The Interaction of the Platelet and von Willebrand Factor

A culture of pig aortic endothelial cells was used for experiments to investigate the interaction between the platelet and von Willebrand factor. An antibody was raised in rabbits to purified porcine von Willebrand factor. A semi-confluent culture of pig endothelial cells was stained immunofluorescently by the sandwich technique using anti-Willebrand factor IgG. An extensive extracellular meshwork of microfilaments was revealed. In endothelial cell cultures from von Willebrand pigs, no immunoreactive microfilaments were found. Immunoelectronmicro-scopy with peroxidase linked antibody has been used to identify similar filaments in normal pig endothelial cells. Washed platelets were shown to adhere to semiconfluent or damaged normal endothelial cell cultures. If the cultures had been previously incubated with anti-Willebrand factor IgG, the washed platelets did not adhere. There was no adherence of platelets when they were added to semiconfluent or damaged von Willebrand endothelial cells.

CHANGES IN SURFACE MORPHOLOGY OF CHINESE HAMSTER OVARY CELLS DURING THE CELL CYCLE

Synchronized populations of Chinese hamster ovary (CHO) cells in confluent culture have been examined by scanning electron microscopy and their surface changes noted as the cells progress through the cycle. During G1 it is characteristic for cells to show large numbers of microvilli, blebs, and ruffles. Except for the ruffles, these tend to diminish in prominence during S and the cells become relatively smooth as they spread thinly over the substrate. During G2 microvilli increase in number and the cells thicken in anticipation of rounding up for mitosis. It appears that the changes observed here reflect the changing capacity of CHO cells during the cycle to respond to contact with other cells in the population, because, as noted in the succeeding paper (Rubin and Everhart), CHO cells in sparse nonconfluent cultures do not show the same wide range of changes during the cell cycle. Normal, nontransformed cells of equivalent type in confluent culture are essentially devoid of microvilli, blebs, and ruffles. The relation of these surface configurations to the internal structure of the cell is discussed.