Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “acclimation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,387 records · Page 77Linked to original sources
PubMed1981

Constancy of liver lipid composition in two genera of toads after a short-term temperature acclimation.

The lipid and fatty acid composition of Bufo calamytes and Alytes obstetricans livers has been studied. Data for both species are similar, and resemble closely those published for Rana sculenta. Total lipids constitute 20-25% of the total liver dry weight; about one fifth of these are phospholipids; cholesterol makes up 1.7-2.2% of the total liver dry weight. The most abundant phospholipids are phosphatidylcholine and phosphatidylethanolamine. The various lipid cases differ in their fatty acid composition: neutral lipids contain high proportions of palmitoleic and linoleic acids; phosphatidylcholine is characterized by its contents in palmitic acid, whereas cardiolipin contains polyunsaturated fatty acids. Thermal acclimation of toads for 96 h produces but few changes in liver lipid composition.

Acclimatization↗
PubMed1978

Acclimation of young calves to high temperatures: composition of blood and skin secretions.

Total nitrogen and sodium and potassium contents of blood serum and of skin secretions were measured in four 2- to 3-month-old male Bos taurus calves subjected to a 2-week acclimation process in a climatic chamber at 40.5 C, 50% relative humidity, 12 hours each day. Secretions from the skin were absorbed in filter papers that were the used for analysis of sodium, potassium, and total nitrogen. Significant change in serum sodium, potassium, or nitrogen was not observed. A significant (P less than 0.01) rise in the nitrogen content of skin secretions was observed on the 1st day of exposure and continued throughout the entire exposure period. Similarly, there was a significant (P less than 0.01) increase in the content of sodium and potassium in skin secretions. The secretions contained about 2 times more potassium than sodium.

Acclimatization↗
PubMed1978

Comparison of the toxicity of some metals and their tetracyanide complexes on the respiration of non acclimated activated sludges.

The toxic effect of the metal ions of cadmium, zinc, nickel and mercury and their tetracyanide salt complexes, on the activated sludge not previously acclimated, has been studied. The evaluation of the effect was carried out using both the Warburg and TTC-method. The results obtained have shown that the toxicity of the cadmium and zinc complexes is higher than that of the corresponding metals, while the toxicity of Ni(CN)4(2-) is lower than that of the corresponding metals. No differences have been found between the effect of mercury and the corresponding tetracyanide complex. From the data obtained it appears that it is not possible to generalize about the biological effect of complexation with the CN- group, but it should be stated that, generally, there are substantial differences between metals and their cyanide complexes as far as toxicity for activated sludge is concerned.

Cadmium↗
PubMed1994

[Regulatory mechanism of non-shivering thermogenesis in cold acclimation--with special reference to in vitro thermogenic activity and lipolysis of brown adipose tissue].

In vitro brown adipose tissue (BAT) thermogenesis from cold-acclimated (CA) rats has been shown to exhibit the decreased responses to noradrenaline (NA) and glucagon (G), although an enhanced biochemical machinery for thermogenesis develops in the tissue. The present study was undertaken to clarify the inhibitory mechanism of in vitro thermogenic responses of BAT in CA rats. NA-treated rats were injected NA (40 micrograms/100g BW) twice a day for 2 or 4 weeks. The other rats were kept at 25 +/- 1 degree C (warm controls: WC), 5 +/- 1 degree C (CA), or 5 +/- 1 degree C/6h/day (intermittent cold exposure: ICE) for 5-6 weeks. The oxygen consumption, and glycerol as well as free fatty acids (FFA) release were measured on finely minced tissue blocks in Krebs-Ringer phosphate buffer at 37 degrees C. In vitro BAT thermogenic responses to NA and G in NA-treated rats did not differ from those in vehicle-injected controls. NA as well as G increased-oxygen consumption was greatest in WC, followed by ICE and CA. NA as well as G increased glycerol and FFA releases in WC and ICE, but the degree of increment was greater in WC than that in ICE, while NA or G did not increase glycerol and FFA releases in CA. FFA/glycerol ratio in WC was decreased by NA as well as G, but it was not changed in ICE, and increased in CA. Mitochondrial GDP binding as an index of BAT thermogenic capacity did not differ between CA and WC under resting state (CA rats were transferred in warm condition before 18h at the beginning of the experiment), but it was significantly greater in ICE. GDP binding was significantly greater in CA sacrificed at 5 degrees C compared with WC and CA resting. Acute cold exposure (5 degrees C/1h) enhanced GDP binding in WC, resting CA and ICE resting, but the degree of increment was greater in CA and ICE than in WC. These findings suggest that cold exposure inhibits BAT thermogenic responses according to the duration NA action during cold exposure, by means of suppressing fatty acid utilization and/or masking uncoupling protein.

Acclimatization↗
PubMed1993

Changes in body fluid compartments during hypohydration and rehydration in heat-acclimated tropical subjects.

Body fluid compartments at different levels of graded hypohydration and partial rehydration were determined using radiotracers in 28 heat-acclimated, male volunteers from tropical regions of India, in hot dry conditions in a climatic chamber. These subjects were hypohydrated to varying degrees (i.e., 1%, 2%, 3%, and 4% body mass deficit) by moderate work in hot conditions in a climatic chamber maintained at 45 degrees C dry bulb temperature and 30% relative humidity. Rehydration study was carried out only in those subjects who were hypohydrated to 3% and 4% body mass and who were brought back to 2% level of hypohydration by receiving a calculated amount of water. Up to the 2% level of hypohydration, a major contribution towards sweat loss was observed from the interstitial fluid (ISF) compartment. At higher levels of hypohydration, no further significant loss from ISF was seen, though significant losses in intracellular fluid (ICF) and plasma volume (PV) were apparent. The present study also found that at the 4% hypohydration level, a maximum fluid contribution was met by the ICF compartment. Significant increases observed in sweat K+ at 3 and 4% also indicate the ICF mobilization, which is rich in K+ ions. On partial rehydration, the ISF compartment held the repletion fluid in excess, and was found to be enough to restore sweat rate to euhydration level. This study clearly indicates that sudorific gain is achieved with partial restoration alone in subjects hypohydrated to 3 and 4% levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1995

Growth and photosynthetic activities of acclimated cyanobacteria in sewage effluents.

Various types of cyanobacteria were isolated from sewage of Kuwait. The growth and photosynthesis of these acclimated cyanobacteria on sterilized sewage effluents were studied. Primary treated effluent was found to support the growth of the cyanobacteria more than treated effluent. This indicated the possible tolerance of such cyanobacteria to more organic pollution in comparison with unacclimated cyanobacteria. The results explain in part the possible hazards of dumping sewage effluents into the sea or the possible uses of such cyanobacteria in mass culture as an animal food.

Acclimatization↗
PubMed1996

Physiological responses in nonheat acclimated horses performing treadmill exercise in cool (20 degrees C/40% RH), hot dry (30 degrees C/40% RH) and hot humid (30 degrees C/80% RH) conditions.

The aim of the present study was to determine the effect of different environmental conditions on physiological response to exercise. Four winter acclimatised, nonheat acclimated horses of different breeds were exercised at 20 degrees C/40% RH (CD), 30 degrees C/40% RH (HD) and 30 degrees C/80% RH (HH). The exercise test was designed to represent the structure and intensity of a One star Speed and Endurance test (competition exercise test [CET]). All 4 horses were able to complete the full CET (60 min + 30 min active recovery) in CD and HD, but only one horse completed the CET in HH. Two horses were stopped because of pronounced general fatigue and one because of a right atrial temperature (TRA) of 43 degrees C. Oxygen uptake on each phase was not different between CD and HD, but was higher during Phases B, C and D in HH. Mean peak TRA at the end of Phase D was 40.3 +/- 0.2, 41.6 +/- 0.4 and 42 +/- 0.3 degrees C for CD, HD and HH, respectively. Corresponding, mean peak rectal temperatures (TREC) following Phase D were 39.5 +/- 0.1, 40.6 +/- 0.1 and 41.5 +/- 0.1 degree C for CD, HD and HH, respectively. Mean time to peak TREC was 9.3 +/- 1.1 (CD), 7.3 +/- 1.8 (HD) and 10.8 +/- 2.3 (HH) min and was not significantly different between conditions (P > 0.05). Heat dissipation amounted to 83 +/- 1, 73 +/- 2 and 70 +/- 1% of heat production in CD, HD and HH, respectively. Weight loss was significantly correlated with both body surface area (CD r = 0.85; HD r = 0.87; HH r = 0.81) and bodyweight (CD r = 0.97; HD r = 0.93; HH r = 0.94). The greatest weight loss recorded was 4.6% bodyweight in one horse in HD. The mean increase in exercise intensity over the whole CET (in terms of VO2) of HD and HH and HH compared with CD was 5 +/- 3 and 14 +/- 3% higher, respectively. The exercise induced hyperthermia and the reduced capacity for heat dissipation produced partial compensatory responses in minute ventilation (VE), particularly during Phase C, when the horses were trotting. In HD, the increase in VE was achieved mainly through an increase in frequency, whilst in HH it was achieved through an increase in tidal volume (VT). The horses demonstrated a high degree of tolerance to environmental heat load, suggesting a high thermoregulatory capacity. However, for unacclimatised animals exercising in severely hot and humid conditions, performance may be limited.

Acclimatization↗
PubMedDate not supplied

[Effect of temperature acclimation on glucose-6-phosphate dehydrogenase activity in various tissues of the Mullus barbatus ponticus].

Acclimation of the Mullus barbatus ponticus to the temperature fall (from 16 to 8 degrees C) induces an increase in the activity of glucose-6-phosphate dehydrogenase both in summer and in autumn. These changes are more expressed in the liver and red muscle than in the white ones. The values of Km of glucose-6-phosphate (only in autumn) and NADP are also higher at 8 than at 16 degrees C. Actinomycin D does not prevent from cold activation of this enzyme in liver only in autumn, when the activity of glucose-6-phosphate dehydrogenase is 8-10 times higher than in summer, and in the red muscle in the both seasons, although this injection decreases the level of enzyme activity in this muscle. This injection does not change the values of Km for glucose-6-phosphate and NADP. It is supposed that the activation of glucose-6-phosphate dehydrogenase in the liver and red muscle during cold adaptation may be a result of change of substrate-binding ability and enzyme interaction with NADP without changes in the enzyme biosynthesis.

Acclimatization↗
PubMed1979

HCO3-stimulated Cl efflux in the gulf toadfish acclimated to sea water.

Unidirectional efflux of Cl was examined in the Gulf toadfish, Opsanus beta, in artificial seawater solutions with modified concentrations of Cl and HCO3. Removal of Cl HCO3 reduced Cl efflux. Addition of HCO3 at typical seawater concentrations stimulated Cl efflux, independent of changes in the transepithelial potential. This active, HCO3-stimulated Cl efflux is saturable, with a Km of 2.4 mM, typical of the concentration of HCO3 found in sea water, and independent of external pH. Active extrusion of Cl offsets the net diffusional and oral gain of Cl faced by O. beta in sea water.

Animals↗
PubMed1982

The relation of Na and Cl extrusion in Opsanus beta, the Gulf toadfish, acclimated to seawater.

A model has been proposed by Silva et al. ('77) to describe the manner by which Cl extrusion occurs across the gills of the eel and seawater fish in general. Aspects of the model include (1) passive distribution of Na across the gill surface, and (2) Cl extrusion dependent on Na-K-ATPase and thus dependent on the transport of Na. In order to test various aspects of this model, we examined, using the appropriate radiotracers, the relationship of Na and Cl efflux in the gulf toadfish, Opsanus beta. The model of Silva et al. does not apply to the toadfish because (1) Na cannot be passively distributed across the gills of the toadfish, because the transepithelial potential is several millivolts negative with respect to seawater, and (2) Cl efflux (unlike Na efflux) is not dependent on external K. Additionally, Cl efflux is dependent on the seawater Na concentration, and both Na and Cl efflux are dependent on seawater HCO3. Thus Na and Cl efflux appear to be linked in the toadfish, but not as proposed in the model suggested by Silva et al.

Adaptation, Physiological↗
PubMed1992

The expression of a rab-related gene, rab18, is induced by abscisic acid during the cold acclimation process of Arabidopsis thaliana (L.) Heynh.

We have isolated a rab-related (responsive to ABA) gene, rab18 from Arabidopsis thaliana. The gene encodes a hydrophilic, glycine-rich protein (18.5 kDa), which contains the conserved serine- and lysine-rich domains characteristic of similar RAB proteins in other plant species. The rab18 mRNA accumulates in plants exposed to low temperature, water stress or exogenous ABA but not in plants subjected to heat shock. This stress-related accumulation of the rab18 mRNA is markedly decreased in the ABA-synthesis mutant aba-1, the ABA-response mutant abi-1 or in wild-type plants treated with the carotenoid synthesis inhibitor, fluridone. Exogenous ABA treatment can induce the rab18 mRNA in the aba-1 mutant but not in the abi-1 mutant. These results provide direct genetic evidence for the ABA-dependent regulation of the rab18 gene in A. thaliana.

Abscisic Acid↗
PubMed1994

Characterization and differential expression of dhn/lea/rab-like genes during cold acclimation and drought stress in Arabidopsis thaliana.

We have characterized cDNAs for two new dhn/lea/rab (dehydrin, late embryogenesis-abundant, responsive to ABA)-related genes from Arabidopsis thaliana. The two genes were strongly induced in plants exposed to low temperature (4 degrees C) and were accordingly designated lti45 and lti30 (low temperature-induced). The lti45 gene product contains the conserved serine stretch and three lysine-rich repeats characteristic of DHN/LEA/RAB proteins and is very similar to another low temperature-responsive protein of A. thaliana, COR47 [17]. Both proteins have the same repeat structure and an overall amino acid identity of 64%. This structural similarity of the proteins and the tandem array of the genes suggest that this gene pair arose through a duplication. The other polypeptide, LTI30, consists of several lysine-rich repeats, a structure found in CAP85, a low temperature- and water stress-responsive protein in spinach [41] and similar proteins found in wheat [20]. The expression pattern of the five dhn/lea/rab-related genes (cor47, dhnX, lti30, lti45 and rab18) identified so far in A. thaliana, was characterized in plants exposed to low temperature, drought and abscisic acid (ABA). Expression of both lti30 and lti45 was mainly responsive to low temperature similar to cor47. The lti45 and lti30 genes show only a weak response to ABA in contrast to cor47, which is moderately induced by this hormone. The three genes were also induced in severely water-stressed plants although the expression of lti30 and lti45 was rather low. In contrast to these mainly low temperature-induced genes, the expression of rab18 was strongly induced both in water-stressed and ABA-treated plants but was only slightly responsive to cold. The dhnX gene showed a very different expression pattern. It was not induced with any of the treatments tested but exhibited a significant constitutive expression. The low-temperature induction of the genes in the first group, lti30 and lti45, is ABA-independent, deduced from experiments with the ABA-deficient (aba-1) and ABA-insensitive (abil) mutants of A. thaliana, whereas the induction of rab18 is ABA-mediated. The expression of dhnX was not significantly affected in the ABA mutants.

Abscisic Acid↗