Toxin Reviews gathers the latest interdisciplinary findings on toxins and toxin mechanisms into one convenient, extraordinarily valuable compendium. Featuring a dual emphasis on classifying toxins by their mechanisms of action, and on new, underutilized substances, this outstanding journal brings scientists exactly the right combination of up-to-date, easily absorbed and applied information and bold new ideas in lively brief notices and reviews. Discontinued in 2005 - now Toxin Reviews.
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The venom of many of the snakes of the Elapidae and Hydrophiidae is highly toxic, producing flaccid paralysis and respiratory failure in animals. These effects mainly are attributable to postsynaptic neurotoxins known to bind specifically and tightly to the nicotinic acetylcholine receptor (AChR). Sequence analyses findings for postsynaptic neurotoxins from many snake species show they can be classified into short (61-62 amino acid residues) and long (71-74 amino acid residues) neurotoxins. Short-chain neurotoxins bind specifically, but weakly to AChRs, and the binding is slowly reversible. This property makes them particularly useful for the purification of AChRs. Long-chain neurotoxons, such as α-Bungarotoxin (α-BuTx), bind specifically and tightly to AChRs and are useful as probes to measure the number of AChRs in the bound radioiodinated neurotoxin contents. The most common clinical application of neurotoxin is in the detection of nicotinic AChRs and their antibodies in research related to the pathogenesis of myasthenia gravis (MG). We have developed new assay systems for detecting antibodies that recognize different antigenic determinants in AChR protein. Using them, we detected a markedly high prevalence of anti-AChR antibodies in MG. This determination now allows for a definite diagnosis of MG. We also show that the blocking effect of the anti-AChR antibodies in MG sera is due to steric hindrance caused by their binding to a region other than that for α-BuTx.
Haemorrhagic factors were purified from many snake venoms belong to Crotalid and Viperid snakes, and they were characterized. These results indicate that they are metalloproteinases, and divided into four groups by their molecular weights and domain compositions, such as small (15~30 kDa), medium (30~50 kDa), large (50~80 kDa) and extra large (> 80 kDa). And their enzymatic properties were differed from each other. Antihaemorrhagic factors were purified from the serum of venomous, non-venomous and warm-blooded animals, and characterized. In this review, we describe the properties of these haemorrhagic factors and antihaemorrhagic factors.
One of the largest groups of snakes is the family Colubridae. This is a paraphyletic assemblage that includes a few venomous species, but most pose no special health risk to humans. Thirty to forty percent of colubrids possess a Duvernoy's gland, a specialized oral gland located in the temporal region. Although it is a homologue to the venom glands of viperid and elapid snakes, the Duvernoy's gland is anatomically and functionally distinct. Generally it lacks a large internal reservoir of secretion, emptying is under low-pressure flow, and the secretion is not delivered via hollow fangs. In contrast, true venom glands hold a large store of ready venom, expel the venom under direct action of striated muscles, and inject it as a high-pressure pulse via hollow fangs. Both the Duvernoy's gland and the venom gland are part of a snake's trophic system, involved primarily in predatory behavior. True venoms are composed of potent toxins whose main biological role is to bring about rapid prey death. Although the secretion from the Duvernoy's gland may include toxins, surprisingly only a few colubrids deploy it similarly to kill prey quickly. In fact, the biological role(s) of Duvernoy's secretion remain today largely unknown. Therefore, it is misleading, in a functional and evolutionary context, automatically to call Duvernoy's secretion a venom (biological role) when only its pharmacology (property) is known. Although Duvernoy's secretion has some components in common with true venoms, some may be fundamentally different in chemical composition, likely because it is involved in different biological roles than a true venom. This means it likely includes novel chemical components with a promise of interest to human medicine.
Contributions of Japanese scientists in tetanus toxin research in various aspects are described in relation to the progress in this field. Their fundamental studies as well as practical works gave breakthroughs to elucidate the biochemical mechanism of action of tetanus toxin and pathophysiology of tetanus. Future problems in tetanus toxin research are discussed.
Conotoxins are peptide toxins synthesized by marine cone snails for both prey entrapment and defense. The peptides, when injected into the prey, cause immobilization and death. Cone snails are widely distributed in tropical waters, their prey includes fish, worms and other marine snails. The peptide toxins have very high specificity and selectivity for a variety of neuro receptors and ion channels. This makes the toxins very useful in studies aimed at identifying receptors and their ligands, as well as in drug development studies. Conotoxins are notable at the level of primary amino acid sequence for their high percentage of cysteine residues and other post-translational modifications including hydroxylation of proline, γ-carboxylation of glutamate, pyroglutamic acid formation, bromination of tryptophan and C-terminal amidation. This review describes traditional and more novel techniques for the characterization of conotoxins. In particular, the identification of the nature and the site of post-translational modifications is emphasized. Among the different techniques used to characterize the conotoxins, the important role played by mass spectrometry is emphasized.
There are several groups of medically important araneomorph and mygalomorph spiders responsible for serious systemic envenomation. These include spiders from the genus Latrodectus (family Theridiidae), Phoneutria (family Ctenidae) and the subfamily Atracinae (genera Atrax and Hadronyche); The venom of these spiders contains potent neurotoxins that cause excessive neurotransmitter release via vesicle exocytosis or modulation of voltage-gated sodium channels.-In addition, spiders of the genus Loxosceles (family Loxoscelidae) are responsible for significant local reactions resulting in necrotic cutaneous lesions. This results from sphingomyelinase D activity and possibly other compounds. A number of antivenoms are currently available to treat envenomation resulting from the bite of these spiders. Particularly efficacious antivenoms are available for Latrodectus and Atrax/Hadronyche species, with extensive cross-reactivity within each genera. In the case of Latrodectus antivenoms this is of considerable importance in countries where antivenom is unavailable or where certain antivenoms are associated with an unacceptably high risk,of adverse reactions. Moreover, Latrodectus and Atrax antivenoms appear, to be effective in the treatment of envenomation by closely related Steatoda spiders (family Theridiidae) or the unrelated spider Missulena bradleyi (family Actinopodidae), respectively., The effectiveness of Loxosceles antivenom in the treatment of the necrotic arachnidism resulting from the bite of recluse spiders is less clear mainly due to late presentation of victims. Antivenom is also available for Phoneutria envenomation but is reserved only for severe cases.
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