Catabolite repression is defined as the inhibition of enzyme induction by glucose or related substances. In the bacterium E. coli, the effect of glucose appears to be due to a lowering of the cyclic AMP level. A DNA-directed cell-free system for beta-galactosidase synthesis has served as a model system for studying the mechanism of action of cyclic AMP. Previously, it was reported that in this ...

A pheochromocytoma was maintained in rats from the New England Deaconess Hospital by giving the rats s.c. injections of isolated tumor cells. The animals were sac rificed 3 to 4 weeks after transplantation, the tumors were excised, and purified tumor cells were prepared. Cyclic nucleotide phosphodiesterase of the purified tumor cells was characterized and compared with that of the adrenal medul...

An indirect method for obtaining a reliable measure of the rate of glucose transport into adipocytes is described. Evidence is presented that altered levels of 3':5'-cyclic AMP can influence the transport of glucose into adipocytes. When cyclic AMP levels were lowered with antilipolytic agents (insulin, nicotinic acid, or clofibrate), rates of glucose transport were increased. In contrast, when...

In epithelial cells isolated from rat small intestine, we have studied the influence of vasoactive intestinal peptide (VIP), a neurotransmitter which markedly increases enterocyte cyclic AMP, and of two cyclic AMP analogues (8-bromo cyclic AMP and N6,2'-O-dibutyryl cyclic AMP) on the rate of glycolysis, fructose 2,6-bisphosphate concentration and 6-phosphofructo-2-kinase activity, as well as on...

A cyclic AMP binding protein has been purified over 100-fold from E. coli extracts. Protein purified from wild-type strains binds cyclic AMP with an apparent dissociation constant of 1-2 x 10(-6)M. Two mutant strains that are unresponsive to exogenous cyclic AMP have altered binding activity; the protein purified from one of these mutants has a decreased affinity for cyclic AMP (apparent dissoc...

A pheochromocytoma was maintained in rats from the New England Deaconess Hospital by giving the rats s.c. injections of isolated tumor cells. The animals were sac rificed 3 to 4 weeks after transplantation, the tumors were excised, and purified tumor cells were prepared. Cyclic nucleotide phosphodiesterase of the purified tumor cells was characterized and compared with that of the adrenal medul...

Both adrenocorticotropin (ACTH) and its o-nitrophenyl sulfenyl derivative (NPS-ACTH) in which the single tryptophan residue of the hormone is modified, were able to stimulate corticosterone synthesis to the same maximal rate in isolated rat adrenal cells. The concentration of NPS-ACTH required for half-maximal steroidogenesis was approximately 70 times that of ACTH. Although both ACTH and NPSAC...

The action of prostaglandins on cyclic AMP levels in rat epididymal fat pads, isolated fat cells, and other tissues was studied. Fat pads incubated with prostaglandin El (PGE1) contained higher levels of cyclic AMP than controls but lipolysis was not stimulated. However, PGEr did not cause increased cyclic AMP levels in isolated fat cells, suggesting that the stimulatory action occurred in anot...

Paramecium tetraurelia is attracted to cyclic AMP, which probably, as other attractants, signifies the presence of food. Attraction to cyclic AMP was specific, saturable, and, therefore, likely to be receptor-mediated. In these studies, we measured the binding of cyclic [3H]AMP to whole cells and found it to be saturable, reversible, and displaying specificity similar to that of attraction. An ...

The comparative effects of angiotensin II and adrenocorticotropic hormone (ACTH) on cyclic AMP and steroidogenesis were investigated employing isolated bovine adrenal cells from the zona fasciculata. Like ACTH, angiotensin produced a prompt increase in cyclic AMP which preceded the increase in corticosteroid production. Although this increase in cyclic AMP was small when compared to that induce...