Segment duplications in subtelomeric regions of human chromosome 13

Owing to a great progress in studying the human genome, its euchromatic portion is almost completely sequenced; the complete sequence is still unknown only for pericentric and telomeric regions and short arms of acrocentric chromosomes. Extended satellite blocks and segment duplications located in these regions substantially hinder the joining of the sequenced fragments and construction of the full-length genome map. The sequence was established for a 1.5-kb human chromosome 13 subtelomeric region, which is about 10 kb away from the rDNA cluster, and deposited in GenBank under accession no. AF478540. The region showed 83-84% homology to the pericentric region of human chromosome 19, and contained short fragments homologous to the pericentric region of human chromosome 13. The results may contribute to the current revision of genome evolution concepts in view of numerous segment duplications revealed.     

Cloning and comparative characterization of the rIGS regulatory regions in humans and the pygmy chimpanzee Pan paniscus

Investigation of randomly cloned genomic and chromosome-specific sequences of ribosomal DNA (rDNA) from different organisms show that different regions of this long repeat unit evolve at different rates. This proves to be true not only with regard to evolutionary variability of transcribed and nontranscribed intergenic (spacer) regions of rDNA. The intergenic spacer (rIGS) of human ribosomal DNA contains both highly variable and more conservative regions with putative regulatory functions. In the present study a comparative analysis of some segments of the rIGS pre-promoter (regulatory) region in human and pygmy chimpanzee (Pan paniscus) was carried out. For these purposes, the corresponding DNA fragments were amplified in PCR with oligonucleotide primers specific to human rIGS and sequenced. Our results show that at the background of substantial structural similarity of these regions in man and chimpanzee, i.e., the presence of highly homologous sequences and similar repetitive units, there are substantial differences between them. These differences are associated with point mutations, insertions, deletions, and complex structural rearrangements.     

'Navius' kissing stents for coronary bifurcation stenosis,recreating a new metallic carina: an IVUS-assessed case report

We report a case of implantation of a new design of stent which allows creation of a double-hemispheric lumen for the treatment of a bifurcational stenosis. The unfavourable outcome following the implantation of this stent is described.     

Secondary structure of pre-rRNA 41S spacers and its possible role in determining the processing sites

The mechanism of pre-rRNA processing is still unknown. In this paper we discuss a possible role of the secondary structure of the internal transcribed spacer region (ITS-1 and ITS-2) in processing of 41S pre-rRNA. Potential possibilities for double strand structure formation in ITS-1 and ITS-2 and its rearrangement in the course of processing of 41S pre-rRNA with involvement of U3 RNA were analyzed for a number of species. We have concluded that this rearrangement is the necessary stage in 41S pre-rRNA processing when every functionally designated area (for mature 18S, 28S and 5,8S rRNAs, for ITS-1, ITS-2 and 21S pre-rRNA) has to be organized into an individual domain. In these strongly structured domains 5'- and 3'-ends are spatially brought together whereas processing sites are localized between these compactised areas.     

Study of the surface of cytolytic T-lymphocytes by scanning electron microscopy

Scanning electron microscopy revealed three types of cytolytic T lymphocytes (CTL) interacting with target cells (TC). The type I cells occurred as smooth spherical lymphocytes with single microvilli; the type II rounded or oval cells were uniformly covered with microvilli; the type III cells were marked by an irregular shape, were densely covered with microvilli, while their surface was folded or tuberous. Within the first several minutes after absorption the surface of TC was largely covered by the type I lymphocytes. The proportion of the type III cells rose with the time of interaction. At the beginning it was 8-9%, reaching 30-71% after 30-60 minutes of incubation. It is assumed that the 3 types of the cells described mirror 3 stages of CTL activation. The increase in number of microvilli and appearance of the membranous folds may be a consequence of exocytosis and incorporation of the membrane of secretory granules into the plasma membrane of lymphocytes. The data obtained support the authors' assumption about the secretory mechanism of the action of CTL, whose contact with TC stimulated secretion activation.     

Biosynthesis of chlorophyll P-680 of photosystem II in greening leaves of plants adapted to heat shock

In etiolated pea and maize leaves illuminated after incubation at 38 degreesC, a new dark reaction was shown manifested in the bathochromic shift of spectral bands and accompanied by esterification of the product of protochlorophyllide photochemical reduction--Chld 684/676: Chld 684/676 --> Chl 688/680. After completion of the reaction a rapid (20-30 sec) quenching of the fluorescence of the reaction product (Chl 688/680) was observed. The reaction Chld 684/676 --> Chl 688/680 is inhibited under anaerobic conditions and in the presence of cyanide; the reaction accompanied by Chl 688/680 fluorescence quenching is not observed in pea mutants with impaired function of photosystem II reaction centers. The spectral properties of the formed Chl form with the absorption maximum at 680 nm, fluorescence quenching, and simultaneous synthesis of pheophytin suggest that the reaction is connected with the chlorophyll of photosystem II reaction center--P-680.     

Effect of exogenous ribonucleases on the propagation of Candida tropicalis yeast]

The effect of exogenic microbial and tissue RNAses on the reproduction of Candida tropicalis yeasts were studied. Catalytically active and inactive forms of ribonucleases were shown to stimulate yeast organism reproduction. Using immunochemical and radioisotopic methods, it was found that RNAses penetrated into yeast cell. The correlation between yeast cell penetration by exogenic enzymes and the physiological state of the cells was revealed. The activation of the chromatin associated RNAse-polymerase under the action of the catalytically active binase was observed in in vitro experiments. The mechanisms of the stimulatory effect of catalytically active and inactive RNAses on growth and reproduction of C. tropicalis are discussed.     

The effect of DNAse I on bacterial growth depending on the cultivation conditions and on the physiological characteristics of the inoculate

The stimulating effect of DNAase 1 on Escherichia coli reproduction has been studied depending on the content of slowly growing cells in the inoculation culture in the phase of delayed growth. Three cell fractions of E. coli have been obtained using the stepwise separation of the population in terms of buoyant density in the phase of delayed growth. In contrast to fractions I and II the fraction III contains cells with delayed growth, permeable to exogenous DNAase 1 and sensitive to the action of this enzyme. The faster growth of bacterial cells has been shown to be caused by the direct ferment action on the slowly growing cells. The autometabolites and autolysates don't take part in this process.     

The dynamics of histograms of difference between successive RR intervals of ECG during 24 hours as index of the balanced state of neurogenic influences on the heart rate

The quantitative parameters of neurogenic influences on the heart rate is offered: the dispersion of histograms of differences between successive RR intervals of ECG, the number of zero differences and the value of sum of differences between successive RR intervals.