brevetoxin and maitotoxin

Ciguatoxins (CTX) and brevetoxins (BTX) are polycyclic ethereal compounds biosynthesized by the worldwide distributed planktonic and epibenthic dinoflagellates of

Topics: Animals; Ciguatera Poisoning; Ciguatoxins; Dinoflagellida; Humans; Ligands; Marine Toxins; Oxocins; Potassium Channels, Voltage-Gated

Synapses are specialised structures where interneuronal communication takes place. Not only brain function is absolutely dependent on synaptic activity, but also most of our organs are intimately controlled by synaptic activity. Synapses re therefore an ideal target to act upon and poisonous species have evolved fascinating neurotoxins capable of shutting down neuronal communication by blocking or activating essential components of the synapse. By hijacking key proteins of the communication machinery, neurotoxins are therefore extremely valuable tools that have, in turn, greatly helped our understanding of synaptic biology. Moreover, analysis and understanding of the molecular strategy used by certain neurotoxins has allowed the design of entirely new classes of drugs acting on specific targets with high selectivity and efficacy. This chapter will discuss the different classes of marine neurotoxins, their effects on neurotransmitter release and how they act to incapacitate key steps in the process leading to synaptic vesicle fusion.

Topics: Acrylamides; Amino Acid Sequence; Animals; Calcium Channel Blockers; Calcium Channels; Ciguatoxins; Cnidarian Venoms; Ion Channels; Marine Toxins; Models, Molecular; Molecular Sequence Data; Neurotoxins; Neurotransmitter Agents; Oxocins; Potassium Channels; Saxitoxin; Sea Anemones; Synaptic Transmission; Tetrodotoxin

We have modified the cell-based directed cytotoxicity assay for sodium channel and calcium channel active phycotoxins using a c-fos-luciferase reporter gene construct. In this report we describe the conceptual basis to the development of reporter gene assays for algal-derived toxins and summarize both published and unpublished data using this method. N2A mouse neuroblastoma cells, which express voltage-dependent sodium channels, were stably transfected with the reporter gene c-fos-luc, which contains the firefly luciferase gene under the transcriptional regulation of the human c-fos response element. The characteristics of the N2A reporter gene assay were determined by dose response with brevetoxin and ciguatoxin. Brevetoxin-1 and ciguatoxin-1 induced c-fos-luc with an EC50 of 4.6 and 3.0 ng ml(-1), respectively. Saxitoxin caused a concentration-dependent inhibition of brevetoxin-1 induction of c-fos-luc with an EC50 of 3.5 ng ml(-1). GH4C1 rat pituitary cells, which lack voltage-dependent sodium channels but express voltage-dependent calcium channels, were also stably transfected with the c-fos-luc. GH4C1 cells expressing c-fos-luciferase were responsive to maitotoxin (1 ng ml(-1)) and a putative toxin produced by Pfiesteria piscicida. Although reporter gene assays are not designed to replace existing detection methods used to measure toxin activity in seafood, they do provide a valuable means to screen algal cultures for toxin activity, to conduct assay-guided fractionation and to characterize pharmacologic properties of algal toxins.

Topics: Animals; Biological Assay; Ciguatoxins; Dose-Response Relationship, Drug; Genes, fos; Genes, Reporter; Luciferases; Marine Toxins; Mice; Neuroblastoma; Neurotoxins; Oxocins; Pfiesteria piscicida; Pituitary Gland; Proto-Oncogene Proteins c-fos; Rats; RNA, Messenger; Saxitoxin; Transfection; Tumor Cells, Cultured

A range of marine polyether toxins from dinoflagellates were analysed by ionspray mass spectrometry. Ciguatoxin-1 ([M+H]+ m/z = 1,111.8) purified from several fish species yielded singly charged ions corresponding to the parent ion, sodium and H2O adducts and ions for the loss of up to five H2O molecules. Ciguatoxin-1 was detected to 1 ng; however, interference from fish lipids precluded direct detection of ciguatoxin-1 in crude extracts from fish flesh spiked with ciguatoxin-1 at a level equivalent to 1.5 ng ciguatoxin-1/g of extracted flesh. Maitotoxin-2 yielded doubly and triply charged ions for sodium and potassium salts and likely possessed only one sulphate ester (M(r) = 3,298 for the mono-sodium salt). Maitotoxin-3, a recently isolated small maitotoxin, yielded singly charged ions including ions for the loss of one sulphate and up to four H2O molecules. Maitotoxin-3 is proposed to be a polyether compound possessing two sulphate esters (M(r) = 1,060.5 for the disodium salt). Brevetoxin-A ([M+H]+ m/z = 867.5) and brevetoxin-B ([M+H]+ m/z = 895.5) yielded singly charged ions corresponding to the parent ion, Na+ adducts and the loss of up to four H2O molecules. Okadaic acid ([M+H]+ m/z = 805.5) yielded singly charged ions corresponding to the parent ion and ions for the loss of up to three H2O molecules. A signal for M + 18 Da species that may represent [M+NH4]+ was observed for ciguatoxin-1, brevetoxin-A and -B, and okadaic acid. For all polyethers examined, the orifice potential influenced the relative intensity of the ions detected in a predictable manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Carcinogens; Chromatography, High Pressure Liquid; Ciguatoxins; Dinoflagellida; Eels; Ethers, Cyclic; Fishes; Marine Toxins; Mass Spectrometry; Okadaic Acid; Oxocins; Spectrometry, Mass, Fast Atom Bombardment

This study examined the development of a highly simplified solid-phase colored latex immunobead assay for the detection of ciguatoxin and related polyethers. This procedure was compared with the stick enzyme immunoassay previously reported. Chi-square analysis of two separate experiments on 153 and 283 fish of various species gave chi 2 values of p less than 0.001 and p less than 0.005, respectively. Agreement between the two procedures with 26 fish implicated in ciguatera poisoning was 100%. A preliminary assessment in the field showed encouraging results. The procedure appears to be simple and applicable to field use. Furthermore, this procedure should be applicable to other antibody-antigen detections, especially low dalton determinations.

Topics: Animals; Ciguatoxins; Fishes; Humans; Immunoassay; Marine Toxins; Monensin; Oxocins