[Scorpions and scorpionism in Brazil. I. Maintenance of scorpions in captivity and extraction of venom].
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SCORPION, a molecular database of scorpion toxins.
Increasing interest in the studies of toxins and the requirements for better structural and functional annotations have created a need for improved data management in the field of toxins. The molecular database, SCORPION, contains more than 200 entries of fully referenced scorpion toxin data including primary sequences, three-dimensional structures, structural and functional annotations of scorpion toxins along with relevant literature references. SCORPION has a set of search tools that allow users to extract data and perform specific queries. These entries have been compiled from public databases and literature, cleaned of errors and enriched with additional structural and functional information. The grouping of scorpion toxins provides a basis for extending and clarifying the existing structural and functional classifications. The bioinformatics modules in SCORPION facilitate analyses aimed at classification of scorpion toxins and identification of sequence patterns associated with specific structural or functional properties of scorpion toxins. The SCORPION database is accessible via the Internet at sdmc.krdl.org.sg:8080/scorpion.
Animals↗
The myth of scorpion suicide: are scorpions insensitive to their own venom?
The resistance of the scorpion Androctonus australis to its own venom, as well as to the venom of other species, was investigated. A comparison of the electrical and pharmacological properties of muscle and nerve fibres from Androctonus australis with those from the crayfish Procambarus clarkii enabled us to understand the lack of effect of scorpion venom (110-180 microg ml-1) and purified toxins, which are active on voltage-gated Na+ and K+ channels, Ca2+-activated K+ channels, on scorpion tissues. Voltage-clamp experiments showed that peptide K+ channel blockers from scorpion and snake have no effect on currents in muscle and nerve fibres from either scorpions or crayfish. The scorpion toxin kaliotoxin (KTX), a specific blocker of Kv1.1 and Kv1.3 K+ channels, had no effect on muscle fibres of A. australis (2 micromol l-1) or P. clarkii (400 nmol l-1). Similarly, charybdotoxin (ChTX) had no effect on the muscle fibres of A. australis (10 micromol l-1) or P. clarkii (200 nmol l-1) and neither did the snake toxin dendrotoxin (DTX) at concentrations of 100 nmol l-1 in A. australis and 200 nmol l-1 in P. clarkii. These three toxins (KTX, ChTX and DTX) did not block K+ currents recorded from nerve fibres in P. clarkii. The pharmacology of the K+ channels in these two arthropods did not conform to that previously described for K+ channels in other species. Current-clamp experiments clearly indicated that the venom of A. australis (50 microg ml-1) had no effect on the shape of the action potential recorded from nerve cord axons from A. australis. At a concentration of 50 microg ml-1, A. australis venom greatly prolonged the action potential in the crayfish giant axon. The absence of any effect of the anti-mammal -toxin AaH II (100 nmol l-1) and the anti-insect toxin AaH IT1 (100 nmol l-1) on scorpion nerve fibres revealed strong pharmacological differences between the voltage-gated Na+ channels of scorpion and crayfish. We conclude that the venom from A. australis is pharmacologically inactive on K+ channels and on voltage-sensitive Na+ channels from this scorpion.
Journal Article↗
Envenomation by the scorpion (Centruroides limbatus) outside its natural range and recognition of medically important scorpions.
A 67-year-old woman presented to a community emergency department in Orange County, CA, after she was stung by a scorpion identified as Centruroides limbatus from Central America. She developed local pain and systemic symptoms, including parasthesias, flushing, hypertension, and wheezing. Envenomation by this genus of scorpion has not previously been reported in Orange County. Scorpions have been reported to be accidentally transported to areas where they are not indigenous, and patients may present anywhere with envenomation by dangerous scorpion species. Physicians should recognize general identifying characteristics of dangerous scorpions and serious signs of envenomation. Almost all dangerous genera of scorpions (including Centruroides sp.) are in the family Buthidae, which can be identified by a triangular sternal plate. Severe systemic signs of envenomation by Centruroides sp. may include respiratory difficulty, somatic neuromuscular dysfunction, and cranial nerve dysfunction. Patients stung by dangerous scorpions may require airway support, extended observation, antivenin, and avoidance of respiratory depressive medications.
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Studies of scorpion antivenins. 2. Venom collection and scorpion colony maintenance.
This paper describes methods used successfully in a large-scale programme for the collection of scorpion venom. Effective methods were developed for the maintenance of a laboratory colony of over 5000 adult scorpions. Electrical stimulation of the scorpions to induce venom emission was greatly facilitated by tranquillizing them with CO(2) and using a slightly modified, snap-type mousetrap as a scorpion-holding device. This technique made for rapid handling of specimens with little risk to the technicians and minimal trauma to the scorpions. Specimens held under proper conditions yielded venom from six to eight times at two-week intervals. As much as 66.4% of the venom content of the telson was emitted by an electrically stimulated scorpion. Venom collected in this manner was air-dried at room temperature, then placed in a calcium chloride desiccator and stored at 44 degrees F (6.6 degrees C). Venoms of medically important scorpions from Mexico, Brazil, Israel, India, Panama and the USA were collected during this programme.
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Purification and characterization of a scorpion defensin, a 4kDa antibacterial peptide presenting structural similarities with insect defensins and scorpion toxins.
Insect defensins are a group of inducible small-sized antibacterial peptides with three intramolecular disulfide bridges. NMR studies have recently shown that they share striking structural similarities with scorpion toxins. We have investigated in a scorpion species, Leiurus quinquestriatus, the potential presence of antibacterial molecules and report the isolation and structural characterization of a novel insect defensin homologue, which we refer to as scorpion defensin. This peptide shows a remarkably high degree of sequence homology with a defensin recently characterized in a species belonging to the ancient insect order of the Odonata with which it defines a novel ancient subclass of defensins. The scorpion defensin has in common with the scorpion toxins a consensus sequence Cys-[...]-Cys-Xaa-Xaa-Xaa-Cys-[...]-Gly-Xaa-Cys-[...]-Cys-Xaa-Cys present in all scorpion toxins characterized so far.
Amino Acid Sequence↗
Body distribution of Tityus serrulatus scorpion venom in mice and effects of scorpion antivenom.
In the present study we report the distribution of Tityus serrulatus scorpion venom in serum and various tissues of CFI mice and the efficacy of antivenom in reducing venom concentration. The animals were injected s.c. with 10 micrograms of scorpion venom, divided into groups of four animals and killed at different times from 15 min to 24 hr. Blood samples and samples of different tissues (heart, lung, liver, kidney, spleen, brain and injection site) were collected. Maximum venom levels occurred at 15 min in the kidney and liver and at 30 min in serum, lung, heart and spleen. After 2 hr the venom decreased rapidly in serum and in all other organs until venom levels were no longer detectable after 8 hr. No venom was detected in the central nervous system. In another experiment, 10 microliters of scorpion antivenom was injected i.v. together with the venom, and a rapid reduction of venom concentration was observed in the blood and tissues. In the third experiment, anti-scorpion venom was injected i.v. 1 hr after venom administration, and partial reduction of venom concentration was detected in tissues (lung and kidney). These studies contribute to the elaboration of more objective treatment that may result in a more economic, efficient and controlled use of scorpion antivenom in stings involving humans.
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[A control program for an outbreak of the scorpion Tityus serrulatus, Lutz and Mello 1922 in the town of Aparecida, São Paulo state (Scorpiones, Buthidae)].
A scorpion control program was proposed for the town of Aparecida (SP), an endemic region of Tityus serrulatus. Clusters of scorpions in urban and rural areas, environmental degradation of the town's outskirts and new scorpion procreation and dispersal habitats were studied. In addition, infrastructure problems such as the disposal and collection of residential and municipal refuse, sanitation (sewage and storm sewer), condition of vacant lots and constructions in the urban area were evaluated. After an epidemiological study, educational measures such as the distribution of pamphlets, cleaning group work, visits to residences and cooperation from High School teachers and students were also suggested. Chemical control was indicated in high-risk sites, especially those of near-school buildings. Furthermore, the use of natural predators was also mentioned within the present sanitation regulations for urban areas. The authors assert that these procedures must be integrated and continued uninterruptedly for several years. They also suggest a collaborative work with those responsible for the dengue eradication program, as well as the institution of the "scorpion study week", which would greatly contribute to the education of the population, to preventive programs and to scorpion control.
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Refined solution structure of the anti-mammal and anti-insect LqqIII scorpion toxin: comparison with other scorpion toxins.
The solution structure of the anti-mammal and anti-insect LqqIII toxin from the scorpion Leiurus quinquestriatus quinquestriatus was refined and compared with other long-chain scorpion toxins. This structure, determined by 1H-NMR and molecular modeling, involves an alpha-helix (18-29) linked to a three-stranded beta-sheet (2-6, 33-39, and 43-51) by two disulfide bridges. The average RMSD between the 15 best structures and the mean structure is 0.71 A for C alpha atoms. Comparison between LqqIII, the potent anti-mammal AaHII, and the weakly active variant-3 toxins revealed that the LqqIII three-dimensional structure is closer to that of AaHII than to the variant-3 structure. Moreover, striking analogies were observed between the electrostatic and hydrophobic potentials of LqqIII and AaHII. Several residues are well conserved in long-chain scorpion toxin sequences and seem to be important in protein structure stability and function. Some of them are involved in the CS alpha beta (Cysteine Stabilized alpha-helix beta-sheet) motif. A comparison between the sequences of the RII rat brain and the Drosophila extracellular loops forming scorpion toxin binding-sites of Na+ channels displays differences in the subsites interacting with anti-mammal or anti-insect toxins. This suggests that hydrophobic as well as electrostatic interactions are essential for the binding and specificity of long-chain scorpion toxins.
Amino Acid Sequence↗
Development of segments and appendages in embryos of the desert scorpion Paruroctonus mesaensis (Scorpiones: Vaejovidae).
The scanning electron microscope was used to study the changing features of scorpion embryos from the blastula through early stages in the development of appendages. The earliest scorpion fossils (Silurian period) have structures more advanced than the embryos herein, so the possibility is considered that these embryos still retain and display some features indicative of evolutionary patterns in adult pre-Silurian ancestors. The blastodisc stage is followed by a knob-like germinal center that gives rise to most of the embryo body. The germinal center elongates on the ventral surface of the spherical yolk mass. The broad cephalic lobe is first delineated from the following pedipalpal segment. The limbbuds for the pedipalps and anterior walking legs appear, as additional segments are added at a growth zone at the rear of the embryo body. Initially, in the cephalic lobe there are no limbbuds; then the cheliceral buds emerge from the posterior part of the lobe. The stomodeum appears first in the anterior half of the cephalic lobe, but an oral groove forms and the mouth is displaced posteriorly within the groove. This repositioning allows space anteriorly for invagination (semilunar grooves) of epithelium for the brain and medial eyes. The mouth is directed ventrally in all stages of this study. The widespread chelicerae are initially posterior to the mouth, but later move anterior and dorsal to it. Small limbbud bulges on mesosomal segments disappear later and never become protruding appendages. Metasomal segments are produced free from the yolk surface in a ventral flexure beneath the embryo body. The telson starts as two spherical lobes, but later elongates and tapers distally, not yet developing the sharp sting (aculeus) seen in Silurian and all subsequent scorpions. The walking legs are digitigrade, as in most fossil aquatic scorpions. Segments are delineated in the appendages; the chelicerae and pedipalps are divided distally for chela (claw) formation. Bilateral swellings (limbbuds) on the third abdominal segment become larger than the others, indicating the site of pectine formation. The early fin-like pectines are somewhat posterior in the mesosoma, suggesting ancestral swimming, maneuvering, and balancing for the elongate abdomen. The pectinal surface is initially smooth but later transverse striations increase the surface area as a possible respiratory adaptation. Pectinal teeth (present in Silurian and all subsequent scorpions) and forward movement and merging of anterior abdominal segments are not yet evident in embryos of this study.
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Preparation of a potent anti-scorpion-venom-serum against the venom of red scorpion (Buthus tamalus).
A number of children and adults, especially pregnant women succumb to the sting by red Scorpion (Buthus tamalus) in Konkan region--particularly on the coastal line. No specific antiserum or any other antidote is available to treat a victim of scorpion bite and hence the need to prepare a potent antiserum. Red Scorpion (B. tamalus) venom is a mixture of a number of protein moieties and neurotoxins of low molecular weight. Therefore, the venom is poor in antigenic composition and it is difficult to get antibodies specific to neutralise lethal factor/factors. Using Bentonite as an adjuvant and extending the period of immunization a potent antiserum has been prepared capable of neutralising the lethal factor/factors. In vivo testing carried out in albino mice, guinea pigs, dogs and langurs confirms this finding and shows that the antiserum is quite effective in neutralising the scorpion venom to save the life of envenomated animals.
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[Scorpion sting (Euscorpius, sp.) in Italy and review of scorpionism].
Although they are very common arachnids, the scorpions (Euscorpius, sp.) do not constitute a sanitary problem in Italy, given that their sting determines only local effects. Scorpionism can anyway verify itself following sting exemplaries in Italy with imported gaods or caused by Buthus occitanus, that lives in the south of France. In this review the Authors treat briefly the biology and the toxicology of scorpions, describing the clinical picture of Scorpionism and the relative therapy.
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Three-dimensional model of the insect-directed scorpion toxin from Androctonus australis Hector and its implication for the evolution of scorpion toxins in general.
The three-dimensional structure of the insect-directed toxin from the scorpion Androctonus australis Hector has been modelled using computer graphics and energy-minimization techniques. The model-building procedure was based on the known high resolution structures of two scorpion toxins of different types: toxin II from A. australis Hector, an alpha-toxin, and variant 3 from Centruroides sculpturatus Ewing that belongs to the beta-toxin structural group. Although the insect-directed toxin has one atypical disulfide bridge, the general structural features of the scorpion toxin family, including the presence of a "conserved-hydrophobic" surface, seem to be well-conserved. However, the orientation and length of some loops and regions thought to be important for toxicity are different for alpha-toxins, beta-toxins, and the insect-directed toxin. Thus, the binding of a scorpion toxin to its site on the Na+ channel seems to be based on (1) the presence of a surface containing a series of conserved and/or hydrophobic residues, more or less common to all these molecules, and (2) an adjacent area that modulates the specificity of the interaction.
Amino Acid Sequence↗
Immunoreactivity and pharmacokinetics of horse anti-scorpion venom F(ab')2-scorpion venom interactions.
The immunoreactivity and pharmacokinetics of a new horse F(ab')2 scorpion antivenom and its effect on Buthus occitanus mardochei venom plasma disposition in the rabbit were studied. The scorpion venom-specific F(ab')2 affinity constant determined by immunoradiometric assay was 1.6 +/- 0.6 10(8) M-1. One group received a F(ab')2 bolus dose of 9.57 mg.kg-1 i.v. bolus or i.m.. The plasma F(ab')2 concentration followed a biexponential decline after i.v. administration with distribution and elimination half-lives of 2.54 +/- 0.36 and 49.52 +/- 3.07 hr, respectively. The total volume of distribution (Vdss or Vd beta) was between 230 and 255 ml.kg-1. Total body clearance was 3.56 +/- 0.34 ml.kg-1.hr-1. After intramuscular administration, Tmax was 48 hr and the absolute bioavailability was 36%. Two other groups of rabbits received i.v.60 micrograms.kg-1 B. occitanus mardochei venom either alone (control group) or followed by 3 mg.kg-1 scorpion venom-specific F(ab')2 administered by intravenous infusion 1.75 hr later. In the rabbits treated with horse F(ab')2 antivenom the venom concentration profile was initially identical to that observed in the control group which received venom alone before F(ab')2 administration. Subsequent infusion of antivenom induced a 1.5-fold elevation of the plasma venom concentration with a Tmax 0.5 hr after F(ab')2 administration. The AUC was 10-fold higher in the F(ab')2-treated group than in the control group in the post-F(ab')2 infusion period. Twelve hours after F(ab')2 administration the venom disposition declined with a terminal half-life equal to that of F(ab')2 (49.49 +/- 7.53 hr). These data show the ability of F(ab')2 to alter venom pharmacokinetics and demonstrate that the scorpion toxins adopt the F(ab')2 elimination properties.
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Lack of effect of a neurotoxin from the scorpion Buthus martensi Karsch on nerve fibers of this scorpion.
A neurotoxin (BmK I) was purified from the venom of the scorpion species Buthus martensi Karsch. Effects of this toxin on the excitability of the abdominal nerve fibers of the same scorpion were examined. The toxin had no effect at all on the action and resting potentials recorded intracellularly even at a concentration as high as 100 microM. A similar result was obtained through optical measurements of the action potential using a potential sensitive dye. Sea anemone toxin II (8 microM) had no effect on nerve excitability either. However, tetrodotoxin (50 nM) reversibly suppressed the action potential and grayanotoxin II (20 microM) induced a sustained depolarization of the nerve membrane which resulted in a reversible suppression of the action potential. BmK I at a concentration of 0.1 microM greatly prolonged the action potential in the crayfish giant axon. We conclude that the Na channel of nerve fibers of this scorpion is totally insensitive to the neurotoxin in this scorpion's venom.
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Second degree atrio-ventricular block and cardiotoxicity secondary to envenomation by the scorpion Leiurus quinquestriatus ('yellow scorpion')--an indication for serotherapy?
Tachyarrhythmia following scorpion envenomation might be an indication for anti venin therapy. We present a case of an unusual cardiotoxic response to Leiurus quinquestriatus ('yellow scorpion') venom-second degree atrio-ventricular block (Mobitz type 1). We review the biological activities of L. quinquestriatus' venom and the arrhythmia's possible pathophysiology. The question arising from this case is the therapeutic approach to cardiotoxicity and bradyarrhythmias induced by scorpion envenomation-mainly, the indication for anti serum therapy.
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A naturally occurring non-coding fusion transcript derived from scorpion venom gland: implication for the regulation of scorpion toxin gene expression.
Scorpion venom glands synthesize and secrete a great number of low molecular mass toxic peptides for prey and defense. Many cDNAs and genomic genes encoding these toxins have been isolated and sequenced. However, their expression regulation mechanism is not yet known at present. During screening of a cDNA library prepared from venom glands of the scorpion Buthus martensii Karsch, we isolated a natural fusion cDNA composed of the 5'-untranslated region (UTR) and upstream coding sequence of a long-chain toxin transcript and the downstream coding sequence and 3'-UTR of a short-chain toxin transcript. The junction site is just the overlapping region of 11 nucleotides (GGCAAGGAAAT) between the two wild transcripts, and thus leads to the formation of an early stop codon, which will cause premature translation. Based on the above observations, combined with the genomic data, we proposed a characteristic regulation mechanism of scorpion toxin genes, in which trans-splicing and nonsense mediated mRNA decay are involved.
3' Untranslated Regions↗
Scorpionism in South Africa. A report of 42 serious scorpion envenomations.
Forty-two cases of serious scorpion envenomation, of which 4 had a fatal outcome, are presented. The clinical profile, differential diagnosis and management of scorpionism are discussed. Most envenomations occurred in the summer months, peaking in January and February. An immediate local burning pain was the most prominent symptom. Systemic symptoms and signs developed within 4 hours of the sting in most instances, characterised by general paraesthesia, hyperaesthesia, muscle pain and cramps. Other striking features included dysphagia, dysarthria and sialorrhoea with varying degrees of loss of pharyngeal reflexes. The blood pressure and the temperature were often raised and the tendon reflexes increased, while motor power was often impaired. In a considerable number of patients the course was complicated by varying degrees of respiratory dysfunction, which tended to be more serious in children. The oustanding feature in children was an extreme form of restlessness characterised by excessive neuromuscular activity. Victims of scorpion sting, particularly in high-risk localities, should be closely observed for 12-24 hours. Children and other high-risk patients should be hospitalised. All patients with symptoms and signs of systemic envenomation should receive antivenom. Parabuthus granulatus (Hemprich & Ehrenberg, 1828) has been identified as the most important venomous species in the western Cape. The antivenom is produced from the venom of the medically less important P. transvaalicus Purcell, 1899. A strong case can therefore be made for the inclusion of P. granulatus venom in the production of a polyvalent antivenom.
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