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S Yamada

Publications and source records attributed to S Yamada.

At least 253 records · Page 14Linked to original sources
PubMed2000

Electrophysiological correlates of recollecting faces of known and unknown individuals.

We recorded brain potentials from healthy human subjects during a recognition test in order to monitor neural processing associated with face recollection. Subjects first attempted to memorize 40 faces; half were accompanied by a voice simulating that person speaking (e.g., "I'm Jimmy and I was a roadie for the Grateful Dead") and half were presented in silence. In the test phase, subjects attempted to discriminate both types of old faces (i.e., "named" and "unnamed" faces) from new faces. Recognition averaged 87% correct for named faces, 74% correct for unnamed faces, and 91% correct for new faces. Potentials to old faces were more positive than those to new faces from 300 to 600 ms after face onset. For named faces, the old-new ERP difference was observed at anterior and posterior scalp locations. For unnamed faces, the old-new ERP difference was observed only at posterior scalp locations. Results from a prior experiment suggest that these effects do not reflect perceptual priming of faces. The posterior portion of the old-new ERP difference was thus interpreted as a neural correlate of retrieval of visual face information and the anterior portion as an indication of retrieval of person-specific semantic information.

Adolescent↗
PubMed2000

Minimally invasive lung and pleural biopsies using 2-mm and standard thoracoscopic equipment.

Videoendoscopic surgery is commonly used to obtain a definitive diagnosis in a patient with pleural lesions or pulmonary infiltration of unknown etiology. We have performed minimally invasive pleural and lung biopsies, using 2-mm mini-videoscopic instruments supported by standard thoracoscopy via one 11.5-mm port, in 10 patients. These involved 8 patients with diffuse pulmonary infiltration, and two with diffuse pleural thickening. They underwent thoracoscopic pulmonary wedge resection and pleural biopsy using one 11.5-mm port and two or three 2-mm mini-ports. The mean operating time was 37 minutes. This procedure was successful in establishing a definitive diagnosis in each patient. Complications included subacute acceleration in pulmonary infiltration in one patient. No patient complained of pain or discomfort at the 2 mm-thoraco port sites. Healing of this port site resulted in excellent cosmesis. Mini-videoscopic surgery supported by standard thoracoscopic equipment can be used to perform lung or pleural biopsy less invasively than standard thoracoscopic approach.

Aged↗
PubMed2000

Cloning of cDNA and the gene encoding human hepatocyte nuclear factor (HNF)-3 beta and mutation screening in Japanese subjects with maturity-onset diabetes of the young.

AIMS/HYPOTHESIS: Molecular defects of the genes for transcription factors, hepatocyte nuclear factor (HNF)-4 alpha, HNF-1 alpha, HNF-1 beta and insulin promoter factor-1 cause maturity-onset diabetes of the young (MODY1, 3, 5, and 4, respectively). This suggests the HNF-related transcription cascade is important in insulin secretion which is induced by glucose. These genes and the gene encoding glycolytic enzyme glucokinase (MODY2) are, however, responsible for only 15-20% of cases of MODY in the Japanese. Searching for a novel form of MODY in this population, we cloned a new candidate gene encoding human HNF-3 beta, a winged helix transcription factor, which also belongs to the same HNF-transcription cascade. METHODS: The cDNA clone for human HNF-3 beta was isolated from a liver cDNA library. The gene was also cloned from a genomic library and its organization and chromosomal localization were determined. We screened 68 Japanese subjects with MODY/early-onset diabetes for mutations in this gene. RESULTS: Human HNF-3 beta is composed of 457 amino acids. The human gene, which was mapped to the segment 30 cR from SHGC-37039 on chromosome 20p by radiation hybrid mapping, spans approximately 4.5 kb and consists of three exons. Direct sequencing of the exons and flanking regions identified one missense mutation A328 V and seven polymorphisms, although the functional significance of the mutation in the pathogenesis of diabetes is not known. CONCLUSION/INTERPRETATION: The characterization of the structure of the HNF-3 beta gene and its mapping in the framework of markers will be helpful in genetic studies of the various forms of diabetes mellitus.

Amino Acid Sequence↗
PubMed2000

Identification of missense mutations in the hepatocyte nuclear factor-3beta gene in Japanese subjects with late-onset Type II diabetes mellitus.

AIMS/HYPOTHESIS: Hepatocyte nuclear factor (HNF)-3beta, a transcription factor expressed in pancreatic beta cells, is an upstream regulator of HNF-1alpha/MODY3, HNF-4alpha/MODY1 and IPF1/MODY5 genes. Our previous screening of MODY subjects showed that mutations in the HNF-3beta gene are not a common cause of this form of diabetes in the Japanese. We tested the hypothesis that mutations in the HNF-3beta gene cause late-onset Type II (non-insulin-dependent) diabetes mellitus in this population. METHODS: Genotyping of the polymorphic TCC repeat in the HNF-3beta gene was done in 112 Japanese subjects with Type II diabetes (age at diagnosis > 35 and family history of Type II diabetes among their second-degree relatives) and 96 Japanese control subjects. Furthermore, we screened 57 Type II diabetic patients for mutations of the HNF-3beta gene. Transactivation activity of variant HNF-3beta was investigated by transfection assay. RESULTS: The distribution of alleles of the TCC repeat was similar between diabetic and control groups. Mutation screening identified two missense mutations, A86T and G114E. Neither mutation was observed in 225 control subjects. The transactivation activity of G114E-HNF-3beta was similar to that of wild typeHNF-3beta. In contrast, the activity of A86T-HNF-3beta was statistically significantly reduced to 83-86 % of that of wild type. CONCLUSIONS/INTERPRETATION: The A86T mutation in the HNF-3beta gene might be involved in the development of late-onset Type II diabetes in a small group of Japanese people.

Adult↗
PubMed2000

Fluorometric determination of Ethofenprox in water by using solid-phase extraction.

Ethofenprox (pesticide) exhibits a relatively strong fluorescence in the UV region. Its fluorescence properties were investigated in aqueous solution, organic solvents, and micellar media. The fluorescence intensity of Ethofenprox was enhanced by a factor of 1.2 to 2.7 in the presence of surfactants and by 1.4 in pure organic solvents without significant shift of the excitation and emission wavelengths. The conditions for solid-phase extraction of Ethofenprox from water samples were examined. Among the solid-phase extraction cartridges studied, a Sep Pak C8 with weak sorption ability was found to be the most useful due to the extremely high hydrophobicity of Ethofenprox. For the complete elution of Ethofenprox from the sorbent, an addition of 40%v/v methanol to the sample water was necessary and effective to eliminate the fluorescent impurities of the matrix. The calibration graph obtained was linear over the range of 0.03 to 2.4 mg L(-1) in 100 mL sample. The method was successfully applied to the determination of Ethofenprox in tap, well, and river waters with recoveries of 93.2-95.7%.

Journal Article↗
PubMed2000

Early colorectal cancer with special reference to the superficial nonpolypoid type from a histopathologic point of view.

The incidence and histopathologic characteristics of nonpolypoid (superficial type) early colorectal carcinomas were studied and compared with those of the polypoid type. The superficial type was subclassified as elevated (type IIa), type IIa with central depression (type IIa + IIc), plain (type IIb), depressed (type IIc), and IIc with marginal elevation (type IIc + IIa). The superficial type comprised 22% and 27% of intramucosal and submucosal carcinomas, respectively. Pure type IIb was not found, and there were only three pure type IIc lesions. Type IIa + IIc and IIc + IIa (and IIc) showed a significantly higher rate of submucosal invasion among the small tumors (59% and 71% less than 20 mm, respectively) compared to the polypoid type; type IIa showed no significant difference. The incidence of lymph node metastasis among submucosal carcinomas showed no significant difference between the superficial type and the polypoid type. About 64% and 52% of type IIa and IIa + IIc tumors accompanied residual adenoma, suggesting that they originated from small, flat adenomas through the adenoma-carcinoma sequence, whereas type IIc + IIa (and IIc) did not have an adenomatous component, implying that they arose de novo or originated through an adenoma-carcinoma sequence at a smaller size than the type IIa and IIa + IIc lesions. Superficial-type early colorectal carcinomas are not rare, and they are not uniform in nature. Rapid growth and invasion to the submucosa is characteristic of superficial-type lesions with a central depression, and only superficial depressed (type IIc + IIa, IIc) lesions can arise de novo. Although they grow rapidly to invade the submucosa, it cannot be said that they show more aggressive behavior than the polypoid type.

Adenocarcinoma↗
PubMed2000

Mechanics of living cells measured by laser tracking microrheology.

To establish laser-tracking microrheology (LTM) as a new technique for quantifying cytoskeletal mechanics, we measure viscoelastic moduli with wide bandwidth (5 decades) within living cells. With the first subcellular measurements of viscoelastic phase angles, LTM provides estimates of solid versus liquid behavior at different frequencies. In LTM, the viscoelastic shear moduli are inferred from the Brownian motion of particles embedded in the cytoskeletal network. Custom laser optoelectronics provide sub-nanometer and near-microsecond resolution of particle trajectories. The kidney epithelial cell line, COS7, has numerous spherical lipid-storage granules that are ideal probes for noninvasive LTM. Although most granules are percolating through perinuclear spaces, a subset of perinuclear granules is embedded in dense viscoelastic cytoplasm. Over all time scales embedded particles exhibit subdiffusive behavior and are not merely tethered by molecular motors. At low frequencies, lamellar regions (820 +/- 520 dyne/cm(2)) are more rigid than viscoelastic perinuclear regions (330 +/- 250 dyne/cm(2), p < 0.0001), but spectra converge at high frequencies. Although the actin-disrupting agent, latrunculin A, softens and liquefies lamellae, physiological levels of F-actin, alone (11 +/- 1.2 dyne/cm(2)) are approximately 70-fold softer than lamellae. Therefore, F-actin is necessary for lamellae mechanics, but not sufficient. Furthermore, in time-lapse of apparently quiescent cells, individual lamellar granules can show approximately 4-fold changes in moduli that last >10 s. Over a broad range of frequencies (0.1-30, 000 rad/s), LTM provides a unique ability to noninvasively quantify dynamic, local changes in cell viscoelasticity.

Actins↗
PubMed2000

T102C polymorphism of the serotonin (5-HT) 2A receptor gene in patients with non-fatal acute myocardial infarction.

Serotonin (5-HT), released from activated platelets, has been implicated in the pathogenesis of acute myocardial infarction (AMI). 5-HT induces platelet aggregation and vascular contraction through 5-HT2A receptor activation at sites of coronary atherosclerosis, leading to thrombus formation. Recently, a 5-HT2A receptor gene T102C polymorphism has been reported to be associated with clinical response to 5-HT2A receptor antagonist in patients with schizophrenia, suggesting this polymorphism of the gene affects the 5-HT2A receptor function. To investigate the relationship between the T102C polymorphism and AMI, we conducted a case-control study of 255 non-fatal AMI patients and 255 control subjects. Among the patients, the prevalence of TT genotype was significantly higher than in controls (32.5 vs. 24.3%; P<0.05). In male patients (n=216), the prevalence was much higher than in control subjects (33.8 vs. 24. 1%, P<0.03). In multiple logistic regression models, odds ratio of TT genotype was 1.45 (95% CI 0.96-2.20) in all and 1.61 (95% CI 1. 03-2.53) (P<0.05) in males. The association of T102C polymorphism of the 5-HT2A receptor gene with non-fatal AMI was statistically significant and independent of other risk factors in males. The TT genotype of the 5-HT2A receptor gene may enhance susceptibility to AMI. Our observations suggest that the T102C polymorphism of the 5-HT2A receptor gene can serve as a new genetic marker for AMI.

Aged↗
PubMed2000

Brain distribution of 6-mercaptopurine is regulated by the efflux transport system in the blood-brain barrier.

6-mercaptopurine (6-MP) has been used clinically for 40 years to maintain remission in patients with acute lymphoblastic leukemia (ALL). However, central nervous system (CNS) relapses frequently occur in patients with ALL who continuously receive anticancer drugs, including 6-MP, during remission maintenance therapy. The cause of such CNS relapse is not well understood. One possible reason may involve the restricted distribution of 6-MP in the brain. This study, therefore, investigates the blood-brain barrier (BBB) transport which largely regulates 6-MP distribution in the brain using a quantitative microdialysis technique and centers on the efflux transport of 6-MP across the BBB. The brain tissue, cerebrospinal fluid (CSF), or hippocampal interstitial fluid (ISF) concentration of 6-MP was very low compared with the unbound plasma concentration, suggesting that 6-MP distribution in the brain is highly restricted. Kinetic analyses of this BBB transport showed that the efflux clearance from brain ISF to plasma across the BBB (CLout) is approximately 20-times greater than the influx clearance from plasma to brain (CLin). The CLout was significantly reduced by 1mM N-ethylmaleimide (NEM), a sulfhydryl-modifying agent, suggesting the participation of transport protein in the efflux of 6-MP across the BBB. In addition, efflux transport was inhibited by an intracerebral infusion of probenecid (1.5 mM), p-aminohippuric acid (PAH, 3.0 mM), benzoate (3.6 mM), or salicylate (3.7 mM) administered through a microdialysis probe, but neither choline (0.8 mM) nor tetraethylammonium (TEA, 0.7 mM) had any effect. These data suggest that the restricted 6-MP brain distribution may be ascribed to efficient efflux from the brain, possibly via both the organic anion transport system, shared with probenecid and PAH, and the monocarboxylic acid transport system, shared with benzoate and salicylate.

Animals↗
PubMed2000

Immunoaffinity purification method for detection and quantification of microcystins in lake water.

We have developed a new clean-up method, which consisted of solid-phase extraction on a Sep-Pak PS-2 (styrene-divinylbenzene copolymer) or Excelpak SPE-GLF (polymethacrylate) cartridge instead of conventional ODS silica gel and silica gel together with following immunoaffinity purification using anti-microcystin-LR monoclonal antibodies. This newly developed method was demonstrated to eliminate co-existing substances and to concentrate microcystins in the lake water. The recoveries from lake water (1 liter) spiked with 100 ng each of microcystins-RR, -YR and -LR were 85.5, 89.2 and 92.2%, respectively, with coefficients of variation of 3.3-7.6%. Only 3 h were required to complete the total procedures starting from the microcystin extraction, the immunoaffinity purification, and the quantification using HPLC. The detection limits for all of the 3 microcystins in lake water were 0.005 microg/l. Applicability of this method has been demonstrated by measuring the concentrations of microcystins in water samples collected from lakes where water blooms occurred, which turned out to be 0.012-0.177 microg/l of total microcystins.

Antibodies, Monoclonal↗
PubMed2000

Introduction of a specific binding domain on myoglobin surface by new chemical modification.

A new myoglobin, reconstituted with a modified zinc protoporphyrin, having a total of four ammonium groups at the terminal of the two propionate side chains was constructed to introduce a substrate binding site. The protein with a positively charged patch on the surface formed a stable complex with negatively charged substrates, such as hexacyanoferrate(III) and anthraquinonesulfonate via an electrostatic interaction. The complexation was monitored by fluorescence quenching due to singlet electron transfer from the photoexcited reconstituted zinc myoglobin to the substrates. The binding properties were evaluated by Stern-Volmer plots from the fluorescence quenching of the zinc myoglobin by a quencher. Particularly, anthraquinone-2,7-disulfonic acid showed a high affinity with a binding constant of 1.5 x 10(5) M(-1) in 10 mM phosphate buffer, pH 7.0. In contrast, the plots upon the addition of anthraquinone-2-sulfonic acid at different ionic strengths indicated that the complex was formed not only by an electrostatic interaction but also by a hydrophobic contact. The findings from the fluorescence studies conclude that the present system is a useful model for discussion of electron transfer via non-covalently linked donor-acceptor pairing on the protein surface.

Anthraquinones↗
PubMed2000

The 'ins' and 'outs' of intermediate filament organization.

A major function shared by several types of cytoplasmic intermediate filaments (IFs) is to stabilize cellular architecture against the mechanical forces it is subjected to. As for other fibrous cytoskeletal arrays, a crucial determinant of this function is the spatial organization of IFs in the cytoplasm. However, very few crossbridging proteins are specific for IFs - most IF-associated proteins known to exert a structural role act to tether IFs to other major cytoskeletal elements, such as F-actin, microtubules or adhesion complexes. In addition, IFs are endowed with the ability to participate in their own organization. This intriguing property is probably connected to the unusual degree of sequence diversity and sequence-specific regulation that characterize IF genes and their proteins. This dependence upon a combination of extrinsic and intrinsic determinants contributes to distinguish IFs from other fibrous cytoskeletal polymers and is key to their function.

Eukaryotic Cells↗
PubMed2000

Calcium-channel blocker attenuates Kupffer cell production of cytokine-induced neutrophil chemoattractant following ischemia-reperfusion in rat liver.

We investigated the effects of the calcium-channel blocker verapamil hydrochloride on the production of cytokine-induced neutrophil chemoattractant (CINC) following reperfusion injury in rat liver. Ischemia was induced for 30 min by portal vein occlusion. Animals were pretreated with intravenous injection of verapamil hydrochloride (2.5 mg/kg) 5 min before vascular clamp. Verapamil hydrochloride limited increases in the chemoattractant compared with nonpretreated rats. Most cells immunostained for chemoattractant were ED2-positive macrophages in sinusoids. In vitro chemoattractant production by Kupffer cells isolated from animals pretreated with verapamil hydrochloride was significantly lower than by Kupffer cells from nonpretreated animals. Expression of transcripts in liver for chemoattractant peaked 3 hr after reperfusion in nonpretreated animals, while pretreatment with verapamil hydrochloride significantly decreased chemoattractant mRNA levels. In vitro chemoattractant production could be induced in naive Kupffer cells after stimulation with oxygen radicals generated by hypoxanthine and xanthine oxidase, but verapamil hydrochloride prevented these increases. We concluded that the calcium-channel blocker verapamil hydrochloride significantly attenuates chemoattractant release by Kupffer cells after ischemia-reperfusion in the rat liver.

Animals↗
PubMed2000

Reduced interleukin-12, interleukin-18, and interferon-gamma production with prolonged rat hepatic allograft survival after donor-specific blood transfusion.

Interferon-gamma is a key immunoregulatory cytokine involved in acute graft rejection. Immunologic unresponsiveness to organ allografts has been induced by pretransplantation donor-specific blood transfusion, both experimentally and clinically. We investigated interferon-gamma production and intragraft gene expression of type-1 T-helper cytokines such as interleukin-12 and -18 and type-2 T-helper cytokines such as interleukin-10 and transforming growth factor-beta in rats receiving hepatic allografts after such transfusions. The animals were divided into four groups: group I received isografts; group II received allografts; group III received allografts after donor-specific transfusion; and group IV received allografts and was treated with FK 506. Donor blood given seven days prior to transplantation significantly prolonged allograft survival. The serum interferon-gamma concentrations in group II increased, peaking on day 5 and then decreasing. Serum interferon-gamma concentrations in groups I, III, and IV were significantly lower than those observed in group II, as were levels of interleukin-12 and interleukin-18 mRNA in the graft. Transforming growth factor-beta and interleukin-10 mRNA levels in grafts in transfused animals were significantly greater than those in the untreated allograft group. Interleukin-12 and -18 mRNA transcripts in an allogeneic mixed lymphocyte reaction were inhibited by interleukin-10 and transforming growth factor-beta. These results suggest that interleukin-12 and -18 expression in hepatic allografts is inhibited in the immunologically unresponsive state induced by donor-specific transfusion.

Animals↗
PubMed2000

An iso-integral mapping technique using magnetocardiogram, and its possible use for diagnosis of ischemic heart disease.

We have developed an iso-integral mapping technique that uses magneto-cardiogram (MCG) data to obtain a map as projected total current image on the torso from the heart. We have also investigated the applicability of iso-integral mapping to the diagnosis of ischemic heart disease. We simulated and measured the characteristics of two types of iso-integral maps: one using tangential (Bxy) components, and one using the normal component (Bz). Each vector component was measured by two types of superconducting quantum interference device (SQUID) system to determine the tangential and normal components. The tangential component of the magnetic field appeared to be equivalent to the current image in the myocardium projected on the observing plane, and we were able to obtain a projected total current image by integration of the tangential components during the depolarization and repolarization processes. And we found that the iso-integral maps of normal hearts showed similar pattern in both processes; however, those of ischemic hearts showed different patterns.

Action Potentials↗
PubMed2000

In vivo specific binding characteristics and pharmacokinetics of a 1,4-dihydropyridine calcium channel antagonist in the senescent mouse brain.

PURPOSE: To characterize the in vivo specific binding and pharmacokinetics of a 1,4-dihydropyridine (DHP) calcium channel antagonist, PN 200-110, in the senescent brain, using senescence-accelerated prone mice (SAMP8) and senescence-resistant mice (SAMR1). METHODS: Blood, brain, and heart samples were taken periodically from SAMR1 and SAMP8 following intravenous injection of (+)-[3H]PN 200-110, and the concentration of (+)-[3H]PN 200-110 in the plasma and tissues was determined. In addition, the in vivo specific binding of (+)-[3H]PN 200-110 in the brains of SAMRI and SAMP8 was measured periodically after intravenous injection of the radioligand. RESULTS: There was very little significant difference between SAMR1 and SAMP8 in terms of the half-life (t(1/2)), total body clearance (CL(tot)), steady-state volume of distribution (Vd(ss)). and AUC for the plasma concentration of (+)-[3H]PN 200-110 after intravenous injection of the radioligand. The brain concentration (AUCbrain) for (+)-[3H]PN 200-110 and the brain/plasma AUC ratio (AUCbrain/AUCplasma) were significantly lower in SAMP8 than in SAMR1, and the heart concentration (AUCheart) and the heart/plasma AUC ratio (AUCheart/AUCplasma) were similar in both strains. Also, the brain/plasma unbound AUC ratio (AUCbrain/AUCplasma-free) for (+)-[3H]PN 200-110 was significantly lower in SAMP8 than in SAMRI. The in vivo specific binding (AUCspecific binding, maximal number of binding sites: Bmax) of (+)-[3H]PN 200-110 was significantly lower in brain particulate fractions of SAMP8 than SAMR1. CONCLUSIONS: The concentration and in vivo specific binding of (+)-[3H]PN 200-110 was significantly reduced in the senescent brain. The simultaneous analysis of the concentrations of centrally acting drugs and the in vivo specific binding in the brain in relation to their pharmacokinetics may be valuable in evaluating their CNS effects.

Aging↗
PubMed2000

Blood-brain barrier transport of 125I-labeled basic fibroblast growth factor.

PURPOSE: This study was carried out to examine the blood-brain barrier (BBB) transport of human basic fibroblast growth factor (bFGF) and investigate its mechanism. METHODS: The BBB transport of 125I-bFGF was measured by several in vivo methods including intravenous administration, in situ internal carotid artery perfusion, and intracerebral microinjection. The in vitro binding of 125I-bFGF was characterized using freshly prepared bovine brain capillaries. RESULTS: The distribution volume of 125I-bFGF in the postvascular supernatant increased with the perfusion time, and exceeded the space occupied by the brain microvasculature and its trichloroacetic acid (TCA) precipitability was more than 90%. 125I-bFGF avidly bound to isolated bovine brain capillaries with a Bmax of 206 +/- 48 pmol/mg protein, and a Kd of 36.5 +/- 15.7 nM. This binding was significantly inhibited by unlabeled bFGF and heparin in a concentration-dependent manner. The cationic peptides, protamine and poly-L-lysine (each 300 microM), produced over 85% inhibition of 125I-bFGF binding to brain capillaries. Furthermore, glycosaminoglycans with a sulfate residue, chondroitin sulfate B and C (each 10 microg/mL) also inhibited the binding of 125I-bFGF The in vivo transcytosis of 125I-bFGF from the luminal side to the brain was also inhibited by the presence of heparin (10 microg/mL) and poly-L-lysine (300 microM), whereas neither hyaruronic acid (10 microg/mL) nor insulin (10 microM) had any effect. In addition to these results, the brain efflux index method was used to confirm that the transcytosis of 125I-bFGF from brain to blood across the BBB was negligible. CONCLUSIONS: These results suggest that 125I-bFGF is transported across the BBB, possibly by an adsorptive-mediated transcytosis mechanism that is triggered by binding to negatively charged species on the luminal membrane surface of the brain microvasculature, such as heparan sulfate proteoglycans.

Animals↗