Using pulse labeling techniques with [(3)H]thymidine or [(3)H]cytidine, combined with DNA fiber autoradiography, we have investigated the direction and rate of DNA chain growth in mammalian cells. In general, chain elongation proceeds bidirectionally from the common origin of pairs of adjacent replication sections. This type of replication is noted whether the DNA is labeled first with [(3)H]th...

specific and non- specific cellular immune responses were studied in 20 amoebiasis cases and 10 controls. all the study cases and controls were indians living in varanasi, india. ten amoebic liver abscess cases were patients admitted to university hospital. ten non-invasive intestinal amoebiasis cases constituted the second study group. non-specific immune responses were studied using e-rosette...

5,6-dihydroxy-5,6-dihydrothymidine (thymidine glycol) is a major product of the reaction of thymidine with reactive oxygen species, including those generated by ionizing radiation. Thymidine glycol exists as 2 diastereomeric pairs by virtue of the chirality of the C(5) and C(6) atoms. A simple procedure is described for synthesizing and purifying each of the diastereomeric pairs separately. Aft...

The antimicrobial activity of trimethoprim is antagonized by thymidine in in vitro susceptibility tests. The purpose of this investigation was to determine whether this antagonism also occurred during experimental infection in mice, which have high serum thymidine concentrations. We derived a mutant strain of Escherichia coli, TT-48, incapable of utilizing exogenous thymidine from parent strain...

In cultures of a murine mastocytoma, endogenous synthesis of thymidine phosphates, as determined by the incorporation of [(3)H]deoxyuridine into DNA, was reduced within 15 min to less than 3% of control values by the addition of amethopterin (10 microM) in combination with hypoxanthine and glycine. If [(3)H]thymidine and unlabeled thymidine were added simultaneously with amethopterin, the incre...

The interference of platelets with the estimation of unscheduled DNA synthesis in human peripheral mononuclear leukocytes following genotoxic exposure was studied. A 96% reduction in the unscheduled DNA synthesis value was achieved by incubating [3H]thymidine with platelet-rich plasma for 5 hr at 37 degrees. Using radioactive thymine-containing compounds, together with quantitative analyses bas...

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive disorder characterized by severe gastrointestinal dysmotility, cachexia, ptosis, ophthalmoparesis, peripheral neuropathy and leukoencephalopathy. The disease is due to a thymidine phosphorylase defect. This enzyme catalyses the phosphorolysis of thymidine to thymine and deoxyribose 1-phosphate. For this reas...

The influence of ribo- and deoxyribonucleosides and ribo- and deoxyribonucleotides on the uptake of radiolabeled thymidine and thymine by Haemophilus influenzae during growth was investigated. A nucleoside-degrading enzyme similar to that reported in Escherichia coli was found to break down thymidine unless other nucleosides were present to divert its action. The presence of other nucleosides p...

The administration of 5-azacytidine to rats resulted in enhancement of thymidine incorporation into liver DNA. Repeated doses of the drug caused a greater than 10-fold increase of thymidine incorporation. In 5-azacytidine-treated intact rats no changes in the activity of thymidine and thymidylate kinases were observed, whereas a marked depression of thymidine phosphorylase activity occurred. In...