Dual nature of the peaks of light scattered during spreading depression in chick retina.

In this work some physical properties of the optical concomitants of spreading depression (SD) are investigated in isolated chick retinas. The two peaks of light scattering during the phenomenon were studied at various wavelengths of the illuminating light. It was shown that the first fast increase in light scattering is highly dependent on the wavelength and seems to be a "blue" scattering. The second slow peak, not so dependent, behaves as a "white" scattering. This implies in different underlying physical mechanisms for the two peaks. Based in this dissimilar behavior, using appropriate optical device and adding some substances to the maintaining Ringer solution it could be observed that the death of tissue is accompanied by a light scattering change comparable to the first peak of SD. The opalescence of the second peak is more similar to the opalescence caused by addition of NaCl to the Ringer in which the fragment of retina is maintained.

On the fine structure of the electrocyte of Electrophorus electricus L.

The general ultrastructure of the electrocyte, the basic unit of the electric organs of Electrophorus electricus, is analyzed. Presented herein are detailed observations of the syncytial surface, its fibrillar coat, invaginations of the plasma membrane and synaptic terminals. Using Thiéry's method glycogen granules were identified in the syncytial cytoplasm and inside the synaptic terminals, their size and structure being compatible with the muscular origin of the electric organs, to which the filamentous meshwork found in the cytoplasm may be related. Among the perinuclear-organelles, are dense bodies with crystalline patterns. The mitochondrial matrix contains dense granules, their size and structure varying according to the organ to which they belong and to the fixation method used.