NUCLEIC ACID SYNTHESIS IN X-IRRADIATED THYMOCYTES

1966 ◽  
Vol 44 (6) ◽  
pp. 839-852 ◽  
Author(s):  
D. K. Myers ◽  
Kirsten Skov
Keyword(s):  
Dna Synthesis ◽  
Rna Synthesis ◽  
Acid Synthesis ◽  
X Irradiation ◽  
High Concentrations ◽  
Effects Of Radiation ◽  
Inhibition Of Dna Synthesis ◽  
Thymus Cells ◽  
Rna And Dna

The rate of incorporation of thymidine into the deoxyribonucleic acid (DNA) of rat thymocytes in vitro was not immediately affected by low doses of X-radiation, but became progressively more inhibited as the irradiated cells were incubated at 37 °C for periods of up to 6 hours. Ribonucleic acid (RNA) synthesis deteriorated almost at the same rate as DNA synthesis after X-irradiation in vitro, but protein synthesis was slightly more resistant. Addition of 10–50 mM nicotinamide to the irradiated cell suspensions tended to retard the development of this inhibition, particularly at low temperatures, but high concentrations of nicotinamide were also toxic to these cells. The inhibition of DNA synthesis by X-irradiation appeared to follow a qualitatively similar pattern in thymus, spleen, and regenerating liver in vivo.In addition to the inhibition resulting from degenerative processes in the irradiated cells, DNA synthesis in vitro was directly inhibited by 20–30 kr X-radiation. The effects of radiation on DNA synthesis paralleled to some extent its effects on the gel-forming capacity of the deoxyribonucleoprotein from the thymus cells. It is suggested that the normal synthesis of both RNA and DNA in thymocytes depends on the integrity of the deoxyribonucleoprotein.

scholarly journals Lomofungin as an inhibitor of nucleic acid synthesis in Saccharomyces cerevisiae

1974 ◽  
Vol 142 (3) ◽  
pp. 457-463 ◽  
Author(s):  
Michael Cannon ◽  
Antonio Jimenez
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Synthesis ◽  
Rna Synthesis ◽  
Acid Synthesis ◽  
Growth Conditions ◽  
Dna And Rna ◽  
Dna And Rna Synthesis ◽  
Inhibition Of Dna Synthesis ◽  
Rna And Dna Synthesis ◽  
Rna And Dna

1. The antibiotic lomofungin was found to be a potent inhibitor of both DNA and RNA synthesis in Saccharomyces cerevisiae. Under selected growth conditions inhibition of DNA synthesis by the drug preceded inhibition of RNA synthesis. 2. Although in general lomofungin inhibited synthesis of ribosomal RNA and polydisperse RNA more effectively than that of low-molecular-weight RNA, under certain conditions the drug inhibited almost completely synthesis of both 4S and 5S RNA. 3. Inhibition of both RNA and DNA synthesis may be explained if RNA synthesis is required for DNA synthesis in yeast. Alternatively, lomofungin, in addition to interacting with DNA-dependent RNA polymerase, might interfere with a component(s) of the DNA-synthetic apparatus. The drug may thus prove to be of considerable value in studies of DNA synthesis in eukaryotes.

Effect of Daunorubicin and Adriamycin on Nucleic ACID Synthesis of Serum Stimulated Mouse Embryo Fibroblasts

1977 ◽  
Vol 63 (1) ◽  
pp. 31-41 ◽  
Author(s):  
Rosanna Supino ◽  
Anna M. Casazza ◽  
Aurelio Di Marco
Keyword(s):  
Dna Synthesis ◽  
Mouse Embryo ◽  
Rna Synthesis ◽  
Calf Serum ◽  
Acid Synthesis ◽  
Anthracycline Antibiotics ◽  
Simple Method ◽  
Mouse Embryo Fibroblasts ◽  
Embryo Fibroblasts

This paper reports the effects of daunorubicin and adriamycin on DNA and RNA synthesis of in vitro cultured mouse embryo fibroblasts (MEF) stimulated by fetal calf serum (FCS). The addition of FCS to quiescent MEF cultures brings about a wave of RNA synthesis, followed by DNA synthesis which starts between 8 and 12 h after change of medium and proceed for up to 24 h. These cells are therefore partially synchronized. The level of DNA synthesis depends on the amount of FCS added. Daunorubicin and adriamycin are almost equally effective in inhibiting DNA synthesis, as well as cell proliferation, which takes place later. Adriamycin is more active than daunorubicin on RNA synthesis. In cultures treated for an 8 h period starting at different times after FCS addition, the highest DNA synthesis inhibition is achieved by treatment during the first 8 h, when DNA synthesis has not yet started. The cellular uptake of daunorubicin is constantly higher than that of adriamycin, in any experimental condition tested. The results show that FCS-stimulated MEF can provide a simple method for studying the effects of anthracycline antibiotics on partially synchronized cells.

scholarly journals The inhibition of nucleic acid synthesis by mycophenolic acid

1969 ◽  
Vol 113 (3) ◽  
pp. 515-524 ◽  
Author(s):  
T J Franklin ◽  
Jennifer M. Cook
Keyword(s):  
Dna Synthesis ◽  
Mycophenolic Acid ◽  
Early Stage ◽  
Acid Synthesis ◽  
Purine Nucleotides ◽  
Free System ◽  
L Cells ◽  
A Cell ◽  
Inhibition Of Dna Synthesis

1. Mycophenolic acid, an antibiotic of some antiquity that more recently has been found to have marked activity against a range of tumours in mice and rats, strongly inhibits DNA synthesis in the L strain of fibroblasts in vitro. 2. The extent of the inhibition of DNA synthesis is markedly increased by preincubation of the cells with mycophenolic acid before the addition of [14C]thymidine. 3. The inhibition of DNA synthesis by mycophenolic acid in L cells in vitro is reversed by guanine in a non-competitive manner, but not by hypoxanthine, xanthine or adenine. 4. The reversal of inhibition by guanine can be suppressed by hypoxanthine, 6-mercaptopurine and adenine. 5. Mycophenolic acid does not inhibit the incorporation of [14C]thymidine into DNA in suspensions of Landschütz and Yoshida ascites cells in vitro. 6. Mycophenolic acid inhibits the conversion of [14C]hypoxanthine into cold-acid-soluble and -insoluble guanine nucleotides in Landschütz and Yoshida ascites cells and also in L cells in vitro. There is some increase in the radioactivity of the adenine fraction in the presence of the antibiotic. 7. Mycophenolic acid inhibits the conversion of [14C]hypoxanthine into xanthine and guanine fractions in a cell-free system from Landschütz cells capable of converting hypoxanthine into IMP, XMP and GMP. 8. Preparations of IMP dehydrogenase from Landschütz ascites cells, calf thymus and LS cells are strongly inhibited by mycophenolic acid. The inhibition showed mixed type kinetics with Ki values of between 3·03×10−8 and 4·5×10−8m. 9. Evidence was also obtained for a partial, possibly indirect, inhibition by mycophenolic acid of an early stage of biosynthesis of purine nucleotides as indicated by a decrease in the accumulation of formylglycine amide ribonucleotide induced by the antibiotic azaserine in suspensions of Landschütz and Yoshida ascites cells and L cells in vitro.

EFFECT OF X-IRRADIATION ON DNA SYNTHESIS IN EHRLICH ASCITES CARCINOMA CELLS

1965 ◽  
Vol 43 (7) ◽  
pp. 859-864 ◽  
Author(s):  
Shan-Ching Sung
Keyword(s):  
Protein Synthesis ◽  
Dna Synthesis ◽  
Rna Synthesis ◽  
Ehrlich Ascites Carcinoma ◽  
Carcinoma Cells ◽  
Total Rna ◽  
Ehrlich Ascites ◽  
Ehrlich Ascites Cells ◽  
X Irradiation

The rate of DNA synthesis in Ehrlich ascites cells measured immediately after X-irradiation of 500 r for 6 minutes in vitro showed about 15% reduction. However, if X-irradiation was followed by preincubation of the cells, the subsequent synthesis of DNA in the X-irradiated cells was markedly inhibited. Under the same condition, the uptake of thymidine-2-C14, uridine-2-C14, adenine-8-C14, and glycine-1-C14, and protein synthesis in the X-irradiated cells were found to be almost the same as those in the non-irradiated control. RNA synthesis measured as total RNA was only slightly inhibited.

scholarly journals INHIBITING EFFECT OF THE NEW CYTOTOXIC ANTIBIOTIC DAUNOMYCIN ON NUCLEIC ACIDS AND MITOTIC ACTIVITY OF HELA CELLS

1965 ◽  
Vol 27 (3) ◽  
pp. 545-550 ◽  
Author(s):  
A. Di Marco ◽  
R. Silvestrini ◽  
S. Di Marco ◽  
T. Dasdia
Keyword(s):  
Mitotic Activity ◽  
Rna Synthesis ◽  
Thymidine Incorporation ◽  
Acid Synthesis ◽  
Acetyl Derivative ◽  
Total Inhibition ◽  
Nuclear Rna ◽  
Nucleolar Rna ◽  
Higher Doses

The effect has been studied of Actinomycin D, Daunomycin (Da.), and Da. N acetyl derivative on mitotic activity and on the nucleic acid synthesis of in vitro HeLa cell cultures. The experiments were carried out by means of the radioautographic technique using stripping films. The relative uptake of thymidine-H3 and uridine-H3 was determined by means of the reduced silver grain count present in the nuclei of controls and treated cells. The mitotic activity and thymidine incorporation were noticeably reduced by Daunomycin and Actinomycin, whereas both processes appeared less affected by Da. N acetyl derivative. As regards nuclear RNA synthesis, all three antibiotics at low doses chiefly inhibit nucleolar RNA synthesis. On the other hand, whilst Actinomycin at higher doses causes an almost total inhibition of the synthesis of the whole nuclear RNA, in Daunomycin- and Da. N acetyl derivative-treated cells extranucleolar RNA synthesis is less susceptible to inhibition.

scholarly journals INDUCTION OF A HEMOLYSIN RESPONSE IN VITRO

1971 ◽  
Vol 133 (6) ◽  
pp. 1325-1333 ◽  
Author(s):  
Klaus-Ulrich Hartmann
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
B Cells ◽  
Close Contact ◽  
Precursor Cells ◽  
Spleen Cells ◽  
High Concentrations ◽  
Thymus Cells ◽  
Bone Marrow Chimeras

Spleen cells of bone marrow chimeras (B cells) and of irradiated mice injected with thymus cells and heterologous erythrocytes (educated T cells) were mixed and cultured together (17). The number of PFC developing in these cultures was dependent both on the concentration of the B cells and of the educated T cells. In excess of T cells the number of developing PFC is linearly dependent on the number of B cells. At high concentrations of T cells more PFC developed; the increase in the number of PFC was greatest between the 3rd and 4th day of culture. Increased numbers of educated T cells also assisted the development of PFC directed against the erythrocytes. It is concluded that the T cells not only play a role during the triggering of the precursor cells but also during the time of proliferation of the B cells; close contact between B and T cells seems to be needed to allow the positive activity of the T cells.

scholarly journals Light and electron microscopical observations of the effects of high-density lipoprotein on growth of Plasmodium falciparum in vitro

Parasitology ◽  
2004 ◽  
Vol 128 (6) ◽  
pp. 577-584 ◽  
Author(s):  
H. IMRIE ◽  
D. J. P. FERGUSON ◽  
M. CARTER ◽  
J. DRAIN ◽  
A. SCHIFLETT ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
High Density Lipoprotein ◽  
Light And Electron Microscopy ◽  
Density Lipoprotein ◽  
Acid Synthesis ◽  
High Density ◽  
High Concentrations ◽  
Electron Microscopical ◽  
Necessary And Sufficient

Human serum high-density lipoprotein (HDL) is necessary and sufficient for the short-term maintenance of Plasmodium falciparum in in vitro culture. However, at high concentrations it is toxic to the parasite. A heat-labile component is apparently responsible for the stage-specific toxicity to parasites within infected erythrocytes 12–42 h after invasion, i.e. during trophozoite maturation. The effects of HDL on parasite metabolism (as determined by nucleic acid synthesis) are evident at about 30 h after invasion. Parasites treated with HDL show gross abnormalities by light and electron microscopy.

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