1. In the isolated perfused rat heart, the contractile activity and the oxygen uptake were varied by altering the aortic perfusion pressure, or by the atrial perfusion technique (;working heart'). 2. The maximum increase in the contractile activity brought about an eightfold increase in the oxygen uptake. The rate of glycolytic flux rose, while tissue contents of hexose monophosphates, citrate,...

Adenosine has been proposed as an endogenous anticonvulsant which can play an important role in seizure initiation, propagation and arrest. Extracellular ATP and adenosine are able to modulate synaptic activity through activation of P2 (P2X and P2Y) and P1 receptors (A1, A2A, A2B, and A3), respectively. Besides the release of adenosine per se, the levels of ATP and adenosine in the synaptic cle...

Comparing growing and density-inhibited cultures of mouse 3T3 cells, we have determined that when cells became density-inhibited: 1. The sizes of the ribonucleotide pools and of the inorganic and organic phosphate pools dropped only slightly, if at all. 2. The sizes of the deoxyribonucleotide pools dropped several-fold. 3. The rate of 32POq transport across the cell membrane declined 5-fold. 4....

1This study was supported by American Cancer Society Grant E587. 'Present address: University of Pennsylvania, School of Veterinary Medicine, New Bolton Center, Kennen Square, Pa. 19348. 3To whom reprint requests should be addressed. Present address: University of Colorado Medical Center, Department of Microbiology, Denver, Colo. 80220. 4The abbreviations used are: FdUrd, 5-fluoro-2-deoxyuridin...

The electrochromatographic separations of 2'-, 3'- and 5'-monophosphates of adenosine, guanosine, cytidine, and uridine were carried out with an open-tubular capillary column which was wall-coated with a highly selective reagent, 28-membered macrocyclic polyamine, 4, 8, 12, 18, 22, 26-hexaaza-1,15-dioxacyclooctaeicosane ([28]ane-N6O2). The effects of pH, composition and concentration of backgro...

In 1998, the world was formally introduced to Viagra (sildenafil), the first oral agent to be approved in the United States for the treatment of erectile dysfunction. Developed by Pfizer chemists, sildenafil inhibited phosphodiesterase type 5 (PDE5), one of the 11-member superfamily of enzymes that hydrolyze cyclic nucleotide monophosphates and among the first discovered that was selective for ...

1This study was supported by American Cancer Society Grant E587. 'Present address: University of Pennsylvania, School of Veterinary Medicine, New Bolton Center, Kennen Square, Pa. 19348. 3To whom reprint requests should be addressed. Present address: University of Colorado Medical Center, Department of Microbiology, Denver, Colo. 80220. 4The abbreviations used are: FdUrd, 5-fluoro-2-deoxyuridin...

Cyclic nucleotide phosphodiesterases (PDEs) regulate intracellular levels of cAMP and cGMP by hydrolyzing them to their corresponding 5' monophosphates. We report here the cloning and characterization of a novel cAMP-specific PDE from mouse testis. This unique phosphodiesterase contains a catalytic domain that overall shares <40% sequence identity to the catalytic domain of all other known PDEs...

In exponentially growing cultures of the extreme halophile Halobacterium halobium and the moderate halophile Haloferax volcanii, growth characteristics including intracellular protein levels, RNA content, and nucleotide pool sizes were analyzed. This is the first report on pool sizes of nucleoside triphosphates, NAD, and PRPP (5-phosphoribosyl-alpha-1-pyrophosphate) in archaea. The presence of ...