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At least 1,423 records · Page 79Linked to original sources
PubMed1974

Inhibition of thermoregulatory non-shivering thermogenesis by trauma in cold-acclimated rats.

1. Heat production and blood flow in the interscapular brown adipose tissue of 3 degrees C acclimated rats have been measured by the heated thermo-couple technique.2. When the environmental temperature (T(a)) was reduced from 30 to 3 degrees C heat production by the brown adipose tissue began to increase at the lower limit of the thermoneutral zone and then increased linearly.3. Blood flow also increased when T(a) was reduced but was not so well correlated with T(a). There was however a good positive correlation between blood flow and heat production.4. During the first hour after a 4 hr period of bilateral hind-limb ischaemia in a 20 degrees C environment the percentage of rats not producing heat in the interscapular brown adipose tissue increased and the tissue blood flow fell.5. By varying the T(a) of the injured rat it was found that the T(a) at which heat transfer from the interscapular brown adipose tissue commenced was significantly lower than in the controls although the slope of the regression lines relating heat production and T(a) was unaltered.6. Blood flow also increased in the injured rat when T(a) was lowered but the increase in the tissue blood flow per unit increase in heat production was less than in the controls.7. In a 5 degrees C environment heat production in the interscapular brown adipose tissue of the injured rat was further increased by the S. C. injection of L-isoprenaline or L-noradrenaline.8. It is concluded that the central control of thermoregulatory non-shivering thermogenesis is inhibited after injury in the rat.

Adipose Tissue, Brown↗
PubMed2004

The Yana RHS site: humans in the Arctic before the last glacial maximum.

A newly discovered Paleolithic site on the Yana River, Siberia, at 71 degrees N, lies well above the Arctic circle and dates to 27,000 radiocarbon years before present, during glacial times. This age is twice that of other known human occupations in any Arctic region. Artifacts at the site include a rare rhinoceros foreshaft, other mammoth foreshafts, and a wide variety of tools and flakes. This site shows that people adapted to this harsh, high-latitude, Late Pleistocene environment much earlier than previously thought.

Animals↗
PubMed2003

Seasonal dynamics of previously unknown fungal lineages in tundra soils.

The finding that microbial communities are active under snow has changed the estimated global rates of biogeochemical processes beneath seasonal snow packs. We used microbiological and molecular techniques to elucidate the phylogenetic composition of undersnow microbial communities in Colorado, the United States. Here, we show that tundra soil microbial biomass reaches its annual peak under snow, and that fungi account for most of the biomass. Phylogenetic analysis of tundra soil fungi revealed a high diversity of fungi and three novel clades that constitute major new groups of fungi (divergent at the subphylum or class level). An abundance of previously unknown fungi that are active beneath the snow substantially broadens our understanding of both the diversity and biogeochemical functioning of fungi in cold environments.

Ascomycota↗
PubMed1987

Microbial trace-fossil formation, biogenous, and abiotic weathering in the Antarctic cold desert.

In the Antarctic cold desert (Ross Desert), the survival of the cryptoendolithic microorganisms that colonize the near-surface layer of porous sandstone rocks depends on a precarious equilibrium of biological and geological factors. An unfavorable shift of this equilibrium results in death, and this may be followed by formation of trace fossils that preserve the characteristic iron-leaching pattern caused by microbial activity. Similar microbial trace fossil may exist in the geological record. If life ever arose on early Mars, similar processes may have occurred there and left recognizable traces.

Antarctic Regions↗
PubMed1992

Oxygen supersaturation in ice-covered Antarctic lakes: biological versus physical contributions.

Freezing in ice-covered lakes causes dissolved gases to become supersaturated while at the same time removing gases trapped in the ablating ice cover. Analysis of N2, O2, and Ar in bubbles from Lake Hoare ice shows that, while O2 is approximately 2.4 times supersaturated in the water below the ice, only 11% of the O2 input to this lake is due to biological activity: 89% of the O2 is derived from meltwater inflow. Trapped bubbles in a subliming ice cover provide a natural "fluxmeter" for gas exchange: in Lake Hoare as much as 70% of the total gas loss may occur by advection through the ice cover, including approximately 75% of the N2, approximately 59% of the O2, and approximately 57% of the Ar losses. The remaining gas fractions are removed by respiration at the lower boundary (O2) and by molecular exchange with the atmosphere in the peripheral summer moat around the ice.

Antarctic Regions↗
PubMed1974

Aglomerularism in Antarctic fish.

Urine formation in antarctic bony fish does not involve glomerular filtration. Evidence for aglomerularism came from both direct observation of kidney serial sections by light microscopy and the low concentrations of inulin labeled with carbon-14 that were excreted into the urine when this renal clearance tracer was injected into the bloodstream via a cannula implanted in the caudal vein. Aglomerularism most likely prevents urinary loss of glycoproteins with biological antifreeze properties.

Animals↗