Early Stages Of Fertilization Research Articles

Deep infiltrating endometriosis: cine magnetic resonance imaging in the evaluation of uterine contractility.

To evaluate uterine function by using cine magnetic resonance imaging to visualize the contractile movements of the uterus in patients with and without deep infiltrating endometriosis (with or without associated adenomyosis). This was a prospective case-control study. The study sample comprised 43 women: 18 in the case group and 25 in the control group. We performed cine magnetic resonance imaging in a 3.0 T scanner, focusing on the presence, direction, and frequency of uterine peristalsis. The frequency of uterine peristalsis was higher in the case group than in the control group, in the periovulatory phase (3.83 vs. 2.44 peristaltic waves in two minutes) and luteal phase (1.20 vs. 0.91 peristaltic waves in two minutes). However, those differences were not statistically significant. There was a significant difference between the patients with adenomyosis and those without in terms of the frequency of peristalsis during the late follicular/periovulatory phase (0.8 vs. 3.18 peristaltic waves in two minutes; p < 0.05). The frequency of uterine peristalsis appears to be higher during the periovulatory and luteal phases in patients with deep infiltrating endometriosis, whereas it appears to be significantly lower during the late follicular/periovulatory phase in patients with adenomyosis. Both of those effects could have a negative impact on sperm transport and on the early stages of fertilization.

Effect Analysis of Degranulated Cell in Early Fertilization on FET Outcome and Offspring Safety with Data Mining.

In vitro fertilization and embryo transfer is one type of assisted reproductive technology, although the technology is now more mature. Many factors, however, will have an impact on oocyte fertilization, embryo growth, pregnancy outcome, and child safety due to the journey from clinical to the laboratory. The influence of degranulated cells early in fertilization on frozen embryo transfer (FET) results is investigated in this study. This article analyzes 255 patients who underwent in vitro fertilization (IVF) and FET transplantation at the author's central unit from January 1, 2015, to June 30, 2021. Among them, IVF-assisted conception is the early degranulation of homologous oocyte fertilization. Correlation analysis is performed by observing the embryonic outcome of the early degranulation group and the overnight fertilization group and the clinical outcome after FET. Through data mining analysis, the results show that the polyfertilization rate and 0PN rate for the early degranulation group are significantly higher than the overnight fertilization group (9.87% vs. 8.24% and 3.14% vs. 1.69%). In terms of normal fertilization rate, there is no significant difference between D3 high-quality embryo rate and D5 high-quality blastocyst rate (64.07% vs. 65.15%, 27.5% vs. 26.5%, and 15.97% vs. 17.35%). There is no significant difference in the complete recovery rate of embryos after thawing (93.24% vs. 93.46%), and the implantation rate, clinical pregnancy rate, abortion rate, and live birth rate are not significantly different between the two groups after FET. The offspring outcomes of singletons do not differ significantly between the two groups; however, twins born early degranulate have much greater rates of ultralow birth weight and ultrapreterm children than twins born overnight fertilization (14.29% vs. 0). Therefore, it can be concluded that degranulation of cells early in fertilization is a desirable method to prevent fertilization disorders. However, under the premise of ensuring that no fertilization disorder occurs, it is not appropriate to degranulate all the oocytes of the patient at the early stage of fertilization.

CD9 and CD81 Interactions and Their Structural Modelling in Sperm Prior to Fertilization.

Proteins CD9 and CD81 are members of the tetraspanin superfamily and were detected in mammalian sperm, where they are suspected to form an active tetraspanin web and to participate in sperm–egg membrane fusion. The importance of these two proteins during the early stages of fertilization is supported by the complete sterility of CD9/CD81 double null female mice. In this study, the putative mechanism of CD9/CD81 involvement in tetraspanin web formation in sperm and its activity prior to fertilization was addressed. Confocal microscopy and colocalization assay was used to determine a mutual CD9/CD81 localization visualised in detail by super-resolution microscopy, and their interaction was address by co-immunoprecipitation. The species-specific traits in CD9 and CD81 distribution during sperm maturation were compared between mice and humans. A mutual position of CD9/CD81 is shown in human spermatozoa in the acrosomal cap, however in mice, CD9 and CD81 occupy a distinct area. During the acrosome reaction in human sperm, only CD9 is relocated, compared to the relocation of both proteins in mice. The structural modelling of CD9 and CD81 homologous and possibly heterologous network formation was used to propose their lateral Cis as well as Trans interactions within the sperm membrane and during sperm–egg membrane fusion.

[Characteristics of N2O and NOx Emissions from Purple Soil Under Different Fertilization Regimes].

N2O and NOx emissions from a winter wheat-summer maize rotation system in purple soil were measured on a long-term fertilization platform of purple soil for two consecutive cropping years (from November 2014 to September 2016) by using a closed-chamber and gas chromatography-based system. Chemical fertilizer (NPK), pig manure (OM), incorporation of crop residues plus synthetic NPK fertilizer (RSDNPK), pig manure plus synthetic NPK fertilizer (OMNPK), and nitrification inhibitor with NPK fertilizer (DCDNPK) under the same rate of total nitrogen were involved in monitoring N2O and NOx emissions. Short-term fertilizer-free treatment (CK) was used as a control for emission coefficient calculation. The results showed that N2O emission peaks appeared in the early stage of fertilization and in the period of heavy rainfall for all fertilization regimes. The NOx emission process was similar to that of N2O, in that emission peaks appeared at the early stage of fertilization, yet no obvious emission peaks were observed during heavy rainfall. The annual cumulative emissions of N2O from NPK, OM, RSDNPK, OMNPK, and DCDNPK were 1.35, 4.38, 1.43, 2.46, and 0.92 kg·hm-2, respectively, and the emission coefficients were 0.33%, 1.41%, 0.36% 0.73%, and 0.18%. The annual emissions of NOx from NPK, OM, RSDNPK, OMNPK, and DCDNPK were 0.11, 0.38, 0.10, 0.27, and 0.04 kg·hm-2, respectively, and the cumulative emission coefficients were 0.03%, 0.13%, 0.03%, 0.09%, and 0.01%. Amendment of organic material was the main stimulator for N2O and NOx emissions, as they significantly increased 226% and 262% (for OM) and 83% and 157% (for OMNPK), respectively (P<0.01), compared with conventional synthetic fertilizers. The application of synthetic fertilizers combined with nitrification inhibitor (DCDNPK) significantly reduced N2O emissions 32% and NOx emissions 62% (P<0.01), whereas straw returning with NPK application increased N2O emissions 6% and reduced NOx emissions 5% (P>0.05). Furthermore, statistical analyses showed that soil inorganic N content was the main regulating factor of N2O and NOx emissions together, whereas soil water-filled pore space (WFPS) and temperature were the respective main regulating factors of N2O and NOx emissions individually.

[Effects of soil water condition on N2O emission and its sources in vegetable farmland of North China Plain].

To understand the mechanisms of agricultural N2O emission, we investigated the N2O emission dynamics, the N2O isotope signatures, and the site preference value under different soil water conditions in the vegetable farmland of North China, by using the stable isotope technique and the acetylene inhibition method. The results demonstrated that N2O emission was significantly affec-ted by the water condition, and N2O emissions from soil with water-filled pore space (WFPS) of 70% were significantly higher than that with 50% WFPS. N2O emission occurred mostly in the early stage of fertilization, and decreased rapidly in the later stage of fertilization. At 50% WFPS, nitrification was the major process generating N2O during the early fertilization stage, accounting for approximately 90% of the N2O emission. However, the contribution of nitrification decreased sharply, whereas denitrification became the dominant process, accounting for 80% of the N2O emission 7 days after the fertilization. On the other hand, at 70% WFPS, denitrification was the main process releasing N2O during the early fertilization stage, decreasing from 70% to 40% and then gradually increasing to 80% 10 days after the fertilization. Overall, N2O emission was mainly dominated by the denitrification. The effect of different water treatments on soil nitrification and denitrification took place mainly in the early stage of fertilization, and N2O emission was gradually dominated by the denitrification at the later stage. These results suggested we could reduce N2O emission by approp-riately reducing the amount of irrigation in the vegetable farmland of North China.

Spermatogenic ultrastructure in the anomalodesmatan bivalve Myochama anomioides (Mollusca: Myochamidae) – does the nucleus help position the ‘temporary’ acrosome?

AbstractSpermatogenic ultrastructure in the marine bivalve mollusc Myochama anomioides (Myochamidae) is described and contrasted with other bivalves, especially other euheterodonts. Small (0.1 μm diameter), primary proacrosomal vesicles produced in spermatocytes give rise to much larger (0.4 μm diameter) secondary proacrosomal vesicles in early spermatids, which in turn form the dished‐shaped, definitive acrosomal vesicle (diameter 1.0 μm) of later spermatids. The acrosomal vesicle acquires a deposit of subacrosomal material and comes to lie close to or in contact with the plasma membrane. The acrosomal complex (acrosomal vesicle + subacrosomal material) initially positions itself at the apex of the condensing, fibrous nucleus (the so‐called temporary acrosome position), but subsequently begins to move posteriorly. The condensing nucleus becomes markedly folded so that its apex is posteriorly orientated towards the migrating acrosomal complex and the midpiece (mitochondria and centrioles). The close spatial relationship of nuclear apex to acrosomal complex during this folding strongly suggests that acrosomal migration in M. anomioides is assisted, at least in part, by movement of the late spermatid nucleus. Similar nuclear folding has previously been demonstrated in an early stage of fertilization in another anomalodesmatan (Laternula limicola) raising the possibility that one event might be a reversal of the other.

Expression analysis and enzymatic characterization of phospholipase Cδ4 from olive flounder (Paralichthys olivaceus)

Phospholipase Cδ4 (PLCδ4) plays a significant role in cell proliferation, tumorigenesis, and in an early stage of fertilization. Despite the characterization of the mammalian PLCδ4, extensive study in aquatic organisms has not been carried out so far. Here, we performed the molecular and biochemical characterization of flatfish Paralichthys olivaceus PLCδ4 (PoPLCδ4) to understand its enzymatic properties and physiological functions. The olive flounder PLCδ4 cDNA has an open reading frame (ORF) of 2,268 bp, and encodes a 755 amino acid polypeptide with a predicted molecular weight of 86 kDa. All the characteristic domains found in mammalian PLCδ isoforms (PH domain, EF hands, an X-Y catalytic region, and a C2 domain) were found to be present in PoPLCδ4. The mRNA expression analysis of PoPLCδ4 showed that PoPLCδ4 is predominantly expressed in the brain, eye and heart tissues. Like other mammalian PLCδ proteins, the enzyme activity of recombinant PoPLCδ4 to phosphatidylinositol-4,5-bis-phosphate (PIP2) was noted to be concentration- and Ca(2+)-dependent. The structural features and biochemical characteristics of PoPLCδ4 were found to be similar to those of mammalian PLCδ4. This is the first demonstration of the expression analysis and enzymatic characterization of piscine PLCδ4.

Relocalization of STIM1 in mouse oocytes at fertilization: early involvement of store-operated calcium entry

Calcium waves represent one of the most important intracellular signaling events in oocytes at fertilization required for the exit from metaphase arrest and the resumption of the cell cycle. The molecular mechanism ruling this signaling has been described in terms of the contribution of intracellular calcium stores to calcium spikes. In this work, we considered the possible contribution of store-operated calcium entry (SOCE) to this signaling, by studying the localization of the protein STIM1 in oocytes. STIM1 has been suggested to play a key role in the recruitment and activation of plasma membrane calcium channels, and we show here that mature mouse oocytes express this protein distributed in discrete clusters throughout their periphery in resting cells, colocalizing with the endoplasmic reticulum marker calreticulin. However, immunolocalization of the endogenous STIM1 showed considerable redistribution over larger areas or patches covering the entire periphery of the oocyte during Ca(2+) store depletion induced with thapsigargin or ionomycin. Furthermore, pharmacological activation of endogenous phospholipase C induced a similar pattern of redistribution of STIM1 in the oocyte. Finally, fertilization of mouse oocytes revealed a significant and rapid relocalization of STIM1, similar to that found after pharmacological Ca(2+) store depletion. This particular relocalization supports a role for STIM1 and SOCE in the calcium signaling during early stages of fertilization.

Calcium-induced Acrosomal Exocytosis Requires cAMP Acting through a Protein Kinase A-independent, Epac-mediated Pathway

Epac, a guanine nucleotide exchange factor for the small GTPase Rap, binds to and is activated by the second messenger cAMP. In sperm, there are a number of signaling pathways required to achieve egg-fertilizing ability that depend upon an intracellular rise of cAMP. Most of these processes were thought to be mediated by cAMP-dependent protein kinases. Here we report a new dependence for the cAMP-induced acrosome reaction involving Epac. The acrosome reaction is a specialized type of regulated exocytosis leading to a massive fusion between the outer acrosomal and the plasma membranes of sperm cells. Ca2+ is the archetypical trigger of regulated exocytosis, and we show here that its effects on acrosomal release are fully mediated by cAMP. Ca2+ failed to trigger acrosomal exocytosis when intracellular cAMP was depleted by an exogenously added phosphodiesterase or when Epac was sequestered by specific blocking antibodies. The nondiscriminating dibutyryl-cAMP and the Epac-selective 8-(p-chlorophenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate analogues triggered the acrosome reaction in the effective absence of extracellular Ca2+. This indicates that cAMP, via Epac activation, has the ability to drive the whole cascade of events necessary to bring exocytosis to completion, including tethering and docking of the acrosome to the plasma membrane, priming of the fusion machinery, mobilization of intravesicular Ca2+, and ultimately, bilayer mixing and fusion. cAMP-elicited exocytosis was sensitive to anti-alpha-SNAP, anti-NSF, and anti-Rab3A antibodies, to intra-acrosomal Ca2+ chelators, and to botulinum toxins but was resistant to cAMP-dependent protein kinase blockers. These experiments thus identify Epac in human sperm and evince its indispensable role downstream of Ca2+ in exocytosis.

Delineation of the functional domains of the extracellular region of YWK-II Protein/APLP2 of sperm membrane

The sperm membrane protein, designated as YWK-II protein/APLP2, is a member of the amyloid precursor protein (APP) superfamily and is a type I transmembrane protein involved in fertilization. Here, the structure-function of the domains of YWK-II protein was examined. Five segments with overlapping ends encompassing the entire extracellular region of mouse YWK-II gene were prepared, cloned and separately expressed in E. coli. The recombinant YWK-II segments were fused with glutathione S-transferase (GST), purified and evaluated for their antifertility activities by measuring their capacity to block in vitro mouse sperm-egg interaction. The structural domain(s) involved in the fertilization process was identified. The polypeptide segment corresponding to position 22-207 of YWK-II-763 inhibited the early stage of fertilization when the spermatozoa interacted with zona-free eggs; whereas the polypeptide segment 201-395 (lacking 309-364) of YWK-II-763 blocked sperm-egg membrane fusion. The remaining three segments, 201-395, 389-574 and 517-704 (lacking 613-624) of YWK-II-763, did not influence the in vitro fertilization process. The present results suggest that segment 22-308 of YWK-II-763 participates in the binding and fusion of sperm and egg plasma membranes thereby promoting fertilization.

A Mouse Serine Protease TESP5 Is Selectively Included into Lipid Rafts of Sperm Membrane Presumably as a Glycosylphosphatidylinositol-anchored Protein

We have previously indicated that at least in mouse, sperm serine protease(s) other than acrosin probably act on the limited proteolysis of egg zona pellucida to create a penetration pathway for motile sperm, although the participation of acrosin cannot be ruled out completely. A 42-kDa gelatin-hydrolyzing serine protease present in mouse sperm is a candidate enzyme involved in the sperm penetration of the zona pellucida. In this study, we have PCR-amplified an EST clone encoding a testicular serine protease, termed TESP5, and then screened a mouse genomic DNA library using the DNA fragment as a probe. The DNA sequence of the isolated genomic clones indicated that the TESP5 gene is identical to the genes coding for testicular testisin and eosinophilic esp-1. Immunochemical analysis using affinity-purified anti-TESP5 antibody revealed that 42- and 41-kDa forms of TESP5 with the isoelectric points of 5.0 to 5.5 are localized in the head, cytoplasmic droplet, and midpiece of cauda epididymal sperm probably as a membranous protein. Moreover, these two forms of TESP5 were selectively included into Triton X-100-insoluble microdomains, lipid rafts, of the sperm membranes. These results show the identity between TESP5/testisin/esp-1 and the 42-kDa sperm serine protease. When HEK293 cells were transformed by an expression plasmid carrying the entire protein-coding region of TESP5, the recombinant protein produced was released from the cell membrane by treatment with Bacillus cereus phosphatidylinositol-specific phospholipase C, indicating that TESP5 is glycosylphosphatidylinositol-anchored on the cell surface. Enzymatic properties of recombinant TESP5 was similar to but distinguished from those of rat acrosin and pancreatic trypsin by the substrate specificity and inhibitory effects of serine protease inhibitors.

Increase of cGMP, cADP-ribose and inositol 1,4,5-trisphosphate preceding Ca(2+) transients in fertilization of sea urchin eggs.

Transient increases, or oscillations, of cytoplasmic free Ca(2+) concentration, [Ca(2+)](i), occur during fertilization of animal egg cells. In sea urchin eggs, the increased Ca(2+) is derived from intracellular stores, but the principal signaling and release system involved has not yet been agreed upon. Possible candidates are the inositol 1,4,5-trisphosphate receptor/channel (IP(3)R) and the ryanodine receptor/channel (RyR) which is activated by cGMP or cyclic ADP-ribose (cADPR). Thus, it seemed that direct measurements of the likely second messenger candidates during sea urchin fertilization would be essential to an understanding of the Ca(2+) signaling pathway. We therefore measured the cGMP, cADPR and inositol 1,4,5-trisphosphate (IP(3)) contents of sea urchin eggs during the early stages of fertilization and compared these with the [Ca(2+)](i) rise in the presence or absence of an inhibitor against soluble guanylate cyclase. We obtained three major experimental results: (1) cytosolic cGMP levels began to rise first, followed by cADPR and IP(3) levels, all almost doubling before the explosive increase of [Ca(2+)](i); (2) most of the rise in IP(3) occurred after the Ca(2+) peak; IP(3) production could also be induced by the artificial elevation of [Ca(2+)](i), suggesting the large increase in IP(3) is a consequence, rather than a cause, of the Ca(2+) transient; (3) the measured increase in cGMP was produced by the soluble guanylate cyclase of eggs, and inhibition of soluble guanylate cyclase of eggs diminished the production of both cADPR and IP(3) and the [Ca(2+)](i) increase without the delay of Ca(2+) transients. Taken together, these results suggest that the RyR pathway involving cGMP and cADPR is not solely responsible for the initiating event, but contributes to the Ca(2+) transients by stimulating IP(3) production during fertilization of sea urchin eggs.

Differential subcellular distribution of tubulin epitopes in boar spermatozoa: recognition of class III beta-tubulin epitope in sperm tail.

The exposure of tubulin epitopes was studied in ejaculated boar spermatozoa using a panel of four monoclonal antibodies specific to the N-terminal or C-terminal structural domains of tubulin and three monoclonal antibodies against class III beta-tubulin. The specificity of the antibodies was confirmed by immunoblotting. Immunocytochemical staining showed that antibodies discriminated between various parts of a spermatozoon, and that epitopes of class III beta-tubulin were present in the flagellum. A tubulin epitope from the C-terminal domain of beta-tubulin was detected in the triangular segment of the postacrosomal part of the sperm head. Its distribution changed after an A23187 ionophore-induced acrosome reaction, indicating that tubulin participates in the early stages of fertilization. Three monoclonal antibodies, TU-20, SDL.3D10, and TUJ1 directed against epitopes on the C-terminal end of neuron-specific class III beta-tubulin that is widely used as a neuronal marker, stained the flagella. The reactivity of TU-20 was further confirmed by absorbing the antibody with the immunizing peptide and by immunoelectron microscopy. Immunoblotting after two-dimensional electrophoresis revealed that the corresponding epitope was not present on all beta-tubulin isoforms. These results suggest that various tubulins are involved in the functional organization of the mammalian sperm flagellum and head.

Genome organization in the human sperm nucleus studied by FISH and confocal microscopy

The sperm nucleus has a unique chromatin structure where the DNA is highly condensed and associated with specific proteins, the protamines. It is a nondividing cell which is also transcriptionally inactive. After fusion with an oocyte, the sperm nucleus undergoes decondensation and, in the same time, starts replication and transcription. It has been suggested that somatic chromosomes during interphase are organized in territories which display a cell type and cell cycle specific distribution. The purpose of this work was to investigate whether chromosomes would also have a specific distribution in the sperm nucleus, which could be related to its inactive state, and have implications on the early stages of fertilization. In the present study, centromeric and telomeric sequences were detected by fluorescent techniques performed on human decondensed spermatozoa. Chromosome painting probes were used to detect the chromosome X and chromosome 13 on interphase sperm nuclei. The fluorescent signals were captured in 3D with a confocal microscope. For each of these chromatin structures, the volume, position, and distribution of the signals were analyzed in samples of 30 nuclei with the help of image analysis software. The centromeres appeared grouped in several foci that were randomly distributed within the sperm nucleus. The telomeres gave an approximately haploid number of small signals, evenly distributed throughout the nucleus. The chromosomes X and 13 occupied 4.7% and 3. 7% of the total nuclear volume, respectively. Interestingly, the X chromosome territory showed a preferential position in the anterior half of the volume of the nucleus, whereas chromosome 13 had a random position. This work shows a particular distribution of chromosome territories in the human sperm nucleus that could be related to mechanisms implicated in its specific functions. The analysis of more chromosomes and chromosomal structures, including the Y chromosome, would help to understand the structure of the human sperm chromatin, and its fundamental and clinical implications.

Maitotoxin (MTX) activates a nonselective cation channel in Xenopus laevis oocytes.

Maitotoxin (MTX) may exert its toxic effect by activating ion conductances and has been shown to elicit a fertilization-like response in Xenopus laevis oocytes. In the present study we investigated the electrophysiological response of stage V-VI Xenopus oocytes to MTX using the two-microelectrode voltage-clamp technique. Membrane voltage (Vm) measurements demonstrated that MTX (50 pM to 1 nM) depolarized the oocytes from -49+/-7 to -14+/-1 mV. Subsequent replacement of bath Na+ by the impermeant cation NMDG (N-methyl-d-glucamine) shifted Vm from -14+/-1 to -53+/-5 mV (n=29). This indicates that MTX activates a cation conductance. Indeed, current measurements at a holding potential of -60 or -100 mV showed that within 10 s of MTX application an inward current component developed which was largely abolished by extracellular Na+ removal. After a 1-min application of 1 nM MTX the NMDG-sensitive current increased more than 100-fold from 0.14+/-0.03 microA to a peak value of 21+/-3 microA (n=11). The effect of MTX was concentration dependent with an EC50 of about 250 pM but only slowly reversible. Ion substitution experiments indicated that the stimulated conductance was nonselective for monovalent cations with a slight preference for NH4+ (2.1) > K+ (1.5) > Na+ (1.0) > Li+ (0.7). Regarding divalent cations, a complex biphasic response to extracellular Na+ replacement by Ca2+ was observed, which suggests that the stimulated channels may have a small Ca2+ permeability but that exposure to high extracellular Ca2+ enhances recovery from MTX stimulation. No significant conductance for Mn2+ was observed. Application of 1 mM benzamil, 1 mM amiloride, or 100 microM 1-(beta-[3-(4-Methoxyphenyl)-propoxy]-4-methoxyphenethyl)-1H-imidazol e hydrochloride (SK&F 96365) reduced the MTX-stimulated inward current by 81%, 62%, or 65%, respectively. Gd3+ had an inhibitory effect of 29% and 38% at concentrations of 10 microM or 100 microM, respectively. Flufenamic acid, niflumic acid, (RS)-(3,4-dihydro-6, 7-dimethoxyisoquinoline-1-gamma1)-2-phenyl-N,N-di-[2-(2,3, 4-trimethoxyphenyl)-ethyl]-acetamide (LOE908), and 3', 5'-dichlorodiphenylamine-2-carboxylic acid (DCDPC), known blockers of other nonselective cation channels, had no significant effect. We conclude that MTX activates a nonselective cation conductance in Xenopus oocytes. The underlying channels may be involved in changes in Vm that occur during the early stages of fertilization.

Specific localization in the equatorial region of gp20, a 20 kDa sialylglycoprotein of the capacitated human spermatozoon acquired during epididymal transit which is necessary to penetrate zona-free hamster eggs.

In this study we set out to characterize gp20, a 20 kDa glycoprotein of the human sperm surface, first identified by us by radiolabelling the sialic acid residues of the sperm surface [R. Focarelli et al. (1995), Mol. Hum. Reprod., 2, 2755-2759]. The protein was partially purified from pooled sperm samples of several healthy donors and used to raise a specific antiserum to study its localization in the reproductive system. When tested with freshly ejaculated spermatozoa, the anti-gp20 antibody intensely stained the head and midpiece. However, on capacitated spermatozoa the antigen was restricted to a sharp zone in the equatorial region. The antibody did not bind to differentiating germ cells but the antigen was present in epididymal epithelial cells and also in seminal plasma. Anti-gp20 exerted a blocking effect in a test for sperm penetration of zona-free hamster eggs, thus suggesting that gp20 is involved in the early stages of fertilization.

Changes in calpain during meiosis in the rat egg

Resumption of meiosis at fertilization is mediated by increased levels of calcium which activate several calcium-dependent enzymes. Calpain, a neutral calcium-activated thiol protease, is present in the cytoplasm of many cells. Its activation is associated with limited autolysis and relocalization in the cell. Calpain is thought to participate in the regulation of mitosis and resumption of meiosis in Xenopus oocytes. In this study we followed the activation and localization of calpain during maturation and fertilization in rat eggs using a polyclonal antibody raised against chicken muscle calpain. A band of 80 kDa was detected in GV oocytes and its level increased in unfertilized MII eggs. At the early stages of fertilization, we observed a transient decrease in the level of calpain which was regained at the pronuclear stage. Adding Ca2+ to lysate of MII eggs resulted in an additional band, representing the degraded fragment of the activated protein. In eggs activated by ionomycin, calpain level decreased, followed by an increase in a dynamic similar to that observed in fertilized eggs. Egg activation also led to changes in calpain localization. A homogenous distribution was observed in GV and in MII eggs, while in activated eggs it was localized predominantly overlying the metaphase plate. In the current study we demonstrate the presence of calpain in the rat egg. During maturation, calpain level increases; however, during egg activation, in response to [Ca2+]i changes, calpain undergoes autolysis, translocation, and fluctuation in its level. We therefore suggest a correlation between calpain activation and fertilization. Mol. Reprod. Dev. 48:119–126, 1997. © 1997 Wiley-Liss, Inc.

Changes in calpain during meiosis in the rat egg.

Resumption of meiosis at fertilization is mediated by increased levels of calcium which activate several calcium-dependent enzymes. Calpain, a neutral calcium-activated thiol protease, is present in the cytoplasm of many cells. Its activation is associated with limited autolysis and relocalization in the cell. Calpain is thought to participate in the regulation of mitosis and resumption of meiosis in Xenopus oocytes. In this study we followed the activation and localization of calpain during maturation and fertilization in rat eggs using a polyclonal antibody raised against chicken muscle calpain. A band of 80 kDa was detected in GV oocytes and its level increased in unfertilized MII eggs. At the early stages of fertilization, we observed a transient decrease in the level of calpain which was regained at the pronuclear stage. Adding Ca2+ to lysate of MII eggs resulted in an additional band, representing the degraded fragment of the activated protein. In eggs activated by ionomycin, calpain level decreased, followed by an increase in a dynamic similar to that observed in fertilized eggs. Egg activation also led to changes in calpain localization. A homogenous distribution was observed in GV and in MII eggs, while in activated eggs it was localized predominantly overlying the metaphase plate. In the current study we demonstrate the presence of calpain in the rat egg. During maturation, calpain level increases; however, during egg activation, in response to [Ca2+]i changes, calpain undergoes autolysis, translocaton, and fluctuation in its level. We therefore suggest a correlation between calpain activation and fertilization.

Translocation of active mitochondria during hamster preimplantation embryo development studied by confocal laser scanning microscopy.

The role of mitochondrial metabolism in the development of preimplantation embryos is unclear. To clarify the importance of mitochondria in early development, the fluorescent probes rhodamine 123 (Rh123: stains active mitochondrial membrane) and nonyl acridine orange (NAO: stains active and inactive mitochondrial membrane) were used with confocal laser scanning microscopy to study the distribution of mitochondria in hamster unfertilized follicular and oviductal eggs (11.5 hr and 16 hr post-hCG, respectively) and preimplantation embryos (1-cell to blastocyst). Rh123 staining indicated that active mitochondria were homogeneously distributed in unfertilized follicular and oviductal eggs. At 3 hr post egg activation (PEA) by sperm, active mitochondria were still found throughout the cytoplasm of the activated egg although they were slightly clustered around the pronuclei and were intensely active in the second polar body. During the next 9 hr, the majority of active mitochondria encircled the apposing pronuclei. By this time the second polar body no longer stained. In 2-cell, 4-cell and 8-cell embryos, there was a striking constancy in the pattern of active mitochondria which were clustered around the nuclei and delineating the cytocortex subjacent to the plasma membrane. In the blastocyst, active mitochondria were most readily detected in the trophectoderm cells in a homogeneous distribution. Staining mitochondria with NAO showed the same distribution patterns as Rh123, indicating that perinuclear clustering of active mitochondria involves the physical movement of these organelles rather than simply changes in their activity. Distribution of actin microfilaments and microtubules showed similar patterns to mitochondria and may be involved in their movement. This migration of mitochondria, beginning during the early stages of fertilization in the hamster egg and persisting until blastocoel formation, must have some functional correlation with successful preimplantation development.

Purification and Characterization of a 38-kDa Protein, sp38, with Zona Pellucida-Binding Property from Porcine Epididymal Sperm

A 38-kDa protein, sp38, was purified from the detergent extract of porcine epididymal sperm. Sp38 showed zona pellucida-binding properties similar to those of proacrosin. These two proteins specifically bound to the 90-kDa glycoprotein form of the zona pellucida components in a calcium-dependent manner. The binding of sp38 to the zona pellucida glycoprotein was inhibited by proacrosin. These findings suggest that the two proteins competitively interact with the zona pellucida during the early stage of fertilization.