Author
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Richards, Mark |
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Submitted to: Trace Elements in Man and Animals (TEMA)
Publication Type: Abstract Only Publication Acceptance Date: 5/5/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Trace element metabolism during avian development begins with the formation of the egg and the trace element stores contained within it. Vitellogenin, a yolk precursor protein, serves to transport trace elements from stores within the liver of the hen to the ovary and developing oocyte and hence to the yolk of the egg. Lipovitellin and phosvitin, derived from the intraoocytic proteolytic processing of vitellogenin, are also trace element binding proteins that form important metal storage sites within the granule subfraction of yolk. The mobilization and uptake of egg trace element stores are mediated by the extra-embryonic membranes, principally the yolk sac membrane. The yolk sac can also serve as a short-term storage site for trace elements through its synthesis of specific metal-binding proteins like metallothionein. Because it is an important site of plasma protein synthesis (including metal-transporting proteins like albumin and transferrin), the yolk sac has the potential to regulate the export of trace elements to the embryo. Within the embryo, specific metalloproteins function in the interorgan transport, cellular uptake, and intracellular storage of trace elements. Thus, embryonic trace element homeostasis is established through the coordinated actions of the yolk sac, which mobilizes and exports trace elements derived from egg stores, the vitelline circulation, which transports them to the embryo, and the liver, which accumulates trace elements and distributes them to other tissues of the embryo via embryonic circulation. |
