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Biomedical subjects

Q C Wang

Publications and source records attributed to Q C Wang.

At least 37 records · Page 2Linked to original sources
PubMed1993

Macroporous polymeric stationary-phase rod as continuous separation medium for reversed-phase chromatography.

A macroporous poly(styrene-co-divinylbenzene) rod has been prepared by a free-radical polymerization of a mixture containing monomers, initiator, and porogenic solvent in the confines of a chromatographic column and used for the first time in the very fast reversed-phase HPLC of proteins. Characterization of the pore structure of the continuous rod by mercury intrusion porosimetry revealed a large volume of pores with a diameter of about 1 micron to pores below 100 nm. Size exclusion chromatography and scanning electron microscopy confirmed the unusual pore size distribution. The presence of large pores make the rod easily permeable to eluents, and therefore, the back pressure of the rod column is modest even at high flow rates. The efficiency of the polymerized column is almost independent of the flow rate. The slope of the line showing capacity factor vs composition of the mobile phase was determined for several proteins, and a gradient for the separation of their mixtures was developed. Excellent separation was achieved even at a high flow rate of 25 mL/min as documented by the resolution data. Tripling the length of the column did not improve the column resolution in protein separation.

Chromatography, High Pressure Liquid↗
PubMed1993

Effects of an acidic phospholipase A2 purified from Ophiophagus hannah (king cobra) venom on rat heart.

An acidic phospholipase A2 (OHV A-PLA2) purified from Ophiophagus hannah venom had a cardiotoxic action on rat heart. In rats OHV A-PLA2 (2-4 mg/kg) caused ECG abnormalities including decreased heart rate, prolonged P-R interval, widened QRS complex and complete A-V block. When tested on isolated rat right atria, OHV A-PLA2 (10-20 micrograms/ml) produced a positive chronotropic effect. When tested on isolated rat left atria or papillary muscle preparations, OHV A-PLA2 (2.5-20 micrograms/ml) caused positive inotropic effect, followed by contracture. The positive inotropic effects could be abolished by high Ca2+ and enhanced by low Ca2+; both treatments accelerated contracture. The contracture could be inhibited in Mn2+ (5 mM)-containing medium and abolished by Ca(2+)-free bath solution containing 1 mM EDTA. The cardiotoxic action of OHV A-PLA2 was not influenced by verapamil, tetrodotoxin, propranolol, phentolamine, atropine or indomethacin. It is suggested that the cardiotoxic effects of OHV A-PLA2 may result from increasing intracellular levels of Ca2+.

Anesthesia↗
PubMed1993

Pharmacokinetics of cytotoxin from Chinese cobra (Naja naja atra) venom.

The pharmacokinetics of cytotoxin from Chinese cobra (Naja naja atra) venom was studied in rabbits after i.v. and i.m. injection of 0.2 and 0.5 mg.kg-1, respectively. The plasma levels of the cytotoxin were analysed by a biotin-avidin enzyme-linked immunosorbent assay. The plasma concentration-time course after i.v. administration fitted a two-compartment open model. The half-life (mean +/- S.D.) of the alpha-phase was 5.8 +/- 0.6 min and that of the beta-phase 3.5 +/- 0.2 hr. Apparent volume of distribution was 1.7 +/- 0.3 litres.kg-1, and clearance was 5.6 +/- 1.4 ml.min-1. A rapid absorption was observed after i.m. injection with peak plasma level of 260 +/- 90 ng.ml-1 reached within 13.6 +/- 2.4 min. The absorption rate constant was 0.16 +/- 0.03 ml-1. The area under the plasma concentration-time curve was 33 +/- 15 micrograms.min.ml-1.

Animals↗
PubMed1993

[Purification and anticancer activity of cytotoxin-14 from venom of Naja naja atra].

Ion-chromatography of lyophilized cobra (Naja naja atra) venom on SP-Sephadex C-50 yielded 14 fractions, of which 7, 8, 9, and 10 possessed neurotoxic actions and 11, 12, 13, and 14 had cytotoxic activities. Chromatography of fraction 14 on SP-Sephadex C-25 gave cytotoxin-14. It was homogeneous on polyacrylamide gel electrophoresis with m = 7448 Da. It was a typical cytotoxin without phospholipase A2 activity and had a selective cytotoxic action on human cancer cell lines.

Animals↗
PubMed1992

Polymeric porogens used in the preparation of novel monodispersed macroporous polymeric separation media for high-performance liquid chromatography.

A novel approach to monosized macroporous polymeric separation media with vastly enhanced pore size distributions and chromatographic properties has been developed. Key to this approach is the combined use of monodispersed polymeric particles and suitable solvents as porogens in the copolymerization of styrene and divinylbenzene. Following polymerization, the polymeric porogen is dissolved, leaving behind the monosized beads with a controlled pore structure. The exact pore size and pore size distribution of the final beads are largely controlled by the amount of soluble polymer in the polymerizing mixture: the larger the proportion of soluble polymer in the system, the larger the pores. The uniformly sized macroporous beads prepared with an optimized ratio of polymeric and low molecular weight porogens proved to be very efficient even in short columns for the separation of polystyrene standards in the SEC mode and the separation of proteins in the reversed-phase mode. The relationship between pore size and specific surface area, on one hand, and chromatographic properties of the stationary phase, on the other, have been clearly documented.

Chromatography, High Pressure Liquid↗
PubMed1992

[Pharmacokinetics of cytotoxin 14 from Naja naja atra venom].

The pharmacokinetics of cytotoxin 14 (CT 14) from Naja naja atra venom was studied with biotin-avidin enzyme-linked immunosorbent assay. The plasma concentration-time curve of CT 14 after bolus i.v. 0.2 mg.kg-1 into rabbits was found to fit a two-compartment open model. T1/2 alpha was 5.8 +/- 0.6 min and T1/2 beta was 3.5 +/- 0.2 h. A rapid absorption was seen after im injection (0.5 mg.kg-1) to rabbits. The peak level was 260 +/- 90 ng.ml-1 and Tpeak was 13.6 +/- 2.4 min. The absolute bioavailability was 34 +/- 9%. It was shown that CT 14 was absorbed by gut. The peak level was 75 +/- 15 ng.ml-1 after a gastric gavage of 50 mg.kg-1 to rats.

Animals↗
PubMed1992

[Biotin-avidin-ELISA for cytotoxin purified from cobra venom].

A technique combining the biotin-avidin amplifying system with sandwich enzyme-linked immunosorbent assay (B-A-ELISA) was developed for the microassay of the cytotoxin from Naja naja atra venom. The horse-peroxidase was used as the marker and polystyrene microhemagglutination plates as solid carrier. The sensitivity was 0.5 ng.ml-1. The assay range was 1.25-320 ngml-1 with coefficient of variation of 4.9% (intragroup) and 8.1% (intergroups), respectively.

Animals↗
PubMed1991

Trichosanthin-monoclonal antibody conjugate specifically cytotoxic to human hepatoma cells in vitro.

A plant single-chain ribosome-inactivating protein derived from the root tuber of Trichosanthes kirilowii, termed trichosanthin (TCS), was modified with 2-iminothiolane. It was not like trichokirin, a ribosome-inactivating protein derived from the seeds of the same plant, in that TCS retained full activity when 1.5 sulfhydryl groups were introduced into each TCS molecule by 2-iminothiolane modification. The 2-iminothiolane-TCS was conjugated to Hepama-1, a monoclonal antibody directed against human hepatoma with a cross-linking reagent, N-succinimidyl-3-(2-pyridyl)-dithiopropionate. The hepatoma cytotoxicity of the immunotoxin, TCS-Hepama-1, was 500-fold higher than that of free TCS and only 1 log lower than that of free ricin. However, the immunotoxin was approximately 600-fold less cytotoxic to HeLa cells. The results suggested that the immunotoxin was a potent and quite specific antihepatoma agent and might have considerable potential in hepatoma therapy.

Antibodies, Monoclonal↗
PubMed1986

Mechanism of action of the platelet function inhibitor from Vipera russelli siamensis snake venom.

Human platelet aggregation induced by ADP, adrenaline, collagen or thrombin was inhibited by the venom inhibitor. Heating reduced both its phospholipase A2 enzymatic and anti-aggregatory activities, although not in parallel. The inhibitor caused significant dose-related inhibitory effects on the clot retraction of rabbit platelet-rich plasma caused by thrombin, while platelet malondialdehyde formation stimulated by thrombin was not affected. Furthermore, the venom inhibitor increased basal cyclic AMP levels in platelets, while cyclic GMP content was slightly lowered, but not in a dose-dependent manner. In addition, microscopic study revealed that the cytoskeleton was disordered after treatment of platelets with the venom inhibitor. The platelets lost their discoid form, while the ultrastructural changes of platelet aggregation induced by ADP were blocked. It is concluded that increasing platelet cyclic AMP and the disorder of the cytoskeleton may be the mechanism of action of the venom inhibitor on platelet function.

Adenosine Diphosphate↗
PubMed1985

A platelet function inhibitor purified from Vipera russelli siamensis (Smith) snake venom.

By means of CM-Sephadex C-50 column chromatography and gel filtration on Sephadex G-75, a potent platelet function inhibitor was purified from Vipera russelli siamensis venom. It appeared as a single protein band on polyacrylamide gel electrophoresis in the presence or absence of SDS, and consists of 123 amino acid residues. Its NH2-terminal residue is serine. It showed the following characteristics: molecular weight, 13,800; isoelectric point, 10.4; LD50, 0.5 +/- 0.12 mg/kg (i.v.). The platelet inhibitor exhibited phospholipase A2 activity with a specific activity of 35 mumoles/min/mg. From 2 g of the venom, 70 mg of the purified inhibitor was obtained. Inhibition of human platelet aggregation induced by ADP or adrenaline was dose-dependent, with ID50 of 1.14 micrograms/ml or 0.37 microgram/ml, respectively. The platelet aggregation induced by thrombin or collagen was also inhibited and the inhibitory activity on platelet aggregation was heat stable (at 100 degrees C, 20 min) in an acidic medium (pH 5.8), while its phospholipase A2 activity was relatively heat labile under the same condition. The release of 3H-serotonin in platelets stimulated by ADP was also inhibited and this was positively correlated with inhibition of platelet aggregation induced by ADP (r = 0.998, P less than 0.002).

Amino Acids↗
PubMed1985

Kinetics of protein synthesis inactivation in human T-lymphocytes by selective monoclonal antibody-ricin conjugates.

Immunotoxins synthesized with the pan-T-cell monoclonal antibody T101 and ricin, acetylricin, or ricin A-chain have been compared. Native ricin was acetylated with N-acetylimidazole to block the galactose-binding site of the toxin B (binding)-chain. In the presence of lactose, both whole-ricin-containing immunotoxins were selectively cytotoxic but the ricin A-chain conjugate was less effective in blocking cellular protein synthesis. Immunotoxin-treated cells cultured in fresh growth medium exhibited no growth, declining viabilities, and no protein synthesis activity. Lymphocytes treated with T101:ricin or ricin did not form clusters or colonies when plated in 0.3% Bacto-agar. Ammonium chloride markedly enhanced the efficacy of T101:ricin and T101:ricin A-chain. Our results suggest that: (a) all immunotoxins were selectively cytotoxic; (b) in the presence of ammonium chloride the effectiveness of the T101:ricin A-chain conjugate approached that of T101:ricin; and (c) the toxin B-chain may facilitate conjugate internalization and/or processing.

Acetylation↗
PubMed1983

Monoclonal antibody and an antibody-toxin conjugate to a cell surface proteoglycan of melanoma cells suppress in vivo tumor growth.

A monoclonal antibody directed against a cell surface chondroitin sulfate proteoglycan of human melanoma cells, 9.2.27, and its diphtheria toxin A chain (DTA) conjugate were investigated for their effects on in vitro protein synthesis and in vivo tumor growth of human melanoma cells. The 9.2.27 IgG and its DTA conjugate display similar serological activities against melanoma target cells but only the conjugate can induce consistent in vitro inhibition of protein synthesis and toxicity in M21 melanoma cells. However, both 9.2.27 IgG and its DTA conjugate effect significant suppression of M21 tumor growth in vivo in an immunotherapy model of a rapidly growing tumor in athymic nu/nu mice, suggesting that other host mechanisms may mediate monoclonal antibody-induced tumor suppression.

Animals↗