REVERSIBLE AND IRREVERSIBLE CHANGES IN THE FINE STRUCTURE OF NERVOUS TISSUE DURING OXYGEN AND GLUCOSE DEPRIVATION

Rabbit retinas were fixed for electron microscopy immediately after removing the eye and after incubations in a control medium and in three different deprivation media that were identical with the control except for the omission of glucose, oxygen, or both. A systematic comparison was made of the electron microscopic appearance of the different retinas with particular attention to four regions: rod inner segments, rod synapses, bipolar cell bodies, and ganglion cell myelinated axons. Retinas fixed after 1 hour of incubation in the control medium appeared virtually identical with those fixed immediately after ocular removal. Retinas deprived of oxygen and glucose for only 3 minutes showed generalized swelling of mitochondria and alterations in the structure of the synapses with loss of synaptic vesicles. Extending the combined deprivation caused further mitochondrial swelling and synaptic changes and also led to progressive swelling of the Golgi membranes and the granular endoplasmic reticulum. All these changes were almost completely reversible for up to 20 minutes but were irreversible by 30 minutes, at which time multiple discontinuities had appeared in cell and organelle membranes. Anoxia alone produced alterations similar to those found after somewhat shorter periods of the combined deprivation, whereas glucose withdrawal produced only minor changes. These electron microscopic results correlate quite well with previously reported electrophysiological measurements.     

Characterization of Clostridium perfringens (welchii) Isolated from Market Poultry

Strains of Clostridium perfringens capable of producing heat-resistant spores, characteristic of the food-poisoning types, were not recovered in a random survey of feces and livers of market poultry. Favorable growth response with a known food-poisoning strain indicated that the media and methods employed were adequate. Spores produced in vitro from this strain survived at 100 C for several hours. Animal feeding experiments with this strain showed that heat-resistant spores (surviving for 1 hr at 100 C) could be readily demonstrated 24 hr after oral instillation of vegetative cells in mouse feces, but not in chicken feces. One experiment suggests that this strain might adapt to the environment of the intestinal tract of chickens, but not all of the spores recovered were as heat resistant as those of the parent culture.