[Ultracytological studies of the morphogenesis and structure of the nuclear polyhedrosis virus in the silkworm moth, Bombyx mori L].

An electron-microscopic investigation was made on hypodermal tissues of silkworms spontaneously infested by nuclear polyhedral disease, due to low temperature stress. It was established that the polyhedral virus is formed in the viroplasma produced after viral cell infection, is included in the intimate and developing membrane singly or in fascicles containing several (up to 9) and is finally incapsulated in polyhedral protein. Besides viral rods, various polymorphic forms were observed in the nucleus and around the polyhedras in the process of formation, which are considered as viral substructures (or nucleocapsidless viruses), membrane structures and surplus synthetized polyhedral protein. It can be presumed that virus replication in single cell nucleus is a continuous process which goes on until complete nuclear structure depletion.