Studies on Pattern Formation in Chick Limb Bud.

1.ZPA的生长因子：(1)采用鸡肢芽断片器官培养法，证实了包括ZPA在内的后区存在生长因子(S)，并证明了前区对生长因子的反应性。(2)将肢芽沿前后轴分为四个区域，每个区域的游离细胞与后区的断片共培养。共培养可促进前区细胞的增殖，且对促生长因子有一定的反应性。当与前部片段一起培养时，没有观察到促进作用。(3)对一些已知的生长因子检测了反应梯度的存在。成纤维细胞生长因子(成纤维细胞生长因子)表现出类似的促生长作用，提示ZPA产生和释放成纤维细胞生长因子样生长因子。(4)观察了肢体芽形态发生中的促生长因子维甲酸的作用。在视网膜条件培养液中，10-100 ng/ml的维甲酸可促进远端中胚层细胞的增殖和软骨结节的形成。采用双向电泳法和银染法。一种肢体特异性蛋白L-1已被发现。对该蛋白在不同肢芽区域的分布的研究正在进行中。肢芽区特异性抗原AV-1是一种糖蛋白，其相对分子质量为135kD。

1. Growth factor of ZPA.(1) By the use of organ culture of chick limb bud fragments, the presence of growth factor(s) in the posterior region including ZPA and the responsiveness of the anterior region to the factor have been demonstrated.(2) The limb bud was divided into four regions along the anteroposterior axis, and dissociated cells of each region were cocultured with the fragments of the posterior region. The proliferation of the cells from the anterior region was promoted by the coculture, and a gradient of responsiveness to the growth promoting factor was found. No promotion was observed when cultured with anterior fragments.(3) The presence of the gradient of responsiveness was examined on some known growth factors. Fibroblast growth factor(FGF) showed similar pattern of growth promotion, suggesting that ZPA produces and releases FGF-like growth factor.(4) Growth promotion effect of retinoic acid, a canidate of morphogen in limb bud morphogenesis, was examined. In retina-conditoned medium, the retinoic acid at 10-100ng/ml promoted the proliferation and cartilage nodule formation of distal mesodermal cells.2. Limb bud specific protein.Using the method of two dimensional electrophoresis and silver staining. a limb specific protein, L-1, has been found. The study on the distribution of the protein in various limb bud region is now in progress.3. Limb bud region specific antigen, AV-1.The position specific antigen, AV-1, was found to be a glycoprotein with a molecular weight of 135kD.