PubMed Health⌕ Search

Biomedical subjects

T Yamagata

Publications and source records attributed to T Yamagata.

At least 19 recordsLinked to original sources
PubMed1992

Full activation without calmodulin of calmodulin-dependent cyclic nucleotide phosphodiesterase by acidic glycosphingolipids: GM3, sialosylneolactotetraosylceramide and sulfatide.

Among calmodulin-non-binding glycosphingolipids, GM3, sialosylneolactotetraosylceramide (LM1), and sulfatide potently activated calmodulin-dependent cyclic nucleotide phosphodiesterase with or without Ca2+ showing ED50 1-5 microM. In contrast to calmodulin-binding gangliosides, these glycosphingolipids activated the enzyme up to the maximum level achieved by Ca2+/calmodulin and did not inhibit the activity at higher concentrations. Competition studies with GD1b that bind both to calmodulin and the enzyme suggest that the calmodulin-non-binding glycosphingolipids activate the enzyme through interaction with the same site of the enzyme as GD1b interacts.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1992

Atrial natriuretic peptide suppresses renal vasoconstriction induced by angiotensin II and norepinephrine in dogs.

Atrial natriuretic peptide (ANP, 10 and 50 ng/kg per min), infused into the renal artery, suppressed decreases in renal blood flow induced by intrarenal arterial injection of angiotensin II (Ang II, 25-100 ng) and norepinephrine (NE, 0.25-1 microgram) in anesthetized dogs. Sodium nitroprusside (SNP, 0.1-5.0 micrograms/kg per min) slightly attenuated the blood flow response to Ang II but not the response to NE. 8-Bromo cyclic GMP (8bcGMP, 0.5-25 micrograms/kg per min) did not suppress the blood flow response to Ang II. Although at a high dose ANP attenuated the blood flow response to Bay K 8644 (1-4 micrograms), nifedipine pretreatment (20 micrograms/kg plus 1 microgram/kg per min i.v.) did not affect the inhibitory effect of ANP on the NE-induced response. The vaso-inhibitory effects of ANP therefore could not be related exclusively to stimulation of cGMP production or inhibition of voltage-dependent Ca2+ channels.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1992

A novel ganglioside expressed by mouse hematopoietic cell lines.

Mouse progenitor T cell-derived cell lines were established by fusion of cells of hematopoietic organs such as bone marrow and fetal liver with T lymphoma (BW5147) to determine their characteristic cell-surface components. The hybridomas with the phenotype of Thy-1+, CD3-, CD4-, CD8- and expression of T cell receptor gene mRNA (BM216 and FL339) were selected for progenitor T cell-derived cell lines, and their ganglioside compositions were studied. A ganglioside component with a mobility slightly faster than that of bovine brain GD1a on high-performance thin-layer chromatography was found in the cell extracts of these cell lines as one of the most abundant components and was absent in the extract of the parental cell line (BW5147). The structure of the ganglioside was determined to be: NeuAc alpha-Gal beta-Gal beta-Gal alpha-Gal beta-Glc beta-ceramide. Gangliosides with such a sequence have never been found before, suggesting the possibility that the ganglioside is expressed as a surface marker of the cells in hematopoietic organs committed to a specific cell lineage, presumably to T cell lineage. cells in hematopoietic organs committed to a specific

Animals↗
PubMed1992

Mechanism for ganglioside-mediated modulation of a calmodulin-dependent enzyme. Modulation of calmodulin-dependent cyclic nucleotide phosphodiesterase activity through binding of gangliosides to calmodulin and the enzyme.

Gangliosides were recently shown to bind to calmodulin (Higashi, H., Omori, A., and Yamagata, T. (1992) J. Biol. Chem. 267, 9831-9838). This prompted us to investigate the effects of gangliosides on the calmodulin-dependent enzyme, cyclic nucleotide phosphodiesterase. Several species of gangliosides competitively inhibited calmodulin-stimulated phosphodiesterase activity, with GD1b, GT1b, and GD1a being noted to do so particularly (group 1). GM1, GQ1b, and GM2 (group 2) were less inhibitory, and GM3, GM3(NeuGc), GalCer, sulfatide, GgOse4Cer, and oligosaccharide portions of inhibitory gangliosides showed no inhibition in accordance with the binding specificity of calmodulin to gangliosides. Trypsin-activated phosphodiesterase was inhibited by gangliosides with similar specificity, indicating interactions of gangliosides with the enzyme. Inhibition, however, was less than that of calmodulin-dependent activity by these compounds and, in both cases, was eliminated by excess calmodulin. In the absence of calmodulin, group 1 gangliosides at lower concentrations activated the intact enzyme but inhibited it over a certain range of increase in concentration. Ganglioside-dependent modulation of calmodulin-dependent phosphodiesterase activity is thus shown to be due to interactions of gangliosides with both calmodulin and the enzyme, and consequently, ganglioside-calmodulin binding is likely the mechanism for regulation of the enzyme.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1992

Calmodulin, a ganglioside-binding protein. Binding of gangliosides to calmodulin in the presence of calcium.

Ca(2+)-dependent ganglioside-binding protein was isolated from a soluble cytosol fraction of mouse brains using a ganglioside affinity column prepared with a mixture of bovine brain gangliosides. It was identified as calmodulin based on the following features identical with those of calmodulin: molecular weight, pI, chromatographic profile and amino acid sequences of lysyl-endopeptidase digests, and ability to activate cyclic nucleotide phosphodiesterase. Bovine brain calmodulin derivatized with 5-dimethylaminonaphthalene-1-sulfonyl (dansyl-calmodulin), tetramethylrhodamine isothiocyanate, or biotin was also shown to bind to the ganglioside affinity column Ca2+ dependently and elute with gangliosides GD1a, GD1b, GT1b, GQ1b, GM1, and GM2, melittin, and trifluoperazine but not with GgOse4Cer and oligosaccharides of GM1, GD1a, and GT1b. Modification of the Lys94 residue of calmodulin by biotinylation drastically reduced the capacity for ganglioside binding. Ganglioside GD1b caused a blue shift and increase in intensity of the fluorescence emission spectrum of dansyl-calmodulin in the presence of Ca2+. The increment in fluorescence was proportional to the amount of GD1b added and was maximal at the molar ratio of GD1b to calmodulin, approximately 7.8. Gangliosides are thus shown to specifically bind to calmodulin, and this binding may be a general mechanism for regulating calmodulin-dependent enzymes with consequent cellular response, such as cell differentiation.

Amino Acid Sequence↗
PubMed1992

Presence of murine fetal liver cells capable of being induced to differentiate in vitro into T cell receptor-positive cells.

Mouse fetal liver cells were analyzed for the surface expression of T cell markers. Fetal liver cells prepared from mouse embryos at 14.5 days of gestation contained a small number of CD4+ cells (1.4%), but virtually no cells positive for any other T cell markers such as CD8, CD3 and T cell receptor (TcR). When a fetal liver cell suspension prepared from BALB/c(male) x AKR(female) F1 embryos at 14.5 days of gestation was cultured in medium supplemented with culture supernatants of both WEHI-3 and concanavalin A-stimulated rat spleen cells, TcR alpha beta+ and CD4+ cells were generated, whereas CD8+ and TcR gamma delta+ cells were hardly detectable. Most of TcR alpha beta+ and CD4+ cells were H-2d+, thus clearly showing their fetal origin. Treatment with anti-CD4, anti-CD3 or anti-TcR alpha beta antibodies plus complement or electronic sorting to remove cells expressing these markers failed to inhibit the generation of T cell marker-positive cells following culture in vitro. On the other hand, depletion of Thy-1.2+ cells reduced their generation. These findings indicate the presence of some progenitor T cells in fetal liver with the Thy-1+, CD3-, CD4-, CD8-, TcR- phenotype, which can be induced to differentiate into TcR alpha beta+ cells in the presence of specific humoral supplements without the influence of the thymus.

Animals↗
PubMed1992

Inheritance and breeding of the waltzing mutant in the musk shrew (Suncus murinus, Insectivora) characterized by the circling and head-shaking behaviors.

A behavioral mutant was found in the laboratory-bred musk shrew (Suncus murinus). The affected shrews were characterized by the behaviors of tight circling in both directions and frequent head shaking in horizontal. They could definitely be identified by at least day 10 after birth. These abnormal behaviors were steady and permanent through life. Mating experiments demonstrated that the mutant character is expressed by a single autosomal recessive gene in homozygote with complete penetrance. The pedigree analysis indicated that the gene was derived from one heterozygous male captured in Ginowan city, Okinawa. The name, waltzing, was proposed for this mutant character with the gene symbol wz. An abnormality of the balance organ was predicted for a cause of the abnormal behaviors, since, besides the circling and head shaking behaviors, the affected shrews could not keep the body stretching but twisted it frequently when they were held up by the tail and further they could not keep the head on the water surface at all. Nevertheless, the affected shrews were almost normal in gestation period, litter size, weaning ratio and body weight in comparison with the phenotypically normal ones. The mutant shrews have been maintained as a closed colony, the WZ line involved more than 30 individuals at every one generation.

Animals↗
PubMed1992

Hemodynamic changes due to afterload reduction as a predictor of exercise capacity in patients with dilated cardiomyopathy.

Sixteen patients with dilated cardiomyopathy were examined hemodynamically in order to clarify the relationship between the exercise capacity and the effects of afterload reduction at rest using supine graded bicycle exercise testing before and after sublingual administration of 10 mg nifedipine. 1) The integration of work loads was weakly correlated with the stroke index (r = 0.64), heart rate (r = -0.58) and plasma norepinephrine concentration at rest (r = 0.49), but not with the left ventricular ejection fraction, cardiac index, pulmonary arterial diastolic pressure or the mean arterial pressure at rest. 2) Changes in stroke index and heart rate after administration of nifedipine correlated well with the integration of work loads (r = -0.84, r = 0.81, respectively). Thus, in patients with dilated cardiomyopathy changes in stroke volume and heart rate due to afterload reduction at rest were better predictors of exercise capacity than the baseline left ventricular hemodynamic parameters.

Adult↗
PubMed1992

Haematopoietic cell lines capable of colonizing the thymus following in vivo transfer expressed T-cell receptor gamma-gene immature mRNA.

To clarify the mechanism by which progenitor T (pro-T) cells recognize and enter the thymus, an attempt was made to produce haematopoietic cell lines by the fusion of BALB/c nude mouse bone marrow or foetal liver cells (gestation 14 and 15 days) with AKR thymoma BW5147, thereby immortalizing cells with potency to colonize the thymus, a characteristic of pro-T cells rarely found in adult bone marrow or foetal liver. The hybridomas thus produced were classified according to the phenotype of surface markers, T-cell receptor (TcR) gene configuration and expression. All hybridomas were negative in the surface expression of T-cell markers such as TcR alpha beta, TcR gamma delta, CD3, CD4 and CD8. They had TcR beta-, gamma- and delta-genes, each with a different status with respect to configuration and transcription. Some possessed partially rearranged TcR genes and others expressed immature TcR mRNA. The cell lines were examined for their capacity to colonize the thymus following intravenous injection into recipient mice. It was found that the cells with capacity of colonizing the thymus expressed immature TcR delta mRNA, while the cell lines lacking TcR delta-genes did not home to the thymus. These findings imply that the potency for migrating to thymus is closely associated with the particular stage of prethymic cell differentiation which could be estimated by the analysis of TcR genes, and that some cell lines with the expression of TcR delta-gene mRNA and the ability to colonize the thymus are derived from pro-T cells.

Animals↗
PubMed1991

Implanting mouse embryo stain with a LNF-I bearing fluorescent probe at their mural trophectodermal side.

Mouse embryos at implantation stage were stained successfully with lacto-N-fucopentaose I (LNF-I) bearing neoglycoprotein labeled with rhodamine synthesized by us for the first time. The fluorescent neoglycoproteins carrying LNF-II, -III, LND-I, or LNT failed to stain the embryos. The embryo was stained only at the cell surface of trophectoderm at the mural side. Since the attachment of the mouse embryo to the uteric epithelium occurs at its mural side trophectoderm and LNF-I is the key substance in mouse implantation (Lindenberg, S. et al, (1988) J. Reprod. Fert. 83, 149-158), the material stained with the probe carrying LNF-I appears to be the molecule responsive to attachment to the endometrium surface and leading to implantation.

Animals↗
PubMed1991

The retarded rate of acid-catalyzed solvolysis of glycoside bonds between reducing-end glucose residue and ceramide in glycosphingolipids compared with that of glycoside bonds between hexopyranosides.

Rates of acid-catalyzed solvolysis of glycoside bonds in glycosphingolipids were compared to establish a basis for conducting saccharide analysis. Permethylated globotetraosylceramide and asialogangliotriaosylceramide as model compounds for methylation and sugar composition analysis, respectively, were solvolyzed under acidic conditions and the sugar components thus obtained were determined at specified times by gas liquid chromatography, after they had been derivatized. Reducing-end glucose residues in both compounds were liberated more slowly than other sugar residues. Glycoside bonds between reducing-end glucose and ceramide in glycosphingolipids would thus appear to be more resistant towards acid-catalysed solvolysis than other glycoside bonds between hexopyranosides.

Acids↗
PubMed1991

Effects of atrial natriuretic peptide on adrenergically induced norepinephrine release and vasoconstriction in the dog kidney.

The effects of atrial natriuretic peptide (ANP) on the neural control of renal blood flow were examined in anesthetized dogs. Intrarenal arterial infusion of ANP (alpha-hANP, 10 and 50 ng/kg per min) suppressed the decrease in renal blood flow but not the increase in renal venous plasma norepinephrine concentration induced by renal nerve stimulation (1 and 2 Hz, for 1 min). ANP also attenuated the blood flow response to intrarenal arterial injection of methoxamine (5-20 micrograms). These results suggest that ANP acts at a postsynaptic site to suppress adrenergically induced vasoconstriction in the dog kidney.

Animals↗
PubMed1991

Activator proteins for glycosphingolipid hydrolysis by endoglycoceramidases. Elucidation of biological functions of cell-surface glycosphingolipids in situ by endoglycoceramidases made possible using these activator proteins.

Endoglycoceramidase (EGCase) cleaves the linkage between oligosaccharides and ceramides of various glycosphingolipids (Ito, M., and Yamagata, T. (1986) J. Biol. Chem. 261, 14278-14282). Recently, by extensive purification, it was separated from cell-lytic factor (hemolysin) and found to consist of three molecular species each with its own specificity (EGCases I, II, and III) (Ito, M., and Yamagata, T. (1989) J. Biol. Chem. 264, 9510-9519). A detergent was required for EGCases to express full activity, possibly due to their hydrophobic nature, and thus EGCases cannot be used for research on live cells. This paper presents findings on activator proteins in the culture supernatant of Rhodococcus sp. M-777 regarding the stimulation of EGCase activity in the absence of detergents. The activator protein, exhaustively purified and designated as activator II in this study, showed a single protein band on sodium dodecyl sulfate-, native-, and isoelectrofocussing-polyacrylamide slab gel electrophoresis after being stained with Coomassie Brilliant Blue. Its molecular weight and pI were 69,200 and 4.0, respectively. The activator protein enhanced the hydrolysis of glycosphingolipids in vitro and on the cell-surface by EGCase II in the absence of detergents in a concentration-dependent manner. Interestingly, activator II stimulated the activity of EGCase II much more than that of EGCase I on using asialo-GM1 as the substrate. This activator protein was found nonspecific to substrates susceptible to hydrolysis with EGCase II. Besides activator II, strain M-777 produced a second minor molecular species of activator protein designated as activator I which appeared specific for stimulating the activity of EGCase I in contrast to activator II. Following the addition of activator II, EGCase II hydrolyzed cell-surface glycosphingolipids quite efficiently at neutral pH at which hydrolysis hardly occurred at all in its absence. When using activator II in place of Triton X-100 for stimulating EGCase II activity, it was also noted to cause no damage to intact cells. It is thus possible by activator proteins to elucidate the biological functions of endogenous glycosphingolipids in situ by EGCases.

Amino Acid Sequence↗
PubMed1991

Effects of volume loading on left atrial systolic time intervals.

The effects of volume loading on the left atrial preejection period (LAPEP) and left atrial ejection time (LAET) were examined in 24 patients with various heart diseases using pulsed Doppler echocardiography. In response to volume loading, the left atrial dimension before atrial contraction significantly increased from 30.6 mm +/- 5.8 mm to 32.4 mm +/- 5.4 mm and the change in the left atrial dimension during atrial contraction tended to increase. The peak velocity in the atrial contraction phase significantly increased from 58 cm/s +/- 14 cm/s to 63 cm/s +/- 13 cm/s, and the integral of the atrial contraction phase tended to increase. LAPEP significantly decreased from 114 ms +/- 16 ms to 104 ms +/- 14 ms and LAET significantly decreased from 128 ms +/- 15 ms to 124 +/- 12 ms. The relation between LAET and left ventricular end-diastolic pressure, and that between LAPEP and mean pulmonary capillary wedge pressure, shifted downward to the right after volume loading. Thus, left atrial ejection is augmented by volume loading according to the Frank-Starling mechanism, while LAPEP decreases due to an increase in preload and LAET decreases due to an increase in afterload.

Atrial Function, Left↗