The Journey of the Porcine Spermatozoa from Its Origin to the Fertilization Site: The Road In Vivo vs. In Vitro
Juan Carlos Gardón, Katy Satué in Biotechnologies Applied to Animal Reproduction, 2020
After spermatozoa penetration of the egg vestments, the acrosome-reacted sperm goes through the perivitelline space and adheres its equatorial region and fuses with the egg plasma membrane, the oolemma (sperm-egg fusion). The cortical reaction then takes place, which results in changes to the structure of the ZP and its proteins (Wolf, 1981). This converts the ZP into a ‘hardened’ state, which helps to block polyspermy. This particular phenomenon is of special interest in porcine because this species has a high incidence of polyspermy under in vitro conditions (Funahashi et al., 2000). The spermatozoon next penetrates the oocyte and introduces its nucleus into the ooplasm (Yanagimachi, 1994b). Despite the continuous advance in the knowledge of the physiology of gametes as well as their interaction, there are still many aspects to be clarified to efficiently extrapolate the in vivo environment in the oviduct to the in vitro conditions in the laboratory. Many strategies and protocols have been carried out so far; however, the efficiency obtaining quality embryos in vitro remains lower than that of them in vivo counterparts.
Regulation of Reproduction by Dopamine
Nira Ben-Jonathan in Dopamine, 2020
After digesting a hole in the ZP, the sperm head enters the egg’s parenchyma and the membranes of the two cells fuse. The next critical step is prevention of polyspermy, given that polyploidy is not compatible with life. Within seconds of contact with a sperm, Na+ channels in the egg’s membrane are activated, and a rushed entry of sodium depolarizes the egg’s resting potential of –70 mV. The fast, although transient, electrical block to polyspermy is followed within 10–15 min by the cortical reaction. The lysosome-like cortical granules are released from the egg’s membrane, destroying the oocyte’s sperm receptors, and modifying the extracellular matrix around the egg, which becomes impenetrable to additional sperm entry. Although there are several publications on DAR expression and putative functions of DA in Drosophila, Xenopus, and Zebrafish oocytes, there are no comparable records on mammalian oocytes.
The Energetics of Fish Sperm Motility
Claude Gagnon in Controls of Sperm Motility, 2020
In fish with external fertilization, the pattern is directly put in contact (usually after simultaneous release). For motility, spermatozoa rely entirely on endogenous energy readily available and transportable by appropriate shuttle to cover the needs for a short period of high activity. The primitive structure of the spermatozoa (limited midpiece, lack of important endogenous metabolic substrates) seems to be compensated by a complex capacity of biosynthesis and reuse of various compounds and by a contribution (sometimes limited) of all metabolic pathways, at least to cover the basal metabolism of the spermatozoa during storage and before their release and activation. The external fertilization model has been documented from studies on rainbow trout and may be representative of fresh water fish. In this group, gametes survival is usually short after release in fresh water; spermatozoa are sensitive to osmotic shock and the cortical reaction rapidly prevents fertilization in eggs. In these conditions, the strategy of the spermatozoa is to move very rapidly during a short period of time and enter into the micropyle before it becomes incapacitated by hypoosmotic shock and before the cortical reaction occurs. The preaccumulated amount of ATP seems sufficient to cover the energetic demand for motility. In some cases, it may be that the endogenous ATP is not sufficient because of the decline in mitochondrial respiration capacity of the mitochondria due to aging (a long period of in vitro or in vivo storage) or possibly bad husbandry in fish farms (anoxic conditions, inappropriate feeding regime, etc.).
A tree of life? Multivariate logistic outcome-prediction in disorders of consciousness
Published in Brain Injury, 2020
Inga Steppacher, Peter Fuchs, Michael Kaps, Fridtjof W. Nussbeck, Johanna Kissler
Various cerebral measures of information processing have also been found to correlate with outcome (see, for example (8,9)). These include several, mostly auditory, electroencephalographic event-related potentials (ERPs). For example, the absence of the N100, an index of cortical sensory stimulus registration, is considered to be predictive of a negative outcome (10). The presence of the so-called mismatch negativity (MMN), indicating an automatic detection of deviant stimuli in continuous auditory stimulation streams, on the other hand, has been shown to be a positive sign (11,12). The presence of a P300, reflecting higher-order stimulus discrimination, also often correlates with a positive outcome (12,13). Another recently discussed and possibly very promising ERP is the N400, the cortical reaction to semantic violations in spoken speech. Although rarely found in patients, its presence correlates highly with a positive outcome (14).
A retrospective analysis of artificial oocyte activation in patients with low or no fertilisation in intracytoplasmic sperm injection cycles
Published in Journal of Obstetrics and Gynaecology, 2022
Kevin K. W. Lam, Jacki Y. Y. Wong, Tak-Ming Cheung, Raymond H. W. Li, Ernest H. Y. Ng, William S. B. Yeung
Successful oocyte activation is triggered by a sperm borne soluble factor, the phospholipase C (PLC) zeta (Kashir et al. 2010). It is generally agreed that PLC-zeta hydrolises inositol 4, 5-bisphosphate (PIP2), producing inositol triphosphate (IP3) which induces calcium ion (Ca2+) oscillation through interaction with receptors on the endoplasmic reticulum of oocytes (Swain and Pool 2008). Upon oocyte activation, a series of biological events, such as cortical reaction, resumption of meiosis and formation of pronuclei, leading to successful fertilisation (Ducibella et al. 2006).
Related Knowledge Centers
- Cell Cortex
- Glycosaminoglycan
- Peroxidase
- Polyspermy
- Protease
- Fertilisation
- Perivitelline Space
- Hyalin
- Exocytosis
- Endoplasmic Reticulum