A study of toxic effect of amyloid substance in brain

研究了淀粉样物质对组织的毒性作用。弥漫型老年斑被认为是淀粉样蛋白形成的初始步骤。应用免疫组化和甲硫氨酸-银浸渍法，通过电子显微镜观察弥漫斑块中的β-淀粉样蛋白或β-淀粉样蛋白。该结构中的淀粉样物质由细小的短纤维束组成，部分无定形。大部分类胶质沉积在小突起之间。这些突起的细胞膜与其他无类胶质的部位的相同结构相比，显示出不清晰的外观。这一发现可能表明，类淀粉样蛋白由于其毒性作用而引起周围组织的变性。另一种重要的具有淀粉样蛋白性质的异常蛋白--神经纤维缠结（NFT）也被研究以阐明其毒性作用。与神经元内NFT不同，细胞外NFT被变性的神经元突起包围，并被大量星形胶质细胞突起和小胶质细胞侵入。细胞外NFT的免疫组化和超微结构也有改变。这些结果可能是NFT对周围组织毒性作用的证据。

Toxic effect of amyloid substances against tissue was investigated. Diffuse type of senile plaques are thought to be an initial step of amyloid-formation. beta-amyloid or preamyloid in diffuse plaque was observed by electron microscopy applying immunohistochemical and methemanine-silver impregnation methods. The amyloid substance in this structure consisted of fine short fibrillar bundle and was partially amorphic. Most of the preamyloid deposited between small processes. The membrane of these processes showed unclear appearance in comparison to the same structure in other portion without preamyloid. This finding may indicate that the preamyloid induce the degeneration of the surrounding tissue due to its toxic effect.Another important abnormal protein with amyloid nature, the neurofibrillary tangles (NFT) , was also investigated to elucidate its toxic effect. Extracellular NFT was, differ from intraneuronal NFT,surrounded by degenerated neuronal processes and invaded by numerous astrocytic processes and microglia. The Immunohistochemical and ultrastructural alteration of extracellular NFT was also noticed. A series of these findings may be the evidence of toxic effect of NFT against the surrounding tissue.