COMPARISON OF NEURONAL AND LENS PHENOTYPE EXPRESSION IN THE TRANSDIFFERENTIATING CULTURES OF NUERAL RETINA WITH DIFFERENT CULTURE MEDIA*

The effects of three different culture media (Eagle's MEM, F-12 and L-15) on the transdifferentiation of 8-day chick embryonic neural retina into lens cells, were examined with respect to the expression of two phenotypes. One type referred to neuronal specificity (as represented by the level of cholineacetyl-transferase, CAT, activity) and the other to lens specificity (as represented by content of α-and δ-crystallin). In 7-day cell cultures before the visible differentiation of lentoid bodies, CAT activity was detected in all media. But, its level was about 9 times higher in cultures with L-15 than in those with MEM and 3 times higher than in F-12. In 26-day cultures, CAT activity was practically undetectable. The production of α-and δ-crystallin was detected in cultures at 26 days. There were quantitative differences in the crystallin content with different media, and it was highest in cultures with L-15. The results indicate that conditions most favourable to the maintenance of the neuronal specificity in cell cultures of neural retina, can also support the most extensive transdifferentiation. The possibility of direct transdifferentiation of once neuronally specified cells into lens cells in cultures with L-15 has been suggested to explain the present results.     

Analysis of molecular differentiation in a hybrid zone between chromosomally distinct races of the common shrew Sorex araneus (Insectivora: Soricidae) suggests their common ancestry

During postglacial colonization, populations that diverged in different refugia produced a patchwork of genomes, often delimited with sharp hybrid zones. The outcome of hybridization following the secondary contact of two genetically distinct populations is hard to predict. In this context, the present study investigated the genetic structure of the hybrid zone between the Drnholec and Białowieża chromosome races of the common shrew ( Sorex araneus ) in Poland using biparentally inherited (seven autosomal microsatellites) and uniparentally inherited (Y-linked microsatellite and mtDNA) molecular markers. On the basis of diagnostic chromosomes, the Drnholec and Białowieża races were classified to different karyotypic groups, which were believed to have independent glacial histories. It was found that genetic differentiation between the Drnholec and Białowieża races was weak and nonsignificant with respect to all molecular markers. However, these results are in contrast with the chromosomal structure of this hybrid zone. The very sharp frequency clines of the diagnostic chromosomes strongly suggest that gene flow between the Drnholec and Białowieża races was reduced. Nonsignificant correlations between genetic differentiation and both the presence of an environmental barrier and geographical distance reveal that only differences in karyotypes might be a reason for limited gene exchange between the races. It is assumed that a lack of molecular differences between the Drnholec and Białowieża races results from a shared ancestral variation.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 79–90.     

Genetic variability in the European bison (Bison bonasus) population from Białowieża forest over 50 years

The aim of this study was to assess potential post-bottleneck temporal genetic differentiation following the reintroduction of the species into the Białowieża Forest. Variability of 12 polymorphic microsatellite markers was analysed for 178 individuals born between 1955 and 2005, divided by birth year into five temporal groups. Low overall allelic richness (AR) per locus (AR = 2.0) and a low overall expected heterozygosity (H_E = 0.28) were observed. The overall F _IS was not significantly different from zero. The mean F _IS values were, however, significantly different from zero for individuals born between 1955 and 1965 ( F _IS = 0.19). A Bayesian computation was used to estimate effective population size (N_e) for each temporal group. We observed relatively small values of N_e ranging from 7.9 to 28.4. The low N_e values confirm that, despite a rapid growth of the bison population following the founder event, N_e increased only slowly.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 801–809.     

Climate and refugial origin influence the mitochondrial lineage distribution of weasels (Mustela nivalis) in a phylogeographic suture zone

Overarching trends can be seen in European mammalian phylogeography, yet it is clear that species responded differently depending on adaptations to past environments. We built upon previous work on the phylogeography of weasels (Mustela nivalis) in Europe by using well‐preserved museum specimens from a proposed phylogeographic suture zone. The complete cytochrome b gene was amplified from 49 individuals from present‐day Poland and analyzed with previously published data on a European scale to identify glacial refugia and infer recolonization processes. Bayesian coalescent analysis revealed the importance of the Last Glacial Maximum and the Younger Dryas in the diversification of, and demographic changes in, identified mitochondrial lineages. Our analysis, in conjunction with the available fossil data, strongly points to a Carpathian origin for one of the lineages, and further highlights the importance of this region as a refugium for European mammals. Mustela nivalis originating from this refugium appear to have a selective advantage over M. nivalis from other lineages in certain environments in the suture zone in central Europe, with climate clearly influencing the distribution of mitochondrial DNA lineages. This has important implications not only for our understanding of how past climatic events shaped the genetic architecture of species, but also how they will respond to current and future climatic changes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 57–69.     

Immunological Relationships among Embryonic and Adult Chicken Pepsinogens: A Study with Monoclonal and Polyclonal Antibodies

To investigate the immunological relationships of pepsinogen isozymes present in embryonic and adult chicken proventriculi, we obtained monoclonal and polyclonal antibodies to these pepsinogens. Zymograms and immunoblots demonstrated that monoclonal antibody Y37 reacted with both embryonic and slow-migrating adult pepsinogens, while polyclonal antibodies against embryonic pepsinogen and fast-migrating adult pepsinogen were specific for these respective antigens. Shift from embryonic to adult-type pepsinogen occurred at about the time of hatching and the localizations of embryonic and adult-type pepsinogens within proventricular gland cells were found to differ by the indirect immunofluorescence method. Results with these antibodies revealed the immunological relations of these pepsinogens and the unique properties of embryonic chicken pepsinogen.     

Antibiotic and Disinfectant Resistance in Tap Water Strains – Insight into the Resistance of Environmental Bacteria

Although antibiotic-resistant bacteria (ARB) have been isolated from tap water worldwide, the knowledge of their resistance patterns is still scarce. Both horizontal and vertical gene transfer has been suggested to contribute to the resistance spread among tap water bacteria. In this study, ARB were isolated from finished water collected at two independent water treatment plants (WTPs) and tap water collected at several point-of-use taps during summer and winter sampling campaigns. A total of 24 strains were identified to genus or species level and subjected to antibiotic and disinfectant susceptibility testing. The investigated tap water ARB belonged to phyla Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes. The majority of the isolates proved multidrug resistant and resistant to chemical disinfectant. Neither seasonal nor WTP-dependent variabilities in antibiotic or disinfectant resistance were found. Antibiotics most effective against the investigated isolates included imipenem, tetracyclines, erythromycin, and least effective – aztreonam, cefotaxime, amoxicillin, and ceftazidime. The most resistant strains originate from Afipia sp. and Methylobacterium sp. Comparing resistance patterns of isolated tap water ARB with literature reports concerning the same genera or species confirms intra-genus or even intra-specific variabilities of environmental bacteria. Neither species-specific nor acquired resistance can be excluded.