Study of the structural and structure-functional subdomains in the interphase nucleus by photostabilization

The role of the nuclear matrix components in the organization of structural and functional domains of interphase nuclei was studied using irradiation with blue light in the presence of a photosensibilized agent (Ethidium bromide). Nuclear domain resistance to extractive solution (2 M NaCl) treatment served as a criterion of irradiation-induced stabilization of different nuclear domains. The following results have been obtained: 1) the structural organization of the complexes of chromatin and clusters of replication does not depend on the state of the nuclear matrix in isolated nuclei; 2) chemical stabilization of the nuclear matrix by Cu(2+)-ions is not sufficient for the organization of chromatin domains; 3) irradiation in the presence of Ethidium bromide stabilizes domains of the nuclei, but does not lead to stabilization of the nuclear matrix internal network. Hence, the irradiation prevented extraction from the nuclear domains of nonhistone proteins which were not standard matrix proteins. Based on the results obtained, a hypothesis was proposed about a coexistence of two groups of nonhistone proteins in the cell nucleus. The first group includes proteins of the nuclear matrix involved in immobilization of scafford attachment regions and active genes. The second group includes some hypothetical structural proteins participating only in compaction of DNA of condensed chromatin.     

Tumor cell proliferative activity in aggressive human lymphomas: the influence of reactive cell admixture on the assessment of proliferative indices

Uncontrolled proliferation is one of the main features of tumor cells, and therefore proliferative indices provide prognostic information, which might be valuable for treatment selection. However, in aggressive human lymphoid tumors, an admixture of normal (reactive) cells may be available in all organs infiltrated by neoplastic cells. We have presented data on determining proliferative activity using Ki-67 immunostaining, and demonstrated that an admixture of reactive cells could exert significant influence on the assessments of proliferative indices. We developed an experimental approach, which makes it possible to select neoplastic cells from the overall lymphoid population and to assess their proliferative activity - tumor cell proliferative indices. Tumor cell proferative indices determined in large cell lymphomas might be significantly higher than proliferative indices of overall populations, and the use of tumor cell proliferative indices will result in a more accurate assessment of disease prognosis.     

Larvae of related Diptera species from thermally contrasting habitats exhibit continuous up-regulation of heat shock proteins and high thermotolerance

A population of Stratiomys japonica, a species belonging to the family Stratiomyidae (Diptera), common name ‘soldier flies’, occurs in a hot volcanic spring, which is apparently among the most inhospitable environments for animals because of chemical and thermal conditions. Larvae of this species, which naturally often experience temperatures more than 40 °C, have constitutively high concentrations of the normally inducible heat-shock protein Hsp70, but very low level of corresponding mRNA. Larvae of three other species of the same family, Stratiomys singularior, Nemotelus bipunctatus and Oxycera pardalina, are confined to different type semi-aquatic habitats with contrasting thermal regime. However, all of them shared the same pattern of Hsp70 expression. Interestingly, heat-shock treatment of S. japonica larvae activates heat-shock factor and significantly induces Hsp70 synthesis, whereas larvae of O. pardalina, a species from constant cold environment, produce significantly less Hsp70 in response to heat shock. Adults of the four species also exhibit lower, but detectable levels of Hsp70 without heat shock. Larvae of all species studied have very high tolerance to temperature stress in comparison with other Diptera species investigated, probably representing an inherent adaptive feature of all Stratiomyidae enabling successful colonization of highly variable and extreme habitats.     

Molecular phylogeny of fungus gnats (Diptera: Mycetophilidae) revisited: position of Manotinae,Metanepsiini, and other enigmatic taxa as inferred from multigene analysis

The phylogeny of selected genera from four subfamilies of fungus gnats (Diptera: Mycetophilidae) – Manotinae, Leiinae, Sciophilinae and Gnoristinae (including Metanepsiini) – is reconstructed based on the combined analysis of five mitochondrial (12S, 16S, COI, COII, cytB) and two nuclear (28S, ITS2) gene markers. Results of the different analyses all support Manotinae as a monophyletic group, with Leiinae as the sister group. Allactoneura DeMeijere is nested in the monophyletic and strongly supported clade of Leiinae. The tribe Metanepsiini is revealed as paraphyletic and the genera Metanepsia Edwards and Chalastonepsia Søli do not appear to be closely related. The genera Docosia Winnertz, Ectrepesthoneura Enderlein, Novakia Strobl and Syntemna Winnertz were placed with a group of genera included traditionally in the Gnoristinae. The monophyly of Dziedzickia Johannsen and Phthinia Winnertz is not supported. The genera of Sciophilinae (excluding Paratinia Mik but including Eudicrana Loew) form a monophyletic group in the Bayesian model.     

A genomic walking method for screening sequence length polymorphism

We adapted a recently developed nonrestrictional, nonligational genome walking method, Universal Fast Walking (UFW), for detection of length polymorphism in the proximal promoter region of genes. We demonstrate its efficacy at discovering naturally occurring transposition into heat‐shock genes of wild Drosophila and show that it surmounts limitations of simple polymerase chain reaction (PCR) approaches. We further present modifications to the standard UFW protocol and provide some guidelines to improve specificity. Although the resultant banding pattern of a standard UFW can be regarded as a DNA fingerprint, many amplicons result from false priming and not real polymorphisms. We describe ways to distinguish between UFW amplicons and false priming products in a high‐throughput assay.     

The composition of the gut microbiota shapes the colon mucus barrier

Two C57BL/6 mice colonies maintained in two rooms of the same specific pathogen-free (SPF) facility were found to have different gut microbiota and a mucus phenotype that was specific for each colony. The thickness and growth of the colon mucus were similar in the two colonies. However, one colony had mucus that was impenetrable to bacteria or beads the size of bacteria—which is comparable to what we observed in free-living wild mice—whereas the other colony had an inner mucus layer penetrable to bacteria and beads. The different properties of the mucus depended on the microbiota, as they were transmissible by transfer of caecal microbiota to germ-free mice. Mice with an impenetrable mucus layer had increased amounts of Erysipelotrichi, whereas mice with a penetrable mucus layer had higher levels of Proteobacteria and TM7 bacteria in the distal colon mucus. Thus, our study shows that bacteria and their community structure affect mucus barrier properties in ways that can have implications for health and disease. It also highlights that genetically identical animals housed in the same facility can have rather distinct microbiotas and barrier structures.     

Chromosome scaffold and structural integrity of mitotic chromosomes

Chromosome scaffold represents a continuous protein substructure revealed in isolated metaphase chromosomes after harsh extraction. According to postulates of the widespread radial loop model the scaffold plays an important role in the formation and maintenance of structural integrity of the mitotic chromosomes. Here, the data concerning the structure and major components of the chromosome scaffold are presented. The experiments suggesting that the scaffold represents a system of discrete linker proteins and the data about high mobility of scaffolding proteins are discussed. Furthermore, the data about higher-level chromatin structures (elementary chromonema and 200-250 nm fibers) and behavior of scaffolding proteins are compared. The results presented agree with the idea that at the present stage it is possible to discriminate chromatin complexes, whose structural integrity is not maintained by the chromosome scaffold.