Different responses of marine microalgae Phaeodactylum tricornutum upon exposures to WAF and CEWAF of crude oil: A case study coupled with stable isotopic signatures.

Increasing use of chemical dispersants for oil spills highlights the need to understand their adverse effects on marine microalgae and nutrient assimilation because the toxic components of crude oil can be more bioavailable. We employed the crude oil water-accommodated fraction (WAF) and chemically enhanced WAF (CEWAF) to compare different responses in marine microalgae (Phaeodactylum tricornutum) coupled with stable isotopic signatures. The concentration and proportion of high-molecular-weight polycyclic aromatic hydrocarbons (HMW PAHs), which are key toxic components in crude oil, increased after dispersant addition. CEWAF exposure caused higher percent growth inhibition and a lower chlorophyll-a level of microalgae than those after WAF exposure. Compared with WAF exposure, CEWAF led to an enhancement in the self-defense mechanism of P. tricornutum, accompanied by an increased content of extracellular polymeric substances. 13C-depletion and carbon assimilation were altered in P. tricornutum, suggesting more HMW PAHs could be utilized as carbon sources by microalgae under CEWAF. CEWAF had no significant effects on the isotopic fractionation or assimilation of nitrogen in P. tricornutum. Our study unveiled the impact on the growth, physiological response, and nutrient assimilation of microalgae upon WAF and CEWAF exposures. Our data provide new insights into the ecological effects of dispersant applications for coastal oil spills.

Structural and digestion properties of potato starch modified using an efficient starch branching enzyme AqGBE.

Modified potato starch with slower digestion may aid the development of new starch derivatives with improved nutritional values, and strategies to increase nutritional fractions such as resistant starch (RS) are desired. In this study, a correspondence between starch structure and enzymatic resistance was provided based on the efficient branching enzyme AqGBE, and modified starches with different amylose content (Control, 100%; PS1, 90%; PS2, 72%; PS3, 32%; PS4, 18%) were prepared. Through SEM observation, NMR and X-ray diffraction analyses, we identified that an increased proportion of α-1,6-linked branches in potato starch changes its state of granule into large pieces with crystallinity. Molecular weight and chain-length distribution analysis showed a decrease of molecular weight (from 1.1 × 106 to 1.1 × 105 g/mol) without an obvious change of chain-length distribution in PS1, while PS2-4 exhibited an increased proportion of DP 6-12 with a stable molecular weight distribution, indicating a distinct model of structural modification by AqGBE. The enhancement of peak viscosity was related to increased hydrophobic interactions and pieces state of PS1, while the contents of SDS and RS in PS1 increased by 37.7 and 49.4%, respectively. Our result provides an alternative way to increase the RS content of potato starch by branching modification.

Comparative Studies on Bioactive Compounds, Ganoderic Acid Biosynthesis, and Antioxidant Activity of Pileus and Stipes of Lingzhi or Reishi Medicinal Mushroom, Ganoderma lucidum (Agaricomycetes) Fruiting Body at Different Growth Stages.

Total phenolics, flavonoids, and polysaccharides, and individual ganoderic acid (GA) contents, antioxidant capacity, and transcription levels of key enzyme genes involved in GA biosynthesis in pileus and stipes of Ganoderma lucidum fruiting body at different growth stages were investigated in this study. Results showed that the highest total phenolics and total flavonoids contents were determined in stipes at spore maturity stage, resulting in high antioxidant activity, while the highest total polysaccharide content was found in pileus at the same stage. The pileus contained more GA than the stipes, and higher contents of ganoderic acid A and D were found at fruiting body mature stage while that of ganoderic acid B, C2, and G were found at bud elongation stage. Results from quantitative real-time PCR indicated that higher gene transcription levels of hydroxyl methylglutaryl-CoA reductase (hmgr), farnesyl pyrophosphate synthase (fps), squalene synthase (sqs), and oxidosqualene cyclase (osc) were found in pileus at bud elongation stage. Our findings will be helpful for understanding the biosynthesis of bioactive components and determining the harvest time for the desired G. lucidum fruiting bodies.

The effects of CYP1A inhibition on alkyl-phenanthrene metabolism and embryotoxicity in marine medaka (Oryzias melastigma).

Alkylated polycyclic aromatic hydrocarbons (alkyl-PAHs) are the predominant form of PAHs in crude oils, of which, 3-5 ring alkyl-PAH may cause dioxin-like toxicity to early life stages of fish. Retene (7-isopropyl-1-methylphenanthrene), a typical alkyl-phenanthrene compound, can be more toxic than phenanthrene, and the mechanism of retene toxicity is likely related to its rapid biotransformation by cytochrome P450 (CYP) enzymes to metabolites with a wide array of structures and potential toxicities. Here, we investigated how α-naphthoflavone (ANF), a cytochrome P450 1A (CYP1A) inhibitor, affected the embryotoxicity of retene and the role that CYP1A inhibition may play in the interactions. Marine medaka (Oryzias melastigma) embryos were exposed, separately or together, to 200 µg/L retene with 0, 5, 10, 100, and 200 µg/L ANF for 14 days. The results showed that ANF significantly inhibited the induction of CYP1A activity by retene; however, ANF interacted with retene to induce significant developmental toxicity and genotoxicity at 10, 100, and 200 µg/L (p < 0.01). Tissue concentrations of retene and its metabolites and lipid hydroperoxide (LPO) activity also increased, whereas the inhibition of the glutathione S-transferase (GST) activity and the alteration in metabolic profiles of retene were observed. The interactions of retene with ANF indicate that CYP1A inhibition was possibly act through different mechanisms to produce similar developmental effects and genotoxicity. Retene metabolites and altered metabolic profile were likely responsible for retene embryotoxicity to marine medaka. Therefore, elevated toxicity of alkyl-phenanthrene under CYP1A inhibitor suggested that the ecotoxicity of PAHs in coastal water may have underestimated the threat of PAHs to fish or ecosystem.

Comparative effects of biological and chemical dispersants on the bioavailability and toxicity of crude oil to early life stages of marine medaka (Oryzias melastigma).

The authors assessed the bioavailability and chronic toxicity of water-accommodated fractions of crude oil (WAFs) and 2 dispersants plus dispersed crude oil (chemical dispersant + crude oil [CE-WAF] and biological dispersant + crude oil [BE-WAF]) on the early life stages of marine medaka, Oryzias melastigma. The results showed that the addition of the 2 dispersants caused a 3- and 4-fold increase in concentrations of summed priority polycyclic aromatic hydrocarbons (PAHs) and high-molecular-weight PAHs with 3 or more benzene rings. The chemical and biological dispersants increased the bioavailability (as measured by ethoxyresorufin-O-dethylase activity) of crude oil 6-fold and 3-fold, respectively. Based on nominal concentrations, chronic toxicity (as measured by deformity) in WAFs exhibited a 10-fold increase in CE-WAF and a 3-fold increase in BE-WAF, respectively. When total petroleum hydrocarbon was measured, the differences between WAF and CE-WAF treatments disappeared, and CE-WAF was approximately 10 times more toxic than BE-WAF. Compared with the chemical dispersant, the biological dispersant possibly modified the toxicity of oil hydrocarbons because of the increase in the proportion of 2- and 3-ringed PAHs in water. The chemical and biological dispersants enhanced short-term bioaccumulation and toxicity, through different mechanisms. These properties should be considered in addition to their efficacy in degrading oil when oil spill management strategies are selected.

[Effect of baicalin on HSP70 expression of hippocampal neurons in focal brain ischemia-reperfusion injury rats].

AIM: To investigate the effect of baicalin on the hippocampal neuronal apoptosis and the expression of HSP70 in rats with focal brain ischemia-reperfusion injury. METHODS: One hundred and twenty male Wistar rats were randomly divided into six groups:sham operated group, ischemia-reperfusion group, nimodipine group and three baicalin groups,to which baicalin was administered at doses of 50, 100 and 200 mg x kg(-1), separately. The models of focal brain ischemia-reperfusion injury induced by middle cerebral artery occlusion (MCAO) were used in this study. HE stain was used to observe the pathological changes. Flow cytometry (FCM) was used for determination of neuronal apoptosis. HSP70 protein expression of the neurons was detected with immunohistochemistry. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect the expression of the mRNA level of HSP70. RESULTS: Baicalin can significantly relieve the pathological changes and inhibit apoptosis in hippocampus CA1 area, and at the same time increase the expression of HSP70 and HSP70 mRNA. CONCLUSION: Baicalin can relieve brain damage induced by focal brain ischemia-reperfusion in rats, which may be related to inhibiting the process of the neuronal apoptosis. The mechanism of antiapoptosis effect of baicalin may be related to the promotion of transcription of HSP70 mRNA and increasing the expression of the protein.

[Studies on liver-toxicity in rhigoma of Dioscorea bulbifera].

OBJECTIVE: To explore the liver-toxic fraction in Rhigoma of Dioscorea bulbifera. METHOD: The rats were randomized into four groups: control group (20% PVP-water), T001(10% total methanol extraction), F002(5% chloroform fraction) and F003(5% methanol fraction). Direct bilirubin (DBil) and Glutamic-pyruvic transaminase (GPT) were examined, and liver index was measured. The histological and morphological observations were performed with optical and electrical microscope. RESULT: T001 and F002 showed significant liver toxicity. CONCLUSION: The chloroform fraction was the liver-toxic fraction of D. bulbifera.