Purine and pyrimidine bases and nucleosides of germinating Triticum aestivum seeds

Adenine, guanine, uracil and the corresponding nucleosides were identified in mature wheat grain. On germination, contents of these compounds changed in a regular pattern. Amounts of the free bases rose immediately and remained at the increased levels for a short period (3–6 hr). Nucleoside content decreased at the initial phase and increased sharply 12 to 48 hr after germination.     

DNA and RNA Syntheses by Intraerythrocytic Stages of Plasmodium knowlesi*

Incorporation of the nucleic acid precursors, orotic acid, adenosine, thymidine, and uridine, was studied in various stages of intraerythrocytic Plasmodium knowlesi from infected rhesus monkeys. Incubation of the parasitized erythrocytes with the precursors was for 3 hr periods using a plasma-free culture medium. The samples containing primarily rings, early trophozoites, or late trophozoites incorporated orotic acid, adenosine, and uridine into RNA; however, these stages exhibited negligible or very low levels of incorporation of any of the precursors into DNA. The sample containing late trophozoite and schizont stages incorporated orotic acid, adenosine, and uridine into RNA, and orotic acid, adenosine, and very low levels of thymidine into DNA. These results indicate that DNA synthesis (the S phase of the cell cycle) occurs very close to the time of nuclear division, and that either the G1 or G2 phase is very short in P. knowlesi. It was also observed that adenosine and orotic acid, 2 precursors which are incorporated into both DNA and RNA, are utilized differently by the intraerythrocytic parasites. Incorporation of orotic acid into RNA and DNA and adenosine incorporation into DNA were continuous for the entire incubation period, whereas incorporation of adenosine into RNA was very low during the last 2 hr of each period. It was further demonstrated that the parasites utilized exogenous uridine for synthesis of RNA, and that the older parasite stages incorporated thymidine into DNA.     

The incorporation of radio-labelled nucleic acid precursors by Theileria parva in bovine blood and salivary glands of Rhipicephalus appendiculatus ticks

Irvin A.D., Boarer C.D.H., Kurtti T.J. and Ocama J.G.R. 1981. The incorporation of radio-labelled nucleic acid precursors by Theileria parva in bovine blood and salivary glands of Rhipicephalus appendiculatus ticks. International Journal for Parasitology11:451–456. The uptake of radio-labelled nucleic acid precursors by blood and tick salivary gland forms of Theileria pana was studied. Piroplasms took up tritiated purines, particularly hypoxanthine, but not pyrimidines. Similar uptake was recorded by T. parva, both in tick saliva and in salivary glands maintained in vitro. Intermediate parasite stages were those most readily labelled in glands; this reflected active nucleic acid synthesis associated with rapid parasite division. Radio-labelling of T. parva in tick salivary glands could be of value in procedures used for concentrating and purifying theilerial sporozoites.     

Colorimetric Determination of α-Amino Nitrogen in Urine and Plasma with Ninhydrin Reaction

Bacillus stearothermophilus TH 6–2 has two kinds of purine nucleoside phosphorylases (Pu-NPase I and Pu-NPase II). The Pu-NPase I is a functional homolog of eukaryotic purine nucleoside phosphorylases that can catalyze the phosphorolysis of inosine and guanosine, but not adenosine, the primary substrate of Pu-NPase II. The Pu-NPase I gene of TH 6–2 has been cloned, sequenced, and expressed in E. coli. The gene corresponded to an open reading frame of 822 nucleotides that translates into a putative 274-amino acid protein with a molecular weight of 29,637. The deduced amino terminus sequence completely coincided with that found for the purified enzyme. The cloned gene was overexpressed in E. coli by using the trc promoter to produce an active enzyme in large quantities. The amino acid sequence of Pu-NPase I shared 50% similarity with those of human and mouse purine nucleoside phosphorylases.     

Stereoselective Nucleoside Deuteration for NMR Studies of DNA

A procedure has been elaborated for stereoselective deuterium substitution of one of the diastereotopic 5′-protons in 2′-deoxynucleotides. The synthetic scheme uses the reduction of the 5-oxosugar derivative with deuterated Alpine-Borane. The resulting deuterosugar is converted into pyrimidine nucleosides and incorporated into DNA using standard protocols. Comparison of two-dimensional NMR spectra of the fully protonated and partially deuterated duplexes allowed us to assign diastereotopic 5′ protons, increasing the number of experimental restraints used for structure determination.     

Synthesis of Monomers Bearing at the 2′‐Position Cyanomethoxycarbonyl Group for Phosphoramidite Oligonucleotide Synthesis

A novel series of phosphoroamidites for the synthesis of 2′‐modified oligonucleotides was designed and synthesized on the base of 2′‐amino uridine and 2′‐amino arabinoadenosine. The amino groups in these compounds were acidified by bis‐cyanomethyl esters of different dicarbonic acids. Generated reactive linker groups containing cyanomethoxycarbonyl groups are stable under conditions of oligonucleotide synthesis but could be easily functionalised in post‐synthetic stage by treatment with compounds bearing primary amino groups.     

Tomato Thymidine Kinase Is Subject to Inefficient TTP Feedback Regulation

A promising suicide gene therapy system to treat gliomas has been reported: the thymidine kinase 1 from tomato (toTK1) combined with the nucleoside analog pro-drug zidovudine (azidothymidine, AZT), which is known to penetrate the blood–brain barrier. Transduction with toTK1 has been found to efficiently increase the sensitivity of human glioblastoma cells to AZT, and nude rats with intracranial glioblastoma grafts have shown significantly improved survival when treated with the toTK1/AZT system. We show in our paper that the strong suicidal effect of AZT together with toTK1 may be explained by reduced TTP-mediated feedback inhibition of the AZT phosphorylation.     

Synthesis and In Vitro Antitumor Activity of New Substituted Thiopyrimidine Acyclic Nucleosides and Their Thioglycoside Analogs

Some new thiopyrimidine acyclic nucleosides and thioglycoside derivatives 3a-c, 4a-c, 6a,b, and 7a,b were synthesized. The cytotoxicity and antitumor evaluation of all prepared compounds have been tested in vitro against Ehrlich's ascites carcinoma cell line and their activity against glutathione peroxidase and catalase were reported. The role of the prepared compounds as free radical regulators and the therapeutic antitumor effect of a balanced generation of free radicals are discussed. Compounds 2, 3b, 3c, 4a, and 4c inhibited significantly in a dose dependent manner the growth of Ehrlich ascites carcinoma cells while the other compounds did not show any antitumor activity even at higher concentrations.