Alunni A, Vaccari S, Torcia S, Meomartini M E, Nicotra A, Alfei L
Department of Animal and Human Biology, University of Rome La Sapienza, Rome, Italy.
Eur J Histochem. 2005 Apr-Jun;49(2):157-66.
Unlike mammals, some fish, including carp and trout, have a continuously growing brain. The glial architecture of teleost brain has been intensively studied in the carp and few data exist on trout brain. In this study, using immunoblotting we characterized the topographic distribution of glial fibrillary acidic protein (GFAP) in larval and adult rainbow trout brain and studied by immunohistochemistry the distribution and morphology of GFAP-immunoreactive cell systems in the rainbow trout hindbrain and spinal cord. Immunoblotting yielded a double band with an apparent molecular weight of 50-52 kDa in the spinal cord homogenate in the trout larval and adult stages. In the adult hindbrain and forebrain, our antibody cross reacted also with a second band at a higher molecular weight (90 kDa). Because the forebrain contained this band alone the two brain regions might contain two distinct isoforms. Conversely, the larval total brain homogenate contained the heavy 90 kDa band alone. Hence the heavy band might be a GFAP protein dimer or vimentin/GFAP copolymer reflecting nerve fiber growth and elongation, or the two isoforms might indicate two distinct astroglial cell types as recently proposed in the zebrafish. In sections from trout hindbrain and spinal cord the antibody detected a GFAP-immunoreactive glial fiber system observed in the raphe and in the glial septa separating the nerve tracts. These radial glia fibers thickened toward the pial surface, where they formed glial end feet. The antibody also labeled perivascular glia around blood vessels in the white matter, and the ependymoglial plexus surrounding the ventricular surface in the grey matter. Last, it labeled round astrocytes. The GFAP-immunoreactive glial systems had similar distribution patterns in the adult and larval spinal cord suggesting early differentiation.
与哺乳动物不同，一些鱼类，包括鲤鱼和鳟鱼，其大脑会持续生长。硬骨鱼脑的神经胶质结构已在鲤鱼中得到深入研究，而关于鳟鱼脑的相关数据较少。在本研究中，我们使用免疫印迹法对虹鳟鱼幼体和成体大脑中胶质纤维酸性蛋白（GFAP）的拓扑分布进行了表征，并通过免疫组织化学研究了虹鳟鱼后脑和脊髓中GFAP免疫反应性细胞系统的分布和形态。免疫印迹法在鳟鱼幼体和成体阶段的脊髓匀浆中产生了一条表观分子量为50 - 52 kDa的双条带。在成体后脑和前脑中，我们的抗体还与一条分子量更高（90 kDa）的第二条带发生交叉反应。由于前脑单独含有这条带，这两个脑区可能包含两种不同的异构体。相反，幼体全脑匀浆仅含有重的90 kDa条带。因此，重条带可能是反映神经纤维生长和延伸的GFAP蛋白二聚体或波形蛋白/GFAP共聚物，或者这两种异构体可能表明如最近在斑马鱼中所提出的两种不同的星形胶质细胞类型。在鳟鱼后脑和脊髓的切片中，抗体检测到在中缝以及分隔神经束的胶质隔中观察到的GFAP免疫反应性胶质纤维系统。这些放射状胶质纤维向软脑膜表面增厚，在那里它们形成胶质终足。抗体还标记了白质中血管周围的血管周胶质细胞，以及灰质中围绕脑室表面的室管膜胶质丛。最后，它标记了圆形星形胶质细胞。GFAP免疫反应性胶质系统在成体和幼体脊髓中的分布模式相似，表明其早期分化。
