Javois L C, Bessette D R
Department of Biology, The Catholic University of America, Washington, DC, 20064, USA.
Dev Biol. 1996 Jul 10;177(1):323-31. doi: 10.1006/dbio.1996.0166.
Normal hydra head-body proportions were altered by axially grafting a second head in place of the lower body column. The resulting animals had double the head tissue and one-quarter the normal body column. Changes in the head activation potential of tissue subjacent to both heads were monitored by assaying the ability of these animals to regenerate heads. The host head, the grafted head, or both heads were removed at varying times following graft construction and the animals were scored for head regeneration and/or the ability to express a head-specific antigen recognized by monoclonal antibody, CP8. In the presence of the grafted head, tissue subjacent to the host head lost the ability to regenerate a head or express the head-specific antigen over a 48-hr period. In the presence of the host head, tissue subjacent to the grafted head regenerated heads at a very low frequency and lost the ability to express the head-specific antigen over the same 48-hr period. Following simultaneous removal of both heads, animals initially regenerated both heads for the first 48 hr after graft construction. Then, both head regeneration and expression of the head-specific antigen declined gradually over the next 3 days, though not to the very low levels observed when one head remained. These data, especially the loss of CP8 labeling, support the hypothesis that loss of regeneration ability was due to a loss of head activation potential in tissues subjacent to the heads. We propose that this reflected the attempt of grafted animals to compensate for the altered head-body proportions through reproportioning. In keeping with this hypothesis, feeding the grafted animals to stimulate growth of body column tissue and a shift toward more normal head-body proportions prior to decapitation resulted in animals which were capable of regenerating heads when decapitated. Several interpretations of the results based on the Gierer-Meinhardt reaction-diffusion model of pattern formation are discussed.
通过轴向移植第二个头部来替代下部体柱，改变了正常水螅头部与身体的比例。由此产生的动物头部组织加倍，体柱仅为正常的四分之一。通过检测这些动物再生头部的能力，监测了两个头部下方组织的头部激活潜能变化。在移植构建后的不同时间，切除宿主头部、移植的头部或两个头部，对动物进行头部再生和/或表达单克隆抗体CP8识别的头部特异性抗原能力的评分。在移植头部存在的情况下，宿主头部下方的组织在48小时内失去了再生头部或表达头部特异性抗原的能力。在宿主头部存在的情况下，移植头部下方的组织以极低的频率再生头部，并在相同的48小时内失去表达头部特异性抗原的能力。同时切除两个头部后，动物在移植构建后的最初48小时内最初会再生两个头部。然后，在接下来的3天里，头部再生和头部特异性抗原的表达逐渐下降，尽管没有降至保留一个头部时观察到的极低水平。这些数据，尤其是CP8标记的丧失，支持了再生能力丧失是由于头部下方组织中头部激活潜能丧失的假设。我们提出，这反映了移植动物试图通过重新调整比例来补偿改变的头部与身体比例。与此假设一致的是，在断头前喂养移植动物以刺激体柱组织生长并向更正常的头部与身体比例转变，结果导致动物在断头时能够再生头部。基于Gierer-Meinhardt反应扩散模式形成模型对结果进行了几种解释。
