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PubMed1978

Polyamine and magnesium effects on mitochondrial respiration in control and heat-acclimated rats.

Studies were made of polyamine and Mg++ effects on rat liver mitochondrial alpha ketoglutarate oxidase (alphaKGO) and succinoxidase (SO). High spermidine levels suppress S3 and S4 of alphaKGO at 0.6-1.17 mM Mg++: some combinations of it and Mg++ increase the respiratory control ratio (RCR). Spermine suppresses S4 of alphaKGO and increases the RCR but suppresses the RCR of SO at high levels. In heat-acclimated (HA) animals in which we have studied only spermine effects on alphaKGO, RCRs of HA rats are greatly increased compared to those of controls.

Acclimatization↗
PubMed1978

Effects of diets and cold acclimation on lipoprotein lipase activity and cyclic nucleotide levels in some tissues of rats.

In view to study a possible regulation of lipoprotein lipase (LPL) activity by tissue cyclic nucleotide levels (cAMP and cGMP), parallel determinations of the three factors were performed on brown adipose tissue (BAT), epidymal fat (WAT) and heart of rats. Opposite variations of cAMP levels and LPL activity were only observed in WAT following high fat diet administration. The enhancement of LPL activity in BAT and in heart by cold acclimation or feeding an hyperlipidic diet was never associated with a decrease in cAMP content. The variations of cAMP and cGMP levels were not dependent. It is concluded that there is no effect of cyclic nucleotide levels in the enhancement of LPL activity in these tissues.

Acclimatization↗
PubMed1995

Acclimation of Arabidopsis thaliana to the light environment: changes in photosynthetic function.

Arabidopsis thaliana (L.) Heynh. cv. Landsberg erecta was grown under light regimes of differing spectral qualities, which results in differences in the stoichiometries of the two photosynthetic reaction centres. The acclimative value of these changes was investigated by assessing photosynthetic function in these plants when exposed to two spectrally distinct actinic lights. Plants grown in an environment enriched in far-red light were better able to make efficient use of non-saturating levels of actinic light enriched in long-wavelength red light. Simultaneous measurements of chlorophyll fluorescence and absorption changes at 820 nm indicated that differences between plants grown under alternative light regimes can be ascribed to imbalances in excitation of photosystems I and II (PSI, PSII). Measurements of chlorophyll fluorescence emission and excitation spectra at 77 K provided strong evidence that there was little or no difference in the composition or function of PSI or PSII between the two sets of plants, implying that changes in photosynthetic stoichiometry are primarily responsible for the observed differences in photosynthetic function.

Adaptation, Physiological↗
PubMed1994

Long photophase is not a sufficient stimulus to reduce thermogenic capacity in winter-acclimatized short-tailed field voles (Microtus agrestis) during long-term cold acclimation.

The thermogenic capacity of brown adipose tissue in winter- and summer-acclimatized short-tailed field voles (Microtus agrestis) was investigated by examining changes in mass of brown adipose tissue, the ratio of white adipose tissue to brown adipose tissue, the concentration of the uncoupling protein (thermogenin) in whole depots (micrograms) and in mitochondrial mass (micrograms.mg-1) and the activity of cytochrome c oxidase in the depots (mmol.min-1). The concentration of thermogenin in winter-acclimatized voles (n = 8), per brown adipose tissue depot and per mitochondrial mass, was significantly higher than in summer-acclimatized voles (n = 6). There was no significant difference in the level of cytochrome c oxidase activity between these two groups. Four groups of winter-acclimatized voles (n = 6 in each group) were exposed to 5 degrees C for 10, 20, 50 and 100 days in a 14L:10D photoperiod. Body mass, brown adipose tissue mass, white adipose tissue mass and basal metabolic rate were significantly positively related to the length of time cold exposed up to 100 days. There was a significant inverse relationship between the ratio of white to brown adipose tissue mass and the duration of cold exposure. There was no significant relationship between thermogenin concentration, either per depot or in mitochondrial mass of brown adipose tissue, with the length of time cold exposed. The level of cytochrome c oxidase activity increased significantly from control levels to a maximum after 10 days in the cold but decreased from 10 days onwards. In winter-acclimatized M. agrestis, a 14L:10D photoperiod is not a sufficient stimulus to reduce thermogenic capacity during cold acclimation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1989

Freeze/thaw-induced destabilization of the plasma membrane and the effects of cold acclimation.

Disruption of the plasma membrane is a primary cause of freezing injury. In this review, the mechanisms of injury resulting from freeze-induced cell dehydration are presented, including destabilization of the plasma membrane resulting from (a) freeze/thaw-induced osmotic excursions and (b) lyotropic phase transitions in the plasma membrane lipids. Cold acclimation dramatically alters the behavior of the plasma membrane during a freeze/thaw cycle--increasing the tolerance to osmotic excursions and decreasing the propensity for dehydration-induced lamellar to hexagonal-II phase transitions. Evidence for a casual relationship between the increased cryostability of the plasma membrane and alterations in the lipid composition is reviewed.

Cell Membrane↗
PubMed1991

Alterations of GABA metabolism and seizure susceptibility in the substantia nigra of the kindled rat acclimating to changes in osmotic state.

Seizure susceptibility and GABA metabolism were altered in the substantia nigra [SN] of adult male Sprague Dawley rats when these animals were acclimating to an altered plasma osmolality. Changes in GABA metabolism were measured in vivo in SN of the freely moving rat. Suitable precautions were taken to avoid any post-mortem flux of glutamate to GABA and to correct for the underestimation of GABA build up in SN due to the finite diffusion rate of gamma-vinyl GABA [GVG] after stereotaxic injection of small amounts into one side of the brain. Control experiments provided evidence that changes in osmolality, within a normal physiological range, did not affect significantly gamma-aminobutyric acid transaminase [GABA-T]. Also kindling via the medial septum [MS], in the absence of electrical stimulation did not alter GABA metabolism in SN, thus providing a stable baseline for studies of osmotic effects. Hyperosmolality was associated with a rise in seizure thresholds, with a marked reduction of the rate of GABA synthesis in SN, and with a substantial increase in turnover time of the GABA pool. Hypoosmolality, of a degree known to be associated with mild cerebral edema and swelling localized to astrocytes, markedly reduced seizure threshold, and reduced GABA pool size in SN, but did not alter the rate of GABA synthesis significantly. These results demonstrate by new and independent means the relationship between GABA metabolism in the SN and seizure susceptibility in vivo.

4-Aminobutyrate Transaminase↗
PubMed1983

Adaptive changes in the concentration of the mitochondrial 'uncoupling' protein in brown adipose tissue of hamsters acclimated at different temperatures.

The effect of acclimation at different temperatures on the activity of interscapular brown adipose tissue has been investigated in the hamster, a hibernator. Between 31 degrees and 4 degrees C the cytochrome oxidase activity of the tissue increased 4- to 5-fold, mitochondrial GDP binding per mg of mitochondrial protein doubled, and the amount of uncoupling protein rose from 1.7% to 5.4% of total mitochondrial protein. It is concluded that there are clear adaptive changes induced by temperature in brown adipose tissue of the hamster, but the changes are limited in comparison with those in the mouse.

Acclimatization↗
PubMed1983

Measurement of rat brown-adipose-tissue mitochondrial uncoupling protein by radioimmunoassay: increased concentration after cold acclimation.

A specific antiserum has been raised against the 32 000-mol.wt. uncoupling protein from the mitochondria of rat brown adipose tissue and a sensitive radioimmunoassay for the protein has been developed. The uncoupling protein is present in large amounts in brown adipose tissue; its concentration is increased substantially by cold acclimation. The protein has not been detected in the liver, heart, or parametrial white adipose tissue of rats.

Adaptation, Physiological↗
PubMed1986

Hypophysectomy and the sympatho-adrenal system in cold acclimation.

Hypophysectomy does not impair the increase in weight of brown adipose tissue and adrenals following cold acclimation of the rat. In brown fat, the cold-induced increases in NE and 5 HT contents are not modified by hypophysectomy. In adrenals, hypophysectomy does not change the NE content, but a fall in epinephrine content was observed.

Acclimatization↗
PubMed1996

Hypothermic general cold adaptation induced by local cold acclimation.

To study relationships between local cold adaptation of the lower limbs and general cold adaptation, eight subjects were submitted both to a cold foot test (CFT, 5 degrees C water immersion, 5 min) and to a whole-body standard cold air test (SCAT, 1 degree C, 2 h, nude at rest) before and after a local cold acclimation (LCA) of the lower limbs effected by repeated cold water immersions. The LCA induced a local cold adaptation confirmed by higher skin temperatures of the lower limbs during CFT and a hypothermic insulative general cold adaptation (decreased rectal temperature and mean skin temperature P < 0.05) without a change either in metabolic heat production or in lower limb skin temperatures during SCAT after LCA. It was concluded that local cold adaptation was related to the habituation process confirmed by decreased plasma concentrations of noradrenaline (NA) during LCA (P < 0.05). However, the hypothermic insulative general cold adaptation was unrelated either to local cold adaptation or to the habituation process, because an increased NA during SCAT after LCA (P < 0.05) was observed but was rather related to a "T3 polar syndrome" occurring during LCA.

Acclimatization↗
PubMedDate not supplied

Reciprocal effects of an acute load of thyroxine or triiodothyronine on their peripheral metabolism and deiodination in the cold-acclimated rat.

Wistar rats acclimated to cold received iv 25 micrograms T 4/100 g bw, 21 micrograms T 3/100 g bw or 2.5 micrograms T 3/100 g bw, to observe the changes induced in the peripheral metabolism of 125I-T4 and 125I-T3 relative to cold-adapted untreated animals. Each animal was injected with a tracer dose of either labelled hormone in addition to the T4 or T3 load, and placed in metabolic cages for 24 hour collection of urine and feces. Sequential heparinized blood samples were obtained by cardiac puncture. A T4 load decreased the deiodination of 125I-T4 and 125I-T3 (p less than 0.01) as revelated by urinary 125I. A T3 load, in the two dosages employed, decreased the deiodination of 125I-T3 (p less than 0.01) but had no effect on deiodination of 125I-T4. Similarly, a T4 load increased the fecal excretion of both radioactive iodothyronines (p less than 0.01) whereas a T3 load failed to alter the excretion of 125I-T4. In cold-adapted animals plasma TSH was elevated (p less than 0.05) and plasma T4 was low (p less than 0.001) as compared to rats housed at 22 C. It is concluded that the relative contribution of T4 and T3 to the metabolic state in the rat is not significantly altered by cold exposure.

Acclimatization↗
PubMed2004

Metabolite production during transformation of 2,4,6-trinitrotoluene (TNT) by a mixed culture acclimated and maintained on crude oil-containing media.

Metabolites formed during 2,4,6-trinitrotoluene (TNT) removal by a mixed bacterial culture (acclimated and maintained on crude oil-containing medium and capable of high rates of TNT removal) were characterized. In resting cell experiments in the absence of glucose, 46.2 mg/l TNT were removed in 171 h (87.5% removal), with a combined total formation of 7.7 mg/l amino-4,6-dinitrotoluene (ADNT) and 0.3 mg/l 4,4'-azoxytetranitrotoluene and 2',4-azoxytetranitrotoluene, leaving 70% of the initial TNT unaccounted for. In the presence of glucose, resting cells removed 45.4 mg/l TNT in 49 h (95.5% removal), with 9.1 mg/l ADNT and 2.4 mg/l azoxy compounds being produced, leaving 70.3% of the TNT unaccounted for. Growing cells (glucose present) were capable of removing 44.2 mg/l TNT within 21 h (97.9% removal), with the concomitant formation of 1.8 mg/l ADNTs and 2.2 mg/l azoxy compounds. Denitrated TNT in the form of 2,6-dinitrotoluene was also produced in growing cells with a maximum amount of 1.31 mg/l after 28 h, followed by a slight decrease with time, leaving 88.5% of the initial TNT unaccounted for after 171 h. Radiolabeled (14)C-TNT studies revealed 4.14% mineralization after an incubation period of 163 days with growing cells.

Aniline Compounds↗
PubMed2005

Evaluation of procedures to acclimate a microbial fuel cell for electricity production.

A microbial fuel cell (MFC) is a relatively new type of fixed film bioreactor for wastewater treatment, and the most effective methods for inoculation are not well understood. Various techniques to enrich electrochemically active bacteria on an electrode were therefore studied using anaerobic sewage sludge in a two-chambered MFC. With a porous carbon paper anode electrode, 8 mW/m2 of power was generated within 50 h with a Coulombic efficiency (CE) of 40%. When an iron oxide-coated electrode was used, the power and the CE reached 30 mW/m2 and 80%, respectively. A methanogen inhibitor (2-bromoethanesulfonate) increased the CE to 70%. Bacteria in sludge were enriched by serial transfer using a ferric iron medium, but when this enrichment was used in a MFC the power was lower (2 mW/m2) than that obtained with the original inoculum. By applying biofilm scraped from the anode of a working MFC to a new anode electrode, the maximum power was increased to 40 mW/m2. When a second anode was introduced into an operating MFC the acclimation time was not reduced and the total power did not increase. These results suggest that these active inoculating techniques could increase the effectiveness of enrichment, and that start up is most successful when the biofilm is harvested from the anode of an existing MFC and applied to the new anode.

Alkanesulfonic Acids↗
PubMed2005

Differential expression of manganese superoxide dismutase sequence variants in near isogenic lines of wheat during cold acclimation.

Numerous sequence variants of wheat (Triticum aestivum L.) manganese superoxide dismutase (MnSOD) genes have been found. Quantitative real-time PCR was used to measure the expression levels of three MnSOD genes distinguished by a variable amino acid, and three genes distinguished by sequence variation in the 3' untranslated region (3' UTR), in wheat plants grown at 20 degrees C and cold-acclimated for 1-4 weeks at 2 degrees C. The amino acid variants did not differ significantly in expression levels, however, differential expression of genes differing in the 3' UTR was observed. Diploid wheat-related species also carried sequence variants of MnSOD, with differing levels of expression, suggesting diversification of the MnSOD gene family occurred prior to the polyploidization events of hexaploid wheat.

3' Untranslated Regions↗
PubMed1999

Natriuretic peptides and the acclimation of aglomerular toadfish to hypo-osmotic media.

Since the aglomerular toadfish (Opsanus tau) experiences a natriuresis following transfer to 10% seawater, we examined the role of natriuretic peptides in the acclimation of toadfish to hypo-osmotic media. Gel filtration chromatography of acid extracts of toadfish heart and kidney identified a broad peak of atrial natriuretic peptide-like immunoreactivity in both tissues, with maximal immunoreactivity in fractions coeluting with human alpha-atrial natriuretic peptide. Using a homologous bioassay to measure changes in aortic ring tension, both vasorelaxing and, surprisingly, vasoconstricting bioactivities were identified in gel fractions of heart extract. No significant vasorelaxing activity was identified in kidney extract or fractions. Instead, a potent vasoconstricting activity was observed, with maximal activity in gel fractions with an estimated MW greater than 1000 Da. Levels of atrial natriuretic peptide immunoreactivity in plasma from the caudal vein were very low in seawater toadfish and were unchanged 12 h after transfer of toadfish to 10% seawater. We conclude, that natriuretic peptides are present in the heart and kidney of toadfish. However, atrial natriuretic peptide-like peptides of cardiac origin circulating to the kidney via the caudal vein do not appear responsible for the natriuresis that ensues upon the transfer of toadfish to 10% seawater. In the absence of glomeruli, this tubular natriuresis may be regulated by natriuretic peptides present in the kidney.

Angiotensin II↗
PubMed2005

Decay of heat acclimation during exercise in cold and exposure to cold environment.

Sixteen male students exercised for 14 days (1 h/day) in the heat for heat acclimation (HA). During deacclimation (DA) one group exercised in the cold (EXG, n=8) for 60 min/day (morning) and was exposed to the cold for another hour (afternoon) for 14 days. The other group was exposed to the cold (EPG, n=8) for 1 h each in the morning and afternoon (Ta: 18.0 degrees C, RH: 58%) over the same period. All returned to exercise in the heat for reacclimation (RA) for 10 days. Subjects were tested on days 1, 16, 21, 32, 36 and 44 on a bicycle ergometer for 60 min at 60% of VO(2max) in the heat (Ta: 31.1 degrees C, RH: 70%). Rectal temperature (T (re)) and heart rate (HR) at 40 min of exercise were used to determine the decay/gain of HA, which was calculated using the formula described by Pandolf et al. (Ergonomics, 20:399-408, 1977). After HA (day 16) T (re) and HR decreased significantly. During DA, EXG showed decay in T (re) of 24 and 35% and HR of 29 and 35% on days 21 and 32, respectively. For EPG the corresponding decay was of 2 and 9% for T (re) and 17 and 17% for HR. After 10 days of RA, EXG showed gains of 11% in T (re) and 12% in HR, while EPG showed gains of 47% in T (re) and 38% in HR. In conclusion, EXG had greater decay during DA and lower gains in RA compared to EPG. However, the differences between groups were significant only for T (re) after 4 days of DA.

Acclimatization↗