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Biomedical subjects

M Izhar

Publications and source records attributed to M Izhar.

At least 19 recordsLinked to original sources
PubMed2002

Correlation of Helicobacter pylori in dental plaque and gastric mucosa of dyspeptic patients.

OBJECTIVE: To establish the prevalence of Helicobacter pylori colonization of dental plaque and its correlation with Helicobacter pylori infection of the antral mucosa in patients with symptomatic dyspepsia. METHODS: Seventy eight adult dyspeptic patients undergoing upper gastrointestinal tract endoscopy were prospectively enrolled. Four air dried dental plaque cytology slides and four gastric antral mucosal biopsies were stained with Giemsa stain. CLO test was used for detection of urease activity of Helicobacter pylori in the dental plaque specimens and antral mucosal biopsies. Data on endoscopic findings and orodental hygiene were recorded. RESULTS: Dental plaque colonization using CLO test and cytology was found to be 100% and 88% respectively. Antral biopsy for H. pylori was positive in 61% cases by CLO test and 57% cases on histopathology. Forty four out of 69 patients (63%) had both dental plaque and antral biopsy positive for H. pylori. No patient with negative dental plaque cytology was positive for H. pylori in gastric mucosa. A statistically significant correlation was found between H. pylori colonization of dental plaque and gastric antrum. The sensitivity and specificity of dental plaque cytology in diagnosing H. pylori antral colonization was 100% and 26% while the positive and negative predictive values were 64% and 100% respectively. CONCLUSION: The prevalence of H. pylori in dental plaque of patients with dyspepsia was very high in our patients indicating it to be a major reservoir of infection.

Adult↗
PubMed2000

In-vitro antimicrobial activity of Cefpirome: a new fourth-generation cephalosporin against clinically significant bacteria.

OBJECTIVE: To study the in-vitro antimicrobial activity of Cefpirome: A new fourth generation Cephalosporin in comparison with other agents against clinically significant Gram-negative and Gram-positive bacteria. SETTING: A multi-center in-vitro study was conducted in 13 centers. MATERIALS AND METHODS: Bacterial isolates--A total of 1300 isolates were collected from different clinical laboratories and hospitals at 13 centers. Organisms were identified by the API identification systems (API systems, SA Vericeu, France). The age and sex of each patient, type of hospital unit, source of the isolate and genus and species of the bacteria were recorded on standardized report forms. The sensitivity testing was carried out by the "NCCLS (modified Kirby-Bauer) method"--using Mueller-Hinton agar. RESULTS: The results suggest that Cefpirome has a potential clinical advantage against gram-positive and gram-negative bacteria resistant to other third generation cephalosporins. CONCLUSION: Cefpirome was active against both gram-negative and gram-positive organisms. Cefpirome was more active than ceftazidime, cefoperazone, ceftizoxime and ceftriaxone against E. coli, Klebsiella spp, Enterobacter spp, Proteus spp, Salmonella typhi, Enterococci, methicillin sensitive Staphylococci and Betahemolytic Streptococci. The activity of Cefpirome was comparable with ceftazidime against pseudomonas aeruginosa. Cefpirome had the smallest numbers of resistant isolates. Cefpirome was more active than other third generation cephalosporins compared in this study against E. coli (87% vs 61%), Klebsiella spp (84% vs 56%), Enterobacter spp (88% vs 59%), Proteus spp (97% vs 92%), Salmonella typhi (98% vs 96%), methicillin sensitive Staphylococci (86% vs 59%) and Enterococci spp (82% vs 72%).

Bacteria↗
PubMed1992

Dexamethasone inhibition of cyclooxygenase expression in bovine term placenta.

Since both prostaglandin (PG) F2 alpha and corticosteroids are elevated in mammals before the onset of parturition, we studied the effect of the synthetic corticosteroid dexamethasone on PGF2 alpha accumulation and cyclooxygenase (prostaglandin synthase, PGS) expression in the bovine fetal placenta. Cultures were prepared from cotyledons at different stages of gestation. The effect of dexamethasone on PGF2 alpha accumulation and PGS expression was determined by radioimmunoassay and [35S]methionine metabolic labeling followed by immunoprecipitation with specific anti-cyclooxygenase antibodies, respectively. Data demonstrate that in fetal placental cells at term, both PGF2 alpha accumulation and cyclooxygenase expression are significantly inhibited after 18 hours of dexamethasone treatment (150 nM). In contrast, neither first nor second trimester cells were sensitive to dexamethasone treatment. Dexamethasone inhibition of PGF2 alpha synthesis in fetal cells at term was abolished in the presence of RNA or protein synthesis inhibitors (actinomycin D or puromycin, 10 micrograms/ml each). Neither progesterone nor 17 beta-estradiol accumulation were affected by dexamethasone treatment at any stage of gestation. Data suggest that corticosteroids play a role in parturition through PGF2 alpha synthesis regulation by fetal placental cells. Since abnormalities during parturition e.g. retained placenta, are common following dexamethasone induction of labor in cows, we postulate that the local inhibition of PGF2 alpha accumulation by cotyledon cells after corticosteroid administration, may be involved in placental retention.

Animals↗
PubMed1992

Bovine placental progesterone synthesis: comparison of first and second trimesters of gestation.

We have previously reported that dispersed caruncle cells from cows during the first trimester of pregnancy, in comparison to caruncle cells from cows of more than 90 days of gestation, produce little progesterone (P4) and are refractory to agents that enhance steroidogenesis. To explain this refractoriness of the first-trimester cells, we determined (1) the expression of cytochrome P450 side-chain cleavage (P450scc) and its mRNA, (2) the expression of adrenodoxin, and (3) 3 beta-hydroxysteroid dehydrogenase activity. We first determined P4 and pregnenolone (P5) production by dispersed caruncle cells from the two gestation periods using RIA. It was found that P4 synthesis by bovine maternal caruncle cells was low or undetectable in the first trimester but increased more than 10-fold in the second trimester of gestation. Addition of 25-OH-cholesterol (5 micrograms/ml) to second-trimester maternal cells increased P5 production, but no effect was observed in first-trimester cells. With [3H]P5 used as substrate, analysis of metabolites on thin-layer chromatography indicated that first-trimester maternal cells synthesized a small amount of P4 (3.02% of total radioactivity) compared to second-trimester cells (16.4%). A readily detectable amount of 17 alpha-OH-P5 was produced by the second-trimester cells (5.02%) but not by the first-trimester cells (0.6%). No other metabolites could be characterized (less than 0.5%). Cytochrome P450scc expression and its mRNA and adrenodoxin content were determined by use of Western blot or dot-blot techniques. Proteins and mRNA were detected in maternal tissues of first and second trimesters of gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

Regulation of steroidogenesis in the bovine placenta.

As pregnancy progresses in the cow, the secretory activity of the corpus luteum is markedly diminished. This reduced secretion is due to a decline in the number of viable luteal cells as well as reduction in the secretory activity and responsiveness of the cells to trophic agents. The principal extra-ovarian source of progesterone (P4) by mid-gestation therefore appears to be the placenta. Uniquely this P4 biosynthesis is cyclic-nucleotide independent, but the Ca+2 dependent. It therefore appears that the Ca+2 second messenger and protein kinase C systems are responsible for regulation of sterol biosynthesis in the cow placenta. Dispersed bovine caruncle cells from the first trimester of pregnancy in comparison to caruncle cells of older than 90 days of gestation produce little P4 and are refractory to agents which enhance placental steroidogenesis. In order to explain this refractoriness of the first trimester cells, we determine (1) the expression of P450scc and its mRNA and (2) the expression of adrenodoxin. It was found that P4 synthesis by bovine maternal caruncle cells was low or undetectable in the first trimester but increased more than 10-fold in the second trimester of gestation. Addition of 25-OH-cholesterol to second trimester maternal cells increased P5 production but no effect was observed in first trimester cells. Cytochrome P450scc and its mRNA and adrenodoxin content were determined using Western blot or dot-blot techniques. Both proteins and the mRNA were detected in maternal tissue of first and second trimesters of gestation. In conclusion low P4 levels synthesized by first trimester maternal cells are not due to the absence of either cytochrome P450scc or adrenodoxin protein or production of P450scc mRNA. The data suggest that the refractoriness of the maternal caruncle cells during the first trimester is the result of post-translational regulation.

Adrenodoxin↗
PubMed1991

Immunity conferred by Aro- Salmonella live vaccines.

The specificity of protection conferred by Aro- salmonellae was studied in BALB/c mice challenged 3 months after intravenous (i.v.) vaccination, more than 1 month after the vaccine had been cleared. Oral challenge showed better protection than i.v. challenge. Salmonella typhimurium aroA SL3261 conferred very good protection against wild-type S. typhimurium C5 (over 10,000 x LD50). Cross protection experiments were performed using S. typhimurium, S. enteritidis and S. dublin for vaccination and challenge, including variants of S. typhimurium and S. enteritidis of similar virulence differing in the main LPS antigen (O-4 or O-9). Salmonella typhimurium aroA conferred solid protection against S. typhimurium (O-4), but no protection against wild-type S. enteritidis (O-9). However challenge with LPS variant strains showed that although protection was generally better to strains of the homologous LPS type, specificity of protection was determined more by the parent strain background (S. typhimurium or S. enteritidis) of the challenge than by O-factors 4 or 9, suggesting that other antigens are involved. The nature of the protective antigen(s) in this model is unclear, but it does not appear to be the main O-specific antigen. A S. enteritidis Se795 aroA vaccine gave good protection against wild-type S. enteritidis Se795 2 weeks after vaccination, but much less at 3 months (approximately 10-200 x LD50), although the persistence of the S. enteritidis aroA vaccine in the liver and spleen was similar to that of the S. typhimurium vaccine, and the wild-type Se795 challenge strain was of similar virulence to S. typhimurium C5. A S. dublin aroA vaccine conferred similar protection against wild-type S. dublin (approximately 300 x LD50).

Administration, Oral↗
PubMed1991

Dexamethasone inhibition of prostaglandin production in human term placental cells is protein and ribonucleic acid synthesis dependent.

A key enzyme in the regulation of prostaglandin (PG) synthesis is PG synthase (PGS; cyclooxygenase), which converts arachidonic acid to PGs. Since both PGs and glucocorticoids are elevated before parturition, we studied the regulation of dexamethasone (DEX; 150 nM) on PGF2 alpha synthesis and PGS expression in human placental cells in vitro. Both first trimester and term placental cells were used. DEX reduced PGF2 alpha synthesis in human term placental cells, in contrast to first trimester cells which were unaffected by the same treatment. DEX inhibition of PGF2 alpha production by term placental cells was time and dose dependent. PGS expression was analyzed by [35S]methionine metabolic labeling and immunoprecipitation using polyclonal antibodies developed in rabbits against ram seminal vesicle PGS. DEX reduced PGS expression in term placental cells, but not in first trimester cells. In contrast to the effect of DEX on PGF2 alpha, progesterone and estradiol production by cells were unaffected at any stage of gestation examined. DEX inhibition of PGF2 alpha synthesis required de novo biosynthesis of RNA and proteins. These results suggest 1) corticosteroids play a role in the regulation of placental PG synthesis during parturition; 2) the inhibition of PG synthesis and PGS expression by glucocorticoids is RNA and protein biosynthesis dependent; and 3) induction of labor by glucocorticoids is not directly related to changes in placental progesterone or estradiol biosynthesis.

Arachidonic Acid↗
PubMed1990

Effect of beta-endorphin on steroidogenesis by bovine luteal cells.

To determine if opioid peptides have a local effect on the modulation of progesterone (P4) synthesis, a study was made of the effect of beta-endorphin and leu-enkephalin on P4 production by pure preparations of small luteal cells and dissociated luteal cells comprising both small and large cells from cows 2-3 months pregnant. Corpora lutea were dispersed by collagenase, and the large and small luteal cells were separated using Percoll gradients. Viable luteal cells (5 x 10(5)) were incubated in 0.5 mL of Eagle medium for 2 h at 37 degrees C, in an atmosphere of 5% CO2. Cells were treated with 8-bromoadenosine 3',5'-monophosphate (8Br-cAMP), hCG, beta-endorphin (BE) and leu-enkephalin (LE) alone or in combination. When small luteal cells were used, P4 synthesis was significantly enhanced in the presence of opioid peptides alone (P less than 0.01); there was an additive effect with 8Br-cAMP and with hCG. For dissociated luteal cells, opioid peptides alone had no effect on P4 production but the stimulation of P4 production induced by 8Br-cAMP or hCG was significantly (P less than 0.01) inhibited in the presence of opioid peptides. In contrast, dissociated luteal cells that were preincubated with PGF2 alpha (degranulation) responded to the presence of BE with increased P4 synthesis similar to that seen with the pure preparation of small luteal cells. It is concluded that opioid peptides play an auto/paracrine role in both basal and tropic hormone-induced stimulation of steroidogenesis by the bovine luteal cell.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1990

Moderate immunodeficiency does not increase susceptibility to Salmonella typhimurium aroA live vaccines in mice.

Salmonellae carrying appropriate mutations in genes of the aromatic biosynthesis pathway are effective as live vaccines in animals, and they are candidate typhoid vaccines for human use. They are also very effective as carriers of recombinant antigens from other pathogens to the immune system, eliciting circulatory, secretory, and cell-mediated immunity to foreign antigens. Their attenuation is believed to be due to their requirement for the metabolites p-aminobenzoic acid and 2,3-dihydroxybenzoate, which are not available in mammalian tissues. Immunosuppression (e.g., acquired immunodeficiency syndrome) is a major contraindication to the use of live vaccines. If the avirulence of Aro mutants is largely due to their auxotrophy, they should not be markedly more invasive in immunosuppressed animals. We report that wild-type Salmonella typhimurium M525 of intermediate virulence was much more invasive in sublethally irradiated BALB/c mice than in normal BALB/c mice, whereas sublethal irradiation had little if any effect on the invasiveness of an S. typhimurium aorA vaccine strain apart from a delay in its clearance from the reticuloendothelial system. xid mutant CBA/N mice carry an X-linked B-cell functional defect which results in immunoglobulin G3 agammaglobulinemia, and they are known to be more susceptible to salmonellae in late stages of the infection. We found that whereas male (CBA/N x BALB/c)F1 mice (immunodefective) were more susceptible to wild-type S. typhimurium C5 than female littermates (immunocompetent), there was no difference in the response to the S. typhimurium aroA vaccine strain. The results indicate that moderate immunosuppression does not markedly enhance susceptibility to S. typhimurium aroA live vaccines.

Animals↗
PubMed1989

Partial purification of a luteotrophic substance from bovine fetal cotyledon granules.

To determine whether luteotrophic activity is present in the bovine placental granules, fetal cotyledons from fetuses of 50-100 days of gestation were used. Enriched granules were prepared using a Percoll gradient. Active substances were obtained from the granules by freeze-thawing. The extracts thus obtained were then eluted on a Sephacryl S-300 column. The resultant fractions were then analysed by (1) a radioreceptor assay for hCG-like substances and (2) a bioassay using progesterone production by bovine luteal cells. There were two peaks of activity, one indicative of a high molecular weight substance and the second of a low molecular weight substance. Higher molecular weight substances were eliminated by using acidic extracts. The low molecular weight fraction was further analysed using reverse phase h.p.l.c. (acetonitrile:water gradient). The elution of this substance at 45% acetonitrile resulted in a 100-fold increase in luteotrophic activity in the bioassay compared to the Sephacryl fraction. The small molecular weight substance is heat-stable and not extracted to the organic phase when partitioned between methanol and chloroform.

Animals↗
PubMed1988

Control of bovine placental progestin synthesis: calcium dependent steroidogenesis is modulated at the site of the cholesterol side chain cleavage enzyme.

We have previously reported that progesterone synthesis in the bovine placenta is regulated by Ca2+ dependent and cyclic nucleotide independent mechanism. In studies conducted to further define the role of Ca2+ in the synthesis of progestins in bovine placental tissue, it was found that both protein kinase C (PKC), as determined by phosphorylation, and cytochrome P-450 side chain cleavage, as determined by Western blot analysis, were detectable in the steroidogenetically active portion of the placentome. To determine the site of action of PKC, fetal cotyledon cells were incubated in media containing 25-hydroxycholesterol in the absence or or presence of 10 ng/ml 12-O-tetradecanoyl-phorbol-13-acetate (TPA). It was found that TPA significantly (P less than 0.05) increased the conversion of the exogenous cholesterol analog to progesterone. To determine if the TPA could act synergistically with calcium activators, fetal cotyledon cells were incubated with either methyl isobutyl xanthine (MIX), an activator of intracellular calcium, or the calcium ionophore, A23187, which increases extracellular calcium influx, or both of these agents, in the presence or absence of TPA. It was found that TPA synergistically increased the conversion of sterol to progestins induced by submaximal concentrations of either MIX or A23187. In the presence of both compounds, TPA induced an even more dramatic increase in progestin synthesis. In experiments in which cyanoketone, an agent that inhibits the conversion of pregnenolone to progesterone, was added, TPA addition resulted in increased pregnenolone production, indicating that side chain cleavage of cholesterol is the site of action. The data, therefore, suggest that: (a) Ca2+ affects mechanisms regulating placental steroidogenesis; (2) one locus of Ca2+ is the cholesterol side chain cleavage reaction; and (3) PKC found in this tissue has a role in the Ca activated progestin production.

1-Methyl-3-isobutylxanthine↗
PubMed1988

Control of bovine placental progesterone synthesis: roles of cholesterol availability and calcium-activated systems.

It was previously reported that dispersed bovine placentome secretes progesterone and that the steroidogenic activity of these cells is stimulated by a calcium-mediated, cyclic nucleotide independent mechanism. In the present study, the influence of substrate availability was explored and the roles of calmodulin and protein kinase C in progestin production examined. Incubation of dispersed fetal cotyledon cells with 25-hydroxycholesterol (25-OH-C), a soluble sterol which readily enters cells and is metabolized to steroid hormones, increased progesterone secretion in a dose-dependent manner. The response to 25-OH-C was dependent on the extracellular calcium concentration. Methyl isobutyl xanthine (MIX) alone also increased pregnenolone as well as progesterone secretion, and the combination of 25-OH-C and MIX stimulated progesterone secretion was inhibited by trifluoperazine. The phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), caused no major effects on steroidogenesis but the stimulatory effects of MIX or the ionophore A23187 were enhanced in its presence. These findings suggest that (1) basal progesterone secretion by fetal cotyledon cells is limited by cholesterol availability; (2) MIX increases steroidogenesis in part by increasing the synthesis of pregnenolone, but its actions are expressed independently of cholesterol availability; (3) both calmodulin and protein kinase C may participate in the modulation of bovine placental steroidogenesis.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Trophoblastic differentiation of human teratocarcinoma cell line HT-H1.

In culture the human teratocarcinoma cell line HT-H generates both adherent monolayer and free-floating aggregates. Some populations of aggregated cells develop further to form cystic bodies. A previous study showed the morphological resemblance of the cystic bodies to cells of blastocyst of preimplantation embryo. In this study, HT-H adherent cells were further separated into two subpopulations, fast adhering and slow adhering cells. Fast adhering cells produce fibronectin, spread well onto substratum, and do not proliferate. In contrast, slow adhering cells do not produce fibronectin. Trophoblastic markers were examined in each morphological stage of HT-H cells and the following results were obtained. Only fast adhering cells produce progesterone. Human chorionic gonadotropin was secreted preferentially by fast adhering cells, about six times less by slow adhering cells, and was not secreted by aggregates or cystic bodies. All stages of HT-H cells express c-fos but only fast adhering cells express c-fms oncogene. Cytokeratin 18 was expressed in all stages of HT-H cells. The level of cytokeratin 18 is modestly decreased from adherent to aggregates further into cystic bodies. These results indicate that HT-H cells share properties with cells in trophoblast, placenta, and extraembryonic endoderm. Spontaneous differentiation of HT-H cultures results in the appearance of fast adhering cells which exhibit biochemical properties expected for syncytiotrophoblast.

Cell Adhesion↗
PubMed1982

Adherence of Shigella flexneri to guinea pig intestinal cells is mediated by a mucosal adhesion.

Guinea pig colonic epithelial cells released by treating sections of the colon with solutions containing EDTA, dithiothreitol, and citrate avidly adhered Shigella flexneri bacteria. Separation of the intestinal cells from nonbound bacteria was achieved by differential sedimentation on a Percoll gradient. Adherence of S. flexneri to the colonic cells was Ca2+ (1 mM) and time dependent. The pH optimum was pH 6.2, and almost no attachment (less than 5%) was observed at low temperature (4 degrees C). The average number of bacteria which bound to colonic cells was 70 bacteria per cell, whereas attachment to cells isolated from the ileum region was 6 bacteria per cell. Colonic cells obtained from the intestine of rabbits or rats did not adhere Shigella. Adherence to guinea pig colonic cells was inhibited (50%) by several carbohydrates, such as 0.1% fucose or 0.5% glucose, as well as by a lipopolysaccharide preparation (10 micrograms /ml) isolated from S. flexneri. Fixation of the bacteria with glutaraldehyde or preincubation of the bacteria with lectins or proteolytic enzymes did not affect their adherence. Proteolytic digestions or fixation of the epithelial cells, as well as pretreatments with lipopolysaccharide or fucose solutions, abolished their ability to adhere bacteria. These results indicate that a carbohydrate-binding substance on the surface of guinea pig colonic epithelial cells is responsible for the attachment of the Shigella bacilli.

Adhesiveness↗
PubMed1982

Isolated colonic loop in the rabbit: an in vivo system for studying intestinal mucus.

A method for preparing an isolated colonic loop (Thiry-Vella) in a living rabbit is described. The loop, with its intact neurovascular supply, continues to secrete clear colonic mucus for more than 2 months. The chemical composition of the mucus, collected daily for 2 months, was analyzed and shown to be a high molecular weight glycoprotein composed of approximately equimolar amounts of protein and carbohydrate. The main sugars found were N-acetylgalactosamine, N-acetylglucosamine, galactose, and sialic acid. The most prominent amino acids were threonine, aspartic acid, glycine and serine. A considerable flattening and atrophy of the glandular structure of the isolated colonic loop was observed during the 2 months. This fact did not markedly affect the amount and chemical composition of the mucus that was collected daily from this loop. This model can be used in vivo to investigate colonic mucus in normal and diseased animals, or even following the administration of various drugs.

Animals↗