Deficiency of folate or vitamin B(12) (cobalamin) causes megaloblastic anemia, a disease characterized by pancytopenia due to the excessive apoptosis of hematopoietic progenitor cells. Clinical and experimental studies of megaloblastic anemia have demonstrated an impairment of DNA synthesis and repair in hematopoietic cells that is manifested by an increased percentage of cells in the DNA synth...

Regulation of colonic motility depends on the integrity of enteric inhibitory neurotransmission mediated by nitric oxide (NO), purine neurotransmitters, and neuropeptides. Intramuscular interstitial cells of Cajal (ICC-IM) and platelet-derived growth factor receptor-α-positive (PDGFRα+) cells are involved in generating responses to NO and purine neurotransmitters, respectively. Previous studies...

Two experiments were conducted to assess the endogenous fraction of purine derivative (PD) excretion, urinary recovery, and intestinal digestibility of purines in Nellore heifers. For both experiments, 8 Nellore heifers fitted with ruminal and abomasal cannulas were allocated to two 4 × 4 Latin squares. The diets were based on corn silage and concentrate (60 and 40% DM basis, respectively); fec...

Purine inhibitors of cyclin-dependent kinases attract attention as potential anticancer drugs because their first representative roscovitine recently entered clinical trials. Although well described in terms of structure-activity relationships, we still present here a novel modification of the purine scaffold influencing their inhibitory properties. The introduced C-8 substituents, however, low...

The article by Tölle et al1 claims to show for the first time that adenosine 5 -tetraphosphate (AP4) is released on mechanical stimulation from human microvascular endothelial cells in the perfused rat kidney and, further, that AP4 is the most potent mediator of vascular smooth muscle constriction via P2X1 receptors or, indeed, via noradrenaline. It is well established that ATP and UTP released...

Recent studies on the fate of labeled dietary purines in the rat have shown t,hat dietary adenine is a precursor of t,he adenine and of the guanine of tissue nucleic acids (l), but that guanine (2), hypoxanthine (3), and xanthine (3) are not utilized for nucleic acid synthesis. Similar experiments have shown that the pyrimidines, uracil, thymine (2), and cytosine (4) are not incorporated into t...