Temporal and spatial trends in heavy metal concentrations in the marine mussel Mytilus edulis from the Western Scheldt estuary (The Netherlands)

Since the first North Sea Conference (1984, Bremen), all countries bordering the North Sea made commitments to reduce discharge of hazardous substances into the North Sea. From Belgium and The Netherlands, large reductions (upto 90) in heavy metal emissions from land-based sources have been reported between 1985 and 2000. Recently, some studies in the Western Scheldt estuary (WS) have shown that total metal concentration in the water, sediments and suspended particles have decreased compared to levels in the 70s. However, data on aquatic organisms is still very limited and it is therefore difficult to confirm whether the reductions in pollution input and generally improving water quality in the WS have a corresponding impact on the levels of heavy metals in aquatic organisms. The current study measured metal concentrations in the soft tissues of mussels, Mytilus edulis (known to be good indicators of environmental metal pollution) during the period 1996–2002. Spatial (salinity and pollution gradients), temporal and seasonal variations were also studied. Results showed a down-stream decreasing trend for the metals studied (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) during all sampling campaigns. There was also a significant seasonal effect on tissue metal concentrations, with a peak observed around spring in both WS and the nearby less polluted Eastern Scheldt (ES). On temporal trends, a clear drop of metals in mussels was observed in the early 80s coinciding with the start of the efforts to reduce chemical pollution input into the North Sea. Since those early reductions, metal concentrations in mussels generally remained unchanged upto mid 90s. However, in recent times metal concentration in mussels have increased significantly, for example Cd in 2002 was almost 10 times the values in 1983 and similar to levels seen during the peak in the 70s. Other metals also increased in the 90s also reaching levels seen in the 70s. As there is no indication of recent increase in metal input into the estuary, we suggest that increased metal concentrations observed in mussels in recent years especially in the upper estuary are most likely a result of changes in physical and chemical speciation and metal bioavailability. Such changes may be caused by changes in some water quality parameters in the estuary (i.e. increased dissolved oxygen, concentration of organic matter), resulting in conditions that favour releases of sediment-bound metals into the water column. The relationship between metal content and season showed very similar annual profiles in the polluted WS and less polluted ES. Thus, seasonal variations in metal concentrations appear to be largely controlled by biological processes, while total body burdens are dependent on environmental levels and bioavailability.     

The Streptomyces K15 DD-peptidase/penicillin-binding protein. Active site and sequence of the N-terminal region.

Fragments of the lipophosphoglycan of Leishmania donovani were generated by phospholipase C digestion and mild acid hydrolysis. The fragments were purified and examined for inhibitory activity on protein kinase C isolated from rat brains. On a molar basis, the 1-O-alkylglycerol portion of LPG exhibited the most inhibitory activity, whereas the carbohydrate domain was not as effective. In addition, several glycolipid antigens from L. major, which contain short carbohydrate chains attached to phosphatidylinositol, were also efficient inhibitors of the enzyme. These results are consistent with the hypothesis that protein kinase C may be a key target for the parasites to overcome within host macrophages.     

A microfibril-generating factor from the cellulase of Trichoderma reesei

A combination of ionic strength reduction and diafiltration of Trichoderma reesei cellulate complex through a hollow fiber apparatus of 5000 molecular weight (MW) cutoff and subsequent passage of filtrate over a Spherogel-TSK 3000-SW column provided extracts that had the ability to generate microfibrils in filter paper and to disrupt filter paper and corn leaf tissue. Milligram quantities of material obtained from these extracts released small amounts of soluble carbohydrate from filter paper, required ferric iron for increased activity, and contained amino acids. Short fiber formation and disruption of filter paper during interaction with these extracts was enhanced by prior acid treatment and eliminated by prior base treatment. The amount of soluble carbohydrate hydrolyzed in 24 h from filter paper by whole cellulase complex was not changed by first disrupting the substrate with the extracts.     

Additional regular echinoids from the upper cretaceous in the maastricht area (belgium)

Four additional species of regular echinoids from the Maastricht type-area, brought to light by intensive collecting, are described. Three of these were never reported before from the Low Countries. Their taxonomic status is discussed.     

Glycerol accumulation while recycling thin stillage in corn fermentations to ethanol

Summary By succesive recycling of the thin stillage in mashing and fermenting fresh corn, the glycerol content in each fermentation increased by about 0.4% and accumulated to a high of 2.1% in the beer of the fifth recycle. Glycerol concentration declined after the fifth recycle. The original fermentation contained 0.8% glycerol.Presented in part at the Society for Industrial Microbiology Annual Meeting, August 7–12, 1988, Chicago, IL.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.