The parameters of protein metabolism, such as the levels of soluble, structural and total proteins, free amino acids, and the activity levels of protease, aspartate and alanine aminotransferases and glutamate dehydrogenase were assayed in the hemolymph, silk-gland, muscle and fat-body on different days of the 5 th instar larva of the silkworm, Bombyx mori, following exposure of the silkworm eggs to 1 MHz continuous wave of ultrasound at an intensity of 9W/cm 2 for 2 minutes. Ultrasound was found to promote the accumulation of proteins, which include silk proteins as well, while retarding proteolysis and turnover of proteins towards the release of amino acids, keto-acids etc. Changes in the levels of these biochemical constituents are correlated with the events of histogenesis and histolysis associated with metamorphosis. It may be inferred that protein metabolism is stimulated by ultrasound, resulting in greater turnover of silk proteins, spinning activity and silk output.
The objective of the present study was to examine the variations in the levels of spontaneous electrical activity during the 5 th instar development of the silkworm Bombyx mori and the possible mode of its regulation. The spontaneous electrical activity of the ventral nerve cord (VNC) showed an increase from the 2 nd day to the 7 th day of the 5 th instar. Treatment of the VNC with extracts of the central nervous system (CNS) from the 2 nd day larvae or hemolymph from the 7 th day larvae elevated the spontaneous electrical activity of the VNC in both the 2 nd and 7 th day larvae, while extracts from the 7 th day larvae or hemolymph from the 2 nd day larvae did not cause any perceptible effect. Acetylcholine (ACh, 10 -7 M) elevated the activity in both the 2 nd and 7 th day larvae. It is suggested that synthesis and release of neuromodulators from the CNS into the hemolymph could modify the activity of the nervous system at different stages of the life cycle and consequently the behavior in the silkworm.
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