The effect of inflammation on serum zinc concentrations and the prevalence estimates of population-level zinc status among Congolese children aged 6-59 months.

BACKGROUND/OBJECTIVES: Zinc is a negative acute-phase reactant; hence, its concentration decreases in the presence of inflammation. There is no current consensus on how to control for the effect of inflammation on serum zinc, which has implications for accurate estimates of population-level zinc status. We aimed to measure the association between inflammation and serum zinc concentrations and to compare the means and the prevalence of zinc deficiency using unadjusted and inflammation-adjusted serum zinc concentrations among Congolese children. SUBJECTS/METHODS: Non-fasting blood was collected in the afternoon in trace element-free vacutainers from 744 apparently healthy children aged 6-59 months in the Democratic Republic of the Congo. Serum was analyzed for zinc, C-reactive protein (CRP) and α-1 acid glycoprotein (AGP) for 665 children with complete data for all three biomarkers. Linear regression was used to generate correction factors (CFs) based on three stages of inflammation: incubation (CRP >5 mg/l and normal AGP), early convalescence (CRP >5 mg/l and AGP >1 g/l) and late convalescence (AGP >1 g/l and normal CRP), relative to no inflammation. RESULTS: Overall unadjusted mean±s.d. serum zinc concentration was 9.4±2.1 µmol/l. Study-generated CFs (95% confidence interval) for incubation, early and late convalescence were 1.01 (0.88, 1.14), 1.15 (1.11, 1.21) and 1.07 (1.03, 1.11), respectively. After applying the CFs, overall adjusted mean±s.d. serum zinc concentration was 10.1±2.2 µmol/l, and prevalence of zinc deficiency (<8.7 µmol/l) decreased from 35% (n=234/665) to 24% (n=160/665). CONCLUSIONS: Adjustment of zinc concentrations for inflammation is warranted when assessing population-level zinc status.European Journal of Clinical Nutrition advance online publication, 23 August 2017; doi:10.1038/ejcn.2017.127.

Bioavailability of elemental iron powder in white wheat bread.

OBJECTIVE: Iron fortification of wheat flour is widely used. In most cases, elemental iron powders are utilized as fortificants due to their lower cost and few, if any, sensory problems. However, their bioavailability is unknown. We aimed to measure the bioavailability of H(2)-reduced elemental iron powder in white wheat bread made from 72% extraction flour. DESIGN: A stable isotope of H(2)-reduced iron powder (mean particle size 15 microm) was used as fortificant in bread prepared from unfortified wheat flour. In all, 12 5- to 7-y-old children were fed bread with 4 mg of H(2)-reduced (58)Fe /100 g of flour. The next day (57)Fe ascorbate was given as reference dose. After 14 days, erythrocytes were analyzed for isotopic enrichment using mass spectrometry. RESULTS: When normalized to 40% absorption of the reference dose, the geometric mean (+/-range of 1 s.d.) bioavailability of reduced (58)Fe in wheat bread rolls was 6.5% (3.7-11.8). CONCLUSIONS: When compared to previous radioiron studies of ferrous sulfate showing 10% absorption from an identical meal in adult women, the relative bioavailability can be estimated at about 65%. However, the bioavailability of this smaller particle size (58)Fe (15 microm) is likely to be higher than that of commercial iron powder (45 microm) although the precise difference cannot be ascertained with current methods. Thus, the bioavailability of commercial elemental iron powders currently used in fortification programs is likely to be substantially lower than that of ferrous sulfate. SPONSORSHIP: This work was funded in part by Grant No 910313 by Micronutrient Initiative, IDRC, Ottawa, Canada.

Indoor biofuel air pollution and respiratory health: the role of confounding factors among women in highland Guatemala.

BACKGROUND: A number of studies have reported associations between indoor biofuel air pollution in developing countries and chronic obstructive lung disease (COLD) in adults and acute lower respiratory infection (ALRI) in children. Most of these studies have used indirect measures of exposure and generally dealt inadequately with confounding. More reliable, quantified information about this presumed effect is an important pre-requisite for prevention, not least because of the technical, economic and cultural barriers to achieving substantial exposure reductions in the world's poorest households, where ambient pollution levels are typically between ten and a hundred times higher than recommended standards. This study was carried out as part of a programme of research designed to inform the development of intervention studies capable of providing quantified estimates of health benefits. METHODS: The association between respiratory symptoms and the use of open fires and chimney woodstoves ('planchas'), and the distribution of confounding factors, were examined in a cross-sectional study of 340 women aged 15-45 years, living in a poor rural area in the western highlands of Guatemala. RESULTS: The prevalence of reported cough and phlegm was significantly higher for three of six symptom measures among women using open fires. Although this finding is consistent with a number of other studies, none has systematically examined the extent to which strong associations with confounding variables in these settings limit the ability of observational studies to define the effect of indoor air pollution adequately. Very strong associations (P < 0.0001) were found between the type of fire and a number of household and socioeconomic factors including the arrangement of rooms, floor type, and possession of a radio and television. The spouse's economic activity type was also significantly associated (P < 0.05). Thus, while 82% of open fire users had dirt floors and only 18% cement or tile floors, the situation was reversed for plancha users, only 16% of whom had dirt floors. CONCLUSIONS: Confounding presents a substantial problem for observational studies of indoor air pollution and health, although there is a reasonable case for believing that the observed association is causal. Intervention studies are required for stronger evidence of this association, and more importantly, to determine the size of health benefit achievable through feasible exposure reductions.

PIP: The authors investigated the association between respiratory symptoms and the use of open fires and chimney woodstoves, as well as the distribution of confounding factors, in a cross-sectional study of 340 women aged 15-45 years living in a poor rural area in the western highlands of Guatemala, and found a significantly higher prevalence of reported cough and phlegm for 3 of 6 symptom measures among women using open fires. When considering confounding factors, very strong associations were found between the type of fire and a number of household and socioeconomic factors including the arrangement of rooms, floor type, and possession of a radio and television. The spouse's economic activity type was also significantly associated. 82% of open fire users had dirt floors, with the remaining 18% having cement or tile floors, while only 16% of chimney woodstove users had dirt floors.

[Personnel standardization in clinical diagnosis of goiter: how to evaluate agreement among thyroid examiners?]. / Estandarización de personal en diagnóstico clínico de bocio: Cómo evaluar la concordancia entre examinadores de la tiroides?

The use of the t Student and Cochran tests to evaluate central tendency measures, as well as the F test to evaluate variability and correlation analysis, have been incorrectly used for the evaluation of concordance between thyroid examiners. This paper presents the intraclass Kappa test (Bloch & Kraemer, 1989), as well as the experience of its use in Central America to standardize thyroid examiner personnel who participated in national surveys carried out during 1990 to determine goiter prevalence.

The relA locus and the regulation of lysine biosynthesis in Escherichia coli.

The allelic state of relA influences the phenotype of Escherichia coli strains carrying the lysA22 mutation:lysA22 relA strains are Lys- where lysA22 relA+ strains grow (slowly) in the absence of lysine. This physiological effect has been related to an effect of the expression of the relA locus on the regulation of lysine biosynthesis. The fully derepressed levels of some lysine enzymes (aspartokinase III, aspartic semialdehyde dehydrogenase, didhydrodipicolinate reductase) are observed under lysine limitation only in rel+ strains. And the induction of DAP-decarboxylase by DAP is much higher in rel+ than in rel- strains when an amino acid limitation of growth is also realised. These results are in agreement with the hypothesis of Stephens et al. (1975) on a possible role of the stringent regulation as a general signal for amino acid deficiency.

Isolation and identification of mutants constitutive for aspartokinase III synthesis in Escherichia coli K 12.

We devised a procedure in order to isolate, in Escherichia coli, constitutive mutants for aspartokinase III synthesis, the first enzyme of the lysine regulon. It consists of the introduction of a limiting step in lysine biosynthesis, by the use of the partial suppression of a nonsense mutation. For the first time we could isolate many constitutive mutants. Their characteristics (cotransduction with the lysC structural gene; no effect on the synthesis of other enzymes of the regulon; cis-dominance) lead to classify these mutations as operator-type. The fact that no repressor mutations could be isolated is discussed.

Effect of mutations affecting lysyl-tRNAlys on the regulation of lysine biosynthesis in Escherichia coli.

When studying mutants affecting lysyl-tRNA synthetase or tRNAlys (hisT, hisW), a lack of correlation is clearly observed between the amount of lysyl-tRNA and the level of derepression of several lysine biosynthetic enzymes. This exlcudes the possible role of lysyl-tRNA as the specific corepressor of the lysine regulon. However, the level of derepression of DAP-decarboxylase, the last enzyme of the lysine pathway, is very low in the hisT mutant; this indicates that tRNAlys is a secondary effector involved in the regulation of the synthesis of this enzyme.

Regulation of lysine biosynthesis in Escherichia coli K12.

A general survey of the regulation in lysine biosynthesis in Escherichia coli K12 is presented. No polygenic operon exists for the genes that code for enzymes of the lysine biosynthetic pathway. Lysyl-tRNA is not directly involved as a co-repressor in the pathway. Different regulation mechanisms must exist for the different enzymes. In the case of the last enzyme, diaminopimelate decarboxylase, its synthesis is induced in vivo by the lysine-sensitive aspartokinase under its non-inhibited allosteric conformation.

Role of lysyl-tRNA in the regulation of lysine biosynthesis in Escherichia coli K12.

A mutant of lysyl-tRNA synthetase has been isolated in Escherichia coli K12. With this strain the Kmapp for lysine is 25 fold higher than with the parental strain. The percentage of charged tRNAlys in vivo is only 7 per cent (as against 65 per cent with HFR H). Under these conditions no derepression of synthesis is observed for three lysine biosynthetic enzymes (AK III, ASA-dehydrogenase, DAP-decarboxylase) ; a partial derepression is obtained in the case of the dhdp-reductase. Thus lysyl-tRNA does not act as the only corepressor molecule in the lysine regulon.

Regulation of the lysine biosynthetic pathway in Escherichia coli K-12: isolation of a cis-dominant constitutive mutant for AK III synthesis.

A method for isolating regulatory mutants for the synthesis of lysine biosynthetic enzymes in Escherichia coli is described. One of them is identified as a cis-dominant constitutive mutant for the synthesis of the lysine-sensitive asportokinase AK III (lysC gene).

[Regulation of lysyl-tRNA synthetase of Escherichia coli K12]. / Régulation de la lysyl-tARN synthétase d'Escherichia coli K 12

In Escherichia coli K 12, addition of lysine to the growth medium does not lead to a repression of the synthesis of the lysyl-tRNA synthetase. On the contrary, by use of a strain bradytrophic for one of the lysine biosynthetic enzymes, a shift from a medium containing lysine to minimal medium leads to an increase in the specific activity for this enzyme. This increase is discrete (1.5 fold) but reproducible. Thus it may be assumed that lysyl-tRNA synthetase belongs to the lysine regulon.

Multivalent repression of aspartic semialdehyde dehydrogenase in Escherichia coli K-12.

Mutants of Escherichia coli in which the lysine-sensitive aspartokinase is feedback-resistant are described. In these strains, as well as in the wild type, aspartic semialdehyde dehydrogenase is subject to multivalent repression by lysine, threonine, and methionine. When these amino acids were added to a culture in minimal medium, the differential rate of synthesis of the enzyme dropped to zero and remained there for about one generation.