) of temperature tolerance range appears to be the important parameters. By model experiments it was established that stable values of temperature (a), favorable for development of highly specialized algae (d is low) were close to minimum and maximum of temperature curve. And for the low specialized algae (d is high) this values were close to the average temperature of environment. In a similar manner, a set of evolutionally stable parameters (a, d) was established for either of the two interacted populations (competitors and "predator-prey"). The hypotheses concerning it's geometric structure and the process of coevolution is formulated.

Adaptation, Physiological↗
PubMed1996

A psychrophilic crenarchaeon inhabits a marine sponge: Cenarchaeum symbiosum gen. nov., sp. nov.

Archaea, one of the three major domains of extant life, was thought to comprise predominantly microorganisms that inhabit extreme environments, inhospitable to most Eucarya and Bacteria. However, molecular phylogenetic surveys of native microbial assemblages are beginning to indicate that the evolutionary and physiological diversity of Archaea is far greater than previously supposed. We report here the discovery and preliminary characterization of a marine archaeon that inhabits the tissues of a temperate water sponge. The association was specific, with a single crenarchaeal phylotype inhabiting a single sponge host species. To our knowledge, this partnership represents the first described symbiosis involving Crenarchaeota. The symbiotic archaeon grows well at temperatures of 10 degrees C, over 60 degrees C below the growth temperature optimum of any cultivated species of Crenarchaeota. Archaea have been generally characterized as microorganisms that inhabit relatively circumscribed niches, largely high-temperature anaerobic environments. In contrast, data from molecular phylogenetic surveys, including this report, suggest that some crenarchaeotes have diversified considerably and are found in a wide variety of lifestyles and habitats. We present here the identification and initial description of Cenarchaeum symbiosum gen. nov., sp. nov., a symbiotic archaeon closely related to other nonthermophilic crenarchaeotes that inhabit diverse marine and terrestrial environments.

Animals↗
PubMedDate not supplied

Relationship between clothing ventilation and thermal insulation.

Air layers trapped within a clothing microenvironment contribute to the thermal insulation afforded by the ensemble. Any exchange of air between the external environment and these trapped air layers results in a change in the ensemble's thermal insulation and water vapor resistance characteristics. These effects are seldom taken into account when considering the effects of clothing on human heat balance, the thermal characteristics usually being restricted to intrinsic insulation and intrinsic evaporative resistance measurements on static manikins. Environmental assessments based on these measurements alone may therefore lead to under-(or over-) estimation of thermal stress of the worker. The aim of this study was to quantify the relationship between clothing ventilation and thermal insulation properties. A one-layer, air-impermeable ensemble and a three-layer, air-permeable ensemble were tested using an articulated, thermal manikin in a controlled climate chamber (ta = tr = 10 degrees C, PaH2O = 0.73 kPa). The manikin, which was designed for thermal insulation measurements, was also equipped with a system to determine clothing ventilation. Baseline measurements of clothing ventilation (VT) and thermal insulation (total clothing insulation: I(T)--measured, intrinsic insulation: Icl--calculated) were made of the clothing with the manikin standing stationary in still air conditions. Increased clothing ventilation was induced when the manikin "walked" (walking speeds of 0.37 m/sec and 0.77 m/sec) and by increasing the environmental air speed (Va = 1.0 m/sec). These increases in VT reduced Icl, this being ascribed to the increased heat transfer from the manikin skin surface to the cooler external environment due to the exchange of air between the clothing microenvironment and the external environment. Measured air exchanges were shown to have a potential heat exchange capacity of up to 17 and 161 W/m2 for the one- and three-layer ensembles, respectively, emphasizing the need to take clothing ventilation characteristics into consideration during thermal audits and thermal risk assessments.

Body Temperature Regulation↗
PubMed1998

Melting points of lysozyme and ribonuclease A crystals correlated with protein unfolding: a Raman spectroscopic study.

The effects of a temperature increase on monoclinic and tetragonal lysozyme single crystals were investigated by polarizing microscopy, X-ray diffraction and laser Raman spectroscopy. To prevent dissolution, the mother liquor was removed, and the crystals were covered by the oil poly-(chlorotrifluoroethylene). Upon heating, their macroscopic shape was stable beyond 453 K but a change (or loss) of birefringence was observed around 352 and 367 K for the tetragonal and monoclinic crystal forms, respectively, which is associated with tighter packing and higher crystal forces in monoclinic lysozyme. Raman spectral changes in the amide I and amide III regions indicated denaturation of the protein within the crystalline environment at temperature where birefringence changes, and differences in the S-S band suggest that in monoclinic lysozyme, denaturation is accompanied with disruption of some S-S bonds. Comparison with thermal denaturation and gel formation (beta-aggregation) of lysozyme in solution indicates that intermolecular interactions are mainly involved in the stabilization of the denatured lysozyme crystals. The behavior of ribonuclease A is very different. This protein unfolds and refolds reversibly in solution and its crystals melt at the unfolding temperature at 333 K, i.e. loss of structure induces breakdown of crystal lattice and macroscopic shape. Although the crystal lattice of proteins is stabilized by only few intermolecular contacts, its breakdown with increasing temperature is primarily a result of thermal unfolding of the polypeptide chains.

Calorimetry↗
PubMed1977

Temporal and climatic variables in naturalistic observation.

Home-observation data on 5- to 7-yr-old boys collected over 2 yr were examined for systematic variations in rates of desirable and undesirable behaviors associated with several temporal and climatic variables. Significant effects associated with time of day, day of the week, precipitation, and temperature were found. No significant effects on the naturalistic observation data were found for environmental factors associated with lunar phase. It was noted that the correlational nature of the findings did not obviate the necessity for control of the influence of temporal and climatic variables. Several methodological strategies for such control were discussed.

Astronomical Phenomena↗
PubMed1971

The effect of environmental conditions on the growth and function of brown adipose tissue.

1. Rabbits were reared from birth under one of two contrasting conditions. They were either well-fed and kept in a cool environment, or kept warm but fed on alternate days only. When they were a week old their metabolic responses to cold or the net exchanges of glucose, free fatty acid and glycerol by their brown adipose tissue in vivo before and during noradrenaline infusions were measured.2. The cold-reared rabbits grew normally, the under-fed rabbits were undersized; in both groups the brown adipose tissue wet weights were less than those normally found at birth. In cold-reared rabbits this was due largely to the low fat content, in the under-fed rabbits it was not.3. The rabbits' rates of oxygen consumption at a thermoneutral temperature and in response to cold was greater in the cold-reared rabbits.4. The increase in temperature over brown adipose tissue and the increase in blood flow in response to noradrenaline infusion was also greater in the cold-reared rabbits.5. Although the brown adipose tissue of cold-reared rabbits contained 30% fat it did not release fatty acids 24 hr after a feed. In contrast the brown adipose tissue of the under-fed rabbits released fatty acids at a high rate.6. It was concluded that both prolonged cold exposure and undernutrition influenced the function and development of brown adipose tissue during the first week of life. Cold exposure increases the thermogenic capacity of the tissue, undernutrition reduces it. The net release of fatty acids from brown adipose tissue, is, in part, dependent on the tissues' own intracellular requirements.

Adipose Tissue↗
PubMed1985

Melatonin and N-acetylserotonin stress responses: effects of type of stimulation and housing conditions.

The effects of housing condition and type of stimulation on serum melatonin and N-acetylserotonin (NAS) were investigated. Male rats were housed under a 12/12-hour light-dark cycle, with ad libitum food and water, either individually or in groups of four. At the start of the light phase, separate groups were sacrificed at rest or subjected for 3 minutes to the stimulation of cold water, noise, novel environment, or ether vapour and then decapitated at 0, 5, 15, 30 or 60 minutes after the end of stimulation. Melatonin was measured by a modified radioimmunoassay and NAS by a specific radioimmunoassay. Melatonin levels responded to stimulation with an increase, while NAS levels responded with a decrease. Housing condition had no effect on hormone response. However, the pattern of response for each of the two hormones differed greatly among the stimuli. For melatonin, cold water was the most potent stimulus, followed by noise, novel environment, and ether. NAS responded most to ether, fleetingly to cold, and in a bimodal manner to noise. The data are interpreted as suggesting that separate mechanisms regulate serum melatonin and serum NAS is response to environmental stimulation and that under appropriate control conditions melatonin from the pineal is very responsive to environmental stimuli, in a manner similar to that of pituitary hormones.

Animals↗
PubMed1998

The quantum event of oceanic crustal accretion: impacts of diking at mid-ocean ridges.

Seafloor diking-eruptive events represent the irreducible, quantum events of upper oceanic crustal accretion. They record events by which a large portion of the oceanic crust has formed through geological history. Since 1993, the U.S. Navy's real-time Sound Surveillance System has allowed location of ongoing acoustic signatures of dike emplacement and basalt eruptions at ridge crests in the northeast Pacific. These diking-eruptive events trigger a sequence of related, rapidly evolving physical, chemical, and biological processes. Magmatic volatiles released during these events may provide nutrients for communities of subsea-floor microorganisms, some of which thrive in high-temperature anaerobic environments. Many of the organisms identified from these systems are Archaea. If microorganisms can thrive in the water-saturated pores and cracks within deep, volcanically active portions of our planet, other hydrothermally active planets may harbor similar life forms.

Archaea↗
PubMed2005

Preliminary evaluation of implantable MOSFET radiation dosimeters.

In this paper, we report on measurements performed on a new prototype implantable radiation detector that uses metal-oxide semiconductor field effect transistors (MOSFETs) designed for in vivo dosimetry. The dosimeters, which are encapsulated in hermetically sealed glass cylinders, are used in an unbiased mode during irradiation, unlike other MOSFET detectors previously used in radiotherapy applications. They are powered by radio frequency telemetry for dose measurements, obviating the need for a power supply within each capsule. We have studied the dosimetric characteristics of these MOSFET detectors in vitro under irradiation from a 60Co source. The detectors show a dose reproducibility generally within 5% or better, with the main sources of error being temperature fluctuations occurring between the pre- and post-irradiation measurements as well as detector orientation. A better temperature-controlled environment leads to a reproducibility within 2%. Our preliminary in vitro results show clearly that true non-invasive in vivo dosimetry measurements are feasible and can be performed remotely using telemetric technology.

Calibration↗
PubMed1993

Lowering of body core temperature by exposure to a cold environment and by a 5-HT1A agonist: effects on physiological and psychological variables and blood serotonin levels.

The present study was designed to compare the effects of a pharmacologically induced decrease in body core temperature to the effects observed with lowering of body temperature by exposure to a cold environment. Our special interest was the involvement of 5-HT in thermoregulatory responses. Sixty healthy male volunteers were randomly assigned to one of the following conditions: exposure to normal ambient temperature (28 degrees C) and placebo, exposure to cold ambient temperature (5 degrees C) and placebo, or normal ambient temperature and 10 mg of the partial 5-HT1A agonist ipsapirone. As indicators of physiological responses to lowering of body temperature, tympanic temperature, skin temperature, EMA, metabolic rate, and heart rate were monitored and saliva cortisol levels and peripheral 5-HT concentrations were determined. In addition, ratings on ambient temperature, thermal discomfort, and feelings of irritability were obtained. While lowering of body core temperature was associated with marked counterregulations (decrease of skin temperature, increase in EMA and metabolic rate) and feelings of discomfort, this was not observed with ipsapirone. An increase in cortisol levels was primarily observed in the ipsapirone group and was not reflected by respective changes in whole blood or platelet 5-HT indicating that brain and platelet 5-HT are not related.

Adult↗
PubMed2003

The gut morphology of the African ice rat, Otomys sloggetti robertsi, shows adaptations to cold environments and sex-specific seasonal variation.

We studied the gut morphology of the ice rat Otomys sloggetti robertsi, a non-hibernating murid rodent endemic to the sub-alpine and alpine regions of the southern African Drakensberg and Maluti mountains. The gut structure of O. s. robertsi is well adapted for a high fibre, herbivorous diet, as is the case with other members of its subfamily Otomyinae. Despite the broad similarity in gross gut morphology with mesic- and arid-occurring otomyines, O. s. robertsi has a larger small intestine, caecum, stomach volume and parts of the colon, which we suggest are adaptations for increased energy uptake and/or poor diet quality in alpine environments. However, O. s. robertsi has a smaller larger intestine than other otomyines, perhaps because it occupies a mesic habitat. Seasonal sexual differences occurred, with females increasing dimensions of the stomach, small intestine length, caecum, and large intestine in summer. Sexual asymmetry in gut morphology may be related to increased energy requirements of females during pregnancy and lactation, indicating phenotypic plasticity in response to poor quality vegetation and a shorter growing season in alpine habitats.

Adaptation, Physiological↗
PubMed1987

Environmental variables and releasing-valence transfer in stimulus-directed pecking of chicks.

Releasing valence transfer occurs when the power or valence to release responses is transferred from a primary releasing stimulus to a second, initially neutral, stimulus. In the exemplar, pecking responses by neonatal chicks are released and directed by a pointed object operated to make pecking movements. Stimuli attached to or pecked by the arrow thereby acquire enhanced releasing valence. Chicks peck at matching stimuli in preference to comparable but unenhanced stimuli. Research reported here shows that primary and transferred releasing valences are differentially affected by environmental variables. Specific findings were Pecking by chicks occurs only within a narrow range of ambient temperature. Outside of this range, pecking is low in frequency and insensitive to valence-enhanced release. Pecking by chicks appears to be finely tuned to arrow peck rates between 120 and 180 pecks per minute. Within this range, frequency of pecks by chicks is low whereas the percentage of pecks to the valence-enhanced stimulus is maximal. The maternal food call was a weak releaser of pecking by chicks with no valence-enhancing properties.

Animals↗
PubMed1989

Prevention of hyperthermia-induced seizures in immature rats by a hydantoin derivative of naloxone.

The non-specific opiate antagonist naloxone protects immature rats from hyperthermic seizures which occur when the animals are exposed to an environment of 40 degrees C and 55% humidity. Most of the currently used antiepileptic therapeutic agents can be said to contain either a hydantoin or a moiety stereochemically closely related to one. We have added a hydantoin group to naloxone and created a new combined chemical, naloxyl-6-alpha spirohydantoin. The new compound was ten times as effective as naloxone against hyperthermic seizures in 15-day old rat pups. Unlike naloxone, the new naloxone-hydantoin derivative retained a protective effect 24 hrs after injection.

Animals↗
PubMed1993

[Sequential observation on the influence of artificial wind-cold environment to immunologic function of mononuclear phagocytic system in mice].

According to TCM theory of Six Evils, the Wind-Cold is one of the pathogen. In order to find the mechanism of Wind-Cold in causing disease, the effect of subacute Wind-Cold stimulation on the phagocyte immunization in mice was observed. Results showed that through exposing in the Wind-Cold environment, the reticuloendothelial system (RES) clearance function and the hydrogen-peroxide releasing of peritoneal macrophage were suppressed. Sequential observation showed that the peak of immunosuppression occurred on the 3rd day after stimulation and began to normalize at 5th day. These results suggested that Wind-Cold stimulation could inhibit temporary phagocytosis of macrophage and bacteriocidal effect. Action of immunosuppression was believed to be produced by the increase of stress hormone after stimulation. Results also suggested that the pathogenic action of Wind-Cold on disease is somewhat related with the suppression of nonspecific cellular immunity.

Animals↗
PubMed1985

Genetic variation in body size, composition, temperature, and feed intake in mature chickens.

Genetic variation for more than 40 traits was assessed in 26 stocks of mature chickens reared together and fed ad libitum from hatching to slaughter at 507 days of age. There was greater genetic variation among males than among females. The intraclass correlation, t, was high (greater than .75) for measures of size and weight and moderate (.20 to .60) for most other traits (P less than .05) including a measure of lean distribution (.37). Three main categories of stocks were studied, viz. outbred Leghorns, medium-sized stocks, and contemporary heavy meat chickens. Differences in lean distribution were not associated with category, but differences of 40 to 50 g/kg lean in the breast of some stocks may be caused by a single gene. Lean:bone ratios were similar in medium and heavy stocks but were greater (P less than .05) in heavy meat-types compared with outbred Leghorns. Bone density was higher (P less than .01) in females compared with males and in outbred Leghorns compared with heavier stocks (P less than .01). Heavy meat-type males were leaner (P less than .01) and had proportionately less fat in the abdominal cavity than outbred Leghorns. Carcass fatness was similar among stocks of females, but abdominal fat was lower in Leghorns selected for high egg production compared with unselected Leghorns (P less than .05) and heavy stocks (P less than .001). One resistant and two Marek's disease-susceptible stocks were replicated in a specific pathogen-free (SPF) environment. Spleen weight was larger (P less than .001) in the conventional environment. Females were relatively smaller (P less than .05) than males in the conventional environment. Body temperature (t = .25, P less than .05) and feed intake were assessed in males. Heavy meat birds had a lower (P less than .01) body temperature than outbred Leghorns and medium-sized stocks. Differences among stocks for feed intake (t = .77) were significant (P less than .05); however, they were greatly reduced when feed intake was expressed as g/kg liveweight (LW) (t = .49) or g/kg LW.75 (t = .25). Outbred Leghorns ate less in absolute terms but significantly more (P less than .01) as a proportion of LW or LW.75 than the medium and heavy lines.

Animals↗
PubMed1976

Effect of extreme factors on micro-organisms used for the control of the effectiveness of sterilization.

Survival of micro-organisms used for control of sterilization procedures was studied under conditions simulating the Martian environment (daily temperature change from +20 degrees to -20 degrees in 99.98% CO2 + 0.02% air at 0.13 x 10(-6) N m-2 pressure, with ultraviolet radiation spanning the whole range of the solar spectrum 300-350 MkW cm-2). The test organisms were four strains of Bacillus subtilis and one strain of Bacillus anthracoides, and were inoculated on to four materials, smooth metal, porous plastic, multilayer composition material and powdered limonite. Some organisms survived on all materials, the greatest on the limonite. The resistance of the survivors to disinfectants was the same as that of the original cultures.

Bacillus↗
PubMed2003

Driving performance in cold, warm, and thermoneutral environments.

Driving performance deteriorates at high ambient temperatures. Less is known about the effect of low ambient temperatures and the role of subjective aspects like thermal comfort and having control over the ambient temperature. Therefore, an experiment was constructed in which 50 subjects performed a road-tracking task in a cold (5 degrees C), a thermoneutral (20 degrees C) or a warm (35 degrees C) climate. All subjects had a heater/blower (H/B) which generated a fixed amount of heat/wind that could either be controlled or not controlled. In the cold climate, averaged leg skin temperature dropped to 18.5 degrees C and head skin temperature to 24.9 degrees C; the thermal comfort was rated between 'cold' and 'very cold'. In the warm climate, averaged leg skin temperature rose to 36.6 degrees C and head skin temperature to 30.8 degrees C; the thermal comfort was rated as 'hot'. Driving performance in the ambient temperature extremes decreased 16% in the cold environment and 13% in the warm situation. Having control over the local head temperature by adjusting a H/B affected neither thermal comfort nor driving performance. In agreement with the literature on priming effects, subjects who started with the no-control condition performed much better in all driving tasks because they were primed to focus on the driving task as such, rather than the complex combination of temperature controls and driving task. It can be concluded that a thermoneutral temperature in a car enhances driving performance and may thus positively affect safety. Using manual climatic controls in hot or cold cars may interfere with the driving task.

Adult↗