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Elucidation of a profile of scallop vitellin formation associated with oogenesis and its endocrine control, and identification of a vitellogenin synthesizing site were immunologically undertaken by using anti-scallop Vn serum. Vn content increased during ovarian growth and accounted for more than 80% of the water soluble protein of the ovary at the mature stage. In vivo injection of estradiol-17 beta (E(2)) resulted in an increase in Vn content in the ovary. In vitro accumulation of Vn in the ovarian tissue was promoted with E2 and a vitellogenesis promoting factor (VPF) from cerebral plus pedal ganglion which was heat stable, less than MW 10,000 and trypsin/chymotrypsin resistant. Estrogen receptor (ER)-like immunoreactivity was found in the growing oocyte and the auxiliary cell in close contact with growing oocytes, in which Vn immunoreactivity was also found. It is suggested that the vitellogenin synthesis occurred inside the ovary, especially in the auxiliary cell, and is controlled by E2 and VPF via ER.

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SUMMARY : The morphological profile and changes in biochemical composition of the ovary and testis of the Pacific oyster Crassostrea gigas cultured in Onagawa Bay during maturation were examined. As sexual maturity progressed, the glycogen content in the ovaries and testes decreased. The increases in the protein content in the ovaries corresponded with increases in oocyte diameters. The largest variations in gonadal lipids during sexual maturation occurred with the triglycerides. An increase in the ovary was associated with oogenesis and a decrease in the testis was associated with spermatogenesis. The RNA content of the ovaries was consistently greater than that of the testes, while the DNA content was lower. The RNA content and the RNA/DNA ratio are good indicators of sexual maturity in the ovary; the increasing RNA/DNA ratio in the ovary appears to show the rising synthetic activity of vitellin as one of the proteins produced within the ovary.

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