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D Salomon

Publications and source records attributed to D Salomon.

At least 109 records · Page 6Linked to original sources
PubMed1987

Nitrogenase MoFe protein subunits from Klebsiella pneumoniae expressed in foreign hosts. Characteristics and interactions.

The expression of selected nitrogen fixation (nif) genes from Klebsiella pneumoniae in foreign hosts provides an approach to determine the pathway, minimal genetic requirements, and host dependence of nitrogenase assembly. In this study, we investigated the assembly of the alpha 2 beta 2 MoFe protein, responsible for substrate binding and reduction, by introducing nifD and nifK (encoding respectively, the alpha and beta subunits) into Escherichia coli and the yeast Saccharomyces cerevisiae. In E. coli, both genes were expressed from the nifHDKY operon; in yeast, the genes, separately fused to the yeast ADH1 promoter, were introduced on two different plasmids. Denaturing immunoblot analyses demonstrated the presence of significant amounts of NifD and NifK in both hosts. In E. coli, the level or perhaps modification of NifD depended on the growth medium of the bacteria. Nondenaturing, anaerobic immunoblot assays revealed in E. coli, nif-specific antigens of lower electrophoretic mobility than Kp1, which may represent assembly intermediates. In yeast, no putative assembled products were evident, and the predominant antigens corresponded to the monomeric forms of the polypeptides. These results indicate that, unlike NifH, the Fe protein subunit (Berman, J., Gershoni, J. M., and Zamir, A. (1985) J. Biol. Chem. 260, 5240-5243), NifD and NifK are insufficient for the assembly of an electrophoretically Kp1-like structure. Homodimerization of nifK and probably of nifD primary gene products does not appear to occur spontaneously and hence is unlikely to represent the initial step in the assembly. The difference between the two hosts suggests that the cellular environment or mode of expression could affect the interaction between the two subunits.

Escherichia coli↗
PubMed1987

Contact-dependent regulation of vinculin expression in cultured fibroblasts: a study with vinculin-specific cDNA probes.

Vinculin specific cDNA clones were isolated from chicken embryo fibroblast (CEF) cDNA library in lambda gt11. The clones, ranging in size from 2.8 to 5.0 kb, were initially selected by rabbit antibodies to vinculin. Their identity was further confirmed by their specific reactivities with a battery of different vinculin-specific monoclonal antibodies. Southern blot analysis of restriction enzyme digested chicken spleen DNA suggested that all the isolated cDNA clones correspond to the same gene(s). Northern blot hybridization revealed that the vinculin-specific cDNA clones react with a single 6.5 kb mRNA in total cellular RNA preparations of CEF, whole chicken embryos and chicken gizzard smooth muscle. Moreover, fractionation of CEF poly(A)+ RNA by sucrose gradient centrifugation followed by translation in cell free system indicated that the mRNA coding for vinculin has a size of about 6.0-7.0 kb. The identity of these clones was finally confirmed by selection hybridization assay. The isolated vinculin-specific cDNA probes were subsequently used in order to study the effect of substrate adhesiveness on the expression of vinculin. We show here that cells cultured on highly adhesive substrate, such as endothelial extracellular matrix (ECM), form large vinculin-rich focal contacts, while cells grown on poorly adhesive substrate poly(2-hydroxyethyl methacrylate) [poly(HEMA)] contain only small distorted vinculin spots. These morphological differences were accompanied by over 5-fold reduction in vinculin synthesis in cells growing on poly(HEMA), compared to those cultured on the ECM and over 7.5-fold decrease in the levels of vinculin-specific mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Pathway of granule formation in Merkel cells: an ultrastructural study.

Merkel cells (MC) are characterized by dense core granules morphologically similar to secretory granules of endocrine cells, as well as the presence in their cytoplasm of organelles involved in polypeptide synthesis. The aim of this study was to follow the pathway of granule formation in MC. Four compartments, the cis and trans Golgi cisternae, the condensing granules in the Golgi stacks, the bristle-coated granules, and the noncoated granules, are observed by transmission electron microscopy in MC. This suggests that: (1) the organelles usually involved in the formation of secretory polypeptides are present in the cytoplasm of MC; (2) the pathway of Merkel cell granule (MCG) formation appears to be similar to that of secretory endocrine or exocrine cells; and (3) MC might be involved in a secretory process.

Animals↗
PubMed1987

Human skin retinoid-binding proteins and therapy with synthetic retinoids: a still unexplained link.

Human skin contains several proteins that could bind retinoids. One is the retinol-binding protein (RBP, the plasma carrier of natural vitamin A, retinol, which was found to also bind retinoic acid (RA) in vitro. A polyacrylamide gel electrophoresis technique followed by protein immunoblot analysis with an antiserum specific against RBP was developed. This technique allowed us to study the binding of several natural and synthetic retinoids to the plasma RBP; it was found that only natural retinoids bind to RBP in vitro; RA binding was found to induce major conformational changes in the protein. The technique was then used for the study of RBP in human epidermal and dermal extracts; this showed that RBP degradation with loss of binding properties for retinol occurred within the epidermis. A polyacrylamide gel electrophoresis binding assay was developed for studying cellular retinol-(CRABP) and retinoic acid-(CRABP) binding protein in human skin cytosolic extracts. CRABP was (1) found at much higher levels in normal epidermis than in the dermis (2); dramatically elevated in psoriatic plaques and in some retinoid-responsive dermatoses, and (3) up-modulated by both topical and systemic administration of natural and synthetic retinoids. Such alterations were not observed for CRBP. From these and other observations presented here, it appears that CRABP should be one of the first candidates to be carefully analyzed in the search of the cellular receptor for the mediation of the synthetic retinoids pharmacological effects.

Benzoates↗
PubMed1986

Immunological detection and quantitation of alpha transforming growth factors in human breast carcinoma cells.

Alpha transforming growth factors (alpha TGFs) were immunologically detected in the concentrated conditioned medium (CM) prepared from four human breast cancer cell lines and from primary cultures of human mammary epithelial cells, and in the tissue extracts prepared from normal, benign, and malignant breast biopsies. Immunoreactive alpha TGFs were quantitated by a competitive radioimmunoassay (RIA) using affinity-purified polyclonal sheep anti-rat alpha TGF antibodies which react with human alpha TGF but not with human epidermal growth factor (EGF). The relative level of RIA-detectable alpha TGFs in the CM from the breast cancer cell lines MCF-7, ZR-75-1, T47-D, and MDA-MB-231, and from the CM of primary cultures of human mammary epithelial cells, ranged from 0.02 to 0.85 ng/ml. MCF-7 or ZR-75-1 cells grown in the presence of 17 beta-estradiol (10(-8) M) for 48 h were found to release two- to three-fold more alpha TGFs into their CM than the same cells grown in the absence of estrogen. In detergent extracts prepared from normal breast tissue, a benign fibrocystic lesion, fibroadenomas and primary breast carcinomas, the relative alpha TGF concentrations were found to range from 1.5 to 6 ng/mg cell protein. No significant correlations were found between the alpha TGF levels and the pathological state of the tissues, the estrogen receptor status of the tumors, or the relative amounts of the ras gene protein p21ras in the tissues as determined by Western immunoblot analysis. The question of biological relevancy of alpha TGF for human mammary tumors will require further studies on synthesis and turnover of alpha TGF, the relationship between immunoreactivity and biological activity of alpha TGF, and differences in biological responsiveness of mammary tumor cells.

Breast Neoplasms↗
PubMed1986

Heterogeneity and contact-dependent regulation of hormone secretion by individual B cells.

A reverse hemolytic plaque assay was developed to visualize insulin release from individual adult pancreatic B cells. Cells obtained by mechanical dispersion of isolated rat islets of Langerhans were mixed with protein A-coated sheep red blood cells and incubated in the presence of an anti-insulin serum, under conditions known to affect insulin release. The cell mixture was further incubated with complement and finally fixed. Insulin release was revealed by the presence of hemolytic plaques which resulted from the complement-mediated lysis of red blood cells bearing insulin-anti-insulin complexes bound to protein A. Quantitation of hemolytic plaques around trypan blue-unstained and immunohistochemically identified B cells showed that stimulation of insulin release results in the recruitment of increasing numbers of secreting B cells as well as in the enhanced response of individual B cells. Reverse changes occur upon inhibition of insulin release. Comparison of freshly dispersed and one-day-cultured preparations did not reveal significant differences in the secretory response of undamaged B cells. In both preparations, single B cells responded to secretagogues in smaller proportions and to a lesser extent than clusters in which B cells had either maintained or restored contacts and junctional communication with their neighbours. However, the overall preponderant response of clusters was less than expected from the number of individually secreting B cells they contained. The data show that B cells are heterogeneous in terms of their ability to release insulin and provide evidence that cell-to-cell adhesion and/or junctional communication regulate hormone secretion from individual B cells.

Animals↗
PubMed1986

Skin cellular retinoid-binding proteins and retinoid-responsive dermatoses.

We have previously found an important increase of cellular retinoic acid-binding protein (CRABP) in psoriatic plaques whereas the cellular retinol-binding protein (CRBP) was not elevated compared to normal human skin and nonlesional psoriatic skin. In the present study we analyzed CRABP and CRBP levels in a panel of dermatoses in order to address several questions raised by the above findings. Three observations were made: CRBP showed little or no variations whereas CRABP was either normal (seborrheic keratosis, lichenification, nonlesional psoriatic and nonlesional Darier disease skin) or elevated (psoriatic plaques, lamellar ichthyosis, lesional Darier disease, pityriasis rubra pilaris, keratosis pilaris); high levels of CRABP might indicate a greater sensitivity of the lesions to systemic synthetic retinoids with a carboxyl group in the C15 position, and systemic administration of etretin increased the levels of CRABP but not CRBP. These observations suggest that CRABP might be the receptor for synthetic retinoids in the skin and that its analysis might be useful in monitoring retinoid therapy.

Acitretin↗
PubMed1986

Oral gold therapy (Auranofin) in pemphigus vulgaris.

Auranofin (AF), an oral gold salt, was given for 9-18 months to 3 patients with pemphigus vulgaris. There was a slight improvement with significant oral pain relief in 2, and a complete remission in 1. Two patients including the one with the remission, subsequently flared up under AF therapy. Although AF is said to be better tolerated than parenteral gold this limited series suggests that it does not seem to have a superior therapeutic effect in PV.

Administration, Oral↗
PubMed1985

Priming immunization against cholera toxin and E. coli heat-labile toxin by a cholera toxin short peptide-beta-galactosidase hybrid synthesized in E. coli.

A synthetic oligodeoxynucleotide encoding for a small peptide was employed for the expression of this peptide in a form suitable for immunization. The encoded peptide, namely, the region 50-64 of the B subunit of cholera toxin (CTP3), had previously been identified as a relevant epitope of cholera toxin. Thus, multiple immunizations with its conjugate to a protein carrier led to an efficient neutralizing response against native cholera toxin. Immunization with the resulting fusion protein of CTP3 and beta-galactosidase, followed by a booster injection of a sub-immunizing amount (1 microgram) of cholera toxin, led to a substantial level of neutralizing antibodies against both cholera toxin and the heat-labile toxin of Escherichia coli.

Animals↗
PubMed1985

Expression of a nitrogen-fixation gene encoding a nitrogenase subunit in yeast.

Biological nitrogen fixation is catalyzed by nitrogenase, an enzyme complex exclusive to prokaryotes. We used the yeast Saccharomyces cerevisiae to study the synthesis, and subsequently the assembly, of nitrogenase components in a eukaryote. Here, the Klebsiella pneumoniae nifH gene, encoding the subunit of the Fe protein (Kp2) component of nitrogenase, was expressed in S. cerevisiae from the yeast ADHI promoter. The nifH gene product, detected in yeast by immunoblot analysis with anti-Kp2 antibodies, exhibited the same electrophoretic mobility in SDS-polyacrylamide gels as that of the Kp2 subunit synthesized in K. pneumoniae. Estimates of Kp2 antigen and assays of beta-galactosidase activity specified by nifH'-'lacZ fusions showed that the level of nifH product was similar in anaerobically and aerobically grown yeast, but varied with different transforming plasmids and in various haploid and diploid yeast strains. A cistron located downstream to nifH in a transcript resembling the polycistronic mRNA of the nifHDKY operon in K. pneumoniae is not translated in yeast.

Gene Expression Regulation↗
PubMed1985

Influence of spatial configuration of carcinoma cell populations on the expression of a tumor-associated glycoprotein.

Monoclonal antibody B72.3 was generated using a membrane-enriched fraction of cells from a mammary carcinoma metastasis and has been shown previously to have a high degree of selective reactivity for human breast and colon carcinoma versus normal adult tissues. The reactive antigen has been shown to be a high-molecular-weight glycoprotein complex of approximately 220,000 to 400,000 and is termed tumor-associated glycoprotein 72 (TAG-72). We report here a dichotomy in the expression of TAG-72 in carcinoma biopsy material versus carcinoma cell lines. While 44% (25 of 56) of human breast carcinoma and 80% (16 of 20) of colon carcinoma biopsies express TAG-72 as assayed by radioimmunoassay or immunohistochemistry, only one of 25 breast cancer cell lines [MCF-7 (one variant)] and one of 18 colon cancer cell lines (LS-174T) express this antigen. Furthermore, TAG-72 expression in these two cell lines was shown to be a property of a low percentage of cells within each culture. Attempts to enhance TAG-72 expression in LS-174T cells by propagation on extracellular matrix proteins, such as collagen, laminin, and fibronectin, or in serum-containing or serum-free, hormone-supplemented medium proved unsuccessful. A pronounced increase in TAG-72 expression was observed, however, when the LS-174T cells were grown under culture conditions which promote three-dimensional growth. LS-174T cells grown in spheroid or suspension cultures demonstrated a 2- to 7-fold increase in TAG-72 antigen expression, while those grown on agar plugs demonstrated a 10-fold increase. When the LS-174T cell line was injected into athymic mice to generate tumors, the level of TAG-72 antigen increased over 100-fold, to levels comparable to those seen in the metastatic tumor masses from patients. Thus, spatial configuration of carcinoma cell populations is shown to influence the expression of a tumor-associated antigen and the subsequent surface binding of monoclonal antibody B72.3. The implications of these findings in the potential utility of monoclonal antibodies for the in vivo detection and destruction of carcinoma masses are discussed.

Antibodies, Monoclonal↗
PubMed1982

A cloned immunoglobulin cDNA fragment enhances transposition of IS elements into recombinant plasmids.

Evidence is presented indicating that a novel DNA sequence arrangement generated by in vitro recombination may elicit high frequency transpositions of IS elements. A 109 bp Bam HI fragment of the cDNA for the immunoglobulin kappa light chain from MOPC 321 myeloma was cloned into the Bam HI site of pBR313. The cloned fragment extends from the codon for Gly 57 to the V-J junction. Insertions of IS1 or IS5 were identified in 6 of 50 plasmid DNAs isolated from freshly transformed clones. Additional transposition events were detected after subculturing for several growth cycles. Three independent insertions of IS1 occurred in the promoter region of the TcR operon. All IS5 and the remaining IS1 insertions were located in the TcR region upstream to the cloned DNA sequence. Sequences homologous to the ends of IS1, or corresponding to the consensus sequence at the target site of IS5 are present near the estimated sites of insertion of IS1 or IS5 respectively. Bacteria harboring recombinant plasmids carrying the cloned DNA in either orientation grew at a reduced rate relative to cells harboring pBR313, suggesting that fused gene products made from the two types of plasmid were inhibitory to cell growth. IS insertions, which relieved this inhibitory effect and thereby provided a selective advantage, were found exclusively in plasmids carrying the cloned DNA in only one of the two orientations. The fact that IS elements were not observed in the other type of recombinant plasmid indicates that selective pressure alone is not sufficient to account for the frequent IS insertions observed and that sequences at a distance from the site of IS insertion may be critical in the regulation of transposition frequency.

Animals↗
PubMed1980

Synthesis of part of a mouse immunoglobulin light chain in a bacterial clone.

We have cloned double stranded cDNA sequences encoding a mouse immunoglobulin light chain (L-321) into the PstI site of the beta-lactamase gene of plasmid pBR322 by the oligo (dG)-oligo (dC) tailing procedure. Escherichia coli X1776 transformed by the recombinant plasmids were screened for the expression of L-321 antigenic determinants by a newly developed in situ radio-immunoassay. One out of seven transformants screened was found to synthesize an L-chain like protein. Each bacterial cell produces about 550 molecules of the L-chain sequence. Preferential segregation of the L-chain sequence to the periplasmic space suggest covalent attachment of the L-chain sequence to the N-terminal portion of beta-lactamase. Restriction mapping of the plasmid DNA isolated from the positive clone indicated the presence of a DNA sequence coding for the entire constant region and extending into the variable region for a length corresponding to about 40 amino acid residues. The orientation of the cloned cDNA with respect to the plasmid DNA is compatible with the formation of a fused beta-lactamase-L-321 peptide.

Animals↗
PubMed1980

A phospholipase A2 inhibitory protein in rabbit neutrophils induced by glucocorticoids.

When rabbit peritoneal neutrophils were treated with glucocorticoids, their chemotactic response to stimulation by the chemoattractant fMet-Leu-Phe was markedly reduced. Preincubation of cells with glucocorticoids also decreased phospholipase A2 (phosphatide 2-acylhydrolase, EC 3.1.1.4) activity in situ as measured by the release of [1-14C]arachidonic acid previously incorporated into phospholipids. The inhibitory potencies of glucocorticoids on phospholipase A2 activity correlated well with their anti-inflammatory activities and their abilities to bind to glucocorticoid receptors. Inhibitors of RNA and protein synthesis suppressed the inhibitory effect of glucocorticoids on phospholipase A2 activity. Digestion of the glucocorticoid-treated cells by Pronase overcame the inhibitory activity. Phospholipase A2 activity induced by Ca2+ ionophore A23187 was not affected by Pronase treatment. Gel filtration of proteins from neutrophil membranes labeled with [3H]lysine showed an induction of protein(s) (about 40,000 daltons) after glucocorticoid treatment. This protein inhibited a partially purified pancreatic phospholipase A2 and reduced the peptide-initiated chemotactic response of neutrophils.

Animals↗
PubMed1975

Inhibitory effects of lipophilic acids and related compounds on bacteria and mammalian cells.

The inhibitory effect of lipophilic acids, antimicrobial food additives, and analgesics-antipyretics was examined at concentrations from 0.1 to 100 mM in bacteria (Bacillus subtilis and Escherichia coli) and mammalian cells (HeLa, human fibroblasts, and mouse neuroblastoma cells). Most compounds inhibit the growth of HeLa cells about as efficiently as that of B. subtilis. However, butyrate and propionate, as well as acetaminophen, antipyrene, phenacetin, and salicylamide, inhibit HeLa at millimolar concentrations whereas, at least 10 times higher concentrations are needed to inhibit B. subtilis. The concentrations needed to inhibit growth by 50% decrease with increasing octanol-water partition coefficients of the compound. Growth of E. coli is inhibited similar to that of B. subtilis by all compounds except butylbenzoate, decanoate, and linoleate which cannot penetrate the lipopolysaccharide layer. All growth inhibitors inhibit amino acid uptake into bacteria and their vesicles, and oxygen consumption in bacteria. In HeLa cells or human fibroblasts, neither amino acid uptake nor adenine 5'-triphosphate synthesis are inhibited by fatty acids at concentrations that completely inhibit growth. Short chain fatty acids (propionate, butyrate, and pentanoate) induce in HeLa the formation of cell processes. In neuroblastoma cells, grown in the presence of 10% fetal calf serum, butyrate also induces such processes which slowly continue to grow in length for at least 7 days; these processes differ in speed of formation, width, and cycloheximide susceptibility from the thin processes produced by serum deprivation alone.

Bacteria↗
PubMed1973

Growth inhibition and morphological changes caused by lipophilic acids in mammalian cells.

Human (HeLa, Chang liver, L-132, and Intestine 407) and other mammalian (XC, SV3T3, and chick-embryo) cells in tissue culture are at least as sensitive to inhibition by lipophilic acids and nitrite as bacteria. Some of these compounds are the most frequently used antimicrobial food additives. Short-chain fatty acids (up to hexanoate) and parabens induce, at partially inhibitory concentrations, a jagged cell shape in continuous epithelial-like cell lines, such as HeLa, Chang liver, L-132, and Intestine 407. This morphological effect is not mediated or enhanced by butyryl cyclic AMP, which specifically affects fibroblasts.

Animals↗