title: Two-step consumption of yolk granules during the development of quail embryos.
abstract: The mechanism of yolk consumption was studied morphologically and biochemically in Japanese quail Coturnix japonica. The amount of yolk granules in the yolk (or 'yolk cell') decreased in two steps during embryonic development. In the first step, during days 0-4 of incubation, the yolk-granule weight decreased at a rate of 13 mg/day. This decrease was due to segregation by endodermal cells that were newly formed in the developing yolk sac. In the second step after day 6, the decrease was drastic at a rate of 29.8 mg/day during days 6-12 and very slow thereafter. The decrease at the second step was due to the enzymatic digestion of yolk granules by cathepsin D that coexisted in yolk spheres. This digesting reaction was triggered by the solubilization of the granules with high concentrations of salts that were supplied after disruption of the limiting membrane of yolk spheres. The 'yolk cell' seemed to die around day 5 of incubation. Thus the digestion products might be taken up together with yolk lipids by endocytosis into the endodermal cells and transported to blood vessels.
authors.affiliation: Department of Biological Diversity, Faculty of Agriculture, Gifu University, Gifu 501-1193, Japan. pflayer@cc.gifu-u.ac.jp
authors.forename: Norio
authors.initials: N
authors.lastname: Yoshizaki
authors.forename: Marie
authors.initials: M
authors.lastname: Soga
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ito
authors.forename: Kun Ming
authors.initials: KM
authors.lastname: Mao
authors.forename: Fowzia
authors.initials: F
authors.lastname: Sultana
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yonezawa
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003370:Coturnix / Q000196:embryology*; D004527:Egg Proteins / Q000378:metabolism; D004530:Egg Yolk / Q000378:metabolism*; D004707:Endoderm / Q000378:metabolism; D009929:Organ Size; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D015017:Yolk Sac / Q000378:metabolism
chemical_list: D004527:Egg Proteins; D012964:Sodium; D011188:Potassium