Publications by authors named "Ryuichi Watanabe"

Recently, an instrumental analysis using LC-MS/MS has been developed and validated for paralytic shellfish toxins (PSTs) and tetrodotoxin (TTX) in bivalve molluscs in Japanese domestic and overseas. The method for 11 PSTs and TTX in scallops was validated in accordance with a previous report and CODEX-STAN. The samples were prepared by adding the standard mixture of PSTs and TTX to scallop (Patinopecten yessoensis) homogenates, extracted with 1% acetic acid and then cleaned up using an ENVI-Carb (250 mg/3 mL) cartridge.

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The definitive diagnosis of patients with indeterminate biliary strictures remains challenging. Probe-based confocal laser endomicroscopy (pCLE) provides real-time histological assessment of bile duct tissues. Since no previous studies have evaluated the efficacy of pCLE under direct cholangioscopic visualization for biliary strictures that cannot be definitively diagnosed through endoscopic retrograde cholangiopancreatography using fluoroscopy, we prospectively assessed the feasibility and safety of this procedure in three cases.

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  • The study aimed to explore the relationship between CD8 expression in tumors and patient outcomes in those with unresectable pancreatic ductal adenocarcinoma (PDAC) by examining tissue samples obtained through endoscopic ultrasound-guided tissue acquisition (EUS-TA).
  • A total of 169 patients participated, and findings indicated that the median overall survival for patients was only 171 days, with no significant difference in survival rates between high and low CD8-positive groups.
  • Ultimately, the results concluded that CD8 expression in tissue samples did not correlate with the clinical progression or chemotherapy response of patients with unresectable PDAC.
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  • Amphidoma languida, a dinoflagellate known for producing the toxin azaspiracids, has been detected in environmental DNA in the Asia Pacific, despite no confirmed sightings.
  • The study examined the morphology, ultrastructure, and phylogeny of nine recently isolated strains of Amphidoma from Japan, Malaysia, and the Philippines, revealing differences from the Atlantic species.
  • Findings indicate that these Pacific strains, proposed as a new species named Amphidoma fulgens sp. nov., are non-toxigenic and display unique structural features compared to Am. languida.
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Absolute configuration at 12 stereocenters in the 36-membered macrocyclic ring portion of poecillastrin C () was disclosed by chemical degradation and NMR analyses of , chemical synthesis, and molecular modeling techniques.

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  • In March 2018, Japan experienced a rare food poisoning incident linked to eating geoduck, resulting in a patient suffering from paralytic shellfish poisoning (PSP) with symptoms like lip numbness and weakness.
  • The patient was treated successfully with mechanical ventilation and recovered after three days, while scientific analysis of their urine confirmed high levels of saxitoxins (STXs).
  • The geoducks harvested from the same region also showed dangerously high STX levels, conclusively linking the food poisoning incident to toxins accumulated in the geoducks, marking it as the first recorded case of PSP from geoduck consumption in Japan.
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Lipophilic marine biotoxin azaspiracids (AZAs) are produced by dinoflagellates Azadinium and Amphidoma. Recently, several strains of Azadinium poporum were isolated from Japanese coastal waters, and detailed toxin profiles of two strains (mdd421 and HM536) among them were clarified by several detection techniques on liquid chromatography-tandem mass spectrometry (LC-MS/MS) and liquid chromatography-quadrupole time of flight mass spectrometry (LC-QTOFMS). In our present study, AZA analogues in seven strains of A.

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A new lipopeptide, N-desmethylmajusculamide B (1), was isolated from the Okinawan cyanobacterium Okeania hirsuta along with 2 known compounds majusculamide A (2) and majusculamide B (3). The planar structure of (1) was elucidated by a detailed analysis of mass spectrometry and nuclear magnetic resonance spectra. The absolute configurations of the amino acid residues were determined using Marfey's analysis.

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The filter-feeding bivalves often accumulate marine toxins by feeding on toxic dinoflagellates that produce marine toxins. Azaspiracids (AZAs) are a group of lipophilic polyether toxins which have been detected in a variety of organisms in many countries. In our present study, accumulation kinetics and toxin distributions in the tissues of seven bivalve species and ascidians relevant to Japanese coastal waters were investigated by experimentally feeding a toxic dinoflagellate Azadinium poporum, which produces azaspiracid-2 (AZA2) as the dominant toxin component.

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  • - Saxitoxin (STX) is a powerful neurotoxin produced by toxic dinoflagellates and accumulates in shellfish, requiring monitoring due to its health risks.
  • - Monitoring STX in shellfish is challenging because it’s classified as a chemical warfare agent, complicating the import of calibration standards for testing.
  • - The study suggests using non-toxic variants of STX (called -STXs) as safe substitutes for calibration standards, which can aid in effective monitoring without violating chemical weapons regulations.
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In the coastal countries of Southeast Asia, fish is a staple diet and certain fish species are food delicacies to local populations or commercially important to individual communities. Although there have been several suspected cases of ciguatera fish poisoning (CFP) in Southeast Asian countries, few have been confirmed by ciguatoxins identification, resulting in limited information for the correct diagnosis of this food-borne disease. In the present study, ciguatoxin-1B (CTX-1B) in red snapper () implicated in a CFP case in Sabah, Malaysia, in December 2017 was determined by single-quadrupole selected ion monitoring (SIM) liquid chromatography/mass spectrometry (LC/MS).

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Balenine (Bal) in opah muscle was extracted using hot water and purified by ion-exchange chromatography and recrystallization to provide 41 g of over 95% pure Bal from 1 kg of opah muscle. The structure of purified Bal was identical to that of an authentic Bal standard by NMR analysis. The antioxidant (ORAC and HORAC values) and Fe(II) ion-chelating abilities of purified Bal were examined by comparison with two major imidazole dipeptides, carnosine (Car) and anserine (Ans).

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The mouse bioassay (MBA) for paralytic shellfish toxins (PSTs) in bivalves has been used as an official method in Japan. It is necessary to develop an alternative method to animal experiments in PSTs assay because 3Rs (Replacement, Reduction, and Refinement) of animal experiments are required from the animal welfare point of view. Various methods such as HPLC-FL, receptor binding assay, LC-MS/MS and ELISA have been established to detect PSTs without performing animal experiments.

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Lipophilic marine biotoxins azaspiracids (AZAs) are produced by dinoflagellates Azadinium and Amphidoma. Recently, several strains of Azadinium poporum were isolated from Japanese coastal waters. In our present study, AZA analogues in two strains (mdd421 and HM536) of A.

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The consumption of contaminated shellfish with okadaic acid (OA) group of toxins leads to diarrhoeic shellfish poisoning (DSP) characterized by a set of symptoms including nausea, vomiting and diarrhoea. These phycotoxins are Ser/Thr phosphatase inhibitors, which produce hyperphosphorylation in cellular proteins. However, this inhibition does not fully explain the symptomatology reported and other targets could be relevant to the toxicity.

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  • Researchers collected macroalgal samples from various coastal waters in Japan and identified 32 non-motile dinoflagellate-like protist strains, classifying them into three new phylotypes within the genus Alexandrium.
  • Molecular analysis indicated that the three types closely relate to the species A. ostenfeldii, and most strains were non-motile with an average diameter of 35 to 39 µm, exhibiting different distributions in water depths.
  • Despite showing lethal toxicity to mice, the strains did not produce any tested toxins associated with paralytic shellfish poisoning, marking this as the first study to find Alexandrium linked to marine macroalgae in Japan.
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Okadaic acid (OA) and its main structural analogs dinophysistoxin-1 (DTX1) and dinophysistoxin-2 (DTX2) are marine lipophilic phycotoxins distributed worldwide that can be accumulated by edible shellfish and can cause diarrheic shellfish poisoning (DSP). In order to study their toxicokinetics, mice were treated with different doses of OA, DTX1, or DTX2 and signs of toxicity were recorded up to 24 h. Toxin distribution in the main organs from the gastrointestinal tract was assessed by liquid chromatography-mass spectrometry (LC/MS/MS) analysis.

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This paper argues the effectiveness of Ecohealth education for improving the quality of health and environmental education and for achieving sustainable development in developing countries. To illustrate the need for Ecohealth education, we review the transitions in health education, environmental education and Education for Sustainable Development (ESD) in various developing countries. Moreover, we discuss issues relating to these disciplines and consider the possible roles that Ecohealth education can play.

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  • NMR spectroscopy is being used to precisely measure organic molecules, with Hydrogen nucleus quantification (H qNMR) emerging as the primary method for assessing chemical purity.
  • A collaborative study involving 13 labs was conducted to validate the H qNMR method, measuring the purity of three samples certified by conventional methods.
  • Results showed that H qNMR measurements matched reference values closely, demonstrating its reliability and accuracy comparable to traditional measurement techniques.
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Rationale: The dinoflagellate genera Gambierdiscus and Fukuyoa are producers of toxins responsible for Ciguatera Poisoning (CP). Although having very low oral potency, maitotoxins (MTXs) are very toxic following intraperitoneal injection and feeding studies have shown they may accumulate in fish muscle. To date, six MTX congeners have been described but two congeners (MTX2 and MTX4) have not yet been structurally elucidated.

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An extensively -methylated linear nonapeptide heptavalinamide A () was isolated from the marine cyanobacterium sp. collected at Kabira Reef of Ishigaki Island, Okinawa. The amino acid sequence of was assigned by interpretation of 2D NMR and MS/MS data.

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  • * The research involved monitoring sewage flow over 68 days in dry season and 82 days in rainy season, finding that rainfall significantly diluted sewage concentration and that infiltration made up 62% of inflow during wet periods.
  • * The study revealed that only 23% of water supplied to the area reached the sewer in dry months, suggesting exfiltration reduces flow in dry seasons while infiltration boosts it in rainy seasons, making this the first detailed analysis of these dynamics in Southeast Asia
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  • Tetrodotoxin, the toxic substance responsible for pufferfish poisoning, has been found in bivalve mollusks in New Zealand and Europe, prompting the need for better monitoring methods.
  • The study utilized quantitative H-nuclear magnetic resonance (qNMR) spectroscopy to accurately measure tetrodotoxin and its analogues in commercial reagents.
  • Results showed that specific forms of tetrodotoxin generate distinct responses in hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC/MS/MS), which can aid in the quantification and standardization of this toxin.
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