Cilt.3 Sayı.1-2 2009 / Volume.3 Number.1-2 2009

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  • Publication
    Open Access
    Heat stress and wounding response in expression and RNAi impact on Arabidopsis thaliana soluble pyrophosphatase isoforms
    (İstanbul Kültür Üniversitesi, 2009) Ergen, Z. Neslihan; greiner, Steffen; Rausch, Thomas
    Mature plants are assumed to lack cytoplasmic soluble pyrophosphatase activity and vacuolar membrane-bound proton-pumping pyrophosphatase is generally accepted as the sole enzyme responsible for the removal of pyrophosphate accumulated in the cytosol as a by-product of several biosynthetic pathways. On the contrary, Arabidopsis thaliana genome encodes six soluble pyrophosphatase isoforms, which were shown to be highly conserved both in nucleic and in amino acid sequences. There is only one isoform that is shown to be localized in plastids and there is no data available on the localization and/or possible expressional regulation of other isoforms. The analyses of the change in transcription of all A. thaliana soluble pyrophosphatases showed isoform-specific regulation, indicating the role of these isoforms during stress response. Furthermore, we have selected two isoforms through Digital Northern analysis derived from UniGene database and specifically knockdown these isoforms by RNAi approach. The results indicated that A. thaliana soluble pyrophosphatases have specific function in vivo and the loss of function of one or more isoforms can not be compensated by the function of others. Data obtained from this study indicates the possible critical role of soluble pyrophosphatases during plant development and stress response.
  • Publication
    Open Access
    In vitro antisense activity of chitosan/AsODN complexes
    (İstanbul Kültür Üniversitesi, 2009) Enneli, Burcu; Özabaş Turan, S.; Uslu, B.; Akbuğa, J.
    In this study, the complex forms of AsODNs (phosphodiester and phosphorothioate forms) were prepared by using a cationic polymer called chitosan. The effect of chitosan mol wts and chitosan/AsODN ratio on the complex properties was studied. Afterwards, the physicochemical properties such as zeta-potential and particle size of complexes were measured and the in vitro antisense activities of the appropriate formulations were investigated. Full complexation was observed with phosphorothioate AsODN at the ratio of 10:1 (+/-), however phosphodiester AsODN could not be formed full complex with chitosan. The antisense activity of 100:1 (chitosan/AsODN) complexes which have approximately 200 nm particle size, was measured based on the inhibition of β-galactosidase by the antisense containing formulations into the b-Gal transfected HeLa cell lines. Eventually, both of these complex forms protected AsODNs from potential enzymatic degradations. In 100:1 (+/-) complex formulations, high antisense activity (88- 90%) was observed. As a result, chitosan can be considered as a suitable carrier especially for phosphorothioate modified AsODNs. Molecular weight of chitosan and chitosan/AsODN mass ratio had no importance in in vitro inhibition. This study can form the basis for the forthcoming studies related with carrier systems of AsODNs that will be done with chitosan polymer
  • Publication
    Open Access
    Spatial arrangement of the animal male germ cell genome: IV. Radiation-induced locus-specific translocations (2;3) and large-scale organization of Drosophila sperm nucleus
    (İstanbul Kültür Üniversitesi, 2009) Alexandrov, Igor D.; Stepanenko, Victor A.; Alexandrova, Margarita V.; Korablinova, Svetlana V.; Korovina, Larisa N.
    At the previous papers (Alexandrov et al., 2007b, 2008), the specific megarosette-loop organization (but not polar-linear Rabl-configuration) of major haploid autosome 2 in Drosophila sperm nucleus has been proposed and experimentally substantiated by analysis of radiation-induced locus-specific inversions showing highly nonrandomly distribution of the second inversion breakpoints over the entire autosome. We have speculated that spatial organization of the other major chromosomes in Drosophila sperm nucleus must be the same. To test this expectations, the nature and frequency of radiation-induced interchromosomal exchanges (reciprocal translocations) between autosomes 2 and 3 with the first breaks invariantly associated with the same genetic loci (black or vestigial) on the autosome 2 were studied and, at once, the distribution patterns of the second translocation breakpoints over the entire autosome 3 were detected. Analysis of 23 translocations scored has shown that both black and vestigial loci highly non-randomly interact with certain, including pericentromeric heterochromatin, “hot” areas of autosome 3. Surprisingly, positioning of these areas found to be co-linear with that of “hot” areas for inversion breakpoints on the autosome 2 if both euchromatic arms and pericentromeric heterochromatic regions of two major autosomes arrange in parallel to each other, showing thereby that spatial organization of both autosomes 2 and 3 goes on concurrently with space and time. Using these data, 2D and 3D models of spatial arrangement of autosome 3 in Drosophila haploid sperm nucleus were constructed the principle features of which found to be well consistent with the megarosette-loop configuration proposed for the second chromosome. Independent reciprocal translocations (2;3) scored in the genome of the eight radiation-induced “point” black or vestigial mutants turned out to have the breakpoints within the autosomes 2 and 3 areas proximity of which is predetermined by the megarosette-loop configuration of these major chromosomes. These results show that approaches of the classical radiation cytogenetics and genetics employed in our genomic investigations may be useful strategy to assist in the elucidation of the other conceptual point in the dynamics of sperm nucleus as a self-organizing system, namely, whether the chromatic protein remodeling (histon -to- protamine transition) in late spermatids is coupled with the structural reorganization of primary polar-linear Rabl’s state of chromosomes in the early post-meiotic spermatids into the compact megarosette-loop structures in the fully mature spermatozoa.
  • Publication
    Open Access
    Human growth hormone
    (İstanbul Kültür Üniversitesi, 2009) Çoker, Ajda; Arman, Ahmet
    Growth hormone (GH), is expressed from anterior pituitary gland as a 191 amino acid long polypeptide hormone, has essential role on postnatal growth. In addition to longitudinal growth, GH has various effects on carbohydrate, lipid, protein and mineral metabolisms. GH is expressed from GH-N gene which is located within the GH gene cluster consisting three chorionic somatomammotropin (CS) and GH-V genes on chromosome 17q22-24. Secretion of GH is under control of hypothalamic hormones; somatostatin (SRIF) and growth hormone releasing hormone (GHRH). GH shows it’s biological activities by binding to growth hormone receptor (GHR). After dimerization of GHR, JAK2 is associated with GHR and activated, and JAK2 phosphorylates itself, GHR, signal transducer and activator of transcription (STAT) and intracellular proteins. Activated STAT dimers enter into nucleus, bind to promoter of the target genes such as Spi and activate transcription. Also, RAS/MAPK and PKC signal transduction pathways are known to take role in GH signaling. GH signaling is negatively controlled by SHP via the reduction of intracellular Ca++ levels and also suppressors of cytokine signaling (SOC) with dephosphorilation of JAK2.
  • Publication
    Open Access
    Therapeutical potential of mitochondrial reactive oxygen species in carcinogenesis
    (İstanbul Kültür Üniversitesi, 2009) Arısan, Elif Damla; Palavan-Ünsal, Narçin
    Mitochondria is a gatekeeper of cell death with dual function in survival and death decision. Mitochondria is also an important center for reactive oxgen species (ROS) production within most mammalian cells. The bulk of mitochondrial ROS generation can occur at relatively high rates compared to cytosolic ROS production and is primarily determined by metabolic conditions. This event contributes to mitochondrial damage in a range of pathologies and is also important in redox signalling from the organelle to the rest of the cell. Mitochondria targetting strategies in the therapeutical options are promising to increase the ROS generation to induce the apoptosis in cancer cells. Identification of molecular basis of therapeutic potential of mitochondrial ROS generation may provide more successful therapeutic tools in cancer therapy.