Properties of Duvernoy's secretions from opisthoglyphous and aglyphous colubrid snakes

Local envenoming by the eastern Montpellier snake, Malpolon insignitus fuscus (Fleischmann, 1831), Psammophiidae, and review of the evidence-based medical risks of bites by Malpolon spp

For more than a century, concerns about the medical significance of Montpellier snakes, Malpolon spp. (Psammophiidae) have been expressed by herpetologists and toxinologists. Although some of the opinions have suggested that the most familiar species, the Western Montpellier snake, Malpolon monspessulanus, poses a significant medical risk, only a few detailed, formally documented reports have been published that describe effects in humans. Two reports support a rare risk of systemic envenoming (cranial nerve palsies) after prolonged bites by M. monspessulanus. Relevantly, there has been only one previous report describing a bite by the Eastern Montpellier snake, Malpolon insignitus. Reported here are the effects of a bite inflicted by a 1.1-m female Malpolon insignitus fuscus in Alborz Province, Iran. The 40-yr-old male victim was handling the snake while preparing to photograph it when he was bitten on the right wrist. The snake remained attached for approximately 40-s during which it repeatedly advanced its jaws. The bite caused moderate local envenoming that featured moderate but reportedly notably uncomfortable sharp pain, moderate edema, erythema and pruritis; wound site bleeding was transient and proportional. Full resolution required 5-days; there were no sequelae. The clinical evolution included signs/symptoms consistent with Type I hypersensitivity and subtype Type IV hypersensitivity. Detailed reports of medically significant bites by Malpolon spp. are briefly reviewed and the evidence for medical significance of the genus is evaluated. Management of envenoming by Malpolon spp. is supportive only; almost all victims with qualified medical review have developed only local envenoming that is often mild-moderate. Notably rare systemic effects, e.g., neurotoxicity so far limited to non-progressive cranial nerve palsies, should prompt airway protection, ICU admission, and consultation as indicated. Future study of Malpolon venoms and formal documentation of their bites should increase the evidence quality for the medical risk profile of the genus.

Highly conserved and extremely variable: The paradoxical pattern of toxin expression revealed by comparative venom-gland transcriptomics of Phalotris (Serpentes: Dipsadidae)

Although non-front fanged snakes account for almost two-thirds of snake diversity, most studies on venom composition and evolution focus exclusively on front-fanged species, which comprise most of the clinically relevant accidents. Comprehensive reports on venom composition of non-front fanged snakes are still scarce for several groups. In this study, we address such shortage of knowledge by providing new insights about the venom composition among species of Phalotris, a poorly studied Neotropical dipsadid genus. Phalotris are known for their specialized venom delivery system and toxic venoms, which can cause life-threatening accidents in humans. We evaluate the venom-gland transcriptome of Phalotris, comparing the following three South American species: P. reticulatus for the Araucaria Pine forests, P. lemniscatus for the Pampa grasslands, and P. mertensi for the Brazilian Cerrado. Our results indicate similar venom profiles, in which they share a high expression level of Kunitz-type inhibitors (KUNZ). On the other hand, comparative analyses revealed substantial differences in the expression levels of C-type lectins (CTL) and snake venom metalloproteinases (SVMP). The diverse set of SVMP and CTL isoforms shows signals of positive selection, and we also identified truncated forms of type III SVMPs, which resemble type II and type I SVMPs of viperids. Additionally, we identified a CNP precursor hosting a proline-rich region containing a BPP motif resembling those commonly detected in viperid venoms with hypotensive activity. Altogether, our results suggest an evolutionary history favoring high expression levels of few KUNZ isoforms in Phalotris venoms, contrasting with a highly diverse set of SVMP and CTL isoforms. Such diversity can be comparable with the venom variability observed in some viperids. Our findings highlight the extreme phenotypic diversity of non-front fanged snakes and the importance to allocate greater effort to study neglected groups of Colubroidea.

Venom production and secretion in reptiles

The venom glands of reptiles, particularly those of front-fanged advanced snakes, must satisfy conflicting biological demands: rapid synthesis of potentially labile and highly toxic proteins, storage in the gland lumen for long periods, stabilization of the stored secretions, immediate activation of toxins upon deployment and protection of the animal from the toxic effects of its own venom. This dynamic system could serve as a model for the study of a variety of different phenomena involving exocrine gland activation, protein synthesis, stabilization of protein products and secretory mechanisms. However, these studies have been hampered by a lack of a long-term model that can be propagated in the lab (as opposed to whole-animal studies). Numerous attempts have been made to extend the lifetime of venom gland secretory cells, but only recently has an organoid model been shown to have the requisite qualities of recapitulation of the native system, self-propagation and long-term viability (>1 year). A tractable model is now available for myriad cell- and molecular-level studies of venom glands, protein synthesis and secretion. However, venom glands of reptiles are not identical, and many differ very extensively in overall architecture, microanatomy and protein products produced. This Review summarizes the similarities among and differences between venom glands of helodermatid lizards and of rear-fanged and front-fanged snakes, highlighting those areas that are well understood and identifying areas where future studies can fill in significant gaps in knowledge of these ancient, yet fascinating systems.

Venom Collection from Spiders and Snakes: Voluntary and Involuntary Extractions ("Milking") and Venom Gland Extractions

Venom collection (often called "milking") provides the toxic secretions essential for studying animal venoms and/or generating venom products. Methods of venom collection vary widely, falling into three broad categories: voluntary venom extraction (inducing the animal to willingly release its venom), involuntary venom extraction (glandular massage, electrical stimulation, or administration of induction chemicals to promote venom expulsion), and venom gland extraction (surgical aspiration or trituration of homogenized gland tissue). Choice of method requires consideration of animal species, animal welfare, human safety (avoiding envenomation), venom yield and composition desired, and level of toxin purity required. Here, we summarize the materials and methods used to obtain venom by each of these approaches from spiders and snakes.

Envenomation by opisthoglyphous snake Thamnodynastes hypoconia (Cope, 1860) (Dipsadinae: Tachymenini) in southern Brazil

We report here a case of human envenoming by Thamnodynastes hypoconia, a common and abundant non-front-fanged snake belonging to the subfamily Dipsadinae. The case was registered in the municipality of Tapes, Rio Grande do Sul state, Brazil, in a 27-year-old female. The snakebite was on the wrist of the left arm while handling the snake in a field outing. No pain sensation was noted during the bite, and after 20 minutes edema developed along the hand and forearm with a slight sensation of numbness and mild pain when moving the fingers. After 15 hours, the victim began to develop erythema, paraesthesia, and a sensation of warmth at the bite site. After 30 hours, ecchymosis occurred on the fingers and forearms, and the edema began to decrease. After 70 hours from the time of the bite, ecchymosis along with pruritus and mild pain were still evident. The patient was treated with prescribed medications, and after 7 days no further symptoms were observed. This is the first reported case of envenoming by T. hypoconia.

Preliminary Biochemical and Venomic Characterization of the Venom of Phalotris lemniscatus (Serpentes, Colubridae)

BACKGROUND

For many decades, research on snake venom toxinology focused mainly on the venoms of Viperidae and Elapidae species, which were traditionally the only ones considered as venomous. However, much less interest has been given to the venom produced by opisthoglyphous colubrid snakes, since they were typically considered of no clinical relevance.

OBJECTIVE

The aim of this work is to perform a preliminary biochemical and venomic characterization of the venom of the colubrid snake Phalotris lemniscatus, a species that has been responsible for two relevant cases of envenomation in Uruguay.

METHODS

We extracted venom from collected specimens and performed different biochemical and proteomic assays to understand its toxin composition.

RESULTS

We found that the venom of P. lemniscatus is composed of protein families typically present in snake venoms, such as metallo and serine preoteases, L-amino acid oxidases, phospholipases A2s, Ctype lectines-like, Kunitz-type proteins and three-finger toxins. Activity assays demonstrated a highly active gelatinolytic component as well as a potent capability to induce blood coagulation.

CONCLUSION

The results indicate that the venom of P. lemniscatus contains hemotoxic activities and components that resemble those found in Viperidae (Bothrops) snakes and that can induce a clinically relevant accident. Further studies are needed to better understand the venom composition of this colubrid snake and its most active compounds.

Comparative Study of Biological Activities of Venom from Colubrid Snakes Rhabdophis tigrinus (Yamakagashi) and Rhabdophis lateralis

Rhabdophis lateralis, a colubrid snake distributed throughout the continent of Asia, has recently undergone taxonomic revisions. Previously, Rhabdophis lateralis was classified as a subspecies of R. tigrinus (Yamakagashi) until 2012, when several genetic differences were discovered which classified this snake as its own species. To elucidate the toxicity of venom from this poorly studied colubrid, various biological activities were compared between the venom from the two snake species. The components of their venom were compared by the elution profiles of reversed-phase HPLC and SDS-PAGE, and gel filtrated fractions were tested for effects on blood coagulation. Proteolytic activities of these fractions were also assayed by using synthetic substrates, fibrinogen, and matrix proteins. Similar to the R. tigrinus venom, the higher molecular weight fraction of R. lateralis venom contained a prothrombin activator. Both prothrombin time (PT) and activated partial thromboplastin time (APTT) of human plasma were shortened by the addition of R. lateralis and R. tigrinus venom. The thrombin formation was estimated by the uses of SDS-PAGE and chromogenic substrates. These venom fractions also possessed very specific proteinase activity on human fibrinogen, but the substrates for matrix metalloproteinase, such as collagen and laminin, were not hydrolyzed. However, there were some notable differences in reactivity to synthetic substrates for matrix metalloproteinase, and R. tigrinus venom possessed relatively higher activity. Our chemical investigation indicates that the components included in both venoms resemble each other closely. However, the ratio of components and proteolytic activity of some ingredients are slightly different, indicating differences between two closely-related snakes.

A survey on some biochemical and pharmacological activities of venom from two Colombian colubrid snakes, Erythrolamprus bizona (Double-banded coral snake mimic) and Pseudoboa neuwiedii (Neuwied's false boa)

Colombian colubrid snake venoms have been poorly studied. They represent a great resource of biological, ecological, toxinological and pharmacological research. We assessed some enzymatic properties and neuromuscular effects of Erythrolamprus bizona and Pseudoboa neuwiedii venoms from Colombia. Proteolytic, amidolytic and phospholipase A₂ (PLA₂) activities were analyzed using colorimetric assays and the neuromuscular activity was analyzed in chick biventer cervicis (BC) preparations. The venom of both species showed very low PLA₂ and amidolytic activities; however, both exhibited high proteolytic activity, which in E. bizona venom surpassed that of P. neuwiedii venom. E. bizona and P. neuwiedii venoms provoked partial neuromuscular blockade, which was more prominent in P. neuwiedii venom. E. bizona venom (30 μg/ml) induced a significant potentiation of the contracture response to exogenous ACh (110 μM), which was not accompanied by twitch height alteration, whereas the highest venom concentration (100 μg/ml) inhibited contracture responses to both ACh and KCl (40 mM). In contrast, P. neuwiedii venom (30 and 100 μg/ml) caused significant reduction in the contracture responses to exogenous ACh and KCl. The morphological analyses showed high myotoxic effects in the muscle fibers of BC incubated with either venoms; however, they are more prominent in the P. neuwiedii venom. Our results suggest that the myotoxicity of the venom of the two Colombian species can be ascribed to their high proteolytic activity. An interesting data was the potentiation of the ACh-induced contracture, but not the twitch height, caused by E. bizona venom, at a concentration that is harmless to muscle fibers integrity. This phenomenon remains to be further elucidated, and suggest that a possible involvement of post-synaptic receptors cannot be discarded. This work is a contribution to expand the knowledge on colubrid venoms; it allows envisaging that the two venoms offer the potential to go further in the identification of their components and biological targets.

What killed Karl Patterson Schmidt? Combined venom gland transcriptomic, venomic and antivenomic analysis of the South African green tree snake (the boomslang), Dispholidus typus

Background

Non-front-fanged colubroid snakes comprise about two-thirds of extant ophidian species. The medical significance of the majority of these snakes is unknown, but at least five species have caused life-threatening or fatal human envenomings. However, the venoms of only a small number of species have been explored.

Methods

A combined venomic and venom gland transcriptomic approach was employed to characterise of venom of Dispholidus typus (boomslang), the snake that caused the tragic death of Professor Karl Patterson Schmidt. The ability of CroFab™ antivenom to immunocapture boomslang venom proteins was investigated using antivenomics.

Results

Transcriptomic-assisted proteomic analysis identified venom proteins belonging to seven protein families: three-finger toxin (3FTx); phospholipase A₂ (PLA₂); cysteine-rich secretory proteins (CRISP); snake venom (SV) serine proteinase (SP); C-type lectin-like (CTL); SV metalloproteinases (SVMPs); and disintegrin-like/cysteine-rich (DC) proteolytic fragments. CroFab™ antivenom efficiently immunodepleted some boomslang SVMPs.

Conclusions

The present work is the first to address the overall proteomic profile of D. typus venom. This study allowed us to correlate the toxin composition with the toxic activities of the venom. The antivenomic analysis suggested that the antivenom available at the time of the unfortunate accident could have exhibited at least some immunoreactivity against the boomslang SVMPs responsible for the disseminated intravascular coagulation syndrome that caused K.P. Schmidt's fatal outcome.

General significance

This study may stimulate further research on other non-front-fanged colubroid snake venoms capable of causing life-threatening envenomings to humans, which in turn should contribute to prevent fatal human accidents, such as that unfortunately suffered by K.P. Schmidt.

•

The venom proteome of Dispholidus typus (boomslang) is reported.

•

Transcriptomic-assisted proteomic analysis identified venom proteins belonging to seven protein families.

•

Boomslang venom proteome is dominated (75%) by snake venom PIII-metalloproteinases (PIII-SVMPs).

•

CroFab™ antivenom efficiently immunodepleted some boomslang PIII-SVMPs.

Colubrid Venom Composition: An -Omics Perspective

Snake venoms have been subjected to increasingly sensitive analyses for well over 100 years, but most research has been restricted to front-fanged snakes, which actually represent a relatively small proportion of extant species of advanced snakes. Because rear-fanged snakes are a diverse and distinct radiation of the advanced snakes, understanding venom composition among "colubrids" is critical to understanding the evolution of venom among snakes. Here we review the state of knowledge concerning rear-fanged snake venom composition, emphasizing those toxins for which protein or transcript sequences are available. We have also added new transcriptome-based data on venoms of three species of rear-fanged snakes. Based on this compilation, it is apparent that several components, including cysteine-rich secretory proteins (CRiSPs), C-type lectins (CTLs), CTLs-like proteins and snake venom metalloproteinases (SVMPs), are broadly distributed among "colubrid" venoms, while others, notably three-finger toxins (3FTxs), appear nearly restricted to the Colubridae (sensu stricto). Some putative new toxins, such as snake venom matrix metalloproteinases, are in fact present in several colubrid venoms, while others are only transcribed, at lower levels. This work provides insights into the evolution of these toxin classes, but because only a small number of species have been explored, generalizations are still rather limited. It is likely that new venom protein families await discovery, particularly among those species with highly specialized diets.

Non-front-fanged colubroid ("colubrid") snakebites: three cases of local envenoming by the mangrove or ringed cat-eyed snake (Boiga dendrophila; Colubridae, Colubrinae), the Western beaked snake (Rhamphiophis oxyrhynchus; Lamprophiidae, Psammophinae) and the rain forest cat-eyed snake (Leptodeira frenata; Dipsadidae)

CONTEXT

Non-front-fanged colubroid snakes (NFFC; formerly and artificially taxonomically assembled as "colubrids") comprise the majority of extant ophidian species. Although the medical risks of bites by a handful of species have been documented, the majority of these snakes have oral products (Duvernoy's secretions, or venoms) with unknown biomedical properties/unverified functions and their potential for causing harm in humans is unknown.

CASE DETAILS

Described are three cases of local envenoming from NFFC bites inflicted respectively by the mangrove or ringed cat-eyed snake (Boiga dendrophila, Colubridae), the Western beaked snake (Rhamphiophis oxyrhynchus, Lamprophiidae) and the rain forest cat-eyed snake (Leptodeira frenata, Dipsadidae). The effects ranged from mild pain, edema and erythema to severe pain, progressive edema, and blistering with slowly resolving arthralgia; there were no systemic effects.

DISCUSSION

Although these three taxa occasionally inflict bites with mild to moderate local effects, there is no current evidence of systemic involvement. Two of these cases were reported to one of the authors for medical evaluation, and although verified, thus constitute reliably reported cases, but low-quality evidence. Type-1 local hypersensitivity may contribute to some cases, but most local effects observed or reported in these three cases were consistent with the effects of venom/oral product components.

Non-front-fanged colubroid snakes: a current evidence-based analysis of medical significance

Non-front-fanged colubroid snakes (NFFC; formerly and artificially taxonomically assembled as "colubrids") comprise about 70% of extant snake species and include several taxa now known to cause lethal or life threatening envenoming in humans. Although the medical risks of bites by only a handful of species have been documented, a growing number of NFFC are implicated in medically significant bites. The majority of these snakes have oral products (Duvernoy's secretions, or venoms) with unknown biomedical properties and their potential for causing harm in humans is unknown. Increasingly, multiple NFFC species are entering the commercial snake trade posing an uncertain risk. Published case reports describing NFFC bites were assessed for evidence-based value, clinical detail and verified species identification. These data were subjected to meta-analysis and a hazard index was generated for select taxa. Cases on which we consulted or personally treated were included and subjected to the same assessment criteria. Cases involving approximately 120 species met the selection criteria, and a small subset designated Hazard Level 1 (most hazardous), contained 5 species with lethal potential. Recommended management of these cases included antivenom for 3 species, Dispholidus typus, Rhabdophis tiginis, Rhabdophis subminiatus, whereas others in this subset without commercially available antivenoms (Thelotornis spp.) were treated with plasma/erythrocyte replacement therapy and supportive care. Heparin, antifibrinolytics and/or plasmapheresis/exchange transfusion have been used in the management of some Hazard Level 1 envenomings, but evidence-based analysis positively contraindicates the use of any of these interventions. Hazard Level 2/3 species were involved in cases containing mixed quality data that implicated these taxa (e.g. Boiga irregularis, Philodryas olfersii, Malpolon monspessulanus) with bites that caused rare systemic effects. Recommended management may include use of acetylcholinesterase inhibitors (e.g. neostigmine) and wound care on a case-by-case basis. Hazard level 3 species comprised a larger group capable of producing significant local effects only, often associated with a protracted bite (eg Heterodon nasicus, Borikenophis (Alsophis) portoricensis, Platyceps (Coluber) rhodorachis). Management is restricted to wound care. Bites by Hazard level 4 species comprised the majority of surveyed taxa and these showed only minor effects of no clinical importance. This study has produced a comprehensive evidence-based listing of NFFC snakes tabulated against medical significance of bites, together with best-practice management recommendations. This analysis assumes increasing importance, as there is growing exposure to lesser-known NFFC snakes, particularly in captive collections that may uncover further species of significance in the future. Careful and accurate documentation of bites by verified species of NFFC snakes is required to increase the evidence base and establish the best medical management approach for each species.

A bite by the Twin-Barred Tree Snake, Chrysopelea pelias (Linnaeus, 1758)

INTRODUCTION

The Twin-Barred Tree Snake, Chrysopelea pelias, is a colubrine that, like other members of the genus Chrysopelea, is able to glide in the arboreal strata. Little is known about the effects of its bite. This report is the first clinically documented bite by this relatively uncommon rear-fanged species.

CASE REPORT

The patient was a 19-year-old female who arrived at the Emergency Department (ED) of an urban teaching hospital 6 h after being bitten by a snake that was later provisionally identified as a C. pelias. Noted on presentation were bite marks on the right middle toe with minimal inflammation and tenderness. There was slight numbness over the dorsum of the right foot and discomforting sensation radiating up the thigh that persisted for several days. There was mild pyrexia, but no evidence of any systemic effects. The full blood count did show neutrophil leucocytosis, and transient hemoglobinuria was noted in an initial urine analysis.

DISCUSSION

The properties of Duvernoy's secretion of C. pelias remain uncharacterized. In this case, the clinical course featured only the local effects noted above. However, the significant local pain reported by the patient suggests that bites by C. pelias are not necessarily trivial and do require full evaluation and observation in a medical facility. Discussed also is the importance of the establishment of a national registry for animal bites and stings in Malaysia.

CONCLUSION

Such a facility could expedite safe and appropriate management of envenomed patients.

Biological and proteomic analysis of venom from the Puerto Rican Racer (Alsophis portoricensis: Dipsadidae)

The Puerto Rican Racer Alsophis portoricensis is known to use venom to subdue lizard prey, and extensive damage to specific lizard body tissues has been well documented. The toxicity and biochemistry of the venom, however, has not been explored extensively. We employed biological assays and proteomic techniques to characterize venom from A. portoricensis anegadae collected from Guana Island, British Virgin Islands. High metalloproteinase and gelatinase, as well as low acetylcholinesterase and phosphodiesterase activities were detected, and the venom hydrolyzed the alpha-subunit of human fibrinogen very rapidly. SDS-PAGE analysis of venoms revealed up to 22 protein bands, with masses of approximately 5-160 kDa; very little variation among individual snakes or within one snake between venom extractions was observed. Most bands were approximately 25-62 kD, but MALDI-TOF analysis of crude venom indicated considerable complexity in the 1.5-13 kD mass range, including low intensity peaks in the 6.2-8.8 kD mass range (potential three-finger toxins). MALDI-TOF/TOF MS analysis of tryptic peptides confirmed that a 25 kDa band was a venom cysteine-rich secretory protein (CRiSP) with sequence homology with tigrin, a CRiSP from the natricine colubrid Rhabdophis tigrinus. The venom was quite toxic to NSA mice (Mus musculus: LD(50)=2.1 microg/g), as well as to Anolis lizards (A. carolinensis: 3.8 microg/g). Histology of the venom gland showed distinctive differences from the supralabial salivary glands (serous vs. mucosecretory), and like the Brown Treesnake (Boiga irregularis), another rear-fanged snake, serous secretory cells are arranged in densely packed secretory tubules, with little venom present in tubule lumina. These results clearly demonstrate that venom from A. portoricensis shares components with venoms of front-fanged snakes as well as with other rear-fanged species. Venom from A. portoricensis, in particular the prominent metalloproteinase activity, likely serves an important trophic function by facilitating prey handling and predigestion of prey.

Prey envenomation does not improve digestive performance in western diamondback rattlesnakes (Crotalus atrox)

Although the toxic properties of snake venoms have been recognized throughout history, very little is known about the adaptive significance of these powerful mixtures. This study examined the popular hypothesis that prey envenomation enhances digestion by influencing the energetic costs of digestion and assimilation, gut passage time, and apparent assimilation efficiency (ASSIM) in western diamondback rattlesnakes (Crotalus atrox), a species whose venom is recognized for its comparatively high proteolytic activities. A complete randomized block design allowed repeated measures of specific dynamic action and gut passage time to be measured in eight snakes ingesting four feeding treatments (i.e., artificially envenomated live mice, artificially envenomated prekilled mice, saline injected live mice, and saline injected prekilled mice). A second experiment measured ASSIM in eight snakes ingesting a series of six artificially envenomated or six saline injected mice meals over an 8-week period. Contrary to expectations, the results of both these experiments revealed that envenomation had no significant influence on any of the measured digestive performance variables. Gut passage time averaged 6 days and ASSIM averaged 79.1%. Twenty-one hours following ingestion, postprandial metabolic rates exhibited factorial increases that averaged 3.9-fold greater than resting metabolic rate. Specific dynamic action lasted on average 88 hr and accounted for 26% of the total ingested energy. The results of this study reinforce the need to systematically examine the potential adaptive advantages that venoms confer on the snakes that produce them.

Neuromuscular action of venom from the South American colubrid snake Philodryas patagoniensis

Snakes of the opisthoglyphous genus Philodryas are widespread in South America and cause most bites by colubrids in this region. In this study, we examined the neurotoxic and myotoxic effects of venom from Philodryas patagoniensis in biventer cervicis and phrenic nerve-diaphragm preparations and we compared the biochemical activities of venoms from P. patagoniensis and Philodryas olfersii. Philodryas patagoniensis venom (40 microg/mL) had no effect on mouse phrenic nerve-diaphragm preparations but caused time-dependent neuromuscular blockade of chick biventer cervicis preparations. This blockade was not reversed by washing. The highest concentration of venom tested (40 microg/mL) significantly reduced (p<0.05) the contractures to exogenous acetylcholine (55 microM and 110 microM) and K(+) (13.4 mM) after 120 min; lower concentrations of venom had no consistent or significant effect on these responses. Venom caused a concentration- and time-dependent release of creatine kinase (CK) from biventer cervicis preparations. Histological analysis showed contracted muscle fibers at low venom concentrations and myonecrosis at high concentrations. Philodryas venoms had low esterase and phospholipase A(2) but high proteolytic activities compared to the pitviper Bothrops jararaca. SDS-PAGE showed that the Philodryas venoms had similar electrophoretic profiles, with most proteins having a molecular mass of 25-80 kDa. Both of the Philodryas venoms cross-reacted with bothropic antivenom in ELISA, indicating the presence of proteins immunologically related to Bothrops venoms. RP-HPLC of P. patagoniensis venom yielded four major peaks, each of which contained several proteins, as shown by SDS-PAGE. These results indicate that P. patagoniensis venom has neurotoxic and myotoxic components that may contribute to the effects of envenoming by this species.

Experimental evidence that oral secretions of northwestern ring-necked snakes (Diadophis punctatus occidentalis) are toxic to their prey

Ring-necked snakes (Diadophis punctatus) are suspected of being venomous because their Duvernoy's gland secretions have high levels of phospholipase activity, which is characteristic of many viperid and elapid venoms, and because anecdotal reports of feeding behavior are consistent with the use of a venom. We tested the toxicity of northwestern ring-necked snake oral secretions to a natural prey species, northwestern garter snakes (Thamnophis ordinoides), by injecting 2-35 microl of oral secretions intraperitoneally. All doses were 100% lethal within 180 min. The dose significantly affected the time to loss of a righting response. Neither injection of saline nor denatured oral secretions resulted in loss of a righting response or any visible detrimental effects. We suggest that northwestern ring-necked snakes may have evolved venom to subdue larger prey items than the snake would otherwise be capable of taking.

Análise das atividades biológicas dos venenos de Philodryas olfersii (Lichtenstein) e P. patagoniensis (Girard) (Serpentes, Colubridae)

Philodryas olfersii (Lichtenstein, 1823) e P.patagonienis (Girard, 1857) são serpentes colubrídeas da série opistóglifa, restritas à América do Sul. Vários acidentes ocasionados por estas serpentes têm sido relatados, caracterizando-se por ação local importante: dor, edema e hemorragia. É um acidente muito semelhante àquele causado por serpentes do gênero Bothrops Wagler, 1824 e muitas vezes os pacientes são tratados com soro antibotrópico. Poucos estudos tratam da caracterização destes venenos, assim tivemos como objetivo de trabalho o estudo dos venenos de P.olfersii e P.patagonienis. Os venenos apresentaram teor de proteínas entre 75 e 90%. A atividade desfibrinante não foi detectada quando testada em camundongos. O quadro de dor causado pelo envenenamento experimental, em camundongos, mostrou que os venenos de P.olfersii e P.patagoniensis causaram intensa reatividade, sendo que o veneno de P.patagoniensis foi o mais ativo. Ambos os venenos apresentaram dose mínima edematogênica em torno de 1 µg/camundongo com ação máxima em 30 minutos.A ação hemorrágica se instalou rapidamente, com doses mínimas semelhantes. As atividades tóxicas foram semelhantes, com valores em torno de 60,0 µg/camundongo, comparáveis aos venenos botrópicos.

Systemic pathological alterations caused by Philodryas patagoniensis colubrid snake venom in rats

Very little is known about the systemic effects caused by Philodryas patagoniensis colubrid snake venom. In this work, this venom was tested for its ability to induce histopathological changes in rats after its intramuscular, subcutaneous or intravenous administration, by light microscopic examination of some organs (cerebellum, cerebrum, lung, liver, kidney and heart). Four rats were used for each dose of 0.23, 0.45 and 0.90 mg of venom in 0.3 ml of phosphate-buffered saline solution (pH 7.4). Aliquots of blood were withdrawn at different time intervals for enzymatic determination of alanine aminotransferase, aspartate aminotransferase and creatine kinase levels. After 2h the animals were killed by an overdose of anesthetic, and samples of kidney, heart, liver, lung, cerebrum and cerebellum were taken to microscopic examination (hematoxylin and eosin stain). Histologically, no abnormality was observed in heart tissue, in none of the administration routes of the venom used. However, histological observations showed multifocal hemorrhage in cerebellum, cerebrum and lung sections, severe peritubular capillary congestion in kidney sections and hydropic degeneration in liver sections, when venom was administrated intravenously. The subcutaneous route showed similar results to the previous one, with the exception of cerebellar hemorrhage. Intramuscularly, neither cerebral nor cerebellar hemorrhage was observed. Plasma alanine aminotransferase and aspartate aminotransferase increased levels were demonstrated, mainly when venom was administered intravenously or subcutaneously. Our results suggest that P. patagoniensis venom induces moderate histopathological changes in vital organs of rats. These changes are initiated at early stages of the envenomation and may be associated with a behavioral or functional abnormality of those organs during envenoming.

Some aspects of the venom proteome of the Colubridae snakePhilodryas olfersiirevealed from a Duvernoy's (venom) gland transcriptome

We investigated the putative toxins of Philodryas olfersii (Colubridae), a representative of a family of snakes neglected in venom studies despite their growing medical importance. Transcriptomic data of the venom gland complemented by proteomic analysis of the gland secretion revealed the presence of major toxin classes from the Viperidae family, including serine proteases, metalloproteases, C-type lectins, Crisps, and a C-type natriuretic peptide (CNP). Interestingly, the phylogenetic analysis of the CNP precursor showed it as a linker between two related precursors found in Viperidae and Elapidae snakes. We suggest that these precursors constitute a monophyletic group derived from the vertebrate CNPs.

Experimental ophitoxemia produced by the opisthoglyphous lora snake (Philodryas olfersii) venom

Several colubrid snakes produce venomous oral secretions. In this work, the venom collected from Venezuelan opisthoglyphous (rear-fanged) Philodryas olfersii snake was studied. Different proteins were present in its venom and they were characterized by 20% SDS-PAGE protein electrophoresis. The secretion exhibited proteolytic (gelatinase) activity, which was partially purified on a chromatography ionic exchange mono Q2 column. Additionally, the haemorrhagic activity of Philodryas olfersii venom on chicken embryos, mouse skin and peritoneum was demonstrated. Neurotoxic symptoms were demonstrated in mice inoculated with Philodryas olfersii venom. In conclusion, Philodryas olfersii venom showed proteolytic, haemorrhagic, and neurotoxic activities, thus increasing the interest in the high toxic action of Philodryas venom.

Characterization and identification of disintegrins inCrotalushorridusvenom by liquid chromatography and tandem matrix-assisted laser desorption ionization - quadrupole ion trap time-of-flight (MALDI-QIT-TOF) mass spectrometry

Two disintegrins were purified from the venom of Crotalus horridus by multiple-dimension liquid chromatography (MDLC) (specifically C18 reverse phase (RP) high-performance liquid chromatography followed by size exclusion chromatography (SEC), and anion exchange chromatography (SCX)). Both disintegrins were subjected to mass spectrometry to determine their intact molecular mass, the number of disulfide linkages, and protein sequence, respectively. These disintegrins were named horrdistatin 1 (nominal mass, 7231 Da) and horrdistatin 2 (nominal mass, 7451 Da), and had IC50(inhibitory concentrations) of 12.5 and 16.2 nmol/L (at 50%), respectively. For sequence confirmation from the C-terminal end, both disintegrins were derivatized using chemical-assisted fragmentation (CAF) and subsequently unzipped via collision-induced dissociation (CID) by matrix-assisted laser desorption – ionization – quadrupole ion trap time-of-flight (MALDI-QIT-TOF) mass spectrometry.Key words: disintegrins, mass spectrometry, snake venom, Timber rattlesnake, Crotalus horridus.

Disintegrin, hemorrhagic, and proteolytic activities of Mohave rattlesnake, Crotalus scutulatus scutulatus venoms lacking Mojave toxin

Venom from the Mohave rattlesnake, Crotalus scutulatus scutulatus, has been reported to be either: (1) neurotoxic; (2) hemorrhagic, or both (3) neurotoxic and hemorrhagic. In this study, 14 Mohave rattlesnakes from Arizona and Texas (USA) were analyzed for the presence of disintegrins and Mojave toxin. All venom samples were analyzed for the presence of hemorrhagic, proteolytic and disintegrin activities. The venoms were each chromatographed by reverse phase and their fractions tested for disintegrin activity. All specimens containing Mojave toxin were the most toxic and lacked proteolytic, hemorrhagic and disintegrin activities. In contrast, the venoms containing these activities lacked Mojave toxin. Two disintegrin genes, scutustatin and mojavestatin, were identified by PCR of genomic sequences. Scutustatin is a highly conserved disintegrin, while mojavestatin shows low conservation to other known disintegrins. Venoms with the highest LD50 measurements lacked both disintegrin genes, while the specimens with intermediate and low LD50 contained both genes. The intermediate LD50 group contained Mojave toxin and both disintegrin genes, but lacked hemorrhagic and disintegrin activity. Our results raise the possibility that scutustatin and mojavestatin are not expressed in the intermediate LD50 group, or that they may not be the same disintegrins responsible for the disintegrin activity found in the venom. Therefore, it is possible that Mohave rattlesnakes may produce more than two disintegrins.

The in vitro and in vivo pharmacological activity of Boiga dendrophila (mangrove catsnake) venom

The great taxonomic and prey base diversity of colubrids (non-front-fanged snakes) suggests that their venoms may represent a 'literal gold mine' for scientists eager to find novel pharmacological probes. While pharmacological characterization is lacking for most of these venoms, this is even more so with regard to activity of colubrid venoms on the mammalian autonomic nervous system. This study characterizes the activity of venom from the colubrid, Boiga dendrophila using in vitro smooth muscle preparations and the anaesthetized rat. In the prostatic segment of the rat vas deferens, cumulative additions of venom (1-150 microg ml(-1)) induced concentration-dependent inhibition of electrically evoked (0.2 Hz, 0.3 ms, 70-100 V) twitches. The inhibitory effect of venom (100 microg ml(-1)) was attenuated by 8-phenyltheophylline (8-PT) (20 microM) and 8-cyclopentyl-1, 3-dipropylxanthine (20 microM) but not idazoxan (1 microM), or a combination of ranitidine (0.2 microM) and thioperamide (10 microM). The inhibitory effect of venom (100 microg ml(-1)) was augmented by dipyridamole (10 microM) but abolished by pretreatment with adenosine deaminase (7.5 units/100 microl) suggesting that it contains components with adenosine A(1) receptor activity, most likely adenosine. In isolated segments of guinea-pig ileum, venom (10-100 microg ml(-1)) caused concentration-dependent contractions which were inhibited by the muscarinic receptor antagonist atropine (0.1 microM) but not by the histamine receptor antagonist mepyramine (0.5 microM). In the anaesthetized rat, venom (5-7.5 mg kg(-1), i.v.) caused a hypotensive effect. Our data suggest that the venom contains components with purinergic and muscarinic receptor activity.

Duvernoy's gland secretion of Philodryas patagoniensis from the northeast of Argentina: its effects on blood coagulation

Duvernoy's gland secretion of Philodryas patagoniensis exhibits high hemorrhagic activity, containing enzymes that are able to degrade the vascular wall. In this work we aim to determine if the secretion can also affect the hemostatic system by causing changes in blood coagulation. Procoagulant and coagulant activities were evaluated on plasma and fibrinogen, respectively. The delay in the thrombin clotting time of fibrinogen previously incubated with the secretion was also determined. Specific hydrolysis of fibrinogen and fibrin incubated with the secretion at different time intervals was shown by electrophoresis on polyacrylamide gel. To determine the structural characteristics of the enzymes degrading fibrinogen and fibrin, secretion were incubated in the presence of 45 mM Na(2)EDTA, 40 mM Benzamidine, and/or 2 mM PMSF before the incubation with fibrinogen or fibrin, respectively. The effect in vivo was investigated in adult male rats injected with different dose of secretion, aliquots of blood were withdrawn at different time intervals, and the fibrinogen concentration was determined. Duvernoy's gland secretion of P. patagoniensis did not clot plasma or fibrinogen. It exhibited a potent fibrinogenolytic activity degrading the Aalpha-chain faster than the Bbeta-chain, whereas gamma-chain was resistant. This latter corresponded with a strong delay in the thrombin clotting time of fibrinogen (4 mg/ml) pre-incubated with the secretion, being 9.53 microg the amount of protein from Duvernoy's gland secretion that increased the thrombin clotting time from 20 to 60 s. In vivo, the loss of rat plasma fibrinogen was proportional to the amount of secretion injected. The secretion also hydrolyzed fibrin degrading the alpha-monomer. Inhibition studies with Na(2)EDTA, Benzamidine, and/or PMSF showed that metalloproteinases and serinoproteinases are the main enzymes responsible for the hydrolyzing activity on fibrinogen and fibrin. All these results demonstrate that Duvernoy's gland secretion of P. patagoniensis possesses enzymes able to hydrolyze plasma components playing a relevant role in the blood coagulation. These hydrolyzing activities and those acting on the wall of blood vessels let the secretion exhibit a high hemorrhagic activity, which may result in permanent sequelae or even cause the death of the victims bitten by this colubrid snake.

Muscle and skin necrotizing and edema-forming activities of Duvernoy's gland secretion of the xenodontine colubrid snake Philodryas patagoniensis from the north-east of Argentina

Philodryas patagoniensis is a colubrid snake spread by all South America, but very little is known about the composition and biological activities of its Duvernoy's gland secretion. In order to characterize it, we studied edematogenic, dermonecrotic and myonecrotic activities. For edematogenic activity, solutions containing different amounts of secretion were injected s.c. in the right foot pad of mice, both feet were subsequently cut off and weighed individually. For myonecrotic activity, mice were injected i.m. with solutions containing 40 microg of secretion, and at various time intervals mice were bled to determine serum creatine kinase activity and gastrocnemius muscles were removed for microscopic examination (Hematoxylin-Eosin stain). For dermonecrotic activity, solutions containing different amounts of secretion were injected into the shaved dorsal skin of mice; the necrotic lesion was measured on the inner surface of the skin and trimmed for microscopic examination (Hematoxylin-Eosin stain). Phospholipase A(2) activity was evaluated using a kinetic method. Results showed that P. patagoniensis Duvernoy's gland secretion exhibits a high edematogenic activity and moderate myonecrotic and dermonecrotic activities, while lacking phospholipase A(2) effect. Regarding edema, a 30% increase in the weight was produced by injecting 0.26 microg of Duvernoy's gland secretion. Microscopically, myonecrosis reached its highest intensity 12 h after injection, which was also demonstrated by serum creatine kinase levels. Dermonecrosis was proportional to the amount of secretion injected, with a minimum necrotizing dose of 15.7 microg. Myonecrotic, edematogenic and dermonecrotic activities were inhibited when the secretion was pre-incubated with 1 mM Na(2)EDTA. This suggests that the enzymes responsible for those activities are mostly metalloproeinases. All the studies carried out up to now demonstrate the potential toxicity of P. patagoniensis Duvernoy's gland secretion (which inhabits the north-east region of Argentina) and that the local lesions caused by this colubrid snake are very similar to those found in bothropic accidents. This latter suggests a more careful evaluation of the victims when considering the medical treatment to be adopted.

Hemorrhagic activity of the Duvernoy's gland secretion of the xenodontine colubrid Philodryas patagoniensis from the north-east region of Argentina

Colubrid snakes belonging to Philodryas genus, widespread all over South America, bring about lesions (swelling, ecchymosis, transient bleeding from the bite site punctures), that are similar to those produced by Bothrops species (yarará). In the present work we began the characterization of Philodryas patagoniensis venom. We examined if this venom produces hemorrhagic lesions as those observed in victims bitten by Philodryas olfersii. Hemorrhagic, proteolytic and fibrinogenolytic activities were evaluated, and histological observations in samples of gastrocnemius muscle were carried out. Inhibition studies were carried out in metal chelator (ethylenediaminetetraacetic acid) presence. Our results show a small Minimum Hemorrhagic Dose (MHD=0.035 microg) and a high proteolytic activity (143 U/mg), and prove the capacity of this venom to degrade fibrinogen in vitro rendering it unclottable by thrombin, supporting the presence of proteases, principally metalloproteases, in P. patagoniensis venom that are able to alterate the vascular wall and degrade fibrinogen, being both activities responsible of a high hemorrhagic activity.

Characterization of venom (Duvernoy's secretion) from twelve species of colubrid snakes and partial sequence of four venom proteins

R.E. Hill and S.P. Mackessy. Characterization of venom (Duvernoy's secretion) from twelve species of colubrid snakes and partial sequence of four venom proteins. Toxicon XX, xx-yy, 2000. - Venomous colubrids, which include more than 700 snake species worldwide, represent a vast potential source of novel biological compounds. The present study characterized venom (Duvernoy's gland secretion) collected from twelve species of opisthoglyphous (rear-fanged) colubrid snakes, an extremely diverse assemblage of non-venomous to highly venomous snakes. Most venoms displayed proteolytic activity (casein), though activity levels varied considerably. Low phosphodiesterase activity was detected in several venoms (Amphiesma stolata, Diadophis punctatus, Heterodon nasicus kennerlyi, H. n. nasicus and Thamnophis elegans vagrans), and acetylcholinesterase was found in Boiga irregularis saliva and venom, but no venoms displayed hyaluronidase, thrombin-like or kallikrein-like activities. High phospholipase A(2) (PLA(2)) activity was found in Trimorphodon biscutatus lambda venom, and moderate levels were detected in Boiga dendrophila and D. p. regalis venoms as well as B. dendrophila and H. n. nasicus salivas. Non-reducing SDS-PAGE revealed 7-20 protein bands (3.5 to over 200 kD, depending on species) for all venoms analyzed, and electrophoretic profiles of venoms were typically quite distinct from saliva profiles. Components from A. stolata, Hydrodynastes gigas, Tantilla nigriceps and T. e. vagrans venoms showed protease activity when run on gelatin zymogram gels. N-terminal protein sequences for three 26 kD venom components of three species (H. gigas, H. torquata, T. biscutatus) and one 3.5 kD component (T. nigriceps) were also obtained, and the 3.5 kD peptide showed apparent sequence homology with human vascular endothelial growth factor; these data represent the first sequences of colubrid venom components. Protease, phosphodiesterase and PLA(2) activities are also common to elapid and viperid snake venoms, but it is apparent that numerous other (as yet undescribed) components make up the majority of colubrid venom proteins. The complex nature of venoms produced by most species surveyed, and the high levels of protease or phospholipase A(2) activity of some venoms, suggest that many colubrids could become an important source of human health concern as encounters with these snakes increase.

Mass spectrophotometric evidence for P-III/P-IV metalloproteinases in the venom of the Boomslang (Dispholidus typus)

The Boomslang, Dispholidus typus, is a mid- to rear-fanged arboreal colubrid widely distributed throughout much of the African continent. Envenoming by this species is rare although deaths have been recorded. Typical symptoms associated with envenoming include diffuse intravascular coagulation (DIC) caused by fibrinogen consumption and consequent incoagulable blood together with haemorrhage into tissues such as muscle and brain; together, these procoagulant and haemorrhagic effects of the venom result in a very poor prognosis in patients who receive a large dose of venom and who are not treated with antivenom. Renal failure may also result from acute tubular necrosis resulting from pigment nephropathy. Little is known about the toxic components present in the venom; however, proteolytic activity has been reported although the proteinases involved have not been identified. In this study we provide LC/MS/MS (liquid chromatography/mass spectrometry/mass spectrometry) data supporting the presence of class P-III/P-IV snake venom metalloproteinases (SVMPs) in Boomslang venom. Using a polyclonal antibody raised against the P-III haemorrhagic toxin (Jararhagin) obtained from the venom of the Brazilian pit viper, Bothrops jararaca, we identified by western blot a 65 kDa protein from Boomslang venom which cross-reacted with the jararhagin antibody. A corresponding band from SDS-PAGE was subjected to tryptic digestion followed by LC/MS/MS sequence analysis of the digestion mixture. A variety of peptide sequences were identified in the digest, one of which was clearly homologous with a highly conserved region of the disintegrin-like domains of P-III/P-IV SVMPs. These data provide the first structural evidence for the presence of SVMPs in Boomslang venom; it is possible that SVMPs may also be present in the venoms of other colubrids, which cause similar symptoms in envenomed humans. In other snake venoms, most notably those of the Viperinae and Crotalinae subfamilies, many of the coagulopathic and haemorrhagic syndromes associated with systemic and local envenoming are attributed to SVMPs. The identification of a P-III/P-IV SVMP sequence in D. typus venom suggests that many of the pathological signs resulting from envenoming by this species may also be due to the presence of SVMPs in the venom. It is hoped that these results may accelerate research into colubrid venoms and may provide new insights into novel and more efficacious treatments for colubrid envenoming.

Phylogenetic relationships of xenodontine snakes inferred from 12S and 16S ribosomal RNA sequences

The phylogenetic relationships of xenodontine snakes are inferred from sequence analyses of portions of two mitochondrial genes (12S and 16S ribosomal RNA) in 85 species. Although support values for most of the basal nodes are low, the general pattern of cladogenesis observed is congruent with many independent molecular, morphological, and geographical data. The monophyly of xenodontines and the basal position of North American xenodontines in comparison with Neotropical xenodontines are favored, suggesting an Asian-North American origin of xenodontines. West Indian xenodontines (including endemic genera and members of the genus Alsophis) appear to form a monophyletic group belonging to the South American clade. Their mid-Cenozoic origin by dispersal using ocean currents is supported. Within South American mainland xenodontines, the tribes Hydropsini, Pseudoboini, and Xenodontini are monophyletic. Finally, our results suggest that some morphological and ecological traits concerning maxillary dentition, macrohabitat use, and foraging strategy have appeared multiple times during the evolution of xenodontine snakes.

Characterization of a myotoxin from the Duvernoy's gland secretion of the xenodontine colubrid Philodryas olfersii (green snake): effects on striated muscle and the neuromuscular junction

A myotoxin has been isolated from the Duvernoy's gland (DG) secretion of the xenodontine colubrid Philodrvas olfersii (green snake) by gel filtration on Sephadex G-100 SF. Under non-reducing and reducing conditions in SDS-PAGE, the myotoxin migrates as a single band with a mol. wt. of 20000. The toxin has 182 amino acid residues (approximately 20% acidic), a pI of 4.8 and a blocked N-terminal. In the chick biventer cervicis preparation, P. olfersii myotoxin partially blocks potassium-evoked contractures without affecting either the twitch-tension resulting from indirect stimulation or the contractures evoked by acetylcholine. Both the DG secretion and the myotoxin increase the serum creatine kinase (CK) levels of mice and stimulate the release of CK from the biventer cervicis preparation in a dose- and time-dependent manner. The varying degrees of muscle cell lysis and extensive widening of the intercellular spaces caused by the DG secretion are reproduced by the myotoxin, with the exception that in the latter the partial or total loss of transverse muscle striations is restricted to the muscle periphery. This myotoxin is the first such protein to be characterized from a DG secretion.

Enzymatic properties of the Duvernoy's secretion of Blanding's tree snake (Boiga blandingi) and of the mangrove snake (Boiga dendrophila)

Duvernoy's secretion from representatives of the colubrid genus Boiga has been shown by other workers: (1) to contain an alpha-bungarotoxin-like component (Blanding's tree snake, Boiga blandingi); (2) to exhibit acetylcholine receptor binding activity (the brown tree snake, Boiga irregularis); and (3) to react strongly (B. blandingi and the mangrove snake, Boiga dendrophila) with antisera raised against elapid venoms. The present study provides the first evidence for the presence of acetylcholinesterase, a common elapid enzyme, in the Duvernoy's secretion of B. dendrophila and B. blandingi at levels of 122 +/- 7 and 0.36 +/- 0.02 International Enzyme Units, respectively. Constants for inhibition by eserine were 1.25 x 10(-7) M and 2.79 x 10(-7) M, respectively. The Duvernoy's secretion of B. dendrophila exhibited significant phospholipase and haemolytic activities, whereas phosphodiesterase was only weakly present and no thrombin-like activity was observed.

Venom yields from several species of colubrid snakes and differential effects of ketamine

The composition of rear-fanged colubrid snake venoms is largely unknown due primarily to the difficulty involved in venom collection. Several different methods have been used to maximize the yield of Duvernoy's secretions. The method proposed by Rosenberg in 1992, which includes the use of ketamine hydrochloride anesthetic and pilocarpine to induce Duvernoy's glands secretion, was used in the present study to collect venom from eight species of colubrids. Protein concentrations, using a dye-binding microassay technique, were determined for the venoms collected. Average protein concentrations ranged from 49.8 to 96.4%. Most yields (dry weight/snake) obtained from specimens in this study were significantly greater than yields previously reported. There was a wide range of effects that occurred due to the ketamine injections; however, all snakes recovered from the effects of the ketamine hydrochloride/pilocarpine with no apparent ill effects. Recommended doses of ketamine hydrochloride have thus been adjusted, depending on previous reactions to the drug. The use of ketamine/pilocarpine in the collection of Duvernoy's secretion has proven to be highly effective in increasing yields. Some caution should be observed when administering ketamine to various species of colubrids, as effects do not necessarily scale to body mass.

Mode of action of Duvernoy's gland extracts from the colubrid Dryadophis bifossatus in the chick biventer cervicis nerve-muscle preparation

Extracts and secretion of the Duvernoy's gland are venomous, inducing in several cases motor paralysis in experimental animals. The extracts of the Duvernoy's gland from the aglyphous colubrid Dryadophis bifossatus are very toxic, eliciting flaccid paralysis in pigeons, rabbits and Hylae (Brazil and Vellard, 1926). In the present study, the neuromuscular action of the extracts of Duvernoy's gland from this Colubridae was investigated in the chick biventer cervicis nerve-muscle preparation. The muscle was indirectly stimulated with supramaximal pulses, and by addition of acetylcholine or carbachol to the organ bath. Direct muscle stimulation was carried out in curarized preparations. The extracts induced an irreversible neuromuscular blockade and also inhibited irreversibly the contracture of the biventer cervicis produced by either acetylcholine or carbachol. The twitches elicited by direct muscle stimulation were not depressed. These results show that the neurotoxin(s) of the extracts interact with the end-plate cholinergic receptors.