FIBER CELL JUNCTIONS IN NORMAL AND CATARACTOUS LENSES

无血管哺乳动物晶状体中的纤维细胞是偶联的 广泛地通过缝隙(通信)连接(GJS)来实现 促进离子和小分子的流动 镜头。第二种类型的结，其特征在于6.6 nm正方形 膜平面上的蛋白质阵列也是一个突出的 纤维细胞的特征，尤指晶状体核中较老的细胞。 正方形阵列结(SAJ)的功能未知， 尽管已经注意到SAJ与 很可能会产生起伏的舌膜- 和-凹槽交错。我们建议量化 连接的分布，从皮质中较年轻的纤维到 核内较老的纤维，用电子显微镜观察 以及一种保存晶状体组织的新程序。新的镜片将会是 用可控震荡器(振动刀)切开给出 50-200 PM厚的部分，将进行化学固定 冷冻固定的。冷冻固定的厚片将被冷冻处理- 替代/薄切或冷冻断裂。交汇性 冷冻过程中薄片和膜内颗粒的分布 骨折图像将用于区分GJS和SAJ，并 将功能分布与细胞年龄相关联。 我们建议评估一种假设，即主膜 蛋白质(MP26)或其降解产物(MP22)形成两个GJS 通过定位具有完整抗体的MP26和MP22和SAJ 膜和分离自不同区域的膜中。 冷冻水合方块的低剂量电子显微镜图像 在X射线衍射图中提供1.0纳米分辨率的阵列， 并将获得SAJ的高分辨率钽复制品，以 确定正方形数组内的子结构是否为 与航道形成相一致。此外，我们建议 测试假设，在起伏的膜中，SAJ 通过以下方式最大限度地减少细胞外空间 静电相互作用。 初步结果表明，膜连接是 在某些类型的白内障中结构异常。因此， 我们建议在三种类型中确定结的结构 白内障晶状体：牛皮质性白内障 暴露于低pH值；药物性糖尿病所致的糖性白内障 兔；以及手术摘除人类老年性白内障。

Fiber cells in the avascular mammalian lens are coupled extensively by gap (communicating) junctions (GJS) which facilitate the flow of ions and small molecules throughout the lens. A second type of junction characterized by a 6.6 nm square array of protein in the membrane plane is also a prominent feature of fiber cells, especially of older cells in the lens nucleus. The function of the square array junction (SAJ) is not known, although it has been noted that SAJs are intimately associated and probably produce the undulating membranes of the tongue- and-groove interdigitations. We propose to quantitate the distribution of junctions, from the younger fibers in the cortex to the older fibers in the nucleus, by the use of electron microscopy and a new procedure to preserve lens tissue. Fresh lenses will be sectioned with a vibrotome (oscillating knife microtome) to give 50-200 pm thick sections which will be chemically fixed of cryofixed. Cryofixed thick sections will be processed by freeze- substitution/thin sectioning or by freeze-fracture. Junctional profiles in thin sections and intramembrane particles in freeze- fracture images will be used to distinguish GJs and SAJs and to correlate the distributions of functions with the age of the cells. We propose to evaluate the hypothesis that the major membrane protein (MP26), or its degradation product (MP22), forms both GJs and SAJs by locating MP26 and MP22 with antibodies in intact membranes and in membranes isolated from different regions. Low-dose electron microscopic images of frozen-hydrated square arrays, which give 1.0 nm resolution in x-ray diffraction patterns, and high resolution tantalum replicas of SAJs will be obtained to determine whether the substructure within square arrays is consistent with channel formation. Furthermore, we propose to test the hypothesis that, in undulating membranes, the SAJs minimize the extracellular space between cells through electrostatic interactions. Preliminary results indicate that membrane junctions are structurally abnormal in certain types of cataracts. Therefore, we propose to determine the structure of junctions in three types of cataractous lenses: bovine cortical cataracts induced by exposure to low pH; sugar cataracts from drug induced diabetic rabbits; and surgically removed human senile cataracts.