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Environmental Stress (environmental + stress)
Terms modified by Environmental Stress Selected AbstractsComputational Biology Approaches to Plant Metabolism and Photosynthesis: Applications for Corals in Times of Climate Change and Environmental StressJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 8 2010M. James C. Crabbe Knowledge of factors that are important in reef resilience helps us to understand how reef ecosystems react following major anthropogenic and environmental disturbances. The symbiotic relationship between the photosynthetic zooxanthellae algal cells and corals is that the zooxanthellae provide the coral with carbon, while the coral provides protection and access to enough light for the zooxanthellae to photosynthesise. This article reviews some recent advances in computational biology relevant to photosynthetic organisms, including Beyesian approaches to kinetics, computational methods for flux balances in metabolic processes, and determination of clades of zooxanthallae. Application of these systems will be important in the conservation of coral reefs in times of climate change and environmental stress. [source] Recovery of Growth of Hyphochytrium catenoides after Exposure to Environmental StressTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 4 2008FRANK H. GLEASON ABSTRACT. The survival of an isolate of Hyphochytrium catenoides collected from soil in the Blue Mountains in eastern New South Wales, Australia, was tested under extreme conditions in the laboratory. This isolate recovered growth after being subjected to drying on filter paper, to heat while desiccated, to hypersalinity, to strict anaerobic conditions, to freezing temperatures, and to a short period in solutions at pH 2.8,11.2. The capacity to survive under these conditions in the laboratory suggests adaptation to fluctuating conditions in the soil. The partial DNA sequence of the 28S ribosomal RNA gene in the isolate from New South Wales was 98% similar to that in an isolate from Arizona with a similar morphology. [source] Effects of NHE1 Expression Level on CHO Cell Responses to Environmental StressBIOTECHNOLOGY PROGRESS, Issue 2 2005Lisa R. Abston Ammonia, lactate and CO2 inhibit animal cell growth. Accumulation of these metabolic byproducts also causes a decrease in intracellular pH (pHi). Transport systems regulate pHi in eukaryotic cells. Ion transporters have been cloned and overexpressed in cells but have not been examined for protection against the buildup of ammonia, lactate or CO2. The Na+/H+ exchangers (NHE) transport H+ ions from cells during acidification to increase pHi. We examined whether overexpression of NHE1 would provide CHO cells with greater protection from elevated ammonia, lactate or CO2. NHE1 CHO cells were compared to MT2,1-8 ("normal" levels of NHE) and AP-1 (devoid of any NHE activity) CHO cell lines. Expression of at least "normal" levels of NHE1 is necessary for CHO cell survival during exposure to 30 mM lactic acid without pH adjustment or to 20 mM NH4Cl with pH adjustment. Resistance to an acute acid-load increased when NHE1 was overexpressed in CHO cells. Surprisingly, the inhibitory effect on cell growth at 195 mmHg pCO2/435 mOsm/kg (normal levels are 40 mmHg pCO2/320 mOsm/kg) was not affected by the NHE1 level. Also, there was no further decrease in CHO cell growth in the absence of NHE1 expression during elevated osmolality alone (up to 575 mOsm/kg). [source] Photosynthetic Acclimation to Simultaneous and Interacting Environmental Stresses Along Natural Light Gradients: Optimality and ConstraintsPLANT BIOLOGY, Issue 3 2004ü. Niinemets Abstract: There is a strong natural light gradient from the top to the bottom in plant canopies and along gap-understorey continua. Leaf structure and photosynthetic capacities change close to proportionally along these gradients, leading to maximisation of whole canopy photosynthesis. However, other environmental factors also vary within the light gradients in a correlative manner. Specifically, the leaves exposed to higher irradiance suffer from more severe heat, water, and photoinhibition stresses. Research in tree canopies and across gap-understorey gradients demonstrates that plants have a large potential to acclimate to interacting environmental limitations. The optimum temperature for photosynthetic electron transport increases with increasing growth irradiance in the canopy, improving the resistance of photosynthetic apparatus to heat stress. Stomatal constraints on photosynthesis are also larger at higher irradiance because the leaves at greater evaporative demands regulate water use more efficiently. Furthermore, upper canopy leaves are more rigid and have lower leaf osmotic potentials to improve water extraction from drying soil. The current review highlights that such an array of complex interactions significantly modifies the potential and realized whole canopy photosynthetic productivity, but also that the interactive effects cannot be simply predicted as composites of additive partial environmental stresses. We hypothesize that plant photosynthetic capacities deviate from the theoretical optimum values because of the interacting stresses in plant canopies and evolutionary trade-offs between leaf- and canopy-level plastic adjustments in light capture and use. [source] WATER STRESS ALTERS THE GENETIC ARCHITECTURE OF FUNCTIONAL TRAITS ASSOCIATED WITH DROUGHT ADAPTATION IN AVENA BARBATAEVOLUTION, Issue 3 2009Mark E. Sherrard Environmental stress can alter genetic variation and covariation underlying functional traits, and thus affect adaptive evolution in response to natural selection. However, the genetic basis of functional traits is rarely examined in contrasting resource environments, and consequently, there is no consensus regarding whether environmental stress constrains or facilitates adaptive evolution. We tested whether resource availability affects genetic variation for and covariation among seven physiological traits and seven morphological/performance traits by growing the annual grass Avena barbata in dry and well-watered treatments. We found that differences in the overall genetic variance,covariance (G) matrix between environments were driven by physiological traits rather than morphology and performance traits. More physiological traits were heritable in the dry treatment than the well-watered treatment and many of the genetic correlations among physiological traits were environment dependent. In contrast, genetic variation and covariation among the morphological and performance traits did not differ across treatments. Furthermore, genetic correlations between physiology and performance were stronger in the dry treatment, which contributed to differences in the overall G -matrix. Our results therefore suggest that physiological adaptation would be constrained by low heritable variation in resource-rich environments, but facilitated by higher heritable variation and stronger genetic correlations with performance traits in resource-poor environments. [source] Growth and population size of crayfish in headwater streams: individual- and higher-level consequences of acidificationFRESHWATER BIOLOGY, Issue 7 2004Steven M. Seiler Summary 1. Environmental stress may have indirect positive effects on population size through modification of food-web interactions, despite having negative effects on individuals. Here we evaluate the individual- and population-level effects of acidification on crayfish (Cambarus bartonii) in headwater streams of the Allegheny Plateau (PA, U.S.A.) with field experiments and survey data. Median baseflow pH of 24 study reaches in nine streams varied from 4.4 to 7.4, with substantial variation found both among and within streams. 2. Two bioassays were conducted to evaluate the relationship between stream pH and crayfish growth rates. Growth rates were always higher in circumneutral reaches than in acidic reaches. Crayfish originating in acidic water grew less when transplanted into neutral water than did crayfish originating in neutral water, providing some evidence for a cost of acclimation to acidity. 3. Stream surveys showed that fish were less abundant and crayfish more abundant in acidified streams than in circumneutral streams. Crayfish density was sixfold higher in reaches with the lowest pH relative to circumneutral reaches. Large crayfish made up a higher proportion of crayfish populations at sites with high fish biomass, consistent with the hypothesis that fish predation on small individuals may be limiting crayfish population size at these sites. 4. Although individual crayfish suffered lower growth in acidified streams, increased acidity appeared to cause an increase in crayfish population size and shifts in size structure, possibly by relieving predation pressure by fish. [source] Environmental stress and the costs of whole-organism phenotypic plasticity in tadpolesJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2008U. K. STEINER Abstract Costs of phenotypic plasticity are important for the evolution of plasticity because they prevent organisms from shaping themselves at will to match heterogeneous environments. These costs occur when plastic genotypes have relatively low fitness regardless of the trait value expressed. We report two experiments in which we measured selection on predator-induced plasticity in the behaviour and external morphology of frog tadpoles (Rana temporaria). We assessed costs under stressful and benign conditions, measured fitness as larval growth rate or competitive ability and focused analysis on aggregate measures of whole-organism plasticity. There was little convincing evidence for a cost of phenotypic plasticity in our experiments, and costs of canalization were nearly as frequent as costs of plasticity. Neither the magnitude of the cost nor the variation around the estimate (detectability) was sensitive to environmental stress. [source] Genetic and environmental effects on morphology and fluctuating asymmetry in nestling barn swallowsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2000Cadée A barn swallow Hirundo rustica partial cross-fostering experiment with simultaneous brood size manipulation was conducted in two years with contrasting weather conditions, to estimate heritable variation in tarsus, tail and wing size and fluctuating asymmetry. Environmental stress had contrasting effects depending on trait type. Significant heritabilities for tarsus, tail and wing size were found only in enlarged broods irrespective of year effects, while tarsus asymmetry was significantly heritable in the year with benign weather conditions irrespective of brood size manipulation effects. Tail, wing and composite (multicharacter) asymmetry were never significantly heritable. The environment with the higher heritability generally had higher additive genetic variance and lower environmental variance, irrespective of trait type. Heritability was larger for trait size than for trait asymmetry. Patterns of genetic variation in nestlings do not necessarily translate to the juvenile or adult stage, as indicated by lack of correlation between nestling and fledgling traits. [source] Nucleation and facilitation in salt pans in Mediterranean salt marshesJOURNAL OF VEGETATION SCIENCE, Issue 6 2001A.E. Rubio-Casal Tutin et al. (1992) Abstract. Arthrocnemum macrostachyum is a perennial species acting as a primary colonizer of salt pans in Mediterranean high salt marshes. Salicornia ramosissima, an annual, occurs in salt pans under Arthrocnemum canopies and in open areas. The aim of this study was to analyse, in wild populations and a transplant experiment, how S. ramosissima population dynamics and growth are affected by A. macrostachyum. The environmental conditions within the patches of Arthrocnemum were less stressful than in the open areas, with lower radiation levels and salinity concentrations. In the inner areas of A. macrostachyum patches, density-dependent mortality processes of S. ramosissima seedlings led to low densities of adult individuals with greater morphological development and reproductive success than in open areas. However, at the edges of Arthrocnemum patches facilitation of seedling survival favoured high densities. Environmental stress hindered development, decreased reproduction and premature death. These results are in agreement with the general theory of factors controlling vegetation distribution that biotic interactions dominate in low stress environments, while abiotic interactions dominate under harsher environmental conditions. A. macrostachyum plays an essential role in the succession in these salt pans, facilitating seed production and stimulating nucleation processes in S. ramosissima. [source] Toxic effect of environmental acid-stress on the sperm of a hill-stream fish Devario aequipinnatus: A scanning electron microscopic evaluationMICROSCOPY RESEARCH AND TECHNIQUE, Issue 2 2009Sudip Dey Abstract Environmental stress due to acidic pH of water was found to be one of the major factors leading to toxic effects on the sperm of a hill-stream fish Devario aequipinnatus of Meghalaya, India. The Scanning Electron Microscopy of the transverse section of testes of the fish collected from its natural habitat with acidic pH (5.6,6.0) showed that the sperms were clumped together and their tails were either absent or were of extremely small length. The acrosome and midpiece were also not well differentiated. When the fingerlings from the natural habitat were reared to maturity in aquarium with water from natural habitat after changing the pH to alkaline range (8.0,8.2), the clumping of the sperm was not observed. The sperm tail was found to be well-developed along with well-differentiated acrosome and midpiece. Since the only change in the water quality parameters of the experimental aquarium as compared to those of the natural habitat was the pH, it is evident that the abnormal features of the sperm observed in fish from natural habitat is mainly because of environmental acid stress. Microsc. Res. Tech., 2009. © 2008 Wiley-Liss, Inc. [source] Environmental stresses induce the expression of putative glycine-rich insect cuticular protein genes in adult Leptinotarsa decemlineata (Say)INSECT MOLECULAR BIOLOGY, Issue 3 2008J. Zhang Abstract The deposition of cuticular proteins in insects usually occurs during the moulting process. Three putative glycine-rich insect cuticular proteins, Ld-GRP1 to 3, were identified and characterized from the Colorado potato beetle, Leptinotarsa decemlineata. The Ld-GRPs contained conserved GXGX and/or GGXG sequence repeats. Ld-GRP1 also contained a conserved AAPA/V motif commonly found in cuticular proteins. The transcripts of Ld-GRP1 and Ld-GRP2 were detected in the epidermal cell layer by in situ hybridization, making them putative insect cuticular proteins. The putative cuticular protein genes were highly induced by the insecticide azinphosmethyl (organophosphorous) 2,3 weeks after adult moulting. Putative cuticular protein gene expression level was higher in azinphosmethyl-resistant beetles than in susceptible beetles. Furthermore, two of the putative cuticular protein genes were highly induced by dry environmental conditions. These results suggest that the insect might increase cuticular component deposition in the adult stage in response to environmental stresses. This ability may allow the insect to adapt to new or changing environments. [source] Environmental stresses mediate endophyte,grass interactions in a boreal archipelagoJOURNAL OF ECOLOGY, Issue 2 2010Nora M. Saona Summary 1.,Both evolutionary theory and empirical evidence from agricultural research support the view that asexual, vertically transmitted fungal endophytes are typically plant mutualists that develop high infection frequencies within host grass populations. In contrast, endophyte,grass interactions in natural ecosystems are more variable, spanning the range from mutualism to antagonism and comparatively little is known about their range of response to environmental stress. 2.,We examined patterns in endophyte prevalence and endophyte,grass interactions across nutrient and grazing (from Greylag and Canada geese) gradients in 15 sites with different soil moisture levels in 13 island populations of the widespread grass Festuca rubra in a boreal archipelago in Sweden. 3.,In the field, endophyte prevalence levels were generally low (range = 10,53%) compared with those reported from agricultural systems. Under mesic-moist conditions endophyte prevalence was constantly low (mean prevalence = 15%) and was not affected by grazing pressure or nutrient availability. In contrast, under conditions of drought, endophyte prevalence increased from 10% to 53% with increasing nutrient availability and increasing grazing pressure. 4.,In the field, we measured the production of flowering culms, as a proxy for host fitness, to determine how endophyte-infected plants differed from uninfected plants. At dry sites, endophyte infection did not affect flowering culm production. In contrast, at mesic-moist sites production of flowering culms in endophyte-infected plants increased with the covarying effects of increasing nutrient availability and grazing pressure, indicating that the interaction switched from antagonistic to mutualistic. 5.,A concurrent glasshouse experiment showed that in most situations, the host appears to incur some costs for harbouring endophytes. Uninfected grasses generally outperformed infected grasses (antagonistic interaction), while infected grasses outperformed uninfected grasses (mutualistic interaction) only in dry, nutrient-rich conditions. Nutrient and water addition affected tiller production, leaf number and leaf length differently, suggesting that tillers responded with different strategies. This emphasizes that several response variables are needed to evaluate the interaction. 6.,Synthesis. This study found complex patterns in endophyte prevalence that were not always correlated with culm production. These contrasting patterns suggest that the direction and strength of selection on infected plants is highly variable and depends upon a suite of interacting environmental variables that may fluctuate in the intensity of their impact, during the course of the host life cycle. [source] Plant responses to drought and phosphorus deficiency: contribution of phytohormones in root-related processesJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2005Lutz Wittenmayer Abstract Environmental stresses are one of the most limiting factors in agricultural productivity. A large portion of the annual crop yield is lost to pathogens (biotic stress) or the detrimental effects of abiotic-stress conditions. There are numerous reports about chemical characterization of quantitatively significant substrate fluxes in plant responses to stress factors in the root-rhizosphere system, e.g., nutrient mobilization, heavy-metal and aluminum immobilization, or establishment of plant-growth-promoting rhizobacteria (PGPR) by exudation of organic anions, phytosiderophores, or carbohydrates into the soil, respectively. The hormonal regulation of these responses is not well understood. This paper highlights this complex process, stressing the involvement of phytohormones in plant responses to drought and phosphorus deficiency as examples. Beside ethylene, abscisic acid (ABA) plays an important role in drought-stress adaptation of plants. This hormone causes morphological and chemical changes in plants, ensuring plant survival under water-limited conditions. For example, ABA induces stomata closure, reduction in leaf surface, and increase in root : shoot ratio and, thus, reduction in transpiration and increase in soil volume for water uptake. Furthermore, it supports water uptake in soil with decreasing water potential by osmotic adjustment. Suitability of hormonal parameters in the selection for improving stress resistance is discussed. Auxins, ethylene, and cytokinins are involved in morphological adaption processes to phosphorus (P) deficiency (increase in root surface, e.g., by the formation of more dense root hairs or cluster roots). Furthermore, indole-3-acetic acid increases root exudation for direct and indirect phosphorus mobilization in soil. Nevertheless, the direct use of the trait "hormone content" of a particular plant organ or tissue, for example the use of the drought-stress-induced ABA content of detached leaves in plant breeding for drought-stress-resistant crops, seems to be questionable, because this procedure does not consider the systemic principle of hormonal regulation in plants. Reaktionen von Pflanzen auf Trockenstress und Phosphormangel: Die Rolle von Phytohormonen in wurzelbezogenen Prozessen Umweltstress stellt den wesentlichsten Limitierungsfaktor für die landwirtschaftliche Produktion dar. Ein erheblicher Teil der jährlichen Ernten geht durch pathogene Organismen (biotischer Stress) oder durch die verheerende Wirkung abiotischer Stressoren verloren (v. a. Trockenstress und Nährstoffmangel). Es gibt zahlreiche Untersuchungen zur stofflichen Charakterisierung der pflanzlichen Stressreaktion an der Wurzel, z.,B. Nährstoffmobilisierung, Schadstoffimmobilisierung oder Etablierung von wachstumsfördernden Rhizobakterien durch Wurzelabscheidungen. Die hormonelle Steuerung dieser Prozesse ist bisher weniger erforscht. Der Artikel geht dieser Problematik am Beispiel von Trockenstress und Phosphormangel unter besonderer Berücksichtigung von Phytohormonen nach. Bei der Anpassung von Pflanzen an Wassermangelbedingungen spielt neben Ethylen das Phytohormon Abscisinsäure (ABA) eine wichtige Rolle. Es induziert morphologische und chemische Veränderungen in der Pflanze, die ein Überleben unter Wassermangelbedingungen ermöglichen. Beispielsweise induziert die ABA den Stomataschluss, eine Verringerung der Blattoberfläche sowie eine Erhöhung des Wurzel:Spross-Verhältnisses und bewirkt dadurch eine verringerte Transpiration und Vergrößerung des Bodenvolumens zur Erschließung von Wasservorräten. Darüber hinaus kann eine ABA-induzierte Anreicherung von osmotisch wirksamen Verbindungen zur Wasseraufnahme bei sinkendem Wasserpotential im Boden beitragen. Bei Phosphat (P)-Mangel sind vor allem Auxine, Cytokine und Ethylen an der morphologischen Anpassung der Wurzeln (Vergrößerung der Wurzeloberfläche durch verstärkte Bildung von Wurzelhaaren oder Proteoidwurzeln) beteiligt. Darüber hinaus bewirkt Indolyl-3-Essigäure eine Intensivierung der Abgabe von Wurzelabscheidungen zur direkten oder indirekten P-Mobilisierung in der Rhizosphäre. Trotzdem wird die unmittelbare Verwendung des Indikators "Hormongehalt" eines bestimmten Pflanzenorganes, beispielsweise der trockenstressinduzierte ABA-Gehalt von abgeschnittenen Blättern, für die Züchtung auf Stressresistenz als problematisch angesehen, da sie das systemische Prinzip der Hormonregulation nicht berücksichtigt. [source] Effect of environmental stresses on the sensitivity of Enterobacter sakazakii in powdered infant milk formula to gamma radiationLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2008T. Osaili Abstract Aim:, To evaluate the effect of starvation, heat, cold, acid, alkaline, chlorine and ethanol stresses on the resistance of Enterobacter sakazakii in powdered infant milk formula (PIMF) towards gamma radiation. Methods and Results:, Stressed cells of E. sakazakii ATCC 51329 and four other food isolate strains were mixed individually with PIMF, kept overnight at room temperature, and then exposed to gamma radiation up to 7·5 kGy. The D10 -values were determined using linear regression and for the stressed E. sakazakii strains these values ranged from 0·82 to 1·95 kGy. Conclusions:, Environmental stresses did not significantly change the sensitivity of most E. sakazakii strains to ionizing radiation. Significance and Impact of the Study:, Data obtained established that most forms of environmental stress are unlikely to significantly enhance the resistance of E. sakazakii strains to lethal, low dose irradiation treatment. [source] Expression and promoter activity of the desiccation-specific Solanum tuberosum gene, StDS2PLANT CELL & ENVIRONMENT, Issue 9 2002R. Dóczi Abstract Environmental stresses induce the expression of several plant genes via multiple and cross-talking signalling pathways. Previously it was shown that ScDS2, a gene of the wild potato species, Solanum chacoense, is highly inducible by dehydration but not by abscisic acid (ABA), the mediator of many plant stress responses. Herein it is shown that ScDS2 -related genes are present in the cultivated potato, Solanum tuberosum (StDS2) and also in the non-tuberizing Solanum species, Solanum brevidens (SbDS2). We show that expression of StDS2 is dehydration-specific, is not inducible by cold, heat, salt, hypoxia or oxidative stresses, and is independent of ABA. Signalling of StDS2 induction, however, is dependent on the synthesis of novel proteins because cycloheximide can block StDS2 expression. To analyse the promoter region of StDS2 a genomic library of Solanum tuberosum was established and 1140 and 498 bp regions of the StDS2 promoter were isolated. The promoter fragments were fused to the , -glucuronidase (GUS) reporter gene and tested in transgenic potato plants. Both promoter fragments were able to induce GUS activity in response to dehydration. This result suggests that drought-specific cis -elements are located within 498 bp upstream to the StDS2 coding sequence. [source] Stress Resistance and Environmental Dependency of Inbreeding Depression in Drosophila melanogasterCONSERVATION BIOLOGY, Issue 4 2000Jesper Dahlgaard Two important issues are whether stress and inbreeding effects are independent as opposed to synergistic, and whether inbreeding effects are general across stresses as opposed to stress-specific. We found that inbreeding reduced resistance to acetone and desiccation in adult Drosophila melanogaster, whereas resistance to knockdown heat stress was not affected. Inbred flies, however, experienced a greater proportional decrease in productivity than outbreds following heat stress. Correlations using line means indicated that all resistance traits were uncorrelated in the inbred as well as in the outbred flies. Recessive, deleterious alleles therefore did not appear to have any general deleterious effects on stress resistance. Inbreeding within a specific environment and selection for resistant genotypes may therefore purge a population of deleterious genes specific to only one environmental stress. Resumen: Tanto la endogamia como el estrés ambiental pueden tener efectos adversos sobre la adaptabilidad afectando la conservación de especies en peligro de extinción. Dos temas importantes son determinar si los efectos del estrés y la endogamia son independientes en lugar de ser sinérgicos, y determinar si los efectos de la endogamia son generales para distintos tipos de estrés o si son específicos para un tipo determinado de estrés. Encontramos que la endogamia reduce la resistencia a la acetona y la desecación en adultos de Drosophila melanogaster, mientras que la resistencia al efecto demoledor del estrés por calor no fue afectada. Sin embargo, las moscas endogámicas experimentaron una disminución proporcionalmente mayor en la productividad que aquellas moscas sin endogamia después de experimentar un estrés por calor. Las correlaciones obtenidas usando líneas medias indicaron que las características de resistencia no estuvieron correlacionadas ni en moscas con endogamia, ni en moscas sin ella. Aparentemente los alelos nocivos recesivos no tuvieron ningún efecto nocivo general en la resistencia al estrés. La endogamia dentro de un ambiente específico y la selección por genotipos resistentes podrían, por lo tanto, eliminar una población de genes nocivos específicos a un solo estrés ambiental. [source] Cardiac hypertrophy and failure: lessons learned from genetically engineered miceACTA PHYSIOLOGICA, Issue 1 2001Y. Takeishi Congestive heart failure is a major and growing public health problem. Because of improved survival of myocardial infarction patients produced by thrombolytic therapy or per-cutaneous revascularization it represents the only form of cardiovascular disease with significantly increased incidence and prevalence. Clinicians view this clinical syndrome as the final common pathway of diverse pathologies such as myocardial infarction and haemodynamic overload. Insights into mechanisms for heart failure historically derived from physiological and biochemical studies which identified compensatory adaptations for the haemodynamic burden associated with the pathological condition including utilization of the Frank Starling mechanism, augmentation of muscle mass, and neurohormonal activation to increase contractility. Therapy has largely been phenomenological and designed to prevent or limit the deleterious effects of these compensatory processes. More recently insights from molecular and cell biology have contributed to a more mechanistic understanding of potential causes of cardiac hypertrophy and failure. Many different analytical approaches have been employed for this purpose. These include the use of conventional animal models which permit serial observation of the onset and progression of heart failure and a sequential analysis of underlying biochemical and molecular events. Neonatal murine cardiomyocytes have been a powerful tool to examine in vitro subcellular mechanisms devoid of the confounding functional effects of multicellular preparations and heterogeneity of cell type. Finally, significant progress has been made by utilizing tissue from human cardiomyopathic hearts explanted at the time of orthotopic transplantation. Each of these methods has significant advantages and disadvantages. Arguably the greatest advance in our understanding of cardiac hypertrophy and failure over the past decade has been the exploitation of genetically engineered mice as biological reagents to study in vivo the effects of alterations in the murine genome. The power of this approach, in principle, derives from the ability to precisely overexpress or ablate a gene of interest and examine the phenotypic consequences in a cardiac specific post-natal manner. In contrast to conventional animal models of human disease which employ some form of environmental stress, genetic engineering involves a signal known molecular perturbation which produces the phenotype. [source] Bacterial traits, organism mass, and numerical abundance in the detrital soil food web of Dutch agricultural grasslandsECOLOGY LETTERS, Issue 1 2005Christian Mulder Abstract This paper compares responses to environmental stress of the ecophysiological traits of organisms in the detrital soil food webs of grasslands in the Netherlands, using the relationship between average body mass M and numerical abundance N. The microbial biomass and biodiversity of belowground fauna were measured in 110 grasslands on sand, 85 of them farmed under organic, conventional and intensive management. Bacterial cell volume and abundance and electrophoretic DNA bands as well as bacterial activity in the form of either metabolic quotient (qCO2) or microbial quotient (Cmic/Corg) predicted the response of microorganisms to stress. For soil fauna, the logarithm of body mass log(M) was approximately linearly related to the logarithm of numerical abundance log(N) with slope near ,1, and the regression slope and the proportion of predatory species were lower in intensive agroecosystems (more reduced substrates with higher energy content). Linear regression of log(N) on log(M) had slope not far from ,3/4. The approach to monitoring data illustrated in this paper could be useful in assessing land-use quality. [source] Timing of foetal growth spurts can explain sex ratio variation in polygynous mammalsECOLOGY LETTERS, Issue 1 2000M.C. Forchhammer The prediction from sex ratio theory that natural selection on sexually dimorphic mammals should favour an excess of male offspring only when mothers are in good condition, has been tested extensively but with little consistency in results. Although recent studies have shown that environmental variations may cause some of the discrepancy, there have also been reports of contrasting sex ratios under similar environmental settings. Here it is suggested that variation in timing of environmental stress and sex-specific differences in foetal growth pattern in relation to maternal condition, may explain such seeming contradictions in sex ratio variation of polygynous mammals. [source] Stationary phase mutagenesis: mechanisms that accelerate adaptation of microbial populations under environmental stressENVIRONMENTAL MICROBIOLOGY, Issue 10 2003Maia Kivisaar Summary Microorganisms are exposed to constantly changing environmental conditions. In a growth-restricting environment (e.g. during starvation), mutants arise that are able to take over the population by a process known as stationary phase mutation. Genetic adaptation of a microbial population under environmental stress involves mechanisms that lead to an elevated mutation rate. Under stressful conditions, DNA synthesis may become more erroneous because of the induction of error-prone DNA polymerases, resulting in a situation in which DNA repair systems are unable to cope with increasing amounts of DNA lesions. Transposition may also increase genetic variation. One may ask whether the rate of mutation under stressful conditions is elevated as a result of malfunctioning of systems responsible for accuracy or are there specific mechanisms that regulate the rate of mutations under stress. Evidence for the presence of mutagenic pathways that have probably been evolved to control the mutation rate in a cell will be discussed. [source] Genetic indicators of herbicide stress in the pacific oyster Crassostrea gigas under experimental conditionsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2000Dario Moraga Abstract This study examined use of the oyster Crassostrea gigas as a bioindicator of experimental pollution caused by two concentrations of five pesticides (atrazine, isoproturon, alachlore, metolachlore, and diuron) used in agricultural and urban activities. The effect of these pesticides on the genetic structure of the marine bivalve was studied as part of an environmental biomonitoring project. This research was performed on two natural estuarine populations sampled along the French Atlantic coast as part of an ongoing monitoring program to survey the ecosystem of Brittany using two approaches: identifying the genetic markers based on the alleles and genotypes associated with pollution effects, and searching for a correlation between these markers and the sensitivity or tolerance of individuals under stress conditions. Results indicate a differential survival of individuals subjected to the various pollutants examined. The sensitivity of alleles and genotypes to environmental stress can be assessed based on the significant differences in allele and genotype frequencies observed between resistant and sensitive individuals when subjected to the pesticides. This genetic study included examination of five enzyme systems (Ak, Pgi, Cap, Pgm, and Mdh) involved in physiologic processes. A total of six alleles and five genotypes at three loci (Ak, Pgi, and Pgm) were identified as being markers of resistance or sensitivity. It is hypothesized that these markers could be used as potential genetic markers in estuarine ecosystem monitoring. [source] Measuring the amount of statistical information in the EPT indexENVIRONMETRICS, Issue 1 2005Patty L. Kitchin Abstract Biological monitoring is the process of measuring the effect of environmental stress on the environment. Aquatic macroinvertebrates are widely used in the monitoring of freshwater lotic systems. The macroinvertebrate fauna of a reference stream is commonly compared to the fauna of an impacted stream that is affected by an environmental stressor. The smaller the similarity between these two streams, the greater the effect of pollution or stress on the impacted stream. Many richness measures, or statistics, exist for measuring similarity. These statistics can be computed using different levels of taxonomic resolution (species, genus and family). Many aquatic biologists believe that species-level identifications, which require exorbitant time and expertise, are needed for correct data interpretations. The actual amount of information provided by these statistics at different taxonomic levels has never been measured. This article evaluates the amount of statistical information provided by the EPT index as compared to a sufficient statistic at the various levels of taxonomic resolution. Copyright © 2004 John Wiley & Sons, Ltd. [source] WATER STRESS ALTERS THE GENETIC ARCHITECTURE OF FUNCTIONAL TRAITS ASSOCIATED WITH DROUGHT ADAPTATION IN AVENA BARBATAEVOLUTION, Issue 3 2009Mark E. Sherrard Environmental stress can alter genetic variation and covariation underlying functional traits, and thus affect adaptive evolution in response to natural selection. However, the genetic basis of functional traits is rarely examined in contrasting resource environments, and consequently, there is no consensus regarding whether environmental stress constrains or facilitates adaptive evolution. We tested whether resource availability affects genetic variation for and covariation among seven physiological traits and seven morphological/performance traits by growing the annual grass Avena barbata in dry and well-watered treatments. We found that differences in the overall genetic variance,covariance (G) matrix between environments were driven by physiological traits rather than morphology and performance traits. More physiological traits were heritable in the dry treatment than the well-watered treatment and many of the genetic correlations among physiological traits were environment dependent. In contrast, genetic variation and covariation among the morphological and performance traits did not differ across treatments. Furthermore, genetic correlations between physiology and performance were stronger in the dry treatment, which contributed to differences in the overall G -matrix. Our results therefore suggest that physiological adaptation would be constrained by low heritable variation in resource-rich environments, but facilitated by higher heritable variation and stronger genetic correlations with performance traits in resource-poor environments. [source] Evolutionary origins of invasive populationsEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 3 2008Carol Eunmi Lee Abstract What factors shape the evolution of invasive populations? Recent theoretical and empirical studies suggest that an evolutionary history of disturbance might be an important factor. This perspective presents hypotheses regarding the impact of disturbance on the evolution of invasive populations, based on a synthesis of the existing literature. Disturbance might select for life-history traits that are favorable for colonizing novel habitats, such as rapid population growth and persistence. Theoretical results suggest that disturbance in the form of fluctuating environments might select for organismal flexibility, or alternatively, the evolution of evolvability. Rapidly fluctuating environments might favor organismal flexibility, such as broad tolerance or plasticity. Alternatively, longer fluctuations or environmental stress might lead to the evolution of evolvability by acting on features of the mutation matrix. Once genetic variance is generated via mutations, temporally fluctuating selection across generations might promote the accumulation and maintenance of genetic variation. Deeper insights into how disturbance in native habitats affects evolutionary and physiological responses of populations would give us greater capacity to predict the populations that are most likely to tolerate or adapt to novel environments during habitat invasions. Moreover, we would gain fundamental insights into the evolutionary origins of invasive populations. [source] The allene oxide cyclase family of Arabidopsis thaliana , localization and cyclizationFEBS JOURNAL, Issue 10 2008Florian Schaller Jasmonates are derived from oxygenated fatty acids (oxylipins) via the octadecanoid pathway and are characterized by a pentacyclic ring structure. They have regulatory functions as signaling molecules in plant development and adaptation to environmental stress. Recently, we solved the structure of allene oxide cyclase 2 (AOC2) of Arabidopsis thaliana, which is, together with the other three AOCs, a key enzyme in the biosynthesis of jasmonates, in that it releases the first cyclic and biologically active metabolite , 12-oxo-phytodienoic acid (OPDA). On the basis of models for the bound substrate, 12,13(S)-epoxy-9(Z),11,15(Z)-octadecatrienoic acid, and the product, OPDA, we proposed that a conserved Glu promotes the reaction by anchimeric assistance. According to this hypothesis, the transition state with a pentadienyl carbocation and an oxyanion is stabilized by a strongly bound water molecule and favorable ,,, interactions with aromatic residues in the cavity. Stereoselectivity results from steric restrictions to the necessary substrate isomerizations imposed by the protein environment. Here, site-directed mutagenesis was used to explore and verify the proposed reaction mechanism. In a comparative analysis of the AOC family from A. thaliana involving enzymatic characterization, in vitro import, and transient expression of AOC,enhanced green fluorescent protein fusion proteins for analysis of subcellular targeting, we demonstrate that all four AOC isoenzymes may contribute to jasmonate biosynthesis, as they are all located in chloroplasts and, in concert with the allene oxide synthase, they are all able to convert 13(S)-hydroperoxy-9(Z),11(E),15(Z)-octadecatrienoic acid into enantiomerically pure cis(+)-OPDA. [source] Amino acids Thr56 and Thr58 are not essential for elongation factor 2 function in yeastFEBS JOURNAL, Issue 20 2007Galyna Bartish Yeast elongation factor 2 is an essential protein that contains two highly conserved threonine residues, T56 and T58, that could potentially be phosphorylated by the Rck2 kinase in response to environmental stress. The importance of residues T56 and T58 for elongation factor 2 function in yeast was studied using site directed mutagenesis and functional complementation. Mutations T56D, T56G, T56K, T56N and T56V resulted in nonfunctional elongation factor 2 whereas mutated factor carrying point mutations T56M, T56C, T56S, T58S and T58V was functional. Expression of mutants T56C, T56S and T58S was associated with reduced growth rate. The double mutants T56M/T58W and T56M/T58V were also functional but the latter mutant caused increased cell death and considerably reduced growth rate. The results suggest that the physiological role of T56 and T58 as phosphorylation targets is of little importance in yeast under standard growth conditions. Yeast cells expressing mutants T56C and T56S were less able to cope with environmental stress induced by increased growth temperatures. Similarly, cells expressing mutants T56M and T56M/T58W were less capable of adapting to increased osmolarity whereas cells expressing mutant T58V behaved normally. All mutants tested were retained their ability to bind to ribosomes in vivo. However, mutants T56D, T56G and T56K were under-represented on the ribosome, suggesting that these nonfunctional forms of elongation factor 2 were less capable of competing with wild-type elongation factor 2 in ribosome binding. The presence of nonfunctional but ribosome binding forms of elongation factor 2 did not affect the growth rate of yeast cells also expressing wild-type elongation factor 2. [source] Lipid biomarkers, pigments and cyanobacterial diversity of microbial mats across intertidal flats of the arid coast of the Arabian Gulf (Abu Dhabi, UAE)FEMS MICROBIOLOGY ECOLOGY, Issue 3 2008Raeid M.M. Abed Abstract Variations in morphology, fatty acids, pigments and cyanobacterial community composition were studied in microbial mats across intertidal flats of the arid Arabian Gulf coast. These mats experience combined extreme conditions of salinity, temperature, UV radiation and desiccation depending on their tidal position. Different mat forms were observed depending on the topology of the coast and location. The mats contained 63 fatty acids in different proportions. The increased amounts of unsaturated fatty acids (12,39%) and the trans/cis ratio (0.6,1.6%) of the cyanobacterial fatty acid n- 18:1,9 in the higher tidal mats suggested an adaptation of the mat microorganisms to environmental stress. Chlorophyll a concentrations suggested lower cyanobacterial abundance in the higher than in the lower intertidal mats. Scytonemin concentrations were dependent on the increase in solar irradiation, salinity and desiccation. The mats showed richness in cyanobacterial species, with Microcoleus chthonoplastes and Lyngbya aestuarii morphotypes as the dominant cyanobacteria. Denaturing gradient gel electrophoresis patterns suggested shifts in the cyanobacterial community dependent on drainage efficiency and salinity from lower to higher tidal zones. We conclude that the topology of the coast and the variable extreme environmental conditions across the tidal flat determine the distribution of microbial mats as well as the presence or absence of different microorganisms. [source] RpoS involvement and requirement for exogenous nutrient for osmotically induced cross protection in Vibrio vulnificusFEMS MICROBIOLOGY ECOLOGY, Issue 3 2005Thomas M. Rosche Abstract Vibrio vulnificus is an opportunistic human pathogen which is the causative agent of food-borne disease and wound infections. V. vulnificus is able to adapt to a variety of potentially stressful environmental changes, such as osmotic, nutrient, and temperature variations in estuarine environments, as well as oxidative, osmotic, and acidity differences following infection of a human host. After exposure to sub-lethal levels of a particular environmental stress, many bacteria become resistant to unrelated stresses, a phenomenon termed cross protection. In this study, we examined the ability of osmotic shock to cross protect V. vulnificus to high temperature as well as oxidative stress. Log phase cells of V. vulnificus strain C7184o were cross protected by prior osmotic shock to both heat and oxidative challenge, but only when exogenous nutrient was present during the osmotic upshift. Further, and unlike other bacteria, nutrient starvation alone did not result in cross protection against either stress. When small amounts of nutrient were present during osmotic shock, cross protection to an otherwise lethal heat challenge developed extremely rapidly, with significant protection seen within 10 min. Cross protection to oxidative stress was slower to develop, requiring several hours. Although stationary phase alone conferred some cross protection to heat and oxidative stress, the alternate sigma factor RpoS was required for complete cross protection of log phase cells to oxidative stress but not for resistance to heat challenge. Together these findings suggest that the cross protective response in V. vulnificus is complex and appears to involve multiple mechanisms. [source] The response of the yeast Saccharomyces cerevisiae to sudden vs. gradual changes in environmental stress monitored by expression of the stress response protein Hsp12pFEMS YEAST RESEARCH, Issue 6 2008Ildar Nisamedtinov Abstract The response of the yeast Saccharomyces cerevisiae to sudden vs. gradual changes in different environmental stress conditions during both respiratory growth and aerobic fermentative growth in the presence of excess glucose was investigated by monitoring the level and rate of expression of the stress response protein Hsp12p using the fluorescent fusion construct Hsp12p-Gfp2p. The initial expression level and the rate of Hsp12p synthesis was significantly greater under glucose-limited conditions in the chemostat (D<0.14 h,1) compared with when excess glucose was present in the auxostat. Decreasing the dilution rate and the glucose concentration further in the A-stat resulted in increased Hsp12p expression, which was more marked when a rapid rather than a gradual change was affected. Common stress factors such as NaCl, ethanol and elevated temperature caused stress responses in both D-stat and auxo-accelerostat culture. The magnitude of the stress response depended on the stress factor, cultivation conditions as well as the rate of change of the stress factor. The rate of Hsp12p synthesis increased due to all applied stresses, with the observed increase between 2 and 20 times lower when the stress was applied gradually rather than rapidly. The results suggested that the Hsp12p expression rate is a good indicator of applied stress in S. cerevisiae. [source] Spatial and temporal variability of the Aleutian climateFISHERIES OCEANOGRAPHY, Issue 2005SERGEI N. RODIONOV Abstract The objective of this paper is to highlight those characteristics of climate variability that may pertain to the climate hypothesis regarding the long-term population decline of Steller sea lions (Eumetopias jubatus). The seasonal changes in surface air temperature (SAT) across the Aleutian Islands are relatively uniform, from 5 to 10°C in summer to near freezing temperatures in winter. The interannual and interdecadal variations in SAT, however, are substantially different for the eastern and western Aleutians, with the transition found at about 170°W. The eastern Aleutians experienced a regime shift toward a warmer climate in 1977, simultaneously with the basin-wide shift in the Pacific Decadal Oscillation (PDO). In contrast, the western Aleutians show a steady decline in winter SATs that started in the 1950s. This cooling trend was accompanied by a trend toward more variable SAT, both on the inter- and intra-annual time scale. During 1986,2002, the variance of winter SATs more than doubled compared to 1965,1985. At the same time in Southeast Alaska, the SAT variance diminished by half. Much of the increase in the intra-seasonal variability for the western Aleutians is associated with a warming trend in November and a cooling trend in January. As a result, the rate of seasonal cooling from November to January has doubled since the late 1950s. We hypothesize that this trend in SAT variability may have increased the environmental stress on the western stock of Steller sea lions and hence contributed to its decline. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||