5-Bromodeoxyuridine inhibition of the transformation of Rous sarcoma virus-infected chicken cells]

The transformation of Rous-Sarcoma-Virus-infected synchronized Chicken cells is prevented when 5-bromodeoxyuridine is added for 3 hrs. at time of the peak of the first S phase following infection. Virus progeny is normally released. The inhibitory effect of BrdU is reversed by simultaneous addition of thymidine, but not by that of deoxyuridine. Hence, the inhibition of the transformation seems to result from the incorporation of the analogue into the nuclear DNA.     

The effect of 5-bromodeoxyuridine on mouse embryos during neurulation in vitro

Mouse embryos explanted at various stages during neurulation were cultured for 20-28 h in the presence of 25-900 micrograms/ml of 5-bromodeoxyuridine (BUdR). BUdR strongly inhibited closure of the cranial neural tube, which was found to be stage-dependent. When mouse embryos were exposed to BUdR after development of the concave curvature in the neuroepithelium of the midbrain to the upper hindbrain regions, they became insensitive to the drug-induced open cranial neural tube. Histological observations showed that BUdR interfered with interkinetic migration and cytokinesis of the neuroepithelial cells. These cellular abnormalities were not dependent on the morphological development of the cranial neural folds. The 3H-BUdR experiment confirmed that the label was mostly incorporated into the DNA fraction.     

Effects of 5-bromodeoxyuridine on in vitro development of mouse embryos in the early somitic stage

Summary The inhibitory effect of 5-bromodeoxyuridine on the early somitic stages of mouse embryos was largely prevented in the presence of excess thymidine but only partially prevented by deoxycytidine.     

Participation of DNA repair in the response to 5-fluorouracil

The anti-metabolite 5-fluorouracil (5-FU) is employed clinically to manage solid tumors including colorectal and breast cancer. Intracellular metabolites of 5-FU can exert cytotoxic effects via inhibition of thymidylate synthetase, or through incorporation into RNA and DNA, events that ultimately activate apoptosis. In this review, we cover the current data implicating DNA repair processes in cellular responsiveness to 5-FU treatment. Evidence points to roles for base excision repair (BER) and mismatch repair (MMR). However, mechanistic details remain unexplained, and other pathways have not been exhaustively interrogated. Homologous recombination is of particular interest, because it resolves unrepaired DNA intermediates not properly dealt with by BER or MMR. Furthermore, crosstalk among DNA repair pathways and S-phase checkpoint signaling has not been examined. Ongoing efforts aim to design approaches and reagents that (i) approximate repair capacity and (ii) mediate strategic regulation of DNA repair in order to improve the efficacy of current anticancer treatments. Received 08 September 2008; received after revision 25 September 2008; accepted 03 October 2008     

A combination of sister chromatid differential staining and giemsa banding.

We report a procedure for combining sister chromatid differential staining and G banding in the same metaphase plate. Mammalian cells in culture are grown in medium containing 5-bromodeoxyuridine for two cell cycles, and conventional air-dried preparations are made. The slides are treated with a trypsin or a urea solution the same way as for regular G banding. This method is simple and fast and provides additional information for cytogeneticists.     

A combination of sister chromatid differential staining and giemsa banding

Summary We report a procedure for combining sister chromatid differential staining and G banding in the same metaphase plate. Mammalian cells in culture are grown in medium containing 5-bromodeoxyuridine for two cell cycles, and conventional air-dried preparations are made. The slides are treated with a trypsin or a urea solution the same way as for regular G banding. This method is simple and fast and provides additional information for cytogeneticists.     

The effect of 5-bromodeoxyuridine on mouse embryos during neurulation in vitro

Summary Mouse embryos explanted at various stages during neurulation were cultured for 20–28 h in the presence of 25–900 g/ml of 5-bromodeoxyuridine (BUdR). BUdR strongly inhibited closure of the cranial neural tube, which was found to be stage-dependent. When mouse embryos were exposed to BUdR after development of the concave curvature in the neuroepithelium of the midbrain to the upper hindbrain regions, they became insensitive to the drug-induced open cranial neural tube. Histological observations showed that BUdR interfered with interkinetic migration and cytokinesis of the neuroepithelial cells. These cellular abnormalities were not dependent on the morphological development of the cranial neural folds. The³H-BUdR experiment confirmed that the label was mostly incorporated into the DNA fraction.Acknowledgment. This work was supported by Grant-in-Aids for scientific research No. 557469 and 58480391 from the Ministry of Education, Japan.     

Cell proliferation in the rat pituitary gland: a mechanism of control in prolactin cells.

We investigated the relationship between prolactin content and DNA replication in the anterior pituitary gland. Thymidine incorporation in pregnant rats is significantly lower than in virgin controls. This is accompanied by a decreased activity of DNA polymerase. Sulpiride administration to pregnant rats enhances thymidine incorporation to levels similar to virgin controls. The results indicate a negative feedback between prolactin content and DNA synthesis in the rat anterior pituitary gland.     

A differential effect of L-serine on the incorporation of 3H-deoxycytidine and 3H-thymidine into DNA of rat thymocytes.

The addition of L-serine to short-term cultures of rat thymocytes stimulated the incorporation of 3H-deoxycytidine into DNA, but simultaneously depressed the incorporation of 3H-thymidine into DNA.     

Kinetics of DNA repair synthesis in guinea-pig pancreatic slices following in vitro exposure to N-methyl-N-nitrosourethane

Summary In vitro exposure of guinea-pig pancreatic slices to NMUT resulted in an increase in hydroxyurea-insensitive³H-TdR incorporation into DNA; this represents DNA repair synthesis following NMUT-induced DNA damage. The kinetics of this hydroxyurea-insensitive³H-TdR incorporation suggest that the NMUT-induced DNA damage is largely repaired within 2 hours.Environmental Health Programs, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 (USA). These studies were supported by National Cancer Institute (Bethesda, Md., USA). Contract No. N01-CP-23284. Technical assistance of MS.Mary Majdan is gratefully acknowledged.     

Isostaining and iso-nonstaining in 5-bromodeoxyuridine-substitutedVicia faba chromosomes

Summary Isostaining and iso-nonstaining was studied by the fluorescent plus Giemsa (FPG) technique after immersion ofVicia faba roots in 5-bromodeoxyuridine (BrdUrd) for about 1 cell cycle (17 h) and in thymidine (19 h) for another one. Both phenomena were seldom observed, never occurred together in the same cell, and are interpreted as being due to deviations of the cell cycle duration.Acknowledgments. S. Sturelid is grateful to the Academy of Sciences of the GDR for financing his stay in Gatersleben.     

A differential effect of L-serine on the incorporation of3H-deoxycytidine and3H-thymidine into DNA of rat thymocytes

Summary The addition of L-serine to short-term cultures of rat thymocytes stimulated the incorporation of³H-deoxycytidine into DNA, but simultaneously depressed the incorporation of³H-thymidine into DNA.This investigation was supported by NIH grants No. CA-10291 and T12CA8021 from the National Cancer Institute.     

Effects of prolactin and growth hormone on DNA synthesis of rat mammary carcinomas in vitro

Summary Explants derived from mammary carcinomas of DMBA-treated female Sprague-Dawley rats were cultured for 5 days in Medium 199 containing insulin and corticosterone. The addition of ovine prolactin to the culture media resulted in a consistent significant increase in H³-thymidine incorporation into DNA. DNA synthesis of explants treated with either ovine or human growth hormone was intermediary to prolactin-treated cultures and control cultures. A combination of prolactin and human growth hormone often increased DNA synthesis above either hormone alone, suggesting a possible growth synergism between these peptides.Supported by NIH research grant No. CA-13777 and American Cancer Society research grant No. ET-59.NIH Research Career Development Awardee No. CA-35027.     

Relationship between DNA and cholesterol synthesis in kidney after refeeding

Summary DNA and cholesterol synthesis were investigated in the kidneys of fasted-refed rats. Refeeding resulted in an increase in kidney DNA synthesis, as measured by³H-thymidine incorporation, starting at 72 h. The increase in DNA synthesis was accompanied by a stimulation of cholesterol synthesis, as measured by¹⁴C-acetate incorporation into cholesterol.     

Effects of butyrate and insulin and their interaction on the DNA synthesis of rumen epithelial cells in culture

Rumen epithelial cells (REC) were incubated in the presence of various concentrations of butyrate or insulin or with both of them, to obtain information on their effect on the DNA synthesis of cultured cells. The 24-h values of 3H-thymidine incorporation into cellular DNA were measured in the presence of butyrate, insulin or butyrate plus insulin. While butyrate reduced DNA synthesis, insulin produced an increase over the control. Combined butyrate plus insulin treatment influenced the incorporation of label in accordance with the relative proportion of these two substances.     

Effects of butyrate and insulin and their interaction on the DNA synthesis of rumen epithelial cells in culture

Summary Rumen epithelial cells (REC) were incubated in the presence of various concentrations of butyrate or insulin or with both of them, to obtain information on their effect on the DNA synthesis of cultured cells. The 24-h values of³H-thymidine incorporation into cellular DNA were measured in the presence of butyrate, insulin or butyrate plus insulin. While butyrate reduced DNA synthesis, insulin produced an increase over the control. Combined butyrate plus insulin treatment influenced the incorporation of label in accordance with the relative proportion of these two substances.     

Cell proliferation in the rat pituitary gland: A mechanism of control in prolactin cells

Summary We investigated the relationship between prolactin content and DNA replication in the anterior pituitary gland. Thymidine incorporation in pregnant rats is significantly lower than in virgin controls. This is accompanied by a decreased activity of DNA polymerase. Sulpiride administration to pregnant rats enhances thymidine incorporation to levels similar to virgin controls. The results indicate a negative feedback between prolactin content and DNA synthesis in the rat anterior pituitary gland.We are grateful to Prof. Carlos J. Gómez for the opportunity to perform this work. These studies were supported by PLA-MIRH 99.178.1.78, by the Consejo Nacional de Investigaciones Científicas y Técnicas and by the Comisión Nacional de Energía Atómica (Argentina).     

Regulation of macronuclear DNA content during the cell cycle of the ciliate Tetrahymena paravorax (microstome form)]

Results of autoradiographic studies of 3H-thymidine incorporation support a model of macronuclear DNA content regulation involving an action upon the extremes of DNA content: elimination of S phase in cells with large DNA content, additional S phase in cells with DNA content. The frequency of each of these phenomena is about 20%: the inequality of frequencies obtained with the two types of sister cells (proters and opisthes) is relatable to the asymetry of cytodieresis observed in this ciliate.     

Thymidine H3 incorporation in the nurse cells of amphigonic and parthenogenetic ovaries ofMegoura viciae (Horn. Aph.)

Conclusions In the amphigonic females ofM. viciae an active nuclear incorporation of thymidine H³ occurs during growth which may be attributed to continuous endomitotic divisions. However, even when the nurse cells are functioning fully, and when the nuclei appear to have achieved maximum development, incorporation of the thymidine H³ continues, and, as was seen in other insects, does not affect all the nuclei. Incorporation would therefore seem to be due not to the continuance of endomitotic divisions but rather to the synthesis of metabolic DNA. On the other hand, even if one supposes that in the nurse cells of the amphigonic ovary endomitotic processes continue right up to the end of vitellogenesis of the amphigonic winter egg, this is quite out of the question so far as the parthenogenetic ovary is concerned. Diploid nurse cells are functioning continuously, since in a parthenogenetic ovary a great many ovocytes reach maturity one after the other, passing through all stages of development to produce the embryos. The nurse cells always retain, in such cases, their characteristic appearance right from the beginning of their differentiation³ and therefore thymidine H³ incorporation cannot be ascribed to continuous endomitotic divisions. It can therefore be assumed that the active synthesis which occurs in the nuclei does not concern genetically stable DNA but a metabolic DNA. The above results thus add new weight to the assumption by former authors that metabolic DNA may be synthesized in the nurse cells of amphigonic insects as well.

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Riassunto Nell'afideMegoura viciae le cellule nutrici diploidi dell'ovario partenogenetico e quelle poliploidi dell'ovario anfigonico si comportano in maniera analoga incorporando timidina H³ durante l'accrescimento ovocitario. Tale incorporazione viene attribuita alla sintesi di DNA metabolico.

     

Inhibition and stimulation by 5-bromodeoxyuridine of erythropoiesis by chick blood island cells

Summary Erythropoiesis in liquid cultures of cell populations resolved from chick blastodiscs at the primitive streak and head-fold stages was totally inhibited by 5–8 g/ml of 5-bromodeoxyuridine. However, concentrations of 0.2 /ml of the nucleoside enhanced the number of erythroid cells formed.This work was supported by grants from the Medical Research Council and National Research Council of Canada. We thank MissesK. Beall andN. N. McGrath for technical assistance. S. D. W. is an Associate of the Medical Research Council.