Incorporation Of Nucleic Acid Precursors Research Articles

Effect of abscisic acid on activity of chromatin.

THE pretreatment of dark-grown radish hypocotyls with abscisic acid (ABA) reduces their capacity for extension growth. Accompanying the growth response there is a small reduction in incorporation of nucleic acid precursors into RNA (Table 1) so it is possible that one of the primary effects of the hormone is to decrease the transcription of RNA at the nuclear level (refs. 1 and 2 and our unpublished work with L. Beevers). To investigate this possibility an in vitro chromatin-dependent RNA polymerase system was isolated from radish hypocotyl tissue and we have investigated the effect of ABA on this system.

Differential effect of sodium azide on the incorporation of nucleic acid precursors into Chinese hamster cells [formula omitted

Nucleic acid metabolism in Chinese hamster fibroblasts grown in vitro noting effects of concentrations of sodium azide

ONTOGENY AND CYTOCHEMISTRY OF THE CHALAZAL PROLIFERATING CELLS OF CAPSELLA BURSA‐PASTORIS (L.) MEDIC.

SummaryThis paper describes the ontogenic development and cytochemistry of a group of cells which proliferate from the chalaza of the ovule of Capsella bursa‐pastoris. These cells arise from nucellar tissue in the chalaza at the time of embryo development and develop a consistent morphology which seems to protrude into the embryo sac. Azure B staining and intensity of incorporation of nucleic acid precursors indicates a high rate of activity of these cells up to the time that the embryo is in the heart stage. They then begin to disintegrate quickly with but a few cells remaining in the mature seed. The evidence suggests that they may play a physiological role in early embryo development.

Studies on kidney tubulogenesis. VI. Survival and nucleic acid metabolism of differentiating mouse metanephrogenic mesenchyme in vitro.

AbstractResults obtained from analysis of the early development of embryonic cells under tissue culture conditions apparently reflect both true developmental events and artificial changes consequent upon the isolation and transplantation of the tissues. The magnitude and mechanisms of such changes were examined in a model system, the differentiating metanephrogenic mesenchyme of mouse embryos, which we have used for several analytical studies in developmental biology. The results indicate that isolating and transplanting this tissue to organ culture conditions causes a marked decrease in nucleic acid metabolism, as measured in incorporation experiments. This lag period extends through the first 20 to 30 hours of in vitro cultivation, after which normal metabolism is restored. The change does not seem to be related to cell loss, since viability counts reveal only a small percentage of cells to be dying during this period. Adding Zn++ ions to the culture medium had a favorable effect on the incorporation of nucleic acid precursors during the lag period, suggesting that the enzyme treatment employed during isolation might have removed bivalent cations from this tissue.

The effect of actidione on mitosis in the slime mold Physarum polycephalum.

Actidione, reportedly a specific inhibitor of protein synthesis, was found to reduce the incorporation of labeled amino acids into proteins of the slime mold Physarum polycephalum without drastically inhibiting the incorporation of nucleic acid precursors into RNA. This inhibitor was found to completely block the ensuing mitosis if it was added at any time between telophase and late prophase. Plasmodia given Actidione in late prophase (about the time of nucleolar dissolution) went on through telophase to reconstruction even though nuclear amino acid incorporation was drastically reduced during that period.

An autoradiographic study of the incorporation of nucleic-acid precursors by neurones and glia during nerve stimulation.

An autoradiographic study of the incorporation of nucleic-acid precursors by neurones and glia during nerve stimulation.

Effects of colchicine on the incorporation of nucleic acid precursors into rat liver ribosenucleic acid

Subcutaneous injection of 1.0–1.l mg of colchicine/kg body weight into adult Sprague-Dawley rats 16–18 hr prior to the administration of radioactive nucleic acid precursors led to elevation over control values of the specific activities of the pyrimidines and purines of liver RNA. The greatest changes were in the specific activities of cytosine after orotic acid-6- 14C and uridine-2- 14C and of guanine after adenine-8- 14C and inosine8- 144C. When xanthosine-8- 14C was given, colchicine treatment increased the specific activity of RNA guanine at least twofold. The results indicate that treatment of rats with colchicine may lead to enhancement of amination reactions in the liver, whereby a uracil nucleotide is converted to a cytosine nucleoide, and xanthosine-5'-phosphate is converted to guanosine-5'-phosphate. The change produced by colchicine in the liver concentration of free glutamine, the amino-group donor in these reactions, was of insufficient magnitude to account for the results.

RNA synthesis and ribosome production in puromycin-treated cells

1. 1. Puromycin is an effective inhibitor of protein synthesis in Escherichia coli 15T when treatment takes place in a medium lacking magnesium. Although incorporation of labelled amino acid is prevented in this system, incorporation of nucleic acid precursors continues. RNA, from cells treated with puromycin, labelled with [8- 14C]adenine and separated on a sucrose density gradient exhibits the same sedimentation profile as the RNA from normal cells. The RNA accumulated during treatment with puromycin is stable after removal of the inhibitor, provided glucose is added to the medium in which the bacteria are resuspended. The ribosomal RNA, furthermore, can be incorporated into ribosomal particles during recovery from puromycin treatment. 2. 2. During this recovery phase there appears to be a preferential synthesis of ribosomal protein. Thus, the simultaneous sysnthesis of ribosomal RNA and ribosomal protein is not a necessary requirement for the formation of ribosome particles. 3. 3. In resting cell cultures (absence of glucose) nucleic acid formation, as measured by [8- 14C]adenine incorporation is increased by the addition of puromycin to the incubation medium.

Groupes Sulfhydriles et Morphogénèse: IV. Effets du β-Mercaptoéthanol et de l’Acide-α-Lipoïque sur le Métabolisme des Acides Nucléiques chez les Embryons de Batracien et de Poulet

ABSTRACT A study has been made of the incorporation of nucleic acid precursors (thymidine, uridine, cytidine) in two embryonic materials: Pleurodeles and Chicken, in the presence of two substances known to have a morphostatic effect on the closure of the neural plate: β-mercaptoethanol and lipoic acid. The results reveal a marked similarity of action. Thymidine incorporation into DNA is stimulated by mercaptoethanol and lipoic acid. Both substances also stimulate the incorporation of cytidine and uridine into RNA. But there is a difference in the case of DNA : mercaptoethanol has a slight stimulatory effect on the incorporation of the two nucleosides, whereas lipoic acid is definitely inhibitory. All the evidence suggests a specific effect of lipoic acid on the reduction of ribonucleosides to deoxyribonucleosides. The results have been discussed.