Application of metabolite profiling to the identification of traits in a population of tomato introgression lines.

Naturally occurring variation in wild species can be used to increase the genetic diversity of cultivated crops and improve agronomic value. Populations of introgression lines carrying wild species alleles afford an opportunity to identify traits associated with the introgressed regions, and facilitate characterization of the biochemistry and genetics underlying these phenotypes. Understanding plant metabolic pathways and the interactions between genes, phenotype, and environment is fundamental to functional genomics. Successful analysis of the complex network of plant metabolism requires analytical methods able to record information on as many metabolites as possible. Metabolite profiling is used to provide a snapshot of the metabolome in samples which differ in a known factor such as genetic background. Differences between the metabolite profiles can identify those metabolites/metabolic pathways affected by the introgression and allow genetic maps for metabolic alterations to be established. A Time-of-Flight Mass Spectrometry method is presented, with associated data reduction, used for profiling aqueous metabolites fom tomato. Analysis of ripe fruits of two tomato species, Lycopersicon esculentum and L. pennellii, showed differences in the amounts of many metabolites, including organic acids and sugars. Six introgression lines, L. pennellii introgressions within L. esculentum, were also examined and showed that Principal Component Analysis can reveal subtle differences in metabolism of the introgressed lines when compared to their parents.

Reading the tuberculin skin test. Who, when, and how?

A prospective study of 806 healthy volunteers was carried out to determine the value of induration 24 hours after placement of purified protein derivative, if patients can accurately read their own tests, and if the pen and palpation methods are comparable. Subjects were actively employed health workers between 20 and 64 years of age without active tuberculosis. All subjects were tested using 5 tuberculin units of purified protein derivative via the Mantoux technique. Induration was quantitated by trained readers at 24 hours and at 48 to 72 hours. Patients were asked to read their own tests as well at 48 to 72 hours. The amount of induration at 24 hours was highly predictive of eventual findings at 48 to 72 hours. The patients' abilities to read their own tests were poor. Significant differences were noted between the pen and palpation methods. The degree of induration noted 24 hours after placement of 5 tuberculin units of purified protein derivative is valuable in a screening population. Most decisions, however, should still be based on results measured at 48 to 72 hours. Results with the pen technique must be interpreted with caution in the 5- to 14-mm range. The patients' readings of their own results are inaccurate and should never be relied on to make clinical decisions.