Trace elements in foods and meals consumed by students attending the faculty cafeteria

The content and intake of some trace elements (Pb, Cd, Ni, Hg, Cr) in meals, consumed by students attending the Faculty Cafeteria, were assessed. The study was carried out over 6 days of the 2nd week of February, 1993 and in three consecutive days of the second week of May. In those periods 10453 and 4055 students attended the cafeteria, respectively. After recording the ingredients and the preparation and cooking methods, some edible portions of foods and dishes were collected, homogenised, lyophilised and kept in polyethylene bottles until analysis. We found few differences in food content and dietary intake of some (Ni and Cr) but not all trace elements between February and May. Higher levels of Pb, Cd, Ni, Cr were present in bread (21.5+/-14.0, 5.6+/-0.02, 55.6+/-1.7 and 66.9+/-0.1 microg/100 g of edible portion, respectively), followed by meat, filled pasta and cheese, whereas lower values were observed in vegetables and fruit. The highest Hg content was recorded in the pasta group. Among the most frequently consumed foods and meals, the highest levels of P, Pb, Cr, Hg, Ni were found in bread, meat and pasta. The calculation of mean trace element intake, corrected for leftovers, showed pasta, bread and meat as the main sources of Pb, Cd, Ni, Hg and Cr over the two periods. The estimated potential tolerated weekly intake (PTWI) resulted high for Pb and Cd and low for Hg. Finally, a large variability in trace element content between raw and cooked foods was observed. These results give valuable information on trace element content of foods to be used for preparation of meals at the Faculty cafeteria in different seasons.     

Modelling and control of variable‐speed multi‐pole permanent magnet synchronous generator wind turbine

Emphasis of this article is on variable‐speed pitch‐controlled wind turbines with multi‐pole permanent magnet synchronous generator (PMSG) and on their extremely soft drive‐train shafts. A model and a control strategy for a full back‐to‐back converter wind turbine with multi‐pole PMSG are described. The model comprises submodels of the aerodynamic rotor, the drive‐train by a two‐mass model, the permanent magnet generator and the full‐scale converter system. The control strategy, which embraces both the wind turbine control itself and the control of the full‐scale converter, has tasks to control independently the active and reactive powers, to assist the power system and to ensure a stable normal operation of the wind turbine itself. A multi‐pole PMSG connected to the grid through a full‐scale converter has no inherent damping, and therefore, such configuration can become practically unstable, if no damping by means of external measures is applied. In this work, the frequency converter is designed to damp actively the drive‐train oscillations, thus ensuring stable operation. The dynamic performance of the presented model and control strategy is assessed and emphasized in normal operation conditions by means of simulations in the power system simulation tool DIgSILENT. Copyright © 2008 John Wiley & Sons, Ltd.     

Systematic analysis of yeast strains with possible defects in lipid metabolism

Lipids are essential components of all living cells because they are obligate components of biological membranes, and serve as energy reserves and second messengers. Many but not all genes encoding enzymes involved in fatty acid, phospholipid, sterol or sphingolipid biosynthesis of the yeast Saccharomyces cerevisiae have been cloned and gene products have been functionally characterized. Less information is available about genes and gene products governing the transport of lipids between organelles and within membranes or the turnover and degradation of complex lipids. To obtain more insight into lipid metabolism, regulation of lipid biosynthesis and the role of lipids in organellar membranes, a group of five European laboratories established methods suitable to screen for novel genes of the yeast Saccharomyces cerevisiae involved in these processes. These investigations were performed within EUROFAN (European Function Analysis Network), a European initiative to identify the functions of unassigned open reading frames that had been detected during the Yeast Genome Sequencing Project. First, the methods required for the complete lipid analysis of yeast cells based on chromatographic techniques were established and standardized. The reliability of these methods was demonstrated using tester strains with established defects in lipid metabolism. During these investigations it was demonstrated that different wild‐type strains, among them FY1679, CEN.PK2‐1C and W303, exhibit marked differences in lipid content and lipid composition. Second, several candidate genes which were assumed to encode proteins involved in lipid metabolism were selected, based on their homology to genes of known function. Finally, lipid composition of mutant strains deleted of the respective open reading frames was determined. For some genes we found evidence suggesting a possible role in lipid metabolism. Copyright © 1999 John Wiley & Sons, Ltd.     

Protein Phosphatase 2A Improves Cardiac Functional Response to Ischemia and Sepsis

Reversible protein phosphorylation is a posttranslational modification of regulatory proteins involved in cardiac signaling pathways. Here, we focus on the role of protein phosphatase 2A (PP2A) for cardiac gene expression and stress response using a transgenic mouse model with cardiac myocyte-specific overexpression of the catalytic subunit of PP2A (PP2A-TG). Gene and protein expression were assessed under basal conditions by gene chip analysis and Western blotting. Some cardiac genes related to the cell metabolism and to protein phosphorylation such as kinases and phosphatases were altered in PP2A-TG compared to wild type mice (WT). As cardiac stressors, a lipopolysaccharide (LPS)-induced sepsis in vivo and a global cardiac ischemia in vitro (stop-flow isolated perfused heart model) were examined. Whereas the basal cardiac function was reduced in PP2A-TG as studied by echocardiography or as studied in the isolated work-performing heart, the acute LPS- or ischemia-induced cardiac dysfunction deteriorated less in PP2A-TG compared to WT. From the data, we conclude that increased PP2A activity may influence the acute stress tolerance of cardiac myocytes.