[en] Three cattle calves (Bos Taurus) and three buffalo calves (Bos bubalus) were weaned after receiving colostrum and reared by bottle-feeding of milk. During the first month the animal did not have access to solid food. Urinary purine derivative (PD), concentration, basal PD excretion and glomerular filtrate rate (GFR) were determined during fasting and feeding. After one month the animals were given access to solid feed (urea-treated rice straw 80% and molasses 20%) to stimulate rumen development. At three months of age, while the solid food was given, urinary PD, basal PD excretion and GFR were again determined. Urinary PD excretion both during fasting and milk feeding did not differ significantly between buffaloes to cattle during the period of milk feeding (P > 0.05), but there were highly significant differences between cattle and buffaloes after 3 months of age and two months of access to solid feed (P < 0.01). The GFR was lower in buffaloes than cattle on both milk fed and solid feed periods. It is suggested that the lower GFR found in buffaloes may be the reason for the differences as PD stay longer in the blood to give more time for recycling to the rumen when the rumen is developed and are then metabolized by bacteria. Whether permeability of PD from blood to rumen is an additional factor is not known. (author)

[en] Purine nucleoside phosphorylases (PNPs) catalyze the reversible phosphorolysis of nucleosides and are key enzymes involved in nucleotide metabolism. They are essential for normal cell function and can catalyze the transglycosylation. Crystals of E. coli PNP were grown in microgravity by the capillary counterdiffusion method through a gel layer. The three-dimensional structure of the enzyme was determined by the molecular-replacement method at 0.99 Å resolution. The structural features are considered, and the structure of E. coli PNP is compared with the structures of the free enzyme and its complexes with purine base derivatives established earlier. A comparison of the environment of the purine base in the complex of PNP with formycin A and of the pyrimidine base in the complex of uridine phosphorylase with thymidine revealed the main structural features of the base-binding sites. Coordinates of the atomic model determined with high accuracy were deposited in the Protein Data Bank (PDB-ID: 4RJ2).

[en] Publsihed in summary form only

[en] Mutations in the gene encoding 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC), a bifunctional enzyme that catalyzes the final 2 steps of the purine de novo biosynthetic pathway, were identified in a subject referred for radiation sensitivity testing. Functional studies were performed to determine whether ATIC inhibition was radiosensitizing and, if so, to elucidate the mechanism of this effect and determine whether small molecule inhibitors of ATIC could act as effective radiosensitizing agents.

[en] This survey focuses on recent developments in the radiation chemistry of purine bases in nucleic acids and related model compounds. Both direct and indirect effects of ionizing radiation are investigated with special emphasis on the structural characterization of the final decomposition products of nucleic acid components. Available assays for monitoring radiation-induced base lesions are critically reviewed. (author)

[en] We have found that isoguanine (iG) can pair with thymine (iG · T) non-natural base, 5-methylisocytosine (iG · iCM) during template directed synthesis catalyzed by AMV reverse transcriptase. The ratio of these pairings is about 1:10, irrespectively which of the templates, poly(C,iG) or poly(I,iG) is used. This ratio corresponds to the ratio of 2-OH and 2-keto tautomers in monomer in aqueous solution and apparently it is not influenced by the template context. Our results indicate also that formation of the reverse transcriptase catalyzed base pairs between iG and A, G or C can occur only at low frequency. (author). 21 refs, 5 figs, 1 tab

[en] This study assessed the effects of 6-Benzylaminopurine and wood vinegar on in vitro shoot multiplication, and as elicitors in enhancing the phytochemical content of Clinacanthus nutans extract. A nodal explant of C. nutans was cultured in vitro with single or combination treatments in MS medium supplemented with 6-Benzylaminopurine (BAP) or wood vinegar (WV). The growth performance of regenerated shoots was documented after eight weeks of culture. The total phenolic content, total flavonoid content, and antioxidant activities of the leaf extracts were also studied. The results demonstrated that all single treatments with BAP successfully regenerated and multiplied shoots and leaves. While in combination treatments, the data revealed that 2 mg/L BAP with 1% WV (B2WV1) medium treatment led to the highest number of shoots and leaves per explant and the highest total phenolic content and antioxidant activities in the leaf extract. This concludes that combining wood vinegar and BAP treatments in the culture medium caused significant shoot and leaf growth and enhanced the production of leaf’s secondary metabolites. These findings highlight the potential of 6-Benzylaminopurine and wood vinegar as elicitors to enhance the production of secondary metabolites in Clinacanthus nutans, providing valuable insights for further research in plant biotechnology. (author)

No abstract available

No abstract available

No abstract available