The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform

Damian J Krysan - One of the best experts on this subject based on the ideXlab platform.

  • host Carbon Dioxide Concentration is an independent stress for cryptococcus neoformans that affects virulence and antifungal susceptibility
    Mbio, 2019
    Co-Authors: Damian J Krysan, Bing Zhai, Sarah R Beattie, Kara M Misel, Melanie Wellington
    Abstract:

    ABSTRACT The ability of Cryptococcus neoformans to cause disease in humans varies significantly among strains with highly related genotypes. In general, environmental isolates of pathogenic species such as Cryptococcus neoformans var. grubii have reduced virulence relative to clinical isolates, despite having no differences in the expression of the canonical virulence traits (high-temperature growth, melanization, and capsule formation). In this observation, we report that environmental isolates of C. neoformans tolerate host CO2 Concentrations poorly compared to clinical isolates and that CO2 tolerance correlates well with the ability of the isolates to cause disease in mammals. Initial experiments also suggest that CO2 tolerance is particularly important for dissemination of C. neoformans from the lung to the brain. Furthermore, CO2 Concentrations affect the susceptibility of both clinical and environmental C. neoformans isolates to the azole class of antifungal drugs, suggesting that antifungal testing in the presence of CO2 may improve the correlation between in vitro azole activity and patient outcome. IMPORTANCE A number of studies comparing either patient outcomes or model system virulence across large collections of Cryptococcus isolates have found significant heterogeneity in virulence even among strains with highly related genotypes. Because this heterogeneity cannot be explained by variations in the three well-characterized virulence traits (growth at host body temperature, melanization, and polysaccharide capsule formation), it has been widely proposed that additional C. neoformans virulence traits must exist. The natural niche of C. neoformans is in the environment, where the Carbon Dioxide Concentration is very low (∼0.04%); in contrast, mammalian host tissue Carbon Dioxide Concentrations are 125-fold higher (5%). We have found that the ability to grow in the presence of 5% Carbon Dioxide distinguishes low-virulence strains from high-virulence strains, even those with a similar genotype. Our findings suggest that Carbon Dioxide tolerance is a previously unrecognized virulence trait for C. neoformans.

  • host Carbon Dioxide Concentration is an independent stress for cryptococcus neoformans that affects virulence and antifungal susceptibility
    bioRxiv, 2019
    Co-Authors: Damian J Krysan, Bing Zhai, Sarah R Beattie, Kara M Misel, Melanie Wellington, Xiaorong Lin
    Abstract:

    Abstract The ability of Cryptococcus neoformans to cause disease in humans varies significantly among strains with highly related genotypes. In general, environmental isolates of pathogenic species such as C. neoformans var. grubii have reduced virulence relative to clinical isolates, despite having no differences in the expression of the canonical virulence traits (high temperature growth, melanization and capsule formation). In this observation, we report that environmental isolates of C. neoformans tolerate host CO2 Concentrations poorly compared to clinical isolates and that CO2 tolerance correlates well with the ability of the isolates to cause disease in mammals. Initial experiments also suggest that CO2 tolerance is particularly important for dissemination of C. neoformans from the lung to the brain. Furthermore, CO2 Concentrations affect the susceptibility of both clinical and environmental C. neoformans isolates to the azole class of antifungal drugs, suggesting that antifungal testing in the presence of CO2 may improve the correlation between in vitro azole activity and patient outcome. Importance A number of studies comparing either patient outcomes or model system virulence across large collections of Cryptococcus isolates have found significant heterogeneity in virulence even among strains with highly related genotypes. Because this heterogeneity cannot be explained by variations in the three well-characterized virulence traits (growth at host body temperature; melanization; and polysaccharide capsule formation), it has been widely proposed that additional C. neoformans virulence traits must exist. C. neoformans natural niche is in the environment where the Carbon Dioxide Concentration is very low (∼0.04%); in contrast, mammalian host tissue Carbon Dioxide Concentrations are 125-fold higher (5%). We have found that the ability to grow in the presence of 5% Carbon Dioxide distinguishes low virulence strains from high virulence strains, even those with a similar genotype. Our findings suggest that Carbon Dioxide tolerance is a previously un-recognized virulence trait for C. neoformans.

James A. Bunce - One of the best experts on this subject based on the ideXlab platform.

  • Responses of Respiration to Increases in Carbon Dioxide Concentration and Temperature in Three Soybean Cultivars
    Annals of Botany, 1996
    Co-Authors: James A. Bunce, Lewis H Ziska
    Abstract:

    The purpose of this experiment was to determine how respiration of soybeans may respond to potential increases in atmospheric Carbon Dioxide Concentration and growth temperature. Three cultivars of soybeans (Glycine max L. Merr.), from maturity groups 00, IV, and VIII, were grown at 370, 555 and 740 cm$ m’$ Carbon Dioxide Concentrations at 20}15, 25}20, and 31}26 ∞C day}night temperatures. Rates of Carbon Dioxide eux in the dark were measured for whole plants several times during exponential growth. These measurements were made at the night temperature and the Carbon Dioxide Concentration at which the plants were grown. For the lowest and highest temperature treatments, the short term response of respiration rate to measurement at the three growth Carbon Dioxide Concentrations was also determined. Elemental analysis of the tissue was used to estimate the growth conversion eciency. This was combined with the observed relative growth rates to estimate growth respiration. Maintenance respiration was estimated as the dierence between growth respiration and total respiration. Respiration rates were generally sensitive to short term changes in the measurement Carbon Dioxide Concentration for plants grown at the lowest, but not the highest Carbon Dioxide Concentration. At all temperatures, growth at elevated Carbon Dioxide Concentrations decreased total respiration measured at the growth Concentration, with no significant dierences among cultivars. Total respiration increased very little with increasing growth temperature, despite an increase in relative growth rate. Growth respiration was not aected by Carbon Dioxide treatment at any temperature, but increased with temperature because of the increase in relative growth rate. Values calculated for maintenance respiration decreased with increasing Carbon Dioxide Concentration and also decreased with increasing temperature. Calculated values of maintenance respiration were sometimes zero or negative at the warmer temperatures. This suggests that respiration rates measured in the dark may not have reflected average 24-h rates of energy use. The results indicate that increasing atmospheric Carbon Dioxide Concentration may reduce respiration in soybeans, and respiration may be insensitive to climate warming. # 1996 Annals of Botany Company

  • Elevated Atmospheric Carbon Dioxide Concentration Affects Interactions Between Spodoptera exigua (Lepidoptera: Noctuidae) Larvae and Two Host Plant Species Outdoors
    Environmental Entomology, 1994
    Co-Authors: Frances Caulfield, James A. Bunce
    Abstract:

    Beet armyworm, Spodoptera exigua (Huebner), larvae were placed on sugarbeet (Beta vulgaris L.) and pigweed (Amaranthus hybridus L.) plants in outdoor chambers in which the plants were growing at either the ambient ([approximately] 350 [mu]l liter[sup [minus]1]) or ambient plus 350 [mu]l liter[sup [minus]1] ([approximately] 700 [mu]l liter[sup [minus]1]) Carbon Dioxide Concentration. A series of experiments was performed to determine if larvae reduced plant growth differently at the two Carbon Dioxide Concentrations in either species and if the insect growth or survival differed with Carbon Dioxide Concentration. Leaf nitrogen, water, starch, and soluble carbohydrate contents were measured to assess Carbon Dioxide Concentration effects on leaf quality. Insect feeding significantly reduced plant growth in sugarbeet plants at 350 [mu]l liter[sup [minus]1] but not at 700 [mu]l liter[sup [minus]1] nor in pigweed at either Carbon Dioxide Concentration. Larval survival was greater on sugarbeet plants at the elevated Carbon Dioxide Concentration. Increased survival occurred only if the insects were at the elevated Carbon Dioxide Concentration and consumed leaf material grown at the elevated Concentration. Leaf quality was only marginally affected by growth at elevated Carbon Dioxide Concentration in these experiments. The results indicate that in designing experiments to predict effects of elevated atmospheric more » Carbon Dioxide Concentrations on plant-insect interactions, both plants and insects should be exposed to the experimental Carbon Dioxide Concentrations, as well as to as realistic environmental conditions as possible. « less

  • stomatal conductance photosynthesis and respiration of temperate deciduous tree seedlings grown outdoors at an elevated Concentration of Carbon Dioxide
    Plant Cell and Environment, 1992
    Co-Authors: James A. Bunce
    Abstract:

    Seedlings of temperate deciduous tree species were grown outdoors at ambient and at an elevated Concentration of Carbon Dioxide to examine how aspects of their gas exchange would be altered by growth at elevated Carbon Dioxide Concentration. Leaf conductances to water vapour and net Carbon Dioxide exchange rates were determined periodically near midday. Whole-plant Carbon Dioxide efflux rates in darkness were also determined. The stomatal conductance of leaves of plants grown and measured at 700 cm3 m−3 Carbon Dioxide did not differ from that of plants grown and measured at 350 cm3 m−3 in Malus domestica, Quercus prinus and Quercus robur at any measurement time. In Acer saccharinum, lower conductances occurred for plants grown and measured at elevated Carbon Dioxide Concentration only at measurement temperatures above 33°C. Photo-synthetic adjustment to elevated Carbon Dioxide Concentration was evident only in Q. robur. All species examined had lower rates of dark respiration per unit of mass when grown and measured at elevated Carbon Dioxide Concentration.

Melanie Wellington - One of the best experts on this subject based on the ideXlab platform.

  • host Carbon Dioxide Concentration is an independent stress for cryptococcus neoformans that affects virulence and antifungal susceptibility
    Mbio, 2019
    Co-Authors: Damian J Krysan, Bing Zhai, Sarah R Beattie, Kara M Misel, Melanie Wellington
    Abstract:

    ABSTRACT The ability of Cryptococcus neoformans to cause disease in humans varies significantly among strains with highly related genotypes. In general, environmental isolates of pathogenic species such as Cryptococcus neoformans var. grubii have reduced virulence relative to clinical isolates, despite having no differences in the expression of the canonical virulence traits (high-temperature growth, melanization, and capsule formation). In this observation, we report that environmental isolates of C. neoformans tolerate host CO2 Concentrations poorly compared to clinical isolates and that CO2 tolerance correlates well with the ability of the isolates to cause disease in mammals. Initial experiments also suggest that CO2 tolerance is particularly important for dissemination of C. neoformans from the lung to the brain. Furthermore, CO2 Concentrations affect the susceptibility of both clinical and environmental C. neoformans isolates to the azole class of antifungal drugs, suggesting that antifungal testing in the presence of CO2 may improve the correlation between in vitro azole activity and patient outcome. IMPORTANCE A number of studies comparing either patient outcomes or model system virulence across large collections of Cryptococcus isolates have found significant heterogeneity in virulence even among strains with highly related genotypes. Because this heterogeneity cannot be explained by variations in the three well-characterized virulence traits (growth at host body temperature, melanization, and polysaccharide capsule formation), it has been widely proposed that additional C. neoformans virulence traits must exist. The natural niche of C. neoformans is in the environment, where the Carbon Dioxide Concentration is very low (∼0.04%); in contrast, mammalian host tissue Carbon Dioxide Concentrations are 125-fold higher (5%). We have found that the ability to grow in the presence of 5% Carbon Dioxide distinguishes low-virulence strains from high-virulence strains, even those with a similar genotype. Our findings suggest that Carbon Dioxide tolerance is a previously unrecognized virulence trait for C. neoformans.

  • host Carbon Dioxide Concentration is an independent stress for cryptococcus neoformans that affects virulence and antifungal susceptibility
    bioRxiv, 2019
    Co-Authors: Damian J Krysan, Bing Zhai, Sarah R Beattie, Kara M Misel, Melanie Wellington, Xiaorong Lin
    Abstract:

    Abstract The ability of Cryptococcus neoformans to cause disease in humans varies significantly among strains with highly related genotypes. In general, environmental isolates of pathogenic species such as C. neoformans var. grubii have reduced virulence relative to clinical isolates, despite having no differences in the expression of the canonical virulence traits (high temperature growth, melanization and capsule formation). In this observation, we report that environmental isolates of C. neoformans tolerate host CO2 Concentrations poorly compared to clinical isolates and that CO2 tolerance correlates well with the ability of the isolates to cause disease in mammals. Initial experiments also suggest that CO2 tolerance is particularly important for dissemination of C. neoformans from the lung to the brain. Furthermore, CO2 Concentrations affect the susceptibility of both clinical and environmental C. neoformans isolates to the azole class of antifungal drugs, suggesting that antifungal testing in the presence of CO2 may improve the correlation between in vitro azole activity and patient outcome. Importance A number of studies comparing either patient outcomes or model system virulence across large collections of Cryptococcus isolates have found significant heterogeneity in virulence even among strains with highly related genotypes. Because this heterogeneity cannot be explained by variations in the three well-characterized virulence traits (growth at host body temperature; melanization; and polysaccharide capsule formation), it has been widely proposed that additional C. neoformans virulence traits must exist. C. neoformans natural niche is in the environment where the Carbon Dioxide Concentration is very low (∼0.04%); in contrast, mammalian host tissue Carbon Dioxide Concentrations are 125-fold higher (5%). We have found that the ability to grow in the presence of 5% Carbon Dioxide distinguishes low virulence strains from high virulence strains, even those with a similar genotype. Our findings suggest that Carbon Dioxide tolerance is a previously un-recognized virulence trait for C. neoformans.

Elizabeth A Ainsworth - One of the best experts on this subject based on the ideXlab platform.

  • growth at elevated ozone or elevated Carbon Dioxide Concentration alters antioxidant capacity and response to acute oxidative stress in soybean glycine max
    Journal of Experimental Botany, 2011
    Co-Authors: Kelly M Gillespie, Alistair Rogers, Elizabeth A Ainsworth
    Abstract:

    Soybeans (Glycine max Merr.) were grown at elevated Carbon Dioxide Concentration ([CO2]) or chronic elevated ozone Concentration ([O3]; 90 ppb), and then exposed to an acute O3 stress (200 ppb for 4 h) in order to test the hypothesis that the atmospheric environment alters the total antioxidant capacity of plants, and their capacity to respond to an acute oxidative stress. Total antioxidant metabolism, antioxidant enzyme activity, and antioxidant transcript abundance were characterized before, immediately after, and during recovery from the acute O3 treatment. Growth at chronic elevated [O3] increased the total antioxidant capacity of plants, while growth at elevated [CO2] decreased the total antioxidant capacity. Changes in total antioxidant capacity were matched by changes in ascorbate content, but not phenolic content. The growth environment significantly altered the pattern of antioxidant transcript and enzyme response to the acute O3 stress. Following the acute oxidative stress, there was an immediate transcriptional reprogramming that allowed for maintained or increased antioxidant enzyme activities in plants grown at elevated [O3]. Growth at elevated [CO2] appeared to increase the response of antioxidant enzymes to acute oxidative stress, but dampened and delayed the transcriptional response. These results provide evidence that the growth environment alters the antioxidant system, the immediate response to an acute oxidative stress, and the timing over which plants return to initial antioxidant levels. The results also indicate that future elevated [CO2] and [O3] will differentially affect the antioxidant system.

Lewis H Ziska - One of the best experts on this subject based on the ideXlab platform.

  • observed changes in soyabean growth and seed yield from abutilon theophrasti competition as a function of Carbon Dioxide Concentration
    Weed Research, 2013
    Co-Authors: Lewis H Ziska
    Abstract:

    Summary Soyabean (Glycine max) was grown at ambient and projected levels of atmospheric Carbon Dioxide (+250 μmol mol−1 above ambient) over two field seasons with and without the presence of a weed, Abutilon theophrasti, to quantify the potential effect of rising atmospheric Carbon Dioxide Concentration on weed–crop interactions and potential yield loss in soyabean. Under weed-free conditions, elevated CO2 resulted in stimulations in soyabean seed yield and associated components, including pod number. At an approximate density of 6 plants m−2, A. theophrasti competition resulted in a significant reduction (−40%) in soyabean seed yield. Although differences in seed yield reduction by A. theophrasti were observed as a function of year, the relative decrease in seed yield with A. theophrasti biomass did not differ in response to CO2. Although careful weed management will be necessary if CO2-induced increases in seed yield for soyabean are to be achieved, these data suggest that soyabean seed yield may be more resilient in competition with A. theophrasti as a function of rising atmospheric levels of Carbon Dioxide.

  • Responses of Respiration to Increases in Carbon Dioxide Concentration and Temperature in Three Soybean Cultivars
    Annals of Botany, 1996
    Co-Authors: James A. Bunce, Lewis H Ziska
    Abstract:

    The purpose of this experiment was to determine how respiration of soybeans may respond to potential increases in atmospheric Carbon Dioxide Concentration and growth temperature. Three cultivars of soybeans (Glycine max L. Merr.), from maturity groups 00, IV, and VIII, were grown at 370, 555 and 740 cm$ m’$ Carbon Dioxide Concentrations at 20}15, 25}20, and 31}26 ∞C day}night temperatures. Rates of Carbon Dioxide eux in the dark were measured for whole plants several times during exponential growth. These measurements were made at the night temperature and the Carbon Dioxide Concentration at which the plants were grown. For the lowest and highest temperature treatments, the short term response of respiration rate to measurement at the three growth Carbon Dioxide Concentrations was also determined. Elemental analysis of the tissue was used to estimate the growth conversion eciency. This was combined with the observed relative growth rates to estimate growth respiration. Maintenance respiration was estimated as the dierence between growth respiration and total respiration. Respiration rates were generally sensitive to short term changes in the measurement Carbon Dioxide Concentration for plants grown at the lowest, but not the highest Carbon Dioxide Concentration. At all temperatures, growth at elevated Carbon Dioxide Concentrations decreased total respiration measured at the growth Concentration, with no significant dierences among cultivars. Total respiration increased very little with increasing growth temperature, despite an increase in relative growth rate. Growth respiration was not aected by Carbon Dioxide treatment at any temperature, but increased with temperature because of the increase in relative growth rate. Values calculated for maintenance respiration decreased with increasing Carbon Dioxide Concentration and also decreased with increasing temperature. Calculated values of maintenance respiration were sometimes zero or negative at the warmer temperatures. This suggests that respiration rates measured in the dark may not have reflected average 24-h rates of energy use. The results indicate that increasing atmospheric Carbon Dioxide Concentration may reduce respiration in soybeans, and respiration may be insensitive to climate warming. # 1996 Annals of Botany Company