Biomedical subjects

Hiroshi Sasada

Publications and source records attributed to Hiroshi Sasada.

At least 19 recordsLinked to original sources

PubMed2006

Role of the hyaluronan receptor CD44 during porcine oocyte maturation.

Previous our studies have shown that CD44, the principal receptor for hyaluronan, is present on cumulus cells during oocyte maturation. Although hyaluronan-CD44 interaction has been implicated in cumulus expansion and/or oocyte maturation, the full significance of CD44 remains unknown. The objective of the present study was to further investigate the role of CD44 in cumulus expansion and oocyte maturation in pigs. We demonstrate here in that CD44 has a key role in oocyte maturation but not in cumulus expansion. Previous studies have reported the physiological significance of cumulus expansion in oocyte maturation. However, our results suggest that cumulus expansion is a necessary condition for oocyte maturation, but that it is not sufficient on its own. Furthermore, western blot analysis demonstrated that the CD44 of the in vitro-matured cumulus-oocyte complexes (COCs) had a larger molecular weight and more terminal sialic acid, which has been proven to inhibit the hyaluronan-binding ability of the receptor, than the CD44 of the in vivo-matured COCs, indicating that the hyaluronan-CD44 interactions during in vitro maturation might be insufficient compared with those in vivo. The insufficient interactions of hyaluronan-CD44 during in vitro maturation may cause the inferior capacity of fertilization and development of oocytes matured in vitro.

Animals↗

PubMed2006

Effect of relaxin on in vitro fertilization of porcine oocytes.

Porcine relaxin is a peptide hormone belonging to the insulin super family that has a variety of biological functions. The present experiment was designed to investigate the effects of relaxin on sperm function and on in vitro fertilization (IVF) of porcine oocytes. Porcine spermatozoa were washed, swum-up, and incubated for 1-4 h in mTALP medium supplemented with 0, 20 or 50 ng/ml porcine relaxin. Motility was determined by observing the type of forward movement of the spermatozoa, and acrosome status was evaluated by applying the triple staining technique. Immature oocytes were aspirated from antral follicles and matured in IVM medium (modified NCSU-37). Matured oocytes were co-cultured with spermatozoa in IVF medium (mTALP) supplemented with 0, 5, 10, 15 or 20 ng/ml relaxin. After 6 h of sperm-oocyte co-incubation, putative zygotes were cultured for 18 h in oocyte culture medium NCSU-37 and then assessed for the rates of monospermy, polyspermy, and male pronucleus formation after acetic orcein staining. Relaxin improved (P<0.05) sperm motility and increased the percentage of acrosome-reacted live spermatozoa during 1-4 h of incubation, although viability was not significantly improved. Significantly (P<0.05) the highest percentage of monospermic (31.7%) and lowest percentage of polyspermic (16.5%) fertilization was achieved from the sperm-oocyte co-culture group treated with 20 ng/ml relaxin as compared to other groups. The percentage of male pronucleus formation was significantly (P<0.05) greater in the 20 ng/ml relaxin-treated sperm-oocyte co-culture group than in the other groups. These results indicate that supplementation with relaxin is capable of improving sperm function and fertilization of porcine oocytes in vitro.

Acrosome Reaction↗

PubMed2006

PKA implicated in the phosphorylation of Cx43 induced by stimulation with FSH in rat granulosa cells.

Connexin 43 (Cx43)-mediated gap junctional communication in granulosa cells is crucial for germ line development and postnatal folliculogenesis. We previously showed that follicle-stimulating hormone (FSH) promoted phosphorylation of Cx43 in rat primary granulosa cells. We further identified Ser365, Ser368, Ser369, and Ser373 in the carboxy-terminal tail as the major sites of phosphorylation by FSH, and found that the phosphorylation of these residues was essential for channel activity. In this study, we investigated the protein kinase(s) responsible for FSH-induced phosphorylation. H89, a cyclic AMP-dependent protein kinase (PKA) inhibitor, inhibited FSH-induced phosphorylation both in vivo and in vitro, whereas PD98059, a mitogen-activated protein kinase kinase (MEK) inhibitor, had little effect on the phosphorylation level. Ca2+-dependent protein kinase (PKC) appeared to negatively regulate phosphorylation. Phosphopeptide mapping with or without H89 treatment indicated that PKA could be responsible for phosphorylation of the four serine residues. In addition, the purified catalytic subunit of PKA could phosphorylate the recombinant C-terminal region of Cx43, but not the variant in which all four serine residues were substituted with alanine. These results suggest that FSH positively regulates Cx43-mediated channel formation and activity through phosphorylation of specific sites by PKA.

Animals↗

PubMed2005

Expression of Pin1, a peptidyl-prolyl isomerase, in the ovaries of eCG/hCG-treated immature female mice.

Protein phosphorylation on certain serine or threonine residues preceding proline (Ser/Thr-Pro) is a pivotal signaling mechanism in diverse cellular processes. Pin1 is a highly conserved enzyme that isomerizes only the phosphorylated Ser/Thr-Pro bonds in certain proteins, thereby inducing conformational changes. Although much protein is phosphorylated in the ovary, the role of Pin1 in the ovary is still unknown. The purpose of this study is to investigate the effects of gonadotropins on protein and mRNA expression of Pin1 in mice ovaries. Quantitative PCR analysis showed that the expression of Pin1 mRNA significantly increased in the ovaries of equine chorionic gonadotropin (eCG)-treated mice compared with those of untreated mice (P<0.05). However, human chorionic gonadotropin (hCG) attenuated the expression of Pin1 mRNA increased by eCG. The protein level of Pin1 showed the same tendency as the expression of mRNA. The mRNA expression of E2F transcription factor, which controlled the expression of Pin1, was significantly decreased in the eCG-treated ovaries compared with the controls (P<0.05). These observations suggest that gonadotropins may regulate the expression of Pin1 without E2F transcription factor, indicating that Pin1 might be an important factor for protein signal transduction during follicular development.

Animals↗

PubMed2005

Expression and glycosylation with polylactosamine of CD44 antigen on macrophages during follicular atresia in pig ovaries.

Macrophages are essential in cleaning up apoptotic debris during follicular atresia. However, the key factors of this process are still unclear. In the present study, we evaluated CD44 mRNA, CD44 protein, and CD44 antigen glycosylation on macrophages during follicular atresia in the pig. Atresia was classified into five stages: stage I, healthy follicles; stage II, early atretic follicles having apoptotic granulosa cells with an unclear basement membrane; stage III, progressing atretic follicles having apoptotic granulosa cells completely diffused from the basement membrane; stage IV, late atretic follicles with increasing lysosomal activity; and stage V, disintegrated atretic follicles having collapsed theca cells and strong lysosomal activity. Immunohistological analysis showed that macrophages expressing CD44 invaded the inside of stage III follicles, accompanied by a collapse of basement membrane. Semiquantitative RT-PCR showed that only mRNA of the CD44 standard isoform (CD44s) was present in inner cells of follicles, and not any CD44 variant isoform (CD44v) mRNAs. The amount of CD44s mRNA was increased at stage III. Western blot and lectin blot analyses showed that CD44 was markedly expressed at stage III and glycosylated with polylactosamine at the same time. After macrophages invaded atretic follicles at stages III-V, the CD44 expressed on macrophages was glycosylated with polylactosamine. The lysosomal activity began to increase at stage IV, and reached the highest level at stage V. Increased CD44s protein and posttranslational modification of CD44 with polylactosamine on macrophages from stage III could be involved in the cleaning up apoptotic granulosa cells.

Amino Sugars↗

PubMed2005

Differences in gene expression patterns between somatic cell nuclear transfer embryos constructed with either rabbit granulosa cells or their derivatives.

Successful production of offspring by somatic cell nuclear transfer (SCNT) is affected by the nature of the donor cells used. The purpose of this study was to determine whether characteristic changes induced in donor cells by culture conditions influenced gene expression patterns in the resultant SCNT embryos. Rabbit granulosa cells (rGC) were cultured under different conditions, either with or without hCG, and the two derivative cell types obtained (named respectively cGC+ and cGC-) were used as donor cells for SCNT. There were characteristic differences between fresh rGC and the two derivative cell types: p450scc expression and progesterone secretion were both higher in cGC+ than in cGC-; expression of bmp4 and fgfr2 was decreased in cGC+ and cGC- compared with rGC; and cGC+ and cGC- cell types gained collagenIV expression. Use of fresh rGC, or cGC+ and cGC- derivative cells, did not alter either the developmental potencies of SCNT oocytes or cell numbers at the blastocyst stage. The expression patterns of four genes (bmp4, fgfr2, gata4, oct3/4) in SCNT embryos and in fertilized embryos were analyzed by quantitative RT-PCR. We found that oct3/4 was expressed in all embryos. The expression patterns of the other three genes showed considerable variation between the different types of embryo: bmp4 was found in most fertilized embryos but only some of rGC and none of cGC+ and cGC- derived SCNT embryos; fgfr2 was present in fertilized embryos but was present in some rGC and cGC- NT embryos and in all cGC+ NT embryos; gata4 was not expressed in fertilized embryos but was present in a few rGC and cGC+ NT embryos and in most cGC- NT embryos. Our results suggest that the gene expression patterns in SCNT embryos derived from granulosa donor cells are affected by characteristic changes to the cells during in vitro culture.

Animals↗

PubMed2005

Changes of mRNA expression of vascular endothelial growth factor, angiopoietins and their receptors during the periovulatory period in eCG/hCG-treated immature female rats.

Angiogenic factors can induce the perifollicular capillary network in the theca interna that shows marked changes in and around the preovulatory luteinizing hormone (LH) surge. To get more information on their functional crosstalk, the aim of the present study was to investigate the manner of mRNA expression of vascular endothelial growth factors (VEGFs) 120, 164, angiopoietin (Ang)-1, Ang-2 and their specific receptors during the periovulatory phase. We used an established equine and human chorionic gonadotropins (eCG/hCG)-derived experimental model capable of stimulating naturally occurring follicular maturation, ovulation and corpus luteum (CL) formation. On day 28 postpartum, immature female rats were administrated s.c. with 10 IU of eCG to promote follicular development, followed 48 hr later by i.p. administration of 20 IU of hCG. Ovaries were dissected at 0, 6, 12, 18 and 24 hr after hCG treatment, and were obtained on day 30 in the untreated control. After induction of follicular growth by the eCG treatment, each mRNA expression of VEGF 120, VEGF 164, Neuropilin-1 and Flt-1 significantly increased. The peaks in mRNA expressions of VEGF120 and VEGF164 were both found at 18 hr after hCG treatment. Flk-1 mRNA expression maintained up to 6 hr after hCG treatment, and then decreased at 12, 18 and 24 hr after hCG treatment. Ang-2 mRNA expression increased in the ovaries at 6 and 12 hr after hCG treatment. Tie-2 mRNA expression decreased at 24 hr after the treatment of gonadotropins. Our findings suggest that ovarian vascular formation during the periovulatory period including preovulatory follicles, ovulation and CL formation may develop via crosstalk of the VEGF-Flt-1 and Ang-Tie2 systems.

Analysis of Variance↗

PubMed2005

Feasibility of a nylon-mesh holder for vitrification of bovine germinal vesicle oocytes in subsequent production of viable blastocysts.

To improve the feasibility of nylon-mesh holder for vitrification of bovine cumulus-oocytes complexes (GV-COCs) having germinal vesicle, this study was conducted to demonstrate effects of sugars and protocol of exposure in vitrification on subsequent in vitro maturation, ultrastructural changes, and in vitro development in bovine immature oocytes after cryopreservation using nylon mesh. Before vitrification, GV-COCs were exposed to the cryoprotectant, which was composed of 40% (v/v) ethylene glycol, 18% (w/v) Ficoll-70, and 0.3 M sucrose (EFS40) or 0.3 M trehalose (EFT40), either by single step or in a stepwise way. The maturation rates in the stepwise exposure with EFS40 or EFT40 were significantly higher (P < 0.05) compared with the corresponding rates in the single step. In the stepwise exposure, few abnormalities were observed compared with the single-step exposure, where most oocytes showed a highly vacuolated cytoplasm with many ruptured mitochondria. Cleavage rates in fertilized oocytes previously exposed stepwise to EFS40 or EFT40 were significantly higher than those exposed by the single-step procedure. The cleaved embryos derived from the stepwise exposure to EFS40 developed to blastocysts. After transfer of blastocysts derived from vitrified GV oocytes, a female calf was born. These results indicate that vitrification of large numbers of bovine GV-COCs using a nylon-mesh holder accompanied with stepwise exposure minimizes structural damage in organelles, resulting in yield of viable blastocysts following in vitro embryo production.

Animals↗

PubMed2005

Extrusion and removal of lipid from the cytoplasm of porcine oocytes at the germinal vesicle stage: centrifugation under hypertonic conditions influences vitrification.

In the present study, we examined a novel lipid removal method, centrifugation in solutions made hypertonic by adding 0.27 M sugar. This allowed the lipid to be extruded and removed without the loss of active mitochondria or extra cytoplasm. The type of sugar influenced the proportion of oocytes that could be stratified by centrifugation. Glucose induced the highest extrusion rate of lipid droplets. After vitrification the rates of survival, germinal vesicle breakdown and metaphase II were 30, 26, and 7%, respectively, for lipid-removed GV oocytes; this was significantly higher (P<0.05) than for corresponding vitrified lipid-intact oocytes (2, 0, and 0%, respectively). These results indicated that this method is useful to remove whole lipid droplets without losing mitochondria and improves cryotolerance of porcine GV oocytes.

Animals↗

PubMed2005

Production of live offspring from mouse germinal vesicle-stage oocytes vitrified by a modified stepwise method, SWEID.

OBJECTIVE: To evaluate viability and subsequent developmental ability in mouse germinal vesicle (GV) oocytes ultrarapidly vitrified with serial stepwise exposure. DESIGN: Experimental animal study. SETTING: University-based research laboratory. ANIMAL(S): Three- to 4-week-old female (C57BL/6J x CBA) F1 mice in a laboratory environment. INTERVENTION(S): Vitrified and thawed GV oocytes were subjected to in vitro maturation, fertilization, and culture, some of which were transferred to recipients. MAIN OUTCOME MEASURE(S): Postthaw survival, maturation, cleavage, development to blastocysts, and live births. RESULT(S): In the single-step preequilibrium, the rates of postthaw survival, maturation to metaphase II, and development to blastocysts were 97.5%, 95.8%, and 23.7%, respectively. In the serial 10-step preequilibrium developed in this study, which is named SWEID, the corresponding rates were 98.6%, 92.6%, and 42.9%, respectively, showing a statistically significantly higher rate of development to blastocysts in the SWEID group than in the single-step group. Transfer of two-cell-stage embryos derived from the GV oocytes vitrified by SWEID resulted in the production of live offspring. CONCLUSION(S): This is the first report that shows live birth after cryopreservation of mouse GV oocytes using an ultrarapid vitrification. Our method, SWEID, may have advantage in allowing storage of female gametes toward advances in infertility treatment and reproductive biology.

Animals↗

PubMed2005

Development of the pulsation device for rotary blood pumps.

A rotary blood pump (RP) is desirable as a small ventricular assist device (VAD). However, an RP is nonpulsatile. We tried to develop a device that attaches a pulse to the RP. We also tried to develop a pulse-generating equipment that was not air-pressure driven. The ball screw motor was considered a candidate. The application of a small-sized shape memory alloy was also attempted. An electrohydraulic system was adopted, and actuator power was connected to the diaphragm. The diaphragm was placed on the outer side of the ventricle. Most RPs that have been developed all over the world drain blood from the ventricle. The wave of a pulse should be generated if a pulse is added by the drawn part. The output assistance from the outer side of the ventricle was attempted in animal experiments, and the device operated effectively. This device can be used during implantable operation of RP. This may serve as an effective device in patients experiencing problems in peripheral circulation and in the function of internal organs.

Animals↗

PubMed2005

Acceleration of follicular development by administration of vascular endothelial growth factor in cycling female rats.

To address the role of follicular angiogenesis in the determination of ovulatory follicles and the effects of different vascular endothelial growth factor (VEGF) isoforms on follicular angiogenesis and development, mature female rats were treated with an angiogenic inhibitor (TNP-470), and also with VEGF 120 or 164 at different dosages (0.4, 0.8, 4.0 or 8.0 microg/kg body weight) for 3 days during the estrous cycle. Ovarian follicular angiogenesis, the population of large follicles and ovulation were examined. VEGF 120 (0.8 microg/kg) and 164 (8.0 microg/kg) treatments stimulated follicular angiogenesis in the theca interna layer, while TNP-470 treatment showed severe depression of follicular angiogenesis, and completely inhibited ovulation. After administration of VEGF 120 or 164, the number of healthy preovulatory follicles and ovulated oocytes increased significantly, concomitantly with a decrease in the number of atretic preovulatory follicles. The oocytes ovulated had normal fertilizability and developed to term with the same litter size as in the control rats. Our findings suggest that follicular angiogenesis may be a determinant of follicular development during the periovulatory phase, and that VEGF isoforms may play different important roles in regulating follicular angiogenesis.

Angiogenesis Inhibitors↗

PubMed2005

Caffeine promotes premature chromosome condensation formation and in vitro development in porcine reconstructed embryos via a high level of maturation promoting factor activity during nuclear transfer.

When the nucleus in G0/G1 phase is transferred to an enucleated oocyte by nuclear transfer (NT), its nuclear envelope is broken, followed by condensation of chromosome structure by maturation promoting factor (MPF). This morphological remodeling of the transferred interphase nucleus seems to be essential for subsequent development of NT embryos. In this study, we treated porcine NT embryos with caffeine, which has been reported to increase MPF activity, to keep their MPF level high during NT. When 2.5 mM caffeine was added to the handling medium, the proportion of NT embryos showing condensed chromosome increased significantly (P < 0.05). In NT embryos treated with caffeine, the activity of p34(cdc2) kinase was significantly (P < 0.05) higher than in those without caffeine at 3 h post-injection. In addition, the rate of development to the blastocyst stage after activation was significantly (P < 0.05) higher in NT embryos treated with caffeine. These results indicate that caffeine treatment can increase not only the rate of chromosome condensation but also the developmental rate to the blastocyst stage of porcine NT embryos. This action is most likely due to the support/increase of MPF activity throughout the process of NT.

Animals↗

PubMed2004

Comparison of heart rate variability and stroke volume variability.

In order to compare the heart rate variability (HRV) and stroke volume variability (SVV), supine electrocardiographic (ECG) and the time series data of left ventricular (LV) volume recordings were taken in 12 healthy adult male volunteers. The low frequency (LF) and high frequency (HF) peaks of HRV and SVV were evaluated quantitatively by power spectral analysis. The fractal dimension (FD) of the time series data was analyzed by the box-counting method. A LF peak around 0.1 Hz and a HF peak around 0.3 Hz were as clearly observed in the SVV spectrum as in the HRV spectrum. The LF/HF ratio in SVV was significantly lower than that in HRV, while the FD was significantly higher in SVV than in HRV. No significant correlation of HF, LF or FD was observed between HRV and SVV. Our results indicate that SVV provides different information about the activity of the autonomic nervous system than HRV.

Adult↗

PubMed2004

Bax-inhibiting peptide derived from mouse and rat Ku70.

Bax is a proapoptotic protein that plays a key role in the induction of apoptosis. Ku70 has activities to repair DNA damage in the nucleus and to suppress apoptosis by inhibiting Bax in the cytosol. We previously designed peptides based on the amino acid sequence of Bax-binding domain of human Ku70, and showed that these peptides bind Bax and inhibit cell death in human cell lines. In the present report, we examined the biological activities of other pentapeptides, VPTLK and VPALR, derived from mouse and rat Ku70. Cells in culture accumulated FITC-labeled VPTLK and VPALR, indicating that these peptides are cell permeable (human, mouse, rat, and porcine cells were examined). These peptides bound to Bax and suppressed cell death in various cell types including primary cultured cells. These data suggest that such Bax inhibiting peptides from three mammalian species may be used to protect healthy cells from apoptotic injury under pathological conditions.

Amino Acid Sequence↗

PubMed2004

Increased ovarian follicular angiogenesis and dynamic changes of follicular vascular plexuses induced by equine chorionic gonadotropin in the gilt.

Follicular angiogenesis and capillary degeneration are crucial ovarian processes in folliculogenesis. The present study was conducted to assess the changes in population of follicular vascular plexuses with different capillary status in prepubertal gilts 72 h after equine chorionic gonadotropin (eCG) (1,250 IU) treatment, using combined vascular corrosion casting and scanning electron microscopy. Follicular fluid concentrations of estradiol, progesterone and vascular endothelial growth factor (VEGF) were determined to confirm the follicular status. Based on the proliferative or degenerative characteristics of their capillaries, follicles were classified into three categories: active angiogenesis, low angiogenesis and degeneration. Irrespective of exogenous gonadotropin treatment in vivo, small follicular vascular plexuses (<4 mm in diameter) exhibited all three conditions in casted ovaries, while medium (4-5 mm) and large (>5 mm) plexuses showed only active angiogenesis or degeneration. eCG treatment significantly increased the population of large, but decreased that of small follicular plexuses. Most large follicular vascular plexuses showed active angiogenesis with higher follicular fluid estradiol: progesterone ratios and VEGF concentration. eCG also increased the percentage of medium follicular plexuses with active angiogenesis. The populations of small follicular plexuses with active angiogenesis were higher in controls, but decreased after eCG treatment. However, treatment of gilts with the gonadotropin increased the percentage of small plexuses (<1.0 mm) with low angiogenesis and those (1-3.9 mm) with extensive capillary degeneration. These findings are consistent with the hypothesis that angiogenesis is involved in selection and growth of small follicles in gilts under the regulation of gonadotropin.

Animals↗

PubMed2004

Differential effect of recipient cytoplasm for microtubule organization and preimplantation development in rat reconstituted embryos with two-cell embryonic cell nuclear transfer.

In the present study, we examined the developmental ability of enucleated zygotes, MII oocytes, and parthenogenetically activated oocytes at pronuclear stages (parthenogenetic PNs) as recipient cytoplasm for rat embryonic cell nuclear transfer. Enucleated zygotes as recipient cytoplasm receiving two-cell nuclei allowed development to blastocysts, whereas the development of embryos reconstituted with MII oocytes and parthenogenetic PNs was arrested at the two-cell stage. Previous observations in rat two-cell embryos suggested that the distribution of microtubules is involved in two-cell arrest. Therefore, we also examined the distribution of microtubules using immunofluorescence. At the two-cell stage after nuclear transfer into enucleated zygotes, microtubules were distributed homogeneously in the cytoplasm during interphase, and normal mitotic spindles were observed in cleaving embryos from the two- to four-cell stage. In contrast, embryos reconstituted with MII oocytes and parthenogenetic PNs showed aberrant microtubule organization. In enucleated zygotes, fibrous microtubules were distributed homogeneously in the cytoplasm. In contrast, dense microtubules were localized at the subcortical area in the cytoplasm and strong immunofluorescence intensity was observed at the plasma membrane, while very weak intensity was detected in the central part of enucleated MII oocytes. In enucleated parthenogenetic PNs, high-density and fibrous microtubules were distributed in the subcortical and central areas, respectively. Pre-enucleated parthenogenetic PNs also showed lower intensity of microtubule immunofluorescence in the central cytoplasm than zygotes. In conclusion, the results of the present study showed that zygote cytoplasm is better as recipient than MII oocyte and parthenogenetic PNs for rat two-cell embryonic cell nuclear transfer to develop beyond four-cell stage. Furthermore, microtubule organization is involved in the development of reconstituted embryos to overcome the two-cell arrest.

Animals↗

PubMed2004

Phosphatidylinositol 3-kinase and Akt participate in the FSH-induced meiotic maturation of mouse oocytes.

Phosphatidylinositol 3-kinase (PI3K) is known to play critical roles in signal transduction processes related to a variety of cellular activities. In the present study, we investigated the role of PI3K during meiotic maturation in mouse oocytes using a specific inhibitor, LY294002. In follicle-stimulating hormone (FSH)-induced reversal of hypoxanthine-mediated meiotic arrest of cumulus oocyte complexes (COCs), LY294002 suppressed germinal vesicle breakdown (GVBD), first polar body (PB1) emission, and cumulus expansion. To examine the effect of LY294002, denuded oocytes (DOs) were cultured in medium containing follicular fluid meiosis-activating sterol (FF-MAS) since absence of gonadotropin receptors in oocytes has been reported and FSH did not stimulate meiotic maturation of DOs in the presence of hypoxanthine. In FF-MAS-induced maturation of DOs, LY294002 suppressed PB1emission, but not GVBD. In spontaneous gonadotropin-independent oocyte maturation, LY294002 had no effect on COCs and DOs. Akt/protein kinase B, a serine-threonine kinase, is a key downstream effector of the PI3K pathway. Therefore, we also examined the distribution of Akt during FSH-induced meiotic maturation. The distribution of Ser(473) phosphorylated Akt was similar to the localization of microtubules, while Thr(308) phosphorylated Akt was present in the pericentriolar materials (PCM) in metaphase I (MI) and II (MII) oocytes. LY294002 decreased the amount of Thr(308) phosphorylated Akt to very low to undetectable levels in MI and MII oocytes. Ser(473) phosphorylated Akt showed aberrant distribution and very low to undetectable levels of expression in LY294002-treated MI and MII oocytes, respectively. These results suggest that PI3K and Akt participate in mouse meiotic maturation.

Animals↗