Flow cytometry has been used to estimate nuclear DNA amounts in a wide variety of plant species, but has not previously been applied to mulberry (Morus sp.). In this study, we compared the nuclear DNA amounts of some mulberry varieties with those of Arabidopsis and rice. As a result, we estimated the nuclear DNA amount per monoploid genome of the diploid mulberry species to be in the range 345-366Mbp (0.352-0.373pg), which was smaller than rice.

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In this report, we extracted a characteristic of the cocoon shape by the Fourier coefficient. It was known that the basic cocoon shape of the Dumbbell (Japanese race) type, the Oval (Chinese race) type, and the Hybrid (Hybridized race) type could be mainly defined by the Fourier coefficients a2, a4, and a6 of the cosine terms. The principal components were obtained by using these coefficients that were standardized as a0/2=12 millimeters. The cocoon shapes of a Dumbbell (Japanese race) type, a Oval (Chinese race) type and the Hybrid (Hybridized race) type are distinguishable by Fourier coefficients. In addition, using these coefficients, the Mahalanobis’s generalized-distance between arbitrarily chosen two silkworm races is obtained.

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Certain insect viruses produce stable infectious micro-crystals called polyhedra which function to protect the virus after the death of infected larvae. Polyhedra form within infected cells and contain numerous virus particles embedded in the crystalline lattice of the viral protein polyhedrin. We have previously demonstrated a novel protein engineering technology for the immobilization of protein molecules into Bombyx mori cypovirus (BmCPV) polyhedra. In addition, polyhedra containing foreign proteins have been shown to be highly stable and able to maintain the function of immobilized proteins. In this study, protein kinase C (PKC) was immobilized into polyhedra by using two types of immobilization signals. One immobilization signal was developed by the identification of the BmCPV virus occlusion mechanism into the polyhedra. Another immobilization signal was identified by the atomic structural analysis of the BmCPV polyhedrin. After PKC was fused each with an immobilization signal, the recombinant PKC was immobilized into polyhedra and the enzymatic activities were assayed. These results showed that the activity of PKC immobilized into polyhedra has been maintained and compared with commercially used PKC.

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Larvae of the knobbed mutant (K) of the silkworm, Bombyx mori, have several paired knobs at specific sites of their dorsal segments. In the previous paper, we showed that mitoses occur in the epidermis at knob region during the prolonged period of intermolt/feeding stage. In order to clarify the process of knob formation at cellular level, morphological changes of the epidermis of knobbed region during the 4th instar were investigated by light and electron microscopy. The epidermal cells of the knobbed region were found to be more slender and taller in height than those of the non-knobbed regions, and the basal plasma membrane and attached basement membrane are irregularly distorted during the intermolt/feeding stage. At the mid-molting stage, the epidermal layer is markedly undulated and the basement membrane becomes partially detached from the basal plasma membrane. Based on these morphological characteristics together with our previous findings, the sequential process of knob formation at cellular level was discussed.

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Regenerated Bombyx mori silk fibroin fibers with higher biodegradability were developed by adding calcium chloride to the source fibroin solution for wet spinning. The regenerated fibroin fiber spun from 11 w/w % calcium chloride showed more than 95% degradation at 4 days, where no significant degradation was observed on the ones spun from 0 w/w % calcium chloride. The tensile strength was also partially lost from the fiber by adding calcium chloride, but it retained 50% strength of the one without calcium chloride. These results suggest a possibility to produce a new regenerated silk fiber with controlled biodegradability, which is suitable for bio­medical purposes.

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