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Biomedical subjects

J Epstein

Publications and source records attributed to J Epstein.

At least 199 records · Page 11Linked to original sources
PubMed1979

A method for obtaining human bone marrow specimens enriched for myeloblasts and promyelocytes.

A simple method has been developed for obtaining specimens of human marrow which are enriched for myeloblasts and promyelocytes. The erythrocytes are lysed, the marrow is incubated with iron particles, and the cells that phagocytize the iron are removed with a powerful magnet. The marrow is then subjected to a density-cut centrifugation using Ficol-Hypaque with a density of 1.084 gm/mm3. The cells that do not enter the Ficol-Hypaque are removed from the surface and studied. The proportion of myeloblasts and promyelocytes in this subpopulation of cells exceeds 50%. Total recovery of these immature myeloid progenitor cells is 50% of that in the original marrow specimen. This method has been used for cell suspensions containing as many as 10(9) cells. Cells prepared using this method incorporate 3H-TdR, 3H-UR, and 3H-Leu at a higher rate than the unseparated specimens and have a cloning efficiency of 2.0% to 19.4% compared with 0.1% to 2.17% for the unseparated marrows.

Cell Separation↗
PubMed1978

Enhanced dexamethasone resistance in cystic fibrosis cells: potential use for heterozygote detection and prenatal diagnosis.

Cultured skin fibroblasts from patients with cystic fibrosis (CF) are more resistant to dexamethasone toxicity than are normal cells. We now report that, when fibroblasts cultured from obligate CF heterozygotes are exposed to dexamethasone, they have an intermediate survival compared to normal and homozygous CF cells. When dexamethasone survival was tested on cells from four patients undergoing amniocentesis, cells from a woman at risk of producing a child with CF showed significant dexamethasone resistance, similar to that of fibroblasts derived from lnown CF homozygotes; the other amniotic cell specimens showed dexamethasone sensitivity similar to that of normal skin fibroblasts. These data suggest that the dexamethasone resistance previously observed in skin fibroblasts may also be useful in the prenatal diagnosis of CF.

Amniotic Fluid↗
PubMed1978

Pleiotropic drug resistance in cystic fibrosis fibroblasts: increased resistance to cyclic AMP.

In previous studies, cystic fibrosis (CF) fibroblasts were demonstrated to be resistant to the cytotoxic effects of ouabain, dexamethasone, and the sex hormones, dihydrotestosterone, 17beta-estradiol, and progesterone. We now show that CF fibroblasts also exhibit greatly increased resistance to the cytotoxic effects of exogenous dibutyryl cyclic AMP (cAMP), as well as to isoproterenol and theophylline, drugs which are known to increase endogenous levels of cAMP. CF cells were also shown to have normal amounts of (3H)cAMP binding to protein kinase as well as normal amounts of cAMP-stimulated protein kinase activity. Phosphodiesterase in CF cells was also found to be stimulated by cAMP to the same degree as in normal cells. These findings suggest that there is no detectable protein kinase deficiency in CF cells. cf cells thus appear to be unlike some cAMP-resistant mutants described by others which are defective in protein kinase activity and cAMP regulation of phosphodiesterase levels. The cross-resistance of CF fibroblasts to ouabain, steroid hormones, and cAMP may provide a unique opportunity to study the biochemical events involved in the metabolism of these drugs as well as the basic biochemical defect in a common human genetic disease.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1978

Dexamethasone-resistant cystic fibrosis fibroblasts show cross-resistance to sex steroids.

Diploid skin fibroblasts derived from individuals with the autosomal recessive disease, cystic fibrosis (CF), were shown previously to be significantly more resistant to the cytotoxicity of dexamethasone, a glucocorticoid hormone, than were normal human fibroblasts. Here cystic fibrosis fibroblasts are also shown to be more resistant than normal human fibroblasts to the cytotoxic effects of the sex hormones, 17 beta-estradiol, dihydrotestosterone and progesterone. Since cells are believed to contain different receptors for each of the steroid hormones, it is not probable than the resistance of CF cells to these hormones results from a receptor deficiency. This was shown by the fact that CF cells were found to exhibit the same receptor activity as normal cells for 3-H-dexamethasone. Furthermore, neither normal human nor CF fibroblasts could be demonstrated to contain detectable receptor activity for 3H-17 beta-estradiol. In addition, the studies of fibroblast killing by hormones led to the further interesting observation that normal human diploid fibroblasts, regardless of the sex of the tissue donor, are sensitive to killing by each of the sex hormones. These findings suggest that the cytotoxic effects of the steroid hormones may be observed independently of the specific hormone receptors. The studies reported here thus suggest that the resistance of CF cells to the different steroid hormones is probably the result of a defect in a pathway in cellular steroid hormone metabolism other than that involving receptors.

Cell Survival↗
PubMed1978

Allergic contact photodermatitis to para-aminobenzoic acid.

Allergic photocontact dermatitis developed in a patient to a commercial sunscreen preparation containing para-aminobenzoic acid (PABA) in an alcohol base. Photopatch testing showed photosensitivity to PABA. Sensitization could only be detected when PABA was tested in an alcohol vehicle; a photopatch test to PABA in petrolatum was negative.

4-Aminobenzoic Acid↗
PubMed1977

Characterization and radiobiologic parameters of medulloblastoma in vitro.

Cultured cells from human medulloblastomas were demonstrated to have distinctive features and a "glial" potential from the morphological and ultrastructural parameters. The in vitro radiobiological survival curve parameters of cultured human medulloblastoma and non-malignant skin fibroblasts obtained under the same conditions of exponential growth were similar. In vitro conditions may underestimate the shoulder region of the survival curve. Since the shoulder region is the most important in clinical fractionated radiotherapy, multiple dose experiments might be useful in examining this portion of the survival curve more closely.

Brain Neoplasms↗
PubMed1977

Mutagen-induced diploid human lymphoblast variants containing altered hypoxanthine guanine phosphoribosyl transferase.

The human lymphoblast line MGL8 was treated with HAT and subsequently "mutagenized" with EMS (200 microgram/ml) to give 15% survival, and 6-thioguanine-resistant cells were selected by cloning in soft agarose containing the drug (1 microgram/ml). Eighteen sublines of independently derived resistant clones were isolated and studied in detail. One subline had a low residual HGPRT activity of about 1% of the parental cells. The HGPRT of this subline had a higher Km for PRPP, was more sensitive to heat, and was degraded faster by trypsin than the enzyme in extracts of MGL8 cells. This resistant subline and three others contained CRM levels of 1--38%, compared to the wild-type, so they probably represent true structural mutants of the HGPRT gene. All the variants maintained the karyotype of the parental line (46, XY, 6p-).

Cell Line↗
PubMed1977

Increased dexamethasone resistance of cystic fibrosis fibroblasts.

We demonstrate previously that fibroblasts from cystic fibrosis (CF) patients are significantly more resistant to the toxic effects of ouabain than normal human fibroblasts are. Ouabain is generally assumed to act primarily at the level of the cell membrane and to cause killing of cells by inhibiting ion transport. We have therefore examined the ability of normal and CF cells to survive exposure to ethacrynic acid, another inhibitor of ion transport, and to survive colchicine and aminopterin, resistance to which has been associated with membrane alterations in other cells. The effect of dexamethasone, which has a sterol nucleus similar to that of ouabain but is thought to have a different site of cellular action, was also tested. Exposure of the cells to ethacrynic acid, colchicine, or aminopterin did not reveal any differences in survival between normal and CF fibroblasts. However, CF cells survived exposure to dexamethasone significantly better than normal cells did. These results suggest that normal and CF cells do not differ in terms of a generalized resistance to ion transport inhibitors or to drugs that must pass through the membrane to be active. Instead, the results raise the possibility that CF cells have an enhanced resistance to drugs that have the sterol nucleus found in ouabain and dexamethasone.

Aminopterin↗
PubMed1977

Increased resistance of cystic fibrosis fibroblasts to ouabain toxicity.

Diploid skin fibroblasts derived from several unrelated patients with cystic fibrosis (CF) were tested for resistance to the cytotoxic effects of ouabain in comparison with cells from normal individuals. Cells from CF and normal individuals were plated at low density and exposed to ouabain at different concentrations for 24 hr. Dose-response curves showed that CF cells survived significantly better than did normal cells at all ouabain concentrations from 0.1 nM to 1 micronM in potassium-deficient medium. In medium containing the usual amount of potassium (6.25 mM), survival of the CF cells exposed to ouabain was decreased to that of the normal cells. If the glucose concentration of the potassium-deficient medium was decreased to 10% of the usual amount, the resistance of the CF cells to ouabain disappeared and their survival was identical to that of the normal cells. These findings may be useful in understanding the biochemical basis of CG and its clinical manifestations.

Adolescent↗
PubMed1977

Allergic contact dermatitis from sunscreen preparations complicating photodermatitis.

Two men with known histories of photosensitivity had apparent exacerbations of their dermatoses. Patch-testing showed the presence of allergic contact sensitivity to the sunscreens that they were using. The clinical distribution patterns of adverse reactions to sunscreens naturally simulate sun-induced reactions, thus providing clinical problems that require evaluation by both patch and photo-patch tests. These findings emphasize that allergic contact or photo-contact dermatitis from sunscreens that are used for prophylaxis of photodermatitis can actually complicate or aggravate the preexisting state of photodermatitis for which the sunscreens are prescribed.

Aminobenzoates↗
PubMed1976

A technique for developing established cell lines from human osteosarcomas.

A method is described which has been successfully used to develop two human osteogenic sarcomas into established lines in culture. This method provides a means whereby cells growing from explanted tumor tissue can be immediately cloned and the fibroblastic (nonneoplastic) cells thus selected against. Both lines have been passaged for over 100 population doublings since cloning and have retained the ability to form colonies from single cells plated at low density without the use of feeder layers or conditioned medium. In culture, the osteogenic sarcoma cells are nonfibroblastic, pile up, and appear to retain a morphological similarity to the in vivo tumors from which they were derived. A karyotype of cells derived from one of the tumors containing a marker chromosome is also presented.

Adolescent↗
PubMed1976

In vitro radiosensitivity of human dipliod fibroblasts derived from patients with unusual clinical responses to radiation.

Four diploid cell strains were derived from skin biopsies from patients exhibiting unusually sensitive or resistant clinical responses to ionizing radiation during radiotherapy. The in vitro x-ray survival curve parameters for these strains were determined and compared with those of two normal human skin fibroblast strains. No systematic correlation could be demonstrated between these single dose survival parameters in vitro, and the clinical radiation response in vivo of the normal tissue or the tumor.

Aged↗