Biomedical subjects

Y Ishida

Publications and source records attributed to Y Ishida.

At least 19 recordsLinked to original sources

PubMed1992

Structure-activity relationships of mu-conotoxin GIIIA: structure determination of active and inactive sodium channel blocker peptides by NMR and simulated annealing calculations.

A synthetic replacement study of the amino acid residues of mu-conotoxin GIIIA, a peptide blocker for muscle sodium channels, has recently shown that the conformation formed by three disulfide bridges and the molecular basicity, especially the one around the Arg13 residue, are important for blocking activity. In the present study, we determined the three-dimensional structure of an inactive analog, [Ala13]mu-conotoxin GIIIA, and refined that of the native toxin by NMR spectroscopy combined with simulated annealing calculations. The atomic root-mean-square difference of the mutant from the native conotoxin was 0.62 A for the backbone atoms (N, C alpha, C') of all residues except for the two terminal residues. The observation that the replacement of Arg13 by Ala13 does not significantly change the molecular conformation suggests that the loss of activity is not due to the conformational change but to the direct interaction of the essential Arg13 residue with the sodium channel molecules. In the determined structure, important residues for the activity, Arg13, Lys16, Hyp(hydroxyproline)17, and Arg19, are clustered on one side of the molecule, an observation which suggests that this face of the molecule associates with the receptor site of sodium channels. The hydroxyl group of Hyp17 is suggested to interact with the channel site with which the essential hydroxyl groups of tetrodotoxin and saxitoxin interact.

Alanine↗

PubMed1992

Involvement of MAP kinase activators in angiotensin II-induced activation of MAP kinases in cultured vascular smooth muscle cells.

In cultured vascular smooth muscle cells (VSMC) angiotensin II (ang II) induces tyrosine and serine/threonine phosphorylation and activation of two mitogen-activated protein (MAP) kinases. When extracts of ang II-stimulated VSMC were fractionated by Mono Q anion-exchange column chromatography, three peaks of the activities which in vitro activate inactive MAP kinases were detected. These MAP kinase activator activities were not detected in extracts of unstimulated VSMC. In vitro activation of MAP kinases by the MAP kinase activators was accompanied by tyrosine and serine/threonine phosphorylation of MAP kinases. These results suggest that the MAP kinase activators are involved in the ang II-induced phosphorylation and activation of MAP kinases in VSMC.

Angiotensin II↗

PubMed1992

T cell receptor-mediated recognition of self-ligand induces signaling in immature thymocytes before negative selection.

Shaping of the T cell repertoire by selection during intrathymic maturation involves T cell receptor (TCR) recognition of major histocompatibility complex/self-antigen complexes. In this communication, we studied the ability of minor lymphocyte stimulating (Mls) determinants to act as self-tolerogens in the selection of the T cell repertoire. We demonstrate that unprimed T cells from normal as well as TCR transgenic mice form Mls-specific conjugates with antigen-presenting cells, and that this TCR-ligand interaction leads to elevation of intercellular Ca2+ ([Ca2+]i). Peripheral T cells from TCR transgenic mice expressing receptors specific for self-Mls antigen show no reactivities to Mlsa. However, a proportion of immature thymocytes from these mice show specific binding and strong [Ca2+]i elevation in response to self-antigen-presenting cells, although these thymocytes do not proliferate. This self-reactivity of thymocytes is inhibited by antibodies specific for TCR, CD4, CD8, class II molecules, lymphocyte function-associated antigen 1, and intercellular adhesion molecule 1. These results demonstrate for the first time that before thymic negative selection, immature T cells can specifically interact with cells bearing self-antigen, and suggest that the resulting TCR-dependent signal transduction events provide a basis for negative selection of self-reactive T cells.

Animals↗

PubMed1992

Expression of high affinity binding sites for erythropoietin on L8057 cells, a mouse megakaryoblastic cell line, associated with cell differentiation.

In this study, specific binding sites were examined for erythropoietin (EPO) on the mouse leukemic cell line, L8057. This cell line is megakaryoblastic in origin as evidenced by an enlargement of cell size, multinuclearity, intense activity of acetylcholinesterase, more expression of glycoprotein IIb and IIIa antigen, and higher ploidy distribution after the treatment with 12-o-tetradecanoylphorbor-13-acetate (TPA). The original undifferentiated cells possessed a single class of low affinity binding sites for recombinant human (rh) EPO with a Kd of 3.5 nM. Following the treatment with TPA, high affinity binding sites (Kd; 440 pM) were expressed in addition to the low affinity sites. EPO stimulated the incorporation of 3H-leucine into TPA-treated L8057 cells, and the maximal effect of EPO was observed at the same order as the Kd value of high affinity sites. The present data demonstrates that the expression of high affinity binding sites for EPO is associated with the differentiation of L8057 cells which have megakaryocytic characteristics. Furthermore, protein synthesis stimulated by EPO may be mediated through the high affinity sites.

Acetylcholinesterase↗

PubMed1992

Induced expression of PD-1, a novel member of the immunoglobulin gene superfamily, upon programmed cell death.

The classical type of programmed cell death is characterized by its dependence on de novo RNA and protein synthesis and morphological features of apoptosis. We confirmed that stimulated 2B4.11 (a murine T-cell hybridoma) and interleukin-3 (IL-3)-deprived LyD9 (a murine haematopoietic progenitor cell line) died by the classical type of programmed cell death. Assuming that common biochemical pathways might be involved in the deaths of 2B4.11 and LyD9, we isolated the PD-1 gene, a novel member of the immunoglobulin gene superfamily, by using subtractive hybridization technique. The predicted PD-1 protein has a variant form of the consensus sequence found in cytoplasmic tails of signal transducing polypeptides associated with immune recognition receptors. The PD-1 gene was activated in both stimulated 2B4.11 and IL-3-deprived LyD9 cells, but not in other death-induced cell lines that did not show the characteristic features of the classical programmed cell death. Expression of the PD-1 mRNA in mouse was restricted to the thymus and increased when thymocyte death was augmented by in vivo injection of anti-CD3 antibody. These results suggest that activation of the PD-1 gene may be involved in the classical type of programmed cell death.

Amino Acid Sequence↗

PubMed1992

Treatment of myeloid leukemic cells with the phosphatase inhibitor okadaic acid induces cell cycle arrest at either G1/S or G2/M depending on dose.

The phosphatase inhibitor okadaic acid was found to induce cell cycle arrest of human myeloid leukemic cell lines HL-60 and U937 in a concentration- and time-dependent manner. Exposure to low concentrations of okadaic acid (2-8nM) for 24-48 hr caused greater than 70% of cells to arrest at G2/M, with up to 40% of the cells arrested in early mitosis. Cell viability decreased rapidly after 48 hr of treatment, and morphological and DNA structure analysis indicated that this was primarily due to the induction of apoptosis. The cells arrested in mitosis by 8 nM okadaic acid could be highly enriched by density gradient centrifugation and underwent apoptosis when further cultured either with or without okadaic acid, indicating that the effects of okadaic acid were irreversible. In contrast to the effects of low concentrations of okadaic acid, high concentrations (500 nM), inhibited proliferation in less than 3 hr. Remarkably, the majority of cells also entered a mitosis-like state characterized by dissolution of the nuclear membrane and condensation and partial separation of chromosomes. However, these cells had a diploid content of DNA, indicating that the cell cycle arrest occurred at G1/S with premature chromosome condensation (PCC), rather than at G2/M. If cells were first blocked at G1/S with hydroxyurea and then treated with okadaic acid, greater than 90% developed PCC in less than 3 hr without replicating their DNA. Caffeine was not able to induce PCC in these cells, either with or without prior inhibition of DNA synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Cycle↗

PubMed1992

Age-related alterations in second-messenger systems in the gerbil brain: autoradiographic analysis and effect of vinconate.

Age-related alterations in binding sites of major second-messenger systems in the gerbil brain were analyzed by receptor autoradiography using [3H]phorbol 12,13-dibutyrate (PDBu), and [3H]inositol 1,4,5-trisphosphate (IP3). In middle-aged gerbils (16 months old), the reduction of PDBu-binding sites was noticed in various brain regions compared with young animals (4 weeks old). By contrast, the elevation of IP3-binding sites was seen in most of brain regions except for the reduction in the cerebellum in the middle-aged animals. Chronic treatment with vinconate partly regulated the age-related changes in the binding sites of these second messengers. The result demonstrates the age-related alterations in the binding sites of an intracellular second-messenger system. Furthermore, they suggest that vinconate partly modulates the age-related alterations in the bindings of second messengers.

Aging↗

PubMed1992

Failure of signaling through a chimeric class I-immunoglobulin molecule expressed on the surface of transfected B lymphoma cells and cells of transgenic mice.

To test the possibility that the crosslinkage of molecules expressing a transmembrane region derived from the membrane form of the mu immunoglobulin heavy chain would be sufficient for signal transduction in B cells, a chimeric gene (Kk-mu) consisting of extracellular exons of the class I gene H-2Kk and the transmembrane and cytosolic exons of the mu constant region gene was introduced into WEHI-231 B lymphoma cells and into mouse blastocysts. A protein consistent with the predicted product of the Kk-mu gene was expressed in a transfected cell clone (S18) and in transgenic mice. Crosslinkage of Kk-mu protein with soluble, Sepharose-bound, or dextran-conjugated anti-H-2Kk antibodies failed to induce the accumulation of inositol phosphates or to elevate intracellular calcium concentrations in either S18 cells or B lymphocytes from transgenic mice. Furthermore, crosslinkage of Kk-mu did not inhibit growth of S18 cells or stimulate DNA synthesis by transgenic B cells, in the presence or absence of interleukin-4. The failure of crosslinkage of Kk-mu to initiate detectable intracellular biochemical change or to effect cellular growth suggests that simple crosslinkage of molecules expressing the mu transmembrane region is not sufficient to transduce signals in B cells.

Animals↗

PubMed1992

Stimulation of protein-tyrosine phosphorylation by endothelin-1 in cultured vascular smooth muscle cells.

In cultured rat aortic smooth cells, endothelin-1 induced tyrosine phosphorylation of at least five proteins with molecular masses of about 79, 77, 73, 45 and 40 kDa in dose- and time-dependent manners. Platelet-derived growth factor also induced tyrosine phosphorylation of the same set of proteins in addition to other proteins including platelet-derived growth factor receptors. This growth factor markedly stimulated DNA synthesis and an increase in cell number in this cell type, but endothelin-1 failed to stimulate these responses under the same conditions. These results demonstrate for the first time that endothelin-1 induces tyrosine phosphorylation of some proteins but suggest that these reactions are not enough to stimulate proliferation of vascular smooth muscle cells.

Animals↗

PubMed1992

Neuroepithelial cyst of the lateral ventricle. Clinical features and treatment.

This report concerns eight patients with noncolloid neuroepithelial cyst of the lateral ventricle, including four surgical and four conservative cases. Of the surgical patients, two had headache, one had orbital pain, and one had seizures. In the conservative group there were no symptoms due to the cysts and no changes in computed tomography scan during follow-up for an average of 1.4 years. Magnetic resonance imaging was performed in five cases and showed a cyst with an intensity similar to cerebrospinal fluid, while a cyst membrane was also detected in three cases. Our findings suggest that (1) the majority of symptomatic neuroepithelial cysts in the lateral ventricle are located in the trigone; (2) the cause of symptoms suggestive of obstruction, such as headache, is an isolated ventricle that demonstrates dilatation of the inferior horn on computed tomography and magnetic resonance imaging; (3) the operative indication is obstructive symptoms; and (4) cyst-peritoneal shunt is an effective procedure.

Adult↗

PubMed1992

Autoradiographic mapping of neurotransmitter system receptors in mammalian brain.

Regional localization of neurotransmitter system receptors was visualized in the gerbil grain and in the rat brain using receptor autoradiography. [3H]Quinuclidinyl benzilate (QNB), [3H]cyclohexyladenosine (CHA), [3H]muscimol, [3H]MK-801, [3H]SCH 23390, [3H]PN200-110, [3H]spiperone, and [3H]naloxone were label muscarinic receptors, adenosine A1 receptors, GABAA receptors, N-methyl-D-aspartate (NMDA) receptors, dopamine D1 receptors, L-type calcium channels, spirodecanone receptors, and opioid receptors, respectively. Regional localization of [3H]QNB, [3H]muscimol, [3H]MK-801, [3H]SCH 23390, and [3H]PN200-110 binding sites in the gerbil brain was relatively similar to that in the rat brain. In contrast, the autoradiographic distribution of [3H]spiperone and [3H]naloxone binding sites in the gerbil was quite different from that in the rat. This phenomenon was found especially in the hippocampus and the cerebellum. The results suggest that the gerbil differs from the rat with respect to spirodecanone and opioid binding sites in the hippocampus and the cerebellum. This finding may help to further elucidate the species differences and relationships for brain function and behavioral pharmacology.

Animals↗

PubMed1992

Endothelin-1 stimulates tyrosine phosphorylation and the activities of two mitogen-activated protein kinases in cultured vascular smooth muscle cells.

OBJECTIVE: Endothelin-1 (ET-1) has been reported to stimulate the expression of the proto-oncogenes c-fos and c-myc, and to cause DNA synthesis in vascular smooth muscle cells (VSMC). The purpose of this study was to clarify the signalling pathway from ET receptors to the nucleus. DESIGN: Mitogen-activated protein (MAP) kinase, which is activated by various growth factors via phosphorylation of tyrosine and threonine residues, plays important roles as an intermediate in the signalling pathways from growth factor receptors to the ribosomes and nucleus. We examined the effect of ET-1 on the phosphorylation and activation of MAP kinase in cultured VSMC. METHODS: Extracts of ET-1-stimulated VSMC were analysed by one- and two-dimensional gel electrophoresis and anion-exchange column chromatography. Tyrosine-phosphorylated proteins and MAP kinases were detected by immunoblot analyses with anti-phosphotyrosine and anti-MAP kinase antibodies, respectively. The MAP kinase activity was measured using myelin basic protein as a substrate. The MAP kinases were isolated from 32P-labelled VSMC and subjected to phosphoamino acid analysis. RESULTS: ET-1 induced tyrosine phosphorylation of at least five proteins of about 79, 77, 73, 45 and 40 kDa in VSMC. The mobilities of the tyrosine-phosphorylated 45- and 40-kDa proteins were identical with those of the two proteins that were recognized by anti-MAP kinase antibody upon one- and two-dimensional gel electrophoresis. ET-1 stimulated MAP kinase activity in a time-course similar to that of the tyrosine phosphorylation of the 45- and 40-kDa proteins. The ET-1-stimulated MAP kinase activity was resolved almost equally into two peaks upon Mono Q column chromatography (kinase 1 and kinase 2). Kinase 1 and kinase 2 were co-eluted with the tyrosine-phosphorylated 40- and 45-kDa proteins, respectively. The apparent molecular masses of kinase 1 and kinase 2 estimated by MAP kinase assay in polyacrylamide gel were identical with those of tyrosine-phosphorylated 40- and 45-kDa proteins, respectively. Upon phosphoamino acid analysis, ET-1 stimulated phosphorylation of MAP kinases not only on tyrosine but also on threonine residues. CONCLUSIONS: ET-1 induces tyrosine and threonine phosphorylation and the activation of two species of MAP kinases of 40 and 45 kDa in VSMC.

Animals↗

PubMed1992

Redundant nerve roots of the cauda equina caused by lumbar spinal canal stenosis.

To investigate pathogenesis of redundant nerve roots of the cauda equina, which were concomitant with severe lumbar spinal canal stenosis, six cadavers were examined anatomically and histopathologically, and quantitative analysis of nerve fibers was performed. In this anatomic study, it was observed that all the redundant nerve roots passed through the constriction of the spinal canal. No significant pathologic change was detected in the spinal ganglia and in the spinal cords except for the posterior column, in which dorsal redundant roots were entering. Redundant nerve roots of unequal length also were observed in the anatomic study. The spatial distribution of redundant nerve roots and the extent of degeneration of nerve fibers in them were established by these histopathologic and quantitative studies. These facts indicated a close causal relationship between redundant nerve roots and constriction of the spinal canal, and that the pathogenesis of redundant nerve roots was a squeezing force acting on the nerve roots at the area of spinal canal constriction.

Cauda Equina↗

PubMed1992

Pulmonary arteriography with retrograde injection of contrast medium via radial artery: efficacy in neonates with ductus-dependent decreased pulmonary flow.

In an attempt to visualize the pulmonary arterial trees of neonates and infants with ductus-dependent decreased pulmonary flow, the efficacy of retrograde injection of contrast from the radial arteries of 11 consecutive patients was tested. All patients had pulmonary atresia and patent ductus arteriosus. A 22- or 24-gauge needle was inserted into the radial artery and contrast medium of 2 ml/kg was injected at flow rates of 3 to 4 ml/sec. The pulmonary arteries were filled by retrograde flow through the ductus arteriosus. This method provided clear visualization of the pulmonary arteries, especially by ductus-sided injections. Developmental anomalies of the pulmonary trunk, localized stenosis at the ductus, and aortopulmonary collateral arteries were demonstrated. No complications occurred during angiography, and all the procedures were completed within 30 minutes. This method appears to be useful in detecting anatomical abnormalities of the pulmonary arteries in neonates and infants with ductus-dependent decreased pulmonary flow.

Angiography↗

PubMed1992

The 11q- syndrome with mosaic partial deletion of 11q.

A female child with mosaic partial deletion of 11q is reported. At 1 month of age she was presented with cogenital glaucoma, trigonocephaly and multiple minor anomalies. She exhibited growth retardation and the typical phenotype of 11q- syndrome. G-banding analysis failed to show any abnormality, although subsequent high resolution banding revealed the abnormal karyotype 46,XX,del(11)(q23.3 q24.2)/46,XX,del(11)(q23.3 q25). This case is a second case of mosaic 11q- syndrome and her karyotype suggests that the region of 11q23.3-11q24.2 is critical in 11q-syndrome. Congenital glaucoma has never been reported as a complication of 11q- syndrome.

Abnormalities, Multiple↗

PubMed1992

Ca2+ release from isolated sarcoplasmic reticulum of guinea-pig psoas muscle induced by K(+)-channel blockers.

A Ca(2+)-sensitive electrode was used to measure the Ca2+ concentration of the medium containing the heavy fraction of the fragmented sarcoplasmic reticulum (SR) prepared from guinea-pig psoas muscle. Among K(+)-channel blockers tested, 4-aminopyridine (4-AP), tetraethylammonium (TEA) and charybdotoxin elicited Ca2+ release from the SR, but apamin and glibenclamide did not. These results suggest that a reduction of SR K+ conductance leads to Ca2+ release from the SR.

4-Aminopyridine↗

PubMed1992

Renal effects of endogenous prostaglandin synthesis promoter ONO-3122.

The renal effects of a prostaglandin synthesis agonist, 1-iodo-3-aminomethyl-5,6,7,8-tetrahydro-2-naphthol (ONO-3122), were investigated in anesthetized rats. ONO-3122 (0.3 mg/kg + 0.3 mg.kg-1.h-1 iv) doubled the urinary excretion of the main metabolites of prostaglandin F, and induced transient increases in renal blood flow and glomerular filtration rate (GFR) with a marked, stable natriuresis. Indomethacin suppressed the natriuresis. When the diuretic fluid losses were replaced, micropuncture showed an unaltered reabsorption of sodium in the proximal tubule but reductions in the loop of Henle (86 +/- 1 vs. 76 +/- 1%) and in the more distal segments (98 +/- 1 vs. 83 +/- 3%) with comparable reductions in water reabsorption. Potassium secretion was seen in the distal and collecting tubules. Without fluid replacement, sodium reabsorption was reduced in the loop and more distal nephron but increased in the proximal tubule. Differences between proximal and distal nephron GFR were unaffected by systemic ONO-3122. Loop perfusion with ONO-3122 did not change tubuloglomerular feedback responses, which were, however, completely suppressed by furosemide. It is concluded that ONO-3122 stimulates renal prostaglandin biosynthesis, transiently dilates renal vasculature, and induces natriuresis mainly by suppressing sodium and water reabsorption in the loop of Henle and the more distal nephron. Luminal ONO-3122 does not affect the tubuloglomerular feedback.

Animals↗

PubMed1992

Phase I/II study of recombinant human granulocyte-macrophage colony-stimulating factor in patients with advanced malignancy. The Multicenter Study Group.

The toxicity and hematologic effects of Escherichia coli-derived recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) were studied in 58 treatment cycles in Japanese patients with advanced malignancy as a phase I/II clinical trial. rhGM-CSF in doses from 30 to 250 micrograms/m2/day was administered by 24-hour continuous intravenous infusion, 8-hour intravenous, or a daily subcutaneous injection for 14 days. The most common adverse drug events (ADE) were fever, nausea/vomiting, diarrhea, skin eruption, and phlebitis. The frequency of moderate and severe ADE was 2.9, 14.7, 35.3 and 47.1% at 30, 60, 125, 250 micrograms/m2/day, respectively. In terms of administration routes, the frequency of ADE was 69% with 24-hour continuous intravenous infusion, 39.1% with 8-hour intravenous infusion and 16.7% with subcutaneous injection. Regarding the hematologic effects of rhGM-CSF, leukopenia improved in a dose-dependent manner. The appropriate dose level to be used in the phase II study was estimated to be in the range between 60 and 250 micrograms/m2/day.

Adult↗