Segments of Djungarian hamster chromosomes, specific for translocation of integration of amplified mdr1 genes, do not possess increased instability]

Earlier we have revealed in Djungarian hamster DM-15 cells three chromosomal segments (2p22, 5p1, 7q23-25) that are specific for transposition of amplified mdr1 genes from the site of location of resident gene copy (it was mapped to 4q21-23). In situ hybridization revealed in wild type cells no mdr1 homologous sequences in all these three segments. In this work we studied distribution of chromosomal breakages induced in DM-15 cells by aphidicolin, 5-fluorodeoxyuridine or N-phosphonacetyl-L-aspartate. The data obtained indicate that two of above mentioned segments. 2p22 and 7q23-25, contain no fragile sites. So, specificity of these segments for the transposition of amplified mdr1 genes is not due to their particular instability or to the presence in them of sequences homologous to amplifiable selectable gene.     

Gene amplification in Djungarian hamster cell lines possessing decreased plasma membrane permeability for colchicine and some other drugs

By multistep selection a set of clones and sublines possessing different levels of resistance to colchicine or adriablastin was obtained from the SV40-transformed Djungarian hamster cell lines, DM-15 and DM^cap. Resistance to both colchicine and adriablastin is associated with an alteration of plasma membrane permeability leading to a decreased uptake of various drugs (³H-colchicine, ³H-cytochalasin B, ³H-actinomycin D, ³H-puromycin, ³H-vinblastine, ¹⁴C-chloramphenicol). The DNA of cells highly resistant to cholchicine can transmit resistance only to low dosages of the drug. Comparison of DNAs from wild-type and resistant cells digested by restriction endonucleases revealed new classes of repeated DNA sequences in resistant cell lines. The degree of DNA repetition was correlated with the level of drug resistance. The repeated DNA sequences evidently represent parts of the genome that are amplified in resistant cells. The size of the amplified sequences is 200–250 kilobase pairs (kb). Cell lines highly resistant to colchicine contain amplified DNA, which like mitochondrial DNA replicate asynchronously with the main portion of the cellular DNA and related but not identical DNA sequences are amplified in independent cell lines selected for resistance to colchicine, adriablastin, and actinomycin D. These cell lines display similar patterns of alterations of plasma membrane permeability. The amplified DNA sequences may contain a gene or genes the overexpression of which leads to change in plasma membrane permeability and a development of resistance to various drugs.     

Regular pattern of karyotypic alterations accompanying gene amplification in Djungarian hamster cells: study of colchicine,adriablastin, and methotrexate resistance

Chromosomal analysis of 26 Djungarian hamster cell lines obtained from 11 independent clones and possessing different levels of resistance to colchicine or adriablastin as a consequence of gene amplification revealed regular patterns in the karyotypic changes that accompanied the development of drug resistance. Usually the sequence of karyotypic changes was as follows: first an additional chromosome 4 appeared; then single unpaired small chromatin bodies (SCBs) arose; later in the middle part of the long arm of one of three chromosomes 4 long homogeneously staining regions (HSRs) and double minute chromosomes (DMs) were formed; and finally in the most resistant variants large clusters of SCBs appeared. The emergence of the clusters of the SCBs correlated well with the occurrence of autonomously replicating, amplified DNA sequences. In contrast to DNA of the HSRs the DNA of the SCBs could replicate outside the S-phase of the cell cycle. When kept in a non-selective medium, the cells gradually lost their resistance to colchicine: 1%–4% of the cells lost the capacity to form colonies in the selective medium independently of the pattern of location in them of amplified genes (in chromosomal HSRs, SCBs, or DMs). Loss of drug resistance was accompanied by disappearance of the chromosomal HSRs, SCBs, and DMs. Chromosomal analysis of the set of methotrexate-resistant Djungarian hamster cell lines indicated the following karyotypic evolution: first the additional material on the distal part of one of two chromosomes 3 appeared; then the light HSRs were formed on the distal part of one of two chromosomes 4; later clusters of SCBs and HSRs arose on the distal part of the short arm of chromosome 3. Probably the amplification of different genes is characterized by specific patterns of karyotypic alterations.     

Chick embryo fibroblasts produce two forms of hyaluronidase

Cultured chick embryo fibroblasts derived from skin and skeletal muscle exhibit hyaluronidase activity both associated with the cell layer and secreted into the medium. Although both forms of the enzyme have a number of similar characteristics (R.W. Orkin and B.P. Toole, 1980, J. Biol. CHem. 255), they differ in thermal stability at neutral pH and in behavior on ion-exchange chromatography. Both forms of the enzyme are equally stable at acidic pH for long intervals, but the cell-associated hyaluronidase is significantly less stable than the secreted froms at neutral pH and at temperatures more than or equal to 30 degrees C. Neither the presence of proteases nor inhibitors of hyaluronidase appear to be involved in the cell-asspcoated enzyme. Chromatography of the two forms of hyaluronidase on carboxymethyl cellulose reveals that most (60-90 percent) of the secreted form of the enzyme elutes at a lower ionic strength than the cell- associated enzyme. Treatment of the secreted form of hyaluronidase with neuraminidase shifts its elution profile on carboxymethyl cellulose toward that of the cell-associated form, and also decreases its thermal stability at neutral pH. In contrast, treatment of the secreted form of hyaluronidase with alkaline phosphatase has no detectable effect. These data suggest that the secreted hyaluronidase differs from the cellular form in possessing additional sialic acid residues which endow the former with increased stability in the extracellular milieu.     

In vitro induction of numerical changes in the karyotype of normal and transformed Djungarian and Chinese hamster cells]

The comparative study of the frequency of colcemid-induced aneuploidy and polyploidy in cultured normal and transformed cells of Djungarian hamster is described. The occurrence of variants with changed chromosome number is much higher in populations of SV40-transformed cell line (4/21) than in normal embryonic cultures. In transformed lines of Djungarian and Chinese hamsters (4/21 and V-79) the frequency of cells with changed chromosome number was found to be dependent on the culture density: the percentage of polyploids was 4-5-fold higher when the number of seeded cells was 2-fold lower. The highest number (18-29%) of hypermodal cells was produced at drug concentrations of 0.02-0.025 mkg/ml. The percengate of polyploids under these conditions reached 10-20. At further increase of colcemid concentrations the proportion of polyploid cells increased. In Djungarian hamster embryonic cell cultures there were single cells with changed chromosome numbers at a concentration of the drug of 0.015-0.1 mkg/ml.     

Intense photon emission induced by fracture of γ–irradiated Dy‐, Tm‐, Sm‐ and Mn‐doped CaSO4 single crystals

When an γ‐irradiated Dy‐, Tm‐, Sm‐ or Mn‐doped CaSO₄ crystal is impulsively deformed, two peaks appear in the ML intensity versus time curve, whereby the first ML peak is found in the deformation region and the second in the post‐deformation region of the crystals. In this study, intensities I_m1 and I_m2 corresponding to first and second ML peaks, respectively, increased linearly with an impact velocity v₀ of the piston used to deform the crystals, and times t_m1 and t_m2 corresponding to the first and second ML peaks, respectively, decreased with impact velocity. Total ML intensity initially increased with impact velocity and then reached a saturation value for higher values of impact velocity. ML intensity increased with increasing γ‐doses and size of crystals. Results showed that the electric field produced as a result of charging of newly‐created surfaces caused tunneling of electrons to the valence band of the hole‐trapping centres. The free holes generated moved in the valence band and their subsequent recombination with electron trapping centres released energy, thereby resulting in excitation of luminescent centres. Copyright © 2012 John Wiley & Sons, Ltd.     

Modified Kadomtsev–Petviashvili Equation for Description of Nonlinear Perturbations in Plasma of Dusty Lunar Exosphere

Plasma Physics Reports - Abstract—Modified Kadomtsev–Petviashvili equation describing nonlinear dynamics of nearly one-dimensional wave structures in dusty plasma above illuminated part...     

Meta-analysis of Correlated Traits via Summary Statistics from GWASs with an Application in Hypertension

Genome-wide association studies (GWASs) have identified many genetic variants underlying complex traits. Many detected genetic loci harbor variants that associate with multiple—even distinct—traits. Most current analysis approaches focus on single traits, even though the final results from multiple traits are evaluated together. Such approaches miss the opportunity to systemically integrate the phenome-wide data available for genetic association analysis. In this study, we propose a general approach that can integrate association evidence from summary statistics of multiple traits, either correlated, independent, continuous, or binary traits, which might come from the same or different studies. We allow for trait heterogeneity effects. Population structure and cryptic relatedness can also be controlled. Our simulations suggest that the proposed method has improved statistical power over single-trait analysis in most of the cases we studied. We applied our method to the Continental Origins and Genetic Epidemiology Network (COGENT) African ancestry samples for three blood pressure traits and identified four loci (CHIC2, HOXA-EVX1, IGFBP1/IGFBP3, and CDH17; p < 5.0 × 10⁻⁸) associated with hypertension-related traits that were missed by a single-trait analysis in the original report. Six additional loci with suggestive association evidence (p < 5.0 × 10⁻⁷) were also observed, including CACNA1D and WNT3. Our study strongly suggests that analyzing multiple phenotypes can improve statistical power and that such analysis can be executed with the summary statistics from GWASs. Our method also provides a way to study a cross phenotype (CP) association by using summary statistics from GWASs of multiple phenotypes.