Revealing mechanisms of triclosan on the removal and distribution of nitrogen and phosphorus in microalgal-bacterial symbiosis system.

Microalgal-bacterial symbiosis (MABS) system performs synergistic effect on the reduction of nutrients and carbon emissions in the water treatment process. However, antimicrobial agents are frequently detected in water, which influence the performance of MABS system. In this study, triclosan (TCS) was selected to reveal the effects and mechanisms of antimicrobial agents on MABS system. Results showed that the removal efficiencies of chemical oxygen demand, NH4+-N and total phosphorus decreased by 3.0%, 24.0% and 14.3% under TCS stress. In contrast, there were no significant decrease on the removal effect of total nitrogen. Mechanism analysis showed that both the growth rate of microorganisms and the nutrients retention capacity of extracellular polymeric substances were decreased. The intracellular accumulation for nitrogen and phosphorus was promoted due to the increased cytomembrane permeability caused by lipid peroxidation. Moreover, microalgae were dominant in MABS system with ratio between microalgae and bacteria of more than 5.49. The main genus was Parachlorella, with abundance of more than 90%. Parachlorella was highly tolerant to TCS, which might be conductive to maintain its survival. This study revealed the nutrients pathways of MABS system under TCS stress, and helped to optimize the operation of MABS system.

Bioactive flavonoids in medicinal plants: Structure, activity and biological fate.

Flavonoids, a class of polyphenol secondary metabolites, are presented broadly in plants and diets. They are believed to have various bioactive effects including anti-viral, anti-inflammatory, cardioprotective, anti-diabetic, anti-cancer, anti-aging, etc. Their basic structures consist of C6-C3-C6 rings with different substitution patterns to produce a series of subclass compounds, and correlations between chemical structures and bioactivities have been studied before. Given their poor bioavailability, however, information about associations between structure and biological fate is limited and urgently needed. This review therefore attempts to bring some order into relationships between structure, activity as well as pharmacokinetics of bioactive flavonoids.

Role of Na+/Ca2+ exchanger (NCX) in modulating postovulatory aging of mouse and rat oocytes.

We studied the role of the Na+/Ca2+ exchanger (NCX) in modulating oocyte postovulatory aging by observing changes in NCX contents and activities in aging mouse and rat oocytes. Whereas the NCX activity was measured by observing oocyte activation following culture with NCX inhibitor or activator, the NCX contents were determined by immunohistochemical quantification. Although NCX was active in freshly-ovulated rat oocytes recovered 13 h post hCG injection and in aged oocytes recovered 19 h post hCG in both species, it was not active in freshly-ovulated mouse oocytes. However, NCX became active when the freshly-ovulated mouse oocytes were activated with ethanol before culture. Measurement of cytoplasmic Ca2+ revealed Ca2+ increases always before NCX activation. Whereas levels of the reactive oxygen species (ROS) and the activation susceptibility increased, the density of NCX member 1 (NCX1) decreased significantly with oocyte aging in both species. While culture with H2O2 decreased the density of NCX1 significantly, culture with NaCl supplementation sustained the NCX1 density in mouse oocytes. It was concluded that (a) the NCX activity was involved in the modulation of oocyte aging and spontaneous activation; (b) ROS and Na+ regulated the NCX activity in aging oocytes by altering its density as well as functioning; and (c) cytoplasmic Ca2+ elevation was essential for NCX activation in the oocyte.

Non-frozen preservation protocols for mature mouse oocytes dramatically extend their developmental competence by reducing oxidative stress.

The objective of this study was to test whether aging induces oxidative stress (OS) during oocyte preservation at different temperatures and whether the oocyte competence can be extended by antioxidant supplementation. The increase in activation susceptibility was efficiently prevented when oocytes were preserved at 37°C for 9 h in HCZB medium with 10.27 mM pyruvate and 10 µM α-tocopherol, at 25°C for 30 h with 20.27 mM pyruvate, and at 15°C for 96 h and at 5°C for 48 h with 10.27 mM pyruvate. Satisfactory blastocyst development was achieved after oocyte preservation at 37°C for 9 h, at 25°C for 30 h, at 15°C for 48 h and at 5°C for 24 h using the above protocols but with cysteamine/cystine supplementation. Transfer of blastocysts obtained from the above protocols showed no difference in pregnancy outcome between newly ovulated and preserved oocytes. Because oocytes preserved at 15°C for 48 h were fertilized after a 6-h recovery culture, aging of ovulated mouse oocytes has been successfully prevented for 54 h. Assays for ROS and glutathione indicated that in vitro preservation caused marked OS in oocytes. In conclusion, marked OS was observed following in vitro preservation of mature oocytes at different temperatures. Whereas any protocol that reduced OS could inhibit activation susceptibility, only those protocols that decreased OS while increasing glutathione synthesis could sustain oocyte competence.

Antioxidant supplementation overcomes the deleterious effects of maternal restraint stress-induced oxidative stress on mouse oocytes.

In this study, using a mouse model, we tested the hypothesis that restraint stress would impair the developmental potential of oocytes by causing oxidative stress and that antioxidant supplementation could overcome the adverse effect of stress-induced oxidative stress. Female mice were subjected to restraint stress for 24 h starting 24 h after equine chorionic gonadotropin injection. At the end of stress exposure, mice were either killed to recover oocytes for in vitro maturation (IVM) or injected with human chorionic gonadotropin and caged with male mice to observe in vivo development. The effect of antioxidants was tested in vitro by adding them to IVM medium or in vivo by maternal injection immediately before restraint stress exposure. Assays carried out to determine total oxidant and antioxidant status, oxidative stress index, and reactive oxygen species (ROS) and glutathione levels indicated that restraint stress increased oxidative stress in mouse serum, ovaries, and oocytes. Whereas the percentage of blastocysts and number of cells per blastocyst decreased significantly in oocytes from restraint-stressed mice, addition of antioxidants to IVM medium significantly improved their blastocyst development. Supplementation of cystine and cysteamine to IVM medium reduced ROS levels and aneuploidy while increasing glutathione synthesis and improving pre- and postimplantation development of oocytes from restraint-stressed mice. Furthermore, injection of the antioxidant epigallocatechin gallate into restraint-stressed mice significantly improved the blastocyst formation and postimplantation development of their oocytes. In conclusion, restraint stress at the oocyte prematuration stage impaired the developmental potential of oocytes by increasing oxidative stress and addition of antioxidants to IVM medium or maternal antioxidant injection overcame the detrimental effect of stress-induced oxidative stress. The data reported herein are helpful when making attempts to increase the chances of a successful outcome in human IVF, because restraint was applied at a stage similar to the FSH stimulation period in a human IVF program.

Control of spontaneous activation of rat oocytes by regulating plasma membrane Na+/Ca2+ exchanger activities.

Inhibiting oocyte spontaneous activation (SA) is essential for successful rat cloning by nuclear transfer (NT). This study tested the hypothesis that activities of the Na(+)/Ca(2+) exchanger (NCX) would decrease with oocyte aging and that SA of rat oocytes could be inhibited if the intraoocyte Ca(2+) rises were prevented by activating the NCX through increasing Na(+) concentrations in the culture medium. Elevating Na(+) levels in culture medium by supplementing NaCl inhibited SA of rat oocytes, while maintaining a constant level of maturation-promoting factor and mitogen-activated protein kinase activities. Experiments using the NCX inhibitor bepridil, the Na(+)/K(+)-ATPase inhibitor ouabain, and an assay for intraoocyte Ca(2+) concentrations showed that extracellular Na(+) inhibited rat oocyte SA by enhancing NCX activity and preventing intracellular Ca(2+) rises. Immunohistochemical quantification indicated that the density of NCX1 decreased significantly in aged oocytes that were prone to SA compared with that in freshly ovulated oocytes whose SA rates were low during in vitro culture. Cumulus cell NT showed that sham enucleation caused marked SA in freshly ovulated rat oocytes and that Na(+) supplementation prevented the manipulation-induced SA and improved the in vitro and in vivo development of rat somatic cell NT embryos. Taken together, the results have confirmed our hypothesis that the NCX is active in rat oocytes and its activity decreases with oocyte aging and that activating the NCX by increasing extracellular Na(+) inhibits SA of rat oocytes and improves the development of rat somatic cell NT embryos. These data are also important for understanding the mechanisms of oocyte aging.