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At least 991 records · Page 55Linked to original sources
PubMed1990

Localization of voltage-sensitive sodium channels on the extrasynaptic membrane surface of mouse skeletal muscle by autoradiography of scorpion toxin binding sites.

Voltage-dependent sodium channels (Na+ channels) were localized by autoradiography on mouse skeletal muscle using both light and electron microscopy. 125I-scorpion toxins (ScTx) of both the alpha and beta type were used as probes. The specificity of labelling was verified by competitive inhibition with unlabelled toxin and by inhibition of alpha ScTx labelling in depolarizing conditions. Under light microscopy, the labelling of the myocyte surface appeared randomly distributed with both the alpha and beta toxins. No difference in the labelling density obtained with beta ScTx was observed between a 2 mm central segment of the fibre containing the endplate and an adjacent segment not containing the endplate. At the endplate, however, the beta ScTx binding site density was about seven fold higher at the edge of the synaptic primary clefts. This density decreased with distance from the synaptic cleft reaching the extrasynaptic value at 30-40 microns. An analysis of myocyte labelling using electron microscopy provided evidence for a specific, but very low labelling of the myocyte interior which can be attributed to the T-tubules. These results confirm a relatively high density of Na+ channels in a perijunctional zone about 50 microns in width, which could ensure the initial spread of the surface depolarization with a high safety factor, and a homogeneous distribution over the remaining surface with a low density evaluated at 5-10 per microns2. However, the very low labelling of T-tubules could be attributed mainly to a low density of tubular Na+ channels.

Animals↗
PubMed1988

Mechanism of inactivation of single sodium channels after modification by chloramine-T, sea anemone toxin and scorpion toxin.

Single sodium-channel currents were measured in neuroblastoma cells after inhibition of inactivation by chloramine-T (CHL-T), sea anemone toxin II (ATX-II) and scorpion toxin (SCT). The decaying phase of the averaged single-channel currents recorded with 90-msec pulses in cell-attached patches was clearly slower than that of the ummodified channels, suggesting inhibition of macroscopic inactivation. Each substance caused repetitive openings and a moderate increase in the channel open time. At Vm = RP + 20 mV and T = 12 degrees C, the mean channel open times were 1.4, 1.6 and 1.8 msec for CHL-T, ATX-II and SCT, respectively, as opposed to 1.07 msec for native channels. Open-time histograms could be best fitted by the sum of two exponentials. The time constants of the fits were similar for histograms constructed from single openings and from openings during bursts. This suggests that the population of channels is homogeneous and that in bursts the same open conformations of channels occur as in single openings. Mean burst durations for bursts consisting of more than one opening at Vm = RP + 20 mV were 4.9, 5.8 and 6.1 msec for CHL-T, ATX-II and SCT, respectively. Burst open-time histograms constructed from two or three openings were fitted by the gamma function. The different time constants of the fits obtained for ATX-II and SCT suggested multiple open conformations of channels for openings of bursts. However, significantly different open-time histograms constructed from the first, second and third openings of bursts could not be obtained systematically. A positive correlation was found for the dwell time of the first and the second, as well as for the second and the third opening of bursts with each substance, but a negative one for the dwell time of an opening and the neighboring closing of bursts with ATX-II. The results suggest a model with multiple open and inactivated states. In this model the inactivated states are weakly absorbing.

Animals↗
PubMed1984

Serum lectins from the scorpion Vaejovis spinigerus Wood bind sialic acids.

We have partially characterized the specificity of serum lectins from the scorpion Vaejovis spinigerus Wood. Agglutination, crossed-absorption and hemagglutination-inhibition patterns were similar but not identical to serum lectins from other members from the family Vaejovidae , and different from the Buthidae species studied so far. V. spinigerus serum lectins bind sialic acids and sialoconjugates , but also bind 2-keto-3-deoxyoctonate, uronic acids and N- acylaminosugars , all substances present in bacterial cell walls suggesting that they might be involved in defense functions.

Animals↗
PubMed1978

Mechanism of the pulmonary edema induced by intravenous injection of scorpion toxin in the rat.

The intravenous injection of purified scorpion toxin (tityustoxin, TsTX) into unanesthetized rats induces a severe systemic hypertension followed by a hemorrhagic edema of the lungs. The edema is focal or diffuse, whereas the hemorrhage is always focal and less prominent than the edema. Anesthesia of the rats prevents the appearance of pulmonary edema. It seems likely that this protective action of the anesthesia is due, at least in part, to an interference with the hypertension induced by TsTX. The pulmonary edema is prevented by bilateral adrenalectomy, guanethidine or phenoxybenzamine. It is suggested that the edema depends on a sympathetic-adrenal discharge and that catecholamines released by TsTX act on alpha adrenergic receptors. The mean kininogen content of the rat plasma, 1 h after TsTX injection, is not significantly different from that found in the control animals. The possible role played by kinins and other mediators in the early phases of the pulmonary edema induced by TsTX is under investigation.

Adrenalectomy↗
PubMed1978

Effect of scorpion toxin (tityustoxin, TsTx) on the salivary gland of the rat, in vivo and in vitro.

Intravenous injection of purified scorpion toxin (tityustoxin, TsTX) brings about the appearance of salivary flow and of kallikrein and amylase secretion in the saliva of rats. In experiments performed in vitro, using slices of parotid gland, a dose-response curve correlating tityustoxin concentration with kallikrein and amylase activities was obtained. The secretion of kallikrein is slower and smaller than that of amylase after up to 60 min of incubation. Experiments in which propranolol, phenoxybenzamine or atropine were injected into rats or added to parotid gland slices showed that the release of kallikrein is more dependent on cholinergic mechanisms, whereas the release of amylase is mainly related to adrenergic effects. Pre-treatment of the animals with reserpine confirms these results. The actions of tityustoxin on the kallikrein and amylase secretions, per min, are more effective than those by pilocarpine and isoproterenol, respectively.

Amylases↗
PubMed1984

Classification of scorpion toxins according to amino acid composition and sequence.

Scorpion venom toxins were systematically classified according to amino acid composition, insertion/deletion events and sequence. The significance of each comparison method and its outcome is discussed in relation to known immunological and structural properties. A general classification of the toxins is proposed that accounts for both the immunological groupings and the differences in mode of action.

Amino Acid Sequence↗
PubMed1983

Production of acute hemorrhagic pancreatitis in the dog using venom of the scorpion, Buthus quinquestriatus.

Acute hemorrhagic pancreatitis has been produced in dogs by two separate intraarterial injections (20 and 10 micrograms/kg) of venom from the scorpion Buthus quinquestriatus. Morphological changes related to the development of the disease were detectable by electron and light microscopy at 1 and 3 hr, respectively, following the injection of venom. Six hours following venom injection, widespread areas of hemorrhage and fat necrosis were observed on the surface of the pancreas and adjacent mesenteries. By 24 hr, areas of fat necrosis more than 1 cm in diameter were present on the surface of the pancreas. No free protease was found in pure pancreatic juice collected at 3, 6, 24, and 96 hr after the injection of Buthus quinquestriatus venom. Amylase concentrations in serum increased to a maximum sevenfold above the basal level at 6-8 hr after injection. Since acute hemorrhagic pancreatitis occurred both with and without pancreatic duct cannulation, it is likely that the pathological process is independent of any venom effect on papillary sphincter tone. The morphological characteristics of the experimental disease appear similar to those observed at autopsy in acute hemorrhagic pancreatitis in humans.

Acute Disease↗
PubMed2004

Antimicrobial peptide induction in the haemolymph of the Mexican scorpion Centruroides limpidus limpidus in response to septic injury.

Antimicrobial peptides (AMPs) are essential components of host defences against infectious microrganisms. In chelicerate organisms they have been implicated in three alternative defensive systems: one is defined by the immediate up-regulation of genes encoding AMPs, another is characterized by the inducible systemic release of AMPs from cellular reservoirs and the third alternative is the systemic constitutive production of AMPs. In this work we used a differential high-performance liquid chromatography and mass spectrometry approach to show that septic injury elicits an immune response in the haemolymph of the Mexican scorpion Centruroides limpidus limpidus. We isolated several haemolymph components, one of which was characterized extensively (amino acid sequence, disulphide pairing, cDNA and genomic clones) and demonstrated to be a novel member of the invertebrate defensin family and consequently named C. limpidus limpidus defensin-like peptide (Cll-dlp). This peptide accumulates in the haemolymph in response to septic injury, independently of transcriptional regulation.

Amino Acid Motifs↗
PubMed1995

Use of dantrolene in experimental scorpion envenomation by Androctonus australis hector.

Hyperthermia and profuse perspiration are rarely absent in severe cases of scorpion envenomation. Based on these observations, the aim of this study was to determine the therapeutic effects of dantrolene, on experimental poisoning by the venom of Androctonus australis hector. Dantrolene is a directly acting muscle relaxant which lowers the body temperature in malignant hyperthermia. The results indicate that the early use of this drug raises the LD50 in experimentally poisoned mice. If these results are transposable to humans, dantrolene could be a useful therapeutic adjuvant.

Animals↗
PubMed1997

A model of scorpion toxin binding to voltage-gated K+ channels.

Mutational studies have identified part of the S5-S6 loop of voltage-dependent K+ channels (P region) responsible for tetraethylammonium (TEA) block and permeation properties. Several scorpion peptide toxins-charybdotoxin (ChTX), kaliotoxin (KITX), and agitoxin (AgTX)-also block the channel with high affinity and specificity. Here, we examine the interaction predicted when the toxins are docked onto the molecular model of the K+ channel pore that we recently proposed. Docking with the model of the Kv1.3 channel started by location of Lys-27 side chain into the central axis of the pore, followed by energy minimization. In the optimal arrangement, Arg-24 of KITX or AgTX forms a hydrogen bond with the Asp-386 carboxyl of one subunit, and Asn-30 is in immediate contact with Asp-386 of the opposing subunit in the tetramer. Toxin residues in proximity to the side chain of Lys-27 (Phe-25, Thr-36, Met-29, and Ser-11 in KITX) interact with the four C-end His-404s. For ChTX the interaction with Asp-386 is reduced, but this is compensated by additional nonbonded interactions formed by Tyr-36 and Arg-34. Comparison of calculated energy of interaction of these specific toxin-channel residues with experimental studies reveals good agreement. The similar total calculated energy of interaction is consistent with the similar IC50 for Kv1.3 block by KITX and AgTX. Steric contacts of residues in position 380 of the S5-P linker with residues on the upper part of toxins permit reconstruction of the K+ channel outer vestibule walls, which are about 30 A apart and about 9 A high. Molecular modeling shows complementarity of the pore model to toxin spacial structures, and supports the proposal that the N-terminal borders of the P regions surround residues of their C-terminal halves.

Amino Acid Sequence↗
PubMed1997

Response properties of chemosensory peg sensilla on the pectines of scorpions.

By behavioral and anatomical criteria, the pectinal sensory appendages of scorpions appear to be chemoreceptive organs specialized for detection of substances on substrates. These comb-like, midventral appendages contain tens of thousands of minute (< 5 microns), truncated setae, called pegs, arranged in dense, two-dimensional arrays on the ventral surface. In this study we used extracellular recording techniques to examine spontaneous and stimulated activity of sensory neurons within individual pegs. Chronic recordings lasting several days showed long-term fluctuations in spontaneous activity of sensory units in single peg sensilla, with peak activity coinciding with the animal's normal period of foraging. Several units were identified by the stereotypical waveforms of action potentials they elicit. Near-range olfactory stimulation of peg sensilla by volatile alcohols, aldehydes, ketones, esters, and carboxylic acids produced dose-dependent patterns of neural response. Contact stimulation with these chemicals, or water, or mechanical deflection of the peg tip also evoked activity in identifiable units. The peg sensilla appear to be broadly sensitive to odorants and tastants, suggesting they function similarly to the antennae of mandibulate arthropods.

Action Potentials↗
PubMed2006

Mechanism of antibacterial action of a synthetic peptide with an Ala-peptoid residue based on the scorpion-derived antimicrobial peptide IsCT.

A novel bacterial cell-selective antimicrobial peptide, IsCT-P (ILKKIWKPIKKLF-NH(2)), was designed based on the scorpion-derived alpha-helical antimicrobial peptide, IsCT. Here, we investigated the effect of substituting Pro(8) of IsCT-P with the Ala-peptoid residue (N-methylglycine) on the peptide's structure and mechanism of action. Circular dichroism analysis revealed that the modified peptide, IsCT-a, has a much lower alpha-helicity than IsCT-P in membrane mimicking conditions, suggesting the peptoid residue provides much more structural flexibility than the proline residue. IsCT-a was also much less effective than IsCT-P at causing leakage of fluorescent dye entrapped within negatively charged vesicles and at dissipating the membrane potential of Staphylococcus aureus. Collectively, our results suggest that the antibacterial action of IsCT-a is due to the inhibition of intracellular targets rather than the disruption and depolarization of bacterial cell membranes.

Amino Acid Sequence↗
PubMed2004

Dopamine release evoked by beta scorpion toxin, tityus gamma, in prefrontal cortical slices is mediated by intracellular calcium stores.

1. We have investigated the effect of tityus gamma (TiTX gamma) scorpion toxin on the release of [3H]dopamine in rat brain prefrontal cortical slices. The stimulatory effect of TiTX gamma on the release of [3H]dopamine was dose/time-dependent with an EC50 of 0.01 microM. 2. Tetrodotoxin blocked the TiTX gamma-induced release of [3H]dopamine, indicating the dependency for Na+ channels. 3. EGTA had no effect on the TiTX gamma-induced release of [3H]dopamine, indicating the process is independent of extracellular calcium. Release of [3H]dopamine evoked by TiTX gamma was inhibited by 57% by BAPTA, a chelator of intracellular calcium. 4. Xestospongin and 2-APB, putative blockers of IP3-sensitive release of intracellular calcium stores, caused an equal and significant inhibition of 24% of the TiTX gamma-induced release of [3H]dopamine, while the slight inhibition evoked by dantrolene, a putative blocker of ryanodine-sensitive calcium store was not significant. 5. Nomifensine and ascorbic acid, blockers of dopamine transporter (DAT), caused an inhibition of 27 and 29%, respectively, on the toxin-induced release of [3H]dopamine suggesting that most of the TiTX gamma-induced release of dopamine is not due to the reversal of Na+ gradient. 6. In conclusion the majority of the TiTX gamma-induced release of [3H]dopamine is exocytotic and mobilizes calcium from the intracellular IP3-sensitive calcium stores.

Animals↗
PubMed2005

Scorpion venom induces glioma cell apoptosis in vivo and inhibits glioma tumor growth in vitro.

Malignant gliomas are the main brain tumors notoriously resistant to currently available therapies, since they fail to undergo apoptosis upon anticancer treatment. Recent progress on enhanced studies of ion channels involved in glioma cells shed new light on the investigation of glioma cell growth and proliferation. Here we report BmK scorpion venom, a rich resource of various ion channels blockers/modulators, induces cell death of cultured malignant glioma U251-MG cells in vitro specifically at a dose of 10 mg/ml while shows no effect on human hepatocellular carcinoma cells and Chinese hamster ovary cells. The glioma cell death was then determined as apoptosis using 4,6-diamidino-2-phenylindole staining and fluorescence-activated cell sorting analysis. After incubation with BmK venom for 32 and 40 h, 36.20% and 63.08% of U251-MG cells showed apoptosis. Furthermore, BmK venom could significantly inhibit the tumor growth in vitro, which was assessed using U251-MG tumor xenografts on severe combined immunodeficiency mice. The tumor volume of the BmK venom treated mice is nearly 1/8 of that of control after 21 days, and the tumor weight is less than half of that of control. That BmK venom induces apoptosis and inhibits growth of glioma may result from the inhibition and/or modulation of various ion channels in glioma cells.

Animals↗
PubMed1984

Toxicity to crustacea due to polypeptide-phospholipase interaction in the venom of a chactoid scorpion.

The toxic factors to isopods (crustacea) were isolated from the venom of the chactoid scorpion Scorpio maurus palmatus (Scorpionidae) by the aid of column chromatography, and their purity was assessed by disc electrophoresis, analytical ultracentrifugation, isoelectrofocusing, and amino acid analysis. The toxicity to isopods is attributed to two groups of components: (a) Low-molecular-weight basic polypeptides possessing about 3 and 8% of the crude venom lethality and paralytic potency to isopods, respectively. These components are characterized by very similar and unique amino acid compositions of 31 to 34 amino acids with molecular mass of about 3.5 kDa and a deficiency in methionine, leucine, phenylalanine, histidine, and tryptophan. (b) Toxic phospholipases are also toxic to insect but not to mammals. A lethal phospholipase which contained 37% of the total venom phospholipase activity and 11% of its toxicity to isopods was purified. This phospholipase consists of 125 amino acids (Mr 14,581) and is a hydrophobic, acidic protein composed of two isoenzymes (pI 4.7 and 4.9). This enzyme demonstrates an A2-type positional specificity (EC 3.1.1.4) with pH and temperature optima of 7.5-8.0 and 40-50 degrees C, respectively, and high calcium requirements. The lethal potency of the basic polypeptides is evidently increased by the addition of low, sublethal doses of the pure phospholipase. Such synergism was not observed with regards to their paralytic activity. The pharmacological significance of these data is discussed.

Amino Acids↗
PubMed1977

Tyrosyl fluorescence in hemocyanin from the scorpion Leirus quinquestriatus.

The fluorescence properties of hemocyanin from the scorpion Leirus quinquestriatus were studied. Emission and excitation spectra were determined for protein in both its oxygenated and deoxygenated forms. Oxygenation was found to bring about a large blue shift in the position of the fluorescence maximum, in addition to a marked quenching of the fluorescence intensity as noted before for another hemocyanin. An appreciable tyrosyl contribution to the fluorscence of oxyhemocyanin was inferred from the wavelength dependence of its emission and excitation spectra. No tyrosyl fluorescence could be observed in either apo- or deoxyhemocyanin. It was concluded that the inability to observe tyrosyl emmision in deoxyhemocyanin is due to the dominating emission to tryptophan. The implication of the findings to the often noted failure to detect tyrosyl emission in proteins containing both tyrosine and tyrptophan is discussed.

Animals↗
PubMed1983

Action of the venom of the scorpion Tityus trinitatis on pancreatic insulin secretion.

In vivo, canine pancreas was stimulated to secrete insulin by the venom of the scorpion Tityus trinitatis; the venom also caused a rise in plasma glucose level as well. The venom-induced insulin secretion was also observed under in vitro conditions in rat pancreatic slices, and this stimulation was dose-related. Maximal effect was observed at 20 micrograms/ml. Atropine (3 x 10(-6) M) completely abolished both venom (20 micrograms/ml)- and acetylcholine (3 x 10(-7) M)-induced insulin secretion. It is suggested that the venom-induced insulin secretion is mediated through muscarinic cholinergic mechanisms.

Animals↗