Itoh Y, Amano N, Inoue M, Yagishita S
Division of Pathology, Kanagawa Rehabilitation Center, Japan.
Acta Neuropathol. 1997 Jul;94(1):78-86. doi: 10.1007/s004010050675.
Neurofibrillary tangles (NFTs) have been ultrastructurally studied by various methods, leading to several three-dimensional models of paired helical filaments (PHFs). In this study, we present the scanning electron microscopic findings of NFTs in an autopsy case of Alzheimer's disease and clarify the three-dimensional structures of NFTs. NFTs were clearly defined in freeze-cracked nerve cells and consisted of two types of filamentous structures, straight and helical filaments. Straight filaments measured from 20 to 25 nm in diameter and had a smooth surface. They were slightly bent but mostly straight with no constrictions. One type of straight filaments ran in a bundle in the same direction, another was intertwined to each other. Most of the helical profiles of filaments usually measured about 28 nm in diameter, with a distance of 100 nm between periodic constrictions. They seemed to consist of a pair of isodiametric filaments of 10 nm in diameter. In addition, two unusual types of helical filaments were occasionally observed. One comprised thick filaments of about 38 nm in diameter, with a distance of 100 nm between constrictions; these helical filaments appeared to consist of two or more strands. The other comprised thin helical filaments of about 20 nm in diameter and regularly constricted at an interval of 50 nm. All types of the helical filaments examined in this case were leotropic. This result supports a protofilament model of PHFs. Scanning electron microscopy using the freeze-cracked and maceration method is a useful and simple method for three-dimensional observation of the filamentous structures in NFTs.
人们已通过各种方法对神经原纤维缠结（NFTs）进行了超微结构研究，从而得出了几种成对螺旋丝（PHFs）的三维模型。在本研究中，我们展示了一例阿尔茨海默病尸检病例中NFTs的扫描电子显微镜检查结果，并阐明了NFTs的三维结构。NFTs在冷冻断裂的神经细胞中清晰可见，由两种丝状结构组成，即直丝和螺旋丝。直丝直径为20至25纳米，表面光滑。它们略有弯曲，但大多是直的，没有收缩。一种直丝以束状同向排列，另一种则相互缠绕。大多数丝状螺旋轮廓的直径通常约为28纳米，周期性收缩之间的距离为100纳米。它们似乎由一对直径为10纳米的等径丝组成。此外，偶尔还观察到两种不寻常的螺旋丝类型。一种由直径约38纳米的粗丝组成，收缩之间的距离为100纳米；这些螺旋丝似乎由两股或多股组成。另一种由直径约20纳米的细螺旋丝组成，每隔50纳米有规则地收缩。在该病例中检查的所有类型的螺旋丝都是左旋的。这一结果支持了PHFs的原丝模型。使用冷冻断裂和浸渍法的扫描电子显微镜检查是一种用于三维观察NFTs中丝状结构的有用且简单的方法。
