Budget Amount *help |
¥10,000,000 (Direct Cost: ¥10,000,000)
Fiscal Year 1985: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1984: ¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 1983: ¥5,000,000 (Direct Cost: ¥5,000,000)
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Research Abstract |
It is desired in sericultural industry to preserve silkworm eggs more than two years. Long-term preservation of diapause type of eggs is assumed to prolong the diapause periods. For this, some attempts were done in view of endocrinonolgy, environmental physiology, biochemistty and genetics. Most significant effects on long-term preservation were obtained by direct transfer of the eggs into below 1゜C and maintenance at this temperature. These eggs remained at diapause state which is characterized by a high accumulation of sorbitol and a trace level of NAD-sorbitol dehydrogenase activity. The diapaude of these eggs were to be terminated by keeping at 5゜C for more than 2 months. Thus, the preservation of eggs closely depends on the chilling periods at 1゜C. Ehereas, non-diapause eggs were safely stored at 10゜C rather than 1゜C. However, dkapause hormone treatment on non-diapause egg producers brought about induction of diapause eggs and these eggs were preserved longer at 1゜C. To maintain diapause, some biochemical adaptation occurred; lipids in chorion, polyols in yolks and DNA and RNA in embryos. These metabolic shifts are indispensably incorporated into the diapause physiology. Developing ovaries were sucessfully preserved in liwuid nitrogen, which maintain their ability to mature eggs in them and larval hatching from embryonated eggs after parthenogenic activation. Further, some grnetical charactors are shown to be included in sensitivity to chilling at 1゛C, suggesting that long-term preservation of silkworm eggs is also inproved by genetical selections.
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