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PubMed1998

[Cardiac failure following sting of yellow scorpion in an adult].

3 men, aged 18, 29, and 47 had severe cardiovascular disturbances following the sting of the yellow scorpion (Leiurus quinquestriatus hebraeus), which is considered the most dangerous scorpion in Israel. Cardiovascular complications are common in children after scorpion sting, but are rare in adults. Pulmonary edema developed in 1 of those being reported and hypertension and arrhythmias in the other 2. Severe deterioration in left ventricle function was confirmed by echocardiographic measurement of diminished ejection fraction. All patients recovered completely. This is the first report of severe cardiac involvement in adults following scorpion sting. We therefore recommend that even adults who develop cardiac symptoms after scorpion sting, particularly those with chronic cardiac disease, be monitored and treated in an intensive care unit.

Adolescent↗
PubMed2004

Scorpion sting syndrome in a general hospital in Saudi Arabia.

OBJECTIVE: To evaluate the incidence of scorpion stings and to draw the attention of clinicians, concerning the dilemma of scorpion sting syndrome and its management in the Kingdom of Saudi Arabia (KSA). METHODS: In a retrospective survey, 251 cases were presented with scorpion stings to the Emergency Department of the Armed Forces Hospital, Riyadh, KSA during a period of 15 years (April 1986 to April 2000). Their ages ranged from 2 months to 101 years (male to female ratio was 2.6:1) and 70.6% of the cases were under 20 years of age. RESULTS: The mean annual incidence of the scorpion sting in the month of May was 16.7%, with the highest mean percentage of approximately 36% each year. The seasonal sting cycle showed the highest record was in the summer period (51%) as compared to the lowest winter period (10%). Local pain was the primary presenting complaint (95%), with a total systemic toxicity of 78.3% and 35.2% of these were children. Hypertension, sweating, salivation and tachycardia were the most common signs of systemic symptoms. The majority of patients received analgesia, local anesthetics, and application of ice and a period of observation dictated by clinical findings. Eighty-two patients (32.6%) had signs of serious envenoming, requiring admission. There were no deaths. All of these cases were mainly treated symptomatically. CONCLUSION: The beneficial effect of antivenom in protecting victims against scorpion stings is still questionable. The higher risk groups of systemic toxicity were either those with ages less than 10 years or greater than 50 years, being more susceptible due to their decreased physiologic reserves and increased debilitation.

Adolescent↗
PubMedDate not supplied

[Scorpion stings: a public health problem in Morelos (Mexico)].

Scorpion stings represent a major public health problem in Mexico. Their annual incidence is estimated at 150,000 cases; 800-1,000 people die from them each year, 72.5% of whom are children younger than 5 years old. The states most affected are Aguascalientes, Colima, Durango, Guanajuato, Guerrero, Jalisco, Michoacán, Morelos, Oaxaca, Puebla, Sinaloa, and Zacatecas. Morelos is an endemic zone, and scorpion stings are relatively frequent, but the indigenous population underestimates the risks. In this locality, scorpion stings lead to high morbidity, with an average of 10,219 cases each year, and a prevalence varying from 584.86 per 100,000 inhabitants in 1994 to 2043.3 per 100,000 inhabitants in 2003. Because of this upsurge, systematic medical supervision and serum therapy are necessary if scorpion poisoning is suspected in a child. The indigenous community as well as tourists visiting Mexico must be informed about the substantial risk of scorpion poisoning.

Adolescent↗
PubMed1994

Positively charged amino acid residues located similarly in sea anemone and scorpion toxins.

Specific groups of sea anemone and scorpion toxins compete on the same pharmacological site, on the voltage-gated sodium channel of mammal excitable membranes. However, these scorpion and sea anemone toxins are two distinct protein families. Here we purified and sequenced a new sea anemone toxin, Bg II, highly toxic to mammals and also a less toxic mutant, Bg III. Two Bg II models were determined from sequence homologies with two sea anemone toxin two-dimensional NMR structures. Only one model conformed to circular dichroism data obtained from Bg II and was compared with an x-ray structure of a scorpion toxin. The comparison of the two structures shows that 5 amino acid residues are located similarly in the sea anemone toxin and the scorpion toxin. From these 5 residues, 4 are basic residues, constituting two distinct positively charged poles on the surface of these toxins. In the sea anemone mutant isolated, a negative charge beside one of the positive poles decreases the toxicity. These results show that positively charged amino acid residues could be essential for the activity of these toxins and outline the role of electrostatic bonds in the interaction of sea anemone and scorpion toxins with their receptor.

Amino Acid Sequence↗
PubMed2004

Arthropod defensins illuminate the divergence of scorpion neurotoxins.

Defensins are phylogenetically ancient antibacterial polypeptides found in plants and animals. Isolation of the cDNA and genomic sequences encoding the scorpion (Leiurus quinquestriatus hebraeus) defensin revealed similarity to scorpion neurotoxins in gene organization (two exons and a phase I intron) and intron characteristics (conserved acceptor, donor and putative branch sites). This commonality, alongside a similar core structure, protein sequence and bioactivity suggest that arthropod defensins and scorpion neurotoxins share a common ancestor. Interestingly, phylogenetic analysis of defensins and scorpion neurotoxins illuminates for the first time a putative evolutionary trajectory for scorpion sodium and potassium channel neurotoxins.

Amino Acid Sequence↗
PubMed1983

Isolation of minax toxins from the venom of the scorpion Buthus minax and their metabolic effects.

Two neurotoxins, minax toxins 1 and 2, were isolated from venom of the scorpion Buthus minax from the Sudan. Molecular weights of 7000 and 6800 and 66 and 62 amino acids were found for minax toxins 1 and 2, respectively. Both toxins contain four disulfide bonds, 1 mol each of phenylalanine, histidine, and tryptophan, no free sulfhydryl groups, and no methionine. Both minax toxins 1 and 2 are basic polypeptides with isoelectric points of 8.2 and 9.0, respectively. There is a significant increase in the calcium content of rat hearts envenomated with minax toxins 1 and 2 or crude venom. This confirms earlier electron microscopic findings of calcium deposits in the heart following scorpion envenomation. There is a concomitant decrease in the calcium and phosphorus content of rat serum following envenomation. It seems that neither scorpion toxins nor scorpion venoms affect the mineral metabolism of the bone. The present investigation indicates that scorpion toxins have not only a neurotoxic action but also broader biological effects such as mineral metabolism.

Amino Acids↗
PubMed1981

Preliminary spectroscopic characterization of six toxins from Latin American scorpions.

This paper reports on spectroscopic studies of six toxins from the Latin American scorpions Centruroides noxius Hoffmann, Centruroides elegans Thorell and Tityus serrulatus Lutz and Mello. The isolation and purification of five of these toxins was described previously. The preparation of toxin II.9.2.2 from the venom of C. noxius is first described here. Circular dichroism and nuclear magnetic resonance spectra indicate similarities and differences between these scorpion toxins and previously characterized snake toxins. While there is evidence that the toxins from scorpions and snakes both contain extended beta-sheet secondary structures, the spectral properties of the scorpion toxins are overall of a different type from those of snake toxins. Among the six scorpion toxins those from T. serrulatus have spectral properties markedly different from those of the Centruroides species. Furthermore, thermal denaturation and amide proton exchange measurements showed that the globular structures of the Tityus toxins were markedly less stable and less rigid than those of the Centruroides toxins.

Amino Acids↗
PubMed1982

Inhibitory effects of scorpion venom on the uptake of amino acids by synaptosomes and synaptosomal membrane vesicles.

Scorpion (Tityus serrulatus) venom strongly inhibited the Na+-dependent uptake of (( 14C ))proline by rat brain synaptosomal preparations. In addition, the efflux of proline was enhanced markedly by scorpion venom. The inhibitory effects of the venom were also demonstrated in synaptosomal vesicle preparations where proline uptake was energized by an artificially imposed Na+ gradient. In both preparations, the effect of scorpion venom was additive with the inhibitory effect of veratridine on Na+-dependent amino acid uptake. The inhibitory effects of both compounds were abolished by tetrodotoxin. The Na+-dependent uptakes of amino acids (e.g. proline, glutamic acid, and gamma-aminobutyric acid) were much more sensitive to inhibition by the toxin than the Na+-independent uptakes (e.g. leucine and phenylalanine). The results of the present study indicate that the scorpion venom may exert its inhibitory effect on Na+-dependent transport by decreasing the transmembrane Na+ gradient. Efflux of accumulated proline, which is presumably controlled by maintenance of this Na+ gradient, was stimulated 3- to 4-fold by the scorpion venom.

Amino Acids↗
PubMed1982

The three-dimensional structure of scorpion neurotoxins.

The crystal and molecular structure of a toxin from the scorpion Centruroides sculpturatus has been solved by standard x-ray crystallographic methods at 3 A resolution. Subsequently the 3 A model has been refined and the resolution has been extended to 1.8 A using the gradient-curvature method. The final reliability index of 0.17 The structure has two and a half turns of alpha-helix, a three-strand stretch of antiparallel beta-sheet and several beta-turns. Three of the four disulfide bridges are found in close interaction with the alpha-helix and beta-sheet structures in what constitutes a very rigid part of the molecule. Examination of available scorpion toxin sequences reveals several sections containing invariant and/or semiinvariant amino acids. Many of these residues are found clustered on a rather large flat surface which is also clearly more hydrophobic than other areas on the molecule. These observations suggest that this surface may play a role in the biological action of scorpion toxins. Secondary structure predictions calculated using the method of Dufton and Hider agree well with the x-ray structure. This is also true for other scorpion toxins and reinforces the idea that scorpion toxins are a family of structurally related proteins.

Amino Acid Sequence↗
PubMed1982

Two types of scorpion receptor sites, one related to the activation, the other to the inactivation of the action potential sodium channel.

The action of the neurotoxin in Buthinae scorpion venoms (Androctonus, Buthus or Leiurus genera) has been extensively studied. These proteins induce a prolongation of the action potential of nerves and muscles by slowing down inactivation of the sodium channel. Their affinity for their receptor site depends on membrane potential. In the present report we describe a toxin from a Centrurinae scorpion, Centruroides suffusus, which binds rat brain synaptosomes at a receptor site distinct from the Buthinae scorpion site independently of voltage. We name Androctonus-like toxins, alpha-scorpion toxins (alpha-ScTX), and Centruroides-like toxins, beta-scorpion toxins (beta-ScTX). We further report that beta-ScTX induces repetitive firing in frog myelinated nerve fibres by producing an abnormal sodium permeability. The beta-toxin binds specifically to rat brain synaptosomes (Kd = 3 nM) and induces an inhibition of the uptake and a stimulation of the release of GABA at concentrations which are in good agreement with the Kd value. These effects are blocked by tetrodotoxin. The binding site of beta -ScTX is distinct from those of other neurotoxins acting on the sodium channel like tetrodotoxin, alpha-ScTX and veratridine. The alpha-ScTX/beta-ScTX binding site capacities decreases as development of rat brain synaptosomes progresses ; at day 7 after birth, it is 1.1. and at day 39, 0.3.

Action Potentials↗
PubMed1991

Effects of Tityus serrulatus scorpion venom and one of its purified toxins (toxin gamma) on the isolated guinea-pig heart.

1. The effects of Tityus serrulatus scorpion venom and its most important toxin (toxin gamma) were investigated on isolated guinea-pig hearts, perfused with Locke solution, by the Langendorff's method. 2. The cardiac contraction, the coronary flow and the electrocardiogram (ECG) were simultaneously recorded. 3. Bolus injections of 25, 50 or 100 micrograms of scorpion venom and 2.5, 5 or 10 micrograms of toxin gamma in the heart evoked complex effects which were divided into 3 phases: an initial phase (tachycardia or bradycardia associated with an increase in contractile force), an intermediate phase (oscillations of cardiac rate, contractile force and coronary flow, due to wandering pacemakers) and a third phase (sinus tachycardia). 4. The bradycardia and the oscillations of rhythm were prevented by atropine, whereas the tachycardia and the increase in contractile force were prevented either by reserpine or propranolol. 5. Scorpion venom or toxin gamma induced a ST segment displacement in the ECG, explained by a transitory myocardial hypoxia, due to an increase in the contractile force and a simultaneous decrease of the coronary flow. 6. Perfusion of the heart with Locke solution containing 2% scorpion antivenom prevented almost totally the effects elicited by the venom. 7. It is concluded that the complex effects induced by scorpion venom and toxin gamma are due to the simultaneous release of acetylcholine and catecholamines from postganglionic nerve fibers in the heart.

Animals↗
PubMed2006

The book lungs of Scorpiones and Tetrapulmonata (Chelicerata, Arachnida): evidence for homology and a single terrestrialisation event of a common arachnid ancestor.

The question of whether Arachnida (Chelicerata) conquered terrestrial habitats only once or several times is controversial. The key group in this respect is the Scorpiones. Several authors claim that they became terrestrial independently of other arachnid lineages. This argumentation uses two lines of evidence. One is that book lungs of scorpions and other arachnids are considered non-homologous because they occur on different segments. The other line is based on fossil evidence which suggests that early scorpions were aquatic, together with a putative sister group relationship between scorpions and the aquatic Eurypterida. To address this problem we undertook a comparative scanning electron microscopical and histological study of the book lungs of scorpions, amblypygids, uropygids, and mesothelid spiders. In addition, we included the book gills of a xiphosuran. We found several detailed similarities in the book lungs shared by all arachnid taxa studied. Based on these findings we conclude that arachnid book lungs are homologous. Furthermore, we suggest that the apomorphic book lungs of arachnids indicate a single terrestrialisation event in the stem lineage leading to Arachnida.

Animals↗
PubMed1998

New toxins acting on sodium channels from the scorpion Leiurus quinquestriatus hebraeus suggest a clue to mammalian vs insect selectivity.

Two new toxins were purified from Leiurus quinquestriatus hebraeus (Lqh) scorpion venom, Lqh II and Lqh III. Lqh II sequence reveals only two substitutions, as compared to AaH II, the most active scorpion alpha-toxin on mammals from Androctounus australis Hector. Lqh III shares 80% sequence identity with the alpha-like toxin Bom III from Buthus occitanus mardochei. Using bioassays on mice and cockroach coupled with competitive binding studies with 125I-labeled scorpion alpha-toxins on rat brain and cockroach synaptosomes, the animal selectivity was examined. Lqh II has comparable activity to mammals as AaH II, but reveals significantly higher activity to insects attributed to its C-terminal substitution, and competes at low concentration for binding on both mammalian and cockroach sodium channels. Lqh II thus binds to receptor site 3 on sodium channels. Lqh III is active on both insects and mammals but competes for binding only on cockroach. The latter indicates that Lqh III binds to a distinct receptor site. Thus, Lqh II and Lqh III represent two different scorpion toxin groups, the alpha- and alpha-like toxins, respectively, according to the structural and pharmacological criteria. These new toxins may serve as a lead for clarification of the structural basis for insect vs mammal selectivity of scorpion toxins.

Amino Acid Sequence↗
PubMed1984

Differential labeling of the alpha and beta 1 subunits of the sodium channel by photoreactive derivatives of scorpion toxin.

The separation of two photoreactive derivatives of the alpha-scorpion toxin from Leiurus quinquestriatus is described. When the two photoreactive derivatives were photolyzed separately in the presence of brain membranes containing voltage-sensitive sodium channels, one labeled the alpha subunit preferentially while the other labeled beta 1 more intensely than alpha. Batrachotoxin enhanced the efficiency of covalent labeling by the photoreactive derivatives of scorpion toxin. In all the labeling experiments, the specific incorporation of radioactive scorpion toxin was eliminated by an excess of nonradioactive scorpion toxin. The alpha polypeptide labeled in synaptosomes by photoreactive scorpion toxin was demonstrated by immunological techniques to be the same large polypeptide identified in sodium channels purified by their saxitoxin binding activity. The alpha and beta 1 subunits were detected by rapid photoaffinity labeling of a freshly prepared brain homogenate in the presence of a mixture of nine protease inhibitors, indicating that they are components of the sodium channel in intact brain tissue. The association of the covalently labeled polypeptides with the membrane was investigated by treatment of labeled synaptosomes with various agents known to remove proteins only indirectly attached to the lipid bilayer via a membrane-bound protein. In all cases, both the alpha and the beta 1 polypeptides remained in the membrane fraction following extraction. This confirms earlier proposals that the alpha polypeptide has a portion of its mass embedded within the lipid bilayer and suggests that the beta 1 polypeptide does as well.

Affinity Labels↗
PubMed1980

Binding of scorpion neurotoxins to chick embryonic heart cells in culture and relationship to calcium uptake and membrane potential.

Stimulation of 45Ca uptake by scorpion neurotoxins in cultured chick embryonic heart cells has been shown to be directly linked to their effect on sodium channels. This property was used to compare the activity of 15 neurotoxins from five different species to their lethal effect in the mouse and immunological properties. As scorpion neurotoxins, the alkaloid neurotoxin veratridine enhanced 45Ca uptake, and an apparent positive cooperativity between the two drugs was observed. 125I-Labeled toxin II from the scorpion Androctonus australis Hector was shown to bind to chick heart cells specifically, saturably, and reversibly with high affinity (KD = 1--3 nM in sodium-free medium) and low capacity (10--20 fmol/mg cell protein). As shown by 45Ca uptake and radioactive toxin binding experiments, the affinity of scorpion neurotoxin to heart cell receptors was dependent on external K+ concentration. Toxin binding was lowered by increasing Na+ concentration in the medium and was abolished by veratridine in a sodium (140 mM) containing medium. As previously reported for neuroblastoma cells, all these results are in agreement with the membrane potential dependence of scorpion neurotoxin affinity for its membrane receptor.

Animals↗
PubMed1976

Membrane potential dependent binding of scorpion toxin to action potential Na+ ionophore.

Depolarization of neuroblastoma cells causes a 70-fold increase in the apparent dissociation constant KD for scorpion toxin enhancement of activation of the action potential Na+ ionophore by veratridine and a large increase in the rate of reversal of scorpion toxin action. Depolarization also inhibits binding of 125I-labeled scorpion toxin to a small number of saturable binding sites on electrically excitable neuroblastoma cells and increases the rate of dissociation of scorpion toxin from these sites. The results suggest that scorpion toxin binds to a regulatory component of the action potential Na+ ionophore whose conformation changes on depolarization.

Action Potentials↗
PubMed1998

delta-Atracotoxins from australian funnel-web spiders compete with scorpion alpha-toxin binding but differentially modulate alkaloid toxin activation of voltage-gated sodium channels.

delta-Atracotoxins from the venom of Australian funnel-web spiders are a unique group of peptide toxins that slow sodium current inactivation in a manner similar to scorpion alpha-toxins. To analyze their interaction with known sodium channel neurotoxin receptor sites, we studied their effect on [3H]batrachotoxin and 125I-Lqh II (where Lqh is alpha-toxin II from the venom of the scorpion Leiurus quinquestriatus hebraeus) binding and on alkaloid toxin-stimulated 22Na+ uptake in rat brain synaptosomes. delta-Atracotoxins significantly increased [3H]batrachotoxin binding yet decreased maximal batrachotoxin-activated 22Na+ uptake by 70-80%, the latter in marked contrast to the effect of scorpion alpha-toxins. Unlike the inhibition of batrachotoxin-activated 22Na+ uptake, delta-atracotoxins increased veratridine-stimulated 22Na+ uptake by converting veratridine from a partial to a full agonist, analogous to scorpion alpha-toxins. Hence, delta-atracotoxins are able to differentiate between the open state of the sodium channel stabilized by batrachotoxin and veratridine and suggest a distinct sub-conductance state stabilized by delta-atracotoxins. Despite these actions, low concentrations of delta-atracotoxins completely inhibited the binding of the scorpion alpha-toxin, 125I-Lqh II, indicating that they bind to similar, or partially overlapping, receptor sites. The apparent uncoupling between the increase in binding but inhibition of the effect of batrachotoxin induced by delta-atracotoxins suggests that the binding and action of certain alkaloid toxins may represent at least two distinguishable steps. These results further contribute to the understanding of the complex dynamic interactions between neurotoxin receptor site areas related to sodium channel gating.

Animals↗
PubMed2005

Predicting scorpion sting incidence in an endemic region using climatological variables.

Scorpionism is a public health problem in several regions of the world. The highest mortality, with over 1000 deaths per year, has been reported in Mexico. We analysed the significance of climatological variables to predict the incidence of scorpion stings in humans in the state of Colima (Mexico) for the years 2000-2001. The pluvial precipitation (mm), the evaporation (mm), and the mean, maximum, and minimum temperatures (degrees C) were obtained from local meteorological offices. There are approximately 3 stings/year per 1000 people in municipalities of Colima and Villa de Alvarez and about 18-30 stings/year per 1000 people in the rest of the municipalities. There is very little rain and there are few stings in the winter when the minimum temperature is below about 16 degrees C. The number of scorpion stings is independent of the actual rainfall when this is above 30 mm/month. Using multiple linear regression, we used a backward model selection procedure to estimate that the minimum temperature is correlated with scorpion sting incidence with a statistically significance of 95%. We briefly discuss the application of predictive models of scorpion sting incidence in the appropriate allocation of antivenom serum in hospital clinics.

Animals↗