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Biomedical subjects

E Chaum

Publications and source records attributed to E Chaum.

8 recordsLinked to original sources
PubMed2001

Comparative analysis of the uptake and expression of plasmid vectors in human ciliary and retinal pigment epithelial cells in vitro.

The retinal pigment epithelium is uniquely suited to gene therapy that uses lipid-mediated DNA transfer due to its high phagocytic activity in situ. We compared the relative efficacy of phagocytosis on the uptake of labeled plasmid vectors by retinal pigment epithelial and ciliary epithelial cells in vitro. Relative levels of endocytosis were then compared with the efficiency of marker transgene expression in these cells. Human retinal pigment epithelial and ciliary epithelial cells from a single donor were isolated and expanded in vitro. Polyplex-mediated transfections were performed using a rhodamine-labeled expression vector for green fluorescent protein. Rhodamine-labeled endosomes were examined by fluorescence microscopy at different time points. Rhodamine labeling and green fluorescent protein expression were analyzed by flow cytometry 48 h after transfection. These gene transfer studies showed that expression of transgenes does occur in both human retinal pigment epithelial and ciliary epithelial cells in vitro. Endocytosis of labeled plasmid vectors occurs at a significantly higher number and density in retinal pigment epithelial cells than in ciliary epithelial cells (P < 0.04). However, the efficiency of marker transgene expression is similar in the two cell types. These studies demonstrate that the higher intrinsic phagocytic activity does not enhance the efficacy of transgene expression in retinal pigment epithelial cells in vitro. Both human retinal pigment epithelial and ciliary epithelial cells are competent recipients for lipid-mediated gene transfer, and transgene expression occurs at similar levels in both cell types.

Animals↗
PubMed2001

Nerve fiber bundle visual field defect resulting from a giant peripapillary cotton-wool spot.

Cotton-wool spots are the clinical manifestation of focal infarcts of the retinal nerve fiber layer. They rarely cause significant visual field loss. A large idiopathic cotton-wool spot in a 34-year-old healthy woman caused a nerve fiber bundle visual field defect and an afferent pupillary defect that remained after the cotton-wool spot had disappeared and the retina and optic nerve appeared normal.

Adult↗
PubMed1999

Polyplex-mediated gene transfer into human retinal pigment epithelial cells in vitro.

The human retinal pigment epithelium (RPE) is a potential target tissue for directed transfer of candidate genes to treat age-related macular degeneration (AMD). The RPE is uniquely suited to gene therapy protocols that use liposome-mediated DNA transfer because of its high intrinsic phagocytic function in vivo. In these studies, we examined the efficacy of human RPE cell uptake and expression of the green fluorescent protein (GFP) and neomycin resistance marker genes by polyplex-mediated gene transfer in vitro. The effects of varying DNA and polyplex concentration and ratios on GFP transgene expression were examined. A narrow range of experimental conditions were found to maximize transgene expression; most important were the DNA concentration and the DNA:polyplex ratio. The transfection efficiency for human RPE cells was reproducibly 20% in vitro by this method and reached a maximum level of expression after 48 h. There was a rapid decline in gene expression over 2 weeks following polyplex-mediated gene transfer, but stable integration does occur at low frequencies with and without selection.

DNA↗
PubMed1985

Molecular and cytologic analysis of DNA amplification in retinoblastoma.

Amplification of two distinct genomic DNA segments is observed in homogeneously staining regions in two sets of retinoblastoma cell lines derived from two different patients. One DNA segment was known to have sequence homology to the c-myc oncogene, and both DNA segments had previously been shown to be amplified in neuroblastoma cells. The absolute degree of amplification differed in all cytogenetically distinct retinoblastoma cell lines tested. Also, the relative amplification of these two DNA segments was unequal within a given cell line. Minimal amplification of both DNA segments was also detected in DNA directly isolated from one primary retinoblastoma. Based on these and previous results, it is concluded that assembly of amplifiable, relocatable units in many human retinoblastoma and neuroblastoma cells may involve a complex process of differential recruitment of separate DNA segments that are located on human chromosome #2.

Cell Line↗
PubMed1984

Cytogenetic analysis of retinoblastoma: evidence for multifocal origin and in vivo gene amplification.

Retinoblastoma (Rb) is an uncommon childhood tumor of the neural retina with a significant genetic component in its etiology. A small proportion of patients have a deletion in chromosome 13 encompassing band 13q14, an observation which permitted the assignment of the RB1 locus to this region. About 20% of Rb tumors exhibit microscopic deletions of band 13q14 or monosomy 13. Trisomy 1q and i(6p) have also been reported in a high percentage of tumors. We analyzed the chromosome complements from direct preparations of 10 Rb tumors derived from seven patients. Modal chromosome numbers ranged from 45 to 48, and occasional duplications of the genomes were noted. In general, the tumors were chromosomally stable, although karyotypic evolution and random chromosome loss were encountered. Consistent abnormalities included trisomy 1q, i(6p), 6q-, and del(13)(q12----14). One patient with bilateral Rb had three tumor clones (two in one eye and one in the other) with chromosome abnormalities unrelated in origin. A second patient with unilateral Rb had two tumor clones with chromosome abnormalities again unrelated in origin. These two patients provide some of the first cytogenetic evidence for the multifocal origin of primary Rb. In the untreated tumor of a third patient, a homogeneously staining region (HSR) was detected in 1p32, indicating gene amplication in vivo; previously, an HSR at this site has been reported in the established Rb cell line Y79.

Adolescent↗
PubMed1984

Bleomycin-induced chromosome breakage in G2 lymphocytes of retinoblastoma patients.

Retinoblastoma (Rb) cells may be more sensitive to X-irradiation than normal cells when assayed for clonogenic survival, suggesting that such sensitivity can be used as a trait for detecting RB1 gene carriers. We studied induction of chromosome damage in lymphocytes from patients with Rb by the radiomimetic antineoplastic antibiotic, bleomycin (BL). Lymphocytes were treated in G2 for 4 h at four concentrations of the drug (0.0, 0.3, 0.9, and 2.7 micrograms/ml), and chromosome damage was evaluated. No difference in levels of spontaneous or induced damage was detected among hereditary Rb, non-hereditary Rb, and normal lymphocytes. The role of X-ray treatment in the induction of second tumors in Rb patients is discussed.

Bleomycin↗