Cytopathology of virus-infected tumor cells

Electron microscopic study of the cytopathology of ECHO virus infection in cultivated cells

The cultivated monkey kidney cell is subject to changes when infected with ECHO viruses 6, 9, and 19. The electron microscope reveals three stages of infection: (a) initial stage. The nucleus appears granular with chromatin condensation on the nuclear envelope. The cytoplasm contains electron transparent vesicles and vacuoles forming nests. (b) Intermediate stage. The nucleus seems to diminish, appearing more pycnotic and displaced toward the periphery. The cytoplasm is filled with electron transparent vacuoles and vesicles, and dense masses as well as some spiral bodies are seen. The mitochondria retain their shape. Dense particles are seen, which are possibly of viral nature. (c) Final stage. The nucleus is contracted to a narrow strip close to the cellular membrane or is completely destroyed. The cytoplasm shows no apparent changes. Crystals are frequently observed in cells infected with ECHO viruses 6 and 19, consisting of dense particles with an average diameter of 14.4 mmicro ranging from approximately 13.2 to 15.6 mmicro for ECHO virus 6, and 14.5 mmicro ranging from approximately 12.5 to 16.5 mmicro for ECHO virus 19. These particles are clustered in hexagonal packages forming angles of 75 degrees and 105 degrees . The particles in most crystals are arranged in rows separated by a constant distance, the latter varying from one crystal to another and being approximately 1.5 and 2.5 times the distance between particles. Other particles were observed which, however, are not considered to be of viral nature.

Structure and development of viruses as observed in the electron microscope. VI. ECHO virus, type 9

Sequential stages in the development and release of ECHO 9 virus have been illustrated and described. It is suggested that viral particles differentiate and become oriented in columns upon a fine filamentous lattice at cytoplasmic template sites which are distinct from the endoplasmic reticulum. Subsequently, virus is dispersed in the peripheral cytoplasm and gains egress from the cell through rents in the plasma membrane. Complete cellular disruption with viral release may supervene. The virus consists of a 13 to 15 mµ dense core and a poorly defined outer membrane, 22 to 24 mµ in diameter. Incomplete forms, lacking the core, are observed in the cytoplasm but have not been seen in the extracellular space.