Micropipette aspiration of guinea pig megakaryocytes: absence of
fragmentation and dependence on maturation stage
CM Smith , SM Burris and JG White
Department of Pediatrics, University of Minnesota Health Science Center,
Minneapolis.
Platelet release has been alternatively viewed as a fragmentation of
platelet territories demarcated within the cytoplasm of mature
megakaryocytes or as a later event involving segmentation of proplatelet
pseudopodia extended from the cell. The mechanical constraints on platelet
release were evaluated by measuring the resistance of guinea pig
megakaryocytes to aspiration into micropipettes of similar diameter to the
width of naturally forming proplatelet projections. Application of
increasing negative pressure to the surface of the cells resulted in
progressively longer extensions being drawn into the pipette until maximal
extension lengths were reached. None of the passively aspirated cytoplasmic
extensions fragmented off the cells even at the highest aspiration pressure
under physiologic study conditions. The longest extensions were aspirated
from megakaryocytes of the most advanced maturation stage, and a proportion
of the mature cells yielded very long extensions over 50 mu and up to 150
mu in length. Surprisingly, the ease of aspiration did not correlate to
cell size during any stage of maturation. The mechanical behavior of guinea
pig megakaryocytes indicates a large availability of surface for extension
in mature cells ideal for active proplatelet projection. The lack of
mechanical fragility suggests that platelet release is a very late
maturational event not yet initiated in the "mature" megakaryocytes
available for study from marrow harvests.
Volume 73,
Issue 6,
pp. 1570-1575,
05/01/1989
Copyright © 1989 by The American Society of Hematology
