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Biomedical subjects

T Yamaguchi

Publications and source records attributed to T Yamaguchi.

At least 19 recordsLinked to original sources
PubMed1995

Changes in the composition of bilirubin-IX isomers during human prenatal development.

We analyzed the isomeric composition of bilirubin-IX in human fetal bile using HPLC. The approximate ratio of the bilirubin-IX isomers obtained from the fetal bile at 20 weeks of gestation was IX alpha, 6%; IX beta, 87%; IX gamma, 0.5%; and IX delta, 6%. From 15 to 22 weeks, bilirubin-IX beta was predominant and bilirubin-IX delta and bilirubin-IX alpha were also present in the bile as minor components. By 28 weeks, bilirubin-IX alpha constituted about 50% of the total bilirubin. There was a general correlation between fetal age and the proportion of bilirubin-IX alpha to bilirubin-IX beta in the bile and the small intestinal contents of fetuses. As development proceeded from mid-gestation to near term, the isomeric composition dramatically changed, with a decrease in the IX beta isomer and a subsequent increment of the IX alpha isomer. In contrast, the IX delta isomer changes little. Recently, we identified four forms of biliverdin reductase including two biliverdin-IX alpha reductases and two biliverdin-IX beta reductases in human liver cytosolic fractions [Yamaguchi, T., Komoda, Y. & Nakajima. H. (1994) J. Biol. Chem. 269, 24,343-24,348]. The proportion of the total activity of biliverdin-IX beta reductases to that of biliverdin-IX alpha reductases was considerably higher in the fetal, than in the adult liver.

Adult↗
PubMed1995

Comparative studies on cysteine synthase isozymes from spinach leaves.

Three types of cysteine synthase (CSase, EC 4.2.99.8) isozymes were purified from spinach leaves. Each isozyme was isolated to homogeneity by preparative PAGE. These isozymes were revealed to have different primary structures by amino-acid and proteinase digestion analyses, respectively. The enzymes designated as CSase 1, CSase 2 and CSase 3 with reference to the mobility on native PAGE were characterized with respect to physicochemical and enzymatic properties, and it was found that those enzymes had similar properties. It was also found that CSase 1 could be attributed to chloroplasts.

Amino Acids↗
PubMed1995

Bilirubin is oxidized in rats treated with endotoxin and acts as a physiological antioxidant synergistically with ascorbic acid in vivo.

We examined the possibility that bilirubin physiologically acts as an antioxidant by using scurvy-prone ODS-od/od rats treated with endotoxin (lipopolysaccharide: LPS). Recently, bilirubin oxidative metabolites were isolated from human urine and named biotripyrrin-a and biotripyrrin-b. The LPS injection markedly increased bilirubin oxidative metabolites in urine of rats fed an ascorbic acid-free diet. This increase was supressed by feeding an adequate amount of ascorbic acid, a physiological antioxidant. the concentrations of biotripyrrin-a and -b in urine collected 6.5-10 h after the LPS injection were lower in rats fed an ascorbic acid-supplemented diet than in rats fed an ascorbic acid-free diet. Moreover, feeding with ascorbic acid suppressed the elevation of hepatic mRNA level of heme oxygenase-1, the rate-limiting enzyme of bilirubin biosynthesis, in rats injected with LPS. These findings suggest that bilirubin is oxidized in rats treated with LPS and acts as a physiological antioxidant synergistically with ascorbic acid in vivo.

Animals↗
PubMed1995

Activation induces dephosphorylation of cofilin and its translocation to plasma membranes in neutrophil-like differentiated HL-60 cells.

We suggested that a cytosolic 21-kDa phosphoprotein played an important role in opsonized zymosan-trigered activation of superoxide-generating enzyme in neutrophil-like HL-60 cells through dephosphorylation (Suzuki, K., Yamaguchi, T., Oshizawa, T., Yamamoto, Y., Nishimaki-Mogami, T., Hayakawa, T., and Takahashi, A (1995) Biochim. Biophys. Acta 1266, 261-267). In the present study, we characterized the phosphoprotein and studied changes in it localization upon activation of phagocytes. The 21-kDa phosphoprotein was rapidly dephosphorylated upon activation not only wit opsonized zymosan but also with formyl-Met-Leu-Phe and arachidonic acid. The peptide fragments derived from the 21-kDa phosphoprotein were found to have the same amino acid sequences as those of cofilin, an actin-binding protein. The phosphoprotein reacted exclusively with anti-cofilin antibody on two dimensional immunoblots. Accordingly, together with its apparent molecular weight, isoelectric point, and detection of phosphoserine as a phosphoamino acid, we concluded that the 21-kDa phosphoprotein was a phosphorylated form of cofilin. The amount of cofilin in membranous fractions was increased upon activation. Furthermore, confocal laser scanning microscopy showed that cofilin existed diffusely in the cytosol and nuclear region of the resting cells, while in the activated cells, it was accumulated at the plasma membrane area, forming ruffles or endocytic vesicles on which O2.- should be produced. These results suggested that in resting cells cofilin exists as a soluble phosphoprotein in the cytosol and nuclei, while upon stimulation a large portion of cofilin is dephosphorylated and translocated to the plasma membrane regions.

Actin Depolymerizing Factors↗
PubMed1995

A preadipocyte clonal line from bovine intramuscular adipose tissue: nonexpression of GLUT-4 protein during adipocyte differentiation.

A clonal bovine intramuscular preadipocyte (BIP) line has been established from the intramuscular white adipose tissue of the M. longissimus thoracis in each of three Japanese Black cattle. Exponentially growing BIP cells exhibited a fibroblastic appearance. Adipocyte differentiation was initiated by treating confluent BIP cells with differentiation medium containing insulin and dexamethasone. Small lipid droplets appeared 5-6 days after stimulation and occupied a large fraction of the cell volume at 10 days and beyond. During the adipose conversion, the incorporation of acetate to the cells gradually increased by 10-fold and reached a maximum at day 5. However, incorporation of glucose increased only 3-folds prior to this conversion, even though GLUT-1 level increased by 13-fold at day 7. GLUT-4, on the other hand, was not detected during the course of differentiation. These results suggested that adipose tissue metabolisms in ruminants were different from that of non-ruminants.

Acetates↗
PubMed1995

Reduction of ubiquinone in membrane lipids by rat liver cytosol and its involvement in the cellular defence system against lipid peroxidation.

Rat liver homogenates reduced ubiquinone (UQ)-10 to ubiquinol (UQH2)-10 in the presence of NADPH rather than NADH. This NADPH-dependent UQ reductase (NADPH-UQ reductase) activity that was not inhibited by antimycin A and rotenone, was located mainly in the cytosol fraction and its activity accounted for 68% of that of the homogenates. Furthermore, the NADPH-UQ reductase from rat liver cytosol efficiently reduced both UQ-10 incorporated into egg yolk lecithin liposomes, and native UQ-9 residing in rat microsomes, to the respective UQH2 form in the presence of NADPH. The gross redox ratios of UQH2-9/(UQ-9 + UQH2-9) in individual tissues of rat correlated positively with the log of their respective cytosolic NADPH-UQ reductase activities, while the redox ratios in every intracellular fraction from liver were at about the same level, irrespective of NADPH-UQ reductase activities in the respective fractions. The combined addition of rat liver cytosol and NADPH inhibited to a great extent 2,2'-azobis(2,4-dimethyl-valeronitrile)-induced lipid peroxidation of UQ-10-fortified lecithin liposomes and completely inhibited such peroxidation in the liposomes in which UQH2-10 replaced UQ-10. The NADPH-UQ reductase activity was clearly separated from DT-diaphorase (EC 1.6.99.2) activity by means of Cibacron Blue-immobilized Bio-Gel A-5m chromatography. In conclusion, the NADPH-UQ reductase in cytosol, which is a novel enzyme to our knowledge, was presumed to be responsible for maintaining the steady-state redox levels of intracellular UQ and thereby to act as an endogenous antioxidant in protecting intracellular membranes from lipid peroxidation that is inevitably induced in aerobic metabolism.

Animals↗
PubMed1995

Thermodynamics of unfolding of ribonuclease A under high pressure. A study by proton NMR.

Thermodynamic stability of ribonuclease A (6.2 mM pH 1.0, 0.15 M KCl, in 2H2O) has been studied in the pressure range of 1 to 2000 atm and in the temperature range of 7.5 to 40 degrees C with a high pressure 1H NMR technique at 400 MHz. His epsilon proton resonances were used as reporter groups to measure fractions of folded and unfolded species. Gibbs energy differences between folded and unfolded species were obtained as functions of pressure for different temperatures and as functions of temperature for different pressures. The volume increase upon unfolding, delta V, was negative and temperature-dependent, decreasing from -10 ml/mol at 7.5 degrees C to -30 ml/mol at 37 degrees C. From the least squares-fitting of experimental Gibbs energy differences to a theoretical expression holding pressure and delta Cp constant, we determined best-fit values of delta G, delta H, delta S and delta Cp for different values of pressure in the temperature range 7.5 to 40 degrees C. We found that delta Cp is dependent on pressure, decreasing from 1.79 kcal/mol K at 1 atm to 1.08 kcal/mol K at 2000 atm. These findings appear to be consistent with a notion that the state of hydration of non-polar side-chains upon unfolding of the protein is a major factor that determines the pressure dependence of the conformational stability of ribonuclease A under the chosen experimental condition.

Animals↗
PubMed1995

Luminal loss and site of restenosis after Palmaz-Schatz coronary stent implantation.

Restenosis has frequently been observed at the articulation of the Palmaz-Schatz stent. However, the precise mechanism for this remains poorly understood. We measured the luminal diameter in 5 segments within the stent in 67 lesions of 63 patients with successful stenting. Luminal diameter at all 5 sites was significantly reduced 6 months after stent implantation (3.2 +/- 0.5 vs 2.4 +/- 0.7 mm, p < 0.05). Angiographic restenosis rate was 18%. Restenosis involving the articulation was found in 75% of the lesions, and that involving the articulation or edges in 83%. The diameter at the articulation was significantly smaller both immediately (3.0 +/- 0.5 mm vs 3.3 +/- 0.5 mm, p < 0.05) and 6 months after (2.1 +/- 0.8 mm vs 2.5 +/- 0.7 mm, p < 0.05) stenting than the diameter of other stent segments. The loss index was significantly greater at the proximal and distal edges than at the bodies of the stent (0.98 vs 0.60, p < 0.05). The edges of the Palmaz-Schatz stent tend to dilate more than the body of the stent during normal inflation. Although this anchoring system protects against dislodgment or migration of the stent, it may cause more injury. The articulation has 2 anchoring edges within only a 1 mm diameter. Thus, restenosis at the articulation may be ascribed to residual stenosis, increased intimal proliferation due to more severe injury, and delayed late vessel remodeling from lack of mechanical support. These characteristics may be attributed to stent design, and design improvement of the articulation may lead to more favorable results after stent implantation.

Aged↗
PubMed1995

Rate of release and retentivity of prostaglandin E1 in lipid emulsion.

The rates of release of prostaglandin E1 (PGE1) from lipid particles into aqueous solution were obtained by the dialysis method, for parenteral lipid emulsion (Lipo-PGE1) diluted 10-times with buffered solutions of various pH. The findings, which were the rates of release of PGE1, were used to calculate the amount of PGE1 distributed in lipid particles when Lipo-PGE1, diluted 100-times with various pH levels of the buffered solution, was administered by intravenous drip infusion. More than 90% of PGE1 was retained in the lipid particles and intravenously infused when transfusion fluid pH was less than 5.5 and 2 ml of Lipo-PGE1 and 198 ml of transfusion fluid had been mixed and were administered over 2 h. Results from simulation showed that half of the PGE1 was retained in lipid particles and was infused, if Lipo-PGE1 was diluted 100-times with pH 8 transfusion fluid. Though PGE1 was sparingly soluble in an aqueous solution, these findings demonstrated that a significant amount of PGE1 was retained in lipid particles. Thus, this dosage form is expected to be highly effective for a drug delivery of PGE1 in clinical treatment.

Alprostadil↗
PubMed1995

Okadaic acid induces both augmentation and inhibition of opsonized zymosan-stimulated superoxide production by differentiated HL-60 cells. Possible involvement of dephosphorylation of a cytosolic 21K protein in respiratory burst.

We found that okadaic acid (OA), a potent tumor promoter and a phosphatase inhibitor, has a unique opposing effect on opsonized zymosan (Op.-zym.)-elicited O2.- production by differentiated HL-60 cells in a narrow range of concentrations but does not induce any O2.- production by itself. Okadaic acid magnified the O2.- production 2.5-fold at 1.0 microM, while it inhibited it at 2.0 microM or higher concentrations. This effect of OA did not correspond to the changes in the expression of surface receptors (CD11b/CD18, CR3) for Op.-zym., because they were weakly down-regulated by OA at any concentration. Two-dimensional gel electrophoresis revealed that in the absence of OA, Op.-zym. induced rapid dephosphorylation of a cytosolic 21K protein with a very slight increase in phosphorylation of membranous p47phox, which is one of the cytosolic factors required for respiratory burst. In the presence of a stimulatory concentration (1.0 microM) of OA, the Op.-zym.-caused dephosphorylation of the 21K protein was still observed and the phosphorylation of p47phox was enhanced. In the presence of an inhibitory concentration (2.0 or 5.0 microM) of OA, the Op.-zym.-induced dephosphorylation of the 21K protein was strongly inhibited while p47phox was heavily phosphorylated. Acid hydrolysis of the 21K phosphoprotein yielded only phosphoserine as a phosphoamino acid. Furthermore, at least part of the 21K protein seemed to be associated with p67phox and p47phox, because it was co-immunoprecipitated with those cytosolic factors. These results suggest that a cytosolic 21K protein plays an important role in respiratory burst through dephosphorylation by a phosphoserine phosphatase, and that the dephosphorylated 21K protein may work synergistically with the phosphorylated p47phox on the pathway for activation of the respiratory burst oxidase.

Cell Differentiation↗
PubMed1995

Comparison of the signaling abilities of the Drosophila and human insulin receptors in mammalian cells.

Chimeric receptors encoding either the whole or a portion of the cytoplasmic domain of the drosophila insulin receptor (IR) with the extracellular domain of the human IR were expressed either transiently in COS cells or stably in Chinese hamster ovary cells and compared with the wild-type human IR. All three receptors bound insulin equally and exhibited an insulin-activated tyrosine kinase activity. The ability of the drosophila cytoplasmic domain to mediate the tyrosine phosphorylation of insulin receptor substrate 1, stimulate cell proliferation, and activate MAP kinase was found to be indistinguishable from that of the human IR. The chimeric drosophila receptors did not bind more phosphatidylinositol 3-kinase than the human IR, despite containing a C-terminal extension with potential tyrosine phosphorylation sites in the motif recognized by the SH2 domain of this enzyme. Thus, the essential signal-transducing abilities of the IR appear to have been conserved from invertebrates to mammals, despite the considerable differences in the sequences of these receptors.

Animals↗
PubMed1995

Deglycosylation of antiherpesviral 5-substituted arabinosyluracil derivatives by rat liver extract and enterobacteria cells.

A number of antiherpesviral 5-substituted derivatives of 1-beta-D-arabinofuranosyluracil (araU) were significantly resistant to phosphorolysis by rat liver extract (S-9), but were gradually deglycosylated in a 2% enterobacteria cell suspension. The relative order of the resistance conferred by the different C-5 substituents was: 5-propynyl > 5-(E)-2-bromovinyl > 5-(E)-2-chlorovinyl > 5-methyl > 5-iodo. The 2'-fluoro derivatives of araU were completely resistant to phosphorolysis by both liver extract and enterobacteria, whereas the corresponding ribofuranosyl and 2'-deoxyribofuranosyl nucleosides were easily phosphorolysed by S-9, and were immediately cleaved in a 1% enterobacteria cell suspension. These findings suggest that antiherpesviral 5-substituted araU analogues can be relatively stable in vivo, when injected intravenously, and that degradation of 1-beta-D-arabinofuranosyl-5-(E-2-bromovinyl)uracil (sorivudine) following oral administration is due primarily to the action of enterobacteria.

Animals↗
PubMed1995

Differential effects of [3H]nemonapride and [3H]spiperone binding on human dopamine D4 receptors.

We compared some binding parameters of [3H]nemonapride and [3H]spiperone in human dopamine D4 (hD4) receptors with three different numbers of tandem repeat units. Although both of the radioligands showed similar affinity constants for each hD4 receptor variant, the maximal number of binding sites labeled by [3H]nemonapride was approximately 1.35-fold higher than that by [3H]-spiperone for all variants. Estimated Ki values for the inhibition of [3H]nemonapride binding by a series of dopaminergic ligands were highly correlated to respective values obtained for the inhibition of [3H]spiperone binding to each hD4 receptor. These results suggest that the hD4 receptor, as shown for the D2 receptor, may exist in multiple molecular forms as a monomer-dimer equilibria, and that [3H]spiperone may discriminate in the multiple molecular forms.

Benzamides↗
PubMed1995

Ageing affects cytosolic Ca2+ binding proteins and synaptic markers in the retina but not in cerebral cortex neurons of the rat.

Two cerebral cortex areas (frontal and occipital) and the retina of rats varying in age from 0.4 to 30 months were investigated for the expression levels and distribution of two cytosolic high affinity Ca2+ binding proteins, calbindin-28 and calretinin, and of two presynaptic protein markers. Of these latter proteins, one is integral (synaptophysin) the other peripheral (synapsin I) to the synaptic vesicle membranes. In the cortex areas, no significant changes of the markers were observed, except for a drop of calretinin from 0.4 to 2 months, probably related to a stage of neuronal development. In the retina, calbindin-28 decreased progressively during ageing (-40% at 30 months) while calretinin remained unchanged. Concomitantly, the two synaptic vesicle proteins dropped, synaptophysin > 50% and synapsin I > 85%. The role of these changes in sustaining the functional alterations previously described in the retina of aged animals remains to be investigated.

Aging↗
PubMed1995

Polymorphic tandem repeats in dopamine D4 receptor are spread over primate species.

The human dopamine D4 receptor has polymorphic tandem repeats in the third cytoplasmic loop. However, these repeats are not present in the rat counterpart. To determine whether the tandem repeats are specific to humans or not, we analyzed genomic DNA sequences for the D4 receptor of six primate species (human, chimpanzee, gorilla, orangutan, macaque, marmoset). Sequencing data revealed that all primates have the 48-bp tandem repeats in the D4 receptor gene. This finding suggests that these repeats originated before the separation of the New World monkey lineage from the Old World monkey and ape-human lineages.

Amino Acid Sequence↗