Rabbit liver microsomal system: study of interaction with two model N-nitrosamines and their metabolism

Rabbit liver microsomes of control (non-treated) or animals induced either by ethanol (EtOH) or phenobarbital (PB) were incubated with N-nitrosodimethylamine (NDMA) or N-nitrosomethylaniline (NMA). Difference spectroscopy showed that NMA is bound to the substrate-binding site of cytochrome P-450 (CYP) isoforms as heme ligand in control and EtOH pre-treated microsomes. On the other hand, PB-induced microsomes exhibit with NMA substrate type of spectra. NDMA does not provide any type of binding spectra with used microsomal systems. Oxidative bio-activation of N-nitrosamines by the microsomal CYP isoforms was measured as formaldehyde formation. Analysis of reaction kinetics in control microsomes revealed, for both substrates, two values of Michaelis-Menten constant (K(m)) for, K(m) values of 0.03 and 0.13 mmol/l for NDMA, and 0.30 and 0.82 mmol/l for NMA. Induction of animals with EtOH resulted in a decrease in the K(m) value for both substrates. In contrast, PB treatment caused an elevation of K(m) value for NDMA. Based on these data, we conclude that EtOH-inducible microsomal CYP isoforms (mainly CYP2E1) are responsible for binding and N-demethylation metabolism of both studied N-nitrosamines in rabbit liver microsomal system. The role of the other CYP isoforms involved in the metabolism of mentioned N-nitrosamines is discussed.     

A monoclonal antibody to Mycobacterium kansasii: preparation and properties

An IgG2/kappa monoclonal antibody specific for a subunit protein antigen (mol.w. 32 KD) obtained by means of gel chromatography of the cell-free sonicate of M. kansasii was generated by the fusion of spleenocytes from BALB/c mice immunized with this antigen and Ag-8 myeloma cells. Its specificity was demonstrated by ELISA and dot blot procedures. This MoAb has potential application in taxonomy and species identification of M. kansasii isolates, in studies relating to the molecular pattern of the bound antigen and in serodiagnostics of the mycobacterial disease due to M. kansasii.     

From Wolves to Dogs,and Back: Genetic Composition of the Czechoslovakian Wolfdog

The Czechoslovakian Wolfdog is a unique dog breed that originated from hybridization between German Shepherds and wild Carpathian wolves in the 1950s as a military experiment. This breed was used for guarding the Czechoslovakian borders during the cold war and is currently kept by civilian breeders all round the world. The aim of our study was to characterize, for the first time, the genetic composition of this breed in relation to its known source populations. We sequenced the hypervariable part of the mtDNA control region and genotyped the Amelogenin gene, four sex-linked microsatellites and 39 autosomal microsatellites in 79 Czechoslovakian Wolfdogs, 20 German Shepherds and 28 Carpathian wolves. We performed a range of population genetic analyses based on both empirical and simulated data. Only two mtDNA and two Y-linked haplotypes were found in Czechoslovakian Wolfdogs. Both mtDNA haplotypes were of domestic origin, while only one of the Y-haplotypes was shared with German Shepherds and the other was unique to Czechoslovakian Wolfdogs. The observed inbreeding coefficient was low despite the small effective population size of the breed, possibly due to heterozygote advantages determined by introgression of wolf alleles. Moreover, Czechoslovakian Wolfdog genotypes were distinct from both parental populations, indicating the role of founder effect, drift and/or genetic hitchhiking. The results revealed the peculiar genetic composition of the Czechoslovakian Wolfdog, showing a limited introgression of wolf alleles within a higher proportion of the dog genome, consistent with the reiterated backcrossing used in the pedigree. Artificial selection aiming to keep wolf-like phenotypes but dog-like behavior resulted in a distinctive genetic composition of Czechoslovakian Wolfdogs, which provides a unique example to study the interactions between dog and wolf genomes.     

Pseudomonas aeruginosa phage lysate as an immunobiological agent

A total of 2087 Pseudomonas aeruginosa isolates collected during the period 1994-1997 were used as starting material. Out of 1704 in-patient isolates, 299 strains were selected for the preparation of phage lysates but only five strains provided stable lysates, i.e., maintained the ability to be repeatedly and completely lysed by the appropriate phage in the course of several years. A set of 193 out-patients (189) and water sources (4) isolates failed to yield strains suitable for phage lysate preparation; 190 strains isolated abroad from patients with cystic fibrosis or respiratory infections included three isolates which, despite having a high degree of mucus production, were suitable for lysate preparation. The antigenic pattern of the phage lysates was ascertained by SDS-polyacrylamide gel electrophoresis.     

Habitats of relict terrestrial snails in southern Siberia: lessons for the reconstruction of palaeoenvironments of full‐glacial Europe

Aim Shells of fossil molluscs are important for palaeoecological reconstructions. However, the habitat requirements of snail species typical of central European full‐glacial loess sediments are poorly known because most of them became very rare or extinct in Europe. The recent discovery of an almost complete extant assemblage of such species in mountainous regions of central Asia enables more precise characterization of their habitats, which may significantly improve reconstructions of Pleistocene environments. Location Altai Mountains, Russia. Methods Terrestrial snail assemblages, vegetation composition and selected environmental variables were recorded at 118 sites along a gradient of climatic continentality in the Russian Altai. Habitat characteristics of sites where species typical of the full‐glacial period occurred were described using a classification tree. Results Seven of the eight species that are typical of central European full‐glacial loess sediments were found in the study area. They were confined to cool areas with January mean temperatures below ?17 °C, but occurred mainly in sheltered habitats with a warmer microclimate, such as scrub or open woodland. Pupilla loessica and Vallonia tenuilabris had the broadest habitat range, occurring from woodland to dry steppe. Unexpectedly, Columella columella, Pupilla alpicola, Vertigo genesii, V. parcedentata and V. pseudosubstriata were found mainly in wooded fens and shrubby tundra rather than in open steppe. Most of these seven species were recorded in base‐rich wooded fens. Very dry open steppe habitats usually supported no snails. Main conclusions Habitat ranges of the studied snails in the Altai indicate that the full‐glacial landscapes of central European lowlands that harboured these species were not completely dominated by open and dry loess steppe. Most probably they contained a significant component of shrubby vegetation, patches of wet habitats, and probably also areas of woodland at sites with a favourable mesoclimate.