We have obtained results suggesting mechanisms how the promoting protein (PP) enhances the Bombyx mori nucleopolyhedrovirus (BmNPV) replication in a B. mori cell line (SES-BoMo-15A; BoMo) cultured in Mitsuhashi-Maramorosh medium supplemented with 3% fetal bovine serum. When dosage effects of PP on BoMo cells were investigated, a high concentration of PP (10 μg/ml) caused significant growth inhibition and serious agglutination of the cells, while such effects were not apparent at a concentration of 1 μg/ml or lower. Using a recombinant BmNPV (CPd-luci), which expresses the firefly luciferase under the control of polyhedrin promoter, we demonstrated that cationic liposomes (Lipofectin reagent) and PP similarly enhanced both virus replication and luciferase activity. In addition, PP inoculation after virus infection also enhanced luciferase activity. These results suggest the possibility that PP reacts with the cell surface in a dose-dependent manner, so that 10 μg/ml of PP caused serious cell agglutination accompanied by the reduction of the cell growth, and 1 μg/ml of PP, and possibly cationic liposomes, promoted virus entry into the cell, resulting in the enhancement of both virus replication and recombinant protein production.

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Asp-Ile-Leu-Arg-Gly-NH₂ (DILRG-NH ₂), a pentapeptide with amidated C-terminus, has been isolated from diapausing pharate first instar larvae of the wild silkmoth Antheraea yamamai. In this study, we examined effects of this peptide and three related compounds on the proliferation of rat hepatoma cells and mouse spleen lymphocytes. The amidated pentapeptide and its truncated version ILRG-NH₂, not LRG-NH₂ and the non-amidated pentapeptide, suppress proliferation of the rat hepatoma cells. This suppression may be due to a cell cycle arrest rather than to an apoptotic/necrotic activity. Amino acid residues 2-5 and carbonyl amidation appear essential for its activity. The results indicate that the isolated pentapeptide is a candidate for therapeutic use.

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In order to clarify the pathways of carbohydrate metabolism during embryonic development in Bombyx mori eggs, changes in oxygen consumption, free sugar content, glycolytic intermediates and selected enzyme activities were monitored during the nine days of embryonic development. Two distinct phases of metabolism were found - a phase of differentiation (phase I), from day 1 to day 4, and then a phase of organogenesis (phase II), from day 5 to day 9. A gradual degradation of glycogen during phase I resulted in the production of trehalose, fructose and sorbitol. In this phase, phosphofructokinase was inhibited due to a sharp fall in levels of its activator, fructose-2,6-bisphosphate. Glycolytic flux leads to lactate formation during phase I. During phase II, activity of the mitochondrial enzyme, NAD-isocitrate dehydrogenase increased eight-fold, and oxygen consumption rose sharply by six-fold. These changes correlated with increased TCA cycle activity and the activated biosynthesis of mitochondria in phase II. Sharp increases in phosphofructokinase (eight-fold) and pyruvate kinase (18-fold) activities were observed during phase II. The increased glycolytic flux correlated with decreases in substrates (glycogen, trehalose, sorbitol and fructose), and the increased carbon flux was funneled into the TCA cycle as indicated by increased oxygen consumption and decreased lactate levels between days 3 and 6. The intense activation of glycolysis apparently overwhelmed mitochondrial capacity from days 6 to 9, as indicated by the marked increase in glycolytic intermediates including phosphoenolpyruvate, dihydroxyacetone phosphate and pyruvate, and the production of lactate even in the presence of high oxygen uptake. Levels of auxiliary enzymes changed during development; NAD-sorbitol dehydrogenase activity increased during phase I and trehalase activity increased during phase II. Glycerol-3-phosphatase activity decreased slightly and fructose-1,6-bisphosphatase-1 increased slightly over the nine days of development. In summary, phase I (differentiation) is fueled by glycogen and characterized by low glycolytic flux under largely anaerobic conditions, whereas phase II (embryogenesis) is characterized by increased glycolytic flux under aerobic conditions fueled by glycogen, in addition to the mixture of sugar substrates.

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BmN-4 cells from the silkworm, Bombyx mori, are permissive for B. mori nucleopolyhedrovirus (BmNPV) replication, whereas infection of BmN-4 cells with Hyphantria cunea NPV (HycuNPV) results in an abortive infection at the step before viral late gene expression. In this study, we found that coinfection of BmN-4 cells with BmNPV and HycuNPV led to severe restriction of BmNPV replication accompanying restricted BmNPV DNA replication and total shutdown of protein synthesis. Northern blot hybridization analysis showed that immediate early gene transcripts of both BmNPV and HycuNPV accumulated abundantly in BmN-4 cells coinfected with BmNPV and HycuNPV. These results indicate that restriction of BmNPV replication in the coinfected BmN-4 cells occurs at a post-entry step prior to viral DNA replication. Superinfection experiments further demonstrate that an intracellular environment that restricts BmNPV replication is established in BmN-4 cells shortly after HycuNPV infection.

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A dominant mutant, “Short Segment” (symbol Seg), was discovered as a spontaneous occurrence. Homozygotes and heterozygotes for Seg possess short body in length in each segment during all the larval stages. Linkage analysis showed that Seg was linked with odk and Nl, which had been mapped at the 32.5 and 35.2 positions, respectively, on the 14th linkage group. The Seg gene was precisely localized by a three-point experiment involving odk, Nl, and Seg. The recombination value between odk and Seg was calculated to be 0.60%, between Seg and Nl 2.51% and between odk and NI 3.11%. Hence, the arrangement of these three gene loci on the chromosome is in the order odk-Seg-Nl. Taking a correction factor into account, the locus of Seg was determined to be 33.0 of the 14th linkage group.

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In this study, three types of Thai hybrid silk waste are considered, the inferior knubbs, filature gum waste and pierced cocoon which represent respectively the outer, middle and mixed portions of cocoon layers. They have been prepared following the main processes, i.e. degumming and bleaching, opening, carding. In order to evaluate the feasibility in blending with cotton, the silk sliver is cut into staple fibre length of 35mm. All types of wastes after preparation process have proved to have similar contents of impurities (sericin and oil content). The physical properties such as length, fineness, tenacity and elongation of the fibres are being studied. The inferior knubbs fibres are finer than the filature gum waste fibres whereas the pierced cocoon fibre fineness is placed betwixt and between. Strength of the inferior knubbs fibre is quite similar to the pierced cocoon and both lower than that of the filature gum waste. The characteristics of the pierced cocoon fibre average those of the inner and the outer layers. In order to obtain further data concerning the physical properties of silk/cotton blended fibres, the pierced cocoon is chosen to be blended and mixed with cotton fibre in the ratio 50/50 by weight in an industrial cotton card. Physical properties of the pierced cocoon, cotton and blended fibre are compared with the same methods. Upper half mean length, tenacity and colour of the silk fibre are higher than those of the cotton fibre. The blended fibres have physical properties between those of the silk and cotton following a mixing law except for the stress-strain behaviour of fibre bundles. The stress-strain curves of pure component and blended fibres are discussed and show that blending improves fibre cohesion.

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Cocoon quality parameters have an important bearing on the quality of the raw silk reeled. Earlier studies have addressed many of the factors but the influence of the gradient of denier variation within a cocoon on uniformity characteristics of raw silk has not been specifically studied. In this work, eleven lots of cocoons of different races were taken and studied for its quality parameters including the slope of the denier curve. Later, these cocoons were reeled on both multiend and automatic reeling machines. The raw silk was tested for its average size, size deviation, maximum deviation, evenness variation and Uster U%. Correlation and regression analysis to study the strength of relationship between the cocoon parameters and raw silk uniformity characteristics were carried out. It was observed that the slope/gradient of the filament denier within a cocoon in addition to other cocoon parameters has significant influence on the raw silk uniformity characteristics.

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