Portal Venous and Hepatic Arterial Coefficients Predict Post-Hepatectomy Overall and Recurrence-Free Survival in Patients with Hepatocellular Carcinoma: A Retrospective Study.

Background: The dominant artery blood supply is a characteristic of hepatocellular carcinoma (HCC). However, it is not known whether the blood supply can predict the post-hepatectomy prognosis of patients with HCC. This retrospective study investigated the prognostic value of the portal venous and arterial blood supply estimated on triphasic liver CT (as a portal venous coefficient, PVC, and hepatic arterial coefficient, HAC, respectively) in patients with HCC following hepatectomy. Methods: HCC patients who were tested by triphasic liver CT 2 weeks before hepatectomy and received R0 hepatectomy at the Second Affiliated Hospital, Kunming Medical University between January 1, 2016 and December 31, 2020, were retrospectively screened. Their PVC and HAC, and other variables were analyzed for the prediction of overall survival (OS) and recurrence-free survival (RFS) using the least absolute shrinkage and selection operator and Cox proportional hazard regression models. Results: Four hundred and nineteen patients (53.2 ± 10.6 years of age and 370 men) were evaluated. A shorter OS was independently associated with higher blood albumin and total bilirubin grade [hazard ratio (HR) 2.020, 95% confidence interval (CI) 1.534-2.660], higher Barcelona Clinic Liver Cancer (BCLC) stage (HR 1.514, 95% CI 1.290-1.777), PVC ≤ 0.386 (HR 1.628, 95% CI 1.149-2.305), and HAC > 0.029 (HR 1.969, 95% CI 1.380-2.809). A shorter RFS was independently associated with male (HR 1.652, 95% CI 1.005-2.716), higher serum α-fetoprotein ≥ 400 ng/mL (HR 1.672, 95% CI 1.236-2.263), higher BCLC stage (HR 1.516, 95% CI 1.300-1.768), tumor PVC ≤ 0.386 (HR 1.641, 95% CI 1.198-2.249), and tumor HAC > 0.029 (HR 1.455, 95% CI 1.060-1.997). Conclusion: Tumor PVC or HAC before hepatectomy is valuable for independently predicting postoperative survival of HCC patients.

Using solid phase adsorption toxin tracking and extended local similarity analysis to monitor lipophilic shellfish toxins in a mussel culture ranch in the Yangtze River Estuary.

Harmful algal blooms (HABs) and their associated phycotoxins are increasing globally, posing great threats to local coastal ecosystems and human health. Nutrients have been carried by the freshwater Yangtze River and have entered the estuary, which was reported to be a biodiversity-rich but HAB-frequent region. Here, in situ solid phase adsorption toxin tracking (SPATT) was used to monitor lipophilic shellfish toxins (LSTs) in seawaters, and extended local similarity analysis (eLSA) was conducted to trace the temporal and special regions of those LSTs in a one-year trail in a mussel culture ranch in the Yangtze River Estuary. Nine analogs of LSTs, including okadaic acid (OA), dinophysistoxin-1 (DTX1), yessotoxin (YTX), homoyessotoxin (homoYTX), 45-OH-homoYTX, pectenotoxin-2 (PTX2), 7-epi-PTX2 seco acid (7-epi-PTX2sa), gymnodimine (GYM) and azaspiracids-3 (AZA3), were detected in seawater (SPATT) or rope farmed mussels. The concentrations of OA + DTX1 and homoYTX in mussels were positively correlated with those in SPATT samplers (Pearson test, p < 0.05), indicating that SPATT (with resin HP20) would be a good monitoring tool and potential indicator for OA + DTX1 and homoYTX in mussel Mytilus coruscus. The eLSA results indicated that late summer and early autumn were the most phycotoxin-contaminated seasons in the Yangtze River Estuary. OA + DTX1, homoYTX, PTX2 and GYM were most likely driven by the local growing HAB species in spring and summer, while Yangtze River diluted water may impact the accumulation of HAB species, causing potential phycotoxin contamination in the Yangtze River Estuary in autumn and winter. Together, the results showed that the mussel harvesting season, late summer and early autumn, would be the season with the greatest phycotoxin risk and would be the most contaminated by local growing toxic algae. Routine monitoring sites should be set up close to the local seawaters.

Brucine suppresses proliferation and promotes apoptosis of human cholangiacarcinoma cells via the inhibition of COX2 expression.

Aims The aim of this study was to investigate the anti-tumor efficacy of brucine on intrahepatic cholangiocarcinoma (ICC). Methods ICC QBC939 cells were treated with brucine, cell viability, cell cycle and apoptosis were analyzed using CCK-8 and flow cytometry. The expression of COX-2 and apoptosis related proteins Casp3, Bax and Bcl-2 were detected by Western blot analysis. QBC939 cells were subcutaneously transplanted into nude mice and the mice were injected with brucine intraperitoneally. The expression of Ki67, COX-2 and apoptosis related proteins were detected by immunohistochemical staining and Western blot analysis. Results Brucine significantly inhibited the proliferation and cell cycle progression while promoted the apoptosis of QBC939 cells. The expression of the apoptotic proteins Casp3 and Bax was upregulated, while the expression of Bcl-2 and COX-2 was downregulated in QBC939 cells with brucine treatment. Moreover, the overexpression of COX-2 could antagonize the effects of brucine on QBC939 cells. In vivo, brucine inhibited subcutaneous tumor formation in nude mice, and the expression of Ki67, COX-2 and Bcl-2 decreased while the expression of Casp3 and Bax increased in tumor tissues from nude mice with brucine treatment. Conclusions Brucine can significantly inhibit the progression of cholangiocarcinoma in vitro and in vivo, and the mechanism may be related to the inhibition of COX-2 expression.

Ag Single Atoms Anchored on CeO2 with Interfacial Oxygen Vacancies for Efficient CO2 Electroreduction.

Ag single-atom catalysts (SACs) have great potential in selective electrocatalysis of the CO2 reduction reaction (CO2RR) to CO, while it is still a challenge to achieve high current density and high atom efficiency simultaneously. Here, we present a new and simple in situ adsorption-reduction method to prepare Ag SACs supported on CeO2 (Ag1/CeO2). It is found that Ag single atoms are anchored on CeO2 through strong metal-support interaction (SMSI), and each Ag atom is accompanied with three interfacial oxygen vacancies. This Ag1/CeO2 exhibits high performance in the electrocatalytic CO2RR with a high CO faradaic efficiency (FE) of >95% under a wide potential range. The turnover frequency (TOF) value can reach 50,310 h-1 at FECO = 99.5% in H-cells. Notably, Ag1/CeO2 achieves an industrial-grade current density of 403 mA cm-2 with a high FECO of 97.2% in flow cells. Experimental results combined with density functional theory calculation revealed that this superior performance was mainly ascribed to the existence of interfacial oxygen vacancies, which lead to the formation of Ag-O-Ce3+ atomic interfaces, and activates the Ce3+-O structures as the synergistic active center of Ag, thus promoting CO2 adsorption and activation and reducing the reaction potential barrier of *COOH-to-*CO.

Self-assembled nanomaterials for ferroptosis-based cancer theranostics.

Most ferroptosis nanomedicines based on organic or inorganic carriers have difficulties in further clinical translation due to their serious side effects and complicated preparation. Self-assembled nanomedicines can reduce the biological toxicity caused by additional chemical modifications and excipients, offering better biocompatibility and safety. Ferroptosis therapy is an iron-associated programmed cell death dependent on lipid peroxidation with efficient tumor selectivity and biosafety. Therefore, the application of self-assembled nanomedicines with good biosafety in the ferroptosis treatment of tumors has attracted extensive attention. In this review, recent advances in the field of ferroptosis-based self-assembled nanomaterials for cancer therapy are presented, with emphasis on how these nanomaterial components interact and their distinct mechanisms for inducing ferroptosis in tumor cells, including iron metabolism, amino acid metabolism and CoQ/FSP1, as well as their respective advantages and challenges. This review would therefore help the spectrum of advanced and novice researchers interested in this area to quickly zoom in on the essential information and glean some thought-provoking ideas to advance this subfield in cancer nanomedicine.

3D Dirac semimetals-dielectric elliptical fiber supported tunable terahertz hybrid waveguide.

Based on the proposed elliptical dielectric fiber-polyethylene gap-3D Dirac semimetal (DSM) hybrid plasmonic waveguide structure, the tunable propagation characteristics have been systematically investigated in the terahertz region, taking into account the influences of the structural parameters, the modified dielectric fiber, and the 3D DSM Fermi levels. The results show that as the ratio of the elliptical semi-axis along the y-direction ay and the x-direction ax (ay/ax) increases, the hybrid mode confinement increases. The real part of the effective mode index and propagation length increase with increasing the refractive index of the elliptical fiber. The propagation length and figure of merit of the hybrid modes reach 1.56×104µm and 300, respectively. In addition, by changing the Fermi level of the 3D DSM layer, the propagation properties of the hybrid modes can also be modulated in a wide range, e.g., the modulation depth of the propagation length reaches about 71.53% if the Fermi level varies in the range of 0.03-0.15 eV. The propagation properties of the hybrid modes are enhanced significantly by utilizing the modified three elliptical fiber structures, the real part of the effective mode index, and the propagation length of the modified structure are enhanced simultaneously. The results are very helpful for understanding the tunable mechanism of the 3D DSM devices and aids the design of novel plasmonic devices, e.g., lasers, modulators, and resonators.

Progress on the investigation and monitoring of marine phycotoxins in China.

Marine phycotoxins associated with paralytic shellfish poisoning (PSP), diarrhetic shellfish poisoning (DSP), amnesic shellfish poisoning (ASP), neurotoxic shellfish poisoning (NSP), ciguatera fish poisoning (CFP), tetrodotoxin (TTX), palytoxin (PLTX) and neurotoxin ß-N-methylamino-L-alanine (BMAA) have been investigated and routinely monitored along the coast of China. The mouse bioassay for monitoring of marine toxins has been progressively replaced by the enzyme-linked immunosorbent assay (ELISA) and liquid chromatography tandem mass spectrometry (LC-MS/MS), which led to the discovery of many new hydrophilic and lipophilic marine toxins. PSP toxins have been detected in the whole of coastal waters of China, where they are the most serious marine toxins. PSP events in the Northern Yellow Sea, the Bohai Sea and the East China Sea are a cause of severe public health concern. Okadaic acid (OA) and dinophysistoxin-1 (DTX1), which are major toxin components associated with DSP, were mainly found in coastal waters of Zhejiang and Fujian provinces, and other lipophilic toxins, such as pectenotoxins, yessotoxins, azaspiracids, cyclic imines, and dinophysistoxin-2(DTX2) were detected in bivalves, seawater, sediment, as well as phytoplankton. CFP events mainly occurred in the South China Sea, while TTX events mainly occurred in Jiangsu, Zhejiang and Fujian provinces. Microalgae that produce PLTX and BMAA were found in the phytoplankton community along the coastal waters of China.

Cryptic speciation in Protoceratium reticulatum (Dinophyceae): Evidence from morphological, molecular and ecophysiological data.

The cosmopolitan, potentially toxic dinoflagellate Protoceratium reticulatum possesses a fossilizable cyst stage which is an important paleoenvironmental indicator. Slight differences in the internal transcribed spacer ribosomal DNA (ITS rDNA) sequences of P. reticulatum have been reported, and both the motile stage and cyst morphology of P. reticulatum display phenotypic plasticity, but how these morpho-molecular variations are related with ecophysiological preferences is unknown. Here, 55 single cysts or cells were isolated from localities in the Northern (Arctic to subtropics) and Southern Hemispheres (Chile and New Zealand), and in total 34 strains were established. Cysts and/or cells were examined with light microscopy and/or scanning electron microscopy. Large subunit ribosomal DNA (LSU rDNA) and/or ITS rDNA sequences were obtained for all strains/isolates. All strains/isolates of P. reticulatum shared identical LSU sequences except for one strain from the Mediterranean Sea that differs in one position, however ITS rDNA sequences displayed differences at eight positions. Molecular phylogeny was inferred using maximum likelihood and Bayesian inference based on ITS rDNA sequences. The results showed that P. reticulatum comprises at least three ribotypes (designated as A, B, and C). Ribotype A included strains from the Arctic and temperate areas, ribotype B included strains from temperate regions only, and ribotype C included strains from the subtropical and temperate areas. The average ratios of process length to cyst diameter of P. reticulatum ranged from 15% in ribotype A, 22% in ribotype B and 17% in ribotype C but cyst size could overlap. Theca morphology was indistinguishable among ribotypes. The ITS-2 secondary structures of ribotype A displayed one CBC (compensatory change on two sides of a helix pairing) compared to ribotypes B and C. Growth response of one strain from each ribotype to various temperatures was examined. The strains of ribotypes A, B and C exhibited optimum growth at 15 °C, 20 °C and 20-25 °C, respectively, thus corresponding to cold, moderate and warm ecotypes. The profiles of yessotoxins (YTXs) were examined for 25 strains using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The parent compound yessotoxin (YTX) was produced by strains of ribotypes A and B, but not by ribotype C strains, which only produced the structural variant homoyessotoxin (homoYTX). Our results support the notion that there is significant intra-specific variability in Protoceratium reticulatum and the biogeography of the different ribotypes is consistent with specific ecological preferences.

Geographical distribution and seasonal variation in paralytic shellfish toxins in the coastal water of the South China Sea.

Paralytic shellfish toxins (PSTs) are a group of the most harmful neurotoxins distributed worldwide. Marine organism samples, including mollusks, crustaceans and fish, collected from 11 sites around the coastal water of the South China Sea, were analyzed in terms of the PST and toxicity via high-performance liquid chromatography. The PST geographical distribution, detectable rate for PST and toxin content all increased slightly from 2006 to 2008 to 2015. High PST content with more than 2 nmol g-1 appeared in Shantou (ST), Shanwei (SW), Zhanjiang (ZJ), Beihai (BH), Xuwen (XW), Haikou (HK), Dongfang (DF), Wanning (WN) and Sanya (SY). Low PST content with less than 2 nmol g-1 appeared in Shenzhen (SZ) and Yangjiang (YJ). High PST toxicity over the safety limit 800 µg STXeq/kg appeared in ST, SW, ZJ, BH, DF, SY and XW. PST has significant seasonal characteristics and was mostly detected in spring, early summer (March-June) and autumn (September-November) in the coastal water of the South China Sea. PST was usually detected in some specific species of scallop, mussel, bloody clam, hard clam, razor clam, oyster, crab, shrimp and fish. Toxin profile variation of marine organism samples was influenced greatly by species, sampling time and site.

Seasonal variability of Protoceratium reticulatum and yessotoxins in Japanese scallop Patinopecten yessoensis in northern Yellow Sea of China.

This paper reports a toxic strain of Protoceratium reticulatum, its morphology, phylogeny, yessotoxins (YTXs) production and abundance in northern Yellow Sea of China from 2011 to 2015 was investigated. YTXs in hepatopancreas and edible parts of bottom sowing cultured Japanese scallop Patinopecten yessoensis in this sea area were determined weekly for 5 years. Other potential producers of YTXs, Gonyaulax spinifera and Lingulodinium polyedrum, were also investigated. Results revealed that Protoceratium reticulatum strain from the northern Yellow Sea belongs to a geographically widely distributed species. Motile cells of Protoceratium reticulatum contribute to YTXs in Japanese scallop, and G. spinifera may also be a potential contributor. Resting cysts of Protoceratium reticulatum, G. spinifera, and L. polyedrum in sediments were possibly important origins of YTXs in scallop cultured at sea bottom. YTXs in scallop decreased from 2011 to 2015, most toxins were concentrated in hepatopancreas, while a small portion in edible parts which was safe for consumption the whole year around.

[Contamination of typical human enteric viruses in economic shellfish along the Chinese coast].

OBJECTIVE: The objective of this study is to understand the contamination of human enteric viruses in economic shellfish along the Chinese coast, an important issue of ensuring the seafood safety. METHODS: We established the specific, sensitive and high-throughput gene chip technology, to investigate the contamination of economic shellfish by enteric viruses across a large geographical region of China. RESULTS: The percentage of positive samples for each virus was as follows: Hepatitis A Virus 4.3%, norovirus 14.8%, rotavirus 6.2%, astrovirus 5.6%, and adenovirus 9.9%. In these five viruses, norovirus was contaminated in the first place. The results detected by gene chip were highly consistent with that of polymerase chain reaction (PCR). The economic shellfishes in shellfish-growing areas along the coastal cities were all contaminated with enteric viruses at different levels. However, there was no significant correlation between any two cities. In the selected 6 economic shellfishes, oyster had the highest positive rate of enteric viruses, followed by blood clam. CONCLUSION: The contamination of shellfish with human enteric viruses was common across the main coastal cities of China, indicating a potential public health threat from seafood.

A Marteilia-like parasite in blue mussels Mytilus edulis in China.

Species of the genus Marteilia (Phylum Paramyxea) are protozoan parasites of marine mollusks. Marteilia spp. have been detected in mollusks from different parts of the world, but the presence of these parasites in China has not been previously reported. Therefore, a survey was conducted to look for the presence of Marteilia spp. in blue mussels Mytilus edulis and Asian green mussels Perna viridis collected along China's coasts. Histological and PCR analyses revealed that 5 of 180 M. edulis (prevalence = 2.8%) were positive for infection with a Marteilia-like organism, whereas the parasite was not detected in any of the 80 P. viridis individuals tested. Total genomic DNA was extracted from the infected tissue sections for PCR amplification. The PCR amplification with Marteilia primers SS1 and SAS1 yielded the expected 641-bp product. Sequencing results showed that the 18S ribosomal RNA gene fragment from the protozoans found in M. edulis from China was 88% similar to that of Marteilia refringens, a species that was reported from M. edulis and European flat oysters Ostrea edulis collected in France. This is the first report of a Marteilia-like organism infecting M. edulis in China.

Haplosporidium nelsoni (MSX) in Japanese scallops Patinopecten yessoensis (Jay, 1857) from Dalian along the northern coast of the Yellow Sea, China.

The protozoan parasite Haplosporidium nelsoni (MSX) was identified in Japanese scallops Patinopecten yessoensis (Jay, 1857) from Dalian along the northern coast of the Yellow Sea, China by histopathologic examination, polymerase chain reaction (PCR) amplification, and in situ hybridization (ISH) assay. H. nelsoni plasmodia-like structures were identified in the digestive glands of scallops by histologic examination, but no parasite spores were observed. PCR using the Hap-F2, R2 primer pair produced a sequence with 100% homology with the corresponding small subunit rDNA region of H. nelsoni. An ISH assay using the oligonucleotide probe MSX1347 produced a positive reaction with the Japanese scallop parasite. This is the first report of H. nelsoni in P. yessoensis in China.

[Self-pollution in Ruditapes philippinarum bottom-cultured area of Zhuanghe coast].

By using sediment trap and closed respirator, a year-round in situ investigation was made on the bio-deposition rate, ammonia excretion rate, and phosphate excretion rate in the Ruditapes philippinarum bottom-cultured area of Zhuanghe coast. The three test rates of R. philippinarum all showed obvious seasonal variability, with the bio-deposition rate ranged in 0.15-1.47 g x ind(-1) x d(-1) (annual average 0.61 g x ind(-1) x d(-1)), ammonia excretion rate ranged in 0.02-0.40 mg x ind(-1) x d(-1) (annual average 0.17 mg x ind(-1) x d(-1)), and phosphate excretion rate ranged in 0.01-0.39 mg x ind(-1) x d(-1)(annual average 0. 13 mg x ind(-1) x d(-1)). Based on these, it was estimated that the annual bio-deposit production by the bottom-cultured R. philippinarum in Zhuanghe coast could reach as high as 5.46 x 10(7) t dry mass, amounting to 9.07 x 10(6) t organic matter (OM), 1.00 x 10(6) t organic carbon (OC), or 1.18 x 10(5) t organic nitrogen (ON), and the annual NH4+ -N and PO4(3-)-P productions were 1.49 x 10(4) t and 1.15 x 10(4) t, respectively. Our results suggested that for the large scale and high density bivalve culture in China coasts, the potential impacts of self-pollutants by filter-feeding bivalves on the environment should not be neglected.

First report on the detection of pectenotoxin groups in Chinese shellfish by LC-MS/MS.

Chinese shellfish samples were harvested from different locations along the Chinese coast. These shellfish were analyzed by liquid chromatography in combination with mass spectrometry to detect the following toxins: okadaic acid (OA), dinophysistoxins (DTXs), petenotoxins (PTXs), azaspiracids (AZAs), yessotoxins (YTXs), spirlides (SPXs) and gymnodimines (GYM). The results revealed the lipophilic toxin profiles varied with shellfish sampling locations. In addition to OA, GYM and YTX derivatives, PTX-2 and its derivatives were found for the first time in the following Chinese shellfish: Crassostrea gigas, Mactra chinensis and Mytilus galloprovincialis. The presence of GYM, YTXs, OA and PTXs in Chinese shellfish collected from regions where no previous record of DSP-neutral toxic compounds was reported. Serious efforts should therefore be made to conduct a phycotoxin monitoring program to detect the presence of lipophilic toxins in biological materials of marine origin, which may ensure that Chinese seafood products do not present a health risk. With respect to suspected carcinogenicity, further research on the distribution and concentrations of toxic compounds are needed, in order to carry out long-term risk assessments, particularly sub-acute and chronic toxicity tests associated with of lower doses.

Haplosporidium nelsoni and H. costale in the Pacific oyster Crassostrea gigas from China's coasts.

We examined 220 Pacific oysters Crassostrea gigas obtained from 11 locations along China's coasts for the presence of the 2 protistan parasites Haplosporidium nelsoni (MSX; multinucleated sphere X) and H. costale (SSO; seaside organism). Haplosporidium-like plasmodia were histologically observed in 9 oysters (4.09%) from 7 locations. Five oysters had mixed infections, and 4 oysters were infected only with H. nelsoni as determined by in situ hybridization (ISH) and polymerase chain reaction (PCR). This is the first report of H. nelsoni and H. costale infection in bivalves in Chinese waters.

A 1-year investigation of the parasite Haplosporidium nelsoni (MSX) in the Pacific oyster Crassostrea gigas from Dayaowan Bay, China.

The infection prevalence of the protozoan parasite Haplosporidium nelsoni (MSX) in Pacific oysters (Crassostrea gigas), collected from Dayaowan Bay on the north coast of the Yellow Sea, China, was investigated in 2007. The traditional histological method of diagnosing H. nelsoni infection in oysters was compared to that of polymerase chain reaction (PCR). Histology and the first PCR analysis detected infection in 21 (a total of 240 oysters) (8.75%) oysters, and the second PCR revealed infection in 26 oysters (10.83%). Only local or epithelial infections were found; no systemic infections were detected. Infection by H. nelsoni mostly occurred from April through October, and the monthly prevalence ranged from 5% to 25%, with a peak in August. These results suggest that the prevalence of the parasite is low in Dayaowan Bay. The prevalence of H. nelsoni is thought to be controlled in some way by temperature and salinity.

[Cyclic imine toxin gymnodimine: a review].

Gymnodimine (GYM), an algal toxin first detected from New Zealand oysters in 1994, is identified as a cyclic imine toxin and produced by Karenia selliformis, with imino nitrogen attached on loop-coil. Imine is the poisonous functional group of the toxin. GYM has a low oral toxicity, but its acute lethal toxicity of intra-peritoneal injection for mice is very high. Up to now, few reports have been published on the detailed information about the toxicity mechanism of GYM. Based on limited literatures, this paper reviewed the GYM's structure, producer, toxicity mechanism, carrying animals, geological distribution, degradation metabolism, dose-effect relation, and risk evaluation, and proposed the further research directions on algal toxin.

[A indirect competitive ELISA to detect domoic acid in seawater and shellfish].

OBJECTIVE: A competitive enzyme-linked immunosorbent assay (ELISA) was developed for measurent domoic acid (DA) in seawater and shellfish. METHODS: DA was coupled to bovine serum albumin (BSA) and ovalbumin (OVA) by carbodiimide reaction. DA-BSA as immunogen was injected in BALB/c mice. Titres of the antisera against DA were determinated using DA-OVA as coating ligand by ELISA method. After female BALB/c mice were immunized six times, the polyclonal antibodies anti-DA was obtained. The competitive indirect ELISA for domoic acid in shellfish and seawater was established. RESULTS: Under optimal condition, the detection limit of DA was 10.0 ng/ml (equal 4 microg/g shellfish meat). The recovery of domoic acid added in seawater was 83.2% - 124.7% with a coefficient of variation of 4.7% - 5.9%, the recovery of domoic acid added in shellfish was 85.9% - 99.9% with a coefficient of variation of 2.4% - 7.1%.

[Preparation and application of the monoclonal antibody against okadaic acid].

An competitive indirect enzyme-linked immunosorbent assay was developed for measurement of okadaic acid (OA), a marine biotoxin associated with red tide. OA was coupled to BSA and OVA by carbodiimide reaction. OA-BSA as immunogen were injected in BALB/c mice. Titres of the antisera against OA were determinated using OA-OVA as coating ligand by ELISA method. The spleen cells of immunized mice were fused with Sp2/O cells. After cloning, four hybridoma cell strains stably produced anti-OA monoclonal antibody were obtained. The monoclonal antibody were produced by the mouse ascites method. The competitive indirect ELISA for okadaic acid in shellfish was established. Under optimal condition, the detection limit of OA was 31.2 ng/ml and the recovery was 87%-112%, with a mean coefficient of variation of 8.1.