Hensen's node from vitamin A-deficient quail embryo induces chick limb duplication and retains its normal asymmetric expression of sonic hedgehog (Shh)

Article Abstract:

Hensen's node is a cluster of organizer cells that has the ability to induce secondary axis formation in the early chick embryo. Retinoic acid (RA) is present in the node but evidence supporting its role as a putative morphogen in chick limb development is lacking. In this study, it was shown that RA functions via induction of the Sonic hedgehog (Shh) morphogen. Retinoid-deficient quail embryos from eggs laid by quail raised on a vitamin A-deficient diet showed normal temporal asymmetric expression of Shh as the control quail embryos. Chick limb buds from quail embryos raised in a vitamin A-deficient diet induced normal limb duplication, suggesting that RA does not directly affect limb bud duplication.

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Left-right asymmetric localization of flectin in the extracellular matrix during heart looping

Article Abstract:

Left-right asymmetric localization of a large extracellular matrix molecule, called flectin, in embryonic hearts during looping was investigated using a monoclonal antibody F-22 on White Leghorn chick embryos. The results revealed a discrete spatiotemporal pattern of extracellular matrix expression during heart development. Asymmetric expression was observed beginning stage 7+/8- in the left precardiac mesoderm until between stages 12 and 14 in the myocardium. The marked reduction in the intensity of localization was apparent at stage 22, with left-right asymmetry becoming absent.

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Anti-retinoic acid monoclonal antibody localizes all-trans-retinoic acid in target cells and blocks normal development in early quail embryo

Article Abstract:

All-trans-retinoic acid is required for normal cardiovascular development and for early development events in the quail embryo. During the development of the quail embryo, it is biosynthesized in the Hensen's node and in the caudal area during stage 5 and in heart-forming areas, head mesenchyme and nephrotome in stage 7 and 8. A monoclonal antibody against all-trans-retinoic acid blocks normal embryonic development in the quail embryo, causing cardiovascular abnormalities.

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