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Mature Sperm (mature + sperm)
Selected AbstractsPreparing to move: Assembly of the MSP amoeboid motility apparatus during spermiogenesis in AscarisCYTOSKELETON, Issue 4 2005Maria Antonia Rodriguez Abstract We exploited the rapid, inducible conversion of non-motile Ascaris spermatids into crawling spermatozoa to examine the pattern of assembly of the MSP motility apparatus that powers sperm locomotion. In live sperm, the first detectable motile activity is the extension of spikes and, later, blebs from the cell surface. However, examination of cells by EM revealed that the formation of surface protrusions is preceded by assembly of MSP filament tails on the membranous organelles in the peripheral cytoplasm. These organelle-associated filament meshworks assemble within 30 sec after induction of spermiogenesis and persist until the membranous organelles are sequestered into the cell body when the lamellipod extends. The filopodia-like spikes, which are packed with bundles of filaments, extend and retract rapidly but last only a few seconds before giving way to, or converting into, blebs. Coalescence of these blebs, each supported by a dense mesh of filaments, often initiates lamellipod extension, which culminates in the formation of the robust, dynamic MSP fiber complexes that generate sperm motility. The same membrane phosphoprotein that orchestrates assembly of the fiber complexes at the leading edge of the lamellipod of mature sperm is also found at all sites of filament assembly during spermiogenesis. The orderly progression of steps that leads to construction of a functional motility apparatus illustrates the precise spatio-temporal control of MSP filament assembly in the developing cell and highlights the remarkable similarity in organization and plasticity shared by the MSP cytoskeleton and the actin filament arrays in conventional crawling cells. Cell Motil. Cytoskeleton 60:191,199, 2005 © 2005 Wiley-Liss, Inc. [source] Expression of Mina53, a product of a Myc target gene in mouse testisINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 2 2006MAKOTO TSUNEOKA Summary Recently we have identified a novel gene mina53 (mina), which is a direct transcriptional target of oncoprotein Myc. Mina53 protein was shown to be highly expressed in tumour cells and to play a role in cell proliferation. Here we report the expression of Mina53 in mouse testis, which contains proliferating cells and expresses many cancer-related genes. Immunohistochemical studies by using newly produced monoclonal antibody to Mina53 showed that Mina53 was expressed in the nuclei of spermatogonia. Mina53 was also expressed in meiotic prophase cells such as preleptotene, leptotene and zygotene, and weakly in early pachytene spermatocytes, but was absent in late pachytene spermatocytes, spermatids and mature sperm. The expression pattern of Mina53 was quite similar to that of proliferation cell nuclear antigen (PCNA). Using experimental cryptorchid testis, it was found that Mina53 was highly expressed in undifferentiated spermatogonia, which were PCNA-positive. These results suggest that Mina53 is prominently expressed in proliferating, undifferentiated spermatogonia, and plays a role in cell proliferation from the spermatogonial stage to the meiotic prophase in spermatogenesis, but not in meiotic divisions per se. [source] Living without mitochondria: spermatozoa and spermatogenesis in two species of Urodasys (Gastrotricha, Macrodasyida) from dysoxic sedimentsINVERTEBRATE BIOLOGY, Issue 1 2007Maria Balsamo Abstract. The spermatozoa of two species of Macrodasyida (Gastrotricha), Urodasys anorektoxys and U. acanthostylis, show an ultrastructural organization diverging from one another and from other gastrotrichs: their main peculiarity is in the absence of mitochondria. In U. anorektoxys, the acrosome is a long, twisted column inserted into the nucleus, which is basally cylindrical, and the flagellum shows rows of peculiar, large globules parallel to the axonemal doublets. In U. acanthostylis, the acrosome is completely cork-screwed and surrounds the nucleus, and the tail shows columnar accessory fibers. At present, the absence of mitochondria in the mature sperm, and the peculiar fingerprint aspect of condensed chromatin are the only traits shared by the two species. The features of the spermatozoa of these two species of Urodasys widen the range of different models of gastrotrich spermatozoa, and place the genus in a peculiar position, from the spermatological point of view, within the Macrodasyida. The loss of mitochondria in mature spermatozoa is possibly related to either the dysoxic habitat of the two species or a peculiar fertilization mechanism. [source] Expression profile of genes identified in human spermatogonial stem cell-like cells using suppression subtractive hybridizationJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 3 2010Jung Ki Yoo Abstract Spermatogenesis is the process by which testicular spermatogonial stem cells (SSCs) self-renew and differentiate into mature sperm in the testis. Maintaining healthy spermatogenesis requires proper proliferation of SSCs. In this study, we sought to identify factors that regulate the proliferation of SSCs. Human SSC (hSSC)-like cells were isolated from azoospermic patients by a modified culture method and propagated in vitro. After four to five passages, the SSC-like cells spontaneously ceased proliferating in vitro, so we collected proliferating (P)-hSSC-like cells at passage two and senescent (S)-hSSC-like cells at passage five. Suppression subtractive hybridization (SSH) was used to identify genes that were differentially expressed between the P-hSSC-like and S-hSSC-like cells. We selected positive clones up-regulated in P-hSSC-like cells using SSH and functionally characterized them by reference to public databases using NCBI BLAST tools. Expression levels of genes corresponding to subtracted clones were analyzed using RT-PCR. Finally, we confirmed the differential expression of 128 genes in positive clones of P-hSSC-like cells compared with S-hSSC-like cells and selected 23 known and 39 unknown clones for further study. Known genes were associated with diverse functions; 22% were related to metabolism. Fifteen of the known genes and two of the unknown genes were down-regulated after senescence of hSSC-like cells. A comparison with previous reports further suggests that known genes selected, SPP1, may be related to germ cell biogenesis and cellular proliferation. Our findings identify several potential novel candidate biomarkers of proliferating- and senescencet-hSSCs, and they provide potentially important insights into the function and characteristics of human SSCs. J. Cell. Biochem. 110: 752,762, 2010. © 2010 Wiley-Liss, Inc. [source] Polycystins: what polycystic kidney disease tells us about spermMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2004Abraham L. Kierszenbaum Abstract Experimental evidence indicates that the membrane-associated proteins polycystin-1 and polycystin-2 operate as a receptor-calcium channel complex that regulates signaling pathways essential for modulation of renal tubulogenesis. Polycystic kidney disease is characterized by defective renal tubular structure and results from mutations in either PKD1 or PKD2 genes. Recent data suggest that polycystin-1 and polycystin-2 might localize to primary cilium in principal cells of renal collecting tubules and are thought to act as mechanosensors of fluid flow and contents. Ciliary bending by fluid flow or mechanical stimulation induce Ca2+ release from intracellular stores, presumably to modulate ion influx in response to tubular fluid flow. Polycystins are also emerging as playing a significant role in sperm development and function. Drosophila polycystin-2 is associated with the head and tail of mature sperm. Targeted disruption of the PKD2 homolog results in nearly complete male sterility without disrupting spermatogenesis. Mutant sperm are motile but are unable to reach the female storage organs (seminal receptacles and spermathecae). The sea urchin polycystin-1-equivalent suPC2 colocalizes with the polycystin-1 homolog REJ3 to the plasma membrane over the acrosomal vesicle. This localization site suggests that the suPC2-REJ3 complex may function as a cation channel mediating acrosome reaction when sperm contact the jelly layer surrounding the egg at fertilization. Future studies leading to the identification of specific ligands for polycystins, including the signaling pathways, might define the puzzling relationship between renal tubular morphogenesis and sperm development and function. Mol. Reprod. Dev. 67: 385,388, 2004. © 2004 Wiley-Liss, Inc. [source] Morphological changes of sperm nuclei during spermatogenesis in the brown alga Cystoseira hakodatensis (Fucales, Phaeophyceae)PHYCOLOGICAL RESEARCH, Issue 2 2003Shinya Yoshikawa SUMMARY Morphological changes and chromatin condensation of sperm nuclei were observed during spermatogenesis in the fucalean brown alga Cystoseira hakodatensis (Yendo) Fensholt. Ultrastructural studies have shown that the mature spermatozoid has an elongated and concave nucleus with condensed chromatin. The morphological changes and the chromatin condensation process during spermatogenesis was observed. Nuclear size decreased in two stages during spermatogenesis. During the first stage, spherical nuclei decreased in size as they were undergoing meiotic divisions and the subsequent mitoses within the antheridium. During the second stage, the morphological transformation from a spherical into an elongated nucleus occurred. Afterwards, chromatin condensed at the periphery in each nucleus, and chromatin-free regions were observed in the center of the nucleus. These chromatin-free regions in the center of nucleus were compressed by the peripheral chromatin-condensed region. As the result, the elongated and concave nucleus of the mature sperm consisted of uniformly well-condensed chromatin. [source] Protamine ratio and the level of histone retention in sperm selected from a density gradient preparationANDROLOGIA, Issue 2 2009S. Hammoud Summary Fertile males express two forms of sperm nuclear proteins, protamine 1 (P1) and protamine 2 (P2), in roughly equal quantities, whereas some infertile men have been shown to have a reduction in protamine content and an increase in the level of histones retained in mature sperm. In this study, we assessed histone and protamine levels in spermatozoa isolated from different layers of a density gradient centrifugation column to evaluate the nuclear protein content of the sperm population selected. Protamine levels were measured using acid gel electrophoresis and immunofluorescence, and the percentage of cells retaining histones was evaluated using aniline staining and immunofluorescence. Our data suggests that there is an inverse correlation between P1/P2 ratio and the level of histone expression in the different layers of the density gradient. Paradoxically, the 90% layer had a lower P1/P2 ratio, which corresponded with an increase in histone expression. It is concluded that although the sperm population selected in the 90% layer of the density gradient columns had a lower P1/P2 ratio, it was yet similar to the P1/P2 ratio observed in previously screened fertile donors. [source] Phenotypic interactions of spinster with the genes encoding proteins for cell death control in Drosophila melanogasterARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 3 2010Akira Sakurai Abstract The spin gene was first identified by its mutant phenotype, which is characterized by extremely strong mate refusal by females in response to male courtship in Drosophila. Spin mutants are also known to be accompanied by a remarkable reduction in programmed cell death in the reproductive and nervous systems. To better understand the molecular functions of spin, we searched for its genetic modifiers. Forced expression of spin+ in somatic cells as driven by ptc-Gal4 in the testis resulted in the invasion of mature sperm into the anterior testes tip, which is otherwise occupied only by immature germ cells. To obtain genes that modulate spin's effect, the gain-of-function spin phenotype was observed in the presence of a chromosome harboring an EP or GS P-element insertion, which initiates transcription of the genomic sequence neighboring the insertion site. We isolated th and emc as suppressors of spin and atg8a as a gene that reproduces the spin phenotype on its own. th encodes Inhibitor of apoptosis-1, and mammalian Id genes homologous to emc are known to inhibit apoptosis. atg8a encodes a protein essential for autophagy. These results suggest that spin promotes cell death mechanisms that are regulated negatively by th and emc and positively by atg8a. © 2010 Wiley Periodicals, Inc. [source] Sperm ultrastructure and spermiogenesis in two Exogone species (Polychaeta, Syllidae, Exogoninae)INVERTEBRATE BIOLOGY, Issue 4 2002Adriana Giangrande The spermatozoa of Exogone naidina and E. dispar are characterized by a prominent bell-shaped acrosome, a spheroidal nucleus, and a conventional flagellum. During spermiogenesis, the acrosomal vesicle undergoes conspicuous modifications leading to its final bell shape with a posterior opening. The subacrosomal material initially shows radiating filaments but in mature sperms it appears as a meshwork of electron-opaque material. The acrosomal axis is oblique with respect to the main longitudinal sperm axis. The chromatin is arranged in electron-opaque strands in the early spermatids, then becomes amorphous, and is finally organized in filaments in mature sperms. Centrioles are orthogonally arranged beneath the nucleus and fibers radiate from the distal centriole to contact the plasma membrane and the single mitochondrion. The latter is located eccentrically on the side of the nucleus opposite the acrosome. A disk-shaped structure is evident beneath the distal centriole. The flagellar axoneme has a 9+2 microtubule pattern. A conspicuous glycocalyx surrounds the flagellar plasma membrane, and an electron-lucent space is present between these two structures at the distal tip of the flagellum. We compare the sperm morphology of these two species of Exogone with that described in other members of the subfamily Exogoninae. The fine structure of these two species supports the occurrence of an ent-aquasperm type within Exogoninae, in accordance with the brood strategy present within this subfamily. The mode of reproduction is of taxonomic importance for defining subfamilies within Syllidae, and is likely also of phylogenetic significance. Because epitoky is probably plesiomorphic, the ent-aquasperm type found in Exogoninae can be considered a derived feature within Syllidae. [source] Differential expression of lysosomal associated membrane protein (LAMP-1) during mammalian spermiogenesisMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 2 2003Ricardo D. Moreno Abstract The mammalian acrosome is a secretory vesicle of mature sperms that plays an important role in fertilization. Recent evidence had pointed out that some components found at endosomes in somatic cells are associated with the developing acrosome during the early steps of spermiogenesis. Moreover, the mammalian acrosome contains many enzymes found within lysosomes in somatic cells. In this work, we studied the dynamics of some components of the endosome/lysosome system, as a way to understand the complex membrane trafficking circuit established during spermatogenesis. We show that the cation independent-mannose-6-phosphate receptor (CI-MPR) is transiently expressed in the cytoplasm of mid-stage spermatids (steps 5,11). On the other hand, ,-adaptin, an adaptor molecule of a complex involved in trafficking from the Golgi to lysosomes, was expressed in cytoplasmic vesicles only in pachytene and Cap-phase spermatids (steps 1,5). Our major finding is that the lysosomal protein LAMP-1 is differentially expressed during spermiogenesis. LAMP-1 appears late in spermatogenesis (Acrosome-phase) contrasting with LAMP-2, which is present throughout the complete process. Both proteins appear to be associated with cytoplasmic vesicles and not with the developing acrosome. None of the studied proteins is present in epididymal spermatozoa. Our results suggest that the CI-MPR could be involved in membrane trafficking and/or acrosomal shaping during spermiogenesis. Mol. Reprod. Dev. 66: 202,209, 2003. © 2003 Wiley-Liss, Inc. [source] | |||||||||||||