Lycium barbarum polysaccharide alleviates nonylphenol exposure induced testicular injury in juvenile zebrafish.

Nonylphenol is an endocrine disrupting chemicals that can disrupt the organisms' reproductive system, and exists widely in rivers and lakes. Lycium barbarum polysaccharide (LBP) is the main active constituent (about 10%) in Lycium barbarum, which is used to protect reproductive health. In this study, we investigated whether LBP can alleviate nonylphenol exposure induced testicular injury in juvenile zebrafish. We detected histological alteration, anti-oxidant enzyme profile and P450 gene transcription to assess LBP effect on testicular development. The GSI reduced significantly due to nonylphenol exposure, while LBP can improve the GSI. The densities of sperms increased and non-celluar zone decreased after LBP treatment. Meanwhile, Cyp11b gene was up regulated to NP group, and cyp19a gene was down regulated to NP group. In sum, the LBP could repair the testicular injury in zebrafish. This findings provide a basis research to remit the estrogen effect of artificial endocrine disruptor.

Effect of environmentally-relevant concentrations of nonylphenol on sexual differentiation in zebrafish: a multi-generational study.

Nonylphenol (NP) is a persistent environmental chemical that can disrupt the organism's endocrine system, and is detected in the surface water and sea. In this study, we investigated whether NP can alter transcriptional expression of sexual differentiation-related genes. Three generations of zebrafish were exposed to 0, 2, 20 and 200 µg·L-1 of NP, and transcriptional expression of sexual differentiation genes were assessed in 10, 20 and 40 dpf in the F1 and F2 generations. Growth of zebrafish exposed to 200 µg·L-1 of NP was inhibited at 125 dpf in the F1 generation. 20 µg·L-1 of NP resulted in 80% females in the F1 generation, but had no effect on the F2 generation. In terms of the sexual differentiation genes, the transcriptional expression of cyp19a1a and esr1 genes were upregulated in 20 µg·L-1 of NP in the F1 generation. But expression of the sexual differentiation genes were not affected in the F2 generation. Overall, NP could affect sexual differentiation and gene transcriptional expression in the F1 generation. The tolerance of contaminant in the offsprings was improved at low concentration.

Ecotoxicity of two organophosphate pesticides chlorpyrifos and dichlorvos on non-targeting cyanobacteria Microcystis wesenbergii.

Organophosphate pesticides (OPs), as a replacement for the organochlorine pesticides, are generally considered non-toxic to plants and algae. Chlorpyrifos and dichlorvos are two OPs used for pest control all over the world. In this study, the dose-response of cyanobacteria Microcystis wesenbergii on OPs exposure and the stimulating effect of OPs with and without phosphorus source were investigated. The results showed that high concentrations of chlorpyrifos and dichlorvos caused significant decrease of chlorophyll a content. The median inhibitory concentrations (EC50) of chlorpyrifos and dichlorvos at 96 h were 15.40 and 261.16 µmol L(-1), respectively. Growth of M. wesenbergii under low concentration of OPs (ranged from 1/10,000 to 1/20 EC50), was increased by 35.85 % (chlorpyrifos) and 41.83 % (dichlorvos) at 120 h, respectively. Correspondingly, the highest enhancement on the maximum quantum yield (F v/F m) was 4.20 % (24 h) and 9.70 % (48 h), respectively. Chlorophyll fluorescence kinetics, known as O-J-I-P transients, showed significant enhancements in the O-J, J-I, and I-P transients under low concentrations of dichlorvos at 144 h, while enhancements of chlorophyll fluorescence kinetics induced by low concentrations of chlorpyrifos were only observed in the J-I transient at 144 h. Significant decreases of chlorophyll content, F v/F m and O-J-I-P transients with OPs as sole phosphorus source were found when they were compared with inorganic phosphate treatments. The results demonstrated an evidently hormetic dose-response of M. wesenbergii to both chlorpyrifos and dichlorvos, where high dose (far beyond environmental concentrations) exposure caused growth inhibition and low dose exposure induced enhancement on physiological processes. The stimulating effect of two OPs on growth of M. wesenbergii was negligible under phosphate limitation.

Sublethal toxic effects of nonylphenol ethoxylate and nonylphenol to Moina macrocopa.

The aim of this paper was to examine the sublethal toxic effects of nonylphenol ethoxylate (NP10EO), its primary degradation product nonylphenol (NP), and their mixture on Moina macrocopa. Chronic toxicity tests were carried out by using sublethal chemical concentrations. Results showed that all treatments reduced the survivorship, body length, and reproduction of M. macrocopa with NP being 10 %-20 % more toxic to M. macrocopa than NP10EO. Results also indicated that the toxic effects of NP10EO and NP mixture on M. macrocopa were more severe than that of any single chemical alone. At the highest concentration in this experiment, 0.337 mg L(-1) NP10EO plus 0.0154 mg L(-1) NP treatment caused the survivorship of M. macrocopa to zero, neonates number of reproductions to zero, 45.5 % reduction in the body length, and 88 % reduction in the total neonates number.

Antifungal effects of citronella oil against Aspergillus niger ATCC 16404.

Essential oils are aromatic oily liquids obtained from some aromatic plant materials. Certain essential oils such as citronella oil contain antifungal activity, but the antifungal effect is still unknown. In this study, we explored the antifungal effect of citronella oil with Aspergillus niger ATCC 16404. The antifungal activity of citronella oil on conidia of A. niger was determined by poisoned food technique, broth dilution method, and disc volatility method. Experimental results indicated that the citronella oil has strong antifungal activity: 0.125 (v/v) and 0.25 % (v/v) citronella oil inhibited the growth of 5 × 105 spore/ml conidia separately for 7 and 28 days while 0.5 % (v/v) citronella oil could completely kill the conidia of 5 × 105 spore/ml. Moreover, the fungicidal kinetic curves revealed that more than 90 % conidia (initial concentration is 5 × 105 spore/ml) were killed in all the treatments with 0.125 to 2 % citronella oil after 24 h. Furthermore, with increase of citronella oil concentration and treatment time, the antifungal activity was increased correspondingly. The 0.5 % (v/v) concentration of citronella oil was a threshold to kill the conidia thoroughly. The surviving conidia treated with 0.5 to 2 % citronella oil decreased by an order of magnitude every day, and no fungus survived after 10 days. With light microscope, scanning electron microscope, and transmission electron microscope, we found that citronella oil could lead to irreversible alteration of the hyphae and conidia. Based on our observation, we hypothesized that the citronella oil destroyed the cell wall of the A. niger hyphae, passed through the cell membrane, penetrated into the cytoplasm, and acted on the main organelles. Subsequently, the hyphae was collapsed and squashed due to large cytoplasm loss, and the organelles were severely destroyed. Similarly, citronella oil could lead to the rupture of hard cell wall and then act on the sporoplasm to kill the conidia. Nevertheless, the citronella oil provides a potential of being a safe and environmentally friendly fungicide in the future.

Antibacterial effect of silver nanoparticles on Staphylococcus aureus.

The antibacterial activity and mechanism of silver nanoparticles (Ag-NPs) on Staphylococcus aureus ATCC 6538P were investigated in this study. The experiment results showed the minimum bactericidal concentration (MBC) of Ag-NPs to S. aureus was 20 µg/ml. Moreover, when bacteria cells were exposed to 50 µg/ml Ag-NPs for 6 h, the cell DNA was condensed to a tension state and could have lost their replicating abilities. When S. aureus cells were exposed to 50 µg/ml Ag-NPs for 12 h, the cell wall was breakdown, resulting in the release of the cellular contents into the surrounding environments, and finally became collapsed. And Ag-NPs could reduce the enzymatic activity of respiratory chain dehydrogenase. Furthermore, the proteomic analysis showed that the expression abundance of some proteins was changed in the treated bacterial cell with Ag-NPs, formate acetyltransferase increased 5.3-fold in expression abundance, aerobic glycerol-3-phosphate dehydrogenase decreased 6.5-fold, ABC transporter ATP-binding protein decreased 6.2-fold, and recombinase A protein decreased 4.9-fold.

[Isolation and characterization of a humic-reducing bacterium Shewanella strain W3 from mangrove sediment].

A humus-reducing bacterium strain W3 was isolated from the mangrove sediment. Based on the analysis of morphology, physiobiochemical characteristics and 16S rDNA gene sequence, this strain was identified as Shewanella sp. W3. Strain W3 was able to reduce humic with lactate, formate and pyruvate as electron donor and the humic reduction rates to 1 mmol/L AQDS were 96%, 40% and 10% respectively within 48 hours. In addition, the bacteria can grow coupled with the humic reduction. Strain W3 grew to maximal density of 1.77 x 10(8) CFU/mL after complete reduction of 1 mmol/L AQDS. However, the growth of strain W3 was light increase in the control experiment in the absence of electron donor. The optimal initial pH, NaCl concentration, and temperature for strain W3 reducing humic were pH 7-9, 5-30 g/L, and 30-35 degrees C, respectively. Combined experimental results showed that the humic reduction was a biochemical process and strain W3 could conserve energy to support growth from lactate oxidation coupled to humic reduction. It is suggested that humic reduction by Shewanella bacteria may play important roles in biogeochemical circulation of elements and have potential application in the microbial bioremediation to contaminations.

Effects of glycerol on the fluorescence spectra and chloroplast ultrastructure of Phaeodactylum tricornutum (Bacillariophyta).

Responses of the photosynthetic activity of Phaeodactylum tricornutum (Bacillariophyta) to organic carbon glycerol were investigated. The growth rate, photosynthetic pigments, 77 K fluorescence spectra, and chloroplast ultrastructure of P. tricornutum were examined under photoautotrophic, mixotrophic, and photoheterotrophic conditions. The results showed that the specific growth rate was the fastest under mixotrophic conditions. The cell photosynthetic pigment content and values of Chl a/Chl c were reduced under mixotrophic and photoheterotrophic conditions. The value of carotenoid/Chl a was enhanced under mixotrophic conditions, but was decreased under photoheterotrophic conditions. In comparison with photoautotrophic conditions, the fluorescence emission peaks and fluorescence excitation peaks were not shifted. The relative fluorescence of photosystem (PS) I and PS II and the values of F685/F710 and F685/F738 were decreased. Chloroplast thylakoid pairs were less packed under mixotrophic and photoheterotrophic conditions. There was a strong correlation between degree of chloroplast thylakoid packing and the excitation energy kept in PS II. These results suggested that the PS II activity was reduced by glycerol under mixotrophic conditions, thereby leading to repression of the photosynthetic activity.

[Overcompensation effect of Pavlova viridis under ultraviolet (UV-B) stress].

To examine the existence of overcompensation growth of microalgae, this paper studied the effects of UV-B stress on the production of bioactive substances during the overcompensation of Pavlova viridis. Six groups of UV-B treatments 18, 36, 54, 65, 86 and 108 J x m(-2) as well as the control were set up for this study. After the UV-B stress relieved, the treated groups and the control were simultaneously cultured for 12 days under the same inoculation density and normal culture conditions, and the parameters OD, biomass, chlorophyll a, carotenoid, cellular protein and carbohydrate were measured. The results showed that under UV-B stress, the growth of P. viridis was inhibited significantly (P < 0.05), with a decrease of relative growth rate being 16.15% - 60.00%, compared with the control. But, after the relief of UV-B stress, the growth rate during anaphase was significantly higher (P < 0.05) in UV-B treatments than in the control, indicating the occurrence of overcompensation growth. On the 12th day of culture, the OD, biomass, chlorophyll a, carotenoid, cellular protein and carbohydrate in treated groups were 22.38%, 15.00%, 26.15%, 23.81%, 11.63% and 27.58% higher than those in the control, respectively. The overcompensation growth of P. viridis provided an effective way to exploit the bioactive substances of microalgae.

Peptide models of four possible insulin folding intermediates with two disulfides.

The single-chain insulin (PIP) can spontaneously fold into native structure through preferred kinetic intermediates. During refolding, pairing of the first disulfide A20-B19 is highly specific, whereas pairing of the second disulfide is likely random because two two-disulfide intermediates have been trapped. To get more details of pairing property of the second disulfide, four model peptides of possible folding intermediates with two disulfides were prepared by protein engineering, and their properties were analyzed. The four model peptides were named [A20-B19, A7-B7]PIP, [A20-B19, A6-B7]PIP, [A20-B19, A6-A11]PIP, and [A20-B19, A7-A11]PIP according to their remaining disulfides. The four model peptides all adopt partially folded structure with moderate conformational differences. In redox buffer, the disulfides of the model peptides are more easily reduced than those of the wild-type PIP. During in vitro refolding, the reduced model peptides share similar relative folding rates but different folding yields: The refolding efficiency of the reduced [A20-B19, A7-A11]PIP is about threefold lower than that of the other three peptides. The present results indicate that the folding intermediates corresponding to the present model peptides all adopt partially folded conformation, and can be formed during PIP refolding, but the chance of forming the intermediate with disulfide [A20-B19, A7-A11] is much lower than that of forming the other three intermediates.