小白鼠精子成形各時期中頂體發育之探討

Abstract

頂體為動物精子中最重要的構造之一，在精子成形的四個發育過程—高基氏體時期、冠時期、頂體時期及成熟時期—中，頂體逐步生長、延展、濃縮變形而成。本研究以超薄切片方法、冷凍斷裂技術、細胞酵素定位以及Osmium-DMSO-Osmium等技術來觀察小白鼠精細胞頂體的發育，發現在高基氏體時期及冠時期時，高基氏體是透過外被小泡的方式提供頂體發育所需成分，這些外被小泡主要由頂體冠延展外緣以及頂體冠正中央處與頂體癒合。隨著外被小泡的加入，頂體會逐漸沿細胞核表面延展擴大，一旦發育進入頂體時期後頂體即停止生長，頂體冠延展外緣也不再有外被小泡出現，因此外被小泡由頂體冠延展外緣處癒合可能有助頂體冠在細胞核表面延展。此外，本研究亦發現經由外被小泡送入頂體中的酵素在頂體內呈特定區域的分佈，其中在發育早期酸性磷酸?經細胞化學標定後只出現在頂體冠位置，當精細胞發育進入成熟時期後，酸性磷酸?則局限在頂體的赤道區。因此，頂體中頂體顆粒與週圍頂體冠可視為兩個獨立的部份，酵素在這些區域的特定分佈可能是經由外被小泡在頂體冠表面不同位置癒合而形成的。另外，本研究中還發現以秋水仙素處理會造成頂體發育出現停滯的現象，推測可能是因為精細胞微管系統遭破壞後，外被小泡無法順利送至頂體冠延展外緣處，因此頂體的延展便發生延緩的現象。綜合各部份的觀察，頂體發育可能是由高基氏體提供原料，以外被小泡的方式經由微管將不同成分送至頂體冠正中央或頂體冠延展外緣處與頂體癒合，一方面藉此建立頂體區域性的差異，另一方面也可促進頂體冠在細胞核表面延展。

The acrosome is one of the most important organelles in animal sperms. Through Glogi, cap, acrosome and maturation phases of spermiogenesis, the acrosome gradually grows, expands and condenses to form a cap covering on the head of the sperm. In this study, thin sectioning, freeze-fracturing, cytochemistry and Osmium-DMSO-Osmium methods were used to investigate the acrosome development in mice. During the Golgi and the cap phases, many coated vesicles were formed and secreted by Golgi complex, and most of them fused with acrosome membrane from the caudal margin and the center of the acrosomal cap. Once spermatids grew into acrosome phase, the acrosome was stopped to grow and no more coated vesicles were found near the caudal margin of the acrosome. This indicates that coated vesicles fused with acrosomal cap from the caudal margin may facilitate the expansion of the acrosomal cap over the nucleus. In cytochemistry study, acid phosphatase was found to be concentrated in the acrosomal cap at cap phase or in the equatorial segments of the acrosome at maturation phase. This specific distribution of enzymes might due to coated vesicles fuse with acrosome from different positions. In addition, acrosome formation could be retarded by colchicine treatment. This phenomenon might be the result of the destruction of microtubule system. According to our observation, it is suggested that the acrosome formation is achieved by fusing with coated vesicles from the center and the caudal margin of the acrosome. These coated vesicles are secreted from Golgi complex and transported by microtubules. With this method, it not only facilitates the expansion of the acrosome on the surface of the nucleus, but also establishes distinct regions of the acrosome.