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Query: UMLS:C0020672 (hypothermia)
 17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The permeability of the rat blood-brain barrier during different levels of hypothermia was examined using a new and more sensitive quantitative radiotracer technique. In contrast to the findings of previous studies, tracer permeation as measured here by the calculated cerebrovascular permeability-area product (PA), did not increase during hypothermia. Rather, rats maintained at specific temperatures between 30-16 degrees C (1 h) by contact surface cooling, displayed lowered permeation (PA) of i.v. injected 14C-sucrose, 125I-bovine serum albumin and 3H-alpha-amino-isobutyric acid in all brain regions examined. This effect was temperature-dependent and reversible on rewarming to normothermic temperature. Elevated plasma tracer concentration vs. time was characteristic of hypothermic rats except those cooled to 30 degrees C. That no elevation in plasma tracer accompanied alterations in tracer permeation at 30 degrees C, indicates hypothermic induced reductions in PA are independent of altered plasma tracer levels. Furthermore, the nature of alpha-amino-isobutyric acid to rapidly distribute to intracellular vs. extracellular sites suggests the effects of hypothermia seen here are due primarily to the condition of cerebrovascular membranes.
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PMID:Hypothermia-induced reduction in the permeation of radiolabelled tracer substances across the blood-brain barrier. 688 Jun 23

The effect of low temperature on cytosolic pH regulation and buffering capacity was evaluated in the isolated rat liver. The pH changes were followed by phosphorus-31 nuclear magnetic resonance. Cooling from 37 to 4 degrees C, with Krebs-Heinseleit perfusion at an external pH of 7.35, induced an alkaline shift in cytosolic pH (pHcyt) of 0.13 or 0.75 pH units in the presence of bicarbonate, respectively (dpH cys/dT values were 0.004 and 0.022 unit/degrees C. With 4 degrees C perfusion, in the presence or absence of bicarbonate, acute changes of external pH (from 7.40 to 5.90) did not affect pHcyt. In contrast, intracellular loading with isobutyric acid or NH4Cl induced rapid pHcyt variations. The intrinsic buffering power value (10 to 50 slykes) measured in the absence of bicarbonate depended on pHcyt. The larger value was observed for pHcyt 7.30, a value near the pK value of the imidazole group of intracellular proteins at 4 degrees C. The presence of bicarbonate modified the amplitude of the pHcyt change by increasing the total buffering power. It was demonstrated that during hypothermia, ionic carriers are inactivated and the charged forms of molecules are unable to cross the cell membrane; thus, the pHcyt homeostasis depends essentially on intracellular buffering power.
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PMID:Cytosolic pH variations in perfused rat liver at 4 degrees C: role of intracellular buffering power. 965 31