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Articles by M Miura
Total Records ( 6 ) for M Miura
  M Miura , N Takahashi , M Nara , N Fujishima , H Kagaya , Y Kameoka , H Saitoh , H Tagawa and K. Sawada
  Background

A steady-state trough plasma itraconazole concentration greater than 500 ng/mL is a therapeutic target for itraconazole. A simple, rapid and sensitive high-performance liquid chromatography-based method was developed for quantitation of itraconazole and hydroxyitraconazole in human plasma.

Methods

Itraconazole and hydroxyitraconazole were separated using a mobile phase of 0.5% KH2PO4 (pH 6.0)-acetonitrile (30:70, v/v) on a CAPCELLPAK C18 MGII column at a flow rate of 0.5 mL/min and ultraviolet absorbance at 260 nm.

Results

The analysis required 200 µL of plasma and involved a rapid, simple solid-phase extraction with an Oasis HLB cartridge, which resulted in recoveries of 87–92% for itraconazole and 91–94% for hydroxyitraconazole. The lower limit of quantification for itraconazole and hydroxyitraconazole was 5 ng/mL each. Intra- and interday coefficients of variation for itraconazole and hydroxyitraconazole were less than 11.3% and 12.2%, respectively, and accuracies were within 11.7% and 4.5% over the linear range, respectively. Although the steady-state plasma concentrations of itraconazole and hydroxyitraconazole ranged from 506 to 2482 ng/mL and from 766 to 2444 ng/mL, respectively, after a two-day loading dose of 400 mg/day intravenous itraconazole followed by the administration of 200 mg/day itraconazole oral solution, calibration curves of itraconazole and hydroxyitraconazole showed positive linearity in a concentration range of 5–2500 and 50–2500 ng/mL, respectively.

Conclusions

Our results indicate that this method is applicable for the monitoring of plasma levels of itraconazole and hydroxyitraconazole in a clinical setting. Furthermore, the regimen presented here might also be effective in preventing infection, but further studies with large sample sizes are necessary to investigate this avenue.

  H Ihara , T Watanabe , N Hashizume , M Totani , K Kamioka , K Onda , S Sunahara , T Suzuki , M Itabashi , Y Aoki , M Ishibashi , S Ito , K Ohashi , T Enomoto , K Saito , K Saeki , Y Nagamura , T Nobori , K Hirota , K Fujishiro , M Maekawa , M Miura and Y. Ohta
  Background

The aim of the present study was to evaluate standard reference material (SRM) 1955 commutability as a reference material for serum folate using automated methods. We also designed so as to reduce the intermethod variability present in different automated methods.

Methods

Using a microbiological assay related to the ‘information value’ of SRM 1955 as a comparison method, we investigated the possibility of standardization for the assay values of serum folate as measured by the automated methods (Access, Centaur and Elecsys). In the assay of 50 patient sera by these automated methods, we corrected observed values by the SRM 1955 and compared with comparison values.

Results

The observed values of SRM 1955 Levels I, II and III were within or outside (but near) a 95% prediction interval obtained from patient sera by the automated methods. The normalized residuals obtained from SRM 1955 were within ±3.0 (in SD units), which enabled us to conclude that the SRM 1955 had a physicochemical characterization similar to native serum. Twelve patients were assessed as hypofolataemia (<6.0 ng/mL) and 38 patients as normal (≥6.0 ng/mL). Before correction, folate levels in six of 12 patients were lower than 6.0 ng/mL, and those in seven of 38 patients were higher than 6.0 ng/mL with the automated methods. After correction, low levels were found in four of 12 patients, and normal levels were found in 33 of 38 patients.

Conclusions

The use of SRM 1955 would help to reduce the intermethod variability present in different automated methods for serum folate measurement.

  A Yasoda , H Kitamura , T Fujii , E Kondo , N Murao , M Miura , N Kanamoto , Y Komatsu , H Arai and K. Nakao
 

Skeletal dysplasias are a group of genetic disorders characterized by severe impairment of bone growth. Various forms of them add to produce a significant morbidity and mortality, yet no efficient drug therapy has been developed to date. We previously demonstrated that C-type natriuretic peptide (CNP), a member of the natriuretic peptide family, is a potent stimulator of endochondral bone growth. Furthermore, we exhibited that targeted overexpression of a CNP transgene in the growth plate rescued the impaired bone growth observed in a mouse model of achondroplasia (Ach), the most frequent form of human skeletal dysplasias, leading us to propose that CNP may prove to be an effective treatment for this disorder. In the present study, to elucidate whether or not the systemic administration of CNP is a novel drug therapy for skeletal dysplasias, we have investigated the effects of plasma CNP on impaired bone growth in Ach mice that specifically overexpress CNP in the liver under the control of human serum amyloid P component promoter or in those treated with a continuous CNP infusion system. Our results demonstrated that increased plasma CNP from the liver or by iv administration of synthetic CNP-22 rescued the impaired bone growth phenotype of Ach mice without significant adverse effects. These results indicate that treatment with systemic CNP is a potential therapeutic strategy for skeletal dysplasias, including Ach, in humans.

  Y Mezaki , N Yamaguchi , K Yoshikawa , M Miura , K Imai , H Itoh and H. Senoo
 

Hepatic stellate cells (HSCs) are the major site of retinoid storage, and their activation is a key process in liver fibrogenesis. We have previously shown that expression of the retinoic acid receptor alpha (RAR) is upregulated in activated rat HSCs at a posttranscriptional level and that these RAR proteins showed a speckled distribution in the cytosol, despite their possession of a nuclear localization signal (NLS). In this report, we further characterize these cytosolic RAR proteins by using exogenously expressed RAR protein fragments or mutants tagged with a green fluorescent protein. Substitution of four amino acids, 161–164 from lysine to alanine, abolished the NLS. Exogenously expressed RAR protein fragments containing an NLS were localized exclusively in the nuclei of activated rat HSCs and never colocalized with the endogenous RAR proteins in the cytosol, suggesting that the NLS of endogenous RAR proteins is masked. Biochemical analysis showed that 65% of RAR proteins in activated HSCs were insoluble in a mixture of detergents. The insolubility of RAR proteins makes it difficult to identify RAR proteins in activated HSCs. Therefore, we propose that insoluble, speckled cytosolic distribution of RAR proteins represents a new marker of HSC activation. (J Histochem Cytochem 57:687–699, 2009)

  H Ageta , S Ikegami , M Miura , M Masuda , R Migishima , T Hino , N Takashima , A Murayama , H Sugino , M Setou , S Kida , M Yokoyama , Y Hasegawa , K Tsuchida , T Aosaki and K. Inokuchi
 

A recent study has revealed that fear memory may be vulnerable following retrieval, and is then reconsolidated in a protein synthesis-dependent manner. However, little is known about the molecular mechanisms of these processes. Activin βA, a member of the TGF-β superfamily, is increased in activated neuronal circuits and regulates dendritic spine morphology. To clarify the role of activin in the synaptic plasticity of the adult brain, we examined the effect of inhibiting or enhancing activin function on hippocampal long-term potentiation (LTP). We found that follistatin, a specific inhibitor of activin, blocked the maintenance of late LTP (L-LTP) in the hippocampus. In contrast, administration of activin facilitated the maintenance of early LTP (E-LTP). We generated forebrain-specific activin- or follistatin-transgenic mice in which transgene expression is under the control of the Tet-OFF system. Maintenance of hippocampal L-LTP was blocked in the follistatin-transgenic mice. In the contextual fear-conditioning test, we found that follistatin blocked the formation of long-term memory (LTM) without affecting short-term memory (STM). Furthermore, consolidated memory was selectively weakened by the expression of follistatin during retrieval, but not during the maintenance phase. On the other hand, the maintenance of memory was also influenced by activin overexpression during the retrieval phase. Thus, the level of activin in the brain during the retrieval phase plays a key role in the maintenance of long-term memory.

  N Nakanishi , M. M Rahman , Y Sakamoto , M Miura , F Takeuchi , S. Y Park and M. Tsubaki
 

Cytochromes b561 constitute a novel class of proteins in eukaryotic cells with a number of highly relevant common features including six transmembrane -helices and two haem groups. Of particular interest is the presence of a large number of plant homologues having putative ascorbate- and monodehydroascorbate radical-binding sites. We conducted a diethylpyrocarbonate-modification study employing Zea mays cytochrome b561 heterologously expressed in Pichia pastoris cells. Pre-treatment of cytochrome b561 with diethylpyrocarbonate in oxidized form caused N-carbethoxylation of His86, His159 and Lys83, leading to a drastic inhibition of the electron transfer from ascorbate. The activity was protected by the inclusion of ascorbate during the treatment. However, midpoint potentials of two haem centres did show only slight decreases upon the treatment, suggesting that changes in the midpoint potentials were not the major cause of the inhibition. Present results indicated that Zea mays cytochrome b561 conducted an ascorbate-specific transmembrane electron transfer by utilizing a concerted H+/e transfer mechanism and that the specific N-carbethoxylation of haem axial His86 that would inhibit the removal of a proton from the bound ascorbate was a major cause of the inhibition. On the other hand, Lys83 might be important for an initial step(s) of the fast electron acceptance from ascorbate.

 
 
 
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