How to use the world's scarce selenium resources efficiently to increase the selenium concentration in food

The world's rare selenium resources need to be managed carefully. Selenium is extracted as a by-product of copper mining and there are no deposits that can be mined for selenium alone. Selenium has unique properties as a semi-conductor, making it of special value to industry, but it is also an essential nutrient for humans and animals and may promote plant growth and quality. Selenium deficiency is regarded as a major health problem for 0.5 to 1 billion people worldwide, while an even larger number may consume less selenium than required for optimal protection against cancer, cardiovascular diseases and severe infectious diseases including HIV disease. Efficient recycling of selenium is difficult. Selenium is added in some commercial fertilizers, but only a small proportion is taken up by plants and much of the remainder is lost for future utilization. Large biofortification programmes with selenium added to commercial fertilizers may therefore be a fortification method that is too wasteful to be applied to large areas of our planet. Direct addition of selenium compounds to food (process fortification) can be undertaken by the food industry. If selenomethionine is added directly to food, however, oxidation due to heat processing needs to be avoided. New ways to biofortify food products are needed, and it is generally observed that there is less wastage if selenium is added late in the production chain rather than early. On these bases we have proposed adding selenium-enriched, sprouted cereal grain during food processing as an efficient way to introduce this nutrient into deficient diets. Selenium is a non-renewable resource. There is now an enormous wastage of selenium associated with large-scale mining and industrial processing. We recommend that this must be changed and that much of the selenium that is extracted should be stockpiled for use as a nutrient by future generations

Effect of sodium selenite-enriched reperfusion solutions on rat cardiac ischemia reperfusion injury

Cardiac surgery often generates oxidative stress leading to ischemia reperfusion injury (I-R). Antioxidants have been shown to prevent this injury and have been added to cardioplegic solutions to assist in recovery. In this study, we tested the effectiveness of sodium selenite in protecting against ischemia reperfusion injury and investigated the mechanisms behind this protection. Hearts from male Wistar rats were subjected to ischemia reperfusion using the Langendorf model. Krebs-Henseleit perfusion solutions were supplemented with 0,0.1, 0.5, 1.0, and 10&mu;M sodium selenite. Hearts were perfused for 30 min and then subjected to 22.5 min of global ischemia followed by 45 min reperfusion. Heart rate, ischemic contracture, end diastolic pressure, and developed ventricular pressure were monitored. At the completion of the experiment, hearts were homogenized and tissue extracts were assayed for glutathione peroxidase (GSH-Px) and thioredoxin reductase (Thx-Red) activity. Sodium selenite, at a concentration of 0.5 &mu;M, demonstrated a protective effect on the recovery of cardiac function following I-R, as evidenced by a lower end diastolic pressure and enhanced recovery of rate pressure product. There was no beneficial effect observed in hearts perfused with 0.1 &mu;M sodium selenite-supplemented buffer, whereas poorer functional recovery was observed in hearts perfused with 10 &mu;M sodium selenite-supplemented buffer. The beneficial effect of sodium selenite was not mediated through increased activity of GSH-Px or Thx-Red. This study demonstrates that the addition of sodium selenite to reperfusion solutions, at an optimal concentration of 0.5 &mu;M, assists in cardiac recovery following ischemia reperfusion.<br /

Induction of autoimmune valvulitis in lewis rats following immunization with peptides from the conserved region of group A streptococcal M protein

Rheumatic heart disease (RHD) is considered to be an autoimmune disorder mediated by group A streptococcal (GAS) M protein-specific T cells and antibodies that cross-react with cardiac antigens and epitopes of the GAS M protein. In this study, Lewis rats were immunized with a pool of overlapping peptides spanning the conserved region of the GAS M protein in Complete Freund's Adjuvant, followed by immunization with Bordetella pertussis. Controls received adjuvants alone. Spleen-derived lymphocytes from rats immunized with the conserved region peptides proliferated in response to the immunogen and to cardiac myosin. Moreover, histological examination of cardiac tissue from rats immunized with conserved region peptides revealed the presence of inflammatory lesions in both the myocardium and valve tissue indicating a role for GAS M protein-specific autoreactive T cells in the development of cardiac lesions. This study may support the use of the rat model of autoimmune valvulitis to investigate the immunopathogenesis of RHD and possible preventive strategies

Animal models to investigate the pathogenesis of rheumatic heart disease

Rheumatic fever (RF) and rheumatic heart disease (RHD) are sequelae of group A streptococcal (GAS) infection. Although an autoimmune process has long been considered to be responsible for the initiation of RF/RHD, it is only in the last few decades that the mechanisms involved in the pathogenesis of the inflammatory condition have been unraveled partly due to experimentation on animal models. RF/RHD is a uniquely human condition and modeling this disease in animals is challenging. Antibody and T cell responses to recombinant GAS M protein (rM) and the subsequent interactions with cardiac tissue have been predominantly investigated using a rat autoimmune valvulitis model. In Lewis rats immunized with rM, the development of hallmark histological features akin to RF/RHD, both in the myocardial and in valvular tissue have been reported, with the generation of heart tissue cross-reactive antibodies and T cells. Recently, a Lewis rat model of Sydenham's chorea and related neuropsychiatric disorders has also been described. Rodent models are very useful for assessing disease mechanisms due to the availability of reagents to precisely determine sequential events following infection with GAS or post-challenge with specific proteins and or carbohydrate preparations from GAS. However, studies of cardiac function are more problematic in such models. In this review, a historical overview of animal models previously used and those that are currently available will be discussed in terms of their usefulness in modeling different aspects of the disease process. Ultimately, cardiologists, microbiologists, immunologists, and physiologists may have to resort to diverse models to investigate different aspects of RF/RHD