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Biomedical subjects

T Masuda

Publications and source records attributed to T Masuda.

At least 235 records · Page 13Linked to original sources
PubMed1997

Transient erythrophagocytosis in Diamond-Blackfan anemia.

We report on a 4-month-old Japanese infant girl with Diamond-Blackfan anemia (DBA) as shown by congenital macrocytic pure red cell hypoplasia with marked reduction of erythroid precursors in bone marrow, reticulocytopenia, increased fetal hemoglobin, and elevated adenosine deaminase activity in peripheral blood. She responded poorly to conventional doses of corticosteroids, however, with high-dose corticosteroids she responded with reticulocytosis and an elevation of hemoglobin level above 12 g/dL. Erythrophagocytosis was noted during the tapering period of prednisone when her hemoglobin level declined to 7.6 g/dL and reticulocyte level to 0.4%. At that time, the erythrophagocytosis was noted in about 60% of marrow histiocytes. These findings were not observed prior to or during the high dose prednisone therapy. We speculate that one of the causes of pure red cell aplasia and reticulocytopenia in DBA is mediated by erythrophagocytosis.

Bone Marrow↗
PubMed1997

Susceptibility of nude mice carrying the Fv-4 gene to Friend murine leukemia virus infection.

Fv-4 is a mouse gene that dominantly confers resistance to infection with Friend murine leukemia virus (F-MuLV) (S. Suzuki, Jpn. J. Exp. Med. 45:473-478, 1975). Despite complete resistance to ecotropic MuLV infection in mice carrying the Fv-4 gene, it is known that cells carrying the resistance gene in tissue culture do not always show resistance as extensive as that in vivo (H. Yoshikura and T. Odaka, JNCI 61:461-463, 1978). To investigate the immunological effect on resistance in vivo, we introduced the Fv-4 gene into BALB/c nude mice (Fv-4-/- nude[nu/nu]) by mating them with Fv-4 congenic BALB/c mice (Fv-4r/r nude+/+) and examined the susceptibility of the F2 progeny to F-MuLV. All BALB/c nude mice without the Fv-4 gene (Fv-4-/- nude[nu/nu]) were permissive to F-MuLV and developed erythroleukemia within 2 weeks after virus inoculation. The BALB/c nude mice with the Fv-4 gene (Fv-4r/r nude[nu/nu]) did not develop leukemia, and no or little virus was detected in the spleen 7 weeks after virus inoculation. The resistance to F-MuLV was dominant in (Fv-4 congenic BALB/c x BALB/c nude) F1 mice with the Fv-4r/- nude(nu/+) genotype as strictly as in (Fv-4 congenic BALB/c x BALB/c) F1 mice with the Fv-4r/- nude+/+ genotype. However, almost all BALB/c nude mice with the Fv-4r/- nude(nu/nu) genotype developed the disease within 7 weeks, and the virus was detected in all of their spleens even in the mice without leukemia. These results show that the resistance caused by the Fv-4 gene is recessive in nude mice and dominant in BALB/c mice. Some immunological effects, perhaps cell-mediated immunity, may play important roles in the resistance to F-MuLV infection in vivo in addition to the dosage effect of the Fv-4 product.

Animals↗
PubMed1997

Expression of neural cell adhesion molecule L1 in human lung cancer cell lines.

To investigate neuron-specific antigens, hybridoma cells were produced between mouse spleen cells immunized with human neuroblastoma cells (IMR-32) and mouse myeloma cells. 247 hybridoma clones were harvested and one of them was further cultured for recloning. Eventually, one hybridoma clone was obtained and its antibody was designated N-A8. The characteristics of this antibody were determined by immunostaining and flow cytometry. First, the antibody recognized the surface antigens of IMR-32 cells. Second, unexpectedly, N-A8 was reactive not only with human neuroblastoma cell lines but also with human lung cancer cell lines. As analyzed by immunoprecipitation method and SDS-PAGE, the molecular size of the antigen recognized by N-A8 was 210 kDa. The antigen was then purified by affinity chromatography and identified as neural adhesion molecule L1 by amino acid sequence analysis. By the present investigation, it was clearly demonstrated that L1 is expressed in human lung cancer cells.

Animals↗
PubMed1997

New curcuminoids isolated from Zingiber cassumunar protect cells suffering from oxidative stress: a flow-cytometric study using rat thymocytes and H2O2.

Effects of new complex curcuminoids (cassumunin A and cassumunin B) isolated from tropical ginger, Zingiber cassumunar, were examined in dissociated rat thymocytes suffering from oxidative stress induced by 3 mM hydrogen peroxide by using a flow cytometer and ethidium bromide. The effects were compared with those of curcumin, a natural antioxidant, whose chemical structure is included in those of cassumunins A and B. Pretreatment of rat thymocytes with the respective cassumunins at concentrations ranging from 100 nM to 3 microM dose-dependently prevented the hydrogen peroxide (H2O2)-induced decrease in cell viability. It had the same action, although less effective, against the treatment with cassumunin A or B (3 microM) immediately after or 60 min after start of the oxidative stress. Respective potencies of cassumunins A and B in protecting the cells suffering from H2O2-induced oxidative stress were greater than that of curcumin. It is suggested that cassumunins A and B may possess a potent protective action on living cells suffering from oxidative stress.

Animals↗
PubMed1997

Disappearance of serum hepatitis C virus RNA within two days after one dose interferon administration is predictive for response to high-dose interferon-alpha 2b treatment for chronic hepatitis C. Keio Interferon-alpha 2b Study Group.

We have reported the Keio multicenter randomized trial of interferon-alpha 2b treatment for chronic hepatitis C, hypothesizing that disappearance of serum hepatitis C virus (HCV) ribonucleic acid (RNA) during the first 2 days by one does administration of interferon is a predictive factor of final response to the high-dose interferon treatment. In this study we quantified HCV RNA by multicyclic reverse transcription-polymerase chain reaction in the stored sera of the same patients with our previous study. The multivariate analysis confirmed that the pretreatment HCV RNA levels and HCV genotype were significantly correlated with the response to the 6-month course interferon treatment. Although the relationship between decreased HCV RNA titers within the first 2 days after one dose administration of interferon and the efficacy of the therapy was not obtained, the cases in which HCV RNA disappeared within 2 days significantly responded to the 6-month course treatment (73.7% vs 12.5% in other cases, p < 0.01). The present study has confirmed the hypothesis suggested in the previous study that clearance of HCV RNA during the first 2 days has a predictive value for the final outcome.

Adult↗
PubMed1997

Myocardial contractility of the canine left ventricle during unsynchronized dual chamber pacing.

The influence of changes of left ventricular (LV) myocardial contractility on the decrease of cardiac output during atrial fibrillation was investigated in dogs using the slope (Ec) and the length intercept (Lo) of the LV end-systolic force-length relationship. The hearts of nine healthy adult mongrel dogs were instrumented with ultrasonic crystals and a micromanometer, after which pharmacologic autonomic blockade was instituted. The LV diameter and pressure data were recorded during inferior vena caval occlusion. Hemodynamic parameters were measured during pacing from the right atrial appendage at a pacing rate 30 beat/min greater than the natural heart rate using a cardiac stimulator (atrial pacing), and during simultaneous pacing from the right atrial appendage and right ventricular apex at the same rate (unsynchronized dual chamber pacing). Cardiac hemodynamics in the absence of synchronized left atrial contraction were simulated by unsynchronized pacing. During atrial pacing, the cardiac output (1.68 +/- 0.25 vs 1.57 +/- 0.21 l/min, p < 0.005) and Ec (110.1 +/- 58.5 vs 81.8 +/- 30.8 g/cm, p < 0.05) were significantly greater than during normal sinus rhythm, whereas the stroke volume (12.4 +/- 2.4 vs 15.1 +/- 3.1 ml, p < 0.005) and LV end-diastolic volume (16.6 +/- 2.7 vs 19.5 +/- 3.4 ml, p < 0.005) were significantly smaller. Lo did not change during pacing. During unsynchronized dual chamber pacing, cardiac output (1.46 +/- 0.17 vs 1.68 +/- 0.25 l/min, p < 0.005), stroke volume (10.8 +/- 1.7 vs 12.4 +/- 2.4 ml, p < 0.005), and LV end-diastolic volume (15.0 +/- 2.0 vs 16.6 +/- 2.7 ml, p < 0.05) were significantly smaller than during atrial pacing. However, Ec and Lo were similar during both types of pacing. These findings suggest that the decrease of cardiac output and stroke volume during atrial fibrillation is chiefly due to the decrease of LV end-diastolic volume through loss of left atrial contraction, and is not due to a change of LV myocardial contractility.

Animals↗
PubMed1997

[Long-term beneficial effect of dual chamber pacing in a patient with hypertrophic obstructive cardiomyopathy].

Dual chamber (DDD) pacing therapy was effective to reduce the left ventricular outflow tract pressure gradient for a long time in a patient with pharmacotherapy-resistant hypertrophic obstructive cardiomyopathy. A 52-year-old man with pharmacotherapy-resistant pressure gradient was treated by a DDD pacemaker implantation, because the pressure gradient was proved to be reduced (94-->16 mmHg) by transient DDD pacing with an atrioventricular delay of 50 msec. Hemodynamics and ventricular wall thickness were serially observed after the implantation for 2 years. The pressure gradient progressively decreased during the pacing period, at 4 months and 2 years follow-up, (10-->2 mmHg) and during the sinus rhythm period (60-->25 mmHg), and left ventricular ejection fraction and end-diastolic volume index were increased. Although the ventricular wall thickness remained constant, the systolic anterior motion of the mitral valve and A/E were reduced during the pacing period in the echocardiography. During the acute effect of DDD pacing, the pressure gradient reduction seemed to be related to dilatation of the left ventricular outflow tract induced by a change of contraction modality of the intraventricular septum. Improved left ventricular diastolic function may contribute to the pressure gradient reduction during extended periods of pacing therapy.

Cardiac Pacing, Artificial↗
PubMed1997

General pharmacological profile of the novel cholecystokinin-A antagonist loxiglumide.

The general pharmacological properties of a novel cholecystokinin-A antagonist, loxiglumide ((+/-)-4-(3,4-dichlorobenzamido)-N-(3-methoxypropyl)-N-pentylgl utaramic acid, CR 1505, CAS 107097-80-3) on central nervous system, autonomic nervous system, cardio-respiratory system, gastrointestinal system, hematological and miscellaneous systems were investigated in experimental animals. 1. Central nervous system: At a dose of 30 mg/kg, i.v. loxiglumide showed ptosis in one of 6 mice, but at doses of 3 and 10 mg/kg, i.v. no change on gross behavior in mice. Loxiglumide had no effect on locomotor activity and thiopental-induced hypnosis, anti-convulsive activity, analgesic activity in mice and rectal temperature changes in rats. 2. Autonomic nervous system: In vitro, loxiglumide at concentrations of 10(-4) and 3 x 10(-4) mol/l slightly inhibited agonist-induced contractions in the isolated guinea pig ileum and spontaneous rhythmic contractions in the isolated non-pregnant rat uterus. But loxiglumide had no effect on oxytocin-induced contraction in isolated non-pregnant rat uterus. 3. Cardio-respiratory system: Loxiglumide had no effect on heart rate and electrocardiogram in anesthetized dogs. But it slightly increased blood pressure and decreased the frequency of respirations at a dose of 30 mg/kg, i.v. Furthermore, loxiglumide slightly decreased femoral arterial blood flow at doses of more than 3 mg/kg, i.v. On the other hand, it had no effect on contractile force or contraction rate in the isolated guinea pig atrium and resting tension in the isolated rabbit aorta. 4. Gastrointestinal system: Loxiglumide increased bile secretion at doses of 10 and 30 mg/kg, i.v. in anesthetized rats and at doses of 3, 10 and 30 mg/kg, i.v. in anesthetized dogs. However, total bile acid output was not affected by loxiglumide. On the other hand, loxiglumide had no effect on pancreatic secretion, gastric secretion and gastric emptying in rats and intestinal transport activity in mice. 5. Hematology: In vitro, in the case of samples without bovine serum albumin, at concentrations of more than 1.9 x 10(-3) mol/l loxiglumide showed hemolysis, while in the case of samples with bovine serum albumin, at concentrations of more than 6.9 x 10(-3) mol/l loxiglumide showed hemolysis, and its maximal potency was weak compared to albumin-free conditions. On the other hand, in vivo, loxiglumide had no effect on hemolysis. In addition, it had no effect on platelet aggregation, prothrombin time and activated partial thromboplastin time. 6. Miscellaneous pharmacological actions: Loxiglumide had no effect on local anesthetic activity in guinea pigs and renal function in mice. These results suggest that loxiglumide seems to produce no serious side effects on the central nervous system, autonomic nervous system, cardio-respiratory system, gastrointestinal system, hematological and miscellaneous systems at pharmacologically effective doses.

Animals↗
PubMed1996

Novel neural adhesion molecules in the Contactin/F3 subgroup of the immunoglobulin superfamily: isolation and characterization of cDNAs from rat brain.

We cloned two kinds of cDNAs encoding novel Contactin/F3-subgroup adhesion molecules, which we termed NB-2 and NB-3. Nucleotide sequence analyses have shown that NB-2 and NB-3 are comprised of 1099 and 1028 amino acid residues, respectively. There was 51% similarity in the amino acid sequence of NB-2 and NB-3. NB-2 shared 46, 43, 55 and 55% identities with Contactin/F3, Tag-1, Big-1 and Big-2, respectively, at the amino acid sequence level. Likewise, the amino acid sequence of NB-3 exhibited 42, 44, 58 and 60% identities with Contactin/F3, Tag-1, Big-1 and Big-2, respectively. Expression of NB-2 mRNA was restricted to cerebrum, cerebellum and was hardly detectable, if any, in spinal cord. On the other hand, high expression of NB-3 mRNA was observed in spinal cord, as well as in cerebrum and cerebellum. In the other tissues, no expression of NB-2 and NB-3 mRNAs was detected.

Animals↗
PubMed1996

Strength of translation initiation signal sequence of mRNA as studied by quantification method: effect of nucleotide substitutions upon translation efficiency in rat preproinsulin mRNA.

Concerning the translation initiation signals in vertebrate mRNAs, both the ATG initiation codon and the sequences flanking the initiation codon are required to direct the position of initiation. A consensus sequence for the signal, (GCC)GCC(A or G)CCATGG, has been proposed, but actual initiation sequences differ from it to a greater or lesser degree. In the present report, the translation initiation signal sequences of rat preproinsulin and its mutant mRNAs were analyzed using a quantification method proposed previously. In this method, each 16 nt sequence in the mRNA was characterized by its sample score, which shows strength of the signal. So far, Kozak has constructed a number of preproinsulin mutant mRNAs in which nucleotides flanking the ATG codon are systematically varied, and measured the translation initiation efficiency in terms of the proinsulin product. Her experimental results were well understood on the basis of the strength of the translation initiation signal sequence.

Animals↗
PubMed1996

Relative ratios of mRNA molecules encoded by genes with homologous sequences using fluorescence-based single-strand conformation polymorphism analysis.

The combination of reverse transcribed (RT)-PCR and fluorescence-based single-strand conformation polymorphism (SSCP) analysis is proposed for the quantitative determination of the ratio of mRNA molecules with homologous sequences. We applied this procedure to lactate dehydrogenase (LDH) subunits A and B. We designed fluorescence labeled common PCR primers in the sequences highly homologous between LDH-A and LDH-B cDNAs and performed RT-PCR-SSCP analysis. When PCR efficiency was almost the same between the different target sequences, analysis of mixtures of known amounts of LDH-A and LDH-B revealed linear and precise proportions of LDH-A mRNA. Template concentrations and PCR cycles did not affect the determination of proportions of LDH-A to total LDH. The present procedure could be easily applied to investigation of expression levels of genes encoding mRNAs with homologous sequences.

Amino Acid Sequence↗
PubMed1996

Difference in the mechanism of interaction of Raf-1 and B-Raf with H-Ras.

Ras is known to possess multiple cellular targets including Raf-1. Here, we measured both direct binding of various H-Ras mutants to two representative mammalian Ras targets, Raf-1 and B-Raf, and the activity of the mutants to stimulate Raf-1 and B-Raf, and analysed the difference in their Ras-interaction mechanisms. B-Raf was shown to share almost the same H-Ras binding-specificity with Raf-1 by examining binding of the H-Ras mutants to Raf-1 and B-Raf in the yeast two-hybrid and in vitro binding assays. Mutants, Y32F, A59E, and V45E bound to Raf-1 in Sf9 cells coexpressing them, but failed to activate Raf-1. On the other hand, Y32F activated B-Raf in a cell-free system which consisted of rat brain cytosol and recombinant MEK. These results suggest that there is a subtle structural difference in requirements for the interaction of Ras with Raf-1 and B-Raf.

Amino Acid Sequence↗
PubMed1996

Thermodynamic aspects of hydrophobicity and the blood-brain barrier permeability studied with a gel filtration chromatography.

It has been said that the selective permeability across the blood--brain barrier depends on several physicochemical properties of drugs such as hydrophobicity, molecular weight, and hydrogen-bonding potential. In order to investigate quantitatively the relationship between the blood--brain barrier permeability and the hydrophobicity of drugs, we have measured the micelle/water partition properties (Pmic) by the MLC (micellar liquid chromatography) method using a gel filtration version and compared with the blood--brain barrier permeability. The thermodynamic aspects of partition were derived by separating the micelle/water partition coefficient (log Pmic) into the enthalpy term PH and the entropy term PS. It was found that the PH shows a good correlation to the permeability, although log Pmic fails to do so. The result means that PH, which is easily obtained from the in vitro experiment, can be used as an excellent standard in discussing the transport phenomena through the blood--brain barrier.

Blood-Brain Barrier↗
PubMed1996

Rice gibberellin-binding phosphoprotein structurally related to ribulose-1,5-bisphosphate carboxylase/oxygenase activase.

A gibberellin A (GA)-binding protein was identified from rice (Oryza sativa L.) leaves by a ligand-binding assay. The dissociation constant of GA-binding protein and GA complex was about 100 nM. This protein has a relative molecular mass of 47 000 and an isoelectric point of 5.1. The partial amino acid sequence of the protein was determined for 54 residues from both the N-terminal and internal regions. A sequence homology search indicated that the amino acid sequence of GA-binding protein was homologous to that of the ribulose-1,5-biphosphate carboxylase/oxygenase activase from barley, Arabidopsis, spinach and Chlamydomonas. The GA-binding protein was immunologically detected in two polypeptides in the protein extract from leaves. The GA-binding protein identified was phosphorylated with Ca2+, Mg2+ and ATP in the leaf protein extracts of rice grown in the presence of exogenous GA.

Amino Acid Sequence↗
PubMed1996

Induction of a novel cytochrome P450 (CYP93 family) by methyl jasmonate in soybean suspension-cultured cells.

We isolated a cDNA encoding a novel cytochrome P450 (CYP93A1) from soybean suspension-cultured cells that had been treated with methyl jasmonate (MeJA). The amino acid sequence of the gene product had 30-40% identity with those of other plant P450s. The protein contained the heme-binding domain which is highly conserved among plant P450s. Transcription of the cytochrome P450 gene in soybean cells was induced by 30 microM MeJA even in the presence of cycloheximide, and reached maximum level 6 h after MeJA treatment. This is the first report of a plant cytochrome P450 gene whose transcription is induced by MeJA even without protein synthesis.

Acetates↗
PubMed1996

Post-translational modification of H-Ras is required for activation of, but not for association with, B-Raf.

B-Raf is regulated by Ras protein and acts as a mitogen-activated protein (MAP) kinase kinase kinase in PC12 cells and brain. Ras protein undergoes a series of post-translational modifications on its C-terminal CAAX motif, and the modifications are critical for its function. To elucidate the role of the post-translational modifications in interaction with, and activation of, B-Raf, we have analyzed a direct association between H-Ras and B-Raf, and constructed an in vitro system for B-Raf activation by H-Ras. By using methods based on inhibition of yeast adenylyl cyclase or RasGAP activity and by in vitro binding assays, we have shown that the segment of B-Raf corresponding to amino acid 1-326 binds directly to H-Ras with a dissociation constant (Kd) comparable to that of Raf-1 and that the binding is not significantly affected by the post-translational modifications. However, when the activity of B-Raf to stimulate MAP kinase was measured by using a cell-free system derived from rat brain cytosol, we observed that the unmodified form of H-Ras possesses an almost negligible activity to activate B-Raf in vitro compared to the fully modified form. H-RasSer-181,184 mutant, which was farnesylated but not palmitoylated, was equally active as the fully modified form. These results indicate that the post-translational modifications, especially farnesylation, are required for H-Ras to activate B-Raf even though they have no apparent effect on the binding properties of H-Ras to B-Raf.

Adenylyl Cyclases↗
PubMed1996

Cardiovascular responses mediated by two types of endothelin ET(B) receptor in spontaneously hypertensive and Wistar-Kyoto rats.

This study shows the effects of a selective endothelin ET(B) receptor agonist, IRL 1720 {Ac-[Ala11,15]endothelin-1-(8-21)}, on cardiovascular responses in anesthetized spontaneously hypertensive rats and Wistar-Kyoto rats. Single intravenous bolus injection of IRL 1720 caused a dose-related short-lasting fall in blood pressure, left ventricular pressure and myocardial contractility. However, repeated intravenous bolus injection of 10(-5) mol/kg IRL 1720 produced a biphasic response consisting of an initial short-lasting decrease followed by a sustained increase in these parameters. The initial decrease was reduced, whereas the following increase was enhanced with the repeated injections of IRL 1720. The cardiovascular pressor response was not inhibited by the endothelin ET(A) receptor antagonist, FR139317 ((R)2-[(R)-2-[(S)-2-[[1-(hexahydro-1H-azepinyl)]carbonyl] amino-4-+methylpentanoyl] amino-3-[3-(1-methyl-1H-indolyl)]propionyl]amino -3- (2-pyridyl)propionic acid). The effects of IRL 1720 were qualitatively similar but more potent in spontaneously hypertensive rats than in Wistar-Kyoto rats. These results suggest the existence of two types of endothelin ET(B) receptor for IRL 1720: a tachyphylactic endothelin ET(B) receptor that mediates cardiovascular depressor responses and a less tachyphylactic endothelin ET(B) receptor that mediates pressor responses in the rat.

Animals↗