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Biomedical subjects

M Martin

Publications and source records attributed to M Martin.

At least 19 recordsLinked to original sources
PubMed1992

Chromosomal anomalies in radiation-induced fibrosis in the pig.

R-banded karyotypes were established on fibroblasts from fibrotic tissues derived from experimental fibrosis induced in pigs, either surgically or by 64 Gy of gamma-rays from iridium-192. No chromosome aberrations were observed in the surgical fibrosis. In radiation-induced fibrosis, the high frequency of abnormal karyotypes and the frequent complexity of the chromosomal rearrangements suggest that the fibroblasts originated either from the 64-Gy area, or from the penumbra, but certainly not from non-irradiated areas. At early passages in vitro, almost all karyotypes were different, demonstrating a multiclonal origin of fibrotic tissue. At late passages (above 24), the situation was quite different, with the persistence of one or two clones only, demonstrating a strong selective pressure occurring in vitro.

Animals↗
PubMed1992

Characterization of high molecular weight FK-506 binding activities reveals a novel FK-506-binding protein as well as a protein complex.

The immunoregulant FK-506 potently inhibits particular calcium-associated signal transduction events that occur early during T-lymphocyte activation and during IgE receptor-mediated exocytosis in mast cells. FK-506 binds to a growing family of receptors termed FK-506-binding proteins (FKBPs), the most abundant being a 12-kDa cytosolic receptor, FKBP12. To date, there is no formal evidence proving that FKBP12 is the sole receptor mediating the immunosuppressive effects or toxic side effects of FK-506. Using gel filtration chromatography as an assay for novel FK-506-binding proteins, we identified FK-506 binding activities in extracts prepared from calf brain and from JURKAT cells. Both of these new activities comigrated with apparent molecular masses of 110 kDa. However, further characterization of both binding activities revealed that the two are not identical. The 110-kDa activity observed in brain extracts appears to be the FKBP12.FK-506.calcineurin (CaN) complex previously reported (Liu, J., Farmer, J., Lane, W., Friedman, J., Weissman, I., and Schreiber, S. (1991) Cell 66, 807-815) while the 110 kDa activity observed in JURKAT cells is a novel FK-506-binding protein. Our characterization of the FKBP12.FK-506.CaN complex reveals a dependence upon calmodulin (CaM) for formation of the complex and demonstrates that the peptidyl-prolyl cis-trans isomerase (PPIase) activity of FKBP12 is not required for binding of FKBP12.FK-506 to CaN or for inhibition of CaN phosphatase activity. The novel FK-506-binding protein in JURKAT cells has been purified to homogeneity, migrates with an apparent mass of 51 kDa on denaturing gels, and has been termed FKBP51. Like FKBP12, FKBP51 has PPIase activity, but, unlike FKBP12.FK-506, FKBP51.FK-506 does not complex with or inhibit the phosphatase activity of, CaN. These results indicate that complex formation with CaN may not be a general property of the FKBPs. Peptide sequencing reveals that FKBP51 may be similar, if not identical, to hsp56, a component of non-transformed steroid receptors.

Amino Acid Isomerases↗
PubMed1992

Adherence of infected erythrocytes to venular endothelium selects for antigenic variants of Plasmodium falciparum.

Erythrocytes (E) infected with asexual forms of malaria parasites exhibit surface antigenic variation. In Plasmodium falciparum infections, the variant Ag is the P. falciparum E membrane protein 1 (PfEMP1). This molecule may also mediate the adherence of infected E to host venular endothelium. We show here that parasite lines selected for increased adherence to endothelial cells have undergone antigenic variation. Three adherent lines selected from the same P. falciparum clone reacted with the same agglutinating antiserum that failed to agglutinate the parental clone. Immunoprecipitation experiments with the agglutinating anti-serum demonstrated that the selected lines expressed cross-reactive forms of PfEMP1 that were of higher m.w. and antigenically distinct from PfEMP1 of the parental clone. When one of the adherent lines was cloned in the absence of selection, a range of variant antigenic types emerged with differing cytoadherence phenotypes. These findings show that selection for cytoadherence in vitro favors the emergence of antigenic variants of P. falciparum and suggest that the requirement for cytoadherence in vivo may restrict the range of antigenic variants of P. falciparum in natural infections.

Animals↗
PubMed1992

Human carcinoembryonic antigen cDNA expressed in rat carcinoma cells can function as target antigen for tumor localization of antibodies in nude rats and as rejection antigen in syngeneic rats.

We have tried to develop a new model consisting of rats transplanted with syngeneic colon carcinoma PROb cells transfected with cDNA coding for the carcinoembryonic antigen (CEA), the human tumor marker most commonly used as target for MAbs. The antigenic density of the 4 CEA-expressing clones selected for a precise characterization ranged from 5 x 10(4) to 1 x 10(6) CEA molecules per cell. In all clones the CEA was shown to be attached to the membrane by a phosphatidylinositol (PI) anchor. Using a panel of radiolabeled MAbs directed against the 5 major epitopes described on the CEA molecule, we showed that all these CEA epitopes were expressed by the 4 transfectants. Southern-blot analysis showed that the entire CEA cDNA was present in the transfectants. Western-blot analysis, however, showed that the size of the CEA expressed by the 4 transfectants was slightly smaller than that of CEA produced by 2 reference human colon-carcinoma cell lines. Two clones, expressing 1 x 10(5) and 1 x 10(6) CEA molecules per cell, respectively, were grafted s.c. in nude mice and rats. Injection of radiolabeled anti-CEA F(ab')2 fragments into these animals showed specific tumor localization with the highest percentages of injected doses for the transfectants expressing the highest CEA level. When grafted into immunocompetent syngeneic BDIX rats, the CEA-expressing clones induced a strong antibody response against CEA and tumor rejections in a majority of the animals. Although the analysis of the immune response against the CEA-cDNA-transfected carcinoma cells is under investigation, the present results demonstrate that human CEA could function as a rejection antigen when transfected into rat carcinoma cells.

Adenocarcinoma↗
PubMed1992

Characterization of the lymphocyte activation gene 3-encoded protein. A new ligand for human leukocyte antigen class II antigens.

The lymphocyte activation gene 3 (LAG-3), expressed in human activated T and natural killer (NK) cells, is closely related to CD4 at the gene and protein levels. We report here the initial characterization of the LAG-3-encoded protein. We have generated two monoclonal antibodies after immunization of mice with a 30-amino acid peptide that corresponds to an exposed extra loop region present in the LAG-3 immunoglobulin-like first domain. The reactivity of these reagents is directed against LAG-3 since they recognize both membrane-expressed and soluble recombinant LAG-3 molecules produced in a baculovirus expression system. The two antibodies are likely to react with the same or closely related epitope (termed LAG-3.1) exposed on the LAG-3 first domain extra loop, as assessed in competition experiments on LAG-3-expressing activated lymphocytes. Cellular distribution analysis indicated that the LAG-3.1 epitope is expressed on activated T (both CD4+ and CD8+ subsets) and NK cells, and not on activated B cells or monocytes. In immunoprecipitation experiments performed on activated T and NK cell lysates, a 70-kD protein was detected after SDS-PAGE analysis. 45-kD protein species were also immunoprecipitated. Both the 70- and 45-kD proteins were shown to be N-glycosylated. In Western blot analysis, only the former molecule was recognized by the anti-LAG-3 antibodies, demonstrating that it is LAG-3 encoded. These anti-LAG-3 antibodies were used to investigate whether the LAG-3 protein interacts with the CD4 ligands. By using a high-level expression cellular system based on COS-7 cell transfection with recombinant CDM8 vectors and a quantitative cellular adhesion assay, we demonstrate that rosette formation between LAG-3-transfected COS-7 cells and human leukocyte antigen (HLA) class II-bearing B lymphocytes is specifically dependent on LAG-3/HLA class II interaction. In contrast to CD4, LAG-3 does not bind the human immunodeficiency virus gp120. This initial characterization will guide further studies on the functions of this molecule, which may play an important role in immune responses mediated by T and NK lymphocytes.

Amino Acid Sequence↗
PubMed1992

Support of human cord blood progenitor cells on human stromal cell lines transformed by SV40 large T antigen under the influence of an inducible (metallothionein) promoter.

We describe the development of a human bone marrow (BM) culture system which allows study of the interaction of stromal cell lines (SCL) and highly purified hematopoietic progenitor cells. Normal BM stromal cells were electroporated with a plasmid containing the simian virus 40 (SV40) large T antigen (SV40 T Ag) under the control of a synthetic metallothionein promoter (MT4); this construct is designated MT4 SV40 T Ag. SCL in which the rate of proliferation could be controlled by altering the zinc (Zn) concentration were characterized, demonstrating that the SCL were heterogeneous with respect to G-CSF and GM-CSF production. Suppression of SCL proliferation on removal of Zn made it possible to use these lines in coculture with purified CD34+ progenitor cells from umbilical cord blood. The ability to control proliferation of SCL has allowed us to maintain the survival and expansion of colony-forming cells in culture for up to 2 months. These lines have enabled us to test for stromal cell characteristics at a clonal level and provided us with a tool to analyze the events leading to lineage commitment and hematopoietic differentiation, as demonstrated by suppression of hematopoiesis by an antibody directed against the c-kit molecule.

Antigens, CD↗
PubMed1992

Transport of 4-hydroxyphenylacetic acid in Klebsiella pneumoniae.

Klebsiella pneumoniae M5a1 has been shown to possess an inducible transport system for 4-hydroxyphenylacetate (4-HPA). This transport system has a Kt of 16.3 microM and a maximal velocity of 31.2 nmol/min (milligrams dry weight). The transport system has been inhibited by inhibitors of energy metabolism with a concomitant decrease in cellular ATP concentrations, and the 4-HPA binding activity has been detected in the crude shock extracts. All these observations indicate that 4-HPA uptake is an active transport which involves a periplasmic binding protein and it seems to be energized by phosphate bond energy.

Adenosine Triphosphate↗
PubMed1992

Comparative investigation of the influence of nizatidine, ranitidine, and cimetidine on the steady-state pharmacokinetics of theophylline in COPD patients.

The influence of usual regimens of the H2 blocking drugs, cimetidine, ranitidine, and nizatidine on the steady-state plasma concentrations and pharmacokinetic characteristics of theophylline was studied in seventeen patients with chronic obstructive pulmonary disease (COPD). Patients were dosed to steady-state with an oral, sustained-release formulation of theophylline given in therapeutic doses twice daily for 2 weeks. Over the next 4 weeks, each patient received a week-long regimen of each H2 blocker concomitantly with theophylline, and a week-long regimen of theophylline alone (control). At the end of each of the latter 4 weeks the steady-state pharmacokinetics of theophylline were assessed. Neither ranitidine nor nizatidine treatment altered the steady-state pharmacokinetics of theophylline relative to the control phase (i.e. no H2 blocker treatment). Values for theophylline C(ave), Cssmax, AUC0-12, and CLoral were significantly different during cimetidine treatment compared with all other treatments (ranitidine, nizatidine, and control). Cimetidine increased theophylline Cssmax, AUC0-12 and Cave by approximately 32%, and decreased theophylline oral clearance by approximately 23%. The authors conclude that cimetidine alters the steady-state pharmacokinetics of theophylline in COPD patients, whereas ranitidine and nizatidine are without effect.

Administration, Oral↗
PubMed1992

Phase I study of mitonafide in 120 hour continuous infusion in non-small cell lung cancer.

Mitonafide is the lead compound of a new series of antitumor drugs, the 3-Nitronaphthalimides, which have shown antineoplastic activity in vitro as well as in vivo. This phase I Mitonafide study in non-small cell lung cancer using a 120-hour continuous infusion (120 h. C.I.) schedule of administration was designed to deliver the maximum amount of drug while avoiding the risk of central nervous system (CNS) toxicity, previously observed in studies with daily short (1 hour) administration schedules. Twenty patients were treated at doses ranging from 107-200 mg/m2 x 120 h. C.I. Dose-limiting toxicity with this schedule of administration was leukopenia. Other toxicities were mild or not relevant. No CNS toxicity was observed. The recommended dose for phase II C.I. Mitonafide studies is 170 mg/m2 x 120 h. C.I. in previously untreated patients. Plasma level monitoring is recommended.

Aged↗