[Chemical profiling for bile acid derivatives in yak bile].

Bile acids( BAs),the major constituents of bile,are also known to be potential biomarkers of various diseases,especially liver disease. The systematic analysis of BAs is believed to be of great importance towards the clarification of the effective material basis for bile-type medicines,and the diagnosis and therapy of related diseases as well. As a part of systematic study on bile-type medicine ongoing in our group,this study lays emphasis on the isomer discrimination,and the improvement of analytical method of BAs. Further,this method was subsequently applied to elucidate in depth the chemical profile of BAs in yak bile. Regarding isomer discrimination for BAs,we constructed relative response-collision energy curves( RRCECs) by high performance liquid chromatographyion trap-time of flight-mass spectrometry( HPLC-IT-TOF-MS) in combination with high performance liquid chromatography-triple quadrupole-linear ion trap mass spectrometry( HPLC-Qtrap-MS). As a result,both the optimum collision energy( OCE) and CE_(50) exhibited great correlations with structural characteristics,thus enabling the isomer distinguishing,such as unconjugated BAs,glycine-conjugated BAs,and taurine-conjugated BAs. According to information provided by mass spectrometry,the comparison of OCE and CE_(50),retention time matching,combined with reference substances and database retrieval,a total of 30 bile acid derivatives were observed and identified in yak bile. The newly developed method could serve as a feasible tool for the in-depth characterization of BAs in bile and biological samples.

MicroRNA-21 promotes cell proliferation, migration, and resistance to apoptosis through PTEN/PI3K/AKT signaling pathway in esophageal cancer.

Our study aimed to explore associations between microRNA-21 (miR-21) and PTEN/PI3K/AKT signaling pathway and, further, to elucidate the regulation of miR-21 on biological behaviors in human esophageal cancer cells. The expressions of miR-21, PTEN, PI3K, and AKT were detected in 89 esophageal cancer samples and 58 adjacent normal tissues respectively. The human esophageal cancer cells (TE11) were grouped as following: blank (TE11 cells without transfection), negative (TE11 cells with miR-21 negative inhibitor), and Inhibition-miR21 (TE11 cells with miR-21 inhibitor). Western blot was used for detection of PTEN, P13K, and AKT protein expressions, MTT method for cell proliferation, Transwell assay for cell migration and invasion, and flow cytometry for cell cycle and apoptosis. MiR-21, PI3K, and AKT have higher expressions, but PTEN has lower expression in esophageal cancer tissues compared with adjacent normal tissues. The esophageal cancer tissues with lymph node metastasis and poor differentiation showed significantly low positive rate of PTEN protein, but high positive rates of PI3K and AKT proteins. Compared with blank and negative groups, PTEN expression of TE11 cells in Inhibition-miR21 group was significantly up-regulated, but PI3K and AKT were down-regulated. Further, PTEN was a target gene of miR-21. Besides, compared with blank and negative groups, the proliferation, migration, and invasion of TE11 cells were less active in Inhibition-miR21 group. TE11 cells were significantly increased in the G0/G1 phase of cell cycles, but decreased in the S and G2/M phase in Inhibition-miR21 group. The TE11 cells exhibited significantly increased apoptosis rates. MiR-21 targets key proteins in PTEN/PI3K/AKT signal pathway, promoting proliferation, migration, invasion, and cell cycle, and inhibiting apoptosis of human esophageal cancer cells. It may serve as a novel therapeutic target in esophageal cancer.

[Matrix Effect of Fe and Ca on EDXRF Analysis of Ce Concentration in Bayan Obo Ores].

When Energy-Dispersive X-RayFluorescence (EDXRF) used for measuring cerium (Ce) content in the Bayan Obo ores, matrix effect mainly comes from iron (Fe) and calcium (Ca). Due to extensive concentration variability of the two elements, commonly employed standard sample method for matrix effect correction is invalid. To overcome the problem, testing samples were prepared based on the average contents of elements in the Bayan Obo ores, and the influence of Fe and Ca on the coefficient in a linear relationship between Ce content and XRF signal was determined by linear least squares fitting for multivariate analysis. The coefficients thus determined reflected the matrix effect on Ce emitted fluorescence from Fe emitted fluorescence and Ca absorption. When the coefficients were used in analyzing Ce content in Bayan Obo mine by EDXRF, the relative error is less than 10%.

Step nonisothermal method to study stability of drugs.

A step nonisothermal experiment under high oxygen pressure and a new computation with optimization for step nonisothermal experiment on stability study of drugs was introduced. The kinetics parameters of captopril oxidation in aqueous solution were determined by this method. It is reported that the reaction of captopril solution occurs under either aerobic or anaerobic condition, giving different products. Then the total rate constant k(total) can be expressed as [image omitted] where k(anaerobic) and k(aerobic) are the rate constants of anaerobic and aerobic degradations, respectively. The results indicated that the parameters obtained in the step nonisothermal experiment were comparable with those obtained in the isothermal-isobaric experiments. By a computer simulation, the estimates for the kinetic parameters (E(a) and k(0)) obtained with step nonisothermal method were statistically evaluated. Results indicated that the estimates obtained with isothermal-isobaric method were somewhat more precise than those obtained with step nonisothermal method. However, the experimental period needed by isothermal-isobaric method was much longer than that needed by step nonisothermal method.

Step nonisothermal method in kinetics studies of captopril oxidation under compressed oxygen.

A step nonisothermal experiment under high oxygen pressure and a computation with optimization for a step nonisothermal experiment on a stability study of drugs are introduced. The kinetics parameters of captopril oxidation in aqueous solution were determined with this method. It is reported that the reaction of captopril solution occurs under either aerobic or anaerobic conditions, giving different products. Then the total rate constant k(total) can be expressed as: k(total)=k(anaerobic)+k(aerobic)=A(anaerobic) exp (-E(a, anaerobic)/RT)+A(aerobic) exp (-E(a, aerobic)/RT)p(O(2)), where k(anaerobic) and k(aerobic) are the rate constants of anaerobic and aerobic degradation, respectively. The results indicate that the parameters obtained in the step nonisothermal experiment are comparable to those obtained in isothermal-isobaric experiments.