Prohibition of occurrence of viral diseases in the silkworm reared with artificial diet

点击翻译按钮获取中文摘要

The series of studies in this project presented the novel understandings on the mechanis of virus infection of the silkworm in which mod-ulation of the infection by chemicals, physiological conditions, diff-erent neutrient condition of diet, and environmental regulation were conducted. The following conclusions were obtained: (1) The rearing metho using artificial diet during young silkworm stage and whole stage had been established.The both rearing procedures of the silk- worm were very useful for the basic and applied studies of the Bombyx-virology. (2) For the study of new rearing system of the silkworm using a bioclean room (BCR), an assay kit for surveying micobes was developed. The distributing patterns of microbes in BCR were clarfied, but microbes once instroduced/ occuurred in a BCR was considered to be difficult with tracing and removing them. (3) A study on a densonucleosis virus-2 (DNV-2) infected silkworm treated with a high temperature showed that inhibition of an accumul … More ation of translatable mRNAs occurred after that treatment. Therefore, it is demomstrated that a condition of viral desease could be controlled by environmental factors. (4) Several cell lines susceptible for the cyto plasmic polyhedrosis virus were established. Serotnine and 5-hydroxytryptophane were recognized as promoting facters of midgut motility resulting that resistance of larvae against viral disease increased. (5) DNV susceptibility in larvae fed on artificial diets were higher 10 times comparison with that in those fed on mulberry leaves. The DNV infected-midget cells were discharged into the gut lumen at molting and regenerative cell located midi of the midgut developed into new epithelial cells for the physiological repair.The regenerative ability of the midgut cells is mainly concerned with the resistance of the silkworm larvae to the infection of DNV. (6) Guanidine hydrochloride (GH) had been demonstrated to supress the incidence of infectious flacherie caused by infectious flacherie virus (IFV). Using a cell-free trasnaltion system, it was clarified that GH inhibits the accumulation of virus-specific translatable mRNAs and structural polypeptides in the IFV-infected midgut. Therefore, it was suggested that one of the primary function of GH action on the IFV infection is the inhibition of translation of input genomic RNA of the virus. (7) It is generally said that larvae reared on artificial diet were more susceptible to a nuclear-polyhedrosis virus than those reared on mulberry leaves, depending on lower antiviral activity in the gut juice. The study indicated that the protease activity in gut juice was highly concerned with the antiviral activity, suggesting difference susceptibility of virus infection through midgut depending on nature of diets. Less