Properties of XXXX cyclase of lymphoid cells.

@entity19 @entity1425 @entity1920 @entity2922 @entity35 @entity1063 @entity1388
@entity1920 cyclase of homogenates or lysates of @entity19 and @entity35 lymphoid tissues was activated by the addition of @entity1388 ion, @entity1425 , or @entity1063 , but not by any of several other hormones. The @entity2922 stimulation was characterized as beta-adrenergic. This activity was localized in the small lymphoid cells, was greater in thymic than in splenic or mesenteric node cells, and also was greater in @entity19 than in @entity35 cells. @entity2922 -stimulated activity of @entity19 thymocytes remained constant from the 17-19th day of fetal development to 5 weeks after birth; it subsequently decreased to about one-half of the activity by 7-8 weeks. Similar decreases with age occurred in @entity19 spleen and @entity35 thymus. In contrast, the glucagon-stimulated activity of @entity35 liver increased during a similar period. Hypophysectomy of @entity35 at 3 weeks did not influence the amount of cyclase activity of thymocytes assayed at 7 weeks. When intact @entity19 thymocytes were first incubated in a culture medium at 37 degrees C with @entity1425 or @entity1063 , a second addition of @entity2922 after cell lysis no longer stimulated the enzymes. This loss of stimulation was selective, since basal activity and stimulation by @entity1388 ion were not affected. Incubation of intact cells with phytohemagglutinin markedly decreased the activity of lysates, whether assayed in the presence or absence of @entity2922 or @entity1388 . In contrast, phytohemagglutinin added directly to the assay had no effect. No alternations occurred in adenylate cyclase activity as a result of the incubation of a 1:1 mixture of thymocytes from two strains of @entity19 selected for the capacity of the cells to produce a mixed lymphocyte response.
