The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.
important mitogcnic action of parathyroid hormone, it is proposed that thyrocalcitonin (calcitonin) may bc a general regulator of cyclic AMP-controlled cell proliferation in vivo.
During the fust 10 min after exposure of rat thymic Iymphocytes (thymocytes) to a high concentration (5.0 /.I8/m!) of prostagiandin EI (PGE I ) in medium without added calcium, there is a 67-fold rise in the ceUular cyclic AMP content which causes strong stimulations of deoxyribunucleic acid (DNA) synthesis and cell proliferation. On the other hand, in the presence of 1.0 mM calcium, PGE I causes a similar (68-fold) rise in the cellular cyclic AMP content and a strong stimulation of DNA synthesis, but the stimulated cells do not enter mitosis. Thus, calcium selectively inhibits the cyclic AMP-induced mitogenic process.The calcium-sensitive phase of the mitogenic reaction is normally completed by only 2.5 min after exposure to PGE I; addition of calcium to the extracellular fluid at, or after, this time does not inhibit the flow of stimulated cells into mitosis which begins between 3 and 4 hr later. Finally, calcium must inhibit the operation, but not the cyclic AMPmediated activation, of the mitogenic system since the inhibition can be fully relieved by removal of calcium at least 4 br after exposure to PGE I.
Growth hormone (GH) considerably increases the flow of cells into mitosis in rat thymic lymphocyte (thymocyte) populations maintained in vitro. This calcium-dependent, cyclic-AMP-mediated mitogenic action of GH is due to the rapid (within 60 minutes) stimulation of the initiation of deoxyribonudeic acid (DNA) synthesis in apart of the thymocyte population which is poised, or blocked, at the threshold of the DNA-synthetic (S) phase of the cell cycle. A possible mechanism by wh ich GH, through the agency of cyclic AMP, could promote the initiation of DNA synthesis is discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.