Search

1. Copper(II) complexation in the eutrophic, humus-rich Lake Tjeukemeer was measured fortnightly for several years by copper titration (Ion Selective Electrode) and by copper solubilization. Additionally, the copper speciation during titration was followed by ultrafiltration. 2. The Tjeukemeer showed high ligand concentrations able to complex up to 8.5×10-5M Cu. 3. Scatchard plots and affinity spectra of the titration data allowed the discrimination of at least three different binding sites. In Scatchard plots log K values ranged from 5 to 9. in affinity spectra from 4.5 to 8.4. The highest log K values coincided with relatively low humus concentrations and blooms of algae, mainly Cyanobacteria. 5. The ultrafiltration experiments indicated that relatively small size fractions (<10 nm) have the highest copper binding affinity. [ABSTRACT FROM AUTHOR]

1. The small Lake Negenmad, in the nature reserve ‘De Oude Venen’, was isolated from the canals and lakes of the Frisian lake system. Its chemistry and phytoplankton were monitored 1 year before (1984) and 2 years after (1985–86) isolation. These characteristics were compared with those of the adjacent Lake Veertigmad which was not manipulated. 2. The hydrological intervention prevented the inflow of chloride-rich IJsselmeer water into Lake Negenmad and made its water table more dependent on evapotranspiration, precipitation and upwelling water. In comparison with the unmanipulated lake. Lake Negenmad became less saline (c. 50%), more humic (c. 50%) and total dissolved (<0.2 μm) iron concentration increased dramatically. 3. During the 2 years of damming no marked differences in the total nutrient concentrations of either lake were observed. However, the maximum phytoplankton density in the dammed lake was half that in the unmanipulated lake. The lower density may have been caused by low P availability after formation of humus-iron phosphate species. 4. Preventing the inflow of water from the Frisian lake system favoured the occurrence in Lake Negenmad of flagellated species (Chrysophyceae, Cryptophyceae) at the expense of filamentous and nuisance-causing cyanobacteria (Oscillatoria, Anabaena, Aphanizomenon spp.). 5. The implications of these results for water quality management of reservoirs in peaty areas are briefly discussed. [ABSTRACT FROM AUTHOR]

In this paper the effect of a fulvic acid fraction on the growth of a Pseudomonas sp. from fresh water is reported. The presence of fulvic acid in the culture medium caused an increase in the cell yield and in the cell yield per μl O2 taken up by the Pseudomonas. The observed stimulating effect has been explained in terms of co-metabolism of fulvic acid by the Pseudomonas. [ABSTRACT FROM AUTHOR]

In this study the use of Sephadex G-25, Sephadex LH-20 and CPG-10-75 for the separation of soluble humic compounds from fresh water is tested. It is shown by Sephadex G-25 gel filtration that differences in molecule-size distribution of soluble humic compounds in one lake at different times and between lakes can be predicted by E250 and E365 measurements. [ABSTRACT FROM AUTHOR]

MicroRNAs have been recognized as critical regulators of gene expression and might affect the risk of venous thrombosis. We aimed to identify 3' untranslated region (UTR) variants in coagulation genes that influence coagulation factor levels and venous thrombosis risk. The 3'UTR of coagulation genes were sequenced in subjects with extremely high or low plasma levels of these factors in two case-control studies. In total, 28 variants were identified. Five single nucleotide polymorphisms (SNPs) were predominantly present in one extreme level group (F2 rs1799963, F8 rs1050705 and F11 rs4253429, rs4253430 and rs1062547). Additional to F2 rs1799963, F8 rs1050705 (in men) and F11 rs4253430 were associated with an increased risk of venous thrombosis albeit confidence intervals were wide. The three F11 SNPs were in high linkage disequilibrium with functional variants rs2289252 and rs2036914. Rs1062547 and rs4253430 were associated with a significant increase of plasma FXI activity in heterozygotes and homozygotes in wild-type controls. In silico prediction revealed that these SNPs might disturb the binding sites of miR-544 and miR-513a-3p. Only miR-544 provoked a significant decrease of the luciferase activity that was not observed with a rs4253430 mutated vector. In conclusion, these results reinforce that microRNAs are candidates to play a role in haemostasis and complex disorders, such as thrombosis., (© 2017 John Wiley & Sons Ltd.)