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Biomedical subjects

R Hamilton

Publications and source records attributed to R Hamilton.

123 records · Page 7Linked to original sources
PubMedDate not supplied

Enteric pathogenic protozoa in homosexual men from San Francisco.

The prevalence of enteric protozoa was studied in a survey conducted among 150 male homosexual patients in San Francisco. All patients were from a private practice in internal medicine. Each was asked to complete a questionnaire and to submit multiple stool specimens for examination. Of this group, 47% were positive for one or more potentially pathogenic intestinal protozoa; Entamoeba histolytica was found in 36%, Entamoeba hartmanni in 35%, Giardia lamblia in 5%, and Dientamoeba fragilis in 1.3%. Symptoms were unreliable as a diagnostic index of intestinal protozoan infection. Colonization rates could not be correlated with any specific sexual technique. The large number of homosexuals at risk, combined with the potential for difficulties in diagnosis and contact-tracing, indicate the possibility that enteric pathogenic protozoa will cause future health problems in this population.

Adult↗
PubMedDate not supplied

Expression of tyrosine hydroxylase in an immortalized human fetal astrocyte cell line; in vitro characterization and engraftment into the rodent striatum.

The use of primary human fetal tissue in the treatment of neurodegenerative disorders, while promising, faces several difficult technical and ethical issues. An alternative approach that would obviate these problems would be to use immortalized cell lines of human fetal central nervous system origin. An immortalized human fetal astrocyte cell line (SVG) has been established (45) and herein we describe the in vitro and in vivo characteristics of this cell line which suggest that it may be a useful vehicle for neural transplantation. The SVG cell line is vimentin, GFAP, Thy 1.1 and MHC class I positive, and negative for neurofilament and neuron specific enolase, consistent with its glial origin. To determine whether the cell line could be used as a drug delivery system, a cDNA expression vector for tyrosine hydroxylase was constructed (phTH/Neo) and stably expressed in the SVG cells for over 18 months as demonstrated by immunohistochemistry and Western blotting of the stable transfectants. HPLC analysis of the supernatant from these cells, termed SVG-TH, consistently found 4-6 pmol/ml/min of l-dopa produced with the addition of BH4 to the media. Furthermore, in cocultivation experiments with hNT neurons, PC-12 cells and primary rat fetal mesencephalic tissue, both the SVG and SVG-TH cells demonstrated neurotrophic potential, suggesting that they constituitively express factors with neuroregenerative potential. To determine the viability of these cells in vivo, SVG-TH cells were grafted into the striatum of Sprague-Dawley rats and followed over time. A panel of antibodies was used to unequivocally differentiate the engrafted cells from the host parenchyma, including antibodies to: SV40 large T antigen (expressed in the SVG-TH cells), human and rat MHC class 1, vimentin, GFAP, and tyrosine hydroxylase. While the graft was easily identified with the first week, over the course of a four week period of time the engrafted cells decreased in number. Concomittantly, rat CD4 and CD8 expression in the vicinity of the graft increased, consistent with xenograft rejection. When the SVG-TH cells were grafted to the lesioned striatum of a 6-hydroxydopamine lesioned rats, rotational behavior of the rat decreased as much as 80% initially, then slowly returned to baseline over the next four weeks, parallelling graft rejection. Thus, the SVG-TH cells can induce a functional recovery in an animal model of Parkinson's disease, however as a xenograft, the SVG cells are recognized by the immune system.

Animals↗
PubMedDate not supplied

Human alveolar macrophage cytokine release in response to in vitro and in vivo asbestos exposure.

The lung macrophage is proposed to be involved in the development of asbestos-induced pulmonary fibrosis. Knowledge of the effects of long-term asbestos exposure on lung macrophage cytokine release should better define the role of the macrophage in fibrogenesis. This study examines the effects of acute in vitro asbestos exposure and chronic in vivo asbestos exposure on human alveolar macrophage cytokine release. As indicators of asbestos-induced macrophage activation, the cellular release of IL-1 beta, TNF-alpha, IL-6, GM-CSF, and PGE2 was measured during a 24-h in vitro culture. Alveolar macrophages from normal volunteers were cultured in vitro with chrysotile asbestos. Of the factors measured, only TNF-alpha was elevated in response to asbestos exposure. Alveolar macrophages from asbestos-exposed individuals were placed into one of two groups based on their exposure history. These two groups were matched for age, smoking history, and diagnosis; none met the criteria for asbestosis. Cells isolated from subjects that had been exposed to asbestos for more than 10 years secreted enhanced basal amounts of IL-1 beta, TNF-alpha, IL-6, and PGE2, while those who had been exposed for less than 10 years did not. The results indicate that while asbestos had minimal acute effects on cytokine production by the human alveolar macrophage, intense, chronic exposure to asbestos leads to the enhanced basal release of significant amounts of several cytokines that have activity for the fibroblast, even in the absence of overt fibrosis.

Aged↗