Cross-hybridizing snake satellite, Drosophila, and mouse DNA sequences may have arisen independently

Previous reports have interpreted hybridization between snake satellite DNA and DNA clones from a variety of distant taxonomic groups as evidence for evolutionary conservation, which implies common ancestry (homology) and/or convergence (analogy) to produce the cross- hybridizing sequences. We have isolated 11 clones from a genomic library of Drosophila melanogaster, using a cloned 2.5-kb snake satellite probe of known nucleotide sequence. We have also analysed published sequence data from snakes, mice, and Drosophila. These data show that (1) all of the cross-hybridization between the snake, fly, and mouse clones can be accounted for by the presence of either of two tandem repeats, [GATA]n and [GACA]n and (2) these tandem repeats are organized differently among the different species. We find no evidence that these sequences are homologous apart from the existence of the simple repeat itself, although their divergence from a common ancestral sequence cannot be ruled out. The sequences contain a variety of homogeneous clusters of tandem repeats of CATA, GA, TA, and CA, as well as GATA and GACA. We suggest that these motifs may have arisen by a self-accelerating process involving slipped-strand mispairing of DNA. Homogeneity of the clusters might simply be the result of a rate of accumulation of tandem repeats that exceeds that of other mutations.      

Family studies of IgA deficiency

Seventeen immunoglobulin A (IgA)-deficient subjects and other members from 13 families were examined at HLA-A, B and DR, C4A, C4B, and Bf loci. Of the 29 independent haplotypes in the IgA-deficient: subjects, 22 included deletions, duplications, or defects at the C4 or 21-hydroxylase loci. It is suggested that there may be a gene regulating serum IgA concentrations in this same region of chromosome 6. Three main supratypes explain most of the previously reported tHLA associations with IgA deficiency. These are A1, Cw7, B8, C4AQ0, C4B1, BfS, DR3, Bw65(14), C4A2, C4B1/2, BfS, and Bw57(17), C4A6, C4B1, BfS. All three are proposed to carry a gene for IgA deficiency, while other supratypes carrying the same B allele generally do not. Other supratypes possibly associated with IgA deficiency were also identified. A survey of about 150 individuals with at least 1 of the 3 main supratypes revealed only 2 IgA-deficient subjects, and these were among the 20 that had 2 of these supratypes. This suggests the possibility of a recessive mode of inheritance, with penetrance determined by another factor which is not major histocompatibility complex-linked. All the supratypes found in this group of IgA-deficient subjects would then carry the putative recessive allele for IgA deficiency.     

The immunological detection of a 21-OH deficiency mutation HLA supratype.

Previous studies have shown that the late-onset and cryptic forms of 21-hydroxylase deficiency are highly associated with the HLA supratype HLA-B14,C4A2,C4B1/2,DR1. Since cells from a number of unrelated normal individuals from different ethnic backgrounds expressing the DR1 associated with this supratype failed to stimulate two different DR1-restricted T-cell clones that proliferated in the presence of most other DR1 cells, we decided to test the hypothesis that cells with this supratype express "abnormal" DR1 molecules that have been affected in some way by the chromosomal mutation responsible for B14,DR1-associated 21-hydroxylase deficiency (21-OH-defL). The results showed an association between "abnormal" DR1 and 21-OH-defL (elevated rates of 17 alpha-hydroxyprogesterone [17-OHP] increase and elevated peak 17-OHP values following ACTH stimulation). The presence of the B14,DR1 supratype can be used to predict the presence of "abnormal" DR1 and the clinical status of individuals not previously known to be 21-OH-defL carriers.     

Eosinophil responses in sheep selected for high and low responsiveness to Trichostrongylus colubriformis

A breeding programme, based on selection for faecal egg counts, has produced lines of sheep which demonstrate either increased resistance (high responder) or susceptibility (low responder) to challenge infection with T. colubriformis after vaccination with irradiated larvae. Circulating blood eosinophilia, a hallmark of helminth infections, was examined in third generation lambs from two separate selective matings and random bred control lambs. Numbers of eosinophils were higher in high responder lambs when compared to low responders after vaccination and challenge infections. Analysis of eosinophil counts confirmed a strong line effect and there was no evidence of a sex effect. Random bred lambs showed wide individual variations in eosinophil numbers and their response to infection. It was concluded that peripheral eosinophilia was more a measure of host responsiveness to infection than an indicator of helminthiasis. As such the eosinophil may serve as an indicator of the hosts ability to respond to T. colubriformis vaccination and infection.     

H. pylori predictors and outcomes among adults undergoing upper endoscopy at a Jamaican teaching hospital: A cross-sectional study

Background

Recent data on the prevalence of H. pylori infection in Jamaica are lacking. It is postulated that there has been a decline in the prevalence of H. pylori infection and its associated complications. We determined sociodemographic characteristics, prevalence of H. pylori infection and clinical outcomes among adults undergoing esophagogastroduodenoscopy (EGD) and histology at the University Hospital of the West Indies (UHWI) between May 2018 and December 2020.

Materials and methods

A cross-sectional study of patients (≥18 years old), who underwent EGD and histological evaluation for H. pylori infection, was conducted. Associations of H. pylori positivity and gastric cancer with sociodemographic/clinical variables and endoscopic findings were determined by stepwise logistic regression using backward selection. Unadjusted and adjusted odds ratios with related 95% confidence intervals (Cis) were calculated for H. pylori positivity and gastric cancer status.

Results

There were 323 participants (mean age 58.6 ± 17.8 years, 54.2% females). H. pylori prevalence was 22.2% (n = 70 of 315), 5.6% had gastric neoplasia (GN), 15.5% gastric atrophy, 11.4% intestinal metaplasia and 3.7% dysplasia on histology. Mucositis (64.5%), gastric ulcer (14.9%), and duodenal ulcer (13.9%) were the most common endoscopic findings. Participants with peptic ulcer disease (PUD) (unOR = 4.0; p = .017), gastric cancer (unOR = 9.5; p = .003), gastric atrophy (unOR = 12.8; p < .001), and intestinal metaplasia (unOR = 5.0; p < .001) had a significantly higher odds of being H. pylori positive, but after multivariable analyses only gastric atrophy remained significant (aOR = 27.3; p < .001). Participants with mucositis had a significantly lower odds of gastric cancer (unOR 0.1; p = .035) while participants with dysplasia had significantly higher odds (unOR 8.0; p = .042), but these were no longer significant after multivariable analyses (aOR = 0.2; p = .156 and aOR = 18.9; p = .070, respectively).

Conclusions

Histology based prevalence of H. pylori infection is lower than previously reported in Jamaica. Gastric atrophy is a significant predictor of H. pylori positivity.     

NMR investigations of protein-carbohydrate interactions: refined three- dimensional structure of the complex between hevein and methyl beta- chitobioside

The specific interaction of hevein with GlcNAc-containing oligosaccharides has been analyzed by1H-NMR spectroscopy. The association constants for the binding of hevein to a variety of ligands have been estimated from1H-NMR titration experiments. The association constants increase in the order GlcNAc-alpha(1-->6)-Man < GlcNAc < benzyl-beta-GlcNAc < p-nitrophenyl-beta-GlcNAc < chitobiose < p- nitrophenyl-beta-chitobioside < methyl-beta-chitobioside < chitotriose. Entropy and enthalpy of binding for different complexes have been obtained from van't Hoff analysis. The driving force for the binding process is provided by a negative DeltaH0which is partially compensated by negative DeltaS0. These negative signs indicate that hydrogen bonding and van der Waals forces are the major interactions stabilizing the complex. NOESY NMR experiments in water solution provided 475 accurate protein proton-proton distance constraints after employing the MARDIGRAS program. In addition, 15 unambiguous protein/carbohydrate NOEs were detected. All the experimental constraints were used in a refinement protocol including restrained molecular dynamics in order to determine the highly refined solution conformation of this protein- carbohydrate complex. With regard to the NMR structure of the free protein, no important changes in the protein nOe's were observed, indicating that carbohydrate-induced conformational changes are small. The average backbone rmsd of the 20 refined structures was 0.055 nm, while the heavy atom rmsd was 0.116 nm. It can be deduced that both hydrogen bonds and van der Waals contacts confer stability to the complex. A comparison of the three-dimensional structure of hevein in solution to those reported for wheat germ agglutinin (WGA) and hevein itself in the solid state has also been performed. The polypeptide conformation has also been compared to the NMR-derived structure of a smaller antifungical peptide, Ac-AMP2.