Shimizu H, Sugiyama T
National Institute of Genetics, Mishima, Japan.
Dev Biol. 1993 Dec;160(2):504-11. doi: 10.1006/dbio.1993.1324.
Published evidence suggests that tissue injury is important for head regeneration in hydra [MacWilliams, 1982, 1983a,b; Kobatake and Sugiyama, 1989]. To investigate this problem in more detail, two experimental manipulations, decapitation and mirror-image grafting, were carried out. In the latter, two decapitated polyps were axially grafted to each other to make the wound openings of the two polyps juxtaposed on each other. In normal regenerates, the wound opening closed and healed in 4 to 5 hr, while in mirror-image grafts it healed in about 1 hr. The percentage of head regeneration was lower in mirror-image grafts than that after decapitation. The effect of mirror-image grafting on morphogenetic potential levels was examined using a lateral transplantation technique. Head inhibition levels dropped in both types of regenerates to a similar extent. Head activation levels rose more in normal regenerates than in mirror-image grafts. These results show clearly that the drop in head inhibition level is due to removal of the head and is not affected by grafting. They also show that the increase in head activation levels and in the percentage of head regeneration is affected substantially by the grafting. These observations are consistent with the view that decapitation produced a greater injury effect than mirror-image grafting, and this injury effect raised the head activation level whereas it did not alter the head inhibition level. The fact that the wound remained open for a longer time in normal regenerates than in the grafts suggests that the injury effect depends not on tissue injury itself but on the length of time the wound is open.
已发表的证据表明，组织损伤对水螅头部再生很重要[麦克威廉姆斯，1982年、1983年a、b；小畑和杉山，1989年]。为了更详细地研究这个问题，进行了两种实验操作，即断头和镜像移植。在镜像移植中，将两个断头的息肉轴向相互移植，使两个息肉的伤口开口彼此并列。在正常再生中，伤口开口在4至5小时内闭合愈合，而在镜像移植中，伤口在约1小时内愈合。镜像移植中头部再生的百分比低于断头后。使用侧向移植技术研究了镜像移植对形态发生潜能水平的影响。两种类型的再生体中头部抑制水平下降的程度相似。正常再生体中头部激活水平的上升幅度大于镜像移植。这些结果清楚地表明，头部抑制水平的下降是由于头部的移除，而不受移植的影响。它们还表明，头部激活水平的增加和头部再生百分比的增加受到移植的显著影响。这些观察结果与以下观点一致，即断头产生的损伤效应比镜像移植更大，这种损伤效应提高了头部激活水平，而没有改变头部抑制水平。正常再生体中伤口保持开放的时间比移植中更长，这一事实表明损伤效应不取决于组织损伤本身，而是取决于伤口开放的时间长度。
