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At least 19 recordsLinked to original sources
PubMed1979

Human enteroviruses in oysters and their overlying waters.

The presence of enteroviruses in oysters and oyster-harvesting waters of the Texas Gulf coast was monitored over a period of 10 months. Viruses were detected in water and oyster samples obtained from areas both open and closed to shellfish harvesting. Viruses were detected periodically in waters that met current bacteriological standards for shellfish harvesting. No significant statistical relationship was demonstrated between virus concentration in oysters and the bacteriological and physiochemical quality of water and shellfish. Viruses in water were, however, moderately correlated with total coliforms in water and oysters and with fecal coliforms in oysters. Total coliforms in water were realted to total coliforms in sediment were related only to total coliforms in sediment. Among the physiochemical characteristics of water, turbidity was related statistically to the organic matter content of water and to fecal coliforms in water. There was a marked effect of rainfall on the bacteriological quality of water. Of a total of 44 water samples, 26 yielded virus in concentrations from 4 to 167 plaque-forming units per 100-gallon (ca. 378.5-liter) sample. Of a total of 40 pools of 10 to 12 oysters each, virus was found in 14 pools at a concentration of 6 to 224 plaque-forming units per 100 g of oyster meat. On five occasions, virus was found in water samples when no virus could be detected in oysters harvested from the same sites. This study indicates that current bacteriological standards for determining the safety of shellfish and shellfish-growing waters do no reflect the occurrence of enteroviruses.

Animals↗
PubMed1976

A comparison of the cholinesterases of an oyster (Crassostrea virginica) and a clam (Macrocallista nimbosa).

Cholinesterase activities in the hearts and ganglia of an oyster (Crassostrea virginica) and a venerid clam (Macrocallista nimbosa) were measured and compared. Tissue extracts were partially purified by ammonium sulfate fractionation followed by gel column chromatography. Enzymatic activity was assayed spectrophotometrically; substrates were acetyl-, butyryl-, and propionylthiocholine (ATC, BTC, PTC). Kinetic constants characterizing each enzyme were derived. At all substrate concentrations, the hydrolysis rates of both clam enzymes were in the order: BTC greater than PTC greater than ATC. With oyster enzymes the ranking was ATC greater than or equal to PTC greater BTC. The specific activities of oyster heart and ganglion enzymes were similar. In contrast, clam ganglion extracts were 75-100 times more active than clam heart extracts and, with any substrate, had greater activity than either oyster enzyme. All enzyme preparations proved to be homogeneous on the bases of constant substrate activity ratios in successive column fractions, and of intermediate velocities with mixed substrates. Six cholinesterase inhibitors were tested. The specific acetylcholinesterase antagonist, B.W. 62C47, WAS MUCH MORE EFFECTIVE AGAINST OYSTER ENZYMES, WHILE THE SPECIFIC ANTIBUTYRYLCHOLINESTERASE, ISO-OMPA, almost totally inhibited calm enzyme activity, but had little effect on oyster. Eserine was the most effective inhibitor of both enzymes. In conclusion, the enzymes in oyster tissues are acetylcholinesterases, while clam enzymes are butyrylcholinesterases. Nevertheless, clam ganglion esterase is sifficiently active to hydrolyze the physiological substrate, acetylcholine. These results explain the long-observed differences in isolated heart pharmacology between ostreid and venerid bivalves.

Acetylcholinesterase↗
PubMed2026

An allograft inflammatory factor enhances sperm viability by modulating intracellular calcium in oyster Crassostrea gigas.

As an important aquaculture bivalve, the Pacific oyster Crassostrea gigas faces severe constraints in artificial reproduction, where low sperm motility often leads to fertilization failure and limits the sustainable development of the oyster aquaculture industry. In the present study, the variation of sperm from different oyster individuals was observed, and high-quality sperm possessed intact, elongated flagella with no structural abnormalities, while low-quality sperm showed shortened flagella with frequent tangling or coiling defects. Transcriptomic analysis comparing high- and low-quality sperm revealed significantly reduced expression of genes associated with sperm motility and release (CgAIF1, CgAchR, CgSEX), sperm quality and development (CgEP4, CgIFi2b), and cryoprotection (CgISPs) in low-quality sperm. Notably, an allograft inflammatory factor (designed as CgAIF1) encoding EF-hand domain, known as Ca2+ binding activity, was among the most significantly downregulated in low-motility sperm. CgAIF1 is highly expressed in haemocytes, ganglia, and gonads of oysters. Incubation with the recombinant AIF1 protein (rCgAIF1) significantly improved sperm curvilinear velocity, thereby enhancing the overall motility of C. gigas sperm. Furthermore, rCgAIF1 incubation increased intracellular Ca2+ levels (2.13-fold at 30 min, 2.71-fold at 60 min) and superoxide dismutase (SOD) activity (1.44-fold at 30 min, 1.24-fold at 60 min) in sperm, suggesting potential roles in calcium homeostasis regulation and antioxidant defense. In conclusion, this study demonstrates that CgAIF1 significantly enhances motility of oyster sperm, providing a scientific basis for artificial breeding and seed production in oyster aquaculture.

Animals↗
PubMed1978

Improved methods for detecting enteric viruses in oysters.

New and improved methods for concentrating enteroviruses, reoviruses, and adenoviruses from oysters have been developed and evaluated. Viruses are efficiently adsorbed to homogenized oyster meat by adjusting the homogenate to pH 5.0 and a conductivity of less than or equal to 2,000 mg of NaCl per liter. After low-speed centrifugation, the virus-free supernatant is discarded and the viruses are eluted from the sedimented oyster solids with pH 7.5 glycine-NaCl having a conductivity of 8,000 mg of NaCl per liter. The oyster solids are removed by low-speed centrifugation and filtration, and the viruses in the filtered supernatant are concentrated to a small volume by either ultrafiltration or acid precipitation at pH 4.5. The concentrate is treated with antibiotics and inoculated into cell cultures for virus isolation and quantitation. When these methods were tested with oysters experimentally contaminated with polioviruses, reoviruses, and adenoviruses, recovery efficiencies averaged about 46%. With the exception of virus assay and quantitation, these methods are simple and inexpensive enough to be done in typical shellfish microbiology laboratories.

Adenoviridae↗
PubMed1975

Development of a simple method for concentrating enteroviruses from oysters.

The development of a simple method for concentrating enteroviruses from oysters is described. In this method viruses in homogenized oyster tissues are efficiently absorbed to oyster solids at pH 5.5 and low salt concentration. After low-speed centrifugation, the supernatant is discarded and viruses are eluted from the sedimented oyster solids by resuspending them in pH 3.5 glycine-buffered saline. The solids are then removed by low-speed centrifugation, and the virus-containing supernatant is filtered through a 0.2-micronm porosity filter to remove bacteria and other small particulates without removing viruses. The virus-containing filtrate is then concentrated to a volume of a few milliliters by ultrafiltration, and the concentrate obtained is inoculated directly into cell cultures for virus assay. When tested with pools of oysters experimentally contaminated with small amounts of different enteroviruses, virus recovery efficiency averaged 63%.

Adsorption↗
PubMed2026

Prior exposure to hypoxia alters DNA methylation patterns in the eastern oyster.

Environmentally induced epigenetic changes (e.g., DNA methylation) can alter genetic activity to help organisms adapt and respond to variable environments. While many studies have investigated DNA methylation as a response to a stressor at a single timepoint, less well-understood is how methylation may encode memory of past environments and influence the response to current environments (i.e., carryover effects). Oysters are an excellent natural system to study carryover effects due to their sessile nature, which may expose them to increased environmental variability. To better understand how methylation changes in response to a previous exposure of environmental stress, we conducted a fully factorial experiment exposing juvenile oysters to either control or hypoxic conditions at two timepoints separated by 60 days. After the second exposure, whole body tissue samples were collected and processed for methylRAD sequencing. Regardless of treatment, methylation was mostly found in exons. We found both the first and second exposure treatments contributed significantly to the observed variation in gene body methylation. Interestingly, oysters that were first exposed to hypoxia and later exposed to control conditions had methylation patterns that differed the most from any other condition. We found that differentially methylated genes identified in pairwise comparisons were mainly involved in the oxidative stress response, metabolism, and transcription. Together, these findings suggest that early life environments have a lasting impact on the epigenome and that the timing of stress elicits unique response strategies, which highlights potential targets of resilience for oysters.

Animals↗
PubMed1976

Purification and properties of adductor muscle phosphofructokinase from the oyster, Crassostrea virginica. The aerobic/anaerobic transition: role of arginine phosphate in enzyme control.

Phosphofructokinase from oyster (Crassostrea virginica) adductor muscle occurs in a single electrophorectic form at an activity of 8.1 mumol of product formed per minute per gram wet weight. The enzyme was purified to homogeneity by a novel method involving extraction in dilute ethanol and subsequent precipitation with polyethylene glycol. Oyster adductor phosphofructokinase has a molecular weight of 3400000 +/- 20000 as measured by Sephadex gel chromatography. Mg2+ or Mn2+ can satisfy the divalent ion requirement while ATP, GTP, or ITP can serve as phosphate donors for the reaction. Oyster adductor phosphofructokinase displays hyperbolic saturation kinetics with respect to all substrates (fructose 6-phosphate, ATP, and Mg2+) at either pH 7.9 OR PH 6.8. The Michaelis constant for fructose 6 phosphate at pH 6.8, the cellular pH of anoxic oyster tissues, is 3.5 mM. In the presence of AMP, by far the most potent activator and deinhibitor of the enzyme, this drops to 0.70 mM. Many traditional effectors of phosphofructokinase including citrate, NAD(P)H,Ca2+, fructose 1,6-bisphosphate, 3-phosphoglycerate, ADP, and phosphoenolpyruvate do not alter enzyme activity when tested at their physiological concentrations. Monovalent ions (K +, NH4+) are activators of the enzyme. ATP and arginine phosphate are the only compounds found to inhibit the adductor enzyme. The inhibitory action of both can be reversed by physiological concentrations of AMP(0.2- 1.0mM) and to a lesser extent by high concentrations of Pi (20 mM) and adenosine 3' :5'-monophosphate (0.1 mM). The two inhibitors exhibit very different pH versus inhibition profiles. The Ki (ATP) decreases from 5.0 mM to 1.3 mM as the pH decreases from 7.9 to 6.8, whereas the Ki for arginine phosphate increases from 1.3 mM to 4.5 mM for the same pH drop. Of all compounds tested, only AMP, within its physiological range, activated adductor phosphofructokinase significantly at low pH values. The kinetic data support the proposal that arginine phosphate, not ATP or citrate, is the most likely regulator of adductor phosphofructokinase in vivo under aerobic, high tissue pH, conditions. In anoxia, the depletion of arginine phosphate reserves and the increase in AMP concentrations in the tissue, coupled with the increase in the Ki for arginine phosphate brought about by low pH conditions, serves to activate phosphofructokinase to aid maintenance of anaerobic energy production.

Adenosine Monophosphate↗
PubMed1978

Virus accumulation by the rock oyster Crassostrea glomerata.

The accumulation of virus by the New Zealand rock oyster Crassostrea glomerata has been studied in a static seawater system using radioactively labeled reovirus type III and Semliki Forest virus. The uptake of virus was found to be less rapid than for the bacterium Escherichia coli and to be unaffected by the presence of the marine alga Dunaliella primolecta in the seawater. Accumulation was dependent on virus concentration, with saturation achieved at 4 X 10(10) reovirus particles per oyster, implying that an oyster possesses a large but finite number of sites for virus adsorption. When the rates of uptake of two viruses of similar size but differing surface properties were compared, the rate of accumulation of the lipoprotein-enveloped Semliki Forest virus was found to be less than that for the protein-enclosed reovirus. This observation, together with the finding that the oyster shell has a strong affinity for virus, suggests that surface properties, rather than size, are the principal factors governing the accumulation of viruses by filter-feeding marine bivalves.

Adsorption↗
PubMed1979

Influences of oyster or clam feeding on lipid metabolism in rats.

Rats were fed on three kinds of diets for two weeks: (I) basal diet, (II) containing 0.1% cholate and (III) containing 0.1% cholesterol and 0.1% cholate. Each dietary group was further divided into subgroups to whose diet was added 0, 5 or 10% (dry weight) of minced oyster (Callocorchina) or clam (Tapes japonica). The serum and liver cholesterol levels of the rats fed the basal diet were reduced by feeding oyster or clam. The serum and liver triglyceride levels of all dietary groups were lowered markedly by feeding oyster or clam. The activities of glucose-6-phosphate dehydrogenase, malic enzyme and acetyl-CoA carboxylase were markedly reduced in the basal groups fed oyster or clam. These effects were observed in 5 and 10% shellfish feeding. These shellfish may be considered hypolipidemic foods.

Acetyl-CoA Carboxylase↗
PubMed1979

An Australia-wide outbreak of gastroenteritis from oysters caused by Norwalk virus.

At least 2000 persons were involved in an Australia-wide outbreak of oyster-associated food poisoning in June and July, 1978. At the time, this episode presented a major health risk to the community as a whole and has subsequently posed a serious economic problem for the oyster farming and distributing industry. Although bacteriological investigations indicated some batches of oysters were contaminated by sewage, no bacterial cause could be established. The causative organism was shown to be Norwalk virus, a known cause of acute non-bacterial gastroenteritis. This virus was found in 39% of faecal specimens examined by electron microscopy and an antibody response was demonstrated by immune electron microscopy in 75% of paired sera tested. Norwalk virus has not been identified previously outside the United States of America and has not been linked to food-borne gastroenteritis before. Purification of oysters and other measures have been instituted to prevent a recurrence of the outbreak.

Antibodies, Viral↗
PubMed2026

Identifying the regulatory network of the key lipid metabolism transcription factor peroxisome proliferator-activated receptor in oysters.

Rising seawater temperatures driven by global warming have led to summer mass mortality events that pose significant challenges for the oyster industry. Peroxisome proliferator-activated receptor (PPAR) serves as a key transcriptional regulator of lipid metabolism and plays an essential role in thermal adaptation. However, the upstream regulatory mechanisms of PPAR remain poorly understood in marine organisms. In this study, we identified two PPAR subtypes (PPARα and PPARβ/δ) in oysters and compared transcriptomic data in different tissues and under various environmental stressors, with PPARα exhibiting higher expression levels and responsiveness to environmental stresses. We observed significantly higher PPARα gene expression levels and promoter activity in the relatively cold-tolerant Crassostrea gigas compared to C. angulata. The low expression of the inhibitory transcription factor CTNNB1 in C. gigas may contribute to higher gene expression of PPARα. Additionally, the expression genome-wide association study (eGWAS) identified 9 significant SNPs and 124 candidate regulatory genes associated with PPARα expression, including ubiquitination, phosphorylation, signaling pathways, lipid metabolism, and glucose metabolism. We provided the first experimental validation of the PPARα ubiquitination-degradation pathway in marine organisms via Co-IP, which was mediated by the E3 ligase RFWD3. The protein kinase SNF1 and signaling-related proteins PIKA and KCNK2 indirectly modulated PPARα downstream pathway activation to varying degrees. This study presents the first systematic investigation of PPARα expression regulation in marine organisms. It identifies key molecular regulators and provides novel insights into lipid metabolic regulation and molecular targets for genetic improvement of heat tolerance in oysters under global warming.

Animals↗
PubMed2026

Culture of infectious human norovirus isolated from live contaminated oysters.

Human noroviruses are a major cause of foodborne outbreaks worldwide. Filter-feeding shellfish, such as oysters, can bioaccumulate these viruses in their digestive tissue when grown in sewage-impacted coastal areas and are often implicated in norovirus foodborne outbreaks. Despite the high sensitivity of current molecular assays, these methods for norovirus detection in shellfish fail to distinguish between infectious and non-infectious particles. Assessing norovirus infectivity in shellfish remains a challenge due to the lack of suitable isolation methods that maintain capsid integrity. In this study, a protocol for isolating infectious norovirus from oyster tissues, based on chloroform-butanol elution and polyethylene glycol concentration (CB-PEG), was optimized for the recovery of human norovirus GI and GII. While CB-PEG method recovered various norovirus GI and GII genotypes, it was less efficient at the genomic level than a protocol based on proteinase K elution (adapted from ISO 15216) and showed genotype-dependent viral recovery rates. By optimizing the flocculation step, we improved the method's compatibility with human intestinal enteroid (HIE) cultures. Using this approach, we successfully quantified infectious norovirus GII.3 titers recovered from artificially-contaminated live oysters. Interestingly, infectious virus was better isolated following a freezing step of the digestive tissues, with titers ranging from 13 to 40 TCID50/mL for positive samples. In conclusion, this study established an optimized methodological approach for the relative quantification of infectious norovirus GII.3 in shellfish, paving the way for future research on viral persistence and inactivation strategies in this foodstuff.

Norovirus↗
PubMed1979

Isolation and partial characterization of a cadmium-binding protein from the American oyster (Crassostrea virginica).

American oysters (Crassostrea virginica) were exposed to 0.1 ppm cadmium for 0--15 days in a flowing seawater system and then placed into clean flowing seawater for 24 h prior to sacrifice. Whole oysters were homogenized and a cadmium-binding protein isolated and purified by a process of centrifugation, heat-treatment, Sephadex G-75 chromatography, DEAE cellulose chromatography and disc gel electrophoresis. A highly anionic protein which is not present in control oysters was found to be present in cadmium-exposed animals after 3 days of treatment and to increase in concentration at succeeding time points. The protein does not extensively bind zinc or copper. Amino acid analysis of the purified protein disclosed an amino acid composition characterized by a high percentage of dicarboxylic amino acids and relatively little cysteine.

Animals↗
PubMed2026

Comparative analysis of genomic variations among different Cdo1 paralogs for salinity-adaptation in oysters.

Under rapid climate change and anthropogenic activities, oysters, a global aquaculture species, are subjected to exacerbated culturing environments, especially for those living in in-shore estuarine species, such as Suminoe oysters Crassostrea ariakensis. This study aims to investigate the molecular mechanisms of salinity adaptation of C. ariakensis. We performed an expression genome-wide association study (eGWAS) to compare genetic regulation among 5 paralogous copies of a key salinity-related gene, cysteine dioxygenase 1 (Cdo1). A total of 40 significant eSNPs with 82 adjacent eGenes were identified in 2 copies (Cdo1_26639 and Cdo1_1666). We identified only trans-eSNPs for Cdo1_26639 and more cis-eSNPs for Cdo1_1666, and different eGenes for these 2 Cdo1 copies, which indicated that the expressional regulation of these paralogs may undergo distinct pathways. We identified 3 eGenes that exhibited identical expression patterns with Cdo1_26639 and Cdo1_1666, including 6-Pgdh, Trapp and tandem copy of Cdo1_27337. The expression correlation between Cdo1 copies and eGenes was enhanced under salinity stresses, suggesting the crucial role of eGenes in regulating Cdo1's expression in response to salinity changes. Our results provide comprehensive identification and comparison of eSNPs across different paralogous copies of one gene, along with insights into the molecular mechanisms underlying salinity tolerance, and genetic markers for breeding salinity-resistant oysters.

Animals↗
PubMed2026

Transcriptomic insights into the molecular mechanism of antifouling agent-induced settlement inhibition in the Pacific oyster Crassostrea gigas.

Marine biofouling remains a persistent challenge to maritime industries and marine ecosystems worldwide. In this study, we systematically evaluated the acute toxicity, settlement inhibitory efficacy, and underlying molecular mechanisms of an N-oleyl-1,3-propanediamine-based antifouling agent using pediveliger larvae of the Pacific oyster Crassostrea gigas. The 96 h-LC50 of the agent was determined to be 0.81 mg/L, and exposure to 1.68 mg/L achieved complete larval settlement inhibition without inducing significant acute toxicity. Transcriptomic analysis identified 791 differentially expressed genes, dominated by downregulated genes associated with ribosomal function, translation, cell adhesion, and cytoskeletal organization. The agent exerts its inhibitory effect primarily through the global suppression of protein synthesis, disruption of cell-substrate adhesion and cytoskeletal integrity, and induction of proteotoxic stress responses. These findings reveal a multi-pathway molecular mechanism underlying antifouling agent-induced settlement inhibition in oyster larvae and provide key molecular biomarkers to support the development of eco-friendly antifouling technologies.

Animals↗
PubMed2025

Chromosome-level haplotype-resolved genome assembly of the giant honeycomb oyster, Hyotissa hyotis.

The giant honeycomb oyster, Hyotissa hyotis, a common bivalve inhabitant of tropical and subtropical coastal waters, holds significant ecological and economic importance due to its shell characteristics, rapid growth, and high-quality adductor muscle. However, the lack of high-quality genome has impeded the genetic study and artificial breeding of this species. In this study, we provided the first chromosomal-level haplotype-resolved assembly for the H. hyotis (2n = 20) by combining PacBio HiFi long-read and Hi-C sequencing. We obtained a haplotype-resolved assembly of 3.39 Gb in size, of which 96.69% were anchored to 20 chromosomes. The haplotype A and B genome (HapA and HapB) was 1,639.90 and 1,643.23 Mb in size, respectively. Accordingly, a total of 28,720 and 29,003 protein-coding genes were annotated from HapA and HapB. Through the BUSCO evaluation, the assembly and annotation results exhibited the completeness value of 94.65% and 94.03% for HapA, while 94.13% and 92.98% for HapB. This high-quality genome assembly provides valuable resource for further genetic studies and genetic improvement of the group of oysters.

Animals↗
PubMed1977

Cystic fibrosis: studies with the oyster ciliary assay.

Bioassays using ciliary systems have detected a factor or factors in cystic fibrosis (CF) sera and tissue culture medium derived from CF cells. The typical shortcomings of an assay measuring biological activity have been studied, and the means to overcome the weaknesses of the oyster gill cilia assay have been established. The presence of the cystic fibrosis mucociliary inhibitor (CFMI) in experimental fractions may be determined by accepting data from only those assays in which authentic CF and normal (non-CF) fractions give defined reactions, by measuring the reaction of each sample at least three times, and by examining each experimental sample at a protein concentration greater than the minimum established in this study. The relative concentrations of the CFMI present in the first steps of purification of serum and medium have been calculated in terms of units of inhibition. Generally, the units of inhibition present in serum and medium fractions from heterozygotes are close to one-half of that in fractions from homozygous sources. Analogous fractions concentrated from a normal (non-CF) source never inhibited mucociliary activity, even when tested at nearly 100 times the CF concentration. Ciliary assays utilizing oyster gills are essential for monitoring fractionation procedures aimed at purifying the CFMI, and have been shown to be capable and reliable enough to do so.

Biological Assay↗
PubMed1979

Vivo clearance of enteric bacteria from the hemolymph of the hard clam and the American oyster.

American oysters, Crassostrea virginica, and hard clams, Mercenaria mercenaria, were experimentally contaminated with Escherichia coli, Salmonella typhimurium, and Shigella flexneri either by intracardial injection or via the natural route of ingestion. Bacterial inactivation in the hemolymph was monitored for 72 h after exposure to these enteric pathogens at 20 and 6 degrees C. At 6 degrees C, both mean bacterial uptake by ingestion and subsequent clearance was singificantly lower that at 20 degrees C. However, substantial bacterial clearance from the hemolymph occurred for both shellfish at each temperature. At 20 degrees C, viable bacteria were no longer detectable after 24 h in hemolymph of either clams or oysters after exposure to contaminated water containing 4 x 10(3) bacteria per ml.

Animals↗