Biomedical subjects

Yang Xin

Publications and source records attributed to Yang Xin.

5 recordsLinked to original sources

PubMed2006

[Determination of corosolic acid in Eriobotrya japonica leaves by reversed-phase high performance liquid chromatography].

Corosolic acid is clinically proven to activate cell glucose-transporter "shuttles" and thus helps balance blood glucose levels. A method was developed for the determination of corosolic acid in Eriobotrya japonica leaves by reversed-phase high performance liquid chromatography (RP-HPLC). The peak of corosolic acid in Eriobotrya japonica leaves was qualitatively analyzed by comparing the retention times and mass spectra of corosolic acid standard and the extract on HPLC-mass spectrometry (MS). Eriobotrya japonica leaves were extracted thrice for 3.0 h at 90 degrees C with 90% ethanol. The extract was concentrated and deposited by water to remove the impurity which interfered the determination. The deposit was dissolved by methanol and separated on an ODS column (250 mm x 4.6 mm i.d., 5 microm). Methanol-1.0% acetic acid (88:12, v/v) was used as the mobile phase with a flow rate of 0.8 mL/min. The detection wavelength was 215 nm. The linearity was good within the range of 1.0-6.0 microg (r = 0.9999). The corosolic acid content of Eriobotrya japonica leaves from Huangshan was 0.36%. The average recovery of corosolic acid was 99%. The method is simple, rapid, accurate and reliable for the determination of corosolic acid in Eriobotrya japonica leaves.

Chromatography, High Pressure Liquid↗

PubMed2005

Segmentation in echocardiographic sequences using shape-based snake model combined with generalized Hough transformation.

A novel method for segmentation of cardiac structures in temporal echocardiographic sequences based on the snake model is presented. The method is motivated by the observation that the structures of neighboring frames have consistent locations and shapes that aid in segmentation. To cooperate with the constraining information provided by the neighboring frames, we combine the template matching with the conventional snake model. It means that the model not only is driven by conventional internal and external forces, but also combines an additional constraint, the matching degree to measure the similarity between the neighboring prior shape and the derived contour. Furthermore, in order to auto or semi-automatically segment the sequent images without manually drawing the initial contours in each image, generalized Hough transformation (GHT) is used to roughly estimate the initial contour by transforming the neighboring prior shape. The method is particularly useful in case of the large frame-to-frame displacement of structure such as mitral valve. As a result, the active contour can easily detect the desirable boundaries in ultrasound images and has a high penetrability through the interference of various undesirables, such as the speckle, the tissue-related textures and the artifacts.

Algorithms↗

PubMed2005

Vaccinating rabbits with a cholesteryl ester transfer protein (CETP) B-Cell epitope carried by heat shock protein-65 (HSP65) for inducing anti-CETP antibodies and reducing aortic lesions in vivo.

Rabbits were vaccinated with a recombinant protein vaccine of HSP65-CETPC comprising mycobacterial heat shock protein-65 (HSP65) and a cholesteryl ester transfer protein (CETP) B-cell epitope in alum adjuvant for inducing anti-CETP antibodies in vivo. After anti-CETP antibodies were successfully produced, rabbits were fed with a high-cholesterol diet for 15 weeks, and then the antiatherogenic effects of anti-CETP antibodies were evaluated. The results showed that the fraction of plasma cholesterol in HDL increased and the fraction of plasma cholesterol in LDL decreased in rHSP65-CETPC-immunized rabbits when compared with those in control animals. The average percentage of aortic lesions in the entire aorta area in rHSP65-CETPC-vaccinated rabbits was 23.8% less than in OVA-immunized rabbits (15.14% vs 19.86%) and 30.8% less than in rHSP65 immunized rabbits (15.14% vs 21.87%). The average thickness of hyperplastic coronary artery in rHSP65-CETPC immunized rabbits was 164 +/- 12 microm, significantly lower than in rHSP65-immunized rabbits (197 +/- 15 microm) and in OVA-immunized rabbits (206 +/- 15 microm). Taken together, vaccination with the rHSP65-CETPC vaccine could significantly attenuate atherosclerosis in a rabbit model. Thus, the chimeric protein of rHSP65-CETPC can be further developed into an antiatherosclerosis vaccine in the future.

Animals↗

PubMed2004

Asparaginase display of polypeptides in the periplasm of Escherichia coli: potential rapid pepscan technique for antigen epitope mapping.

Asparaginase of Escherichia coli, a tetramer of identical subunits, was tested as a vector to display linear peptides on the surface of each enzyme subunit. A recombinant gene encoding a chimeric protein composed of asparaginase, a tetanus toxin peptide (TTP) spacer (831-854 fragment), and the foreign cholesteryl ester transfer protein C-terminal fragment (CETPC) was expressed and targeted to the periplasm of E. coli. The purified chimeric enzyme exhibited approximately 83% activity of the native enzyme, allowing the rapid screening of recombinant clones. In contrast, an asparaginase-CETPC fusion protein without the TTP spacer produced only about 23% activity of the native enzyme. Rats immunized with bacterial cells containing the chimeric enzymes induced CETP-specific immunoresponse. In contrast, rats inoculated with the cells expressing asparaginase only did not generate specific anti-CETP antibodies. Our study showed that asparaginase of E. coli was an effective carrier for displaying foreign peptides or epitopes. Moreover, the use of the TTP spacer appeared to play a critical role in maintaining the catalytic activity of the chimeric enzymes by redirecting the foreign CETPC peptide to the surface of the enzyme. The chimeric enzyme constructs fusing asparaginase with foreign peptides via a TTP spacer could be utilized as a rapid pepscan technique for antigen epitope mapping. The fusion protein of asparaginase-TTP-CETPC could also be useful for the development of a vaccine against atherosclerosis.

Animals↗

PubMed2004

Expressing and purifying an anti-atherosclerosis polypeptide vaccine in Escherichia coli.

A chimeric polypeptide of TTP-CETPC was successfully expressed as inclusion bodies in Escherichia coli by fusing it with the C-terminus of asparaginase and a basic amino acid-rich peptide (KR). After partially purified by washing with 0.5% (v/v) Triton X-100 in 10 mM PB, the pellet was solubilized in 8 M urea. The solution was precipitated with single volume and double volumes of cold ethanol for removing impurities. The fusion protein in solution was precipitated with triple volumes of ethanol to increase purity and then hydrolyzed with 50 mM hydrochloric acid at 55 degrees C for 72 h. The TTP-CETPC polypeptide was released after the unique acid-labile aspartylprolyl bond in the fusion protein was cleaved by acid. After impurities were removed by adjusting the hydrolysis solution pH to 9.45 and then to 8.37, the TTP-CETPC polypeptide was further purified by DEAE-cellulose column. The TTP-CETPC containing fractions were eluted at 60-80 mM NaCl. The purified TTP-CETPC cysteines were oxidized to form into intermolecular disulfide bonded dimers for immunizing mice. Specific anti-CETP antibodies in mice serum were assayed by ELISA and Western blot to verify that antibodies against CETP had been successfully induced and lasted for more than seventeen weeks in vivo.

Amino Acid Sequence↗