Diadem/crater defects in spermatozoa from two related angus bulls

The diadem/crater defect was studied over several months in two related 20-month-old Angus bulls. In bull 1, diadem/crater defects were present in 2-99% of ejaculated spermatozoa at various times during the evaluation period. In bull 2, affected cells varied from 20% to 94%, with other abnormalities (head and acrosome defects, coiled tails, proximal cytoplasmic droplets) also common. Single sire mating trials conducted over 26 days during an apparent recovery phase showed normal fertility (approximately 50% pregnancies per estrus exposed). Both resting and gonadotropin-releasing hormone (GnRH)-stimulated testosterone values were within nor-mal limits. Histopathological evaluation of testes showed no obvious hypoplastic, inflammatory, or degenerative condition. Electron microscopy of ejaculated spermatozoa demonstrated the characteristic diadem pattern of craters in the equatorial region of the head. Many cells from bull 2 contained large craters in other regions of the nucleus. Electron microscopy of testicular tissue demonstrated nuclear invaginations lined by a single unit membrane in round spermatids. Lesions in elongated spermatids were more pronounced, with curling of the nucleus and large membrane-filled cavities in the chromatin occurring in addition to craters in the equatorial region of the nucleus.     

The length of a short sperm: Elongation and shortening during spermiogenesis in Cotesia congregata (Hymenoptera,Braconidae)

The spermatozoon of the parasitoid wasp Cotesia congregata is an extremely short gamete measuring less than 7 μm; it is as yet the shortest flagellated sperm to be identified. The mature sperm consists of an acrosome, surrounded by an extra cellular coat, a condensed nucleus, two uncoiled mitochondrial derivatives and a short axoneme. Testes of young adults contain a continuum of differentiation stages. Initially, the flagellum is approximately 5 μm long. It conserves its length in round, elongated and mature spermatids, but is reduced to less than 3 μm in mature spermatozoa. The nucleus is 2 μm in diameter when round, 10 μm long when it becomes a long boat-hull shaped filament, and then reduces to 3.6 μm. Thus, during development the gamete reaches a total length of 15 μm before finally reducing to less than half that length. Some traits of mature sperm anatomy are similar to related species of the Braconidae family, but others seem to be specific and could be due to the shortness of the cell. This uncommon elongation and subsequent shortening of such a tiny flagellated cell constitutes a model for both nucleus and cilium development.     

Characterization of boar sperm cytoskeletal cylicin II as an actin-binding protein

The presence of actin-binding proteins in the perinuclear theca of boar spermatozoa has been investigated, using stepwise extractions of proteins from sperm heads. Proteins extracted with the alkaline buffer 1M Na(2)CO(3), pH 11, were found to contain a 66kDa protein that binds F-actin in actin pelleting assays. Sequence studies and immunological characterization with antibodies specific for human cylicin II identified the 66kDa protein as the homologue of bovine and human cylicin II. Immunocytochemical studies showed the presence of porcine cylicin II in the acrosomal region of round spermatids and in the postacrosomal region of late spermatids and spermatozoa, in agreement with the previously described localization of cylicins. Taken together, the results suggest that cylicin II, a protein of the sperm perinuclear cytoskeleton, is a novel actin-binding protein, which probably plays a role in the actin-related events that occur during spermiogenesis and the early events of fertilization.     

Reinvestigation of the ultrastructure of spermiogenesis and the spermatozoon of Hymenolepis nana (Cestoda, Cyclophyllidea), parasite of the small intestine of Rattus rattus.

Spermiogenesis in Hymenolepsis nana begins with the formation of a differentiation zone. This is limited at the front by arched membranes, is surrounded by cortical microtubules associated with 12 crested-like bodies, and contains a single centriole made up of doublets. The distal centriole gives rise to a flagellum that grows at the same pace as the cortical microtubules. Migration of the nucleus takes place after the formation of the flagellum. It is followed by the separation of the old spermatid from the residual cytoplasm. The mature H. nana spermatozoon is filiform and lacks mitochondria. The axoneme, of the 9 + "1" pattern of the Platyhelminthes, does not reach the extremities of the spermatozoon. The nucleus is electron dense and is in close contact with the axoneme around which it coils in a spiral making an angle of 10 degrees to 15 degrees with the spermatozoon axis. The cortical microtubules follow a 10 degrees to 15 degrees helicoidal path along almost their whole length, except at their posterior extremity, where they are parallel to the spermatozoon axis. H. nana is distinguished by the early development of 12 crested-like bodies of different lengths and by the existence of a single centriole in the differentiation zone. Such a high number of crested-like bodies had never previously been reported in a cestode.     

Heterotypic tubular connections at the endoplasmic reticulum–Golgi complex interface

Electron microscopy and cryoimmunocytochemistry were used to characterize tubular connections in the secretory pathway using rat spermatids as model. Our results support the existence of a complex tubular network enriched in the Golgi matrix protein GM130 that transiently joins the cis-Golgi side and the endoplasmic reticulum. These tubules occasionally contain the endoplasmic reticulum resident protein PDI but not COPII complexes or KDEL receptor. At the lateral edges of the stacks tubules were seen to connect cisternae belonging to the same or adjacent stacks. These connections were observed in all cisternae but preferentially on the cis side. Giantin, Gos28 and Rab6 were detected in the tubules; importantly, we reported the presence of cis-trans heterotypic connections between cisternae. On the trans-Golgi side, we occasionally observed tubules highly immunoreactive for Rab6 connecting the stack with the forming acrosome. Together, our results support the existence of transient continuities throughout the secretory pathways.     

Nm23/NDP kinases in human male germ cells: role in spermiogenesis and sperm motility?

Nucleoside diphosphate (NDP) kinases, responsible for the synthesis of nucleoside triphosphates and produced by the nm23 genes, are involved in numerous regulatory processes associated with proliferation, development, and differentiation. Their possible role in providing the GTP/ATP required for sperm function is unknown. Testis biopsies and ejaculated sperm were examined by immunohistochemical and immunofluorescence microscopy using specific antibodies raised against Nm23-H5, specifically expressed in testis germinal cells and the ubiquitous NDP kinases A to D. Nm23-H5 was present in sperm extract, together with the ubiquitous A and B NDP kinases (but not the C and D isoforms) as shown by Western blotting. Nm23-H5 was located in the flagella of spermatids and spermatozoa, adjacent to the central pair and outer doublets of axonemal microtubules. High levels of NDP kinases A and B were observed at specific locations in postmeiotic germinal cells. NDP kinase A was transiently located in round spermatid nuclei and became asymmetrically distributed in the cytoplasm at the nuclear basal pole of elongating spermatids. The distribution of NDP kinase B was reminiscent of the microtubular structure of the manchette. In ejaculated spermatozoa, the proteins presented specific locations in the head and flagella. Nm23/NDP kinase isoforms may have specific functions in the phosphotransfer network involved in spermiogenesis and flagellar movement.