Both exposure to cold and administration of aminophylline result in rapid increases in cyclic adenosine monophosphate (cyclic AMP) in the adrenal medulla and adrenal cortex. These increases are followed by dramatic increases in ornithine decarboxylase activity is due to new enzyme systhesis. The data suggest that the decarboxylase activity is regulated by an increase in cyclic AMP.

T he discovery of the cyclic nucleotides 3',5'cyclic monophosphate (cAMP, Prod. No. A 9501, A 4137) and guanosine 3',5'-cyclic monophosphate (cGMP, Prod. No. G 7504, G 6129) led to the first formulation of the second messenger concept. These cyclic nucleotides are now known to be ubiquitous intracellular second messengers that mediate the response of cells to a variety of extracellular stimuli ...

The adenine nucleotides, 5'-AMP and 3',5'-cyclic AMP block L cells in the S-phase of the cell cycle. The intracellular level of cyclic AMP is reduced after incubation of cells with 5'-AMP, and rates of uridine transport are increased after incubation with either 5'-AMP or cyclic AMP. On the contrary, cyclic AMP levels are increased and uridine transport decreased in cells treated with an inhibi...

Concentrations of cyclic AMP and cyclic GMP in arterial and internal jugular venous (IJV) blood were determined at the resting wakeful state in thirty surgical patients without neurological deficits. The levels of cyclic AMP in artery and IJV were 32.1 +/- 3.0 and 40.0 +/- 4.1 pmol/ml (means +/- standard errors), respectively, while those of cyclic GMP in artery and IJV were 12.2 +/- 2.7 and 14...

The cyclic nucleotide phosphodiesterases (PDEs) are intracellular enzymes that catalyze the hydrolysis of 3,'5'-cyclic nucleotides, such as cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), to their corresponding 5'nucleotide monophosphates. These enzymes play an important role in controlling cellular concentrations of cyclic nucleotides and thus regulate a variet...