A sensitive and robust UPLC–MS/MS method for quantitation of estrogens and progestogens in human serum

Objective

With the widespread use of sex-steroid hormones in contraceptives and hormone replacement therapy, there is an increasing need for reliable analytical methods. We report the development of a sensitive and robust UPLC–MS/MS method for quantitation of both endogenous and synthetic sex-steroid hormones in human serum.

Application of quantitative LC–MS surrogate peptide methodology in the analysis of the amyloid beta peptide (Aβ) biosynthetic intermediate protein APP–βCTF

An area of current research in Alzheimer's disease (AD) is the biosynthetic pathway of amyloid beta peptides (Aβ) via consecutive proteolytic cleavages of the amyloid beta precursor protein (APP) by BACE and γ-secretase enzymes. APP is first cleaved by BACE to form a C-terminal fragment APP–βCTF, or also called C99, which then undergoes further cleavage by γ-secretase to form Aβ. Inhibitors of γ-secretase have been observed to yield a so-called ‘Aβ rise’ phenomenon whereby low inhibitor concentrations result in an increase in Aβ levels while high inhibitor concentrations result in lower Aβ levels. A previous report from our labs indicated that this phenomenon was related to ratios of APP–βCTF substrate relative to γ-secretase enzyme. A quantitative Western blot analysis was used with a recombinant C100 protein as calibration standards to assess the relationship of APP–βCTF, γ-secretase enzyme and various inhibitors resulting in the ‘Aβ rise’. An on-line liquid chromatography mass spectrometry (LC–MS) method employing the ‘surrogate peptide’ methodology was developed to accurately quantify the recombinant C100 used in the Western blot analyses. The surrogate peptide approach utilizes tryptic digestion of the protein to stoichiometrically yield a unique peptide fragment, in this case ^C100Aβ17–28 (LVFFAEDVGSNK) that can be readily detected by LC–MS. The absolute quantitative assessment of C100 was accomplished using synthetic Aβ17–28 to generate calibration curves over a 0.001–1 μM range and 15N isotopically labeled Aβ1–40 as the internal standard for enzymatic digestion and its proteolytic peptide [15N]-Aβ17–28 for the analysis.     

In Vivo Quantitation of Intratumoral Radioisotope Uptake Using Micro-Single Photon Emission Computed Tomography/Computed Tomography

Purpose This study was undertaken to determine the ability of micro-single photon emission computed tomography (micro-SPECT)/computed tomography (CT) to accurately quantitate intratumoral radioisotope uptake in vivo and to compare these measurements with planar imaging and micro-SPECT imaging alone.Procedures Human pancreatic cancer xenografts were established in 10 mice. Intratumoral radioisotope uptake was achieved via intratumoral injection of an attenuated measles virus vector expressing the NIS gene (MV-NIS). On various days after MV-NIS injection, ¹²³I planar and micro-SPECT/CT imaging was performed. Tumor activity was determined by dose calibrator measurements and region-of-interest (ROI) image analysis. Agreement and reproducibility of tumor activity measurements were assessed by Bland–Altman plots and Lin’s concordance correlation coefficient (CCC).Results Intratumoral radioisotope uptake was detected in all mice. Scatterplots demonstrate strong agreement (CCC = 0.93) between micro-SPECT/CT ROI image analysis and dose calibrator tumor activity measurements. The differences between dose calibrator activity measurements and those obtained with ROI image analysis of micro-SPECT alone and planar imaging are less accurate and more variable (CCC = 0.84 and 0.78, respectively).Conclusions Micro-SPECT/CT can be used to accurately quantify intratumoral radioisotope uptake in vivo and is more reliable than planar or micro-SPECT imaging alone.     

In vivo proton magnetic resonance spectroscopic signal processing for the absolute quantitation of brain metabolites

Magnetic resonance spectroscopy (MRS) is a non-invasive imaging modality for metabolite detection in different parts of the body (e.g. brain, liver, prostate, breast, kidney, skeletal muscle, and heart) for normal person as well as in various disorders. It aids in providing valuable information for both diagnosis as well as therapeutic monitoring. Though there has been tremendous progress in MRS signal processing techniques for the quantitation of neurometabolites, variability in the absolute quantitation of metabolites persists due to various experimental conditions. In this article, we present in-depth discussion on (1)H MRS data processing and quantitation using different software packages both in frequency (e.g. LCModel) and time domain (e.g. jMRUI). We have included comparative analysis of precision and accuracy of MRS data processing using LCModel and jMRUI (AMARES). Special emphasis has been provided for the handling of macromolecules and lipid in LCModel and jMRUI methods. The author also suggests certain points to be noted while opting for above software packages.     

Identification and quantification of the bioactive components in Osmanthus fragrans roots by HPLC-MS/MS

The roots of O. fragrans are also a valuable resource in addition to its flowers and fruits. In this study, the HPLC-MS/MS method used for analyzing the chemical constituents in O. fragrans roots extract was developed, which showed high sensitivity for both qualitative and quantitative analyses. Thirty-two compounds were first discovered in O. fragrans roots, one compound of which was reported for the first time. The simultaneous determination method for acteoside, isoacteoside, oleuropein and phillyrin was validated to be sensitive and accurate. Then it was applied to determine the content of bioactive components in O. fragrans roots from different cultivars. The content of oleuropein and phillyrin in the twelve batches was relatively stable, while the content of acteoside and isoacteoside varied greatly. Moreover, the therapeutic material basis and mechanism of O. fragrans roots exerting its traditional pharmacodynamics were analyzed by network pharmacology. The results showed that O. fragrans roots might be effective for the treatment of inflammation, cardiovascular diseases, cancer, and rheumatoid arthritis, which is consistent with the traditional pharmacodynamics of O. fragrans roots. This work can provide an analytical method for the comprehensive development of O. fragrans roots.     

脂质体对9-硝基喜树碱内酯型和羧酸盐型体外平衡的影响

目的:考察脂质体包封对9-硝基喜树碱(9-nitrocamptothecin,9-NC)内酯型和羧酸盐型体外平衡的影响。方法:考察不同pH对9-NC内酯型和羧酸盐型相互转变动力学和平衡比例的影响。建立了同时测定脂质体中9-NC内酯型和羧酸盐型含量的HPLC方法,并用于考察在pH 7.4条件下脂质体包封对9-NC内酯型平衡比例和水解动力学的影响。结果:在pH9.0的条件下,以羧酸盐型存在。在pH 6.5条件下,9-NC内酯型和羧酸盐型的相互转变速度最慢。脂质体包封能显著提高9-NC内酯型的平衡比例,降低内酯型水解开环转变为羧酸盐型的速度。结论:脂质体可以使9-NC内酯型和羧酸盐型的平衡向内酯型方向移动,能够提高内酯型的稳定性。     

运用实时荧光定量RT-PCR和ELISA方法定量检测SHIV的对比分析

目的建立一种实时、灵敏、特异的针对人/猴免疫缺陷病毒(SHIV)的RNA载量检测方法,通过与酶联免疫吸附试验(ELISA)进行比较,成为监测SHIV病毒体外复制过程的常用方法。方法体外转录制备RNA标准品,利用TaqMan EZ逆转录聚合酶链反应(RT-PCR)试剂盒的反应体系和针对SHIV gag保守区91个碱基的Taq-Man探针与引物,建立一步法实时荧光定量RT-PCR。三种SHIV感染性分子克隆体外转染293T细胞,在不同的时间点采样,通过实时荧光定量RT-PCR和ELISA两种方法监测SHIV病毒复制过程。结果两种方法监测的病毒复制过程基本一致,转染后2~48小时病毒复制出现明显的对数生长期,之后进入平台期,p24浓度大约103pg/ml,而RNA载量大约在108拷贝/ml。两者具有很好的相关性(r2=0.834;P<0.001)。实时荧光定量RT-PCR灵敏度更高,检测范围更广,费用更低。结论所建立的一步法检测SHIV病毒载量的实时荧光定量RT-PCR方法,可以作为监测SHIV体外扩增的常用方法。