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At least 343 records · Page 19Linked to original sources
PubMed1981

[Isolation and properties or uridine kinase from Zajdela hepatoma cells].

Uridine kinase (ATP: uridine-5-phosphotransferase, EC 2.7.1.48) was isolated from cytosol of rat Zajdela ascite hepatoma cells by fractionation with ammonium sulfate and gel-filtration on Sephadex G-200. The enzyme has a pH optimum of 7.2 - 7.8; Km for uridine is 4.8 . 10(-5) M, that for ATP - 1.9 . 10(-4) M. The optimal ratio of ATP of Mg2+ is 2.6. The enzyme activity is inhibited by end products of pyrimidine biosynthesis with Ki for CTP of 6.0 . 10(-4) M and for UTP of 1.2 . 10(-3) M. The Ki values for uridine competitive analogs, i. e. 6-azauridine, 5-bromuridine and 5-azacytidine are equal to 4.0 . 10(-4) M, 1.5 . 10(-3) M and 2.5 . 10(-3) M, respectively. Further purification of the enzyme on Sepharose 4B allowed to obtain the most active, although heterogeneous fractions purified 86-fold, with specific activity of 11.2 mkmole/hour per mg of protein. Using electrofocusing, uridine kinase was found to consist of two major and one minor active fractions with pH of 6.2, 6.7 and 6.35, respectively. Chromatography on DEAE-cellulose DE-32 resulted in two major active fractions of the enzyme, differing in thermal stability and inhibition by CTP. It may be concluded that Zajdela ascite hepatoma cells contain at least two isoforms of uridine kinase.

Animals↗
PubMed1983

Inhibition of bovine heart adenosine deaminase activity by some pyrimidine analogues.

Some pyrimidine analogues--especially 6-azauridine and 5-azacytidine at a final concentration of 1 mmol dm-3--significantly depressed adenosine deaminase activity isolated and purified from bovine heart. Both the above mentioned azapyrimidine nucleosides were effective competitive inhibitors of this enzyme. The inhibitory effect of some clinically used pyrimidine analogues may be of importance for explanation of their mechanisms of action on the cell metabolism.

Adenosine↗
PubMed1982

Cytokinetically based induction chemotherapy and splenectomy for childhood acute nonlymphocytic leukemia.

A four-drug regimen, based on cell kinetic principles, induced complete remissions in 68 of 95 children (72%) with acute nonlymphocytic leukemia (ANLL). Patients entered remission after 2-5 weekly cycles of vincristine-daunorubicin (day 1) followed by sequential cytosine arabinoside and 6-azauridine (days 4-7). With continuation therapy of monthly vincristine-doxorubicin-cyclophosphamide, weekly cytosine arabinoside, and daily 6-mercaptopurine, the median duration of complete remission was 10 mo and the median survival time 21 mo. Portal triaditis, evident in 11 of 23 patients with liver biopsies, was associated with long remissions. A larger spleen size (greater than 5 cm) and a higher myeloblast labeling index (greater than 10%) at diagnosis were clearly related to shorter durations of remission. Splenectomy within 1 mo of remission had no statistically significant effect on the frequency of relapse or length of remission. Patients without central nervous system (CNS) leukemia at diagnosis, all treated prophylactically with intrathecal methotrexate, had a low frequency of initial CNS relapse (3/56, 5%). The 2-yr disease-free survival rate is 29% (20 of 68 patients attaining complete remission). fifteen patients have completed 2.5 yr of therapy, and each remains in continuous complete remission, off treatment, for 1+ -36+ mo. This induction chemotherapy was as effective as more intensive regimens, with the advantage of less toxicity and shorter periods of hospitalization.

Acute Disease↗
PubMed1982

Isolation and characterization of drug resistant mutants of Crithidia fasciculata.

Mutants of Crithidia fasciculata, resistant to Actinomycin D, Tubercidin, Crystal Violet, 6-Azauridine, and 5-Fluorouracil were obtained and characterized. The mutants were stable when maintained under nonselective conditions, and could be grouped in several subclasses on the basis of cross-resistance to other drugs. Actinomycin D- and Crystal Violet-resistant mutants appeared spontaneously whereas the others appeared only after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. Analysis with a cell sorter indicated no large scale meiotic changes in ploidy under the various culture conditions employed. These mutants may provide suitable, selectable, genetic markers for use in studying the possibility of a sexual mating process in Crithidia.

Animals↗
PubMed1993

Sedative and hypnotic activities of pyrimidine nucleoside derivatives.

N3-Substituted pyrimidine nucleoside and their related compounds were synthesized. The central nervous system (CNS) depressant effect of the compounds such as hypnotic activity and synergistic effect with pentobarbital have been evaluated. N3-Phenacyl derivatives of uridine (2), thymidine (3), deoxyuridine (4), 6-azauridine (5) and arabinofuranosyluracil (6) exhibited the hypnotic activity, whereas N3-phenacyl-2',3'-O-isopropylideneuridine did not. Compound 2, 3, 4 and 6 significantly enhanced pentobarbital-induced sleep. The results indicate that CNS depressant effect of pyrimidine nucleoside derivatives might relate to functional group at the N3-position on oxopyrimidine ring and stereospecificity of sugar moiety at the N1-position.

Animals↗
PubMed1995

Binding affinity of N3-substituted uridine for synaptic membrane and their CNS depressant effects.

The binding affinity for synaptic membrane from bovine thalamus of N3-phenacyl substituted pyrimidine nucleosides having CNS depressant activity was examined by radio receptor assay. N3-Phenacyl derivatives of uridine, thymidine, deoxyuridine, 6-azauridine and arabinofuranosyluracil inhibited specific [3H]uridine binding and exhibited hypnotic activity. However, N3-phenacyl-2',3'-O-isopropylideneuridine, of which structure was different from sugar moiety of N3-phenacyluridine, showed neither the binding affinity nor the hypnotic activity. The results indicated that CNS depressant effect of pyrimidine nucleoside derivatives might relate to uridine binding affinity, so called uridine receptor.

Animals↗
PubMed1975

Azaribine therapy for psoriasis. Evaluation of potential effects on the liver and other organ systems.

An open study of azaribine was carried out on 38 psoriatic patients for two years. Thirty-five patients had previously taken methotrexate. Thirty-four patients had liver biopsies performed before azaribine therapy and 14 had liver biopsies performed after azaribine therapy. Of these 14, five had grade 1 liver biopsies before and after therapy; one had grade III before and after therapy; and three had grade IV before and after therapy. Liver biopsy findings were slightly worse in two patients, and three patients showed improvement in liver biopsy findings.

Adolescent↗
PubMed1983

Glucocorticoid receptor-mediated teratogenesis in the chick embryo.

The susceptibility of chick embryos to the teratogenic action of intraamniotically injected hydrocortisone increases by several orders during the first four days of incubation. An attempt was made to correlate this phenomenon with the appearance of specific intracellular binding proteins for glucocorticoids. The binding of [3H] corticosterone to the soluble cytoplasmic proteins of the chick embryo was investigated on days 1.5, 2, 3, and 4 of incubation using a gel filtration method. No evidence of high affinity binding was found in embryos on day 1.5. High affinity binding of [3H] corticosterone to the cytosol proteins was first observed in embryos on day 2, but the binding capacity was four times lower than that found in embryos on days 3 and 4. A correlation was obtained between the increasing sensitivity of the chick embryo to hydrocortisone and the appearance of the intracellular binding protein for glucocorticoids. The causal relationship between these two phenomena is further supported by the finding that administration of a nonteratogenic dose of cortexolone completely prevents the teratogenic "cleft beak" action of hydrocortisone, presumably on the basis of competition for binding sites to the glucocorticoid receptor. These findings are consistent with the hypothesis that the teratogenic action of glucocorticoids is mediated by specific cytoplasmic receptors in the chick embryo.

Animals↗
PubMedDate not supplied

Treatment of psoriatic arthritis with azaribine.

Thirty-two patients with psoriatic arthritis unresponsive to conventional therapy were treated wtih the antipyrimidine azaribine. For the group, improvement was highly significant (P less than 0.01) when average painful joint count, ring size, grip strength, pain, and morning gel were compared with baseline measurements. The spectrum of response of individual patients varied from total remission or arthritis in 5 patients to no improvement in 7. Dermatitis improved more than 50% in 26 patients. Reduction in hematocrit, gastrointestinal irritation, and occasional central nervous system toxicity were readily reversed by decreasing or discontinuing dosage. Azaribine appears to be a useful agent for trial in the treatment of refractory psoriatic arthritis.

Adult↗