ZfN: Search Results

1	Author	Regina Teschner, Stefan Postius, Monika Löffler, Friedhelm Schneider	Requires cookie*
	Title	Proliferation and Metabolie Activities of Ehrlich Ascites Tumor Cells in Chemically Defined Albumin Media
	Abstract	, amino acid transport, respiration and lactate/glucose quotient of Ehrlich ascites tumor cells grown in suspension culture in serum free medium supplemented with albumin charges of different origin were studied. Optimal cell growth was obtained in nutrient medium supplemented with 1% bovine serum albumin (Cohn-fraction V, Serva). Cell proliferation under these culture conditions was delayed to 50% as compar ed to controls in normal medium; the rate of synthesis of macromolecules was reduced; energy metabolism was not significantly impaired. The trend of the cells in albumin medium to attach to glass was independent from the pH of the cultures between 7.2 and 8.0; it was enhanced by fatty acid deprivation of the albumin.
	Reference	Z. Naturforsch. 34c, 805 (1979); received May 16 1979
	Published	1979
	Keywords	Cultured Cells, Chemically Defined Albumin Media, Cell Proliferation Cell proliferation, viability, DNA-, RNA-, protein synthesis
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	TEI-XML for	default:Reihe_C/34/ZNC-1979-34c-0805.pdf
	Identifier	ZNC-1979-34c-0805
	Volume	34

2	Author	YousrY M Mostafa, Adam, S.M A D Zayed	Requires cookie*
	Title
	Abstract	Male mice were i.p. injected with two doses (5& 15 m g/kg body weight) o f [l-14C]ethyl-labelled chlorpyrifos. The radioactivity in liver, fat, kidney and urine was measured 6, 24, 48, and 192 h after treatment. Liver R N A and D N A were isolated and hydrolyzed and the bases separated by ion-exchange chromatography. R adioactivity resulting from incorporation and alkylation o f RNA and D N A was measured. Labelled 7-ethylguanine was found in R N A hydrolysate which am ounted 5.5 x 10-3 calculated as fraction o f the applied dose. In D N A hydrolysate [14C]7-ethylguanine was m issing and the major radioactivity was found in two unknown peaks, one o f which corresponds to 3 x 10-2 o f the applied dose. The results indicate that the extent o f alkylation obtained with clorpyrifos is high as com pared with other organophos-phates with methyl esters.
	Reference	Z. Naturforsch. 38c, 461—464 (1983); received Septem ber 22 1982
	Published	1983
	Keywords	DN A, RNA, Alkylation, Insecticides, Chlorpyrifos
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	TEI-XML for	default:Reihe_C/38/ZNC-1983-38c-0461.pdf
	Identifier	ZNC-1983-38c-0461
	Volume	38

3	Author	MounirG. Abouhaidar3, IvanG. Ivanovb	Requires cookie*
	Title	Non-Enzymatic RNA Hydrolysis Promoted by the Combined Catalytic Activity of Buffers and Magnesium Ions
	Abstract	Although Mg2+ is an important cofactor for the specific degradation of RNA by ribozymes, it is not considered as a typical chemical nuclease. In this study we show that in combination with common buffers such as tris(hydroxymethyl)aminomethane and sodium borate. Mg2+ is a powerful catalyst for the degradation of RNA. pH and temperature are found to be the principal factors for the efficient degradation of RNA. Whereas in Tris-HCl/Mg2+ the effi cient cleavage starts at pH values higher than 7.5 and temperatures higher than 37 °C, in sodium borate RNA degradation begins at pH 7.0 and at 37 °C. RNA hydrolysis promoted under the combined catalytic activity of buffer/Mg2+ results in partially degraded RNA and negligible amounts of acid-soluble material. Reaction is insensitive to the concentration of monovalent cations but is completely prevented by chelating agents (E D TA and citrate) at concentrations exceeding that of Mg2+. Borate-magnesium reaction is inhibited also by some polyvalent alcohols (glycerol) and sugars.
	Reference	Z. Naturforsch. 54c, 542 (1999); received January 20/March 23. 1999
	Published	1999
	Keywords	RNA, RNA Degradation, RNA Hydrolysis, Acid-Base Catalysis, Magnesium Catalysis
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	TEI-XML for	default:Reihe_C/54/ZNC-1999-54c-0542.pdf
	Identifier	ZNC-1999-54c-0542
	Volume	54

4	Author	G. Ertraud Ribitsch, Rita De Clercq, Altraud Folkhard, Z. Peter, Ip, E. R3, Josef Schurz3, JuliusC. Lauw Aertc	Requires cookie*
	Title	Small-Angle X-Ray and Light Scattering Studies on the Influence of M g2+ Ions on the Structure of the RNA from Bacteriophage M S 2
	Abstract	The influence o f M g2+ ions on the secondary and tertiary structure o f the RNA from bacteriophage MS2 was investigated by sm all-angle X-ray scattering and light scattering and by sedimentation experiments. The analysis o f the outer part o f the X-ray scattering curve obtained at low temperature in the absence o f Mg2+ yielded a cross-section radius o f gyration o f 0.88 nm and a mass per unit length o f 1720 g m ol-1 nn T 1. Very similar values for these parameters, which refer to the secondary structure o f the RNA m olecule, were also derived from the X-ray scattering curves obtained in the presence o f different am ounts o f Mg2+ (0.07 to 1 ions per nucleotide). On the contrary, the inner part o f the X-ray scattering curves turned out to be highly dependent on the Mg2 + concen tration: the cross-section radius o f gyration and the mass per unit length, which were determined from the scattering curves at small angles as parameters related to the tertiary structure o f the RNA, amounted to 3.11 nm and 4000 g m ol-1 n m -1, respectively, in the absence o f Mg2+ and in creased significantly upon raising the concentration o f M g2+. The increase o f these structural parameters was found to be accom panied by a decrease o f the overall radius o f gyration (as revealed indirectly by X-ray scattering and directly by light scattering m easurem ents) and by an increase o f the sedim entation coefficient. The results from the investigations o f the RNA at low temperature clearly establish the existence o f double-stranded structures dow n to very low M g2+ concentrations as well as the occurrence o f Mg2+ induced changes o f the tertiary structure. In the absence o f Mg2+ the RNA m olecule appears to be a rodlike particle o f about 300 nm length with a lateral diameter o f about 9 to 11 nm. Upon addition o f increasing am ounts o f M g2* this extended structure tightens, eventually forming a coil-like particle. Previous X-ray scattering experiments with MS 2 RNA at ionic strength 0.1 (Zipper, Folkhard and Clauwaert, FEBS Lett. 56, 2 8 3 -2 8 7 (1975)) have already established the axial dim ensions o f such coil-like particles to be about 63, 31 and 14 nm. The results from supplementary X-ray scattering experim ents performed at higher temperatures in the absence or presence o f Mg2+ clearly reflect the loss o f secondary structure due to m elting o f the RNA. This loss is, however, less pronounced at higher concentrations o f Mg2+.
	Reference	Z. Naturforsch. 40c, 234 (1985); received August 20/D ecem b er 14 1984
	Published	1985
	Keywords	RNA, Interaction with M g2+, Small-Angle X -R ay Scattering, Light Scattering, Structural Changes
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	TEI-XML for	default:Reihe_C/40/ZNC-1985-40c-0234.pdf
	Identifier	ZNC-1985-40c-0234
	Volume	40