Aluminum is Harmful to Benthic Invertebrates in Acidified Waters, but at What Threshold(s)?

Throughout many years of research into acidification effects, the contributing impact of increased levels of aluminum (Al), related to low pH, has been discussed and studied, especially for fish, but also for various benthic invertebrates. However, it seems problematic to give general guidelines for concentrations when Al is toxic or in other ways chronically harmful. Reasons for this are that the purpose of the performed research often has been to indicate different effects (or not) and their mechanisms; that the effects vary pronuncedly with the animal studied; that humic substances can ameliorate the effects by complex binding of metals; and also that several methods have been used to measure the toxic inorganic/labile/monomeric Al fractions. This paper considers published papers that describe experiments pertaining to effects of inorganic Al on benthic invertebrates in acidified lakes and streams. The evaluation, of interest for both basic acidification research and liming mitigations, indicate that many authors consider that problems occur in the interval 0.1 – 0.3 mg inorg-Al L^?1. However, many exceptions do exist in the assembled literature with respect to kind of animal and Al fraction and speciation, the presence of humic substances, the applied exposure time, and pH values. Therefore, it seems difficult to recommend Al as a specific instrumental indicator of when to lime.     

Improving nutritional quality of maize proteins by expressing sense and antisense zein genes

The predominant proteins in maize grain are a family of alcohol-soluble prolamin storage proteins called zeins. They account for >50% of total seed proteins but are deficient in several essential amino acids. As a result, the corn grain is considered to be nutritionally poor for monogastric animals with respect to key essential amino acids, most notably lysine, tryptophan, and methionine. Thus, corn mutants with reduced levels of zeins, such as opaque-2 (o2), have been demonstrated to possess grain with improved nutritional quality characteristics. The o2 mutant has a superior amino acid composition and has been used through conventional breeding to develop Quality Protein Maize (QPM) for human and animal consumption in developing countries. With the understanding of molecular genetics of zeins and progress in biotechnology, an alternative approach to zein reduction is explored here. Through the targeted reduction of the 19-kDa alpha-zeins, increased levels of lysine, tryptophan, and methionine have been engineered in grain of transgenic hybrids. Currently, the agronomic properties and nutritional values of these transgenic lines are being evaluated.     

Studies on synchronous egress of coccidian parasites (<Emphasis Type="Italic">Neospora caninum,Toxoplasma gondii,Eimeria bovis)</Emphasis> from bovine endothelial host cells mediated by calcium ionophore A23187

Neospora caninum, Toxoplasma gondii and Eimeria bovis are coccidian parasites of veterinary importance. Tachyzoites of N. caninum and T. gondii and sporozoites of E. bovis are able to invade and replicate in endothelial cells in vivo and in vitro. As it holds true for all eukaryotic cells, the survival of parasitized host cells and the parasites themselves should be dependent on ion balances, especially on extra- and intracellular calcium concentrations. Addition of the calcium ionophore A23187 reliably did release merozoites from mature N. caninum and T. gondii meronts grown in cultured primary bovine umbilical vein endothelial cells (BUVEC). Extent and time course of merozoite release depended on both, maturity of the meronts and concentration of the calcium ionophore. Attempts, however, to achieve synchronous release of merozoites from E. bovis first generation meronts by ionophore treatment failed, suggesting a different biological behaviour of this parasite. According to microscopical observations, the quite variable time of E. bovis macromeront maturation and a hampered merozoite exit owing to dense parasite-induced cytoskeleton elements surrounding the meront may be a reason for the lack of inducible synchronous release. Electronic supplementary materials The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

The effect of different dietary ratios of lysine,arginine and methionine on biochemical parameters and hormone secretion in turkeys

We postulated that the use of optimal levels and proportions of Lys, Arg and Met in compound feed allows for optimal exploitation of the growth potential of contemporary slaughter turkey hybrids and reduces metabolic disorders. The aim of the study was to determine the effect of different proportions of Lys, Arg and Met in diets whose Lys content is in accordance with NRC recommendations, that is a low level, on selected parameters of protein, lipid and carbohydrate metabolism and on hormone secretion in turkeys. The lowest Arg content (90% Lys) in the diet resulted in an increase in plasma total cholesterol levels in the turkeys as compared to higher Arg content (100% or 110% of Lys), (2.50 vs. 2.09 vs. 1.83). Plasma HDL and creatinine concentration increased in turkeys fed diets with higher Arg content (100% and 110% Lys) compared to turkeys receiving the diet with the lowest Arg content (90% Lys). Compared to turkeys receiving the lowest and intermediate Arg content (90% and 100% Lys), the diet with the highest content of this AA (110% Lys) resulted in an increase in the plasma T4 level (71.21 vs. 86.60 vs. 128.2). The varied Arg and Met levels relative to Lys did not affect the secretion of neurotransmitters or hormones regulating glucose metabolism. At low levels of Met in the diet, an decrease in Arg relative to Lys from 100% to 90% caused a growth depression of turkeys (10.68 vs. 10.21 kg), which was not noted in the case of the higher Met content. When using the Lys level recommended by NRC in the turkey diet, the optimal Arg level is 100% and Met is 45% compared to Lys.