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Biomedical subjects

C M Teng

Publications and source records attributed to C M Teng.

At least 253 records · Page 14Linked to original sources
PubMed1985

Species difference in the fibrinogenolytic effects of alpha- and beta-fibrinogenases from Trimeresurus mucrosquamatus snake venom.

Alpha- and beta-fibrinogenases prepared from Trimeresurus mucrosquamatus venom digested specifically the alpha(A) and beta(B) chains of the fibrinogen molecule, respectively. alpha-Fibrinogenase digested bovine fibrinogen more markedly than human fibrinogen, while beta-fibrinogenase digested human fibrinogen more markedly than bovine fibrinogen. Human fibrin was also digested by both enzymes. Plasma fibrinogens of 4 animal species were digested by alpha-fibrinogenase to the same degree, while those by beta-fibrinogenase in the following order: human greater than dog greater than guinea-pig greater than rabbit. The fibrinogenolytic effects of alpha-fibrinogenase on human fibrinogen were strongly inhibited by sera of the 4 animal species, while those of beta-fibrinogenase were inhibited in the following order: rabbit greater than guinea-pig greater than dog greater than human. It was concluded that the different activities of the protease inhibitors in the plasma of animal species are mainly responsible for the sensitivity differences.

Animals↗
PubMed1985

Antiplatelet effect of hsien-ho-t'sao (Agrimonia pilosa).

The water extract of Hsien-Ho-T'sao (HHT) produced a dose-dependent inhibition on collagen-induced aggregation of platelet-rich plasma (PRP). The IC50 was about 3.5 mg/ml. In addition, HHT inhibited also the aggregation induced by ADP, A23187 or arachidonate in PRP. Greater inhibition was observed in the preparation of washed platelets. Increase of the calcium concentration in medium could not overcome the inhibitory effect of HHT. ATP release from platelets induced by collagen or A23187 was inhibited by HHT. In the presence of EDTA, ATP release caused by thrombin or A23187 was also inhibited by HHT. Malondialdehyde and thromboxane B2 formation was greatly inhibited by HHT in platelets challenged by collagen and thrombin. In arachidonate-stimulated platelets, thromboxane B2, but not malondialdehyde formation was inhibited. HHT showed more marked inhibition on aggregation in the presence of indomethacin, creatine phosphate/creatine phosphokinase or a combination of both. Hydrogen peroxide-induced hemolysis was marked reduced by HHT. It was concluded that HHT might have some membrane-active properties which interfered with the activation of phospholipase A2.

Adenosine Triphosphate↗
PubMed1984

Antiplatelet effect of capsaicin.

Capsaicin was found to be a potent inhibitor of platelet aggregation and release reaction. It inhibited the aggregation of rat platelet induced by collagen and thrombin, but only slightly reduced those of AA and A23187. The IC50 on collagen-induced platelet aggregation was about 85 micrograms/ml. Less inhibition was observed in the aggregation of platelet-rich plasma. Increase of the calcium concentration could not overcome the inhibitory effect. Washing of the capsaicin-pretreated platelets only partially reversed the inhibition. Capsaicin also inhibited ATP release induced by thrombin and A23187 in the presence of EDTA. MDA and TXB2 formation were markedly inhibited by capsaicin in platelets challenged by collagen, thrombin and A23187. In AA-stimulated platelets, MDA formation was slightly decreased and TXB2 formation was not affected. Capsaicin showed more marked inhibition in the presence of CP/CPK, indomethacin or a combination of both. Capsaicin reduced the hemolysis of RBCs induced by hydrogen peroxide or hypotonicity. It was concluded that capsaicin had some membrane stabilizing property and this might lead to the interference of the activation of phospholipase A2.

Adenosine Triphosphate↗
PubMed1984

XC 386: a new antiplatelet agent.

XC386 was a new antiplatelet compound, which inhibited the aggregation and release reaction of rat platelet-rich plasma induced by collagen. This inhibition was dose-dependent and the IC50 was calculated to be 1 mM on collagen-induced aggregation. In washed platelets, the aggregations induced by ADP and collagen were much more markedly inhibited by XC386 than those induced by thrombin, A23187 and arachidonate. High calcium (4 to 8 mM) could not antagonize the inhibition. XC386 did not alter the malondialdehyde (MDA) and thromboxane B2 (TXB2) levels of resting platelets. But MDA formation induced by collagen, thrombin and A23187, and TXB2 formation induced by collagen and thrombin were significantly inhibited, while both formations induced by arachidonate were not changed. Combination of indomethacin or CP/CPK and XC386 enhanced markedly the inhibitory effect of XC386 on collagen- or A23187-induced aggregation. It was concluded that XC386 might inhibit platelet aggregation before the step of arachidonic acid release by phospholipase A2.

Adenosine Diphosphate↗
PubMed1984

Biphasic effect on platelet aggregation by phospholipase a purified from Vipera russellii snake venom.

A basic phospholipase A was isolated from Vipera russellii snake venom. It induced a biphasic effect on washed rabbit platelets suspended in Tyrode's solution. The first phase was a reversible aggregation which was dependent on stirring and extracellular calcium. The second phase was an inhibitory effect on platelet aggregation, occurring 5 min after the addition of the venom phospholipase A without stirring or after a recovery from the reversible aggregation. The aggregating phase could be inhibited by indomethacin, tetracaine, papaverine, creatine phosphate/creatine phosphokinase, mepacrine, verapamil, sodium nitroprusside, prostaglandin E1 or bovine serum albumin. The venom phospholipase A released free fatty acids from synthetic phosphatidylcholine and intact platelets. p-Bromophenacyl bromide-modified venom phospholipase A lost its phospholipase A enzymatic and platelet-aggregating activities, but protected platelets from the aggregation induced by the native enzyme. The second phase of the venom phospholipase A action showed a different degree of inhibition on platelet aggregation induced by some activators in following order: arachidonic acid greater than collagen greater than thrombin greater than ionophore A23187. The longer the incubation time or the higher the concentration of the venom phospholipase A, the more pronounced was the inhibitory effect. The venom phospholipase A did not affect the thrombin-induced release reaction which was caused by intracellular Ca2+ mobilization in the presence of EDTA, but inhibited collagen-induced release reaction which was caused by Ca2+ influx from extracellular medium. The inhibitory effect of the venom phospholipase A and also lysophosphatidylcholine or arachidonic acid could be antagonized or reversed by bovine serum albumin. It was concluded that the first stimulatory phase of the venom phospholipase A action might be due to arachidonate liberation from platelet membrane. The second phase of inhibition of platelet aggregation and the release of ATP might be due to the inhibitory action of the split products produced by this venom phospholipase A.

Adenosine Triphosphate↗
PubMed1984

Purification and properties of the main coagulant and anticoagulant principles of Vipera russellii snake venom.

Vipera russellii venom was separated into thirteen fractions by means of DEAE-Sephadex A-50 column chromatography. Fraction III possessed anticoagulant and phospholipase A activities and Fraction XI possessed procoagulant and caseinolytic activities, both were further purified by gel filtration on Sephacryl S-200 column. Purified procoagulant (Component II) was a two-chain protein with molecular weight of 86 000 consisting of A-chain (Mr 66 000) and B-chain (Mr 20 000). It was a glycoprotein containing 7.8% neutral sugar and 715 amino-acid residues. The procoagulant activity was 10-times that of the crude venom. It was an acidic proteinase with isoelectric point of pH 4.2. Upon heat treatment at 60 degrees C, Component II was stable at pH 5.5 and 7.2 for 3 h, but was destroyed completely after 30 min at pH 8.9. It was devoid of esterase or amidase activity. Purified anticoagulant (Component I) was a single peptide chain with molecular weight of 16 000. It was carbohydrate free and contained 136 amino-acid residues. It was a basic protein with an isoelectric point of larger than pH 10. It was a potent phospholipase A with an enzymatic activity of 510 +/- 30 mumol/min per mg using phosphatidylcholine as substrate, and 1 microgram/ml was sufficient to cause 100% hemolysis by the indirect hemolytic method. Upon heat treatment at 90 degrees C, Component I was heat stable at pH 5.5 for more than 3 h, but was destroyed completely after 2 h at pH 7.2 and 8.9. The anticoagulant activity of Component I could be neutralized by platelet factor 3, tissue thromboplastin and cephalin.

Amino Acids↗
PubMed1984

Cardiotoxin from Naja naja atra snake venom: a potentiator of platelet aggregation.

Cardiotoxin, isolated from Naja naja atra snake venom, potentiates platelet aggregation induced by ADP, thrombin, collagen and venom phospholipase A2. The malondialdehyde formation caused by ADP, thrombin and venom phospholipase A2 were also increased in the presence of cardiotoxin. Both potentiation of aggregation and increase in malondialdehyde were blocked by indomethacin or Ca2+ (5 mM or 0.05 mM). Cardiotoxin did not potentiate thrombin-induced aggregation of p-bromophenacyl bromide-modified platelets. Thromboxane B2 formation induced by thrombin or collagen was also increased by cardiotoxin, while that by arachidonate was not affected. As a membrane-active polypeptide, cardiotoxin might augment the Ca2+-flux during the activation of the platelet membrane by aggregation inducers and then increase the activation of endogenous phospholipase A2.

Adenosine Diphosphate↗
PubMed1984

Edema formation and degranulation of mast cells by Trimeresurus mucrosquamatus snake venom.

Trimeresurus mucrosquamatus venom, carrageenin, compound 48/80, trypsin and bovine serum albumin were injected s.c. into the plantar muscle to induce edema formation in the hind paw of rats. The venom was the most potent, and it and compound 48/80 induced the maximum swelling rate of edema within 15 - 30 min after injection. The edema volume induced by the venom was dose-dependent between 2.5 and 10 micrograms. Hydrocortisone, phenylbutazone, indomethacin and diphenhydramine inhibited edema induced by the venom and other inflammatory agents. Diphenhydramine was the most effective inhibitor of edema and increased vascular permeability induced by the venom. Injection of the venom i.p. caused exocytosis and degranulation of mesentery mast cells with a decreased electron density of released granules. Systemic administration of diphenhydramine inhibited the venom-induced exocytosis. Diphenhydramine and pyrilamine inhibited the contraction of guinea-pig ileum caused by venom or compound 48/80. It is concluded that histamine released from mast cells plays an important role in the causation of the edema induced by Trimeresurus mucrosquamatus snakebites.

Animals↗
PubMed1984

Presynaptic and musculotropic effects of a basic phospholipase A2 from the Formosan habu (Trimeresurus mucrosquamatus) venom.

A basic phospholipase A2 purified from the venom of a crotalid snake (Trimeresurus mucrosquamatus) was applied to chick and mouse neuromuscular preparations. The enzyme at lower concentrations (1-3 micrograms/ml) blocks neuromuscular transmission at a presynaptic site, while at higher concentrations (10-30 micrograms/ml) it causes contracture and depolarization of the muscle as well. It is concluded that the mode of action of the enzyme on vertebrate nerve-muscle transmission is similar to that of notexin and ceruleotoxin from elapid snake venoms.

Animals↗
PubMed1984

Antihemostatic effect of Hsien-Ho-T'sao (Agrimonia pilosa).

Bleeding time in rats was markedly prolonged after the administration of the water extract of Hsien-Ho-T'sao. This antihemostatic effect was more marked in the group of i.p. injection of the drug than in the group of p.o. administration for 2 or 7 consecutive days. Blood coagulation studies showed that plasma prothrombin time, activated partial thromboplastin time and stypven time were prolonged, while thrombin time and fibrinogen level were not changed. The thromboelastographic recording showed that reaction time was prolonged and maximal elasticity of clot was decreased. In addition, ADP- and collagen- induced aggregations of platelet-rich plasma were suppressed. In conclusion, the prolongation of the bleeding time might be due to both anticoagulant and antiplatelet action of the drug.

Animals↗
PubMed1983

Liquid-chromatographic quantification of piracetam.

Piracetam, an analog of gamma-aminobutyric acid, absorbs maximally at 197 nm. Its molar absorptivity at 208 nm and pH 4.5 is 3576 (SD 251) L . mol-1 cm-1, approximately 45% of its absorptivity at 197 nm. Direct quantification of piracetam at 197 nm in biological extracts is complicated by the fact that many other compounds absorb between 190 and 220 nm due to carbon-nitrogen bonding. Chromatography of methanol extracts of serum and aqueous humor on a reversed-phase C-18 column developed isocratically with KH2PO4 (0.1 mol/L, pH 4.8) allows detection and quantification of 0.2 mmol of piracetam per liter. Under these conditions the retention time of piracetam is about 5 min. The detector response is linear for quantities between 5 and 15 nmol. The method is rapid, inexpensive, and convenient for the clinical laboratory.

Animals↗