| Great losses in sericulture have been caused by silkworm disease, among which ,Bombyx mori. densovirus (BmDNV) is one of die main causes. DNV-like is a DNV strain from silkworm gene bank of Southwest Agricultural University, hi order to characterize the properties of this virus and prevent the breakout of silkworm disease, studies on its pathogeny, pathology and nucleic acid have been made.The study on DNV-Like's pathogeny in silkworm had been done by dealing with different concentration solution of BmDNV-2 and DNV-like respectively. The results demonstrated that DNV-Like's pathogeny was similar to BmDNV-2. But the virulence of DNV-like was much higher than that of BmDNV-2, and different varieties of silkworm had different sensitivity to them.Histopathology study indicated that the first autoeciousness position was cylindrical cell of midgut. And the nucleus of cylindrical cell extremely inflated, even broke. In Situ Hybridization Histochemistry (ISHH) also demonstrated that DNV-like first multiplied in nucleus of cylindrical cells of midgut, it could also infect the goblet cells, the fat body cells ,even the muscle cells.The result of electrophoresis of DNA extracted from DNV-like has only one band, approximately 6.5kb in length, which is different from that of BmDNV-2 with two bands of approximately 6.6kb and 6.1kb, and is also different from that of BmDNV-1 with only one band approximately 5.0kb.According to the results above, a conclusion can be drawn that DNV-like is a new kind of densoviruses, but lots of data is still needed to determine its accurate classification, v lIn order to make further study on the nosogenesis of DNV-like and other silkworm viruses and establish an efficient replicate system in vitro, a silkworm cell line which would be reproductive and susceptible to silkworm viruses have been tried to establish. Silkworm embryo in blastokinesis was chosen as the materials of primary culture. The embryos were minced by scissors and then digested by trypsin. By this method, cells and tissues could be subsisted in vitro, thus could be subcultured. The differentiation and types of cells and tissue were observed. The types of tissues were as follow: epithelioid tissue, fibroblast tissue, net tissue, glandiform tube -like tissue and fat -like tissue. After a long time of differentiation and filteration, a reproductive cell group consisting of several types of cells was gamed, but had an unstable reproducibility. After a 3-months- successive selection, a cell line was established. This cell line was named as Southwest Agricultural University Bombyx moriEmbryo 1, abbreviated as SWAUl-BmE. The cell line is mainly composed of two cell types: shuttle and spheroid. Also a few protuberant and huge cells were found in culture. The cell population doubling time is 57.6h at 28℃. The chromosome of SWAUl-BmE cells show typical characteristics of lepidoteran insect cell lines that chromosomes of metaphase have no apparent centromere, and are short pole-like and pellet-like. The longest chromosome is about 4 um. The chromosomes are heteroploidy. The infection of BmNPV on the different bisect tines showed that SWAUl-BmE was by far the more sensitive to BmNPV. So it would be a good material for silkworm baculovirus expression system.
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