Biosynthesis of modified peptidoglycan precursors by vancomycin-resistant Enterococcus faecium

In the presence of bacitracin, vancomycin-resistant Enterococcus faecium (vanA phenotype) accumulate UDP-N-acetylmuramyl(UDP-Mur-NAc)-tetrapeptide and a UDP-MurNAc-depsipentapeptide containing lactate substituted for the carboxy-terminal-D-alanine residue. In an in vitro peptidoglycan polymerization assay, the modified precursors function and confer resistance to vancomycin.     

Al3+-Ca2+ interactions in aluminum rhizotoxicity

Several mineral rhizotoxicities, including those induced by Al³⁺, H⁺, and Na⁺, can be relieved by elevated Ca²⁺ in the rooting medium. This leads to the hypothesis that the toxic cations displace Ca²⁺ from transport channels or surface ligands that must be occupied by Ca²⁺ in order for root elongation to occur. In this study with wheat (Triticum aestivum L.) seedlings, we have determined, in the case of Al³⁺, that (i) Ca²⁺, Mg²⁺, and Sr²⁺ are equally ameliorative, (ii) that root elongation does not increase as Ca²⁺ replaces Mg²⁺ or Sr²⁺ in the rooting media, and (iii) that rhizotoxicity is a function solely of Al³⁺ activity at the root-cell membrane surface as computed by a Gouy-Chapman-Stern model. The rhizotoxicity was indifferent to the computed membrane-surface Ca²⁺ activity. The rhizotoxicity induced by high levels of tris(ethylenediamine)cobaltic ion (TEC³⁺), in contrast to Al³⁺, was specifically relieved by Ca²⁺ at the membrane surface. The rhizotoxicity induced by H⁺ exhibited a weak specific response to Ca²⁺ at the membrane surface. We conclude that the Ca²⁺-displacement hypothesis fails in the case of Al³⁺ rhizotoxicity and that amelioration by cations (including monovalent cations) occurs because of decreased membrane-surface negativity and the consequent decrease in the membrane-surface activity of Al³⁺. However, TEC³⁺, but not Al³⁺, may be toxic because it inhibits Ca²⁺ uptake. The nature of the specific H⁺-Ca²⁺ interaction is uncertain.Abbreviations {Al³⁺ }₀ chemical activity of Al³⁺ at the root-cell membrane surface - {Al³⁺ }_E chemical activity of Al³⁺ in the external rooting medium - E₀ electrical potential at the root-cell membrane surface - HXM²⁺ hexamethonium ion - TEC³⁺ tris(ethylenediamine)cobaltic ion     

The phylogenetic position of the zokors (Myospalacinae) and comments on the families of muroids (Rodentia)

Recent molecular studies have concluded that the genus Myospalax evolved from within the rodent subfamily Cricetinae. This conclusion was tested using the complete sequences from the mitochondrial 12S rRNA and cytochrome b genes. Based on our analyses, Myospalax appears to be sister to a clade containing the subfamilies Spalacinae and Rhizomyinae, and all three of these lineages appear to be basal to the superfamily Muroidea. Based on the position of these three lineages, we suggest that they be placed in a distinct family, the Spalacidae, rather than subsumed as subfamilies in the family Muridae. Finally, our analyses suggest that the earlier placement of Myospalax as a member of the Cricetinae is the result of a single misidentified specimen, which was not a Myospalax.     

Distribution,diversity and drivers of blood-borne parasite co-infections in Alaskan bird populations

Avian species are commonly infected by multiple parasites, however few studies have investigated the environmental determinants of the prevalence of co-infection over a large scale. Here we believe that we report the first, detailed ecological study of the prevalence, diversity and co-infections of four avian blood-borne parasite genera: Plasmodium spp., Haemoproteus spp., Leucocytozoon spp. and Trypanosoma spp. We collected blood samples from 47 resident and migratory bird species across a latitudinal gradient in Alaska. From the patterns observed at collection sites, random forest models were used to provide evidence of associations between bioclimatic conditions and the prevalence of parasite co-infection distribution. Molecular screening revealed a higher prevalence of haematozoa (53%) in Alaska than previously reported. Leucocytozoons had the highest diversity, prevalence and prevalence of co-infection. Leucocytozoon prevalence (35%) positively correlated with Trypanosoma prevalence (11%), negatively correlated with Haemoproteus prevalence (14%) and had no correlation with Plasmodium prevalence (7%). We found temperature, precipitation and tree cover to be the primary environmental drivers that show a relationship with the prevalence of co-infection. The results provide insight into the impacts of bioclimatic drivers on parasite ecology and intra-host interactions, and have implications for the study of infectious diseases in rapidly changing environments.     

Estimating the Global Prevalence of Inadequate Zinc Intake from National Food Balance Sheets: Effects of Methodological Assumptions

Background

The prevalence of inadequate zinc intake in a population can be estimated by comparing the zinc content of the food supply with the population’s theoretical requirement for zinc. However, assumptions regarding the nutrient composition of foods, zinc requirements, and zinc absorption may affect prevalence estimates. These analyses were conducted to: (1) evaluate the effect of varying methodological assumptions on country-specific estimates of the prevalence of dietary zinc inadequacy and (2) generate a model considered to provide the best estimates.

Methodology and Principal Findings

National food balance data were obtained from the Food and Agriculture Organization of the United Nations. Zinc and phytate contents of these foods were estimated from three nutrient composition databases. Zinc absorption was predicted using a mathematical model (Miller equation). Theoretical mean daily per capita physiological and dietary requirements for zinc were calculated using recommendations from the Food and Nutrition Board of the Institute of Medicine and the International Zinc Nutrition Consultative Group. The estimated global prevalence of inadequate zinc intake varied between 12–66%, depending on which methodological assumptions were applied. However, country-specific rank order of the estimated prevalence of inadequate intake was conserved across all models (r = 0.57–0.99, P<0.01). A “best-estimate” model, comprised of zinc and phytate data from a composite nutrient database and IZiNCG physiological requirements for absorbed zinc, estimated the global prevalence of inadequate zinc intake to be 17.3%.

Conclusions and Significance

Given the multiple sources of uncertainty in this method, caution must be taken in the interpretation of the estimated prevalence figures. However, the results of all models indicate that inadequate zinc intake may be fairly common globally. Inferences regarding the relative likelihood of zinc deficiency as a public health problem in different countries can be drawn based on the country-specific rank order of estimated prevalence of inadequate zinc intake.     

hapConstructor: automatic construction and testing of haplotypes in a Monte Carlo framework

SUMMARY: Haplotypes carry important information that can direct investigators towards underlying susceptibility variants, and hence multiple tagging single nucleotide polymorphisms (tSNPs) are usually studied in candidate gene association studies. However, it is often unknown which SNPs should be included in haplotype analyses, or which tests should be performed for maximum power. We have developed a program, hapConstructor, which automatically builds multi-locus SNP sets to test for association in a case-control framework. The multi-SNP sets considered need not be contiguous; they are built based on significance. An important feature is that the missing data imputation is carried out based on the full data, for maximal information and consistency. HapConstructor is implemented in a Monte Carlo framework and naturally extends to allow for significance testing and false discovery rates that account for the construction process and to related individuals. HapConstructor is a useful tool for exploring multi-locus associations in candidate genes and regions. AVAILABILITY: http://www-genepi.med.utah.edu/Genie.     

Proteomic analysis of root meristems and the effects of acetohydroxyacid synthase-inhibiting herbicides in the root of Medicago truncatula

Quantitative proteome analyses of meristematic and nonmeristematic tissues from Medicago truncatula primary and lateral roots and meristem tissues from plants treated with acetohydroxyacid synthase-inhibiting herbicides were made. The accumulation of 81 protein spots changed in meristematic and nonmeristematic tissues and 51 protein spots showed significant changes in accumulation in herbicide-treated meristems. Identified proteins indicate two trends, (i) increased accumulation of cell division and redox-mediating proteins in meristems compared to nonmeristematic tissues and (ii) increased accumulation of pathogenesis-related and decreased accumulation of metabolic proteins in herbicide-treated roots.     

The effect of catecholamines and prostaglandins upon human and rat erythrocytes.

Both human and rat erythrocytes respond to low doses (10(-11)--10(-9) M) of L-isoproterenol and L-epinephrine with an increased degree of hypotonic hemolysis and a decreased rate of filtration through standardized paper filters. The receptors in both cell types have many of the characteristics of beta-receptors for catecholamines. However, hormone-receptor interaction in the human cell does not lead to an increase in intracellular cyclic AMP concentration, but in the rat cell, hormone-receptor interaction does lead to a significant increase in cyclic AMP content. Thus, catecholamine-beta-receptor interaction, at least in the human red cell, leads to a change in red cell properties which are not mediated by adenylate cyclase activation. Likewise, prostaglandin E2, at 10(-12)--10(-10) M, causes are increased degree of hypotonic hemolysis and a decreased rate of filtration through standardized paper filters, but it also does not increase the cycliC AMP content of the human erythrocyte but does increase that of the rat erythrocyte. Nevertheless, exogenous cyclic AMP, when added at a concentration of 10(-8) M to washed human erythrocytes, increases the degree of hypotonic hemolysis. Conversely, prostaglandin E1, at 10(-12)--10(-10) M, causes a decreased degree of hypotonic hemolysis and an increased rate of filtration through a standard filter. Both prostaglandin E2 and the catecholamines decrease the size of a rapidly exchangeable calcium pool, and prostaglandin E1 increases it.