Effects Of Purine Derivatives Research Articles

Effects of purine derivatives on calcitriol metabolism in rats

The effects of theophylline and sodium urate on metabolic production (PR) and clearance rate (MCR) of calcitriol were determined by the constant isotope infusion method in normal rats. Calcitriol PR was significantly reduced after infusion for 20 h of either theophylline (1 mg/h, PR = 22.3 +/- 1.6 ng.kg-1.day-1, P less than 0.001, n = 5) or sodium urate (0.5 mg/h, PR = 18.6 +/- 1.2 ng.kg-1.day-1, P less than 0.001, n = 5) compared with control rats infused with saline (PR = 32.0 +/- 1.5 ng.kg-1.day-1, n = 5). Renal 1 alpha-hydroxylase activity of kidney homogenate was significantly inhibited in rats infused with theophylline or urate. Suppression of 1 alpha-hydroxylase activity was also observed when the kidney homogenate was preincubated for 3 h with various concentrations of xanthine (0.11-3.0 mg/dl). In addition, the MCR of calcitriol was decreased in rats infused with either theophylline (MCR = 21.0 +/- 0.88 microliter.min-1.100 g-1, P less than 0.005) or urate (MCR = 22.9 +/- 0.91 microliter.min-1.100 g-1, P less than 0.05) compared with saline-infused control rats (MCR = 25.2 +/- 0.41 microliter.min-1.100 g-1). Because calcitriol degradation is a receptor-mediated process that requires binding of the receptor-hormone complex to chromatin, we studied the binding affinity of labeled calcitriol receptor for DNA-cellulose in the presence of theophylline or urate. Both theophylline and urate inhibited receptor binding affinity for DNA-cellulose. We conclude that these purine derivatives suppress calcitriol synthesis and inhibit receptor binding affinity for DNA. The altered receptor binding affinity could explain the decreased MCR of calcitriol.

Induced meiotic reductions in root-tips. I Effect of purine derivatives.

Effect of caffeine, xanthine and xanthosine has been studied on the root-tips of Pterotheca falconeri. This plant is very suitable for such studies since there are only 3 pairs of chromosomes, each easily identifiable. Caffeine induced maximum “meiotic reductions” (54.5%) in 57 mM/ 1 HT/72 HR, followed by xanthosine (33.33%) in 60 mM/1 HT/0 HR, and xanthine (25%) in 57 mM/1 HT/6 HR. Spo-radic pairing of chromosomes and formation of what look like chiasmata, followed by second meiotic division and formation of haploid cells with complete chromo-somal complement, have been observed. In addition, reductional groupings with no precise distribution of homologues have also been noticed, but their percentage is far less than “meiotic reductions”. In caffeine treatment mitotic index was found to be dependent upon concentration, time of treatment and recovery period, while in the other two purine derivatives it was independent of the first two in the con-centrations tried.

Effect of Purine Derivatives on Light-induced Betacyanin Formation in Amaranthus

Summary The effect of adenine, 2,6-diaminopurine and 6-methylaminopurine was tested in the blue and red light induced betacyanin formation in Amaranthus seedlings. None of these 3 purines could distinguish between blue and red light action. Adenine and, to a lesser extent, 6-methylarninopurine were found to interfere with both blue and red light signals. Highest concentrations of all the three purine derivatives were found to be more or less inhibitory, but the inhibition was more pronounced in the cotyledon blade than in the apical zone. The meaning and possible explanation of these findings are discussed.

Effect of purine derivatives, papaverine hydrochloride, and imidazole on enterotoxin formation by Clostridium perfringens type A

The percentage sporulation and enterotoxin specific activity were improved for all of five Clostridium perfringens strains, and numbers of heat-resistant spores were improved for four of five strains by replacing proteose peptone with peptone in Duncan-Strong (DS) medium. When raffinose replaced starch in DS, peptone was superior to proteose peptone in increasing percentage sporulation, numbers of heat-resistant spores, and enterotoxin formation for four of five strains. Enterotoxin levels for a strain varied when different lots of the same peptone were used. Additional experiments were conducted with three C. perfringens strains grown in DS medium with peptone. Enterotoxin specific activity was increased for three strains by adding papaverine (hydrochloride crystalline), for two strains by adding each of caffeine and 3-isobutyl-l-methylxanthine, for one strain by adding each of theophylline, 6-mercaptopurine, and 2-amino-6-mercaptopurine, and for none of the strains by adding imidazole. When enterotoxin formation was improved for a strain by one of the compounds, percentage sporulation increased, but growth decreased. Effective compounds also increased numbers of heat-resistant spores for strains H6 and R42, but slightly or not at all for strain E13. The action of these compounds was concentration dependent, with the optimal concentration differing between compounds and between strains grown in the presence of the same compound.

Effect of purine derivatives on regeneration and immunologic reactivity in animals

The effect of azathioprine and of KI-7 (the new purine derivative) on the immunogenesis and regeneration in mammals was studied comparatively, KI-7 with a lesser toxicity than azathioprine proved to suppress the synthesis of antibodies to the SRBC in mice in case of administration of the preparation one day before or on the day of immunization; it also considerably prolonged the survival of skin allografts in rabbits in comparison with control. At the same time it was shown that under conditions of suppression of the immunogenesis system hepatic regeneration did occur in rats, but the correlation of the proliferation processes and cellular hypertrophy differed from that under ordinary restoration conditions, depending on the immunodepressor used. Thus, in difference from azathioprine, KI-7 not only inhibited the mitotic activity of the regenerating liver, but even stimulated it somewhat.

Effect of purine derivatives on Trypanosoma cruzi in vitro

One pyrimidine and nine purine derivatives were studied in vitro against T. cruzi. Concentrations of 1/750 to 1/30,000 inhibited the trypanosomes studied manometrically and also in cultures both aerobically and anaerobically. 2,6-diamino purine hydrate appeared to be the most active of the agents studied.

Effects of Purine Derivatives and Analogues on Multiplication of the Vaccinia Virus

Summary 2,6-diaminopurine inhibits multiplication of the vaccinia virus in an in vitro system containing chick embryonic tissue. This inhibition is abolished by adenine at an equivalent concentration, and by adenylic and guanylic acids, yeast nucleic acid, diphosphopyridine nucleotide and hypoxanthine at somewhat higher concentrations. Guanine, xanthine and uracil are inactive. Several halogenated purines appear to be virostatic in the same system, but adenine did not prevent the inhibition of viral growth produced by 2,6,8-trichloropurine. Three triazolopyrimidines, including 8-azaguanine, failed to prevent multiplication of the virus. Benzimidazole is inhibitory but the toxicity is not abolished by adenine, guanine or yeast nucleic acid. Mice inoculated intracerebrally with a neurotropic strain of vaccinia virus (IHD) were not protected by 2,6-diaminopurine, 2,6-dichloro-7-methyl purine or benzimidazole.

The Effects of Purine Derivatives and other Organic Compounds on Growth and Cell-Division in Plants

The Effects of Purine Derivatives and other Organic Compounds on Growth and Cell-Division in Plants