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Hot Environments (hot + environment)
Selected AbstractsExposure to a hot environment can activate rostral ventrolateral medulla-projecting neurones in the hypothalamic paraventricular nucleus in conscious ratsEXPERIMENTAL PHYSIOLOGY, Issue 1 2008Joo Lee Cham A major integrative site within the brain for autonomic function is the hypothalamic paraventricular nucleus (PVN). Several studies have suggested that the PVN may be involved in the responses regulating body temperature. Hyperthermia elicits redirection of blood flow from the viscera to the periphery and involves changes in sympathetic nerve activity mediated by the central nervous system. The hypothalamic PVN includes neurones that project to the rostral ventrolateral medulla (RVLM), an important autonomic region involved in the tonic regulation of sympathetic nerve activity. This pathway could contribute to the cardiovascular changes induced by hyperthermia. The PVN has a high concentration of nitrergic neurones and it is known that nitric oxide within the brain mediates heat dissipation. Thus the aims of this study were to determine whether RVLM-projecting neurones in the PVN are activated by heat and whether those neurones are also nitrergic. The results show that, compared with control conditions, exposure of conscious rats to a hot environment of 39°C significantly increased the number of neurones containing a Fos-positive nucleus (a marker of activation) and significantly increased the number of activated RVLM-projecting neurones in the PVN. Also, although heating significantly increased the number of activated nitrergic PVN neurones, triple-labelled neurones (i.e. activated, nitrergic and RVLM projecting) in the PVN were rarely observed. The results suggest that RVLM-projecting neurones in the PVN may play a role in responses to heat exposure but these are not nitrergic. [source] Genotypic and temperature effects on wheat grain yield and quality in a hot irrigated environmentPLANT BREEDING, Issue 4 2006I. S. A. Tahir Abstract High temperature influences both grain yield and end-use quality of wheat. The objectives of this study were to evaluate the performance of selected wheat genotypes under heat stress and to examine the effects of high temperatures during grain filling on grain yield and end-use quality parameters. Fifteen bread wheat genotypes in 2000/2001 and 18 genotypes in 2002/2003 were evaluated under the optimum and late-sowing conditions of the irrigated hot environment of the Gezira Research Farm, Wad Medani, Sudan. The genotypes comprised released varieties and elite lines from the Sudanese wheat improvement programme. Data collected included grain yield, grain weight and grain end-use quality including protein content, protein composition, SDS sedimentation values (SDSS) and gluten strength as determined by mixograph analyses. High temperatures significantly decreased grain yield by decreasing grain weight. Although genotypes exhibited variation in magnitude of response, results indicated that high temperature during grain filling increased both soluble and insoluble protein contents, SDSS, mixograph peak height (MPH) and the descending slope at 2 min past peak (MDS). In contrast, mixograph peak time (MPT) and the curve width at 2 min past peak (MCW) were significantly decreased. Flour protein correlated positively with SDSS, MPH and MDS and negatively with MCW. MPT correlated negatively with MDS and positively with MCW. Results indicate that high temperature increased both soluble and insoluble protein contents, SDSS and MPH, and hence the gluten strength, but decreased flour mixing time and tolerance and hence the dough elasticity. Variation observed among genotypes suggests that grain end-use quality could be improved under high temperature conditions utilizing the available variability; however, it might require evaluation under various growing conditions. [source] Quantifying phenotypic plasticity of berry traits using an allometric-type approach: A case study on anthocyanins and sugars in berries of Cabernet SauvignonAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2 2007V.O. SADRAS Abstract In this paper we advance a novel allometric-type approach to quantify the stability of key berry traits viz. anthocyanins and sugars. To test the concept, we used data from Cabernet Sauvignon grown in a hot environment of South Australia. Sources of variation in berry traits included water supply, fruit load, seasonal conditions and their interactions. Anthocyanins and sugars were measured in berry samples taken 7,8 times between veraison and harvest. Rates and durations of accumulation of anthocyanins and sugars per berry were derived from a bi-linear model between amount of compound and thermal time. We develop a framework based on ,,' a parameter representing the slope of the regression between rate and duration in a log-log scale. This relationship accommodates three conditions viz. (a) potentially plastic, rate-driven trait (,,1), (b) potentially plastic, duration-driven trait (, < ,1), and (c) a stable trait, whereby variation in rate and variation in duration cancel each other (,=,1). Under our experimental conditions, amount of anthocyanins (range of variation 148%) was more plastic than amount of sugars per berry (range of variation 37%). The slope , captured the differential plasticity of these traits: , was significantly greater than ,1 for anthocyanins and statistically undistinguishable from ,1 for sugars. The rate-dominated accumulation of anthocyanins explained the relatively large variation in this constituent whereas the tightly coupled, inverse relationship between duration and rate (,,1) explained the relative stability of sugars per berry. We conclude that our allometric-type relationship between rate and duration allows for the quantification of cultivar-environment specific plasticity of important berry traits. [source] Characterization of DNA transport in the thermophilic bacterium Thermus thermophilus HB27FEBS JOURNAL, Issue 18 2006Cornelia Schwarzenlander Horizontal gene transfer has been a major force for genome plasticity over evolutionary history, and is largely responsible for fitness-enhancing traits, including antibiotic resistance and virulence factors. In particular, for adaptation of prokaryotes to extreme environments, lateral gene transfer seems to have played a crucial role. Recently, by performing a genome-wide mutagenesis approach with Thermus thermophilus HB27, we identified the first genes in a thermophilic bacterium for the uptake of free DNA, a process called natural transformation. Here, we present the first data on the biochemistry and bioenergetics of the DNA transport process in this thermophile. We report that linear and circular plasmid DNA are equally well taken up with a high maximal velocity of 1.5 µg DNA·(mg protein),1·min,1, demonstrating an extremely efficient binding and uptake rate of 40 kb·s,1·cell,1. Uncouplers and ATPase inhibitors immediately inhibited DNA uptake, providing clear evidence that DNA translocation in HB27 is an energy-dependent process. DNA uptake studies with genomic DNA of Bacteria, Archaea and Eukarya revealed that Thermus thermophilus HB27 takes up DNA from members of all three domains of life. We propose that the extraordinary broad substrate specificity of the highly efficient Thermus thermophilus HB27 DNA uptake system may contribute significantly to thermoadaptation of Thermus thermophilus HB27 and to interdomain DNA transfer in hot environments. [source] Shuffling genes around in hot environments: the unique DNA transporter of Thermus thermophilusFEMS MICROBIOLOGY REVIEWS, Issue 3 2009Beate Averhoff Abstract Natural transformation permits the transport of DNA through bacterial membranes and represents a dominant mode for the transfer of genetic information between bacteria and between microorganisms of distant evolutionary lineages and even between members of different domains. This phenomenon, known as horizontal, or lateral, gene transfer, has been a major force for genome plasticity over evolutionary history, and is largely responsible for the spread of fitness-enhancing traits, including antibiotic resistance and virulence factors. In particular, for adaptation of prokaryotes to extreme environments, lateral gene transfer seems to have played a crucial role. Here, we present a survey of the natural transformation machinery of the thermophile Thermus thermophilus HB27. A tentative model of the transformation machinery comprising of components similar to proteins of type IV pili and type II secretion systems is presented. A comparative discussion of the subunits and the structure of the DNA translocator and the underlying mechanism of transfer of free DNA in T. thermophilus highlights conserved and unique features of the DNA translocator in T. thermophilus. We hypothesize that the extraordinary broad substrate specificity and the high efficiency of the T. thermophilus DNA uptake system is of major importance for thermoadaptation and interdomain DNA transfer in hot environments. [source] Worldwide allele frequencies of the human apolipoprotein E gene: Climate, local adaptations, and evolutionary historyAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Dan T.A. Eisenberg Abstract The ,4 allele of the apolipoprotein E (APOE) gene is associated with increased cholesterol levels and heart disease. Population allele frequencies of APOE have previously been shown to vary, with ,4 frequencies generally increasing with latitude. We hypothesize that this trend resulted from natural selection protecting against low-cholesterol levels. In high-latitude cold environments and low-latitude hot environments, metabolic rate is elevated, which could require higher cholesterol levels. To explore this hypothesis, we compiled APOE allele frequencies, latitude, temperature, and elevation from populations around the world. ,4 allele frequencies show a curvilinear relationship with absolute latitude, with lowest frequencies found in the mid-latitudes where temperatures generally require less expenditure on cooling/thermogenesis. Controlling for population structure in a subset of populations did not appreciably change this pattern of association, consistent with selection pressures that vary by latitude shaping ,4 allele frequencies. Temperature records also predict APOE frequency in a curvilinear fashion, with lowest ,4 frequencies at moderate temperatures. The model fit between historical temperatures and ,4 is less than between latitude and ,4, but strengthened after correcting for estimated temperature differences during the Paleolithic. Contrary to our hypothesis, we find that elevation did not improve predictive power, and an integrated measure of the cholesterol effect of multiple APOE alleles was less related to latitude than was ,4 alone. Our results lend mixed support for a link between past temperature and human APOE allele distribution and point to the need to develop better models of past climate in future analyses. Am J Phys Anthropol 143:13,20, 2010. © 2010 Wiley-Liss, Inc. [source] The cardiovascular challenge of exercising in the heatTHE JOURNAL OF PHYSIOLOGY, Issue 1 2008José González-Alonso Exercise in the heat can pose a severe challenge to human cardiovascular control, and thus the provision of oxygen to exercising muscles and vital organs, because of enhanced thermoregulatory demand for skin blood flow coupled with dehydration and hyperthermia. Cardiovascular strain, typified by reductions in cardiac output, skin and locomotor muscle blood flow and systemic and muscle oxygen delivery accompanies marked dehydration and hyperthermia during prolonged and intense exercise characteristic of many summer Olympic events. This review focuses on how the cardiovascular system is regulated when exercising in the heat and how restrictions in locomotor skeletal muscle and/or skin perfusion might limit athletic performance in hot environments. [source] Crystallization and preliminary X-ray analysis of mannosyl-3-phosphoglycerate synthase from Thermus thermophilus HB27ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 10 2009Susana Gonçalves Mannosylglycerate (MG) is a compatible solute that is widespread in marine organisms that are adapted to hot environments, with its intracellular pool generally increasing in response to osmotic stress. These observations suggest that MG plays a relevant role in osmoadaptation and thermoadaptation. The pathways for the synthesis of MG have been characterized in a number of thermophilic and hyperthermophilic organisms. Mannosyl-3-phosphoglycerate synthase (MpgS) is a key enzyme in the biosynthesis of MG. Here, the purification, crystallization and preliminary crystallographic characterization of apo MpgS from Thermus thermophilus HB27 are reported. The addition of Zn2+ to the crystallization buffer was essential in order to obtain crystals. The crystals belonged to one of the enantiomorphic tetragonal space groups P41212 or P43212, with unit-cell parameters a = b = 113, c = 197,Ĺ. Diffraction data were obtained to a resolution of 2.97,Ĺ. [source] | |||||||||||||