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Saxitoxin
Saxitoxin (STX) is a potent neurotoxin and the best-known paralytic shellfish toxin. Ingestion of saxitoxin by humans, usually by consumption of shellfish contaminated by toxic algal blooms, is responsible for the illness known as paralytic shellfish poisoning (PSP). The term saxitoxin originates from the genus name of the butter clam ('' Saxidomus'') from which it was first isolated. But the term saxitoxin can also refer to the entire suite of more than 50 structurally related neurotoxins (known collectively as "saxitoxins") produced by protists, algae and cyanobacteria which includes saxitoxin itself (STX), neosaxitoxin (NSTX), gonyautoxins (GTX) and decarbamoylsaxitoxin (dcSTX). Saxitoxin has a large environmental and economic impact, as its presence in bivalve shellfish such as mussels, clams, oysters and scallops frequently leads to bans on commercial and recreational shellfish harvesting in many temperate coastal waters around the world including the Northeastern and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Decarbamoylsaxitoxin
Decarbamoylsaxitoxin, abbreviated as dcSTX, is a neurotoxin which is naturally produced in dinoflagellate. DcSTX is one of the many analogues of saxitoxin (STX). Saxitoxin is a tricyclic alkaloid compound, which has multiple structural related neurotoxins. One of those related neurotoxins is neosaxitoxin (NSTX) in which the nitrogen at position 2 is not bound to a hydrogen, but to a hydroxyl group. Another toxic analogue of saxitoxin is gonyautoxin (GTX). The difference between GTX and STX is that on the carbon at position 11, a hydrogensulfate is bound. Between dcSTX, NSTX and GTX, dcSTX is the one which varies most from saxitoxin. In dcSTX there is a double bond between carbons 2 and 3, while there is a single bond in STX. This also results in that the double-bonded N to carbon number 3 in STX, is a single bound NH2 in dcSTX. Another difference between decarbamoylsaxitoxin and saxitoxin is that the amino-carbonyl-oxy-methyl group at position 1 in STX, is only a CH2OH group in d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Neosaxitoxin
Neosaxitoxin (NSTX) is included, as other saxitoxin-analogs, in a broad group of natural neurotoxic alkaloids, commonly known as the paralytic shellfish toxins (PSTs). The parent compound of PSTs, saxitoxin (STX), is a tricyclic perhydropurine alkaloid, which can be substituted at various positions, leading to more than 30 naturally occurring STX analogues. All of them are related imidazoline guanidinium derivatives. Sources NSTX, and other PSTs, are produced by several species of marine dinoflagellates (eukaryotes) and freshwater cyanobacteria, blue-green algae (prokaryotes), which can form extensive blooms around the world. Under special conditions, during harmful algal blooms (HAB) or red tide, all these toxins may build up in filter-feeding shellfish, such as mussels, clams and oysters, and can produce an outbreak of Paralytic Shellfish Poisoning (PSP). Saxitoxin analogues associated to PSP can be divided into three categories: * Carbamate compounds, including saxitoxin, ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Paralytic Shellfish Poisoning
Paralytic shellfish poisoning (PSP) is one of the four recognized syndromes of shellfish poisoning, which share some common features and are primarily associated with bivalve mollusks (such as mussels, clams, oysters and scallops). These shellfish are filter feeders and accumulate neurotoxins, chiefly saxitoxin, produced by microscopic algae, such as dinoflagellates, diatoms, and cyanobacteria. Dinoflagellates of the genus '' Alexandrium'' are the most numerous and widespread saxitoxin producers and are responsible for PSP blooms in subarctic, temperate, and tropical locations. The majority of toxic blooms have been caused by the morphospecies '' Alexandrium catenella, Alexandrium tamarense'', '' Gonyaulax catenella'' and '' Alexandrium fundyense'', which together comprise the ''A. tamarense'' species complex. In Asia, PSP is mostly associated with the occurrence of the species ''Pyrodinium bahamense''. Some pufferfish, including the chamaeleon puffer, also contain saxitoxin, m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Gonyautoxin
Gonyautoxins (GTX) are a few similar toxic molecules that are naturally produced by algae. They are part of the group of saxitoxins, a large group of neurotoxins along with a molecule that is also referred to as saxitoxin (STX), neosaxitoxin (NSTX) and decarbamoylsaxitoxin (dcSTX). Currently eight molecules are assigned to the group of gonyautoxins, known as gonyautoxin 1 (GTX-1) to gonyautoxin 8 (GTX-8). Ingestion of gonyautoxins through consumption of mollusks contaminated by toxic algae can cause a human illness called paralytic shellfish poisoning (PSP). Natural sources Gonyautoxins are naturally produced by several marine dinoflagellates species ('' Alexandrium'' sp., ''Gonyaulax'' sp., '' Protogonyaulax'' sp.). The paralytic shellfish poisoning caused by these toxins is connected with dinoflagellate blooms known as “red tides”, even though the coloration of the water isn't a necessity. The threshold concentration of the organisms that are capable to produce the toxins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Alexandrium (dinoflagellate)
''Alexandrium'' is a genus of dinoflagellates. It contains some of the dinoflagellate species most harmful to humans, because it produces toxic harmful algal blooms (HAB) that cause paralytic shellfish poisoning (PSP) in humans. There are about 30 species of ''Alexandrium'' that form a clade, defined primarily on morphological characters in their thecal plates. Introduction The group was not well-defined in the past and thus, due to interest of its toxic behaviour, people have revised the group through formal tabulation and usage of molecular markers such as the toxic gene, stx4A, to better understand not just the relationship between each species; but more importantly, to tell something about the spread and barriers to the bloom. Even if, much is known about the life cycles related to the blooms, much is still unknown as to how each life stage is triggered and transitions to the next stage. Predation and parasitism have proven to be great barriers for population growth. Lear ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Cyanobacteria
Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteria's informal common name, blue-green algae. Cyanobacteria are probably the most numerous taxon to have ever existed on Earth and the first organisms known to have produced oxygen, having appeared in the middle Archean eon and apparently originated in a freshwater or terrestrial environment. Their photopigments can absorb the red- and blue-spectrum frequencies of sunlight (thus reflecting a greenish color) to split water molecules into hydrogen ions and oxygen. The hydrogen ions are used to react with carbon dioxide to produce complex organic compounds such as carbohydrates (a process known as carbon fixation), and the oxygen is released as a byproduct. By continuously producing and releasing oxygen over billions of years, cyanobacte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Dinoflagellates
The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also common in freshwater habitats. Their populations vary with sea surface temperature, salinity, and depth. Many dinoflagellates are photosynthetic, but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey ( phagotrophy and myzocytosis). In terms of number of species, dinoflagellates are one of the largest groups of marine eukaryotes, although substantially smaller than diatoms. Some species are endosymbionts of marine animals and play an important part in the biology of coral reefs. Other dinoflagellates are unpigmented predators on other protozoa, and a few forms are parasitic (for example, '' Oodinium'' and '' Pfiesteria''). Some dinoflagellates produce resting stages, called dinoflagellate cysts ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
