Qualitative investigations on vital blood platelets by reflection contrast microscopy

Light-microscopic visualization of vital human blood platelets is improved by reflection contrast microscopy. The light reflected from the specimen causes interference patterns which are used for the assessment of surfaces or adhesion areas. By means of this technique we studied the activation process of unstimulated platelets. During the observation the following two features were assessed: (1) Platelet adhesion areas and their shape change: two main types of adhesion patterns were found for activated platelets. Type A was characterized by flat spreading and extensive adhesion zones, whereas type B showed only focal contacts in the center and long and sometimes dichotomously split pseudopodia. Both adhesion types coexisted in each sample but did not change into one another during the observation period of 25 min. (2) Pseudopodia formation: initially, a rapid evagination of mobile pseudopodia could be observed which lasted for approximately 2 min. After reaching their final individual length, the pseudopodia adhered to the glass and remained stationary.