| Abstract: | Specimens of Amoeba proteus and Chaos carolinensis were vitally stained with Alcian blue and subjected to pulsed laser microbeam irradiation in the flux density range of 0.5–4.0 joules/cm2. Sublytic doses of microbeam irradiation influenced streaming and cell movement only in vitally stained cells and when delivered to the frontal regions of pseudopodia. The effect was temporary, as streaming resumed after some seconds. Exposure of the uroid to similar amounts of radiation undoubtedly had a stronger heating effect because of greater dye accumulation in the uroid; however, there was no detectable instantaneous or delayed effect of irradiation of the uroid. Higher doses of irradiation in Marshall's medium cause rupture of the plasmalemma and rapid flow of cytoplasm from the point of injury, irrespective of its location, followed in 1.0–1.2 sec by an elastic recoil. The initial rapid flow toward the wound was apparently caused by a slightly higher hydrostatic pressure within the cell because it was reduced in 0.25 M sucrose. When the uroid was suddenly opened to the sucrose medium by a lytic dose of microbeam irradiation, cytoplasm continued to flow into extending pseudopodia. Present results are not only consistent with the frontal contraction theory, but indicate that it is unnecessary to postulate an additional contraction of the uroid as a contributing factor in steady-state amoeboid movement. The results in addition shed some light on the speed of the surface precipitation reaction in wound-healing, on the existence of an internal hydrostatic pressure but not a pressure gradient along the axis of movement and on the viscoelastic properties of the cytoplasm. |
