Mechanisms of the filtering area adaptation in Daphnia

The changes of selected parameters of the filtering comb of the third thoracic limb were studied in a natural population of Daphnia pulicaria Forbes, as well as in experimental enclosures and in lab cultures, including individual life history. Two hypotheses were tested: 1. either these changes are related to the succession of clones coexisting within one population, or 2. the size of the filtering area changes gradually as an individual adaptation during the moulting. No evidence supporting the clonal hypothesis was found. On the contrary, the adaptability of the filtering comb is the same in a natural population as it is in a clone and in individuals.     

Construction and properties of K1 type killer wine yeasts

Summary With the use of a protoplast fusion technique the killer character of K1 type was transferred into four industrial Saccharomyces wine yeasts. The prototrophic yeast strains active against standard sensitive and K2 killer Saccharomyces strains, resistant to K1 killer toxin were constructed with no changes in technological properties.     

Accelerated uptake of 5-hydroxytryptamine by human blood platelets enriched in a sialic acid.

The enzymically catalysed incorporation of N-acetylneuraminic acid into human platelets, whether suspended in their own citrated plasma or in buffered saline containing 0.17 mM-sucrose, accelerated the uptake of 5-hydroxytryptamine. This acceleration decreased with time. The observations may be explained by assuming that N-acetylneuraminic acid is a component of a transport receptor for 5-hydroxytryptamine.     

Genetic Variability within Borrelia burgdorferi Sensu Lato Genospecies Established by PCR-Single-Strand Conformation Polymorphism Analysis of the rrfA-rrlB Intergenic Spacer in Ixodes ricinus Ticks from the Czech Republic

In Europe the Borrelia burgdorferi sensu lato complex is represented by five distinct genospecies: Borrelia burgdorferi sensu stricto, Borrelia afzelii, Borrelia garinii, Borrelia valaisiana, and Borrelia lusitaniae. These taxonomic entities are known to differ in their specific associations with vertebrate hosts and to provoke distinct clinical manifestations in human patients. However, exceptions to these rules have often been observed, indicating that strains belonging to a single genospecies may be more heterogeneous than expected. It is, therefore, important to develop alternative identification tools which are able to distinguish Borrelia strains not only at the specific level but also at the intraspecific level. DNA from a sample of 370 Ixodes ricinus ticks collected in the Czech Republic was analyzed by PCR for the presence of a ~230-bp fragment of the rrfA-rrlB intergenic spacer of Borrelia spp. A total of 20.5% of the ticks were found to be positive. The infecting genospecies were identified by analyzing the amplified products by the restriction fragment length polymorphism (RFLP) method with restriction enzyme MseI and by single-strand conformation polymorphism (SSCP) analysis. The two methods were compared, and PCR-SSCP analysis appeared to be a valuable tool for rapid identification of spirochetes at the intraspecific level, particularly when large samples are examined. Furthermore, by using PCR-SSCP analysis we identified a previously unknown Borrelia genotype, genotype I-77, which would have gone unnoticed if RFLP analysis alone had been used.     

Promotion of hyperphosphorylation by frontotemporal dementia tau mutations

Mutations in the tau gene are known to cosegregate with the disease in frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17). However, the molecular mechanism by which these mutations might lead to the disease is not understood. Here, we show that four of the FTDP-17 tau mutations, R406W, V337M, G272V, and P301L, result in tau proteins that are more favorable substrates for phosphorylation by brain protein kinases than the wild-type, largest four-repeat protein tau4L and tau4L more than tau3L. In general, at all the sites studied, mutant tau proteins were phosphorylated faster and to a higher extent than tau4L and tau4L > tau3L. The most dramatic difference found was in the rate and level of phosphorylation of tau4L(R406W) at positions Ser-396, Ser-400, Thr-403, and Ser-404. Phosphorylation of this mutant tau was 12 times faster and 400% greater at Ser-396 and less than 30% at Ser-400, Thr-403, and Ser-404 than phosphorylation of tau4L. The mutated tau proteins polymerized into filaments when 4-6 mol of phosphate per mol of tau were incorporated, whereas wild-type tau required approximately 10 mol of phosphate per mol of protein to self-assemble. Mutated and wild-type tau proteins were able to sequester normal tau upon incorporation of approximately 4 mol of phosphate per mol of protein, which was achieved at as early as 30 min of phosphorylation in the case of mutant tau proteins. These findings taken together suggest that the mutations in tau might cause neurodegeneration by making the protein a more favorable substrate for hyperphosphorylation.