Seroprevalence and Potential Risk Factors for Helicobacter pylori Infection in Brazilian Children

Background: Helicobacter pylori infection has been proved to be of great relevance to public health in unindustrialized countries, especially in low socioeconomic groups. Poor hygiene, deficient sanitation, and crowded conditions have been reported as risk factors for this infection. In this work, we investigated whether social and demographic characteristics were associated with anti‐H. pylori IgG antibodies in 1104 children aged 4–11 years old from Salvador, a large city located in northeastern Brazil. Methods: Standardized questionnaires were used to obtain social, demographic, and environmental data for the studied population in two periods of time (from 1997 to 2003 and in 2005). Anti‐H. pylori IgG antibodies were assessed by indirect enzyme‐linked immunosorbent assay in 2005. Results: Anti‐H. pylori IgG antibody was present in 28.7% of the children. Among the studied variables, the following were positively associated with the presence of anti‐H. pylori antibodies in multivariable analyses: age above 8 years old (OR = 1.72, 95% CI = 1.23–2.40), a larger sibling number (OR = 1.66, 95% CI = 1.26–2.18), nursery attendance (OR = 1.49, 95% CI = 1.04–2.12), location of the house at an unpaved street (OR = 2.03, 95% CI = 1.44–2.87) and absence of a flush toilet (OR = 1.32, 95% CI = 1.00–1.74). Conclusion: Our data show that H. pylori infection in children from a major Brazilian city is associated with variables indicative of a crowded environment and deficient sanitation/habitation conditions, leading to the conclusion that improvements in hygiene and social conditions may protect children against this infection.     

Progesterone receptor detection and quantification in breast tumors by bivariate immunofluorescence/DNA flow cytometry

A method was developed for the detection of progesterone receptors (PgR) by flow cytometry (FCM) in cell suspensions obtained from mechanically dispersed fragments of operated breast cancers. Two monoclonal antibodies were tested for sensitivity and specificity on four breast cancer cell lines of known PgR expression and a calibration curve thus established. A simple procedure was used to calculate the level of PgR expression, taking into account the relative displacement of total cellular fluorescence compared to nonspecific fluorescence for each sample and the average DNA content of the cells derived from the corresponding histograms. The PgR-specific immunofluorescence of the tumor specimens measured in arbitrary units (channels) was then transformed to fmoles/mg DNA by comparison with the calibration curve. The FCM-derived results were compared with those of a conventional immunoenzymatic PgR assay on 30 surgical samples. PgR content ranged from 10 to 22,000 fmoles/mg DNA and linear regression analysis yielded a good correlation (r = 0.86). With a threshold of positivity of 300 fmoles/mg DNA, the two methods concurred for 28 of 30 tumors (93%). Nine specimens were analyzed repeatedly, showing good reproducibility. This method could prove to be more useful than the biochemical assays on homogenates, since it allows the simultaneous analysis of receptor expression in individual cells and of DNA index (ploidy).     

Specific interactions of pancreatic amylase at acidic pH. Amylase and the major protein of the zymogen granule membrane (GP-2) bind to immobilized or polymerized amylase.

Regulated secretory proteins are thought to be sorted in the trans-Golgi network towards the secretory granule via acidic aggregation. In the exocrine pancreas, amylase is one of the major zymogens. It is a basic protein of pI 8.6 and does not precipitate in acidic conditions. To identify the mechanism by which amylase aggregates in the acidic cisternae of the pancreatic trans-Golgi network, we have developed an in vitro model in which amylase was fixed to plastic microtiter plates. The fixed amylase was probed with two ligands: amylase itself and GP-2, the major protein of the zymogen granule membrane. Biotinylated amylase bound to fixed amylase in a strict pH-dependent manner with optimal binding between pH 5.0 and 5.7. The affinity of binding was in the nanogram range (Kd approximately 20.0 ng/mL) at pH 5.5. Acid binding of amylase was not reversible by incubation at neutral pH, nor could it be displaced by native amylase. GP-2 binding to fixed amylase was also pH dependent with optimal binding between pH 5.0 and 5.7. As for amylase, it was not reversible by incubation at neutral pH. GP-2 binding sites on fixed amylase appeared to be different from those of biotinylated amylase. While native and biotinylated amylase did not bind to GP-2, polymerized amylase precipitated GP-2 at acidic pH. Taken together these data suggest that slight modifications are sufficient to reveal on the amylase molecule binding sites for GP-2 and for amylase itself. These new binding capacities acquired at acidic pH could be involved in the cascade of reactions that lead to the in vivo formation of the immature secretory granule.     

Effect of black widow spider venom on the cockroach heart

The effect of black widow spider venom [crude gland extract (CGE), gland lumen venom (GLV), or from direct bite] on the cardiac activity of Periplaneta americana was assayed both in vivo and in vitro. It was shown that these different forms of venom in all cases blocked the cockroach heart-beat. Both CGE and GLV showed a selective activity on the heart function compared with their effect on the CNS. It is suggested that cardiac block is due to impairment of either the cardiac nerve ganglia function or the myocardial neuromuscular junctions, or of both of them. The mode of action of the toxic effects on the heart is discussed. Experiments with antiserum from CGE indicate that the antigenic fractions of CGE and GLV affecting the heart function, as well as those affecting the insect motor functions, are common to both toxic materials.