Da-Yong Zhou

Stimulation of lymphocyte proliferation by oyster glycogen sulfated at C-6 position

In this study, glycogen was extracted from oyster Ostrea talienwhanensis Crosse and used as a model to investigate the structure-activity correlation of polysaccharides. Purified oyster glycogen was characterized by methylation analysis, nuclear magnetic resonance (NMR) spectroscopy and infrared spectroscopy (IR). The oyster glycogen was subsequently sulfated by chlorosulfonic acid-pyridine method, and a C-6 substituted species (SOG) was identified to be the primary sulfated oyster glycogen species by (13)C NMR spectroscopy. The molecular weight and sulfate content of the SOG was determined to be 3.2×10(4) g/mol and 33.6%, respectively. Another sulfated oyster glycogen species (SOG1) with C-2 and C-3 substitution was also identified at a lesser amount in the final product. SOG exhibited a much stronger stimulation effect to splenic lymphocyte proliferation than SOG1 in vitro, indicating that the position of sulfate substitution is a major determining factor on the efficacy of sulfated glycogens to stimulate lymphocyte proliferation.

Characterization of glycerophospholipid molecular species in six species of edible clams by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry

The molecular species of glycerophosphocholine (GPCho), glycerophosphoethanolamine (GPEtn), glycerophosphoserine (GPSer), lysoglycerophosphocholine (LGPCho) and lysoglycerophosphoethanolamine (LGPEtn) from six species of edible clams were characterized by using high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. At least 435, 453, 468, 443, 427 and 444 glycerophospholipid (GP) molecular species were characterized, respectively, from Cyclina sinensis, Mactra chinensis Philippi, Mactra veneriformis Reeve, Meretrix meretrix, Ruditapes philippinarum and Saxidomus purpurata. Most of the predominant GP molecular species in clam contained polyunsaturated fatty acids (PUFA), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), indicating that clam is a potential resource of GP enriched PUFA. According to the amount of the major molecular species containing EPA and DHA, Cyclina sinensis was the best fit species for GPCho, Mactra veneriformis Reeve was the best fit species for GPEtn, Mactra chinensis Philippi was the best fit species for GPSer and LGPEtn, and Saxidomus purpurata was the best fit species for LGPCho.

Optimisation of hydrolysis of purple sea urchin (Strongylocentrotus nudus) gonad by response surface methodology and evaluation of in vitro antioxidant activity of the hydrolysate

BACKGROUND Hydrolysates prepared from sea urchin (Strongylocentrotus nudus) gonad by enzymatic treatment showed strong 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and reducing power. RESULTS Hydrolysis of S. nudus gonad by the commercial protease papain was optimised for maximum degree of hydrolysis (DH) and trichloroacetic acid-soluble peptide index (TCA-SPI) using response surface methodology. Results showed that the optimal conditions were the following: temperature of 48.83 °C, pH of 6.92, enzyme-to-substrate ratio of 3143 U g(-1), and substrate concentration of 83.5 g L(-1). Under these conditions, a DH of 27.96 ± 0.54% and a TCA-SPI of 57.32 ± 0.63% were obtained. The hydrolysate prepared in the optimal conditions was fractionated by an ultra-filtration system and the resultant fraction below 10 kDa was found to effectively scavenge hydroxyl radical (EC(50) = 13.29 ± 0.33 mg mL(-1)) and hydrogen peroxide (EC(50) = 16.40 ± 0.37 mg mL(-1)), inhibit lipid peroxidation (EC(50) = 11.05 ± 0.62 mg mL(-1)), chelate Fe(2+) (EC(50) = 7.26 ± 0.44 mg mL(-1)), and protect mice macrophages against death induced by tert-butyl hydroperoxide. CONCLUSION Hydrolysates prepared from S. nudus gonad have the potential to be applied as natural antioxidant agents.

Anticoagulant Activity and Structural Characterization of Polysaccharide from Abalone (Haliotis discus hannai Ino) Gonad

In this study, we aimed at characterizing the structure and the anticoagulant activity of a polysaccharide fraction (AGP33) isolated from the gonads of Haliotis discus hannai Ino. AGP33 was extracted by enzymatic hydrolysis and purified by ion-exchange and gel-filtration chromatography. The backbone fraction of AGP33 (BAGP33), which appeared to contain of mannose, glucose and galactose, was prepared by partial acid hydrolysis. According to methylation and nuclear magnetic resonance (NMR) spectroscopy, the backbone of AGP33 was identified as mainly consisting of 1→3-linked, 1→4-linked, and 1→6-linked monosaccharides. AGP33 is a sulfated polysaccharide with sulfates occur at 3-O- and 4-O-positions. It prolonged thromboplastin time (APTT), thrombin time (TT) and prothrombin time (PT) compared to a saline control solution in a dosage-dependent manner. AGP33 exhibited an extension (p < 0.01) of APTT compared to the saline group at concentrations higher than 5 μg/mL. AGP33 exhibited higher anticoagulant activity than its desulfated product (AGP33-des) and BAGP33. The results showed that polysaccharide with higher molecular weight and sulfate content demonstrated greater anticoagulant activity.

Analysis of Apoptosis in Ultraviolet-Induced Sea Cucumber (Stichopus japonicus) Melting Using Terminal Deoxynucleotidyl-Transferase-Mediated dUTP Nick End-Labeling Assay and Cleaved Caspase-3 Immunohistochemistry.

The sea cucumber body wall melting phenomenon occurs under certain circumstances, and the mechanism of this phenomenon remains unclear. This study investigated the apoptosis in the ultraviolet (UV)-induced sea cucumber melting phenomenon. Fresh sea cucumbers (Stichopus japonicus) were exposed to UV radiation for half an hour at an intensity of 0.056 mW/cm(2) and then held at room temperature for melting development. The samples were histologically processed into formalin-fixed paraffin-embedded tissues. The apoptosis of samples was analyzed with the terminal deoxynucleotidyl-transferase-mediated dUTP nick end-labeling (TUNEL) assay and cleaved caspase-3 immunohistochemistry. The emergence of TUNEL-positive cells speeds up between 0.5 and 2 h after UV irradiation. Cleaved caspase-3 positive cells were obviously detected in sample tissues immediately after the UV irradiation. These results demonstrated that sea cucumber melting induced by UV irradiation was triggered by the activation of caspase-3 followed by DNA fragmentation in sea cucumber tissue, which was attributed to apoptosis but was not a consequence of autolysis activity.

Changes in collagenous tissue microstructures and distributions of cathepsin L in body wall of autolytic sea cucumber (Stichopus japonicus)

The autolysis of sea cucumber (Stichopus japonicus) was induced by ultraviolet (UV) irradiation, and the changes of microstructures of collagenous tissues and distributions of cathepsin L were investigated using histological and histochemical techniques. Intact collagen fibers in fresh S. japonicus dermis were disaggregated into collagen fibrils after UV stimuli. Cathepsin L was identified inside the surface of vacuoles in the fresh S. japonicus dermis cells. After the UV stimuli, the membranes of vacuoles and cells were fused together, and cathepsin L was released from cells and diffused into tissues. The density of cathepsin L was positively correlated with the speed and degree of autolysis in different layers of body wall. Our results revealed that lysosomal cathepsin L was released from cells in response to UV stimuli, which contacts and degrades the extracellular substrates such as collagen fibers, and thus participates in the autolysis of S. japonicus.

Effect of pH on the physicochemical and heat-induced gel properties of scallop Patinopecten yessoensis actomyosin

Gelation is an important functional property of protein in meats. In this study, we prepared actomyosin from scallop Patinopecten yessoensis adductor muscles and studied the effects of pH on the physicochemical properties of the actomyosin preparation and on its heat-induced gel-forming properties. The results showed that the turbidity and surface hydrophobicity of scallop actomyosin increased with increases in the heating temperature, while the α-helical content concomitantly decreased. Higher turbidity and surface hydrophobicity and lower α-helical content were found to be easily obtained at lower pH values. A high water-holding capacity, strong gel strength, fine gel network and uniform ice crystals were all clearly observed at pH 7.0, indicating that a neutral pH was most beneficial for formation of the heat-induced scallop actomyosin gel. We therefore conclude that both the physicochemical properties of scallop actomyosin and its gel-forming ability during the heating process are pH dependent.

Physicochemical properties and cytotoxicity of carbon dots in grilled fish

In recent years, the presence of food-borne nanoparticles during food processing has been a controversial issue. In this paper, we introduced a class of extremely low-cytotoxicity carbon dots (CDs) extracted from grilled pike eel which have been consumed for thousands of years. These CDs are water-soluble, quasi-spherical, and nanosized (approximately 2.75 nm). UV illumination can excite CDs to emit a strong sapphire luminescence with a quantum yield as high as 68.7%. X-ray diffraction (XRD) analysis showed that these nanoparticles are amorphous attributed to the disordered carbon atoms. X-ray photoelectron spectroscopy (XPS) measurements showed that the CDs contain a predominant C1s peak at 284.43 eV and an O1s peak at 531.35 eV accompanied by a pronounced N1s peak at 399.34 eV, with the atomic percentages of 66.58%, 17.5% and 15.91%, respectively. Moreover, the CDs also have excellent biocompatibility and could ease into the cytoplasmic region of MC3T3-E1 cells without any seriously imposed toxicity against cells.

Effects of abalone (Haliotis discus hannai Ino) gonad polysaccharides on cholecystokinin release in STC-1 cells and its signaling mechanism

Abalone gonad polysaccharide (AGP) -31, -32 and -33 prepared in this study had the molecular weight (MW) of 37.8, 32.2 and 27.5kDa, respectively. They all contained mannose, rhamnose, glucuronic acid, glucose, galactose, xylose, arabinose, and fucose, with very similar monosaccharide profile. All the three polysaccharides could significantly increase the secretion of cholecystokinin (CCK) in STC-1 cells. Among them, AGP-32 showed the strongest effect. However, the low-MW fragments of AGP-32 showed significantly lower activity than AGP-32 itself. It was also found that the inhibitors on calcium-sensing receptor (CaSR), protein kinase A (PKA), Ca(2+)⁄calmodulin-dependent protein kinase (CaMK) II, p38- mitogen-activated protein kinases (MAPK), and an intracellular calcium chelator all inhibited AGP-induced CCK secretion. To conclude, Ca(2+)/calmodulin (CaM)/CaMK, cyclic adenosine monophosphate (cAMP)/PKA and MAPK pathways are all involved in AGP-induced CCK secretion.

Structural and biochemical changes in dermis of sea cucumber (Stichopus japonicus) during autolysis in response to cutting the body wall

The autolysis of sea cucumber body wall is caused by endogenous proteolysis of its structural elements. However, changes in collagen fibrils, collagen fibres and microfibrils, the major structural elements in sea cucumber body wall during autolysis are less clear. Autolysis of sea cucumber (S. japonicus) was induced by cutting the body wall, and the structural and biochemical changes in its dermis were investigated using electron microscopy, differential scanning calorimetry, infrared spectroscopy, electrophoresis, and chemical analysis. During autolysis, both collagen fibres and microfibrils gradually degraded. In contrast, damage to microfibrils was more pronounced. Upon massive autolysis, collagen fibres disaggregated into collagen fibril bundles and individual fibrils due to the fracture of interfibrillar bridges. Meanwhile, excessive unfolding of collagen fibrils occurred. However, there was only slight damage to collagen monomers. Therefore, structural damage in collagen fibres, collagen fibrils and microfibrils rather than monomeric collagen accounts for autolysis of S. japonicus dermis.