Helicobacter pylori inhibits gastric cell cycle progression.

Helicobacter pylori infection of the gastric mucosa is associated with changes in gastric epithelial cell proliferation. In vitro studies have shown that exposure to H. pylori inhibits proliferation of gastric cells. This study sought to investigate the cell cycle progression of gastric epithelial cell lines in the presence and absence of H. pylori. Unsynchronized and synchronized gastric epithelial cell lines AGS and KatoIII were exposed to H. pylori over a 24-h period. Cell cycle progression was determined by flow cytometry using propidium iodide (PI), and by analysis of cyclin E, p21, and p53 protein expression using Western blots. In the absence of H. pylori 40, 45, and 15% of unsynchronized AGS cells were in G(0)-G(1), S, and G(2)-M phases, respectively, by flow cytometry analysis. When AGS cells were cultured in the presence of H. pylori, the S phase decreased 10% and the G(0)-G(1) phase increased 17% after 24 h compared with the controls. KatoIII cells, which have a deleted p53 gene, showed little or no response to H. pylori. When G1/S synchronized AGS cells were incubated with media containing H. pylori, the G(1) phase increased significantly (25%, P < 0.05) compared with controls after 24 h. In contrast, the control cells were able to pass through S phase. The inhibitory effects of H. pylori on the cell cycle of AGS cells were associated with a significant increase in p53 and p21 expression after 24 h. The expression of cyclin E was downregulated in AGS cells following exposure of AGS cells to H. pylori for 24 h. This study shows that H. pylori-induced growth inhibition in vitro is predominantly at the G(0)-G(1) checkpoint. Our results suggest that p53 may be important in H. pylori-induced cell cycle arrest. These results support a role for cyclin-dependent kinase inhibitors in the G(1) cell cycle arrest exerted by H. pylori and its involvement in changing the regulatory proteins, p53, p21, and cyclin E in the cell cycle.

The effect of placenta on lactogen receptor in pseudopregnant rabbits.

This study examines the effect of placenta on the evolution of lactogen receptor in virgin pseudopregnant rabbit ovary, adrenal gland and mammary gland. Pseudopregnancy was induced with human chorionic gonadotropin. Does were injected with vehicle or placenta daily beginning on day six of the pseudopregnancy. Vehicle-treated rabbits during pseudopregnancy demonstrated a peak of ovarian lactogen receptor on day eight of pseudopregnancy. After treatment with placental homogenate a shift of this peak to twenty days of pseudopregnancy occurred. Lactogen receptor in adrenal and mammary gland membranes had peak receptor concentrations on day 14 of pseudopregnancy. Injection of placenta induced a shift to day 17 and days 17-20 in mammary and adrenal membranes, respectively. Serum concentrations of progesterone, estradiol, 20 alpha dihydroprogesterone and prolactin in placenta-treated groups were not significantly different from those of vehicle-treated groups. Treatment of pseudopregnant does with a composite of hormones at the concentrations found in placental homogenate produced no modulation of tissue lactogen receptor. Fractionation of 20-day pregnant rabbit placenta revealed that 80% of this activity could be found in the acetone extract while 20% was in the bicarbonate extract. These observations suggest that increases of lactogen receptor in ovary, adrenal and mammary glands occur during pseudopregnancy in rabbits and it is further concluded that placenta can alter these receptor induction patterns to ones similar to those seen in these tissues during pregnancy.

Evolution of lactogen receptors in selected rabbit tissues during pregnancy.

The ontogeny of lactogen receptors in brain, adipose, liver, kidney, adrenal gland, mammary gland, ovarian and uterine tissues of pregnant rabbits was evaluated in this study using 125I bovine prolactin as tracer. Brain and adipose tissues were found to have very low receptor numbers throughout pregnancy (less than 20 fmol/mg of protein), while liver and kidney had higher but constant levels of receptor through the same period (200 and 100 fmol/mg of protein, respectively). Mammary gland and adrenal gland tissues exhibited sharp increases in prolactin binding between 15 and 17 days with both having peak receptor binding at 17 days of around 200 fmol/mg of protein. Ovarian and uterine receptor binding increased slowly after day five of pregnancy and reached peak levels of approximately 225 fmol/mg of protein at day 20. Scatchard analysis of the binding of protein in the tissues having increased binding during the course of pregnancy, revealed that its affinity for sites in these tissues was the same at 5 and 20 days of gestation, indicating the rise in binding to be a result of increased numbers of available receptors. Sub-organ localization studies found the binding of prolactin to adrenal gland, ovary and uterus to be essentially located in adrenal cortex, nonluteal ovary and endometrium. Incubation of membranes from each of the tissues showing significant change during pregnancy, from several time points of pregnancy, with 5.0 M MgCl2 produced little change in apparent receptor numbers; suggesting that receptor occupancy levels of endogenous prolactin was low.

Immunoprotective factors in breast milk and sera of mother-infant pairs.

We analysed breast milk and serum samples from 33 healthy Nigerian mother-infant pairs for concentrations of IgG, IgM, IgA, C3, C4 and lysozyme. We found that the mean IgG and IgM concentrations in maternal sera were three to four times higher than the levels in infant sera, and five to ten times higher than in breast milk. The IgA and lysozyme concentrations in breast milk were, however, slightly higher than the levels in infant sera, suggesting an active localized synthesis of these factors in the mammary gland. While 54.5% of the milk samples lacked measurable concentrations of IgM by radial immunodiffusion, IgA was consistently present in all the milk samples. The mean C3 concentration in maternal sera was 164 mg/100 ml, compared to 145 mg/100 ml and 11.5 mg/100 ml in infant sera and breast milk respectively. The C4 concentration was also considerably lower in breast milk than in maternal and infant sera.

A preliminary survey of aerobic bacteria in breast milk of mothers from the low-income group in Nigeria.

The aerobic bacteria colonizing breast milk of the low-income group in Nigeria were quantified to assess its suitability for use in milk banks. In parallel, the nutritional and health status of donating mothers and their infants were assessed by physicians. The aerobic bacteria contained in the specimens included Streptococcus salivarius, Bacillus cereus, Klebsiella pneumoniae, Enterobacter aerogenes, Streptococcus pneumoniae, Streptococcus pyogenes, Pseudomonas aeruginosa and Staphylococcus epidermides. In general, the microbial load found in these milk samples is lower than levels considered dangerous. An analysis of the results showed that 50% of the mother's milk is contaminated, 17% of which was infected with primary pathogens. There was no correlation between demographic data, nutritional or health status of either mother or infant and microbial load in mother's milk. Milk obtained from this socio-economic group, is therefore, considered safe for use in milk banks.

The isolation, enrichment, and comparative electron microscopic characterization of cellular components of the aged rat ventral prostate.

Prostate cells were isolated from 3- and 23-month-old Sprague-Dawley rats. After sequential digestion with 0.1% collagenase at 37 degrees C, a mixed population of cells was obtained. The cells were layered on a five-step discontinuous Percoll gradient (g/ml: 1.024, 1.043, 1.048, 1.060, 1.089), centrifuged at 3,000 rpm X 30 minutes, which produced six distinct cellular subpopulations and a fibromuscular stroma (FMS). Electron microscopic characterization of the 3- and 23-month-old cellular subpopulations identified the following components, g/ml: debris and nonviable cells (1.020-1.025) nonsecretory epithelial cells (1.038-1.039), secretory epithelial cells (1.047-1.048), basal epithelial cells (1.057-1.059), differentiating epithelial cells (1.070-1.075), erythrocytes (1.085-1.089). This study demonstrates that one of the effects of age on the rat ventral prostate is an intracellular disorganization of isolated and enriched cellular components.

Citrate uptake and oxidation by fragments of rat ventral prostate.

Citrate oxidation was studied utilizing an in vitro preparation of rat ventral prostate which was very similar, with respect to citrate metabolish, to the intact prostate. The rate of citrate oxidation was very slow in comparison to kidney, although citrate entered prostatic tissue and accumulated intracellularly. Citrate was converted to isocitrate at a rate which resulted in a constant citrate/isocitrate ratio over a 10-fold variation in medium citrate concentration. The prostate oxidized significantly more alpha-ketoglutarate and malate than citrate. These results suggested that limited citrate oxidation could account for the accumulation of high prostatic citrate levels.