Toenail selenium levels and gastric cancer risk in Cali, Colombia.

To examine an association between selenium level and gastric cancer (GC) risk, a hospital-based case-control study was conducted in Cali, Colombia. Selenium concentrations in toenails were compared between 142 GC patients and 244 controls selected from hospitalized non-cancer patients. GC risk was lowest in the lowest quartile of selenium level and highest in the second highest quartile (age-, sex-, hospital-, and sampling-season-adjusted odds ratio [OR]: 5.9, 95% confidence interval: 2.8, 12.4). This association was not modified by either tumor location or Lauren's histological type. The magnitude of ORs was not affected by other diets that were significantly associated with GC risk. Since selenium levels were relatively high in cases and in controls, our results indicate that an inverse association between selenium level and GC risk may exist only among populations with low selenium levels.

Area under pH 4: a more sensitive parameter for the quantitative analysis of esophageal acid exposure in adults.

OBJECTIVE: Traditional quantitative analysis of 24-h esophageal pH monitoring data does not include the pH of reflux episodes. Area under pH 4 (AU4) is a recently introduced parameter that describes the acid exposure rate through both duration and depth of pH falls. METHODS: In Study A, we enrolled 20 healthy controls and 42 patients (18 without esophagitis, 24 with Savary I-III esophagitis) in a study evaluating reference values for 24-h reflux time at pH <4 (RT) and 24-h AU4 by means of receiver operating characteristic (ROC) discriminant analysis. For Study B, we next prospectively applied the resulting cutoffs to 16 healthy controls and to 110 gastroesophageal reflux (GERD) patients (55 with esophagitis) to adjust sensitivity, specificity, and predictive values of both RT and AU4. RESULTS: In Study A, the best cutoff values were 5.1% for RT (Area Index +/- SE, 0.899 +/- 0.038; 95% confidence interval [C.I.], 0.796 +/- 0.961) and 36.1 pH x min for AU4 (Area Index +/- SE, 0.935 +/- 0.03; 95% C.I., 0.842 +/- 0.981); AU4 gave the best performance (p = 0.038 vs RT) in discriminating controls and GERD patients. In Study B, RT was abnormal in three controls and 79 patients; AU4 identified all the controls and patients with abnormal RT and also 10/31 patients (32.3%) with so-called "normal" acid exposure (according to RT). In the whole GERD group of patients, AU4 and RT specificity was 81.2%, whereas sensitivity was 71.8% for RT and 80.9% for AU4 (chi2, 61.831; DF, 1; p < 0.005); PPV/NPV were 96.3%/29.5% for RT, and 96.7%/38.2% for AU4. CONCLUSIONS: AU4 appears to be a simple and sensitive quantitative parameter to measure the esophageal acid exposure in adults submitted to 24-h pH monitoring, and it could be an useful clinical aid in evaluating normal RT tests where, from a clinical point of view, a reflux disease is highly likely.

Determination of the sedimentation coefficient and molecular weight of proteins by density gradient ultracentrifugation in fixed angle rotor.

The applicability of density gradient ultracentrifugation using fixed angle rotors for the determination of sedimentation coefficient and molecular weight of proteins was studied. Ovalbumin, bovine serum albumin, IgG-, IgA- and IgM-globulin proteins, as standards were, among others, centrifuged in a fixed angle rotor (Beckman type 50) in 5-20% (w/v) sucrose density gradient for 300 min, at a speed of 40,000 rpm, at 5 degrees C. After centrifugation, the sedimentation diagram of the above-mentioned proteins was taken by a spectrophotometer equipped by a flow-through cuvette and a compensator. The sedimentation path was measured on the diagrams. A calibration curve was drawn by plotting the sedimentation coefficients of the standard proteins against the sedimentation paths. This curve, for which the equation y = 1.74x-1.6 is valid, was used for the determination of the sedimentation coefficients of several globular proteins under the conditions described above. The values obtained this way agree within +3-10% with those determined with analytical ultracentrifuge. If the logarithms of proteins molecular weight used as standards were drawn against the logarithms of their sedimentation paths a calibration curve was obtained. This curve for which the equation ln y = 2.022 ln x + 8.71 is valid can be used for the determination of molecular weights of globular or nearly globular proteins.

Curing of 60Co gamma-resistance inducing effect of R46 R-factor by 5-fluorouracil.

The 60Co gamma-resistance inducing effect of R46 factor, and its elimination by 5-fluorouracil were studied. R46 increased the survival of the wild-type strain and its rec- mutants. After treatment with 5-fluorouracil (1 g/liter) the clones lost not only antibiotic resistance, but the 60Co gamma-radioresistance as well, encoded by R46 R-factor.

Elimination of UV-resistance inducing effect of R46 R factor by 5-fluorouracil.

R-factor curing capacity of 5-fluorouracil (5-FU) was studied. Well detectable increase in UV-resistance was found in E. coli K12 AB1157 strain and its recB-, recC-, recF- mutants harbouring R46 R-factor. After treatment with 5-FU, these strains lost not only the antibiotic resistance coded for R46 R-factor but their UV-radioresistance, as well.

Effect of the pKM101 plasmid on the repair of single-strand breaks in DNA induced by ionizing irradiation in Escherichia coli.

The effect of pKM101 plasmid on repair of single-strand breaks in DNA induced by 60Co-gamma irradiation in E. coli K12 AB1157 (wild type) and in its recA- and recB- mutant cells was studied by alkaline sucrose gradient sedimentation method. For quantitative analysis of sedimentation profiles we calculated the S1/2 values described by Veatch and Okada. The S1/2 values of unirradiated cells were 21.10, and after 200 Gray irradiation 11.35, due to the original incidence of single-strand breaks. The presence of pKM101 did not influence these values in either cases. This means that pKM101 had no effect on the rise of single-strand breaks in DNA. During a post-irradiation incubation period at 37 degrees C for 60 min the S1/2 value of the wild type strain increased from 11.35 to 19.22, that of the recB- from 11.50 to 15.23, while the S1/2 value of the recA- mutant did not change owing to the lack of repair of single-strand breaks. pKM101 plasmid markedly increased the S1/2 value in wild type strain and in recB- mutant, while it had no effect on S1/2 in recA- cells, during this post-irradiation incubation period. Thus the effect of pKM101 on the repair of single-strand breaks in DNA proved to be dependent on recA+ genotype. Nalidixic acid at 100 micrograms/ml concentration inhibited the repair of single-strand breaks in both wild type and recB- mutant cells harbouring pKM101 plasmid.

Effect of a calcium-binding gluten fraction on the superprecipitation of actomyosin.

The Ca2+-binding gluten fraction isolated by the authors has been shown to prolong the clearing phase and to shorten the physiological contraction phase of ATP activated natural actomyosin suspension in the presence of physiological potassium chloride in a dose dependent manner. The mean ATPase activity of myosin and actomyosin was calculated for each phase from the actual ATP concentrations, measured at 30 sec intervals, and from the phase lengths. The preparation was found markedly to inhibit the ATPase activity during the clearing and physiological contraction phase. Since both myosin and actomyosin ATPase is Ca2+-dependent, it is assumed that the inhibitory effect of the gluten fraction on ATPase activity may be mediated by its free Ca2+-binding capacity, resulting in modified phase lengths of actomyosin superprecipitation. On the basis of these experimental results a hypothesis is put forward of the part of the Ca2+-binding gluten fraction played in the pathomechanism of coeliac disease.

R46 and pKM101 plasmid-mediated resistance to ionizing radiation in Escherichia coli.

The ability of the R46 R factor and its derivative pKM101 to modify sensitivity to 60Co gamma radiation was studied. In Escherichia coli K12 both plasmids enhanced bacterial survival after 60Co gamma irradiation. This effect was dependent on recA+ genotype but not on recB+, recB+ recC+, and recF+ genotypes. 5-Fluorouracil eliminated the R46 R factor from the parent and its rec- mutant strains. These strains lost not only the antibiotic resistance coded for R46 R factor but their radioresistance as well.

Radioassay of soluble immune complexes using their uptake by macrophage Fc receptors.

Sera from patients were tested for the presence of soluble immune complexes (IC) by a method based on the observation that IC inhibit uptake of aggregated IgG by the Fc receptors of macrophages. From the saturation curve of macrophages with 125I-labelled aggregates the optimal inhibitory effect of a measured amount of IC was determined. This radioassay is highly sensitive, being capable of detecting 20 ng of IC, is reproducible and covers a wide range of measurement (20-2000 ng).