No abstract

No abstract

The kinetic apparatus, the acrosome and associated structures, and the manchette of the spermatid of the domestic chicken have been studied with the electron microscope. The basic structural features of the two centrioles do not change during spermiogenesis, but there is a change in orientation and length. The proximal centriole is situated in a groove at the edge of the nucleus and oriented normal to the long axis of the nucleus and at right angles to the elongate distal centriole. The tail filaments appear to originate from the distal centriole. The plasma membrane is invaginated along the tail filaments. A dense structure which appears at the deep reflection of the plasma membrane is identified as the ring. The fine structure of the ring has no resemblance to that of a centriole and there is no evidence that it is derived from or related to the centrioles. The tail of the spermatid contains nine peripheral pairs and one central pair of tubular filaments. The two members of each pair of peripheral filaments differ in density and in shape: one is dense and circular, and the other is light and semilunar in cross-section. The dense filaments have processes. A manchette consisting of fine tubules appears in the cytoplasm of the older spermatid along the nucleus, neck region, and proximal segment of the tail. The acrosome is spherical in young spermatids and becomes crescentic and, finally, U-shaped as spermiogenesis proceeds. A dense granule is observed in the cytoplasm between acrosome and nucleus. This granule later becomes a dense rod which is interpreted as the perforatorium. INTRODUCTIONThis paper deals with the fine structure of certain features of the developing spermatid of the rooster. Attention is focused on the kinetic apparatus and associated structures. The acrosome and perforatorium are considered briefly.Generally, the kinetic apparatus of the sperm cells from various kinds of animals has a similar basic pattern. It consists of the centriolar and tail filament complexes. Certain variations of the structure of these basic elements have been observed in the species studied with the electron microscope.According to Fawcett's review (10), there are two centrioles in the neck region of the mammalian spermatid, one retaining typical centriolar structure, and one extensively modified to serve as the basal body of the flagellum. Two typical tubular centrioles are also observed in toad spermatids 193 on

Mouse testes of newborn to adult were examined by freeze-fracture. Between the newborn Sertoli cells, gap junctions consisting of aggregations of the intramembranous particles (about 8 nm in diameter) are frequently found. Some of the junctions are about 1 mum in diameter and show particle-free regions in the aggregation. Linear arrangements of a few particles, which appear to be the initial formation of the occluding junctions, are seen in the newborn sertoli cells. The occluding junctions are arranged in a meshwork, in which the gap junctions are situated between the stages of newborn to six days of age. The particles of the occluding junctions are predominantly located on the B face in the center of the groove instead of the A face of the ridge. The occluding junctions do not appear to surround the entire circumference of the Sertoli cell of the 6-day-old mouse. The gap junctions decrease in size. In later stages, many parallel occluding junctions (up to forty in number) are found over one Sertoli cell surface and are distributed circumferentially around the entire cell surface, indicating establishment of the blood-testis barrier. The occluding junctions dominate and the gap junctions diminish in number as development proceeds.

Intercellular junctions of the excurrent duct system of the adult rat testis were studied by freeze-fracture. In the terminal segment of the seminiferous tubule, where there are no spermatogenic cells, the tight junctions of Sertoli cells consist of many parallel strands of particles. The particles of the junctions predominantly appear on the E face instead of the P face, similar to those of the seminiferous tubules reported previously. From the rete testis to the ductus deferens, the tight junctional particles or smooth strands are mainly found on the P face, and the tight junctions show anastomosing networks. In the ductuli efferentes, whose epithelial lining consists of ciliated and nonciliated cells, the tight junctions between two adjacent nonciliated cells and between nonciliated and ciliated cells are poorly developed. In the former, belt-like gap junctions are often associated with segmented tight junctions. In such area, there are tiny regions, where no junctional elements are observed. Between two ciliated cells, several strands of the tight junctions can be seen. The result of the tracer experiment suggests that the barrier of the ductuli efferentes is weak. In the epididymis, the tight junctions are well developed throughout the duct. Corresponding with the regional variation of the epididymal epithelium, the geometrical organization of the tight junction networks varies along the duct. In the ductus deferens, many strands of the tight junctions are scattered throughout the lateral cell surface in addition to the belt-like network of the tight junction in the adluminal area.The number of the tight junctional strands is presented graphically in the various segments of the excurrent duct of the testis.The epithelial lining of the testicular excurrent duct system shows histological variations along its length. The terminal segment of the seminiferous tubules is lined by only Sertoli cells (Perey et al., '61; Dym, '74). The tubuli recti is lined by the simple cuboidal or columnar epithelium (Dym, '74). In rat, the major part of the rete testis is a flattened sac at the periphery of the testis, and a series of straight rete tubes pierce the tunica albuginea joining the ductuli efferentes. According to RoosenRunge ('611, the major part and the tubular part will be referred t o intratesticular rete and extratesticular rete, respectively. The epithelium lining of the rete varies from squamous to low columnar type in the rat (Leeson, '62) as well as other species (Dym, '76; Bustos-Obregon and Holstein, '76).In many species including rats, the epithelial lining of the ductuli efferentes is comprised of two cell types, ciliated and nonciliated cells (Reid and Cleland, '57; Ladman and Young, '58; Ladman, '67; Hamilton, '75). Holstein ('69) reported six cell types in human. In the rat, the nonciliated cells are more numerous than the ciliated cells which are scattered among the nonciliated cells throughout the ductuli efferentes.The epididymis is customarily subdivided into three regions, the caput, corpus...