Determinants of Helicobacter pylori seroprevalence in Mexican adolescents

BACKGROUND: Helicobacter pylori infection is one of the most common human infections and is considered to play an etiologic role in several gastroduodenal diseases. In this study we determined the H. pylori seroprevalence among adolescents in Morelos, Mexico, and explored the association between seroprevalence and socioeconomic, dietary and lifestyle variables. MATERIALS AND METHODS: A cross-sectional study was conducted in 5861 Mexican subjects aged 11-21 years. H. pylori infection was determined by an enzyme-linked immunosorbent assay previously validated in Mexico. A self-administered questionnaire was used to collect information on sociodemographic factors, housing, living conditions and food consumption. Multivariate logistic regression methods were used to obtain odds ratios and 95% confidence intervals. RESULTS: The overall H. pylori seroprevalence was 47.6%; 40.6% in preadolescents (11-14 years), 48.6% in adolescents (15-17 years), and 59.8% in young adults (18-24 years). A positive association was found between age and H. pylori seroprevalence. Inverse associations were found for availability of drinking water, sewerage, and home appliances at the time of the subject's birth, a proxy variable of socioeconomic status. Intake of milk products and total fats was positively associated with infection. CONCLUSIONS: This large seroprevalence study showed that H. pylori infection is frequent among adolescents in Mexico. An early acquisition of infection is indirectly suggested. Some variables denoting low socioeconomic status were inversely associated with H. pylori seroprevalence. Associations with intake of milk products and total fats suggest new hypotheses in this field of research.     

Liquid chromatographic assay for dicloxacillin in plasma

A simple high-performance liquid chromatographic method for the determination of dicloxacillin in plasma has been developed. The method only requires 0.5 ml of plasma, phosphate buffer solution (pH = 4.7), acidification with 0.5N hydrochloride acid and liquid extraction with dichloromethane. Posterior evaporation of organic under nitrogen steam and redissolution in mobile phase is carried out. The analysis was performed on a Spherisorb C18 (5 microm) column, using methanol -0.05 M phosphate buffer, pH = 4.7 (75:25; v/v) as mobile phase, with ultraviolet detection at 220 nm. Results showed that the assay is sensitive: 0.5 microg/ml. The response is linear in the range of 0.5 - 10 microg/ml. Maximum inter-day coefficient of variation was 12.4%. Mean extraction recovery obtained was 96.95%. Stability studies showed that the loss was not higher than 10%, samples are stable at room temperature for 6 h, at -20 Celsius for 2 months, processed samples were stable at least for 24 h and also after two freeze-thaw cycles. The method has been used to perform pharmacokinetic and bioequivalence studies in humans.     

Reversible and strong immobilization of proteins by ionic exchange on supports coated with sulfate-dextran

New and strong ionic exchange resins have been prepared by the simple and rapid ionic adsorption of anionic polymers (sulfate-dextran) on porous supports activated with the opposite ionic group (DEAE/MANAE). Ionic exchange properties of such composites were strongly dependent on the size of the ionic polymers as well as on the conditions of the ionic coating of the solids with the ionic polymers (optimal conditions were 400 mg of sulfate-dextran 5000 kDa per gram of support). Around 80% of the proteins contained in crude extracts from Escherichia coli and Acetobacter turbidans could be adsorbed on these porous composites even at pH 7. This interaction was stronger than that using conventional carboxymethyl cellulose (CMC) and even others such as supports coated with aspartic-dextran polymer. By means of the sequential use of the new supports and supports coated with polyethyleneimine (PEI), all proteins from crude extracts could be immobilized. In fact, a large percentage (over 50%) could be immobilized on both supports. Finally, some industrially relevant enzymes (beta-galactosidases from Aspergillus oryzae, Kluyveromyces lactis, and Thermussp. strain T2, lipases from Candida antarctica A and B, Candida rugosa, Rhizomucor miehei, and Rhyzopus oryzae and bovine pancreas trypsin and chymotrypsin) have been immobilized on these supports with very high activity recoveries and immobilization rates. After enzyme inactivation, the protein could be fully desorbed from the support, and then the support could be reused for several cycles. Moreover, in some instances the enzyme stability was significantly improved, mainly in the presence of organic solvents, perhaps as a consequence of the highly hydrophilic microenvironment of the support.     

Value of percent free prostate-specific antigen for the prediction of pathological stage in men with clinically localized prostate cancer

PURPOSE: To analyze if the percentage of free prostate-specific antigen (PSA) can provide additional information to the combination of local clinical stage, serum PSA and Gleason score in the prediction of final stage and pathological features of prostate cancer. MATERIALS AND METHODS: A group of 480 men with clinically localized prostate cancer underwent lymphadenectomy and radical prostatectomy. Total and free PSA were measured in preoperative serum. Clinical stage was T1 in 70.4% of patients and T2 in 29.6%. The biopsy Gleason score ranged between 2 and 4 in 5.6%, between 5 and 7 in 78.4%, and was higher than 7 in 16%. Total serum PSA was below 4.1 ng/mL in 4.3%, between 4.1 and 10 ng/mL in 66.4%, between 10.1 and 20 ng/mL in 22.5%, and higher than 20 in 6.7% of patients. The tumor was organ-confined in 49.8% and specimen-confined in 64.2%, and its pathological features were favorable in 35%. RESULTS: Multiple logistic regression analysis demonstrated that percent free PSA has independent predictive value for pathological stage only in the subset of patients with cT1 tumors and serum PSA between 4.1 and 10 ng/mL. In this group the probability of organ-confined cancer was 68.3% if the percent free PSA was above 15 and 56.3% if it was lower (p<0.001). The probability of specimen-confined disease was 86.6% and 71.3%, respectively (p<0.007), and the probability of favorable pathology was 59.8% and 39.6%, respectively (p<0.002). We also found higher rates of organ- and specimen-confined tumors and favorable pathology for every Gleason score when the percent free PSA was higher than 15. CONCLUSIONS: Percent free PSA seems to provide additional information to the combination of clinical stage and Gleason score for the prediction of pathological features only in patients with clinical stage T1c and serum PSA between 4.1 and 10 ng/mL.     

Parameters related to oxygen free radicals in erythrocytes,plasma and epidermis of the hairless rat

The following parameters related to oxygen free radicals (OFR) were determined in erythrocytes and the epidermis of hairless rats: catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), reduced (GSH) and oxidized (GSSG) glutathione, glutathione S-transferase (GST), superoxide dismutase (SOD) and thiobarbituric acid reactive substances (TBARS). GSH, GSSG and TBARS were also analyzed in plasma. In erythrocytes, the Pearson correlation coefficients (r) were significant (p < 0.001) between glutathione and other parameters as follows: GSH correlated negatively with GSSG (r = -0.665) and TBARS (r = -0.669); GSSG correlated positively with SOD (r = 0.709) and TBARS (r = 0.752). Plasma GSSG correlated negatively with erythrocytic thermostable GST activity (r = -0.608; p=0.001) and with erythrocytic total GST activity (r = -0.677; p < 0.001). In epidermis (p < 0.001 in all cases), GSH content correlated with GSSG (r = 0.682) and with GPx (r = 0.663); GSSG correlated with GPx (r = 0.731) and with GR (r = 0.794). By multiple linear regression analysis some predictor variables (R(2)) were found: in erythrocytes, thermostable GST was predicted by total GST activity and GSSG, GSSG content was predicted by GSH and by the GSH/GSSG ratio and GPx activity was predicted by GST, CAT and SOD activities; in epidermis, GSSG was predicted by GR and SOD activities and GR was predicted by GSSG, TBARS and GPx. It is concluded that the hairless rat is a good model for studying OFR-related parameters simultaneously in blood and skin, and that it may provide valuable information about other animals under oxidative stress.     

Molecular cloning and characterization of a multidomain endoglucanase from Paenibacillus sp BP-23: evaluation of its performance in pulp refining

The gene celB encoding an endoglucanase from Paenibacillus sp. BP-23 was cloned and expressed in Escherichia coli. The nucleotide sequence of a 4161 bp DNA fragment containing the celB gene was determined, revealing an open reading frame of 2991 nucleotides that encodes a protein of 106,927 Da. Comparison of the deduced amino acid sequence of endoglucanase B with known β-glycanase sequences showed that the encoded enzyme is a modular protein and exhibits high homology to enzymes belonging to family 9 cellulases. The celB gene product synthesized in E. coli showed high activity on carboxymethyl cellulose and lichenan while low activity was found on Avicel. Activity was enhanced in the presence of 10 mM Ca²⁺ and showed its maximum at 53 °C and pH 5.5. The effect of the cloned enzyme in modifying the physical properties of pulp and paper from Eucalyptus was tested (CelB treatment). An increase in mechanical strength of paper and a decrease in pulp dewatering properties were found, indicating that CelB treatment can be considered as a biorefining. Treatment with CelB gave rise to an improvement in paper strength similar to that obtained with 1,000 revolutions increase in mechanical refining. Comparison with the performances of recently developed endoglucanase A from the same strain and with a commercial cellulase showed that CelB produced the highest refining effect. Received: 25 February 2000 / Received revision: 4 July 2000 / Accepted: 9 July 2000     

Localization and expression of BCAT during pregnancy and lactation in the rat mammary gland

During lactation, branched-chain aminotransferase (BCAT) gene expression increases in the mammary gland. To determine the cell type and whether this induction is present only during lactation, female rats were randomly assigned to one of three experimental groups: pregnancy, lactation, or postweaning. Mammary gland BCAT activity during the first days of pregnancy was similar to that of virgin rats, increasing significantly from day 16 to the last day of pregnancy. Maximal BCAT activity occurred on day 12 of lactation. During postweaning, BCAT activity decreased rapidly to values close to those observed in virgin rats. Analyses by Western and Northern blot revealed that changes in enzyme activity were accompanied by parallel changes in the amount of enzyme and its mRNA. Immunohistochemical studies of the mammary gland showed a progressive increase in mitochondrial BCAT (mBCAT)-specific staining of the epithelial acinar cells during lactation, reaching high levels by day 12. Immunoreactivity decreased rapidly after weaning. There was a significant correlation between total BCAT activity and milk production. These results indicate that the pattern of mBCAT gene expression follows lactogenesis stages I and II and is restricted to the milk-producing epithelial acinar cells. Furthermore, BCAT activity is associated with milk production in the mammary gland during lactation.     

Superantigens: the good, the bad, and the ugly

Increasing evidence suggests that superantigens play a role in immune-mediated diseases. Superantigens are potent activators of CD4+ T cells, causing rapid and massive proliferation of cells and cytokine production. This characteristic of superantigens can be exploited in diseases where strong immunologic responses are required, such as in the B16F10 animal model of melanoma. Superantigen administration is able to significantly enhance ineffective anti-tumor immune responses, resulting in potent and long-lived protective anti-tumor immunity. However, superantigens are more well-known for the role they play in diseases. Studies using an animal model for neurologic demyelinating diseases such as multiple sclerosis show that superantigens can induce severe relapses and activate autoreactive T cells not involved in the initial bout of disease. This may also involve epitope spreading of disease. Superantigens have also been implicated in acute diseases such as food poisoning and TSS, and in chronic diseases such as psoriasis and rheumatoid arthritis. Viral superantigens are also involved in the disease process, including superantigens derived from human immunodeficiency virus and mouse mammary tumor virus. Finally, immunotherapies that ameliorate the role played by superantigens in disease are discussed.     

Mapping the energy surface of transmembrane helix-helix interactions

Transmembrane helices are no longer believed to be just hydrophobic segments that exist solely to anchor proteins to a lipid bilayer, but rather they appear to have the capacity to specify function and structure. Specific interactions take place between hydrophobic segments within the lipid bilayer whereby subtle mutations that normally would be considered innocuous can result in dramatic structural differences. That such specificity takes place within the lipid bilayer implies that it may be possible to identify the most favorable interaction surface of transmembrane alpha-helices based on computational methods alone, as shown in this study. Herein, an attempt is made to map the energy surface of several transmembrane helix-helix interactions for several homo-oligomerizing proteins, where experimental data regarding their structure exist (glycophorin A, phospholamban, Influenza virus A M2, Influenza virus C CM2, and HIV vpu). It is shown that due to symmetry constraints in homo-oligomers the computational problem can be simplified. The results obtained are mostly consistent with known structural data and may additionally provide a view of possible alternate and intermediate configurations.