Bites of venomous reptiles

Bites by venomous reptiles are statistically of minor importance in North America, especially as regards medically significant envenomations. However, they may assume a greater relative incidence in warmer regions and always manage to generate public and professional interest wherever they occur. Unproved and potentially hazardous first-aid and institutional therapies must be subjected to scrutiny in the future. Current research in the area of more specific and less reactive antivenin products is encouraging, and it appears that a consensus approach to the care of the bitten patient is emerging. Physicians are encouraged to consult with regional poison control centers in the care of these patients unless they are well experienced in this unique and complicated area.

Coagulant and anticoagulant actions of Australian snake venoms

A systematic study was made of the action on the plasma coagulation system of 20 Australian and Papuan Elapid and Hydrophiid snake venoms and compared with 4 Crotalid venoms and 1 Viper. The majority of Australian venoms were shown to be prothrombin activators with variable dependence on the presence of factor V phospholipid and calcium. None of these venoms had strong thrombin like activity in contrast to the Crotalid venoms which were powerfully thrombin like. The Crotalid venoms were also strongly fibrinolytic unlike the Elapid venoms which showed no or minimal evidence of fibrinolytic activity. Four Elapid venoms and 2 Crotalid venoms showed anticoagulant activity which contained neither antithrombin nor fibrinogenolytic activity and may act upon the prothrombin complex.

Time of onset of clinical envenomation following snakebite

The time of onset of clinical envenomation in 58 cases of snakebite is discussed. In all cases clinical envenomation was manifest within 1 hour. It is suggested that if symptoms and signs of poisoning have not become apparent within 1 hour, clinically significant envenomation has not occurred and will not occur.

Identification of domains of phosphatidylcholine in human erythrocyte plasma membranes. Differential action of acidic and basic phospholipases A2 from Agkistrodon halys blomhoffii

Highly purified acidic (pI 4.9) and basic (pI 8.7) phospholipases A2 from snake (Agkistrodon halys blomhoffii) venom hydrolyzed approximately 20% and 60%, respectively, of the phosphatidylcholine (PC) of intact human erythrocytes prior to hemolysis. Sequential use of the acidic enzyme followed by the basic phospholipase A2 or vice versa manifested a characteristic PC hydrolysis pattern. For example, when acidic enzyme had hydrolyzed nearly 20% of this substrate, a subsequent treatment with the basic enzyme hydrolyzed only an additional 40% of the PC before hemolysis. On the other hand, in experiments where hydrolysis of about 20% of PC of erythrocytes was achieved by a short term incubation with the basic enzyme, then a further treatment of the same cells with the acidic enzyme caused only 10% additional PC hydrolysis before hemolysis. This demonstrated that the acidic enzyme hydrolyzed one domain of PC in the intact erythrocytes, whereas the basic enzyme hydrolyzed not only the same but also another domain of PC in membranes. Analysis of fatty acids released by the action of these two phospholipases A2 on erythrocytes indicated further characteristic differences. In particular, the ratio of released saturated to unsaturated fatty acids was significantly higher with the acidic enzyme as compared with the basic phospholipase A2. These results provide firm support to the conclusion that there are different domains of PC in human erythrocyte membranes and that the acidic and basic phospholipase A2 of A. halys blomhoffii can be used to identify them.

Clinical aspects of bites by viper in Spain

Poisonings due to Viperidae bites are quite common in our country. There is a mortality of 3 to 7 cases out of 35 million inhabitants and a variable morbidity which increases in some years. From 1965 to 1980, about 125 cases of bites by Vipers latasti, 80 by V. aspis and 23 by V. seoanei received treatment. Fifty per cent of the cases received small doses of venom and presented proteolytic and coagulant reactions. With stronger doses the reactions were anticoagulant and hemolytic. Two cases affected by bites of V. aspis developed a neurotoxic syndrome with ptosis, dysphagia, dysphasia and paralysis of the bitten extremity. The specific treatment in the severe and moderate cases has been Pasteur and Zagreb antivenom.

Modification of the tetrodotoxin receptor in Electrophorus electricus by phospholipase A2

The effects of phospholipase A2 treatment on the tetrodotoxin receptors in Electrophorus electricus was studied. (1) The binding of [3H]tetrodotoxin to electroplaque membranes was substantially reduced by treatment of the membranes with low concentrations of phospholipase A2 from a number of sources, including bee venom, Vipera russelli and Crotalus adamanteus and by beta-bungarotoxin. (2) Phospholipase A2 from bee venom and from C. adamanteus both caused extensive hydrolysis of electroplaque membrane phospholipids although the substrate specificity differed. Analysis of the phospholipid classes hydrolyzed revealed a striking correlation between loss of toxin binding and hydrolysis of phosphatidylethanolamine but not of phosphatidylserine. (3) The loss of toxin binding could be partially reversed by treatment of the membranes with bovine serum albumin, conditions which are known to remove hydrolysis products from the membrane. (4) Equilibrium binding studies on the effects of phospholipase A2 treatment of [3H]tetrodotoxin binding showed that the reduction reflected loss of binding sites and not a change in affinity. (5) These results are interpreted in terms of multiple equilibrium states of the tetrodotoxin-receptors with conformations determined by the phospholipid environment.

Optimization of a mechanized amidolytic factor-X assay; influence of reaction conditions and reagents

We describe the effect of pH and NaCl concentration on the activation of factor X in plasma by Russell's viper venom and on the amidolytic activity of the activated enzyme towards factor Xa-sensitive chromogenic substrates. An increasing NaCl concentration results in a decrease in the activation rate of factor X by Russell's viper venom, whereas in this step no pH effect is observed. Increasing NaCl concentrations decrease the Km and Vmax for both the factor Xa-sensitive chromogenic substrates, S 2222 and S 2337. Km values were lowest between pH 7.8 and 8.6; Vmax increased with increasing pH. Comparison of NaCl and KCl in the activation step as well as in the amidolytic step shows that the observed effect is specific for Na+, not just an effect of ionic strength. No difference was detected between activation by the crude venom or its purified factor X-activating enzyme. Also, values with the substrates S 2222 or S 2337 were the same in the mechanized amidolytic factor X assay.

Renal ultrastructure in cortical necrosis following Russell's viper envenomation

Electron microscopic examination of biopsy material from two patients with renal cortical necrosis following Russell's viper bite, showed extensive destruction of glomerular and tubular cells with haemorrhage into the glomerular urinary space and tubules. The non-selective cell destruction seen suggests an ischaemic aetiology and the presence of fibrin in the glomeruli indicates that the ischaemia may be due to intravascular coagulation.

Envenoming by Cerastes viper - a report of two cases

Two cases of envenoming by Cerastes vipera are described Both were in snake collectors who were accidentally bitten on the finger while handling the snake. In both cases, local signs included a haemorrhagic bulla with fang marks, swelling and tenderness. These signs were mild in one case and moderately severe in the other, necessitating fasciotomy. No systemic signs were observed. Some coagulation abnormalities were found in both cases. In one, prolonged bleeding from the wound and a shortened euglobulin lysis time may suggest activation of the fibrinolytic mechanism. In the other, prolongation of prothrombin time occurred with no haemorrhagic diathesis. Treatment included fasciotomy in one case and elevation of the affected part and antibiotics in the other. It appears that the clinical course of this snakebite is relatively benign.

Mechanized amidolytic technique for determination of factor X and factor-X antigen, and its application to patients being treated with oral anticoagulants

We describe a mechanized chromogenic assay for factor X, the results of which correlate well with those for the one-stage clotting assays for factor X in which it is activated either via the extrinsic pathway by thromboplastin or directly by Russell's viper venom. We purified human factor X and raised monospecific antibodies to it in rabbits. We used our chromogenic assay for factor X to develop a factor-X-inhibitor neutralization assay for determination of factor-X antigen. Patients receiving oral anticoagulant treatment had significantly different factor-X activities after activation via thromboplastin or with Russell's viper venom. The concentration of factor-X antigen, although decreased, significantly exceeded factor-X clotting activity or chromogenic activity in this group of patients. Results of the chromogenic assay for factor X correlated well with results of "Thrombotest," a clotting test introduced by Owren (Lancet ii: 754, 1959) to control anticoagulant therapy. For patients taking oral anticoagulant drugs, the therapeutic range by our assay is 180 to 300 units/L.

Comparison of Pasteur and Behringwerke antivenoms in envenoming by the carpet viper (Echis carinatus)

Bites and envenoming by the carpet viper Echis carinatus are common medical emergencies in parts of Nigeria, but the most effective use of the various commercially produced antivenoms in treatment has not been established. Pasteur Paris Echis monospecific and Behringwerke West and North Africa Bitis-Echis-Naja polyspecific antivenoms were compared in two groups of seven patients with incoagulable blood after E carinatus bites. In both groups spontaneous bleeding stopped within a few hours and local swelling subsided within two weeks after the initial antivenom injection. Pasteur antivenom (20-40 ml) restored blood coagulability within 12 hours in all cases, but 60--180 ml of Behringwerke antivenom was effective in only four cases. Persisting venom procoagulant activity was observed in the remaining three cases. Despite its potency in the mouse protection test, Behringwerke antivenom is unreliable and unpredictable in neutralising venom procoagulant in humans bitten by E carinatus.

A kinetic analysis of the hydrolysis of synthetic arginine substrates by arginine esterases from the venom of the gabooon adder, Bitis gabonica

The kinetics of arginine esterases E-I, E-II and E-III from the venom of Bitis gabonica were investigated. With N alpha-benzoyl-L-arginine ethyl ester as substrate linear competitive inhibition versus L-arginine was observed while ethanol gave rise to S-parabolic I-linear noncompetitive inhibition. Hydrolysis of N alpha-benzoyl-L-arginine-p-nitroanilide was noncompetitively inhibited by p-nitroaniline. Both slopes and intercepts of double reciprocal plots were a linear function of inhibitor concentration. Ethanol gave complex inhibition kinetics which could be interpreted in terms of mixed dead-end and alternate product inhibition (S-parabolic I-hyperbolic noncompetitive inhibition). These results imply an ordered uni-bi as the minimal kinetic mechanism wherein ethanol (or amine when amide is used as substrate) is released first from the enzyme surface, followed by the liberation of arginine. The enzymes are inactivated by phenylmethane sulfonyl fluoride which suggests the presence of an essential serine in the active sites of the enzymes. The enzymes may therefore be classified in the group of serine proteases.