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The Neuromuscular Junction
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The drug hemicholinium-3 inhibits the reuptake of choline at the presynaptic terminal, which depresses ACh synthesis because most of the choline needed for ACh synthesis is provided through reuptake of the choline resulting from hydrolysis of ACh in the synaptic cleft, and only a relatively small amount of choline is transported from the cell body. α-latrotoxin is an extremely potent neurotoxin, that is a poison of the nervous system, contained in the venom of the black widow spider. It causes massive exocytosis of ACh from presynaptic terminals either by forming open pores in the presynaptic membrane that allow the influx of Ca2+ and Na+ or by binding to special receptors, thereby initiating processes that lead to exocytosis. The depletion of ACh eventually leads to muscle paralysis. Botulinum toxin, produced by a bacterium found in poisoned foods, is one of the most toxic substances known. Only 2 ng of a form of this toxin, when injected intravenously, can kill a human adult by preventing ACh vesicles from fusing with the presynaptic membrane and releasing ACh into the synaptic cleft. Extremely small doses of other forms of this toxin, commercially known as Botox, are injected into the skin to relax muscles causing wrinkles. Botox is also used in the treatment of disorders caused by overactive muscle movement or conditions arising from hyperactivity of some nerves.
Principles of Treatment for Arthropod Bites, Stings, and Other Exposure
Published in Gail Miriam Moraru, Jerome Goddard, The Goddard Guide to Arthropods of Medical Importance, Seventh Edition, 2019
Gail Miriam Moraru, Jerome Goddard
Widow spiders and some scorpions produce ill effects in humans by neurotoxic venoms. The primary toxin in widow spider (Latrodectus spp.) venom is α-latrotoxin which binds to specific presynaptic receptors (neurexin 1a and CIRL), precipitating neurotransmitter release, particularly norepinephrine and acetylcholine.13 This leads to sweating, piloerection, muscular spasm, weakness, tremor, and sometimes paralysis, stupor, and convulsions. This type of venom may not produce obvious skin lesions but will primarily produce these systemic reactions.
Biology and Distribution of Spiders of Medical Importance
Published in Jürg Meier, Julian White, Handbook of: Clinical Toxicology of Animal Venoms and Poisons, 2017
Probably due to the seriousness of the human accidents and the worldwide occurrence of the spiders of the genus Latrodectus, the venoms, mainly from the species L. tredecimguttatus of the Mediterranean Region and L. mactans from North America, have been studied by several investigators. Grasso54 studied the extract of the venom apparatus of L. tredecimguttatus and isolated and purified a neurotoxin with an amino acid composition consisting of 1219 residues per 130,000 molecular weight molecule. Frontali et al.55 working with the venom of the same species isolated a pure fraction called B 5. Tzeng and Siekevitz56 first called this fraction B 5 α-latrotoxin. This toxin is an active neurotoxin which affects the transmitter release from nerve endings of the vertebrates. Fedorova and Magazanik57 isolated from the α-latrotoxin a homogeneous protein of mol. wt. 120 KDa, labelled α-latroinsectotoxin which acts on presynaptic nerve endings of insects preparations. Akhunov et al.58 succeeded in showing that the venom of L. tredecimguttatus contains peptides possessing bradykinin potentiating activity. Grishin59 purified seven high mol. wt neurotoxins from the venom of L. tredecimguttatus. These protein neurotoxins induce a massive release of the neurotransmitter from affected nerve endings, being specific either for the insect (latroinsectotoxin), or for the vertebrate (α-latrotoxin), or for the crustacean (α latrocrustatoxin). Kiyatkin et al.60 presented the structure of a low molecular weight protein copurified from the α latrotoxin.
Is there actual clinical evidence of necrosis following the Steatoda nobilis bite?
Published in Clinical Toxicology, 2022
Giovanni Paolino, Piergiorgio Di Pompeo, Matteo R. Di Nicola
The venom of S. nobilis is mainly characterized by α-latrotoxins, δ-latroinsectotoxins, latrodectins and enzymes [2], which explains both systemic and local clinical signs, like ulceration and erosion. Necrosis is an inappropriate term referring to a spectrum of morphologic changes that follow cell death in tissues, and it is divisible in six main types: coagulative, liquefactive, caseous, gangrenous, fat and fibrinoid necrosis [3]. Gangrenous necrosis is the one mainly involved in spider bites, as it is induced mostly by proteolytic enzymes that cause cell death (e.g., sphingomyelinase in Loxosceles sp.) [4]. Necrosis induced by spider bites clinically shows specific and progressive pathognomonic aspects, such as prodromal swelling and blisters, followed by a cutaneous discoloration ranging from pale to blue, purple, black, bronze or red. The damaged tissue develops into dark black color, always resulting in a clinically evident scar due to dermal and hypodermic damage.
Venomous bites during pregnancy: the black widow spider (Latrodectus mactans)
Published in Toxin Reviews, 2019
Gianmarco Troiano, Alessandra Bagnoli, Astrid Mercone, Nicola Nante
Widow venom contains α-latrotoxin, which provokes a massive presynaptic release of acetylcholine. Latrotoxin and latrodectin selectively interact with latrophilin and neurexin receptors in the lipid bilayer membrane of presynaptic terminals, resulting in the formation of cation channels allowing an influx of Ca2+ into the cell. Toxin activity causes the release of a large amount of such neurotransmitters as noradrenaline and acetylcholine, as well as calcium-independent gamma-aminobutyric acid, and has an important effect on the neuromuscular junction (Sotelo-Cruz and Gomez-Rivera 2016). After a person has been bitten, crampy muscle spasms usually occur within an hour in the chest (upper extremity bites) or the abdomen (lower extremity bites). The pain may be intense enough to mimic myocardial infarction or acute abdomen, but it is rarely life threatening and typically resolves within 48–72 h (Clark et al.1992, Juckett 2013). Nausea, weakness, local or generalized diaphoresis, and facial edema may occur (Clark et al.1992).
Black widow spider bite in Johannesburg
Published in Southern African Journal of Infectious Diseases, 2018
Teressa Sumy Thomas, Alan Kemp, Kim Pieton Roberg
α-latrotoxin is a neurotransmitter found within black widow venom that binds non-specifically to neuronal presynaptic receptors within the peripheral nervous system. This causes massive release of neurotransmitters, especially acetylcholine and noradrenaline, resulting in the clinical symptoms observed. The toxin is unable to cross the blood–brain barrier, hence no central nervous system symptoms are observed.1