Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SCORPIONS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,027 records · Page 57Linked to original sources
PubMed1986

A comparison of the actions of cobra cardiotoxin and scorpion toxin II on the guinea-pig taenia coli.

Both cobra cardiotoxin (CTX) and scorpion toxin II induce contracture of the guinea-pig taenia coli, the latter being more potent than the former. Tachyphylaxis was observed with each toxin. Acetylcholine (ACh) contracture was enhanced by toxin II but not by CTX. High K+ (152 mM) abolished toxin II contracture but only partially inhibited CTX and ACh contractures. Ca2+-free medium, especially in the presence of 1 mM EGTA, inhibited CTX- and toxin II-contracture by more than 60%, but abolished ACh contracture. On the other hand, high Ca2+ (12 mM) was without effect on ACh contracture but inhibited both CTX- and toxin II-contracture, and enhanced K+ contracture. Contracture was produced after washout of Ca2+-free medium and toxins but not after washout of high Ca2+ medium, suggesting that the binding of toxins was inhibited by high Ca2+. Tetrodotoxin (TTX) abolished toxin II contracture, but only partially inhibited CTX contracture. Atropine markedly inhibited toxin II contracture but did not significantly affect CTX contracture. Procaine potentiated CTX contracture but abolished toxin II contracture. The spontaneous contraction induced by toxin II was also inhibited by TTX, atropine and procaine. ACh contracture was abolished by atropine and potentiated by procaine, but unaffected by TTX. The rate of decline of K+ (60 mM) contracture in Ca2+-free medium was enhanced by CTX but unaffected by toxin II. 45Ca2+ efflux was increased by CTX more than by toxin II. Both toxins also significantly increased 45Ca2+ uptake. These findings indicate that CTX induces contracture of taenia coli mainly by releasing the Ca2+ pool of the muscle membrane, whereas toxin II does so mainly by releasing acetylcholine from nerve terminals and partially by acting on the muscle membrane as a result of an increase of the membrane Na+ permeability.

Acetylcholine↗
PubMed1986

Large scale purification of toxins from the venom of the scorpion Androctonus australis Hector.

A large scale procedure for purification of the toxins in the venom of the North African scorpion Androctonus australis has been developed. This procedure optimizes the sequence of the steps, leading to better yields of toxins and shortening of the time. It is possible to use 10-15 g batches of venom and also prevent cross-contamination of the toxins. High pressure liquid chromatography has been used to separate AaH I and I', two isotoxins which differ by one amino acid residue in position 17: valine or isoleucine. The procedure allows the characterization of a new toxin active in mice, AaH IV, which represents 0.6 and 2.5% of the venom weight and toxicity, respectively. This new component has been characterized as an alpha toxin made up of 61 amino acid residues and having a neutral isoelectric point.

Amino Acids↗
PubMed1987

Re-examination of the specificity of the scorpion Androctonus australis hector insect toxin towards arthropods.

The toxicity of the insect toxin from the venom of the scorpion Androctonus australis Hector has been studied in six species of insects, three species of crustaceans (two terrestrial and one aquatic) and in mice. Paralysing and lethal effects were observed not only in insects but also on the three crustacean species. For insects the LD50 varies from 2 to 1310 ng per 100 mg of insect, according to the species. On crustaceans doses up to 3-9 micrograms per 100 mg of animal induced a paralysing or lethal effect. In mice injections of 0.05 and 1 mg of the toxin intracerebroventricularly and s.c. resulted in no apparent symptoms of intoxication. These results demonstrate that the insect toxin of Androctonus australis Hector has no toxicity for the mouse, but also that it is not absolutely specific for insects.

Animals↗
PubMed1987

Purification of contracture-inducing insect toxins from Buthinae scorpion venoms by immunoaffinity and high pressure liquid chromatography.

A method of rapid and selective detection and purification of contracture-inducing insect toxins from Buthinae scorpion venoms is described in this paper. It consists of two main steps: the first one is specific as it uses immunoaffinity chromatography with antibodies against Androctonus australis Hector IT; the second, reverse phase high pressure liquid chromatography, allows the final separation of the different toxins present in each of the three venoms studied. Two, three and four insect toxins have been purified, respectively, from the venoms of Androctonus australis Hector, Buthus occitanus mardochei and Leiurus quinquestriatus quinquestriatus. This work demonstrates that, in Buthinae venoms, contracture-inducing insect toxins antigenically related to AaH IT, the first one purified, constitute the most important and, in some cases, the only toxins present.

Amino Acids↗
PubMed1987

Antigenicity of peptide 19-28 of toxin II from the scorpion Androctonus australis as measured by different solid-phase tests and characterization of specific antibodies purified by immunoaffinity on the peptide or the toxin.

The antigenicity of peptide 19-28, a model of one of the major antigenic regions of toxin II of the scorpion Androctonus australis Hector was tested in different solid phase radioimmunoassay systems. The type of the solid phase and the mode of binding the synthetic peptide to the phase had a considerable effect on the resulting antigenicity. Two subpopulations of anti-toxin II antibodies were purified by affinity chromatography, one on Sepharose-peptide 19-28, the other on sepharose-toxin. The native or chemically modified toxin bound in the same way to these subpopulations. Denatured toxin was only poorly recognized by these antibodies. This suggests that the antibodies purified on peptide 19-28 recognize the same conformation dependent antigenic surface as do total anti-toxin antibodies.

Antibodies↗
PubMed1988

Isolation of several toxins from the venom of the scorpion Centruroides limpidus tecomanus Hoffmann.

The soluble venom of the scorpion of Colima, Mexico, was fractionated by Sephadex G-50 gel filtration followed by separation of the toxic fraction (number II) with carboxymethyl-cellulose columns in 20 mM ammonium acetate buffer, pH 4.7. Of 24 fractions five were toxic to mice and were further separated in 50 mM phosphate buffer, pH 6.0 using the same ion exchange resin. Final separation included chromatography of the toxic subfractions in the same resin, but in 75 mM ammonium acetate buffer, pH 5.0. By this procedure at least five distinct toxins were obtained in pure form according to gel electrophoresis analysis. Amino acid composition of toxin 1 (component II.20.3.4) and toxic component II.22.5 is included. The N-terminal amino acid sequence of component II.22.5 was shown to be: Lys-Glu-Gly-Tyr-Ile-Val-Asn-Tyr-His-Thr-Gly-Cys-Lys-Tyr-Thr-Cys-Ala-Lys- Leu-Gly - Asp-Asn-Asp-Tyr-Cys-Leu-Arg-Glu-Cys-Lys-.

Amino Acid Sequence↗
PubMed1989

Block of potassium channels and facilitation of acetylcholine release at the neuromuscular junction by the venom of the scorpion, Pandinus imperator.

Venom from the scorpion Pandinus imperator potently and selectively blocks voltage-gated K+ channels in bullfrog neurones (Pappone, P. A. and Cahalan, M. D. 1987, J. Neurosci. 7, 3300-3305). Its effects on neuromuscular transmission have now been assessed. Twitch tension studies on chick biventer cervicis preparations showed that the venom (1 microgram/ml and above) significantly augmented responses to nerve but not muscle stimulation; there was little change in postjunctional sensitivity to cholinoceptor agonists or K+-induced depolarization. Electrophysiological studies on mouse triangularis sterni preparations revealed that the venom had no effect on spontaneous transmitter release, but increased evoked transmitter release. Extracellular recordings of nerve terminal action potentials showed that the venom selectively reduced the component of the waveform associated with K+ currents. These results confirm that this venom can selectively block neuronal K+ currents, and they show that this can facilitate the release of acetylcholine at the neuromuscular junction.

4-Aminopyridine↗
PubMed1990

Isolation and characterization of toxic proteins from the venom of the Venezuelan scorpion Tityus discrepans (Karsch).

Four toxic, electrophoretically homogeneous proteins were isolated by ion-exchange chromatography on CM-cellulose-52 from the venom of the scorpion Tityus discrepans (range North Central Venezuela), named TdIV, TdV, TdVIII and TdIX. Component TdVIII, with 56 amino acid residues and mol. wt 6140 was the most toxic by i.p. injections into mice and had an intracisternal LD50 of 7.9 micrograms protein/kg body weight. Amino acid compositions of components TdIV and TdV were very similar, suggesting that they could be highly homologous proteins, although presumably contaminated one by the other. A fifth component, named TdIII, non-toxic by i.p. injections, was also isolated in homogeneous form. The i.v. and intracisternal LD50 values of the whole T. discrepans venom were 2.5 mg/kg and 16.0 micrograms/kg, respectively.

Amino Acids↗
PubMed1990

Effect of a bradykinin potentiating fraction, from venom of the Egyptian scorpion, Buthus occitanus, on the ovaries and endometrium of mice.

An isolated fraction with bradykinin potentiating activity, from the venom of the Egyptian scorpion Buthus occitanus, was injected i.p. in female mice (35 days old). Five days after the injection of a single sublethal dose (1 micrograms/g), the number of primary multilaminar and secondary follicles of the ovaries was increased. Graafian follicles were observed in 50% of the treated mice but in none of the control mice. The number and size of the uterine glands and endometrium were increased in treated mice. Concomitantly, estradiol was increased in the circulating blood, while progesterone was within the normal limits. The enhancement of cellular growth by the isolated venom fraction with bradykinin potentiating activity, could be attributed to an enhancement of some growth factor(s) responsible for stimulating the ovarian follicles and uterus.

Animals↗
PubMed1991

Further characterization of toxins T1IV (TsTX-III) and T2IV from Tityus serrulatus scorpion venom.

Toxins T1IV (TsTX-III) and T2IV have been purified to homogeneity from Tityus serrulatus scorpion venom and further characterized. Their amino acid composition and SDS-PAGE reveal an approximate mol. wt of 7000. Their intracisternal LD50 (micrograms/kg) in mice were 12.9 +/- 1.6 and 3.0 +/- 0.5, while their N-terminal amino acid sequences were K-E-G-Y-A-M-D-H-E-G-C-K-F-S- and K-E-G-Y-L-M-D-H-E-G-C-K-L-S-C-F-I-R-P-S-G-Y-C-G-R-E-, respectively. This sequence of T2IV, its amino acid composition and its chromatographic and electrophoretic behaviour identify it as toxin gamma (TsTX-I), which is the major toxin from this venom. TsTX-III (13 to 102 micrograms/kg) produced a long lasting enhancement of the hypertensive effect of noradrenaline and a slight decrease of the hypotensive effect of acetylcholine, while T2IV (115 micrograms/kg) induced a prolonged hypotensive effect on the anesthetized rat. On the isolated guinea-pig vas deferens, TsTX-III (2.1 and 3.0 micrograms/ml) produced a horizontal shift of the dose-response curve for noradrenaline to the left with no change of the maximal response. At a concentration of 1.43 microM, it induced a prolongation of the duration of the B component of the compound action potential. This prolongation was strongly reduced after addition of tetrodotoxin.

Acetylcholine↗
PubMed1991

Chloride channel inhibition by the venom of the scorpion Leiurus quinquestriatus.

The venom of the scorpion Leiurus quinquestriatus produced a significant, reversible inhibition of reconstituted Cl- channels of the small conductance type found in rat colonic epithelial cells. The kinetics of single-channel block by this venom were consistent with a first-order binding reaction in which the binding of one ligand molecule is sufficient to induce channel block. Single-channel mean block times were c.6 sec at -20 mV, and a KI in the submicromolar range is predicted. The active component has a mol. wt of roughly 5000 as judged by molecular sieve chromatography.

Animals↗
PubMed1992

The effects of Indian red scorpion Buthus tamulus venom in vivo and in vitro.

The Indian red scorpion Buthus tamulus (or Mesobuthus tamulus) can cause fatal envenoming, but its mechanism of action is unclear. Venom was tested in vivo in anaesthetized rats and in vitro on isolated cardiac and skeletal muscle preparations. In vivo, the venom caused marked rhythmical fluctuations in blood pressure preceding cardiovascular collapse and death. On sheep Purkinje fibres, venom could induce spontaneous action potentials and cause prolongation of action potential duration. In chick biventer cervicis and mouse triangularis sterni preparations, venom enhanced the release of acetylcholine and induced repetitive firing of nerve action potentials in response to single shock stimulation. High concentrations caused stimulation then block of neuromuscular transmission. The main effects of Buthus tamulus venom are likely to be due to toxins that affect the opening of Na+ channels in nerves and muscles. This will cause an increase in the release of neurotransmitters in the peripheral nervous system, which may produce cardiovascular abnormalities and respiratory paralysis.

Action Potentials↗
PubMed1992

Purification of the main beta-toxin from Tityus serrulatus scorpion venom using high-performance liquid chromatography.

The venom of the Brazilian scorpion Tityus serrulatus was fractionated using high-performance liquid chromatography which allowed us to purify in two steps the main beta-type toxin of the venom. The toxin constituted about 15% of the absorbance at 280 nm and 50% of the toxicity of the venom. According to its amino acid content, its electrophoretic migration on Phast-Gel homogenous 20 and its biological properties both in vivo by intracerebroventricular injection to the mouse (LD50 = 30 ng/kg mouse) and in vitro by competition receptor assay on rat brain synaptosomes (K0.5 = 80 pM), the toxin was identified as toxin Ts VII already purified from the same venom using low-pressure liquid chromatography (BECHIS et al., 1984 Biochem. biophys. Res. Commun. 122, 1146). The high-performance liquid chromatographic technique used improved by a factor of four the amount of toxin purified.

Animals↗
PubMedDate not supplied

Effects of Buthus martensii (Karsch) scorpion venom on sodium currents in rat anterior pituitary (GH3/B6) cells.

The effects of two fractions (II, containing anti-insect toxins, and III, containing eight anti-mammal toxins) isolated from the venom of the Old World scorpion Buthus martensii (Karsch) on Na+ currents of rat anterior pituitary cells (GH3/B6 cells) were investigated using the whole-cell configuration of the patch clamp technique. Fraction II induced a temporary, and fraction III a permanent increase of the Na+ current amplitude. Application of each of the venom fractions resulted in a flattening of the curve relating steady state Na+ inactivation to membrane potential. In addition, the two fractions had specific effects. Fraction II shifted the voltage dependence of Na+ current activation by -42 mV, and the voltage dependence of Na+ inactivation by -25 mV in the absence of a conditioning depolarizing pre-pulse. Slowing of Na+ inactivation was most prominent at negative membrane potentials, resulting in a steady Na+ inward current at the holding potential of -80 mV. Fraction III induced a pronounced slowing of Na+ inactivation leading to an increase of peak Na+ currents and to incomplete steady state Na+ inactivation even at positive membrane potentials.

Animals↗
PubMed1992

Effects of toxin Ts-gamma, purified from Tityus serrulatus scorpion venom, on the isolated rat atria.

By using a pair of silver/silver-chloride electrodes it was possible to record, simultaneously, the atrial electrogram and the atrial contractile force of rat atria, in an organ bath, containing Krebs-Ringer solution (30 degrees C, pH 7.4, bubbled with 95% O2 and 5% CO2). Addition of toxin Ts-gamma, purified from Tityus serrulatus scorpion venom, into the bath (1 microgram/ml), evoked complex effects characterized by an initial reduction of both rate and contractile force, followed by increase of force and reduction of rate and finally by reduction of both rate and force. The increase of contractile force was prevented by metoprolol and is, therefore, adrenergic in nature. The reduction of rate was concomitant with changes in the atrial electrogram in which a positive P wave was replaced by a diphasic P wave, while the positive Ta wave was depressed. Experiments with tetrodotoxin, atropine and physostigmine indicate that these effects are due to the release of acetylcholine from vagal endings.

Acetylcholine↗
PubMed1993

Effects of scorpion (Buthus tamulus) venom on neuromuscular transmission in vitro.

The effects of venom from the Indian red scorpion Buthus tamulus (BT) on neuromuscular transmission have been investigated by means of twitch tension and electrophysical recording techniques using isolated skeletal muscle preparations. On chick biventer cervicis preparations, BT (1-3 micrograms/ml) augmented the twitch responses to indirect, but not direct, muscle stimulation. Higher concentrations caused a transient augmentation followed by a large contracture and then a reduction in twitch height. BT at the concentrations tested caused little change in postjunctional sensitivity as assessed by responses to exogenous acetylcholine, carbachol and KCl. Tubocurarine abolished the prolonged contracture induced by BT (10 micrograms/ml) in the presence or absence of nerve stimulation. On mouse hemidiaphragm preparations, BT (3-10 micrograms/ml) increased the twitch responses to indirect stimulation but caused little change in directly stimulated preparations. On mouse triangularis sterni preparations, BT (3-10 micrograms/ml) increased quantal content of the evoked end-plate potentials (epps) by about 70%, without markedly affecting the time course and amplitude of miniature epps. BT also caused repetitive epps in response to single shock nerve stimulation. Extracellular recording of nerve terminal current waveforms in triangularis sterni preparations revealed that BT (10-30 micrograms/ml) slightly reduced the amplitude of the waveform. Subsequently, BT induced repetitive firing of nerve endings in response to single shock stimulation, and eventually markedly prolonged the time course of the nerve terminal waveform. The effects caused by BT were different from those caused by iberiotoxin, the blocker of Ca(2+)-activated K+ currents, isolated from BT. The effects were similar to those caused by ATX-II, a toxin that delays inactivation of Na+ channels. However, BT and ATX-II behaved differently in the presence of K+ channel blockers, 3,4-diaminopyridine (DAP) and tetraethylammonium (TEA). These results confirm that Buthus tamulus venom acts mainly prejunctionally to increase the release of acetylcholine. The effect of BT on the perineural waveforms suggests that some of its actions may be due to effects on Na+ channels at or near the nerve terminals; however, additional effects of K+ channels are likely.

Animals↗
PubMed1993

Peptide T, a novel bradykinin potentiator isolated from Tityus serrulatus scorpion venom.

A bradykinin-potentiating peptide was isolated and characterized from venom of the scorpion Tityus serrulatus by chromatographic techniques followed by biological assays. The complete amino acid sequence (13 residues) of peptide is presented. The peptide potentiated the contractile activity of bradykinin on the isolated guinea-pig ileum, and inhibited the hydrolysis of bradykinin by angiotensin-converting enzyme from B. jararaca plasma and the conversion of angiotensin I to angiotensin II by kininase II from guinea-pig ileum tissue. The peptide also increased the depressor effect of bradykinin on arterial blood pressure in the anaesthetized rat.

Amino Acid Sequence↗
PubMed1993

Behavioural and electroencephalographic effects of Tityus serrulatus scorpion venom in rats.

This study was designed to investigate the convulsant effects of T. serrulatus scorpion venom in rats. Pretreatment of rats with venom increased the minimum convulsant dose of picrotoxin, impaired convulsion generalization and displaced to the left the dose-response curve for picrotoxin. It also decreased the intensity but prolonged the duration of seizures caused by pentylenetetrazol injection. Microinjection of the venom into the dorsal hippocampus induced behavioural alterations and epileptiform waves in the EEG. Venom also altered the threshold for, and intensity of, convulsions induced in different experimental models of epilepsy. Different fractions of the venom may be responsible for these different effects. Therefore, purification of venom toxins is necessary for the complete understanding of the present results.

Animals↗