Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cold tolerance”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed2006

Bacterial endophytes of the wildflower Crocus albiflorus analyzed by characterization of isolates and by a cultivation-independent approach.

The presence and taxonomy of endophytic bacteria of the entire aerial parts of crocus (Crocus albiflorus), a wildflower native in the Alps, were investigated. A combination of plating of plant macerates, isolation and sequence identification of isolates, and direct 16S rDNA PCR amplification followed by whole-community fingerprinting (T-RFLP) and by construction of a bacterial clone library was used. The results clearly indicated that a wide range of bacteria from diverse phylogenetic affiliation, mainly gamma-Proteobacteria and Firmicutes, live in association with plants of C. albiflorus. The community composition of the culturable component of the microflora was remarkably different from that of the clone library. Only three bacterial divisions were found in the culture collection, which represented 17 phylotypes, whereas six divisions were identified in the clonal analysis comprising 38 phylotypes. The predominant group in the culture collection was the low G+C Gram-positive group, whereas in the clone library, the gamma-Proteobacteria predominated. Interestingly, the most prominent bacterium within the uncultured bacterial community was a pseudo monad closely related to a cold-tolerant Pseudomonas marginalis strain. The results suggest that Crocus supports a diverse bacterial microflora resembling the microbial communities that have been described for other plants and containing species that have not been described in association with plants.

Crocus↗
PubMed1983

The effects of food deprivation on beta-adrenergic responsiveness in male rats.

Male rats were deprived of food for varying lengths of time (0-96 h) and their responses to beta-adrenergic stimulation with isoproterenol were tested. Food deprivation for 48 or 96 h attenuated the increase in tail skin temperature normally seen following administration of isoproterenol. The degree of attenuation was dependent on the duration of the deprivation period. Rats deprived of food for 96 h and then refed for 48, 96, or 144 h showed a return of tail skin temperature response to near normal levels. The increase in heart rate observed following administration of isoproterenol was also attenuated following 48 or 96 h of food deprivation. Again, the degree of attenuation was dependent on the duration of the deprivation period. Food deprivation for 96 h led to a decrease in basal plasma levels of T3, T4, and glucose. The increase in plasma glucose following administration of isoproterenol was also attenuated following 96 h of food deprivation. In contrast to the thermal, cardiac, and glucose responses, the dipsogenic response to isoproterenol was increased following food deprivation. The attenuation in beta-adrenergic responses observed in the food-deprived rats might help explain the effects of food deprivation on cold tolerance.

Animals↗
PubMed2005

Folsomia candida (Collembola): a "standard" soil arthropod.

Folsomia candida Willem 1902, a member of the order Collembola (colloquially called springtails), is a common and widespread arthropod that occurs in soils throughout the world. The species is parthenogenetic and is easy to maintain in the laboratory on a diet of granulated dry yeast. F. candida has been used as a "standard" test organism for more than 40 years for estimating the effects of pesticides and environmental pollutants on nontarget soil arthropods. However, it has also been employed as a model for the investigation of numerous other phenomena such as cold tolerance, quality as a prey item, and effects of microarthropod grazing on pathogenic fungi and mycorrhizae of plant roots. In this comprehensive review, aspects of the life history, ecology, and ecotoxicology of F. candida are covered. We focus on the recent literature, especially studies that have examined the effects of soil pollutants on reproduction in F. candida using the protocol published by the International Standards Organization in 1999.

Animals↗
PubMed1981

Regulation of energy balance.

The past 10-15 years have produced a significant increase in knowledge and theories concerning the regulation of energy balance, but the precision of this regulation is still uncertain. However, the fact that investigators have had to resort to a variety of techniques and ploys (some of them bizarre) to produce marked pertubations in body weight is in itself an indication that the regulatory system can be very robust. Although control of food intake obviously plays a major role in this system, control of energy expenditure (i.e. DIT) also has to be considered as an important factor in the maintenance of energy balance. In this review most of the evidence for DIT and its biochemical origins has been derived from studies on experimental animals. Many of the overfeeding studies carried out on man are consistent with the animal work, but because of differences in interpretation and some equivocal results, the role of DIT in human metabolism is still a contentious issue. This problem may not be fully resolved to everyone's satisfaction until complete, continuous, and very precise energy balance measurements are made on chronically overfed lean subjects. Before this expensive and arduous experiment is undertaken, evidence for thermogenesis in man will continue to depend on acute measurements of the metabolic response to various stimuli. An increasing number of studies (e.g. 35, 80) have demonstrated the existence of NST in man, and the possibility that this could originate from BAT is supported by histological (62, 148) and thermographic data (130). Conversely, reductions in cold tolerance (2, 18) and thermogenic responses to noradrenaline (82) with increasing adiposity are similar to the blunted responses seen in genetically obese animals, which suggests that human obesity may also involve an impairment in thermogenesis. At the present time these ideas concerning the important of DIT in man and its role in obesity remain somewhat speculative, but no doubt this area will now be the subject of further research. Similarly, the impact of early nutritional influences on subsequent energy balance regulation and resistance to obesity will receive more attention following the report (144) that hyperphagia in rats during early life results in a reduced body fat content and leanness in adulthood. The relative contributions and interactions between intake and output in energy balance need clarifying, and in terms of central organization, the mechanisms of appetite control should now be considered for their relevance to the control of thermogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)

Adipose Tissue↗
PubMed2004

Structure, function, and dietary regulation of delta6, delta5, and delta9 desaturases.

Fatty acid desaturases introduce a double bond in a specific position of long-chain fatty acids, and are conserved across kingdoms. Degree of unsaturation of fatty acids affects physical properties of membrane phospholipids and stored triglycerides. In addition, metabolites of polyunsaturated fatty acids are used as signaling molecules in many organisms. Three desaturases, Delta9, Delta6, and Delta5, are present in humans. Delta-9 catalyzes synthesis of monounsaturated fatty acids. Oleic acid, a main product of Delta9 desaturase, is the major fatty acid in mammalian adipose triglycerides, and is also used for phospholipid and cholesteryl ester synthesis. Delta-6 and Delta5 desaturases are required for the synthesis of highly unsaturated fatty acids (HUFAs), which are mainly esterified into phospholipids and contribute to maintaining membrane fluidity. While HUFAs may be required for cold tolerance in plants and fish, the primary role of HUFAs in mammals is cell signaling. Arachidonic acid is required as substrates for eicosanoid synthesis, while docosahexaenoic acid is required in visual and neuronal functions. Desaturases in mammals are regulated at the transcriptional level. Reflecting overlapping functions, three desaturases share a common mechanism of a feedback regulation to maintain products in membrane phospholipids. At the same time, regulation of Delta9 desaturase differs from Delta6 and Delta5 desaturases because its products are incorporated into more diverse lipid groups. Combinations of multiple transcription factors achieve this sophisticated differential regulation.

Animals↗
PubMed1992

Fish antifreeze proteins block Ca entry into rabbit parietal cells.

Many fish and insects have adapted to life at subfreezing temperatures by evolving so-called antifreeze proteins (AFP) that noncolligatively depress the freezing temperatures of aqueous solutions without affecting the melting temperature. AFP have been thought to function solely as antifreezes. Recently, however, we discovered that AFP also protect mammalian cells and organs from damage caused by exposure to hypothermic (above freezing) temperatures. It has been proposed that hypothermic damage is caused by changes in intracellular ionic content due to a reduction of active transport that is required to balance passive ion transport across cell membranes. Given this possibility, we tested whether AFP isolated from the Newfoundland ocean pout might reduce the Ca ion permeability of a mammalian cell, the rabbit gastric parietal cell, which has been particularly well studied in terms of Ca transport and signaling. Digital image processing of the Ca-sensitive fluorescent indicator fura-2 was used to measure intracellular free Ca in these cells. During stimulation with the cholinergic agonist carbachol, AFP inhibited passive Ca entry across the cell membrane without interfering with either the release of Ca from internal stores (indicating that the carbachol receptor and other signaling events were operational) or the normal active rates of Ca efflux from the cell (indicating that Ca pumping was also still intact). These results suggest that, in addition to their actual antifreeze properties, AFP may also help to confer cold tolerance in animals by preventing passive Ca entry into epithelial cells.

Action Potentials↗
PubMed2003

Transgenic complementation of leptin receptor deficiency. II. Increased leptin receptor transgene dose effects on obesity/diabetes and fertility/lactation in lepr-db/db mice.

We have generated mice that are homozygous for a leptin receptor transgene that is expressed exclusively in neurons (NSE-LEPR-B). We had previously shown that this transgene in the hemizygous state is effective in ameliorating almost all aspects of leptin receptor deficiency. Now, we show that the transgene, in the homozygous state, almost fully corrects the excess adiposity of LEPR-deficient (db/db) mice. Body composition analyses indicate that the transgene is able to restrain the massive increase in adiposity observed in LEPR-deficient mice. Examination of hypothalamic agouti gene-related peptide and proopiomelanocortin mRNA shows normalization of these leptin-regulated transcripts. Interestingly, despite normalization of circulating leptin concentrations by the transgene in the fed state, transgenic db3J/db mice did not show fasting-induced reductions of circulating leptin. Increased adiposity of the transgenic db/db mice at 4 wk of age, immediately postweaning, suggests that the transgene is less effective in correcting the preferential fat deposition caused by LEPR deficiency. We noted that the morphology of brown adipose tissue is nearly normal, concordant with the cold tolerance conferred by the transgene. Aspects of the diabetes phenotype are also corrected: glucose and insulin concentrations are nearly normal, and islet hyperplasia is greatly diminished. The transgene also corrects the infertility of db/db females and confers the ability to lactate sufficiently to nurse normal-sized litters. Finally, the slightly increased adiposity and mild insulin resistance of transgenic db/db dams were not a contributory factor to the increased fat content of transgenic db/db male progeny.

Adaptation, Physiological↗
PubMed1987

Polyunsaturated lipid diet lengthens torpor and reduces body temperature in a hibernator.

Membrane lipids of vertebrate animals that tolerate cold are high in polyunsaturated fatty acids. Because the lipid composition of cellular membranes in mammals can be experimentally altered by diet, we investigated whether a diet rich in polyunsaturated fatty acids would lengthen bouts of torpor and reduce the minimum body temperature in hibernating chipmunks (Eutamias amoenus) compared with a diet rich in saturated fatty acids. Animals on the highly unsaturated diet showed significantly longer bouts of torpor, lower minimum body temperatures, and lower metabolic rates than those on a saturated diet. Animals on a control diet were intermediate. These dietary adjustments apparently influence the control of body temperature by the central nervous system, which results in a modification of the pattern of torpor. The observations also suggest a role of nutritional ecology in hibernation.

Animals↗
PubMed2006

Thermal plasticity in Drosophila melanogaster: a comparison of geographic populations.

BACKGROUND: Populations of Drosophila melanogaster show differences in many morphometrical traits according to their geographic origin. Despite the widespread occurrence of these differences in more than one Drosophila species, the actual selective mechanisms controlling the genetic basis of such variation are not fully understood. Thermal selection is considered to be the most likely cause explaining these differences. RESULTS: In our work, we investigated several life history traits (body size, duration of development, preadult survival, longevity and productivity) in two tropical and two temperate natural populations of D. melanogaster recently collected, and in a temperate population maintained for twelve years at the constant temperature of 18 degrees C in the laboratory. In order to characterise the plasticity of these life history traits, the populations were grown at 12, 18, 28 and 31.2 degrees C. Productivity was the fitness trait that showed clearly adaptive differences between latitudinal populations: tropical flies did better in the heat but worse in the cold environments with respect to temperate flies. Differences for the plasticity of other life history traits investigated between tropical and temperate populations were also found. The differences were particularly evident at stressful temperatures (12 and 31.2 degrees C). CONCLUSION: Our results evidence a better cold tolerance in temperate populations that seems to have been evolved during the colonisation of temperate countries by D. melanogaster Afrotropical ancestors, and support the hypothesis of an adaptive response of plasticity to the experienced environment.

Analysis of Variance↗
PubMed2001

Leptin-deficient mice backcrossed to the BALB/cJ genetic background have reduced adiposity, enhanced fertility, normal body temperature, and severe diabetes.

A deficiency of leptin synthesis in mice results in a complex phenotype characterized by morbid obesity, diabetes, sterility, and defective thermogenesis. To determine whether the genetic background could alter the pleiotropic effects of leptin deficiency, we backcrossed the ob mutation for 10 generations from the C57BL/6J to the BALB/cJ genetic background. Compared with C57BL/6J ob/ob mice, BALB/cJ ob/ob mice showed at 27 wk of age a 35-40% reduction in body weight attributed to a 60% decrease in white adipose tissue mass. Food intake was not significantly different between the two obese strains, suggesting distinct utilization of energy intake. In the fed state, BALB/cJ ob/ob mice had elevated insulin and triglycerides levels, demonstrating a worsening effect on diabetes. At the reproductive level and in contrast to sterile C57BL/6J ob/ob mice, male and female BALB/cJ ob/ob mice were capable of reproducing after a mating period of 16 and 32 wk, respectively. At thermoneutrality, the body temperature of BALB/cJ ob/ob mice was 2.9 C higher than that of C57BL/6J ob/ob mice, whereas exposure of both groups to 4 C demonstrated a prolonged cold tolerance of BALB/cJ ob/ob mice. These studies show that the abnormalities caused by leptin deficiency can be genetically dissected and separated from each other, suggesting discrete pathways controlled by leptin modifier genes.

Adipose Tissue↗
PubMed2003

Sarcopenia and aging.

Sarcopenia refers to the gradual decline in muscle mass and quality noted with advancing age. There is growing evidence linking sarcopenia to functional disability, falls, decreased bone density, glucose intolerance, and decreased heat and cold tolerance in older adults. Factors implicated in the etiology of sarcopenia include decreased physical activity, malnutrition, increased cytokine activity, oxidative stress, and abnormalities in growth hormone and sex steroid axes. At present, progressive resistance training is the best intervention shown to slow down or reverse this condition. Preliminary studies show that the utilization of several trophic factors, notably testosterone and DHEA, may have a salutary effect on muscle mass and/or strength in older adults. More research is needed, however, before drawing definite conclusion as to the clinical utility of these substances in the management of sarcopenia.

Aged↗
PubMed2003

Biomedical evaluation of free-ranging ring-tailed lemurs (Lemur catta) in Tsimanampetsotsa Strict Nature Reserve, Madagascar.

Complete health assessments were performed on 20 adult ring-tailed lemurs (Lemur catta), 10 males and 10 females, free ranging within the Tsimanampetsotsa Strict Nature Reserve in southwest Madagascar. Each animal was anesthetized using tiletamine and zolazepam, weighed, and given a thorough physical examination. Blood was collected for hematology, determination of plasma total protein concentration, serum chemistry, determination of fat-soluble vitamin and trace mineral concentrations, assessment of iron metabolism, toxoplasmosis and viral serologies, and examination for parasites. Feces were collected for bacterial culture and parasite examination, and representative numbers of ectoparasites were collected. Blood values differed significantly in a number of ways from values in captive lemurs, possibly associated with recent food consumption, hydration, and diet. There was no evidence of serious infectious disease and no hemoparasites. The enteric flora appeared unremarkable, although results may have been skewed toward cold-tolerant bacteria. The fecal parasite burden was low, but there were large numbers of ectoparasites (mites) present. Our study demonstrated that a substantial amount of data can be collected from free-ranging populations, information that is invaluable in the management of captive populations, particularly with regard to disease, and in assessing risks associated with reintroduction programs.

Animals↗
PubMed2004

LRb-STAT3 signaling is required for the neuroendocrine regulation of energy expenditure by leptin.

Secretion of leptin from adipose tissue communicates body energy status to the neuroendocrine system by activating the long form of the leptin receptor (LRb). Lack of leptin or LRb (as in db/db mice) results in obesity that stems from the combined effects of hyperphagia and decreased energy expenditure. We have previously generated mice in which LRb is replaced with a mutant LRb (LRbS1138) that specifically disrupts LRb-->STAT3 (signal transducer and activator of transcription-3) signaling; mice homozygous for this mutant (s/s) display increased feeding and are obese. We have now examined energy expenditure in s/s and db/db mice. Consistent with the increased lean body mass of s/s animals, locomotor activity and acute cold tolerance (partly a measure of shivering thermogenesis) in s/s mice were modestly but significantly improved compared with db/db mice, although they were decreased compared with wild-type mice. Total and resting metabolic rates were similarly depressed in s/s and db/db mice, however. Indeed, s/s and db/db mice display similar reductions in thyroid function and brown adipose tissue expression of uncoupling protein-1, which is regulated by sympathetic nervous system (SNS) tone. Thus, the LRb-->STAT3 signal is central to both the control of energy expenditure by leptin and the neuroendocrine regulation of the SNS and the thyroid axis.

Animals↗
PubMed1999

[Medical aspects of diving--a sport for both women and men].

As interest in scuba diving is increasing in both sexes, doctors need to be aware of the risks encountered when diving and about gender-related differences in these risks. Individuals prone to panic attacks, claustrophobia or reckless risk-taking should avoid diving. In tolerating cold, muscle mass is more important than the amount of subcutaneous fat. The risk of decompression disease seems to be slightly greater among women, probably due to their fat distribution. Pregnant women are recommended not to dive, because the risk of birth defects seems to be greater among those who do, and there is a serious risk of fetal decompression disease. All participants in the sport must be responsible for their own diving safety.

Adaptation, Physiological↗
PubMed2000

Patterns and determinants of potential carbon gain in the C3 evergreen Yucca glauca (Liliaceae) in a C4 grassland.

Yucca glauca is a C(3) evergreen rosette species locally common in the C(4)-dominated grasslands of the central Great Plains. Most congeners of Y. glauca are found in deserts, and Y. glauca's morphological similarities to desert species (steeply angled leaves, evergreen habit) may be critical to its success in grasslands. We hypothesized that the evergreen habit of Y. glauca, coupled with its ability to remain physiologically active at cool temperatures, would allow this species to gain a substantial portion of its annual carbon budget when the C(4) grasses are dormant. Leaf-level gas exchange was measured over an 18-mo period at Konza Prairie in northeast Kansas to assess the annual pattern of potential C gain. Two short-term experiments also were conducted in which nighttime temperatures were manipulated to assess the cold tolerance of this species. The annual pattern of C gain in Y. glauca was bimodal, with a spring productive period (maximum monthly photosynthetic rate = 21.1 ± 1.97 μmol·m·s) in March through June, a period of midseason photosynthetic depression, and a fall productive period in October (15.6 ± 1.25 μmol·m·s). The steeply angled leaves resulted in interception of photon flux density at levels above photosynthetic saturation throughout the year. Reduced photosynthetic rates in the summer may have been caused by low soil moisture, but temperature was strongly related (r = 0.37) to annual variations in photosynthesis, with nocturnal air temperatures below -5°C in the late fall and early spring, and high air temperatures (>32°C) in the summer, limiting gas exchange. Overall, 31% of the potential annual carbon gain in Y. glauca occurred outside the "frost-free" period (April-October) at Konza Prairie and 43% occurred when the dominant C(4) grasses were dormant. Future climates that include warmer minimum temperatures in the spring and fall may enhance the success of Y. glauca relative to the C(4) dominants in these grasslands.

Journal Article↗
PubMed2002

A preliminary characterization of the physiological ecology of overwintering Anopheles mosquitoes in the midwestern USA.

Field-collected Anopheles quadrimaculatus and An. punctipennis adult mosquitoes from various types of overwintering hibernacula in southwestern Michigan and northern Indiana were examined for cold tolerance. Adult mosquitoes were collected on a monthly basis from October 1997 to April 1998. The mean supercooling point for adult for An. punctipennis was significantly lower than that for An. quadrimaculatus. The lower lethal temperatures for these species were -17 degrees C and -15 degrees C for An. punctipennis and An. quadrimaculatus, respectively.

Animals↗
PubMedDate not supplied

Rapid cold hardening: a gut feeling.

This study examined the rate of cold hardening of a field population of Antarctic springtails and the effect of eating food with particular levels of ice nucleating activity on the animal's whole body freezing point. The SCPs of samples of c. 20, freshly collected, Cryptopygus antarcticus were measured hourly over a 32 hour collection period using differential scanning calorimetry and related to habitat temperature. The mean SCP of the springtails increased from -24 to -10 degree C during which time the habitat temperature warmed slowly from -2.5 to +2.5 degree C. In laboratory experiments, previously starved, cold tolerant springtails were fed on selected species of algae with measured SCP's but there was no clear correlation between the SCP of food and that of the animals after feeding. Microscopic examination of faecal pellets and guts from springtails showed that algal cells were completely destroyed during digestion.

Journal Article↗
PubMed2000

[Pharmacological studies on shengenaqi oral liquid on animal model for TCM dyspnea of deficiency].

The Shengenaqi oral liquid has a function of improving the inspiration and can be used in the treatment of chronic bronchitis, pulmonary emphysema and pulmonary heart disease etc. In the research, animal models for TCM dyspnea of deficiency were made by inhaling papain and injection hydrocotison into the abdominal eavity and afterwards, treated with Shengenaqi oral liquid. The effects showed: The medicine can improve the susfainability of swimming mice, increase the ability of cold tolerance and prevent the thymus from atrophy. The SOD activity in the lung tissue of mice can be improved and MDA be decreased.

Animals↗