Organization of higher-level chromatin structures (chromomere,chromonema and chromatin block) examined using visible light-induced chromatin photo-stabilization

The method of chromatin photo-stabilization by the action of visible light in the presence of ethidium bromide was used for investigation of higher-level chromatin structures in isolated nuclei. As a model we used rat hepatocyte nuclei isolated in buffers which stabilized or destabilized nuclear matrix. Several higher-level chromatin structures were visualized: 100nm globules-chromomeres, chains of chromomeres-chromonemata, aggregates of chromomeres-blocks of condensed chromatin. All these structures were completely destroyed by 2M NaCl extraction independent of the matrix state, and DNA was extruded from the residual nuclei (nuclear matrices) into a halo. These results show that nuclear matrix proteins do not play the main role in the maintenance of higher-level chromatin structures. Preliminary irradiation led to the reduction of the halo width in the dose-dependent manner. In regions of condensed chromatin of irradiated nucleoids there were discrete complexes consisting of DNA fibers radiating from an electron-dense core and resembling the decondensed chromomeres or the rosette-like structures. As shown by the analysis of proteins bound to irradiated nuclei upon high-salt extraction, irradiation presumably stabilized the non-histone proteins. These results suggest that in interphase nuclei loop domains are folded into discrete higher-level chromatin complexes (chromomeres). These complexes are possibly maintained by putative non-histone proteins, which are extracted with high-salt buffers from non-irradiated nuclei.     

Mitochondrial H+-ATPase: Identification of Subunits of the F0 Subcomplex that Contact Membrane Lipids

The subunits of the F₀ membrane sector of bovine heart mitochondrial H⁺-ATPase that contact the lipids of the mitochondrial inner membrane were identified with the use of specially synthesized proteoliposomes that contained active mitochondrial H⁺-ATPase and a photoreactive lipid, which was 1-acyl-2-[12-[di-azocyclopentadiene-2-carbonylamino)-[12-¹⁴C]dodecanoyl]-sn-glycero-3-phosphocholine, 1-acyl-2-[11-([¹²⁵I]diazoiodocyclopentadiene-2-carbonyloxy)undecanoyl]-sn-glycero-3-phosphocholine, or 1-acyl-2-[12-(diazocyclopentadiene-2-carbonylamino)dodecanoyl]-sn-glycero-3-phosphocholine, where acyl is a mixture of the residues of palmitic (70%) and stearic (30%) acids. An analysis of the cross-linked products obtained upon the UV-irradiation of these proteoliposomes indicated that subunits c and a of the F₀ membrane sector contact the lipids. The crosslinked products were identified by SDS-PAGE and MALDI mass spectrometry.     

Comparative cytogenetics of hamsters of the genus Calomyscus

Karyotypes of Calomyscus from different regions of Turkmenistan, Iran, and Azerbaijan were studied using chromosome banding (G- and C-banding) and analyses of meiosis in laboratory hybrids. Extensive variation in the diploid number and the number of autosomal arms (FNa) was revealed (2n = 30, FNa = 44; 2n = 32, FNa = 42; 2n = 44, FNa = 46; 2n = 44, FNa = 58; 2n = 37, FNa = 44; 2n = 50, FNa = 50; 2n = 52, FNa = 56). Centric and tandem fusions and heterochromatin changes were identified as the major modes of karyotype evolution in this group. Natural hybrids between individuals with different karyotypes were recorded, and regular chromosome pairing in meiosis was observed in laboratory hybrids. Fluorescence in situ hybridization with a 353-bp BspRI complex tandem repeat indicated that chromosomal repatterning occurred recently within the genus. There is no unequivocal evidence suggesting the role of chromosomal change in the speciation of the populations of Calomyscus examined.     

Genetic structure of the Udmurt population

Integrated study of the genetic structure of the Udmurt population with respect to different genetic systems has been performed. Data on the genes of genetic diseases, abiotic parameters analyzed by population statistic methods, and DNA polymorphism are summarized. The populations of six raions (districts) of Udmurt Republic (the Mozhga, Malaya Purga, Sharkan, Debesy, Igra, and Glazov raions) have been studied. The total population studied was 267 655 people (an urban population of 150 119 people and a rural population of 117 536 people), including 155 346 Udmurts. The population structure has been studied in six districts on the basis of the vital statistics, Crow’s indices, Malecot’s isolation by distance parameters, ethnically assortative marriage parameters, endogamy indices, inbreeding-endogamy (ie) indices, and frequencies of the genotype and allele frequencies of four DNA markers (17 alleles). The prevalences of hereditary diseases have been calculated for different population groups: urban and rural populations, Udmurts and other ethnic groups. These groups, especially the urban and rural populations, substantially differed from one another in the prevalences of autosomal dominant (AD) and autosomal recessive (AR) diseases. The correlation between the prevalence of AD and AR diseases and the ie index is positive and significant. The spectrum of hereditary diseases detected in six districts of Udmurtia comprises 149 diseases (80, 57, and 12 AD, AR, and X-linked diseases, respectively). Accumulation of individual diseases in districts of Udmurtia and accumulation of diseases in Udmurtia as compared to regions studied earlier has been found. Cluster analysis of the frequencies of genes of AD and AR diseases and DNA markers has determined the gene geographic position of Udmurts.     

Elasticity and physico-chemical properties during drinking water biofilm formation

Atomic force microscope techniques and multi-staining fluorescence microscopy were employed to study the steps in drinking water biofilm formation. During the formation of a conditioning layer, surface hydrophobic forces increased and the range of characteristic hydrophobic forces diversified with time, becoming progressively complex in macromolecular composition, which in return triggered irreversible cellular adhesion. AFM visualization of 1 to 8 week drinking water biofilms showed a spatially discontinuous and heterogeneous distribution comprising an extensive network of filamentous fungi in which biofilm aggregates were embedded. The elastic modulus of 40-day-old biofilms ranged from 200 to 9000?kPa, and the biofilm deposits with a height >0.5 μm had an elastic modulus <600?kPa, suggesting that the drinking water biofilms were composed of a soft top layer and a basal layer with significantly higher elastic modulus values falling in the range of fungal elasticity.     

Natural hybridization between extremely divergent chromosomal races of the common shrew (Sorex araneus, Soricidae, Soricomorpha): hybrid zone in Siberia

Chromosomal races of the common shrew differ in sets of metacentric chromosomes and on contact may produce hybrids with extraordinarily complex configurations at meiosis I that are associated with reduced fertility. There is an expectation that these may be some of the most extreme tension zones available for study and therefore are of interest as potential sites for reproductive isolation. Here, we analyse one of these zones, between the Novosibirsk race (characterized by metacentrics go, hn, ik, jl, mp and qr) and the Tomsk race (metacentrics gk, hi, jl and mn and acrocentrics o, p, q and r), which form hybrids with a chain-of-nine (CIX) and a chain-of-three (CIII) configuration at meiosis I. At the Novosibirsk-Tomsk hybrid zone, the CIX chromosomes form clines of 8.53 km standardized width on average, whereas the cline for the CIII chromosomes was 52.83 km wide. The difference in these cline widths fits with the difference in meiotic errors expected with the CIX and CIII configuration, and we produce estimates of selection against hybrids with these types of configurations, which we relate to dispersal and age of the hybrid zone. The hybrid zone is located at the isocline at 200 m altitude above sea level; this relationship between the races and altitude is suggested at both coarse and fine scales. This indicates adaptive differences between the races that may in turn have been promoted by the chromosome differences. Thus, the extreme chromosomal divergence between the Novosibirsk and Tomsk may be associated with genic differentiation, but it is still striking that, despite the large chromosomal differences, reproductive isolation between the Novosibirsk and Tomsk races has not occurred.     

Transthyretin gene V30M,H90N,and (del9) mutations in cardiomyopathy patients from St. Petersburg

A search of transthyretin (TTR) gene mutations was performed in patients with cardiomyopathies from St. Petersburg. Mutations H90N, V30M and deletion (del9) of nucleotides GACTTCTCC in position 6776 from the start codon of the TTR gene (in position 98782 according to reference sequence AC079096 (NCBI) was found. The H90N mutation in the third exon of TTR gene was detected in a son of a cardiomyopathy patient and in his mother, which lacked any clinical manifestations. Mutation V30M in exon 2 of TTR gene was found in heterozygous in one of the probands. Deletion (del9) was revealed in a patient with cardiomyopathy and in his two daughters from different marriages, who had no clinical manifestations of the disease. All the mutations revealed in this study were previously identified in other populations.     

Conditions that influence bacterial luminescence in the presence of blood serum

Conditions that influence the luminescence of natural and recombinant luminescent bacteria in the presence of blood serum were studied. In general, blood serum quenched the luminescence of the marine Photobacterium phosphoreum and the recombinant Escherichia coli strains harboring the luminescent system genes of Photobacterium leiognathi, but enhanced the luminescence of the soil bacterium Photorhabdus luminescens Zm1 and the recombinant E. coli strain harboring the lux operon of P. luminescens Zm1. The quenching effect of blood serum increased with its concentration and the time and temperature of incubation. The components of blood serum that determine the degree and specificity of its action on bacterial luminescence were identified.__________Translated from Mikrobiologiya, Vol. 74, No. 2, 2005, pp. 191–197.Original Russian Text Copyright © 2005 by Deryabin, Polyakov.