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Biomedical subjects

G Poste

Publications and source records attributed to G Poste.

At least 73 records · Page 4Linked to original sources
PubMed1985

Induction of suppressor cells, interleukin-2 production and mitogenesis with monomeric concanavalin A: different actions of tetrameric and monomeric concanavalin A.

The ability of a photoalkylated monomeric concanavalin A (Con A) derivative to induce mitogenesis, interleukin-2 (IL-2) production and suppressor cells in murine spleen cell cultures has been compared with the activity of native, tetrameric Con A. The monomeric derivative was prepared by photochemically induced alkylation of tryptophan residues of tetravalent Con A in the presence of chloroacetamide followed by sizing chromatography [Tanaka et al. (1981) J. Biochem. 89, 1643-1646]. The monomeric derivative appeared to display less mitogenic activity than the tetramer and was also less effective in inducing IL-2 production. No difference was detected between the monomeric and tetrameric forms of Con A in inducing suppressor cells. The data suggest that cross-linking and bridging via sugar-binding sites, while potentiating mitogenesis and IL-2 production, had little effect on suppressor cell induction.

Animals↗
PubMed1985

Tumorigenic and metastatic properties of "normal" and ras-transfected NIH/3T3 cells.

To investigate the role of oncogene activation in the pathogenesis of malignant tumors, we have studied the tumorigenic and metastatic properties of NIH/3T3 secondary transfectants (designated A51) containing an activated c-Ha-ras-1 gene derived from the human T24 bladder carcinoma cell line and compared them with untransfected NIH/3T3 cells. Whereas subcutaneous implantation of NIH/3T3 cells in the supraclavicular region produced palpable tumors that failed to metastasize, NIH/3T3 cells inoculated in the footpad gave rise to malignant tumors that metastasized to the lung. Under identical conditions and irrespective of the site of implantation, A51 cells formed rapidly growing primary tumors that produced pulmonary metastases. In an assay for experimental metastasis, intravenously injected NIH/3T3 cells gave rise to pulmonary nodules only at high cell inocula and in long-term survivors (90 days after injection). In contrast, A51 cells formed multiple lung tumor colonies detectable 14 days after injection. These results indicate that "normal" untransfected NIH/3T3 cultures contain subpopulations of cells that express malignant properties and that transfection of NIH/3T3 cells with activated c-Ha-ras-1 accelerates formation of metastases.

Animals↗
PubMed1985

Effect of 5-azacytidine on DNA methylation and the malignant properties of B16 melanoma cells.

The role of DNA methylation in the expression of the metastatic phenotype in B16 murine melanoma cells in syngeneic C57BL/6 mice has been investigated. B16 cultures were incubated in vitro for either 6 or 18 h with the DNA hypomethylating agents, 5-azacytidine (5-Aza-CR) or 5-fluoro-2'-deoxycytidine (FCdR). At various times (1-13 days) following treatment, tumor cells were tested for their ability to form metastatic deposits when injected at different doses either i.v. (experimental metastasis) or s.c. in the footpad (spontaneous metastasis). Both 5-Aza-CR (0.5-15 microM) and FCdR (0.3-30 microM) caused a dose-dependent increase in the ability of B16 cells to form experimental pulmonary metastases. Increased capacity to form experimental pulmonary metastases was evident 24 h following treatment with 5-Aza-CR and 13 days following treatment with FCdR. The enhanced metastatic burden involved both an increase in the median number of lung colonies and a substantial increase in the size of individual lesions. 5-Aza-CR or FCdR treatment of B16 cell populations did not influence either the tumorigenicity or their ability to form spontaneous metastases. Parallel in vitro experiments using high-performance liquid chromatography analysis of cellular DNA demonstrated that under conditions in which 5-Aza-CR and FCdR enhanced formation of experimental metastases by B16 cells, there were readily detectable alterations in the 5-methylcytosine levels in DNA extracted from drug-treated cultures. These data suggest that drug-induced alterations in DNA methylation can affect biochemical pathway(s) whose expression is associated with the successful organ colonization by circulating tumor cells.

Animals↗
PubMed1985

Binding of histamine and histamine analogs to lymphocyte subsets analyzed by flow cytometry.

The binding of histamine, 4-methylhistamine (a histamine type 2 receptor agonist), cimetidine (a histamine type 2 receptor antagonist), and telemethylhistamine (an inactive analog) to human peripheral blood mononuclear cell subsets was investigated by flow cytometry by using conjugates of these ligands coupled to fluorescein-labeled human serum albumin. Our results indicate that binding of fluorescent protein conjugates of histamine and its analogs does not selectively identify a lymphocyte subset(s) that mediates the immunomodulatory effects of histaminergic ligands. Conjugates with both low (2.5 to 2.8:1) and high (28 to 57:1) ligand to protein coupling ratios were used. No binding above background could be detected for the low mole ratio reagents. The high mole ratio reagents were bound by 95 to 99% of all lymphocytes when used at ligand concentrations of 50 microM or greater. At lower ligand concentrations, the number of lymphocytes exceeding a set fluorescence threshold was decreased, but fluorescence distributions remained unimodal at all concentrations used (1 to 500 microM). Monocytes also bound the high mole ratio reagents and gave rise to a second high-intensity peak in the fluorescence distribution unless they were excluded by other means. Levels of conjugate binding detected by flow cytometry did not parallel ligand potencies at classical histamine type 2 receptors; at equivalent ligand concentrations, approximately equal amounts of histamine or 4-methylhistamine conjugate were bound per lymphocyte, and only 30% less telemethylhistamine conjugate was bound. Competition with free ligands (10(2)- to 10(4)-fold excess histamine, 4-methylhistamine, cimetidine, or telemethylhistamine) did not significantly decrease the level of binding observed for the high mole ratio reagents at bound ligand concentrations of 1 to 25 microM. Dual staining with fluorescein-labeled conjugate and phycoerythrin-labeled monoclonal antibodies Leu-3ab (anti-helper T), Leu-2a (anti-suppressor T), Leu-M3 (anti-monocyte), or anti-HLA-DR (B cells and monocytes) was also carried out. The extent of conjugate binding to helper and suppressor cells was identical for each of the ligands used, but higher levels of conjugate binding were seen for monocytes and B cells than for T cells in every case. Our data do not exclude the possibility of enhanced conjugate binding to small numbers of activated (HLA-DR positive) T cells that might be involved in mediation of histamine effects.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding Sites↗
PubMed1985

Modulation of macrophage-lymphocyte interactions by the antiarthritic gold compound, auranofin.

Auranofin (AF), a new oral gold agent effective for treating rheumatoid arthritis (RA) was evaluated for its ability to alter macrophage and lymphocyte functions of immune mediated chronic inflammation. AF (2 microM) inhibited antigen presentation by splenic macrophages to sensitized (DNFB) lymph node cells in vitro and also inhibited production of IL-2 and IL-1 by lymphocytes and macrophages, respectively. When AF suppressed Con-A induced mitogenesis in vitro, there were no inhibitory effects on Con-A induced suppressor T cell functions. AF administered orally to normal mice did not affect antigen presentation. DNFB contact sensitivity or Con-A induced mitogenesis. High concentrations of topical AF inhibited local immune responses to contact sensitizing agents and enhanced the induction of antigen specific suppressor T cells. Optimally, in vitro or in vivo AF inhibited macrophage and helper T cell functions with impairing the induction of suppressor T cells. After chronic treatment, similar effects could contribute to the efficacy of AF in humans with RA.

Animals↗
PubMed1985

Changes in the macrophage content of lung metastases at different stages in tumor growth.

The macrophage content of experimental B16 melanoma metastases at different stages of their growth has been quantified with the use of morphometry in conjunction with a recently developed histochemical method for selectively staining intratumoral macrophages. Data are presented from analyses of 954 sections of 155 individual lung metastases, showing that the macrophage content of individual B16 melanoma lung metastases not only varies significantly but also falls dramatically once metastases contain more than 700 tumor cells. In addition to providing new information on host response reactions of micrometastases, these experiments also indicate that conclusions on intratumoral macrophages derived from studies of large primary tumors and metastases in advanced stages of growth may have little or no relevance to events in micrometastases.

Animals↗
PubMed1984

Inhibition of macrophage activation and tumor cell cytolysis by cyclosporin-A.

Cyclosporin (CsA)4, a fungal peptide used clinically for its immunosuppressive properties, was investigated for its ability to antagonize the activation of macrophages (PEM) to the tumoricidal state. The acquisition of tumoricidal properties by PEM challenged with macrophage activating factor (MAF) plus lipopolysaccharide (LPS) was inhibited in a dose-dependent fashion by CsA. Similarly, CsA antagonized activation of PEM exposed to the calcium ionophore, A23187. CsA also inhibited macrophage-mediated tumor cell cytolysis in a dose-dependent manner. These data indicate that in vitro, CsA can modulate directly the acquisition and expression of tumoricidal properties by PEM and suggests that the macrophage may be an important target cell for CsA in vivo.

Animals↗
PubMed1984

Production of C3 as a marker of lymphokine-mediated macrophage activation.

C3 production was assayed using an enzyme-linked immunosorbent assay (ELISA) in cell-free supernatants harvested from thioglycollate-elicited macrophages exposed to a variety of macrophage stimulating and activating agents. Macrophage monolayers treated with the stimulating agents starch, glycogen, and zymosan secreted three- to four-fold less C3 (mean 12 ng/10(5) cells/12 hr) than macrophages exposed to lymphokines containing macrophage-activating factor (MAF) (mean C3 production 44 ng/10(5) cells/12 hr). The increased production of C3 in macrophages exposed to MAF parallels the ability of these macrophages to acquire tumoricidal capacity as monitored in an in vitro 72 hr tumor cell cytotoxicity assay using B16 melanoma cells. Macrophages previously rendered tumoricidal by exposure to MAF and which are refractory to further challenge by MAF following decay of their tumoricidal properties, do not produce C3 on rechallenge with MAF. Exposure of refractory macrophages to liposome-encapsulated MAF overcomes the refractory state and induces re-expression of the tumoricidal phenotype and C3 production. We conclude that quantitative detection of macrophage-generated C3 antigen provides a useful biochemical marker for monitoring the acquisition of tumoricidal properties in macrophages exposed to MAF and offers a sensitive assay for screening novel agents that activate macrophages via mechanisms similar to MAF.

Animals↗
PubMed1984

Reversal of histamine-mediated immunosuppression by structurally diverse histamine type II (H2) receptor antagonists.

The effect of a series of structurally-diverse histamine type II (H2)-receptor antagonists on histamine-mediated immunosuppression of human peripheral blood lymphocytes (HPBL) has been examined. This analysis of structure--activity relationships was undertaken to examine the validity of the recent proposal arising from clinical studies that H2-receptor antagonists containing a furan ring were devoid of the effects on lymphocyte function reported previously in studies using cimetidine and other H2-receptor antagonists containing an imidazole nucleus. Cimetidine and two furan-containing antagonists, ranitidine and SKF 93479, were found to be devoid of any effect on PHA-induced proliferation of human peripheral blood lymphocytes over a wide concentration range (10(-4) to 10(-10)M). At high drug concentrations (10(-3)M) significant suppression of mitogen stimulation was observed but this was accompanied by significant cytotoxicity. All three antagonists were effective in reversing the suppression of PHA-stimulation of HPBL induced by exogenous histamine. Reversal of histamine-induced immunosuppression was obtained at drug concentrations (2.0 X 10(-4) to 1.0 X 10(-6)M) which were non-toxic and did not affect PHA-induced proliferation in the absence of histamine. Ranitidine was the most potent antagonist in reversing histamine-mediated immunosuppression. The ability of structurally-diverse H2-receptor antagonists to modify the action of histamine on lymphocyte function lends support to the view that histamine exerts its effects via classical H2-receptors. The ability of ranitidine to alter lymphocyte responsiveness in analogous fashion to cimetidine indicates that the possibility of alterations in immune function should be considered in clinical studies using ranitidine and other furan-containing H2-receptor antagonists.

Animals↗
PubMed1984

Identification and characterization of a monoclonal antibody to an antigen expressed on activated macrophages.

A hybridoma clone secreting a monoclonal antibody, designated MA158.2, that reacts with an antigen expressed on lymphokine-treated macrophages was produced by fusion of mouse myeloma cells with rat spleen cells immunized against C57BL/6 peritoneal macrophages rendered tumoricidal in vitro by incubation with the lymphokine macrophage-activating factor. The specificity of the antibody for activated macrophages and lack of reactivity with histologically diverse cell types was determined by radioimmune indirect binding and flow cytometry. MA158.2 antibody binds to mouse peritoneal macrophages elicited by nonspecific inflammatory agents and to tumoricidal macrophages elicited with Corynebacterium parvum. Resident peritoneal, splenic, and alveolar macrophages were only weakly positive. Several macrophage cell lines (P388D1, WEH1-231, J774, RAW 264.7), murine fibroblasts, and neutrophils did not bind detectable amounts of MA158.2. Radioimmune indirect binding analysis demonstrated that cell suspensions prepared from C57BL/6 mouse spleen, thymus, and lymph node as well as polymorphonuclear leukocytes, lymphocytes, and T- and B-cell murine lymphomas were MA158.2 negative. Expression of the reactive antigen on the macrophage cell surface was enhanced 3-fold following in vitro activation of elicited macrophages with macrophage-activating factor and the kinetics of activation to the tumoricidal state paralleled the increased expression of the antigen recognized by MA158.2. MA158.2 is a rat IgG2a antibody containing a single specific heavy and light chain that does not detect a polymorphic determinant. This monoclonal antibody will be a useful tool for monitoring the efficacy of agents in activating murine macrophages to the tumoricidal state and in analyzing the sequence of biochemical events that culminate in macrophage activation.

Animals↗
PubMed1984

New insights into receptor regulation.

This review provides a brief summary of certain recent advances in our understanding of receptor regulation, signal transduction, and the diverse pathways by which receptor-ligand complexes are internalized and delivered to specific organelles, together with recycling of receptors back to the cell surface. Emphasis is also given to the importance of methodological advances in receptor isolation, immunologic analysis of receptor structure and function, the development of new instrumentation for microchemical characterization of very small amounts of receptor material, and the increasing use of genetic engineering techniques to isolate the genes for receptors and their regulatory subunits, to transfer such genes between cells, and to study receptor function by creating structurally modified receptors via subtle changes in gene structure.

Adenylyl Cyclases↗
PubMed1984

Inhibition of T suppressor cell expression by histamine type 2 (H2) receptor antagonists.

The effect of histamine type 2 (H2) receptor antagonists, cimetidine and ranitidine, on the induction and expression of hapten-specific suppressor T cells was studied. The activity of DNBSO3 -induced suppressor cells was evaluated after adoptive transfer to naive syngeneic recipients. Treatment with cimetidine or ranitidine markedly inhibited suppressor T cell activity in a dose-related manner and enhanced the contact sensitivity response to DNFB. Both H2 antagonists were effective in inhibiting the expression and, to a lesser extent, the induction of suppressor T cells. In contrast, norburimamide , a non-H2 antagonist structurally related to cimetidine, was inactive. The relevance of these findings to the clinical observation of cimetidine-induced reversal of acquired tolerance to dinitrochlorobenzene in anergic patients is discussed.

Animals↗
PubMed1983

The experimental and clinical implications of cellular heterogeneity in malignant tumors.

The growing body of evidence showing that malignant tumors are heterogeneous and contain diverse subpopulations of tumor cells is reviewed, with particular emphasis being given to the presence of tumor-cell subpopulations with differing metastatic properties. The factors that may influence the evolution of cellular diversity at different stages in the progression of malignant neoplasms are discussed. Emphasis is given to the possibility that interactions occurring amongst the constituent subpopulations of a malignant tumor may influence the rate at which new variant subpopulations emerge. Metastatic heterogeneity poses significant problems for experimental efforts to identify features unique to metastatic cells and also for the therapy of metastatic disease.

Animals↗
PubMed1983

Tumor cell diversity and host responses in cancer metastasis--part II--host immune responses and therapy of metastases.

Recent findings that (1) individual tumor cells in a malignant lesion possess widely different metastatic properties and (2) metastases arise from specific subpopulations of metastatic tumor cells have profound implications for eventually understanding and treating metastatic diseases. These findings have also raised serious doubts concerning the appropriateness of many of the experimental approaches currently in use for studying metastasis. Diversity in metastatic phenotype among cells from the same tumor suggests that the usual analyses of tumor cell lines containing multiple heterogeneous subpopulations may not be fruitful. This is especially true for tumors where the metastatic subpopulations represent only an extremely small fraction of the total number of tumor cell subpopulations. In addition, the screening of potential antitumor and antimetastatic agents for their abilities to inhibit the growth of tumors containing widely heterogeneous subpopulations of metastatic and nonmetastatic cells may not be useful in predicting the efficacy of these treatments against metastases. New methodologies must be developed to isolate and characterize the specific cell subpopulations that possess the metastatic phenotype, with the reservation that careful attention must be paid to the stabilities of these malignant cell subpopulations, especially during long-term growth. Understanding the mechanism(s) controlling the rapid generation of phenotypic diversity in tumor subpopulations, and the regulation of subpopulation diversity during progressive growth of primary and metastatic lesions, is of fundamental importance in the design of experimental systems for studying the metastatic process, and eradicating metastases. This review and its companion, as well as our other recent reviews, have dealt with current information on cancer metastasis and where future efforts might be the most promising in discerning this complex process.

Animals↗
PubMed1983

Inhibition of phytohaemagglutinin-induced proliferation of human peripheral blood lymphocytes by histamine and histamine H1 and H2 agonists.

Histamine (10(-3)-10(-8) M) inhibits PHA-induced proliferation of human peripheral blood lymphocytes (HPBL). Inhibition is detected at low concentrations of PHA but is rarely observed at high PHA concentrations. The histamine type II (H2) receptor agonists dimaprit, impromidine and 4-methylhistamine (4MH) inhibit HPBL proliferation and the H2 antagonist, cimetidine, reverses histamine-induced suppression of HPBL proliferation. Lymphocyte proliferation is also inhibited by the H1 receptor agonists, 2-pyridylethylamine and 2-thiazoylylethylamine, but only at high concentrations (10(-3) and 10(-4) M). The H1 agonist 2-methylhistamine, suppresses PHA-induced proliferation of HPBL in analogous fashion to histamine. This effect is reversed by cimetidine but not by diphenhydramine suggesting that an H2 receptor interaction is involved.

Cell Division↗