Solursh M, Reiter R S
Department of Biology, University of Iowa, Iowa City 52242.
J Exp Zool. 1988 Nov;248(2):147-54. doi: 10.1002/jez.1402480204.
Previous studies have indicated possible dual effects of the limb ectoderm in cartilage differentiation. On one hand, explants from early (stage 15) wing buds are dependent on contact with the limb ectoderm for cartilage differentiation (Gumpel-Pinot, J. Embryol. Exp. Morph. 59:157-173, 1980). On the other hand, limb ectoderm from stage 23/24 wing buds inhibits cartilage differentiation by cultured limb mesenchyme cells even without direct contact (Solursh et al., Dev. Biol. 86:471-482, 1981). In the present study, ectoderms from both stage 15/16 and stage 23/24 wings are cultured under the same conditions, and ectoderms from each source are shown to have two effects. Each stimulates chondrogenesis in stage 15 wing bud mesenchyme, and each inhibits chondrogenesis in older wing mesenchyme. The results suggest that the limb ectoderm has at least dual effects on cartilage differentiation, depending on the stage of the mesenchyme. One effect involves an early mesenchymal dependence on the ectoderm. This effect requires contact between the ectoderm and mesoderm (Gumpel-Pinot, J. Embryol. Exp. Morphol. 59:157-173, 1980) but also can be observed at a distance from the ectoderm. Later, the ectoderm can act without direct contact between the ectoderm and mesoderm to inhibit chondrogenesis over some distance.
先前的研究表明，肢体外胚层在软骨分化过程中可能具有双重作用。一方面，早期（第15阶段）翼芽的外植体在软骨分化过程中依赖于与肢体外胚层的接触（冈佩尔 - 皮诺特，《胚胎学与实验形态学杂志》59:157 - 173，1980年）。另一方面，第23/24阶段翼芽的肢体外胚层即使在没有直接接触的情况下，也能抑制培养的肢体间充质细胞的软骨分化（索卢什等人，《发育生物学》86:471 - 482，1981年）。在本研究中，将第15/16阶段和第23/24阶段翅膀的外胚层在相同条件下培养，结果表明来自每个来源的外胚层都有两种作用。它们都能刺激第15阶段翼芽间充质的软骨生成，并且都能抑制较老翅膀间充质的软骨生成。结果表明，肢体外胚层对软骨分化至少具有双重作用，这取决于间充质的阶段。一种作用涉及早期间充质对外胚层的依赖性。这种作用需要外胚层和中胚层之间的接触（冈佩尔 - 皮诺特，《胚胎学与实验形态学杂志》59:157 - 173，1980年），但在离外胚层一定距离处也能观察到。后来，外胚层可以在没有外胚层和中胚层直接接触的情况下，在一定距离内抑制软骨生成。
