Observations of vincristine-induced paracrystals in human erythroblasts in vitro.

Ultrastructural observations were made on human erythroblasts incubated in a vincristine solution. In certain concentrations and at certain incubation time intervals, paracrystals were observed in the erythroblasts. The fine structure of the paracrystals was similar to that described in platelets, leukemic lymphoblasts or cultured fibroblasts. They showed parallel filaments, amorphous mass or honeycomb-like crystalline structure. One paracrystalline form turned into another form when the sections were tilted by the use of goniometer. These paracrystals were often closely related to other organelles, such as lysosome, Golgi apparatus and nucleus. In the mitotic erythroblasts degraded microtubules coexisted with typical paracrystals.