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Akinori Yamauchi

Publications and source records attributed to Akinori Yamauchi.

10 recordsLinked to original sources
PubMed2006

Studies on neurosteroids XVIII LC-MS analysis of changes in rat brain and serum testosterone levels induced by immobilization stress and ethanol administration.

The liquid chromatography-mass spectrometry (LC-MS) methods were developed and validated for the determination of testosterone (T) in the brain and serum of rats and of 5alpha-androstane-3alpha,17beta-diol (ADIOL), a metabolite of T, in the brain of rats. After derivatization of T with 2-hydrazino-1-methylpyridine and of ADIOL with p-nitrobenzoyl chloride, the detection sensitivities of T and ADIOL using LC-MS were increased 70- and 400-times superior to those of intact T and intact ADIOL, respectively. Those LC-MS methods are specific and reliable for the analysis of trace amounts of T and ADIOL in small amounts of samples. The animal studies using the developed methods showed that the brain and serum levels of T and the brain levels of ADIOL were not changed by stress or ethanol administration but the concentration ratio of the brain T to serum T in the stressed rats was higher than that in untreated rats. The low levels of endogenous AIDOL in brain of stressed and unrestrained rats found in this study demonstrated that the contribution to anesthetic and anxiolytic effects of ADIOL via gamma-aminobutyric acid type A receptors may be negligible.

Androstane-3,17-diol↗
PubMed2005

Determination of prostatic androgens in 10 mg of tissue using liquid chromatography-tandem mass spectrometry with charged derivatization.

A practical liquid chromatography-tandem mass spectrometric (LC-MS-MS) method for the determination of prostatic 5alpha-dihydrotestosterone (DHT) and testosterone (T) has been developed. The prostatic androgens were extracted with MeOH-H2O (3:7, v/v), purified with an Oasis HLB cartridge, derivatized with the permanently charged reagent 2-hydrazino-1-methylpyridine (HMP), and subjected to LC-MS-MS analysis using electrospray ionization (ESI) operated in the positive ion mode. The derivatization with HMP was very effective at increasing the detectability using the positive-ESI-MS. The method allowed the reproducible and accurate quantification of ng g(-1) tissue levels of prostatic androgens in 10 mg of tissue. That is, the intra- and inter-assay coefficients of variation were below 8.1 and 9.3%, respectively, and the analytical recoveries of the androgens were quantitative. The limits of quantitation for DHT and T were both 1.0 ng g(-1) tissue. The developed method was used to determine DHT and T in the prostates of patients with benign prostatic hyperplasia and prostate cancer, and satisfactory results were obtained.

Chromatography, Liquid↗
PubMed2004

2-hydrazino-1-methylpyridine: a highly sensitive derivatization reagent for oxosteroids in liquid chromatography-electrospray ionization-mass spectrometry.

A derivatization reagent, 2-hydrazino-1-methylpyridine, was developed for the liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) of oxosteroids. The reagent quantitatively reacted with oxosteroids at 60 degrees C within 1h and the resulting derivatives of the mono-oxosteroids provided a 70-1600-fold higher sensitivity compared to intact steroids. However, HMP was unsuitable for di-oxosteroids, such as androstenedione and progesterone. The developed derivatization procedure was applied to the LC-ESI-MS analysis of 5alpha-dihydrotestosterone in human prostate, and allowed the reproducible quantification of nanogram/gram level of the androgen with a 10-mg sample.

Androgens↗
PubMed2003

Application of 4-(4-nitrophenyl)-1,2,4-triazoline-3,5-dione to analysis of 25-hydroxyvitamin D3 in human plasma by liquid chromatography/electron capture atmospheric pressure chemical ionization-mass spectrometry.

The utility of 4-(4-nitrophenyl)-1,2,4-triazoline-3,5-dione (NPTAD) as a derivatization reagent in the analysis of 25-hydroxyvitamin D3 [25(OH)D3] using liquid chromatography/electron capture atmospheric pressure chemical ionization-mass spectrometry (LC/ECAPCI-MS) was examined. The derivatives of 25(OH)D3 with NPTAD underwent electron capture in the APCI source in the negative-ion mode and provided 30-fold higher sensitivity compared to an intact compound. This derivatization-LC/ECAPCI-MS method was applied to a plasma 25-hydroxyvitamin D3 assay, and gave satisfactory results in sensitivity, specificity, measurable range and throughput of the analysis.

Calcifediol↗
PubMed2002

Electron-capturing derivatization of neutral steroids for increasing sensitivity in liquid chromatography/negative atmospheric pressure chemical ionization-mass spectrometry.

Derivatization of neutral steroids for increasing sensitivity in liquid chromatography/negative atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) has been examined. Under APCI conditions, gas-phase electrons are provided by the corona discharge and captured by electron-affinitive compounds. In negative APCI-MS, therefore, ultrahigh sensitivity can be obtained by tagging neutral steroids, whose ionization efficiencies are low in the conventional APCI-MS, with electron-capturing moieties, such as a nitro group. We synthesized various boronic acid and hydrazine derivatives having electron-capturing moieties as derivatization reagents for 1,2-diol compounds and oxosteroids, respectively. Among reagents examined, those having the 2-nitro-4-trifluoromethylphenyl moiety were most effective in increasing sensitivity. That is, the detection responses of the derivatives with these reagents were increased by several to more than 200-fold over intact steroids, where limits of detection were some picograms. The developed derivatization procedures were applied to analyses of small amounts of steroids in human plasma and gave satisfactory results.

Boronic Acids↗
PubMed2002

[Contamination of oyster sea farm with the Norwalk virus: mechanisms and control].

The Norwalk virus(NV) is widely known as a cause of nonbacterial food poisoning, infant diarrhea, and acute gastroenteritis in the winter months between November and March. While it is strongly suspected that NV that is excreted by humans flows into coastal seawaters via rivers and wastewater treatment facilities to contaminate oysters that are grown in farms in the area, light has yet to be shed on the behavior of this virus in the natural environment. We therefore conducted a polymerase chain reaction (PCR) survey of NV levels in the aquatic environment of the oyster bed area of the Shima region in Mie Prefecture, whereupon the NV was detected in marine sediment, oysters, and mule clams even during the summer months, when food poisoning is infrequent. In order to assess their similarity to human-derived strains, the detected viruses and their human-derived counterparts were subjected to genetic analysis, whereupon some of the detected viruses were found to be remarkably similar to those that were previously detected in humans infected with NV. In the interests of examining methods for decontaminating NV-contaminated oysters, we also conducted an assessment on a system of virus decontamination that focuses on seawater temperature and oyster metabolism, using Poliovirus Sabin strain. The decontamination system mentioned above was a closed loop, water circulating system, built on the same principles as those actually in use at oyster farms. Our experiment indicated that at seawater temperatures of both 10 degrees C and 20 degrees C, virus placed into the water tank was rapidly incorporated into the midgut glands of the oysters. Thereafter, when seawater irradiated with UV was circulated, the virus count in the oysters fell from 1/1,000 to 1/10,000 within 6 hours. These results indicated the utility of this system for virus decontamination, suggesting the possibility of significantly alleviating the risk of NV infection in humans by using this system to maintain the seawater temperature within the decontamination tank above a certain temperature, and to perform decontamination with an adequate water flow.

Animals↗