McCullagh J J, Wilson D J
School of Clinical Dentistry/Dental Surgery, Queen's University of Belfast, Northern Ireland.
Anat Embryol (Berl). 1993 Oct;188(4):371-9. doi: 10.1007/BF00185946.
The mechanism of antero-posterior specification of limb skeletal pattern is still controversial. If, as proposed by the ZPA model, a diffusible morphogen does exist, its route of passage across the limb field has not been resolved. To investigate the contribution of the apical ectodermal ridge (AER) to the control of antero-posterior pattern formation, we examined the consequences of small wounds made to the AER. The wound response was investigated by means of resin histology and scanning electron microscopy; subsequent limb development and cartilage pattern were examined in whole-mount preparations. Although regrowth of the bilaminate dorsal and ventral ectoderm over the wound occurred within 15 h, the more highly differentiated pseudostratified columnar epithelium of the AER did not reform, and there was subsequent retardation of limb outgrowth at the wound site. At 10-11 days of development, the appearance of the limbs allowed them to be placed into one of three categories; presence of supernumerary elements, accentuation of an inter-digital cleft, or normal. The first of these categories included limbs in which digit 3 had bifurcated such that the sum of the parts of the resultant digital skeleton was greater than that which forms in a normal limb. Since in all of the experimental limbs all skeletal elements were present, we propose that continuity of the AER is not a pre-requisite for antero-posterior skeletal pattern formation in the chick wing.
肢体骨骼模式前后轴特化的机制仍存在争议。如果像ZPA模型所提出的那样，确实存在一种可扩散的形态发生素，那么它穿过肢体区域的途径尚未明确。为了研究顶端外胚层嵴（AER）对前后轴模式形成控制的作用，我们检查了对AER造成小伤口的后果。通过树脂组织学和扫描电子显微镜研究伤口反应；在整装标本中检查后续的肢体发育和软骨模式。尽管在15小时内伤口上方的双层背侧和腹侧外胚层重新生长，但AER中分化程度更高的假复层柱状上皮并未重新形成，随后伤口部位的肢体生长受到抑制。在发育的第10 - 11天，根据肢体外观可将其分为三类；有额外的元素、指间隙加深或正常。第一类包括第3指分叉的肢体，使得由此产生的指骨骨骼各部分之和大于正常肢体中形成的指骨骨骼之和。由于在所有实验肢体中所有骨骼元素都存在，我们提出AER的连续性不是鸡翼前后轴骨骼模式形成的先决条件。
