Search PubMed⌕ Search

Biomedical subjects

J Epstein

Publications and source records attributed to J Epstein.

At least 181 records · Page 10Linked to original sources
PubMed1981

Human osteogenic sarcoma cells exhibit enhanced protein phosphorylation.

Protein phosphorylation was compared in normal human cells and human osteogenic sarcoma cells. The phosphorylation of endogenous cellular protein substrates was measured by two independent methods, incubation of homogenized cells with [gamma-32P]ATP or labeling of intact cells with Na2H32PO4. Phosphorylated proteins were identified by SDS-polyacrylamide gel electrophoresis and autoradiography. The stained protein bands of all four osteosarcoma cell lines were nearly identical to those of the normal cells. However, each of the osteosarcoma cell lines showed autoradiographic evidence of enhanced phosphorylation in many different protein bands which was neither cyclic AMP-dependent nor a function of cellular growth rate or density. When normal and tumor cell homogenates were mixed prior to incubation with [gamma-32P]ATP, the resulting phosphoprotein patterns resembled those obtained with the tumor cells alone. In addition, a surgically derived osteogenic sarcoma was cultured and an established line obtained; another portion of the fresh tumor was immediately homogenized and used in a phosphorylation assay. The same enhanced phosphorylation pattern was obtained with the homogenized fresh tumor as with the cell line established from it. These results suggest that human osteogenic sarcoma cells are able to perform a significantly increased amount of phosphorylation of endogenous cellular protein substrates when compared to normal human cells.

Adenosine Triphosphate↗
PubMed1981

Distinguishing homozygous and heterozygous cystic fibrosis fibroblasts from normal cells by differences in sodium transport.

We have found that cultured fibroblasts from patients with cystic fibrosis (CF) accumulate less 22Na in the presence of ouabain than do normal cells. After equilibration with 22Na in ouabain-exposed cells to that in unexposed cells, after five hours of incubation, was 2.34 +/- 0.14 (mean +/- S.D.) in 13 fibroblast strains from normal subjects and 1.33 +/- 0.08 in eight strains from patients with CF. Cells from eight different obligate CF heterozygotes (parents of children with CF) had a ratio of 1.38 +/- 0.07; those from three unaffected siblings (who have a two-thirds chance of carrying the disease) had a ratio of 1.27 +/- 0.04. The differences between CF homozygotes or heterozygotes and normal subjects were highly significant (P < 0.001), but there was considerable overlap between CF homozygotes and heterozygotes. This abnormality of sodium transport provides an unequivocal in vitro test that distinguishes normal cells from cells derived from CF homozygotes or heterozygotes. It should be useful for the identification of carriers of the CF gene.

Biological Transport↗
PubMed1981

A comparison of two methods for determining the sensitivity of human myeloid colony-forming units to cytosine arabinoside.

Studies were carried out to determine the optimal method for measuring the sensitivity of myeloid clonogenic cells to cytosine arabinoside (ara C). Bone marrow or peripheral blood cells were either exposed to different concentrations of ara C for 1 h in vitro and then after washing were plated in agar and cultured for 7 d in vitro, or were directly plated in agar containing different concentrations of the drug. The 3H-TdR suicide index of the clonogenic cells was also determined. Washing the specimens under study subsequent to incubation with ara C prior to plating in agar provided the most accurate measure of the ara C sensitivity of the clonogenic cells. When carried out in conjunction with the 3H-thymidine suicide index, the 'wash' method permitted the simultaneous determination of both the kinetic and metabolic sensitivity of these cells to ara C. Using this combined method, it was observed that the differences between the ara C sensitivity of the CFUc of different individuals resulted from differences in the proportion of clonogenic cells synthesizing DNA in the different marrow specimens.

Agar↗
PubMed1981

Clonal growth of leukaemic cells in vitro.

Human leukaemic cell specimens were obtained from patients and directly plated into soft agar (t = 0) or cultured for 1 week in liquid phase and then plated in soft agar. Growth for 1 week in liquid phase allowed the clonal growth in agar of leukaemic specimens which were unable to clone at t = 0. Clonal growth after liquid culture consisted of the usual leukaemic type of cluster-colonies, growth of a new type of 'syncytial' cell colony or a mixture of colony types. In addition, marrow from a patient with acute lymphocytic leukaemia produced normal-appearing colonies after 1 week of growth in liquid phase. These studies suggest a similarity in the growth requirements of some leukaemic cells and normal CFUd cells.

Adult↗
PubMed1981

Isolated lymphadenitis caused by Candida albicans in a patient with acute leukemia.

Lymphadenitis caused by Candida developed in a patient with acute leukemia but there was no other evidence of disseminated infection. He was successfully treated intravenously with only 800 mg of amphotericin B. The presentation of disseminated candidiasis in immunocompromised hosts is discussed. The unusual finding in this case of Candida infection apparently confined to a lymph node was interpreted as a stage of fungal invasion more limited than the widely disseminated disease. The concept of a locally invasive but nondisseminated Candida infection was the basis for giving this patient a low dose of amphotericin B.

Acute Disease↗
PubMed1980

Biochemical approaches to enhancement of antitumor drug selectivity: selective protection of cells from 6-thioguanine and 6-mercaptopurine by adenosine.

The cytotoxicity of 6-thioguanine and 6-mercaptopurine to cultured lymphoblasts and fibroblasts was strongly antagonized by pretreatment of the cells with 100 microM adenosine. Administration of adenosine 2 hours after the antipurine agent did not cause antagonism. In two rat hepatoma cell lines, adenosine pretreatment did not protect cells from the antipurines. Treatment of lymphoblasts or fibroblasts with 100 microM adenosine gave increases up to 150% in cellular ATP and ADP and decreases greater than 80% in UTP and UDP. In the hepatoma lines, adenine nucleotides did not increase by greater than 45%, and uridine nucleotides did not decrease by greater than 40% following adenosine treatment. The selective protection of the normal cells from 6-thioguanine and 6-mercaptopurine was probably the consequence of phosphoribosylpyrophosphate (PRPP) depletion, since adenosine pretreatment decreased PRPP pools by greater than 90% in the normal cells but by only 30% in the malignant hepatoma cells. In the absence of PRPP the antipurines would not be metabolically activated. The selectivity of the adenosine and antipurine combinations was probably attributable to the low activity of adenosine kinase and high activities of adenosine deaminase and PRPP synthetase characteristic of malignant hepatomas.

Adenosine↗
PubMed1980

A gonadotropin-responsive virilizing granulosa tumor.

A case of a progressive virilizing solid granulosa-theca cell tumor producing high testosterone levels that were suppressed to normal by a course of oral contraceptives is presented. In vitro studies demonstrated significant specific follicle-stimulating hormone (FSH) receptors on the tumor. The studies of the biological response to gonadotropins in terms of cyclic AMP generation also indicate that the tumor is responsive to gonadotropic hormones in vitro, and are consistent with the in vivo clinical response. A discussion of the role of gonadotropins in the etiology or maintenance of ovarian tumors is also presented.

Adult↗
PubMed1980

Effects of cytosine arabinoside on DNA synthesis and the clonogenicity of RF/UN murine myeloid leukemia cells.

Incubation of RF/UN murine myeloid leukemia cells for 60 minutes with 0.3 microgram/ml cytosine arabinoside (ara C) inhibited the incorporation of 3H-TdR in 8 of 10 experiments by 17-90%. Incubation with 3 microgram/ml ara C inhibited DNA synthesis in all experiments by 36-99%. This inhibition of DNA synthesis was highly reversible with the effects produced by the high drug concentration being less reversible than the inhibition produced by 0.3 microgram/ml drug. The same exposure to ara C had little or no killing effect on the colony-forming cells (CFUC). Incubation with ara C and 3H-TdR did not reduce the 3H-TdR suicide index (S.I.). Incubation with ara C for 24 h produced a less reversible inhibition of DNA synthesis and resulted in the death of 60% of the clonogenic cells.

Animals↗
PubMed1980

Effects of cytosine arabinoside on unseparated bone marrow and peripheral blood cells and on specimens enriched for myeloblasts and promyelocytes.

Myeloblast and promyelocyte enriched preparations and the original unseparated specimens were compared in regard to the phosphorylation of cytosine arabinoside (ara C) and the retention of ara CTP as well as the effects of ara C on the clonogenic cells. The immature cell-enriched preparations have a significantly higher rate of ara C phosphorylation, while retention of ara CTP is not significantly different from that of the unseparated cells. No correlation was found between the measured parameters of ara C metabolism and the drug's effects on the clonogenic cells in either cell population.

Blood Cells↗
PubMed1979

Steroid hormone toxicity in human fibroblasts does not correlate with high affinity receptor content.

Human diploid skin fibroblasts derived from normal individuals and those with the testicular feminization syndrome (TFM) have been shown to be killed to the same degree by dihydrotestosterone in spite of the absence of high affinity cellular androgen receptors in the TFM fibroblasts. Furthermore, several different normal fibroblast strains from various anatomical sites all showed similar amounts of androgen-induced cytotoxicity even though their respective receptor contents differed by as much as ten-fold. These results suggest that steroid-induced cytotoxicity in human fibroblasts is not correlated with receptor content, unlike murine lymphoid cells in which the receptor content has been shown to be closely related to their ability to survive hormone exposure.

Androgen-Insensitivity Syndrome↗
PubMed1979

3-Quinuclidinyl benzilate hydrolysis in dilute aqueous solution.

The hydrolysis kinetics of 3-quinuclidinyl benzilate were determined over the pH 0-14 range at different temperatures in solutions buffered to a constant pH. Analysis of data extrapolated to zero buffer concentrations permitted construction of an overall rate expression for pH 0-14 and 0-100 degrees. Reaction mechanisms are discussed.

Catalysis↗
PubMed1979

Analysis of HGPRT- CRM+ human lymphoblast mutants.

Three 6-thioguanine-resistant mutants of the human diploid lymphoblast line MGL-8 were studied. The inactivation by heat of both HGPRT activity and antigenicity of the HGPRT immunologically cross-reacting material of the A30 mutant cells were not protected by PRPP, indicating that the HGPRT in A30 cells has an altered PRPP binding site, leading to lack of stabilization and rapid degradation of the enzyme. Two dimensional separations of the immunoprecipitates from extracts of the parental and mutant cell lines showed that the A35 mutant CRM has a more acidic isoelectric pH, while the A30 CRM has a more basic isoelectric pH and that the A30 protein has a faster rate of degradation than the wild-type HGPRT. The A30 CRM also has a smaller molecular size than the wild-type enzyme.

Cell Line↗
PubMed1979

Enhanced phosphorylation of many endogenous protein substrates in human fibroblasts transformed by simian virus 40.

Protein phosphorylation in normal and in simian virus 40-transformed human skin fibroblasts was assessed by two different methods: incubation of whole-cell homogenates with [gamma-(32)P]ATP or labeling of intact cells with Na(2)H(32)PO(4). Phosphorylated proteins were detected by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and autoradiography. With both methods, the Coomassie-blue-stained protein patterns of the three transformed cell lines studied were similar to the patterns of the nontransformed normal human cells. However, although the phosphoprotein autoradiograms of the three transformed cell lines were nearly identical, their patterns were strikingly different from those of the nontransformed cells. Each of the three transformed lines tested showed approximately 25-30 phosphoprotein bands that were significantly enhanced when compared to the patterns of the nontransformed cells. Quantitation of 12 of the enhanced phosphoprotein bands in one of the transformed cell lines showed an average of 4.4 times as much phosphorylation as in the normal cells. The enhanced phosphorylation observed in the transformed cell lines was not dependent on the growth rate of the cells or on cyclic AMP. Furthermore, when homogenates of transformed and nontransformed cells were mixed prior to incubation with [gamma-(32)P]ATP, the resultant phosphoprotein patterns resembed those obtained with transformed cells alone. In addition, an evaluation of the time course of protein phosphorylation revealed that the initial reaction rate was greater in the transformed than in the normal cells, although in both cell types the reaction was complete after 1 min. The results suggest that the simian virus 40-transformed human fibroblasts possess an increased ability to phosphorylate proteins rather than that the normal cells possess a diffusible inhibitor. There appear to be many endogenous cellular substrates for this increased activity.

Cell Aggregation↗
PubMed1979

Premature menopause: a reversible entity?

Secondary hypergonadotropic, hypoestrogenic amenorrhea, or premature menopause, is usually considered an irreversible process. Four patients with this entity were observed to have evidence of ovulation. Three of these patients became pregnant while they were treated with estrogen replacement therapy (ERT) for their hypoestrogenic symptoms. Estrogen replacement may be effective in reversal of this process.

Adult↗