Some effects of crude venom from the cones Conus striatus and Conus magus on isolated guinea-pig atria.

Long-lasting positive inotropic activity is shown by the venoms of Conus striatus and C. magus. The activity persists after repeated and prolonged washout but is blocked by prior β-adrenoceptor blockade with propranolol and also by the 5-hydroxytryptamine antagonist BOL-148. The activity is not exerted on atria from reserpinized animals. It is suggested that the activity stems from an ability of each venom to release monoamines from cardiac tissues. In addition to their positive inotropic activity the venoms also induce spontaneous contractions in isolated atria. These contractions are not blocked by propranolol or BOL-148.     

Some effects on muscle and nerve of crude venom from the gastropod Conus striatus

The venom of Conus striatus elicits spontaneous activity in nerves and in skeletal muscles. In frog sartorius muscle the venom lowers resting potentials of muscle fibres and triggers action potentials. The action potentials are of smaller amplitude and much longer duration than normal. Skeletal musculature and nerve ultimately become refractory to electrical stimulation if exposed to adequate concentrations of venom. Spontaneous twitches with amplitudes much greater than normal occur in isolated guinea-pig atria exposed to the venom. The venom has a spasmogenic action on the musculature of rat ilea which can be blocked by the 5-hydroxytryptamine antagonist 2-brom-d-lysergic acid diethylamide bitartrate. Active material in the venom is dialysable. The activity of the venom is modified by heating at 100°C. The pharmacological activity of the venom of C. striatus is similar to but not identical with that of the venom of the piscivorous species C. magus.     

The pharmacological actions on guinea-pig ileum of crude venoms from the marine gastropods Conus striatus and Conus magus

The venom of Conus striatus caused an initial contracture of the ileum which was sustained for 20–25 min. In addition, the venom induced a series of shorter, more intense contractions which occurred at intervals of 2–8 min and continued after the initial contracture had declined. The height of the initial long-lasting contracture was markedly reduced by atropine, Lidoflazine and tetrodotoxin and was completely blocked by BOL-148, Melleril, Largactil, phenylbutazone, Dibenzyline and propranolol. Atropine, Dibenzyline and phenylbutazone reduced the heights of the shorter contractions elicited by the venom and these contractions were completely blocked by BOL-148, Largactil, propranolol, Lidoflazine and tetrodotoxin.C. magus venom elicited a single contracture of the ileum which was sustained for 10–17 min. The height of the contracture was reduced by Dibenzyline and atropine and was completely blocked by phenylbutazone, Lidoflazine, propranolol, tetrodotoxin and high concentrations of BOL-148.Differences in the actions of C. striatus and C. magus were detected. The action of C. striatus venom was exerted directly on the ileal musculature as well as indirectly via the ileal nerves. Experiments with antagonists indicate that the venom promotes the release of transmitter substances such as acetylcholine and 5-hydroxytryptamine from the tissues of the ileum. On the other hand, the action of C. magus venom was exerted only indirectly via nervous elements and stems from an excitatory action of the venom on ileal nerves.     

Pharmacology of the venom of the gastropod Conus magus

The venom of Conus magus has a direct action on vertebrate skeletal and cardiac musculature. With vertebrate skeletal musculature a sustained contracture associated with a progressive loss of response to stimulation was elicited by the venom. Isolated mammalian hearts responded to the venom by a marked increase in the amplitude of the contraction cycle. Mammalian extravascular smooth musculature responded to the venom with a sustained contracture but no response was elicited by the venom in vascular smooth musculature or in barnacle musculature.Trains of impulses were generated by the venom in vertebrate motor fibres. The compound action potential exhibited by amphibian sciatic nerve declined slowly and conduction in the nerve was ultimately blocked by high concentrations (100 μg per ml) of venom.Activity of the venom in vertebrate striated muscle fibres is dependent on the existence of a polarized fibre membrane. Transmembrane resting potentials of individual skeletal muscle fibres exposed to adequate concentrations of the venom fell quickly, the extent of the fall being directly related to venom concentration. The venom caused initially a marked increase in ion flux across the short-circuited frog skin. Evidence was obtained which indicated that the venom affected movements of sodium ions across the sarcolemma.     

Effect of venoms from Conidae on skeletal,cardiac and smooth muscles

J. Kobayashi, H. Nakamura, Y. Hirata and Y. Ohizumi. Effect of venoms from Conidae on skeletal, cardiac and smooth muscles. Toxicon20, 823–830, 1982.—The effects of the venoms of 29 species of Conidae were studied on the mouse isolated diaphragm, the guinea-pig isolated left atria and ileum, and the rabbit isolated aorta. When the directly stimulated mouse diaphragm was exposed to the venom (10^?4 g/ml) of C. geographus, there occurred a marked decline in twitch tension. The venoms of C. magus (3 × 10^?6 g/ml) and C. striatus (10^?3 g/ml) also caused complete loss of contractile response to electrical stimulation. This was followed by a gradual rise in the baseline.The venoms (10^?6?3 × 10^?5 g/ml) of C. magus and C. striatus caused dose-dependent increases in the contractile force of the electrically driven guinea-pig left atria. The venoms (10^?5?10^?4 g/ml) of C. eburneus and C. tessulatus also elicited long-lasting positive inotropic actions on the atria. The inotropic actions induced by the venoms of C. magus and C. striatus were abolished by tetrodotoxin (TTX, 10^?6 M), but were not affected by verapamil (3 × 10^?7 M), whereas those induced by the venoms of C. eburneus and C. tessulatus were completely inhibited by verapamil (3 × 10^?7 M), but were not modified by TTX (10^?6 M). These results suggest that the inotropic actions of the venoms of C. magus and C. striatus may be due to an increase in Na⁺ permeability of the cardiac cell membrane, while those of venoms of C. eburneus and C. tessulatus may be due to an increase in Ca²⁺ permeability.The venoms (10^?6 g/ml) of C. magus and C. striatus elicited rhythmic, transient contractions of the guinea-pig ileum followed by relaxations, which were blocked by TTX (10^?6 M). This suggests that these biphasic responses were caused by increasing Na⁺ permeability of the nerve cell membrane. On the other hand, the venoms (10^?4 g/ml) of C. eburneus and C. tessulatus caused transient contractions of the ileum followed by relaxations.The venoms (10^?4 g/ml) of C. tessulatus and C. eburneus caused marked, long-lasting contractions of the rabbit aorta which were abolished by verapamil (10^?6 M), but were not affected by TTX (5 × 10^?7 M) or phentolamine (10^?6 M). It is suggested that these venoms increase the verapamil-sensitive Ca²⁺ influx across the smooth muscle membrane of the aorta, resulting in contractions.The active principles in the venoms of C. geographus, C. textile and C. imperialis were stable at 100°C for 15 min and passed through PM 10 filters, suggesting molecular weights lower than 10,000. On the other hand, the active principles in the venoms of C. magus, C. striatus, C. tessulatus and C. eburneus were partially destroyed with heating and were kept in the retentate of the PM 10 filters.     

Pharmacology of the venom of Conus geographus

Conus geographus venom has a direct action on vertebrate skeletal musculature. When exposed to venom extracts, all mammalian skeletal muscles tested became refractory to 30 V electrical stimulation. Mammalian smooth and cardiac musculature, barnacle musculature and ‘slow’ fibres of amphibian skeletal musculature were not obviously affected by venom extracts. Compound action potentials in amphibian sciatic nerve were not modified by prolonged exposure to venom extracts and conduction in the sciatic nerve did not appear to be affected. Transmembrane resting potentials in fibres from the frog sartorius were maintained essentially unchanged in the presence of the venom. Although it was not possible to induce action potentials in fibres from paralysed musculature, no evidence was obtained that sodium ion movements across membranes are affected by the venom. It was possible to overcome the block of direct electrical stimulation induced by the venom (25 μg per ml) by increasing voltage strength to 90–100 V or by using tetanic stimulation at 30 V. The material in the venom active against muscle was dialysable and stable to heating at 100°C.     

Excitatory and inhibitory effects of a myotoxin from Conus magus venom on the mouse diaphragm,the guinea-pig atria,taenia caeci,ileum and vas deferens

A myotoxin purified from Conus magus venom elicited complete loss of contractile response of the mouse diaphragm to electrical stimulation followed by a gradual rise in the baseline, an increase in the contractile force of the guinea-pig left atria, a tonic contraction of the guinea-pig taenia caeci and powerful rhythmic contractions of the guinea-pig ileum and vas deferens. These excitatory effects of the toxin were blocked by treatment with tetrodotoxin, suggesting that these effects were due to an increase in Na⁺ permeability of the cell membrane.     

Proteomic Analysis of the Predatory Venom of Conus striatus Reveals Novel and Population-Specific κA-Conotoxin SIVC

Animal venoms are a rich source of pharmacological compounds with ecological and evolutionary significance, as well as with therapeutic and biotechnological potentials. Among the most promising venomous animals, cone snails produce potent neurotoxic venom to facilitate prey capture and defend against aggressors. Conus striatus, one of the largest piscivorous species, is widely distributed, from east African coasts to remote Polynesian Islands. In this study, we investigated potential intraspecific differences in venom composition between distinct geographical populations from Mayotte Island (Indian Ocean) and Australia (Pacific Ocean). Significant variations were noted among the most abundant components, namely the κA-conotoxins, which contain three disulfide bridges and complex glycosylations. The amino acid sequence of a novel κA-conotoxin SIVC, including its N-terminal acetylated variant, was deciphered using tandem mass spectrometry (MS/MS). In addition, the glycosylation pattern was found to be consisting of two HexNAc and four Hex for the Mayotte population, which diverge from the previously characterized two HexNAc and three Hex combinations for this species, collected elsewhere. Whereas the biological and ecological roles of these modifications remain to be investigated, population-specific glycosylation patterns provide, for the first time, a new level of intraspecific variations in cone snail venoms.     

The caseinase activity of some vermivorous cone shell venoms

Venom extracted from anterior regions of the venom ducts of Conus arenatus, Conus lividus, and Conus quercinus displayed significant proteolytic activity towards casein with optimal activities between pH 9 and 10. In contrast no caseinase activity was displayed by venoms extracted from the posterior regions of the venom ducts. Starvation of C. lividus for 12 weeks had no effect on the caseinase activity of the venom. EDTA and soybean trypsin inhibitor were also without effect on the enzymatic activity.     

Conus Venoms: A Rich Source of Neuroactive Peptides

Abstract

Purification of toxins from the venoms of two fish-hunting gastropod cone snails, Conus geographus and Conus magus has revealed the presence of three classes of paralytic peptide toxins. These are: 1) the w-conotoxins, which block voltage activated calcium channels at the presynaptic terminus; 2) the α-conotoxins, which block the acetylcholine receptor and 3) the ω-conotoxins, which inhibit muscle sodium channels, and therefore prevent propagation of the muscle action potential. These toxins are basic peptides from 13–27 amino acids long, rich in cystine residues which are present as disulfides. A number of α-conotoxins and one a-conotoxin have been chemically synthesized.

In addition to the paralytic conotoxins, the venoms of Conus have other toxins which have not yet been completely characterized. A large number of neuroactive peptides and proteins have also been found. Since there are approximately 300 species of Conus, all of which produce venoms, the cone snails promise to be a rich source of neuroactive peptides in the years ahead.     

The contryphans,a d-trvptophan-containing family of Conus peptides: interconversion between conformers

We previously characterized contryphan-R, a d -tryptophan-containing octapeptide from the venom of Conus radiatus. In this study, we present evidence that the contryphan family of peptides is widely distributed in venoms of the fish-hunting cone snails. We purified, synthesized and characterized contryphan-Sm from Conus stercusmuscarum venom, and obtained molecular evidence for the existence of a third peptide, contryphan-P from Conus purpurascens venom ducts. The sequences of these three contryphans showed identity in seven of eight amino acids and a conserved pattern of post-translational modification. We also demonstrate that contryphan-Sm equilibrates between two distinct conformational states.     

Venomic study on cone snails (Conus spp.) from South Africa

From six Conus species (Conus coronatus, Conus lividus, Conus mozambicus f. lautus, Conus pictus, Conus sazanka, Conus tinianus) collected off the eastern coast of South Africa the venoms were analyzed using MALDI-TOF mass spectrometry. Between 56 and 151 molecular masses most in a range of 1000 to 2500 Da, were identified. Among the six venoms, between 0 and 27% (C. coronatus versus C. sazanka) of the peptide masses were found to be similar. In a study on venoms from 6 Conus species collected in the Philippines, the percentage of identical masses was between none and 9% only. The venoms from the South African Conus species antagonized the rat neuronal nicotinic acetylcholine receptors (nAChRs) α3β2, α4β2, and α7, except for C. coronatus venom that blocked the α4β2 and α7 nAChRs only. HPLC-fractionation of C. tinianus venom led to the isolation of a peptide that is active on all three receptor subtypes. It consists of 16 amino acid residues cross-linked by two disulfide bridges as revealed by de novo sequencing using tandem mass spectrometry: GGCCSHPACQNNPDYC. Posttranslational modifications include C-terminal amidation and tyrosine sulfation. The new peptide is a member of the α-conotoxin family that are competitive antagonists of nAChRs. Phylogenetic analysis of the 16S RNA from numerous Conus species has clarified the evolutionary position of endemic South African Conus species and provided the first evidence for their close genetic relationships.     

Pharmacological studies with scorpion (Palamneus gravimanus) venom: evidence for the presence of histamine

The venom from the scorpion Palamneus gravimanus caused, in cats, a pronounced hypotensive effect which was blocked by mepyramine. The hypotensive effect was observed in spinal and reserpinized cats, was not affected by carotid sinus and body denervation and bilateral vagotomy, and was not blocked by hexamethonium and atropine treatment. The venom produced hypertension in guinea pigs and rats which was blocked by tolazoline and in the case of the guinea pigs by mepyramine and by phenoxybenzamine in the rats. Treatment of rats with compound 48/80 did not prevent the hypertensive effect of the venom, showing that it is probably due to histamine or histamine-like substance in the venom and not due to releasing of histamine. Dialysis greatly attenuated the hypotensive effect and prevented the hypertensive action of the venom. Histamine in the venom was identified by paper chromatography, and biological assays showed a histamine-like activity corresponding to 5–7.2 μg histamine per mg dry venom. Both the crude and the dialysed venoms produced positive inotropic and chronotropic effects on isolated rabbit's heart that were not affected by pyribenzamine but were blocked by propranolol. The cardiac stimulant effect of the venom was absent in reserpinized hearts. It is concluded that histamine or histamine-like substance is present in P. gravimanus venom; however, all of the venom effects are not due to the presence of that substance.     

疣缟芋螺毒素的二维液相色谱分离方法

目的建立一种新的基于二维液相色谱技术的疣缟芋螺毒素分离方法,了解其毒素组构成特点。方法从疣缟芋螺毒管中提取芋螺毒素总肽,在传统的凝胶色谱和反相色谱方法的基础上,根据芋螺毒素的等电点和疏水性,利用目标蛋白快速分离系统(Proteome Lab TMPF2D),对其进行二维分离。结果经过传统分离方法,能够检测得到40个左右的芋螺毒素条带,且分离效果不明显。而通过二维液相色谱分离方法,pI/UV图谱显示共检测到约200个芋螺毒素条带。结论同传统分离方法相比,采用Proteome LabTMPF2D系统对毒素分离更快速、分辨率更高,因此更利于鉴定芋螺毒素肽组分,也为下游序列结构特征与生物活性研究奠定了良好的基础。     

Basic phospholipase A2 from Naja nigricollis snake venom: phospholipid hydrolysis and effects on electrical and contractile activity of the rat heart

To clarify the mechanism of the cardiotoxic action of the basic phospholipase A₂ from Naja nigricollis snake venom, its effects were tested on the rat heart, including hydrolysis of cardiac phospholipids, electrocardiogram, (Na + K)-ATPase activity, resting and action potentials, and cardiac contractility. Its effects contrasted with those of a noncardiotoxic acidic phospholipase from Naja naja atra snake venom. Only the N. nigricollis enzyme exhibited cardiotoxic effects in isolated perfused rat hearts. The cardiotoxic effects occurred with low levels of phospholipid hydrolysis, phosphatidylserine being hydrolyzed to the greatest extent. Although high concentrations of either phospholipase decreased (Na + K)-ATPase activity in vitro, this reaction did not account for the cardiotoxic effects observed in isolated perfused hearts. In rat atrial preparations the cardiotoxic enzyme depolarizes the cells, decreases action potential amplitude and overshoot, decreases time to 50 and 90% repolarization of action potential, and prolongs the latency to initiation of the action potential. Simultaneously recorded contractile activity showed prolonged latency to initiation of contraction, increased time to peak force of contraction, and decreased amplitude of contraction. These effects were mimicked by caffeine and 7.5 mm Ca²⁺ in the bathing medium. The cardiotoxic effects were blocked by Mn²⁺ (Mn²⁺ also reversed cardiotoxic actions) and 4.0 mm Ca²⁺, but not by lanthanum, tetrodotoxin, lidocaine, acetylcholine, or cyanide. Manganese added to rat atrial preparations before N. nigricollis phospholipase decreased hydrolysis of phosphatidylserine. These results suggest that the N. nigricollis enzyme exerts its cardiotoxic action by increasing intracellular Ca²⁺ levels. The cardiotoxic effects correlate with, but may not be related to, phosphatidylserine hydrolysis.     

Conus toxins: targets and properties

The venoms from Conus snails are rich in peptides with potent specificity for mammalian receptor sites. Each venom typically contains up to 100 conopeptides, and with approximately 500 species of Conus snail, the number of active peptides is considerable. The receptor sites targeted appear to be mostly linked to ion channels, with voltage-gated, ligand-gated and G-protein linked sites identified. Both the central and peripheral nervous system present possible physiological targets for therapeutic products derived from the venoms, although the molecules in the most advanced development target the central nervous system. In turn, this presents problems of bioavailability, while the potency is a potential source of toxicity.     

Action of dimethindene on the electrophysiological and mechanical properties of atrial and ventricular myocardium of guinea-pig

The effect of dimethindene (DMI) on transmembrane potentials and contractile force was studied in atrial and ventricular myocardium of guinea-pigs. DMI reduced the maximum rate of depolarization (Vmax) without changing the resting potential in both preparations. In ventricular myocardium, DMI shortened the action potential duration and exerted a negative inotropic effect. In atrial muscle, the drug prolonged the action potential duration and induced a positive inotropic effect which could be antagonized with neither the alpha-blocker phentolamine, nor the beta-blocker pindolol, H1-blocker mepyramine and H2-blocker cimetidine. DMI had no effect on the slow action potentials induced by caffeine in K+-depolarized myocardial preparations. The drug consistently shifted the sodium inactivation curve to more negative membrane potentials. The results suggest that DMI has a quinidine-like membrane-stabilizing property, which may be due to its fast Na+ channel blocking activity. The differential inotropic action of the drug in atrial and ventricular myocardium is discussed.     

Possible mechanisms for inotropic actions of vanadate in isolated guinea pig and rat heart preparations

Summary The mechanism of inotropic actions of vanadate was studied in isolated, electrically stimulated atrial and ventricular muscle preparations of rat or guinea-pig heart. Vanadate produced a negative inotropic effect in guinea-pig left atrial preparations associated with a marked shortening of the action potential plateau. In guinea-pig papillary muscle, or rat atrial or ventricular muscle preparations, vanadate produced a positive inotropic effect, which was not affected by either propranolol, phentolamine or metiamide. The positive inotropic effect was observed when action potential duration was either increased or decreased. Inotropic concentrations of vanadate failed to significantly alter the ouabain-sensitive ⁸⁶Rb⁺-uptake, an estimate of sodium pump activity, or tissue concentration of cyclic AMP in electrically stimulated preparations. In partially depolarized rat atrial preparations in which fast sodium channels were inactivated in the presence of a high concentration of K⁺ (22 mmol/l), vanadate restored electrical activity (calcium-dependent action potentials) and the contraction, similar to isoproterenol. This action of vanadate was abolished by Mn²⁺, a slow channel inhibitor, but not by tetrodotoxin. The characteristic of vanadate- and isoproterenol-restored preparations, however, were substantially different. Moreover, vanadate failed to restore the contraction or action potential in partially depolarized guinea pig atrial preparations unlike isoproterenol. These results indicate that vanadate may either enhance or inhibit slow channels in cardiac muscle.