Erythrocyte selenium concentration as a marker of selenium status.

BACKGROUND & AIMS: Plasma selenium concentration and glutathione peroxidase (GPx) activity are commonly used as markers of selenium nutritional status. However, plasma selenium concentrations fall independently of selenium status during the acute phase response and GPx is analytically problematic. The assay for erythrocyte selenium is robust and concentrations are unaffected by the systemic inflammatory response. This study was performed to investigate the validity of erythrocyte selenium measurement in assessing selenium status. METHODS: C-reactive protein (CRP), plasma and erythrocyte selenium concentrations and GPx activity were measured in 96 women from two regions of Malawi with low and high selenium dietary intakes. CRP and plasma and erythrocyte selenium was measured in 91 critically ill patients with a systemic inflammatory response. RESULTS & CONCLUSIONS: The median CRP value of all subjects from Malawi was 4.2 mg/L indicating no inflammation. The median CRP value for the critically ill patients was 126 mg/L indicating this group was inflamed. In the non-inflamed population there was a strong positive correlation (r = 0.95) between erythrocyte and plasma selenium and a strong positive correlation (r = 0.77) between erythrocyte selenium and erythrocyte GPx up to 6.10 nmol/g Hb after which maximal activity was reached. In the inflamed population, plasma selenium was low, erythrocyte selenium was normal and there was a weak correlation (r = 0.30) between selenium concentrations in plasma and erythrocytes. This demonstrates that plasma selenium is affected by the inflammatory response while erythrocyte selenium concentration is unaffected and can be used to reliably assess selenium status across a wide range of selenium intakes.

A framework to explore micronutrient deficiency in maternal and child health in Malawi, Southern Africa.

BACKGROUND: Global food insecurity is associated with micronutrient deficiencies and it has been suggested that 4.5 billion people world-wide are affected by deficiencies in iron, vitamin A and iodine. Zinc has also been identified to be of increasing concern. The most vulnerable are young children and women of childbearing age. A pilot study has been carried out in Southern Malawi, to attempt to link the geochemical and agricultural basis of micronutrient supply through spatial variability to maternal health and associated cultural and social aspects of nutrition. The aim is to establish the opportunity for concerted action to deliver step change improvements in the nutrition of developing countries. RESULTS: Field work undertaken in August 2007 and July/August 2008 involved the collection of blood, soil and crop samples, and questionnaires from ~100 pregnant women. Complex permissions and authorisation protocols were identified and found to be as much part of the cultural and social context of the work as the complexity of the interdisciplinary project. These issues are catalogued and discussed. A preliminary spatial evaluation is presented linking soil quality and food production to nutritional health. It also considers behavioural and cultural attitudes of women and children in two regions of southern Malawi, (the Shire Valley and Shire Highlands plateau). Differences in agricultural practice and widely varying soil quality (e.g. pH organic matter, C/N and metal content) were observed for both regions and full chemical analysis of soil and food is underway. Early assessment of blood data suggests major differences in health and nutritional status between the two regions. Differences in food availability and type and observations of life style are being evaluated through questionnaire analysis. CONCLUSION: The particular emphasis of the study is on the interdisciplinary opportunities and the barriers to progress in development support in subsistence communities. Engaging at the community level and the balance of expectations from both study subjects and research team highlight the merit of careful and detailed planning and project delivery.

Micronutrient deficiencies in maternity and child health: a review of environmental and social context and implications for Malawi.

It is well documented that micronutrient malnutrition is of increasing concern in the developing world, resulting in poor health and high rates of mortality and morbidity. During pregnancy, deficiency of iron and zinc can produce cognitive and growth impairment of the foetus, which may continue into infancy. Iron and zinc are essential micronutrients for both plant growth and human nutrition. Despite significant work in the areas of soil fertility, crop biofortification and dietary interventions, the problems of micronutrient deficiencies persist in Africa. There is a need to examine why communities have not embraced intervention strategies which may offer health benefits. Bottom-up, interdisciplinary approaches are required to effectively study the relationships between local communities and their environment, and to assess the impact their behaviour has on the cycling of micronutrients within the soil-plant-human system. From a detailed consideration of diverse influencing factors, a methodological model is suggested for studying the barriers to improving micronutrient uptake within rural communities. It combines environmental understanding with health and social factors, emphasising the need for and potential benefits of understanding and coherence in true interdisciplinary working.

Roles for both cyclic GMP and cyclic AMP in the inhibition of collagen-induced platelet aggregation by nitroprusside.

In studies on human platelets, nitroprusside (NP) alone at 1-10 micromol/l increased platelet cyclic AMP (cAMP) by 40-70%, whereas increases in cyclic GMP (cGMP) were much larger in percentage though not in concentration terms. Collagen enhanced these increases in cAMP up to fourfold, without affecting cGMP. This effect was partly prevented by indomethacin or aspirin, indicating that platelet cyclo-oxygenase products acted synergistically with NP to increase cAMP. ADP released from the platelets by collagen tended to restrict this cAMP accumulation. Addition of 2',5'-dideoxyadenosine (DDA), an inhibitor of adenylyl cyclase, decreased both the inhibition of collagen-induced platelet aggregation by NP and the associated accumulation of cAMP without affecting cGMP, indicating that cAMP mediates part of the inhibitory effect of NP. Unlike DDA, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), an inhibitor of guanylyl cyclase, blocked all increases in both cGMP and cAMP caused by NP, as well as the inhibition of platelet aggregation, suggesting that cAMP accumulation was secondary to that of cGMP. Human platelet cGMP-dependent protein kinase (PKG) coelectrophoresed with the purified bovine type Ibeta isoenzyme. An inhibitor of this enzyme (Rp)-beta-phenyl-1,N2-etheno-8-bromoguanosine 3',5'-cyclic-monophosphorothioate, diminished the inhibition of collagen-induced platelet aggregation by NP, but had little additional effect when DDA was present. This showed that both PKG and cAMP participate in the inhibition of collagen-induced platelet aggregation by NP. Moreover, selective activators of PKG and cAMP-dependent protein kinases had supra-additive inhibitory effects, suggesting that an optimal inhibitory effect of NP requires simultaneous activation of both enzymes.