LASER MICROSCOPE IRRADIATION OF PHYSARUM POLYCEPHALUM: DYNAMIC AND ULTRASTRUCTURAL EFFECTS

Abstract

Streaming plasmodia of Physarum polycephalum were irradiated with a microscope-mounted ruby laser and the resulting changes were recorded by cinemicrography or streak photographs. Some lesions were processed for electron microscopy. By varying the incident energy, three levels of response were detected. Two transient responses, a gelation briefly blocking streams and a more severe gelation with contraction, changed movement patterns but not organelle ultrastructure. At higher energies, a permanently coagulated lesion was rapidly segregated from normal and transiently altered cytoplasm by formation of new membranes. Within the coagulum, pigment granules were destroyed, membranes were disrupted, and cytoplasm was flocculent. Nuclei and mitochondria were compact in the center and swollen in a peripheral space left by contraction of the coagulum.These changes are probably caused by heat produced by the interaction between the laser beam and the pigment granules of the plasmodium. Many of the changes seem to be secondary responses that follow the primary capture of energy during irradiation.

"NEW MEMBRANE" FORMATION IN AMOEBA PROTEUS UPON INJURY OF INDIVIDUAL CELLS

“…The same question can be asked about the plasma membrane, since there is evidence (Chambers and Chambers, 1961) that it can be formed with considerable speed . Also, experiments with laser irradiation of the plasmodium Physarum polycephalum indicate that there is rapid formation of new membranes within 2-10 sec after laser injury (Griffin et al, 1969) ; however, from those experiments it is not clear how these membranes are formed . From the sequence of observations in the present paper, it seems not unreasonable to suspect that the new membrane is formed from material normally present in the cytoplasm and which, under certain circumstances, is extruded to the outside .…”