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S Yamauchi

Publications and source records attributed to S Yamauchi.

At least 37 records · Page 2Linked to original sources
PubMed2000

Improved stereoselective synthesis of optically active methylene lactone, key intermediate for the synthesis of 1,2-oxidized furofuran lignan, by direct alpha-methylenation to butanolide.

(3R)-3-[(1R)-1-(tert-Butyldimethylsilyl)oxy-1-(2-methoxy-4,5-methylenedioxyphenyl) methyl]-2-methylene-4-butanolide, which is a key intermediate for the synthesis of 1,2-oxidized furofuran lignan, was stereoselectively synthesized from L-glutamic acid by applying direct methylenation to butanolide.

4-Butyrolactone↗
PubMed1999

Highly-sensitive micellar electrokinetic chromatographic analysis of dioxin-related compounds using on-line concentration.

An application study of an on-line concentration technique of neutral analytes for micellar electrokinetic chromatography (MEKC) was carried out in environmental analysis to enhance the UV detection sensitivity. Several dioxins and related compounds, such as dibenzofuran, dibenzo-p-dioxin, 2,3- and 2,7-dichlorodibenzo-p-dioxins, and 2,3,7-trichlorodibenzo-p-dioxin, were used as test solutes. For a highly sensitive separation and detection, cyclodextrin-modified MEKC (CD-MEKC) under acidic conditions was employed as a separation mode and stacking using reverse migrating micelles and a water plug (SRW) as an on-line concentration technique. Almost a 200-fold gain in detection sensitivity was obtained for the model compounds in SRW-CD-MEKC compared to that in normal CD-MEKC without on-line concentration and the limit of detection was found to be around 0.1 ppm for each solute.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed1999

Intracoronary flecainide induces ST alternans and reentrant arrhythmia on intact canine heart: A role of 4-aminopyridine-sensitive current.

BACKGROUND: The electrical alternans shown on an ST segment, ST alternans, is known as one of the most important predictors of ventricular fibrillation (VF). It has also been reported that sodium channel inhibition changes action potential configuration, especially on the repolarization phase. Thus, the sodium channel blocker may produce ST alternans and trigger reentrant arrhythmia. METHODS AND RESULTS: A sodium channel blocker (disopyramide, lidocaine, or flecainide) was infused selectively into the left anterior descending coronary artery in anesthetized, open-chest dogs. Sixty unipolar electrograms were simultaneously recorded from the entire cardiac surface of the heart. The amplitude of ST alternans (STa) was determined as the difference in the ST-segment magnitude between 2 consecutive electrograms. We accepted the greatest STa among 60 leads for evaluation. High-dose flecainide (100 microg. kg-1. min-1) increased STa and evoked a spontaneous VF. The STa in high-dose flecainide loading (8.7+/-3.4 mV; mean+/-SEM) was significantly greater than that in disopyramide or lidocaine (0. 9+/-0.4 and 0.8+/-0.2 mV, P<0.05). Treatment of 4-aminopyridine (4-AP) suppressed the increase in STa and the occurrence of VF evoked by flecainide, while E4031 or verapamil did not inhibit those. CONCLUSIONS: Flecainide caused the ST alternans that was closely correlated to the occurrence of VF. Because the ST alternans was suppressed by 4-AP treatment, a 4-AP-sensitive current such as Ito or Isus may play an important role on this phenomenon.

4-Aminopyridine↗
PubMed1999

Purification and characterization of chondroitin 4-sulfotransferase from the culture medium of a rat chondrosarcoma cell line.

Chondroitin 4-sulfotransferase, which transfers sulfate from 3'-phosphoadenosine 5'-phosphosulfate to position 4 of N-acetylgalactosamine in chondroitin, was purified 1900-fold to apparent homogeneity with 6.1% yield from the serum-free culture medium of rat chondrosarcoma cells by affinity chromatography on heparin-Sepharose CL-6B, Matrex gel red A-agarose, 3',5'-ADP-agarose, and the second heparin-Sepharose CL-6B. SDS-polyacrylamide gel electrophoresis of the purified enzyme showed two protein bands. Molecular masses of these protein were 60 and 64 kDa under reducing conditions and 50 and 54 kDa under nonreducing conditions. Both the protein bands coeluted with chondroitin 4-sulfotransferase activity from Toyopearl HW-55 around the position of 50 kDa, indicating that the active form of chondroitin 4-sulfotransferase is a monomer. Dithiothreitol activated the purified chondroitin 4-sulfotransferase. The purified enzyme transferred sulfate to chondroitin and desulfated dermatan sulfate. Chondroitin sulfate A and chondroitin sulfate C were poor acceptors. Chondroitin sulfate E from squid cartilage, dermatan sulfate, heparan sulfate, and completely desulfated N-resulfated heparin hardly served as acceptors of the sulfotransferase. The transfer of sulfate to the desulfated dermatan sulfate occurred preferentially at position 4 of the N-acetylgalactosamine residues flanked with glucuronic acid residues on both reducing and nonreducing sides.

Animals↗
PubMed1999

Immunohistochemistry of myoepithelial cells during development of the rat salivary glands.

Using a battery of monoclonal antibodies specific for rat proteins, immunohistochemistry was carried out on the developing myoepithelial cells (MECs) of the rat major salivary glands. The proteins examined were alpha-smooth muscle actin (alphaSMA), h1-calponin (calponin), keratin 14 (K14), beta subunit of S-100 protein (S-100beta), vimentin and glial fibrillary acidic protein (GFAP). The MECs exhibited immunoreactivity for alphaSMA, calponin and K14, but not that for S-100beta, vimentin and GFAP. Immunoreactivity for alphaSMA appeared in the MECs from the time when the microfilaments were initially deposited in these cells, i.e., at 20 days in utero in the sublingual and submandibular glands and at birth in the parotid gland. Calponin immunoreactivity was seen 1 day earlier than alphaSMA. The appearance was almost at the same time as the onset of the MEC differentiation in each gland. A small number of the MECs expressed weak K14 immunoreactivity from the time when the acinus-intercalated duct structure was established, i.e., at 21 days in utero in the sublingual gland, at 5 days after birth in the perotid gland and after 5 weeks post-natally in the submandibular gland. In addition, K14 immunoreactivity was observed in the basal cells of the striated and excretory ducts. The first appearance of K14 in these cells again coincided with the emergence of the duct system in each gland, i.e., at 20 days in utero in the sublingual gland, at 21 days in utero in the submandibular gland and at 3 days after birth in the parotid gland. Finally, the MECs in all the glands were found to redistribute as the acini matured. As the acini grew rapidly during the weaning period in the parotid and the sublingual glands, the MECs ceased to surround the acini. Thereafter, they disappeared from the acini in the parotid gland, whereas they reappeared in the sublingual gland. In the submandibular gland, the MECs were confined to the terminal tubules until 4 weeks after birth. Thereafter, the acini were established and invested by the MECs. In conclusion, immunohistochemistry of calponin and alphaSMA is a useful tool for identification of the MEC during its earliest differentiation, which has hitherto been possible only electron microscopically. In addition, it is suggested that the MEC is heterogeneous and the functionally differentiated MEC appears after weaning around acini of the mucous and seromucous glands.

Animals↗
PubMed1999

Effects of gender and acute dental pain on thermal pain responses.

OBJECTIVE: Considerable research suggests that females exhibit greater sensitivity to laboratory pain procedures than do males; however, whether the presence of acute clinical pain influences this sex difference in pain sensitivity has not been investigated. The present experiment investigated the effects of sex and acute dental pain on laboratory pain responses. DESIGN: Thermal pain onset and tolerance were determined in 46 dental patients (15 male, 31 female) experiencing pain due to acute irreversible pulpitis and in 33 healthy controls (13 male, 20 female). In addition, measures of mood and coping were obtained in all participants. All subjects participated in two experimental sessions. The first session took place immediately before the patients underwent endodontic treatment for relief of pulpal pain. The second session took place approximately 1-2 weeks later, when pulpitis patients were pain free after treatment. During each session, thermal pain onset and tolerance were assessed with a 1-cm2 contact thermode applied to the right volar forearm using an ascending method of limits. RESULTS: During both sessions, thermal pain onset and tolerance were lower in control females than in control males; however, male and female pulpitis patients did not differ in their thermal pain responses during either session. Pulpitis patients also showed greater affective distress than controls. CONCLUSIONS: These data suggest that the sex difference in thermal pain sensitivity frequently reported in pain-free subjects appears to be absent in patients presenting with acute dental pain. However, this effect cannot be explained solely based on the presence of clinical pain because the effect on pain threshold and tolerance persisted into session 2, when pulpitis patients were pain free. Potential explanations for these results are discussed.

Acute Disease↗
PubMed1999

Wavelength and conduction inhomogeneity in each atrium in patients with isolated mitral valve disease and atrial fibrillation.

INTRODUCTION: Patients with mitral valve disease frequently have atrial fibrillation (AF), and the left atrium is presumed to be the primary atrium that develops AF. However, it is still not clear whether the electrophysiologic abnormalities responsible for AF are confined to the left atrium in this subset of patients. METHODS AND RESULTS: To examine the AF vulnerability of each atrium, we measured the wavelength and inhomogeneity of the conduction at the lateral right atrium, lateral left atrium, and Bachmann's bundle after defibrillation of AF in seven patients undergoing the maze procedure and mitral valve surgery for AF and isolated mitral valve disease, respectively (AF group). The data were compared with five coronary surgery patients in sinus rhythm (SR group). The wavelength in the AF group was significantly shorter (P < 0.05) than in the SR group not only at the lateral left atrium (225 +/- 62 vs 285 +/- 36 mm) but also at the lateral right atrium (214 +/- 54 vs 254 +/- 34 mm). The variation coefficient of the local maximum activation phase difference in the AF group (1.9 +/- 0.8 at the right atrium, 2.1 +/- 0.8 at the lateral left atrium, and 2.0 +/- 0.6 at Bachmann's bundle) was significantly greater (P < 0.05) than in the SR group at all atrial regions. CONCLUSION: AF vulnerability was not confined to the left atrium immediately after defibrillation in AF patients with isolated mitral valve disease. Electrical remodeling resulting from perpetuation of AF, pathological changes extending to the right atrium, geometric changes caused by the atrial interactions occurring across the interatrial septum, or a combination of these may explain the results.

Atrial Fibrillation↗
PubMed1998

"Hexatuple" coronary bypass with in situ arterial grafts.

A fifty-seven year old male patient with severe three-vessel coronary artery disease underwent successful coronary bypass surgery in six vessels utilizing the in situ left internal thoracic and right gastroepiploic arteries. Each arterial conduit was anastomosed sequentially to as many as three coronary vessels respectively. Surgical results were excellent and the patient continues to do very well. A postoperative angiogram showed well-working arterial conduits without any anastomotic problems. Multiple sequential anastomoses of the in situ arterial conduits, although rather technically demanding, can provide better long-term results in patients requiring multiple coronary revascularization. When sequential anastomoses of the right gastroepiploic artery are being considered, the length and caliber of the artery should be evaluated by an angiogram since it varies in size compared to the internal thoracic artery.

Anastomosis, Surgical↗
PubMed1998

The clinical significance of performing preoperative angiography of the internal thoracic artery in coronary artery bypass surgery.

This study was designed to clarify the clinical significance of and indications for performing preoperative internal thoracic artery (ITA) angiography in patients undergoing coronary artery bypass surgery. A total of 300 possible candidates for coronary artery bypass grafting (CABG) underwent ITA angiography during diagnostic catheterization. Semi-selective angiography of bilateral ITAs were performed by injecting contrast medium manually with a 5-F right Judkins coronary catheter. The posteroanterior view of the arteriograms was recorded on a 35-mm cine film or a cut-film. Unusual angiographic findings of the ITAs were observed in nine patients (3%). These findings included: an atrophic ITA in three patients with ipsilateral subclavian artery occlusions; enlarged ITAs giving collaterals to the lower extremities in one patient with extensive aortoiliac occlusive disease; occluded ITAs in one patient with Takayasu's arteritis and two patients with a history of CABG; and a small but nonsclerotic ITA in one patient. Atherosclerotic occlusive ITAs were found in only one patient. Thus, we concluded that routine preoperative angiography of the ITA is not necessary because it is rarely affected by atherosclerosis. However, it should be performed for any of the following reasons: a cervical or supraclavicular bruit; an upper extremity blood pressure difference of greater than 20 mmHg; an extensive aortoiliac occlusion; and certain disorders such as Takayasu's arteritis or Kawasaki disease, or a history of open heart surgery.

Adult↗
PubMed1998

Pirfenidone induces intercellular adhesion molecule-1 (ICAM-1) down-regulation on cultured human synovial fibroblasts.

Pirfenidone has been shown to modify some cytokine regulatory actions and inhibit fibroblast biochemical reactions resulting in inhibition of proliferation and collagen matrix synthesis by fibroblast. We have investigated the effect of pirfenidone on the expression of cell adhesion molecules. The synovial fibroblasts were treated with IL-1alpha in the presence or absence of pirfenidone (range 0-1000 microM), and assayed for the expression of adhesion molecules such as ICAM-1 and endothelial-leucocyte adhesion molecule-1 (E-selectin) by cell ELISA. Pirfenidone significantly down-regulated the expression of ICAM-1 on cultured synovial fibroblasts in a dose-dependent manner. In contrast, expression of E-selectin was not affected. Furthermore, we examined whether pirfenidone affects the cellular binding between cultured lymphocytes and IL-1alpha-stimulated synovial fibroblasts by in vitro binding assay and found their mutual binding was significantly suppressed in a dose-dependent manner by pirfenidone. It is speculated that down-regulation of ICAM-1 might be one of the novel mechanisms of action of pirfenidone. These data indicate a novel mechanism of action for pirfenidone to reduce the activation of synovial fibroblasts.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1998

Varying types of circus movement re-entry with both normal and dissociated contralateral conduction causing different right and left atrial rhythms in canine atrial flutter.

The purpose of this study was to develop an animal model of atrial flutter (AFL) or fibrillation (AFB) and to determine precisely the pathway of atrial activation during arrhythmias induced by programmed stimulation. In 10 dogs, a shunt from the left subclavian artery to the left upper pulmonary vein was created to produce left atrial enlargement. Five months later, using programmed electrical stimulation, it was possible to induce 17 sustained atrial tachycardias in 9 of the 10 dogs, including 9 episodes of AFL caused by circus movement re-entry, 6 episodes of focal tachycardia, and 2 episodes of AFB. Short cycle length left atrial tachycardias caused by either circus movement or a focus did not propagate in a uniform 1:1 pattern to the right atrium (RA), resulting in RA dissociation. In these arrhythmias, complex wavefronts from both current and preceding left atrial cycles coexisted in the RA. Circus movement was associated with a spectrum of different re-entrant pathways with different path lengths. These differences in the path length were determined by various ways in which obstacles such as the superior vena cava and orifice of the right atrial appendage or pulmonary vein orifices were combined by contiguous areas of functional block.

Animals↗
PubMed1998

Reduction of alkyl (2-oxocyclohexyl)acetates by baker's yeast.

Baker's yeast reduction of methyl and ethyl (2-oxocyclohexyl) acetates proceeded with enantio- and diastereo-selectivity, affording the corresponding (2S)-trans-alcohols (major), (2S)-cis-alcohols (minor), and the unaltered (1S)-ketones with high optical purity.

Acetates↗
PubMed1997

Simultaneous subclavian artery reconstruction in coronary artery bypass grafting.

BACKGROUND: Subclavian artery occlusive lesion, although rare, is sufficiently important to consider before coronary artery bypass grafting because it can cause not only symptoms of the lesion per se, but also the postoperative coronary-subclavian steal phenomenon. METHODS: Four patients undergoing coronary artery bypass grafting received simultaneous reconstruction of the subclavian artery. During aortic cross-clamping, an 8-mm ring-reinforced polytetrafluoroethylene graft was attached to the aorta perpendicularly. The prosthetic graft was led to the proximal segment of the axillary artery through the second intercostal space and anastomosed to the inferior surface of the artery. RESULTS: Three patients received unilateral reconstruction of the subclavian artery, whereas another received bilateral reconstruction. There were no complications related to the subclavian reconstruction procedure. Post-operative angiograms revealed excellent patency of the prosthetic grafts. All of the patients have been asymptomatic with follow-up periods ranging from 9 to 50 months. CONCLUSIONS: To perform simultaneous subclavian artery reconstruction along with coronary artery bypass grafting, the aortoaxillary bypass procedure using an 8-mm polytetrafluoroethylene graft may be the method of choice because it has lower potential for complications and is less technically demanding.

Aged↗
PubMed1997

Simultaneous surgical correction of a common atrium and impure flutter.

We performed surgical correction and treatment of a common atrium and chronic impure flutter using a computerized mapping system in a 49-year-old man. A reentrant circuit was observed to exist around the left atrial appendage. In contrast to the regular activation in the left atrium, the activation sequence of the right atrium was extremely chaotic. Cryolesions were applied to the area of the reentrant pathway. After the operation, sinus rhythm was restored.

Atrial Fibrillation↗