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847 results on '"YAMAGUCHI, Hiroaki"'

202. Quantitative determination of paclitaxel and its metabolites, 6α‐hydroxypaclitaxel and p‐3′‐hydroxypaclitaxel, in human plasma using column‐switching liquid chromatography/tandem mass spectrometry

Author

Yamaguchi, Hiroaki, primary, Fujikawa, Asuka, additional, Ito, Hajime, additional, Tanaka, Nobuaki, additional, Furugen, Ayako, additional, Miyamori, Kazuaki, additional, Takahashi, Natsuko, additional, Ogura, Jiro, additional, Kobayashi, Masaki, additional, Yamada, Takehiro, additional, Mano, Nariyasu, additional, and Iseki, Ken, additional

Published
2012
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205. Simultaneous quantitation of sphingoid bases and their phosphates in biological samples by liquid chromatography/electrospray ionization tandem mass spectrometry

Author

Saigusa, Daisuke, primary, Shiba, Kanako, additional, Inoue, Asuka, additional, Hama, Kotaro, additional, Okutani, Michiyo, additional, Iida, Nagisa, additional, Saito, Masayoshi, additional, Suzuki, Kaori, additional, Kaneko, Tohru, additional, Suzuki, Naoto, additional, Yamaguchi, Hiroaki, additional, Mano, Nariyasu, additional, Goto, Junichi, additional, Hishinuma, Takanori, additional, Aoki, Junken, additional, and Tomioka, Yoshihisa, additional

Published
2012
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206. Intestinal Ischemia-Reperfusion Increases Efflux for Uric Acid Via Paracellular Route in the Intestine, but Decreases that Via Transcellular Route Mediated by BCRP

Author

Ogura, Jiro, primary, Kuwayama, Kaori, additional, Takaya, Atsushi, additional, Terada, Yusuke, additional, Tsujimoto, Takashi, additional, Koizumi, Takahiro, additional, Maruyama, Hajime, additional, Fujikawa, Asuka, additional, Takahashi, Natsuko, additional, Kobayashi, Masaki, additional, Itagaki, Shirou, additional, Hirano, Takeshi, additional, Yamaguchi, Hiroaki, additional, and Iseki, Ken, additional

Published
2012
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210. The Effectiveness of Antidiabetic Drugs in Treating Dementia: A Peek into Pharmacological and Pharmacokinetic Properties.

Author

Ogura, Jiro and Yamaguchi, Hiroaki

Subjects
*DRUG efficacy, *PHARMACOKINETICS, *DEMENTIA, *THERAPEUTICS, *DRUG repositioning, *PERIPHERAL circulation
Abstract

Dementia dramatically affects the activities of daily living and quality of life; thus, many therapeutic approaches for overcoming dementia have been developed. However, an effective treatment regimen is yet to be developed. As diabetes is a well-known risk factor for dementia, drug repositioning and repurposing of antidiabetic drugs are expected to be effective dementia treatments. Several observational studies have been useful for understanding the effectiveness of antidiabetic drugs in treating dementia, but it is difficult to conclusively analyze the association between antidiabetic drug treatment and the risk of developing dementia after correcting for potential confounding factors. Mechanism-based approaches may provide a better understanding of the effectiveness of antidiabetic drugs for treating dementia. Since the peripheral circulation and the central nerve system are separated by the blood–brain barrier, it is important to understand the regulation of the central glucose metabolism. In this review, we discuss the pharmacological and pharmacokinetic properties of antidiabetic drugs in relation to treating dementia. [ABSTRACT FROM AUTHOR]

Published
2022
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211. Functional characterization of 9 CYP2A13 allelic variants by assessment of nicotine C-oxidation and coumarin 7-hydroxylation

Author

Kumondai, Masaki, Hosono, Hiroki, Maekawa, Masamitsu, Yamaguchi, Hiroaki, Mano, Nariyasu, Oda, Akifumi, Hirasawa, Noriyasu, and Hiratsuka, Masahiro

Abstract

Cytochrome P450 2A13 (CYP2A13) is responsible for the metabolism of chemical compounds such as nicotine, coumarin, and tobacco-specific nitrosamine. Several of these compounds have been recognized as procarcinogens activated by CYP2A13. We recently showed that CYP2A13*2contributes to inter-individual variations observed in bladder cancer susceptibility because CYP2A13*2might cause a decrease in enzymatic activity. Other CYP2A13 allelic variants may also affect cancer susceptibility. In this study, we performed an in vitroanalysis of the wild-type enzyme (CYP2A13.1) and 8 CYP2A13 allelic variants, using nicotine and coumarin as representative CYP2A13 substrates. These CYP2A13 variant proteins were heterologously expressed in 293FT cells, and the kinetic parameters of nicotine C-oxidation and coumarin 7-hydroxylation were estimated. The quantities of CYP2A13 holoenzymes in microsomal fractions extracted from 293FT cells were determined by measuring reduced carbon monoxide-difference spectra. The kinetic parameters for CYP2A13.3, CYP2A13.4, and CYP2A13.10 could not be determined because of low metabolite concentrations. Five other CYP2A13 variants (CYP2A13.2, CYP2A13.5, CYP2A13.6, CYP2A13.8, and CYP2A13.9) showed markedly reduced enzymatic activity toward both substrates. These findings provide insights into the mechanism underlying inter-individual differences observed in genotoxicity and cancer susceptibility.

Published
2018
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212. Functional Characterization of 21 Allelic Variants of Dihydropyrimidine Dehydrogenase Identified in 1070 Japanese Individuals

Author

Hishinuma, Eiji, Narita, Yoko, Saito, Sakae, Maekawa, Masamitsu, Akai, Fumika, Nakanishi, Yuya, Yasuda, Jun, Nagasaki, Masao, Yamamoto, Masayuki, Yamaguchi, Hiroaki, Mano, Nariyasu, Hirasawa, Noriyasu, and Hiratsuka, Masahiro

Abstract

Dihydropyrimidine dehydrogenase (DPD, EC 1.3.1.2), encoded by the DPYDgene, is the rate-limiting enzyme in the degradation pathway of endogenous pyrimidine and fluoropyrimidine drugs such as 5-fluorouracil (5-FU). DPD catalyzes the reduction of uracil, thymine, and 5-FU. In Caucasians, DPYDmutations, including DPYD*2A, DPYD*13, c.2846A>T, and c.1129-5923C>G/hapB3, are known to contribute to interindividual variations in the toxicity of 5-FU; however, none of these DPYDpolymorphisms has been identified in the Asian population. Recently, 21 DPYDallelic variants, including some novel single-nucleotide variants (SNVs), were identified in 1070 healthy Japanese individuals by analyzing their whole-genome sequences (WGSs), but the functional alterations caused by these variants remain unknown. In this study, in vitro analysis was performed on 22 DPD allelic variants by transiently expressing wild-type DPD and 21 DPD variants in 293FT cells and characterizing their enzymatic activities using 5-FU as a substrate. DPD expression levels and dimeric forms were determined using immunoblotting and blue-native PAGE, respectively. Additionally, the values of three kinetic parameters—the Michaelis constant (Km), maximum velocity (Vmax), and intrinsic clearance (CLint= Vmax/Km)—were determined for the reduction of 5-FU. Eleven variants exhibited significantly decreased intrinsic clearance compared with wild-type DPD. Moreover, the band patterns observed in the immunoblots of blue-native gels indicated that DPD dimerization is required for enzymatic activity in DPD. Thus, the detection of rare DPYDvariants might facilitate severe adverse effect prediction of 5-FU–based chemotherapy in the Japanese population.

Published
2018
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214. Potential Drug Interactions Mediated by Renal Organic Anion Transporter OATP4C1▪

Author

Sato, Toshihiro, Mishima, Eikan, Mano, Nariyasu, Abe, Takaaki, and Yamaguchi, Hiroaki

Abstract

Organic anion-transporting polypeptide 4C1 (OATP4C1) is an organic anion transporter expressed in the basolateral membrane of the renal proximal tubules. It plays a major role in the urinary excretion of both exogenous drugs and endogenous compounds. Our previous studies have indicated the importance of OATP4C1 in pathologic and physiologic conditions; however, the majority of its pharmacologic characteristics remained unclear. Therefore, to provide essential information for clinical drug therapy decisions and drug development, we clarified drug interactions mediated by OATP4C1. To elucidate potential drug interactions via OATP4C1, we screened 53 representative drugs commonly used in clinical settings. Next, we evaluated the IC50values of drugs that inhibited OATP4C1 by more than 50%. To apply our results to clinical settings, we calculated the drug-drug interaction (DDI) indices. The screening analysis using an OATP4C1-expressing cell system demonstrated that 22 out of 53 therapeutic drugs inhibited OATP4C1-mediated triiodothyronine transport. In particular, OATP4C1-mediated transport was strongly inhibited by 10 drugs. The IC50values of 10 drugs—nicardipine, spironolactone, fluvastatin, crizotinib, levofloxacin, clarithromycin, ritonavir, saquinavir, quinidine, and verapamil—obtained in this study were 51, 53, 41, 24, 420, 200, 8.5, 4.3, 100, and 110 µM, respectively. The IC50values of these drugs were higher than the plasma concentrations obtained in clinical practice. However, ritonavir showed the highest DDI index (1.9) for OATP4C1, suggesting that it may strongly influence this transporter and thus cause drug interactions seen in clinical settings. Our finding gives new insight into the role of OATP4C1 in clinical DDIs.

Published
2017
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215. Acoustic properties for Ga–Sn–Zn liquid metal coupler with low melting point and high acoustic impedance

Author

Ohashi, Yuji, Murakami, Rikito, Yamaguchi, Hiroaki, Yokota, Yuui, and Yoshikawa, Akira

Abstract

Acoustic properties of Ga–Sn–Zn (GSZ) liquid alloy coupler with high acoustic impedance were investigated to evaluate materials with high acoustic impedance. GSZ liquid alloy was prepared and its longitudinal wave velocity and attenuation coefficient were measured using the plane-wave ultrasonic material characterization system. Density of the GSZ liquid alloy was also measured by a constant volume expansion method. The acoustic impedance of the GSZ was 12 times higher than that of the water. Attenuation coefficient of GSZ is much smaller than that of water, exhibiting 7.6 dB mm−1for water and 0.5 dB mm−1for GSZ at 200 MHz. Considering the reflection and transmission coefficients at each medium boundary calculated from the experimentally obtained acoustic impedance, it was suggested that the amplitude of the reflected wave from the back surface of the Ir sample can be made about 30 times larger with the GSZ coupler than with the water coupler.

Published
2023
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216. Quantification of intracellular and extracellular prostanoids stimulated by A23187 by liquid chromatography/electrospray ionization tandem mass spectrometry

Author

Furugen, Ayako, primary, Yamaguchi, Hiroaki, additional, Tanaka, Nobuaki, additional, Ito, Hajime, additional, Miyamori, Kazuaki, additional, Fujikawa, Asuka, additional, Takahashi, Natsuko, additional, Ogura, Jiro, additional, Kobayashi, Masaki, additional, Yamada, Takehiro, additional, Mano, Nariyasu, additional, and Iseki, Ken, additional

Published
2011
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230. SLCO4C1 Transporter Eliminates Uremic Toxins and Attenuates Hypertension and Renal Inflammation

Author

Toyohara, Takafumi, primary, Suzuki, Takehiro, additional, Morimoto, Ryo, additional, Akiyama, Yasutoshi, additional, Souma, Tomokazu, additional, Shiwaku, Hiromi O., additional, Takeuchi, Yoichi, additional, Mishima, Eikan, additional, Abe, Michiaki, additional, Tanemoto, Masayuki, additional, Masuda, Satohiro, additional, Kawano, Hiroaki, additional, Maemura, Koji, additional, Nakayama, Masaaki, additional, Sato, Hiroshi, additional, Mikkaichi, Tsuyoshi, additional, Yamaguchi, Hiroaki, additional, Fukui, Shigefumi, additional, Fukumoto, Yoshihiro, additional, Shimokawa, Hiroaki, additional, Inui, Ken-ichi, additional, Terasaki, Tetsuya, additional, Goto, Junichi, additional, Ito, Sadayoshi, additional, Hishinuma, Takanori, additional, Rubera, Isabelle, additional, Tauc, Michel, additional, Fujii-Kuriyama, Yoshiaki, additional, Yabuuchi, Hikaru, additional, Moriyama, Yoshinori, additional, Soga, Tomoyoshi, additional, and Abe, Takaaki, additional

Published
2009
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241. Simultaneous quantification of seven prostanoids using liquid chromatography/tandem mass spectrometry: The effects of arachidonic acid on prostanoid production in mouse bone marrow-derived mast cells

Author

Hishinuma, Takanori, primary, Suzuki, Kaori, additional, Saito, Masayoshi, additional, Yamaguchi, Hiroaki, additional, Suzuki, Naoto, additional, Tomioka, Yoshihisa, additional, Kaneko, Izumi, additional, Ono, Masao, additional, and Goto, Junichi, additional

Published
2007
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244. Catheter ablation for paroxysmal atrial fibrillation concomitant with Brugada syndrome

Author

Komiyama, Kota, primary, Mizusawa, Yuka, additional, Yuba, Takao, additional, Kujime, Shingo, additional, Tatsumoto, Akiko, additional, Tanabe, Yasuhiro, additional, Fukamizu, Seiji, additional, Yamaguchi, Hiroaki, additional, Okazaki, Hidetaka, additional, Tejima, Tamotsu, additional, Sakurada, Harumizu, additional, Nishizaki, Mitsuhiro, additional, and Hiraoka, Masayasu, additional

Published
2007
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245. Japanese Journal of Electrocardiology

Author

Tatsumoto, Akiko, primary, Sakurada, Harumizu, additional, Komiyama, Kota, additional, Okazaki, Hidetaka, additional, Yuba, Takao, additional, Tanii, Hironobu, additional, Koizumi, Akiko, additional, Tanabe, Yasuhiro, additional, Fukamizu, Seiji, additional, Yamaguchi, Hiroaki, additional, Tejima, Tamotsu, additional, Nishizaki, Mitsuhiro, additional, and Hiraoka, Masayasu, additional

Published
2007
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246. Simultaneous quantification of leukotrienes and hydroxyeicosatetraenoic acids in cell culture medium using liquid chromatography/tandem mass spectrometry.

Author

Furugen, Ayako, Yamaguchi, Hiroaki, and Mano, Nariyasu

Abstract

Leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs) are important bioactive lipid mediators that participate in various pathophysiological processes. To advance understanding of the mechanisms that regulate these mediators in physiological and pathological processes, an analytical method using liquid chromatography/tandem mass spectrometry for the simultaneous quantification of LTB4, LTC4, LTD4, LTE4, 5-HETE, 8-HETE, 12-HETE and 15-HETE in cell culture media was developed. A Supel™-Select HLB solid-phase extraction cartridge was used for sample preparation. The compounds were separated on a C18 column using gradient elution with acetonitrile-water-formic acid (20:80:0.1, v/v/v) and acetonitrile-formic acid (100:0.1, v/v). The calibration curves of LTB4, LTD4, LTE4 and HETEs were linear in the range of 0.025-10 ng/mL, and the calibration curve of LTC4 was linear in the range of 0.25-10 ng/mL. Validation assessment showed that the method was highly reliable with good accuracy and precision. The stability of LTs and HETEs was also investigated. Using the developed method, we measured LTs and HETEs in the culture supernatant of the human mast cell line HMC-1. The present method could facilitate investigations of the mechanisms that regulate the production, release and signaling of LTs and HETEs. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2015
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247. cGMP transport by vesicles from human and mouse erythrocytes

Author

de Wolf, Cornelia J. F., primary, Yamaguchi, Hiroaki, additional, van der Heijden, Ingrid, additional, Wielinga, Peter R., additional, Hundscheid, Stefanie L., additional, Ono, Nobuhito, additional, Scheffer, George L., additional, de Haas, Marcel, additional, Schuetz, John D., additional, Wijnholds, Jan, additional, and Borst, Piet, additional

Published
2006
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248. Transport of fluorescent chenodeoxycholic acid via the human organic anion transporters OATP1B1 and OATP1B3

Author

Yamaguchi, Hiroaki, primary, Okada, Masahiro, additional, Akitaya, Shou, additional, Ohara, Hiroshi, additional, Mikkaichi, Tsuyoshi, additional, Ishikawa, Haruna, additional, Sato, Mayumi, additional, Matsuura, Masaki, additional, Saga, Toshihide, additional, Unno, Michiaki, additional, Abe, Takaaki, additional, Mano, Nariyasu, additional, Hishinuma, Takanori, additional, and Goto, Junichi, additional

Published
2006
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250. Utility of gallium-67 scintigraphy for evaluation of cardiac sarcoidosis with ventricular tachycardia

Author

Futamatsu, Hideki, primary, Suzuki, Jun-ichi, additional, Adachi, Susumu, additional, Okada, Hiroyuki, additional, Otomo, Kenichiro, additional, Ohara, Takahiro, additional, Hashimoto, Yuji, additional, Kakuta, Tsunekazu, additional, Iesaka, Yoshito, additional, Yamaguchi, Hiroaki, additional, Sakurada, Harumizu, additional, Sato, Akira, additional, Obayashi, Tohru, additional, Niwa, Akihiro, additional, Hirao, Kenzo, additional, and Isobe, Mitsuaki, additional

Published
2006
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