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At least 37 records · Page 2Linked to original sources
PubMed2006

Gene transfer of cytidine deaminase protects myelopoiesis from cytidine analogs in an in vivo murine transplant model.

Hematopoietic stem cell gene transfer of the drug-resistance gene cytidine deaminase (CDD) protecting cells from the cytotoxic cytidine analogs cytarabine and gemcitabine was investigated in a murine transplant model. Following transplantation of CDD-transduced cells and cytarabine application (500 mg/kg; days 1-4; intraperitoneally) significant myeloprotection was demonstrated with nadir counts of peripheral blood granulocytes and thrombocytes of 2.9 +/- 0.6/nL versus 0.7 +/- 0.1/nL (P < .001) and 509 +/- 147/nL versus 80 +/- 9/nL (P = .008), respectively (CDD versus control). Protection also was observed from otherwise lethal gemcitabine treatment (250 mg/kg; days 1-3). Stable levels of gene-marked cells in primary and secondary recipients were demonstrated for up to 9 months, and whereas CDD overexpression clearly reduced B- and T-lymphocyte numbers, no major toxicity was observed in the myeloid compartment. Despite the profound myeloprotective properties, however, CDD overexpression did not allow for pharmacologic enrichment of transduced hematopoiesis in our model. Thus, in summary, our data establish CDD as a drug-resistance gene highly suitable for myeloprotective purposes, which, given the lack of selection observed in our hands, might best be used in combination with selectable drug-resistance genes such as MGMT (P140K) or MDR1.

3T3 Cells↗
PubMed1984

Interaction of (dien)Pd(II) with cytidine and cytidine 5'-monophosphate. Influence of the phosphate group on the kinetics and mechanism.

The kinetics and the equilibrium of (dien)PdCl+ interaction with cytidine (C) and cytidine 5'-monophosphate (CMP) were studied by spectrophotometry and by stopped-flow methods. In both cases, the mechanism implies a (dien)Pd(H2O)2+ intermediate with a significant contribution of the solvent path at low chloride concentrations. With CMP, the rate is affected due to the addition of a mechanistic path via an intermediate formed between (dien)Pd(II) and the phosphate group of CMP. The kinetic and thermodynamic parameters have been determined and reflect the favorable electrostatic interactions due to the presence of the phosphate group of CMP. Furthermore, these parameters are in agreement with a transient (dien)Pd(II)-phosphate complex of CMP leading to the formation of the thermodynamically favored (dien)Pd(II)-N3 complex as final product.

Journal Article↗
PubMed1985

Cyclopentenyl cytidine analogue. An inhibitor of cytidine triphosphate synthesis in human colon carcinoma cells.

The mechanism of action of the cyclopentenyl analogue of cytidine, cCyd, was investigated in human colon carcinoma cell line HT-29. Upon exposure of cells to 10(-6)M cCyd, cell viability was reduced to 20% of control, whereas cytocidal activity was not present after 2 hr of drug exposure. Cell lethality was partially reversible by Urd, Cyd or dCyd at 10(-6)M cCyd, and fully reversible by these nucleosides at 2.5 X 10(-7)M cCyd. The incorporation of [14C]dThd and [3H]Urd into DNA and RNA was inhibited by 50% by exposure for 2 hr to 2.5 X 10(-7) and 1.5 X 10(-6)M cCyd respectively. Upon 24 hr of drug exposure, the IC50 for RNA synthesis was reduced 2.5-fold, whereas DNA synthesis was almost totally inhibited. cCyd produced a rapid and preferential reduction of CTP synthesis with a half-life of 1 hr at 10(-6)M drug. The IC50 of cCyd for reducing CTP concentrations after 2 hr of drug exposure was 4 X 10(-7)M. Concomitant with the reduction of CTP levels was the inhibition of transcription of rRNA and, to a lesser extent, tRNA, without changes in the processing nucleolar RNA. No changes in the size of DNA were produced following treatment with cCyd. These results indicate that cCyd is a potent and rapid inhibitor of CTP synthesis and that this effect correlates with its cytocidal activity.

Antineoplastic Agents↗
PubMed1999

Cytidine diphosphate choline administration activates brain cytidine triphosphate: phosphocholine cytidylytransferase in aged rats.

Beneficial effects of cytidine (5') diphosphocholine (CDP-choline) administration on several diseases including brain aging, ischemia and stroke are based on an increase in membrane phospholipid turnover. We have studied the possible involvement of CTP:phosphocholine cytidylyltransferase (CT) in this mechanism by measuring its gene expression and enzyme activity in the brains of young and aged rats treated with 500 mg/kg per day of CDP-choline. Older animals showed higher (57%) of total CT activity in particulate (active) fraction than younger animals (46%). Treatment of aged animals for 8, 16, or 60 days had no effect on the CT gene expression but increased activation of the CT by translocation to membranes. The particulate fraction rose from 57% of total activity to more than 65% after 2 months of treatment. This may explain the long-term repairing effects of CDP-choline on damaged membranes of aged animals.

Age Factors↗
PubMed1983

Presence of cytidine 5'-tetraphosphate in commerical samples of cytidine 5'-triphosphate.

A contaminant compound has been isolated from commercial samples of CTP by ion-exchange chromatography on a Dowex-1 column. It has been characterized as cytidine 5'-tetraphosphate from its ultraviolet spectrum, labile and total phosphate content, and periodate consumption. It is present in proportions from 0.3 to 3.9%, apparently regardless of the method of preparation, age of sample, or commericial source of CTP.

Chromatography, Ion Exchange↗
PubMed1979

[Comparison of reactivities or uridine- and cytidine-2',3'-cyclophosphates as donors and uridine and cytidine as acceptors of phosphate under dinucleoside monophosphate synthesis catalyzed by RNAase A].

In order to determine the relative activity of pyrimidine nucleoside-2',3'-cyclophosphates as donors and nucleosides as acceptors of phosphate in the reaction of the internucleotide bond formation catalyzed by RNAase A (EC 3.4.1.22), a comparative synthesis of dinucleoside monophosphates UpU, UpC, CpU and CpC at three different enzyme concentrations (20, 40 and 70 mkg/ml) and two temperatures (0 degrees and -15 degrees) was carried out. The conversion rate of donor (U greater than p and C greater than p) during the synthesis and in the competitive reaction of hydrolysis strongly depends on the type of acceptor activity as compared to uridine. Based on the data of synthesis and simultaneous hydrolysis of U greater than p and C greater than p it may be concluded that in the both cases the latter donor is more reactive. The approaches to the determination of the substrate activity of the donors and acceptors for the evaluation of optimal conditions of the dinucleoside monophosphate synthesis depending on the donor--acceptor combination are discussed.

Cytidine↗