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Biomedical subjects

P Gergely

Publications and source records attributed to P Gergely.

At least 163 records · Page 9Linked to original sources
PubMed1985

Effect of histamine-receptor blocking on human natural and lectin-dependent cell-mediated cytotoxicity against adherent HEP-2 cells.

The effect of histamine (H) and H1-, H2-receptor blocking agents was studied on natural (NCMC) and lectin-dependent cell-mediated cytotoxicity (LDCC) of peripheral blood lymphocytes (PBL) from eight healthy subjects on HEP-2 adherent human epipharynx carcinoma target cells. Cytotoxicity was measured by detachment from the monolayer of 3H-TdR-prelabelled HEp-2 cells. LDCC was evaluated in a 24 h assay with a Concanavalin A (Con A) dose of 25 micrograms/ml at 50:1 effector-target cell ratio. Under these conditions, but without Con A, considerable NCMC was not elicited by normal lymphocytes. The presence of histamine and the H2-receptor blocker cimetidine resulted in a significant NCMC to HEp-2 cells. On the contrary, histamine and cimetidine reduced LDCC. The H1-receptor blocker clemastine had no significant effect on either NCMC or LDCC to HEp-2 targets. The possible involvement of H2-receptor bearing cells in the regulation of cytotoxicity to HEp-2 cells is suggested.

Cell Adhesion↗
PubMed1984

Heparin inhibits the activity of protein phosphatase-1.

Heparin inhibited the dephosphorylation of rabbit skeletal muscle or liver phosphorylase a by protein phosphatase-1. Other glycosaminoglycans (chondroitin sulfates) and their constituents were found to be without effect. The chromatography of a partially purified phosphatase preparation on heparin-Sepharose CL-6B resulted in a fraction that did not bind to the matrix and its activity was not inhibited by heparin or inhibitor-1. The phosphatase bound to heparin-Sepharose was eluted by 0.2 M NaCl and was inhibited by heparin or inhibitor-1.

Animals↗
PubMed1984

Effector activity of OKT4+ and OKT8+ T-cell subsets in lectin-dependent cell-mediated cytotoxicity against adherent HEp-2 cells.

The role of OKT4+ and OKT8+ T-cell subsets was studied in lectin-dependent cell-mediated cytotoxicity (LDCC) against adherent HEp-2 human epipharynx carcinoma target cells. LDCC was evaluated by detachment from the monolayer of [3H]thymidine prelabeled HEp-2 cells in a 24-hr assay with a concanavalin A (Con A) dose of 25 microgram/ml at effector:target cell ratios of 5:1, 25:1, and 50:1. Under these conditions but without Con A considerable natural cell-mediated cytotoxicity (NCMC) was not elicited; however, the cytotoxicity was significantly augmented in the presence of Con A (=LDCC) by sheep erythrocyte rosette-forming T lymphocytes and by both OKT4+ and OKT8+ T-cell fractions. LDCC activity by isolated OKT8+ T cells was superior to that by OKT4+ T cells and unfractionated T lymphocytes. By contrast, addition of either OKT4+ or OKT8+ T cells together with unfractionated T lymphocytes, or OKT4+ and OKT8+ T cells mixed at ratios of 1:1, 1:2, and 2:1, to target cells did not result in major differences in comparison of LDCC activities by these mixed effector cell populations with each other or with that by unfractionated T lymphocytes. Parallel studies were carried out to determine the effect of OKT4+ and OKT8+ T-cell subsets on the Con A-induced proliferation of peripheral blood mononuclear cells (PBMC). While OKT8+ T cells inhibited the mitogenic response to Con A, OKT4+ T lymphocytes had no major effect. A higher responsiveness of the OKT8+ to OKT4+ T-cell subset in LDCC to HEp-2 targets and in Con A-induced lymphocyte proliferation is suggested.

Antibodies, Monoclonal↗
PubMed1984

Ca2+-dependent stimulation of muscle and liver phosphorylase kinase by heparin.

Heparin stimulates the activity of nonactivated and activated skeletal muscle phosphorylase kinase in a Ca2+-dependent manner. The stimulatory effect of heparin on the activity of nonactivated phosphorylase kinase is also expressed in the presence of calmodulin and glycogen. Heparin acted in synergism with glycogen. Heparin increases the affinity of phosphorylase kinase to Ca2+ 5-12 fold depending upon the activation conditions. Ca2+ influences the stimulation of liver phosphorylase kinase by heparin in a similar way.

Animals↗
PubMed1984

Ketoconazole in vitro inhibits mitogen-induced blastogenesis, antibody-dependent cellular cytotoxicity, natural killer activity and random migration of human leukocytes.

Ketoconazole at concentrations of 1-10 micrograms/ml dose dependently inhibits mitogen-induced blastogenesis, antibody-dependent and spontaneous cytotoxic (natural killer) activity of human lymphocytes and random migration of human leukocytes. Lectin-dependent cytotoxic activity is not affected by the drug.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1984

Inhibitory effect of tumour cells on leukocyte motility.

Hep-2 cells inhibit the random migration of human polymorphonuclear leukocytes in a tumour cell-leukocyte microenvironmental model, which is a special form of co-migration. The inhibition is indomethacin-sensitive. It is very likely that prostaglandins, produced as a consequence of interaction between tumour cells and leukocytes, are the mediators of this phenomenon. The tumour-induced inhibition of leukocyte motility may represent a tumour-protective mechanism.

Cell Line↗
PubMed1984

Depressed effector activity of OKT4+ and OKT8+ T cell subsets in lectin-dependent cell-mediated cytotoxicity to HEP-2 cells in patients with systemic lupus erythematosus.

The role of OKT4+ and OKT8+ T cell subsets was studied in depressed lectin-dependent cell-mediated cytotoxicity (LDCC) against adherent HEp-2 target cells by peripheral blood mononuclear cells (PBMC) from patients with active systemic lupus erythematosus (SLE). LDCC activity was evaluated by detachment from the monolayer of 3H-TdR-prelabelled HEp-2 cells in a 24 hr assay at 50:1 effector-target cell ratio in the presence of 25 micrograms/ml concanavalin A (Con A). Decreased levels of LDCC were performed by all studied effector cell populations of SLE patients, including both OKT4+ and OKT8+ T cell fractions. LDCC by isolated OKT8+ T cells was superior to that by OKT4+ and unfractionated T lymphocytes from all healthy and SLE subjects. This suggests that the defect of LDCC activity in SLE did not affect the inherently higher LDCC effector activity of OKT8+ to OKT4+ cells. In parallel studies a reduced proliferation of PBMC in response to Con A and failure of OKT8+ T cells to suppress Con A-induced blastogenesis was observed in patients with SLE.

Adult↗
PubMed1984

Structural changes in phosphorylase b as revealed by proteolysis with subtilisin BPN'.

The proteolysis of rabbit skeletal muscle phosphorylase b was studied with Sepharose 4B bound subtilisin BPN' in the absence and presence of various ligands. The proteolysis was carried out at pH 7.0 and pH 8.5 and was followed by measuring phosphorylase b activity and by SDS gel electrophoresis. The effect of ligands proved to be qualitatively the same at both pH values. It was found that AMP and alpha-D-glucose-1-phosphate accelerated the inactivation of phosphorylase b by subtilisin, two main proteolytic products (Mr 70 000 and 30 000) were formed in the presence of these ligands. IMP and glycogen protected phosphorylase b against proteolytic attack. Subtilisin treatment in the presence of D-glucose, caffeine and D-glucose-6-phosphate produced a reproducible increase (about 20%) of phosphorylase b activity. This "activation" resulted in an increased Vmax of phosphorylase b though did not alter the subunit size, the aggregation state and the ligand binding capacity of the enzyme.

Animals↗
PubMed1983

Heterotropic interactions of AMP and glucose binding sites in phosphorylase a are destroyed by limited proteolysis.

Subtilisin BPN' hydrolyses a single peptide bond in phosphorylase a. The two proteolytic fragments are attached to each other by noncovalent bonds in solution as shown by gel filtration and ultracentrifugation studies. The subtilisin nicked phosphorylase a is inactive, however, still binds AMP and glucose as judged by equilibrium dialysis and fluorescence experiments. The modified enzyme can be dephosphorylated by protein phosphatase and AMP is an effective inhibitor of the dephosphorylation reaction. Glucose cannot cancel the AMP inhibition as well as cannot expel AMP from the nucleotide binding site. Thus a single nick in the polypeptide chain breaks the "communication" between the two ligand binding domains.

Adenosine Monophosphate↗
PubMed1983

Depressed lectin-dependent cell-mediated cytotoxicity against adherent HEP-2 cells in patients with carcinoma of the uterine cervix.

Lectin-dependent cell-mediated cytotoxicity of peripheral blood mononuclear cells from patients with uterine cervix carcinoma was evaluated using human adherent 3H-TdR-prelabeled HEp-2 epipharynx carcinoma cells as targets at a 50:1 effector-target cell ratio with 25 micrograms concanavalin A/ml in a 24-h assay. Peripheral blood mononuclear cells from 13 patients with cervical carcinoma in stage IV failed to exert cytotoxicity against HEp-2 targets. In contrast, an increased survival (decreased detachment from the monolayer) of HEp-2 cells was observed in the presence of peripheral blood mononuclear cells from patients, this being significantly enhanced by addition of concanavalin A during the lectin-dependent cell-mediated cytotoxicity assay.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1983

Limited proteolysis of glycogen phosphorylase a by subtilisin BPN'.

The limited proteolysis of rabbit skeletal muscle phosphorylase a was undertaken with subtilisin BPN' immobilized to Sepharose 4B. The effect of substrates, activators and inhibitors of phosphorylase a was investigated by monitoring the changes in phosphorylase activity in the SDS gel electrophoretic pattern and in the 32P-content of 32P-labeled phosphorylase a. Phosphorylase a loses its activity upon subtilisin treatment. All ligands tested protect phosphorylase a activity against subtilisin action, probably by inducing structural changes in the tower loop of the enzyme. Glucose-6-P significantly accelerates [32P]peptide release from phosphorylase a through altering the structure of the N-terminal tail segment. The two subunits of dimeric phosphorylase a are held together by strong interactions--deduced from the correlation of the rate of proteolysis and the disappearance of catalytic activity.

Adenosine Monophosphate↗
PubMed1983

Limited proteolysis by subtilisin reveals structural differences between phosphorylase a and b.

The limited proteolysis of rabbit skeletal muscle phosphorylase a and b was studied with subtilisin BPN' immoblized to Sepharose 4B. The activity of phosphorylase b is nearly resistant to subtilisin under the conditions (pH 7.0, 30 degrees C) where phosphorylase a rapidly loses its activity. The pH profile of phosphorylase a and b digestion is different. Proteolytic fragments of mol. wt 70,000 and 30,000 generated from phosphorylase a, while mol. wt 80,000 and 70,000 generated from phosphorylase b can be detected by SDS gel electrophoresis. Addition of AMP to phosphorylase b favours a conformation similar to--but not identical with--phosphorylase a as recognised by subtilisin action.

Adenosine Monophosphate↗
PubMed1983

Effect of prostaglandins on polymorphonuclear leukocyte motility.

The effect of prostaglandins (PGE1, E2, F2 alpha on LIF production, LIF activity, and on the random migration of polymorphonuclear leukocytes was investigated. Concanavalin A-induced LIF production was tested in an indirect LIF assay using agarose microdroplet technique; PGE1 and PGE2 inhibited the LIF production. PGE1, PGE2, and F2 alpha in physiological concentration, decreased the random migration of leukocytes, they also interfered with the LIF activity of supernatants, decreasing their inhibitory effect on cell migration; but the opposite explanation that LIF-treated PMNs escaped the inhibitory effect of PGs, cannot be ruled out. Macrophages produce supernatant factor(s) in the course of phagocytosis which inhibit the motility of polymorphonuclear leukocytes. The active component of supernatant seems to be PG, since its production can be blocked by indomethacin. These data indicate that prostaglandins may have different sites of attack in the local regulation of leukocyte motility.

Adult↗
PubMed1983

Effect of Fc receptor blocking on human natural and lectin-dependent cell-mediated cytotoxicity against adherent HEp-2 cells.

The effect of Fc receptor (FcR) blocking by aggregated human gamma-globulin (AGG) was studied on natural (NCMC) and lectin-dependent cell-mediated cytotoxicity (LDCC) against adherent HEp-2 human epipharynx carcinoma target cells. Cytotoxicity was measured by detachment from the monolayer of [3H]TdR-prelabelled HEp-2 cells. LDCC was evaluated in a 24 h assay at 50:1 effector-target cell ratio in the presence of 25 micrograms/ml concanavalin A (Con A). Under these conditions but without Con A considerable NCMC was not elicited by normal lymphocytes. FcR blocking by AGG treatment of effector cells resulted in a significant NCMC activity to HEp-2 targets. In contrast, AGG treatment profoundly depressed LDCC. Monocyte depletion of effector cells had no major influence on the effect of AGG on NCMC and LDCC activities. An interference of FcR blocking by AGG and LDCC in response to Con A is suggested.

Cell Line↗