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At least 19 recordsLinked to original sources

PubMed1992

Effect of inhaled methanol on pituitary and testicular hormones in chamber acclimated and non-acclimated rats.

Two experiments were conducted in which the acute effects of inhaled methanol on serum hormones associated with reproductive function in the male rat were evaluated. In the first experiment, rats exposed to methanol (0, 200, 5000 and 10,000 ppm) for 6 h were killed at the end of the exposure period (6 h) or the following morning (24 h). Also, because the process of exposure itself could modify neuroendocrine function, the effect of the handling associated with placing the rat in the exposure chamber was evaluated further by dividing the exposed animals into acclimated (2 weeks of prior handling) and non-acclimated groups. At 6 h, an effect of prior handling was noted in the sham-exposed rats, with serum luteinizing hormone (LH) of the non-acclimated group being greater than that of the acclimated group. Serum LH concentrations were altered by methanol exposure, but the direction of change and the exposure level at which an effect was noted differed between the acclimated and non-acclimated rats. Methanol (5000 ppm) reduced serum LH in the non-acclimated animals, while 10,000 ppm increased LH in the acclimated rats. Follicle stimulating hormone (FSH) and testosterone were unchanged by methanol in rats killed at 6 h. Thus, this experiment did not confirm earlier reports that exposure to 200 ppm for 6 h reduced serum testosterone. At 24 h, an effect of prior handling was still present in the hormonal measures, with serum and interstitial fluid testosterone concentrations being greater in the non-acclimated rats. Also, there was a dose x handling interaction with methanol exposure inducing an increase in serum testosterone in the non-acclimated rats (up to 5000 ppm) and a decrease in the acclimated rats (up to 10,000 ppm). In the second experiment, groups of acclimated and non-acclimated rats were exposed to 0 or 5000 ppm methanol for 1, 2 and 6 h and killed immediately after removal from the chamber. Serum LH, testosterone and FSH values were not different in sham- vs methanol-exposed rats at any time point. As in experiment 1, an effect of prior handling was noted. In general, the concentrations of these hormones and serum prolactin in the non-acclimated rats were greater than those observed for acclimated rats. Methanol exposure resulted in increased prolactin concentrations under both handling conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Acclimatization↗

PubMed2003

Plasma clearance of cadmium and zinc in non-acclimated and metal-acclimated trout.

Adult rainbow trout were pre-exposed to a sublethal concentration of waterborne cadmium (Cd, 26.7 nmol/l) or waterborne zinc (Zn, 2294 nmol/l) for 30 days to induce acclimation. A single dose of radiolabeled Cd (64.4 nmol/kg) or Zn (183.8 nmol/kg) was injected into the vascular system of non-acclimated and Cd- or Zn-acclimated trout through indwelling arterial catheters. Subsequently, repetitive blood samples over 10 h and terminal tissue samples (liver, heart, bile, stomach, intestine, kidney, gills, muscle, and spleen) were taken to characterize the effect of metal acclimation on clearance kinetics in vivo. Plasma clearance of Cd in Cd-acclimated fish (0.726+/-0.015 and 0.477+/-0.012 ml/min per kg for total and newly accumulated Cd, respectively), was faster than that in non-acclimated trout (0.493+/-0.013 and 0.394+/-0.009 ml/min per kg). Unlike plasma Cd, the levels of Cd in red blood cells (RBCs) were 1.2-2.2 times higher in Cd-acclimated fish than in non-acclimated fish. At 10 h post-injection, the liver accumulated the highest proportion ( approximately 22%) of the injected Cd dose in both non-acclimated and Cd-acclimated fish but did not account for the difference in plasma levels of Cd between two groups. Plasma clearance of Zn ( approximately 0.23 ml/min per kg for new Zn) was substantially lower than Cd clearance. Pre-acclimation to waterborne Zn reduced the new Zn levels in RBCs, but did not affect the clearance of Zn from blood plasma or tissue burdens of Zn in fish. Bile concentrations of both Cd and Zn were elevated in acclimated fish, but total bile burden accounted for <1% of the injected metal dose. The results suggest that the detoxification process of injected plasma Cd is stimulated by pre-acclimation to waterborne Cd, and that Zn levels are homeostatically controlled in both non-acclimated and acclimated trout.

Adaptation, Physiological↗

PubMed2002

Regulation of frost resistance during cold de-acclimation and re-acclimation in oilseed rape. A possible role of PSII redox state.

A possible role of photosynthetic apparatus during cold de-acclimation was studied in oilseed rape (Brassica napus var. oleifera). Plants of spring (Star) and winter (Górczañski) cultivars were cold acclimated at + 5 degrees C, and de-acclimated during 4 weeks at combinations of + 12 and + 20 degrees C operating in the light or/and dark, with a 12-h photoperiod. Evidence is presented that the photosynthetic apparatus may be involved in temperature perception during de-acclimation. De-acclimation was faster under a 20/12 degrees C (day/night) treatment than under the reverse 12/20 degrees C (day/night). De-acclimation rate was constant when the day temperature was constant, irrespective of the night temperature both under cold day temperature regimes (12/20, 12/12 degrees C (day/night) and warm-day treatments (20/12, 20/20 degrees C (day/night). The fast decrease in frost resistance observed under warm-day de-acclimation was always accompanied by an acceleration of elongation growth. In the spring cultivar, elongation growth increased starting from the second week of de-acclimation, regardless of temperature conditions. Once elongation growth had commenced during de-acclimation, it continued throughout the period necessary for re-acclimation to low temperature. Re-acclimation to the initial freezing tolerance level was only possible when plant elongation was reduced. In addition re-acclimation of the photosynthetic apparatus to low temperature was impossible in fast growing plants. A possible relationship between PSII, growth rate and frost resistance during cold acclimation and de-acclimation is discussed.

Journal Article↗

PubMed1994

Temperature acclimation and competitive fitness: an experimental test of the beneficial acclimation assumption.

Phenotypic acclimation is generally assumed to confer an advantage in the environment that stimulates the response. To test this beneficial acclimation assumption explicitly, we investigated the consequences of temperature acclimation for the fitness of Escherichia coli at two temperatures, 32 degrees C and 41.5 degrees C. Both temperatures permit growth and long-term persistence of the genotypes in serial culture. We found that prior acclimation to 32 degrees C, relative to acclimation to 41.5 degrees C, enhanced fitness at 32 degrees C, consistent with the assumption. But prior acclimation to 41.5 degrees C actually reduced fitness at 41.5 degrees C, relative to acclimation to 32 degrees C. Hence, the assumption that acclimation always confers an advantage is demonstrated to be false. Acclimation to 41.5 degrees C did, however, improve survival at 50 degrees C, a lethal temperature. This protective response has been shown to be associated with the induction of stress proteins. The reduced competitive fitness caused by acclimation at 41.5 degrees C may reflect a physiological burden associated with expression of stress proteins when they are not needed to prevent lethal damage. Whatever the cause, acclimation to the higher temperature decreased competitive fitness at that temperature.

Acclimatization↗

PubMed1999

Heterothermal acclimation: an experimental paradigm for studying the control of thermal acclimation in crabs.

A method for the study of the control of the attainment of thermal acclimation has been applied to the crabs, Cancer pagurus and Carcinus maenas. Crabs were heterothermally acclimated by using an anterior-posterior partition between two compartments, one at 8 degrees C and the other at 22 degrees C. One compartment held a three-quarter section of the crab including the central nervous system (CNS), eye stalks, and ipsilateral legs; the other held a quarter section including the contralateral legs. Criteria used to assess the acclimation responses were comparisons of muscle plasma membrane fatty acid composition and "fluidity." In both species, the major fatty acids of phosphatidylcholine were 16:0, 18:1, 20:5, and 22:6, whereas phosphatidylethanolamine contained significantly less 16:0 but more 18:0; these fatty acids comprised 80% of the total. Differences in fatty acid composition were demonstrated between fractions obtained from the ipsilateral and contralateral legs from the same heterothermally acclimated individual. In all acclimation states (except 22CNS, phosphatidylcholine fraction), membrane lipid saturation was significantly increased with acclimation at 22 degrees as compared with 8 degrees C. Membrane fluidity was determined by using 1,3-diphenyl-1,3,5 hexatriene (DPH) fluorescence polarization. In both species, membranes from legs held at 8 degrees were more fluid than from legs held at 22 degrees C irrespective of the acclimation temperature of the CNS. Heterothermal acclimation demonstrated that leg muscle membrane composition and fluidity respond primarily to local temperature and were not predominately under central direction. The responses between 8 degrees C- and 22 degrees C-acclimated legs were more pronounced when the CNS was cold-acclimated, so a central influence cannot be excluded.

Acclimatization↗

PubMed1999

Heterologous acclimation: a novel approach to the study of thermal acclimation in the crab Cancer pagurus.

The control of the attainment of acclimation in Cancer pagurus has been studied. Homologous (8 or 22 degrees C) and heterologous acclimation [central nervous system (CNS) and periphery of crabs simultaneously held at 8 or 22 degrees C] were used. The dependence of electrophysiological parameters of dactylopodite closer muscles of walking legs on nerve stimulation was determined between 6 and 26 degrees C. Muscle resting potential (RP) hyperpolarized linearly with increasing measurement temperatures and showed a 69% compensation between 8 and 22 degrees C on homologous acclimation. With the CNS temperature constant at 8 degrees C, the leg muscle RP showed a 72% compensation on heterologous acclimation to 8 and 22 degrees C; when CNS temperature was constant at 22 degrees C, leg muscle RP showed a 48% compensation on heterologous acclimation to 8 and 22 degrees C. In homologous acclimation, the shape of the excitatory junction potential vs. temperature relationship was characteristic of acclimation temperature. In heterologous acclimation, the shape of this plot was related to the temperature experienced by the leg and not by the CNS. Thus acclimation was principally dependent on local tissue temperature and was relatively independent of CNS or hormonal influences.

Acclimatization↗

PubMed2006

Changes in freezing tolerance, plasma membrane H+-ATPase activity and fatty acid composition in Pinus resinosa needles during cold acclimation and de-acclimation.

It has previously been suggested that plasma membrane ATPase (PM H+-ATPase, EC 3.6.1.3.) is a site of incipient freezing injury because activity increases following cold acclimation and there are published data indicating that activity of PM H+-ATPase is modulated by changes in lipids associated with the enzyme. To test and extend these findings in a tree species, we analyzed PM H+-ATPase activity and the fatty acid (FA) composition of glycerolipids in purified plasma membranes (PMs) prepared by the two-phase partition method from current-year needles of adult red pine (Pinus resinosa Ait.) trees. Freezing tolerance of the needles decreased from -56 degrees C in March to -9 degrees C in May, and increased from -15 degrees C in September to -148 degrees C in January. Specific activity of vanadate-sensitive PM H+-ATPase increased more than two-fold following cold acclimation, despite a concurrent increase in protein concentration. During de-acclimation, decreases in PM H+-ATPase activity and freezing tolerance were accompanied by decreases in the proportions of oleic (18:1) and linoleic (18:2) acids and increases in the proportions of palmitic (16:0) and linolenic (18:3) acids in total glycerolipids extracted from the plasma membrane fraction. This pattern of changes in PM H+-ATPase activity and the 18:1, 18:2 and 18:3 fatty acids was reversed during cold acclimation. In the PM fractions, changes in FA unsaturation, expressed as the double bond index (1 x 18:1 + 2 x 18:2 + 3 x 18:3), were closely correlated with changes in H+-ATPase specific activity (r2 = 0.995). Changes in freezing tolerance were well correlated with DBI (r2 = 0.877) and ATPase specific activity (r2 = 0.833) in the PM fraction. Total ATPase activity in microsomal fractions also closely followed changes in freezing tolerance (r2 = 0.969). We conclude that, as in herbaceous plants, simultaneous seasonal changes in PM H+-ATPase activity and fatty acid composition occur during cold acclimation and de-acclimation in an extremely winter hardy tree species under natural conditions, lending support to the hypothesis that FA-regulated PM H+-ATPase activity is involved in the cellular response underlying cold acclimation and de-acclimation.

Acclimatization↗

PubMed1975

Reduced urinary noradrenaline excretion during rest, exercise and cold stress in trained rats: a comparison between physically-trained rats, cold-acclimated rats and warm-acclimated rats.

Physically trained rats were compared with cold-acclimated rats. Trained as well as cold-acclimated rats showed cardiac and adrenal hypertrophy. Cardiac noradrenaline (NA) content was increased in both groups of rats but only the trained rats had an increased cardiac NA concentration. The adrenal NA content was increased in both groups but only the trained rats had an increased adrenal content of adrenaline (A). The spleen of trained rats had an increased NA content, while that of cold-acclimated rats had a decreased NA content. The submandibular glands of cold-acclimated rats were enlarged and had an increased NA content. Trained as well as cold-acclimated rats had lower urinary NA excretions during rest, after exercise and during cold stress when compared with controls. However, only the trained rats had a reduced net increment in NA excretion after exercise, whereas there was no difference between the increments of cold-acclimated and control rats. Six months after cessation of training, ex-trained rats still had an increased heart ratio and a reduced urinary NA excretion after exercise. It is suggested that physical training induces "cross tolerance" to cold stress, while cold-acclimation does not lead to "cross tolerance" to acute exercise.

Acclimatization↗

PubMed1979

Thermogenic responses of brown adipocytes to noradrenaline and glucagon in heat-acclimated and cold-acclimated rats.

Heat production of isolated brown-fat cells by addition of noradrenaline and glucagon was measured in warm-acclimated control, cold-acclimated and heat-acclimated rats by use of a twin-type conduction microcalorimeter. Noradrenaline and glucagon induced maximum heat production per 10(6) cells in dose of 1 microgram/ml. Heat produced by maximum thermogenic response to glucagon was twice as much as that to noradrenaline. Thermogenic response to noradrenaline was markedly increased in cold-acclimated brown adipocytes, while it was reduced in heat-acclimated ones. Thermogenic response to glucagon was significantly reduced in heat-acclimated brown adipocytes, while it was not affected in cold-acclimated brown adipocytes.

Acclimatization↗

PubMed1984

Lowered cold tolerance in cold-acclimated and non-acclimated guinea pigs treated with diazepam.

The effects of the clinically most commonly used minor tranquilizer, diazepam, on the survival time and on the mechanism of death in non-acclimated and cold-acclimated guinea pigs in severe cold exposure (-20 degrees C) were studied. Cold acclimation for 2 months increased the average survival time from 4 h to 10 h. The lowest rectal temperature at death (14.6 degrees C) was seen in the cold-acclimated animals. Diazepam at a dose of 5 or 15 mg/kg i.p. 30 min before the beginning of the exposure reduced dose-dependently the cold endurance of both cold-acclimated and non-acclimated guinea pigs. The serum glucose and free fatty acid concentrations were low in the animals with the long survival time. Histological studies of liver, kidney, and adrenal glands showed no specific changes. Exposure seemed to increase the frequency of contraction bands and to decrease focally the intensity of beta-hydroxybutyrate dehydrogenase reaction in the myocardium, which indicates a mild hypoxic lesion of the muscle cells.

Acclimatization↗

PubMed2004

Acclimation of anaerobic sludge degrading chlorophenols and the biodegradation kinetics during acclimation period.

The acclimation of sludge from Hangzhou citrate factory and Hangzhou municipal wastewater treatment plant for degradation dechlorination of chlorophenols (CPs) compounds, and its biodegradation kinetics were studied in batch process with or without addition of sucrose. Three monochlorophenols (2-CP; 3-CP; 4-CP) and pentachlorophenol (PCP) were concurrently fed to different bioreactors. The parameters that were monitored included biogas production, biogas composition and chemical oxygen demand (COD). The results showed that acclimation with chlorophenol can increase the degradation activity of anaerobic sludge and degradation rate of chlorophenolic compounds, and reduce the lag time. Degradation dechlorination activity of the acclimated sludge strongly depended on sludge source, microorganism population and chlorophenol congener. 2-CP was more easily acclimated than 3-CP and 4-CP. Among the four tested compounds, 4-CP was the most difficult to be acclimated. The observed degradation rate with presence of sucrose was higher than that with absence of sucrose, suggesting that addition of the external carbon source can stimulate the formation of acclimated sludge which could effectively degrade chlorophenols. Kinetic equations of biodegradation of chlorophenols were also presented in this paper.

Anaerobiosis↗

PubMed2004

Heterosis in the freezing tolerance of crosses between two Arabidopsis thaliana accessions (Columbia-0 and C24) that show differences in non-acclimated and acclimated freezing tolerance.

Heterosis is broadly defined as the increased vigour of hybrids in comparison to their parents. In the model plant Arabidopsis thaliana, a significant heterosis effect on leaf-freezing tolerance was observed in the F(1) generation of a cross between the accessions Columbia-0 (Col) and C24. Parental Col plants were significantly more freezing-tolerant than C24 plants in both the acclimated and non-acclimated (NA) states. Mid-parent heterosis was observed in the F(1) plants, both in the basic tolerance of non-adapted plants and in freezing tolerance after cold acclimation. Best-parent heterosis, on the other hand, was only found after cold acclimation. The heterosis effect was reduced in the F(2) populations such that only mid-parent heterosis was evident. The leaf content of soluble sugars (fructose (Fru), glucose (Glc), sucrose (Suc) and raffinose (Raf)) increased dramatically in the F(1) plants after cold acclimation as compared to the parental lines. The content of proline (Pro), however, was only moderately increased in the F(1) plants under the same conditions. Correlation analyses showed that only Raf content was consistently related to leaf-freezing tolerance in both the acclimated and NA states. A quantification of mRNA levels in leaves of parental and F(1) lines using quantitative real-time RT-PCR showed no clear indication for an involvement of the investigated genes (CBF (C-repeat binding factor)1, CBF2, (cold-regulated protein (COR) 6.6, COR15a, COR15b, COR47 and COR78) in the heterosis effect.

Acclimatization↗

PubMed2000

Acclimation response of spring wheat in a free-air CO(2) enrichment (FACE) atmosphere with variable soil nitrogen regimes. 1. Leaf position and phenology determine acclimation response.

We have examined the photosynthetic acclimation of wheat leaves grown at an elevated CO(2) concentration, and ample and limiting N supplies, within a field experiment using free-air CO(2) enrichment (FACE). To understand how leaf age and developmental stage affected any acclimation response, measurements were made on a vertical profile of leaves every week from tillering until maturity. The response of assimilation (A) to internal CO(2) concentration (C(i)) was used to estimate the in vivo carboxylation capacity (Vc(max)) and maximum rate of ribulose-1,5-bisphosphate limited photosynthesis (A (sat)). The total activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and leaf content of Rubisco and the Light Harvesting Chlorophyll a/b protein associated with Photosystem II (LHC II), were determined. Elevated CO(2) did not alter Vc(max) in the flag leaf at either low or high N. In the older shaded leaves lower in the canopy, acclimatory decline in Vc(max) and A (sat) was observed, and was found to correlate with reduced Rubisco activity and content. The dependency of acclimation on N supply was different at each developmental stage. With adequate N supply, acclimation to elevated CO(2) was also accompanied by an increased LHC II/Rubisco ratio. At low N supply, contents of Rubisco and LHC II were reduced in all leaves, although an increased LHC II/Rubisco ratio under elevated CO(2) was still observed. These results underscore the importance of leaf position, leaf age and crop developmental stage in understanding the acclimation of photosynthesis to elevated CO(2) and nutrient stress.

Journal Article↗

PubMed1994

Cold acclimation in genetically related (sibling) deciduous and evergreen peach (Prunus persica [L.] Batsch). II. A 60-kilodalton bark protein in cold-acclimated tissues of peach is heat stable and related to the dehydrin family of proteins.

In several plant species, certain cold-regulated proteins share unique properties. These proteins are (a) heat stable and (b) hydrophilic and are related to the Group 2 late embryogenesis abundant or dehydrin family of proteins. Our previous work with sibling deciduous and evergreen peach genotypes demonstrated a correlation between the level of accumulation of certain bark proteins and cold-acclimation potential of these tissues. Here we identify a 60-kD bark protein in peach (Prunus persica [L.] Batsch), PCA60 ("peach cold acclimation"), that is accumulated during cold acclimation and is heat stable. Immunological studies indicated that this protein is related to the dehydrin family of proteins and accumulates at much higher levels in the bark tissues of the deciduous genotype than in the evergreen. Amino acid composition indicated that the 60-kD protein has a compositional bias for glycine (24%), glutamic acid/glutamine (11.4%), aspartic acid/asparagine (10%), and threonine (9.6%), contains relatively low levels of aromatic amino acids (phenylalanine and tyrosine), and is rich in hydrophilic amino acids. A novel characteristic of the 60-kD cold-acclimation protein is the presence of a repeating nine-amino acid sequence. A five-amino acid stretch, which is included within this repeating motif, shares striking homology with other cold-regulated proteins and dehydrins.

Acclimatization↗

PubMed1989

Changes in body temperature of rats acclimated to heat with different acclimation schedules.

Male Wistar rats, initially maintained at an ambient temperature (Ta) of 23.8 degrees C, were subjected to one of seven different heat acclimation schedules under a 12:12-h light-dark cycle (lights on at 0600 h). Two groups of rats were exposed to Ta of 32.4 degrees C all day for 5 (HC5) or 10 (HC10) days. The other four groups were exposed to Ta of 32.8 degrees C for 5 h/day during the last half of the dark phase for 5 (NI5) or 10 (NI10) consecutive days or during the last half of the light phase for 5 (DI5) or 10 (DI10) consecutive days. Control rats (C) were kept at 23.8 degrees C throughout the experiment. Hypothalamic temperature (Thy) was measured every 5 min with a chronically implanted thermocouple from 1 day before the beginning to 2 days after the end of the heat acclimation periods. During the heat acclimation periods, daily mean Thy rose significantly in HC5 and HC10 rats but decreased significantly in NI5 and NI10 rats. Daily mean Thy did not change in C, DI5, and DI10 rats. Thy in HC10 rats sharply decreased at the end of the heat acclimation periods and remained at low levels for approximately 3 h. On the 2nd postacclimation day, however, mean Thy returned and remained at a significantly higher level. In NI10 rats, the mean Thy in the postacclimation period was significantly lower than the preacclimation values. No such changes in mean Thy were observed in DI10 rats. Five-days of heat exposure had little effect on the postacclimation Thy.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗

PubMed2004

Acclimation of sperm motility apparatus in seawater-acclimated euryhaline tilapia Oreochromis mossambicus.

Euryhaline tilapia Oreochromis mossambicus can reproduce in freshwater and in seawater. Regulation of sperm motility appears to be modulated during acclimation of the fish from freshwater to seawater, being independent of extracellular Ca2+ in freshwater and dependent on extracellular Ca2+ in seawater. In the presence of extracellular Ca2+, sperm of seawater-acclimated tilapia (SWT) showed motility even in a hypertonic environment, whereas sperm of freshwater-acclimated tilapia (FWT) were not motile. The Ca2+ indicator, fluo-3, revealed that intracellular Ca2+ concentration, [Ca2+]i, of SWT sperm increased only in the presence of extracellular Ca(2+) in hypotonic or hypertonic conditions. Since the increased [Ca2+]i in FWT sperm occurred under hypotonic conditions via intracellular Ca2+ stores, it is likely that tilapia modulate their source of increasing [Ca2+]i from intracellular stores (in FWT sperm) to extracellular stores (in SWT sperm). Experiments using demembranated sperm revealed that Ca2+ is necessary for activation of motility, suggesting that Ca2+ plays a key role in motility regulation in SWT sperm. We detected three phosphoproteins associated with the activation of sperm motility. Serine and threonine residues of two proteins of 15 kDa and 18 kDa became dephosphorylated in hypotonic conditions but remained phosphorylated in hypertonic conditions, suggesting that these protein phosphorylations were not only related to motility activation under hypertonic conditions but also resistant to osmotic pressure. The threonine residue(s) of a 41 kDa protein was also phosphorylated in dry sperm, even in FWT sperm in motility-feasible hypotonic conditions. It is likely that acclimation of the motility apparatus is associated with modulation of the flow of Ca2+ to increase [Ca2+]i and protein phosphorylation.

Acclimatization↗

PubMed2005

Comparative analysis of expressed sequence tags from cold-acclimated and non-acclimated leaves of Rhododendron catawbiense Michx.

An expressed sequence tag (EST) analysis approach was undertaken to identify major genes involved in cold acclimation of Rhododendron, a broad-leaf, woody evergreen species. Two cDNA libraries were constructed, one from winter-collected (cold-acclimated, CA; leaf freezing tolerance -53 degrees C) leaves, and the other from summer-collected (non-acclimated, NA; leaf freezing tolerance -7 degrees C) leaves of field-grown Rhododendron catawbiense plants. A total of 862 5'-end high-quality ESTs were generated by sequencing cDNA clones from the two libraries (423 from CA and 439 from NA library). Only about 6.3% of assembled unique transcripts were shared between the libraries, suggesting remarkable differences in gene expression between CA and NA leaves. Analysis of the relative frequency at which specific cDNAs were picked from each library indicated that four genes or gene families were highly abundant in the CA library including early light-induced proteins (ELIP), dehydrins/late embryogenesis abundant proteins (LEA), cytochrome P450, and beta-amylase. Similarly, seven genes or gene families were highly abundant in the NA library and included chlorophyll a/b-binding protein, NADH dehydrogenase subunit I, plastidic aldolase, and serine:glyoxylate aminotransferase, among others. Northern blot analyses for seven selected abundant genes confirmed their preferential expression in either CA or NA leaf tissues. Our results suggest that osmotic regulation, desiccation tolerance, photoinhibition tolerance, and photosynthesis adjustment are some of the key components of cold adaptation in Rhododendron.

Acclimatization↗

PubMed1982

Modified metabolic responsiveness to glucagon in cold-acclimated and heat-acclimated rats.

Calorigenic effect of glucagon on whole body oxygen consumption and interscapular brown adipose tissue (BAT) was investigated in unanesthetized and unrestrained warm controls (WC), cold-acclimated rats (CA) and heat-acclimated rats (HA). Glucagon produced significant elevation of oxygen consumption, body temperature and BAT temperature in all experimental groups. Such increased calorigenic responses to glucagon were significantly potentiated in CA and reduced in HA compared with those in WC. Thermogenic response of BAT to norepinephrine was also similar to that to glucagon; it was potentiated in CA, reduced in HA. These results indicate that glucagon would serve thermoregulatory nonshivering thermogenesis in temperature acclimation as calorigenic hormone, at least in part, through its action on BAT.

Adipose Tissue, Brown↗