OBJECTIVE Adenosine may play a role in the pathophysiology of schizophrenia, since it modulates the release of several neurotransmitters such as glutamate, dopamine, serotonin and acetylcholine, decreases neuronal activity by pos-synaptic hyperpolarization and inhibits dopaminergic activity. Adenosine deaminase participates in purine metabolism by converting adenosine into inosine. The most fre...

Based on enzyme-regulated unmodified gold nanoparticle aggregation, a visual and homogeneous assay of adenosine deaminase (ADA) activity without any other coupling enzymes, aptamers or additional modifications has been developed. The present strategy is simple, cost-effective, high throughput, selective and sensitive for ADA with a detection limit of 0.8227 U L(-1).

Selective inhibitors of adenosine production, degradation and transport were used to potentiate in vivo levels of adenosine and to determine the source of both basal and N-methyl-D-aspartate (NMDA)-induced increases in levels of endogenous adenosine in vivo. Male Sprague-Dawley rats receiving unilateral intrastriatal injections of pharmacological agents were sacrificed 15 min postinjection by h...

Pulmonary endothelial cell (EC) apoptosis has been implicated in the pathogenesis of emphysema. Cigarette smoke (CS) causes lung EC apoptosis and emphysema. In this study, we show that CS exposure increased lung tissue adenosine levels in mice, an effect associated with increased lung EC apoptosis and the development of emphysema. Adenosine has a protective effect against apoptosis via adenosin...

The purine nucleoside adenosine (9-beta-D-ribofuranosyladenine) inhibits a number of lymphocyte functions in vitro, including the ability of activated T lymphocytes and natural killer cells to adhere to and kill tumor targets. Solid tumors, such as adenocarcinomas of the lung and colon, are frequently hypoxic and are, therefore, likely to exhibit increased adenine nucleotide breakdown through t...

To re-examine how the basal extracellular concentration of adenosine is regulated in acutely isolated cerebellar slices we have combined electrophysiological and microelectrode biosensor measurements. In almost all cases, synaptic transmission was tonically inhibited by adenosine acting via A1 receptors. By contrast, in most slices, the biosensors did not measure an adenosine tone but did recor...

Recent advances in the application of kinetic isotope effects to enzyme-catalyzed reactions have provided reliable information for enzymatic transition state structures. A method is presented for quantifying the similarity of substrates and inhibitors with their enzyme-stabilized transition states. On the basis of transition-state stabilization theory for enzymatic reactions, molecules most sim...

We compared the response of rat PC12 cells and a derivative PC18 cell line to the effects of adenosine receptor agonists, antagonists, and adenine nucleotide metabolizing enzymes. We found that theophylline (an adenosine receptor antagonist), adenosine deaminase, and AMP deaminase all decreased basal cyclic AMP content and tyrosine hydroxylase activity in the PC12 cells, but not in PC18 cells. ...

In 32PO4-labeled adipocytes, isoproterenol (ISO) or physiologically relevant concentrations of insulin rapidly increased phosphorylation of a particulate 135-kDa protein which has been identified as a cGMP-inhibited "low Km" cAMP phosphodiesterase (CGI-PDE) by several criteria, including selective immunoprecipitation with anti-CGI-PDE IgG (Degerman, E., Smith, C.J., Tornqvist, H., Vasta, V., Be...