197 resultados para Skeggs, Beverly


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Auxin (IAA) is an important regulator of plant development and root differentiation. Although recent studies indicate that salicylic acid (SA) may also be important in this context by interfering with IAA signaling, comparatively little is known about its impact on the plant’s physiology, metabolism, and growth characteristics. Using carbon-11, a short-lived radioisotope (t 1/2 = 20.4 min) administered as 11CO2 to maize plants (B73), we measured changes in these functions using SA and IAA treatments. IAA application decreased total root biomass, though it increased lateral root growth at the expense of primary root elongation. IAA-mediated inhibition of root growth was correlated with decreased 11CO2 fixation, photosystem II (PSII) efficiency, and total leaf carbon export of 11C-photoassimilates and their allocation belowground. Furthermore, IAA application increased leaf starch content. On the other hand, SA application increased total root biomass, 11CO2 fixation, PSII efficiency, and leaf carbon export of 11C-photoassimilates, but it decreased leaf starch content. IAA and SA induction patterns were also examined after root-herbivore attack by Diabrotica virgifera to place possible hormone crosstalk into a realistic environmental context. We found that 4 days after infestation, IAA was induced in the midzone and root tip, whereas SA was induced only in the upper proximal zone of damaged roots. We conclude that antagonistic crosstalk exists between IAA and SA which can affect the development of maize plants, particularly through alteration of the root system’s architecture, and we propose that the integration of both signals may shape the plant’s response to environmental stress.

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This study applies the multilevel analysis technique to longitudinal data of a large clinical trial. The technique accounts for the correlation at different levels when modeling repeated blood pressure measurements taken throughout the trial. This modeling allows for closer inspection of the remaining correlation and non-homogeneity of variance in the data. Three methods of modeling the correlation were compared. ^

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Ordinal outcomes are frequently employed in diagnosis and clinical trials. Clinical trials of Alzheimer's disease (AD) treatments are a case in point using the status of mild, moderate or severe disease as outcome measures. As in many other outcome oriented studies, the disease status may be misclassified. This study estimates the extent of misclassification in an ordinal outcome such as disease status. Also, this study estimates the extent of misclassification of a predictor variable such as genotype status. An ordinal logistic regression model is commonly used to model the relationship between disease status, the effect of treatment, and other predictive factors. A simulation study was done. First, data based on a set of hypothetical parameters and hypothetical rates of misclassification was created. Next, the maximum likelihood method was employed to generate likelihood equations accounting for misclassification. The Nelder-Mead Simplex method was used to solve for the misclassification and model parameters. Finally, this method was applied to an AD dataset to detect the amount of misclassification present. The estimates of the ordinal regression model parameters were close to the hypothetical parameters. β1 was hypothesized at 0.50 and the mean estimate was 0.488, β2 was hypothesized at 0.04 and the mean of the estimates was 0.04. Although the estimates for the rates of misclassification of X1 were not as close as β1 and β2, they validate this method. X 1 0-1 misclassification was hypothesized as 2.98% and the mean of the simulated estimates was 1.54% and, in the best case, the misclassification of k from high to medium was hypothesized at 4.87% and had a sample mean of 3.62%. In the AD dataset, the estimate for the odds ratio of X 1 of having both copies of the APOE 4 allele changed from an estimate of 1.377 to an estimate 1.418, demonstrating that the estimates of the odds ratio changed when the analysis includes adjustment for misclassification. ^

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http://download.journals.elsevierhealth.com/pdfs/journals/0010-7824/PIIS0010782412006439.pdf

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http://pdfs.journals.lww.com/greenjournal/2008/12000/Two_Distinct_Oral_Routes_of_Misoprostol_in.18.pdf?token=method|ExpireAbsolute;source|Journals;ttl|1369920806057;payload|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;hash|BM4+yd44xH/IRKdsrM1Wzg==

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