Subacrosomal Space Research Articles

Ultrastructural observations on spermatozoa retained within the seminiferous epithelium after treatment with dibutyryl cyclic AMP

Spermiation was inhibited in the Syrian hamster by administering large doses of dibutyryl cyclic AMP. After treatment with dibutyryl cyclic AMP most stage VIII, IX, and X seminiferous tubules contained some mature spermatozoa within the seminiferous epithelium. The acrosomal membranes and plasma membranes of the unreleased spermatozoa remained intact, indicating that the spermatozoa had not been phagocytized by the Sertoli cells. Sertoli-spermatid junctional specializations were usually applied to the heads of the mature spermatozoa. The unreleased spermatozoa often appeared swollen with accumulated fluid located in the subacrosomal space. The accumulation of subacrosomal fluid in the unreleased spermatozoa seems to result from the absence of tubulobulbar complexes. That is, when tubulobular complexes fail to form the normal flow of cytoplasm into the tubulobular complexes is blocked resulting in an accumulation of fluid around the nucleus. Inhibition of spermiation may result from the absence of tubulobulbar complex formation. It is postulated that the tubulobulbar complex functions to transfer a chemical trigger from the maturing spermatid into the Sertoli cell. This chemical trigger may initiate the disappearance of the Sertoli-spermatid junctional specialization and induce spermiation.

An ultrastructural study of microtubules and the acrosome in spermiogenesis of tubificidae (oligochaeta)

Limnodriloides winckelmanni shows stages in condensation of the nucleus and development of microtubules in the maturing spermatid similar to those formerly described for Limnodrilus and Tubifex . Contrary to previous reports, the total number of perinuclear and cytoplasmic microtubules does not appear constant. The midpiece in the tubificids, consisting of two to six radially adpressed unspiraled mitochondria, is less elongated than that of megascolecids and lumbricids. The flagellum is similar to that previously described for earthworms. Two centrioles are demonstrated for the first time in tubificids. The proximal centriole loses its association with the flagellum but its subsequent fate is unknown. The acrosome shows general homology with that of other oligochaetes investigated (enchytraeids, megascolecids, and lumbricids). Shared features are the external plasma membrane; the apical primary acrosome vesicle; the subvesicular space (subacrosomal space) invaginated into this and giving rise to the axial rod which is injected into the acrosome tube; a periaxial sheath (secondary tube) dependent from the primary vesicle and encircling the rod; and a dense ring within the primary vesicle. Spermatozoa of Branchiobdellidae and leeches are compared with those of oligochaetes. Each of the three groups has a distinctive spermatozoal morphology, though that of Branchiobdellids is in some respects intermediate between leeches and oligochaetes.

Cytochemical localization of cations in the testis of the syrian hamster, utilizing potassium‐pyroantimonate

AbstractPyroantimonate has long been used as a cytochemical technique for the localization of cations. Although the technique was originally alleged to be specific for Na+, other cations, including Mg++, Ba++, Ca++, Zn++ and polycationic amines, form pyroantimonate precipitates. In seminiferous tubules treated with antimonate‐osmium fixation, the nuclei of the Sertoli cells and germ cells contained precipitates. In regions of condensed chromatin the precipitates were dense while, in dispersed chromatin, precipitates were sparse or absent. It is postulated that the dense precipitates observed in the condensed chromatin may represent an accumulation of calcium that may facilitate chromatin condensation. The Sertoli cell nucleolar apparatus contained light precipitates in the pars amorpha, moderate precipitates in the nucleolonema, and heavy precipitates in the perinucleolar heterochromatin bodies. The nuclei of the maturation‐phase spermatids lacked any precipitates. The perinuclear ring of the acrosome‐phase spermatids contained pyroantimonate deposits. In the maturation‐phase spermatids, staining occurred in the postacrosomal dense lamina, in the subacrosomal space between the perforatorium and the inner acrosomal membrane, and in the central mass of the residual bodies. Since the postacrosomal dense lamina is the portion of the spermatozoon that initially fuses with the ovum, it is postulated that its cationic properties in some way facilitate this fusion.

Electron Microscope Study of Lizard Spermiogenese inTropidurus Torquatos(Lacertilia)

SUMMARYIn the course on an investigation on lizard spermiogenesis, we have observed events connected with the differentiation of the acrosome and middle-piece of the spermatozoa. Some differences from other reptilians were found as well as: the presence of a subacrosomal space, the absence of the fibrous sheath in the middle-pice and a very short neck in the mature spermatozoa.

The subacrosomal granule and its evolution during spermiogenesis in a lizard

Some aspects of spermiogenesis have been studied in the testis of the teiid lizard Cnemidophorus lemniscatus lemniscatus by electron microscopy. Shortly after the acrosomal vesicle is lodged in a nuclear concavity of the spermatid, a dense granule differentiates in the center of the subacrosomal space. It is cone-shaped and shows a longitudinal striation. Its base applies to the acrosomal membrane and, through this, to the acrosomal granule. Its rounded vertex causes a depression of the nuclear membranes which, initially juxtaposed, separates at this point to form a vesicle. The granule develops and becomes a rod when spermiogenesis is advanced and the subacrosomal space has taken the form of a secondary cap. The rod is cylindrical, retains its original striation and has a convex acrosomal end. It encloses the vesicle formed by the nuclear envelope in its base and follows the apex of the nucleus. Meanwhile, the acrosomal granule loses its identity and the acrosomal cap is filled with a dense substance, in which a fringe of translucent material differentiates. This fringe lies in the dorsal and apical margins of the acrosome and is incompletely divided by longitudinal crests of the dense acrosomal substance. A projection of the Sertoli cell forms an accessory cap which envelops the acrosome and is in turn covered by the cytoplasm of the spermatid, constituting an intricate association. Two reflex membranes underlie the plasmalemma in the outer surface of the projection of the Sertoli cell. They are continuous with one another at their ends and with the cell membrane in the edge of pores. In the peripheral cytoplasm of the spermatid facing the accessory cap, numerous microtubules run longitudinally. By means of thin membranes some are interconnected or connected with the plasmalemma, from which they seem to originate.

An ultrastructural study of the head region of bovine spermatozoa.

Differential interference micrographs, electron micrographs of thin sections, and electron micrographs of freeze-etched preparations have been used in a coordinated study of the head structure of bovine spermatozoa. The equatorial segment can be visualized by all three methods but it is more clearly defined in aged cells in which the plasmalemma covering the apical region is loosened. The thinning of the acrosome in the equatorial segment allows the penetration of postnuclear-cap material both into the subacrosomal space and into the transition zone between the acrosome and the plasmalemma to produce an 'overlap' structure in this region.The plasmalemma cleaves predominantly in the median hydrophobic zone and this cleavage plane is both distorted by underlying structures and physically modified by its apposition to these structures. These physical modifications are reflected in the formation of 'plaques' by departures from the median cleavage plane in some areas and in the arrangements of globular particles, which are equated with protein complexes. Rings of globular particles within the cleavage plane of the plasmalemma are coincident with underlying nuclear pores in the diverticula. The median cleavage of the outer acrosomal membrane exposes numerous globular particles in linear arrays. Spiralized linear structures resembling microtubules are seen in the postnuclear cap.

Spermiogenesis in the brush-tailed possum, Trichosurus vulpecula (Marsupialia). The development of the acrosome.

Acrosome development in the Australian Brush-tailed possum, Trichosurus vulpecula, displays a number of extraordinary features. This is particularly evident in the later stages of spermiogenesis, when the area of the nuclear surface bounded by the nuclear ring, and covered by the acrosome, is reduced considerable. As a result, the acrosomal material becomes located over its definitive position on the anterior third of the dorsal nuclear surface; in this process it is thrown into a series of folds, and a wide subacrosomal space is formed. Further changes around the time of spermiation result in the release of a spermatozoon in which a thin layer of acrosomal material is closely applied to the nucleus over the area of the definitive location of the acrosome, whilst its margins are greatly extended and project freely away from the nucleus. The latter feature does not appear to have been reported for the sperm of other mammals.

The head, neck and midpiece of cock spermatozoa examined with the transmission electron microscope.

Cock spermatozoa were isolated from fresh ejaculates and prepared for transmission electron microscopy. The subacrosomal space of the head separated the conical-shaped acrosome from the elongated nucleus. A prominent perforatorium was observed in the subacrosomal space. The neck region consisted of a centriolar complex and a non-striated connecting piece which extends apically into the implantation fossa. Approximately 30 mitochondria surround the distal centriole and the proximal portion of the axonemal complex of the midpiece.

An electron microscope study of the immediate effects on spermateleosis of a short-time experimental cryptorchidism in the rabbit.

The immediate effects on rabbit spermateleosis of experimental cryptorchidism for 12, 24, and 48 hs were studied in the electron microscope. Prominent changes were observed in the nucleus, in the acrosome system, in the forming tail, in the perinuclear ring, and in the postacrosomal dense lamina. The nucleus showed abnormal shape and various chromatin defects. Local dilations of the subacrosomal space were very common and various abnormalities of the acrosome were observed in most stages of spermateleosis. Split coarse fibres, disintegration of the fibrous sheath, and defects of the mitochondrial sheath were observed in the forming tail. Total or partial disintegration of the perinuclear ring as well as defects in the postacrosomal dense lamina were found. Various other changes were also found in some spermatids. Some possible biochemical explanations of the changes are suggested, and similarities to changes described in cases of spontaneous sterility are briefly discussed.

A previously unrecognized material in mammalian spermatozoa as revealed by malachite green and pyronine.

Fixation of rabbit spermatozoa with glutaraldehyde containing either malachite green or pyronine demonstrated a material which has not been previously described. In ejaculated spermatozoa, this malachite green and pyronine-affinity material (MOP-AM) appeared as a compact mass localized between the nuclear envelope and dense lamina of the posterior portion of the postacrosomal region. MOP-AM was absent in testicular spermatozoa and gradually accumulated during passage of spermatozoa through the epididymis, suggesting a possible correlation between the accumulation of this material and maturation of the spermatozoa. Among eighteen other cationic dyes tested, only methyl violet 2B could preserve this material. Similar MGP-AM was demonstrated in the spermatozoa of other species (human, rat, mouse, mongoose and hamster) within: subacrosomal space and nuclear vacuoles (human), redundant nuclear envelopes (human and mongoose), middle-piece mitochondria (human and hamster), and between nuclear envelope and dense lamina of the postacrosomal region (hamster, mouse and rat). The possible mechanisms by which MGP-AM is preserved by this technique are discussed.

Electron microscopic studies of the testis after vasectomy in rats and men

Ultrastractural studies of the testes of the adult rats and men after vasectomy were performed. The rats were killed at intervals ranging from 2 weeks to 3 months after vasectomy, and small pieces of their testes dissected from each animal were fixed in 2% osmium tetroxide or 3% potassium permanganate buffered with veronal acetate to pH7.4. The biopsied materials of testes from 29 to 36-year-old men who had been vasectomized for sterility 3 to 7 years ago, were also examined in the present experiment.The results were summarized as follows:1) Cells bearing a close resembrance to smooth muscle cells, and fibrocytes were observed in the boundary tissue of seminiferous tubules in both the normal rats and men. In the rats there existed one layer of the smooth muscle-like cells and in the men 4 layers of them in their boundary tissue of seminiferous tubules, where no significant structural changes were detected after vasectomy.2) No histological differences were recognized in the process of spermatogenesis among the rats with and without vasectomy, while the spermatids of vasectomized men showed degenerative features, to some extent. They were mainly manifested by discontinuity of the nuclear membrane, widening of the subacrosomal space, appearance of many small vacuoles in the post nuclear region and abnomal formation of the acrosome.3) There were no structural alterations in the interstitial cells of the vasectomized men and rats.4) Many vacuoles of unidentifiable nature were found in the Sertoli cells.In rats and men, the effects of vasectomy on the process of spermatogenesis were discussed on the basis of the ultrafine structure.

Observations on the fine structure of spermatozoa of the bush baby (Galago senegalensis), the African green monkey (Cercopithecus aethiops) and man.

AbstractA description is given of some fine structural features of mature spermatozoa from the bush baby (Galago senegalensis), the African green monkey (Cercopithecus aethiops) and man, with additional comments on sperm from the slow loris (Nycticebus coucang) and the crab‐eating macaque (Macaca irus). The arrangement of the sperm organelles in these primates is similar to that demonstrated in the sperm of other mammals, but notable species differences do occur. The bush baby spermatozoon, for instance, displays a complex system of membranes which envelop the neck and anterior midpiece. The human spermatozoon, unlike that of many other mammals, has no subacrosomal space or “perforatorium.” This structure is quite prominent, however, in lorisoid and macaque spermatozoa, and it is shown in the bush baby that its electron‐dense material extends posteriorly from the apex of the head in the space between the inner acrosome and nuclear membranes. In electron microscope preparations of anthropoid spermatozoa, the cell membrane which overlies the acrosome cap only occasionally displays the swollen distorted form seen commonly here in the spermatozoa of prosimiae, and previously in various other mammals.In contrast to the uniform spermatozoa obtained from the lorisoid and macaque monkeys, a significant proportion of spermatozoa in the human samples examined showed many abnormal features including misshapen sperm nuclei, cystic formations in the rostral region of the acrosome cap, and irregular alignment of mitochondria in the neck and midpiece.