Reaction of mouse CNS cells to the scrapie agent in early stages of experimental infection.

Accumulation of the scrapie agent, histological lesions and cytometric parameters in layers III and V of the cerebral cortex and caudate nucleus were investigated in BALB/c mice during the incubation period of scrapie after intracerebral (i.c.) inoculation of the agent. The following cell parameters were determined: areas of the body, nucleus, and cytoplasm of neurons, concentration and amount of protein within the nucleus and cytoplasm. One month after i.c. inoculation, titre of the agent in the brain was 6.3 log LD50/g. Histological examinations of the infected brains revealed no lesions. Cytointerferometric studies showed a statistically significant increase in the size of the body, nucleus and cytoplasm of neurons, namely in the layer III of brain cortex. Increased amounts of protein were observed only in the nuclei of these cells. No such changes were found following i.c. inoculation of normal brain tissue used as a substrate for the agent.