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Temperature Stress (temperature + stress)
Selected AbstractsRole of laccase in the biology and virulence of Cryptococcus neoformansFEMS YEAST RESEARCH, Issue 1 2004Xudong Zhu Abstract Laccase is an important virulence factor for the human pathogen, Cryptococcus neoformans. In this review, we examine the structural, biological and genetic features of the enzyme and its role in the pathogenesis of cryptococcosis. Laccase is expressed in C. neoformans as a cell wall enzyme that possesses a broad spectrum of activity oxidizing both polyphenolic compounds and iron. Two paralogs, CNLAC1 and CNLAC2, are present in the fungus, of which the first one expresses the dominant enzyme activity under glucose starvation conditions. Regulation of the enzyme is in response to various environmental signals including nutrient starvation, the presence of multivalent cations and temperature stress, and is mediated through multiple signal transduction pathways. Study of the function and regulation of this important virulence factor has led to further understanding of mechanisms of fungal pathogenesis and the regulation of stress response in the host cell environment. [source] Growth and physiological acclimation to temperature and inorganic carbon availability by two submerged aquatic macrophyte species, Callitriche cophocarpa and Elodea canadensisFUNCTIONAL ECOLOGY, Issue 2 2000B. Olesen Abstract 1.,Interactive effects of temperature and inorganic carbon availability on photosynthetic acclimation and growth of two submerged macrophyte species, Elodea canadensis and Callitriche cophocarpa, were examined to test the hypotheses that: (1) effects of temperature on growth rate and photosynthetic acclimation are suppressed under low inorganic carbon availability; (2) the plants compensate for the reduction in activity of individual enzymes at lower temperatures by increasing the activity per unit plant mass, here exemplified by Rubisco. The experiments were performed in the laboratory where plants were grown in a factorial combination of three temperatures (7,25 °C) and three inorganic carbon regimes. 2.,The relative growth rate of both species was strongly affected by growth conditions and increased by up to 4·5 times with increased temperature and inorganic carbon availability. The sensitivity to inorganic carbon was greatest at high temperature and the sensitivity to temperature greatest at high carbon concentrations. 3.,Photosynthetic acclimation occurred in response to growth conditions for both species. The affinity for inorganic carbon and the photosynthetic capacity, both measured at 15 °C, increased with reduced inorganic carbon availability during growth and were greater at warmer than at cooler growth temperature. The acclimative change in photosynthesis was related to the extent of temperature and inorganic carbon stress. Using data for Elodea, a negative relationship between degree of temperature stress and photosynthetic performance was found. In relation to inorganic carbon, a linear increase in CO2 affinity and photosynthetic capacity was found with increased inorganic carbon stress during growth. 4.,The total Rubisco activity declined with increased inorganic carbon availability during growth and with enhanced growth temperature. In addition, the activation state of Rubisco was higher at cooler than at warmer temperatures for Callitriche. This suggests that low-temperature grown plants compensate for the temperature-dependent reduction in activity of the individual Rubisco molecules by enhancing resource allocations towards Rubisco. [source] Synergistic effects associated with climate change and the development of rocky shore molluscsGLOBAL CHANGE BIOLOGY, Issue 3 2005R. Przeslawski Abstract Global climate change and ozone layer thinning will simultaneously expose organisms to increasingly stressful conditions. Early life stages of marine organisms, particularly eggs and larvae, are considered most vulnerable to environmental extremes. Here, we exposed encapsulated embryos of three common rocky shore gastropods to simultaneous combinations of ecologically realistic levels of ultraviolet radiation (UVR), water temperature stress and salinity stress to identify potential interactions and associated impacts of climate change. We detected synergistic effects with increases in mortality and retardation in development associated with the most physiologically stressful conditions. The effects of UVR were particularly marked, with mortality increasing up to 12-fold under stressful conditions. Importantly, the complex outcomes observed on applying multiple stressors could not have been predicted from examining environmental variables in isolation. Hence, we are probably dramatically underestimating the ecological impacts of climate change by failing to consider the complex interplay of combinations of environmental variables with organisms. [source] Cognate Hsp70 gene is induced during deep larval diapause in the moth Sesamia nonagrioidesINSECT MOLECULAR BIOLOGY, Issue 2 2009T. Gkouvitsas Abstract The complete cDNA sequences of Heat shock cognate protein 70 (SnoHsc70) and Heat shock protein 70 (SnoHsp70) were determined from the corn stalk borer Sesamia nonagrioides (Lef.). They encode 653 amino acids (Hsc70) and 633 amino acids (Hsp70), with calculated molecular masses of 71.5 kDa and 70.2 kDa respectively. SnoHsc70 is constitutively expressed, and SnoHsp70 is heat-inducible in non-diapausing insects. SnoHsp70 is down regulated during diapause, while SnoHsc70 is induced as the larvae enter deep diapause. High temperature stress during diapause has no further effect on transcript levels of SnoHsc70. Our results show that SnoHsc70 may play important roles in assisting protein conformation during specific stages of diapause. [source] Physiological Responses of Nile Tilapia, Oreochromis niloticus, Fed Vitamin C- and Lipid-Supplemented Diets and Submitted to Low-Temperature Stress,JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 2 2007Dario R. Falcon This study evaluated the effects of different levels of vitamin C and lipids on physiological responses of Nile tilapia, Oreochromis niloticus, submitted to temperature stress. There were two phases: Phase I , preparing fish to store vitamin C and lipid at appropriate temperature, and Phase II , evaluating the contributions these reserves make to fish physiology under low-temperature stress. The experiment used a 3 × 2 factorial design with three vitamin C levels (300, 600, and 1200 mg/kg diet) and two lipid levels (8.0 and 12.0%), plus absence of nutrient test and a diet of 6.0% lipids and 125.0 mg/kg vitamin C. In Phase I, 192 fish were kept at 26.0 ± 1.0 C for 112 d, and in Phase II, 48 fish were kept at 18.0 ± 0.5 C for 32 d and at 15.0 ± 0.5 C for 11 d. Fish fed C0L0 diet showed lower erythrocytes values in both phases; higher vitamin C supplement determined higher red blood cell (RBC) number and higher hematocrit (Htc) (Phase II); Htc was significantly lower in Phase II; after temperature stress, fish fed C0L0 diet had higher mean corpuscular volume, lower hemoglobin corpuscular concentration, and significantly lower vitamin C concentration in the liver; and higher supplementation determined a higher concentration in the liver (Phases I and II). Higher plasmatic cortisol concentration was seen in fish fed C0L0 diet. In conclusion, our results show that the absence of vitamin C in diets impairs RBC formation and does not enable fish to cope with stress; excess vitamin C is efficient in mitigating stress and 600 mg/kg diet is economic and physiologically sufficient to prepare fish for coping with low-temperature stress. Lipid supplementation does not determine alterations in stress biochemical parameters. [source] Environmental temperature stress on drugs in prehospital emergency medical serviceACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 4 2003M. Helm Background: Drugs used in prehospital emergency medical service (EMS) in principle are subject to the same storage restrictions as hospital-based medications. The prehospital emergency environment however, often exceeds these storage recommendations. Main stress factors are sunlight, vibration and extreme temperature, which may lead to alteration in chemical and physical stability of stored pharmaceuticals, as well as microbiological contamination and concentration enhancement of pharmacological inserts. Methods: The purpose of this study was to determine the environmental temperature stress upon drugs used in the prehospital EMS under real mission conditions within different types of rescue vehicles (rescue helicopter [HEMS], ambulance [AMB] and emergency physician transport vehicle [EPTV]) during a ,summer' and ,winter' monitoring period (2 months duration each/location: southern Germany). Results: Recorded temperatures varied from ,13.2°C to +50.6°C. The recommended maximum storage temperature (+25°C) was exceeded in all rescue vehicles (33,45% of total exposure time), whereas the recommended minimum storage temperature (0°C) only fell short in the EPTV (19% of total exposure time). The daily maximum temperature variations ranged from 19.0°C (winter) to 32.9°C (summer). Conclusions: These results show that even in a moderate climatic zone, drugs used in prehospital EMS are significantly influenced by temperature stress; furthermore, these results recommend the usage of temperature-controlled drug boxes. [source] Plant survival after freezing in wheat ,Cappelle Desprez' (,Bezostaya 1') intervarietal chromosome substitution linesPLANT BREEDING, Issue 2 2008G. Ganeva Abstract The effect of individual chromosomes of the wheat variety ,Bezostaya 1' on plant resistance to low temperatures was studied using the available set of intervarietal ,Cappelle Desprez' (,Bezostaya 1') chromosome substitution lines. The number of plants surviving after freezing at ,12, ,15 and ,17°C was determined for both parents and lines in trials in 2004/2005 and 2005/2006. Significant differences between the three temperature treatments and between lines were found, implying that two factors, the level of temperature stress and chromosome substitutions, were influencing plant survival. Improved frost resistance in both trials was associated with genes located on five chromosomes: 5A, 2D, 4A, 5D and 6A. An increase in the plant frost resistance because of the effects of 7A and 1A chromosomes was also observed in the 2005/2006 trial, when the overall autumn and winter (January) temperatures were lower than in 2004/2005. [source] Temperature Stress Tolerance of Conifer Seedlings after Exposure to UV-B RadiationPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2005Sylvia J. L'Hirondelle ABSTRACT Ground-level UV-B radiation has increased globally due to a thinning stratospheric ozone layer. We estimated the effects of increased UV-B on 10 conifer species grown in chambers in greenhouses with supplemental UV-B. Species were selected from a wide range of geographic locations. Plant material of two ages (germinants, first growing season; seedlings, second season) were exposed to three levels of UV-B from ambient (at Victoria, B.C., Canada) to three times ambient (12 kJ m,2 d,1) for up to four months. Frost hardiness and heat tolerance of shoots were estimated from changes in chlorophyll fluorescence after exposure to test temperatures. There were no significant differences among seed sources from different elevations in their response to temperature stresses. When UV-B increased above the ambient level, three species (interior Douglas-fir, Engelmann spruce, and interior lodgepole pine) increased in frost hardiness and four (grand fir, interior spruce, yellow-cedar, and western redcedar) decreased. Two species (western redcedar and western hemlock) increased in heat tolerance when UV-B increased to the 12 kJ level. The main differences in stress tolerance were between the triple ambient and the other two treatments, not between ambient and double ambient, suggesting that any changes in UV-B would have to be large to elicit physiological changes in conifer seedlings. [source] | ||||||||||