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At least 91 records · Page 5Linked to original sources
PubMed2005

Enhanced cold tolerance in transgenic tobacco expressing a chloroplast omega-3 fatty acid desaturase gene under the control of a cold-inducible promoter.

A new cold-inducible genetic construct was cloned using a chloroplast-specific omega-3-fatty acid desaturase gene (FAD7) under the control of a cold-inducible promoter (cor15a) from Arabidopsis thaliana. RT-PCR confirmed a marked increase in FAD7 expression, in young Nicotiana tabacum (cv. Havana) plants harboring cor15a-FAD7, after a short-term exposure to cold. When young, cold-induced tobacco seedlings were exposed to low-temperature (0.5, 2 or 3.5 degrees C) for up to 44 days, survival within independent cor15a-FAD7 transgenic lines (40.2-96%) was far superior to the wild type (6.7-10.2%). In addition, the major trienoic fatty acid species remained stable in cold-induced cor15a-FAD7 N. tabacum plants under prolonged cold storage while the levels of hexadecatrienoic acid (16:3) and octadecatrienoic acid (18:3) declined in wild type plants under the same conditions (79 and 20.7% respectively). Electron microscopy showed that chloroplast membrane ultrastructure in cor15a-FAD7 transgenic plants was unaffected by prolonged exposure to cold temperatures. In contrast, wild type plants experienced a loss of granal stacking and disorganization of the thylakoid membrane under the same conditions. Changes in membrane integrity coincided with a precipitous decline in leaf chlorophyll concentration and low survival rates in wild type plants. Cold-induced double transgenic N. alata (cv. Domino Mix) plants, harboring both the cor15a-FAD7 cold-tolerance gene and a cor15a-IPT dark-tolerance gene, exhibited dramatically higher survival rates (89-90%) than wild type plants (2%) under prolonged cold storage under dark conditions (2 degrees C for 50 days).

Arabidopsis↗
PubMed2006

[Seasonal changes in foliar micro-and ultra structure of two Sabina species and their relationships with cold tolerance].

In this paper, the foliar micro-and ultra structure of Sabina przewalskii and S. chinensis during growth and dormancy seasons was observed under microscope and transmission electron microscope, and the foliar soluble sugar content was measured, aimed to probe into their relationships with cold tolerance. The results showed that the foliar surface cells of these two Sabina species were covered with thick cuticular membrane, and the well-developed arenchyma appeared in the mesophyll. In growth season, starch grains accumulated in chloroplasts, but in dormancy season, the accumulated starch grains disappeared or diminished, while soluble sugar content had a larger increase. In wintertime, the chloroplasts of S. chinensis were injured, with some abnormal chloroplasts, increased plastoglobuli and some lipid drops, while those of S. przewalskii were not obviously injured. It was suggested that the cold tolerance of the two Sabina species was related to their well-developed arenchyma, accumulation of starch grains in growth season, and increase of soluble sugar content in dormancy season. S. przewalskii had more marked increase of soluble sugar content, and its chloroplasts were more stable than S. chinensis.

Adaptation, Physiological↗
PubMed2000

Aspects of natural cold tolerance in ectothermic animals.

Polar, alpine and temperate ectothermic (cold-blooded) animals encounter temperatures below the melting point of their body fluids either diurnally or seasonally. These animals have developed a number of biochemical and physiological adaptations to survive the low temperatures. The problems posed to the animals during cold periods include changes in membrane and protein structure due to phase changes in these molecules, changes in electrolyte concentrations and other solutes in the body fluids as well as changes in metabolism. Cold-tolerant ectothermic animals can be divided into two groups depending which of two 'strategies' they employ to survive the low temperatures: freeze-tolerant animals which survive ice formation in the tissues and freeze-avoiding animals which tolerate the low temperatures but not crystallization of the body fluids. The adaptations are mainly directed towards the control or avoidance of ice formation and include the synthesis of low mol. wt cryoprotectants, ice-nucleating agents and antifreeze proteins. However, some of the adaptations such as the synthesis of low mol. wt cryoprotectants are also more specific in their mechanism, e.g. direct stabilizing interaction with membranes and proteins. The mechanisms employed by such animals may offer ideas and information on alternative approaches which might be usefully employed in the cryopreservation of cells and tissues frequently required in assisted reproductive technology.

Adaptation, Physiological↗
PubMed1993

Cold tolerance and water content of current-year red spruce foliage over two winter seasons.

Red spruce (Picea rubens Sarg.) in high elevation forests of northeastern North America suffers from frequent and severe winter injury, leading to apical dieback, decreased growth, and high mortality. To examine the role of winter desiccation and freezing injury in winter damage, weekly assessments of cold tolerance and water content were made on current-year foliage collected from native red spruce trees at a high elevation site over two winter seasons. In both years, foliage maintained high water contents and adequate cold tolerance; nonetheless, slight to moderate injury was observed each year on some trees. Despite brief thaw periods each winter, no mid-winter dehardening sufficient to put foliage at risk of freezing injury was evident. These findings suggest that, at least in some years, winter injury to current-year red spruce foliage is produced by a mechanism other than desiccation or absolute low temperatures.

Journal Article↗
PubMed1993

Effects of ephedrine/xanthines on thermogenesis and cold tolerance.

This paper reviews the use of ephedrine (E) and xanthines (X) to improve thermogenesis and cold tolerance. Recent experiments in cold-exposed subjects have shown that the beneficial effects of ingesting an E/caffeine (C) capsule on metabolic rate (M), heat debt, deep body core temperature (Tre) (P < 0.05) is entirely comparable to that observed with an E/C/theophylline (T) capsule. Although T has been reported to reduce the drop in Tre in several studies, these improvements are difficult to explain in the absence of changes in M. A theobromine-based commercial sports bar (Cold Buster) has been similarly shown to reduce the drop in Tre. However, such a claim could not be confirmed in our lab, even in two studies performed under different environmental conditions. Despite an increase in M in some studies, C had no effect on Tre in the cold. It is concluded that E/X represent, at the moment, the best pharmacological agents to enhance cold thermogenesis and to delay the onset of hypothermia in humans.

Basal Metabolism↗
PubMed1985

Influence of the menstrual cycle on Raynaud's phenomenon and on cold tolerance in normal women.

Digital strain gauge plethysmography during a controlled cycle of hand warming and cooling was performed at weekly intervals through a single menstrual cycle in 10 normal women and 6 patients with idiopathic Raynaud's phenomenon (RP). Results were compared to those in 16 additional RP patients and 5 normal males. Maximum digital arterial flow at finger temperature 38 degrees C and reactive hyperemia following three minute arterial occlusion at 30 degrees C was comparable for all groups and did not vary with menstrual status. During cooling, normal women manifested plethysmographic loss of digital arterial flow at finger temperatures (18.1 degrees C +/- 7.9) intermediate between those of normal men (13.7 degrees C +/- 4.3, P less than 0.05) and RP patients (26.0 degrees C +/- 6.1, P less than 0.001). RP patients showed no change in cold tolerance in relation to menstrual status. However, normal women had variable responses to cooling and were found least cold tolerant at the time of menstruation with RP-like responses in all 10 cases although digital color changes were absent. These data support the hypothesis that RP in the premenopausal woman is physiologic and thus, in the majority of cases, not likely to evolve into a definable connective tissue disease.

Adolescent↗
PubMed1997

Chromosome mapping of low-temperature induced Wcs120 family genes and regulation of cold-tolerance expression in wheat.

Low-temperature (LT) induced genes of the Wcs120 family in wheat (Triticum aestivum) were mapped to specific chromosome arms using Western and Southern blot analysis on the ditelocentric series in the cultivar Chinese Spring (CS). Identified genes were located on the long arms of the homoeologous group 6 chromosomes of all 3 genomes (A, B, and D) of hexaploid wheat. Related species carrying either the A, D, or AB genomes were also examined using Southern and Western analysis with the Wcs120 probe and the WCS120 antibody. All closely related species carrying one or more of the genomes of hexaploid wheat produced a 50 kDa protein that was identified by the antibody, and a Wcs120 homoeologue was detected by Southern analysis in all species. In the absence of chromosome arm 6DL in hexaploid CS wheat no 50 kDa protein was produced and the high-intensity Wcs120 band was missing, indicating 6DL as the location of Wcs120 but suggesting silencing of the Wcs120 homoeologue in the A genome. Levels of proteins that cross-reacted with the Wcs120 antibody and degrees of cold tolerance were also investigated in the Chinese Spring/Cheyenne (CS/CNN) chromosome substitution series. CNN chromosome 5A increased the cold tolerance of CS wheat. Densitometry scanning of Western blots to determine protein levels showed that the group 5 chromosome 5A had a regulatory effect on the expression of the Wcs120 gene family located on the group 6 chromosomes of all three hexaploid wheat genomes.

Adaptation, Physiological↗
PubMed1977

Significance of anomalous thermoregulation in the pre-diabetic spiny mouse (Acomys cahirinus): cold tolerance: blood glucose and food consumption responses to environmental heat.

Decreased cold tolerance, reduced food requirement for body weight maintenance and comparative resistance to the hypoglycaemic effect of fasting in high ambient temperatures have been demonstrated in the spiny mouse. These phenomena could be related to anomalous spiny mouse thermoregulation, a phenomenon which is common in desert rodents and is simulated by mutant and artificially diabetic rodent species. The data can be interpreted as showing evidence for a survival advantage of genotypes with potential diabetic expression, and may provide an explanation of the geographic distribution of certain species.

Animals↗
PubMed1997

The Arabidopsis TCH4 xyloglucan endotransglycosylase. Substrate specificity, pH optimum, and cold tolerance.

Xyloglucan endotransglycosylases (XETs) modify a major component of the plant cell wall and therefore may play critical roles in generating tissue properties and influencing morphogenesis. An XET-related gene family exists in Arabidopsis thaliana, the members of which show differential regulation of expression. TCH4 expression is rapidly regulated by mechanical stimuli, temperature shifts, light, and hormones. As a first step in determining whether Arabidopsis XET-related proteins have distinct properties, we produced recombinant TCH4 protein in bacteria and determined its enzymatic characteristics. TCH4 specifically transglycosylates only xyloglucan. The enzyme prefers to transfer a portion of a donor polymer onto another xyloglucan polymer (acceptor); TCH4 will also utilize xyloglucan-derived oligosaccharides as acceptors but discriminates between differentially fucosylated oligosaccharides. TCH4 is most active at pH 6.0 to 6.5 and is surprisingly cold-tolerant with an optimum of 12 to 18 degrees C. TCH4 activity is enhanced by urea and bovine serum albumin, but nor cations, reducing agents, or carboxymethylcellulose. These studies indicate that TCH4 is specific for xyloglucan, but that the molecular mass and the fucosyl content of the substrates influence enzymatic reaction rates. TCH4 is unlikely to play a role in acid-induced wall loosening but may function in cold acclimation or cold-tolerant growth.

Animals↗
PubMed1994

Sympathetic nervous activity to brown adipose tissue increases in cold-tolerant mice.

Brown adipose tissue (BAT) is thought to be responsible for increased heat production in cold-acclimated rodents. We measured sympathetic nerve activity (SNA) in interscapular BAT (IBAT) during cold stimulation in cold-acclimated C57BL/6J mice (ACCLI). Cold acclimation was achieved (cold tolerance was increased) by repeated exposure to cold stress every other week for 3 weeks. We compared SNA in these animals with SNA in mice that had no previous cold stress experience (naive). During the test, mice were anesthetized by urethane and isoflurane and were paralyzed with vecuronium bromide. Sympathetic nerve activity was recorded directly from one of the fine nerves to IBAT. The animal's body caudal to the pelvic area was covered with a plastic bag containing a slurry of ice water to decrease colonic temperature 7 degrees C below control level, which took approximately 20 min. Interscapular BAT-SNA increased during cold stress in both groups, but ACCLI mice had higher IBAT-SNA during cold stress than naive mice. These findings confirmed the hypothesis that during the acute cold exposure, cold-acclimated mice have greater sympathetic outflow to BAT adipocytes.

Acclimatization↗
PubMed1992

Decrease in cold tolerance of aged rats caused by the enhanced endogenous adenosine activity.

During severe cold exposure, old rats (24-28 months) were less capable of maintaining their body temperature compared to young rats (3-6 months) due to lower rate of heat production. Single injection of adenosine deaminase (AD) (converts adenosine to inosine) significantly increased thermogenesis in both young and old rats. However, doubling the dose of AD was required for optimal thermogenic response in old rats. In contrast, the similar enhancements in both thermogenesis and cold tolerance were observed in both young and old rats receiving the same optimal doses of specific adenosine receptor antagonists. These results lead to the suggestion that the lower capability of aged rats to withstand cold exposure could be due to an increase in adenosine stimulation because of the decreased endogenous AD activity rather than an increase in adenosine receptor sensitivity. This notion is further supported by the finding that the AD activity in the neck muscle, a key site for shivering thermogenesis, was significantly lower in old rats as compared to their younger counterparts before and after cold exposure.

Adenosine↗
PubMed2001

Cold stress induced high molecular weight membrane polypeptides are responsible for cold tolerance in Rhizobium DDSS69.

Cold stress induces a lag phase in the growth cycle of Rhizobium DDSS69. Two cold sensitive mutants of DDSS69 were generated through Tn5 tagged mutagenesis. These mutants do not grow below 15 degrees C but show a growth curve comparable with the wild type grown at 5 degrees C. There is a rapid induction of two high molecular weight membrane polypeptides of 135 and 119 kDa within 15 min of exposure to 5 degrees C in DDSS69. PAGE membrane protein profiles of stressed and non-stressed cells reveal differential regulation of genes. At 15 degrees C both mutants lack the high molecular weight polypeptides, suggesting a role in alleviation of cold stress.

Acclimatization↗
PubMed2004

Dietary phytoestrogens increase metabolic resistance (cold tolerance) in long-chain acyl-CoA dehydrogenase-deficient mice.

We evaluated the role of dietary phytoestrogens (PE) in the disease phenotype of cold intolerance that characterizes long-chain acyl-CoA dehydrogenase-deficient (LCAD-/-) mice, a model of inborn errors of mitochondrial fatty acid beta-oxidation. Male LCAD-/- mice were fed a standard diet containing endogenous PE, a PE-free diet, or a PE-free diet that was supplemented with genistein (250 microg/g diet). The standard diet did not restore complete cold tolerance, but it provided more resistance (P = 0.004) to cold challenge than the PE-free diet. There was a nonsignificant difference (P < 0.07) between LCAD-/- mice fed the genistein-supplemented diet and those fed the PE-free diet. There were no differences in end-point serum glucose concentrations among the 3 groups. Serum FFA were decreased in LCAD-/- mice fed the standard diet compared with those fed the PE-free diet (P = 0.005) and the diet supplemented with genistein (P < 0.001). Serum triglyceride concentrations were greater (P < 0.05) only in LCAD-/- mice fed the genistein-supplemented diet than those fed the standard diet. These results demonstrate the beneficial effects of dietary PE on metabolic tolerance in LCAD-/- mice. Furthermore, they suggest changes that could improve pediatric formula constituents, especially with regard to management of children with inborn errors of fatty acid oxidation.

Acclimatization↗
PubMedDate not supplied

[Analysis of structural characteristics of alpha-tubulins in plants with enhanced cold tolerance].

The uniqueness of the point substitutions in the sequences of two alpha-tubulin isotypes from psychrophilic alga Chloromonas that can determine the increased cold tolerance of this alga was analyzed. The comparison of all known amino acid sequences of plant alpha-tubulins enabled to ascertain that only M268-->V replacement is unique and may have a significant influence on spatial structure of plant alpha-tubulins. Modeling of molecular surfaces of alpha-tubulins from Chloromonas, Chalmydomonas reinhardtii and goose grass Eleusine indica showed that insertion of the amino acid replacement M268-->V into the sequence of goose grace tubulin led to the likening of this protein surface to the surface of native alpha-tubulin from Chloromonas. Alteration of local hydrophobic properties of alpha-tubulin molecular surface in interdimeric contact zone as a result of the mentioned replacement was shown that may play important role in increasing the level of cold resistance of microtubules. The crucial role of amino acid residue in 268 position for forming the interdimeric contact surface of alpha-tubulin molecule was revealed. The assumption is made about the importance of replacements at this position for plant tolerance to abiotic factors of different nature (cold, herbicides).

Amino Acid Sequence↗
PubMed2001

Cold tolerance and proline metabolic gene expression in Drosophila melanogaster.

Treatment of Drosophila melanogaster adults with an inhibitor of protein synthesis led to a decrease in intrinsic cold-shock tolerance, but no difference in the rapid cold hardening response, which is apparent only if a period at 4 degrees C precedes the cold stress. Increases in energy reserves, including proline, were found in lines of flies selected for resistance to chilling injury. Since an increase in proline levels has been associated with overwintering in insects, and for salt and cold tolerance in plants, an RNase protection assay was developed to assess changes in transcript abundance for two genes encoding enzymes important for proline metabolism, pyrroline 5-carboxylate reductase and proline oxidase. The mRNA levels did not change in response to low temperature, but the high level of pyrroline 5-carboxylate reductase transcript is consistent with the interpretation that a large proline pool is important for Drosophila metabolism and survival during cold stress.

Journal Article↗
PubMed1999

Effects of prepartum supplementary fat and muscle hypertrophy genotype on cold tolerance in newborn calves.

Effects of feeding pregnant dams supplemental dietary fat during the last 55 d of gestation on cold tolerance of newborn crossbred calves with (Piedmontese cross, P, n = 15) or without (Hereford cross, H, n = 16) the muscle hypertrophy allele was determined. Primiparous F1 dams gestating F2 calves of the respective breeds were assigned randomly within breed to receive gestation diets containing either 2.2 (Low Fat; LF) or 5.1% fat (High Fat; HF). Safflower (Carthamus tinctorius L.) seeds containing 37% oil with 79% linoleic acid were the supplemental fat source in diets formulated to be isocaloric-isonitrogenous. At parturition, calves were separated from their dams, fed 38 degrees C pooled dairy cow colostrum (30 mL/kg BW), muzzled to prevent suckling, and returned to their dams in a heated (22 degrees C) room for 3.5 h. At 4 h of age (birth = 0 h), a catheter was inserted into the jugular vein. At 5 h of age, calves were placed in a 0 degrees C room for 140 min, and rectal temperatures and blood samples were obtained at 10- and 20-min intervals. Blood was assayed for cortisol and glucose. Rectal temperature was affected by diet (P<.05), time, diet x time, and breed x time (P<.01 for time and the interactions). Cortisol and glucose concentrations were not affected by diet, breed, or the diet x breed interaction, but they were affected by time, breed x time (both P<.01), and diet x time (P = .06). Calves from HF dams had higher rectal temperatures than calves from LF dams, and the HF calves maintained higher rectal temperatures throughout cold exposure. Cortisol concentrations were lower (P = .06) in calves from HF dams, and these calves had more (P = .06) glucose available for metabolic heat production than calves from LF dams. Piedmontese-cross calves maintained higher (P<.01) rectal temperatures and had higher cortisol and glucose (both P<.01) concentrations than did H-cross calves. We conclude that feeding dams supplemental fat during late gestation increased heat production in newborn calves and potentially could increase calf survival; calves with muscle hypertrophy may have a different ratio of shivering vs nonshivering thermogenesis due to differences in body composition or relationships among uncoupling proteins.

Adaptation, Physiological↗
PubMed2006

[Cold tolerance and its seasonal variation of Catantops pinguis Stal].

By the method of supercooling point (SCP) determination, this paper studied the cold tolerance of Catantops pinguis Stal in different seasons, and the effects of insect body water content, crude fat, total protein and total sugar on it. The results showed that there was a significant seasonal variation in the SCP of C. pinguis. The mean SCP value of fall C. pinguis population was (-23.1 +/- 0.2) degrees C, while that of post-winter and summer C. pinguis populations was (-19.3 +/- 0.1) degrees C and (-4.0 +/- 0.1) degrees C, respectively. The water content in summer population was significantly higher than that in winter population, but little difference was observed in fall and post-winter populations, indicating that C. pinguis had eliminated the redundant dissociate water during the preparation period for its over-wintering. After winter, the contents of fat and sugar in C. pinguis decreased significantly because the storage of these compounds was expended to maintain the body temperature at winter time, and consequently, resulted in a marked increase of SCP in post-winter population. There was no significant difference in the contents of water and crude fat between female and male C. pinguis, but the total protein content of female C. pinguis was higher than that of male C. pinguis in summer while significantly lower in winter, because large amount of nutrients was expended by the female C. pinguis to form eggs.

Adaptation, Physiological↗
PubMed2001

Rapid low temperature-induced stomatal closure occurs in cold-tolerant Commelina communis leaves but not in cold-sensitive tobacco leaves, via a mechanism that involves apoplastic calcium but not abscisic acid.

Commelina communis stomata closed within 1 h of transferring intact plants from 27 degrees C to 7 degrees C, whereas tobacco (Nicotiana rustica) stomata did not until the leaves wilted. Abscisic acid (ABA) did not mediate cold-induced C. communis stomatal closure: At low temperatures, bulk leaf ABA did not increase; ABA did not preferentially accumulate in the epidermis; its flux into detached leaves was lower; its release from isolated epidermis was not greater; and stomata in epidermal strips were less sensitive to exogenous ABA. Stomata of both species in epidermal strips on large volumes of cold KCl failed to close unless calcium was supplied. Therefore, the following cannot be triggers for cold-induced stomatal closure in C. communis: direct effects of temperature on guard or epidermal cells, long-distance signals, and effects of temperature on photosynthesis. Low temperature increased stomatal sensitivity to external CaCl(2) by 50% in C. communis but only by 20% in tobacco. C. communis stomata were 300- to 1,000-fold more sensitive to calcium at low temperature than tobacco stomata, but tobacco epidermis only released 13.6-fold more calcium into bathing solutions than C. communis. Stomata in C. communis epidermis incubated on ever-decreasing volumes of cold calcium-free KCl closed on the lowest volume (0.2 cm(3)) because the epidermal apoplast contained enough calcium to mediate closure if this was not over diluted. We propose that the basis of cold-induced stomatal closure exhibited by intact C. communis leaves is increased apoplastic calcium uptake by guard cells. Such responses do not occur in chill-sensitive tobacco leaves.

Abscisic Acid↗