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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.
Immunopathogenesis and Therapy of Gonadal Disorders and Infertility
Published in George S. Eisenbarth, Immunotherapy of Diabetes and Selected Autoimmune Diseases, 2019
There are several potential mechanisms by which antisperm antibodies could interfere with reproduction. The first of these could occur within the testes in the form of degeneration of spermatids and phagocytosis by the Sertoli cells.37 Sperm motility may be affected and cervical mucous penetration may be prevented.38 The activation of macrophages may increase the resultant clearing of spermatozoa.39 Sperm cytotoxicity may occur in those portions of the female reproductive tract where complement levels are in the range of plasma.40 Defects in capacitation, the acrosome reaction, interference with sperm-egg interaction, and embryonal loss could all occur.41,42 In unexplained instances of infertility it has been estimated that up to 30% of cases may be due to immunologic causes.43
Effects of zinc deficiency on impaired spermatogenesis and male infertility: the role of oxidative stress, inflammation and apoptosis
Published in Human Fertility, 2020
Asghar Beigi Harchegani, Heydar Dahan, Eisa Tahmasbpour, Hamid Bakhtiari kaboutaraki, Alireza Shahriary
Zinc plays a multifaceted role in sperm function and fertility of men through various mechanisms (Figure 1). It is now considered as one of the main nutrients in the male reproductive system for proper sperm formation and motility (Khan et al., 2011). Zinc is not only a cofactor for various proteins involved in antioxidant defence, and electron transport, but also it is essential for the production, storage, secretion and function of numerous enzymes such as RNA polymerases, alcohol dehydrogenase, carbonic anhydrase (CA), alkaline phosphatase that are important in normal function of spermatozoa and prevention of sperm damage (Omu et al., 2015). Numerous studies have shown positive effects of zinc on semen quality and male factor infertility (Guzikowski et al., 2015). Zinc is necessary for testicular development and normal spermatogenesis (Colagar et al., 2009). It is also a main factor for DNA replication and packaging, DNA transcription, protein synthesis, cell proliferation, differentiation and apoptosis, which are major parts of sperm development (Chia et al., 2000; Croxford, McCormick, & Kelleher, 2011). Zinc has a regulatory function in steroid hormone synthesis as a critical step for normal spermatogenesis. It plays a regulatory role in the process of sperm capacitation and acrosome reaction (Kothari & Chaudhari, 2016). Zinc protects Leydig cells from damage due to its anti-oxidative properties (Colagar et al., 2009). As the body has no specialized zinc storage system, a daily intake of zinc is, therefore, critical for normal function of the male reproductive system.
Role of reactive oxygen species in male infertility: An updated review of literature
Published in Arab Journal of Urology, 2018
Hillary Wagner, Julie W. Cheng, Edmund Y. Ko
For optimal sperm function and for fertilisation to occur, there must be a balance of ROS and antioxidants (Fig. 3 ). ROS induces cyclic adenosine monophosphate (cAMP) in spermatozoa that inhibits tyrosine phosphatase leading to tyrosine phosphorylation [25]. In particular, H2O2 stimulates capacitation via tyrosine phosphorylation triggering a cell signalling cascade [26]. Capacitation not only requires ROS, but it can be inhibited by catalase (CAT) [26]. It has been described that high levels of ROS promote the acrosome reaction, whereas the presence of CAT or superoxide dismutase (SOD) inhibits the acrosome reaction [27]. The mechanism of inducing the acrosome reaction appears to be ROS-modulated tyrosine phosphorylation [26]. Motility can also be affected by ROS. Hyperactivation is increased when spermatozoa are exposed to ROS [28]. ROS-mediated tyrosine phosphorylation in the flagellum causes hyperactivation [13,25]. Tyrosine phosphorylation also augments sperm membrane binding to the zona pellucida ZP-3 protein, promoting sperm–oocyte fusion [29].
Effect of combined calcium, magnesium, vitamin C and E supplementation on seminal parameters and serum oxidative stress markers in fructose-induced diabetic Wistar rats
Published in Archives of Physiology and Biochemistry, 2022
Iya Eze Bassey, Daniel Ewa Ikpi, Idongesit Kokoabasi Paul Isong, Uwem Okon Akpan, Chibuzor Charles Onyeukwu, Nnenna Princess Nwankwo, Inyene Gordon Udofia
Diabetes mellitus is a disease that affects both glucose and mineral metabolism. Low magnesium levels have been associated with increased thromboxane level which leads to increased vasoconstriction and nitric oxide which may cause premature ejaculation (Omu and Fernandes 2001). Calcium is also needed to initiate the acrosome reaction with its accompanying release of enzymes and membrane alteration required for successful egg-sperm interaction as well as maximum motility of sperm cells. Bassey et al. (2019) showed that calcium and magnesium levels were significantly lower in seminal plasma of diabetic and non-diabetic infertile males compared to that in fertile males. These findings suggest that infertile males may benefit from calcium and magnesium supplementation.