Characteristics of paralytic shellfish poisoning toxins derived from short-necked clams (Tapes japonica) in Mikawa Bay

A case of paralytic shellfish poisoning caused by consumption of visceral balls from geoduck Panopea japonica in Japan

In the end of March 2018, an unprecedented food poisoning incident due to ingestion of the visceral balls of geoduck Panopea japonica occurred in Japan. The patient, presented with symptoms of numbness on the lips and general weakness, was diagnosed as paralytic shellfish poisoning (PSP). The patient immediately treated with the mechanical ventilation recovered and left the hospital after 3 days treatment. Saxitoxins (STXs) in the plasma and urinary samples collected from the patient on the first and second day after hospitalization were analyzed by ultra high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC/MS/MS) and liquid chromatography with post-column fluorescent detection (LC/FLD). The STXs levels of 499.1 and 6.0 μg/L of STX dihydrochloride equivalent (STX·2HCl eq.) were quantitated by LC/FLD in the urinary samples on the first and second day, respectively. In addition, geoducks harvested from the same areas of the PSP causative specimens after the incident were analyzed by LC/FLD, and the results showed the level of STXs in their whole bodies of the geoducks exceeding 0.8 mg STX·2HCl eq./kg which is the maximum levels of STX in CODEX STAN 292-2008. Prominent toxins in STXs that detected in urinary and geoduck samples and identified by UHPLC/MS/MS and LC/FLD were gonyautoxin-1+4 (GTX1+4). These results concluded that the incident was the food poisoning due to STXs accumulated in the geoducks. This is the first PSP case caused by consumption of geoducks in Japan. This is also the first PSP case that causative toxins are detected in urinary samples of patients involved in PSP in Japan.

Cell bioassay for paralytic shellfish poisoning (PSP): comparison with postcolumn derivatization liquid chromatographic analysis and application to the monitoring of PSP in shellfish

We performed a neuroblastoma cell (Neuro2a) culture assay modified slightly from a method reported previously to provide a simple and sensitive evaluation of paralytic shellfish poisoning (PSP) toxicity in shellfish. The cell bioassay was just as sensitive for C-toxins as for gonyautoxins. The sensitivity of our cell bioassay was 4 times that of the current standard mouse bioassay. Using the cell bioassay, we evaluated PSP toxicity in 361 shellfish samples collected from Mikawa Bay and Ise Bay, Aichi Prefecture, Japan, from April 1999-March 2002. The results were compared with those obtained in a postcolumn derivatization liquid chromatographic analysis. PSP toxins were detected in 236/361 samples by both assays, and there was a fairly good correlation (r = 0.9001, n = 236, p < 0.001) between the results from the two assays. We applied this cell bioassay when short-necked clams in the bay turned poisonous in 2001. The chronological changes in PSP toxicity in the short-necked clams were analyzed and compared with those of the cell density of poisonous plankton (Alexandrium tamarense) occurring in the bay. The PSP toxicity in shellfish peaked 2 weeks after the cell density reached a maximum. We recommend using the cell bioassay for routine monitoring of PSP toxicity in shellfish living in natural marine environments.

Development and application of an enzyme immunoassay based on a monoclonal antibody against gonyautoxin components of paralytic shellfish poisoning toxins

With a gonyautoxin 2/3 (GTX2/3)-specific monoclonal antibody (designated GT-13A) and a saxitoxin-horseradish peroxidase conjugate (STX-HRP), a direct competitive enzyme immunoassay (GTX-EIA) was established and its sensitivity to various toxin components was investigated. The concentrations resulting in 50% inhibition of the binding of STX-HRP to the solid-phase GT-13A antibody for GTX2/3, decarbamoyl-GTX2/3 (dc-GTX2/3), N-sulfocarbamoyl-GTX2/3 (C1/2), GTX1/4, STX, and neosaxitoxin (neoSTX) in GTX-EIA were found to be 0.28, 0.41, 0.52, 3.46, 4.06, and 89.37 ng/ml, respectively. When the minimum detection limit was assumed to be at a toxin concentration causing 30% inhibition of the binding of STX-HRP to the solid-phase GT-13A antibody, the detection limits for GTX2/3, dc-GTX2/3, C1/2, GTX1/4, STX, and neoSTX were found to be 0.15, 0.18, 0.19, 1.09, 1.50, and 22.93 ng/ml, respectively. These results indicate that all of the GTX components examined and STX are detectable at concentrations lower than the regulatory limit of 80 microg/100 g of shellfish tissue, even when a minimum dilution factor of 100 is applied to tissue extracts with the extraction procedure of the Association of Official Analytical Chemists. Therefore, GTX-EIA is thought to be a useful qualitative screening method for GTX components and STX in the mass monitoring of toxin-contaminated shellfish.

Dinoflagellates from marine algal blooms produce neurotoxic compounds: effects on free calcium levels in neuronal cells and synaptosomes

In this report, evidence is presented that the marine unicellular eukaryotic dinoflagellates can cause neurotoxicity very likely by an increase in intracellular free calcium ions ([Ca(2+)](i)). Determinations of the effects of culture supernatants from different clones of the dinoflagellate Alexandrium sp. isolated from algal blooms on the viability of rat primary neuronal cells revealed that all clones tested were toxic for these cells. In addition, all Alexandrium clones tested, except for A. ostenfeldii BAH ME-141, were found to be toxic for rat pheochromocytoma PC12 cells. No toxicity was observed for culture supernatants from Gonyaulax and Coolia monotis. Calcium ions are important in the process of apoptotic cell death; our studies revealed that the dinoflagellate supernatants from A. lusitanicum K2, A. lusitanicum BAH ME-091, and A. tamarense 1M caused an increase in [Ca(2+)](i) levels in both PC12 cells and primary neuronal cells. These dinoflagellate supernatants, as well as the A. tamarense ccmp 115 supernatant, were found to cause also an increase in free calcium concentration in isolated synaptosomes. Our results suggest that the neurotoxic effects of certain dinoflagellate supernatants may be associated with disturbances in [Ca(2+)](i) levels.