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Biomedical subjects

Y Toyoda

Publications and source records attributed to Y Toyoda.

At least 109 records · Page 6Linked to original sources
PubMed1998

Monoclonal antibody against Babesia equi: characterization and potential application of antigen for serodiagnosis.

Monoclonal antibody (MAb) BEG3 was produced against Babesia equi parasites to define a species-specific antigen for diagnostic use. The MAb reacted with single, paired, and Maltese cross forms of B. equi, and no reaction was observed with this MAb on acetone-fixed Babesia caballi, Babesia ovata, or Babesia microti parasites in the indirect immunofluorescent antibody test. Confocal laser and immunoelectron microscopic studies showed that the antigen which was recognized by this MAb was located on the surface of B. equi parasites. This MAb recognized a 19-kDa protein of B. equi antigen and did not react with B. caballi antigen or normal horse erythrocytes in immunoblot analysis. This MAb also significantly inhibited the in vitro growth of the B. equi parasite. Preliminary studies using partially purified antigen, which was separated by high-pressure liquid chromatography and recognized by the MAb, suggested that it is a suitable antigen for enzyme-linked immunosorbent assay detection of anti-B. equi antibodies in naturally infected horse sera.

Animals↗
PubMed1998

Evidence of apoptosis induced by myocardial ischemia: A case of ventricular septal rupture following acute myocardial infarction.

Recent studies have reported that apoptosis may be induced by reperfusion injury following ischemia in cardiomyocytes. We present a case with evidence of apoptosis induced by myocardial ischemia without reperfusion. DNA fragmentation was demonstrated in the nuclei of the myocardial cells surrounding the ventricular septal rupture following acute myocardial infarction without reperfusion in the infarct-related left anterior descending coronary artery. This finding suggests that ischemia without reperfusion may induce apoptosis in myocardial cells.

Aged↗
PubMed1998

A premenopausal woman presenting with acute myocardial infarction of three different coronary vessels within 1 year: role of lipoprotein(a).

A premenopausal female patient presented with acute myocardial infarction of 3 different coronary vessels at different times within 1 year. These events were caused not by restenotic lesions after balloon angioplasty but by new lesions, which were successfully treated by primary angioplasty. Although she had a history of hypertension, type IIB hyperlipidemia, and diabetes, they had been well-controlled on medication. An elevated serum lipoprotein(a) level may have played a role in this rapid angiographic progression.

Angioplasty, Balloon↗
PubMed1998

Identification of carbohydrates on Eimeria stiedai sporozoites and their role in invasion of cultured cells in vitro.

Invasion specificity of Eimeria stiedai sporozoites in cultured cells was examined. Intracellular sporozoites were observed in hepatobiliary epithelial cells, as early as 3 hours post inoculation (p.i.) but the infection rate was monitored for 6 hours. No intracellular parasites were found in rabbit parenchymal hepatocytes and rabbit kidney cells, even on prolonged culturing. In the hepatobiliary epithelial cells inoculated with fixed sporozoites, no intracellular parasite were found. Sporozoites attached on the cell surface of the hepatobiliary epithelial cells fixed with paraformaldehyde but did not penetrate. The carbohydrates present on Eimeria stiedai sporozoites and their functional role in the process of invasion of host cells were also examined. Lectin binding sites on the surface of sporozoites were detected by means of peroxidase-conjugated lectins. Sporozoites showed specific binding with UEA-I and PNA lectins, which bind L-fucose and D-galactose, respectively. Exposure of sporozoites to 100 microg/ml UEA-I significantly reduced their ability to invade primary rabbit hepatobiliary epithelial cells, but similar treatment with PNA had no such effect. Preincubation of these cells in Dulbecco's minimum essential medium containing 10% fetal bovine serum and 1% L-fucose suppressed the invasion activity of the sporozoites, but preincubation of the sporozoites in the same medium without L-fucose had no effect on cell penetration. D-galactose added to the medium had no effect on the invasion activity of sporozoites. These results indicate that L-fucose residues on E. stiedai sporozoites and L-fucose binding sites on host cells both are associated with recognition and/or invasion process.

Animals↗
PubMed1998

[CarboMedics "Top Hat" supraannular prosthesis in the small aortic root with severe calcification: a case report].

A 71-year-old man with aortic stenosis due to calcification successfully underwent aortic valve replacement with a 21-mm CarboMedics "Top Hat" supraannular prosthesis. We were able to implant a "Top Hat" valve one size larger than would have been possible using a standard bileaflet valve. The postoperative recovery was uneventful, and echocardiography showed a peak gradient of 23 mmHg for this prosthesis. The CarboMedics supraannular valve allowed a gain in size over standard prostheses, resulting in favorable hemodynamics. This valve may be useful in difficult or unsuitable cases to enlarge the narrow aortic valve ring, such as patients with severe calcification of aortic root, elderly patients with less activity, or patients who can tolerate only short cardiopulmonary bypass time due to cardiac dysfunction.

Aged↗
PubMed1998

Clear cell sarcoma of kidney with tumor extension into the right atrium.

A 28-year-old man with a Wilms tumor extending into his right atrium was successfully treated using cardiopulmonary bypass. Histologic examination revealed clear cell sarcoma with invasion of the inferior vena cava. This case represents the oldest patient with clear cell sarcoma of the kidney ever published in the English literature.

Adult↗
PubMed1997

Glucokinase is located in secretory granules of pancreatic D-cells.

We immunohistochemically examined the distribution of glucokinase in rat pancreatic islets. Glucokinase immunoreactivity under light microscopy was detected in the cytoplasm of somatostatin cells as well as in that of insulin cells. No specific immunoreactivity was detected in glucagon and pancreatic polypeptide cells. In somatostatin cells, glucokinase immunoreactivity was located by electron microscopy exclusively within secretory granules.

Animals↗
PubMed1997

Motor evoked potentials (MEPs) and H-reflexes are not equally sensitive to voluntary motor commands.

To investigate the sensitivity to changes in excitability of motoneuron pool dependent on voluntary motor commands, we recorded motor evoked potentials (MEPs) and H-reflexes from the right flexor carpi radialis (FCR) muscle of normal human subjects. Amplitudes of MEPs were always larger than those of the H-reflex in both tonic and phasic muscle contractions. Furthermore, amplitudes of MEP and H-reflex were larger in phasic than in tonic muscle contraction. These results indicate that there are differences in the sensitivity to changes in motoneuronal excitability related to the production of excitatory postsynaptic potentials for H-reflex and MEP responses, respectively.

Adult↗
PubMed1997

Alternative usage of exon 1 of bovine PrP mRNA.

Here we report two types of bovine prion protein (PrP) mRNA that possessed different lengths of the 5'-untranslated region and were expressed in various bovine tissues. The two mRNA species were transcribed from identical positions but differed in the usage of the splice site for exon 1/intron. One mRNA possessed exon 1 consisting of 53 nucleotides and the other possessed exon 1 consisting of 168 nucleotides. Usage of exons 2 and 3 was identical for the two mRNA species. The two mRNA species were detected in all but spleen tissue; the mRNA possessing 168-nt exon 1 was not detected in bovine spleen. This is the first report on the tissue-specific alternative splicing of PrPc mRNA in any other species. Only a low level of PrPc appeared to be present in bovine spleen. These results suggested the possibility that the mRNA possessing 53-nt exon 1 was inefficiently translated into Prp; however, in vitro translation analysis showed no marked difference in translational efficiency between the two mRNA species.

Alternative Splicing↗
PubMed1997

Co-localization of glucokinase with actin filaments.

A portion of glucokinase appeared to be co-localized with actin filaments in the cytoplasm of cultured rat hepatocytes incubated with 25 mM glucose. When liver- or islet-type glucokinase was transiently expressed in COS-7 cells, the expressed glucokinase was also co-localized with actin filaments in the cytoplasm of these transfected cells. Although co-localization of glucokinase with actin filaments was not clearly demonstrated in the pancreatic beta-cell line MIN6, islet glucokinase was found to be present in both the nucleus and the cytoplasm, though predominantly in the nucleus. These findings suggest that subcellular localization of glucokinase, including co-localization with actin filaments, may have an important physiological role in metabolic regulation.

Actins↗
PubMed1997

A role for macrophage scavenger receptors in atherosclerosis and susceptibility to infection.

Macrophage type-I and type-II class-A scavenger receptors (MSR-A) are implicated in the pathological deposition of cholesterol during atherogenesis as a result of receptor-mediated uptake of modified low-density lipoproteins (mLDL). MSR-A can bind an extraordinarily wide range of ligands, including bacterial pathogens, and also mediates cation-independent macrophage adhesion in vitro. Here we show that targeted disruption of the MSR-A gene in mice results in a reduction in the size of atherosclerotic lesions in an animal deficient in apolipoprotein E. Macrophages from MSR-A-deficient mice show a marked decrease in mLDL uptake in vitro, whereas mLDL clearance from plasma occurs at a normal rate, indicating that there may be alternative mechanisms for removing mLDL from the circulation. In addition, MSR-A-knockout mice show an increased susceptibility to infection with Listeria monocytogenes or herpes simplex virus type-1, indicating that MSR-A may play a part in host defence against pathogens.

Animals↗
PubMed1997

Increased Ca2+ sensitivity of contractile elements via protein kinase C in alpha-toxin permeabilized SMA from young spontaneously hypertensive rats.

OBJECTIVE: The purpose of the present investigation was to examine the Ca2+ sensitivity of the contractile elements via protein kinase C (PKC) in superior mesenteric artery (SMA) from young (5-6 weeks old) spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). METHODS: Staphylococcal aureus alpha-toxin, which produces pores in the plasma membrane too small to allow passage of proteins such as PKC, was used to investigate the signal transduction system in vascular smooth muscle cells. We investigated the Ca2+ sensitivity of the contractile apparatus via PKC in intact and alpha-toxin skinned SMA from young SHR and WKY. RESULTS: In intact SMA, high K+ responses were not different between SHR and WKY. However, phorbol 12,13-dibutyrate (PDBu, a PKC activator) augmented high K(+)-evoked contractions and PKC inhibitors, such as 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) and calphostin C, suppressed them more in SHR as compared with WKY. In alpha-toxin skinned SMA, the [Ca2+]i-force relationship curve was not significantly different between SHR and WKY. However, PDBu augmented [Ca2+]i-evoked contractions and PKC inhibitors suppressed them more in SHR than in WKY. CONCLUSION: These results suggest that the Ca2+ sensitivity of the contractile elements via PKC is significantly greater in prehypertensive SHR than in age-matched WKY. This abnormality in small muscular arteries may be involved in the pathogenesis of hypertension in SHR.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1997

Developmental fate of single embryonic stem cells microinjected into 8-cell-stage mouse embryos.

Embryonic stem (ES) cells are pluripotent and capable of differentiating into somatic as well as germ cell lineages when conjoined with blastomeres of early mouse embryos. However, the developmental potential of single ES cells has not been fully investigated. We injected single murine ES cells (A3-1 cell line) of 129 origin into 8-cell mouse embryos (B6xBDF1) and examined the patterns of distribution of ES-cell-derived cells in the blastocysts as well as in the fully grown chimeric mice. The ES cells underwent 1-2 cycles of mitosis between the 8-cell and the blastocyst stage when they were introduced as single cells, whereas those introduced as groups of 2-5 cells did not proliferate during the same period of development. The ES cells and their daughter cells were predominantly incorporated into the ICM. From the 63 8-cell embryos which received single ES cells microinjected into the perivitelline space, 24 newborns were obtained, and 4 (2 fertile males, 1 sterile female and 1 hermaphrodite) of them (16.6%) were chimeric. The test breeding studies revealed that all the progeny of the two chimeric males were derived from spermatozoa of 129 genotype. The relative contribution of the host-derived and the ES-cell-derived cells in different tissues of the chimeric mice was assessed by PCR analyses of the microsatellite polymorphism of genomic DNA extracted from the tissues. In two male germ line chimeras, the testes, the kidneys and the dorsal skeletal muscles exhibited exceptionally high 129 contents. Our results demonstrated that single ES cells which maintain totipotency or pluripotency of high degree are present in a colony of ES cells, and that single ES cells conjoined with the blastomeres of 8-cell-stage embryos may colonize, if the circumstances allow, almost exclusively the germ cells and concomitantly the urogenital cell lineages. Possible correlation between the allocation of the germ line and the urogenital lineages is discussed.

Animals↗
PubMed1997

Improved in vitro cultivation of Babesia caballi.

Babesia caballi infected erythrocytes were collected from the blood of an experimentally infected horse and could be continuously cultivated in vitro with parasitemia ranging from 2-4% in RPMI 1640 medium supplemented with 2 mM L-glutamine, 20 mM HEPES and 40% adult horse serum in a low oxygen atmosphere (2% O2, 5% CO2 and 93% N2). All attempts to increase parasitemia failed using other culture media, serum concentrations and culture vessels. However, parasite growth was enhanced by transfer of cultures from a low oxygen to 5% CO2 in air, with parasitemia ranging from 8-10%.

Animals↗
PubMed1997

Characterization of embryonic stem-like cell lines derived from embryoid bodies.

Embryoid bodies (EB) were formed by TT2 embryonic stem (ES) cells in vitro. ES-like cell lines (ESLC) were established by culturing cells obtained by disaggregation of EB at 4, 8 and 20 days after culture, and designated ESLC4, ESLC8 and ESLC20, respectively. Flow cytometric analysis indicated that the cell surface expression of Le(a) on ESLC was less than that of original TT2 ES cells, but the expression of L-CAM was comparable. After suspension culture, all of the ESLC cells formed cystic EB in vitro. In addition, some ESLC4- and ESLC8-derived EB showed signs of beating. Although coat color chimeras were able to be produced with ESCL4 at a lower rate than parental ES cells, the cells did not contribute to germ line cells in chimeras. These results suggest that the ESLC had less pluripotent than parental ES cells and also that EB formation is not useful in obtaining pluripotent cells.

Animals↗
PubMed1997

Germ-line contribution of embryonic stem cells in chimeric mice: influence of karyotype and in vitro differentiation ability.

The effect of the karyotype and the ability to differentiate in vitro upon germ-line transmission by A3-1 embryonic stem (ES) cells in chimeric mice were examined. Germ-line transmission was confirmed in ES cells exhibiting 38% and more of the normal karyotype, but no chimeric mice and/or germ-line transmitters were observed regardless of the karyotype when the cystic embryoid body (CEB) was formed on day 8 and later in the suspension culture. Germ-line transmission of the ES cells was not significantly influenced by formation of the simple embryoid body (SEB). Germ-line transmitters were preferentially observed in chimeras when the ES cell contribution to coat color was markedly increased, but this contribution to coat color varied regardless of the karyotype or in vitro differentiation ability. These results suggest that A3-1 ES cells which exhibit CEB at 7 days after suspension culture and approximately 40% of normal karyotype are capable of germ-line transmission in chimeric mice.

Animals↗
PubMed1997

Shuttling of glucokinase between the nucleus and the cytoplasm in primary cultures of rat hepatocytes: possible involvement in the regulation of the glucose metabolism.

Glucokinase (GK) is believed to play a key role in the control of the hepatic glucose metabolism. To address the mechanism of the regulation of glucose metabolism through GK action, we immunohistochemically studied changes in GK distribution in primary cultures of rat hepatocytes. In hepatocyte monolayers incubated in 5 mM glucose, GK staining by the immunoperoxidase method was observed predominantly in the nucleus. When cultured hepatocytes were incubated for 30 min in various concentrations (5-45 mM) of glucose, there was an appreciable decrease in nuclear GK immunoreactivity, even at 10 mM compared with that at 5 mM. After the shift of glucose concentration from 5 mM to 25 mM, the GK distribution changed time-dependently over 1 h. A time-dependent change in GK distribution was also observed when the glucose concentration was shifted from 25 mM to 5 mM. Reversal of GK distribution in response to the change in glucose concentration from 5 to 25 mM and vice versa was shown to repeatedly occur. Lower concentrations (0.05-5 mM) of fructose, which is known to stimulate glucose phosphorylation by GK, in combination with 5 mM glucose, induced the translocation of GK from the nucleus to the cytoplasm. Mannose (20 mM), a substrate of GK, and sorbitol (1 mM), a stimulator of glucose phosphorylation by GK, induced the translocation of GK from the nucleus to the cytoplasm in the presence of 5 mM glucose. L-glucose, galactose, 3-O-methylglucose, and 2-deoxyglucose at 20 mM each did not affect the GK distribution observed in the presence of 5 mM glucose. The results suggest that GK is present mainly in the nucleus under conditions where GK action is not much needed, whereas the enzyme exists mainly in the cytoplasm under conditions where it must function extensively. Our findings indicate that the shuttling of GK between the nucleus and the cytoplasm is essential for the regulation of the glucose metabolism in the liver.

Animals↗