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Capacitation, the Acrosome Reaction, and Motility in Mammalian Sperm
Published in Claude Gagnon, Controls of Sperm Motility, 2020
Susan S. Suarez, John W. Pollard
The acrosome is a membrane bounded organelle containing a variety of hydrolytic enzymes (see Reference 1 for a list). At least some of these enzymes, most notably acrosin,47 assist in the penetration of the zona pellucida by weakening its structure. The enzymes are evidently released via a reaction that resembles exocytosis. It was first reported in 1958 by Austin and Bishop,48 and the process was described in 1967 by Barros et al.49 The major events of the acrosome reaction can best be seen in electron micrographs as shown in Figure 2, taken from Suarez et al.50 The first sign of the acrosome reaction, which can occur in human spermatozoa within 1 min of the application of a stimulus, is the apparent decondensation of the acrosomal contents.51 This is followed by the fusion of the plasma membrane in limited areas with the underlying outer acrosomal membrane. Fenestration occurs at the points of fusion, followed by the formation of vesicles comprised of plasma and outer acrosomal membranes.51,52 Acrosomal enzymes may escape by passing between the vesicles or may be exposed after the vesicles are sloughed off. In the latter case, they may be adherent to the exposed surface of the inner acrosomal membrane.53
Prostaglandins and Semen
Published in Murray D. Mitchell, Eicosanoids in Reproduction, 2020
Before a mature, ejaculated spermatozoon can fertilize an egg, it undergoes a process termed capacitation which allows it to acrosome react, a procedure associated with the ingress of calcium ions, resulting in the loss of the acrosome. The acrosome reaction is an essential preliminary to sperm-oocyte fusion. This fusion is not normally possible when the egg and the sperm are from different species since a block to interspecific fertilization is found at the zona pellucida, which surrounds the egg, the vitelline membrane, or both. In the case of the hamster, the block is solely at the zona pellucida, which can be removed with tryspin, allowing a human (or any other species) spermatozoon to fuse with and “fertilize” the egg. The observation of this phenomenon, and in particular the scoring of the decondensed sperm heads, allows an objective assessment of the acrosome reaction.
Regulation of Reproduction by Dopamine
Published in Nira Ben-Jonathan, Dopamine, 2020
ZP3, a glycoprotein in the zona pellucida (ZP), serves as a sperm recognition site. Species-selective sperm “receptors” account, in part, for the failure of fertilization between germ cells from unrelated species. The acrosome reaction is triggered by contact of the sperm with the egg, enabling sperm penetration into the ZP and its fusion with the oocyte’s membrane [80]. The acrosome reaction involves calcium-dependent release of hyaluronidase and exposure of masked membrane domains in the sperm’s head. In one study, heat-solubilized human ZP was used to study the induction of the acrosome reaction in capacitated human spermatozoa [81]. Pimozide, a D2R antagonist, prevented the activation of voltage-operated calcium channels (VOCCs), which mediate acrosomal exocytosis in response to contact with the ZP. In contrast, L-type VOCCs inhibitors such as nifedipine and verapamil failed to inhibit the ZP-mediated acrosome reaction.
Mapping the human sperm proteome – novel insights into reproductive research
Published in Expert Review of Proteomics, 2023
Mika Alexia Miyazaki, Raquel Lozano Guilharducci, Paula Intasqui, Ricardo Pimenta Bertolla
The consequences of the absence of Testis-expressed protein 101 (TEX101), a validated biomarker of male infertility, were also investigated, and it was noticed that in infertile men with a natural absence of TEX101. This protein is a glycosylphosphatidylinositol-anchored protein (GPI-AP) and in mice was found to be expressed in precursors of adult-type germ cells, spermatogenesis cells, and seminiferous tubules cells in mice [29,30]. Although knockout mice Tex101−/− background presented normal sperm morphology structure and motility, they were not fertile due to failure to induce pregnancy [31]. Other important proteins for fertilizing process were also downregulated, such as Acrosin, Acrosin-binding protein (ACRBP) and Izumo sperm-egg fusion protein 3 (IZUMO3), that participate in the acrosome structure and function, and Zona pellucida-binding protein 2 (ZPBP2), that acts in spermatozoa-zona pellucida binding [32]. IZUMO3 is a protein from protein family IZUMO, exclusively expressed on membrane of cells testes. In mice Izumo3-/- model, fertilization rates were lower compared to the wild-type and heterozygous mutants. Moreover, litter sizes were also significantly reduced. This outcome is likely due to a deficient acrosome [33]
Toxicity and antimicrobial effect of silver nanoparticles in swine sperms
Published in Systems Biology in Reproductive Medicine, 2020
Francisco Pérez-Duran, Laura Susana Acosta-Torres, Paloma Netzayeli Serrano-Díaz, Irma Arcelia Toscano-Torres, Ingrid Brenda Olivo-Zepeda, Edwin García-Caxin, Rosa Elvira Nuñez-Anita
A volume of 0.5 ml of semen was placed in Eppendorf tubes and centrifuged at 2000 rpm for 10 minutes. The sperm button was suspended in 100 μl of fixing buffer (0.2% glutaraldehyde, 0.5 M Tris; final pH 7.4). According to the procedure by Fraser and Herod (1990), the sperm was stained with chlortetracycline (CTC, Sigma Aldrich) (stock solution, 0.0020 gr of CTC diluted in 3 ml buffer (20 mM Tris, NaCl 130 mM, 5 mM L-cisteína pH 7.8). Mixing a suspension of 5 μl of fixed spermatozoa with 5 μl of CTC on a glass slide was then incubated at room temperature during 60 seconds. Subsequently, a drop of 1.4-Diaza-bicyclo (2.2.2) octane (0.22 M, DABCO, Sigma Aldrich) in 90% glycerol was added to preserve fluorescence. Incubation took place for 24 h at room temperature in the dark. Sperm smears were analyzed under fluorescence confocal microscopy and photographed (FluoView FV1000 Confocal Microscope, Olympus). The results are described as distinctive staining patterns as follows: Non-capacitated spermatozoa showed uniform fluorescence in the head and intact acrosome, whereas capacitated spermatozoa presented fluorescence concentrated in the acrosomal region, non-fluorescent band in the post acrosomal region, and intact acrosome. Sperm with acrosome reaction, presented no fluorescence in the head but a thin band in the equatorial region. Counts of a minimum of 200 sperm cells per preparation were carried out.
Prediction of male infertility by the World Health Organization laboratory manual for assessment of semen analysis: A systematic review
Published in Arab Journal of Urology, 2018
Amir S. Patel, Joon Yau Leong, Ranjith Ramasamy
Another absolute predictor for male infertility is the detection of globozoospermia on semen analysis. It is a rare but severe form of teratozoospermia, characterised by the presence of round-headed spermatozoa lacking an acrosome [42]. The acrosome contains the digestive enzyme, acrosin, which is essential for binding and penetration of the zona pellucida of the ovum. It also facilitates cervical mucus penetration and intrauterine sperm migration. It also participates in chromatin decondensation in the oocyte [43]. Considering these factors, we can understand how globozoospermic cells have difficulties adhering and fusing with the oocyte membrane, ultimately causing infertility. A microscopic image of globozoospermic spermatozoa can be seen in Fig. 2 [44].