Biomedical subjects

L Yang

Publications and source records attributed to L Yang.

At least 469 records · Page 26Linked to original sources

PubMed1998

[HIM82 protects RBC from the ROS damage produced by activated PMN].

OBJECTIVE: To investigate the protection of RBC from ROS damage produced by activated PMN with McAb-HIM82. METHODS: RBC was injured by ROS produced from PMN activated with PMA and the injury was antagonised by adding HIM82(30 micrograms/ml) to the medium with PMN. RESULTS: Comparing antagonitic group with injured group, the activity of AchE on RBC membrane after adding HIM82 was recovered from (71.36 +/- 22.15)% to (87.66 +/- 14.78)% (n = 6 P < 0.001). The proportion of MDA was decreased from (52.42 +/- 20.63)% to (23.81 +/- 12.4)%(n = 9 P < 0.001); the hemolysis rate was decreased from (80.76 +/- 20.23)% to (66.30 +/- 7.08)% (n = 6 P < 0.05); CONCLUSIONS: The result showed that the McAb HIM82 could protect RBC from injury by down-reguration of ROS level in activated PMN. It could help to establish a newer approach to study the regulation effect of McAb HIM82 on ROS production from PMN actived with relerant cytokines as well as mediators.

Acetylcholinesterase↗

PubMed1998

[Construction of a pufferfish bacterial artificial chromosome library].

OBJECTIVE: Study of human genome by taking advantage of investigating pufferfish's (Fugu rubripes), compact model vertebrate genome. METHODS: Construct a pufferfish bacterial artificial chromosome (BAC) library using Japanese pufferfish (Fugu rubripes) sperm DNA and pBelo BAC11 vector. RESULTS: The library consists of 23,040 clones, which have been arrayed in 240,96-well microtiter plates. 100 BAC clones have been selected at random and analyzed for estimation of the average insert size, which turns out to be 100 kb indicating its nearly 6-fold coverage of pufferfish haploid genome. Restrict analysis of 10 BAC clones show that these inserts are stable even propagated for at least 100 cell generations. CONCLUSIONS: The library accords with the demands of a BAC library.

Animals↗

PubMed1998

[The property of protein A affinity membrane cartridge and purification of IgG from human plasma].

A new protein A affinity membrane based on composite matrix formed by covalent cross-linking of the glycidyl methylacrylate to softwood cellulose fiber was developed. The study focused on the physical properties and adsorption capacity of the affinity membrane cartridge. The results showed that the relationship between flow-rate and backpressure was linear. When flow-rate was 3 mL/min, backpressure attained 160 kPa. The effects of IgG mass concentration and sampling flow-rate on the binding capacity by protein A cartridge were studied for the optimum purification of IgG. A 21.7 mg/g dry matrix of maximum dynamic binding capacity for IgG was obtained by dynamic adsorption. The cartridge was loaded with human plasma to test its ability to fractionate IgG. The IgG purified from human plasma was analysed by capillary zone electrophoresis (CZE). The results showed that the protein A affinity membrane cartridge had high selectivity for IgG from human plasma. The purity of IgG from human plasma purified by the immobilized protein A membrane cartridge was over 98%. The fast-flow property of the membrane cartridge made from such a matrix and its simplicity in operation provide effective means for purifying immunoglobulins on a relatively large scale.

Chromatography, Affinity↗

PubMed1998

[Determination of felodipine concentration in human plasma by GC-ECD and study of its pharmacokinetics].

A rapid, accurate and sensitive gas chromatographic method using electron-capture detector (GC-ECD) was developed for the determination of felodipine concentration in human plasma. Nimodipine was used as internal standard. The plasma samples were extracted using a mixture of ethyl ether and n-hexane (2:1) to give mean recoveries of 97.3% of felodipine. The extracts were separated by a 5% SE-30 glass packed column (2 m x 3 mm). The detection limits for felodipine was 0.25 ng.ml-1. The precisions (RSD%, n = 5) of within-day and day-to-day were less than 5.09% and 8.62%, respectively. The pharmacokinetic parameters of felodipine in ten men were investigated by this method. The concentration-time curve was fitted to a two-compartment model. Its main pharmacokinetic parameters were: T1/2 alpha = 0.76 h, T1/2 beta = 16.09 h, Cmax = 4.78 ng.ml-1, Tmax = 2.01 h, AUC = 45.2 h.ng.ml-1.

Adult↗

PubMed1998

[The preparation and bioactivities of chiral analogs of baogongteng A].

Eight chiral analogs of baogongteng A were prepared from (+/-)-3 alpha-hydroxy-6 beta-acetoxytropane by chemical resolution. In myotic or mydriatic tests in rabbits, (-)-3 alpha-paramethyl benzenesulfonyloxy-6 beta-acetoxytropane showed cholinergic activities, while (+)-3 alpha-benzoyloxy-6 beta-acetoxytropane and (+)-3 alpha-parachloro benzoyloxy-6 beta-acetoxytropane showed anticholinergic activities.

Animals↗

PubMed1998

[Expression of P21 and P185 in benign and malignant epithelia of cheek mucosa].

To analyze the expression of P21 and P185 in normal epithelia, chronic non-specific inflammatory epithelia, squamous cell carcinoma and epithelia immediately adjacent to carcinoma of cheek mucosa, immunohistochemistry technique and image analysis technique were used. The results showed: there was excellently higher expression of P21 and P185 in squamous cell carcinoma and epithelia immediately adjacent to carcinoma than in normal and inflammatory epithelia of cheek mucosa, which were compactly correlative.

Carcinoma, Squamous Cell↗

PubMed1998

[Effect of dihydroquinghaosu on the development of Plasmodium yoelii yoelii in Anopheles stephensi].

AIM: To observe the effect of dihydro qinghaosu (DQHS) on the development of Plasmodium yoelii yoelii in Anopheles stephensi and to explore the possibility of whether DQHS has preventive effect against malaria. METHODS: Plasmodium yoelii yoelii-infected mice that had been administered with a single dose of different dosages (60 mg/kg, 120 mg/kg, 180 mg/kg and 240 mg/kg) of DQHS were exposed to mosquitoes to suck blood. The development of malaria parasites in the mosquitoes of the control group and the treated group were observed by light microscopy (LM) and transmission electron microscopy (TEM). RESULTS: DQHS exhibited certain inhibitory effect on the infectivity of gametocyte. The degree of inhibition was related to the developmental stages of gametocyte and the drug dosage. Immature gametocytes were more sensitive to DQHS than the mature gametocytes. With the increases in dosage, the positive rate and the density of oocyst and sporozoite decreased. However, the difference in the density of sporozoite between 180 mg/kg and 240 mg/kg treated groups was insignificant. TEM result showed damage of the membrane system and vacuolation in the cytoplasm of the oocysts (12-13 d) on mosquito midgut of 60 mg/kg 16 h treated group. The oocysts in the mosquitoes continued to develop after treated with 120 mg/kg of DQHS for 16 h on 3-day-instar. There was no significant difference (P > 0.05) in the density of oocyst and sporozoite between the control group and the treated group. CONCLUSION: DQHS can affect the infectivity of gametocyte and decrease the malaria transmission but cannot inhibit the sorogonic stage directly.

Animals↗

PubMed1998

[Study of the physiological characteristics of a strain which can change the color of red lead on Dunhuang mural].

A strain which was isolated from Dunhuang Murual was investigated. It belongs to Flavobacterium. In media added in Pb3O4, colonies show brown and black. After identified pigments, it showed that the brown was caused by the oxidation of Pb3 O4 into PbO2 by the strain. The optimal oxidative condition is at pH 9.8, 37 degrees C and dark environment. The genes for oxidation is on plasmid and the oxidation was inhibited under pure O2 and N2 conditions, too 5 x 10(-3) mol/ml NaN3 is enough. The strain was able to absorb lead initiative. The transmission electron microscope showed that lead locate in protoplasts.

Color↗

PubMed1998

[Studies on microbial factor on color change of Dunhuang mural. III. Effect of Cladosporium sp. on color-change of red lead in the surface of mural].

The conditions isolated Cladosporium sp. from Mural of Dunhuang grottoe germinated on the surface of imitated mural were as follows: 20 degrees C RH 60% or 30 degrees C RH 50%, which could be reached occasionally in some grottoes. Bone glue had protective function on red lead, while Cladosporium sp. could decompose bone glue and form some metabolite (such as oxalic acid, etc) as it grows. Then it could form a special chemical circumstance, which promoted the change from red lead to while lead.

Cladosporium↗

PubMed1998

Mechanisms for ganciclovir resistance in gastrointestinal tumor cells transduced with a retroviral vector containing the herpes simplex virus thymidine kinase gene.

Transfer of the herpes simplex thymidine kinase (HSV-TK) gene into tumor cells confers sensitivity to the cells to the viral drug ganciclovir (GCV). Although the efficacy of the HSV-TK/GCV approach is well studied, the mechanisms for the resistance of HSV-TK-transduced tumor cells to GCV are poorly understood. Here, we examined the mechanisms for GCV resistance in HSV-TK-transduced gastrointestinal (GI) cell lines. Our results show that GCV sensitivities vary in vitro and in vivo among the different HSV-TK-transduced GI tumor cell lines. GCV-resistant colonies were isolated from several different HSV-TK-transduced GI tumor cell lines after 14 days of GCV treatment. Characterization of GCV-resistant colonies demonstrated that the HSV-TK gene was either partially or completely deleted from the resistant HSV-TK-transduced cells. In the HT-29 RM and MIAPACA-2 RM cells, a 220-bp deletion of the gene was found, whereas in the HT-29 R1-R5-resistant cells, the whole TK gene was found to be absent. Immunocytochemical studies using a polyclonal antibody to the TK protein demonstrated that the HSV-TK protein was absent in the GCV-resistant, HSV-TK-transduced cells. Transfection of the resistant cells with an adenoviral vector containing a HSV-TK gene restored sensitivity to GCV. The presence of GCV-resistant cells was only demonstrable in GI tumor cell lines that also demonstrated a poor bystander effect. Our results suggest that GCV resistance found in tumor cells transduced with a retroviral HSV-TK gene is due to the lack of a functional TK protein in the tumor cells rather than any intrinsic resistance of the cells to GCV. In tumor cells with a good bystander effect, the small percentage of TK-transduced cells that do not express the TK protein are probably killed by the bystander effect because GCV-resistant tumor cells were not found in these cell lines. GCV-resistant tumor cells were found only in tumor cell lines with a poor bystander effect, by which, presumably, the transduced tumor cells lacking a functional TK gene were not killed by the bystander killing effect.

Antiviral Agents↗

PubMed1998

Induction of sensitivity to doxorubicin and etoposide by transfection of MCF-7 breast cancer cells with heregulin beta-2.

HER2 (erbB-2) proto-oncogene amplification and/or overexpression correlate with poor prognosis in many malignancies. The precise biological role of this oncogenic signaling pathway (which also involves the HER4 gene) in breast cancer is unclear. One property conferred by this oncogene relates to response to drug therapy. Clinical studies support an association between HER2 overexpression and resistance to alkylating agents (cisplatinum and cyclophosphamide). Data from the Cancer and Leukemia Group B 8869/8541 study indicate enhanced dose responsiveness to doxorubicin (Adriamycin) in patients who overexpress the HER2 receptor. Heregulin beta-2, a naturally occurring ligand that activates the HER2 receptor by inducing its heterodimerization with the HER4 receptor, has recently been cloned. The ability of this ligand to phosphorylate the HER2 receptor exogenously allows us to study the effect of HER2 activation on cancer cell behavior. To study the relationship between chemotherapy response and activation of HER2, MCF-7 cells expressing biologically active heregulin were assessed for response to doxorubicin and etoposide, both of which are topoisomerase IIalpha (topo IIalpha) inhibitors. Several clones show markedly increased sensitivity to these drugs. In addition, the same wild-type MCF-7 cells transfected with heregulin beta-2 under the control of an inducible promoter also show this dose-response relationship to doxorubicin after the expression of heregulin beta-2 is activated by zinc. The modulation of topo IIalpha was studied in the cell lines transfected with heregulin. topo IIalpha mRNA and protein (total protein and enzymatic decatenating activity) were found to be up-regulated in heregulin beta-2-transfected cells. Moreover, topo IIalpha promoter activity was also modestly increased in heregulin beta-2-transfected cells. Because up-regulation of topo IIalpha in vitro and in clinical specimens is associated with increased response to doxorubicin (presumptively by an increase in drug substrate), this may be the mechanism of the increased sensitivity to doxorubicin seen in heregulin beta-2-transfected cells. This implies that activation of HER2 or one of the other members of the receptor family may increase sensitivity to doxorubicin by up-regulation of topo IIalpha. This finding suggests the use of receptor/ligand expression to direct patient-specific therapeutic choices (e.g., doxorubicin versus alkylator-based regimens) and the use of biological agents (such as heregulin) in combination with certain chemotherapeutic agents to enhance response to treatment in breast cancer patients.

Antibiotics, Antineoplastic↗

PubMed1998

The social course of schizophrenia: local and societal factors.

In this paper, we propose a model of social course of schizophrenia based on cross-cultural research on the influence of family, wider social network, work, political economy, and legal and mental health care institutions on the experience of illness. We posit the way these ordinary arrangements of daily living organize the course of schizophrenia in part through cultural processes that affect the body-self in suffering and in part through social processes that establish an intersubjective matrix for the experience of illness. We believe this model can be generalized to other chronic illness such as depression, diabetes, asthma, osteoarthritis, chronic pain syndrome, chronic fatigue syndrome, and even heart disease and cancer. We develop the implications of this anthropological approach for research and practice.

Adaptation, Psychological↗

PubMed1997

Lamin-binding fragment of LAP2 inhibits increase in nuclear volume during the cell cycle and progression into S phase.

Lamina-associated polypeptide 2 (LAP2) is an integral membrane protein of the inner nuclear membrane that binds to both lamin B and chromatin and has a putative role in nuclear envelope (NE) organization. We found that microinjection of a recombinant polypeptide comprising the nucleoplasmic domain of rat LAP2 (residues 1-398) into metaphase HeLa cells does not affect the reassembly of transport-competent nuclei containing NEs and lamina, but strongly inhibits nuclear volume increase. This effect appears to be specifically due to lamin binding, because it also is caused by microinjection of the minimal lamin-binding region of LAP2 (residues 298-373) but not by the chromatin-binding domain (residues 1-88). Injection of the lamin-binding region of rat LAP2 into early G1 phase HeLa cells also strongly affects nuclear growth; it almost completely prevents the threefold nuclear volume increase that normally occurs during the ensuing 10 h. Moreover, injection of the fragment during early G1 phase strongly inhibits entry of cells into S phase, whereas injection during S phase has no apparent effect on ongoing DNA replication. Since the lamin-binding fragment of LAP2 most likely acts by inhibiting dynamics of the nuclear lamina, our results suggest that a normal function of LAP2 involves regulation of nuclear lamina growth. These data also suggest that lamina dynamics are required for growth of the NE and for nuclear volume increase during the cell cycle, and that progression into S phase is dependent on the acquisition of a certain nuclear volume.

Animals↗

PubMed1997

Induction of retinoid resistance in breast cancer cells by overexpression of cJun.

To investigate the role of AP-1 transcription factors in mediating retinoid-induced growth suppression of breast cells, we studied the sensitivity of MCF7 breast cancer cells with different levels of AP-1 activity to all-trans retinoic acid (atRA). AP-1 activity was increased in MCF7 cells by stably transfecting c-jun cDNA into these cells. Parental and vector-transfected MCF7 cells, which were sensitive to the growth-inhibitory effects of atRA, exhibited atRA-dependent retinoic acid receptor (RAR) transactivation and transrepression of 12-O-tetradecanoylphorbol-13-acetate-induced AP-1 activity. The c-jun-transfected MCF7 cells had increased basal AP-1 transactivation activity and increased expression of AP-1-regulated genes but were resistant to the antiproliferative effects of atRA. However, MCF7 cells transfected with a deletion mutant of c-jun, TAM-67, which lacks most of the amino-terminal transactivation domain of cJun and is unable to activate AP-1-dependent gene expression, were sensitive to the growth-inhibitory effects of atRA. These results suggest that the transactivation domain of cJun is required for induction of retinoid resistance in these breast cancer cells. atRA did not activate RAR-dependent gene transcription or transrepress 12-O-tetradecanoylphorbol-13-acetate-induced AP-1 activity in these cJun-overexpressing cells. Investigation of the RAR and retinoic acid X receptor expression level demonstrated that RAR alpha and RAR gamma RNA expression was reduced in the c-jun-transfected MCF7 cells, whereas RAR beta expression was up-regulated. However, retinoic acid responsive element DNA binding activity was intact in c-jun-transfected cells. Therefore, the mechanism by which cJun overexpression induces resistance to the growth-inhibitory effect of atRA may be through interference with atRA-dependent RAR transactivation or AP-1 transrepression, possibly through titration of essential coactivators. These results suggest that the antiproliferative effects of retinoids can be overcome by cJun overexpression.

Breast Neoplasms↗

PubMed1997

The beta2 subunit inhibits stimulation of the alpha1/beta1 form of soluble guanylyl cyclase by nitric oxide. Potential relevance to regulation of blood pressure.

Cytosolic guanylyl cyclases (GTP pyrophosphate-lyase [cyclizing; EC 4.6.1.2]), primary receptors for nitric oxide (NO) generated by NO synthases, are obligate heterodimers consisting of an alpha and a beta subunit. The alpha1/beta1 form of guanylyl cyclase has the greatest activity and is considered the universal form. An isomer of the beta1 subunit, i.e., beta2, has been detected in the liver and kidney, however, its role is not known. In this study, we investigated the function of beta2. Immunoprecipitation experiments showed that the beta2 subunit forms a heterodimer with the alpha1 subunit. NO-stimulated cGMP formation in COS 7 cells cotransfected with the alpha1 and beta2 subunits was approximately 1/3 of that when alpha1 and beta1 subunits were cotransfected. The beta2 subunit inhibited NO-stimulated activity of the alpha1/beta1 form of guanylyl cyclase and NO-stimulated cGMP formation in cultured smooth muscle cells. Our results provide the first evidence that the beta2 subunit can regulate NO sensitivity of the alpha1/beta1 form of guanylyl cyclase. Northern analysis for guanylyl cyclase subunits was performed on RNA from kidneys of Dahl salt-sensitive rats, which have been shown to have decreased renal sensitivity to NO. Compared to the Dahl salt-resistant rat, message for beta2 was increased, beta1 was decreased, and alpha1 was unchanged. These results suggest a molecular basis for decreased renal guanylyl cyclase activity, i.e. , an increase in the alpha1/beta2 heterodimer, and decrease in the alpha1/beta1 heterodimer.

Animals↗

PubMed1997

Micellar electrokinetic chromatography-mass spectrometry.

The combination of micellar electrokinetic chromatography (MEKC) with mass spectrometry (MS) is very attractive for the direct identification of analyte molecules, for the possibility of selectivity enhancement, and for the structure confirmation and analysis in a MS-MS mode. The direct coupling of MEKC with MS can be hazardous due to the effect of nonvolatile MEKC surfactants on MS performance, including the loss of analyte sensitivity and ion source contamination. The possibility of off-line coupling between MEKC and matrix-assisted laser desorption/ionization (MALDI)-MS remains to be investigated. Various approaches for on-line coupling MEKC with electrospray ionization (ESI)-MS, including the use of high-molecular-mass surfactant, an electrospray-chemical ionization (ES-CI) interface, a voltage switching and buffer renewal system, partial-filling micellar plug and anodically migrating micelles, are reviewed and evaluated. The use of an ES-CI interface is most promising for routine operation of on-line MEKC-MS under the influence of nonvolatile salts and surfactants. The use of a high-molecular-mass surfactant allows the formation of a micellar phase at very low surfactant concentrations and avoids the generation of a high level of background ions in the low m/z region. Alternatively, the application of a partial-filling micellar plug and anodically migrating micelles eliminate the introduction of MEKC micelles into the ESI-MS system. It is possible to directly transfer the conventional MEKC separations to partial-filling MEKC-ESI-MS and MEKC-ESI-MS using anodically migrating micelles without any instrument modifications.

Electrophoresis, Capillary↗

PubMed1997

A new function for phospholipase C-gamma1: coupling to the adaptor protein GRB2.

Epidermal growth factor (EGF)-induced autophosphorylation of the EGF receptor results in high-affinity binding of the adaptor protein GRB2, which serves as a convergence point for multiple signaling pathways. Present studies demonstrate that EGF induces the co-immunoprecipitation of phospholipase C (PLC)-gamma1 with the adaptor protein GRB2 and the guanine nucleotide exchange factor Sos, but not with the adaptor protein SHC, in WB cells. Inhibition of PLC-gamma1 tyrosine phosphorylation by phenylarsine oxide reduces the co-immunoprecipitation of PLC-gamma1 with GRB2. Furthermore, angiotensin II, a G protein-coupled receptor agonist, also induces the tyrosine phosphorylation of PLC-gamma1 and its co-immunoprecipitation with GRB2 in WB cells. Interestingly, angiotensin II stimulation also causes tyrosine phosphorylation of the EGF receptor, suggesting that angiotensin II-induced PLC-gamma1 tyrosine phosphorylation in WB cells may be via EGF receptor tyrosine kinase activation. In addition, there is some level of association between PLC-gamma1 and GRB2 that is independent of the tyrosine phosphorylation of PLC-gamma1 in both in vivo and in vitro studies. In vitro studies further demonstrate that the Tyr771 and Tyr783 region of PLC-gamma1 and the SH2 domain of GRB2 are potentially involved in the tyrosine phosphorylation-dependent association between PLC-gamma1 and GRB2. The association of PLC-gamma1 with GRB2 and Sos suggests that PLC-gamma1 may be directly involved in the Ras signaling pathway and that GRB2 may be involved in the translocation of PLC-gamma1 from cytosol to the plasma membrane as a necessary step for its effect on inositol lipid hydrolysis.

Adaptor Proteins, Signal Transducing↗

PubMed1997

Biphasic transitions of a hairpin hexanucleotide triplex DNA.

The conformational transitions (helix-coil transitions) of three hairpin triple helices, models 5'-(A-G)(3) + 5'-(T-C)(3)-T(4)-((br)C-T)(3) [CY], 5'-(A-G)(3) + 5'-(T-(br)C)(3)-T(4)-(C-T)(3) [YC] and 5'-(A-G)(3) + 5'-(T-(br)C)(3)-T(4)-((br)C-T)(3) [YY], are characterized in this work by UV spectroscopy. Melting of these triplexes is biphasic, and the profiles are used to obtain the thermodynamic parameters. The thermodynamic properties of the hairpin triplex are T(m) = 19.45 degrees C and DeltaH(vH) = 293.12 kJ mol(-1) for CY, T(m) = 22.85 degrees C and DeltaH(vH) = 256.63 kJ mol(-1) for YC and T(m) = 28.47 degrees C and DeltaH(vH) = 234.68 kJ mol(-1) for YY at pH 4.4. Those of the duplex are T(m) = 30.50 degrees C and DeltaH(vH) = 427.09 kJ mol(-1) for CY, T(m) = 32.96 degrees C and DeltaH(vH) = 374.47 kJ mol(-1) for YC and T(m) = 33.24 degrees C and DeltaH(vH) = 329.67 kJ mol(-1) for YY at pH 4.4. The distinct transitions of triplex to duplex and duplex to single strands are analyzed using the nearest-neighbor Ising model. Electrostatic effects on each conformation are also analyzed.

Journal Article↗