PubMed Health⌕ Search

Biomedical subjects

G D Liu

Publications and source records attributed to G D Liu.

18 recordsLinked to original sources
PubMed2001

Renewable amperometric immunosensor for Schistosoma japonium antibody assay.

A renewable amperometric immunosensor has been proposed for the determination of Schistosoma japonium antibody (SjAb) in rabbit serum. A paraffin-graphite-Schistosoma japonium antigen (SjAg) biocomposite, which needs no additional curing, was directly used to construct the immunosensors. The analytical sample containing the desired SjAb was mixed with SjAb labeled with horseradish peroxidase (HRP) to form the incubation solution for the competitive binding assay. Amperometry was used to determine the amount of HRP fixed on the sensor surface, which was related to the content of desired SjAb. Assay conditions were optimized, including the selection of substrate, the loading of SjAg in the biocomposite, the amount of labeled SjAb in the incubation solution, the incubation time, and the temperature. Using o-aminophenol (o-AP) as a substrate, amperometric detection at -200 mV (vs SCE) resulted in a pseudolinear detection range of about 0.36 to 14 microg/mL, with a detection limit of 0.36 microg/mL. Rabbit serum samples with varying infection degrees were analyzed, and the results demonstrated that the concentration that is detectable in this system meets the demands of clinical analyses. A new surface on the immunosensor for use in another competitive assay can be obtained by removing the original one and polishing the surface.

Animals↗
PubMed2001

Renewable amperometric immunosensor for complement 3 assay based on the sol-gel technique.

A renewable amperometric immunosensor based on the sol-gel technique has been constructed by dispersing graphite, complement 3 (C3) antiserum, and sol-gel at low temperature. The prepared immunosensor is rigid, porous, and has a renewable external surface. A competitive binding assay has been used to determine C3 in human serum with the aid of C3 labeled with horseradish peroxidase. The enzyme-labeled antigen can readily diffuse toward the encapsulated antibody, which retains its binding properties. The experimental conditions for the assay with the biocomposite, including the loading of C3 antiserum in the biocomposite, the amount of labeled C3 in incubation solution, incubation time, and temperature, have been optimized. Using C3 labeled with horseradish peroxidase, and o-AP as the substrate, amperometric detection at -150 mV (relative to the SCE) results in a linear detection range of 1.17-35.1 microg mL(-1), with a detection limit of 0.56 microg mL(-1). Serum samples have been assayed and the results demonstrate the feasibility of the proposed immunosensor for clinical analysis. The surface of the immunosensor can be renewed simply by polishing to obtain a fresh immunocomposite ready to use in a new competitive assay.

Biosensing Techniques↗
PubMed2001

Fluorescence spectral study of interaction of water-soluble metal complexes of Schiff-base and DNA.

The fluorescence spectral characteristics and the interaction of several water-soluble metal complexes of Schiff-base with DNA are described. Among the complexes tested, Mn-Schiff-base bound to DNA showed a marked decrease in the fluorescence intensity with a blue shift of the excitation and emission peaks. Some hypochromism in the UV absorption spectra was also observed. KI quenching and competitive binding to DNA between Mn-Schiff-base and ethidium bromide (EB) were studied in connection with other experimental observations to show that the interactive model between Mn-Schiff-base and DNA is an intercalative one. The pH and salt effect on the fluorescence properties was also investigated. The linear relationship between F/F0 and the concentration of calf thymus DNA covers 3.0 x 10(-6)-2 x 10(-4) mol L-1, which can be utilized for determining traces of calf thymus DNA with a detection limit of 8.0 x 10(-7) mol L-1 in base pairs.

DNA↗
PubMed2001

Hepatitis C virus infection of human hepatoma cell line 7721 in vitro.

AIM: To establish a cell culture system with long-term replication of hepatitis C virus in vitro. METHODS: Human hepatoma cell line 7721 was tested for its susceptibility to HCV by incubating with a serum from a patient with chronic hepatitis C. Cells and supernatant were harvested at various phases during the culturing periods. The presence of HCV RNA, the expression of HCV antigens in cells and/or supernatant were examined by RTPCR, in situ hybridization and immunohistochemistry respectively. RESULTS: The intracellular HCV RNA was first detected on d2 after infection and then could be intermittently detected in both cells and supernatant over a period of at least three months. The expression of HCV NS3,CP10 antigens could be observed in cells. The fresh cells could be infected by supernatant from cultured infected cells and the transmission of viral genome from HCV-infected 7721 cells to PBMCs was also observed. CONCLUSION: The hepatoma line 7721 is not only susceptible to HCV but also supports its long-term replication in vitro.

Antigens, Viral↗
PubMed2000

Renewable amperometric immunosensor based on paraffin-graphite-transferrin antiserum biocomposite for transferrin assay.

A renewable electrochemical immunosensor was developed for the determination of transferrin in human serum. It is based on a paraffin-graphite-transferrin antiserum biocomposite, which needs no additional curing. A competitive binding assay was used to determine transferrin in human serum with the aid of transferrin labeled with horseradish peroxidase. The assay conditions were optimized, including the loading of transferrin antiserum in the biocomposite, the amount of labeled transferrin in the incubation solution, incubation time and temperature. Serum samples were analyzed and the results demonstrate that the concentration range of determination with this system meets the demands of clinical analysis. The surface of the immunosensor can be regenerated by simply polishing to obtain a fresh immunocomposite ready to be used in a new competitive assay.

Biosensing Techniques↗
PubMed1999

Basic fibroblast growth factor enhanced LAK cell cytotoxicities against human bladder neoplasm cells.

AIM: To study the effects of basic fibroblast growth factor (bFGF) on the proliferation of lymphokine-activated killer (LAK) cells from patients with bladder cancer and LAK cells cytolysis against bladder tumor cells. METHODS: LAK cell proliferation was assayed in the presence of various concentrations of bFGF combined with interleukin-2 (IL-2) by cell count. Cytotoxicity of LAK cells against bladder cancer cell line EJ cells and bladder tumor cells (BTC) from patients was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. RESULTS: The proliferation of peripheral blood monocytes (PBMC) was inhibited by bFGF 5 micrograms.L-1. bFGF did not affect the stimulation of LAK cells induced by IL-2. The LAK cell numbers in the combination of IL-2 with bFGF were not significantly different compared with that treated with IL-2 alone. bFGF enhanced cytotoxicity of LAK cells against bladder cancer cell line EJ cells or BTC, respectively. CONCLUSION: Although the proliferation of PBMC was inhibited by bFGF, bFGF increased LAK cell cytotoxicity against bladder neoplasm cells.

Carcinoma, Transitional Cell↗
PubMed1998

Modulating effect of mitomycin or cisplatin on lymphokine-activated killer cell proliferation and antitumor activity to bladder cancer cell lines in vitro.

AIM: To study the effect of mitomycin (Mit) or cisplatin (Cis) on the proliferation of lymphokine-activated killer (LAK) cells in patients with transitional cell cancer of bladder and their cytolysis to bladder tumor cells. METHODS: LAK cell proliferation was assayed in the presence of Mit or Cis by cell counting. Bladder cancer cell lines BIU-87 and EJ were cultured as target cells and cytotoxicity of LAK cells was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. RESULTS: The proliferation of LAK cells induced by recombinant interleukin-2 (IL-2) was inhibited by Cis in a concentration-dependent manner and was decreased to 55.3% at 100 mg.L-1 compared with control at 96 h. The enhanced growth of the LAK cells was observed with Mit 5-10 mg.L-1 from 48 to 96 h. Cis 10 mg.L-1 increased the cytotoxicity against BIU-87 and EJ cells. CONCLUSION: Immunomodulatory effect of chemotherapeutic agents on LAK cell proliferation induced by IL-2 in patients with bladder cancer mainly depends on the drug itself.

Antibiotics, Antineoplastic↗
PubMed1997

Tretinoin or retinol enhancement of lymphokine-activated killer cell proliferation and cytotoxicity against human bladder cancer cells in vitro.

AIM: To study the effect of tretinoin (Tre) or retinol (Ret) on the proliferation of lymphokine-activated killer (LAK) cells in patients with transitional cell cancer of bladder and their cytolysis to bladder tumor cells. METHODS: LAK cell proliferation was assayed in the presence of either Tre or Ret by cell counting. Human transitional bladder cancer cell lines BIU-87, EJ, or bladder tumor cells (BTC) from patients with bladder cancer were used as target cells and cytotoxicity of LAK cells was determined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. RESULTS: The proliferation of LAK cells induced by interleukin-2 (IL-2) was stimulated by Tre or Ret (10-100 nmol.L-1). The cytotoxicity of LAK cells against BIU-87, EJ cells, or BTC was enhanced by pretreatment of LAK cells with Tre or Ret 10-100 nmol.L-1. CONCLUSION: Tre or Ret enhances the proliferation and cytotoxicity of LAK cells from patients with bladder cancer. Retinoids are potential in adoptive immunotherapy of bladder cancer.

Antineoplastic Agents↗
PubMed1989

Effect of extract of Hirudo Medicinalis L. against adherence of calcium oxalate crystals to acid-injured bladder mucosa.

The effect of extract of Hirudo Medicinalis L. on preventing the adhesion of calcium oxalate crystals to 0.1 M hydrochloric acid-injured bladder urothelium of the rat was studied. It was found that in this species the extract coated to the bladder mucosa after it was instilled into the chemically injured bladder; and the adhesion of calcium oxalate crystals was prevented. In regard to the anti-adhesion property the Hirudo extract appears more effective than heparin, a documented glycosaminoglycan.

Adhesiveness↗
PubMed1989

Prevention of postischemic reperfusion damage on isolated working rat hearts by bopindolol and propranolol.

Reperfusion after 30-min regional or global ischemia of the isolated working rat hearts did not restore the cardiac functions (as measured by cardiac output and power production), but exacerbated the existing damages. The lipid peroxidation product malondialdehyde (MDA) in the regional and global ischemic-reperfused myocardium increased by 37.6 and 45.2%, respectively. Bopindolol 0.1 mumol/L and propranolol 10 mumols/L protected the myocardium against the postischemic reperfusion damages, accelerated the recovery of cardiac functions during reperfusion and decreased the MDA content in the ischemic-reperfused myocardium. It is postulated that the prevention of cardiac cells from lipid peroxidation injury is related to the protection afforded by the drugs to the ischemic-reperfused hearts.

Adrenergic beta-Antagonists↗