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At least 1,099 records · Page 61Linked to original sources
PubMed1990

Effect of gonadal steroid hormones on the metabolic rate of the cold-acclimated gonadectomized male and female Chalcides ocellatus (Forskal).

Male and female Chalcides ocellatus were gonadectomized and cold acclimated at 15 degrees for 1 week. Lizards were injected with testosterone and estradiol, and their oxygen consumption was determined at 15 degrees. Testosterone and estradiol caused a significant increase in the whole body rate of oxygen consumption in male and female lizards, respectively.

Acclimatization↗
PubMed1986

Non relationship of climatologic factors and painful sickle cell anemia crisis.

Conflicting results have arisen from studies concerning the correlation (if any) between climatological changes and the frequency of painful episodes in the sickle cell population. During a 13 month period records of 71 patients with hemoglobin genotypes SS or SC were reviewed. Data analysis failed to reveal an association between the frequency of painful sickle cell crisis and a number of weather and environmental variables. We were unable to demonstrate relationships between the climatologic factors of temperature, humidity, carbon monoxide level and precipitation in the frequency of 362 pain crises in 71 sickle cell patients during a 13 month period.

Adolescent↗
PubMed1995

Effects of the menstrual cycle on dressing behavior in the cold.

The purpose of the present study was to determine the effect of the menstrual cycle on dressing behavior in cold exposure. Rectal and skin temperatures, temperature sensation and metabolic rate were measured in seven women during the luteal (L) and the follicular (F) phases of the menstrual cycle, as was their dressing behavior in these two phases. The subjects were instructed to dress so as to feel comfortable when the ambient temperature was decreased from 30 degrees C to 15 degrees C (07:00-09:00). Most subjects dressed more quickly and with thicker clothing in the L phase. They felt cooler in the L phase during the last 30 min of the temperature fall. Rectal and skin temperatures showed significant differences between L and F phases and metabolic rate was significantly higher in the L phase. The results can be interpreted in terms of the establishment of a higher set-point in core temperature during the L phase.

Adult↗
PubMed1995

Influence of different light intensities during the daytime on evening dressing behavior in the cold.

The primary purpose of this study was to determine the effect of bright light exposure during the daytime on dressing behavior in the cold. Seven female volunteers were exposed to bright light of 4,000 lx ("Bright") or dim light of 10 lx ("Dim") from 10 h to 18 h, complete darkness during the sleep period (22:30 h-06:00 h), and 10 lx for the rest of the time. The subjects were instructed to dress to remain comfortable when the ambient temperature was decreased from 30 degrees to 15 degrees C (20:30 h-22:30 h). Most subjects dressed more quickly and with thicker clothing in the Dim condition and felt cooler during the last 30 min of the temperature fall. The rectal temperature showed clear circadian rhythm both under Bright and Dim conditions, but it was significantly lower during sleep in the Bright condition. It is suggested that the set-point of core temperature is reduced at night during the Bright condition.

Adult↗
PubMed1994

Further studies on the development and survival at low temperatures of the free living stages of Trichostrongylus tenuis.

To assess the ability of the free living stages of Trichostrongylus tenuis, a pathogen of red grouse, to survive the winter in significant numbers, the temperatures prevailing during the autumn, winter and spring of 1991-92 on the North Yorkshire moors were simulated in an incubator into which replicate cultures of T tenuis eggs were placed at intervals. September and early October eggs developed into larvae which survived over winter and were infective the following spring. Few November to February eggs survived to become larvae but early March eggs were reasonably successful. Continuous temperatures of -15 degrees C were lethal to infective larvae within 12 days, but significant numbers of larvae survived temperatures of -10 degrees C or higher for up to three weeks and remained infective.

Animals↗
PubMed1991

The lactate dehydrogenase of the icefish heart: biochemical adaptations to hypoxia tolerance.

Cardiac lactate dehydrogenase from the hemoglobin- and myoglobin-free antarctic icefish has been purified by affinity chromatography. Structural and kinetic properties of the enzyme were found close or identical to those of its skeletal muscle counterpart and other M-type lactate dehydrogenases. A model involving a dual oxidative-anaerobic metabolism of the icefish heart is proposed.

Acclimatization↗
PubMed1991

Calorimetric analysis of antifreeze glycoproteins of the polar fish, Dissostichus mawsoni.

Solutions of antifreeze glycoproteins 1 through 5 and 8 were analyzed for activity by differential scanning calorimetry. With a scan rate of 1 degree C min-1, antifreeze glycoproteins 1-5 (20 mg/ml) revealed antifreeze activity with a delay in the freeze exotherm during cooling in the presence of ice. Antifreeze glycoprotein 8 (60 mg/ml), however, did not reveal antifreeze activity. When a 0.1 degree C min-1 scan rate was used, glycoproteins 1-5 again yielded a delay in the freeze onset, but the exotherm consisted of multiple events. At the slower scan glycoprotein 8 revealed an initial freeze followed by multiple exothermic events resembling those of glycoproteins 1-5. Thermograms exhibiting antifreeze activity had an initial shoulder in the exotherm direction upon cooling followed by a delay before the exotherm. The shoulders were correlated with c-axis ice growth observed in visual methods. The glycoprotein antifreezes had a linear increase in activity with decreased ice content.

Animals↗
PubMed1983

Characterization of a halotolerant-psychroloterant bacterium from dry valley Antarctic soil.

The saline soils of the ice free dry valleys of Victoria Land, Antarctica may provide the closest analog on Earth to Martian conditions. We have initiated a study aimed at examining microbial adaptations to the harsh environment of these dry valley soils. In this report we describe the characterization of one bacterium, strain A4a, isolated from Taylor Valley soil. Strain A4a was an obligately aerobic, orange-pigmented, Gram-positive coccus that grew over wide ranges of both temperature (0 degrees C-40 degrees C) and sodium chloride concentration (0-2.0M). The optimal temperature for growth at all NaCl concentrations was 25 degrees C. Phospholipid composition and guanine plus cytosine content of the DNA of the isolate indicate a close relation to the genus Planococcus.

Adaptation, Physiological↗
PubMed1986

Molecular aspects of adaptation to extreme cold environments.

Here are reviewed and summarized the strategies adopted by living organisms to survive low temperatures, from a molecular and membrane point of view. The presentation is aimed at a wide variety of readers. Two prime examples of connections between biological cold adaptation and the molecular level are (1) antifreeze proteins in fish from cold sea water, (the DNA sequence of the protein gene is now known) (2) the fluidity characteristics of cell membranes in a wide variety of organisms. In model membranes of phospholipids, stabler "s-phases" have recently been found to form at low temperatures. Antarctic endolithic organisms, living just under the surface of rocks, are exposed to long periods of low temperatures, and may develop such phases in their membranes. In the saturated phosphatidyl cholines, only lipids with a restricted range of acyl chain lengths show simultaneously s-phases and a main transition : This restricted range is about the restricted range found in natural membranes. The s-phases also form in the presence of natural cryoprotectants, and may be connected with botanical vernalization.

Acclimatization↗
PubMed1986

The Antarctic cold desert and the search for traces of life on Mars.

The cryptoendolithic microorganisms that live inside rocks in the frigid Ross Desert of Antarctica can serve as a terrestrial model for what may have happened to life forms on Mars when the planet became dry and cold. Trace fossils of microbial rock colonization exist in Antarctica, and similar structures could have formed on Mars. In some respects, such trace fossils could be an easier target for life-detection systems than fossils of cellular structures.

Adaptation, Biological↗
PubMed1986

Exobiology and future Mars missions: the search for Mars' earliest biosphere.

The primordial Mars may have possessed a thick carbon dioxide atmosphere, with liquid water common on the surface, similar in many ways to the primordial Earth. During this epoch, billions of years ago, the surface of Mars could have been conducive to the origin of life. It is possible that life evolved on Mars to be later eliminated as the atmospheric pressure dropped. Analysis of the surface of Mars for the traces of this early martian biota could provide many insights into the phenomenon of life and its coupling to planetary evolution.

Aluminum Silicates↗
PubMed1989

Early martian environments: the Antarctic and other terrestrial analogs.

The comparability of the early environments of Mars and Earth, and the biological evolution which occurred on early earth, motivates serious consideration of the possibility of an early martian biota. Environments which could have contained this early martian life and which may presently contain evidence of this former life include aquatic, ice, soil, and rock habitats. Several analogs of these potential early martian environments, which can provide useful information in searching for extinct life on Mars, are currently available for study on Earth. These terrestrial analogs include the perennially ice-covered lakes and sandstone rocks in the Polar Deserts of Antarctica, surface of snowfields and glaciers, desert soils, geothermal springs, and deep subsurface environments.

Antarctic Regions↗