サンショウウオ幼生にみられる指間突起の異属間誘導(続) : 肢芽中胚葉と外胚葉の相互作用と, 外胚葉の反応性の変化

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To study the interaction between ectoderm and mesoderm in limb development, heteroplastic recombinations were made with limb-bud mesoderm and flank ectoderm from Hynobius and Triturus larvae at various developmental stages. All resultant chimeric limbs composed of Hynobius mesoderm and Triturus epidermis developed the interdigital process, peculiar to the limb of Hynobius larva. However, in the chimeric limb composed of Triturus mesoderm and Hynobius epidermis, the interdigital process did not develop when the host (Hynobius) was in stage 35 to 37. The degree of development of the chimeric limbs and interdigital process varied according to the host stage and the methods of transplantation. From the present experiments, we can conclude that: 1) the Hynobius epidermis at stages 35 to 37 can react to the limb mesoderm, and after stage 38, the epidermis produces a factor (Ge factor) which promotes cell division and growth in the limb mesoderm-the activity of this factor lasts until stage 53; 2) Triturus limb mesoderm, after stage 36, produces another factor (Gm factor) which maintains the Ge factor and stimulates the growth of ectoderm, peaking at stage 39; 3) after the Gm factor regressed, the mesoderm produces a second factor (D factor) which promotes degeneration of interdigital tissue and development of the digits.
1978-03-25