Summary
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1) Theiler's FA mouse encephalomeylitis virus grows equally well when suspensions of infected mouse brain are inoculated into embryonated chicken eggs by either the intra-embryonic or chorio-allantoic membrane routes.
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2) The optimal temperature of incubation after inoculation is 34–36 C. Lower temperatures result in low embryo survivals and irregular growth of virus, and at higher temperatures satisfactory growth is only occasionally obtained.
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3) There is little difference in virus growth whether embryos are inoculated after six or eight days of preliminary incubation.
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4) When inoculated by a peripheral route, virus growth in the embryo starts building up by the fourth to the fifth days after inoculation and reaches a peak by the eighth to tenth days after inoculation.
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5) The highest titres of virus will be found in the embryo, irrespective of the relative amounts of nervous tissue. The embryonic membranes contain the next largest amounts of virus, and the fluids the least amount.
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6) The concentration of virus in the inoculum has little effect on subsequent infectivity titres.
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7) One fundamental difference was noted in the behavior of FA virus from infected mouse brains and virus from infected embryonic products. Whereas original mouse brain virus would not propagate when inoculated into the yolk sac, egg adapted virus grew as well or better when inoculated by the yolk sac route as by the embryonic or chorio-allantoic membrane routes.
Footnotes
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↵1 Aided by a grant from the National Foundation for Infantile Paralysis.
- Received May 19, 1949.
- Copyright © 1952 by The American Association of Immunologists, Inc.
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