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PubMed1995

Presence of curarizing polypeptides and a pancreatitis-inducing fraction without muscarinic effects in the venom of the Venezuelan scorpion Tityus discrepans (Karsch).

Four toxic polypeptidic fractions (TdF-I-IV) were purified from the venom of the Venezuelan scorpion Tityus discrepans by means of gel filtration on Sephadex G'-50. The peptides have mol. wts of approx. 6000 and normalized elution volumes (Vn = Elution volume/Total column volume) of: TdF-I = 0.27 (0.26, 0.28), n = 13; TdF-II = 0.40 (0.39, 0.41), n = 15; TdF-III = 0.57 (0.56, 0.59), n = 14, and TdF-IV = 0.68 (0.67, 0.70), n = 13 (median and its 95% confidence interval, n = number of elutions used to calculate the median). Mice (white, male, 16-19 g, IVIC strain) were injected with these fractions and sacrificed 48 hr later. No toxicity was observed when fraction I (0.93 microgram/g mice) or IV (2.51 micrograms/g mice) was injected i.p. into mice. TdF-II (9 to 50 micrograms/g mice) produced sialorrhea, dyspnea and death 1 hr after i.p. injection. Light microscopy of the pancreas revealed that TdF-III (3.42 micrograms/g mice) produced structural modifications such as acinar cell vacuolization, degranulation and interstitial swelling; these changes are characteristic of acute pancreatitis. No effects on the islets of Langerhans or the pancreatic ducts were observed. TdF-III had no overt muscarinic effects when injected i.p. into mice. On the neuromuscular preparation of the frog (Hyla crepitans) TdF-I blocked neuromuscular transmission at the postsynaptic membrane; TdF-II depolarized the muscle membrane by opening sodium channels and TdF-IV prolonged action potentials, suggesting potassium channel blockage.

Action Potentials↗
PubMed1994

Prejunctional action of the venom from the Indian red scorpion Mesobuthus tamulus on adrenergic transmission in vitro.

Venom (RSV) from the Indian red scorpion, Mesobuthus tamulus (Buthus tamulus), can cause increased peripheral sympathetic activity with consequent enhancement of adrenergic responses. We have therefore investigated the effects of RSV on adrenergic transmission in the rat isolated anococcygeus muscle. The effects of phentolamine (5 microM), tetrodotoxin (2 microM), guanethidine (5 microM), desipramine (1 microM) and reserpine pretreatment in vivo (5 mg/kg s.c. x 24 hr and 5 mg/kg i.p. x 3 hr) on the contractile responses of the rat anococcygeus muscle to RSV (1.5 microgram/ml), field stimulation, noradrenaline (NA, 1 microM or 3 microM) and tyramine (15 microM) were compared. The contractile responses to RSV and to field stimulation were completely blocked by phentolamine, tetrodotoxin, guanethidine and reserpine pretreatment, but the responses were potentiated by desipramine. The contractile responses to tyramine were completely blocked by phentolamine, reserpine pretreatment as well as desipramine. The responses to NA were completely blocked by phentolamine, but were potentiated by guanethidine, desipramine and reserpine. Relatively low concentrations (0.1 microgram/ml x 4) of RSV which did not produce any observable increase in tone of the anococcygeus muscle, potentiated the contractile response of the anococcygeus muscle to field stimulation, but not the responses to exogenous NA; 4-aminopyridine (25 microM x 2) also potentiated the muscle responses to field stimulation. HPLC measurements revealed only very low concentrations (0.10 +/- 0.03 mumol/g venom) of NA in RSV. Thus, the adrenergic agonist action of RSV in the rat isolated anococcygeus muscle can be attributed to the involvement of some prejunctional mechanism(s) of action that stimulates the release of neurotransmitter which differs from the indirect action mediated by tyramine.

Animals↗
PubMed1994

Scorpion sting-induced pulmonary oedema: evidence of increased alveolocapillary membrane permeability.

A 16-year-old boy died with acute pulmonary oedema and shock after Tityus serrulatus scorpion sting. The patient showed evidence of cardiac dysfunction and damage, an increase in tracheobronchial aspirate/plasma protein concentration, light microscopic features of the lung compatible with the adult respiratory distress syndrome and electron microscopic findings compatible with acute lung injury and increased alveolocapillary membrane permeability.

Adolescent↗
PubMed1994

Neuromuscular effects of some potassium channel blocking toxins from the venom of the scorpion Leiurus quinquestriatus hebreus.

The scorpion venom Leiurus quinquestriatus hebreus was fractionated by chromatography in order to isolate toxins that affected binding of radiolabelled dendrotoxin to K+ channel proteins on synaptosomal membranes and that facilitated acetylcholine release in chick biventer cervicis nerve-muscle preparations. In addition to the previously characterized charybdotoxin, three toxins were isolated: 14-2, 15-1 and 18-2. Toxin 14-2 has a blocked N-terminus and because of low quantities, it has not been sequenced; 15-1 is a newly sequenced toxin of 36 residues with some overall homology to charybdotoxin and noxiustoxin; 18-2 is identical to charybdotoxin-2. The apparent Ki against dendrotoxin binding were: charybdotoxin, 3.8 nM; 14-2, 150 nM; 15-1, 50 nM; and 18-2, 0.25 nM. Toxin 14-2 (75 nM-1.5 microM) had a presynaptic facilitatory effect on neuromuscular preparations. Toxin 15-1 augmented responses to direct muscle stimulation, probably because it blocked Ca(2+)-activated K+ currents in muscle fibres. Toxin 18-2 (charybdotoxin-2) had a potent presynaptic facilitatory action, with less effect on direct muscle stimulation. This contrasts with the relatively weak neuromuscular effects of the highly homologous charybdotoxin. On a Ca(2+)-activated K+ current in mouse motor nerve endings, charybdotoxin and toxin 18-2 produced maximal block at around 100 nM, whereas 15-1 was inactive at 300 nM. Charybdotoxin can increase quantal content, but this is more likely to result from block of voltage-dependent K+ channels than Ca(2+)-activated channels: the increase in transmitter release occurred in conditions in which little IKCa would be present; higher concentration of charybdotoxin and longer exposure times were required to increase transmitter release than those needed to block IKCa, and the facilitatory effects of charybdotoxin and toxin 18-2 correlated more with their effects on dendrotoxin binding than on block of IKCa.

Acetylcholine↗
PubMed1995

Cloning and characterization of the cDNAs encoding Na+ channel-specific toxins 1 and 2 of the scorpion Centruroides noxius Hoffmann.

Using a cDNA library prepared from venomous glands of the Mexican scorpion Centruroides noxius Hoffmann the genes that encode toxins 1 and 2 were identified, cloned and sequenced. In view of the proposed mechanism for processing the mature peptides coded by these two genes, the corresponding peptide-toxins were sequenced de novo. Mass spectrometric and 1H-NMR analyses of the C-terminal peptide produced by enzymatic digestion of both toxins indicated that the last residue is serine-amide. Sequence comparison revealed that these two genes have a similarity of 56% and 80% at the amino acid and nucleotide levels, respectively. Small corrections to the published primary structures were introduced: Cn toxin 1 has an extra serine residue at position 65 and the residue in position 60 is a proline, while the amino acids at positions 34 and 35 of Cn 2 are, respectively, tyrosine and glycine. Sequence comparison of toxins from the genus Centruroides suggests the presence of at least three classes of distinct peptides in these venoms.

Amino Acid Sequence↗
PubMed1995

Anxiogenic activity of centrally administered scorpion (Mesobuthus tamulus) venom in rats.

The anxiogenic action of intracerebroventricularly (i.c.v.) administered Mesobuthus tamulus venom (MTV) was investigated in rats. MTV (1, 3 and 5 g/rat, i.c.v.) induced a dose-related anxiogenic response which was qualitatively comparable to that produced by yohimbine (2 mg/kp, i.p.), an established anxiogenic agent. Both MTV and yohimbine reduced exploratory activity and rears, while increasing immobility and defaecation, in the open-field test. Likewise, both the drugs decreased the number of entries and time spent on the open arms of the elevated plus-maze, reduced social interaction and increased feed-latency in a novel environment. Rat brain levels of tribulin, a postulated endocoid indicator of anxiety, assessed in terms of endogenous monoamine oxidase (MAO) A and B inhibitor activity, were increased by both MTV and yohimbine. The results indicate that the venom has significant anxiogenic activity, which is consonant with some of the clinical symptoms seen after scorpion sting.

Animals↗
PubMed1995

Positive cooperativity among insecticidal scorpion neurotoxins.

The insecticidal activity of scorpion neurotoxic polypeptides increased 5-10-fold with no apparent increase in mammalian toxicity when a combination of two toxins was injected. Synergistic combinations could be predicted from binding studies and competitive displacement assays. Our results indicate that simultaneous expression in baculovirus or other transgenic organisms of the synergistic combinations of insecticidal toxins may result in more potent insect-selective biopesticides.

Animals↗
PubMed1996

Is the severity of Tityus serrulatus scorpion envenoming related to plasma venom concentrations?

Plasma venom concentrations were measured by enzyme-linked immunosorbent assay at the time of hospital admission in 56 patients stung by the scorpion Tityus serrulatus. According to clinical and laboratory manifestations patients were classified into two groups: patients with only local pain at the site of the sting (n = 37), and patients with systemic manifestations of envenoming (n = 19). Circulating venom concentrations of these two groups of patients were cross-tabulated and the results showed that patients with systemic manifestations of envenoming had significantly higher plasma venom concentrations than patients with only local pain at the site of the sting.

Absorption↗
PubMed1996

Noxiustoxin 2, a novel K+ channel blocking peptide from the venom of the scorpion Centruroides noxius Hoffmann.

A novel peptide called Noxiustoxin 2 (NTX2) was purified from the venom of the scorpion Centruroides noxius and characterized chemically and functionally. It is composed of 38 amino acid residues linked by three disulfide bridges and its primary structure is 61% identical to that of Noxiustoxin (NTX). It is not toxic to mice (using up to 200 micrograms/20 g mouse weight) and crustaceans (up to 30 micrograms/g of crayfish), but has a paralysing effect on crickets (30 micrograms/g animal). It displaces the binding of [125I]NTX to rat brain synaptosome membranes with a Ki of 0.1 microM, in comparison NTX has a Ki of 100 pM. Similarly, using single Ca2+ activated K+ channels of small conductance obtained from cultured bovine aortic endothelial cells it was shown that NTX2 is over two logarithm units less potent than NTX in producing 50% blockade of the probability of opening the channels. NTX2 is not recognized by a panel of six distinct monoclonal antibodies against NTX, however it is recognized by polyclonal antibodies raised in mouse, with native NTX. Primary structure comparison of both NTX and NTX2 suggests that the N-terminal segments of these peptides are important for channel affinity.

Amino Acid Sequence↗
PubMed1996

Fab fragments of the monoclonal antibody BCF2 are capable of neutralizing the whole soluble venom from the scorpion Centruroides noxius Hoffmann.

BCF2 is a murine hybridoma cell line that produces a neutralizing antibody against toxin 2 (Cn2) from the scorpion Centruroides noxius Hoffmann of Mexico. In this communication we report the preparation and use of the BCF2 antibody and its antigen binding fragments (Fab) in experiments aiming at obtaining protection of experimental albino mice (strain CD1) challenged with purified toxin Cn2, as well as, with whole soluble venom from C. noxius. The monoclonal antibody BCF2 in amounts of 1 mg neutralizes 28 LD50 of soluble venom of C. noxius, whereas the Fab fragments of BCF2 (1 mg) are capable of neutralizing 43 LD50 dose of the same venom. To reach the same level of neutralization, with the commercially available horse antiserum [F(ab')2], we need to use about ninefold more material.

Animals↗
PubMed1986

Serological characterization of humoral lectin from Heterometrus granulomanus scorpion hemolymph.

A lectin in the hemolymph of Indian scorpion Heterometrus granulomanus was detected by agglutination of human and animal erythrocytes. The agglutinating activity was enhanced in presence of Ca2+ ion. The lectin shows specificity for sialic acid like many other sialic acid-specific lectins such as "Limulin", as the agglutination of erythrocytes was completely abolished by treatment with Vibrio cholerae neuraminidase. However, neuraminidase-treated rat and mouse erythrocytes exhibited high titers. This result was substantiated by crossed-absorption test which suggests the adjunct specificity of the Heterometrus lectin for these cells. Hemagglutination-inhibition results of the lectin indicate that sialic acid including its derivatives and sialoglycoconjugates are the inhibitors among which glycophorin was most potent.

Animals↗
PubMed1991

Characterization of a naturally occurring protease inhibitor in the hemolymph of the scorpion, Heterometrus bengalensis.

A protease inhibitor has been purified by ultracentrifugation, affinity chromatography on trypsin-sepharose 4B, and chromatofocusing on PBE-94 from hemolymph of the scorpion Heterometrus bengalensis. Homogeneity of the protease inhibitor was demonstrated by high performance liquid chromatography (HPLC). The protease inhibitor is a monomeric glycoprotein with a molecular weight of 120,000 dalton, which is stable between pH 4 and pH 8. The molecule inhibits serine proteases like trypsin and alpha-chymotrypsin and shows a noncompetitive mode of inhibition towards trypsin, with a Ki value of 6.1 x 10(-6) mM. Amino acid analysis shows a preponderance of aspartic acid, glutamic acid, serine, and glycine. The protease inhibitor is efficient in inhibiting phenoloxidase activity in both the hemolymph and the isolated phenoloxidase. Melanin synthesis by phenoloxidase may be influenced by this protease inhibitor.

Amino Acids↗
PubMed1983

Immunochemistry of scorpion alpha-neurotoxins. Determination of the antigenic site number and isolation of a highly enriched antibody specific to a single antigenic site of toxin II of Androctonus australis Hector.

Scorpion neurotoxins active on mammals, i.e. alpha- and beta-toxins, have been divided into several groups according to structural and also immunological criteria. A study of the alpha-toxins has been performed in order to determine the number of antigenic sites; a minimum of four Fab fragments were found to bind simultaneously to toxins I and II of Androctonus australis Hector, and toxin I of Buthus occitanus tunetanus. Taking advantage of the loss of one common antigenic site between toxin II of Androctonus australis Hector and toxin III of Buthus occitanus tunetanus, a highly purified antibody population towards a single site of toxin II of Androctonus australis Hector was isolated and characterized. This result is discussed in terms of sequence homologies between the two proteins as the amino acid sequence of toxin III of Buthus occitanus tunetanus has been determined using standard procedures: the two proteins differ at three positions, two of which (positions 10 and 64) are in the vicinity of the disulfide bridge Cys 12-Cys 63, the third (position 51) is the only one to be conservative.

Amino Acid Sequence↗
PubMed1986

Immunochemistry of scorpion alpha-toxins: study with synthetic peptides of the antigenicity of four regions of toxin II of Androctonus australis Hector.

Sequences 19-29 and 28-39 of toxin II of the North African scorpion Androctonus australis Hector have been synthesized. These two peptides correspond to the highest peaks in the hydrophilicity profile of toxin II and were thus believed to account for a significant proportion of toxin antigenicity. Affinity chromatography of solid-phase-bonded peptides allowed us to purify two sub-populations from the total IgGs raised against the native toxin. They both still bound to 125I-toxin II and showed a restricted heterogeneity in their specificity. Solid-phase immunoassays confirmed the antigenicity of these synthetic peptides and also that of two other previously described synthetic replicates of the antigenic regions of toxin II: sequences (5-14) S-S (60-64) and 50-59. The location of the four antigenic regions relative to the postulated location of the receptor-binding site of the toxin is discussed.

Amino Acid Sequence↗
PubMed1987

Raman and infrared spectra of toxin gamma from the venom of the scorpion Tityus serrulatus.

Toxin gamma is a basic, low-molecular-weight, neurotoxic protein, isolated from the venom of the Brazilian scorpion, Tityus serrulatus. Raman spectra (400-1800 cm-1 region) of this toxin in both the lyophilized state and in 0.1 M acetate buffer (pH 4.5) and the infrared spectrum (700-4000 cm-1 region) of a solid film were investigated. From the vibrational spectra, it can be concluded that the polypeptide backbone of toxin gamma consists of a mixture of the different secondary structures, with predominance of beta-sheet, followed by unordered structure and alpha-helix, with some evidence of beta-turn structures. The four disulfide bridges assume the gauche-gauche-gauche conformation of the CCSSCC fragments. The intensity ratio of the doublet at 853 and 828 cm-1 suggests that four out of the five tyrosine residues are exposed. The three tryptophan residues are exposed on the surface, and the single methionine residue assume the gauche-gauche conformation. Toxin gamma retains full activity in the pH 4.5-7.5 range, but is almost completely inactivated at pH 11.5.

Animals↗
PubMed1984

Purification and partial characterization of an erythroagglutinin from the hemolymph of scorpion, Heterometrus bengalensis.

An erythroagglutinin from the hemolymph of the scorpion, Heterometrus bengalensis, has been purified by gel filtration and ion-exchange chromatography. Its homogeneity has been demonstrated by polyacrylamide gel electrophoresis. The purified agglutinin appears to be a monomeric protein having a possible molecular weight between 146,000 and 148,000. It has no divalent cation requirement for erythroagglutination. The erythroagglutination is not inhibited by saccharides, glycoproteins and mucin. Identical erythroagglutination pattern is obtained with normal as well as neuraminidase treated erythrocytes.

Animals↗
PubMed1982

Oscillation in resting tension of chick skeletal muscle treated with toxin V from scorpion venom, reduced [calcium]o and cadmium.

1. An oscillation in resting tension of the chick biventer cervicis muscle is induced by scorpion toxin (CsT-V), reduced [Ca]o and by Cd2+. Other chick muscles, e.g. semispinalis cervicis, anterior and posterior latissimus dorsi, also oscillate with the same treatments. The period of the oscillation in the biventer cervicis muscle is uniform, averaging 5-6 min. 2. The oscillation and the period are very sensitive to changes in temperature, [Ca]o, [K]o, ouabain and tetrodotoxin [TTX]. The oscillation is resistant to twitch blocking dosages of nicotinic antagonists. 3. The period of the oscillation varies inversely as the temperature (26-37 degrees C), log [K]o and [ouabain] and directly as the log [Ca]o and [TTX]. 4. These data support the inference that the oscillator is postjunctional and results from fluctuation in the electrochemical gradient of ions across the muscle cell membrane. The role, if any, of the Na+, K+ pump in the primary oscillogenic mechanism is not evident from our data.

Animals↗
PubMed1983

Spontaneous, rhythmic myoelectric activity induced by scorpion neurotoxin, reduced [calcium]0 and cadmium in chick striated muscle.

The cellular electrical activity accompanying the very slow resting-tension oscillation (period 4-13 min) in chick skeletal muscle caused by scorpion neurotoxin, reduced [Ca2+]0 and Cd2+ was investigated. All three oscillogenic treatments were found to induce spontaneous, periodically recurring, electrical activation of muscle cells, including periodic bursting activity of individual cells. The period of the recurrent electrical activation approximated the period of the resting-tension oscillation. The data suggest that the three oscillogenic treatments act by way of a common mechanism, possibly a critical Ca2+ moiety, to effect the periodic electrical activation of the cells. Analysis of single cell and group discharge activity suggests that the cells are coupled by non-specific, electrotonic interactions, resulting in the integration of their individual periodic activities into a resting-tension oscillation of the whole muscle.

Action Potentials↗