Anezary L, Medina J I, Sánchez-Nogueiro J, López-Gallardo M, Prada C
Departamento de Fisiología, Facultad de Medicina, Universidad Complutense, 28040 Madrid, Spain.
J Comp Neurol. 2001 Sep 10;438(1):32-49. doi: 10.1002/cne.1300.
It is currently believed that in each vertebrate species Müller cells in the central retina constitutes a fairly homogeneous population from the morphologic point of view and that particularly the chick Müller cell attains full shape differentiation at prenatal stages. However, in this study of the chick retina, from day 1 to day 55 of life, we show that there is a large variety of Müller cell shapes and that many of them complete shape differentiation postnatally. We used a cell dissociation method that preserves the whole shape of the Müller cells. Unstained living and unstained fixed cells were studied by phase-contrast microscopy, and fixed cells immunostained for intermediate filaments of the cytoskeleton were studied by fluorescence microscopy. Our results show that (1) Müller cell shapes vary in the origination of the hair of vitread processes, in the shape of the ventricular (outer or apical) process, in the presence or absence of an accessory process, as well as in the number and shape of processes leaving from the ventricular process at the level of the outer nuclear and outer plexiform layers (ONL/OPL); (2) during the first month of life, many Müller cells differentiate the portion of the ventricular process that traverses the ONL, most Müller cells differentiate the ONL/OPL processes, and all Müller cells differentiate the thin short lateral processes leaving from the vitread hair processes at the level of the inner plexiform layer (IPL). The number of cells differing in the shape of the ventricular process and that of cells with and without accessory process were estimated. The spatial relationship between the outer portion of the ventricular process of the Müller cell and the photoreceptor cells was also studied. Our results show that the branching of the ventricular process and the refinement of Müller cell shape is achieved without apparent participation of growth cones. We give a schematic view of how the branching of the ventricular process might take place and propose the size increase of photoreceptor soma as a factor responsible for this branching.
目前人们认为，从形态学角度来看，在每个脊椎动物物种的中央视网膜中，穆勒细胞构成了一个相当均匀的群体，特别是鸡的穆勒细胞在产前阶段就实现了完全的形态分化。然而，在这项对鸡视网膜从出生第1天到第55天的研究中，我们发现穆勒细胞的形态多种多样，而且其中许多细胞在出生后才完成形态分化。我们使用了一种能保留穆勒细胞整体形态的细胞解离方法。通过相差显微镜研究未染色的活细胞和未染色的固定细胞，通过荧光显微镜研究用细胞骨架中间丝进行免疫染色的固定细胞。我们的结果表明：（1）穆勒细胞的形态在玻璃体侧突起的起始、室管膜（外或顶端）突起的形状、是否存在副突起以及在核外和外网状层（ONL/OPL）水平从室管膜突起发出的突起数量和形状方面存在差异；（2）在出生后的第一个月内，许多穆勒细胞分化出穿过ONL的室管膜突起部分，大多数穆勒细胞分化出ONL/OPL突起，并且所有穆勒细胞都分化出在内网状层（IPL）水平从玻璃体侧突起发出的细短侧突起。估计了室管膜突起形状不同的细胞数量以及有和没有副突起的细胞数量。还研究了穆勒细胞室管膜突起外部与光感受器细胞之间的空间关系。我们的结果表明，室管膜突起的分支和穆勒细胞形态的细化是在没有生长锥明显参与的情况下实现的。我们给出了室管膜突起分支可能发生方式的示意图，并提出光感受器胞体大小的增加是导致这种分支的一个因素。
