scholarly journals RELATIONSHIPS BETWEEN NUCLEIC ACID SYNTHETIC PATTERNS AND ENCYSTMENT IN AGING UNAGITATED CULTURES OF ACANTHAMOEBA CASTELLANII

1971 ◽  
Vol 49 (2) ◽  
pp. 498-506 ◽  
Author(s):  
V. L. Rudick
Keyword(s):  
Nucleic Acid ◽  
Dna Synthesis ◽  
Dna Content ◽  
Rna Synthesis ◽  
Actinomycin D ◽  
Acanthamoeba Castellanii ◽  
Disc Electrophoresis ◽  
Dna And Rna ◽  
Inhibition Of Dna Synthesis ◽  
Growth Deceleration

Changes in the levels of DNA and RNA syntheses have been studied in unagitated cultures of Acanthamoeba castellanii during the phases of logarithmic multiplication (LM) and population growth deceleration (PGD). Pulse-labeling experiments show that the rate of DNA synthesis decreases at the same time that DNA per cell is known to drop by 50%. The drop in DNA content has been explained by demonstrating with hydroxyurea that the majority of LM amebas can replicate once when DNA synthesis is inhibited and, therefore, must be in G2, whereas the PGD amebas cannot multiply in the presence of inhibitor and, therefore, must be in G1. The inhibition of DNA synthesis in LM or PGD cells has been shown to induce encystment. The rate of RNA synthesis, as illustrated by pulse-labeling experiments, increases 25% in late LM-early PGD while RNA per cell increases 75%. The rate of synthesis then decreases 65%. The majority of accumulated RNA has been demonstrated to be ribosomal by disc electrophoresis. By using actinomycin D at different stages during the RNA build-up, the ability of the amebas to encyst has been shown to depend on the presence of this RNA. The observations on DNA and RNA are discussed with respect to the occurrence of cysts in the cultures during PGD.

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.

scholarly journals The Effect of L-Asparaginase on the Nucleic Acid Metabolism and Cell Cycle of Human Leukemia Cells

Blood ◽  
1972 ◽  
Vol 39 (4) ◽  
pp. 575-580 ◽  
Author(s):  
E. Fred Saunders
Keyword(s):  
Cell Cycle ◽  
Nucleic Acid ◽  
Dna Synthesis ◽  
Rna Synthesis ◽  
Lymphoblastic Leukemia ◽  
Buffy Coat ◽  
Leukemic Cells ◽  
Nucleic Acid Metabolism ◽  
Rapid Decline ◽  
Human Leukemia

Abstract The effect of L-asparaginase on the cell cycle and nucleic acid synthesis of leukemic cells was studied in five children with acute lymphoblastic leukemia. Following an intravenous infusion of the drug, serial marrow samples were obtained for buffy coat volume, mitotic index, and autoradiographic assessment of DNA and RNA synthesis using tritiated thymidine and tritiated uridine, respectively. A rapid decline in buffy coat volume indicated a lytic effect on lymphoblasts. There was a greater kill of proliferative (blasts in the cell cycle) than nonproliferative (G0) leukemic cells. Mitotic indices changed little until 24 hr; in contrast, thymidine labeling indices decreased markedly to less than 50% of control by 6 hr. The changes in labeling indices prior to changes in mitotic indices indicated that L-asparaginase blocked the entrance of cells into the DNA synthesis period of the cell cycle. Cells already in DNA synthesis appeared to continue into mitosis. Uridine labeling indices decreased progressively in all patients. Uridine uptake was inhibited equally in both proliferative and nonproliferative blasts. Therefore, inhibition of RNA synthesis by L-asparaginase was independent of the proliferative activity of the marrow.

Effect of infection with R23 on DNA and RNA synthesis in Escherichia coli

1971 ◽  
Vol 17 (4) ◽  
pp. 461-466 ◽  
Author(s):  
Hiroko Watanabe ◽  
Mamoru Watanabe
Keyword(s):  
Escherichia Coli ◽  
Dna Synthesis ◽  
Rna Synthesis ◽  
Rrna Synthesis ◽  
Maximal Inhibition ◽  
Dna And Rna ◽  
Marked Inhibition ◽  
Dna And Rna Synthesis ◽  
Infected Cells

Infection of Escherichia coli by R23 results in a marked inhibition of rRNA synthesis. Both 16 S and 23 S RNA are inhibited with maximal inhibition occurring at 30 min. Inhibition of 4 S RNA is not as profound. DNA synthesis is also inhibited after R23 infection although infected cells continue to divide for about one generation (45–60 min) after infection.

Microtubules, colchicine, and lymphocyte blastogenesis

1979 ◽  
Vol 57 (6) ◽  
pp. 673-683 ◽  
Author(s):  
Christopher E. Rudd ◽  
Kem A. Rogers ◽  
David L. Brown ◽  
J. Gordin Kaplan
Keyword(s):  
Dna Synthesis ◽  
Time Course ◽  
Human Lymphocytes ◽  
Colchicine Treatment ◽  
Con A ◽  
Lymphocyte Blastogenesis ◽  
Dna And Rna ◽  
Microtubule Disruption ◽  
Inhibition Of Dna Synthesis ◽  
Mouse Lymphocytes

We have studied the time course of disassembly of microtubules of resting and stimulated mouse lymphocytes caused by the drug colchicine, as well as the effect of this compound on DNA and RNA synthesis of human and mouse lymphocytes. Fine-structure studies with the electron microscope showed a great increase in number of microtubules resulting from stimulation of mouse lymphocytes by the mitogenic lectin Con A. The presence of a network of microtubules was demonstrated in resting lymphocytes by use of the technique of immunofluorescence; this technique was not effective for the study of the microtubules of stimulated lymphocytes in the blast stage. The disappearance of microtubular networks in some cells (approximately 25%) was caused by the protocol of colchicine treatment used in many laboratories (30 min at 10−6 M); a 6- to 8-h treatment was required to cause all cells to lose their microtubules. It is indicated in these findings that there is need for extreme caution in implicating microtubule disruption as the cause of certain colchicine effects, such as that on the Con A-induced inhibition of receptor–ligand migration. The addition of colchicine to stimulated cells at varying times of culture caused marked inhibition of DNA synthesis provided that sufficient time (approximately 20 h for maximum inhibition) elapsed between addition of the drug to the stimulated culture and assay of DNA synthesis. Our data on the time course of inhibition of DNA synthesis by α-methyl mannoside (αMM) and by colchicine do not exclude the possibility that the latter compound may act partly by affecting the commitment of stimulated lymphocytes to DNA synthesis but they show that it can inhibit well after commitment is complete. The later the time of assay of thymidine incorporation, the more disparate were the curves relating the effects of αMM and colchicine to DNA synthesis of human cells. In the case of mouse splenic lymphocytes, there was no resemblance between the time course of the αMM and of the colchicine effects. Synthesis of RNA after 12 h of culture of stimulated human lymphocytes was also sensitive to colchicine.

scholarly journals EFFECTS OF CYTOSINE ARABINOSIDE ON DIFFERENTIAL GENE EXPRESSION IN EMBRYONIC NEURAL RETINA

1974 ◽  
Vol 61 (3) ◽  
pp. 688-700 ◽  
Author(s):  
R. E. Jones ◽  
A. A. Moscona
Keyword(s):  
Cytosine Arabinoside ◽  
Rna Synthesis ◽  
Actinomycin D ◽  
De Novo ◽  
Neural Retina ◽  
Regulatory Genes ◽  
De Novo Synthesis ◽  
Macromolecular Synthesis ◽  
Differential Gene ◽  
Inhibition Of Dna Synthesis

The analogue of cytidine, cytosine arabinoside (Ara-C), elicited a significant increase in the level of glutamine synthetase (GS) in embryonic chick neural retina in the absence of the steroid inducer of the enzyme. The increase was due to de novo synthesis of GS and was mediated by RNA which accumulated in the presence of the effective concentration of Ara-C. Accumulation of GS did not result from the inhibition of DNA synthesis for which Ara-C is best known. This new effect of Ara-C involves differential suppression of macromolecular synthesis in this system: the concentration of Ara-C which caused maximum GS accumulation suppressed overall protein and RNA syntheses 65–75% without inhibiting the transcription and translation of templates essential for GS synthesis. Withdrawal of Ara-C resulted in restoration of RNA synthesis and cessation of GS accumulation, even though preformed templates for the enzyme were present; however, if all RNA synthesis was arrested with actinomycin D at the time of Ara-C withdrawal, GS continued to accumulate. The results are consistent with the hypothesis that Ara-C differentially affects the activity of structural and regulatory genes involved in the regulation of GS levels in the retina: Ara-C allows transcription of the enzyme-specific templates, but reversibly inhibits the expression of regulatory genes which limit the accumulation of GS.

DNA synthesis in the developing rat brain

1969 ◽  
Vol 47 (1) ◽  
pp. 47-50 ◽  
Author(s):  
Shan-Ching Sung
Keyword(s):  
Dna Synthesis ◽  
Rat Brain ◽  
Rna Synthesis ◽  
Actinomycin D ◽  
Rapid Rate ◽  
In Vitro Synthesis ◽  
Infant Rat ◽  
Developing Rat

The in vitro synthesis of DNA as measured by the incorporation of thymidine-2-14C into DNA has been studied for various regions of the infant rat brain. Both intact cerebellum and cell-free extracts of cerebellum from newborn and infant rat brain showed a very rapid rate of DNA synthesis which was highest around 6 days after birth and decreased rapidly thereafter up to 18 days. This DNA synthesis in developing rat brain was strongly inhibited by hydroxyurea but was much less sensitive than was RNA synthesis to inhibition by actinomycin D.

Inhibition of nucleic acid synthesis in L1210 cells by nucleoside analogs

1984 ◽  
Vol 49 (11) ◽  
pp. 2551-2556 ◽  
Author(s):  
Jiří Beránek ◽  
Edward M. Acton
Keyword(s):  
Nucleic Acid ◽  
Rna Synthesis ◽  
Nucleoside Analogs ◽  
Acid Synthesis ◽  
Pyrimidine Nucleoside ◽  
Dna And Rna ◽  
L1210 Cells ◽  
Structure Activity ◽  
Dna And Rna Synthesis ◽  
Chloro Derivatives

Series of pyrimidine nucleoside analogs were tested for inhibition of DNA and/or RNA synthesis at L1210 cells. The structure-activity relationship was studied at the analogs of cancerostatic agents 5-fluorouracil and arabinosylcytosine. Out of them the 5'-chloro derivatives give some promise. The inhibitory activity of cyclocytidine vs DNA and RNA synthesis approaches the activity of cancerostatic antibotics.

scholarly journals DNA and RNA Synthesis of Circulating Atypical Lymphocytes in Infectious Mononucleosis

Blood ◽  
1965 ◽  
Vol 25 (2) ◽  
pp. 197-203 ◽  
Author(s):  
LOIS B. EPSTEIN ◽  
GEORGE BRECHER
Keyword(s):  
Dna Synthesis ◽  
Infectious Mononucleosis ◽  
Rna Synthesis ◽  
Mononuclear Cells ◽  
Early Period ◽  
Dna And Rna ◽  
Atypical Cells ◽  
Dna And Rna Synthesis ◽  
Considerable Period ◽  
Active Proliferation

Abstract The percentages of mononuclear cells synthesizing DNA and RNA in serial studies of blood from 13 patients with infectious mononucleosis were determined. Early in the disease a high percentage of atypical lymphocytes were in DNA synthesis but this percentage decreased rapidly as the disease progressed. Late in the disease many atypical lymphocytes were still present but few, if any, were synthesizing DNA. Similar results were found for RNA synthesis. Presumably active proliferation of atypical cells in the tissues is restricted to an early period of the disease, whereas release of such atypical cells may continue for a considerable period.

scholarly journals Transient inhibition of DNA synthesis results in increased dihydrofolate reductase synthesis and subsequent increased DNA content per cell.

1986 ◽  
Vol 6 (10) ◽  
pp. 3373-3381 ◽  
Author(s):  
R N Johnston ◽  
J Feder ◽  
A B Hill ◽  
S W Sherwood ◽  
R T Schimke
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Gene Amplification ◽  
Dihydrofolate Reductase ◽  
Dna Content ◽  
S Phase ◽  
Phase Cell ◽  
Drug Inhibition ◽  
Specific Proteins ◽  
Inhibition Of Dna Synthesis

We examined the role that blockage of cells in the cell cycle may play in the stimulation of gene amplification and enhancement of drug resistance. We found that several different inhibitors of DNA synthesis, which were each able to block cells at the G1-S-phase boundary, induced an enhanced cycloheximide-sensitive synthesis of an early S-phase cell cycle-regulated enzyme, dihydrofolate reductase, and of other proteins as well. This response was specific, in that blockage at the G2 phase did not result in overproduction of the enzyme. When the cells were released from drug inhibition, DNA synthesis resumed, resulting in a cycloheximide-sensitive elevation in DNA content per cell. We speculate that the excess DNA synthesis (which could contribute to events detectable later as gene amplification) is a consequence of the accumulation of S-phase-specific proteins in the affected cells, which may then secondarily influence the pattern of DNA replication.

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