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Kentaro Takagi

Publications and source records attributed to Kentaro Takagi.

15 recordsLinked to original sources
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

Xanthogranulomatous pyelonephritis with a renocolic fistula caused by a parapelvic cyst.

Fistula formation between the upper urinary tract and bowel is an uncommon complication in urogenital diseases. We present a rare case of focal xanthogranulomatous pyelonephritis with a renocolic fistula. This is the first case where a parapelvic cyst obstructs the caliceal outflow and leads to the formation of a renocolic fistula in renal inflammatory disease. It is difficult to make a preoperative diagnosis of focal xanthogranulomatous pyelonephritis with widespread involvement that is caused by non-calculous urinary tract obstruction.

Colonic Diseases↗
PubMed2005

Effects of electroacupuncture stimulation applied to limb and back on mesenteric microvascular hemodynamics.

The effects of electroacupuncture stimulation (EAS) of the hind paw and the back on the mesenteric microhemodynamics in anesthetized rats were investigated using an intravital microscope system. Red blood cell (RBC) velocity in the mesenteric arterioles was measured by the dual-sensor method developed by the authors. Electrical stimulation was applied using two acupuncture needles inserted into the skin and the underlying muscles of the hind paw and the dorsal Th13-L1 level area. The hind-paw EAS evoked intensity-dependent pressor responses and increase responses in RBC velocity in mesenteric precapillary arterioles, while the back EAS evoked depressor responses and decrease responses in RBC velocity. Heart rate showed increase responses accompanying EAS either on the hind paw or the back. The pressor responses and increase responses in RBC velocity in mesenteric precapillary arterioles accompanying the hind paw EAS were abolished by an intravenous administration of alpha-adrenergic receptor antagonist (phenoxybenzamine; POB), and the tachycardiac responses were abolished by administration of beta-adrenergic receptor antagonist (propranolol). Occasional but notable reflex vasoconstrictions in the mesenteric terminal arteriole were induced by EAS either on the hind paw or the back. These vasoconstrictive responses were not affected by the administration of POB. The present study directly demonstrated that hemodynamic changes at the level of precapillary arterioles accompanying EAS either on the hind paw or the back mainly depend on the changes of systemic arterial pressure regardless of stimulus current intensities. Moreover, the results in the present study suggest some receptors other than alpha-adrenergic receptor might be involved in the mechanism of EAS-induced vasoconstriction in the mesenteric arteriole.

Acupuncture Points↗
PubMed2004

Overexpression of RhoA, Rac1, and Cdc42 GTPases is associated with progression in testicular cancer.

The Rho family of GTPases are involved in actin cytoskeleton organization and associated with carcinogenesis and progression of human cancers. We investigated the roles of Rho family GTPases, prototypes RhoA, Rac1, and Cdc42, and the major downstream targets of RhoA, ROCK-I, and ROCK-II in testicular cancer. We quantified protein expression in paired tumor and nontumor samples from surgical specimens from 57 consecutive patients with testicular germ cell tumors using Western blotting. Protein expression of RhoA, ROCK-I, ROCK-II, Rac1, and Cdc42 was significantly higher in tumor tissue than in nontumor tissue (P < 0.0001). Expression of protein for RhoA, ROCK-I, ROCK-II, Rac1, and Cdc42 was greater in tumors of higher stages than lower stages (P < 0.0001, P < 0.001, P < 0.001, P < 0.0001, P < 0.0001, respectively). Within stage II nonseminoma (31 patients), protein levels of RhoA, ROCK-I, ROCK-II, Rac1, and Cdc42 in the primary tumor were lower in the group of 24 patients with no evidence of disease after therapy compared with 7 patients with disease that was refractory/recurrent (P < 0.05). Rho family GTPases may be involved in the progression of testicular germ cell tumors.

Adolescent↗
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↗
PubMed2003

Digoxin up-regulates multidrug resistance transporter (MDR1) mRNA and simultaneously down-regulates steroid xenobiotic receptor mRNA.

A steroid xenobiotic receptor (SXR) is involved in the induction of MDR1/P-glycoprotein. MDR1 up-regulation by digoxin was previously demonstrated in human colon adenocarcinoma Caco-2 cells, but the participation of SXR remains unclear. Herein, the participation of SXR in MDR1 up-regulation was examined using reverse transcription-polymerase chain reaction in Caco-2 cells, and digoxin-tolerant cells (Caco/DX) as well as human colon carcinoma LS180 cells, which expressed SXR. MDR1 mRNA expression in Caco-2 or LS180 cells was increased by exposure to 1 microM digoxin for 24h, in a concentration-dependent manner, but SXR mRNA decreased concentration-dependently and was undetectable or significantly lower at 1 microM digoxin, indicating antithetical changes in MDR1 and SXR mRNA expression. Moreover, the MDR1 mRNA level was higher in Caco/DX cells than Caco-2 cells, whereas the SXR mRNA level was lower in Caco/DX cells. Consequently, digoxin was demonstrated to up-regulate MDR1 mRNA and simultaneously down-regulate SXR mRNA expression.

Adenocarcinoma↗
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

Lymphadenopathy of sinus histiocytosis mimicking metastatic bladder cancer: a case report.

A case of invasive bladder cancer accompanied with enlarged pelvic lymph nodes, which were interpreted as metastasis, is reported. The lymphadenopathy eventually regressed spontaneously while the bladder cancer increased in size. Total cystectomy and pelvic lymph node dissection were performed. Histopathological examination of the lymph nodes revealed dilation of the sinuses and marked increase in the number of histiocytes, which suggested sinus histiocytosis. Sinus histiocytosis is often associated with malignant tumor. It is considered as a sign of the host's immune activation with favorable prognostic significance. Nevertheless, such lymphadenopathy mimics a metastatic lymph node, making proper staging difficult.

Aged↗
PubMed2003

Significant association of Rho/ROCK pathway with invasion and metastasis of bladder cancer.

PURPOSE: The small GTP-binding protein Rho and its best-characterized downstream effector Rho-associated serine-threonine protein kinase, ROCK, participate in actin cytoskeleton organization, and are linked to pathogenesis and progression of several human tumors. We investigated the roles of Rho and ROCK in bladder cancer. EXPERIMENTAL DESIGN: Using Western blotting, we quantitated Rho and ROCK protein expression in paired tumor and nontumor surgical samples from 107 consecutive Japanese patients with bladder cancer. RESULTS: RhoA, RhoC, and ROCK were more abundant in tumors and metastatic lymph nodes than in nontumor bladder and uninvolved lymph nodes (P < 0.0001). Amounts of RhoA and RhoC protein, and ROCK protein expression correlated positively with one another (P < 0.0001). High RhoA, RhoC, and ROCK expression were related to poor tumor differentiation (P < 0.05, P < 0.01, and P < 0.01, respectively), muscle invasion (P < 0.001), and lymph node metastasis (P < 0.05). Kaplan-Meier plots linked high RhoA, RhoC, and ROCK protein expression to shortened disease-free and overall survival (P < 0.0001). By univariate analysis, high RhoA, RhoC, and ROCK protein expression predicted shortened disease-free and overall survival (P < 0.0001). By multivariate analysis, only RhoC was independently influenced in disease-free survival (P < 0.05), and RhoA and RhoC in overall survival (P < 0.001). In contrast, RhoB expression was inversely related to the grade and stage (P < 0.05), and its higher expression is associated with better overall survival (P < 0.05). In superficial tumors (Ta or T1; 63 patients), RhoA, RhoC, and ROCK were unrelated with recurrence-free survival. Overall survival in tumors invading muscle (T2 to T4; 44 patients) was significantly influenced by RhoA, RhoC, and ROCK in a Kaplan-Meier analysis (P < 0.0001, P < 0.0001, and P < 0.01, respectively). Whereas RhoA, RhoC, and ROCK independently predicted shortened overall survival in patients with invasive tumor by univariate analysis (P < 0.0001, P < 0.0001, and P < 0.01, respectively), only RhoC did so by multivariate analysis (P < 0.05). CONCLUSION: Rho/ROCK pathway apparently involved in occurrence and progression of bladder cancer may be valuable prognostic markers.

Actins↗
PubMed2002

Rhodium complex-catalyzed Pauson-Khand-type reaction with aldehydes as a CO source.

With aldehydes as a CO source under solvent-free conditions, rhodium complex efficiently catalyzed an intramolecular carbonylative alkene-alkyne coupling (Pauson-Khand-type reaction) and various bicyclic enones were obtained in high yield. Experiments under argon flow and a 13C-labeling experiment suggested that almost no free carbon monoxide was generated in this reaction. When noncationic rhodium complex with chiral phosphine was used as a chiral catalyst, the reaction proceeded enantioselectively to give various chiral cyclopentenones in up to 90% ee under solvent-free conditions.

Journal Article↗
PubMed2002

MEG responses during rhythmic finger tapping in humans to phasic stimulation and their interpretation based on neural mechanisms.

The phase-resetting experiment was applied to human periodic finger tapping to understand how its rhythm is controlled by the internal neural clock that is assumed to exist. In the experiment, the right periodic tapping movement was disturbed transiently by a series of left finger taps in response to impulsive auditory cues presented randomly at various phases within the tapping cycle. After each left finger tap, the original periodic tapping was reestablished within several tapping cycles. Influences of the disturbance on the periodic right finger tapping varied depending on the phase of the periodic right finger tapping at which each left finger tap was made. It was confirmed that the periodic tapping was disturbed not by the auditory cues but by the left finger taps. Based on this fact, in this paper each single left tap was considered as the stimulus, and the phase of the periodic tapping of the right index finger when the left tap was executed as the phase of the stimulus. Responses of the neural activities (magnetoencephalography, MEG), the tapping movement, and the corresponding muscle activities (electromyography) were simultaneously measured. Phase-resetting curves (PRCs) representing the degree of phase reset as a function of the phase of the stimulus were obtained both for the left sensorimotor cortex MEG response and for the right index finger tapping response. The shapes of both PRCs were similar, suggesting that the phase reset of the left sensorimotor cortex activities and that of the finger tapping rhythm were the same. Four out of eight subjects showed type-0 reset in Winfree's definition, and the others showed type-1 reset. For general limit-cycle oscillators, type-0 reset is obtained for relatively strong perturbations and type 1 for weak perturbations. It was shown that the transient response of MEG to the single left tap stimuli in type-0 subjects, where the phase was progressively reset, were different from those in type-1 subjects. Based on detailed analysis of the differences, a neural network model for the phase reset of the tapping rhythm is proposed.

Acoustic Stimulation↗
PubMed2002

[Bladder cancer producing granulocyte colony-stimulating factor (G-CSF): a case report].

A case of bladder cancer producing granulocyte colony-stimulating factor (G-CSF) is reported. A 76-year-old male was admitted to our hospital with gross hematuria and leukocytosis. He was diagnosed with advanced bladder cancer. His white blood cell (WBC) count and serum granulocyte colony-stimulating factor (G-CSF) level were elevated (peak WBC 22,010/microliter, peak G-CSF 351 pg/ml), which immediately normalized after cystectomy. The histopathological diagnosis was transitional cell carcinoma, grade 3, pT4, pN1. Immunohistochemical examination was positive for G-CSF and G-CSF receptor. There has been no recurrence of cancer for more than 23 months since the operation without any additional therapy.

Aged↗