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Mature oocyte, the outer surface of the zona pellucida looks spongy. SEM, 1200X. 

Mature oocyte, the outer surface of the zona pellucida looks spongy. SEM, 1200X. 

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Article
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The zona pellucida (ZP) is a unique extracellular coat surrounding the maturing oocyte, during ovulation, fertilization, and early embryo development. It is formed by three/four glycoproteins. Ultrastructural data obtained with transmission (TEM) and scanning electron microscopy (SEM) were compared with molecular data on the glycoproteins network f...

Citations

... U myszy ZP cechuje się w tym czasie zmniejszeniem zawartości porów w wyniku wzrostu jej gęstości (47). Zgodnie z obserwacjami ludzkich embrionów w mikroskopie elektronowym sugeruje się, że wiązki filamentów na wewnętrznej powierzchni ZP ulegają fuzji i kondensacji (20). ...
Article
In mammals, oocytes, fertilized eggs and pre-implantation embryos are surrounded by an acellular zona pellucida (zona pellucida – ZP). This structure has a fibro-spongy character but it undergoes constant modifications throughout its existence depending on many internal and external factors. ZP consists of glycoproteins marked as ZP1, ZP2, ZP3 and ZP4, the presence of which is species different. ZP1 and probably ZP4 molecules stabilize the fibrillary skeleton of the zona pellucida formed of ZP2 and ZP3 protein polymers which are ligands for specific spermatozoid receptors. The oligosaccharide chains of ZP3 are responsible for the primary attachment of the male gamete which induces the acrosomal reaction. ZP2 enhances this connection by secondary binding to an acrosome-free spermatozoid. Additionally, oviductal specific glycoprotein 1 which plays a role in interspecific oocyte-sperm interactions, appears around the postovulatory oocyte surrounded by ZP. In addition, this protein modifies the resistance of ZP to the action of proteases released as a result of the cortical reaction during polyspermia block. After fertilization, ZP not only protects the egg and then the embryo until implantation, but also has an embryotrophic effect. Understanding the molecular basics of the structure and properties of ZP can significantly improve animal fertility as well as reproductive rates.
... Polyspermy is inhibited by the hardening of the zona pellucida with the surface reaction of the cell membrane of the ooplasm after membrane fusion with sperm and oocyte 15 . Exocytosis of cortical granules and modification of the zona pellucida occur within a few minutes after fertilisation 16 . After exocytosis of the cortical granule, ovastacin and spark inhibited sperm binding to zona pellucida within a few minutes to 30 min [17][18][19][20][21][22] . ...
Article
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Shipment of laboratory rats between animal facilities is frequently performed using special containers. However, the shipment of live animals is associated with potential risks of infectious diseases, escape and death during shipment and animal welfare issues. The transport of cold-stored sperm avoids such risks; however, there have been no reports on cold storage of rat sperm. We previously reported that dimethyl sulfoxide (DMSO) and quercetin maintained the motility and fertilising abilities of cold-stored mouse sperm stored for 10 days. The present study investigated the efficacy of DMSO and quercetin in the cold storage of rat sperm. Quercetin maintained motility and fertility of cold-stored rat sperm stored for 5 days. After in vitro fertilisation using cold-stored sperm, pronuclear and two-cell embryos developed normally to pups following embryo transfer. Therefore, we demonstrated that live pups could be obtained from sperm transported using the cold-storage system. We conclude that cold storage of rat sperm may provide an efficient system for transporting rat resources as an alternative to shipping live animals.
... It is generally believed that zona Pellucida (ZP) outside embryo cells could protect the embryo from external damage [20] . The surface of ZP presents reticular structure. ...
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Objective: This study aimed to clarify the infection state of early embryos by HBV and the effect of HBV infection on embryo development. Methods: In vitro culture was carried out on the fresh surplus embryos from infertile couples on the third day (D3) who received routine in vitro fertilization and embryo transfer (IVF-ET) treatment. The embryo cells were infected in vitro by the serum of HBV infected patients with different viral loads. HBsAg quantity in the supernatant secreted by embryo and HBV mRNA in embryo cells were detected. The development of embryo cells after HBV infection was evaluated by embryo morphological parameter score and fragment score in embryo cells. Results: From May 2013 to July 2015, 238 cases of D3 fresh surplus embryos from 120 infertile couples and 128 samples of embryo culture supernatant were collected. The HBsAg positive rate in the supernatant of embryos in the high viral load infection group was significantly higher than that in the low viral load infection group (40.0% vs.15.6%, p<0.05). HBV mRNA was detected in 2 of 17 HBsAg positive embryos. The scores of embryos in the high load HBV culture solution group were higher than those in the low load group (p=0.04). There was one formed blastocyst in low load HBV culture group, but there was no blastocyst formation in all embryo cells of high load group (p<0.001). Conclusion: The results suggest that embryo cells can be directly infected by HBV in vitro. HBV infection affects the development of embryos.
... The ZP plays important roles both during fertilization, where it acts to block polyspermy, and during embryo development, to protect the growing embryo. EM showed that structural changes in the ZP are associated with these changing roles, revealing remarkable architectural plasticity in this large extracellular scaffold [31,33,59,60]. ...
... (a) Thin-section TEM micrograph through the cortex of a mouse oocyte, showing the extent of the zona pellucida (ZP) and numerous transzonal projections (*), which are thin cytoplasmic extensions of the cumulus granulosa cells connecting them to the oocyte, penetrating through it [30]. (b) SEM micrograph of a mature human oocyte, showing the porous nature of the outer surface of the ZP (×1200)[31]. (c) SEM micrograph of the outer surface of the ZP of a mature human ooctye at a higher magnification, showing the filamentous-like arrangement of globule-bearing structures (×50 000)[31]. ...
... (b) SEM micrograph of a mature human oocyte, showing the porous nature of the outer surface of the ZP (×1200)[31]. (c) SEM micrograph of the outer surface of the ZP of a mature human ooctye at a higher magnification, showing the filamentous-like arrangement of globule-bearing structures (×50 000)[31]. (d ) SEM micrograph at a very high magnification of an unfertilized mouse oocyte, showing a branch of the filamentous structure of the ZP (×50 000)[32]. ...
Article
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Mammalian gametes-the sperm and the egg-represent opposite extremes of cellular organization and scale. Studying the ultrastructure of gametes is crucial to understanding their interactions, and how to manipulate them in order to either encourage or prevent their union. Here, we survey the prominent electron microscopy (EM) techniques, with an emphasis on considerations for applying them to study mammalian gametes. We review how conventional EM has provided significant insight into gamete ultrastructure, but also how the harsh sample preparation methods required preclude understanding at a truly molecular level. We present recent advancements in cryo-electron tomography that provide an opportunity to image cells in a near-native state and at unprecedented levels of detail. New and emerging cellular EM techniques are poised to rekindle exploration of fundamental questions in mammalian reproduction, especially phenomena that involve complex membrane remodelling and protein reorganization. These methods will also allow novel lines of enquiry into problems of practical significance, such as investigating unexplained causes of human infertility and improving assisted reproductive technologies for biodiversity conservation.
... 23 In response to an ovulatory surge in luteinizing hormone, this cushion thickens to form the zona pellucida. 24 The zona pellucida is a transparent membrane which is composed of a hyaluronic acid and specialized glycoproteins that protects the egg during release from the ovary and facilitates fertilization. 25 If matrix molecules or their crosslinkers are disrupted or missing from the zona pellucida, oocyte release and fertilization are impaired, resulting in infertility or sterility. ...
Article
Impact statement: Extracellular matrix in the womb regulates the initiation, progression, and completion of a healthy pregnancy. The composition and physical properties of extracellular matrix in the uterus and at the maternal-fetal interface are remodeled at each gestational stage, while maladaptive matrix remodeling results in obstetric disease. As in vitro models of uterine and placental tissues, including micro-and milli-scale versions of these organs on chips, are developed to overcome the inherent limitations of studying human development in vivo, we can isolate the influence of cellular and extracellular components in healthy and pathological pregnancies. By understanding and recreating key aspects of the extracellular microenvironment at the maternal-fetal interface, we can engineer microphysiological systems to improve assisted reproduction, obstetric disease treatment, and prenatal drug safety.
... Accordingly, transmission and scanning EM studies of human embryos suggest that filament bundles on the inner surface of the ZP are fused together and condensed (Familiari, Heyn, Relucenti, & Sathananthan, 2008). Consistent with these observations, the ZP of embryos becomes thinner (Garside, Loret de Mola, Bucci, Tureck, & Heyner, 1997;Pelletier, Keefe, & Trimarchi, 2004) and stiffer (Drobnis, Andrew, & Katz, 1988;Sun, Nelson, & Greminger, 2005). ...
Article
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Fertilization by more than one sperm causes polyploidy, a condition that is generally lethal to the embryo in the majority of animal species. To prevent this occurrence, eggs have developed a series of mechanisms that block polyspermy at the level of the plasma membrane or their extracellular coat. In this review, we first introduce the mammalian egg coat, the zona pellucida (ZP), and summarize what is currently known about its composition, structure, and biological functions. We then describe how this specialized extracellular matrix is modified by the contents of cortical granules (CG), secretory organelles that are exocytosed by the egg after gamete fusion. This process releases proteases, glycosidases, lectins and zinc onto the ZP, resulting in a series of changes in the properties of the egg coat that are collectively referred to as hardening. By drawing parallels with comparable modifications of the vitelline envelope of nonmammalian eggs, we discuss how CG‐dependent modifications of the ZP are thought to contribute to the block to polyspermy. Moreover, we argue for the importance of obtaining more information on the architecture of the ZP, as well as systematically investigating the many facets of ZP hardening. Post‐fertilization modifications of the zona pellucida (ZP) alter its properties and impact its ability to interact with sperm. In this review, we discuss how the contents of the exocytosed cortical granules may induce ZP hardening and establish the egg coat block to polyspermy.
... The most commonly pattern, a flat and tangential attachment of the sperm head to the surface of the ZP, which is then followed by intrusion into the zona in precisely this horizontal position 43 and a vertical sperm binding with ZP penetration by the tip of the head. This last pattern is found in oocytes where large, cluster-like numbers of bound spermatozoa are visible 44 . Both binding patterns are observed in the B ZP models. ...
Article
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The egg is a spherical cell encapsulated by the zona pellucida (ZP) which forms a filamentous matrix composed of several glycoproteins that mediate gamete recognition at fertilization. Studies on molecular mechanisms of sperm-egg binding are limited in many mammalian species by the scarcity of eggs, by ethical concerns in harvesting eggs, and by the high cost of producing genetically modified animals. To address these limitations, we have reproduced a three-dimensional (3D) model mimicking the oocyte’s shape, by means of magnetic sepharose beads coated with recombinant ZP glycoproteins (BZP) and cumulus cells. Three preparations composed of either ZP2 (C and N-termini; BZP2), ZP3 (BZP3) or ZP4 (BZP4) were obtained and characterized by protein SDS-PAGE, immunoblot and imaging with confocal and electron microscopy. The functionality of the model was validated by adhesion of cumulus cells, the ability of the glycoprotein-beads to support spermatozoa binding and induce acrosome exocytosis. Thus, our findings document that ZP-beads provide a novel 3D tool to investigate the role of specific proteins on egg-sperm interactions becoming a relevant tool as a diagnostic predictor of mammalian sperm function once transferred to the industry.
... The zona pellucida is a unique extracellular coat that cinctures the maturing oocyte during ovulation, fertilization, and first embryo development [15]. A correlation between zona birefringence and the potential for an embryo to develop to the blastocyst stage has already been shown [15,16]. ...
... The zona pellucida is a unique extracellular coat that cinctures the maturing oocyte during ovulation, fertilization, and first embryo development [15]. A correlation between zona birefringence and the potential for an embryo to develop to the blastocyst stage has already been shown [15,16]. ...
Article
Full-text available
In assisted reproductive techniques, the operator attempts to select morphologically best embryos to predict embryo viability. Development of polarized light microscope, which evaluates the oocytes' spindles according to birefringence of living cells, had been helpful in oocyte selection. The aim of this study is evaluating the relationship between meiotic spindles visualization and intracytoplasmic sperm injection (ICSI) outcomes in human oocytes. In this study, 264 oocytes from 24 patients with an average age of 30.5±7.5 years with infertility duration of 1 to 10 years were collected. The oocytes were randomly allocated to the control injection group (n=126) and the oocyte imaging group (spindle-aligned group) (n=138). In the spindle-aligned group, the meiotic spindle was identified by means of polarized light microscope to align the spindle at 6 or 12 o'clock. Then the spindle-aligned group was divided into three sub-groups based on spindle morphology: fine, average, and (poor). After ICSI, embryos were checked every 24 hours and scored; 72 hours later, high-grade embryos were transferred intravaginally to uterus. This study showed that the fertilization rate in the spindle-aligned group was higher than the control group (P<0.05). After cleavage, a positive correlation was observed between spindle morphology and embryo morphology. Among the sub-groups of spindle-aligned group, the embryos' morphology of the fine group was better than the other subgroups and embryos of the poor group had lower quality and more fragmentation. The results revealed that the selection of oocytes based on meiotic spindle imaging can significantly improve the rate of fertilization and embryo cleavage and certainly increase the rate of implantation.
... In addition, MS structure may reflect oocyte quality by serving as a marker for cytoplasmic maturation and pH or temperature fluctuations during handling [16]. The ZP is a unique extracellular coat composed of filaments organized in different orientations surrounding the maturing oocytes during ovulation, fertilization and early embryonic development [17]. Therefore, the present study was designed to assess the association between selection of IVM oocytes on the basis of the ZP birefringence and MS detection, with fertilization and subsequent embryo development in ICSI program. ...
Article
Full-text available
Recently, the upgrading of in vitro maturation (IVM) of human oocytes as a promising strategy has emerged in assisted reproductive technology (ART). The goal was to evaluate the correlation of the in vitro matured oocytes selected on the basis of the zona pellucida (ZP) birefringence and meiotic spindles (MS) detection with fertilization and subsequent embryo development in ICSI program. A total of 168 immature oocytes [germinal vesicle (n = 140) and metaphase I (n = 28)] obtained from patients undergoing oocytes retrieval for ICSI. After in vitro culture for 24-40 h, 112 (67 %) oocytes reached to MII stage. Using a polarized microscopy, the presence of MS and ZP birefringence were assessed in matured oocytes, followed by ICSI performance. The rates of fertilization in oocytes with spindles (51.3 %) were similar to that of the oocytes without spindles (50.7 %; P = 1.00). Moreover, the fertilization rates in high birefringence (HB) oocytes was not statistically different than oocytes with low birefringence (LB) (P = 0.44). The findings also showed that 64.9 % of the fertilized oocytes developed to embryos, in which 33.3 % were derived from spindle-detected oocytes. Regarding the ZP birefringence, 35.5 % of the embryos were derived from HB oocytes. There were insignificant relationships between the MS detection and ZP birefringence score with the rates of fertilization and embryo development in IVM oocytes.
... Cinematography [113] and more recent, cinematography (time-lapse imaging) by Lemmen et al. [114], and scanning electron microscopy (SEM) [115] have been reported. ...