The quantitation of platelets in peripheral blood is a well-recognized tool. However, other platelet parameters that recently have become available on a routine basis with the introduction of automated cell sizers may become increasingly important in evaluating the integrity of the thrombocytic function. These parameters include mean platelet volume (MPV) and platelet-crit (PCT). This study established reliable reference ranges for these platelet parameters while taking into consideration the effects of age and sex in a study population of 447 normal persons. There was an inverse, nonlinear relationship between MPV and platelet count, with no statistical difference (P greater than 0.05) seen between males and females. Platelet-crit showed no variation with respect to age or sex, however, a direct, linear relationship was suggested between PCT and platelet count. These relationships provide a better understanding of these platelet parameters and may contribute to their use as helpful diagnostic aids.

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Infusible platelet membranes (IPMs) prepared from fresh or outdated human platelets have been shown to correct prolonged bleeding times in thrombocytopenic rabbits. In previous trials, IPMs did not seem to be immunogenic and lacked dose-limiting toxicity. The present study was undertaken to explore whether the platelet glycoprotein (GP) Ib/IX/V complex might retain functionality in the IPM preparation. IPMs did not spontaneously bind von Willebrand factor (vWF), but saturable binding could be induced by ristocetin, with a dissociation constant (Kd) of 0.31 +/- 0.03 microgram/mL at 1.0 mg/mL of ristocetin. Of 4 anti-GPIb-alpha monoclonal antibodies tested, AN-51 inhibited vWF binding 67.8% +/- 5.8%, whereas AS-2, AS-7, and SZ-2 were ineffective. Maximal vWF binding induced by botrocetin was only 10% to 15% of that observed with ristocetin. Retention of partial functionality of the GPIb/IX/V receptor allowing vWF binding in a modulated manner seems to represent a critical mechanism by which IPMs may provide hemostatic efficacy.

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1'0 N.m.r. data for intramolecular hydrogen bonded 2'-amino and amido substituted acetophenones are factored into electronic, torsion angle, and hydrogen bonding components which show that the most acidic proton donor yields the largest shielding effect: MM2 calculations predict consistent hydrogen bonding distances of -1.97 A but variation in torsion angles.