Non-amoeboid locomotion of cultured microglia obtained from newborn rat brain

The movements of cultured microglia obtained from newborn rat brain were examined by video enhanced-differential interference contrast (VEC-DIC) microscopy. Active microglia measured 9.03 +/- 1.06 microns in diameter (mean +/- SD, n = 33; range, 7.03-10.36 microns). The microglia appeared to become smaller with spread of lamellipodia. The short axis of actively moving microglia measured 7.03 +/- 0.49 microns (n = 7). The lamellipodia were thin, transparent and developed rapidly around the cell body (maximal speed of extension, 4 or 5 microns/s). When shear stress from the medium was applied to the surface of cultured cells, the microglia swam with flat lamellipodia serving as sails in the stream. Spontaneous non-amoeboid movements of microglia were observed: they pivoted, circled and marched in various directions using their lamellipodia. The angular speed of rotation was maximally 3 degrees/s. In 5 marching cells, the average speed (distance/s) was calculated at 1.01 +/- 0.54 microns/s (ca. 60 microns/min or 3.6 microns/h).