Metabolic changes in diseased insects: Radioautographic studies on DNA and RNA synthesis in nuclear-polyhedrosis and cytoplasmic-polyhedrosis virus infections

Abstract

The metabolism of DNA and RNA in Lepidoptera and Hymenoptera tissues infected with a nuclear- or cytoplasmic-polyhedrosis virus was studied by radioautography. Glutaraldehyde fixative caused greater tissue shrinkage than did freeze-substitution but was satisfactory for this technique. In Lepidoptera fat body infected with nuclear-polyhedrosis virus, DNA, nuclear RNA, and cytoplasmic RNA synthesis first increased and then decreased. In the midgut of Hymenoptera, DNA synthesis and nuclear swelling were as in the Lepidoptera, but RNA synthesis first decreased and then increased. Large amounts of lysine-, arginine-, and histidine-rich substances accumulated in the nuclei during early stages of infection. Both DNA and RNA syntheses were generally low in the gut of early pupae of Hymenoptera infected as larvae with nuclear virus. Cytoplasmic polyhedrosis in Lepidoptera midgut epithelium produced only a minor effect on DNA synthesis of infected cells. As this disease progressed, nuclear RNA synthesis remained relatively constant, but cytoplasmic RNA synthesis decreased sharply.