Search PubMed⌕ Search

Biomedical subjects

R Yamamoto

Publications and source records attributed to R Yamamoto.

At least 73 records · Page 4Linked to original sources
PubMed2000

A microfilament formation inhibitor, cytochalasin strongly enhances the low-affinity Fc epsilon receptor II (CD23) expression on the human monocyte-like cell line, U937.

Enhancement of the low-affinity Fc epsilon receptor (CD23) expression by cytochalasin was analyzed on the human monocytelike cell line, U937. The CD23 expression on the U937 cells was enhanced at 24 hr after culture with cytochalasin B, D, or E, especially cytochalasin E having the most remarkable effect on it at the low concentration. This enhanced expression was found to be associated with a concomitant increase of a CD23 (about 45-kDa) protein on the U937 cells as assessed by Western blotting analysis. On the other hand, CD11a, CD18, CD31, CD49d, or CD54 was not markedly enhanced on the U937 cells by culture with cytochalasin E, although the mean fluorescence intensities (MFIs) of CD11a, CD18, and CD54 on U937 was partially up-regulated. Cell growth of U937 cultured with cytochalasin E was completely suppressed for 72 hr, but cell viability was sufficiently maintained (more than 95%). Soluble-formed CD23 (sCD23) also was released from the U937 cells at 24 to 72 hr after culture with cytochalasin E. In addition, the protein tyrosine kinase activity was detected in the U937 cells cultured with cytochalasin E for 24 hr using the enzyme immunoassay. Enhancement of the CD23 expression on the U937 cells at 24 to 72 hr cultured with cytochalasin E was sufficiently blocked by protein tyrosine kinase inhibitors herbimycin A and genistein, and a protein synthesis inhibitor, cychloheximide. On the other hand, protein kinase C inhibitors such as H-7 and H-8 had no effect on this CD23 expression. These results suggest that a mechanism underlying enhancement of the CD23 expression on the U937 cells cultured with cytochalasin E is mediated through tyrosine phosphorylation and protein synthesis.

Actin Cytoskeleton↗
PubMed2000

Adrenomedullin inhibits spontaneous and bradykinin-induced but not oxytocin- or prostaglandin F(2alpha)-induced periodic contraction of rat uterus.

In isolated rat uterine strips, adrenomedullin (AM) inhibited the spontaneous periodic contraction in a concentration-dependent manner (IC(50)=22.3+/-0.7 nM). The inhibitory effect of AM was prevented by either AM(22-52), a putative antagonist for AM receptors, or calcitonin gene-related peptide (CGRP)(8-37), a putative antagonist for CGRP receptors. AM also attenuated bradykinin (BK)-induced periodic uterine contraction, which was blocked by AM(22-52) or CGRP(8-37), whereas AM had no effect on the periodic contraction caused by oxytocin or prostaglandin F(2alpha) (PGF(2alpha)). RT-PCR analysis showed that mRNAs for calcitonin receptor-like receptor (CRLR), receptor-activity-modifying protein (RAMP)1, RAMP2 and RAMP3 were expressed in the rat uterus. These results demonstrate that AM selectively inhibits spontaneous and BK-induced periodic contraction via activating receptors for AM and CGRP.

Adrenomedullin↗
PubMed2000

Short- and long-term differential effects of neuroprotective drug NS-7 on voltage-dependent sodium channels in adrenal chromaffin cells.

In cultured bovine adrenal chromaffin cells, NS-7 [4-(4-fluorophenyl)-2-methyl-6-(5-piperidinopentyloxy) pyrimidine hydrochloride], a newly-synthesized neuroprotective drug, inhibited veratridine-induced (22)Na(+) influx via voltage-dependent Na(+) channels (IC(50)=11.4 microM). The inhibition by NS-7 occurred in the presence of ouabain, an inhibitor of Na(+),K(+) ATPase, but disappeared at higher concentration of veratridine, and upon the washout of NS-7. NS-7 attenuated veratridine-induced (45)Ca(2+) influx via voltage-dependent Ca(2+) channels (IC(50)=20.0 microM) and catecholamine secretion (IC(50)=25.8 microM). Chronic (>/=12 h) treatment of cells with NS-7 increased cell surface [(3)H]-STX binding by 86% (EC(50)=10.5 microM; t(1/2)=27 h), but did not alter the K(D) value; it was prevented by cycloheximide, an inhibitor of protein synthesis, or brefeldin A, an inhibitor of vesicular transport from the trans-Golgi network, but was not associated with increased levels of Na(+) channel alpha- and beta(1)-subunit mRNAs. In cells subjected to chronic NS-7 treatment, (22)Na(+) influx caused by veratridine (site 2 toxin), alpha-scorpion venom (site 3 toxin) or beta-scorpion venom (site 4 toxin) was suppressed even after the extensive washout of NS-7, and veratridine-induced (22)Na(+) influx remained depressed even at higher concentration of veratridine; however, either alpha- or beta-scorpion venom, or Ptychodiscus brevis toxin-3 (site 5 toxin) enhanced veratridine-induced (22)Na(+) influx as in nontreated cells. These results suggest that in the acute treatment, NS-7 binds to the site 2 and reversibly inhibits Na(+) channels, thereby reducing Ca(2+) channel gating and catecholamine secretion. Chronic treatment with NS-7 up-regulates cell surface Na(+) channels via translational and externalization events, but persistently inhibits Na(+) channel gating without impairing the cooperative interaction between the functional domains of Na(+) channels.

Animals↗
PubMed2000

Myopericarditis caused by cyclophosphamide used to mobilize peripheral blood stem cells in a myeloma patient with renal failure.

Cyclophosphamide (CPA) is widely used for peripheral blood stem cell mobilization, and a dose adjustment of CPA in the presence of renal failure has not been suggested. However, we describe a myeloma patient with renal failure (serum creatinine 4.2 mg/dl, creatinine clearance 11.2 ml/min) receiving CPA 2 g/m2 for 2 days, who developed unexpectedly severe toxicity, including myopericarditis and prolonged myelosuppression. The serial serum concentrations of CPA metabolites were persistently much higher than those in a myeloma patient with normal renal function. We consider, therefore, that the dose of CPA should be reduced in the presence of severe renal failure when used as high-dose therapy or to mobilize peripheral blood stem cells.

Adult↗
PubMed2000

A novel RNA motif that binds efficiently and specifically to the Ttat protein of HIV and inhibits the trans-activation by Tat of transcription in vitro and in vivo.

BACKGROUND: To find a novel RNA that would bind efficiently and specifically to Tat protein but not to other cellular factors, we used an in vitro selection method and isolated a novel aptamer RNATat, a 37-mer RNA oligomer, that binds efficiently to the Tat protein of HIV-1. In the present study, we analysed various properties of aptamer RNATat, including binding kinetics, identification of functional groups for Tat binding, and inhibition of Tat function. RESULTS: The binding affinity of the isolated aptamer RNATat to Tat-1 was 133 times higher than that of authentic TAR-1 RNA. RNATat is composed of inverted repeats of two TAR-like motifs, and even though RNATat had two Tat-binding core elements, the interaction with Tat took place at a molar ratio of 1 : 1. Several functional groups of aptamer RNATat responsible for Tat binding were identified. The selected aptamer RNATat competed effectively for binding to Tat even in the presence of a large excess of TAR-1 or TAR-2 RNA in vitro, and specifically prevented Tat-dependent trans-activation both in vitro and in vivo. CONCLUSIONS: Our results indicate that a novel aptamer, RNATat, retained strong affinity for Tat even in the presence of a large excess of HIV TAR. RNATat binds efficiently to Tat proteins or peptides derived from either HIV-1 or HIV-2. Unlike TAR RNA, RNATat affinity does not depend upon cellular proteins such as cyclin T1, thus RNATat has the potential for use as a molecular recognition element in biosensors.

Base Sequence↗
PubMed2000

Molecular beacon aptamer fluoresces in the presence of Tat protein of HIV-1.

BACKGROUND: We reported an aptamer, RNATat that binds to the Tat protein of HIV with two orders of magnitude greater (133-fold) affinity over the TAR RNA of HIV-1 and specifically inhibits the Tat-dependent trans-activation of transcription, both in vitro and in vivo (demonstrated in the accompanying article, Yamamoto et al., this issue pp. 371-388). We now report the use of aptamer-derived oligomers to analyze the Tat of HIV and the possible applications of such constructs in the field of biosensors. RESULTS: To make new molecular beacon, we constructed two RNA oligomers that derived from RNATat. To one of the split RNA oligomers that forms a hairpin structure, the fluorophore and quencher were attached at the 5'- and 3'-ends, respectively. Specifically in the presence of Tat or its peptides, but not in the presence of other RNA binding proteins, the two oligomers undergo a conformational change to form a duplex that leads to relieving of fluorophore from the quencher, and thus a significant enhancement of the fluorescence of fluorescein was observed. CONCLUSION: A novel strategy for exploiting aptamers in the analysis of Tat (analyte) has been described. A similar strategy could be used to study other analytes such as proteins and small molecules. In addition, the molecular beacon aptamer requires half the length of target sequence (eight nucleotides) in comparison with molecular beacons. Thus, it is conceivable that we could insert an analyte-binding site into molecular beacons to convert them to signalling beacons.

Biosensing Techniques↗
PubMed2000

Protein kinase C-alpha and -epsilon down-regulate cell surface sodium channels via differential mechanisms in adrenal chromaffin cells.

In cultured bovine adrenal chromaffin cells, our [3H]saxitoxin ([3H]STX) binding, immunoblot, and northern blot analyses specified protein kinase C (PKC) isoform-specific posttranscriptional and posttranslational mechanisms that direct down-regulation of cell surface Na channels. Immunoblot analysis showed that among 11 PKC isoforms, adrenal chromaffin cells contained only conventional (c)PKC-alpha, novel (n)PKC-epsilon, and atypical (a)PKC-zeta. Treatment of adrenal chromaffin cells with 100 nM 12-O-tetradecanoylphorbol 13-acetate (TPA) or 100 nM phorbol 12,13-dibutyrate (PDBu) caused a rapid (<15 min) and sustained (>15 h) translocation of PKC-alpha and -epsilon (but not -zeta) from cytosol to membranes, whereas a biologically inactive 4alpha-TPA had no effect. Thymeleatoxin (TMX), an activator of cPKC, produced similar membrane association of only PKC-alpha at 100 nM, with the potency of TMX being comparable with those of TPA and PDBu. Treatment with either 100 nM TPA or 100 nM TMX reduced cell surface [3H]STX binding to a comparable extent at 3, 6, and 12 h, whereas TPA lowered the binding to a greater extent than TMX at 15, 18, and 24 h; at 15 h, Gö6976, a specific inhibitor of cPKC, completely blocked TMX-induced decrease of [3H]STX binding while preventing by merely 57% TPA-induced decrease of [3H]STX binding. Treatment with 100 nM TPA lowered the Na channel alpha-subunit mRNA level between 3 and 12 h, with its maximum 52% fall at 6 h, and it was accompanied by a subsequent 61 % rise of the beta1-subunit mRNA level at 24 h. Gö6976 failed to prevent TPA-induced reduction of the alpha-subunit mRNA level; TMX did not change the alpha- and beta1-subunit mRNA levels throughout the 24-h treatment. Brefeldin A, an inhibitor of vesicular exit from the trans-Golgi network, augmented TPA- and TMX-induced decrease of [3H]STX binding at 1 and 3 h. Our previous and present studies suggest that PKC down-regulates cell surface Na channels without altering the allosteric gating of Na channels via PKC isoform-specific mechanisms; cPKC-alpha promotes Na channel internalization, whereas nPKC-epsilon decreases the alpha-subunit mRNA level by shortening the half-life of alpha-subunit mRNA without changing its gene transcription.

Adrenal Glands↗
PubMed2000

Up-regulation of cell surface insulin receptor by protein kinase C-alpha in adrenal chromaffin cells: involvement of transcriptional and translational events.

Our previous study showed that treatment of cultured bovine adrenal chromaffin cells with phorbol 12, 13-dibutyrate (PDBu) or 12-O-tetradecanoylphorbol 13-acetate (TPA) caused a rapid (<15 min) and persistent (>15 h) translocation of both conventional (c) protein kinase C-alpha (PKC-alpha) and novel PKC-epsilon (but not atypical PKC-zeta) from cytosol to membranes, whereas thymeleatoxin (TMX) increased the similar but selective membrane association of only cPKC-alpha. In the present study, chronic (>/=12 h) treatment of chromaffin cells with PDBu raised cell surface (125)I-insulin binding without altering the K(D) value; it developed in a concentration (EC(50) = 1.9 nM)-and time (t(1/2) = 14.6 h)-dependent manner, reaching its maximum 115% increase at 48 h. Either TPA (30 nM) or TMX (EC(50) = 6.4 nM) also increased (125)I-insulin binding by 97 or 88%, whereas the biologically inactive 4alpha-TPA had no effect. The increasing effect of PDBu (30 nM for 24 h) on (125)I-insulin binding was significantly blocked, even when H7, an inhibitor of PKC, was added at 8 h after the initiation of PDBu treatment. Concurrent treatment with brefeldin A, an inhibitor of vesicular transport from the trans-Golgi network, cycloheximide, an inhibitor of protein synthesis, or 5,6-dichlorobenzimidazole riboside, an inhibitor of RNA synthesis, abolished the PDBu-induced increment of (125)I-insulin binding. Western blot analysis, using antibody against the beta-subunit of the insulin receptor, showed that treatment with PDBu (30 nM) or TMX (EC(50) = 2.3 nM) increased levels of insulin receptor precursor (approximately 190 kDa; t(1/2) = 7.1 h) and insulin receptor beta-subunit (t(1/2) = 15.4 h), causing their almost maximum 52 and 59% rises, respectively, at 24 h. Northern blot analysis revealed that PDBu or TMX increased levels of insulin receptor mRNAs by approximately 35% as soon as 3 h, producing its monophasic peak approximately 76% increases at 24 h. All of these increasing effects of PDBu and TMX on (125)I-insulin binding and insulin receptor beta-subunit and insulin receptor mRNA levels were entirely prevented by simultaneous treatment with Gö6976, a selective inhibitor of cPKC. These results suggest that long-term activation of cPKC-alpha up-regulates the density of the cell surface insulin receptor via transcriptional/translational events.

Adrenal Medulla↗
PubMed2000

Ultrasound biomicroscopy for examination of the sclerotomy site in eyes with proliferative diabetic retinopathy after vitrectomy.

PURPOSE: We evaluated the capability of ultrasound biomicroscopy (UBM) to predict fibrovascular proliferation at sclerotomy sites in eyes with postoperative vitreous hemorrhage due to proliferative diabetic retinopathy (PDR). METHODS: Ultrasound biomicroscopy was used for examining the sclerotomy sites in 13 eyes of 11 patients with PDR experiencing postoperative vitreous hemorrhage (PDR group). Thirty-nine sclerotomy sites (all entry sites of each eye) were examined before reoperation, and the UBM images were compared with findings obtained during revision of the vitrectomy. Thirteen eyes of 13 patients undergoing vitrectomy for nondiabetic diseases were used as controls and examined after vitrectomy. RESULTS: The UBM images were classified into the following four categories: A, tent; B, spheroid; C, trapezoid; and N, none. The findings were distributed as follows in the PDR group: category A, 18%; B, 5%; C, 56%; and N, 21 %; and as follows in the control group: category A, 28%; B, 5%; C, 5%; and N, 62%. In the PDR group, 11 of 12 sclerotomy sites disclosing fibrovascular proliferation possessed the trapezoidal image. Mean length of trapezoidal base was 2.49+/-0.97 mm and 1.51+/-0.75 mm in the groups with and without fibrovascular proliferation, respectively (P<0.01). The average relative reflectivity of the trapezoidal image against the sclera was 0.501+/-0.169 in the fibrovascular proliferation group and 0.891+/-0.183 in the fibrous ingrowth group (P<0.01). CONCLUSION: Ultrasound biomicroscopy is useful in detecting fibrovascular proliferation at sclerotomy sites because a large and low-reflecting trapezoidal UBM image is highly correlated to its presence.

Adult↗
PubMed2000

RIKEN integrated sequence analysis (RISA) system--384-format sequencing pipeline with 384 multicapillary sequencer.

The RIKEN high-throughput 384-format sequencing pipeline (RISA system) including a 384-multicapillary sequencer (the so-called RISA sequencer) was developed for the RIKEN mouse encyclopedia project. The RISA system consists of colony picking, template preparation, sequencing reaction, and the sequencing process. A novel high-throughput 384-format capillary sequencer system (RISA sequencer system) was developed for the sequencing process. This system consists of a 384-multicapillary auto sequencer (RISA sequencer), a 384-multicapillary array assembler (CAS), and a 384-multicapillary casting device. The RISA sequencer can simultaneously analyze 384 independent sequencing products. The optical system is a scanning system chosen after careful comparison with an image detection system for the simultaneous detection of the 384-capillary array. This scanning system can be used with any fluorescent-labeled sequencing reaction (chain termination reaction), including transcriptional sequencing based on RNA polymerase, which was originally developed by us, and cycle sequencing based on thermostable DNA polymerase. For long-read sequencing, 380 out of 384 sequences (99.2%) were successfully analyzed and the average read length, with more than 99% accuracy, was 654.4 bp. A single RISA sequencer can analyze 216 kb with >99% accuracy in 2.7 h (90 kb/h). For short-read sequencing to cluster the 3' end and 5' end sequencing by reading 350 bp, 384 samples can be analyzed in 1.5 h. We have also developed a RISA inoculator, RISA filtrator and densitometer, RISA plasmid preparator which can handle throughput of 40,000 samples in 17.5 h, and a high-throughput RISA thermal cycler which has four 384-well sites. The combination of these technologies allowed us to construct the RISA system consisting of 16 RISA sequencers, which can process 50,000 DNA samples per day. One haploid genome shotgun sequence of a higher organism, such as human, mouse, rat, domestic animals, and plants, can be revealed by seven RISA systems within one month.

Animals↗
PubMed2000

Replica-exchange molecular dynamics simulation for supercooled liquids

We investigate to what extend the replica-exchange Monte Carlo method is able to equilibrate a simple liquid in its supercooled state. We find that this method does indeed allow us to generate accurately the canonical distribution function even at low temperatures and that its efficiency is about 10-100 times higher than the usual canonical molecular dynamics simulation.

Journal Article↗
PubMed2000

Apparent finite-size effects in the dynamics of supercooled liquids

Molecular dynamics simulations are performed for a supercooled simple liquid with changing the system size from N=108 to 10(4) to examine possible finite-size effects. Although almost no systematic deviation is detected in the static pair correlation functions, it is demonstrated that the structural alpha relaxation in a small system becomes considerably slower than that in larger systems for temperatures below T(c) at which the size of the cooperative particle motions becomes comparable to the unit cell length of the small system. The discrepancy increases with decreasing temperature.

Journal Article↗
PubMed2000

Prevention of vaginal shortening following radical hysterectomy.

We describe a surgical procedure and post-operative management for the prevention of vaginal shortening following radical hysterectomy. A total of 452 patients who underwent hysterectomies were examined prospectively depending on the operation method. This study showed that our procedure was effective in the prevention of vaginal shortening following radical hysterectomy. Preservation of the ovaries appeared to be important in preventing vaginal shortening, and post-operative hormone replacement therapy was not as effective as the preservation of the ovaries. The effect of external irradiation on vaginal shortening was not conspicuous in the case that the ovaries were preserved.

Adolescent↗
PubMed2000

Activation of the visual cortex imaged by 24-channel near-infrared spectroscopy.

Near-infrared spectroscopy (NIRS) is a noninvasive technique for continuous monitoring of the amounts of total hemoglobin (total-Hb), oxygenated hemoglobin, (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb). The purpose of the present study was to demonstrate the utility of NIRS in functional imaging of the human visual cortex. A new NIRS imaging system enabled measurements from 24 scalp locations covering a 9 cm sq area. Topographic images were obtained from interpolations of the concentration changes between measurement points. Five healthy subjects between 25 and 49 years of age were investigated. After a resting baseline period of 50 s, the subjects were exposed to a visual stimulus for 20 s, followed by a 50 s resting period in a dimly lit, sound attenuating room. The visual stimulus was a circular, black and white, alternating checkerboard. In four of five subjects the visual cortex was the most activated area during visual stimulation. This is the first reported use of a NIRS-imaging system for assessing hemodynamic changes in the human visual cortex. The typical hemodynamic changes expected were observed; the total-Hb and oxy-Hb increased just after the start of stimulation and plateaued after 10 s of the stimulation period.

Adult↗
PubMed2000

Assessment of aortic atherosclerosis and carotid atherosclerosis in coronary artery disease.

The present study investigated the relationship between aortic atherosclerosis and carotid atherosclerosis, and studied the effects of coronary risk factors for these arteries. The subjects consisted of 78 patients with coronary artery disease (CAD) and 69 patients without CAD. All subjects underwent enhanced computed tomography and B-mode ultrasonography within a short time period to determine the extent of aorta and carotid atherosclerosis. Significant correlations between maximal aortic wall thickness (MAWT) and aortic wall volume (AWV) with carotid intima-media thickness (IMT) were demonstrated. MAWT, AWV and IMT were significantly higher in patients with CAD compared with controls (p=0.009, p=0.024, p=0.001, respectively). Furthermore, there were significant differences in MAWT, AWV and IMT among groups classified by the number of coronary artery stenoses, and no significant differences among groups classified by risk factors, but it was shown that MAWT, AWV and IMT increased gradually as the risk factors increased in number. MAWT, AWV and IMT had positive correlations with age, systolic blood pressure and triglyceride, and a negative correlation with high density lipoprotein-cholesterol. This study demonstrated that both aortic atherosclerosis and carotid atherosclerosis are closely correlated with coronary atherosclerosis, and that the atherosclerosis indices are independently associated with age and hyperlipidemia.

Aortic Diseases↗
PubMed2000

Descending aorta wall volume and coronary artery disease: a comparative study using enhanced computed tomography of the chest and coronary angiography.

The study examined the association between aortic wall volume (AWV) detected by enhanced computed tomography and coronary artery atherosclerosis observed on angiography. In 180 cases, AWV was measured as the total wall volume of a 7-cm portion of the descending thoracic aorta distal from the tracheal bifurcation. Coronary artery atherosclerosis was angiographically quantified by both Gensini score, in terms of the severity of coronary artery stenosis, and Extent score, in terms of the severity of coronary artery involvement. Mean AWV values between the patients with significant coronary artery stenosis and those without significant stenosis were 9.83+/-4.04 cm3 and 8.09+/-2.39 cm3, respectively (p<0.001). AWV was a significantly independent variable for significant coronary artery disease (p=0.0097) and an Extent score > or = 60 (p=0.0092). Calcification of AWV, however, was not associated with coronary atherosclerosis. The quantification of aortic atherosclerosis was useful for diagnosing coronary artery disease.

Aged↗
PubMed2000

[Effects of low concentration of styrene monomer vapor on pregnancy].

To investigate the effects of exposure to styrene vapor on pregnancy, mice proved to be pregnant were exposed to 0, 2, 20 and 100 ppm styrene continuously for 24 hours during the period from day 0 to day 15 of gestation. A special small exposure chamber which can accurately maintain a constant low concentration of styrene vapor was made and used in the experiment. 1) In the 100 ppm group, hyperkinesis was presented in the chamber during the exposure period and inhibition of body weight gain was found (p < 0.01). No deaths occurred in any of the groups. 2) At necropsy of dams, no significant difference was found between the styrene exposed groups and the control group in any of the fertility indices, number of implantations, number of live fetuses, percentage of resorptions, or in the percentage of dead fetuses. The 100 ppm group showed lower fetal and placental weights (p < 0.01). 3) Gross necropsy of dams in the 100 ppm group showed significantly decreased adipose tissue. The liver, kidney and spleen weights were also low (p < 0.01). 4) When exposed to 100 ppm, which corresponds to 5 times the permissible concentration, i.e., 20 ppm, for 24 hours, non-pregnant dams showed no abnormality, while pregnant dams showed inhibition of body weight gain and significantly lower fetal and placental weights and maternal organ weights. Therefore, careful consideration should be given to exposure of women of childbearing age to styrene.

Animals↗