Olson G E, Hamilton D W
Anat Rec. 1976 Nov;186(3):387-91. doi: 10.1002/ar.1091860304.
Several ultrastructural changes were found to occur in the midpiece region of wooly opossum spermatozoa during epididymal maturation. The changes include alterations in mitochondrial morphology, development of structural specializations of the plasma membrane, and acquisition of a prominent extracellular coating. The lamellar membrane network which is wound about the periphery of the mitochondria becomes more densely packed during sperm development and the reticular network of membranes noted in the center of the mitochondria of immature sperm disappears leaving a homogeneous electron dense central zone. During epididymal transit the plasma membrane over the sperm midpiece region shows extensive structural modification. In cross sections of paired spermatozoa the plasma membrane of the midpiece regions shows a very regular, repetitive scalloping. In longitudinal sections the scalloping is observed as continuous parallel ridges which extend slightly obliquely to the flagellar long axis. Each ridge appears to be greater in density than the interridge areas. In the epididymis a prominent extracellular coating of dense material is deposited over the midpiece surface; this material is similar in appearance to dense material seen in restricted areas of the epididymal lumen. At the proximal and distal ends of the midpiece the plasma membrane comes into intimate contact with underlying structural specializations and it is suggested that these zones of fusion may serve to preserve regional differences in membrane composition.
在附睾成熟过程中，发现绵毛负鼠精子的中段区域出现了几种超微结构变化。这些变化包括线粒体形态的改变、质膜结构特化的发展以及获得一层显著的细胞外涂层。缠绕在线粒体周边的层状膜网络在精子发育过程中变得更加密集，未成熟精子线粒体中央的网状膜网络消失，留下一个均匀的电子致密中央区。在附睾转运过程中，精子中段区域的质膜显示出广泛的结构修饰。在成对精子的横切面上，中段区域的质膜呈现出非常规则、重复的扇贝状。在纵切面上，扇贝状表现为连续的平行嵴，略微倾斜于鞭毛长轴延伸。每个嵴的密度似乎比嵴间区域更大。在附睾中，一层由致密物质构成的显著细胞外涂层沉积在中段表面；这种物质在外观上与附睾管腔受限区域中看到的致密物质相似。在中段的近端和远端，质膜与下方的结构特化紧密接触，有人认为这些融合区域可能有助于维持膜成分的区域差异。
