Prenatal differentiation of colliculus superior in the rat.

Bibliotheca anatomica Pub Date : 1981-01-01
E Raedler, A Raedler, S Feldhaus
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Abstract

Up till emybryonic day (ED) the 13 the prenatal histogenesis of rat mesencephalic roof is characterized by an exclusive proliferation of ventricular cells. Then the first differentiating postmitotic cells are found above the ventricular layer, so that proliferation and differentiation occur simultaneously. On ED 15 a lamination typical for embyronic CNS with ventricular, subventricular, intermediate layers and stratum zonale can be observed in the area of presumptive colliculus superior. A definite demarcation between ventricular and subventricular layers, however, is only possible by means of autoradiograpahic methods. At the end of gestation the lamination of adult colliculus superior is already noticeable. During early prenatal development, cells which originate on one single day can autoradiographically be demonstrated in different cell layers and particularly over the whole width of the intermediate layer, while towards the end of gestation time of cell origin and location inside the mesencephalic roofs are closely correlated: cells that originate on ED 13 can be found predominantly in deeper cell layers (stratum griseum profundum, lower stratum griseum intermedium), while cells originating on EDs 15 and 17 are on ED 21 situated in the upper cell layers (upper stratum griseum intermedium, stratum griseum superficiale). This results in an inside-outside gradient of cell origin, which corresponds to an inside-outside gradient of cell differentiation. Besides, a rostro-caudal and a lateromedial gradient can be observed. On ED 13 a median ventriculaar formation (MVF) can be distinguished displaying a significantly lower mitotic activity than the cells of the neighbouring ventricular layer as could be demonstrated by autoradiographic investigation. This difference is even more pronounced in latter embryonic stages. From ED 17 on the cells of this particular structure are arranged in a typical onion-like pattern. Towards the end of gestation the MVF expands considerably as compared with the surrounding ventricular layer. As long-time experiments with 3H-thymidine reveala this increase in area is brought about by the immigration of numerous ventricular cells which originated on earlier embryonic days. The apical processes of the cells of the MVF form a thick fibre bundle which can be followed upwards to the stratum zonale. Ulstructurally these strictly parallel arranged fibers mainly resembly astroglial processes, but possess, in contrast to the latter, numerous microtubules. Because of their morphological characteristics a classification of these cells as tanycytes appears justified. The MVF is compared with similar structures in other regions of the CNS and its possible function as a guide for migrating preneurons is discussed.

大鼠上丘的产前分化。
直到胚胎日(ED),大鼠中脑顶的产前组织发生以心室细胞的排他性增殖为特征。第一批分化的有丝分裂后细胞位于心室层上方,因此增殖和分化同时发生。在ed15上,可以在假定的上丘区域观察到典型的胚胎中枢神经系统层压,包括脑室、脑室下、中间层和带状层。然而,只有通过放射自显影方法才能明确区分心室和室下层。在妊娠末期,成人上丘的层压已经很明显。在产前早期发育过程中,在不同的细胞层中,特别是在中间层的整个宽度上,可以显示出在一天内产生的细胞,而在妊娠末期,细胞产生的时间和中脑顶内的位置密切相关。起源于ED 13的细胞主要位于较深的细胞层(深层灰质层,下层灰质层),而起源于ED 15和17的细胞位于ED 21上的上层细胞层(上层灰质层,中层灰质层)。这导致了细胞起源的内向外梯度,这对应于细胞分化的内向外梯度。此外,还可以观察到纵向和纵向梯度。在ED 13中心室形成(MVF)可以被区分出来,显示有丝分裂活性明显低于邻近心室层的细胞,这可以通过放射自显像检查证实。这种差异在胚胎后期更为明显。从ED 17开始,这种特殊结构的细胞以典型的洋葱状模式排列。临近妊娠末期,与周围心室层相比,MVF明显扩大。用3h -胸腺嘧啶进行的长期实验表明,这种面积的增加是由起源于早期胚胎时期的大量心室细胞的迁移引起的。MVF细胞的顶端突起形成一个厚纤维束,可以向上延伸到带状层。在结构上,这些严格平行排列的纤维主要类似星形胶质突起,但与后者相反,它们具有许多微管。由于它们的形态特征,将这些细胞分类为伸长细胞似乎是合理的。将MVF与CNS其他区域的类似结构进行了比较,并讨论了其作为迁移前神经元指南的可能功能。
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