Search PubMed⌕ Search

Biomedical subjects

R Mihalik

Publications and source records attributed to R Mihalik.

At least 37 records · Page 2Linked to original sources
PubMed1995

Modulation of drug-induced apoptosis in a human B-lymphoma cell line (HT58).

The cytotoxic effect of etoposide (ETO), a topoisomerase II inhibitor, and staurosporine (STA), a non-selective protein kinase inhibitor, were studied on a human lymphoma cell line of B-cell origin (HT58). Apoptosis, induced dose dependently by both drugs, was accompanied with nucleosomal DNA fragmentation detected by flow cytometry. On the other hand, induction of cell death failed using phorbol ester (PMA), anti-IgM antibody (a-IgM) or dexamethasone (DEX), although, all of these agents arrested the cells in G1. Furthermore, PMA pretreatment retarded ETO-induced apoptosis, but enhanced STA cytotoxicity. DEX increased the sensitivity of cells to STA, but did not to ETO. Activity of STA or DEX was only slightly modified by a-IgM pretreatment. The results support the possibility that different apoptotic pathways exist in HT58 cells. The differences in pathways could be manifested either in the signaling routes, or in the molecular effectors of apoptosis.

Alkaloids↗
PubMed1995

Immunophenotypic and functional characteristics of haemopoietic cells from human cord blood.

Cord blood (CB) as a new source for bone marrow transplantation represents advantageous features concerning stem cell and leucocyte compartments and function. We attempted to get more information about the phenotypes and function of CB cells by investigating their cell surface markers and also the production of IL-2, IFN-gamma and IL-6 by mitogen and alloantigen stimulation. The CB cells were characterized by a low proportion of CD3+ T cells, CD4+ T subpopulation, activated T cells and CD3+CD16/CD56+ cytotoxic cells, suggesting reduced graft versus host potential. The significant increase of CD19/CD3 double positive cells and decrease of CD19/HLA-DR double positive mature B cells reflect that immature B cells exist in CB. In the functional studies, a 27- and 5-fold reduction was observed in the production of IFN-gamma by CB cells stimulated with PHA and allogeneic cells, respectively. The production of IL-2 in PHA-stimulated CB cells also showed a 50% determination. Decrease in the production of these cytokines by CB cells is supported by the decline of the proportion of CD3+ T cells. However, an increase was observed in the production of IL-6 by CB cells stimulated with allogeneic cells as compared with the controls. These results suggest a difference in the functional activity of the T helper cell subsets between the CB and peripheral blood and/or differences in the functional maturity of T helper cell subsets and B cells in these compartments.

Cells, Cultured↗
PubMed1995

Functional heterogeneity of in vitro selected variants from an IgM-secreting rat immunocytoma.

A long-term tissue culture line of highly metastatic IR202 immunocytoma of LOU rats, and five of its clones (B4, C2, C4, C5, and D3) were established and studied comparatively. All such cells were similar in terms of: (i) light microscopic morphology, (ii) growth rate, (iii) saturation density, (iv) cell cycle progression, and (v) cell surface IgM, major histocompatibility complex (MHC) class I and class II antigen expression, but (vi) showed a non-homogeneous pattern of chromosomal constitution, with both numerical and structural abnormalities detected in variable proportions of the different cell variants. Moreover, IR202 variants exhibited a marked difference in the production of soluble factors which was closely associated with the ability of their supernatants to inhibit mitogen (affinity-purified goat F(ab')2 fragments specific for rat mu-chains (anti-mu antibody), lipopoly saccharide (LPS), or concanavalin A (ConA))-induced proliferation of normal splenic B and/or T lymphocytes. These results are consistent with the concept of intratumor heterogeneity and the ability of immunoglobulin-secreting tumors to induce severe immune dysfunction in host animals and humans.

Animals↗
PubMed1994

Phosphorylation of poly(ADP-ribose)polymerase protein in human peripheral lymphocytes stimulated with phytohemagglutinin.

Intracellular phosphorylation of poly(ADP-ribose)polymerase was assayed in streptolysin-O-permeabilized human lymphocytes. Whereas 32P incorporation from [gamma-32P]ATP into immunoprecipitated enzyme protein was undetectable in resting cells, significant phosphorylation of this enzyme was observed in lymphocytes treated with phytohemagglutinin. The phosphorylation of poly(ADP-ribose)polymerase in permeabilized cells was not stimulated by phorbol ester, while phorbol-induced phosphorylation of other proteins and of a specific oligopeptide substrate of protein kinase C was observed. However, the specific inhibitory pseudosubstrate peptide of protein kinase C blocked the phosphorylation of poly(ADP-ribose)polymerase induced by phytohemagglutinin. Therefore, a potential role of a member of the protein kinase C family in the phytohemagglutinin stimulated intracellular phosphorylation of poly(ADP-ribose)polymerase is conceivable.

Bacterial Proteins↗
PubMed1994

Cell density-dependent regulation of cell surface expression of two types of human tumor necrosis factor receptors and its effect on cellular response.

Tumor necrosis factor (TNF) is a multipotential cytokine known to regulate the growth of a wide variety of normal and tumor cells. It has been shown that the density of cells in culture can modulate the growth regulatory activities of TNF, the mechanism of which, however, is not understood. In this report, we investigated the effect of cell density on the expression of TNF receptors. The receptors were examined on epithelial cells (e.g., HeLa), which primarily express the p60 form, and on myeloid cells (e.g., HL-60) known to express mainly the p80 form. We observed that binding of TNF to both cell lines decreased with increase in cell density. Scatchard analysis of binding on HeLa and HL-60 cells revealed a 4- to 5-fold reduction in the number of TNF receptors without any significant change in receptor affinity in both cell types at high density. The decrease in TNF receptor numbers at high cell density was also observed in several other epithelial and myeloid cell lines. The downmodulation at high cell density was unique to TNF receptors, since minimum change in other cell surface proteins was observed as revealed by fluorescent activated cell sorter analysis. Neutralization of binding with antibodies specific to each type of the receptors revealed that both the p60 and p80 forms of the TNF receptor were equally downmodulated. A decrease in leucine incorporation into proteins was observed with increase in cell density, suggesting a reduction in protein synthesis. Since inhibition of protein synthesis by cycloheximide also leads to a decrease in TNF receptors, it is possible that the density-dependent reduction in TNF receptor number is due to an overall decrease in protein synthesis. The density-dependent decrease in TNF receptors was accompanied by a decrease in intracellular reduced glutathione levels. A reduction in the number of receptors on TNF sensitive tumor cells induced by cell-density correlated with increase in resistance to the cytokine.

Cell Count↗
PubMed1994

A mouse monoclonal antibody reacting with swine leukocytes: a flow cytometrical and immunohistochemical study.

A mouse monoclonal antibody (Mab) was prepared by immunization of Balb/c mice with porcine peripheral blood mononuclear cells. Its reactivity was studied by flow cytometry and immunohistochemistry. By flow cytometry 75-90% of blood lymphocytes and 93-97% of blood granulocytes showed positivity, while all monocytes were labelled. The specificity of the Mab was investigated further by immunohistochemical methods using different tissues of swine. Both cortical and medullary thymocytes strongly expressed the target antigen of Mab 335-2. Intensive staining of T cell dependent areas in the lymph nodes, spleen and tonsils was also observed. Many positive cells occurred in the red pulp of the spleen. In the non-lymphoid tissues no organ-specific staining was observed, except for the connective tissue which contained scattered positive cells. Kupffer's cells and some glial cells reacted with this Mab. These results suggest that this novel Mab recognizes a major antigen present on immature and mature T cells; however, subpopulations of myeloid cells (neutrophils, monocytes, and some types of macrophages) share this antigen.

Animals↗
PubMed1994

Hypotensive action of aggregated IgG in rats. Study of the unresponsiveness to a second dose following restoration of the blood pressure.

Human IgG preparations containing aggregates have been reported to induce hypotension in rats. Animals surviving a hypotensive dose of such a preparation were found unresponsive to a second dose given the next day. Unresponsiveness was induced by an isolated fraction of aggregated IgG, but not by purified monomers. Preparations containing aggregated and monomeric IgG appeared more efficient in inducing unresponsiveness than aggregates alone. The phagocyte function in vivo was assessed in unresponsive animals. No significant difference was found in the carbon clearance and in the human erythrocyte clearance test suggesting that a general impairment of the phagocyte function is not necessary for unresponsiveness. Previous studies indicated the involvement of PAF in hypotension by aggregated IgG. Hypotension was elicited by the injection of PAF in rats made "refractory" to aggregated IgG like in controls.

Animals↗
PubMed1993

[Leukocyte adhesion defect--a rare form of congenital immune deficiency].

Leukocyte adhesion defect (LAD) is an inherited defect of phagocytic function. This disorder is characterised by delayed separation of the umbilical cord, severe recurrent bacterial infections, impaired formation of pus, and high leukocyte counts. The granulocytes have severe defect in their chemotactic mobility and endocytosis. The disease is attributed to the absence of the leukocyte adhesion molecules. (CD11/CD18), which can be verified with monoclonal antibodies. The authors describe the disease-process of the first patient diagnosed in Hungary. Perinatally the omphalitis, periumbilical abscess and periproctal abscess leading to rectovaginal fistula, in the first months the otitis, mastoiditis, and expressed leukocytosis referred to the impaired function of phagocytic cells, which was verified by laboratory tests as well. The decreased inflammation and cicatrization were also striking. This severe form of LAD can be cured only by bone marrow transplantation with preliminary sanitation of the foci of infection. It took about six months. Unfortunately, the patient died of sepsis immediately before transplantation.

Antibodies, Monoclonal↗
PubMed1993

Significance of cellular DNA content in human liver tumors.

The nuclear DNA content of 26 liver tumors (1 adenoma, 10 focal nodular hyperplasia and 15 hepatocellular carcinoma) was measured by flow cytometry (FCM) on formalin-fixed, paraffin-embedded tissues. All lesions developed in noncirrhotic liver and were negative for HBsAg. DNA aneuploidy was found in 1/10 FNH (one hypodiploid) and in 11/15 HCC (73%). Intratumoral heterogeneity was observed in three cases. In HCC the ploidy level showed no correlation with tumor size or histopathological grading. Results support the potential of FCM to measure DNA content in archival pathological specimens, and also that DNA content itself has no diagnostic value.

Adenoma↗
PubMed1992

Down-regulation of murine B lymphocyte growth: arrest of B cells in G1 underlies immunosuppression induced by an IgM antibody.

Previous studies have demonstrated that culture supernatants of LPS-stimulated murine splenic B lymphocytes (BLPSSN) are able to inhibit the growth of freshly isolated B cells via an IgM antibody. In this work we investigated the progress of LPS-activated B lymphocytes through the cell cycle in the presence of this antibody. We found that the regulatory IgM did not affect the entry of LPS-stimulated B lymphocytes into G0*, as assessed by the increased expression of I-A antigens. Events that characterize the early G1 phase (G1A), such as cell enlargement and increased RNA synthesis, also occurred in the presence of the antibody. In contrast, events which mark the G1B phase, such as further cell enlargement and late RNA synthesis were inhibited. Moreover, a significant portion of the cells failed to incorporate [3H]thymidine and did not progress through S, G2, or M, as revealed by their DNA content. Therefore, our work points toward a well-defined stage of the early G1 phase at which the antibody inhibits the progression of B lymphocyte activation. This result shows a new insight into the mechanism of antibody-mediated down-regulation of polyclonal B cell responses.

Animals↗
PubMed1992

Autocrine regulation of murine B lymphocyte growth by an IgM antibody.

Culture supernatants of LPS-stimulated murine B lymphocytes are able to inhibit the growth of freshly isolated splenic B cells via an IgM antibody. The binding specificity of this IgM is not yet defined, but appears to be a B lymphocyte surface structure distinct from membrane immunoglobulin, MHC class II antigen, transferrin and Fc gamma receptors, and B220. The regulatory autoantibody allows the normal progression of early, but not late steps in the cycle of polyclonally-stimulated B lymphocytes and does not affect the increased antigen-presenting capacity of activated B cells. Therefore, this autoregulatory cycle is apparently ubiquitous and may be a major component of B lymphocyte homeostasis under physiological, as well as pathological conditions. Moreover, these findings bring into focus a possible regulating role of B lymphocytes in the humoral immune response.

Animals↗
PubMed1991

Correlation of the percentage of activated, CD3 + DR + lymphocytes to serum neopterin level in HIV-seropositive haemophiliacs.

The percentage of activated, CD3+ DR+ and CD8+ Leu7+ lymphocytes and the serum neopterin concentration were determined in 17 HIV-seropositive and 10 HIV-seronegative haemophiliacs and in 11 healthy control subjects. All three parameters tested were found to be significantly higher in the seropositive patients than in the seronegative controls. In the seropositive group, a significant positive correlation was found between the neopterin levels and the percentage of CD3+ DR+ cells. By contrast, no significant negative or positive correlation was observed between the neopterin levels and the percentage of the CD8+ Leu7+ subset. These data suggest that in the HIV-infected patients the activated T cells responsible for the stimulation of macrophages to produce neopterin are those that do not carry CD8.

Adolescent↗
PubMed1991

[Heterogeneity of surface antigens in chronic B-cell lymphoid leukemia].

Clinical and immunological studies of fifty patients with CLL have been performed. No correlation was found either between the clinical stage or clinical course of the disease and the distribution of cell surface makers characteristic of CLL (CD19, CD20, CD21, HLA-DR, sIg). Therapy did not influence the distribution of B lymphocyte subpopulations. On the other hand we recognized differences when examining the B-cell specific features. The CD21 antigen was present in significantly lower proportion when compared to all other B-cell markers. This suggests the presence of immature B-cell population. Correlation studies showed a strong correlation between the presence of the CD5 antigen and the antigens CD19, CD20, HLA-DR and sIg, while a similar correlation could not be proved between the CD5 antigen and CD21 marker. Thus the application of the CD5 antibody together with any of the B-cell markers seems to be sufficient for the diagnostics of CLL with the exception of the CD21 antibody that marks only a small proportion of the B-cell population in CLL, so it can be used for purposes of clinical diagnostics.

Adult↗
PubMed1991

The complement system in HIV disease.

Different aspects of the relationship between the HIV infection and the complement system were studied. 1. No significant differences were found between seronegative controls, asymptomatic, and symptomatic (ARC, AIDS) HIV-seropositive patients in the plasma levels of complement components C4, Bf, and C3. 2. Using sensitive ELISA assays, a significant increase was observed in the levels of protein-protein complexes which are formed at the activation of the classical (C1r-C1s-C1-INH) and alternative (C3b-Bb-P) pathways, indicating that both complement pathways are activated in the HIV disease. No significant differences were found, however, in the levels of these complexes between the groups of asymptomatic and symptomatic HIV-infected patients. 3. Artificial immune complexes of synthetic peptides representing some immunodominant epitopes of HIV envelope (gp120, and gp41) proteins, and human polyclonal anti-HIV IgG were found to weakly activate both the classical and alternative complement pathways. 4. An elevated percentage of the lymphocytes carrying a complement activation fragment, C3d, was detected in the blood of HIV seropositive patients as compared to the seronegative controls. No significant positive correlation was found between the percentage of these cells and that of any T cell subsets tested.

Complement Activation↗
PubMed1991

Flow cytometric analysis of DNA content in focal nodular hyperplasia and hepatocellular carcinoma.

DNA index of twenty-three surgically removed, formalin-fixed and paraffin-embedded liver specimens (10 focal nodular hyperplasias--FNH, and 13 hepatocellular carcinomas--HCC) were studied by flow cytometry. Diploid value appeared in 9/10 FNH (one was hypodiploid), while 10/13 HCC (77%) had DNA aneuploidy (one hypo- and 9 hyperdiploid). The presence of normal DNA content in 3 HCCs suggests that DNA aneuploidy only cannot indicate the malignant transformation of a benign lesion (e.g. FNH).

Adolescent↗
PubMed1991

Characterization of T lymphocyte subsets in hairy cell leukaemia: influence of splenectomy and correlations with the clinical stage of the disease.

Peripheral blood mononuclear cell surface markers were studied in a series of 26 hairy cell leukaemia patients 19 of whom were splenectomized previously. Patients with non-symptomatic and stable disease were distinguished from those with symptomatic and/or progressive disease (also termed "active" clinical stages). In all HCL patients as a group, the absolute number of CD4+ MN cells did not differ statistically from that of the controls, while the number of CD8+ MN cells was significantly increased. The reduction of the CD4/CD8 ratio in the peripheral blood of HCL patients as compared to the controls was explained by the reduction of this ratio in patients with "active disease", while the CD4/CD8 ratio of patients with non-symptomatic and stable disease did not differ statistically from that of the controls. The CD4/CD8 ratio was found to be influenced mainly by the clinical stage of the disease, and not by the effect of splenectomy.

Adult↗