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PubMed2006

A R2R3 type MYB transcription factor is involved in the cold regulation of CBF genes and in acquired freezing tolerance.

Cold temperatures trigger the expression of the CBF family of transcription factors, which in turn activate many downstream genes that confer freezing tolerance to plants. It has been shown previously that the cold regulation of CBF3 involves an upstream bHLH-type transcription factor, ICE1. ICE1 binds to the Myc recognition sequences in the CBF3 promoter. Apart from Myc recognition sequences, CBF promoters also have Myb recognition sequences. We report here that the Arabidopsis MYB15 is involved in cold-regulation of CBF genes and in the development of freezing tolerance. The MYB15 gene transcript is up-regulated by cold stress. The MYB15 protein interacts with ICE1 and binds to Myb recognition sequences in the promoters of CBF genes. Overexpression of MYB15 results in reduced expression of CBF genes whereas its loss-of-function leads to increased expression of CBF genes in the cold. The myb15 mutant plants show increased tolerance to freezing stress whereas its overexpression reduces freezing tolerance. Our results suggest that MYB15 is part of a complex network of transcription factors controlling the expression of CBFs and other genes in response to cold stress.

Acclimatization↗
PubMed2006

Identification and kinetic characterization of HtDTC, the mitochondrial dicarboxylate-tricarboxylate carrier of Jerusalem artichoke tubers.

Jerusalem artichoke (Helianthus tuberosus L.) tubers were reported to be tolerant to cold and freezing. The aim of this study was to perform a kinetic characterization of the mitochondrial dicarboxylate-tricarboxylate carrier (HtDTC) and to assess a possible involvement of this carrier in the cold tolerance of tubers. The HtDTC was purified from isolated mitochondria by sequential chromatography on hydroxylapatite/celite and Matrex Gel Orange A. SDS gel electrophoresis of the purified fraction showed a single polypeptide band with an apparent molecular mass of 31.6 kDa. A polyclonal antibody raised against the tobacco DTC cross-reacted with the purified protein on Western blot analysis. In gel trypsin, digestion of the purified HtDTC yielded peptides that exhibited strong amino acid sequence similarity to previously identified plant DTCs. Furthermore, using degenerate primers, a portion of the Htdtc cDNA was amplified and sequenced; this cDNA encoded for a protein with high sequence similarity to known plant homolog DTCs. When reconstituted in liposomes loaded with dicarboxylate (2-oxoglutarate, malate, malonate, succinate, and maleate) or tricarboxylate anions (citrate, trans-aconitate, and isocitrate), the purified HtDTC transported all these anions in exchange with external [14C]2-oxoglutarate. A kinetic characterization of HtDTC was performed: (a) the half-saturation constant Km and the Vmax at 25 degrees C of the 2-oxoglutarate/2-oxoglutarate exchange by reconstituted HtDTC were found to be 360 microM and 10.9 micromol/(min mg protein), respectively; (b) the activation energy Ea of the succinate/2-oxoglutarate exchange by the reconstituted HtDTC was found to be 50.7 kJ/mol constant between -5 and 35 degrees C. Similarly, the activation energy Ea of succinate respiration of isolated Jerusalem artichoke mitochondria, measured between -2 and 35 degrees C, was shown to be constant (65.3 kJ/mol). The physiological relevance of kinetic properties and temperature dependence of transport activities of HtDTC is discussed with respect to the cold tolerance ability of Jerusalem artichoke tubers.

Amino Acid Sequence↗
PubMed1996

Cold acclimation-associated changes in brown adipose tissue do not necessarily indicate an increase of nonshivering thermogenesis in C57BL/6J mice.

We have reported previously that a cold acclimation procedure (3-hr partial restraint at 6 degrees C, repeated 3 times at 2-week intervals) usually improves the cold tolerance of adult C57BL/6J mice. Those mice that did not improve their cold tolerance had lower cold-induced sympathetic nervous outflow to the interscapular brown adipose tissue (IBAT), suggesting a failure in the mechanisms of nonshivering thermogenesis. To understand the origin of this failure, this study was intended to measure nonshivering thermogenesis in mice that did not improve their cold tolerance after the cold acclimation procedure. After being subjected 3 times to a partial restraint at 6 degrees C, mice were anesthetized with urethane, immobilized with vecuronium bromide, and placed on artificial ventilation. The VO2 and VCO2 in expired air were measured and metabolic heat production (MHP) was calculated while body temperature was artificially lowered to 7.5 degrees C below control level. In a separate group of mice, the total amount and concentration of mitochondrial uncoupling protein, thermogenin (UCP), in IBAT was measured immediately after completion of the cold-acclimation procedure. The concentration and the amount of UCP in the mitochondria of IBAT was significantly higher in all mice that had been presented to the cold acclimation procedure, regardless of its outcome, than in mice that had never been exposed to an environment below room temperature (NAIVE). MHP increased significantly during body cooling in all mice. However, MHP before and during cold stimulation in mice that did not improve their cold tolerance as a result of the cold-acclimation procedure was significantly lower than the MHP of animals in which cold tolerance was improved, and was not different from MHP of the NAIVE group. Therefore, in mice in which cold tolerance did not improve after repeated cold exposure, the anatomical and biochemical changes in brown adipose tissue typical of cold acclimation were not associated with a cold-induced increase in MHP. We infer that the expression of UCP in brown adipose tissue is a necessary, but not sufficient, attribute of cold acclimation. Cold acclimation, measured as increased cold tolerance, occurs only if synthesis of UCP in BAT is associated with an increased cold-induced response of the sympathetic nervous system.

Acclimatization↗
PubMed1996

Effects of oral morphine on cold pressor tolerance time and neuropsychological performance.

We investigated the analgesic effects of escalating doses (0.214, 0.286, 0.357, and 0.429 mg/kg) of oral morphine on tolerance to painful cold pressor in a double-blind, active placebo-controlled (diphenhydramine) study in 45 normal volunteers. The highest dose of morphine administered is equivalent to the starting dose recommended by the Agency for Health Care Policy and Research for the management of cancer pain and acute postoperative pain. We assessed analgesia in terms of cold pressor tolerance time and self-reported ratings of pain intensity and unpleasantness. Subjects receiving the highest dose of oral morphine showed significantly higher tolerance time than subjects receiving diphenhydramine. Neither morphine or diphenhydramine significantly reduced ratings of pain intensity and unpleasantness. Neuropsychological testing revealed that the two highest doses of morphine impaired the episodic retrieval of a word list, but the same doses did not affect motor, perceptual, or attentional tasks.

Administration, Oral↗
PubMed1996

Constitutive expression of the cold-regulated Arabidopsis thaliana COR15a gene affects both chloroplast and protoplast freezing tolerance.

Cold acclimation in plants is associated with the expression of COR (cold-regulated) genes that encode polypeptides of unknown function. It has been widely speculated that products of these genes might have roles in freezing tolerance. Here we provide direct evidence in support of this hypothesis. We show that constitutive expression of COR15a, a cold-regulated gene of Arabidopsis thaliana that encodes a chloroplast-targeted polypeptide, enhances the in vivo freezing tolerance of chloroplasts in nonacclimated plants by almost 2 degrees C, nearly one-third of the increase that occurs upon cold acclimation of wild-type plants. Significantly, constitutive expression of COR15a also affects the in vitro freezing tolerance of protoplasts. At temperatures between -5 and -8 degrees C, the survival of protoplasts isolated from leaves of nonacclimated transgenic plants expressing COR15a was greater than that of protoplasts isolated from leaves of nonacclimated wild-type plants. At temperatures between -2 and -4 degrees C, constitutive expression of COR15a had a slight negative effect on survival. The implications of these data regarding possible modes of COR15a action are discussed.

Journal Article↗
PubMed1998

Physiology of drought tolerance and cold hardiness of the Mediterranean tiger moth Cymbalophora pudica during summer diapause.

Prepupae of the arctiid moth Cymbalophora pudica spend spring and summer months in a summer diapause (aestivation), the duration of which is photoperiodically controlled. Cold hardiness, drought tolerance and some physiological and biochemical parameters were measured in aestivating prepupae. Large amounts of metabolic reserves, in the form of lipids and glycogen, accumulated prior to aestivation. Glycogen served as the main metabolic fuel for aestivating prepupae. Metabolic rate decreased rapidly after the onset of the inactive prepupal stage and remained low (5-15% of the level in active larva) during aestivation. A spontaneous increase of the respiration rate occurred before pupation. Neither low mol. wt sugars or alcohols (polyols) accumulated nor the haemolymph osmotic pressure changed during aestivation. Drought tolerance of aestivating prepupae was high (no decrease in survival after exposure to r.h.<10% at a temperature of 23 degrees C for a substantial part of diapause) owing to their extensive capacity to stabilize the relative body water content irrespective of the r.h. of surrounding air. Cold hardiness was low (>90% decrease in survival after exposure to -7 degrees C for 24h). Cold and drought acclimations did not lead to significant changes in the measured physiological and biochemical parameters but cold (not drought) acclimation caused a significant increase in cold hardiness. Neither drought tolerance nor the increase in cold hardiness after cold acclimation appear to be related to presence/accumulation of polyols in aestivating C. pudica prepupae.

Journal Article↗
PubMed2006

A putative Arabidopsis nucleoporin, AtNUP160, is critical for RNA export and required for plant tolerance to cold stress.

To study the genetic control of plant responses to cold stress, Arabidopsis thaliana mutants were isolated by a screen for mutations that impair cold-induced transcription of the CBF3-LUC reporter gene. We report here the characterization and cloning of a mutated gene, atnup160-1, which causes reduced CBF3-LUC induction under cold stress. atnup160-1 mutant plants display altered cold-responsive gene expression and are sensitive to chilling stress and defective in acquired freezing tolerance. AtNUP160 was isolated through positional cloning and shown to encode a putative homolog of the animal nucleoporin Nup160. In addition to the impaired expression of CBF genes, microarray analysis revealed that a number of other genes important for plant cold tolerance were also affected in the mutants. The atnup160 mutants flower early and show retarded seedling growth, especially at low temperatures. AtNUP160 protein is localized at the nuclear rim, and poly(A)-mRNA in situ hybridization shows that mRNA export is defective in the atnup160-1 mutant plants. Our study suggests that Arabidopsis AtNUP160 is critical for the nucleocytoplasmic transport of mRNAs and that it plays important roles in plant growth and flowering time regulation and is required for cold stress tolerance.

Arabidopsis↗
PubMedDate not supplied

The effect of exercise training in a cold environment on thermoregulation in adult and aged C57BL/6J mice.

We studied the effect of exercise training in cold environment (six weeks of daily, one-hour runs on a treadmill at ambient temperature of 6 +/- 1 degrees C at 60-65% of VO2max) on cold-induced metabolic heat production, heat loss, and cold tolerance in adult and aged C57BL/6J male mice. In adult mice, exercise training in cold environment resulted in greater cold-induced heat production and cold tolerance without changes in heat loss, similar to the effects of daily cold exposure without exercise. In aged mice, daily cold exposures did not affect cold tolerance and cold-induced heat production, but exercise training in the cold resulted in greater cold-induced heat production and cold tolerance. Heat loss in aged mice increased similarly after both repeated cold exposures and exercise training in the cold. Therefore, mechanisms of effect of exercise training on cold tolerance are different in adult and aged animals. Exercise training in cold environment does not affect cold-induced heat production and cold tolerance in adult mice, but improves them in aged animals.

Acclimatization↗
PubMed2001

Are summit metabolism and thermogenic endurance correlated in winter-acclimatized passerine birds?

Small birds exhibiting marked winter improvement of cold tolerance also show elevated summit metabolic rates (maximum cold-induced metabolic rate) in winter relative to summer. However, relatively large increases in cold tolerance can occur with only minor increments of maximum cold-induced metabolic rate and geographic variation in cold tolerance is not always positively correlated with variation in maximum cold-induced metabolic rate. Thus, it is uncertain whether maximum cold-induced metabolic rate and cold tolerance are phenotypically correlated in small birds and no previous study has directly examined this relationship. I measured maximum cold-induced metabolic rate and cold tolerance (i.e., thermogenic endurance) over three winters in black-capped chickadees Poecile atricapillus, American tree sparrows Spizella arborea, and dark-eyed juncos Junco hyemalis. For raw thermogenic endurance data, residuals of maximum cold-induced metabolic rate and thermogenic endurance from mass regressions were significantly and positively correlated in juncos and tree sparrows, and their correlation approached significance for chickadees. Log10 transformation of thermogenic endurance and mass data gave similar results. These data provide the first direct evidence for a phenotypic correlation between maximum cold-induced metabolic rate and thermogenic endurance in small birds, although much of the variance in thermogenic endurance is explained by factors other than maximum cold-induced metabolic rate and the degree of correlation differs among species. Nevertheless, these data suggest that physiological adjustments producing elevated thermogenic endurance also produce elevated maximum cold-induced metabolic rate in small birds.

Acclimatization↗
PubMed1988

A case study on the induction of clinical tolerance in cold urticaria.

The mechanism(s) by which repeated cold challenge in a patient with idiopathic acquired cold urticaria resulted in the induction of clinical tolerance to cold stimuli was studied. Plasma histamine levels, mast cell ultrastructure, and the cutaneous response to intradermal injections of morphine, histamine, and substance P were examined before and after the induction of tolerance. Plasma histamine levels draining cold-challenged, clinically tolerant skin were markedly diminished compared to histamine levels obtained during cold-induced angioedema. Furthermore, electronmicroscopy of skin samples taken from tolerant skin after cold challenge revealed intact, largely normal appearing mast cells. Intradermal injection of mast cell secretagogues and vasoactive agonists into normal and tolerant skin sites resulted in similar whealing responses. Thus, these studies suggest that the state of clinical tolerance to cold stimuli is due neither to mast cell-mediator depletion or tachyphylaxis of the cutaneous vasculature to vasoactive agonists. It appears likely that tolerance may be due to the induction of a specific state of unresponsiveness of mast cells to cold stimuli or possibly to depletion of a cold-induced cutaneous antigen capable of triggering mast cell degranulation.

Adaptation, Physiological↗
PubMed2001

Expression of a cold-responsive Lt-Cor gene and development of freezing tolerance during cold acclimation in wheat (Triticum aestivum L.).

Time-courses of the development of freezing tolerance and the expression of a cold-responsive gene wlt10 were monitored during cold acclimation in wheat (Triticum aestivum L.). Bioassay showed that cold acclimation conferred much higher freezing tolerance on a winter cultivar than a spring cultivar. Northern blot analysis showed that the expression of wlt10 encoding a novel wheat member of a cereal-specific LT-COR protein family was specifically induced by low temperature. A freezing-tolerant winter cultivar accumulated the mRNA more rapidly and for a longer period than a susceptible spring cultivar. The increase in the amount of mRNA was temporary but the peak occurred at the time when the maximum level of freezing tolerance was attained. The mRNA accumulated more in the leaves than in the roots, and different light/dark regimes modulated the level of mRNA accumulation. Genomic Southern blot analyses using the nulli-tetrasomic series showed that the wlt10 homologues were located on the homologous group 2 chromosomes.

Acclimatization↗
PubMed2002

Alexithymia is not related to tolerance for cold pressor pain.

To test the hypothesis that higher scores on alexithymia are associated with reduced tolerance for cold pressor pain, 116 college undergraduates completed the Toronto Alexithymia Scale-20 of Bagby, Parker and Taylor and engaged in the cold pressor test. Their alexithymia scores were not associated with tolerance for cold pressor pain, suggesting that individuals scoring high on alexithymia do not show a general hypersensitivity to a cold stimulus.

Adolescent↗
PubMed1989

Inheritance of cold shock tolerance in hybrids of Drosophila virilis and Drosophila lummei.

The genetic basis of the difference in cold shock tolerance between the southern temperate Drosophila virilis and its boreal relative D. lummei is studied. After adult eclosion, the parental stocks, reciprocal F1 and backcross hybrids were pretreated for eight days at 18 degrees C or at 6 degrees C. The cold shock used consisted of fast cooling to -10 degrees C and exposure to this temperature for varying lengths of time. D. lummei tolerated such exposure for 40-50% longer than did D. virilis (100-135% after acclimation). Reciprocal F1 females, differing only in their maternal cytoplasm deviated significantly from each other, and the reciprocal F1 males even more so, the contribution of the X chromosome being three to four times that of the cytoplasm. The cold resistance scores of the hybrid males were more extreme than those of the parental stocks. Autosomally heterozygous males with the X chromosome and cytoplasm of virilis were the weakest flies studied. The reciprocal males (X chromosome and cytoplasm of lummei) survived better than the parental lummei stock. The reciprocal differences decreased after cold temperature acclimation. The roles of the four major autosomes were analyzed by backcrossing the reciprocal F1 males with females of the virilis marker stock. The third chromosome of lummei as heterozygous contributed most to cold tolerance, while the other autosomes had a rather weak effect in the opposite direction (virilis homozygotes survived better), which disappeared after acclimation at 6 degrees C. Some of the cold susceptibility of F1 hybrids disappeared in chromosomally identical backcross flies, indicating complex cytoplasm-chromosomal interactions.

Animals↗
PubMed1987

Enhancement of cold-stimulated thermogenesis in the corpulent rat (LA/N cp) by aminophylline.

Previous studies on obese strains of rats (e.g., Zucker and LA/N cp) have shown that they are deficient in nonshivering thermogenesis and poor in cold tolerance. Our earlier studies have established that aminophylline (AMPY; 85% theophylline-15% ethylenediamine) is effective in significantly improving cold tolerance in the lean Sprague-Dawley rat regardless of age or thermogenic capacity. The present study tested whether AMPY may be also effective in improving cold tolerance in both young (12-18 wk) and older (36-42 wk) lean and corpulent LA/N cp rats. Contrary to previous reports, however, the norepinephrine (NE)-stimulated nonshivering thermogenesis was not only present but also equal in magnitude in the corpulent rats to that of their lean controls. Further, no difference in cold tolerance was observed between the two groups regardless of age. Similarly, AMPY (18.7 mg/kg ip) significantly improved thermogenesis and cold tolerance in both lean and corpulent rats, again without any age-related difference in response. These results indicate that, despite the existence of obesity, no difference in thermogenic capacity to either NE or cold stimulation is evident in the LA/N cp rats. Thus the ontogeny of obesity in this strain may be caused by factors other than deficiency in NE- or cold-stimulated thermogenesis at the end-organ level.

Aminophylline↗
PubMed1985

Effect of intermittent feeding on thermoregulatory abilities of young and aged C57BL/6J mice.

At 6 mth of age, male C57BL/6J mice were subjected to an intermittent schedule of feeding (every-other-day) or continued to be maintained on an ad libitum diet (24% protein). This regimen of dietary restriction resulted in increased mean and maximum lifespan (11%) compared to the survival of ad libitum-fed mice. At 8 and 26 mth of age, different groups of mice were tested for cold tolerance during 3 h exposure to 10 degrees C. Aged mice (26 mth) fed ad libitum compared to young mice (8 mth) on the same diet had significantly lower baseline colonic temperatures prior to cold exposure, and impaired cold tolerance, as measured by the rate of decline in colonic temperature during cold exposure. Dietary restriction by intermittent feeding had no significant effect on cold tolerance in young mice or baseline colonic temperature in young or aged mice. However, the cold tolerance of aged mice subjected to 20 mth of intermittent feeding was markedly improved over that of aged cohorts maintained on an ad libitum diet and in fact was indistinguishable from that of young counterparts. Thus, it appeared that this regimen of dietary restriction when implemented in young adults prevented the age-related decline in cold tolerance observed among ad libitum fed mice of this strain.

Adaptation, Physiological↗
PubMed2006

Genetic and QTL analysis for low-temperature vigor of germination in rice.

The quantitative trait loci (QTLs) for low-temperature vigor of germination (LVG) with a germination period of 7 d, 11 d, 14 d, and 17 d at 14 degrees C was identified using F(2:3) population, which included 200 individuals and lines derived from a cross of indica and japonica "Milyang 23/Jileng 1" with microsatellite markers. The correlation coefficient between LVG and other cold tolerance traits was analyzed. LVG and the cold response index for vigor of germination (CIVG) detected when the germination period was 7 d showed a continuous distribution, which was partial to lower LVG and lower CIVG in F(3) lines. LVG and CIVG detected when the germination periods were 11 d, 14 d, and 17 d showed a continuous distribution near normal, which were quantitative traits controlled by multiple genes. LVG detected when the germination period was 14 d was more correlated with other cold tolerance traits than LVG detected when the germination periods were 7 d, 11 d, and 17 d, which was significantly associated with cold tolerance during the bud bursting period, the seedling stage, the booting stage, and the growing ability under cold conditions. qLVG2 located in RM29-RM262 on chromosome 2, qLVG7-2 and qCIVG7-2 located in RM336-RM118 on chromosome 7 were detected when the germination periods were 11 d, 14 d, and 17 d. qCIVG2 located in RM29-RM262 on chromosome 2 was detected when the germination periods were 11 d and 14 d. The variation is due to the observed phenotypic variation by the above QTLs, which was increased following the germination. The variation of qLVG2 related to LVG was increased from 6.9% to 14.2%. The variation of qLVG7-2 associated with LVG was increased from 9.9% to 11.2%. The variation of qCIVG2 correlated with CIVG was increased from 6.3% to 9.0%. The variation of qCIVG7-2 associated with CIVG was increased from 8.3% to 12.9%. These QTL alleles were obtained from the tolerant parent Jileng 1, and the gene action was most likely to be partially dominant.

Breeding↗
PubMed1998

Infant cold exposure changes Fos expression to acute cold stimulation in adult hypothalamic brain regions.

It is known that cold exposure as an infant results in a permanent cold tolerance which is accompanied by a reduced rate of colonic temperature decline and increased metabolic heat production to cold stimulation. The present study was aimed to elucidate the central mechanism of cold tolerance of adult rats with cold exposure as infants. Newborn infants were exposed to cold ambient (4 degrees C) daily for 2 weeks, and when they were 15-weeks old, Fos expression to acute cold stimulation (10 degrees C) in whole brain regions was investigated using quantitative immunohistochemistry. Acute cold stimulation induced a significant increase of Fos-positive neurons in many nuclei of whole brain areas in adult rats both with and without cold exposure as infants. However, the number of Fos-positive neurons was significantly less in the rats with cold exposure than without cold exposure as infants, particularly in the hypothalamic nuclei such as the lateral septal nucleus (LS), preoptic area (POA), parvocellular paraventricular nucleus (pPVN0, ventromedial hypothalamic nucleus (VMH) and supramammillary nucleus (SuM). However, there was no significant difference in the number of Fos-positive neurons in the extra-hypothalamic regions between the rats with and without cold exposure as infants. These results suggest that the central mechanism of cold tolerance with cold exposure as infants is due to metabolic changes of the hypothalamic brain regions.

Animals↗
PubMed1990

Cold-induced vasodilatation of finger and maximal oxygen consumption of young female athletes born in Hokkaido.

To determine whether there is a direct correlation between endurance capacity and cold tolerance, maximal oxygen consumption (VO2max), and cold-induced vasodilatation (CIVD), we measured these factors in 14 young female athletes born in Hokkaido, Japan's northernmost island. We determined the VO2max by a standard incremental test on a cycle ergometer and measured the oxygen consumption (VO2) by means of the Douglas-bag method. We determined the CIVD reaction by measuring the skin temperature of the left middle finger during immersion in cold water at 0 degree C for 20 min. The athletes showed significant positive correlations between VO2max, expressed as 1/min, and CIVD as well as other peripheral cold tolerance indexes (resistance index against frostbite and CIVD index). The body weight VO2max (VO2max/kg body weight) failed to correlate significantly with either the CIVD or with other cold tolerance indexes. These results suggest that CIVD in females may depend on factors other than those determined in this study, in addition to the functional spread of the vascular beds in peripheral tissues, including striated muscle; it is known that the size and the vascular bed in this tissue are affected by exercise training and that this results in the elevation of VO2max and VO2max/kg body weight.

Acclimatization↗