Influence of mercury exposure on blood pressure, resting heart rate and heart rate variability in French Polynesians: a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Populations which diet is rich in seafood are highly exposed to contaminants such as mercury, which could affect cardiovascular risk factors</p> <p>Objective</p> <p>To assess the associations between mercury and blood pressure (BP), resting heart rate (HR) and HR variability (HRV) among French Polynesians</p> <p>Methods</p> <p>Data were collected among 180 adults (≥ 18 years) and 101 teenagers (12-17 years). HRV was measured using a two-hour ambulatory electrocardiogram (Holter) and BP was measured using a standardized protocol. The association between mercury and HRV and BP parameters was studied using analysis of variance (ANOVA) and analysis of covariance (ANCOVA)</p> <p>Results</p> <p>Among teenagers, the high frequency (HF) decreased between the 2^ndand 3^rdtertile (380 vs. 204 ms², p = 0.03) and a similar pattern was observed for the square root of the mean squared differences of successive R-R intervals (rMSSD) (43 vs. 30 ms, p = 0.005) after adjusting for confounders. In addition, the ratio low/high frequency (LF/HF) increased between the 2^ndand 3^rdtertile (2.3 vs. 3.0, p = 0.04). Among adults, the standard deviation of R-R intervals (SDNN) tended to decrease between the 1^stand 2^ndtertile (84 vs. 75 ms, p = 0.069) after adjusting for confounders. Furthermore, diastolic BP tended to increase between the 2^ndand 3^rdtertile (86 vs. 91 mm Hg, p = 0.09). No significant difference was observed in resting HR or pulse pressure (PP)</p> <p>Conclusions</p> <p>Mercury was associated with decreased HRV among French Polynesian teenagers while no significant association was observed with resting HR, BP, or PP among teenagers or adults</p

Perspective: Food Environment Research Priorities for Africa-Lessons from the Africa Food Environment Research Network

Over the last 2 decades, many African countries have undergone dietary and nutrition transitions fueled by globalization, rapid urbanization, and development. These changes have altered African food environments and, subsequently, dietary behaviors, including food acquisition and consumption. Dietary patterns associated with the nutrition transition have contributed to Africa's complex burden of malnutrition—obesity and other diet-related noncommunicable diseases (DR-NCDs)—along with persistent food insecurity and undernutrition. Available evidence links unhealthy or obesogenic food environments (including those that market and offer energy-dense, nutrient-poor foods and beverages) with suboptimal diets and associated adverse health outcomes. Elsewhere, governments have responded with policies to improve food environments. However, in Africa, the necessary research and policy action have received insufficient attention. Contextual evidence to motivate, enable, and create supportive food environments in Africa for better population health is urgently needed. In November 2020, the Measurement, Evaluation, Accountability, and Leadership Support for Noncommunicable Diseases Prevention Project (MEALS4NCDs) convened the first Africa Food Environment Research Network Meeting (FERN2020). This 3-d virtual meeting brought researchers from around the world to deliberate on future directions and research priorities related to improving food environments and nutrition across the African continent. The stakeholders shared experiences, best practices, challenges, and opportunities for improving the healthfulness of food environments and related policies in low- and middle-income countries. In this article, we summarize the proceedings and research priorities identified in the meeting to advance the food environment research agenda in Africa, and thus contribute to the promotion of healthier food environments to prevent DR-NCDs, and other forms of malnutrition

The Cell Wall Peptidoglycan of Bacillus megaterium KM. I. Studies on the Stereochemistry of α,α'-Diaminopimelic Acid

α,α'-Diaminopimelic acid (DAP) occurs in the wall peptidoglycan of Bacillus megaterium KM predominantly in the form of its meso isomer (about 85% of the total residues) and, in minor amounts, in the form of its DD isomer. The amino groups on the L carbon of the meso-DAP residues are involved in peptide linkages to the glutamic acid residues. Most of the amino groups on the D carbon of the meso-DAP residues are free; some of them are substituted, thus probably serving to cross-link peptide subunits. These amino groups can be liberated by a Streptomyces endopeptidase. None of the DD-DAP residues have amino groups free. Moreover, these groups are not liberated by endopeptidase treatment. The peptidoglycan upon enzymatic degradation yields mainly two fractions. A major fraction is composed of disaccharide peptide monomer subunits containing only the meso isomer of DAP. A second minor fraction is composed of disaccharide peptide oligomers containing both meso and DD isomers of DAP. The meso-DAP residues isolated as monodinitrophenyl derivatives from both fractions have optical rotations and optical rotatory dispersions identical with that of synthetic monodinitrophenyl-meso-DAP obtained by dinitrophenylation of the amino group on the D carbon. The assignment of the DD configuration to the DAP residues which are not meso rests upon the optical rotatory properties of their bisdinitrophenyl derivatives

The peptide N alpha-(L-alanyl-D-isoglutaminyl)-N epsilon-(D-isoasparaginyl)-L-lysyl-D-alanine and the disaccharide N-acetylglucosaminyl-beta-1,4-N-acetylmuramic acid in cell wall peptidoglycan of Streptococcus faecalis strain ATCC 9790

A major portion of the cell wall peptidoglycan in Streptococcus faecalis is composed of the disaccharide tetrapeptide β-1,4-N-acetylglucosaminyl-N-acetylmuramyl-Nα-(L-alanyl-D-isoglutaminyl)-L-lysyl-D-alanine. The tetrapeptides are cross-linked through single D-isoasparaginyl residues extending from the C-terminal D-alanine of one tetrapeptide unit to the Nє-terminal L-lysine of another. It is the first time that the occurrence of an isoasparaginyl residue in a natural product has been described. The Streptomyces SA en-dopeptidase cleaves D-alanyl-D-isoasparaginyl linkages and is thus the first enzyme known to hydrolyze D-D peptide bonds. Treatment of the disaccharide Nα-( L-alanyl-D-isoglutaminyl)-N є-(D-isoasparaginyl)- L-lysil-D-alanine with 10 equiv of NaOH at 37° for 1 hr results in deamidation of the isoasparaginyl residue together with migration of the aspartyl-lysine peptide bond giving rise to a mixture of Nє-(β-aspartyl)- and N є-(α-aspartyl)lysyl peptides. Under the same alkaline treatment, the N-acetylmuramyl residue undergoes a lactyl elimination which results in the production of acyl peptides and a Morgan-Elson prochromogenic compound, without hydrolysis of the glycosidic linkage. This conversion, interpreted to be the result of a β elimination, also occurs in the other disaccharide peptide monomers previously isolated from Staphylococcus aureus, Micrococcus roseus, and Streptococcus pyogenes

Structure of the meso-diaminopimelic acid containing peptidoglycans in Escherichia coli B and Bacillus megaterium KM

The peptide subunit of the peptidoglycan of the envelope of Escherichia coli B has the sequence L-Ala-γ-D-Glu-(L)-meso-diaminopimelic acid-(L)-D-Ala. D-Ala-(D)-meso diaminopimelic acid linkages are involved in the cross-linking between peptide subunits. A major part of the wall peptidoglycan of Bacillus megaterium KM is composed of the same aforementioned peptide subunits and peptide cross-linkages. In this latter case, however, the D-Ala-(D)-meso-diaminopimelic acid linkages are not the only important ones. As previously shown, about 15% of the diaminopimelic acid residues are DD and they seem to be involved in another type of peptide cross-linkage. Streptomyces KM endopeptidase solubilizes the walls of Bacillus megaterium. Although this enzyme is not lytic upon Escherichia coli envelope, it liberates disaccharide peptide monomer from a bis-disaccharide peptide dimer, isolated from the same envelope. This dimer is composed of two β-1,4-N-acetylglucosaminyl-N-acetylmuramyl-L-Ala-γ-D-Glu-(L)-meso-diaminopimelic acid-(L)-D-Ala units, joined by a D-Ala-(D)-meso-diaminopimelic acid linkage

LL-diaminopimelic acid containing peptidoglycans in walls of Streptomyces sp. and of Clostridium perfringens (type A).

In a major part of the wall peptidoglycans of Streptomyces sp. and of Clostridium perfringens, L-alanyl-D-isoglutaminyl-(L1)-LL-diaminopimelyl-(L1)-D-alanine peptides are cross-linked via D-alanylglycyl-(L2)-LL-diaminopimelic acid linkages (peptidoglycan of the chemotype II group). The Myxobacter AL-I endopeptidase hydrolyzes both D-alanyl-glycine and glycyl-LL-diaminopimelic acid linkages in the walls of C. perfringens, liberating free glycine. In contrast, the Myxobacter AL-I endopeptidase hydrolyzes only D-alanyl-glycine linkages in walls of Streptomyces sp. and the liberation of the glycine residues requires subsequent treatment with an aminopeptidase. No explanation for this observation can be proposed at this time. A minor component of the AL-I endopeptidase hydrolysate of the Streptomyces and C. perfringens walls is a resistant peptide dimer. Analyses indicate that the cross-link in this dimer may be mediated through LL-diamino-pimelylglycyl-LL-diaminopimelic acid linkages. The C termini of the peptide moieties in the wall peptidoglycans are either D-alanine or LL-diarninopimelic acid but never D-alanyl-D-alanine, thus indicating the presence in these microorganisms of carboxypeptidases similar to those of Escherichia coli