Microscopic Invader

The virus of poliomyelitis, one of the smallest disease-causing organisms, is less than a millionth of an inch long. Trying to follow this minute invader as it attacks the nerve cells in the brain and spinal cord has long been a baffling problem for polio researchers. Last week two Yalemen, Drs. Joseph L. Melnick and John B. LeRoy, told how they had used the electron microscope to study this microcosmic warfare--with surprising results.

Most cytologists (cell scientists) had believed that the virus multiplies in the protoplasm which surrounds the nerve cell's nucleus, much as the white of an egg enfolds the yolk. Not so, the Yale researchers found: the virus invades the nucleus itself as well as the cytoplasm. Apparently it multiplies within the nucleus and, while there, competes with the host cell for the nourishing nucleoproteins which are manufactured in the nucleus.

The crisis in a single cell may come when it is no longer able to manufacture enough nucleoproteins to sustain both itself and the multiplying virus. What happens when this takes place on a large scale is that many nerve cells are destroyed. Unlike most of the body's other cells, they cannot be replaced. Once they are destroyed, the muscles controlled by them wither from disuse, and lasting paralysis results; if the cells are only damaged, the paralysis may be temporary as the cells are repaired and again control the muscles.

The virus's appetite for nucleoproteins suggested an explanation of the oft-reported link between physical fatigue and the severity of a polio attack, said Dr. Melnick. The nucleoproteins are believed to be reduced by extreme fatigue. Therefore, if the polio virus attacks an exhausted person, the supply of nucleoproteins will be at a minimum and the virus will soon consume it, causing the death of the nerve cells. But if the infected person is well rested and has an abundant store of nucleoproteins in his nerve cells, the virus may be able to satisfy its own needs without destroying the cells and causing permanent paralysis.

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