Platelet functions beyond hemostasis.

Although their central role is in the prevention of bleeding, platelets probably contribute to diverse processes that extend beyond hemostasis and thrombosis. For example, platelets can recruit leukocytes and progenitor cells to sites of vascular injury and inflammation; they release proinflammatory and anti-inflammatory and angiogenic factors and microparticles into the circulation; and they spur thrombin generation. Data from animal models suggest that these functions may contribute to atherosclerosis, sepsis, hepatitis, vascular restenosis, acute lung injury, and transplant rejection. This article represents an integrated summary of presentations given at the Fourth Annual Platelet Colloquium in January 2009. The process of and factors mediating platelet-platelet and platelet-leukocyte interactions in inflammatory and immune responses are discussed, with the roles of P-selectin, chemokines and Src family kinases being highlighted. Also discussed are specific disorders characterized by local or systemic platelet activation, including coronary artery restenosis after percutaneous intervention, alloantibody-mediated transplant rejection, wound healing, and heparin-induced thrombocytopenia.

Collective responsibility and the practice of medicine.

In the following essay, the theoretical apparatus for distinguishing various types of collectivities (aggregates and conglomerates) is described. This is followed by a consideration of how responsibility ascriptions to different types of collectivities are to be understood vis à vis those to individual group members. It is suggested that the "medical profession" (distinctly different from the "medical team" and the "hospital corporation") is an aggregate collectivity. That is, the "medical profession" consists of the "sum" of the identities of its membership, which can be shown to entail that if the "profession" is held responsible for something, each of its members is responsible, in some way, for it. This is to suggest that the "medical profession" is not a shield that hides individual medical practitioners from responsibility for the general state of health care. Quite the contrary. The use of the name of the aggregate in such a responsibility ascription puts each and every one of them "on call."

KIE: Two types of collectivities, aggregate and conglomerate, are analyzed. Moral responsibility cannot be ascribed to aggregates because they are comprised of individuals who have little or no relationship to each other. In contrast, conglomerates are comprised of individuals within an organizational system that has a "corporate internal decision structure"; the conglomerate can be held morally responsible for its actions without blame being necessarily placed on individual members. The medical profession is considered to be an aggregate collectivity, in which each individual practitioner bears at least some responsibility for the delivery of health care.