Birth of mice from meiotically arrested spermatocytes following biparental meiosis in halved oocytes.

Microinjection of spermatozoa or spermatids into oocytes is a major choice for infertility treatment. However, the use of premeiotic spermatocytes has never been considered because of its technical problems. Here, we show that the efficiency of spermatocyte injection in mice can be improved greatly by reducing the size of the recipient oocytes. Live imaging showed that the underlying mechanism involves reduced premature separation of the spermatocyte's meiotic chromosomes, which produced much greater (19% vs. 1%) birth rates in smaller oocytes. Application of this technique to spermatocyte arrest caused by STX2 deficiency, an azoospermia factor also found in humans, resulted in the production of live offspring. Thus, the microinjection of primary spermatocytes into oocytes may be a potential treatment for overcoming a form of nonobstructive azoospermia caused by meiotic failure.

Sperm acrosome status before and during fertilization in the Chinese hamster (Cricetulus griseus), and observation of oviductal vesicles and globules.

The present study was conducted to determine exact location where the acrosome reaction of fertilizing spermatozoa begins in the oviduct of the Chinese hamster. Unlike spermatozoa of other rodent species, Chinese hamster spermatozoa did not spontaneously undergo the acrosome reaction in fertilization-supporting media. In naturally mated females, spermatozoa in the uterus had intact acrosomes, whereas those in the lower oviductal isthmus had visibly thin acrosomal caps. The acrosomal cap was lost when spermatozoa passed through the cumulus oophorus. Thus, Chinese hamster spermatozoa begin the acrosome reaction in the lower isthmus and complete it in the cumulus oophorus. The mucosal epithelium of the oviductal isthmus released many "transparent" vesicles into the lumen, was very fragile and readily sloughed off by rough handling or rapid flushing with medium. Globular materials that oozed out of the dissected oviduct were most likely mucosa cells destroyed by rough handling. Although the oviducts of Chinese hamsters may be exceptionally delicate, this observation nevertheless warns us to cautiously handle the oviducts of any species when studying oviduct secretions that could be involved in inducing capacitation and the acrosome reaction of spermatozoa within the female genital tract.

Effect of Pd Precursor Salts on the Chemical State, Particle Size, and Performance of Activated Carbon-Supported Pd Catalysts for the Selective Hydrogenation of Palm Biodiesel.

To improve the oxidative stability of biodiesel fuel (BDF), the polyunsaturated fatty acid methyl esters (poly-FAME) presented in commercial palm oil-derived biodiesel fuel (palm-BDF) were selectively hydrogenated to monounsaturated fatty acid methyl esters (mono-FAME) under a mild condition (80 °C, 0.5 MPa) using activated carbon (AC)-supported Pd catalysts with a Pd loading of 1 wt.%. The partially hydrotreated palm-BDF (denoted as H-FAME) which has low poly-FAME components is a new type of BDF with enhanced quality for use in high blends. In this study, we reported that the chemical states and particle sizes of Pd in the prepared Pd/AC catalysts were significantly influenced by the Pd precursors, Pd(NO3)2 and Pd(NH3)4Cl2, and thus varied their hydrogenation activity and product selectivity. The 1%Pd/AC (nit) catalyst, prepared using Pd(NO3)2, presented high performance for selective hydrogenation of poly-FAME into mono-FAME with high oxidation stability, owning to its large Pd particles (8.4 nm). Conversely, the 1%Pd/AC (amc) catalyst, prepared using Pd(NH3)4Cl2, contained small Pd particles (2.7 nm) with a little Cl residues, which could be completely removed by washing with an aqueous solution of 0.1 M NH4OH. The small Pd particles gave increased selectivity toward unwanted-FAME components, particularly the saturated fatty acid methyl esters during the hydrogenation of poly-FAME. This selectivity is unprofitable for improving the biodiesel quality.

Applications of Flow Microreactors in Electrosynthetic Processes.

The fundamental advantages and potential benefits of flow microreactor technology include extremely large surface-to-volume ratios, precise control over temperature and residence time, extremely fast molecular diffusion, and increased safety during reactive processes. These advantages and benefits can be applied to a wide range of electrosynthetic techniques, and so the integration of flow microreactors with electrosynthesis has received significant research interest from both academia and industry. This review presents an up-to-date overview of electrosynthetic processes in continuous-flow microreactors. In addition, the advantages of continuous-flow electrochemistry are discussed, along with a thorough comparison of microreactor-based processes and conventional batch reaction systems.

Photo-Electrochemical C-H Bond Activation of Cyclohexane Using a WO3 Photoanode and Visible Light.

The photo-electrochemical C-H bond activation of cyclohexane to produce cyclohexanol and cyclohexanone (KA oil) with high partial oxidation selectivity (99 %) and high current utilization ratio (76 %) was achieved in air at room temperature at atmospheric pressure. The production rate of KA oil was accelerated by applying a bias. The incident photon to current efficiencies at 365 and 420 nm were 57 % and 24 %, respectively.

Preservation of chromosomal integrity in murine spermatozoa derived from gonocytes and spermatogonial stem cells surviving prenatal and postnatal exposure to γ-rays in mice.

Pre- and postnatal male mice were acutely (659-690 mGy/min) and continuously (0.303 mGy/min) exposed to 2 Gy γ-rays to evaluate spermatogenic potential and chromosome damage in their germ cells as adults. Acute irradiation on Days 15.5, 16.5, and 17.5 post-coitus affected testicular development, as a result of massive quiescent gonocyte loss; the majority of the seminiferous tubules in these testes were devoid of germ cells. Acute irradiation on Days 18.5 and 19.5 post-coitus had less effect on testicular development and spermatogenesis, even though germ cells were quiescent gonocytes on these days. Adverse effects on testicular development and spermatogenesis were observed following continuous irradiation between Days 14.5 and 19.5 post-coitus. Exposure to acute and continuous postnatal irradiation after the differentiation of spermatogonial stem cells and spermatogonia resulted in nearly all of the seminiferous tubules exhibiting spermatogenesis. Neither acute nor continuous irradiation was responsible for the increased number of multivalent chromosomes in primary-spermatocyte descendents of the exposed gonocytes. In contrast, a significant increase in cells with multivalent chromosomes was observed following acute irradiation on Days 4 and 11 post-partum. No significant increases in unstable structural chromosomal aberrations or aneuploidy in spermatozoa were observed, regardless of cell stage at irradiation or the radiation dose-rate. Thus, murine germ cells that survive prenatal and postnatal irradiation can restore spermatogenesis and produce viable spermatozoa without chromosome damage. These findings may provide a better understanding of reproductive potential following accidental, environmental, or therapeutic irradiation during the prenatal and postnatal periods in humans.

Prevention of high-temperature-induced chromosome damage in mouse spermatozoa freeze-dried using Ca2+ chelator-containing buffer alkalinized with NaOH or KOH.

In order to protect sperm chromosomes against degradation when they are being stored for relatively high temperatures, we investigated the optimal pH of the freeze-drying solution, EGTA/Tris-HCl buffered solution alkalinized by NaOH (Na-ETBS) or KOH (K-ETBS). Mouse spermatozoa suspended in Na-ETBS or K-ETBS were freeze-dried at pH 5.0-8.4 and stored at 4 °C or 50 °C for 3 days. Some freeze-dried samples were stored at 25 °C for 3 days or 1 month. After storage, samples injected into oocytes using intracytoplasmic sperm injection were assessed for chromosome damage in resulting zygotes. Irrespective of freeze-drying solutions and storage temperatures, almost all the zygotes (97-100%) produced using the spermatozoa freeze-dried at pH 5.0 had structural chromosome aberrations of sperm origin. When freeze-drying was conducted at pH 8.0-8.4 using Na-ETBS, the incidence of chromosome damage decreased to 14-17% in 4 °C storage and 24-26% in 50 °C storage. When freeze-dried in K-ETBS, the lowest level of chromosome damage occurred at pH levels of 7.7-8.4 at 4 °C storage (13-15%) and at pH 7.7-8.0 at 50 °C storage (16-23%). Spermatozoa freeze-dried in Na-ETBS at pH 8.2 and K-ETBS at pH 7.7 showed no significant increase in chromosome damage during 25 °C storage from 3 days to 1 month (11%-20% in Na-ETBS; 13%-18% in K-ETBS). Thus, use of the solutions optimized for short-term storage at high temperature (50 °C, 3 days) permits prolonged storage (1 month) of freeze-dried spermatozoa at room temperature.

Influence of radiofrequency-electromagnetic waves from 3rd-generation cellular phones on fertilization and embryo development in mice.

The purpose of this study was to evaluate the effects of 3rd-generation (3G) cellular phone radiofrequency-electromagnetic wave (RF-EMW) exposure on fertilization and embryogenesis in mice. Oocytes and spermatozoa were exposed to 3G cellular phone RF-EMWs, 1.95 GHz wideband code division multiple access, at a specific absorption rate of 2 mW/g for 60 min, or to sham exposure. After RF-EMW exposure, in vitro fertilization and intracytoplasmic sperm injection were performed. Rates of fertilization, embryogenesis (8-cell embryo, blastocyst), and chromosome aberration were compared between the combined spermatozoa and oocyte groups: both exposed, both non-exposed, one exposed, and the other non-exposed. Rates of fertilization, embryogenesis, and blastocyst formation did not change significantly across the four groups. Considering that the degree of exposure in the present study was ≥100 times greater than daily exposure of human spermatozoa and even greater than daily exposure of oocytes, the present results indicate safety of RF-EMW exposure in humans. Bioelectromagnetics. 38:466-473, 2017. © 2017 Wiley Periodicals, Inc.

Cathodic Aromatic C,C Cross-Coupling Reaction via Single Electron Transfer Pathway.

We have successfully developed a novel cathodic cross-coupling reaction of aryl halides with arenes. Utilization of the cathodic single electron transfer (SET) mechanism for activation of aryl halides enables the cross-coupling reaction to proceed without the need for any transition metal catalysts or single electron donors in a mild condition. The SET from a cathode to an aryl halide initiates a radical chain by giving an anion radical of the aryl halide. The following propagation cycle also consists entirely of anion radical intermediates.

The Behavior and Acrosomal Status of Mouse Spermatozoa In Vitro, and Within the Oviduct During Fertilization after Natural Mating.

Although 90%-100% of mouse oocytes can be fertilized in vitro with capacitated spermatozoa within 1 h after insemination, oocytes within the oviduct are fertilized one by one over a period of several hours. In vitro experiments showed that both acrosome-intact and acrosome-reacted spermatozoa entered the cumulus oophorus, but that acrosome-reacted spermatozoa reached the surface of oocytes more readily than acrosome-intact spermatozoa. During the period of fertilization within the oviduct, acrosome-reacted spermatozoa were seen throughout the isthmus, but with higher incidence in the upper than in the mid- and lower segments of the isthmus. Very few spermatozoa were present in the ampulla, and almost all were acrosome reacted. Although the cumulus oophorus and zona pellucida are known to be able to induce or facilitate the acrosome reaction of spermatozoa, this picture makes it likely that almost all fertilizing mouse spermatozoa within the oviduct begin to react before ascending from the isthmus to the ampulla. We witnessed a reacted spermatozoon that stayed on the zona pellucida of a fertilized oocyte for a while; it then moved out of the cumulus before reaching the zona pellucida of the nearby unfertilized oocyte. We noted that only a few spermatozoa migrate from the isthmus to the ampulla during the progression of fertilization, and this must be one of the reasons why we do not see many spermatozoa swarming around a single oocyte during in vivo fertilization.

Developmental potential of 2n/3n mixoploid mouse embryos produced by fusion of individual second polar bodies and blastomeres of 2-cell embryos.

Using 2n/3n mixoploid mouse embryos produced by fusion of individual second polar bodies (PB2s) with individual blastomeres of 2-cell embryos, the dynamics of PB2 nuclei in the host blastomeres during mitosis were examined and the fate of the 3n cell line in the mixoploid embryos was followed. Most of the PB2 nuclei were synchronised with the cell cycle of the host blastomeres and all chromosomes were incorporated into a single mitotic spindle. The majority of the mixoploid embryos developed to blastocysts with 3n cells. In conceptuses at Day 11.5 and Day 18.5 of gestation, 3n cells were recognised in both of the embryonic/fetal and placental tissues. When green fluorescent protein (GFP)-transgenic mice were used as a donor of PB2, GFP-positive 3n cells were found in more than 40% of morulae and blastocysts, indicating that the PB2 genome can be reactivated during the pre-implantation stage. GFP-positive 3n cells were non-randomly allocated in trophectoderm in blastocysts. These findings may explain the production mechanism of 2n/3n mixoploid human embryos, that is, a PB2 is incorporated into one daughter blastomere during the early cleavage period.

Ca2+ ionophore A23187 can make mouse spermatozoa capable of fertilizing in vitro without activation of cAMP-dependent phosphorylation pathways.

Ca(2+) ionophore A23187 is known to induce the acrosome reaction of mammalian spermatozoa, but it also quickly immobilizes them. Although mouse spermatozoa were immobilized by this ionophore, they initiated vigorous motility (hyperactivation) soon after this reagent was washed away by centrifugation. About half of live spermatozoa were acrosome-reacted at the end of 10 min of ionophore treatment; fertilization of cumulus-intact oocytes began as soon as spermatozoa recovered their motility and before the increase in protein tyrosine phosphorylation, which started 30-45 min after washing out the ionophore. When spermatozoa were treated with A23187, more than 95% of oocytes were fertilized in the constant presence of the protein kinase A inhibitor, H89. Ionophore-treated spermatozoa also fertilized 80% of oocytes, even in the absence of HCO3(-), a component essential for cAMP synthesis under normal in vitro conditions. Under these conditions, fertilized oocytes developed into normal offspring. These data indicate that mouse spermatozoa treated with ionophore are able to fertilize without activation of the cAMP/PKA signaling pathway. Furthermore, they suggest that the cAMP/PKA pathway is upstream of an intracellular Ca(2+) increase required for the acrosome reaction and hyperactivation of spermatozoa under normal in vitro conditions.

Experimental approach to prezygotic chromosome screening using only a single pair of gametes in mice.

During in vitro embryo production, chromosome screening is essential to prevent pregnancy losses caused by embryonic chromosome aberrations. When the chromosome screening is completed before fertilization, gametes are effectively utilized as genetic resources. The aim of this study was to investigate whether chromosome screening of gametes accompanied by fertilization would be feasible using a single mouse spermatozoon and oocyte. Metaphase II oocytes were divided into a cytoplast and a karyoplast. For genome cloning of the gametes, androgenic and gynogenic embryos were produced by microinjection of sperm into cytoplasts and parthenogenetic activation of karyoplasts, respectively. Pairs of blastomeres from androgenic and gynogenic embryos were fused electrically to produce diploid embryos, which were transferred into pseudopregnant surrogate mothers to examine fetal development. Blastomeres from androgenic and gynogenic embryos were individually treated with calyculin A-a specific inhibitor of type 1 and 2A protein phosphatases-for 2 h to induce premature chromosome condensation. Thereafter, chromosome analysis of blastomeres, reflecting the genetic constitution of individual spermatozoa and oocytes, was performed, and we confirmed that most of the androgenic and gynogenic 2-cell embryos had a haploid set of chromosomes in their sister blastomeres. The reconstructed embryos from blastomeres of androgenic and gynogenic 2-cell embryos could be implanted and develop into live fetuses, albeit at low efficiency. This study indicates that prezygotic chromosome screening and embryo production using a single pair of gametes may be practicable.

Chromosomal stability of second polar bodies in mouse embryos.

PURPOSE: Incorporation of a second polar body (PB2) into one of the blastomeres has been considered as a causal mechanism underlying diploid/triploid mixoploidy in humans. Using a mouse model, we examined whether PB2s can participate in the formation of mixoploidy. METHODS: Uptake of BrdU was examined to determine DNA synthesis in PB2s up to 28 h after fertilization. PB2s from embryos at 4-6 (1-cell), 24 (2-cell), 48 (4-cell), and 72 h (morula) were fused with MII oocytes to induce premature chromosome condensation. Caspase and TUNEL assays were used to detect apoptotic PB2s at 24, 48, and 72 h. PB2s were fused with one of the blastomeres of the 2-cell embryos to produce mixoploid embryos. RESULTS: DNA synthesis in the PB2s continued until 22 h after fertilization. At 4-6 h, nearly all of the PB2s showed G1-type chromosomes and there was no significant increase in chromosome damage. At 24, 48, and 72 h, S-type chromatin predominated. Few PB2s showed apoptotic response until 72 h. Regardless of the fusion with the PB2, more than 90 % of the embryos developed to 4-cell stage, and over 80 % of the resultant 4-cell embryos had daughter blastomeres with a morphologically normal nucleus. Some of the daughter blastomeres displayed triploidy. CONCLUSIONS: The PB2 is viable for at least 72 h after fertilization, with slow progression through the cell cycle. Once the PB2 has been incorporated into a blastomere, the cell cycle of the PB2 might be synchronized with that of the host resulting in diploid/triploid mixoploidy.

Main-chain engineering of polymer photocatalysts with hydrophilic non-conjugated segments for visible-light-driven hydrogen evolution.

Photocatalytic water splitting is attracting considerable interest because it enables the conversion of solar energy into hydrogen for use as a zero-emission fuel or chemical feedstock. Herein, we present a universal approach for inserting hydrophilic non-conjugated segments into the main-chain of conjugated polymers to produce a series of discontinuously conjugated polymer photocatalysts. Water can effectively be brought into the interior through these hydrophilic non-conjugated segments, resulting in effective water/polymer interfaces inside the bulk discontinuously conjugated polymers in both thin-film and solution. Discontinuously conjugated polymer with 10 mol% hexaethylene glycol-based hydrophilic segments achieves an apparent quantum yield of 17.82% under 460 nm monochromatic light irradiation in solution and a hydrogen evolution rate of 16.8 mmol m-2 h-1 in thin-film. Molecular dynamics simulations show a trend similar to that in experiments, corroborating that main-chain engineering increases the possibility of a water/polymer interaction. By introducing non-conjugated hydrophilic segments, the effective conjugation length is not altered, allowing discontinuously conjugated polymers to remain efficient photocatalysis.

Characterization of chromosomal damage accumulated in freeze-dried mouse spermatozoa preserved under ambient and heat stress conditions.

Structural chromosome aberrations and DNA damage generated in freeze-dried mouse spermatozoa were investigated. Freeze-dried sperm samples were preserved at 4, 25 and 50°C for short duration (1 day to 2 months) and at 25°C for long duration (2 years). The spermatozoa were injected into mouse oocytes to analyse the chromosomes of the zygotes at the first cleavage metaphase. Chromosome break of the chromosome-type aberrations was the most common type of structural chromosome aberrations observed in all freeze-dried samples. The frequency of chromatid exchanges rapidly increased in freeze-dried spermatozoa preserved at 50°C for 1-5 days. The frequency of chromatid-type aberrations (break and exchange) gradually increased in freeze-dried spermatozoa preserved at 25°C for up to 2 months. Alkaline comet assay revealed significant migration of damaged DNA accumulated in freeze-dried spermatozoa preserved at 50°C for 3 days and 25°C for 2 years. However, no DNA damage was detected using the same sperm samples by neutral comet assay, which can detect mostly DNA double-strand breaks in cellular DNA. These results suggest that DNA single-strand breaks were accumulated in freeze-dried spermatozoa preserved under ambient or heat conditions, and then chromatid-type aberrations, especially the chromatid exchanges, were formed via post-replication repair system in zygotes.

Accelerated modification of the zona pellucida is the primary cause of decreased fertilizability of oocytes in the 129 inbred mouse strain.

We investigated whether the small litter size in the 129 inbred mouse strain results from a reduction in oocyte fertilizability. Sensitivity of the zona pellucida to α-chymotrypsin was examined for oocytes collected at 14 h (shortly after ovulation), 17 h, and 20 h after hCG injection. Passage of spermatozoa through the zona pellucida (using an in vitro fertilization (IVF) technique) and the density of cortical granules were examined for oocytes collected at 14 and 17 h after hCG injection. The capability of the oolemma to fuse with the sperm plasma membrane was also evaluated by IVF using zona-free eggs. The zona pellucida became markedly resistant to the enzyme 17 h after hCG injection. IVF rates significantly decreased at this time. In addition, there was a significant reduction in the density of cortical granules. When zona-free oocytes were inseminated, high fertilization rates were obtained at both 17 and 14 h after hCG injection. These results indicate that accelerated modification of the zona pellucida primarily causes a decreased fertilizability of oocytes in 129 mice, resulting in the low reproductive performance of this strain.

Solar-to-Pharmaceutical Raw Material Production: Photoelectrochemical Naphthoquinone Formation Using Stabilized BiVO4 Photoanodes in Acid Media.

In the quest for efficient use of solar energy to produce high-value-added chemicals, we first achieved the photoelectrochemical (PEC) diketonization of naphthalene, using a BiVO4/WO3 photoanode, to obtain naphthoquinone, an important pharmaceutical raw material with excellent efficiency by solar energy conversion. In the electrochemical (EC) reaction using F-doped SnO2 (FTO) substrates and a 0.5 M H2SO4 H2O-acetone (60 vol %) mixed solution containing 5 mM naphthalene, we produced a small amount of naphthoquinone evolution in the dark. However, naphthoquinone (ηNQ)'s Faradic efficiency and its evolution rate at 1.7 VAg/AgCl were only 28.5% and 0.48 µmol·cm-2·h-1, respectively. The PEC reaction using a WO3 photoanode had very low efficiency for naphthalene diketonization, with low ηNQ and evolution rate values at 1.1 VAg/AgCl of 0.3% and 0.039 µmol·cm-2·h-1, respectively. In contrast, the BiVO4/WO3 photoanode strongly enhanced the PEC reaction, and the ηNQ and evolution rates at 1.1 VAg/AgCl were boosted up to 37.5% and 4.7 µmol·cm-2·h-1, respectively. The evolution rate of the PEC reaction in the BiVO4/WO3 photoanode was 10 times higher than that of the EC reaction with the FTO substrate regardless of the very low bias voltage. This result suggests that the BiVO4-based photoanode was very efficient for the selective oxidation of naphthalene even in acid media because of the acetone-mixed electrolyte's anti-photocorrosion effect and the multilayering of WO3 and BiVO4. At a naphthalene concentration of 20 mM, the naphthoquinone evolution rate reached its maximum value of 7.1 µmol·cm-2·h-1. Although ηNQ tended to decrease with the increase in the electric charge, it reached 100% at a low bias voltage of 0.7 VAg/AgCl. An intensity-modulated photocurrent spectroscopy analysis indicated the rate constant of charge transfer at the photoanode surface to the naphthalene molecules was strongly enhanced at a low bias voltage of 0.7-1.1 VAg/AgCl, resulting in the high ηNQ value. The acid-resistant BiVO4/WO3 photoanode functioned in acetone-mixed electrolytes enabled the realization of a new PEC oxidation reaction driven by solar energy to produce high-value-added pharmaceutical raw materials.

Acid-Resistant BiVO4 Photoanodes: Insolubility Control by Solvents and Weak W Diffusion in the Lattice.

We have revealed for the first time that BiVO4 photoanodes can be used even in strong acid media by mixing organic solvents into the electrolyte and depositing multilayers with a WO3 bottom layer. In general, the BiVO4 photoanodes are photocorrosive, especially in acid solutions. However, this shortcoming has been overcome using a combination of the two aforementioned modifications. We deduced that the contribution of each mixing organic solvent for the anti-photocorrosion of BiVO4 in sulfuric acid solutions can be evaluated on the basis of a new empirical indicator that incorporates molecular density, the Hansen solubility parameter, and molecular polarizability. Acetone and tert-butyl alcohol were especially promising solvents for stabilizing BiVO4 in acid media. We confirmed that the mixed organic solvents stabilized surface-emergent Bi oxide species as a passivation layer, which was generated via multilayering with a WO3 bottom layer. During heat treatment in the fabrication process, W weakly diffused into the BiVO4 layer and a Bi oxide layer was formed on the outermost surface because of the Bi segregation that arose from the charge compensation between W6+ and V5+ in the BiVO4 lattice. The surface Bi oxide layer, which was protected by the mixed organic solvents, steadily served as a passivation layer for anti-photocorrosion of the underlying BiVO4 layer. We have confirmed that the BiVO4/WO3 photoanodes in acetone-mixed aqueous sulfuric acid solution reliably functioned for a photoelectrochemical reaction under simulated sunlight illumination, and photoelectrochemical production of S2O82- ions was confirmed under light irradiation at λ > 480 nm. These results suggest that the BiVO4-based photoanodes have significant potential for use in acid media in conjunction with very straightforward modifications.

Chromosome analysis of mouse zygotes produced by intracytoplasmic injection of spermatozoa exposed to acrosome reaction inducing agents methyl-beta-cyclodextrin and calcium ionophore A23187.

PURPOSE: This study was performed to investigate whether removal of cholesterol from the plasma membrane and collapse of the acrosome can prevent structural chromosome aberrations of paternal origin in mouse zygotes produced by intracytoplasmic sperm injection (ICSI). METHODS: Mouse spermatozoa were treated with methyl-beta-cyclodextrin (M beta CD) to remove cholesterol from the plasma membrane and with calcium ionophore A23187 to collapse the acrosome. Chromosomes of zygotes derived from M beta CD- and ionophore-treated spermatozoa were analyzed at the first mitotic metaphase. RESULTS: Both chemical agents effectively induced the acrosome reaction. Incidence of structural chromosome aberrations in ICSI zygotes derived from M beta CD-treated spermatozoa was similar to that in zygotes produced by in vitro fertilization (IVF) with the same spermatozoa, but significantly lower compared to ICSI zygotes derived from acrosome-intact spermatozoa. Chromosome aberration rates in ICSI zygotes derived from ionophore-treated spermatozoa were evidently high compared to IVF zygotes. CONCLUSIONS: Induction of the acrosome reaction through cholesterol efflux by M beta CD can prevent chromosome aberrations of paternal origin, while use of ionophore to induce the acrosome reaction exerts detrimental effect on paternal chromosomes in ICSI zygotes.