Dhouailly D, Hardy M H, Sengel P
J Embryol Exp Morphol. 1980 Aug;58:63-78.
In the chick embryo, large scales (scuta) form on days 9-11 on the anterior face of the shank and the upper surface of the toes; smaller scales (scutella) appear on day 11 on the posterior face of the shank; most of the smallest scales (reticula) form on days 12 and 13 on the plantar surface of the foot. A single injection of 125 micrograms of retinoic acid (RA) into the amniotic cavity caused the formation of feathers on the foot scales in locations and percentages differing according to the age of embryos at the time of treatment. Injection at 10 days caused feathers to form on the feet in 57% of the embryos, almost all of which bore feathers on their scuta and scutella; a few reticula were occasionally affected. When treated at 11 days, 48% of embryos had feathered feet, the tarsometatarsal scutella and digital reticula being most frequently affected. Treatment at 12 days resulted in feathers on the feet of 15% of the embryos, all of which bore feathers on the reticula only, while the scuta and scutella were not affected. It was concluded that the foot skin regions which were affected by RA treatment were those in which scale morphogenesis was starting or about to start at the time of injection. These regions contained pre-placodal or placodal stages of scuta and scutella, and the pre-elevation or elevation stages of reticula.
在鸡胚中，第9至11天在小腿前面和脚趾上表面形成大鳞片（盾鳞）；第11天在小腿后面出现较小的鳞片（小盾鳞）；大多数最小的鳞片（网鳞）在第12和13天在足底形成。向羊膜腔内单次注射125微克视黄酸（RA）会导致足鳞片上形成羽毛，其位置和比例因处理时胚胎的年龄而异。在第10天注射导致57%的胚胎足部形成羽毛，几乎所有这些胚胎的盾鳞和小盾鳞上都有羽毛；偶尔有一些网鳞受到影响。在第11天处理时，48%的胚胎足部有羽毛，跗跖小盾鳞和指部网鳞受影响最为频繁。在第12天处理导致15%的胚胎足部有羽毛，所有这些胚胎仅在网鳞上有羽毛，而盾鳞和小盾鳞未受影响。得出的结论是，受RA处理影响的足部皮肤区域是注射时鳞片形态发生开始或即将开始的区域。这些区域包含盾鳞和小盾鳞的前基板或基板阶段，以及网鳞的前隆起或隆起阶段。
