R Uyar | PubMed Health

PubMed1988

Effects of rat platelet extracts and human platelet-derived growth factor on megakaryocytopoiesis in vitro.

An improved plasma clot culture system was developed for the culture of rat megakaryocyte colonies in vitro. Greater stimulation of megakaryocyte colony growth was provided when both serum and plasma were added to the culture medium than when plasma was added alone. Freeze-thawed extracts prepared from 900 x 10(6) platelets/ml saline and also 9 ng/ml of human platelet-derived growth factor (PDGF) caused maximum increases over the controls of 71% and 42%, respectively, in the numbers of megakaryocyte colonies. The increase in the numbers of megakaryocyte colonies induced by platelet extracts and by PDGF implied that substance(s) released by platelets might play an important role in the control of megakaryocytopoiesis.

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PubMedDate not supplied

Prostaglandin-independent decrease of sheep ureter contractility induced by bradykinin.

The mechanisms that mediate the actions of bradykinin on ureteral motility are poorly defined and mediation via prostaglandins has not been examined. Therefore, the effects of bradykinin on contractility and the possible mediator role of prostaglandins have been investigated in sheep ureter. At the concentrations of 10(-8), 10(-7) and 10(-6) M, bradykinin elicited marked reductions in contractile force. When ureteral strips were treated separately with 10(-6) M indomethacin, 2 x 10(-6) M sodium salicylate and 10(-5) M aspirin, each drug produced a significant decrease in contractile force. In strips in which prostaglandin synthesis was inhibited by the above concentrations of indomethacin, sodium salicylate and aspirin, 10(-7) M bradykinin significantly decreased the contractility. From these data, we concluded that in ureter bradykinin decreases contractility via a mechanism not involving prostaglandin generation.

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