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PubMed2002

Thermogenic changes with chronic cold exposure in the naked mole-rat (Heterocephalus glaber).

The naked mole-rat (Heterocephalus glaber) lives communally in a thermally buffered underground habitat. Here, it relies primarily on ectothermic (behavioral) mechanisms to maintain body temperature (T(b)). Outside this milieu, it is unable to effectively regulate T(b) and T(b) tracks that of ambient temperature (T(a)). Although naked mole-rats, in their natural habitat have little need for cold-tolerance, we questioned whether or not thermogenic capacity would change with prolonged (>1 year) exposure to cooler conditions. We hypothesized that these rodents would not conform to common mammalian patterns and that non-shivering thermogenic (NST) capacity would be unchanged with chronic cold exposure. The capacity for NST was assessed following noradrenaline administration (0.8 mg/kg, s.c.) to lightly anesthetized (pentobarbital 6% m/v 40 mg/kg) animals and monitoring the concomitant changes in oxygen consumption and T(b). Results concur with the null hypothesis in that prolonged cold exposure did not elicit any increase in NST capacity (1.52+/-0.17 ml O(2)/g/h, cold-acclimated; 1.73+/-0.31 ml O(2)/g/h, control; P>0.05). Rapid heat loss across their uninsulated integument may necessitate continuous maximal stimulation of brown adipose tissue (BAT), and as such, prevent any further increase in thermogenic capacity following cold exposure.

Acclimatization↗
PubMed2007

Isolation of cold stress-responsive genes in the reproductive organs, and characterization of the OsLti6b gene from rice (Oryza sativa L.).

During their reproductive stage, rice crops often are exposed to cold stress, which leads to sterility and reduced yields. To understand the cold response mechanism at that stage, we used an mRNA differential display method to isolate cold-responsive genes from pre-anthesis flowers. Approximately 5,000 transcripts were identified here, of which 123 were found to be displayed differentially between the control (30 degrees C) and cold-treated (12 degrees C) flowers. Among them, 26 were analyzed by northern analysis; 8 of those clones were confirmed as cold-responsive. OsLti6b, encoding a hydrophobic protein homologous to Arabidopsis RCI2, was analyzed in detail. RNA blot analysis revealed that its transcript is increased by cold, salt, drought, or ABA treatments. In situ hybridization indicated that this transcript is highly accumulated in the ovaries and stamens of cold-treated flowers, particularly in the anther walls and vascular tissues of the filaments. Over-expression of OsLti6b increased cold tolerance as revealed by seedling wilting rates and ion leakages of mature leaves, demonstrating that the extent of the tolerance correlates well with its expression level.

Cold Temperature↗
PubMed1979

Responses of high altitude natives a standard cold test at sea level.

Studies have been conducted to evaluate the thermoregulatory, calorigenic, and peripheral vascular responses to cold of high altitude (HA) natives on their descent to sea level. Two groups of subjects (18 each), one representing high altitude (3500 m) natives and the other lowlanders, were exposed to a standard cold test at 10 degrees C wearing only shorts for 2 h. Their heart rate (HR), blood pressure (BP), oxygen consumption (VO2), oral temperature (Tor), mean weighted skin temperature (Ts) and shivering activity were recorded initially in a thermoneutral room, and 30 min intervals during the cold exposure. Afterwards, their cold-induced vasodilatation (CIVD) response was studied and the peripheral blood flow during local cold stress was calculated. The responses were statistically compared. The highlanders maintained significantly higher Tor, Tb (mean body temperature), Ts and peripheral Ts during cold stress, and they shivered much less and showed higher CIVD response and peripheral blood flow than the other group. The rise in VO2 on cold stress was identical. The observations showed better cold tolerance for high altitude natives compared to lowlanders, even at sea level.

Adult↗
PubMedDate not supplied

Cold-induced fever and peak metabolic rate in the nine-banded armadillo (Dasypus novemcinctus).

In response to cold exposure, some mammals, including the nine-banded armadillo (Dasypus novemcinctus), exhibit an increase in core temperature. This response, which can be qualified as a cold-induced fever, could increase cold tolerance by increasing peak metabolic rates because of the Q(10) effects. This hypothesis, however, is not compatible with the observation that peak core temperature can occur up to 100 min before peak metabolic rate in nine-banded armadillos during acute exposure to cold heliox (79% He; 21% O(2)). This temporal separation between the timing of peak metabolic rate and core temperature could be the result of regional heterothermy, of the confounding effects of activity, or of using heliox as a respiratory gas. We tested these potential sources of error by exposing nine-banded armadillos to cold air while simultaneously monitoring behavior, metabolic rates (V dot o2 and V dot co2), and four core temperatures. Cold air exposure resulted in a smaller but significant temporal separation, with peak core temperature occurring on average 10 min before peak metabolic rate. Animals exhibited low activity levels, and the four core temperatures changed according to the same temporal pattern, thus eliminating the possibility that activity or regional heterothermy caused the temporal separation. Using a conceptual model, we propose that the temporal separation resulted from a rate of cooling that was too fast.

Animals↗
PubMed1997

Importance of supercooling points in the overwintering of the horn fly and stable fly (Diptera:Muscidae).

Supercooling points were determined for eggs, 3rd instars, pupae, newly emerged unfed adults and 3-d-old engorged laboratory reared adults of Haematobia irritans (L.) and Stomoxys calcitrans (L.). Wild nondiapausing and diapausing pupae of H. irritans also were tested. Mean supercooling points ranged from -28.0 degrees C for H. irritans eggs to -6.8 degrees C for H. irritans larvae. Mean supercooling points of all H. irritans developmental stages were lower than those of comparable S. calcitrans developmental stages, with the exception of larvae where the reverse was true. The mean supercooling point of diapausing H. irritans pupae (-23.5 degrees C) was significantly lower than those of nondiapausing laboratory pupae (-20.8 degrees C) or nondiapausing wild pupae (-20.2 degrees C). Developmental stages of both species were freeze intolerant, with no survival following exposures to temperatures below the supercooling points. Results are discussed with respect to the disparate overwintering strategies of these species and in relation to typical climatic minima experienced in south central Texas. The cold tolerance of H. irritans and S. calcitrans pupae was compared at 4 degrees C, a temperature below their developmental threshold of 11.5 degrees C and above their mean supercooling points. The survival of H. irritans pupae was significantly greater than the survival of S. calcitrans pupae. Cold injury was a significant mortality factor for both species.

Animals↗
PubMed2006

Drosophila melanogaster holocarboxylase synthetase is a chromosomal protein required for normal histone biotinylation, gene transcription patterns, lifespan, and heat tolerance.

Post-translational modifications of histones play important roles in chromatin structure and genomic stability. Distinct lysine residues in histones are targets for covalent binding of biotin, catalyzed by holocarboxylase synthetase (HCS) and biotinidase (BTD). Histone biotinylation has been implicated in heterochromatin structures, DNA repair, and mitotic chromosome condensation. To test whether HCS and BTD deficiency alters histone biotinylation and to characterize phenotypes associated with HCS and BTD deficiency, HCS- and BTD-deficient flies were generated by RNA interference (RNAi). Expression of HCS and BTD decreased by 65-90% in RNAi-treated flies, as judged by mRNA abundance, BTD activity, and abundance of HCS protein. Decreased expression of HCS and BTD caused decreased biotinylation of K9 and K18 in histone H3. This was associated with altered expression of 201 genes in HCS-deficient flies. Lifespan of HCS- and BTD-deficient flies decreased by up to 32% compared to wild-type controls. Heat tolerance decreased by up to 55% in HCS-deficient flies compared to controls, as judged by survival times; effects of BTD deficiency were minor. Consistent with this observation, HCS deficiency was associated with altered expression of 285 heat-responsive genes. HCS and BTD deficiency did not affect cold tolerance, suggesting stress-specific effects of chromatin remodeling by histone biotinylation. To our knowledge, this is the first study to provide evidence that HCS-dependent histone biotinylation affects gene function and phenotype, suggesting that the complex phenotypes of HCS- and BTD-deficiency disorders may reflect chromatin structure changes.

Animals↗
PubMed2006

Methionine-rich storage protein gene in the rice stem borer, Chilo suppressalis, is expressed during diapause in response to cold acclimation.

Gene expressions of acclimatized and non-acclimatized diapausing larvae were examined in Chilo suppressalis using a subtraction technique. A gene encoding a methionine-rich storage protein, CsSP1, was cloned and its complete cDNA sequence was determined. Potentially, CsSP1 encoded a 758-amino acid protein, with a calculated molecular weight of 88.8 kDa. The expression level of CsSP1 was higher in nondiapausing larvae than in diapausing ones. The CsSP1 expression was up-regulated in diapausing larvae when the temperature of cold acclimation was shifted to 5 degrees C. The up-regulated level was maintained at 40 days after incubation at 5 degrees C. In nondiapausing larvae, CsSP1 expression was down-regulated when the temperature was below developmental zero. Involvement of CsSP1 in diapause, cold tolerance acquisition and postdiapause development in C. suppressalis is discussed.

Acclimatization↗
PubMedDate not supplied

Cold acclimation in eucalypt hybrids.

We evaluated cold resistance and the capacity for cold acclimation of different Eucalyptus genotypes. Seedlings of half-sib families of E. globulus and hybrids E. gunnii x globulus, E. viminalis x globulus and E. cypellocarpa x globulus were exposed daily for 56 days to a 9-h photoperiod at 14.7 degrees C, followed by 15 h in a dark cold room maintained at 2.5 degrees C with the root system maintained at 8 degrees C to cold harden the seedlings. Unhardened seedlings were maintained at about 16 degrees C during the dark period. Cold acclimation occurred in all families with decreases in the temperature causing 50% mortality (LT(50)) of between 1.5 and 3 degrees C. Both hardened and unhardened plants of hybrid families were more cold tolerant than E. globulus. A significant correlation between LT(50) and leaf osmotic pressure was observed; the increase in osmotic pressure in hardened plants was predominantly a result of an increase in the concentration of soluble sugars. Exotherm peaks were similar in hardened and unhardened plants. These results indicate that cold hardening increased the ability of eucalypts to endure extracellular ice formation. The maintenance of photosynthetic capacity in cold-hardened plants may also play a role in their response to freezing.

Journal Article↗
PubMed1997

Seasonal expression of a dehydrin gene in sibling deciduous and evergreen genotypes of peach (Prunus persica [L.] Batsch).

A cDNA library was created from cold-acclimated bark tissue of peach and selectively probed using an antibody directed against the lysine-rich consensus region of dehydrin proteins. Several clones were thus obtained which had a high degree of sequence similarity to other dehydrin genes. Northern analysis, using clone 5a, indicated that a 1.8 kb transcript was seasonally expressed in sibling deciduous and evergreen genotypes of peach, and also inducible by water deficit in cv. Rio Oso Gem. The evergreen and deciduous genotypes differ significantly in both their ability to cold-acclimate and in the seasonal expression of the dehydrin transcript and protein. In both genotypes, the transcript was maximally expressed during winter and undetectable in May-July. The evergreen genotype (less cold-tolerant), however, displayed transcript accumulation which lagged behind and declined sooner than in the deciduous genotype. Protein expression was similar to transcript expression, however, protein expression in the evergreen genotype lagged considerably behind transcript accumulation in the fall. This indicates that several levels of regulation of dehydrin proteins may exist during cold acclimation. A genomic clone (G10a) was isolated which contained the full-length dehydrin gene, designated ppdhn1. The peach dehydrin gene encodes 472 amino acids with a predicted size of 50,020 Da. The encoded protein (PCA60) contains nine of the lysine-rich repeats characteristic of dehydrins and two DEYGNP motifs at the amino acid terminus. A genomic blot, probed with clone 5a under stringent conditions, indicated that one or two highly homologous genes are present in peach, whereas an additional member was detected under low-stringency conditions. It is suggested that several members of the dehydrin gene family may exist in peach that vary in their relation to ppdhn1.

Acclimatization↗
PubMed1996

Survival and water-balance characteristics of unfed adult Amblyomma cajennense (Acari: Ixodidae).

Off-host survival, water balance, and cold tolerance of unfed adult, Cayenne ticks, Amblyomma cajennense (F.), were examined to evaluate species characteristics important to zoogeography and off-host ecology. Survivorship decreased when males and females were subjected to progressively drier constant environmental conditions. Average maximum survival was 641.2 and 682.5 d at 85% RH and 23 degrees C (2.98 mm Hg) for males and females, respectively. Mean survival in both sexes was progressively less variable in drier conditions. Slopes of log-linear models of survival days based on saturation deficit (mm Hg) were significantly different between males and females at 50%, but not at 25 or 0%. Whole-body water loss rates for 4-wk-old adults were measured at 0% RH and 23 degrees C until ticks became nonambulatory. The mean whole-body water loss rate of females, 0.06128% h-1, was 11.3% less than for males, 0.06914% h-1. Although nonambulatory ticks appeared dead, >1/2 of the individuals from each sex regained ambulatory status after they were removed from 0% RH and exposed to 96% RH for 24 h. Among these, male ticks averaged 0.44 more recuperative (ambulatory) cycles than females, although, the duration encompassing all recuperative cycles was generally longer for females and on average, females gained 8.16% more weight than males upon each rehydration. Estimates of the mean critical equilibrium activity for males and females were 0.74 av and 0.79 av, respectively. A. cajennense adults were found to be less tolerant to -12.5 degrees C than adult lone star ticks, Amblyomma americanum (L.), whose distribution encompasses more temperate regions. Although A. cajennense exhibit little host preference and are capable of extended off-host survival, the establishment of populations beyond this species zoogeographic distribution may be constrained by an intolerance to cold.

Animals↗
PubMed2025

Genetic and phenotypic diversity of wine-associated Hanseniaspora species.

The genus Hanseniaspora includes apiculate yeasts commonly found in fruit- and fermentation-associated environments. Their genetic diversity and evolutionary adaptations remain largely unexplored despite their ecological and oenological significance. This study investigated the phylogenetic relationships, genome structure, selection patterns, and phenotypic diversity of Hanseniaspora species isolated primarily from Australian wine environments, focusing on Hanseniaspora uvarum, the most abundant non-Saccharomyces yeast in wine fermentation. A total of 151 isolates were sequenced, including long-read genomes for representatives of the main phylogenetic clades. Comparative genomics revealed ancestral chromosomal rearrangements between the slow-evolving lineage (SEL) and fast-evolving lineage (FEL) that could have contributed to their evolutionary split, as well as significant loss of genes associated with mRNA splicing, chromatid segregation and signal recognition particle protein targeting in the FEL. Pangenome analysis within H. uvarum identified extensive copy number variation, particularly in genes related to xenobiotic tolerance and nutrient transport. Investigation into the selective landscape following the FEL/SEL divergence identified diversifying selection in 229 genes in the FEL, with significant enrichment in genes within the lysine biosynthetic pathway. Furthermore, phenotypic screening of 116 isolates revealed substantial intraspecific diversity, with specific species exhibiting enhanced ethanol, osmotic, copper, SO₂, and cold tolerance.

Wine↗
PubMed2004

Investigation of the interactive effects of gender and psychological factors on pain response.

OBJECTIVES: There is growing evidence to suggest that certain psychological modulators of pain sensitivity are dependent on gender. The aim of the present study was to examine further whether cognitive-affective factors (with specific focus on situational anxiety) shown to modulate pain report and behaviour have differential effects on men's and women's response to experimentally induced pain. METHOD: A sample of 80 healthy university students (40 women, 40 men) was assessed on subjective measures of anxiety (situational and dispositional), anxiety-sensitivity and attitudes toward the experimental pain procedure prior to being exposed to a cold pressor test (constant temperature + 1 degrees C; +/- 1 degrees C, cut-off limit 240 s). RESULTS: The present study produced three main findings: (1) No effect of gender was found on any of the pain measures; however, an interactive effect of anxiety and gender was found on measures of pain tolerance with low anxiety men displaying significantly higher pain tolerance than both low and high anxiety women. (2) Men classified as low-anxious tolerated cold pressor pain significantly longer than men classified as high-anxious, while no such effect of anxiety on pain response was observed in women. (3) Gender-specific associations were observed between other psychological variables (including anxiety-sensitivity and attitudes toward pain) and thermal pain response. CONCLUSION: Results from the present study suggest that there are important differences in the way cognitive-affective factors impact on the pain response of men and women. Further research is needed to explore potential psychosocial and physiological mechanisms that may underlie such differences.

Adult↗
PubMed2004

In vitro opioid induced proliferation of peripheral blood immune cells correlates with in vivo cold pressor pain tolerance in humans: a biological marker of pain tolerance.

There is substantial evidence for bidirectional communication between the immune system and the central nervous system, as the cells and signalling molecules of the immune system influence many central nervous system functions, for instance nociception. Opioids, such as morphine, produce analgesia and numerous other central and peripheral effects including sedation and euphoria, while their effects on the immune system are wide-ranging. There is considerable interindividual variability in basal nociception and response to opioids, however, the physiological and biological mechanisms underlying this are unclear. Therefore, we investigated the relationship between the immune system and basal nociceptive thresholds, using the proliferative response of isolated peripheral blood mononuclear cells and cold pressor pain tolerance. Here we show that the percent increase in proliferation of peripheral immune cells from 13 healthy subjects incubated with morphine ex vivo is highly correlated with the subjects' tolerance to noxious cold stimuli (Pearson r = 0.92, P < 0.0001). These pilot data provide evidence of a novel objective biological marker of pain tolerance in humans, which also links the immune and opioid systems with basal pain tolerance.

Adult↗
PubMed1995

Cold stability of pyruvate, orthophosphate dikinase of Flaveria brownii.

The nucleotide sequences of the complementary DNA of pyruvate, Pi dikinase (PPDK) from Flaveria bidentis, a C4 plant which possesses a cold-sensitive form of PPDK, and Flaveria brownii, a 'C4-like' plant which possesses a cold-tolerant form of PPDK, were determined. PPDK was isolated from the leaves of both Flaveria species and purified and the N-terminal amino acid sequences characterised. Together with a maize PPDK cDNA, cDNA inserts which code for the mature form of PPDK of F. bidentis and of F. brownii were expressed in bacteria and the cold sensitivity of the expressed PPDK studied. The cold sensitivity of the PPDK expressed in bacteria mimics the cold sensitivity of PPDK found in vivo in all three plant species. This study indicates that the cold sensitivity of plant PPDK is controlled by the primary structure of the enzyme.

Amino Acid Sequence↗
PubMed2001

Simultaneous observations of haemolymph flow and ventilation in marine spider crabs at different temperatures: a flow weighted MRI study.

In vivo magnetic resonance imaging (MRI) and angiography were applied to the marine spider crab Maja squinado for a study of temperature effects and thermal tolerance. Ventilation and haemolymph circulation were investigated during progressive cooling from 12 degrees C to 2 degrees C. The anatomical resolution of MR images from Maja squinado obtained with a standard spin echo sequence were suitable to resolve the structures of various internal organs. The heart of the animal could be depicted without movement artifacts. The use of a flow compensated gradient echo sequence allowed simultaneous observations of ventilation, reflected by water flow through the gill chambers as well as of haemolymph flow. Simultaneous investigation of various arteries was possible by use of flow weighted MRI. In addition to those accessible by standard invasive flow sensitive doppler sensors, flow changes in gill, leg arteries and the venous return could be observed. Both ventilation and haemolymph flow decreased during progressive cooling and changes in haemolymph flow varied between arteries. Haemolymph flow through the Arteria sternalis, some gill and leg arteries was maintained at low temperatures indicating a reduced thermal sensitivity of flow in selected vessels. In support of previous invasive studies of haemolymph flow as well as heart and ventilation rates, the results demonstrate that the operation of gills and the maintenance of locomotor activity are critical for cold tolerance. A shift in haemolymph flow between arteries likely occurs to ensure the functioning of locomotion and ventilation in the cold.

Animals↗
PubMed2000

Phylogenetic relationships and climatic adaptations in the Drosophila takahashii and montium species subgroups.

We analyze phylogenetic relationships among temperate, subtropical highland, and subtropical lowland species of the Drosophila takahashii and montium species subgroups based on sequence data of COI and Gpdh genes and discuss the evolution of temperate species in these subgroups with reference to their climatic adaptations. In the takahashii subgroup, D. lutescens (the temperate species) branched off first in the tree based on the combined data set, but D. prostipennis (the subtropical highland species) branched off first in the trees based on single genes. Thus, phylogenetic relationships in this subgroup are still ambiguous. In the montium subgroup, the cool-temperate species are phylogenetically close to the warm-temperate species, and these cool- and warm-temperate species form a cluster with the subtropical highland species. This suggests that perhaps the cool-temperate species derived from the warm-temperate species and the warm-temperate species derived from the subtropical highland species. In comparison with the subtropical lowland species, the subtropical highland species may be better able to colonize temperate areas since, as in the temperate species, they have an ability to develop their ovaries at moderately low temperature. However, the subtropical highland species, as well as the subtropical lowland species, were much less cold tolerant than the temperate species. Therefore, considerable genetic reformation would be required for both the subtropical highland and the subtropical lowland species to adapt to temperate climates.

Acclimatization↗
PubMed1990

Thermogenesis and thermoregulatory function of iron-deficient women without anemia.

Physiological responses at 16 degrees C were studied in 11 women, age 28 +/- 2(mean +/- S.E.) years and 26 +/- 2% fat, after their body iron stores were depleted by diet (5.0 mg iron x 2,000 kcal-1 x d-1), phlebotomy and menstruation for about 80 d and were repleted by diet (13.7 mg iron x 2,000 kcal-1 x d-1) for about 100 d, including daily iron supplementation (50 mg of iron as ferrous sulfate) for the last 14 d of repletion. Iron depletion was characterized by a decline (p less than 0.05) in hemoglobin (12.0 +/- 0.2 g x dl-1), ferritin (5.5 +/- 0.5 ng x ml-1) and body iron balance (-9.1 +/- 2.6 mg x 6 d-1). Iron repletion, including supplementation, increased (p less than 0.05) hemoglobin (12.6 +/- 0.1 g x dl-1), ferritin (9.5 +/- 0.4 ng x ml-1) and iron balance (+67 +/- 6.7 mg x 6 d-1). Iron depletion reduced (p less than 0.05) metabolic heat production (49.6 +/- 1.1 vs 53.6 +/- 1.2 W x m-2) during acute cold exposure. The rates of cooling of the core and periphery were greater (p less than 0.05) during iron depletion than repletion. A shift in the lower core temperature threshold for shivering was paralleled by an earlier onset of shivering (p less than 0.05) in iron depletion indicating an adaptation in cold tolerance in an attempt to maintain core temperature. Iron depletion was associated with blunted post-exposure increases in plasma thyroid hormone concentrations and greater (p less than 0.05) increases in plasma norepinephrine concentrations as compared to iron repletion. In a subsample of the women, no significant effect of calcium or ascorbic acid supplementation was found on responses to cold exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed2003

ICE1: a regulator of cold-induced transcriptome and freezing tolerance in Arabidopsis.

Cold temperatures trigger the expression of the CBF family of transcription factors, which in turn activate many downstream genes that confer chilling and freezing tolerance to plants. We report here the identification of ICE1 (inducer of CBF expression 1), an upstream transcription factor that regulates the transcription of CBF genes in the cold. An Arabidopsis ice1 mutant was isolated in a screen for mutations that impair cold-induced transcription of a CBF3 promoter-luciferase reporter gene. The ice1 mutation blocks the expression of CBF3 and decreases the expression of many genes downstream of CBFs, which leads to a significant reduction in plant chilling and freezing tolerance. ICE1 encodes a MYC-like bHLH transcriptional activator. ICE1 binds specifically to the MYC recognition sequences in the CBF3 promoter. ICE1 is expressed constitutively, and its overexpression in wild-type plants enhances the expression of the CBF regulon in the cold and improves freezing tolerance of the transgenic plants.

Acclimatization↗