Biomedical subjects
Publications and source records attributed to S Gordon.
A case report of post-traumatic brachymetatarsia of the fourth right metatarsal is presented. The literature is reviewed and surgical alternatives are discussed. Treatment consisted of a step-up elongational osteotomy with good results and rapid patient recovery.
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A linear model relating levels of volatile organic chemicals (VOCs) in exhaled breath to personal exposures at environmental (parts per billion) levels has been developed and evaluated in a chamber study of four human volunteers. The purpose of the model is to allow estimation of VOC concentrations in the body from measurements of exposure, or conversely to estimate previous exposure from a measurement of exhaled breath. The model differs from previous models in considering long-term inhalation at low or moderate concentrations rather than instantaneous intake (as in drug administration) or intermittent exposure at high concentrations (as in occupational situations). The model is based on a mass balance approach using one or more compartments to represent distribution of the chemical in the body. The main observable parameters in the model are the residence times tau 1 in the compartments, their "capacities" Ai, and the fraction f of the parent compound that is exhaled under equilibrium conditions. The basic equations for the one-, two-, three-, and n-compartment cases are derived. Solutions to these equations for the cases of a sudden constant high exposure, a sudden constant low exposure, and a linearly increasing exposure are provided. These solutions can be readily applied to more complex exposure scenarios. The chamber study suggests residence times on the order of a few minutes in the blood and 1-2 hr in the vessel-rich group of tissues. The design of the chamber study did not allow an estimate of the model parameters for fat; a subsequent chamber study has provided initial estimates of 50-100 hr. Field studies of personal exposures and breath concentrations of several hundred persons suggest values of f ranging from 0.1 for xylenes and ethylbenzene to about 0.9 for tetrachloroethylene.
The objective of this proposed Phase I field study is to determine the distributions of total human exposures to multimedia pollutants in the classes of metals, pesticides, and volatile organic compounds (VOCs). This will be achieved by studying a proportion-based sample of the total population in Arizona with a nested design for the different stages of sampling. Specific objectives are: (1) to document the occurrence, distribution, and determinants of total exposures in the general population; (2) to characterize the 90th percentiles of total exposures to each pollutant; (3) to monitor geographic and temporal trends of the multimedia exposures; (4) to evaluate the different media, personal, time-activity, and geographical factors that contribute to current total exposure; (5) to evaluate biomarkers in blood and urine for the target pollutants; (6) to perform evaluations of relationships between exposure reports, environmental measurements, and biomarkers of the target pollutants; (7) to predict total exposures; and (8) to assess total exposures in minority and disadvantaged subsets of the population. The latter is particularly feasible in Arizona due to the large proportions of such population subgroups. The proportionate-based population sampling of households within blocks will occur in Stage 1; the target is 1,200 such households. They will be interviewed utilizing National Human Exposure Assessment Survey (NHEXAS) questionnaires. In Stage 2, additional questionnaires will be completed; environmental sampling will take place in 450-900 households representatively selected from the respondents. Environmental sampling will include: metals in dust, soil, outside air, and some tap water; pesticides in dust, soil, and some tap water; total VOCs in air. In Stage 3, a subset of representative households will be reevaluated for metals, pesticides, and VOCs using methods with greater resolution and reliability; subjects in these households will be asked to complete questionnaires and provide biological samples. Follow-up temporal evaluations will be performed in a randomly selected subset of homes evaluated during this stage.
Differential display polymerase chain reaction (DD-PCR) is a powerful technique for comparing gene expression between cell types, or between stages of development or differentiation. Differentially expressed genes may be cloned and analysed further. Here we extend the use of DD-PCR to analyse differences in gene expression between two complex epithelia: that of the small intestine and of the large intestine. The aim of this study was to identify genes expressed preferentially in Paneth cells. Paneth cells are secretory epithelial cells putatively involved in host defense and regulation of crypt cell proliferation and are found at the base of the small intestinal crypts adjacent to the stem cell zone. Of 34 clones that were analysed, partial sequencing identified two clones related to known Paneth cell products: a homologue of secretory phospholipase A2 (clone B1) and a homologue of a neutrophil defensin (clone C5). B1 was strongly expressed in Paneth cells, as demonstrated by in-situ hybridization. B1 was also expressed at a lower level in the large intestinal epithelium. A full length B1 cDNA clone was isolated and sequenced, and shown to be highly homologous to type II secretory phospholipase A2 genes, and almost identical to the enhancing factor gene and the putative gene for the MOM-1 locus. B1 expression is limited to the intestinal tract, and we propose that it be designated intestinal phospholipase A2, or i-PLA2. The method we describe is well suited to the rapid identification of genes expressed exclusively or predominantly in Paneth cells.