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PubMed1983

Purification and physiological characterization of neurotoxins from venoms of the scorpions centruroides sculpturatus and leiurus quinquestriatus.

Several different toxins having specific effects on the kinetics of sodium channels have been isolated from the venoms of two scorpions. A combination of two steps of ion-exchange chromatography has been used to purify these toxins, whose sizes and purities have been assayed by gel filtration, urea/sodium dodecyl sulfate/polyacrylamide gel electrophoresis, and isoelectric focusing. The actions of the toxins and their relative potencies have been determined by studying the modifications they produce in action potential shape, using the sucrose-gap method, and in ionic current kinetics, measured under voltage-clamp, both assays performed on myelinated axons of frogs and toads. The venom of Leiurus quinquestriatus scorpions yielded two active neurotoxins; the major neurotoxin has a mass of approximately 7000 daltons. This major toxin affected the sodium channel inactivation process exclusively, slowing the rates of inactivation as well as preventing complete inactivation from occurring in some of the channels. Such slowed and incomplete sodium inactivation resulted in action potentials that were prolonged, from their usual duration of 5-8 msec to hundreds of milliseconds or even seconds. Five toxins were isolated from the venom of Centruroides sculpturatus Ewing scorpions, all of which also had masses of approximately 7000-7500 daltons. Four of these toxins acted primarily on the activation process of sodium channels, producing a novel increase in sodium permeability upon repolarization of the nerve membrane following a depolarizing pulse, as previously described for the crude venom [Cahalan, M. D. J. Physiol. (Lond.) 244:511-534 (1975)]. These toxins also caused repetitive firing of action potentials in single axons in response to one stimulating pulse, as well as spontaneous impulse firing. A fifth neurotoxin from C. sculpturatus venom had effects similar to those of the L. quinquestriatus toxins, slowing and preventing complete sodium inactivation. The effect of this toxin was slowly removed during external perfusion by Ringer's solution.

Action Potentials↗
PubMed1984

Fluorescence resonance energy transfer on the voltage-dependent sodium channel. Spatial relationship and site coupling between the batrachotoxin and Leiurus quinquestriatus quinquestriatus alpha-scorpion toxin receptors.

A fluorescent N- methylanthraniloyl derivative of the potent depolarizing agent batrachotoxin has been used to probe the structural and conformational properties of the neurotoxin receptor site on the voltage-dependent sodium channel. Batrachotoxin A 20-alpha-N- methylanthranilate (BTX-NMA) retains high affinity for its receptor site on the synaptosomal sodium channel with a Kd between 78 and 91 nM and an average site capacity of 2 pmol/mg of synaptosomal protein in the presence of Leiurus quinquestriatus quinquestriatus alpha-scorpion toxin. The fluorescence emission of BTX-NMA upon binding to synaptosomes indicates a hydrophobic environment. Toxin V from L. quinquestriatus, an allosteric activator, effects a 20-nm red shift in the spectrum of bound BTX-NMA and a 4-fold enhancement in the fluorescence quantum yield disclosing a conformational change into a hydrophilic environment. Fluorescence resonance energy transfer measurements show that the distance separating the receptor sites is 37 +/- 10 A. Thus, the binding of alpha-scorpion toxin must involve conformational changes that extend over large distances from the batrachotoxin-binding locus. This information together with the distance measurements between the tetrodotoxin and alpha-scorpion toxin receptors and the conformational transition associated with this distance upon batrachotoxin addition indicate a conformationally flexible channel with coupling of sites through the polyatomic framework of individual subunits or through extensive alterations in subunit/subunit interactions.

Animals↗
PubMed1995

[Influence of the 2nd and 3rd grade abstracts from scorpion venom of Buthus martensii Karsch on action potentials of fast response myocardiocytes].

AIM: To screen the active components of sodium channel blockade action from Buthus martensii Karsch (BMK) scorpion venom. METHODS: Myocardiocytes of mice were cultured. Action potentials of fast response myocardiocytes were recorded. The effects of 22 contents of BMK scorpion venom in a concentration of 3 mg.L-1 were tested and compared with that of TTX 2.5 mg.L-1, nimodipine (Nim) 3 mg.L-1 and BaCl2 24.4 mg.L-1. RESULTS: BMK-1 and other 19 contents significantly decreased depolarization parameters Vmax, APA, OS, and MDP, which was similar to that of TTX and different from that of Nim and BaCl2. CONCLUSION: The variations in the action potentials of fast response myocardiolcytes indicated that 20 contents of BMK scorpion venom had sodium channel blockade action.

Action Potentials↗
PubMed1994

Amino acid sequence of an excitatory insect-selective toxin (BmK IT) from venom of the scorpion Buthus martensi Karsch.

The insect-selective neurotoxin (BmK IT) of scorpion Buthus martensi Karsch was first reduced and S-alkylated, and then digested by TPCK-trypsin and Staphylococcus aureus V-8 Protease. The enzymatic peptides were purified on TLC-plastic sheet and submitted to determine their amino acid compositions and sequences. The sequence of the 70 amino acid residues of BmK IT was established with reference to the primary structure of AaH IT, another excitatory insect-selective toxin from the venom of North African scorpion Androctonus australis Hector. About 75% of the homologous sequence was found in the molecules of BmK IT and AaH IT. It is obvious that the results contribute toward better understanding of the molecular structure characteristics, structure/activity relationship of scorpion insect-selective toxins, and they can serve as the molecular basis for utilizing the toxins as a tool to clarify molecular mechanism involved in channel gating, and to infer the possibility of developing them as new selective bioinsecticides.

Amino Acid Sequence↗
PubMed1997

[Scorpion toxins].

Scorpion are known to use a cocktail of toxins to immobilize their prey. So, their venoms constitute a complex mixture of polypeptides exhibiting different pharmacological activities. These polypeptides are small (between 30 and 70 amino acids long), basic and highly reticulated (3 or 4 disulfide bridges). They bind with very high affinities to specific targets, which are different ionic channels of excitable cells. Thus, they constitute usefull tools for the neurobiologist. The scorpion toxins can be divided into: 1) "long chain toxins" (60-70 amino acids residues cross-linked by 4 disulfide bridges) that affect exclusively voltage-dependent Na+ channels of excitable cells; 2) "short chain toxins" (30-40 amino acids residues cross-linked by 3 disulfide bridges) that block several types of K+ channels in different cells (not only potassium channels of excitable cells are affected by these toxins, but also those of erythrocytes or lymphocytes). Specificities or affinities of "long" and "short" chain toxins have been studied using structure-function relationships. Conformational analysis gave the three dimensional structures of an alpha, beta and anti-insect selective toxins. The molecules show a dense core of secondary structure, 2 1/2 turns of alpha-helice, and a short segment of anti-parallel beta-sheet, which exists in all known structures of scorpion toxins, irrespective of their size, sequence and function. From cDNA libraries, full-length cDNAs of about 370 nucleotides encoding precursors of these toxins have been isolated. Sequence analysis of these cDNAs show that the precursors contain signal peptides of about 20 amino acid residues. In addition, precursors of the toxins on mammalian Na+ have extensions at their COOH-terminal ends and have to be processed by specific exopeptidases to give the mature toxins. The cloning and sequencing of their genes revealed that they contain two exons and one intron near the end of the signal peptide sequence of the toxins precursors.

Animals↗
PubMed1996

Crystal structure determination of an acidic neurotoxin (BmK M8) from scorpion Buthus martensii Karsch at 0.25 nm resolution.

The crystal structure of an acidic neurotoxin, BmK M8, from Chinese scorpion Buthus martensii Karsch was determined at 0.25 nm resolution. The X-ray diffraction data of BmK M8 crystals at 0.25 nm resolution were collected on a Siemens area detector. Using molecular replacement method with a basic scorpion toxin AaH II in a search model, the cross-rotation function, PC-refinement and translation function were calculated by X-PLOR program package. The correct orientation and position of BmK M8 molecule in crystal were determined in a resolution range of 1.5-0.35 nm. The crystallographic refinement was further performed by stereo-chemical restrict least-square technique, followed by simulated annealing, slow-cooling protocols. The final crystallographic R-factor at 0.8-0.25 nm is 0.171. The standard deviations of bond length and bond angle from ideality are 0.0017 nm and 2.24 degrees, respectively. The final model of BmK M8 structure is composed of a dense core of secondary structure elements by a stretch of alpha-helix with two and a half turns (residues 19-28) and a three-stranded antiparallel beta-sheet (residues 2-4, 32-37, 45-51). In addition, three loops protruded from the structural core. The general folding properties of BmK M8 molecule were described; a common structure motif which may appear in all scorpion neurotoxins was identified. The conserved aromatic residues and charged residues were found to be distributed on two roughly opposite surfaces of the molecule. The relationship between these two faces and receptor-binding sites are also discussed.

Animals↗
PubMed1997

[The rational evolution of scorpion toxins].

A theoretical method for the rational design of a "universal" scorpion toxin with a wider spectrum of specificity for K+ channels and a more stable alpha/beta-folding than in its natural homologues is described. On the basis of the analysis of molecular hydrophobic potentials (MHP) of the protein spatial structures, structural features for a family of five short scorpion toxins were revealed. The analysis of the maps of two-dimensional intramolecular MHP contacts allowed the identification of amino acid residues responsible for the folding of the protein and/or for the manifestation of its specific function. The theoretically predicted structure-function roles of the residues were compared with experimental data on the mutagenesis of charybdotoxin. Based on the results of MHP calculations and with the theory of protein molecular evolution used as an additional criterion for the selection of mutations, the amino acid sequence and the spatial structure of a "universal" scorpion toxin were determined.

Amino Acid Sequence↗
PubMed1998

Effect of Indian red scorpion (Mesobuthus tamulus concanesis, Pocock) venom on thyroxine and triiodothyronine in experimental acute myocarditis and its reversal by species specific antivenom.

Acute myocarditis was induced in dogs and rabbits by injection of scorpion (M. tamulus concanesis, earlier called Buthus tamulus) venom by s.c., i.m. or i.v. routes. A decrease in thyroxine (T4) levels was observed following i.v. injection of venom in dogs. In rabbits the venom (i.m.) did not elicit any change in T4 levels. Envenomation (s.c.) resulted in a reduction in triiodothyronine (T3) levels in dogs. Venom injection (s.c.) along with i.v. administration of the species specific antivenom (AScVS) did not cause any change in T3 and T4 levels in general. However an increase in T3 levels following AScVS was observed in envenomated dogs. The results suggest that scorpion envenomation caused an autonomic storm releasing massive amounts of catecholamines, angiotensin II, suppressed insulin secretion and reduced circulating T4 and T3 levels. Decrease in thyroid hormones results in fall in body temperature. Changes in the body temperature may increase the sensitivity of the scorpion venom and influence the course of toxicity.

Animals↗
PubMed1992

Scorpion venom cardiomyopathy.

Cardiac function was evaluated by serial echocardiography in 30 children affected by scorpion stings. They could be separated into two groups on the basis of the initial echocardiogram. Group 1, consisting of 18 children, had normal left ventricular function, whereas group 2, consisting of 12 children, showed compromised left ventricular function (ejection fraction less than 0.55; fractional shortening less than 27%). In group 2 the left ventricular end-systolic dimension was increased significantly and the interventricular septal thickening fraction was depressed significantly, compared with group 1. Nine children in group 2 showed improvement in all measurements of contractility, usually within 24 to 48 hours. Of the remaining children, one showed no echocardiographic changes and subsequently died. Another child made a slow improvement over several weeks. We conclude that myocardial toxicity is a common and serious complication of scorpion stings in children. Systolic function appears to be affected predominantly. Serial echocardiography is useful to follow changes in left ventricular function, which are generally matched by clinical improvement. Patients who fail to improve within 24 to 48 hours require particularly close observation.

Animals↗
PubMed1990

Do changes in body temperature following envenomation by the scorpion Leiurus quinquestriatus influence the course of toxicity?

Four fatal cases following scorpion sting in children are presented. Two victims had rectal temperature above 41 degrees C, the third exhibited a temperature of 40.9 degrees C from the combined effects of scorpion sting and heat stroke, while the fourth was hypothermic. All victims developed hypothermia 48 hr following the sting. The hyperthermia was effectively treated by acetaminophen suppositories, ice packs and water sponges. All victims showed late hypotension that was refractory to dopamine infusion. This was explained by bradykinin released by the venom blocking the dopaminergic receptors. Deterioration of the cortical activity of the victims maintained on mechanical ventilation before the incidence of asystole suggests a central component in the cardiovascular manifestations of envenomation. A. amoreuxi venom was selected as a model for the pharmacokinetic and quantitative toxicological studies since it has no effect on body temperature. In hyperthermic rabbits injected with labelled lethal fraction of A. amoreuxi venom, there was a significant decrease in the elimination half-life, t1/2 beta, the apparent volume of the tissue compartment, Vt, the apparent volume of distribution, Vdss, and the intercompartmental rate constant, kCT. Hypothermic rabbits showed a significant decrease in the apparent first-order elimination rate constant, kd, and a significant increase in the elimination half-life. In both states a higher concentration of the lethal fraction in the blood was calculated. This would explain the rapidity of onset of the electrocardiographic effects and the decreased survival time in both the hyperthermic and hypothermic rabbits injected with venom when compared to normothermic animals. The s.c. LD50 in mice and the i.v. MLD in rats were significantly reduced in the hypothermic mice and hypothermic and hyperthermic rats.

Animals↗
PubMed1994

ELISA for the detection of toxic antigens in experimental and clinical envenoming by Tityus serrulatus scorpion venom.

An ELISA was developed for identification of circulating toxic antigens from Tityus serrulatus scorpion venom. The toxic fraction from the scorpion venom was purified by Sephadex G-50 chromatography and immunoaffinity techniques were used for identifying antibodies that reacted with this fraction. These antibodies were used to develop a sandwich-type ELISA. The specificity of the assay was demonstrated by its capacity for identifying mice that were experimentally inoculated with T. serrulatus venom from those inoculated with Phoneutria nigriventer spider venom, Apis mellifera bee venom and Bothrops atrox, Crotalus durissus terrificus, Lachesis muta muta and Micrurus frontalis snake venoms. Measurable absorbance signals were obtained with 0.1 ng of venom per assay. The ELISA also detected antigens in the sera of patients systemically envenomed by T. serrulatus. Therefore, this ELISA could be a valuable tool for clinicians and epidemiologists, owing to its sensitivity and specificity.

Animals↗
PubMed1994

Abnormal coronary perfusion in experimental scorpion envenomation.

Perfusion defects and left ventricular dilation after experimental scorpion envenomation were evaluated in five dogs. Left Left ventricular dilation was observed in three dogs and right ventricular dilation in one other, in scans immediately after envenomation. Perfusion defects were inferred from scans in four dogs. The data are strongly suggestive of coronary hypoperfusion, and the mechanics of abnormal coronary flow after scorpion envenomation are discussed.

Animals↗
PubMed1994

The treatment of the scorpion envenoming syndrome: the Saudi experience with serotherapy.

A protocol for treatment of scorpion sting based mainly on antivenom therapy was applied nation-wide in Saudi Arabia. At least 5 x 1 ml ampoules of antivenom diluted in 20-50 ml saline were injected slowly i.v. in all patients confirmed to have scorpion stings or suspected stings with systemic manifestations. A list of drugs was specified to be used in adjunctive therapy, when required. Analysis of 1033 cases at Al-Baha region, 791 cases at Al-Qassim region and more than 600 cases from 12 central and specialist hospitals in the Central Province revealed impressive results. Except for a 12-year-old boy who was inadequately treated with antivenom and died from pulmonary oedema, haematemesis, severe neurotoxicity and circulatory failure, no other fatalities occurred. The incidence of pulmonary oedema, hypertension, hypotension, cardiac dysrhythmias and neurological symptoms requiring drug therapy following antivenom administration was very slight. The period of stay in the hospital was reduced; most patients were symptom-free within 1-2 days. The early reaction to antivenom administration was lower than expected, amounting to 6.6% and 1.7% among Al-Qassim and Al-Baha victims, respectively. The severity of the reaction in both groups was low, consisting mainly of skin rashes, urticaria, wheezing and bronchial secretion, but no anaphylaxis. About 13.8% of Al-Baha victims were previously treated with antivenom but only 1.7% of the patients showed positive skin tests. This might be due to the low protein content of the antivenom and the action of the venom in releasing massive amounts of catecholamines.

Animals↗
PubMedDate not supplied

Myocardial necrosis after envenomation by the scorpion Tityus serrulatus.

A 4 years old boy died a few hours after he had been stung by a scorpion (Tityus serrulatus). At necropsy, there were multiple foci of coagulative myocytolysis in the myocardium and pulmonary oedema. Myocardial necrosis was probably associated with the sympathetic storm induced by scorpion envenomation, and may have contributed to cardiac failure and death.

Animals↗
PubMed2003

Epidemiological and clinical aspects of scorpionism by Tityus trivittatus in Argentina.

This is a descriptive study of epidemiological and clinical aspects of stings caused by the scorpion Tityus trivittatus in Argentina. We analyzed 511 cases recorded from different health centers in 22 provinces. Most accidents took place during the period November-April (76%), in or nearby houses (86%). Over 50% of the accidents involved children and teenagers. Envenomation by T. trivittatus was mainly characterized by local symptoms: pain (85%), edema (26.6%), burning sensation (24.7%), erythema (20.7%), local hyperthermia (13.1%), paresthesia (9.8%) and general manifestations such as vomiting (25%), paleness (18.8%), headache (11.4%) and sweating (8.2%). Neurological, cardiovascular and respiratory disorders were uncommon. Almost 90% of the injured people got treated with specific antivenom within 2 h, 6% were treated 2-h after the accident and only 2 people were treated 12 or more hours after being stung. The global mortality recorded was 6 per 1000 cases. Scorpionism in Argentina is a public health problem under control due to the relatively low incidence and the accessibility of specific antivenom.

Adolescent↗
PubMed1992

Antivenin administration for Centruroides scorpion sting: risks and benefits.

STUDY OBJECTIVES: To assess the clinical severity of envenomation by the Centruroides scorpion in young children; the potential benefit of antivenin administration with regard to time to resolution of symptoms, prevention of hospitalization, and prevention of invasive intervention; and the risk of acute and delayed hypersensitivity reaction. DESIGN: Retrospective chart review with follow-up contact. SETTING: Referral toxicology management center. TYPE OF PARTICIPANTS: Children less than 10 years of age experiencing severe Centruroides scorpion envenomation. INTERVENTIONS: Administration of goat serum-derived anti-Centruroides antivenin. MEASUREMENTS AND MAIN RESULTS: Stings in young children may be life threatening, resulting in extreme neuromuscular activity, tachycardia, and respiratory distress. Administration of anti-Centruroides antivenin resulted in rapid resolution of all symptoms without acute reaction in all 12 patients so treated; 58% of patients treated with antivenin had a delayed onset of rash or symptoms of serum sickness. CONCLUSION: The benefit of rapid resolution of life-threatening symptoms and potential for outpatient management of severe envenomation in young children may justify the risk of acute and delayed reaction associated with antivenin use in this group. The use of antivenin for the less severe envenomation common in older children and adults may subject them to unjustified risk.

Animals↗
PubMed2003

Treatment of the scorpion envenoming syndrome: 12-years experience with serotherapy.

The pathophysiology of the scorpion envenoming syndrome is described with emphasis on the body systems commonly affected. Concepts of the mechanisms underlying venom action, as can be explained by the recently discovered effects on ionic channels, are discussed. A protocol for the treatment of scorpion stings based mainly on antivenom therapy was applied nationwide in Saudi Arabia. A list of drugs with alternatives was specified to be used in adjunctive therapy, when required. Analysis of the outcome from 1,033 cases at Al-Baha region, 791 cases at Al-Qassim region and more than 2,000 cases from 12 central and specialist hospitals in the Central Province, Saudi Arabia gave impressive results. The incidence of severe venom toxicity following antivenom administration was almost negligible. The period of stay in the hospital was reduced. The early reaction to antivenom administration was lower than expected the severity of the reaction consisting mainly of skin rashes, urticaria, wheezing and bronchial hypersensitivity, but no anaphylaxis. About 13.8% of the victims had been previously treated with antivenom but only 1.7% of the patients showed positive skin tests. This might be due to the low protein content of the antivenom and the action of the venom in releasing massive amounts of catecholamines.

Analgesics, Non-Narcotic↗