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Biomedical subjects

G Medgyesi

Publications and source records attributed to G Medgyesi.

At least 19 recordsLinked to original sources
PubMed1992

[Reactivity of hepatitis C virus (HCV) antibody among blood donors in Hungary].

The anti-HCV results of 1958 donors are discussed. The Elisa positivity of high risk subjects was as follows: 60% in coagulopathies, 14% in transfused haematological patients and 32% in patients on dialysis. Elisa reactivity of random blood donors was 1.82%, in the group, selected on the basis of transaminase positivity it was over 8%. The confirmed results were compared by the commercially available Elisa tests. 30 positive samples were confirmed by RIBA or Abbott confirmation assay. 35 of the 55 anti-HCV positives were reactive by all the Elisa, 19 samples could be confirmed, 25 were not subjected to any confirmatory assay. Further studies, and the introduction of mandatory screening of blood donors for anti-HCV are necessary.

Blood Donors↗
PubMed1992

[The role of HCV in the pathogenesis of post-transfusion hepatitis].

Between January 1987 and April 1988 following 462 open heart surgery operations, 83 patients with icteric hepatitis were seen. Among them 59 patients were anti-HCV positive with the Ortho anti-HCV test, these findings suggested a hepatitis C virus infection. The source of viral infection was searched, and a prothrombin complex concentrate which had been used during that period, seemed to be the potential cause of bloodborne hepatitis C. The results suggest that special care is required when using such blood products.

Cardiac Surgical Procedures↗
PubMed1991

[Hepatitis C virus antibody in Hungarian blood donors, persons at risk and patients with post-transfusion hepatitis].

The authors screened blood donors, persons at high risk of infection and patients with post-transfusion hepatitis by the use of the new hepatitis C antibody test. 1.7% of persons donating blood acceptable for use according to current criteria were found positive. This ratio was markedly higher among donors displaying an elevated transaminase level. Among the various patients tested 85% of the haemophiliacs, 14% of the transfused haematology patients, and 40% of those on dialysis were found positive. In two groups of patients with post-transfusion non-A, non-B hepatitis the ratio of positives was 69% and 92%, respectively. The frequency of hepatitis C antibody was not sizably higher in the health personnel tested than that found in blood donors. The results indicate hepatitis C virus to be the main source of post-transfusion non-A, non-B hepatitis in Hungary too. As expected, HBc antibody revealing a previous contact with hepatitis B virus was found very frequent in patients with coagulopathies and in those on dialysis. A relatively high anti-HBc prevalence was found among health personnel and blood donors too. Authors intend to emphasize the need of thorough consideration of indications in hemotherapy although improvements in the screening of donations can diminish the risk of virus transmission by blood or blood derivatives.

Blood Donors↗
PubMed1990

Fine specificity of a rabbit antibody interacting with human IgG Fc receptor-like molecules.

A polyclonal rabbit antibody raised against an Fc receptor (FcR)-like membrane glycoprotein fraction of chronic leukaemic lymphocytes has previously been prepared and partially characterized. This antibody, called AbA, was found to precipitate a 70-kDa and a 45-kDa fraction of the detergent lysate of U937 cells and to inhibit ligand binding to Fc gamma R on the P388D1 murine macrophage cell line. In the present work we have characterised this antibody further. All Fc gamma RII-positive B lymphoblastoid cell lines, as well as resting human B lymphocytes, were positively stained with the AbA antibody. U937 cells were found to be negative, but after stimulation with phorbol ester (PMA), 50% of the cells became positive. AbA antibody did not react with human T cell lines or with the T + 0 cell subset of peripheral blood. Monocytes were also negative. On the other hand, AbA antibody exhibited a dose-dependent inhibition of antibody-mediated cytotoxic reaction (ADCC) of monocytes, while not affecting K cell-mediated ADCC. It had an inhibitory effect of EA rosette formation of B cells and stimulated U937 cells. Furthermore, it interacted with the soluble form of Fc gamma RII released by activated B lymphocytes, and--similarly to IgG--precipitated a 33 kDa fraction from the supernatant of B cells.

Animals↗
PubMed1983

Potentiation of factor H by heparin: a rate-limiting mechanism for inhibition of the alternative complement pathway.

The mechanism by which heparin inhibits the alternative complement pathway (ACP) by a fluid-phase activator, CoVF, has been studied. Results presented here indicate that heparin's major (rate-limiting) effect on the fluid-phase activation of the ACP was to potentiate Factor H activity. Such an effect results in a very efficient inhibition of C3b and C3bBb function and restriction of subsequent complement activation and hemolytic activity. Evidence was obtained to indicate that soluble heparin H shifted anodally. Assuming that the rate-limiting inhibitory effect of heparin is to potentiate Factor H, then C3-converting complexes such as CoVF-Bb, which do not require C3b for activity, should not be effected by heparin. Indeed, the inhibitory effect of heparin on C3 conversion in EGTA-Mg2+ serum-CoVF mixtures was lost with a prolonged incubation time (i.e. 60-90 min at 37 C). This finding indicated that with time ACP-mediated cleavage of C3 was able to bypass the heparin-mediated inhibitory step. From these studies it is suggested that heparin restricts the C3-converting activity due to soluble C3bBb complexes but not the C3 conversion due to CoVF-Bb complexes. Heparin-mediated restriction of the ACP activation by CoVF was used to calculate the relative percentages of C3 conversion due to C3bBb or CoVF-Bb complexes. In carefully controlled experiments, heparin could not prevent the spontaneous conversion of C3 which occurs upon removing functional Factor H from the sera. Addition of isolated Factor H restored heparin's inhibitory effect on the ACP. Kinetic studies of heparin's inhibition of ACP-mediated lysis of rabbit erythrocytes indicated that heparin's inhibitor functions did not occur until after the addition of an ACP activator. Each of these findings is consistent with the postulate that the major (rate-limiting) effect of heparin on the ACP is to potentiate the function of Factor H on activated C3b.

Complement Activation↗
PubMed1982

Rat lymphoid leukemia of T cell type induced by 7,12-dimethylbenz(alpha)anthracene. Immunological and enzymological characterization.

Lymphoid leukemia induced by 7,12-dimethylbenz(alpha)anthracene (DMBA) in rats and maintained by serial intraperitoneal transplantations in newborn rats was subjected to immunological and enzymological characterization. The Thy-1 antigen positivity rendered evidence for the T cell origin of the leukemia studied. Expression of cell surface complement binding receptors and patterns of cytoplasmic acid phosphatase and nonspecific acid alpha-naphthyl acetate esterase enzymes drew the attention to the dominance of lymphoblasts and prolymphocytes.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1981

Role of the cytoskeleton in the Fc receptor activity of rat peritoneal macrophages.

High concentration of cytochalasin B (CB) and vinblastine (Vb) inhibited the erythrocyte-antibody (EA) rosette formation of rat peritoneal macrophages (PM). Low concentration of Vb enhanced rosette formation. CB and Vb had the same effect on the rosette formation when anti-SRBC immunoglobulin (Ig) had been previously bound in vivo or in vitro to the Fc receptors (FcR) of the macrophages, suggesting that the intact function of the cytoskeleton is required for the last step of rosette formation. CB and Vb exert a reversible effect on FcR activity. Regeneration of FcR activity was observed also in the presence of 10 microgram/ml cycloheximide. The effect of CB and Vb on rosette formation depends both on the (sub)classes of antibody involved and on the nature of the particulate antigen. Rosettes with living trypanosomes displayed an extremely high CB sensitivity.

Animals↗
PubMed1979

Correlation between effector lymphocytes in natural and antibody-mediated cytotoxicity.

Human sera enhanced spontaneous cell-mediated cytotoxicity (SCMC), while anti-IgG (Fab') 2 treatment decreased this cytotoxic activity of human lymphocytes for an in vitro growing cell line (K--562). Trypsin treatment of the effector cells considerably decreased the cytotoxic potential. However, a significant cytotoxic activity could always be found in serum-free medium. While these findings suggest the involvement of antibodies in the SCMC, they also reflect the existence of serum-indpendent (sui generis) SCMC activity of lymphocytes. Removal of SCMC of Fc receptor bearing effector cells was performed by target cell adherence (rosetting). Separation of the target cell-bound lymphocytes was done by centrifugation on special Ficoll gradient. The depletion of SCMC effector cells resulted in a 62% reduction of SCMC and in a 39% reduction of ADCC. On the other hand, removal of Fc bearing effector cells showed a similar reduction in both ADCC (66%) and SCMC (78%). Our results suggest that SCMC represents a complex activity, arising partly from the interactions of certain serum-derived or lymphocytes surface-bound antibodies and partly from a spontaneous cytotoxic function of the effector cells. It is possible that the effector cells involved in both SCMC and ADCC derive from the same lymphocyte population and the differences are due mainly to the lower number of SCMC effector cells.

Animals↗