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Biomedical subjects

Y Takei

Publications and source records attributed to Y Takei.

At least 217 records · Page 12Linked to original sources
PubMed1994

Possible involvement of a pertussis toxin-sensitive GTP-binding protein in protein transport into nuclei isolated from rat liver.

Nuclear protein transport was inhibited in permeabilized HeLa cells which had been prepared after culture with pertussis toxin, suggesting that the pertussis toxin-sensitive protein(s) might be involved in the nuclear protein transport. To investigate the mechanism whereby pertussis toxin inhibited the nuclear protein transport, an accumulation of proteins containing a nuclear localization signal sequence (NLS) into isolated rat liver nuclei was investigated. The NLS-containing protein accumulation required ATP and cytosolic proteins, and was temperature- and wheat germ agglutinin-sensitive as had been observed in permeabilized cells. Non-hydrolyzable GTP analogues, such as guanosine 5'-(gamma-thio)triphosphate and guanosine 5'-(beta, gamma-methylene)triphosphate, but not ATP analogues, inhibited the NLS-containing protein accumulation in the isolated nuclei. The NLS-containing protein accumulation was also inhibited by prior treatment of the nuclei with pertussis toxin plus NAD, and the effect of pertussis toxin was blocked when guanosine 5'-(gamma-thio)triphosphate was simultaneously added during the pretreatment with pertussis toxin. The inhibition induced by pertussis toxin and the blockage by guanosine 5'-(gamma-thio)triphosphate were well correlated to ADP-ribosylation of 40-kDa protein in nuclear fraction. These results suggested that the nuclear pertussis toxin-sensitive GTP-binding protein is involved in a pathway of nuclear protein transport.

Adenosine Diphosphate Ribose↗
PubMed1994

Temperature modulated solubility-activity alterations for poly(N-isopropylacrylamide)-lipase conjugates.

Chemical modification of proteins by use of functional polymers is expected to endow them with new properties without destroying their native functions, thus providing useful materials for application in different fields. We have synthesized poly(N-isopropylacrylamide) [poly(IPAAm)] co-oligomer with N,N-dimethylacrylamide (DMAAm) and reactive end groups by telomerization of IPAAm. This co-oligomer exhibits a lower critical solution temperature (LCST) at 37 degrees C. Using this temperature-responsive semitelechelic co-oligomer, we prepared polymer-enzyme conjugates of lipase by covalent coupling via carboxyl end-groups. This bioconjugate exhibits a LCST at 37 degrees C, having rapid, reversible hydration-dehydration changes due to highly mobile free polymer end groups. The conjugate retained its native enzymatic activity below this critical temperature, above which it precipitated and its catalytic function was shut off. This conjugate can be readily separated from reaction mixtures as a precipitate by simple temperature changes after reaction and reused in cycles without denaturation. Such a modulated system is attractive for application as a novel bioreactor system.

Acrylic Resins↗
PubMed1994

Endothelin-1 is involved in hepatic sinusoidal vasoconstriction after ischemia and reperfusion.

Endothelin-1 (ET-1), a vasoactive peptide, causes a significant rise in portal vein pressure, which is most likely a result of severe vasoconstriction in the liver. In this study, the effect of ET-1 on sinusoidal vasoconstriction in the liver after ischemia and reperfusion was directly investigated using intravital microscopy. In anesthetized female Sprague Dawley rats (200-250 g) ischemia of the median and left liver lobes was induced for 90 min by temporary ligation of the left pedicle. After declamping and a 90-min reperfusion period, the livers were exposed for intravital microscopy. Using a Nikon MM-11 fluorescence microscope (545 nm, 330x), a CCD camera (Cohu FK 6990), and a SVHS video recording unit, the hepatic microcirculation was directly investigated. Besides sham groups, two ischemia groups were studied, receiving ET-1 antiserum (anti-ET-1; 0.5 ml; Peptide Inst., Osaka, Japan) or NaCl 0.9% (0.5 ml) 5 min prior to reperfusion of the liver (n = 6/group). Following a transient drop in the mean arterial blood pressure in the anti-ET-1-treated groups, comparable systemic hemodynamic conditions among the four groups were noted during intravital microscopic assessment at the end of the 90-min reperfusion period. Reduction in the sinusoidal diameters during postischemic reperfusion (7.7 +/- 0.5 microm) was prevented by anti-ET-1 treatment (9.6 +/- 0.25 microm; P < 0.01; mean + SEM) back to control values (9.6 +/- 0.32 microm), while most of other microcirculatory parameters did not show significant differences. The results supported further the role of ET-1 in dysregulation of the sinusoidal vascular tone in the liver, e.g., after ischemia and reperfusion.

Animals↗
PubMed1994

Delayed ("secondary") cerebral energy failure after acute hypoxia-ischemia in the newborn piglet: continuous 48-hour studies by phosphorus magnetic resonance spectroscopy.

Phosphorous (31P) spectra from the brains of severely birth-asphyxiated human infants are commonly normal on the first day of life. Later, cerebral energy failure develops, which carries a serious prognosis. The main purpose of this study was to test the hypothesis that this delayed ("secondary") energy failure could be reproduced in the newborn piglet after a severe acute reversed cerebral hypoxic-ischemic insult. Twelve piglets were subjected to temporary occlusion of the common carotid arteries and hypoxemia [mean arterial PO2 3.1 (SD 0.6) kPa]. Mean cerebral phosphocreatine concentration [PCr]/inorganic orthophosphate concentration [Pi] decreased from 1.40 (SD 0.29) to 0.01 (SD 0.02), and nucleotide triphosphate concentration [NTP]/exchangeable phosphate pool concentration [EPP] decreased from 0.19 (SD 0.02) to 0.06 (SD 0.04) (p < 0.001 for each decrease). On reperfusion and reoxygenation of the brain, mean [PCr]/[Pi] and [NTP]/[EPP] returned to baseline. Observations continuing for the next 48 h showed that [PCr]/[Pi] again decreased, in spite of normal arterial PO2, mean arterial blood pressure, and blood glucose, to 0.62 (SD 0.61) at 24 h (p < 0.01) and 0.49 (SD 0.37) at 48 h (p < 0.001). [NTP]/[EPP] also decreased, but to a lesser degree. Intracellular pH remained unchanged. These findings appeared identical with those seen in birth-asphyxiated human infants. No changes in cerebral metabolite concentrations took place in six control piglets. The severity of secondary energy failure, as judged by the lowest [PCr]/[Pi] recorded at 24-48 h, was directly related to the extent of acute energy depletion, obtained as the time integral of reduction in [NTP]/[EPP] (p < 0.0001). This animal model of secondary energy failure may prove useful for testing cerebroprotective strategies.

Acute Disease↗
PubMed1994

Eel ventricular natriuretic peptide: cDNA cloning and mRNA expression.

Ventricular natriuretic peptide (VNP), a newly discovered type of cardiac natriuretic peptide identified in eels, has a unique amino acid sequence and biological activity compared with other members of the natriuretic peptide family. We have cloned a cDNA encoding the eel VNP precursor from a cDNA library of eel ventricles and determined its sequence. Sequence analysis showed that the preproVNP consists of 150 amino acid residues containing a signal sequence of 22 amino acid residues at its N terminus and mature VNP(1-36) at its C terminus. Comparison with two types of mammalian cardiac natriuretic peptides (A and B type natriuretic peptides; ANP and BNP) revealed that VNP showed greater overall sequence identity to ANP than to BNP at both the cDNA and amino acid sequence levels. Since VNP cDNA lacks the repetitive ATTTA sequence in the 3' non-coding region, which is a characteristic common to all BNP cDNAs sequenced to date, VNP may differ from BNP. While mRNA for eel ANP was detected only in the atrium, that for eel VNP was more abundant in the ventricle than in the atrium. Thus VNP is regarded as the first truly ventricular hormone in terms of synthesis and storage. Southern blot analysis indicated that VNP is also present in the quail, which belongs to a taxon where BNP has already been identified.

Amino Acid Sequence↗
PubMed1994

Eel ventricular natriuretic peptide: isolation of a low molecular size form and characterization of plasma form by homologous radioimmunoassay.

Ventricular natriuretic peptide (VNP) with 25 amino acid residues was isolated from the low molecular weight fraction of acid extracts of eel cardiac ventricles. No other short forms of VNP were recovered from the fraction. This peptide was named eel VNP(1-25) because it was a C-terminally truncated form of the previously isolated eel VNP(1-36). As observed before with eel VNP(1-36), eel VNP(1-25) had a much higher (146-fold) vasodepressor activity than human atrial natriuretic peptide (ANP) in eels, but was a third to a half as active in rats with respect to vasodepressor and natriuretic activities. Eel VNP(1-25) was generally less potent than eel VNP(1-36) for vasodepressor and natriuretic effects. A specific radioimmunoassay (RIA) has been developed for the measurement of eel VNP. The antiserum, raised against eel VNP(1-36), was highly specific and did not exhibit significant cross-reactivity with eel ANP and C-type natriuretic peptide, even though their amino acid sequences have more than 60% homology with that of eel VNP. The sensitivity of assay was 0.5 fmol/tube for eel VNP(1-36) with more than 99% confidence. Such high sensitivity permitted direct assaying of VNP with only a few microliters of plasma. In fresh water eels, the concentration of VNP in the cardiac ventricle was higher than those in the atrium or brain and that of ANP in the ventricle. Thus, VNP seems to be a ventricular hormone. Although ANP is a major circulating hormone in mammals, the plasma concentration of VNP was threefold higher than that of ANP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Study on experimental motion sickness in children.

To clarify the characteristics of motion sickness in children we investigated autonomic nervous symptoms and instability evoked by walking while wearing horizontally reversing goggles in 90 children aged 4 to 15 years. Kindergarten children had hardly any autonomic nervous symptoms except headache; however, they often fell, could not stand up or move, and exhibited a to-and-fro deviation gait. Although the frequency and severity of sickness gradually increased during growth, the severity of gait disorder became milder as age increased. On the basis of these findings it seems likely that functions which perceive disorder of spatial orientation and action are immature in young children, and once spatial orientation is impaired, instability becomes very severe, since inadequate control is not stopped by an alarm function against disorientation.

Adolescent↗
PubMed1994

Gypsetin, a new inhibitor of acyl-CoA:cholesterol acyltransferase produced by Nannizzia gypsea var. incurvata IFO 9228. I. Fermentation, isolation, physico-chemical properties and biological activity.

A novel inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT), designated gypsetin, was isolated from the cultured broth of Nannizzia gypsea var. incurvata IFO 9228 by solvent extraction, silica gel chromatography and crystallization. Gypsetin inhibited rat liver microsomal ACAT activity competitively with respect to the substrate oleoyl-CoA with an apparent Ki value of 5.5 microM. In cultured macrophage J774 cells incubated with oxidized low density lipoprotein, gypsetin inhibited cholesteryl ester formation from [14C]oleate by 50% at a concentration of 0.65 microM without affecting cell surface binding, uptake and degradation of the lipoprotein.

Animals↗
PubMed1994

Molecular evolution of shark C-type natriuretic peptides.

C-type natriuretic peptides (CNP) of varying length were isolated from the atrium or ventricle of a shark, Lamna ditropis and their amino acid sequences were determined. Although the sequence of Lamna CNP was highly homologous to those of other CNPs sequenced to date, the Lamna CNP-41, the longest CNP identified in this study, has one amino acid replacement from those of Triakis scyllia and Scyliorhinus canicula, and three amino acid replacements from that of Squalus acanthias. The degree of similarity of CNP molecules coincides well with their systematic positions in the cladogram of elasmobranchs; Lamna, Triakis and Scyliorhinus belong to the same order, but Lamna and Squalus belong to different orders. The facts that Lamna and Triakis are in different suborders but Triakis and Scyliorhinus are in the same suborder and have identical CNP-41, also support this evolutionary implication.

Amino Acid Sequence↗
PubMed1994

Amino acid sequence of sardine calcitonin and its hypocalcemic activity in rats.

A novel calcitonin (CT) was isolated from the spotlined sardine, Sardinops melanostictus. The primary structure of sardine CT was determined as follows: H-Cys-Ser-Asn-Leu-Ser-Thr- Cys-Ala-Leu-Gly-Lys-Leu-Ser-Gln-Glu-Leu-His-Lys-Leu-Gln-Ser-Tyr-Pro-Arg- Thr- Asn-Val-Gly-Ala-Gly-Thr-Pro-NH2. This amino acid sequence was different from that of salmon CT in 4 amino acid residues at positions 8th, 21th, 27th and 29th. As judged by the international method of CT bioassay, hypocalcemic activity of sardine CT was calculated as 4156 IU/mg. When compared for durability of CTs, it was found that sardine CT was significantly more potent than that of salmon CT. This is the first report of CT from a marine species of teleost.

Amino Acid Sequence↗
PubMed1994

Protective effect of ebselen on constrictive hepatic vasculature: prevention of alcohol-induced effects on portal pressure in perfused livers.

The effect of an organoselenium compound, ebselen [2-phenyl-1,2-benzisoselenazol-3-(2H)-one], on ethanol-induced liver damage through perturbation of microcirculation was investigated in perfused livers from fed rats. Infusion of ethanol at concentrations > or = 25 mM into the portal vein increased portal pressure in a concentration-dependent manner. Release of lactate dehydrogenase (LDH) into the effluent perfusate was minimal at 30 min; thereafter LDH release began to increase gradually until the end of the experiment (60 min after the onset of ethanol infusion) and was dependent on ethanol concentration. Simultaneous infusion of ebselen at a concentration of 10 or 30 microM with ethanol reduced significantly this ethanol-induced increase in portal pressure by 50 to 75% (P < .05) and LDH release by 70% (P < .05). When endothelin-1 or phenylephrine was infused into the liver, portal pressure was increased, reaching maximal levels (50 +/- 17 and 46 +/- 7 mm of H2O, respectively) and then decreasing gradually. Ebselen reduced the maximal increase in portal pressure induced by endothelin-1 (18 +/- 2 mm of H2O) by 64% (P < .05). In addition, ebselen decreased the maximal levels of portal pressure induced by phenylephrine (8 +/- 1 mm of H2O) by 83% (P < .05). These data indicate that ebselen has a vasodilative effect on constriction of hepatic vasculature and diminishes ethanol-induced hepatic damage by offsetting ethanol-induced increase in portal pressure. Thus, ebselen may prove useful for treatment of alcoholic liver injury via improvement of microcirculatory disturbances.

Animals↗
PubMed1994

Development of glycosylated human interleukin-1 alpha, neoglyco IL-1 alpha, coupled with D-mannose dimer: synthesis and biological activities in vitro.

Interleukin 1 (IL-1) is a nonglycosylated cytokine with pleiotropic effects on various cell types. In order to investigate the effect of carbohydrate introduction on IL-1 activity and to develop IL-1 with less deleterious effects recombinant human IL-1 alpha was chemically coupled with mannose dimers, alpha-D-Man1-6-D-Man[Man2(alpha 1,6)] and alpha-D-Man1-4-D-Man[Man2(alpha 1,4)]. About 5 molecules of mannose dimers were introduced per molecule of IL-1. Anti-IL-1 alpha antibody reacted only weakly with the glycosylated IL-1s. Conversely, antibody against the mannose dimer reacted with only glycosylated IL-1. The effect of glycosylation on IL-1 activity was evaluated by measuring a variety of IL-1 activities in vitro, including proliferative effect on T cells, antiproliferative effect on melanoma cells, stimulatory effect on IL-6 synthesis by melanoma cells, and stimulatory effect on prostaglandin E2 synthesis by fibroblast cells. Glycosylated IL-1s exhibited reduced activities, which were 10-fold to more than several hundred-fold lower than those of the original IL-1 alpha depending upon different aspects of activities addressed. Man2(alpha 1,6)-introduced IL-1 exhibited lower activity than Man2(alpha 1,4)-introduced IL-1. The competitive binding of 125I-IL-1 alpha to mouse T cells with unlabeled IL-1s suggests that the reduced activity of glycosylated IL-1s is due, at least partially, to the decrease of their receptor binding abilities.

Animals↗
PubMed1994

[5-Fluorouracil plus low-dose leucovorin in the treatment of advanced colorectal cancer].

From September 1989 to September 1992, 17 patients (pts) with non-curative or recurrent colorectal cancer were treated with 5-fluorouracil (FU) plus leucovorin (LV) systemic therapy. The sites of evaluable metastases were liver (10), peritoneum (4), lung (3) and others (6). The LV dosage was 30 mg/body (low-dose method) and the FU dosage was 500-750 mg/body. Both drugs were administered either 5 days/every 4 weeks or one day/every 1 to 2 weeks via protracted or bolus infusion. The regimen was generally well tolerated, although 9 pts (53%) experienced toxicity which required dose reductions. Overall response rate was 29% (5 PR). No CR was observed. Improvement in tumor-related symptoms was noted temporarily in 7 out of 10 pts. Serum CEA level decreased in 13 out of 14 pts. All the response sites were liver (5), with simultaneous lung (1) or peritoneum (1) metastasis. The response duration was 3 to 10 months (mean 6.2 months). Second-line therapy after progression of diseases, such as combination with CDDP, was attempted in some of the PR pts, but no re-response was observed. We conclude that FU plus low-dose LV regimen is an effective therapy for advanced colorectal cancer, but further attempts should be made to increase response rate, prolongation of response duration and effective second-line therapy after progression.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

Role of nitric oxide in ethanol-induced perturbation of hepatic microcirculation in rat liver.

Microcirculatory disturbance is one of the main pathogenetic features of alcoholic liver damage. We have demonstrated that ethanol increased portal pressure, leading to hepatic hypoxia and hepatocellular necrosis. In this ethanol-induced hepatic vasoconstriction, nitric oxide, an endothelial derived relaxing factor, dilated constrictive hepatic vasculature and reduced liver injury by improving the microcirculatory disturbance.

Animals↗
PubMed1994

Alcohol and endogenous nitric oxide in hepatic microcirculation.

This study investigated the role of endogenous nitric oxide in the regulation of hepatic vascular tone in the presence of ethanol. In the perfused rat liver, upon the initiation of ethanol infusion into the liver, portal pressure was increased in a dose-dependent manner, reaching maximal levels in 2-5 min, then decreasing gradually. Simultaneous infusion of N(G)-monomethy 1-L-arginine, a nitric oxide synthesis inhibitor, enhanced this ethanol-induced increase in portal pressure. This enhancement was reversed by simultaneous infusion of a precursor of nitric oxide, L-arginine. These results suggest that endogenous nitric oxide acts as a vasodilator which reduces ethanol-induced vasoconstriction, thus improving the perturbation of hepatic microcirculation by ethanol.

Animals↗