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Biomedical subjects

Yi Wang

Publications and source records attributed to Yi Wang.

At least 163 records · Page 9Linked to original sources
PubMed2005

[Modeling for activating peripheral nerves by transverse electric field].

The classical cable function has been used to represent the response of peripheral nerves stimulated by external parallel electric field. It can not describe the excitation of peripheral nerves stimulated by perpendicular electric field. In this paper, responses of the nodes of Ranvier to transverse-field are deeply investigated by mathematic simulation and in-vitro experiments. The paper demonstrates that, under perpendicular electric field stimulation, the responses evoke a two-stage process including an initial polarization and the actual change of the transmembrane potential. It is the net inward current along a radial direction of the node of Ranvier that causes the peripheral nerve excitation. Based on the two-stage process, a novel model is introduced to describe peripheral nerves stimulated by transverse-field, and the classical cable function is modified. The new model and the improved cable function are verified by several in-vitro experiments. They can be used to represent peripheral nerves responses by arbitrary electric field stimulation.

Animals↗
PubMed2005

[Antitumor effect and mechanism of shikonin derivative SYUNZ-7].

BACKGROUND & OBJECTIVE: Natural shikonin compounds and their derivatives have cytotoxicity and antitumor effects. This study was to explore in vitro and in vivo antitumor effects of SYUNZ-7 [2 or 3, 11-bis(phenylsulfanyl)-6-isohexenylnaphthazarin] and the mechanisms. METHODS: In vitro antiproliferation effects of SYUNZ-7 on human lung adenocarcinoma cell line GLC-82, human nasopharyngeal cancer cell line CNE2, human oral cavity cancer cell line KB, human gastric cancer cell line MGC-803 and human hepatocellular cancer cell line HepG2 were tested by MTT assay. In vivo antitumor effect of SYUNZ-7 was tested using ascitic cancer EAC xenograft in mice and CNE2 xenograft in nude mice models. Cell apoptosis and cell cycle distribution were assessed by flow cytometry. The in vivo effect of SYUNZ-7 on angiogenesis was detected by immunohistochemistry. RESULTS: The 50% inhibitory concentrations (IC(50)) of SYUNZ-7 to GLC-82, CNE2, KB, MGC-803, and HepG2 cells were (2.18+/-0.04) microg/ml, (4.17+/-0.09) microg/ml, (5.41+/-0.10) microg/ml, (6.41+/-0.14) microg/ml, and (9.99+/-0.21) microg/ml, respectively. Under the treatment of 1, 2, 4, and 8 mg/kg of SYUNZ-7, the inhibitory rates of EAC xenografts in mice were (40.5+/-0.14)%, (50.9+/-2.3)%, (61.7+/-1.8)%, and (65.6+/-7.4)%, respectively (P<0.01). Under the treatment of 1, 2, and 4 mg/kg of SYUNZ-7, the inhibitory rates of CNE2 xenografts in nude mice were 24.7%, 38.3%, and 41.2%, respectively (P<0.05). SYUNZ-7 induced apoptosis of CNE2 cells in time- and concentration-dependent manners, and blocked the transition of CNE2 cells from S to G(2)/M phase. SYUNZ-7 also inhibited the angiogenesis of CNE2 xenografts in nude mice in a concentration-dependent manner. CONCLUSION: SYUNZ-7 has strong in vivo and in vitro antitumor effects which are related to inducing cell apoptosis, blocking cell cycle, and inhibiting angiogenesis of tumor.

Animals↗
PubMed2005

[Inducement effect of Meisoindigo on apoptosis of leukemia cell line HL-60 and its mechanism].

BACKGROUND & OBJECTIVE: Meisoindigo is a powerful drug used in treating chronic myeloid leukemia (CML), but little is known about the mechanisms. This study was to investigate the inducement effect of meisoindigo on apoptosis of myelocytic leukemia cell line HL-60, and explore the possible mechanisms. METHODS: After treatment of meisoindigo, the proliferation of HL-60 cells was detected by trypan blue exclusion assay, and DNA fragmentation by agarose electrophoresis; cell morphology was observed under fluorescent microscope. Cell apoptosis and the expression of Fas were detected by flow cytometry. The expression of Caspase-3, Caspase-8, Caspase-9, PARP, Bcl-2, Bax and the concentration of cytochrome c in cytosol were analyzed by Western blot. RESULTS: Meisoindigo inhibited proliferation and induced apoptosis in HL-60 cells. When treated with 20 micromol/L meisoindigo for 12-48 h, the proliferation of HL-60 cells was significantly inhibited. When treated for 1 h, the apoptosis rate of HL-60 cells was (3.70+/-0.56)%; the apoptosis rate was significantly higher in HL-60 cells treated for 3, 6, and 12 h than in control cells [(19.80+/-1.13)%, (29.20+/-2.69)%, and (47.05+/-7.70)% vs. (2.65+/-0.78)%, P<0.05]. When treated with meisoindigo for 3 h, typical changes of apoptosis, such as chromatin condensation and DNA ladder, were detected in HL-60 cells. The positive rate of Fas was significantly higher in cells treated with 20 micromol/L meisoindigo for 1 h than in control cells [(21.30+/-1.27)% vs. (9.35+/-0.21)%, P<0.05]. Meisoindigo activated Caspase-3, Caspase-8, Caspase-9 and PARP, down-regulated the expression of Bcl-2, up-regulated the expression of Bax and the concentration of cytochrome c. Furthermore, pretreatment of caspase-3 inhibitor z-DEVD-fmk partially reversed the inhibitory effect of meisoindigo on cell proliferation, and decreased cell apoptosis; when treated with meisoindigo for 5 h, the apoptosis rate was significantly higher in pretreated cells than in cells without pretreatment [(29.8+/-5.4)% vs. (16.5+/-5.5)%, P<0.05]; when treated with meisoindigo for 12 h, the alive cell number was significantly lower in pretreated cells than in cells without pretreatment [(1.80+/-0.14) x 10(5)/ml vs. (3.57+/-0.18) x 10(5)/ml, P<0.05]. CONCLUSION: Meisoindigo induces apoptosis of HL-60 cells which may relate to regulation of caspases pathway and bcl-2 family proteins.

Apoptosis↗
PubMed2005

[Spectroscopic research on the interaction of 2-(4-dimethylaminophenyl)-5-fluoro-6-(morpholin-4-yl)-1H-benzimidazole and calf thymus DNA].

UV-Vis spectra of the aqueous solutions of 2-(4-dimethylaminophenyl)-5-fluoro-6-(morpholin-4-yl)-1H-benzimidazole (1) at different pH values revealed that compound 1 is a tertiary base, which can combine three protons. Through the non-linear least square method, the logarithm of the three accumulative protonation constants of compound 1, namely, lgbeta1, lgbeta2 and lgbeta3, were determined to be 4.96 +/- 0.03, 5.72 +/- 0.07 and 7.95 +/- 0.10, respectively. UV-Vis and the steady-state fluorescence spectra indicated that a special interaction occurs between compound 1 and calf thymus DNA at the pH value of 3.40, of which thebinding constant, Kb, is (2.30 +/- 0.10) x 10(4) mol(-1) x L. Compound 1 in the concentration range of 10(-8) to 1.2 x 10(-6) mol x L(-1) has a potential application to the quantitative determination of DNA.

Animals↗
PubMed2004

A model for Joule heating-induced dispersion in microchip electrophoresis.

This paper presents an analytical and parameterized model for analyzing the effects of Joule heating on analyte dispersion in electrophoretic separation microchannels. We first obtain non-uniform temperature distributions in the channel resulting from Joule heating, and then determine variations in electrophoretic velocity, based on the fact that the analyte's electrophoretic mobility depends on the buffer viscosity and hence temperature. The convection-diffusion equation is then formulated and solved in terms of spatial moments of the analyte concentration. The resulting model is validated by both numerical simulations and experimental data, and holds for all mass transfer regimes, including unsteady dispersion processes that commonly occur in microchip electrophoresis. This model, which is given in terms of analytical expressions and fully parameterized with channel dimensions and material properties, applies to dispersion of analyte bands of general initial shape in straight and constant-radius-turn channels. As such, the model can be used to represent analyte dispersion in microchannels of more general shape, such as serpentine- or spiral-shaped channels.

Complex Mixtures↗
PubMed2004

[Surgical treatment for the giant hepatic carcinomas occupying the central part of the liver].

OBJECTIVE: To evaluate the techniques and the effects of surgical resection of giant hepatic carcinomas which occupied the central part of the liver. METHODS: A retrospective study was carried out of hepatectomies performed for central giant hepatic carcinomas. The hepatic tumors included in this study were hepatocellular carcinomas, cholangiocarcinomas and hepatic metastases which situated in the central part of the liver (segment IV, V, VIII, I) with a diameter of larger than 10 cm and involved hepatocaval confluence, retrohepatic inferior vena cava (IVC) as well as hepatic portal. RESULTS: A total of 40 central giant hepatic carcinomas were successfully resected, with a mean diameter of 13.6 cm (range 10.5-19.0 cm). The types of the hepatectomies conducted were as follows: extended mid-hepatectomy in 9 cases, atypical mid-hepatectomy in 13 cases, extended left hepatectomy in 13 cases, total caudatectomy plus extended left hepatectomy in 3 cases and extended right hepatectomy in 2 cases. The mean operation time was 197 min (range 90 - 380 min) and the mean intraoperative blood lose 1,596 ml (range 300-11,000 ml), with operative mortality and morbidity being 0 and 20%, respectively. The postoperative 1, 3 and 5 year survival rates for the patients were 88%, 56% and 28%, respectively. CONCLUSIONS: The hepatic carcinomas of central type, when larger than 10 cm in diameter, frequently involves all the hepatic portal, hepatocaval confluence and retrohepatic IVC. Surgical resection of this kind of tumor, though sophisticated in technique, is safe and effective and, therefore, the first choice of the treatments.

Adult↗
PubMed2004

Highly enantioselective conjugate addition of malonate and beta-ketoester to nitroalkenes: asymmetric C-C bond formation with new bifunctional organic catalysts based on cinchona alkaloids.

The development of readily accessible bifunctional chiral catalysts is a desirable yet challenging goal in catalytic asymmetric synthesis. In this communication, we describe the development of a new class of readily accessible chiral bifunctional organic catalysts that could be derived in one or two steps in high yield from either quinidine or quinine. These catalysts have been shown to catalyze a highly enantioselective conjugate addition of methyl and ethyl malonates and beta-ketoesters to a broad range of beta-substituted nitroalkenes, an synthetically important C-C bond-forming reaction utilizing readily available starting materials. This new catalytic asymmetric reaction proceeds in 91-98% ee and 71-99% yield.

Alkenes↗
PubMed2004

Human acyl-coenzyme A:cholesterol acyltransferase 1 (acat1) sequences located in two different chromosomes (7 and 1) are required to produce a novel ACAT1 isoenzyme with additional sequence at the N terminus.

A rare form of human ACAT1 mRNA, containing the optional long 5'-untranslated region, is produced as a 4.3-kelonucleotide chimeric mRNA through a novel interchromosomal trans-splicing of two discontinuous RNAs transcribed from chromosomes 1 and 7. To investigate its function, we express the chimeric ACAT1 mRNA in Chinese hamster ovary cells and show that it can produce a larger ACAT1 protein, with an apparent molecular mass of 56 kDa on SDS-PAGE, in addition to the normal, 50-kDa ACAT1 protein, which is produced from the ACAT1 mRNAs without the optional long 5'-untranslated repeat. To produce the 56-kDa ACAT1, acat1 sequences located at both chromosomes 7 and 1 are required. The 56-kDa ACAT1 can be recognized by specific antibodies prepared against the predicted additional amino acid sequence located upstream of the N-terminal of the ACAT1(ORF). The translation initiation codon for the 56-kDa protein is GGC, which encodes for glycine, as deduced by mutation analysis and mass spectrometry. Similar to the 50-kDa protein, when expressed alone, the 56-kDa ACAT1 is located in the endoplasmic reticulum and is enzymatically active. The 56-kDa ACAT1 is present in native human cells, including human monocyte-derived macrophages. Our current results show that the function of the chimeric ACAT1 mRNA is to increase the ACAT enzyme diversity by producing a novel isoenzyme. To our knowledge, our result provides the first mammalian example that a trans-spliced mRNA produces a functional protein.

Amino Acid Sequence↗
PubMed2004

Crystal structure of 3-carboxy-cis,cis-muconate lactonizing enzyme from Pseudomonas putida, a fumarase class II type cycloisomerase: enzyme evolution in parallel pathways.

3-Carboxy-cis,cis-muconate lactonizing enzymes (CMLEs), the key enzymes in the protocatechuate branch of the beta-ketoadipate pathway in microorganisms, catalyze the conversion of 3-carboxy-cis,cis-muconate to muconolactones. We have determined the crystal structure of the prokaryotic Pseudomonas putida CMLE (PpCMLE) at 2.6 A resolution. PpCMLE is a homotetramer and belongs to the fumarase class II superfamily. The active site of PpCMLE is formed largely by three regions, which are moderately conserved in the fumarase class II superfamily, from three respective monomers. It has been proposed that residue His141, which is highly conserved in all fumarase class II enzymes and forms a charge relay with residue Glu275 (both His141 and Glu275 are in adenylosuccinate lyase numbering), acts as the general base in most fumarase class II superfamily members. However, this charge relay pair is broken in PpCMLE. The residues corresponding to His141 and Glu275 are Trp153 and Ala289, respectively, in PpCMLE. The structures of prokaryotic MLEs and that of CMLE from the eukaryotic Neurospora crassa are completely different from that of PpCMLE, indicating MLEs and CMLEs, as well as the prokaryotic and eukaryotic CMLEs, evolved from distinct ancestors, although they catalyze similar reactions. The structural differences may be related to recognition by substrates and to differences in the mechanistic pathways by which these enzymes catalyze their respective reactions.

Amino Acid Sequence↗
PubMed2004

Photoacoustic and ultrasonic coimage with a linear transducer array.

A technique is developed to simultaneously acquire ultrasound and photoacoustic (PA) images based on a linear transducer array. The system uses conventional ultrasound for rapid identification of potential targets. After a target is identified, the ultrasound echo and PA signals can be simultaneously obtained with optimized excitation and a signal collection sequence. The corresponding ultrasound impedance and optical absorption images are reconstructed with a phase-controlled algorithm. The approach can effectively reduce the artifacts associated with a conventional filter backprojection algorithm used in PA imaging by linear scanning. The technique provides a new approach for practical applications.

Algorithms↗
PubMed2004

System-oriented dispersion models of general-shaped electrophoresis microchannels.

This paper presents a system-oriented model for analyzing the dispersion of electrophoretic transport of charged analyte molecules in a general-shaped microchannel, which is represented as a system of serially connected elemental channels of simple geometry. Parameterized analytical models that hold for analyte bands of virtually arbitrary initial shape are derived to describe analyte dispersion, including both the skew and broadening of the band, in elemental channels. These models are then integrated to describe dispersion in the general-shaped channel using appropriate parameters to represent interfaces of adjacent elements. This lumped-parameter system model offers orders-of-magnitude improvement in computational efficiency over full numerical simulations, and is verified by results from experiments and numerical simulations. The model is used to perform a systematic parametric study of serpentine channels consisting of a pair of complementary turn microchannels, and the results indicate that dispersion in a particular turn can contribute to either an increase or decrease of the overall band broadening. The efficiency and accuracy of the system model is further demonstrated by its application to general-shaped channels that occur in practice, including a serpentine channel with multiple complementary turns and a multi-turn spiral-shaped channel. The results indicate that our model is an accurate and efficient simulation tool useful for designing optimal electrophoretic separation microchips.

Electrophoresis, Capillary↗
PubMed2004

Photoacoustic imaging with deconvolution algorithm.

The impulse response of the ultrasonic transducer used for detection is crucial for photoacoustic imaging with high resolution. We demonstrate a reconstruction method that allows the optical absorption distribution of a sample to be reconstructed without knowing the impulse response of the ultrasonic transducer. A convolution relationship between photoacoustic signals measured by an ultrasound transducer and optical absorption distribution is developed. Based on this theory, the projection of the optical absorption distribution of a sample can be obtained directly by deconvolving the recorded PA signal originating from a point source out of that from the sample. And a modified filtered back projection algorithm is used to reconstruct the optical absorption distribution. We constructed a photoacoustic imaging system to validate the reconstruction method and the experimental results demonstrated that the reconstructed images agreed well with the original phantom samples. The spatial resolution of the system reaches 0.3 mm.

Acoustics↗
PubMed2004

Clinical features, diagnosis, treatment and prognosis of multiple primary colorectal carcinoma.

AIM: To investigate the clinical features, diagnosis, treatment and prognosis of multiple primary colorectal carcinomas (MPCC). METHODS: A retrospective analysis of 37 patients with MPCC from 1974 to 1998 was carried out. RESULTS: The incidence of MPCC was 2.74%(37/1 348) in patients with primary colorectal carcinomas, 15 cases of them were patients with synchronous carcinomas (SC) and 22 cases were diagnosed as metachronous carcinomas (MC). Most tumors were located in the right colon and rectum. Fifty-five percent (12/22) of MC were diagnosed within 3 years after tumor resection and 41%(9/22) of MC occurred after 8 years. Radical resections were performed in all patients except for 1 case. The 5-year survival rate of SC was 72.7%(8/11) and that of MC after the first cancer and second cancer was 71.4%(15/21) and 38.9%(7/18), respectively. CONCLUSION: The results indicate the importance of complete preoperative examination, careful intraoperative exploration and periodic postoperative surveillance. Early diagnosis and radical resection can increase survival rate of MPCC.

Adult↗
PubMed2004

Compound-specific carbon and hydrogen isotope analysis of sub-parts per billion level waterborne petroleum hydrocarbons.

Compound-specific carbon and hydrogen isotope analysis (CSCIA and CSHIA) has been increasingly used to study the source, transport, and bioremediation of organic contaminants such as petroleum hydrocarbons. In natural aquatic systems, dissolved contaminants represent the bioavailable fraction that generally is of the greatest toxicological significance. However, determining the isotopic ratios of waterborne hydrophobic contaminants in natural waters is very challenging because of their extremely low concentrations (often at sub-parts ber billion, or even lower). To acquire sufficient quantities of polycyclic aromatic hydrocarbons with 10 ng/L concentration for CSHIA, more than 1000 L of water must be extracted. Conventional liquid/liquid or solid-phase extraction is not suitable for such large volume extractions. We have developed a new approach that is capable of efficiently sampling sub-parts per billion level waterborne petroleum hydrocarbons for CSIA. We use semipermeable membrane devices (SPMDs) to accumulate hydrophobic contaminants from polluted waters and then recover the compounds in the laboratory for CSIA. In this study, we demonstrate, under a variety of experimental conditions (different concentrations, temperatures, and turbulence levels), that SPMD-associated processes do not induce C and H isotopic fractionations. The applicability of SPMD-CSIA technology to natural systems is further demonstrated by determining the delta13C and deltaD values of petroleum hydrocarbons present in the Pawtuxet River, RI. Our results show that the combined SPMD-CSIA is an effective tool to investigate the source and fate of hydrophobic contaminants in the aquatic environments.

Alkanes↗
PubMed2004

Microvessel density of malignant and benign hepatic lesions and MRI evaluation.

AIM: To study the difference of microvessel density (MVD) between malignant and benign hepatic lesions and study the relationship between MVD and dynamic enhanced magnetic resonance imaging (MRI) for evaluation of microvessels within malignant and benign hepatic lesions. METHODS: A total of 265 specimens of hepatocellular carcinoma (HCC), 122 cirrhosis tissues and 22 hepatic benign lesions were enrolled for MVD by immunohistochemistry on tissue microarray, of which 49 underwent MRI examination before surgery, then contrast-to-noise ratios (CNR) and enhancement index (EI) in all the phases were calculated. Pearson correlation was performed for correlation analysis between CNR, EI and MVD. RESULTS: MVD of HCC was 22.7+/-15.8 (mean+/-SD), which was obviously higher than that of cirrhosis tissue (8.3+/-7.6, P<0.01), but was not statistically different from that of benign lesions (31.3+/-22.7, P>0.05). Among HCC, MVD of grades I-II was 29.9+/-18.6, which was much higher than those of grade III (22.2+/-18.2, P<0.01) and grade IV (22.9+/-19.0, P<0.01). MVD of HCC (P=0.018) and of benign lesions (P=0.014) were both correlative with CNR in arterial phase. CONCLUSION: Neoangiogenesis is an important feature for malignant tumor, and MVD may act as a biological marker in differentiating malignant from benign hepatic lesions. Dynamic enhanced MRI, especially image in arterial phase, may act as an MVD evaluation criterion for malignant and benign hepatic lesions.

Carcinoma, Hepatocellular↗
PubMed2004

Establishment of a P-glycoprotein substrate screening model and its preliminary application.

AIM: To establish a high P-glycoprotein (P-gp) expressing cell line as a model for studying drug absorption and distribution, and to explore the preliminary application of this screening model. METHODS: A full-length MDR1 cDNA fragment in plasmid pMDRA1 was first subcloned into plasmid pET28a(+), then MDR1 cDNA was cut from the recombinant plasmid with double-digestion and ligated into the mammalian expression vector pcDNA3.1(+). The recombinant plasmid pcDNA3.1(+)/MDR1 was transfected into breast cancer cell line Bcap37 using the Superfect transfection reagent. Several stably transfected clones were obtained after selection with G418. Real-time fluorescent quantitative RT- PCR and Western blot methods were used to detect the expression of P-gp, and the cellular location of the expressed protein was determined by immunohistochemical staining. Drug sensitivity assay was used to evaluate the biological function of expressed P-gp. Concentration of quercetin in cells was determined by high-performance liquid chromatography (HPLC). RESULTS: The recombinant plasmid was confirmed to be inserted in the correct orientation by restrictive enzyme digestion and DNA sequencing. Real-time fluorescent quantitative RT-PCR showed a higher level of P-gp mRNA in transfected cells compared to that in the control cells, and the Western blot result also indicated that P-gp expression in transfected cells was higher than that in control cells. The immunohistochemical staining showed that the expressed P-gp was localized on cell membranes. Drug sensitivity assay showed that the IC50 for adriamycin and colchicine of the transfected cells was higher than that of the control cells. The concentration of quercetin in model cells was lower than that in control cells by HPLC. After P-gp inhibitor verapamil was administered, the concentration of quercetin in model cells was increased. CONCLUSION: A high P-gp expressing cell line can be established, which could provide a suitable in vitro model system for studying drug intestinal absorption mechanism, predicting the drug permeability characteristics and screening new multi-drug resistance reversing agents. With this model, quercetin can be found to be transported by P-gp, and it is a P-gp substrate.

ATP Binding Cassette Transporter, Subfamily B, Mem↗