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

Shaven and unshaven rats were exposed to a cold stress at 4 degrees C for 6 hr (SE and UE). Control animals remained at room temperature (SC and UC). Hypothermia was induced in group SE, with mean rectal temperature of 22.0 +/- 2.0 degrees C (+/- S.E.M.). All other groups were normothermic, had similar arterial pO2 and hepatic tryptophan oxygenase levels. Acute hypothermia induced a sloughing of cells from the villi into the lumen of the gut, as indicated by an increased DNA in luminal washings. However, there was an unimpaired 3H-thymidine incorporation into the DNA of the intestinal mucosal cells and those present in lumina washes. Intestinal disaccharidases and alkaline phosphatase were not altered. This suggests that more severe cellular alterations reported earlier in hypothermia may have been caused by associated factors other than a decreased body temperature.
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PMID:Experimental acute hypothermia and intestinal cellular integrity. 67 37

Twenty experiments were conducted on dogs. The effect of hypothermia of different degree (from 18 to 20 degrees C and from 4 to 6 degrees C) on the carbohydrate metabolism and the extent of solubilization of hepatic enzymes (lactate dehydrogenase, glutamate dehydrogenase, urokaninase, DNA-ase, glucose-6-phosphatase) in prefusion-free preservation of the liver was studied. The preservation efficacy was assessed during the subsequent two-hour normothermic perfusion. A marked solubilization of the enzymes under study followed preservation of the liver at 18--20 degrees C; this indicated the loss of intactness of the cell membranes during the preservation. A moderate expenditure of the glycogen stores in the liver, and of sugar in the perfusate followed preservation of the liver at a temperature of 4--6 degrees C; this suggested an even suppression of hepatic metabolism and the prevalence of normal tissue respiration over glycolysis in the restoration of circulation in the liver.
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PMID:[Effect of hypothermia on metabolism in the liver during its preservation]. 68 13

Incorporation of labelled metabolites into proteins, RNA and DNA was completely inhibited in rabbit tissues under conditions of prolonged hypothermia (10 degrees). The incorporation of labelled metabolites into all the biopolymers studied was restored after subsequent warming up to 38 degrees. Within 60-90 min after death of the animals due to acute anoxia, the labelled metabolites did not incorporate into protein, RNA and DNA. Artificial postmortal hypothermia (20 degrees) increased (by about 2.5-3-fold) the period of viability, during which reanimation is possible. The hypothermia enables subsequent restoration of the anabolic processes from the zero level.
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PMID:[Importance of cooling after death for restoration of metabolism during resuscitation]. 73 84

The irradiation of experimental tumors with a dose of 2000--2500 rad (20--25 J/kg) under hypothermia promoted an inhibition of the growth to a greater degree than the irradiation under normal conditions. In Guerin's tumor the inhibition of DNA and RNA synthesis was more expressed after the irradiation under hypothermic conditions than under the irradiation, and/or hypothermia alone. After the irradiation of the Guerin's tumor under hypothermia the cells were synchronized during the presynthetic phase of the cycle (block G1-S), and the effect of synchronization was more expressed in the tumor than in the normal tissue. The irradiation under hypothermia decreased the proliferative pool to a greater degree than the irradiation and/or hypothermia alone.
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PMID:Cellular mechanisms of the radiomodifying effect of hypothermia. 74 58

Reserpine, a well-known CNS depressant which depletes central monoamine stores, was found to produce in the brains of 11-day-old rats a severe depression in cell proliferation in terms of the rate of [3H]thymidine incorporation into DNA. The effect was studied in detail 12 h after ther administration of the drug (2.5 mg/kg, s.c.) when the rate of in vivo DNA synthesis in the forebrain was about one-third of control: the decrease was less marked in the cerebellum (rate about two-thirds of control). It was possible to exclude side effects of the drug, such as restricted food intake, hypothermia and an elevation of the level of blood corticosteroids being responsible for the reduction of [3H]thymidine incorporation into DNA. Kinetic studies showed that reserpine had no marked effect on the entry of [3H]thymidine from blood to brain, but it caused some retardation in the rate of [3H]thymidine conversion into [3H]thymidine nucleotides. Nevertheless, the severe depression of DNA labelling was evident even after correcting the values on the basis of [3H]thymidine nucleotide concentrations. In contrast to these effects, thymidine kinase activity was normal in the brain of reserpine-treated animals.
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PMID:Effect of reserpine on cell proliferation in the developing rat bran: a biochemical study. 88 5

The effect of prolonged light halothane anesthesia (0.8%) on the proliferation rate of different mouse tissues was investigated, using [5-125I]5-iodo-2-deoxyuridine uptake into DNA as the test parameter. It was found that DNA synthesis in spleen, femoral bone marrow, and, occasionally, the small intestine was significantly depressed after exposure for 24 hr to halothane in vivo. The time course of DNA synthesis inhibition was then investigated by utilizing a shorter (6-hr) exposure time. This period was found to be insufficient to cause DNA synthesis inhibition in any of test tissues. Because anesthesia was found to be associated with hypothermia at normal room temperatures, it was established that the inhibition of DNA synthesis was not due to cooling of the mice under anesthesia by demonstrating that inhibition in sensitive tissues occurred at warmer temperatures as well. To examine the specificity of this finding, the DNA synthesis rate of cells in other normal tissues, e.g., skin and muscle, and in s.c.-growing tumor cells of a mouse mammary carcinoma, L1210 leukemia, and a first transplant AKR lymphoma were examined. In none were responses noted with 24 hr of halothane exposure. However, halothane was found to inhibit DNA synthesis in regenerating marrow. Finally, it was found that after significant exposure to halothane, complete recovery was seen in the spleen after 24 hr, whereas femur DNA synthesis was still depressed by 20% at the same time.
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PMID:Preferential inhibition of DNA synthesis in mouse hemopoietic cells by halothane. 97 81

Cardiac hypertrophy was produced in embryonic chicks by decreasing the incubation temperature from 38 degrees C to 32 degrees C on day 11. Increases in ventricular protein, RNA, and DNA support the cardiac enlargement. Cytochrome-c oxidase activity and citrate synthase activity were depressed in hypothermic ventricles by 63% and 56%, respectively. No significant differences were seen in enzyme activities in pectoralis muscles. The involvement of mitochondrial gene replication and transcription was evaluated using a cDNA clone for the mitochondrially encoded subunit III of cytochrome-c oxidase (CO III). Quantitative slot-blot analysis demonstrated that the relative CO III mRNA concentration was reduced in hypothermic ventricles. In contrast, the relative mitochondrial DNA concentration was increased in hypothermic ventricles. Taken together, these data indicate that a hypothermia-induced decrease in cytochrome-c oxidase activity is associated with a decrease in CO III mRNA, which is not coupled to a decrease in the mitochondrial DNA copy number. This dissociation of mitochondrial gene replication and transcription may provide a useful model for examining the regulation of mitochondrial biogenesis.
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PMID:Mitochondrial DNA replication and transcription are dissociated during embryonic cardiac hypertrophy. 166 4

Transient hypothermia was employed to extend the G2 phase of CHO K1 cells in order to facilitate study of the repair of X-ray induced chromatid and DNA damage. Thus G2 + 1/2M at 37 degrees C of 2.9 h was lengthened to 5.7 h at 33 degrees C and 7.3 h at 29 degrees C. While chromatid break kinetics remained essentially unaltered at 33 degrees C, at 29 degrees C there was an initial shoulder followed by a decrease in breaks similar to that at 37 and 33 degrees C. Although fewer exchanges were observed at 33 and 29 degrees C than at 37 degrees C, a similar kinetic involving a sharp initial rise followed by a plateau was observed at 33 and 29 degrees C, and, as far as could be judged, also at 37 degrees C. The failure of G2 prolongation to influence the rate of break disappearance was taken as evidence in support of the view that the disappearance of chromatid breaks represented a repair process rather than the decline of chromosomal radiosensitivity throughout this phase, though the possibility of a reduced sensitivity close to the G2/M border remained open. This hypothesis was supported by the mainly flat kinetics of exchanges. The data were taken as further evidence that chromatid rejoining and misjoining (exchanges) are essentially different processes. The rates of repair of DNA double-strand breaks as measured by neutral filter elution were similar at 37 and 33 degrees C, while there was evidence of inhibition at 29 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Repair kinetics in CHO cells of X-ray induced DNA damage and chromatid aberrations during a cell cycle extended by transient hypothermia. 238 81

Effects of acute or chronic ethanol administration have been studied on protein, RNA and DNA synthesis in the developing brain in the absence or presence of hypothermia. Acute ethanol was given intraperitoneally (4 g/kg) and for chronic ethanol treatment the pups were allowed to suckle on the ethanol-fed dams. Dams were pair-fed on nutritionally adequate liquid-sustacal diet. Ethanol administration, both acutely and chronically, inhibited the in vivo and in vitro protein synthesis in the absence or presence of hypothermia. This data suggests that ethanol per se is capable of producing the inhibition of protein synthesis in brain without its hypothermic effect. However, the inhibitory effect of ethanol is more pronounced in the presence of ethanol-mediated hypothermia. Hypothermia in itself also causes a decrease in the synthesis of proteins. Maternal ethanol consumption results in a significant decrease in the synthesis of both RNA and DNA in the developing brain of suckling newborn either in the absence or presence of hypothermia. RNA and DNA synthesis was measured by following the incorporation of (5-(3)H) uridine and (14C)thymidine respectively. Decrease in body temperature alone also resulted in decreased RNA and DNA synthesis in the developing brain. Ethanol reaching the suckling newborn from maternal milk resulted in decreased brain weights, total protein, ribosomal protein, total RNA, ribosomal RNA, and total DNA of the brain. Neonatal brain proteolytic and DNA-polymerase activities were inhibited in the ethanol-fed group. An inhibition of proteolytic activity reflects a compensatory mechanism of the developing brain to decrease the breakdown of proteins in response to the inhibitory effect of ethanol on protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nucleic acid and protein synthesis inhibition in developing brain by ethanol in the absence of hypothermia. 258 87

A decrease in incubation temperature from 38 to 32 degrees C elicits a decrease in chicken embyro size and weight with concomitant heart enlargement if done after day 10 of incubation. When assayed at day 18 of incubation with the hypothermia started on day 11 or 14, evidence is presented that the heart enlargement is an hypertrophy with no detectable hyperplasia. Supporting data are presented for various physical parameters showing increases in heart wet and dry weight, volume, area, wall thickness, and cell size. There was little difference in DNA content and nuclear [3H]thymidine labeling index between hearts of control and hypothermic embryos. Hearts of hypothermic embryos showed a slight increase in water content and considerable increases in RNA, protein, and glycogen content per unit DNA. The average size of polysomes isolated from hypothermic hearts was larger than that of polysomes isolated from controls. Microscopic studies showed no obvious increase in amount of capillary beds, connective tissue, and myocardial cells. Annulate lamellae were found only in myocardial cells of hypothermic embryos in sparse amounts and low frequency but always associated with large deposits of glycogen.
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PMID:Cardiac hypertrophy in chick embryos induced by hypothermia. 294 25


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