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M K Haddox

Publications and source records attributed to M K Haddox.

65 records · Page 4Linked to original sources
PubMed1974

Alteration of vein cyclic 3':5' nucleotide concentrations during changes in contractility.

The relative changes in vascular tissue levels of cyclic 3':5'-guanosine monophosphate (cGMP) and cyclic 3':5'-adenosine monophosphate (cAMP) were determined in bovine and canine vein strips that were quickfrozen during changes in contractility elicited by prostaglandins (PG) or isoproterenol. Prostaglandin F(2alpha)-induced venoconstriction was associated with increased vascular tissue levels of cGMP and increased ratios of cGMP to cAMP concentrations, but no consistent qualitative change in cAMP levels. In contrast, vein cAMP concentrations were increased during administration of the vasodilators PGE(2) and isoproterenol. The results suggest possible opposing roles for the two cyclic nucleotides in vasomotion.

Animals↗
PubMed1973

Cyclic GMP.

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Acetylcholine↗
PubMed1972

Guanosine 3':5'-cyclic monophosphate: a possible intracellular mediator of mitogenic influences in lymphocytes.

Adenosine 3':5'-cyclic monophosphate (cyclic AMP) has been shown to have an antimitotic role in various cell types, and it has been hypothesized that a decrease of cyclic AMP concentration in the cell initiates or permits cell division. This hypothesis has been evaluated with respect to clonal proliferation of lymphocytes. Two potent mitogenic agents, phytohemagglutinin and concanavalin A, which induce thymic-dependent lymphocytes to undergo clonal proliferation, were examined for their ability to initiate proliferation and to alter the concentrations of cyclic AMP and guanosine 3':5'-cyclic monophosphate (cyclic GMP) in purified human peripheral blood-lymphocytes. Optimal mitogenic concentrations of phytohemagglutinin and concanavalin A produced 10- to 50-fold increases in the concentration of lymphocyte cyclic GMP within the first 20 min of exposure to the mitogens. No changes were seen in the concentration of cyclic AMP after stimulation with either mitogen in purified form. Increases of less than 2-fold in the concentration of lymphocyte cyclic AMP observed with a less purified preparation of phytohemagglutinin could be attributed to the agglutinating rather than the mitogenic properties of the mitogen. A revised hypothesis is presented in which a temporally discrete rise in lymphocyte cyclic GMP concentration is viewed as an active signal to induce proliferation, while the elevation of cyclic AMP concentration in these cells is viewed as a regulatory influence that limits or inhibits mitogenic action.

Agglutination↗