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Biomedical subjects

Y Toyoda

Publications and source records attributed to Y Toyoda.

At least 145 records · Page 8Linked to original sources
PubMed1996

Effects of phosphate on in vitro 2-cell block of AKR/N mouse embryos based on changes in cdc2 kinase activity and phosphorylation states.

This study demonstrated the effects of phosphate on the 2-cell block of AKR/N mouse embryos at the molecular level and focused on changes in the kinase activity and the phosphorylation state of cdc2, which is shown to regulate the cell division cycle. Removal of phosphate from the culture medium dramatically increased developmental rates to the 4-cell (91.8%) and blastocyst (42.6%) stages compared with those of embryos cultured in 1.17 mM phosphate (3.3% and 0%, respectively). The rate of development to the 4-cell stage was significantly inhibited by 0.001 mM phosphate (p < 0.05), and no morula formation was observed at 1.0 mM. The patterns of cdc2 kinase activity during the first cell cycle in AKR/N embryos were similar to those of control MCH embryos, showing the highest activity at M phase and low activity during the interphase. The phosphorylated form of cdc2 increased during the interphase, indicating that the synthesis of cyclin B and accumulation of inactive pre-maturation-promoting factor (pre-MPF) as well as abrupt dephosphorylation of cdc2 at the first cleavage correlated with the activation of cdc2 kinase. When phosphate was absent, the activation pattern of cdc2 kinase during the second cell cycle in AKR/N embryos was similar to that in the first cell cycle. On the other hand, no dephosphorylation of cdc2 was observed and the kinase activity remained at a low level until 56 h after insemination in the presence of phosphate, although an increase in phosphorylated cdc2 was observed as in the phosphate-free group. Treatment of AKR/N embryos arrested at the 2-cell stage with okadaic acid resulted in the dephosphorylation and activation of cdc2, confirming the presence of a sufficient amount of pre-MPF. These results show that phosphate has a deteriorative effect on the in vitro development of AKR/N embryos and suggest that this effect was not on the synthesis of cyclin B but on the dephosphorylation of phosphorylated cdc2.

Animals↗
PubMed1996

Meiotic abnormalities of c-mos knockout mouse oocytes: activation after first meiosis or entrance into third meiotic metaphase.

In Xenopus oocytes, Mos activates the mitogen-activated protein kinase (MAPK) signal transduction cascade and regulates meiosis. In mammalian oocytes, however, the functions of Mos are still unclear. In the present study, we used c-mos knockout mouse oocytes and examined the roles of Mos in mouse oocyte maturation and fertilization, including whether Mos controls MAPK and maturation promoting factor (MPF) activity. The kinetics of germinal vesicle breakdown (GVBD) and the first polar body emission were similar in wild-type, heterozygous mutant, and homozygous mutant mice. Activities of MPF were also not significantly different among the three genotypes until the first polar body emission. In contrast, MAPK activity in c-mos knockout oocytes did not significantly fluctuate throughout maturation, and the oocytes had abnormal diffused spindles and loosely condensed chromosomes, although a clear increase in MAPK activities was observed after GVBD in wild-type and heterozygous mutant oocytes that had normal spindles and chromosomes. After the first polar body emission, 38% of c-mos knockout oocytes formed a pronucleus instead of undergoing second meiosis, indicating the crucial role of Mos in MPF reactivation after first meiosis. When oocytes that reached second metaphase were fertilized or stimulated by ethanol, many c-mos knockout oocytes emitted a second polar body and progressed into third meiotic metaphase instead of interphase, although all fertilized or activated oocytes in the heterozygote progressed to interphase, indicating that Mos deletion leads to compensatory factors that might not be degraded after fertilization or parthenogenetic activation. These results suggest that Mos is located upstream of MAPK in mouse oocytes as in Xenopus oocytes but is independent of MPF activity, and that Mos/MAPK is not necessary go GVBD and first polar body emission. Our results also suggest that Mos plays a crucial role in normal spindle and chromosome morphology and the reactivation of MPF after first meiosis.

Animals↗
PubMed1996

Torsade de pointes ventricular tachycardia following coronary artery spasm during general anaesthesia.

We present a patient who suffered two episodes of torsade de pointes ventricular tachycardia during general anaesthesia for abdominal surgery. The first occurred on suctioning of the tracheobronchial tree and the second while anaesthesia was light. Since ST segment elevation was in each case noted before the onset of torsade de pointes, coronary artery spasm was suspected to be the cause. An intravenous infusion of nitroglycerine was effective in treating and preventing these episodes. These findings suggest that coronary artery dilators such as nitroglycerine are indicated for initial treatment of torsade de pointes following coronary artery spasm in order to facilitate recovery from myocardial ischaemia.

Anesthesia, General↗
PubMed1996

Maintenance of pluripotency in mouse embryonic stem cells persistently infected with murine coronavirus.

A persistently coronavirus-infected embryonic stem (ES) cell line A3/MHV was established by infecting an ES cell line, A3-1, with mouse hepatitis virus type-2. Although almost all A3/MHV cells were found infected, both A3/MHV and A3-1 cells expressed comparable levels of cell surface differentiation markers. In addition, A3/MHV cells retained the ability to form embryoid bodies. These results suggest that persistent coronavirus infection does not affect the differentiation of ES cells.

Animals↗
PubMed1996

Characterization of T cells expanded in vivo during primary mouse hepatitis virus infection in mice.

After intraperitoneal infection with mouse hepatitis virus, strain JHM (JHMV), JHMV replicated in the spleen of C57BL/6 mice for a few days but cleared within a week. The acute viral clearance coincided with moderate expansion of CD8+T cells and modest expansion of CD4+T cells, and was impaired moderately in mice depleted of CD8+T cells and completely in mice depleted of both CD4+ and CD8+T cell subsets. Flow cytometric analysis showed that expression of cell surface markers on the spleen T cells changed during JHMV infection. CD8+T cells expressing increased amounts of CD11a, CD43, CD44 and CD49d, and those expressing decreased levels of T cell receptor alpha beta, CD8, CD45RB and L-selectin were expanded in the spleen after JHMV infection. However, they did not express CD11b, CD25 or NK1.1. They used highly heterogenous V beta chains for their T cell receptors. In addition to CD11ahighCD8+T cells, CD11ahighCD4+T cells were detected transiently after JHMV infection. The virus-specific cytotoxic T lymphocyte (CTL) activity was observed in both CD4+ and CD8+ spleen T cells from mice 7 days post-infection. The present study shows the dynamics of CD8+ and CD4+T cells in the spleen during JHMV infection in mice and suggests that CD11ahighT cells may be involved in JHMV clearance in vivo because their appearance was temporally correlated with T cell-mediated viral clearance in vivo and antiviral CTL activity in vitro.

Animals↗
PubMed1996

Magnetic resonance imaging of the internal structure of the mouse fetus.

Magnetic resonance imaging (MRI) has potential as an imaging technique in fetal anatomy. In this article are presented images obtained from mouse fetuses at 16 days of pregnancy by means of the ultraconductive MRI system (JEOL AIM270). When fetuses removed from the uterus were fixed with 10% neutral formalin, various organs including heart, liver, lungs and bones were clearly seen, and a clear outline was obtained of the fetal skin and subcutaneous tissue by varying the setting. The same specimens were able to be used for histological evaluation. This MRI system will allow wider application in fetal anatomy and provide additional information about the developing mouse fetus.

Abdomen↗
PubMed1996

Typing of X chromosomes bearing Tabby allele in mouse preimplantation embryos by detection of a microsatellite marker.

Tabby (Ta) is a semidominat allele of the locus on the mouse X chromosome, which causes a characteristic coat pattern and developmental defects in endocrinic glands. To establish a method for identifying the X chromosome bearing the Ta allele in early preimplantation embryos, we performed PCR amplification of an X chromosomal microsatellite marker locus from preimplantation embryos obtained from mating between XO female and XY male mice. The microsatellite marker locus was shown to be polymorphic between X chromosomes bearing the Ta and wild-type alleles. The amplification of the marker locus from early preimplantation embryos demonstrated that the Ta locus can be correctly typed by this method from embryos as little as 2 cells.

Animals↗
PubMed1996

Adrenal tumor producing 11-deoxycorticosterone, 18-hydroxy-11-deoxycorticosterone and aldosterone.

A case of adrenal tumor producing 11-deoxycorticosterone, 18-hydroxy-11-deoxycorticosterone and aldosterone is reported. A 55-year-old woman had hypertension, hypokalemia, low plasma renin activity and an adrenal tumor. The plasma level of aldosterone was normal, and the levels of 11-deoxycorticosterone and 18-hydroxy-11-deoxycorticosterone were extremely high. After the tumor removal, the plasma level of aldosterone decreased and plasma levels of 11-deoxycorticosterone and 18-hydroxy-11-deoxycorticosterone were normalized. The tumor was benign adenoma and the production of steroid hormones was under control of adrenocorticotropic hormone. The enzyme activity of 21-hydroxylation in the tumor was elevated and that of 11 beta-hydroxylation was decreased compared with the adjacent tissue.

18-Hydroxydesoxycorticosterone↗
PubMed1996

Successful surgical treatment of cardiac cirrhosis. Tricuspid surgery and plasma exchange.

A patient with cardiac cirrhosis due to severe tricuspid regurgitation associated with a mitral valve lesion successfully underwent mitral and tricuspid valve replacement. Preoperative rest cure with liver supporting therapy for 5 months was used to maximize hepatic and cardiac function. Postoperatively, jaundice developed despite improvements in cardiac function. Plasma exchange was performed nine times over a period of 10 days with the liver function improved. He was discharged with New York Heart Association class I symptoms and normal liver function 2 months following surgery.

Heart Valve Prosthesis↗
PubMed1996

[Detection of early cardiac dysfunction in patients with transfusion-dependent aplastic anemia and chronic iron overload in childhood. Stress-velocity relation as a sensitive index by echocardiography].

In order to detect early-stage left ventricular dysfunction, we examined a load-independent index, that is, the stress-velocity relation, by echocardiography in 13 patients with aplastic anemia including pure red cell anemia. Even when left ventricular contractility and pump function were within the normal range, its afterload had a tendency to increase in transfusion-dependent patients. The patients who had impairment of cardiac pump function died of congestive heart failure within one year after abnormal findings in stress-velocity relation were detected. Therefore, the stress-velocity relation is a sensitive, useful and noninvasive index for detecting asymptomatic myocardial dysfunction in patients with transfusion-dependency and chronic iron overload. It is necessary for these patients to undergo examinations of echocardiography at regular intervals. In case of abnormally in the stress-velocity relation, treatment for afterload mismatch and more effective chelation should be recommended to reduce the burden on the heart. Thereby, the heart is kept in better condition and the prognosis of these patients will be improved.

Adolescent↗
PubMed1995

Nuclear location of the regulatory protein of glucokinase in rat liver and translocation of the regulator to the cytoplasm in response to high glucose.

Rat liver is known to contain a regulatory protein (RP) that inhibits glucokinase competitively with respect to glucose. By an immunohistochemical technique and by cell fractionation in glycerol, we investigated the distribution of RP in rat liver and its changes in response to high glucose. RP was detected almost exclusively in the nuclei of the parenchymal cells of both fed and fasted rats. In situ perfusion of the liver with 20 mM glucose for 10 min caused a marked decrease in nuclear RP and an increase in cytoplasmic RP. These results indicate that RP is present predominantly in the nuclei of hepatocytes and is translocated from the nucleus to the cytoplasm in response to high glucose.

Animals↗
PubMed1995

Allele-dependent recombination frequency: homology requirement in meiotic recombination at the hot spot in the mouse major histocompatibility complex.

Meiotic recombination break joints in the mouse major histocompatibility complex (MHC) are clustered within short segments known as hot spots. We systematically investigated the requirement for sequence homology between two chromosomes for recombination activity at the hot spot next to the Lmp2 gene. The results indicated that a high rate of recombination required a high degree of similarity of overall genome structure at the hot spot. In particular, the same copy number of repetitive sequences within the hot spot was essential for a high frequency of recombination, suggesting that recombination in mouse meiosis is more sensitive to heterozygous deletion or insertion of DNA than to mismatches of single-base substitutions.

Alleles↗
PubMed1995

Changes in subcellular and zonal distribution of glucokinase in rat liver during postnatal development.

Subcellular and zonal distribution of glucokinase in rat liver during postnatal development was examined immunohistochemically. Before day 11 after birth, only some hepatocytes were immunostained, and a positive immunostaining was found in the cytoplasm but not in the nucleus. No zonal distribution of glucokinase was observed in livers of such pups. From day 15, at which time a dietary change from milk to laboratory chow begins to take place, glucokinase immunoreactivity increased; this increase was associated with increases in glucokinase activity and in glucokinase protein, and also the immunostaining was observed mainly in the nuclei. At day 21, the glucokinase immunoreactivity was found almost exclusively in the perivenous zone. At day 30, an intense immunostaining was seen both in the perivenous zone and in the periportal zone, being slightly predominant in the former. The present results indicate that dramatic changes in the distribution of glucokinase in developing rat liver may be related to dietary change.

Aging↗
PubMed1995

Histone H1 kinase activity during in vitro fertilization of pig follicular oocytes matured in vitro.

The present study was conducted to clarify the relationship between histone H1 kinase (H1K) activity and events associated with in vitro fertilization of pig follicular oocytes matured in vitro. Histone H1 kinase has been shown to be homologous with a maturation promoting factor (MPF). Cumulus-oocyte complexes obtained from prepubertal gilts were cultured for 46 h in a modified Waymouth's MB752/1 medium and were then inseminated in vitro with frozen-thawed and preincubated epididymal boar spermatozoa. At 4, 6, 8 and 10 h post insemination, the oocytes were stained with 10 microg/ml Hoechst-33342 and examined under a fluorescent microscope for the stage of fertilization, according to morphological changes of oocyte nuclear chromatin and the extent of sperm penetration. Sperm penetration was observed to occur within 4 h post insemination (20.5%), and the percentage of fertilized oocytes increased (P < 0.01) to 72.9% at 8 h post insemination. Pronuclear formation was observed from 6 h post insemination (3.3%) and the percentage increased (P < 0.01) to 46.8% at 10 h post insemination. In each examination period, H1K activities in unfertilized oocytes at metaphase-II remained unchanged (112.0 fmol/h/oocyte) and were higher (P < 0.01) than those in fertilized oocytes (30.1 fmol/h/oocyte). The H1K activity in fertilized oocytes such as oocytes emitting a second polar body, oocytes with an enlarging sperm head(s) and oocytes with multiple pronuclei did not differ significantly. These results suggest that MPF in pig oocytes is inactivated shortly after sperm penetration and is maintained at the basal level throughout pronuclear formation.

Journal Article↗
PubMed1995

Structural changes in the oviductal wall during passage of unfertilized cumulus-oocyte complexes in mice.

BACKGROUND: Little information is available on the structural relationship of cumulus-oocyte complexes and the oviductal wall during the transport of cumulus-oocyte complexes. METHODS: To this end, morphological changes of the oviductal wall during the passage of unfertilized cumulus-oocyte complexes were examined chronologically in ICR mice 25-27 days of age injected with PMSG and hCG. Mice were sacrificed at 12, 14, 16, 18, and 24 hr after the injection of hCG to remove oviducts, and the height of mucosal folds, muscle layers, and epithelial cells was measured in the serial sections stained with hematoxylineosin or colloidal iron. RESULTS: The height of the mucosal fold and muscle layer where cumulus-oocyte complexes were located was less than that of the adjacent portions. At 12-18 hr of hCG injection (approximately 2-8 hr after ovulation), the ova with surrounding cumulus cells lie free in a wide lumen, and the muscular tissue consists of only 2 or 3 layers of cells, arranged mostly longitudinally. However, a neighboring portion without cumulus-oocyte complexes, where the folds meet in the middle, appreciably restricts the free space in the lumen. After 24 hr of hCG administration, structural changes in the oviductal wall, where cumulus-oocyte complexes were located, were no longer apparent. The number of cumulus cells surrounding the oocyte decreased during the passage through the oviduct. At 12-18 hr after hCG injection, approximately 140 cells were identified in the largest cross section of a cumulus-oocyte complex, but after 24 hr of hCG administration (approximately 14 hr after ovulation), an oocyte was surrounded with only approximately 25 cells. CONCLUSIONS: These results indicate that oocyte-cumulus cell complexes influence the structure of the oviductal wall during the passage in the oviduct.

Animals↗
PubMed1995

Structural changes in the oviductal wall during the passage of unfertilized cumulus-oocyte complexes in mice.

BACKGROUND: Little information is available on the structural relationship of cumulus-oocyte complexes and the oviductal wall during the transport of cumulus-oocyte complexes. Then, morphological changes of the oviductal wall during the passage of unfertilized cumulus-oocyte complexes was examined chronologically in ICR mice 25-27 days of age injected with PMSG and hCG. METHODS: Mice were sacrificed at 12, 14, 16, 18, and 24 hr after the injection of hCG to remove oviducts, and the height of mucosal folds, muscle layers, and epithelial cells were measured in the serial sections stained with hematoxylin-eosin or colloidal iron. RESULTS: The height of the mucosal fold and muscle layer where cumulus-oocyte complexes were located was less than that of the adjacent portions. At 12-18 hr of hCG injection (about 2-8 hr after ovulation), the ova with surrounding cumulus cells lie free in a wide lumen, and the muscular tissue consists of only 2 or 3 layers of cells, arranged mostly longitudinally. However, a neighboring portion without cumulus-oocyte complexes, where the folds meet in the middle, appreciably restricts the free space in the lumen. After 24 hr of hCG administration, structural changes in the oviductal wall, where cumulus-oocyte complexes were located, were no longer apparent. The number of cumulus cells surrounding the oocyte decreased during the passage through the oviduct. At 12-18 hr after hCG injection, about 140 cells were identified in the largest cross section of a cumulus-oocyte complex, but, after 24 hr of hCG administration (about 14 hr after ovulation), an oocyte was surrounded with only about 25 cells. CONCLUSIONS: These results indicate that oocyte-cumulus cell complexes influence the structure of the oviductal wall during the passage in the oviduct.

Animals↗
PubMed1995

Gene transfer and expression in mouse preimplantation embryos by recombinant adenovirus vector.

Replication-defective recombinant adenovirus, Adex4SRLacZL, was used as a vector for transferring exogenous genes in mouse zona pellucida-free eggs at the pronuclear stage. The vector contained the E. coli LacZ reporter gene under the control of the SR alpha promoter (SV40 early promoter-fused HTLV-I LTR), and the expression of the reporter gene was examined during preimplantation development in culture. Histochemical staining of the embryos for beta-galactosidase activity showed that the exogenous LacZ gene as expressed in 98% of the embryos at the morula-blastocyst stages. As in the microinjection method, the exogenous genes could be pursued from the 2-cell stage. Neither apparent morphological changes nor cytotoxic effects were observed. Both the percentages of embryos expressing reporter genes and the rate of development to the blastocyst stage were higher in the adenovirus vector-treated embryos than in the microinjected ones. These results suggest that the adenovirus vector system is a useful tool in investigating the genetic control of early mammalian development.

Adenoviridae↗