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At least 19 recordsLinked to original sources
PubMed1980

Comparative studies on Egyptian elapid venoms.

The immunological properties of Naja haje from Western Desert, Naja haje of the Nile Delta, Naja nigricollis from Upper Egypt and Walternnesia aegyptia from Sinai Desert were compared using horse serum antivenin prepared from the Delta Naja haje venom. All elapid venoms showed very similar precipitin lines with immunodiffusion or immunoelectrophoresis on agar gel. Results of cellulose-acetate electrophoresis showed either different concentration of certain similar protein components or the absence of some major protein fractions. However, different migration and localization of protein components were observed. LD50 of the 4 elapids and their degree of lethality was determined. Naja haje (Delta) antivenin had different degree of neutralization capacity on the investigated elapid venoms. No correlation between immunodiffusion similarities and the degree of neutralization could be deducted.

Animals↗
PubMed1983

Immunological stability of an elapid venom, Tropidechis carinatus, and its relevance to the clinical detection of snake venom.

Using immunological techniques, cases of human snake-bite can be proven and individual snake species identified. A series of experiments is described, to test the antigenic stability and physical properties of an Elapid venom, venom properties which will have implications in field use, transport, or the laboratory procedures relating to the immunological characterization of Australian snake venoms. Using venom from the Elapid, Tropidechis carinatus, we have demonstrated significant immunological stability at a temperature of 37 degrees for 48 h at least, and for 24 h at least when incubated continuously with skin, muscle, and fat homogenates; the venom is stable at 56 degrees for 2 h at least. No loss of venom occurs over the pH range 7-10; at pH ranges less than 4 and at ranges greater than 10 only 30% of venom is detected after 30 min incubation. Sonication (10 min at 100 watts) does not destroy immunological properties of the venom; 10 freeze-thaw cycles result in some 9% loss of immunologically detectable activity. Venom is adsorbed significantly on to dacron swabs, only 13% of the applied does being detected after 48 h incubation at 28 degrees. Sixty-seven percent of applied venom can be recovered from the skin of human volunteers 6 h after a simulated bite. The venom of this Elapid is antigenically robust. With the currently available sensitive assays, venom from human skin should still be detected in material kept without special preparation under field conditions for up to 2 days at least.

Animals↗
PubMed1990

A comparative study of the biological properties of Australian elapid venoms.

1. The hemorrhagic, procoagulant, anticoagulant, protease, phosphodiesterase, alkaline phosphomonoesterase, L-amino acid oxidase, acetylcholinesterase, arginine ester hydrolase, phospholipase A, 5'-nucleotidase and hyaluronidase activities of 39 samples of venoms from 13 species (15 taxa) of Australian elapids were determined and the Sephadex G-75 gel filtration patterns for some of the venoms were also examined. 2. The results indicate that Australian elapid venoms can be divided into two groups: procoagulant Australian venoms (including N. scutatus, N. ater, O. scutellatus, O. microlepidotus, P. porphyriacus, T. carinatus, H. stephensii and P. textilis) and non-procoagulant Australian venoms (including A. superbus, P. colletti, P. australis, P. guttatus and A. antarcticus). 3. The non-procoagulant Australian venoms exhibited biological properties similar to other elapid venoms, while the procoagulant Australian venoms exhibited some properties characteristic of viperid venoms. 4. The data show that information on venom biological properties can be used for differentiation of many species of Australian elapids. 5. Particularly useful for this purpose are the hyaluronidase, alkaline phosphomonoesterase, acetylcholinesterase, and the procoagulant activities and the Sephadex G-75 gel filtration patterns of the venoms.

Animals↗
PubMed1999

Elapid venom toxins: multiple recruitments of ancient scaffolds.

Nigroxins A and B, two myotoxic phospholipases A2 (PLA2s) from the venom of the American elapid Micrurus nigrocinctus, belong to a new PLA2 subclass. Their primary structures were established and compared with those of PLA2s that have already been studied with respect to myotoxic activity. The combination of amino acid residues Arg15, Ala100, Asn108 and a hydrophobic residue at position 109 is present exclusively in class I PLA2s that display myotoxic activity. These residues cluster within a surface region rich in positive charges and are suggested to play a role in the interaction with the target membrane of the muscle fibers. It is concluded that the myotoxic PLA2s resulted from recruitment of an ancient scaffold. Dendrotoxins and alpha-neurotoxins are similarly derived from other old structures, which are, however, now also present in nontoxic proteins that are widely distributed throughout the animal kingdom. The evolutionary pathways by which elapid PLA2s acquired myotoxicity and dendrotoxins acquired K+-channel blocker activity are traced. They demonstrate how existing scaffolds were adapted stepwise to serve toxic functions by exchange of a few surface-exposed residues.

Amino Acid Sequence↗
PubMed2001

Production of potent polyvalent antivenom against three elapid venoms using a low dose, low volume, multi-site immunization protocol.

The purpose of this study was to prepare a potent polyvalent antivenom against three elapids namely, the Thai cobra (Naja kaouthia, NK), the King cobra (Ophiophagus hannah, OH) and the banded krait (Bungarus fasciatus, BF). Two groups of horses were immunized. Group 1, comprising five horses, was immunized twice with a mixture of postsynaptic neurotoxins followed by an additional six immunizations with a mixture of crude venoms of the three elapids. Group 2, comprising four horses, was immunized with a mixture of crude venoms throughout the course. For the first immunization, the immunogens were emulsified in Complete Freund's adjuvant and injected using a low dose, low volume multi-site immunization protocol previously developed in this laboratory (Pratanaphon, R., Akesowan, S., Khow, O., Sriprapat, S. and Ratanabanangkoon, K. (1997) Production of highly potent horse antivenom against the Thai cobra (Naja kaouthia). Vaccine 15, 1523-1528). The second immunization was carried out with the immunogens in Incomplete Freund's adjuvant. Blood was drawn to assay the antibody titer by ELISA. Sera at the peak of ELISA titers were pooled and assayed for the median effective dose (ED(50)). The ED(50)'s of antivenom from Group 1 horses against NK, OH and BF venoms were 1.44, 0.22 and 0.23 ml serum/mg venom, respectively, while those from Group 2 horse sera were 0.88, 0.20 and 0.49 ml serum/mg venom, respectively. The potency of sera from Group 2 against BF venom was significantly higher, while the potencies against NK and OH venoms were comparable to those of the corresponding monovalent antivenoms produced under the same protocol. This potent, truly polyvalent antivenom should be useful in saving lives of victims envenomed by these elapids and the immunization protocol should be useful in the production of potent polyvalent antivenoms against other medically important elapids.

Animals↗
PubMed2003

Non-conventional toxins from Elapid venoms.

Non-conventional toxins constitute a poorly characterized class of three-finger toxins isolated exclusively from Elapidae venoms. These toxins are monomers of 62-68 amino acid residues and contain five disulfide bridges. However, unlike alpha/kappa-neurotoxins and kappa-neurotoxins which have the fifth disulfide bridge in their middle loop (loop II), the fifth disulfide bridge in non-conventional toxins is located in loop I (N-terminus loop). Overall, non-conventional toxins share approximately 28-42% identity with other three-finger toxins including alpha-neurotoxins, alpha/kappa-neurotoxins and kappa-neurotoxins. Recent structural studies have revealed that non-conventional toxins also display the typical three-finger motif. Non-conventional toxins are typically characterized by a lower order of toxicity (LD(50) approximately 5-80 mg/kg) in contrast to prototype alpha-neurotoxins (LD(50) approximately 0.04-0.3 mg/kg) and hence they are also referred to as 'weak toxins'. Further, it is generally assumed that non-conventional toxins target muscle (alpha(2)beta gamma delta) receptors with low affinities several orders of magnitude lower than alpha-neurotoxins and alpha/kappa-neurotoxins. However, it is now known that some non-conventional toxins also antagonize neuronal alpha 7 nicotinic acetylcholine receptors. Hence, non-conventional toxins are not a functionally homogeneous group and other, yet unknown, molecular targets for this class of snake venom toxins may exist. Non-conventional toxins may therefore be a useful source of ligands with novel biological activity targeting the plethora of neuronal nicotinic receptors as well as other physiological processes.

Amino Acid Sequence↗
PubMed1987

Properties of some 3-nitrotyrosyl elapid venom cardiotoxins.

Nitration of the invariant Tyr-22 in Hemachatus haemachates cardiotoxin 12B did not greatly decrease lethality, and the haemolytic potency towards guinea-pig erythrocytes remained unchanged. This residue is thus non-essential for cardiotoxin to exert its biological action. Nitration of Naja haje annulifera and Naja melanoleuca cardiotoxins VII1 decreased but did not abolish the lethalities and haemolytic potencies. Thus Tyr-25 and Tyr-51 were concluded to have no direct functional role in cardiotoxin lethality. The pKa values of the phenolic hydroxyl groups of the tyrosine residues appeared to be important for certain properties of cardiotoxin in solution. No evidence could be produced to show that Tyr-51 is unreactive to nitration under normal (non-denaturing) conditions.

Animals↗
PubMed1987

The selective S-alkylation of a methionine residue in an elapid venom cardiotoxin.

1. The reaction of cardiotoxin with iodoacetamide or iodomethane at pH 3.0 afforded the corresponding methionine sulphonium derivatives. The major products were S-alkylated at Met-26 whilst the minor products were S-alkylated at both Met-24 and -26. 2. Reaction with iodoacetamide under denaturing conditions led to a reversal of the relative abundances of the two derivatives in the respective reaction mixtures. 3. The derivative S-methylated at Met-26 was about 5-fold less toxic than the parent cardiotoxin. That derivatised at both Met-24 and -26 was non-toxic, indicating the importance of Met-24. 4. The results are discussed in the light of a structural model, previous chemical modifications and 1H-NMR data. It appeared that Met-24 is important for the integrity of an important structural feature of cardiotoxin.

Alkylation↗
PubMed1980

The preparation of 3-nitrotyrosyl derivatives of three elapid venom cardiotoxins.

Nitration studies using tetranitromethane were conducted on the tyrosine residues of cardiotoxins, naja melanoleuca VII1, Naja haje annulifera VII1 and Hemachatus haemachates toxin 12B. Various partially and fully nitrated derivatives were formed. Analysis of the products of nitrating naja melanoleuca VII1 showed that the average relative reactivities of the three tyrosine residues were Tyr-25 greater than Tyr-22 greater than Tyr-51. It was significant that Tyr-51 could be easily modified in both N. melanoleuca VII1 and N. haje annulifera VII1. In contrast, other workers had found Tyr-51 in N. naja atra cardiotoxin to be unreactive towards tetranitromethane except under denaturing conditions. Fully nitrated derivatives of N. melanoleuca VII1 (Tyr-22, -25 and -51), N haje annulifera VII1 (Tyr-22 and -51) and H. haemachates 12B (Tyr-22), prepared under mild reaction conditions, were isolated by ion-exchange and hydrophobic interaction chromatographies. All three derivatives were pure by disc gel electrophoresis at pH 8.9 and amino acid analysis. They were therefore suitable for spectral and biological studies. The results were compared and contrasted to; those of other workers.

Amino Acids↗
PubMed2002

Purification and cloning of toxins from elapid venoms that target cyclic nucleotide-gated ion channels.

In 1999, we purified pseudechetoxin (PsTx), the first peptide toxin known to block cyclic nucleotide-gated (CNG) ion channels, from the venom of Pseudechis australis [Brown, R. L., Haley, T. L., West, K. A., and Crabb, J. W. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 754-759]. Here we report the cloning of the cDNA encoding PsTx, as well as the discovery and cloning of pseudecin, a homologous toxin from the venom of Pseudechis porphyriacus. The mature proteins are 211 and 210 amino acids in length, and the amino acid sequences are 96.7% identical, differing in only seven residues. The purified toxins were applied to outside-out patches excised from Xenopus oocytes expressing CNG channels composed of the rod CNGA1 or olfactory CNGA2 channel subunits. Surprisingly, these patch-clamp studies revealed a 30-fold difference in affinity between PsTx and pseudecin for channels composed of CNGA2 subunits. The apparent K(i) of PsTx was 15 nM, while the affinity of pseudecin was 460 nM. The difference in affinities for the CNGA1 subunit from rod photoreceptors was less pronounced, but the affinity of PsTx was 70 nM, compared with 1000 nM for pseudecin. This difference in affinity may be instructive as we attempt to identify the regions of the toxins that contact CNG channels. As the only known protein blockers of CNG channels, these toxins promise to be valuable tools to study the structure of the external face of these channels.

Amino Acid Sequence↗
PubMed2006

North American coral snake antivenin for the neutralization of non-native elapid venoms in a murine model.

OBJECTIVES: North American coral snake antivenin (CSAV; Wyeth Antivenin [Micrurus fulvius], equine origin) is approved for the treatment of coral snake envenomations in the United States. The coral snake is the only elapid that is native to North America, but envenomations from non-native elapids are occurring more commonly in this country. This study was designed to evaluate the efficacy of CSAV in the neutralization of two exotic elapid envenomations: Naja naja (Indian cobra) and Dendroaspis polylepsis (black mamba). METHODS: A randomized, blinded, placebo-controlled murine model of intraperitoneal venom injection was employed. Venom potency was determined in preliminary dosing studies. Study animals then were divided into five groups: 1) N. naja venom + CSAV, 2) N. naja venom + 0.9% normal saline (NS), 3) D. polylepsis venom + CSAV, 4) D. polylepsis venom + NS, and 5) CSAV + NS. The venom dose was chosen to be twice the estimated LD50. The amount of CSAV injected was ten times the amount necessary for neutralization of a 2 x LD50 dose of M. f. fulvius venom in a murine model. Statistical analysis included Fisher's exact and log-rank testing to compare survival rates and times. RESULTS: Preliminary studies estimated the venom LD50 to be 2.58 mg/kg and 0.45 mg/kg, respectively, for the N. naja and D. polylepsis. A significant difference was shown in comparison of survival times between CSAV-venom groups and normal saline-venom groups despite all animals in both treatment and control arms dying. Animals receiving CSAV and N. naja venom survived (mean +/- SD) 24.4 +/- 3.0 minutes, versus 17.8 +/- 1.3 minutes in the control group (p < 0.001), whereas those receiving CSAV and D. polylepsis venom survived 203.8 +/- 37.0 minutes versus 130.0 +/- 42.6 minutes in the control group (p < 0.001). All animals in the CSAV + NS group survived to the conclusion of the study. CONCLUSIONS: When premixed with venom, CSAV increased survival time in a murine model of intraperitoneal N. naja and D. polylepsis venom injection. The clinical implications of this are unclear, given unchanged mortality rates.

Animals↗