Neurogenic and non-neurogenic placodes in Ascidians
Neurogenic and non-neurogenic placodes in Ascidians
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DOI：
10.1002/jez.b.21013
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发表时间：
2004-09-15
影响因子：
2.2
通讯作者：
Burighel, P
中科院分区：
文献类型：
--
作者：
Manni, L;Lane, NJ;Burighel, P
外胚层层的晚期分化进行了分析海鞘玻璃海鞘和Botryllus schlosseri，通过光学和电子显微镜，以验证基板结构的可能存在。颅基板，引起非表皮细胞类型的外胚层区域，是典型的只在脊椎动物中发现的，然而，数据不断积累，以证明非脊椎动物脊索动物拥有基板分化所涉及的遗传机制，外胚层结构可能是脊椎动物基板的同系物。此处，术语“基板”在广义上使用，并且定义了外胚层的增厚，其可以表现出基底层的中断，在基底层处细胞分层，因此能够获得非表皮命运。一些神经原性基板，能够产生神经元，已被确认，他们的衍生物已被分析，并讨论其可能的同源性与脊椎动物基板。特别是，口膜基板可以被认为是一个多基板，由不同种类的基板组成：它的一部分，分化毛细胞，被讨论为同源的octavo-lateralis基板，而其余部分，产生纤毛管的神经腺，被认为是同源的腺垂体基板。神经垂体基板可能包括下丘脑和脊椎动物嗅觉基板的同源物;产生感觉乳头的吻侧基板可能与脊椎动物的粘附腺基板同源。(C)2004 Wiley-Liss，Inc.
The late differentiation of the ectodermal layer is analysed in the ascidians Ciona intestinalis and Botryllus schlosseri, by means of light and electron microscopy, in order to verify the possible presence of placodal structures. Cranial placodes, ectodermal regions giving rise to nonepidermal cell types, are classically found exclusively in vertebrates; however, data are accumulating to demonstrate that the nonvertebrate chordates possess both the genetic machinery involved in placode differentiation, and ectodermal structures that are possible homologues of vertebrate placodes. Here, the term "placode" is used in a broad sense and defines thickenings of the ectodermal layer that can exhibit an interruption of the basal lamina where cells delaminate, and so are able to acquire a nonepidermal fate. A number of neurogenic placodes, ones capable of producing neurons, have been recognised; their derivatives have been analysed and their possible homologies with vertebrate placodes are discussed. In particular, the stomodeal placode may be considered a multiple placode, being composed of different sorts of placodes: part of it, which differentiates hair cells, is discussed as homologous to the octavo-lateralis placodes, while the remaining portion, giving rise to the ciliated duct of the neural gland, is considered homologous to the adenohypophyseal placode. The neurohypophyseal placode may include the homologues of the hypothalamus and vertebrate olfactory placode; the rostral placode, producing the sensorial papillae, may possibly be homologous to the placodes of the adhesive gland of vertebrates. (C) 2004 Wiley-Liss, Inc.