PubMed Health⌕ Search

Biomedical subjects

S Handwerger

Publications and source records attributed to S Handwerger.

At least 73 records · Page 4Linked to original sources
PubMed1993

Endothelins stimulate the synthesis and release of prorenin from human decidual cells.

The factors that regulate the synthesis and release of renin by human decidua and other extrarenal tissues are poorly understood. Recent studies have demonstrated that the potent vasoconstrictive peptide endothelin (ET) inhibits the release of renin from renal juxtaglomerular cells, probably by a calcium-dependent mechanism. To determine whether ET also influences the release of renin from decidual tissue, we have examined the effects of ET on the synthesis and release of renin by primary cultures of human decidual cells. Decidual cells exposed continuously to ET (10(-7) mol/L) for 96 h released significantly more renin than control cells. At 48, 72, and 96 h, the ET-exposed cells released 284, 645, and 1300% more renin, respectively, than control cells. Greater than 95% of the renin released into the medium was in the form of prorenin, the precursor of renin. The stimulation by ET was dose-dependent, with half-maximal stimulation at a concentration of 7 x 10(-9) mol/L. ET-2 and ET-3, as well as the precursor to ET (big ET), also stimulated renin release. The total amount of renin in the media and cells of ET-exposed decidual cells was significantly greater than that of control cells, indicating that the increase in renin release was accompanied by an increase in synthesis. In addition, Northern blot analysis of total RNA from cells exposed for 96 h to ET-1 (10(-7) mol/L) indicated that the renin messenger RNA content of ET-1-exposed cells was approximately 100 times greater than that of control cells. These results indicate that ET is a potent stimulus to the synthesis and release of prorenin from human decidua and that the effect of ET on decidual renin expression is opposite to that observed for the expression of renal renin.

Cells, Cultured↗
PubMed1992

Insertional inactivation of a gene which controls expression of vancomycin resistance on plasmid pHKK100.

Expression of inducible high level vancomycin resistance (Vmr) in enterococci appears to require other plasmid-encoded genes in addition to the previously described structural genes vanA and vanH. Tn917 mutagenesis was used to identify such a region in the Vmr plasmid pHKK100. Insertional inactivation of a 693-bp open reading frame upstream from vanH resulted in complete loss of Vmr. This putative 26,642-Da protein has been designated VanR.

Amino Acid Sequence↗
PubMed1992

Concomitant high-level vancomycin and penicillin resistance in clinical isolates of enterococci.

Enterococci are important nosocomial pathogens among which resistance to multiple antibiotics is being recognized with increasing frequency. We characterized three clinical isolates from three New York City hospitals that demonstrated concomitant resistance to vancomycin (one VanA, two VanB phenotypes) and high-level resistance to penicillin. Two Enterococcus faecium strains were intrinsically highly resistant to penicillin and showed very low affinity for penicillin of penicillin-binding protein 5. Unlike previously described glycopeptide-resistant enterococci, these strains were not hypersusceptible to beta-lactam agents after vancomycin induction, and combinations of penicillin and vancomycin were not synergistic against them. A third isolate, Enterococcus faecalis, produced beta-lactamase. Two of the three strains were also highly resistant to all aminoglycosides. Emergence of concomitant high-level resistance to multiple antibiotic classes among enterococci considerably narrows the therapeutic options for treatment of infections due to these opportunistic pathogens.

Aged↗
PubMed1992

Comparative in vitro activities of teicoplanin, daptomycin, ramoplanin, vancomycin, and PD127,391 against blood isolates of gram-positive cocci.

The in vitro activities of teicoplanin, daptomycin, ramoplanin, and PD127,391, a new quinolone, were compared with that of vancomycin. Teicoplanin showed the lowest MICs against Enterococcus faecalis. Ramoplanin was slightly more active than the other peptide antibiotics against oxacillin-resistant Staphylococcus aureus. The MICs of the four peptide antibiotics were similar for the oxacillin-susceptible S. aureus. Daptomycin had good activity against staphylococci but was the least active agent against E. faecalis. The MICs of vancomycin against all isolates were in general higher than those of the new antibiotics, with the exceptions of the MICs of daptomycin against E. faecalis and teicoplanin against oxacillin-resistant Staphylococcus epidermidis. PD127,391 was the most active agent against all staphylococcal isolates.

Anti-Bacterial Agents↗
PubMed1992

The cytoplasmic peptidoglycan precursor of vancomycin-resistant Enterococcus faecalis terminates in lactate.

Vancomycin resistance plasmids in enterococci carry the genes vanH and vanA, which encode enzymes catalyzing, respectively, the reduction of 2-keto acids to 2-D-hydroxy acids and the addition of D-hydroxy acids to D-alanine. It has therefore been postulated that resistant cells produce peptidoglycan precursors that terminate in the depsipeptide D-alanine-2-D-hydroxy acid rather than the dipeptide D-alanine-D-alanine, thus preventing vancomycin binding (M. Arthur, C. Molinas, T. D. H. Bugg, G. D. Wright, C. T. Walsh, and P. Courvalin, Antimicrob. Agents Chemother. 36:867-869, 1992). In the present work, a cytoplasmic peptidoglycan precursor was isolated from vancomycin-resistant Enterococcus faecalis and analyzed by mass spectrometry, which suggested the structure UDP-N-acetyl-muramyl-L-Ala-D-Glu-L-Lys-D-Ala-D-lactate.

Amino Acid Sequence↗
PubMed1992

High density lipoproteins stimulate molecular weight 80K protein phosphorylation in human trophoblast cells: evidence for a protein kinase-C-dependent pathway in human placental lactogen release.

Previous studies from our laboratory have demonstrated that high density lipoprotein (HDL) HDL and apolipoprotein-AI (apoAI) stimulate human placental lactogen (hPL) release from human trophoblast cells. To determine whether protein kinase-C (PKC) activation is involved in the mechanism of HDL- and apoAI-mediated hPL release, we examined the effects of these factors on the phosphorylation of cytosolic proteins known to be phosphorylated in response to PKC activation by phorbol myristate acetate (PMA). HDL and apoAI each caused a dose- and time-dependent increase in phosphorylation of a PMA-inducible 80K mol wt acidic cytosolic protein in a manner similar to that observed in many other cell types. Stimulation of 80K protein phosphorylation was apparent 5 min after the addition of HDL, apoAI, or PMA and was maximal at 15 min. Maximal 80K protein phosphorylation in cells exposed to PMA (1.6 microM), HDL (1500 micrograms/ml), and apoAI (600 micrograms/ml) was 284%, 206%, and 239% that in untreated cells, respectively. The increase in both 80K protein phosphorylation and hPL release in response to apoAI was prevented by pretreatment of the cells with the PKC inhibitor staurosporine (10 microM) or by down-regulation of PKC after extended preincubation of the cells with 16 microM PMA. (Bu)2cAMP and the adenylate cyclase activator forskolin, which stimulate hPL release, had no effect on 80K protein phosphorylation. These results strongly suggest that HDL- and apoAI-stimulated hPL release involves a PKC-dependent pathway. Since earlier studies also implicate a cAMP-mediated pathway in the stimulation of hPL release by these agents, it appears that multiple intracellular pathways are involved in the stimulation of hPL release.

Apolipoprotein A-I↗
PubMed1991

Melittin stimulates phosphoinositide hydrolysis and placental lactogen release: arachidonic acid as a link between phospholipase A2 and phospholipase C signal-transduction pathways.

Previous investigations from this laboratory have implicated both phospholipase A2 and phospholipase C in the regulation of human placental lactogen release from human trophoblast. To study further the role of endogenous phospholipase A2 and the relationship between phospholipase A2 activation and phosphoinositide metabolism, we examined hPL and [3H]-inositol release from trophoblast cells in response to agents that stimulate or inhibit the endogenous enzyme. Melittin (0.5-2.0 micrograms/ml) stimulated rapid, dose-dependent, and reversible increases in the release of hPL, prostaglandin E, and [3H]-inositol. Mepacrine (0.1-0.25 mM) inhibited this stimulation. However, mepacrine had no effect on the stimulation of hPL and [3H]-inositol release by exogenous arachidonic acid (AA). These results indicate that the stimulation by melittin of phosphoinositide metabolism and hPL release is mediated by initial activation of phospholipase A2. Furthermore, the results support the possibility that AA, released as a consequence of phospholipase A2 activation, can act as a second messenger linking the two phospholipase pathways.

Arachidonic Acid↗
PubMed1991

Autocrine/paracrine regulation of prolactin release from human decidual cells.

Studies from this laboratory indicate that the synthesis and release of prolactin from human decidual cells are regulated by factors released by the placenta, decidua and fetal membranes. A 23.5 kD protein (decidual prolactin-releasing factor, PRL-RF) has been purified to homogeneity from human placental tissue and placental conditioned medium. The releasing factor stimulates an acute release of prolactin that occurs within the first few minutes of exposure and a prolonged release, secondary to new hormone synthesis, that begins about 6-8 hours later. In addition, the synthesis and release of decidual prolactin are stimulated by IGF-I, insulin and relaxin, each acting through distinct plasma membrane receptors. In contrast, the synthesis and release of decidual prolactin are inhibited by arachidonic acid, lipocortin I and a 35-45 kD decidual protein (prolactin-releasing inhibitory factor) that has been partially purified from decidual conditioned medium. Studies of the second messengers involved in the regulation of decidual prolactin release strongly suggest that decidual prolactin release may be mediated, at least in part, by activation of phosphoinositide metabolism and stimulation of adenylate cyclase. The demonstration that the synthesis and release of decidual prolactin are regulated by PRL-RF, IGF-I, insulin, relaxin, arachidonic acid, PRL-IF and lipocortin I strongly suggests that there is novel autocrine/paracrine feedback regulation between the placenta, fetal membranes, and decidua in the regulation of decidual prolactin.

Decidua↗
PubMed1991

Clinical counterpoint: the physiology of placental lactogen in human pregnancy.

In summary, current evidence strongly suggests that PL may play a pivotal role during pregnancy, acting through distinct PL receptors to regulate and coordinate growth and metabolism in the mother and fetus. In early and midgestation, PL may be secreted preferentially into the fetal circulation, exerting growth-promoting effects at a time when the rate of linear growth of the fetus is maximal. Subsequently, during the latter half of pregnancy, the metabolic actions of PL in the mother and fetus may predominate, ensuring the optimal supply of nutrients to the fetus and utilization of the nutrients by fetal tissues. It therefore appears that PL affects fetal growth both by exerting effects on the fetus and the mother. Although hPL acts as "growth hormone of pregnancy," the regulation of the synthesis and secretion of hPL appears to be markedly different than that of GH.

Female↗
PubMed1991

Lipocortin-I inhibits the synthesis and release of prolactin from human decidual cells: evidence for autocrine/paracrine regulation by lipocortin-I.

The lipocortins are a family of calcium-dependent phospholipid-binding proteins that are induced by glucocorticoids and inhibit phospholipase-A2 activity. To determine whether the lipocortins affect the release of PRL from human decidua, decidual cells from term pregnancies were exposed to recombinant lipocortin-I for 96 h, with medium changes at 24-h intervals. Lipocortin-I (0.01-100 nM) caused a time- and dose-dependent inhibition of PRL release, with a half-maximal effective dose of 50 nM. PRL release was inhibited by 27%, 62%, 93%, and 98% at 24, 48, 72, and 96 h, respectively. The cells exposed to lipocortin-I did not release the enzymes alkaline phosphatase and lactic dehydrogenase, indicating that the inhibitory effect on PRL release was not due to cell death. In addition to inhibiting basal PRL release, lipocortin also completely inhibited the stimulation of PRL release by decidual PRL-releasing factor, a 23.5-kDa protein recently purified from human placenta that stimulates the synthesis and release of decidual, but not pituitary, PRL. Hydrocortisone and dexamethasone (0.1-10 microM) had no effect on PRL release, and arachidonic acid (2-100 microM) inhibited rather than stimulated PRL release. Western blot analysis demonstrated the presence of lipocortin-I in decidual cells and conditioned media. On Northern blot, decidual mRNA hybridized to an oligonucleotide for lipocortin-I. These results strongly suggest that lipocortin-I has an autocrine/paracrine role in regulation of the synthesis and release of PRL from human decidual cells.

Annexins↗
PubMed1990

Prognostic significance of quantitative levels of HIV p24 binding capacity in HIV infection.

Human immunodeficiency virus, type 1 (HIV-1), produces a chronic infection with a long latency before clinical disease. We followed 214 untreated subjects for 12-42 months to study the natural history of HIV infection: 110 were classified as asymptomatic, 11 as AIDS-related complex (ARC), 15 as AIDS with Kaposi's sarcoma (KS), 31 as AIDS with opportunistic infections (AIDS/OI), and 47 were HIV-seronegative controls. The quantitative capacity of serum to complex HIV p24 antigen, termed the p24 binding capacity (p24 BC), and quantitative levels of HIV p24 antigen in serum were determined at regular intervals. For people in all diagnostic groups, a p24 BC below 31 ng/ml was more closely associated with progression to AIDS/OI than was p24 antigen positivity; 94% of AIDS/OI, 86% of ARC, 56% of AIDS/KS, and 19% of asymptomatic subjects had p24 BC less than 31 ng/ml during the study period, while 67% of AIDS/OI, 27% of ARC, 61% of AIDS/KS, and 20% of asymptomatic subjects were p24 antigenemic. Prospective analysis of 47 asymptomatic seropositive men followed for 3 years, who showed actuarial progression rates to ARC at 4%, 13%, and 23% and to AIDS at 5%, 8%, and 8% at 1, 2, and 3 years, indicated that entry levels of p24 BC below 31 ng/ml were as strongly associated with progression to ARC/AIDS as was p24 antigenemia (p = 0.0003 vs. p = 0.008). The p24 binding capacity assay is a new and convenient methodology to measure immunocomplexing antibody to HIV p24 and is a powerful indicator of progressive HIV disease.

AIDS-Related Complex↗
PubMed1990

Induction of vancomycin resistance in Enterococcus faecium by inhibition of transglycosylation.

Vancomycin resistance has recently been recognized among clinical isolates of enterococci. Resistance is inducible, and associated with production of a novel 39 kDa membrane protein. The mechanism by which exposure to vancomycin, which does not penetrate the cell membrane, induces resistance is unknown. In the vancomycin resistant strain Enterococcus faecium 228, resistance was also inducible by moenomycin, suggesting that inhibition of the transglycosylation step in peptidoglycan synthesis may be required for induction of resistance. Cytoplasmic pools of peptidoglycan precursors were increased after exposure to vancomycin or moenomycin, representing a potential means for regulation of induction.

Cytoplasm↗
PubMed1990

Vancomycin resistance is encoded on a pheromone response plasmid in Enterococcus faecium 228.

In Enterococcus faecium 228, vancomycin resistance is encoded on a 55-kilobase conjugative plasmid, pHKK100. This plasmid was transferred with high frequency into susceptible strains of Enterococcus faecalis and conferred responses to pheromones produced by E. faecalis and Streptococcus sanguis. pHKK100 is the first plasmid described that mediates both vancomycin resistance and pheromone response.

Conjugation, Genetic↗
PubMed1990

Differential regulation of insulin-like growth factor binding protein secretion from human decidual cells by IGF-I, insulin, and relaxin.

Several growth hormone-independent 25-31,000 kD insulin-like growth factor binding proteins (IGF-BPs) have been identified in plasma, extravascular fluids, and various cell-conditioned media. Cultured human decidual cells release three IGF-BPs with 24,000, 30,000, and 34,000 Mr. Using ligand blot analysis and an RIA for the 30,000-Mr form (IGF-BP-1), we examined the effects of IGF-I (10-1,000 ng/ml), insulin (10-10,000 ng/ml), and relaxin (10-250 ng/ml) on decidual cell IGF-BP release after 120 h of hormone exposure. IGF-I inhibited release of both IGF-BP-1 and the 24,000 Mr form. Inhibition of IGF-BP-1 release was noted after 48 h of treatment and was progressive throughout the subsequent 120 h. Insulin stimulated a fourfold increase in release of the 24,000-Mr protein while inhibiting IGF-BP-1 release comparable to IGF-I, alpha-IR3, a monoclonal antibody to the IGF-I receptor, blocked approximately 33% of the IGF-I response but had no effect on insulin-mediated IGF-BP-1 inhibition. Relaxin stimulated a 2.4-fold increase in release of the 24,000-Mr form and a 16-fold increase in the 30,000-Mr protein after 120 h. Stimulation of the 30,000-Mr protein was inhibited by the addition of cycloheximide (50 micrograms/ml). Both IGF-I and insulin also blocked the relaxin-mediated increase in IGF-BP-1. These studies suggest that three structurally related proteins differentially regulate IGF-BP secretion possibly via activation of distinct receptor subtypes.

Antibodies, Monoclonal↗
PubMed1990

Three distinct forms of insulin-like growth factor binding proteins are released by decidual cells in culture.

Recent studies have shown that human decidual explants synthesize a 25,272 dalton form of insulin-like growth factor binding protein (IGFBP-1) that is identical to the most abundant form of IGFBP detected in human amniotic fluid. To determine whether decidual cells also secrete other structurally distinct forms of IGFBP, conditioned medium obtained from human decidual cells was analyzed by ligand blotting and immunoblotting using antisera that were specific for IGFBP-1 or 2. IGFBP-2 is a form of binding protein that is structurally distinct from IGFBP-1. Ligand blotting analysis (which detects all forms of IGFBPs) showed that 3 forms of IGFBP with Mr estimates of 34,000, 30,000 and 24,000 were present in basal, unstimulated, conditioned media. Immunoblotting showed that the 30,000 Mr form reacted with an antibody that is specific for IGFBP-1, whereas the 34,000 Mr form reacted with an antibody that is specific for IGFBP-2. The 24,000 Mr band did not react with antisera to either IGFBP-1 or 2. Basal IGFBP-1 release from human decidual cultures, as measured by RIA, showed a significant decrease during the 5 day period from 34 +/- 1.6 on day 1 to 12 +/- 1.9 ng/ml on day 5. Exposure of the cells to (Bu)2cAMP (1.0 mM) for 5 days had no significant effect on IGFBP-1 release during the first day of exposure, but caused a progressive stimulation of release during the subsequent 4 days. By day 5, exposure to (Bu)2cAMP induced a 5- to 6-fold increase in IGFBP-1 release that was completely inhibited by exposure to cycloheximide. Exposure of the cells to cholera toxin (0.1 micrograms/ml) for 4 days caused a 3.7-fold increase in IGFBP-1 release. The stimulation of IGFBP-1 release by (Bu)2cAMP was completely inhibited by simultaneous exposure to insulin (100 ng/ml) and/or IGF-I (100 ng/ml) (day 5 control = 35 ng/ml, (Bu)2cAMP alone = 248 ng/ml, insulin + (Bu)2cAMP = 36 ng/ml, or IGF-I + (Bu)2cAMP = 10.1 ng/ml). Hydrocortisone and the phorbol ester (phorbol myristate acetate) caused no significant changes in basal IGFBP-1 release but prevented the decrease in the basal rate of release that occurred between day 1 and 5. Ligand blotting studies showed that the 24,000 Mr form of binding protein was also stimulated by (Bu)2cAMP (3.3-fold increase); however, cholera toxin and phorbol myristate acetate were without effect. In contrast, the release of the 34,000 Mr form was unaffected by exposure to any of these agents, suggesting that regulation of this form of IGFBP is distinct from the other 2 forms.(ABSTRACT TRUNCATED AT 400 WORDS)

Bucladesine↗
PubMed1990

Relaxin stimulates the synthesis and release of prorenin from human decidual cells: evidence for autocrine/paracrine regulation.

Porcine relaxin caused a time- and concentration-dependent increase in the release of renin from decidual cells cultured over a 96 h period. The increase in renin release occurred 24-48 h after exposure and was maximal at 48-72 h. Half-maximal stimulation occurred at a relaxin concentration of 5 ng/ml, and maximal stimulation (250-270%) occurred at concentrations greater than or equal to 10 ng/ml. At each time, greater than 95% of the renin released into the medium was in the form of prorenin. The stimulation of renin release was paralleled by a stimulation of cellular renin content and was completely inhibited by cycloheximide, indicating that relaxin also stimulated renin synthesis. Since renin is present in both cytotrophoblast and decidual cells, these results suggest a paracrine and/or autocrine relationship between relaxin- and prorenin-secreting cells.

Cells, Cultured↗
PubMed1989

Synthetic amphipathic peptides resembling apolipoproteins stimulate the release of human placental lactogen.

Previous studies from our laboratory demonstrated native high density lipoproteins and apolipoproteins AI, AII, and CI, stimulate the release of human placental lactogen (hPL) from trophoblast cells in culture. To examine the mechanisms by which these apolipoproteins stimulate hPL release, we have studied hPL secretion in response to several synthetic peptide analogs of the amphipathic helical structure of the apolipoproteins. The magnitude of the stimulation of hPL release in response to the analog peptides correlated with the ability to displace apolipoproteins from high density lipoprotein and with other measures of phospholipid binding affinity such as the increase in alpha-helicity and the size of complexes formed between the peptide and phospholipid. The correlation of stimulatory ability and lipid affinity suggests that the action of the apolipoproteins on hPL release may be mediated through an interaction with plasma membrane phospholipids.

Amino Acid Sequence↗