title: Formation of the vitelline envelope precedes the active uptake of vitellogenin during oocyte development in the rainbow trout, Oncorhynchus mykiss.
abstract: In order to study the initial formation of the vitelline envelope and the appearance of vitellogenin in oocytes of rainbow trout, females were sampled monthly from 19 to 5 mo before ovulation. Immunohistochemistry revealed that the formation of the vitelline envelope starts when the oocytes reach a diameter of about 450 microns. Oocytes of this size were first found in females sampled a year before ovulation at the time when plasma levels of estradiol-17 beta increased from 0.2 to 0.6 ng/ml. An antiserum directed against vitellogenin crossreacted with small vesicles (around 2 microns) present just inside the oolemma, when the oocytes reached a diameter of 600 microns. This was interpreted as an active uptake of vitellogenin. Oocytes of this size were first found in females sampled 9 mo before ovulation at the time when estradiol-17 beta levels increased from 0.6 to 1.0 ng/ml and the gonadal somatic index was doubled. Oocytes with a diameter of 600 microns had an immunoreactive vitelline envelope with a thickness of about 3 microns. It is apparent that the initial formation of the vitelline envelope starts before the active uptake of vitellogenin and that the low previtellogenic plasma levels of estradiol-17 beta observed in females are of physiological significance.
authors: Department of Zoophysiology, University of Göteborg, Sweden.
authors: S J
authors: SJ
authors: Hyllner
authors: C
authors: C
authors: Silversand
authors: C
authors: C
authors: Haux
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D015153:Blotting, Western; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D004958:Estradiol / Q000097:blood; D005260:Female; D005455:Fluorescent Antibody Technique; D007106:Immune Sera; D007150:Immunohistochemistry; D017686:Oncorhynchus mykiss; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D010060:Ovulation / Q000502:physiology*; D012621:Seasons; D014819:Vitellogenins / Q000032:analysis / Q000378:metabolism*
chemical_list: D007106:Immune Sera; D014819:Vitellogenins; D004958:Estradiol