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Biomedical subjects

J Martin

Publications and source records attributed to J Martin.

At least 523 records · Page 29Linked to original sources
PubMed1994

Interleukin-4 enhances murine bone marrow macrophage M-CSF receptor expression by a posttranscriptional mechanism.

Activated T-lymphocytes secrete interleukin-4 (IL-4), which has been shown to modulate a variety of monocyte activities requiring monocyte/macrophage colony-stimulating factor (M-CSF). To account for this interaction, we postulated that IL-4 acts on target cells by altering the expression of the M-CSF receptor (M-CSFr). To test this hypothesis, murine bone marrow macrophages were cultured under conditions that down-regulate M-CSFr and the effect of IL-4 on the reexpression of the receptor measured by binding of 125I-labeled M-CSF to the cells. The data show that incubation with IL-4 results in a dose-dependent, 2-3 x increase in M-CSFr with no change in binding affinity and a maximal effect on binding at about 12 h. This increase in M-CSFr is dependent upon new, specific protein synthesis as shown by the inhibitory action of cycloheximide, and gel analysis of radiolabeled, specific protein, immunoprecipitated with anti-M-CSFr antibody. Treatment with IL-4 does not stimulate M-CSFr mRNA expression but, consistent with enhanced receptor levels, does result in a heightened proliferative response to M-CSF. Thus, IL-4 affects M-CSF treated monocytic cells, at least in part, by altering the expression of M-CSFr.

Animals↗
PubMed1994

Uncommon location of persistent ectopic pregnancy following laparoscopic surgery.

BACKGROUND: Laparoscopic surgery has become an important tool in the treatment of tubal pregnancy. Skillful operative technique should prevent tissue spread and thus avoid persistence of ectopic trophoblastic cells. CASE: A laparotomy with complete salpingectomy was performed in a patient with rising serum hCG levels after a previous laparoscopic partial salpingectomy for ampullary tubal pregnancy. The only residual trophoblastic tissue found was an implant in the abdominal wall at the site of auxiliary puncture. CONCLUSION: Extra-abdominal dispersion of active trophoblastic cells may lead to increasing hCG levels, mimicking persistent tubal pregnancy.

Adult↗
PubMed1993

The reaction cycle of GroEL and GroES in chaperonin-assisted protein folding.

The reaction mechanism of protein folding by the chaperonin GroEL and its regulator GroES has been defined. GroES and substrate protein counteract each other's effects on GroEL: whereas GroES stabilizes GroEL in the ADP-bound state, binding of unfolded polypeptide within the cavity of the GroEL cylinder triggers ADP and GroES release. Upon ADP-ATP exchange, GroES reassociates with GroEL and ATP hydrolysis discharges the bound protein for folding. Partially folded protein rebinds to the chaperonin, thus perpetuating the cycle until folding is complete.

Adenosine Diphosphate↗
PubMed1993

Identification of nucleotide-binding regions in the chaperonin proteins GroEL and GroES.

The chaperonin GroEL, a tetradecameric cylinder consisting of subunits of M(r) approximately 60,000 (60K), and its cofactor GroES, a heptameric ring of 10K subunits, mediate protein folding in the cytosol of Escherichia coli. In the presence of nucleotide, GroES forms a 1:1 complex with GroEL which binds unfolded protein in its central cavity and releases it to allow folding upon ATP hydrolysis. Using labelling with azido-ATP, we have identified a protease-stable nucleotide-binding domain of M(r) 40K in the GroEL subunits (residues 153-531). Azido-ATP is crosslinked to the highly conserved Tyr 477, indicating that this residue is close to the purine ring of the bound nucleotide. Surprisingly, GroES also binds ATP cooperatively and with an affinity comparable to that of GroEL. Azido-nucleotide labelling of GroES subunits occurs at the conserved Tyr 71 in a protease-stable 6.5K domain (starting at residue 33). Proteinase K cleavage at residue 32 is prevented when GroES is bound to GroEL. ATP binding to GroES may be important in charging the seven subunits of the interacting GroEL ring with ATP to facilitate cooperative ATP binding and hydrolysis for substrate protein release.

Adenosine Triphosphate↗
PubMed1993

Cytoplasmic-nuclear translocation of the Hsp70 protein during environmental stress in Trypanosoma cruzi.

The present study provides immunological evidence of the constitutive presence of the Hsp70 protein in the cytoplasm of logarithmically growing T. cruzi parasites cultured at the normal temperature of 28 degrees C and of the translocation of the protein to the nucleus upon a heat shock treatment (2 hours at 37 degrees C). The nuclear translocation of the protein must depend on other factors beside the temperature per se since at 28 degrees C, in stationary phase growing parasites, the Hsp70 protein was present in both the cytoplasm and the nucleus. During recovery at 28 degrees C the protein leaves the nuclei but the nuclear-cytoplasmic translocation of the protein is a much more gradual process than its initial transport to the nucleus. Since the isoform of the nuclear Hsp70 is different from that found in the cytoplasm it is likely that before translocation to the nucleus the cytoplasmic Hsp70 nuclear precursor must undergo a specific modification.

Animals↗
PubMed1993

Protein folding in the cell: molecular chaperones pave the way.

In vitro, many unfolded polypeptides are able to fold to the native state spontaneously, indicating that the amino acid sequence of a protein contains all the information necessary to specify its three-dimensional conformation. It had been assumed that protein folding in vivo also generally occurs in a spontaneous process. This view has changed only recently due to the discovery of a number of proteins, now commonly called 'molecular chaperones', which are essential for cellular protein folding and occur ubiquitously in eubacteria, archaebacteria and in eukaryotic cells.

Adenosine Triphosphate↗
PubMed1993

Characterization of Clara and type II cells isolated from rat lung by fluorescence-activated flow cytometry.

A novel procedure for the isolation of Clara cells from rat lung is described. Single-cell suspensions from male F344/TOX rat lungs, prepared by subtilisin digestion, were treated with monochlorobimane (10 microM) and anlaysed by fluorescence-activated flow cytometry. A sub-population of about 2.8% of the total, showing the highest blue fluorescence and by inference the highest GSH concentration, was isolated as Clara cells of > 95% purity. Type II cells of similar purity were sorted after treatment with Phosphine 3R. Both sub-populations were > 90% viable, as judged by Trypan Blue exclusion. Comparison of CYP (cytochrome P-450) isoenzymes between these subpopulations, using Western blotting, showed CYP1A1 to be barely detectable. In Clara cells, CYP2B1 was 10-fold higher than in Type II cells. Mono-oxygenase activity towards the O-deethylation of 3-cyano-7-ethoxycoumarin was 2-fold higher in Clara cells. No activity was detected in macrophages. Pretreating rats with the mono-oxygenase inducers phenobarbitone, 3-methylcholanthrene or Aroclor 1254 showed the last-named to be the most potent inducer of CYP1A1. In Clara cells, CYP1A1 concentration and mono-oxygenase activities were induced > 2000- and 50-fold respectively, whereas in Type II cells increases of 300- and 3.6-fold were seen. Clara cells isolated from the lungs of control rats had a concentration of GSH (2.7 nmol/10(6) cells) that was 9- and 2-fold higher than that in Type II cells or macrophages respectively. GSH depleted by monochlorobimane treatment was restored after 2-3 h incubation with 0.2 M N-acetylcysteine. gamma-Glutamyltranspeptidase activity in Clara cells was 6- and 50-fold higher than in Type II cells or macrophages respectively.

Animals↗
PubMed1993

Localization of the mitogen activated protein kinase ERK2 in Alzheimer's disease neurofibrillary tangles and senile plaque neurites.

The phosphorylation of normal tau by mitogen activated protein (MAP) or extracellular signal related kinases (ERKs) induces tau to acquire biochemical properties of Alzheimer's disease (AD) paired helical filament (PHF) proteins in vitro. We show here that a monoclonal antibody to MAP kinases recognizes ERK2 in normal and AD cortex, but ERK2 levels are slightly reduced in the AD brain. Since ERK2 was detected in neurofibrillary tangles and senile plaque neurites in the AD hippocampus, ERK2 is positioned to phosphorylate normal tau and could play a role in the generation of PHFs in AD.

Aged↗
PubMed1993

Homology cloning of rat 72 kDa type IV collagenase: cytokine and second-messenger inducibility in glomerular mesangial cells.

Glomerular mesangial cells (MC) play a central role in the synthesis and turnover of the glomerular extracellular matrix. Prior studies [Davies, Thomas, Martin and Lovett (1988) Biochem. J. 251, 419-425; Martin, Davies, Thomas and Lovett (1989) Kidney Int. 36, 790-801] have characterized at the protein level a 72 kDa type IV collagenase that is secreted by cultured human and rat MC. While exposure of most cell types to interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha) or phorbol ester has little or even an inhibitory effect on 72 kDa type IV collagenase secretion, these factors significantly increased the synthesis of this enzyme by rat MC. Given this divergent pattern of expression, a homology-based PCR cloning strategy using rat MC cDNA templates was employed to define at the molecular level the structure of the mesangial 72 kDa type IV collagenase. The nucleotide sequence within the open reading frame of the rat mesangial 72 kDa type IV collagenase cDNA diverges from the sequence of the human homologue by approx. 9%. The divergence in the 3' untranslated region was much more extensive. Steady-state levels of the 3.1 kb transcript of the 72 kDa type IV collagenase were low or undetectable in resting MC, but were greatly stimulated following incubation with IL-beta, TNF-alpha or phorbol ester. None of these factors induced synthesis by MC of the closely related 92 kDa type IV collagenase. Synthesis by MC of the 72 kDa type IV collagenase was also induced by second-messenger analogues, including 8-bromo-cyclic AMP and forskolin. It is concluded that MC regulate the expression of this enzyme in an unusual, tissue-specific fashion. Cytokine and second-messenger inducibility may contribute to the enhanced expression of the enzyme during glomerular inflammatory disorders.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1993

Alteration in Gs-mediated signal transduction in S49 lymphoma cells treated with inhibitors of microtubules.

We have assessed the possible interaction between the microtubular component of the cytoskeleton and signal transducing GTP-binding (G) proteins by examining the ability of colchicine and vinblastine (two microtubule disrupters) to alter Gs and Gi protein activity in S49 lymphoma cells. Treatment of wild type S49 cells with cholchicine and vinblastine increased beta-adrenergic agonist- and prostaglandin (PG) E1-stimulated formation of cAMP. The microtubular inhibitor nocodazole also enhanced isoproterenol-stimulated cAMP accumulation, whereas the inactive analog of colchicine, beta-lumicolchicine, did not have this action. Based on data obtained with wild type, cyc-, and UNC S49 cells, we determined that enhancement in cyclic AMP accumulation is proximal to the catalytic (C) unit of adenylylcyclase, distal to hormone receptors, and seems to be located on Gs. Treatment with colchicine increased guanosine 5'-(gamma-thio)triphosphate-stimulated accumulation of cAMP in permeabilized wild type cells. The increase in activity of Gs appeared not to result from a change in the intracellular concentration of GTP. Treatment of cells with colchicine or vinblastine also increased the amount of the alpha s-C complex, as assessed by the binding of [3H]forskolin to intact cells at 37 degrees C. In contrast to the observed effect on Gs, treatment of wild type S49 cells with colchicine failed to modify the degree of inhibition of cAMP formation produced by somatostatin, which acts via the activation of Gi. These data suggest that microtubules regulate the ability of Gs to interact with and activate the catalyst of adenylylcyclase.

Adenylyl Cyclases↗
PubMed1993

Interferon-gamma regulation of C4 gene expression in cultured human glomerular epithelial cells.

The fourth component of human complement is mainly produced in liver, but extrahepatic gene expression has been reported in human renal tissue and other tissues, and is thought to contribute to the inflammatory reaction in local tissue. To identify the cellular origin of C4 synthesis in human kidney, we studied C4 gene expression and regulation by interferon-gamma (IFN-gamma) and C4 protein biosynthesis in isolated glomerular epithelial cells. cDNA/polymerase chain reaction analysis showed that C4 transcripts are present in glomerular epithelial cells (GEC), and that gene expression is up-regulated by IFN-gamma. Metabolic labeling studies showed that GEC synthesize and secrete C4 as three polypeptide chains of approximately 90, 70, and 30 kDa, which correspond to the bands produced by hepatoma cells. These results suggest that the fourth component of complement is produced by GEC. The GEC has an important role in the maintenance of glomerular barrier function, which is lost in a number of complement-dependent conditions; glomerular epithelial synthesis of C4 could have a bearing on the possible physiological or pathological roles of complement under different circumstances.

Base Sequence↗
PubMed1993

Pilot study of recombinant human granulocyte-macrophage colony-stimulating factor in the treatment of chronic hepatitis B.

Recombinant human granulocyte-macrophage colony-stimulating factor is being used to improve the immunological function of patients with various diseases and to ameliorate hematological disorders. We investigated the tolerance and possible antiviral effect of the administration of daily doses of recombinant human granulocyte-macrophage colony-stimulating factor (3, 1 or 0.5 micrograms/kg body wt) to nine patients with chronic hepatitis B, alone or in combination with 5 MU interferon-alpha 2b. Recombinant human GM-CSF reduced significantly (p < 0.02) hepatitis B virus DNA levels. The three doses used were equally effective. Of the eight patients who completed the study, four became negative for HBV DNA and HBeAg; two of them seroconverted to HBe antibody. These four patients showed improvement in the histological activity of their liver disease. Ultimately, two patients regained normal ALT values. 2',5'-Oligoadenylate synthetase activity increased significantly (p < 0.01) in cell lysates of mononuclear cells cultured in vitro, coinciding with the reductions in hepatitis B virus DNA levels. Recombinant human granulocyte-macrophage colony-stimulating factor was well tolerated but produced a dose-dependent increase in white blood cell counts. It became intolerable at doses of 3 micrograms (and was reduced to 1.5 microgram); this effect was reversible after cessation of recombinant human granulocyte-macrophage colony-stimulating factor treatment. No remarkable variations occurred in other parameters. In conclusion, recombinant human granulocyte-macrophage colony-stimulating factor administration is safe and tolerable at doses of 0.5 to 1 microgram/kg body wt and may exert an antiviral effect in chronic hepatitis B.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

1,25-Dihydroxyvitamin D3 and macrophage colony-stimulating factor-1 synergistically phosphorylate talin.

Macrophage colony stimulating factor (CSF-1) and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) are potent inducers of macrophage differentiation. Both appear to modulate protein phosphorylation, at least in part, through protein kinase C (PKC) raising the question as to whether they concurrently impact on macrophage-like cells. In this regard, we utilized the CSF-1 dependent murine macrophage-like line BAC 1.25F5. CSF-1 treatment of these cells for 30 min leads to particular phosphorylation of a 165 kDa protein, the putative CSF-1 receptor, and a 210 kDa moiety. 1,25(OH)2D3 exposure for 24 h prior to addition of CSF-1 enhances phosphorylation of the 165 kDa species and, especially, the 210 kDa protein. Phosphorylation of the latter protein is 1,25(OH)2D3 dose- and time-dependent and the molecule is specifically immunoprecipitated with a rabbit polyclonal anti-talin antibody. Experiments with okadaic acid show that the enhanced phosphorylation of talin does not result from serine phosphatase inhibition. CSF-1 and 1,25(OH)2D3, alone or in combination, do not increase talin protein expression. The tyrosine kinase inhibitor, genestein, blocks 1,25(OH)2D3/CSF-1 induced phosphorylation of the putative CSF-1 receptor but has no effect on talin phosphorylation which occurs exclusively on serine. In contrast to genestein, staurosporin, an inhibitor of PKC, inhibits phosphorylation of talin. Moreover, exposure of 1,25(OH)2D3 pretreated cells to phorbol 12-myristate 13-acetate (PMA) in place of CSF-1 also prompts talin phosphorylation. Finally, 1,25(OH)2D3 enhances 3[H]PDBu binding, indicating that the steroid increases PMA receptor capacity. Thus, CSF-1 and 1,25(OH)2D3 act synergistically via PKC to phosphorylate talin, a cytoskeletal-associated protein.

Alkaloids↗
PubMed1993

Characterization of minor and major antigenic regions within the hepatitis B virus nucleocapsid.

Hepatitis B core antibodies (anti-HBc) appear very early during the course of the hepatitis B virus infection and often persist years after viral clearance. In order to characterize the immunodominant domain of the HBcAg, the human immune response against the HBV nucleocapsid (HBcAg) was analyzed by using 14 synthetic peptides. Anti-HBc antibodies were detected by an indirect enzyme-linked immunosorbent assay (ELISA) with HBc peptides. Results suggest that the anti-HBc response is heterogeneous and directed against the whole primary structure of the HBc protein. Results also indicate that the epitopes recognized by anti-HBc antibodies can vary with the stages of the disease. In most sera from patients with serological evidence of acute HBV infection, anti-HBc antibodies recognized all the HBc peptides; conversely, after the acute phase, anti-HBc antibodies recognized predominantly epitopes located within the central region of the HBc protein from residue 74 to 123. Our results suggest that the HBV core protein is made up of two antigenic regions: a major one expressing a family of immunodominant epitopes from residue 74 to 123, whereas the minor encompasses the rest of the protein. The concept of the conformational nature of the unique HBcAg determinant is discussed, suggesting numerous families of linear epitopes.

Amino Acid Sequence↗