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At least 649 records · Page 36Linked to original sources
PubMed1986

Conformational variations amongst scorpion toxins.

Circular dichroism spectra were obtained for ten scorpion neurotoxins (representing five species of scorpion) in order to provide an understanding of their relative conformations in solution. Despite a high degree of amino acid sequence homology, the toxins clearly differ from each other in terms of CD-detectable structure. When superimposed, the CD spectra suggest that the toxins form a series of related conformational variants. Since the resemblances amongst the individual CD spectra can be correlated to degrees of sequence resemblance and pharmacological specificity, conformational balance could be an important factor in both toxin evolution and target recognition.

Animals↗
PubMed1991

In vivo protection against scorpion toxins by liposomal immunization.

The possibility of raising a humoral immune response able to induce protection from the lethal effects of scorpion toxins was evaluated in the mouse model. A toxic fraction from the venom of the scorpion Tityus serrulatus was entrapped in sphingomyelin-cholesterol liposomes which yielded a conveniently detoxified immunogen. After three injections of this immunogen, all but three of a group of 18 mice developed an IgG response which was shown to be both specific and of good affinity for the toxic antigen. In vitro neutralization assays indicated that pre-incubation of a lethal dose of the toxic fraction with immune sera strongly diminished its toxicity. In vivo protection assays showed that mice with the highest levels of circulating anti-toxin antibodies could resist the challenge by double the normal LD50 of the toxic fraction, which killed all control non-immune mice. The protection was, however, found to be limited both in its duration and its effectiveness against higher amounts of toxin.

Animals↗
PubMed1995

The use of synthetic peptides can be a misleading approach to generate vaccines against scorpion toxins.

Seven peptides corresponding to the amino acid sequence of toxin 2 from the scorpion Centruroides noxius were chemically synthesized, purified and assayed in mice for their putative neutralizing properties against scorpion toxins. All the peptides were immunogenic and some produced neutralizing antibodies, as verified by injecting the antisera with toxin into naive animals. However, direct challenge of pre-immunized mice (with the longest synthetic peptides of 27 and 57 amino acid residues) revealed an unexpected sensitization phenomena: the animals did not resist injection of one LD50 of purified toxin 2 (5% survival), but pre-immunization of mice with native toxin protected 100% of the animals. These findings suggest that vaccine preparations with synthetic peptides corresponding to the amino acid sequence of certain toxins should be analyzed cautiously.

Amino Acid Sequence↗
PubMed1995

Amino acid sequence of TsTX-V, an alpha-toxin from Tityus serrulatus scorpion venom, and its effect on K+ permeability of beta-cells from isolated rat islets of Langerhans.

Highly purified Tityustoxin V (TsTX-V), an alpha-toxin isolated from the venom of the Brazilian scorpion Tityus serrulatus, was obtained by ion exchange chromatography on carboxymethylcellulose-52. It was shown to be homogeneous by reverse phase high performance liquid chromatography, N-terminal sequencing (first 39 residues) of the reduced and alkylated protein and by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate and tricine. Following enzymatic digestion, the complete amino acid sequence (64 residues) was determined. The sequence showed higher homology with the toxins from the venoms of the North African than with those of the North and South American scorpions. Using the rate of 86Rb+ release from depolarized rat pancreatic beta-cells as a measure of K+ permeability changes, TsTX-V (5.6 micrograms/ml) was found to increase by 2.0-2.4-fold the rate of marker outflow in the presence of 8.3 mM glucose. This effect was persistent and slowly reversible, showing similarity to that induced by 100 microM veratridine, an agent that increases the open period of Na+ channels, delaying their inactivation. It is suggested that, by extending the depolarized period, TsTX-V indirectly affects beta-cell voltage-dependent K+ channels, thus increasing K+ permeability.

Alkylation↗
PubMed1996

Effects of Androctonus crassicauda scorpion venom on endothelium-dependent and -independent vascular responses of rabbit aorta.

The effects of Androctonus crassicauda scorpion venom on acetycholine (ACh)-induced relaxations and contractions of rabbit thoracic aorta were studied. Endothelium-dependent relaxations induced by ACh in phenylephrine-precontracted arteries were enhanced by the scorpion venom. ACh-induced contractions in endothelium-intact open aortic rings were less than those obtained in denuded preparations (n = 6, P < 0.05, ANOVA). Venom (5, 10 and 30 micrograms/ml) potentiated ACh-induced contractions in intact and denuded segments. In the denuded segments, this potentiation was inhibited by indomethacin (10 microM). Thromboxane synthase inhibitor, BW 149H (100 microM) and thromboxane A2 (TXA2) receptor antagonist, R 68070 (10 microM) partly inhibited venom-induced potentiation. NG-nitro-L-arginine (100 microM) increased venom-potentiated ACh responses in intact arterial segments. Venom increased the basal tone by 25-35% at 30 micrograms/ml. These results suggest that A. crassicauda venom may release a relaxing factor from endothelium and contracting factor from the smooth muscle of rabbit isolated thoracic aorta. The contracting factor may be a cyclooxygenase-like product, most likely TXA2. The increase in basal tone by 30 micrograms/ml venom was inhibited by phentolamine (10 microM) and guanethidine (10 microM), indicating a venom-induced release of a neurotransmitter from adrenergic nerve endings.

Acetylcholine↗
PubMed1982

A mammal toxin derived from the venom of a chactoid scorpion.

1. It has been shown that the low toxicity to mammals (LD50 of about 200 mg per kg mice body weight) of the chactoid scorpion venom Scorpio maurus palmatus (Scorpionidae) is due to a single low molecular weight basic protein. 2. This compound was purified by the aid of gel filtration and ion exchange column chromatography, possessed about 80% of the mice lethality of the crude venom with an increase of about 60 fold in its specific toxicity. 3. It is composed of 32 amino acids (mol. wt = 3478) and devoid of isoleucine, leucine, phenylalanine, histidine and tryptophan. 4. The unique amino acid composition of the present toxin is compared to those of the well known buthoid scorpion venom mammal toxins and some other toxins derived from the same venom. 5. It is the first chemically characterized chactoid toxin.

Amino Acids↗
PubMed1986

Comparison of the effect of scorpion venom (Buthus martensii Kashi) on the rat brain and heart mitochondria.

A partially purified fraction SVc and a purified homogeneous polypeptide SVIII were isolated from the scorpion (Buthus martensii Kashi) venom, collected in Shan Dong Province of China. SVc decreased the RCR, ADP/O and Qo2 of the rat brain mitochondria. It also decreased the cytochrome oxidase activity and increased the membrane lipid fluidity of the mitochondria. Effect of scorpion venom on the rat heart mitochondria was somewhat different from that of rat brain mitochondria. SVc also decreased RCR, ADP/O and increased the membrane lipid fluidity of heart mitochondria. However, the Qo2 and cytochrome oxidase activity were increased. SVIII has a similar effect on the rat brain and heart mitochondria, but its concentration used is only 1/10 of the effective concentration of SVc.

Animals↗
PubMed1992

Expression of a gene encoding a scorpion insectotoxin peptide in yeast, bacteria and plants.

The nucleotide sequence encoding the scorpion insectotoxin I5A was chemically synthesized and expressed in yeast, bacteria and tobacco. The I5A peptides produced in these organisms were purified using an immunoaffinity chromatography procedure. I5A produced using the bacterial secretion system was efficiently secreted and released into the culture medium. In contrast, only a trace amount of I5A was detected in bacterial cytosols when expressed from a direct expression vector, suggesting that I5A was unstable in bacterial cells. I5A secreted from yeast using an alpha-factor signal sequence was shown to have an N-terminal (Glu-Ala)2 extension, indicating incomplete processing of the secreted peptide by dipeptidyl aminopeptidase A. In tobacco, a nonsecreted form of the protein was produced. No measurable insect toxicity was observed when insect larvae were assayed, regardless of whether I5A was produced in yeast, bacteria or tobacco. The lack of toxicity is almost certainly the result of improper folding due to incorrect disulfide bond formation. The inability to produce a biologically active peptide must be overcome before scorpion toxins might be used for the genetic engineering of plants for insect resistance. The yeast and bacterial expression systems described here may be useful for further studies on the problem of expressing a biologically active peptide.

Amino Acid Sequence↗
PubMed2005

Solution structure of BmP08, a novel short-chain scorpion toxin from Buthus martensi Karsch.

A novel short-chain scorpion toxin BmP08 was purified from the venom of the Chinese scorpion Buthus martensi Karsch by a combination of gel-filtration, ion exchange, and reversed-phase chromatography. The primary sequence of BmP08 was determined using the tandem MS/MS technique and Edman degradation, as well as results of NMR sequential assignments. It is composed of 31 amino acid residues including six cysteine residues and shares less than 25% sequence identity with the known alpha-KTx toxins. BmP08 shows no inhibitory activity on all tested voltage-dependent and Ca(2+)-activated potassium channels. The 3D-structure of BmP08 has been determined by 2D-NMR spectroscopy and molecular modeling techniques. This toxin adopts a common alpha/beta-motif, but shows a distinctive local conformation and features a 3(10)-helix and a shorter beta-sheet. The unique structure is closely related to the distinct primary sequence of the toxin, especially to the novel arrangement of S-S linkages in the molecule, in which two disulfide bridges (C(i)-C(j) and C(i+3)-C(j+3)) link covalently the 3(10)-helix with one strand of the beta-sheet structure. The electrostatic potential surface analysis of the toxin reveals salt bridges and hydrogen bonds between the basic residues and negatively charged residues nearby in BmP08, which may be unfavorable for its binding with the known voltage-dependent and Ca(2+)-activated potassium channels. Thus, finding the target for this toxin should be an interesting task in the future.

Amino Acid Sequence↗
PubMed2006

Temperature dependence of water loss rates in scorpions and its effect on the distribution of Buthotus judaicus (Buthidae) in Israel.

Scorpions of the family Buthidae have been shown to be more desiccation resistant in comparison with sympatric Scorpionidae species. This has been attributed to the surface-dwelling existence of the former, which unlike most other scorpion species do not avoid environmental extremes by burrowing. Still, within Buthidae, the mesic Buthotus judaicus showed better osmoregulatory capacities than the xeric Leiurus quinquestriatus, largely as a result of its high resistance to water loss. However, B. judaicus exhibited poor ability to regulate its haemolymph osmolarity at 37 degrees C. In this study we report a sharp increase in water loss rates of B. judaicus at the 30-35 degrees C temperature range compared to that measured for L. quinquestriatus, which could explain the poor osmoregulatory performance of the former at higher ambient temperatures. The increase in water loss rates of B. judaicus at high temperatures is not coupled with a similar increase in respiratory rate, suggesting an increase in cuticular permeability. We suggest that this increase in cuticular permeability, which may result from a relatively low critical transition temperature, contributes to limiting the distribution of B. judaicus to habitats of moderate environmental conditions.

Animals↗
PubMed2003

Humicolous buthoid scorpions: a new genus and species from French Guiana.

A new genus and species of humicolous buthid scorpion are described on the basis of a single specimen collected in French Guyana. New considerations on the taxonomy and morphology of some micro-buthoid humicolous scorpions are proposed, mainly based on the study by scanning electron microscopy of the peg-shaped sensillae of the pectines.

Animals↗
PubMed2004

Humicolous microcharmid scorpions: a new genus and species from Madagascar.

A new genus and species of humicolous microcharmid scorpion are described on the basis of a single specimen collected in the Ankarana Reserve, Madagascar. New considerations regarding the taxonomy and morphology of micro-buthoid Malagasy scorpions are proposed, based mainly on the study of the peg-shaped sensillae of the pectines by scanning electron microscopy.

Animals↗
PubMed2005

Humicolous buthoid scorpions: a new species from Brazilian Amazon.

A new species of humicolous buthid scorpion is described on the basis of a single specimen collected in the Brazilian Amazonia. New considerations on the taxonomy and biogeography of some micro-scorpions of the subfamily Ananterinae Pocock, 1900 are proposed in relation to their possible evolution from endogeous to epygean environments.

Animals↗
PubMed2005

A reappraisal of the geographical distribution of the genus Pseudouroplectes Lourenço (Scorpiones: Buthidae) in Madagascar.

We review aspects of the distributional patterns of Malagasy scorpions belonging to the endemic genus Pseudouroplectes (family Buthidae), restricted to dry forests formations in the south and southwest. One species is described here as new to science. We propose that the observed distributional pattern of members of this genus is not only a consequence of recent ecological features of the landscape, but also of historical biogeographical factors associated with the antiquity of this scorpion lineage.

Animals↗
PubMed2006

Acute left ventricular dysfunction of severe scorpion envenomation is related to myocardial perfusion disturbance.

BACKGROUND: Scorpion envenomation (SE) may present severe cardiac dysfunction with acute pulmonary edema and cardiogenic shock. The pathophysiology of this acute heart failure is still controversial. We aimed at assessing the contribution of the myocardial ischemia to the left ventricular dysfunction in SE by using 99mTc-Sestamibi myocardial perfusion scintigraphy (MPS). METHODS: Twelve children (7 males, 1-12 years old) presenting severe Tityus serrulatus envenomation were prospectively submitted to MPS within 72 h (acute) and 15 days (follow-up) after the event. MPS images were interpreted using a visual semi-quantitative uptake score (0 = normal, 4 = absent). Echocardiography was used for the assessment of left ventricular (LV) ejection fraction (EF) and regional wall motion (WM) by using a semi-quantitative score (0 = normal, 4 = akinesia). A 16-segment LV model was used. RESULTS: Initial echocardiography showed marked WM abnormalities with a mean score of 31.4+/-13.9, and a reduced EF (36+/-16%). All patients exhibited myocardial perfusion (MP) defects. The mean MP uptake score was 14.6+/-7.8. A significant topographic association between MP and WM changes was obtained (p<0.0001, Fischer exact test). A positive correlation was obtained between the summed WM and MP scores (R=0.68, p=0.016). Follow-up evaluation showed a significant improvement of LVEF (65+/-10%) and WM score (3.9+/-4.2), parallel to the normalization of MP. CONCLUSIONS: These observations strongly support the participation of transitory myocardial ischemia in the mechanism of the acute cardiac dysfunction caused by severe scorpion envenoming. Micro vascular spasm related to the catecholamine over stimulation may be the pathophysiologic link triggering the myocardial perfusion disturbance in this syndrome.

Acute Disease↗
PubMed2026

Scorpion venom peptides: Novel therapeutic approaches for inflammatory and hepatic disorders.

Chronic hepatic disorders, such as metabolic dysfunction associated steatohepatitis (MASH), alcohol associated liver disease (ALD), and viral hepatitis (Hepatitis B virus [HBV]/Hepatitis C virus [HCV]), are primarily driven by persistent immune-mediated inflammation and hepatic stellate cell activation leading to fibrosis, yet conventional therapies lack tissue and molecular specificity. Scorpion venom peptides, refined through evolutionary selection, provide highly potent, target specific scaffolds capable of modulating intrahepatic inflammatory networks. Recent in vivo preclinical studies indicate that voltage gated potassium (Kv1.3) channel blocking peptides, such as BmKK2, significantly reduce macrophage activation and inhibit downstream cytokine production, effectively ameliorating diet-induced steatohepatitis and tissue scarring in murine models. Engineered hepatotropic candidates, such as Smp76 and Mucroporin-M1, demonstrate dual therapeutic functions: they neutralize extracellular Hepatitis C particles and suppress key host transcription factors necessary for Hepatitis B replication. This review systematically examines scorpion venom peptides organized by disease category, covering their historical development, structural classification into disulfide-bridged and non-disulfide-bridged families, ion channel specificity, hepatic anti-inflammatory and antiviral mechanisms, and translational challenges including nano-formulation delivery strategies and computational drug design. These target-specific peptides are ultimately positioned as promising molecular leads that may bridge targeted immunomodulation with the resolution of chronic, progressive liver injury.

Anti-inflammatory effects↗
PubMed2005

Activation of the complement system and leukocyte recruitment by Tityus serrulatus scorpion venom.

The scorpion Tityus serrulatus is considered one of the most dangerous species in Brazil. Its venom evokes an inflammatory response, although the exact mechanism of this effect is still unknown. The aim of the present study was to investigate the effect of Tityus serrulatus venom (TsV) on the complement system (CS) and on leukocyte recruitment. Complement consumption by TsV was evaluated using in vitro hemolytic assays, immunoelectrophoresis and two-dimensional immunoelectrophoresis of complement components (factor B and C3). In order to evaluate neutrophil migration induced in normal human serum (NHS) in the presence of TsV, in vitro chemotaxis assays were performed using the Boyden chamber model. In vitro TsV induced a concentration- and time-dependent reduction in hemolytic activity of the classical/lectin and alternative complement pathways, with samples of 43.0 microg and 43.4 microg, respectively, inhibiting 50% of the lytic activity. Alterations in C3 and factor B electrophoretic mobility after incubation of NHS with TsV, were identical to those obtained with zymosan (positive control). Incubation of NHS with TsV induced neutrophil chemotaxis similar to that observed with zymosan-activated serum. Our results show that TsV activates the CS, leading to factor B and C3 cleavage, to reduction of serum lytic activity and generation of complement chemotactic factors. Therefore, CS may play an important role in the inflammatory response observed upon scorpion envenomation.

Animals↗
PubMed2004

Insulin-like effects of Bauhinia forficata aqueous extract upon Tityus serrulatus scorpion envenoming.

Scorpion envenoming causes an intense autonomic discharge, leading to a massive release of neurotransmitters, giving rise to several pathophysiological effects. In this work we report the effects of a Bauhinia forficata aqueous extract (BfAE) upon hyperglycemia, glycogenolysis, increase of plasma catecholamines, lethality and changes in serum insulin and plasma electrolytes induced by Tityus serrulatus scorpion venom (TSV). We compare them with the effects of the regular insulin therapy. The following treatments were performed: TSV (500 microg/kg, i.p.); BfAE (1g/kg, p.o.), 24, 12 and 1 h before and immediately after TSV or saline and insulin in a single dose (1.5 IU/kg, s.c.) after TSV. BfAE reduces the fast hyperglycemia induced by TSV, but it is deprived of hypoglycemic activity. The extract also did not reduce either the intense glycogenolysis or the release of catecholamines and did not stimulate the release of endogenous insulin, although causing changes in the electrolyte plasma levels similarly to insulin. Although BfAE and insulin antagonize some effects of TSV, they should be avoided in the treatment of Tityus serrulatus envenoming, since they enhance the lethality of the venom.

Animals↗