Ultrastructural morphometric analysis of human blood platelets exposed to minimal handling procedures.

A detailed morphometric study of normal human blood platelets is described. The purpose has been to evaluate the morphological characteristics of platelets exposed to minimal handling procedures in order to obtain an optimal basis for the appraisal of platelets in disease. Blood from 10 healthy volunteers was collected directly into buffered glutaraldehyde and processed for electron microscopy. This platelet fixation procedure resulted in excellent preservation of resting platelet ultrastructure with one exception: the dense bodies. Compared to platelets fixed following washing procedures, our directly fixed platelets comprised fewer pseudopods and contained more glycogen. An unexpected feature of the open canalicular system was the apparent release of blisters interpreted as microvesicles. Employing a computerized image analyzer, 300 of the platelets were examined morphologically. The morphometric data thus obtained were analyzed statistically, resulting in a set of standard values for morphological characteristics of human platelets which we have found useful in subsequent evaluations of platelet morphology in disease. Significant inter-individual variance was, however, detected in two instances, in the section area of the alpha granules, as well as the area fraction of platelet sections occupied by channels of the open canalicular system (OCS). This should be taken into consideration when appraising platelet ultrastructure in health and disease.