Biomedical subjects

Masashi Nagano

Publications and source records attributed to Masashi Nagano.

10 recordsLinked to original sources

PubMed2006

Relationship between bovine oocyte morphology and in vitro developmental potential.

We investigated the relationship between the morphology of oocytes collected from small antral follicles and their developmental capacity. Immature oocytes were classified into seven groups and cultured in vitro for maturation (IVM), fertilization (IVF) and development to blastocysts (IVC). After IVF, sperm penetration and normal fertilization rates were higher in the oocytes whose cytoplasm appeared brown. The rate of polyspermy was highest in the oocytes whose cytoplasm was black. After IVC, the rates of cleavage and of development to the blastocyst stage were also higher in the brown oocytes. Although the oocytes with dark clusters in a pale cytoplasm showed lower cleavage rates, cleaved zygotes had high developmental rates the same as the oocytes with a brown cytoplasm. Transmission electron microscopy showed that the oocytes with a pale or black cytoplasm had organelles arranged differently from other oocytes before IVM. Most of the oocytes with a brown and homogeneous cytoplasm or small diameter had the characteristics of immature cytoplasm (large clusters of cortical granules) even after IVM. On the other hand, the brown oocytes with a dark zone at the periphery or with dark clusters showed the same arrangement of organelles as in vivo matured oocytes. The oocytes with a pale or black cytoplasm appeared to be degenerating and/or ageing. In conclusion, a dark ooplasm indicates an accumulation of lipids and good developmental potential, while a light-coloured ooplasm indicates a low density of organelles and poor developmental potential. A black ooplasm indicates ageing and low developmental potential.

Animals↗

PubMed2006

[Yoke technique for severe proximal hypospadias].

UNLABELLED: PROPOSED: Various techniques have so far been reported for the repair of hypospadias, however, a one-stage procedure for the repair of severe proximal hypospadias still remains difficult to perform. We recently have begun to use the Yoke hypospadias repair technique for the treatment of severe proximal hypospadias. PATIENTS AND METHODS: As the chief surgeon, I performed a one-stage hypospadias repair on 40 proximal hypospadiac patients with severe fibrous chordee between July 1992 and December 2004. During the early period, eleven patients underwent urethroplasty by the Transverse Preputial Island Flap techinique (TPIF). Next, 10 patients underwent One-stage Urethroplasty with Parameatal Foreskin flap technique (OUPF IV). Finally, the most recent 19 had their hypospadias repaired by the Yoke technique. RESULTS: With the TPIF technique in the early periods, only 6 out of 11 patients underwent a successful repair (54.5%). With the OUPF IV technique, the success rate was only 60.0% (6 out of 10 cases). In contrast, 17 out of 19 cases treated by the Yoke technique in the most recent period had a successful repair, although proximal urethrocutaneous fistula and urethral stenosis occurred in one patient, respectively. A relatively high success rate was therefore obtained using the Yoke technique for the repair of severe proximal hypospadias. CONCLUSION: The Yoke techniques for the repair of hypospadias is therefore considered to be a safe and effective technique for the repair of proximal hypospadias because of the continuous skin flap of the ventral urethral plate and the prepuce with a blood supply from the circumferential vascular pedicle. We consider this technique to be very useful for the treatment of severe proximal hypospadias.

Adolescent↗

PubMed2005

Analysis of genetic variations in the exon 27 region of the canine BRCA2 locus.

Mammary tumors are the most common tumor type in women as well as in female dogs. The BRCA2 gene encodes a large nuclear protein that is involved in DNA repair, and mutations in the human BRCA2 confer an increased risk of female mammary tumors. The BRCA2 protein acts as a tumor suppressor, and inactivation of BRCA2 by loss of heterozygosity is implicated in mammary carcinogenesis. In this study, to establish an appropriate polymorphic marker for loss of heterozygosity analysis of the canine BRCA2, we analyzed the genomic sequences of the exon 27 regions of 30 mammary-tumor-bearing and 21 tumor-free dogs. In addition to 10204ins/delAAA, which is the only polymorphism previously identified for the canine BRCA2 locus, we discovered four novel single nucleotide polymorphisms. The analysis of these five polymorphisms revealed the presence of four allele types. Since 10204ins/delAAA was the most common of the five polymorphisms identified, we developed a PCR-based assay method to assay for this polymorphism. We believe that this method is valuable for loss of heterozygosity analysis of the canine BRCA2 gene in tumor pathogenesis.

Animals↗

PubMed2005

Effects of different alpha-1 adrenoceptor blockers on proximal urethral function using in vivo isovolumetric pressure changes.

The effects of different alpha-1 adrenoceptor blockers on the urethra and the cardiovascular system were evaluated using an in vivo isovolumetric intra-urethral pressure model in New Zealand white rabbits. The urethra of anesthetized male rabbits was cannulated through the bladder and secured at the vesico-urethral junction. The distal side of urethra under the pubic bone was also closed to allow measurement of the intra-urethral pressure. Both the intra-urethral pressure and the femoral arterial pressure were monitored. The effects of five different alpha-1 adrenoceptor blockers on the increases in both the intra-urethral pressure and blood pressure induced by phenylephrine were then examined. The inhibition rate of the alpha-1 adrenoceptor blockers prazosin, bunazosin, terazosin, alfuzosin and tamsulosin on the increase in intra-urethral pressure caused as a result of contraction by phenylephrine was 87.5 +/- 4.5% (mean +/- S.E.), 88.0 +/- 7.2%, 86.2 +/- 6.2%, 81.4 +/- 4.8% and 92.5 +/- 5.0% respectively. The potency ranking of these alpha-1 adrenoceptor blockers was tamsulosin > bunazosin > prazosin > terazosin > alfuzosin. Their inhibition rate of the arterial pressure increase induced by phenylephrine was 81.9 +/- 5.0%, 86.2 +/- 5.9%, 76.0 +/- 6.0%, 63.6 +/- 5.7% and 58.0 +/- 5.2% respectively, with a potency ranking of bunazosin > prazosin > terazosin > alfuzosin > tamsulosin. We therefore conclude that the alpha-1 adrenoceptor blockers bunazosin and prazosin have a more potent action on both the urethra and the vascular system. However, tamsulosin and alfuzosin displayed a marked blockade of the increased urethral pressure induced by phenylephrine, with much less of a blockade of arterial pressure. In the present study, tamsulosin has been shown to be the most sensitive and powerful of the alpha-1 adrenoceptor blockers on urethral smooth muscle.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed2005

Insertion/deletion polymorphism in the BRCA2 nuclear localization signal.

Mutations in human BRCA2 confer an increased risk of female breast cancer. In this study, we found a novel insertion/deletion polymorphism (10204insAAA causing amino acid change M3332IK) in canine BRCA2, which is located in the putative second nuclear localization signal (NLS2) and C-terminal Rad51-binding region. The nuclear localization of the insAAA C-terminus was more efficient than localization of the delAAA sequence when NLS1 was mutated. Strong, comparable Rad51 binding was observed for both the insAAA and delAAA C-termini. Dogs with the insertion/deletion polymorphism will provide a new model for studying the function of BRCA2.

Alleles↗

PubMed2004

In vitro culture of mouse preantral follicles using membrane inserts and developmental competence of in vitro ovulated oocytes.

To develop a reliable follicle culture system, mouse preantral follicles 150-200 microm in diameter were cultured individually for 5 or 6 days in membrane inserts or in droplets, and then induced to ovulate with hCG (Experiment 1). The nuclear maturation and developmental competence of the oocytes that ovulated from the follicles cultured in inserts were determined (Experiment 2). There was no significant difference between the two culture systems in the survival rate (83 and 77%). However, follicles cultured in inserts showed a higher ovulation rate (63%) than those cultured in droplets (39%, P<0.05). About 80% of the oocytes that ovulated from the follicles cultured in inserts were at the metaphase II stage. After in vitro fertilization, 75 and 48% of in vitro ovulated oocytes cleaved and developed into blastocysts, respectively. These results demonstrate that the insert culture system is superior to the droplet culture system in terms of follicular growth and ovulation, and can be used to investigate the growth and ovulation of follicles in vitro.

Animals↗

PubMed2004

Follicular development after ovum pick-up and fertilizability of retrieved oocytes in postpartum dairy cattle.

This study aimed to evaluate gonadotropin secretion and the developmental competence of follicular oocytes in dairy cattle during the early postpartum (PP) period. The number of follicles developed after transvaginal ultrasound-guided ovum pick-up (OPU) and fertilizability of retrieved oocytes were compared between cows in which the first dominant follicle (DF) ovulated (ovulated group, n=4) and did not ovulate (non-ovulated group, n=3), and between early PP (early PP group, n=2) and after the resumption of the estrous cycle (cyclic group, n=2). Follicular ablation was performed 2-4 days after the detection of DF in the second follicular wave PP. OPU was repeated 3-5 times at 3 or 4-day intervals from 3-4 days after the follicular ablation. At OPU, the follicles were enumerated and all those > or = 5 mm in diameter were aspirated. Recovered oocytes were subjected to in vitro maturation and fertilization. Both criteria were similar between ovulated and non-ovulated groups, and between early PP and cyclic groups. These results suggest that FSH/LH secretions required for follicle recruitment and subsequent follicular growth during the early PP period are similar to those after resumption of the estrous cycle. They also indicate that follicular oocytes during the early PP period have developmental competence.

Animals↗

PubMed2004

Effects of oxygen tension in the gas atmosphere during in vitro maturation, in vitro fertilization and in vitro culture on the efficiency of in vitro production of mouse embryos.

Effects of oxygen (O2) tension in the gas atmosphere during in vitro maturation (IVM), in vitro fertilization (IVF) and in vitro culture (IVC) on the efficiency of in vitro production of mouse embryos were examined. Mouse oocytes recovered from large antral follicles were subjected to IVM in Waymouth medium for 15, 16 and 17 hr under 5 or 20% O2 and then subjected to IVF and IVC under 5 or 20% O2 tension. Lowering the O2 tension in the gas atmosphere for IVM from 20 to 5% improved the cleavage rate after IVF when the oocytes were subjected to IVM for 15 hr; however, no improvement in the cleavage rate was observed when the culture period for IVM was extended to 16 and 17 hr. Lowering the O2 tension to 5% for IVM and IVC improved the development of the cleaved oocytes to the blastocyst stage, regardless of the culture period for IVM. However, the O2 tension for IVF had no remarkable effect on the subsequent embryonic development. These results demonstrate that 5% O2 is superior to 20% O2 for IVM and IVC, and suggest that 20% O2 for IVM may delay oocyte maturation and/or the acquisition of fertilizability and impair the developmental competence of oocytes.

Animals↗

PubMed2003

Effect of fusion/activation protocol on in vitro development of porcine nuclear transfer embryos constructed with foreign gene-transfected fetal fibroblasts.

The effect of fusion/activation protocol on in vitro development of porcine nuclear transfer (NT) embryos constructed with foreign gene-transfected somatic cells were investigated. NT embryos were produced by using enucleated M II oocytes and enhanced green fluorescence protein (EGFP) gene-transfected or non-transfected porcine fetal fibroblasts. One group of NT embryos received a single electrical pulse to induce fusion and activation simultaneously (FAS). The other group was fused 2 hr before activation (FBA) using two kinds of electrical pulses. Electrically activated NT embryos in both groups were treated with cycloheximide (CHX) before culture to assess the development to the blastocyst stage. After 6 days of culture, all morulae and blastocysts derived from EGFP-transfected fibroblasts emitted green fluorescence without mosaicism, and EGFP-gene product was also detected in all morulae and blastocysts examined. NT embryos undergoing FAS showed higher developmental capacity to blastocysts than those undergoing FBA, regardless of the EGFP transfection into the nuclear donor cells. The results also indicated that EGFP-gene transfection into nuclear donor cells has no obvious deleterious effect on the development of NT embryos to blastocysts.

Animals↗

PubMed2003

Effect of activation treatments of recipient oocytes on subsequent development of bovine nuclear transfer embryos.

Effects of recipient oocyte activation methods on the development of nuclear transfer (NT) embryos were investigated. In Exp. 1, cell-cycle phase of serum-starved bovine cumulus cells was examined by flow cytometry. Majority (95.5%) of medium-sized (16-20 microm) cells that made up 56% of total cells was at the G0/G1 phase. NT embryos were constructed by electric fusion with the medium-sized serum-starved cumulus cells and bovine oocytes of 3 different preparations: enucleated oocytes treated with calcium ionophore A 23187 for 5 min and cycloheximide for 5 hr (A 23187/CHX), those treated with ethanol for 7 min and cycloheximide for 2 hr(ethanol/CHX) and those without treatment. In Exp. 2 and 3, developmental competence of NT embryos constructed with A 23187/CHX- and ethanol/CHX-treated oocytes was compared to that of NT embryos constructed with non-treated oocytes, respectively. Further, nuclear behavior in 3 different NT embryos was examined in Exp. 4. Within 1 hr after fusion, majority of the NT embryos constructed with non-treated oocytes showed condensed chromosome. Three hours after fusion, about 50% of NT embryos constructed with non-treated or ethanol/CHX-treated oocytes showed a single pronucleus-like structure. NT embryos constructed with ethanol/CHX-treated oocytes showed similar rates of fusion, cleavage and blastocyst formation to those of the non-treated oocytes. In contrast, NT embryos constructed with A 23187/CHX-treated oocytes did not show any pronucleus-like structure and showed lower cleavage rate and no development to blastocysts. The results indicate that ethanol/CHX-treated oocytes could support development of somatic cell NT embryos to the blastocyst stage at a similar rate to that of non-treated oocytes.

Animals↗