Study On Regeneration Of The Nervous System Of Notoplana Humilis

Notoplana humilis belongs to the Polycladida, Turbellaria, Platyhelminthes. It is freeliving, sea water platyhelminth species. It has drawn convenient, easy to train in thelaboratory, etc. Platyhelminth plays an important role in the history of animal evolution. Theyfirst inhabited bilateral symmetry and three germ layers. So the origin of the platyhelminthesis one of the most important transitions in animal evolution. From then on, morphologicalstructure and functional of animals have great developed. These developments caused thedifferentiation of the animal body function; so that platyhelminthes possess the anteriornervous system and sense organs. The nervous system is important control system, andregulates the animals’ major vital movement. Furthermore, their peripheral nervous systemhas the subepidermal plexus and submuscle plexus in the parenchyma. They have the basicmodel of the nervous system similar to the most of higher animals. Therefore, theplatyhelminthes are an important material to study the regeneration of the animal nervoussystem.This paper studied the distribution and morphology of Acetylcholine by histologicalmethods and the stem cell by immunohistochemistry methods in different stages duringNotoplana humilis regeneration. The purpose of this study is to reveal the mechanism of thenervous system during the polyclad regeneration. The results are as follows:(1)Histological and immunohistochemistry methods were used to study the stem cell inthe different stages of regeneration in Notoplana humilis. In this study, we cut the worm intothree parts-the head, the trunk and the tail. And the general histological technique was applyedto observe the regeneration of the three parts in different stages. In the end, the microstructurechange of epidermis, basement membranae, muscles, parenchymal tissue, stem cell and so onduring regeneration were discussed. we find that: when the body was cut, the migration ofneoblasts is from the ganglion to the wound; and then when the regeneration was about tocompleted, these neoblasts were came back from the wound to ganglion. Furthermore, weguess the regeneration mechanisms of regeneration such as the crasis of the dorsal and ventralepidermis, forming a cavity near the wound, the migration of neoblasts and so on.(2) Acetylcholinesterase (AChE)-positive cells and positive nerve fibers are detectedfrom the late gastrula stage of Notoplana humilis in their process of regeneration. we observed that: during rotation stage, weak positive reaction of acetylcholinesterase is locatedin the brain region of every stage. At every stage of the regeneration, the location of theAChE-positive region showed the ladder-like nervous system with the anterior pair of brain, apair of thick ventral longitudinal nerve cords that send by the brain and ventral nerve cordneural connections also showed a positive reaction of AChE staining.