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1Author    Kiriakos Kotzabasis, Horst SengerRequires cookie*
 Title    Free, Conjugated and Bound Polyamines during the Ceil Cycle in Synchronized Cultures of Scenedesmus obliquus  
 Abstract    The levels of free, conjugated and bound polyamines (PA) were analyzed during the cell cycle of the synchronized unicellular green alga Scenedesmus obliquus. The polyamines putrescine (PUT) and spermidine (SPD) in their free and conjugated forms accumulated per cell to a maximum in the cell cycle at about the 16 th hour after onset of illumination. The polyamines bound to macromolecules and membrane systems showed an additional peak around the 8-10 th hour of the cell cycle. The possible role of the different forms of poly­ amines in DNA replication, mitosis, cell division and development of the photosynthetic apparatus is discussed. 
  Reference    Z. Naturforsch. 49c, 181—185 (1994); received December 31993 
  Published    1994 
  Keywords    Cell Cycle, Polyamines, Putrescine, Spermidine, Scenedesmus 
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 TEI-XML for    default:Reihe_C/49/ZNC-1994-49c-0181.pdf 
 Identifier    ZNC-1994-49c-0181 
 Volume    49 
2Author    Beate Klein, Hartmut FollmannRequires cookie*
 Title    Deoxyribonucleotide Biosynthesis in Green Algae. S Phase-Specific Thymidylate Kinase and Unspecific Nucleoside Diphosphate Kinase in Scenedesmus obliquus  
 Abstract    NDP kinase and thymidylate kinase are essential for DNA precursor formation in that they phosphorylate the products of de novo deoxyribonucleotide biosynthesis, deoxyribonucleoside 5'-diphosphates and thymidine 5'-monophosphate to the corresponding triphosphates which then serve as DNA polymerase substrates. The two enzymes have been measured in synchronous cultures of the green algae, S. obliquus. Thymidylate kinase exhibits an activity peak at the 11 —12th hour of the 24-hour cell cycle, coinciding with DNA synthesis. Enzyme activity is markedly stimulated in presence of fluorodeoxyuridine in the culture medium. This behaviour of dTMP kinase is very similar to that of three other S phase-specific peak enzymes previously analyzed in synchronous algae, viz. ribonucleotide reductase, thymidylate synthase, and dihydro-folate reductase. In contrast, NDP kinase exhibits high and constant activity through the entire cell cycle. The two kinases have been isolated from cell-free extracts, and separated from each other by chromatography on Blue Sepharose. The peak enzyme, dTMP kinase, has been purified to near homogeneity and its catalytic properties are described; the molecular weight is 56,000. NDP kinase activity is separable into two enzyme fractions, both of molecular weight 100,000 (or higher), which are unspecific with respect to ribonucleotide and deoxyribonucleotide substrates. Characterization and purification of the whole series of deoxyribonucleotide-synthesizing enzymes from one organism provides a basis for in vitro experiments towards reconstitution of an S phase-specific DNA precursor/DNA replication multien-».yme aggregate. 
  Reference    Z. Naturforsch. 43c, 377—385 (1988); received February 12/March 17 1988 
  Published    1988 
  Keywords    Algae, Cell Cycle, Deoxyribonucleotides, Nucleoside Diphosphate Kinase, Scenedesmus obliquus 
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 TEI-XML for    default:Reihe_C/43/ZNC-1988-43c-0377.pdf 
 Identifier    ZNC-1988-43c-0377 
 Volume    43 
3Author    Berthold Scheffczyk, IngoD. Am, L.Horst GrimmeRequires cookie*
 Title    PS IIa/ß Heterogeneity during the Cell Cycle of the Unicellular Green Alga Chlorella fusca  
 Abstract    Fluorescence induction m easurem ents indicate a PS II(L ,p heterogeneity in the unicellular green alga Chlorella fusca. Under normal light the relative amount of PS II" is decreasing from 63% to 43% during the first 8 h o f the cell cycle. The rate constant ka shows a concom itant decrease by 20% in the first 4 h. The relative am ount and antenna size of PS IIa is restored in the dark. In contrast, PS II(rcentres show the sam e rate constant during the whole cell cycle. Under low light ka is increased by approximately 30% over the cell cycle, whereas no change o f kp is observed. It is concluded that the PS II organization of Chlorella is changed both during the cell cycle and the adaptation to light intensity by a com plex regulation (i) involving the antenna size o f a-centres and (ii) changing the quantitative relationship of fast and slow reaction centres. 
  Reference    Z. Naturforsch. 44c, 243 (1989); received Septem ber 14/Decem ber 22 1988 
  Published    1989 
  Keywords    PS II H eterogeneity, Green A lgae, Chlorella fusca, Cell Cycle, Light Intensity 
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 TEI-XML for    default:Reihe_C/44/ZNC-1989-44c-0243.pdf 
 Identifier    ZNC-1989-44c-0243 
 Volume    44 
4Author    FrankI. Bohnenstengel3, KlausG. Steubeb, Corinna Meyerb, Hilmar Quentmeierb, BambangW. Nugroho3, Peter ProkschRequires cookie*
 Title    l//-Cyclopenta[b]benzofuran Lignans from Aglaia Species Inhibit Cell Proliferation and Alter Cell Cycle Distribution in Human Monocytic Leukemia Cell Lines  
 Abstract    Thirteen naturally occurring l//-cyclopenta[b]benzofuran lignans of the rocaglamide type as well as one naturally occurring aglain congener all of them isolated from three Aglaia species (Aglaia duperreana, A. oligophylla and A. spectabilis) collected in Vietnam were studied for their antiproliferative effects using the human monocytic leukemia cell lines MONO-MAC-1 and MONO-MAC-6. Only rocaglamide type compounds showed significant inhibition of [3H-]thymidine incorporation and the most active compound didesmethylrocag-lamide inhibited cell growth in a similar concentration range as the well-known anticancer drug vinblastine sulfate. Detailed structure-activity analysis indicated that the OH-group at C-8b which is a common structural feature of most naturally occurring rocaglamide com­ pounds is essential for the described antiproliferative activity since replacement of this group by methylation led to a complete loss of the inhibitory activity for the resulting derivative. Rocaglamide derivatives rapidly inhibited DNA as well as protein biosynthesis of MONO-MAC-6 cells at concentrations well below those of actinomycin D or cycloheximide which were used as positive controls in the respective experiments. Didesmethylrocaglamide was furthermore able to induce growth arrest of MONO-MAC-1 cells in the G2/M and probably GO/Gl-phase of the cell cycle with no morphological indication of cellular damage. Our data suggests that l//-cyclopenta[b]benzofuran lignans of the rocaglamide type act primarily by a cytostatic mechanism. 
  Reference    Z. Naturforsch. 54c, 1075—1083 (1999); received August 18/September 17 1999 
  Published    1999 
  Keywords    l//-Cyclopenta[b]benzofuran Lignans, Aglaia, Cell Cycle, Cytostatic Activity, Human Leukemia Cells 
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 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-1075.pdf 
 Identifier    ZNC-1999-54c-1075 
 Volume    54