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PubMed2002

An experimental test of stimulus estimation theory: danger and safety with snake phobic stimuli.

The stimulus estimation model (Taylor & Rachman, 1994) asserts that fear overprediction stems from: (a) overprediction of the danger elements of a phobic stimulus, and (b) underprediction of existing safety resources. Using a 2x2 factorial design, with danger (high vs low) and safety (high vs low) as between-subjects variables, an experimental test of the model was conducted with 25 snake-fearful participants per condition. The four experimental conditions were matched on initial levels of snake fearfulness, as assessed by the Snake Questionnaire (SNAQ). For the 51 participants who demonstrated overprediction of fear, high danger led to reliably more fear overprediction than low danger; and low safety led to reliably more fear overprediction than high safety. The interaction between danger and safety was not statistically significant. The results offer the first convincing experimental support for the stimulus estimation model of fear overprediction.

Animals↗
PubMed1997

Parental history, aversive exposure and the development of snake and spider phobia in women.

Parental history and experiential factors in the development of snake and spider phobia were studied. Phobic women (DSM-IV, n = 158) reported on family history of animal phobia and whether direct (being frightened by the phobic object) or indirect (seeing someone else being frightened by and/or being warned of the phobic object) fear exposure predated phobia development. Fifty-nine mothers (37%) and 11 fathers (7%) had snake or spider phobia, which is higher than the upper 95% confidence interval in the populations (Fredrikson, Annas, Fischer & Wik, Behavior Research and Therapy, 34, 33-39). Lifetime Relative Risk, RR, of animal phobia in probands' mother and fathers as a function of at least one phobic grandparent was 3.3 and 13.7 respectively. Indirect fear exposures were more common in snake (45%) than spider (27%) phobics (RR = 1.4). Indirect fear exposures were more common among probands with a positive parental history, the RRs being 3.6 and 2.1 as a function of maternal and paternal family history. Direct exposures were unrelated to parental history. The familial resemblance and transmission of specific phobia could be experiential in origin mediated by indirect exposures or of hereditary origin mediated by genetic factors. It may represent genetically facilitated learning and exemplify imprinting in humans.

Animals↗
PubMed2002

Angiostatin-like molecules are generated by snake venom metalloproteinases.

Angiostatin is a plasminogen-derived anti-angiogenic factor composed of its first four kringle structures. This molecule is generated by proteolytic cleavage of plasminogen by some proteolytic enzymes in vitro. Since venoms of viper snakes are a rich source of both serine- and metalloproteinase, we hypothesized that angiostatin-like polypeptides could be generated during the envenomation after snake bites and play a pathophysiological role in the local tissue damage and regeneration. Our results showed that crude venoms from several species of Bothrops snakes were able to generate angiostatin-like polypeptides and purified metalloproteinases but not serine proteinases from Bothrops jararaca and Bothrops moojeni venoms were responsible for their generation in vitro. The putative plasminogen cleavage sites by the crude venoms and purified proteinases were determined by N-terminal amino acid sequencing of the angiostatin-like molecules. Angiostatin-like peptides derived from human plasminogen digestion by jararhagin, a metalloproteinase isolated from B. jararaca venom, inhibited endothelial cell proliferation in vitro. These results indicate that angiostatin-like molecules can be generated upon snakebite envenomations and may account for the poor and incomplete regenerative response observed in the damaged tissue.

Angiostatins↗
PubMedDate not supplied

Electrocardiographic abnormalities in patients bitten by taipans (Oxyuranus scutellatus canni) and other elapid snakes in Papua New Guinea.

Envenoming by a number of species of snake may affect the myocardium or cause electrocardiographic changes; several different mechanisms have been proposed. In a prospective study of snake bite in Papua New Guinea, electrocardiographic changes were observed in 36 of 69 patients (52%) envenomed by the taipan (Oxyuranus scutellatus), 2 of 6 (33%) envenomed by death adders (Acanthophis sp.) and one envenomed by the brown snake (Pseudonaja textilis). Septal T wave inversion and bradycardias, including atrioventricular block, were the commonest abnormalities. There was no haemodynamic deterioration. The cause of these changes is uncertain; only 2 of 24 patients (8.3%) with electrocardiographic changes had markedly elevated plasma concentrations of cardiac troponin T, a sensitive and specific marker of myocardial damage. This suggests that myocardial damage is uncommon following bites by these species. Electrocardiographic abnormalities are most likely to have been caused by a direct toxic effect of a venom component upon cardiac myocyte function; in taipan bites, taicatoxin, a calcium channel blocker, might be responsible.

Animals↗
PubMed2000

Antibacterial properties of KwaZulu natal snake venoms.

The objective was to ascertain whether local snake venoms have antibacterial properties. The venoms of the common night adder (Causus rhombeatus), gaboon adder (Bitis gabonica), puff adder (Bitis arietans), black mamba (Dendroaspis polylepis), eastern green mamba (Dendroaspis augusticeps), forest cobra (Naja melanoleuca), snouted cobra (Naja annulifera) and Mozambique spitting cobra (Naja mossambica) were collected and, by gel diffusion, tested against the bacteria Staphylococcus aureus, Escherichia coli, Pseudomonas aeriginosa, Bacteriodes fragilis, Bacteroides intermedius, Clostridium sordellii and Clostridium perfringens. All snake venoms showed antibacterial activity, with the adders showing most activity against the aerobes while the cobras showed lesser, but equal activity against the aerobes and anaerobes. Black mamba venom only showed activity against C. perfringens. In conclusion, local snake venoms have antibacterial properties which are dependent on the venom and bacterial type; and in the Naja spp., for anaerobic bacteria, diminish in winter. There is liable to be more than one toxin component responsible.

Anti-Bacterial Agents↗
PubMed1998

Citrate inhibition of snake venom proteases.

Thirty snake venoms had a citrate content of 2.3 to 12.9%, dry basis, by an aconitase isocitric dehydrogenase coupled enzyme assay. This is a venom concentration range of approximately 30 to 150 mM citrate assuming 25% venom solids content. Inhibition of snake venom protease activity by the addition of exogenous citrate was obtained using azure blue hide powder and azocasein as substrates. Protease inhibitions of 7.5% for Crotalus atrox venom to 78% for Bothrops picadoi venom were observed with citrate. Complete inhibition of snake venom protease activity by citrate was not observed. Bothrops asper (Pacifico) venom showed a 41% protease inhibition by citrate with azocasein as the substrate and 46% inhibition of Bothrops asper (Alantico) venom protease with azure blue hide power as a substrate. Trypsin was not inhibited in this system. Citrate may inhibit some venom protease activity by forming a complex with the zinc of zinc-dependent enzymes. reserved.

Animals↗
PubMed1998

Pharmacokinetics of 125I-labelled IgG, F(ab')2 and Fab fractions of scorpion and snake antivenins: merits and potential for therapeutic use.

The immunoglobulin fractions IgG, F(ab')2 and Fab of scorpion and snake antivenoms possess pharmacokinetic characteristics that are significantly different from their respective venoms. The venoms (and their toxins) are several fold faster in their distribution into the tissues than any of the immunoglobulin fraction. In rabbits, F(ab')2 possessed the fastest disposition rate constants and the longest distribution half lives. In the physiologically based pharmacokinetic experiments carried out in mice F(ab')2 possessed the highest Cp(max), smallest AUC and the shortest t1/2beta in the different tissues while Fab had values in between IgG and F(ab')2. Rescue experiments in anaesthetized rats challenged with lethal doses of venoms or toxins and infused with border-line neutralizing doses of antivenoms, showed that rats infused with F(ab')2 completely recovered, those infused with IgG partially rescued and none of the rats infused with Fab survived. It is concluded that F(ab')2 of scorpion and snake antivenoms possess pharmacokinetic characteristics that render it the most suitable for use in serotherapy of scorpion and snake envenoming.

Animals↗
PubMed1980

Incidence and mortality on snake bite in savanna Nigeria.

Snake bite is a major medical problem among farming communities in the Benue and Niger Valley savanna region of Nigeria. Surveys in the more densely populated northern savanna areas such as Malumfashi (incidence 48 per 100 000 population, mortality 5.1%) show that the spitting cobra, Naja nigricollis, was the predominant species of medical importance. In the less cultivated Benue Valley area the annual snake-bite incidence was estimated to be 497 per 100 000 population, with a 12.2% mortality due mainly to the carpet viper, Echis carinatus. From these findings we estimate a yearly total of almost 10 000 deaths from snake bite in savanna Nigeria and about 23 000 deaths in West Africa. To rectify this serious health problem, concerted efforts are urgently needed.

Health Services↗
PubMed2001

Identification and molecular characterization of 18 paramyxoviruses isolated from snakes.

Viral agents from 18 different snake species (families Colubridae, Viperidae, and Crotalidae) showing respiratory symptoms and neuronal disease were identified as paramyxoviruses by typical cytopathogenic effect (CPE), electron microscopy, and hemagglutination inhibition. Detailed molecular characterization of the viruses was performed by partial L- and F-gene-specific reverse transcription polymerase chain reaction (RT-PCR) and sequencing, nucleotide and amino acid sequence alignment, and phylogenetic analysis (PHYLIP). RT-PCR of the partial L-gene (566 nt) was successful for all 18 viruses; amplicons of the partial F-gene (918 nt) could be obtained in 16 cases. F- and L-sequence alignment revealed similarities to Fer de Lance virus (FDLV) ranging from 79 to 88% on a nucleotide basis, and 94 to 99% on an amino acid basis. Phylogenetic analysis of the ophidian paramyxoviruses resulted in three clusters for the L-gene sequence and corresponding clusters for the F-gene sequence, indicating no species specificity. We analyzed the F-protein of the snake paramyxoviruses, which proved to have an identical conserved motif of heptad repeat A and predicted a furin cleavage site. This uniformity distinguishes the snake virus group from the other type species of the subfamily Paramyxovirinae. For further classification, we aligned the sequences of the ophidian paramyxoviruses and members of the Paramyxoviridae, such as Sendai virus (genus Respirovirus), mumps virus (genus Rubulavirus), measles virus (genus Morbillivirus), human respiratory syncytial virus (genus Pneumovirus) (Van Regenmortel and 10 co-authors, 2000) and Hendra virus, which have recently been suggested as type species of the genus Henipavirus (Wang et al., 2000). Maximum sequence similarity was found to the partial L-gene of Sendai virus, with 56% nucleotide and 61% amino acid identity. The FDLV and Sendai virus cluster in the phylogenetic analysis of L- and F-protein regarding the Paramyxovirus type species and Hendra virus and show the closest relationship. Regarding the biological properties, the antigenic distance, and particularly the low homology of available sequences, we propose a new genus for the reptilian paramyxoviruses within the Paramyxoviridae.

Amino Acid Sequence↗
PubMed1991

Immunoglobulins of the snake Psammophis sibilans. Studies using a monoclonal antibody.

A mouse monoclonal antibody (mAb) raised against serum immunoglobulins (Ig) of the snake. Psammophis sibilans stained in indirect immunofluorescence a proportion of snake splenic and peripheral blood lymphocytes, whereas it did not react with thymocytes, erythrocytes, brain, heart, lung, liver or kidney cells. The mAb, designated SR-2, combined in enzyme-linked immunosorbent assay (ELISA) with serum proteins of each of 20 individual P. sibilans tested. On Western blots of P. sibilans reduced whole serum proteins, purified Ig, or anti-rat erythrocyte (RRBC) antibodies eluted from glutaraldehyde-fixed RRBC, mAb SR-2 identified two bands of apparent molecular weight (m.w.) of 60,000 and 51,000 daltons. These bands were due to distinct polypeptides and not resulting from heterogeneous glycosylation of a single polypeptide, as they both were readily detected after periodate oxidation or endoglycosidase-F treatment of serum proteins and isolated Ig. MAb SR-2 bound to CNBr-activated Sepharose 4B precipitated from P. sibilans 125I-labeled serum proteins under non-reducing conditions a band that did not enter 7.5 or 9-16% gel and one of about 150,000 daltons. Under reducing conditions, two heavy bands of approximately 63,000 and 50,000 daltons and two light chains of apparent mass 23,000 and 20,000 bands were precipitated. The data presented provide, for the first time, substantial information on the molecular characteristics of snake Ig.

Animals↗
PubMed1987

Concanavalin A responsiveness and interleukin 2 production in the snake Spalerosophis diadema.

Thymocytes and splenocytes (SC) of adult snakes, Spalerosophis diadema, responded to concanavalin A (Con A) in vitro by strong proliferation during the spring and autumn seasons. Con A-mediated mitogenesis was, however, abrogated in summer and winter. Conditioned medium (CM) collected from snake SC cultures stimulated with Con A in spring or autumn could enhance the Con A summer and winter responses and support the proliferation of splenic lymphoblasts. Gel filtration of native CM on Sephadex G-100 revealed the presence of two biologically active peaks of molecular weight 39-42 and 15 KD. However, only one peak of activity corresponding to molecular weight (m.w.) of 14-15 KD was observed when CM was subjected to analysis by sodium dodecyl sulphate gel electrophoresis (SDS-PAGE). The active molecular forms exhibited isoelectric points of 5.5-5.8 and 6.4-6.6. The findings suggest that Con A activation of snake lymphocytes in optimal seasonal conditions is associated with the secretion of a lymphokine analogous to the interleukin 2 (IL 2) of endothermic vertebrates.

Animals↗
PubMedDate not supplied

Snake venom proteins acting on hemostasis.

The venoms of Viperidae and Crotalidae snakes are a rich source of proteins with activity against various factors involved in coagulation and fibrinolysis. These proteins are very specific for their molecular targets, resistant to physiological inhibitors and stable in vitro and in vivo. They have therefore proved to be useful for diagnostic tests. Based on sequence similarities, these snake venom proteins have been classified into various families, such as serine proteinases, metalloproteinases, C-type lectins, disintegrins and phospholipases A(2). The various members of a given family, although structurally similar, act selectively on different blood coagulation factors. This opens up the possibility of characterizing the structural elements involved in target molecule recognition. Thus, snake venom proteins provide excellent models for studies of structure-function relationships.

Amino Acid Sequence↗
PubMed1998

Modulation of snake hepatic cytochrome P450 by 3-methylcholanthrene and phenobarbital.

Induction mode of the hepatic drug-metabolizing enzymes was studied in Corn snake (Elaphe guttata emoryi). Treatment of snakes with 3-methylcholanthrene or phenobarbital produced no effects on liver weight and total content of cytochromes P450 and b5. Treatment with 3-methylcholanthrene significantly induced the activities of arylhydrocarbon hydroxylase, 7-ethoxyresorufin O-deethylase and 7-pentoxyresorufin O-dealkylase, whereas those of ethoxycoumarin O-deethylase, benzphetamine N-demethylase, erythromycin N-demethylase and testosterone hydroxylases were not affected. 3-Methylcholanthrene-induced activities of 7-ethoxyresorufin O-deethylase and 7-pentoxyresorufin O-dealkylase were inhibited by 20 microM alpha-naphthoflavone by 98% and 73%, respectively. Phenobarbital-treatment caused a significant induction of the activities of erythromycin N-demethylase and testosterone 6 beta-hydroxylase, but did not affect those of the other phase I enzymes and the other testosterone hydroxylases. The activities of UDP-glucuronyltransferase and glutathione S-transferase were not affected by either 3-methylcholanthrene or phenobarbital administration. Immunoblotting showed that 3-methylcholanthrene-treatment induced a protein band related to hamster CYP1A2, and decreased the intensity of the two bands detected with anti-rat CYP2B1. Phenobarbital-treatment did not affect the intensity of CYP2B-related proteins. The results suggest that snake liver has multiple forms of cytochrome P450, notably those inducible by 3-methylcholanthrene.

Animals↗
PubMed1997

Crotalid snake envenomation.

Over 5000 Americans suffer from snake bites annually, and of these, nearly one quarter are from poisonous species. Although these cases are undeniably reported, death appears to occur in only a few cases each year, and often reflects delay in obtaining medical care. Two families of venomous snake indigenous to the United States account for most envenomations: Crotalidae (pit vipers or new world vipers) and Elapidae. This article focuses on the snakes of the Crotalidae family.

Animals↗
PubMed1996

Transfer of a beta-hairpin from the functional site of snake curaremimetic toxins to the alpha/beta scaffold of scorpion toxins: three-dimensional solution structure of the chimeric protein.

The alpha/beta scorpion fold is shared by scorpion toxins, insect defensins, and plant thionins. This small and functionally versatile template contains an alpha-helix and a triple beta-sheet linked by three disulfide bridges. With the view to introduce novel functional centers within this fold, we replaced the sequence (the cysteines and glycines excepted) of the original beta-hairpin of a scorpion toxin by the sequence of a beta-hairpin that forms part of the site by which snake neurotoxins bind to nicotinic acetylcholine receptors (AcChOR). The resulting chimeric protein, synthesized by chemical means, binds to AcChOR, though with a lower affinity than the snake toxins [Drakopoulou; E., Zinn-Justin, S., Guenneugues, M., Gilquin, B., Ménez, A., & Vita, C. (1996) J. Biol. Chem. 271, 11979-11987]. The work described in this paper is an attempt to clarify the structural consequences associated with the transfer of the beta-hairpin. We report the determination of the three-dimensional solution structure of the chimeric protein by proton NMR spectroscopy and molecular dynamics calculations. Comparison of the structure of the chimera with those of the scorpion alpha/beta toxin and of the snake neurotoxin shows that (i) the new protein folds as an alpha/beta motif and (ii) the beta-hairpins of the chimera and of the curaremimetic toxin adopt a similar conformation. A closer inspection of the differences between the structures of the original and transferred beta-hairpins allows rationalization of the biological properties of the chimera.

Amino Acid Sequence↗
PubMed1999

Analyses of glycolipids from fish, shellfish, and sea snake lipids by high-performance liquid chromatography.

To determine the existence of glycolipids (neutral glycosphingolipid and glycoglycerolipid) in sea snake, round frigate mackerel, sardine, sea urchin, and abalone, we performed silica gel chromatography and high-performance liquid chromatography (HPLC) using an Aquasil-SS column and a C(8)-reversed phase silica gel column. HPLC with a UV absorption detector was used to analyze neutral glycosphingolipid. These chromatograms showed typical peaks in round frigate mackerel lipid, in sea snake crude fat, in abalone intestine lipid, and in sea urchin intestine lipid. UV-HPLC was also used to analyze glycoglycerolipid. These chromatograms indicated a large peak in round frigate mackerel lipid and a small peak in purified sardine oil. In addition, we observed the same peaks in the glycolipid fraction of round frigate mackerel muscle lipids and sea snake crude fat using a differential refractometer detector. The results of this study suggest that the peaks are neutral glycosphingolipid or glycoglycerolipid and that neutral glycosphingolipid and glycoglycerolipid may have specific physiological functions in each living creature.

Animals↗
PubMed2000

Determination of whole-body rotenone residues in the brown tree snake (Boiga irregularis).

The brown tree snake (Boiga irregularis) is an introduced pest in Guam, responsible for extensive agricultural damage, the extinction of several bird species, and severe and frequent electrical power outages. Rotenone, a naturally occurring pesticide, has been investigated as a possible chemical control agent. An analytical method was developed to assess whole body rotenone residues ranging in concentration from 0.035 to 250 microg g(-)(1) in snakes. The method employed ethyl acetate extraction of 2 g samples of cryogenically frozen, pulverized snakes, followed by silica and Florisil solid-phase extraction cleanup. Extract analysis was performed using a high-performance liquid chromatography system employing a cyanopropyl analytical column. Tissues fortified to concentrations of 0.035, 4.82, and 250 microg g(-)(1) yielded analyte recoveries of 85.1, 85.6, and 83.5%, respectively. The linear response of rotenone standard solutions was assessed from 0. 025 to 0.25 microg mL(-)(1) (r(2) = 0.9968) and from 0.250 to 125 microg mL(-)(1) (r(2) = 0.9999). The method was simple, rugged, and reliable.

Animals↗
PubMed1999

Sulfated sialic acid-polymers inhibit the cytotoxic action of bee and snake venom.

Colominic acid is an alpha2,8-linked sialic acid polymer produced by Escherichia coli. We found that synthetic sulfated-colominic acids (SC) remarkably inhibited the cytotoxicity of bee and snake venom toward mouse fibroblast cells, but colominic acids showed no inhibition themselves, indicating the important role of sulfate groups in the inhibitory activity of SC. Other sulfated carbohydrates such as chondroitin sulfates, heparin and heparan sulfate showed no inhibition. SC also exhibited potent inhibition of melittin, a highly basic peptide, which is a major cytotoxic component of bee venom. SC did not inhibit phospholipase A2 activity in bee venom. This suggests that the inhibition of bee and snake venom by SC is due to inhibition of melittin and cardiotoxin, which is a cytolytic peptide in snake venom, respectively. SC with a higher sulfur content and a larger molecular mass showed more potent activity. The interaction between SC and melittin basically seems an ionic one, however, the conformation of SC is also likely important. For the binding of SC to melittin leading loss of its cytotoxic activity, the sulfate groups of SC must be properly arranged to interact with lysine and arginine residues of melittin molecules, which play an important role in the cytolytic activity. A higher molecular mass of SC substituted with more sulfate groups is required for more obvious inhibition of the cytotoxic activity.

Animals↗