von Kraft A
Institute for Anatomy and Cytobiology, Philipps-University, Marburg, Germany.
Laterality. 1999 Jul;4(3):209-55. doi: 10.1080/713754336.
Newt embryos of different developmental stages were combined to parabiotic twins in different positions. The exterior appearance and the symmetry relations, particularly of the internal organs (intestinal tract, heart, nuclei habenulae, and vitelline vein) were studied. Experimentally caused organ inversions allowed conclusions with respect to organ asymmetry and unilateral dominance. There was no direct correlation between appearance and symmetry of the exterior and the internal organs. All internal organs showed a continuous transition between normal and ideally inverse situs. The concordance of the organ situs differs greatly. The "left-hand side" or "right-hand side" dominance is not uniform. It depends on the type of fusion, i.e. the relative position of the parabiotic twins, and is often specific for a given organ. In some cases a non-genetic "symmetrisation factor" appears to be strongly active, depending on the fusion type and resulting in a dominant transindividual organ mirror image symmetry in the parabiotic twins. The older twin generally dominates the processes of determination and induction. The "symmetrisation factor" also acts on members of different families, i.e. genetically completely heterogeneous parabiotic twins. The development of organ asymmetry appears to be a process with several phases.
将不同发育阶段的蝾螈胚胎组合成处于不同位置的联体双胎。研究了其外观和对称关系，特别是内部器官（肠道、心脏、缰核和卵黄静脉）的情况。通过实验导致的器官倒置得出了关于器官不对称和单侧优势的结论。外部和内部器官的外观与对称之间没有直接关联。所有内部器官在正常位置和理想的反位之间呈现出连续过渡。器官位置的一致性差异很大。“左侧”或“右侧”优势并不一致。它取决于融合类型，即联体双胎的相对位置，并且通常对特定器官具有特异性。在某些情况下，一种非遗传的“对称化因子”似乎具有强烈活性，这取决于融合类型，并导致联体双胎中出现占主导的跨个体器官镜像对称。年龄较大的双胎通常主导着决定和诱导过程。“对称化因子”也作用于不同家族的成员，即基因上完全异质的联体双胎。器官不对称的发育似乎是一个具有多个阶段的过程。
