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G S Incefy

Publications and source records attributed to G S Incefy.

50 records · Page 3Linked to original sources
PubMed1975

Differentiation of population of peripheral blood lymphocytes into cells bearing sheep erythrocyte receptors in vitro by human thymic extract.

A small population of human marrow cells has been shown to be differentiated in vitro by thymic extract into cells bearing T-lymphocyte (thymus-derived lymphocyte) characteristics. By a similar method, the differentiation of human peripheral blood lymphocytes has been studied. A discontinuous gradient of bovine serum albumin was used to isolate lymphocytes into four layers and cells from layers I and III demonstrated the greatest potential for differentiation by human thymic extract. Appearance of T-lymphocyte characteristics was recognized by the spontaneous E-rosette technique with sheep erythrocytes. Ability of human marrow cells to be differentiated under the influence of human thymic extract was abolished by specific inhibitors of nucleic acid synthesis, however, had no inhibitory effect on the maturation of peripheral blood lymphocytes during a 2 hr incubation with human thymic extract but puromycin, an inhibitor of protein synthesis, abolished this differentiative step in cells of layer I. It is suggested from these studies that many of the cells in peripheral blood that are differentiable by thymic extract are at a stage of maturation more advanced than those in human marrow that are also differentiable by thymic extract.

Amanitins↗
PubMed1975

In vitro differentiation of human marrow cells into T lymphocytes by thymic extracts using the rosette technique.

The manner by which human and calf thymic extracts induce precursor cells of human marrow to differentiate in vitro into T lymphocytes has been studied using as a T-cell marker the spontaneous rosette formation technique of human T lymphocytes with sheep erythrocytes (E rosette). These findings confirm previous observations made in the study of the same process using a different T-cell marker, specific antigenicity recognizable by a heterologous anti-human T-cell serum in a microcytotoxicity test. The number of cells revealing evidence of differentiation demonstrated by the E rosette formation technique is smaller than that obtained with the anti-human T-cell serum, indicating perhaps that a different stage of maturation of T lymphocytes is recognized by the antiserum from the one detected by spontaneous rosette formation. Based on the effects of specific inhibitors of nucleic acids and protein synthesis, it can be concluded that these thymic extracts ultimately act by influences exerted in the cell nucleus and that RNA and protein synthesis are required for the differentiation of precursor cells into T lymphocytes induced by thymic extracts. In addition, continued protein synthesis appears to be required for maintenance of receptors for sheep erythrocytes on the cell surface.

Amanitins↗
PubMed1974

Enhancement of RNA synthesis in avian liver cell cultures by a 5beta-steroid metabolite during induction of delta-aminolevulinate synthase.

The porphyrin-heme pathway is controlled in the liver at the level of the mitochondrial enzyme delta-aminolevulinate synthase (EC 2.3.1.37), a protein inducible in cultured avian hepatocytes by a variety of chemicals including certain 5beta-metabolites of steroid hormones. The great sensitivity of the induction process to inhibition by agents known to block transcriptional activity of genetic material suggests that some control mechanism may be operating at this level to regulate the formation of the enzyme. We report here enhancement of nuclear RNA synthesis and of Mn(2+)-(NH(4))(2)SO(4)-stimulated DNA-dependent RNA polymerase (EC 2.7.7.6) activities by the 5beta-steroid metabolite, 3alpha-hydroxy-5beta-androstan-17-one (etiocholanolone), in cultured avian hepatocytes during induction of the enzyme. These changes were demonstrated in the G(1) phase of the hepatocyte cell cycle at a time when DNA synthesis is constant. Our findings support the view that one of the early steps in the process of induction of delta-aminolevulinate synthase by steroid metabolites requires new RNA synthesis, very probably messenger RNA, suggesting a 5beta-steroid transcriptional control mechanism for induction of this protein.

5-Aminolevulinate Synthetase↗
PubMed1971

Isolation and biochemical characterization of nuclei from chick embryo liver.

A procedure is described for the isolation of enzymatically active nuclei from chick embryo liver. It consists of the homogenization of the pooled tissue in 0.32 M sucrose-3 mM MgCl(2) followed by a slow centrifugation. The resulting nuclear pellet is then purified further in a discontinuous density gradient composed of sucrose solutions containing Mg(2+) ions, the lower portion of the gradient being 2.2 M sucrose-1 mM MgCl(2). Based on DNA recovery, the nuclear fraction isolated by the procedure described contained an average of 62% of the nuclei in the original filtered homogenate. Light and electron microscope examinations showed that 90% of the isolated nuclei were derived from hepatocytes. They appeared intact with well preserved nucleoplasmic and nucleolar components, nuclear envelope, and pores. The isolated nuclei were quite pure, having a very low level of cytoplasmic contamination as indicated by cytoplasmic enzyme marker activities and electron microscope studies. The nuclear fraction consisted of 19.9% DNA, 6.2% RNA, 74% protein, the average RNA/DNA ratio being 0.32. Biosynthetic activities of the two nuclear enzymes NAD-pyrophosphorylase and DNA-dependent RNA polymerase were preserved. The specific activities of these enzymes were: NAD-pyrophosphorylase, 0.049 micromoles nicotinamide adenine dinucleotide (NAD) synthesized/min per mg protein; Mg(2+) activated RNA polymerase, 4.3 micromicromoles UMP-2-C(14) incorporated into RNA/microg DNA per 10 min; and Mn(2+)-(NH(4))(2)SO(4) activated RNA-polymerase, 136 micromicromoles UMP-2-C(14) incorporated into RNA/microg DNA per 45 min.

Animals↗