Factors Influencing the Production of Developmental Defects in the Chick Embryo Following Infection with Newcastle Disease Virus

[摘要] Examinations of whole mounts of chick embryos inoculated with Newcastle disease virus (NDV) revealed gross defects of the lens, otocyst, neural tube and visceral arches. Examination of microscopic preparations showed that the pathological picture was similar in all affected organs and that the specific histopathological changes were noted also in the amnion, neural crests, olfactory pits and apical caps of the limb buds. Using as indicators the three most easily identified defects appearing in whole mounts, i.e., those of the lens, otocysts and neural tube, the influence of the following factors on the production of the defects has been determined: 1. a. The route of inoculation . Inoculations directly over the embryo, where the virus could gain immediate access to the susceptible organs, resulted in a high percentage of abnormal embryos within 24 hours after inoculation, whereas inoculation into the yolk sac, directly beneath the embryo resulted in no abnormal embryos within 24 hours after inoculation. Embryos inoculated by either route died within 48 hours if incubation continued.2. b. Virus strain . Of the three strains tested, the Nothnick, the Roakin and the B-1 strain, all yielded the same types of defects.3. c. Titer of the virus . A high titer of virus in the inoculum was necessary for a consistently high yield of gross developmental defects. Inocula containing an EID50 of 108 per .05 ml gave satisfactory results if diluted 10-1 or 10-2, but the yield of defective embryos dropped in proportion to further decrease in virus titer. Although inocula of very low titer yielded few abnormal embryos, virus was recovered from most of these embryos which showed no gross defects.4. d. Stage of development of the embryo . With the techniques employed, production of gross defects of the lens, otocyst, and neural tube was possible for a very limited period during the development of the chick embryo. Eggs inoculated at 36 hrs. of incubation yielded embryos showing the typical defects but so few survived the inoculation technique that this age was considered impractical for extensive experimental use. Eggs inoculated at 48 hrs. and 60 hrs. yielded a high percentage of surviving embryos showing the specific defects. Eggs inoculated at 72 hrs. revealed few embryos with the three defects described above and in eggs inoculated at 84 hrs. incubation no defects were found on gross examination.

[学科分类] 生物科学（综合）