A review of stonefish venoms and toxins

Armed stem to stinger: a review of the ecological roles of scorpion weapons

Scorpions possess two systems of weapons: the pincers (chelae) and the stinger (telson). These are placed on anatomically and developmentally well separated parts of the body, that is, the oral appendages and at the end of the body axis. The otherwise conserved body plan of scorpions varies most in the shape and relative dimensions of these two weapon systems, both across species and in some cases between the sexes. We review the literature on the ecological function of these two weapon systems in each of three contexts of usage: (i) predation, (ii) defense and (iii) sexual contests. In the latter context, we will also discuss their usage in mating. We first provide a comparative background for each of these contexts of usage by giving examples of other weapon systems from across the animal kingdom. Then, we discuss the pertinent aspects of the anatomy of the weapon systems, particularly those aspects relevant to their functioning in their ecological roles. The literature on the functioning and ecological role of both the chelae and the telson is discussed in detail, again organized by context of usage. Particular emphasis is given on the differences in morphology or usage between species or higher taxonomic groups, or between genders, as such cases are most insightful to understand the roles of each of the two distinct weapon systems of the scorpions and their evolutionary interactions. We aimed to synthesize the literature while minimizing conjecture, but also to point out gaps in the literature and potential future research opportunities.

The Geographic Distribution, Venom Components, Pathology and Treatments of Stonefish (Synanceia spp.) Venom

Stonefish are regarded as one of the most venomous fish in the world. Research on stonefish venom has chiefly focused on the in vitro and in vivo neurological, cardiovascular, cytotoxic and nociceptive effects of the venom. The last literature review on stonefish venom was published over a decade ago, and much has changed in the field since. In this review, we have generated a global map of the current distribution of all stonefish (Synanceia) species, presented a table of clinical case reports and provided up-to-date information about the development of polyspecific stonefish antivenom. We have also presented an overview of recent advancements in the biomolecular composition of stonefish venom, including the analysis of transcriptomic and proteomic data from Synanceia horrida venom gland. Moreover, this review highlights the need for further research on the composition and properties of stonefish venom, which may reveal novel molecules for drug discovery, development or other novel physiological uses.

Is stonefish Synanceia verrucosa envenomation potentially lethal?

Stonefish sting lethality in man has been scarcely documented since the middle of the 20th century. We report three clinical cases, including one fatality, emphasizing the cardiovascular toxicity of the Synanceia verrucosa venom, and its potentially lethal effects. All clinical data have been recently collected in New Caledonia and French Polynesia.

Sequence analysis of the cDNA encoding for SpCTx: a lethal factor from scorpionfish venom (Scorpaena plumieri)

Background

Lethal factors are multifunctional oligomeric proteins found in the venomous apparatus of Scorpaeniformes fish. These toxins elicit not only an array of biological responses in vitro but also cardiovascular disorders and strong hemolytic, nociceptive and edematogenic activities in vivo. This work describes the cloning and molecular identification of two toxin subunits, denominated Sp-CTx-α and Sp-CTx-β, from scorpionfish venom (Scorpaena plumieri).

Methods

The primary structures were deduced after cDNA amplification by PCR with primers from conserved sequences described in Scorpaeniformes toxins. Following DNA sequencing and bioinformatic analysis, the tridimensional structures of both subunits were modeled.

Results

The translated sequences (702 amino acids, each subunit) show homology with other lethal factors, while alignment between Sp-CTx-α and Sp-CTx-β shows 54% identity. The subunits lack N-terminal signal sequences and display masses of approximately 80 kDa each. Both Sp-CTx subunits display a B30.2/SPRY domain at the C-terminal region with typically conserved motifs as described in these toxins. Secondary structure prediction identified six α-helices 18 residues long in both α and β subunits, some of them amphiphilic with their N-terminal flanked by many basic residues, creating a cationic site associated with the cytolytic activity of these toxins. Antimicrobial potential sites were identified in Sp-CTx and share some features with other peptides presenting variable and broad-spectrum activity. A phylogenetic tree built to represent these toxins supports the proximity between scorpionfish, lionfish and stonefish.

Conclusion

The study identified a putative toxin protein whose primary structure is similar to other fish toxins and with potential for production of antivenom against scorpionfish envenomation in Brazil. As a prelude to structure-function studies, we propose that the toxin is structurally related to pore-forming marine toxins.

Electronic supplementary material

The online version of this article (10.1186/s40409-018-0158-7) contains supplementary material, which is available to authorized users.

Biochemical and histopathological effects of the stonefish (Synanceia verrucosa) venom in rats

The Reef Stonefish (Synanceia verrucosa) is one of the most dangerous venomous fish known, and has caused occasional human fatalities. The present study was designed to examine some of the pathological effects of the venom from this fish in Sprague Dawley rats. Crude venom was extracted from venom glands of the dorsal spines of stonefish specimens collected from coral reefs in the Gulf of Aqaba (in the northeastern branch of the Red Sea). The rats were given intramuscular injections of the venom and acute toxicity and effect on selected serum marker enzymes as well as normal architecture of vital organs were evaluated. The rat 24 h LD50 was 38 μg/kg body weight. The serum biochemical markers; alanine transaminase (ALT), lactate dehydrogenase (LDH) and creatine kinase (CK) increased after 6 h of administration of a sub lethal dose of the venom and remained significantly raised at 24 h. Amylase levels also significantly increased after venom injection. The venom caused histological damage manifested as an interstitial hemorrhage, inflammatory cell infiltration, and necrosis. The demonstrated rises in the levels of different critical biochemical parameters in the serum may have led to the observed abnormal morphological changes in these organs. These results may account for some of the clinical manifestations observed in victims of stonefish envenomation. Thus, the presented data provide further in vivo evidence of the stonefish toxic effects that may threaten human life and call for the need for special measures to be considered.

A review on the Scorpaena plumieri fish venom and its bioactive compounds

The most poisonous fish species found along the Brazilian coast is the spotted scorpionfish Scorpaena plumieri. Though hardly ever life-threatening to humans, envenomation by S. plumieri can be quite hazardous, provoking extreme pain and imposing significant socioeconomic costs, as the victims may require days to weeks to recover from their injuries. In this review we will walk the reader through the biological features that distinguish this species as well as the current epidemiological knowledge related to the envenomation and its consequences. But above all, we will discuss the challenges involved in the biochemical characterization of the S. plumieri venom and its compounds, focusing then on the successful isolation and pharmacological analysis of some of the bioactive molecules responsible for the effects observed upon envenomation as well as on experimental models. Despite the achievement of considerable progress, much remains to be done, particularly in relation to the non-proteinaceous components of the venom. Therefore, further studies are necessary in order to provide a more complete picture of the venom’s chemical composition and physiological effects. Given that fish venoms remain considerably less studied when compared to terrestrial venoms, the exploration of their full potential opens a myriad of possibilities for the development of new drug leads and tools for elucidating the complex physiological processes.

Thalassophryne nattereri fish venom: from the envenoming to the understanding of the immune system

Thalassophryne nattereri (niquim) is a venomous fish found off North and Northeast coast of Brazil, where it is known by the severity of the accidents involving humans. This review article is divided into four topics. The first one provides a brief description of the animal biology and its distribution off Brazilian coastal waters, the venom apparatus, signs and symptoms observed in envenomated humans and also describes envenomation in mice. The second topic describes the use of modern genetic approach and mass spectrometry for identification of highly expressed genes in its venom glands and the sequence of major toxins. The third chapter offers a detailed study of tissue injury induced by the venom and reveals the role of toxins that impair inflammation reduction. Finally, the fourth section expands the understanding of many extrinsic and intrinsic essential factors in maintaining survival of memory B cell compartment. Our results demonstrate the wide possibilities for research in the area of toxinology, also the necessity of interconnection among biochemistry, pharmacology and immunology areas for the expansion of knowledge and for generation of innovation.

A potent vasoactive cytolysin isolated from Scorpaena plumieri scorpionfish venom

A new vasoactive cytolytic toxin, referred to as Sp-CTx, has been purified from the venom of the scorpionfish Scorpaena plumieri by a combination of gel filtration and anion exchange chromatographies. An estimation of Sp-CTx native molecular mass, performed by size exclusion chromatography, demonstrated that it is a 121 kDa protein. Further physicochemical studies revealed its glycoproteic nature and dimeric constitution, comprising subunits of approximately 65 kDa (MALDI-TOF-MS). Such protein has proved to possess a potent hemolytic activity on washed rabbit erythrocytes (EC(50) 0.46 nM), whose effect was strongly reduced after treatment with antivenom raised against stonefish venom -Synanceja trachynis (SFAV). This cross-reactivity has been confirmed by western blotting. Like S. plumieri whole venom (100 microg/mL), Sp-CTx (1-50 nM) caused a biphasic response on phenylephrine pre-contracted rat aortic rings, characterized by an endothelium- and dose-dependent relaxation phase followed by a contractile phase. The vasorelaxant activity has been abolished by l-NAME, demonstrating the involvement of nitric oxide on the response. We report here the first isolation of a cytolytic/vasoactive protein from scorpionfish venom and the data provided suggest structural and functional similarities between Sp-CTx and previously published stonefish hemolytic toxins.

Diversity, phylogenetic distribution, and origins of venomous catfishes

Background

The study of venomous fishes is in a state of relative infancy when compared to that of other groups of venomous organisms. Catfishes (Order Siluriformes) are a diverse group of bony fishes that have long been known to include venomous taxa, but the extent and phylogenetic distribution of this venomous species diversity has never been documented, while the nature of the venoms themselves also remains poorly understood. In this study, I used histological preparations from over 100 catfish genera, basic biochemical and toxicological analyses of fin spine extracts from several species, and previous systematic studies of catfishes to examine the distribution of venom glands in this group. These results also offer preliminary insights into the evolutionary history of venom glands in the Siluriformes.

Results

Histological examinations of 158 catfish species indicate that approximately 1250-1625+ catfish species should be presumed to be venomous, when viewed in conjunction with several hypotheses of siluriform phylogeny. Maximum parsimony character optimization analyses indicate two to three independent derivations of venom glands within the Siluriformes. A number of putative toxic peptides were identified in the venoms of catfish species from many of the families determined to contain venomous representatives. These peptides elicit a wide array of physiological effects in other fishes, though any one species examined produced no more than three distinct putative toxins in its venom. The molecular weights and effects produced by these putative toxic peptides show strong similarities to previously characterized toxins found in catfish epidermal secretions.

Conclusion

Venom glands have evolved multiple times in catfishes (Order Siluriformes), and venomous catfishes may outnumber the combined diversity of all other venomous vertebrates. The toxic peptides found in catfish venoms may be derived from epidermal secretions that have been demonstrated to accelerate the healing of wounds, rather than defensive crinotoxins.

Biological and biochemical properties of Scatophagus argus venom

Scatophagus argus of the family Scatophagidae inflicts painful wounds in fishermen during handling. The clinical picture is characterized by excruciating and persistent local pain disproportionate to the size of injury, redness, swelling and a throbbing sensation that extends to the limbs, followed by dizziness. The biological properties of the S. argus venom were studied to assess its risk and lethal factors with regard to human welfare. In contrast to other fish venoms, S. argus showed relatively low LD50 (9.8 mg/kg via i.p.). Haemolytic activity in human erythrocytes was recorded. Platelet lysis expressed as LDH activity of lysed cells was dose dependent. S. argus venom failed to induce any clot in human plasma. No PLA(2) activity was found in S. argus venom. Mild proteolytic activity was observed. The injection of venom in mice produced lesions and nociception, which were not inhibited by antihistamine pheniramine maleate, suggesting that histamine was not involved in the inflammatory process. The increase in serum creatine kinase activity indicated myotoxicity. Cytotoxicity on HeLa cells was observed. The spectrum of activity in experimental animals of S. argus crude venom resembles those of other fish venoms previously studied and well correlated to the systemic manifestations that are described for S. argus envenomation.

Envenomations

Numerous types of envenomations may be encountered by health care workers depending on where in North America they work. Clinicians should be familiar with the animals in their region that may lead to envenomation.A rational approach with use of poison center or medical toxicology consultation services ensures that cases are managed appropriately.

Biological properties of the venom from the scorpionfish (Scorpaena plumieri) and purification of a gelatinolytic protease

In this work we describe some biological properties and a partial biochemical characterization of the Scorpanea plumieri crude venom. The fresh venom induced a decrease in blood pressure, cardiac and respiratory frequency, and exhibited hemorrhagic, hemolytic and proteolytic activities. The LD(50) (i.v. mouse) was 0.28 mg/kg. The pharmacological activities were found to be very unstable and this fact could be associated with proteolytic activity. Enzymes which hydrolyze casein and gelatin were found in this venom. A gelatinolytic protease (Sp-GP) was purified to homogeneity from S. plumieri venom through a combination of three chromatographic steps: gel filtration on Sephacryl S-200; ion exchange on DEAE-cellulose and reverse-phase/HPLC on a Vydac C4 column. The purified protease was approximately 2% of the whole protein in the soluble crude venom. The molecular mass of the Sp-GP scorpionfish gelatinase estimated by SDS-PAGE was around 80,000 Da under reducing conditions and 72,000 Da under non-reducing conditions. Attempts to determine the N-terminal sequence by automatic Edman degradation were unsuccessful, probably due to blockage of the N-terminal group. Gelatinolytic activity was optimal at pH 7-8. This is the first report of the isolation and characterization of a scorpionfish venom protease.

Important biological activities induced by Thalassophryne maculosa fish venom

The accidents caused by Thalassophryne maculosa fish venoms are frequent and represent a public health problem in some regions of Venezuela. Most accidents occur in the fishing communities and tourists. The clinical picture is characterized by severe pain, dizziness, fever, edema, and necrosis. Due to the lack of efficient therapy it may take weeks, or even months for complete recovery of the victims. The investigations presented here were undertaken to assess the eletrophoretical profile and principal biological properties of the T. maculosa venom. Venom obtained from fresh captured specimens of this fish was tested in vitro or in animal models for a better characterization of its toxic activities. In contrast to other fish venoms, T. maculosa venom showed relative low LD50. The injection of venom in the footpad of mice reproduced a local inflammatory lesion similar to that described in humans. Significant increase of the nociceptive and edematogenic responses was observed followed within 48 h by necrosis. Pronounced alterations on microvascular hemodynamics were visualized after venom application. These alterations were represented by fibrin depots and thrombus formation followed by complete venular stasis and transient arteriolar contraction. T. maculosa venom is devoid of phospholipase A2 activity, but the venom showed proteolytic and myotoxic activities. SDS-Page analysis of the crude venom showed important bands: one band located above 97 M(w), one band between 68 and 97 M(w), one major band between 29 and 43 M(w) and the last one located below 18.4 M(w) Then, the results presented here support that T. maculosa venom present a mixture of bioactive toxins involved in a local inflammatory lesion.

Characterization of the mechanism underlying stonustoxin-mediated relaxant response in the rat aorta in vitro

Stonustoxin (SNTX) is a lethal factor isolated from the venom of the stonefish Synanceja horrida. Although SNTX exhibits a multitude of biological activities, the primary cause of death upon administration of the toxin is attributed to marked hypotension. We investigated the possible mechanisms underlying the vascular hyporeactivity of this novel toxin. Cumulative doses of SNTX (5-320 ng/mL) induced concentration-dependent relaxation in phenylephrine (PE)--precontracted rat aortic rings with intact endothelium. Endothelium removal abolished the relaxation induced by SNTX. Tetraethylammonium (TEA), an inhibitor of K(+) channels, partially inhibited SNTX-induced relaxation. Similarly, SNTX-induced relaxation was partially attenuated by the SP receptor antagonist (NATB), whereas the inducible iNOS inhibitor, AMT-HCl, completely abolished the relaxation caused by SNTX. From the results obtained, it can be postulated that a component of SNTX-mediated vasorelaxation is via binding of either SNTX or SP to the SP receptors that are located on the endothelial cells. Occupation of these SP receptors causes subsequent production of NO and activation of K(+) channels, thus leading to vasorelaxation of the rat aortic rings.

Neutralization of Thalassophryne nattereri (niquim) fish venom by an experimental antivenom

T. nattereri (niquim) is a venomous fish involved in many human accidents in Brazil. The clinical picture includes mild local erythema, severe edema, intense pain and rapid progression to necrosis. The present therapy with anti-inflammatory and analgesic drugs is ineffective and, therefore, we decided to assess serum therapy as an alternative treatment using an experimental antivenom. The antivenom used was raised in rabbits showing an ELISA antibody titer of 1:8,192,000 and its ability to neutralize lethality, necrosis, nociception and edema was evaluated both by pre-incubating the venom with antivenom before injection into mice or by independent injections of venom and antivenom. Lethality was completely neutralized by pre-incubation (ED(50)=141.5 microl/mg) while necrosis and nociception were neutralized by pre-incubation or the independent injection of antivenom. Edema was only partially prevented even when large amounts of antivenom were used. These data suggest that antivenom may be a promising treatment for patients stung by T. nattereri and suggest the viability of producing a horse antivenom for use in clinical trials.

Effects of trachynilysin, a protein isolated from stonefish (Synanceia trachynis) venom, on frog atrial heart muscle

The effects of trachynilysin (TLY), a protein toxin isolated from stonefish (Synanceia trachynis) venom, were studied on the electrical and mechanical activities of frog atrial fibres. TLY (1 microg/ml) hyperpolarized the membrane, shortened the action potential (AP) duration (APD), exerted a negative inotropic effect and elicited contracture. These effects did not develop in the presence of atropine. TLY shortened the APD of fibres isolated from a frog completely paralyzed with botulinum type A toxin, in the presence of Ca2+ but not when Ca2+ was replaced by Sr2+. TLY increased the basal and the peak of the fluorescence ratio of stimulated fibres loaded with fura-2. Confocal laser scanning microscopy revealed the existence of a diffuse innervation in atrial tissue. Our results suggest that TLY enhances the release of acetylcholine from atrial cholinergic nerve terminals and activates indirectly muscarinic receptors leading to a shortening of APD. They also show that the mechanical effects induced by TLY are due to an increase of the Ca2+ influx and to a rise in intracellular Ca2+ levels which leads to (i) a slowing of the Na+/Ca2+ exchange activity, which accounts for the contracture and (ii) the activation of a Ca2+-dependent K+ current involved in the APD shortening.

Neurotoxins affecting neuroexocytosis

Nerve terminals are specific sites of action of a very large number of toxins produced by many different organisms. The mechanism of action of three groups of presynaptic neurotoxins that interfere directly with the process of neurotransmitter release is reviewed, whereas presynaptic neurotoxins acting on ion channels are not dealt with here. These neurotoxins can be grouped in three large families: 1) the clostridial neurotoxins that act inside nerves and block neurotransmitter release via their metalloproteolytic activity directed specifically on SNARE proteins; 2) the snake presynaptic neurotoxins with phospholipase A(2) activity, whose site of action is still undefined and which induce the release of acethylcholine followed by impairment of synaptic functions; and 3) the excitatory latrotoxin-like neurotoxins that induce a massive release of neurotransmitter at peripheral and central synapses. Their modes of binding, sites of action, and biochemical activities are discussed in relation to the symptoms of the diseases they cause. The use of these toxins in cell biology and neuroscience is considered as well as the therapeutic utilization of the botulinum neurotoxins in human diseases characterized by hyperfunction of cholinergic terminals.

The role of tryptophan residues in the hemolytic activity of stonustoxin,a lethal factor from stonefish (Synanceja horrida) venom

Stonustoxin (SNTX) is a pore-forming cytolytic lethal factor, isolated from the venom of the stonefish Synanceja horrida, that has potent hemolytic activity. The role of tryptophan residues in the hemolytic activity of SNTX was investigated. Oxidation of tryptophan residues of SNTX with N-bromosuccinimide (NBS) resulted in loss of hemolytic activity. Binding of 8-anilino-1-naphthalenesulphonate (ANS) to SNTX resulted in occlusion of tryptophan residues that resulted in loss of hemolytic activity. Circular dichroism and fluorescence studies indicated that ANS binding resulted in a conformational change of SNTX, in particular, a relocation of surface tryptophan residues to the hydrophobic interior. NBS-modification resulted in oxidised surface tryptophan residues that did not relocate to the hydrophobic interior. These results suggest that native surface tryptophan residues play a pivotal role in the hemolytic activity of STNX, possibly by being an essential component of a hydrophobic surface necessary for pore-formation. This study is the first report on the essentiality of tryptophan residues in the activity of a lytic and lethal factor from a fish venom.

Haemolytic activity of stonustoxin from stonefish (Synanceja horrida) venom: pore formation and the role of cationic amino acid residues

Stonustoxin (SNTX) is a two-subunit protein toxin purified from the venom of the stonefish (Synanceja horrida), which induces potent haemolytic activity. We examined the pore-forming property of this non-enzymic protein by an osmotic protection assay. SNTX-induced haemolysis was completely prevented by osmotic protectants of adequate size [poly(ethylene) glycol 3000; molecular diameter approx. 3.2 nm]. Uncharged molecules of smaller size, such as raffinose and poly(ethylene) glycol 1000-2000, failed to protect against cell lysis. These findings indicate that SNTX induces the formation of hydrophilic pores in the cell membrane, which results in the lysis of erythrocytes. Since cationic residues contribute significantly to the cytolytic activity of several other pore-forming toxins, we examined the role of positively charged lysine and arginine residues in the haemolytic activity of SNTX. SNTX lost its haemolytic activity when the positively charged side chains of lysine residues were neutralized or converted into negatively charged side chains upon carbamylation or succinylation respectively. The haemolytic activity of SNTX was also inhibited by the modification of positively charged arginine residues using 2,3-butanedione. The loss of haemolysis showed strong correlation with the number of Lys or Arg residues modified. CD analyses, however, showed that the conformation of SNTX was not significantly affected by these chemical modifications. Further, the haemolytic activity of SNTX was competitively inhibited by various negatively charged lipids, such as phosphatidylserine, cardiolipin and monosialogangliosides. These results indicate that SNTX induces potent haemolytic activity through the formation of pores in the cell membrane, and that cationic residues play a crucial role in its cytolytic mechanism.

Complete amino-acid sequence of the beta-subunit of VTX from venom of the stonefish (Synanceia verrucosa) as identified from cDNA cloning experiments

A cDNA encoding a subunit of the verrucotoxin (VTX) has been identified from a cDNA library derived from stonefish venom glands. It encodes a polypeptide of 708 amino-acid residues, followed by a 3'-untranslated region of 895 bp long. The ORF contains the complete mature sequence of the beta-subunit of the VTX, as inferred from both the presence of an identical N-terminus sequence and 96% homology among the 506 amino terminus residues found in the partial sequence of the beta-subunit of the stonustoxin from Synanceia horrida (Ghadessy, F.J., Jeyaseelan, K., Chung, M.C.M., Khoo, H.E., and Yuen, R. (1994) Toxicon 32, 1684-1688). Upstream the mature sequence, we noticed the presence of an incomplete peptide of a 13 amino acids, whose unusual primary structure supports the idea of the existence of a propeptide and/or of a new secretion signal.

Cardiotoxicity of verrucotoxin, a protein isolated from the venom of Synanceia verrucosa

Freshly purified but unstable verrucotoxin (VTX) and a more stable proteic complex of the toxin (p-VTX) were isolated from the venom of the stonefish Synanceia verrucosa and applied to frog atrial fibres. VTX and p-VTX decreased the amplitude and the duration of the stimulated peak tension and accelerated the relaxation phase of the contraction. The negative inotropic effect of p-VTX decreased with increasing the external Ca concentration ([Ca]o) in the Ringer solution. The negative chronotropic effect induced by p-VTX was insensitive to change in [Ca]o. It is reversed by glibenclamide. p-VTX shortened the duration of the plateau and the repolarizing phase of the action potential. Glibenclamide but not tetraethylammonium reversed the p-VTX-induced shortening of the AP repolarizing phase. The data suggest that the toxin isolated from the venom of S. verrucosa inhibits Ca channels and might activate ATP-sensitive potassium channels in frog atrial heart muscle.

Pharmacological action of Australian animal venoms

1. Australia has some of the most venomous fauna in the world. Although humans are not usually perceived as being predators against these animals they are often envenomated, accidentally or otherwise. This has led to the development of antivenoms against some of the potentially lethal venoms. However, further understanding of the mechanism(s) of action of these and other venoms is important, not only for developing new treatment strategies but also in the search for novel research tools. 2. The present review discusses the pharmacology of some of the components found in venoms and outlines the research undertaken on some of Australia's venomous animals, with the exception of snakes. 3. Biogenic amines, peptides and enzymes are common venom components and produce a wide range of effects in envenomated humans. For example, respiratory failure observed after envenomation by the box jellyfish (Chirnex fleckeri) and Sydney funnel-web spider (Atrax robustus) is most likely due to potent neurotoxins in the venoms. Stonefish (Synanceja trachynis) and platypus (Ornithorhynchus anatinus) venoms, although not considered lethal, cause severe pain. However, the components responsible for these effects have not been isolated. Venom components, as yet unidentified, may be responsible for the cutaneous necrotic lesions that have been reported after some spider bites (e.g. Lampona cylindrata). Other venoms, such as those of the jumper ant (Myrmecia pilosula) and bull ant (M. pyriformis), may produce only mild skin irritation to the majority of humans but a severe anaphylactic response in sensitized victims. 4. While there has been a renewed interest in toxinology, further research is required to fully elucidate the pharmacological action of many of these venoms.

Presence of norepinephrine and other biogenic amines in stonefish venom

Although fish venoms exert a cardiovascular effect, the presence of adrenergic substances was not previously demonstrated. Chromatographic analysis with electrochemical detection showed the presence of substances co-migrating with norepinephrine, dopamine and tryptophan. Serotonin, which was thought to be implicated in the intense pain following fish envenomation, was not detected. Norepinephrine was identified as a component of the stonefish Synanceia verrucosa venom by gas chromatography-mass spectrometry.

Selective depletion of clear synaptic vesicles and enhanced quantal transmitter release at frog motor nerve endings produced by trachynilysin, a protein toxin isolated from stonefish (Synanceia trachynis) venom

Our previous observation that low concentrations of stonefish (Synanceia trachynis) venom elicit spontaneous quantal acetylcholine release from vertebrate motor nerve terminals prompted our present study to purify the quantal transmitter-releasing toxin present in the venom and to characterize the toxin's ability to alter the ultrastructure and immunoreactivity of frog motor nerve terminals. Fractionation of S. trachynis venom by sequential anion exchange fast protein-liquid chromatography (FPLC) and size-exclusion FPLC yielded a highly purified preparation of a membrane-perturbing (haemolytic) protein toxin, named trachynilysin. Trachynilysin (2-20 micrograms/ml) significantly increased spontaneous quantal acetylcholine release from motor endings, as detected by recording miniature endplate potentials from isolated frog cutaneous pectoris neuromuscular preparations. Ultrastructural analysis of nerve terminals in which quantal acetylcholine release was stimulated to exhaustion by 3 h exposure to trachynilysin revealed swelling of nerve terminals and marked depletion of small clear synaptic vesicles. However, trachynilysin did not induce a parallel depletion of large dense-core vesicles. Large dense core vesicles contained calcitonin gene-related peptide (CGRP), as revealed by colloidal gold immunostaining, and trachynilysin-treated nerve endings exhibited CGRP-like immunofluorescence similar to that of untreated terminals. Our results indicate that the ability of stonefish venom to elicit spontaneous quantal acetylcholine release from vertebrate motor nerve terminals is a function of trachynilysin, which selectively stimulates the release of small clear synaptic vesicles and impairs the recycling of small clear synaptic vesicles but does not affect the release of large dense-core vesicles. Trachynilysin may be a valuable tool for use in other secretory terminals to discriminate between neurotransmitter and neuropeptide release.

Cardiac and vascular responses of isolated rat tissues treated with diterpenes from Sinularia flexibilis (coelenterata: octocorallia)

The marine environment is a rich source of compounds with cardiovascular activity. This study characterizes the cardiac and vascular responses in isolated rat tissues of flexibilide, dihydroflexibilide and sinulariolide, three diterpenes isolated from the soft coral Sinularia flexibilis. On rat left ventricular papillary muscles, dihydroflexibilide and flexibilide showed similar potencies (-log EC50 = 4.69 +/- 0.05 and 4.66 +/- 0.06, respectively); the maximal response to dihydroflexibilide of 1.4 +/- 0.2 mN was 35 +/- 7% that of calcium chloride in the same muscles. All diterpenes relaxed rat thoracic aortic rings precontracted with KC1 (100 mM) with similar potencies (flexibilide, -log EC50 = 4.17 +/- 0.06). Flexibilide was further characterized and shown to increase force in isolated rat left atria by 0.8 +/- 0.5 mN at 1 x 10(-4) M, to increase rate of contraction in isolated rat right atria by 18 +/- 5 beta/min at 3 x 10(-5) M and to completely relax endothelium-denuded rat thoracic aortic rings (-log EC50 = 4.14 +/- 0.05). Toxicity as indicated by the occurrence of ectopic beats was not observed with the diterpenes at concentrations which produced complete relaxation of blood vessels, maximal positive inotropic activity and minor positive chronotropic responses. Thus, these compounds may be useful lead compounds in the search for improved treatment of cardiovascular disease, especially heart failure.

Production and characterization of monoclonal antibodies against stonustoxin from Synanceja horrida

Stonustoxin (SNTX), a lethal factor purified from the venom of stonefish Synanceja horrida, is a protein (148,000 mol. wt) existing as a dimer comprising two subunits (alpha and beta) of mol. wts 71,000 and 79,000, respectively. Its LD50 (i.v.) is 17 ng/g in mice and it causes haemolysis of rat and rabbit erythrocytes in vitro. Eight monoclonal antibodies (Mabs) against SNTX have been developed using the Balb/C mouse. These Mabs have been purified by Protein G affinity membrane disc chromatography. They were all classified as IgG1 with half of them having kappa and the rest lambda light chains. They had affinity constants ranging from 3.75 x 10(-9) to 9.74 x 10(-9) M. Six were able to protect mice from a challenge of a lethal dose of SNTX. However, not all protective Mabs were able to neutralize the haemolytic effect in vitro. Only four Mabs (31A, 32B, 38A and 46A) could inhibit rat and rabbit erythrocyte haemolysis, while one Mab (43D) offered partial inhibition and another Mab (8A) did not inhibit haemolysis at all. The non-protective Mabs (43B and 44G) were also incapable of neutralizing haemolysis. Five epitopes were recognized by the eight Mabs. Four Mabs (31A, 32B, 38A and 46A) were found to have similar epitope specificity while the rest were directed at different epitopes on the SNTX molecule. Thus these results suggest that the domain on the SNTX molecule responsible for lethality is probably distinct from the domain important for in vitro haemolytic activity.

A genomic region encoding stonefish (Synanceja horrida) stonustoxin beta-subunit contains an intron

The polymerase chain reaction (PCR) has been used to amplify a 1899 base pair fragment from stonefish genomic DNA. A comparison of the translated nucleotide sequence of this product with the separately determined N-terminal amino acid sequence of the beta-subunit reveals the presence of a 416 bp intron at Gly 18. The nucleotide sequence following this intron encodes 476 amino acids whose sequence showed no homology to other known toxins. This region, however, contained amino acid sequences identical to internal peptide sequences determined separately from the toxin's beta-subunit.