Experimental concussion. Ultrastructural and biochemical correlates

Ultrastructural and biochemical alterations were studied in the brainstem reticular formation of animals in which transient coma had been induced by controlled blows to the head. After a period of 7-10 days, animals that did not show obvious injury were artificially respired and sacrificed by perfusion with buffered formalin and glutaraldehyde. Histochemistry and light microscopy revealed chromatolysis of 10-15% of the neurons of pertinent segments of the nucleus giganto cellularis. There was much PAS-positive, diastase-sensitive material in the associated neuropil. Electron miscroscopy of the region confirmed the polysaccharide accumulation in dendrites, presynaptic boutons and preterminal axons. Similar material was found in some astrocytes. A longitudinal microchemical investigation with suitable controls of glycogen concentration in the brainstem demonstrated peak values at 5-7 days after concussion. No significant change in phosphorylase activity was demonstrated. The significance of glycogen accumulation in postconcussive injury and possible mechanisms for its accumulation in relation to changes in electrolyte balance and alterations in Kreb's cycle intermediates are discussed.

Analytical studies on regeneration of protoplasts of Geotrichum candidum by quantitative thin-layer-agar plating

A preparation of pure protoplasts of Geotrichum candidum became osmotically stable and colonies developed when the protoplasts were embedded in stabilizing thin-layer-agar and incubated with stabilizing basal medium. When growing protoplasts were exposed to distilled water and then reincubated with basal medium, the process of regeneration of protoplasts could be quantitatively demonstrated by counting colonies. The process was divided into three phases, lag, logarithmic, and stationary. Furthermore, the state of regeneration of protoplasts at each phase could be seen in detail by microscopic studies of protoplasts under similar growth conditions. In the lag phase, which lasted for 2 hr after inoculation, protoplasts were completely destroyed when placed in distilled water. During the logarithmic phase, from 2 to 5 hr after inoculation, protoplasts rapidly became osmotically stable and about 18% of them were growing. In the stationary phase, most protoplasts developed germ tubes within 2 hr. These results suggested that there are two main phases, although individual cells passed through three different conditions, osmotically labile, osmotically stable, and growing. No apparent structure of cell wall material could be detected by electron microscopy on the surface of the membrane of these osmotically stable cells.