Evidence for the presence of proteolytically active secreted aspartic proteinase 1 of Candida parapsilosis in the cell wall

Pathogenic yeasts of the genus Candida produce secreted aspartic proteinases, which are known to enhance virulence. We focused on Sapp1p proteinase secreted by Candida parapsilosis and studied the final stage of its passage through the cell wall and release into the extracellular environment. We found that Sapp1p displays enzyme activity prior to secretion, and therefore, it is probably fully folded within the upper layer of the cell wall. The positioning of cell surface-associated Sapp1p was detected by cell wall protein labeling using biotinylation agents, extraction of cell wall proteins by β-mercaptoethanol, immunochemical detection, and mass spectrometry analysis. All lysine residues present in the structure of soluble, purified Sapp1p were labeled with biotin. In contrast, the accessibility of individual lysines in cell wall-associated Sapp1p varied with the exception of four lysine residues that were biotinylated in all experiments performed, suggesting that Sapp1p has a preferred orientation in the cell wall. As the molecular weight of this partially labeled Sapp1p did not differ among the experiments, we can assume that the retaining of Sapp1p in the cell wall is not a totally random process and that pathogenic yeasts might use this cell-associated proteinase activity to enhance degradation of appropriate substrates.     

Phosphoramidate pronucleotides of cytostatic 6-aryl-7-deazapurine ribonucleosides

A series of O-phenyl methyl-, ethyl- and benzylalanyl phosphoramidate pronucleotides derived from cytostatic 6-aryl-7-deazapurine ribonucleosides were prepared by the cross-coupling reactions of the 2′,3′-isopropylidene protected 6-chloro-7-deazapurine ribonucleoside phosphoramidates with (het)arylboronic acids or -stannanes followed by deprotection. Most of the prepared prodrugs exerted in vitro cytostatic effects against both solid tumor and lymphoid cancer cells within low micromolar range of concentrations. These activities were in general weaker or comparable to the activities of the parent nucleosides. Additional testing of selected prodrugs suggests that the lack of activity improvement over parent nucleosides is not due to the lack of permeability or inefficient catabolism of alanyl-ester by intracellular hydrolases. More likely, active efflux of prodrugs may play a role in their weak cytotoxic activity.     

Synthesis and antiviral activity of N9-[3-fluoro-2-(phosphonomethoxy)propyl] analogues derived from N6-substituted adenines and 2,6-diaminopurines

An efficient method for the synthesis of N(9)-[3-fluoro-2-(phosphonomethoxy)propyl] (FPMP) derivatives of purine bases has been developed. Both (R)- and (S)-enantiomers of the N(6)-substituted FPMP derivatives of adenine and 2,6-diaminopurine were prepared and their anti-human immunodeficiency virus (HIV) and anti-Moloney murine sarcoma virus (MSV) activity was evaluated. Whereas none of the 6-substituted FPMPA derivatives showed any antiviral activity, several FPMPDAP derivatives had a moderate antiretroviral activity. Moreover, the data obtained from the study of the substrate activity of the active derivatives towards N(6)-methyl-AMP aminohydrolase support the notion that the studied N(6)-substituted FPMPDAP derivatives act as prodrugs of the antiretroviral FPMPG analogues.     

The introduction of the aquatic carnivorous plantAldrovanda vesiculosa to new potential sites in the Czech Republic: A five-year investigation

Five microsites in shallow dystrophic waters were selected for the introduction of a critically endangered aquatic carnivorous plantAldrovanda vesiculosa in the Třeboň region in S Bohemia, the Czech Republic. The selected sites were fen pools close to two hypertrophic fishponds, Ptačí blato (four microsites) and Domanínsky (one microsite). In June 1995, 30 plants from an allochthonous population in E Poland were introduced in each of the microsites. Water chemistry and plant growth dynamics were investigated at the microsites throughout the 1995–1996 seasons, and the maximum size of the subpopulations were estimated during the 1997–1999 seasons. The selected waters may be characterized as oligo-mesotrophic. The warm and dry 1995 season resulted in a low water level (ca. 10 cm below average) and plant propagation was poor at all but one microsite. However, the rainy and colder 1996 season resulted in a high water level, and thus rapid plant propagation occurred at all four microsites at the Ptačí blato fishpond and between 841 and 2669 turions were formed. Here, the doubling time of the apices was between 13.5–19.3 days in the summer. At the Domanínsky fishpond, however, the growth was relatively poor in 1996. The overwintering rate of turions (19–100%) was found as being high enough to keep the introduced plant populations stable. At each of the four microsites at Ptačí blato, the maximum numbers of shoot apices were estimated to be between 1,000–20,000 in the 1997–1999 seasons. Depth of free water appears to be the crucial factor for the rapid growth ofAldrovanda at some selected sites; water depth below 5 cm is unfavourable. Overall,Aldrovanda was successfully established in an intensively agricultural landscape in the Třeboň region.     

The Effect of Outflow Depth on Phosphorus Retention in a Small,Hypertrophic Temperate Reservoirwith Short Hydraulic Residence Time

Stratification and phosphorus fluxes (input, output, sedimentation, and release from sediments) were studied in České údolí Reservoir (49°43′N, 13°21′E; V – 2.65 × 10⁶ m³; A – 1.04 × 10⁶ m²; z_max – 5.5 m; surface altitude – 314 m a.s.l.) during two summer stratification periods which differed in outlet operation and in hydraulic residence time (1997: surface outlets and 14 days; 1998: bottom outlets and 23 days). Use of bottom outlets resulted in weaker thermal stratification, a less pronounced oxygen deficit in the hypolimnion, and significantly lower P retention (17%) in comparison with surface discharge (42%). Factors apparently contributing to lower retention of P during the use of bottom outlets were: (i) faster flushing of the hypolimnion which intensified longitudinal transport of particles, (ii) more intense P release from sediments due to a lower concentration of nitrate in the water column and to more frequent contact of sediments in the shallows with water of pH >9. During both periods, phytoplankton production was limited only by light, not by nutrients. Phytoplankton biomass was comparable in both years despite some differences in vertical distribution.     

Glucose oxidase ofAspergillus niger

По методу Raper и Fennel (1953) приготовляли гетерока риотический мицелий двух различных по генотипу штаммов Aspergillus niger. Штаммы, изолированные из одного конидиофора в гетерока риотическом валике, не были однородными ни по своим морфологическим свойствам, ни способности к продукции. Повышенная продукция глюкозооксидазы была временной и в третьей генерации спор уже не наблюдалась. Причиной зтого явления было, по-видимомы, биохимическое взаимодействие между ядром и цитоплазмой двуя различных щтаммов, прекращающееся после восстановления равновесия в следущей генерасии спор.