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Takanori Shibata

Publications and source records attributed to Takanori Shibata.

At least 19 recordsLinked to original sources
PubMed2006

Highly enantioselective construction of a chiral spirocyclic structure by the [2 + 2 + 2] cycloaddition of diynes and exo-methylene cyclic compounds.

The enantioselective [2 + 2 + 2] cycloaddition of 1,6-diynes with alpha-methylene lactones and cyclic ketones gave various chiral spirocyclic compounds. The reaction proceeded with high enantioselectivity when the rhodium-xylylBINAP complex was used as a chiral catalyst. Not only exo-methylene cyclic compounds but also exo-methylene acyclic compounds could be used as coupling partners for diynes. The present protocol provides access to a new chiral library possessing a quaternary carbon center, including a spirocyclic system.

Journal Article↗
PubMed2006

Enantioselective intramolecular [2 + 2 + 2] cycloaddition of 1,4-diene-ynes: a new approach to the construction of quaternary carbon stereocenters.

The intramolecular [2 + 2 + 2] cycloaddition of various 1,4-diene-ynes was examined using a chiral rhodium catalyst. In the case of 1,4-diene-ynes with a substituent at the 2-position of the 1,4-diene moiety, tricyclic compounds possessing a strained bicyclo[2.2.1]heptene skeleton with two quaternary carbon stereocenters were obtained in high enantiomeric excess. On the other hand, in the case of 1,4-diene-ynes with no substituent at this position, bicyclic cyclohexa-1,3-dienes with a quaternary carbon stereocenter were obtained probably by carbon-carbon bond cleavage of the reaction intermediate.

Journal Article↗
PubMed2006

Novel Rh catalysis in cross-coupling between alkyl halides and arylzinc compounds possessing ortho-COX (X = OR, NMe2, or Ph) groups.

[reaction: see text] Rh-dppf was found to be an efficient catalyst for the cross-coupling between primary alkyl halides bearing beta-hydrogens and arylzinc compounds possessing carbonyl groups such as ester, amide, or ketone at the ortho position. Various functional groups such as ester, nitrile, or acyloxylate moieties on the halides were tolerated under the catalysis conditions. Arylzinc compounds free of ortho-carbonyl groups reacted well with ethyl 3-iodopropanoate, suggesting that the essential intramolecular interaction between carbonyl groups and Rh promotes the reductive elimination.

Journal Article↗
PubMed2006

Synthesis of functionalized benzylsilanes from arylzinc compounds and (iodomethyl)trimethylsilane by means of a novel Rh catalysis.

[reaction: see text] The catalytic activity of a Rh complex in cross-coupling between ArZnI and TMSCH2I was examined in which the Rh complex, generated in situ from [RhCl(1,5-cyclooctadiene)]2 and 1,1'-bis(diphenylphosphino)ferrocene, exhibited excellent catalytic activity for the production of various functionalized benzylsilanes in good yields. From 31P NMR studies of various solutions containing several of the reaction components, confirmation of the rapid and quantitative transfer of aryl groups from ArZnI to the Rh complex to form arylrhodium species was ascertained. A catalytic cycle, commencing with the transmetalation, was thus proposed for the reaction.

Journal Article↗
PubMed2006

A novel method for the 3-dimensional simulation of orthognathic surgery by using a multimodal image-fusion technique.

INTRODUCTION: The aim of this study was to establish a novel method for simulating orthognathic surgery in 3-dimensional (3D) space. METHODS: This system mainly consists of 6 procedures: (1) reconstruction of a virtual skull model (VS) from presurgical computed tomography scans; (2) reconstruction of virtual dentition models from 3D surface scanning of dental casts occluded at presurgical and postsurgical intercuspal positions (VD1 and VD2, respectively); (3) reconstruction of a preliminary fusion model of VS and VD1 by an initial intermodality registration; (4) reconstruction of another preliminary fusion model of VS, VD1, and VD2 by a second intramodality registration; (5) repositioning of bony segments by a third intramodality registration and reconstruction of final fusion models at presurgery and postsurgery; and (6) 3D analysis of the movement of bony segments. To test this system, 2 patients with severe skeletal deformities, who had undergone presurgical orthodontic treatment, were used as models. Registration accuracy was determined by the root mean squared distance between the corresponding fiducial markers in a set of 2 images. RESULTS AND CONCLUSIONS: The sum of the root mean squared error of the 3 registration processes was less than 0.4 mm in both patients. This simulation system could be used to precisely realize the presurgical and postsurgical occlusal relationships and craniofacial morphology of a patient with severe skeletal deformities, and to quantitatively describe the movement of a given anatomical point of bony segments. It is assumed that there could be significant benefits in sharing visual and quantitative 3D information from this simulation system among orthodontists and surgeons.

Adult↗
PubMed2005

Enantioselective construction of quaternary carbon centers by catalytic [2 + 2 + 2] cycloaddition of 1,6-enynes and alkynes.

[reaction: see text] The enantioselective [2 + 2 + 2] cycloaddition of 1,6-enynes and alkynes using chiral rhodium catalysts gave cycloadducts containing quaternary carbon stereocenters. Both symmetrical and unsymmetrical alkynes and acetylene could be used as coupling partners, and the corresponding bicyclic cyclohexa-1,3-dienes were obtained in good to excellent ee.

Journal Article↗
PubMed2005

Adjuvant-induced macrophage-dominant nephrotoxic serum nephritis in rats.

BACKGROUND: To investigate cellular mechanisms responsible for the development of crescentic glomerular lesions, we have studied the effects of complete adjuvant (CA) on subnephritogenic nephrotoxic serum (NTS) nephritis (NTS-N) in Brown Norway rats. METHODS: A subnephritogenic dose of NTS, 0.02 ml per rat, was intravenously injected into rats that were previously (14 days earlier) treated intradermally with CA, incomplete adjuvant, or PBS. RESULTS: Proteinuria developed by day 2 only in CA-treated rats. Also, severe glomerular lesions associated with cellular crescent formation developed by day 2 only in the CA-treated rats. The glomerular extent of infiltration of IL-1beta-positive cells, MCP-1 expression level, and the number of ED1 and PCNA double-positive activated macrophages peaked on day 4 and decreased thereafter. The numbers of T lymphocytes and polymorphonuclear neutrophils did not significantly increase throughout the experiments. CONCLUSIONS: These results indicate that CA can potently induce crescentic NTS-N characterized by the infiltration of activated macrophages, which presumably bind to rabbit IgG on the glomerular basement membrane and may play a critical role in the development of severe NTS-N associated with crescent formation.

Animals↗
PubMed2005

Microscopic polyangiitis after silicone breast implantation.

We describe the case of a patient who developed microscopic polyangiitis (MPA) after silicone breast implantation. A 60-year-old woman who had undergone silicone breast implantation was admitted to our hospital with complaints of general malaise and hematoproteinuria. She was diagnosed as having MPA with evidence of acute progressive renal failure, pulmonary hemorrhage, and positivity for myeloperoxidase-antineutrophil cytoplasmic antibody (ANCA). A renal biopsy showed severe necrotizing and crescentic glomerulonephritis with arteriolitis. The patient received high-dose steroids and plasma exchange treatment, but died of progressive pulmonary hemorrhage and multiple cerebral hemorrhage. Silicone implantation is associated with scleroderma, systemic lupus erythematosus, and rheumatoid arthritis. This case report indicates the possibility of the development of MPA after silicone breast implantation.

Acute Kidney Injury↗
PubMed2005

Th2 cytokines increase and stimulate B cells to produce IgG4 in idiopathic membranous nephropathy.

BACKGROUND: The predominant deposition of IgG4 in idiopathic membranous nephropathy indicates that its presence characterizes the systemic immune response of the disease. METHODS: We analyzed the expressions of CD3, CD19, CD4, and CD8 on peripheral blood mononuclear cells (PBMCs) by flow cytometry, and the levels of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), interferon (IFN)-gamma, interleukin (IL)-4, IL-10, and IL-13 mRNAs in PBMCs using real-time reverse transcription-polymerase chain reaction (RT-PCR) in 14 patients with idiopathic membranous nephropathy and 14 normal control donors. The levels of IgG subclasses in the B-cell culture supernatant in the presence or absence of cytokines were quantified by enzyme-linked immunosorbent assay (ELISA). RESULTS: Idiopathic membranous nephropathy patients showed an increased CD4(+)/CD8(+) ratio, although the numbers of peripheral T and B cells were comparable to those of the normal control group. IL-10 and IL-13 mRNA expression levels increased in the idiopathic membranous nephropathy group. The levels of spontaneous production of each IgG subclass by B cells were identical in the two groups. In the presence of Th2 cytokines, B cells from several individuals of the idiopathic membranous nephropathy group augmented the production of IgG4. When the individual levels of each IgG subclass in the presence of cytokines were compared with those in the absence of cytokines in each sample, a significant increase in the production of IgG4 in the presence of IL-4 was observed in the idiopathic membranous nephropathy group. CONCLUSION: These results indicate that the altered functions of T cells to produce Th2 cytokines and the increased production of IgG4 by B cells in response to these cytokines characterize the immune response in idiopathic membranous nephropathy.

Aged↗
PubMed2005

[Case of paroxysmal nocturnal hemoglobinuria complicated with IgA nephropathy who developed acute renal failure induced by hemolytic crisis].

A 60-year-old man, who had been diagnosed as having paroxysmal nocturnal hemoglobinuria(PNH) in 1994, was admitted to our hospital with general fatigue, and dark urine after a common-cold in January 2001. In the peripheral blood, the red blood cell count was 136 x 10(4)/microl, hemoglobin 4.0 g/dl and hematocrit 12.4%. The serum creatinine level was 9.9 mg/dl. Kidney biopsy revealed focal and segmental proliferation of mesangial cells, mesangial matrix expansion, acute tubular necrosis, interstitial fibrosis and hemosiderine deposits in the tubular epithelial cells confirmed by Berlin-blue staining. Immunofluorescence microscopy showed IgA and C3 deposition in the mesangium. Electron microscopy revealed electron dense deposits in the mesangial area and heavy electron-dense hemosiderin pigments in proximal tubular epithelial cells. After the transfusion of six units of washed red blood cells and two sessions of hemodialysis, the renal function returned to the levels before admission.

Acute Kidney Injury↗
PubMed2005

[Focal segmental glomerulosclerosis in a patient with polycythemia vera].

Herein we describe the case of a patient with focal segmental glomerulosclerosis (FSGS) following polycythemia vera (PV) on whom hemodialysis was started 7 years later. A 66-year-old woman who had been treated for PV with hydroxyurea and phlebotomy for three years was referred to our hospital because of nephrotic syndrome. Renal biopsy performed at her local hospital revealed FSGS. Although she had received prednisolone at an initial dose of 45 mg/day, no significant improvement of proteinuria was achieved. The dose of prednisolone was tapered because the second renal biopsy revealed sclerosing glomerulopathy. We considered that FSGS was associated with PV because renal hemodynamic alterations in PV could result in FSGS as in any other secondary FSGS and there was no proteinuria at the initial detection of PV. On January 29, 1999, she developed massive proteinuria (9.6 g/day) and the findings of the third renal biopsy worsened in comparison with that of the first renal biopsy. Thereafter, hydroxyurea or ranimustine was used in treating PV at an outpatient clinic. However severe thrombocytosis was difficult to control, and progressive renal dysfunction finally necessitated hemodialysis on January 18, 2005. In conclusion, physicians should be aware of the risk of progressive renal failure in patients with FSGS following PV, particularly in patients with persistent thrombocytosis.

Aged↗
PubMed2004

Iridium complex-catalyzed highly enantio- and diastereoselective [2+2+2] cycloaddition for the synthesis of axially chiral teraryl compounds.

An asymmetric [2+2+2] cycloaddition of an alpha,omega-diyne, possessing ortho-substituted aryl groups on its terminus, and a monoalkyne with oxygen functionalities gave various axially chiral teraryl compounds. The coupling proceeded with extremely high enantio- (>99.5% ee) and diastereoselectivities (dl/meso = >95/5) when catalyzed by an iridium-chiral phosphine complex. As the products were readily transformed into diol compounds by deprotection without racemization, the present procedure provides access to a new chiral pool of diol compounds with C2 symmetry.

Journal Article↗
PubMed2004

[Gene expression changes of cartilage matrix of condylar cartilage with anterior disc displacement].

OBJECTIVE: To study the gene expression changes in extracellular matrix of condylar cartilage following disc anterior displacement of rabbit TMJ. METHODS: The right sides of 28 joints in 40 rabbits were subjected to surgical operation of disc displacement. The condylar Collagen II and Aggrecan mRNA expression were detected by in situ hybridization. RESULTS: Collagen II and Aggrecan mRNA mainly expressed in the lower zone of condylar chondrocyte. Aggrecan mRNA decreased faster than collagen II following disc displacement, and adjusted to normal later. CONCLUSION: Anterior disc displacement leads to alteration of extracellurar matrix gene expression in the condylar chondrocyte, which means the start of remodeling.

Aggrecans↗
PubMed2003

Functionalized arylzinc compounds in ethereal solvent: direct synthesis from aryl iodides and zinc powder and application to Pd-catalyzed reaction with allylic halides.

Arylzinc compounds, ArZnX, were conveniently prepared in high yields by the reaction of zinc powder with aryl iodides, which contain electron-withdrawing groups such as CO(2)CH(3), CN, Br, or CF(3) at the ortho-, meta- or para-position, or electron-donating groups such as CH(3), OCH(3), or H, at 70 degrees C in THF, at 100 degrees C, or at 130 degrees C in diglyme, respectively. Pd(dba)(2) exhibited an outstanding efficient catalytic effect for the cross-coupling of these ethereal solutions of ArZnX with allylic halides to afford a variety of functionalized allylbenzenes in high yields; the reactions were mostly carried out at 0 degrees C for 5-30 min in the presence of 5 mol % of catalyst. The conversion of the aryl iodides to allylbenzenes via two reactions could be accomplished in one pot.

Journal Article↗
PubMed2003

Type II collagen and aggrecan mRNA expression by in situ hybridization in rabbit temporomandibular joint posterior attachment following disc displacement.

Pathological changes and mRNA expression were studied in the posterior attachment of 40 adult Japanese white rabbits. The right temporomandibular joints of 28 rabbits were subjected to surgical disc displacement. Joints were studied by histochemistry and in situ hybridization. The collagen in the posterior attachment became dense, especially near the posterior band of the disc. Chondrocytes were found not only in the disc but also in the posterior attachment. Sometimes cartilage formation was seen. Type II collagen mRNA expression was first detected in the posterior attachment 4 days postoperatively and became progressively stronger with time. Aggrecan expression in the posterior attachment decreased at first, then increased gradually. It was concluded that, in the temporomandibular joint, chondrocytes appear in the posterior attachment as a result of biomechanical stimuli and the attachment becomes fibrocartilaginous following disc displacement.

Aggrecans↗