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  • 1
    ISSN: 1539-6924
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Food-related illness in the United States is estimated to affect over six million people per year and cost the economy several billion dollars. These illnesses and costs could be reduced if minimum infectious doses were established and used as the basis of regulations and monitoring. However, standard methodologies for dose-response assessment are not yet formulated for microbial risk assessment. The objective of this study was to compare dose response models for food-borne pathogens and determine which models were most appropriate for a range of pathogens. The statistical models proposed in the literature and chosen for comparison purposes were log-normal,(19) log-logistic,(17) exponential,(7,9,17)ß-Poisson(7,9,18) and Welbull-Gamma.(3) These were fit to four data sets also taken from published literature, Shigella fiexneri,(9,12,13)Shigella dysenteriae,(9,11)Campylobacter jejuni,(15,16) and Salmonella typhosa,(7,14) usingthe method of maximum likelihood. The Weibull-gamma, the only model with three parameters, was also the only model capable of fitting all the data sets examined using the maximum likelihood estimation for comparisons. Infectious doses were also calculated using each model. Within any given data set, the infectious dose estimated to affect one percent of the population ranged from one order of magnitude to as much as nine orders of magnitude, illustrating the differences in extrapolation of the dose response models. More data are needed to compare models and examine extrapolation from high to low doses for food-borne pathogens.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Planta 172 (1987), S. 114-120 
    ISSN: 1432-2048
    Keywords: Amylase ; Deepwater rice ; Ethylene and internode growth ; Gibberellin and internode growth ; Internode growth ; Oryza (amylases and growth)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isoelectrofocusing, product analysis, thermal denaturation studies and affinity chromatography on cycloheptaamylose-Sephadex were used to identify the amylolytic enzymes in internodes of deepwater rice (Oryza sativa L.). Amylolytic activity in internodes of deepwater rice consists of α-amylase (sometimes separated into two isoforms) and of β-amylase. During submergence of whole plants, α-amylase activity increases in young, growing internodes, but β-amylase activity declines. Although non-growing, mature internodes contain higher levels of β-amylase than do the elongating younger internodes, the effect of submergence on amylase activities in both tissues follows the same trend. Submergence, gibberellic acid (GA3) and ethylene all promote α-amylase activity in growing and non-growing internodes of excised deepwater-rice stem sections. Inhibitor studies showed that submergence and ethylene promote α-amylase activity in the absence of endogenous gibberellin (GA), and GA3 enhances α-amylase activity when ethylene action is inhibited. Therefore, ethylene and GA appear to increase α-amylase activity independently of each other. Enhanced α-amylase activities are probably responsible for the mobilization of carbohydrates which are needed to support internode elongation during submergence of deepwater rice.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant growth regulation 3 (1985), S. 401-417 
    ISSN: 1573-5087
    Keywords: Pea ; Pisum ; apical senescence ; defruiting ; polyamines ; putrescine ; spermidine ; spermine ; polyamine ; synthesis inhibitors ; gibberellin ; 1-aminocyclopropane-1-carboxylic acid ; aminoethoxyvinyl glycine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of various treatments on the apical senescence and polyamine content of apical buds of G2 peas was analysed. Defruiting prevented senescence and increased bud size and polyamine content. Exogenous applications of GA20 enhanced bud size and spermidine concentration. Applied spermidine had a slight effect on spermidine level but did not delay senescence. ACC strongly induced adecrease in bud size and, at 10 mM, apical senescence. This was accompanied by a steady decline in the level of all polyamines though their concentration remained constant until 10 mM ACC, where a drop was noted. Spermidine in the presence of ACC modulated the effect of ACC on the bud size while returning the internal polyamine content to control levels. AVG, an inhibitor of ACC synthesis produced pronounced increases in putrescine though no apparent effect on apical bud growth. Polyamine synthesis inhibitors were without effect on growth or internal polyamine content. The internal polyamine content appeared to correlate with apical bud size and vigor but did not show any consistent relationship to apical bud senescence.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1539-6924
    Keywords: dose-response ; models ; food-borne ; pathogens ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Food-related illness in the United States is estimated to affect over six million people per year and cost the economy several billion dollars. These illnesses and costs could be reduced if minimum infectious doses were established and used as the basis of regulations and monitoring. However, standard methodologies for dose-response assessment are not yet formulated for microbial risk assessment. The objective of this study was to compare dose-response models for food-borne pathogens and determine which models were most appropriate for a range of pathogens. The statistical models proposed in the literature and chosen for comparison purposes were log-normal, log-logistic, exponential, β-Poisson and Weibull-Gamma. These were fit to four data sets also taken from published literature, Shigella flexneri, Shigella dysenteriae,Campylobacter jejuni, and Salmonella typhosa, using the method of maximum likelihood. The Weibull-gamma, the only model with three parameters, was also the only model capable of fitting all the data sets examined using the maximum likelihood estimation for comparisons. Infectious doses were also calculated using each model. Within any given data set, the infectious dose estimated to affect one percent of the population ranged from one order of magnitude to as much as nine orders of magnitude, illustrating the differences in extrapolation of the dose response models. More data are needed to compare models and examine extrapolation from high to low doses for food-borne pathogens.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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