Toxicity interaction of polystyrene nanoplastics with sulfamethoxazole on the microalgae Chlamydomonas reinhardtii: A closer look at effect of light availability.

The coexistence of nanoplastics and antibiotics in the aquatic environment has raised a complicated risk for ecosystems and human health. How the environmental factors e.g., light, regulate the interaction between nanoplastics and antibiotics and the resulting combined toxicity is poorly understood. Here, we investigated the individual and combined toxicity of polystyrene nanoplastics (nPS, 100 mg L1) and sulfamethoxazole (SMX, 2.5 and 10 mg L-1) toward the microalgae Chlamydomonas reinhardtii under low (LL, 16 µmol m-2·s-1), normal (NL, 40 µmol m-2·s-1), and high light (HL, 150 µmol m-2·s-1) in terms of cellular responses. Results indicated that the joint toxicity of nPS and SMX commonly exhibited a strong antagonistic/mitigative effect under LL/NL at 24 h, and under NL at 72 h. nPS could adsorb more SMX under LL/NL at 24 h (1.90/1.33 mg g-1) and under NL at 72 h (1.01 mg g-1), thereby alleviating SMX toxicity to C. reinhardtii. However, the self-toxicity of nPS had a negative influence on the degree of antagonism between nPS and SMX. The experimental results coupled with computational chemistry further revealed that the adsorption capacity of SMX on nPS was stimulated by low pH under LL/NL at 24 h (∼7.5), while by less co-existing saline ions (0.83 ppt) and algae-derived dissolved organic matter (9.04 mg L-1) under NL at 72 h. nPS toxicity that was responsible for the toxic action modes was mainly attributed to the shading effect induced by hetero-aggregation and hindrance of light transmittance (>60%), as well as being regulated by additives leaching (0.49-1.07 mg L-1) and oxidative stress. Overall, these findings provided a critical basis for the risk assessment and management of multiple pollutants in the complex natural environment.

Effects of polystyrene microplastic on uptake and toxicity of copper and cadmium in hydroponic wheat seedlings (Triticum aestivum L.).

Microplastics are widespread in freshwater environments, their biological effects and combined effects of other pollutants have attracted extensive attention. In this study, we investigated the adsorption properties of heavy metals onto polystyrene (PS) microplastics as well as the bioavailability and toxicity of microplastics and heavy metals by hydroponic wheat seedlings experiment. Results showed that PS microplastics (0.5 µm, 100 mg/L) had no significant effect on wheat seedlings growth, photosynthesis, and reactive oxygen species (ROS) content. However, PS microplastics could adsorb copper and cadmium, with a predominantly chemisorption. The accumulation of copper and cadmium in wheat seedlings reduced in the presence of PS microplastics, which meant the toxic effect by heavy metals might be mitigated. Compared with single heavy metals treatments, the combination of PS microplastics and heavy metals increased chlorophyll content, enhanced photosynthesis and reduced the accumulation of ROS. These findings suggest that PS microplastics (0.5 µm, 100 mg/L) have a mitigating effect on the bioavailability and toxicity of copper and cadmium.

MdMYB88 and MdMYB124 Enhance Drought Tolerance by Modulating Root Vessels and Cell Walls in Apple.

Water deficit is one of the main limiting factors in apple (Malus × domestica Borkh.) cultivation. Root architecture plays an important role in the drought tolerance of plants; however, research efforts to improve drought tolerance of apple trees have focused on aboveground targets. Due to the difficulties associated with visualization and data analysis, there is currently a poor understanding of the genetic players and molecular mechanisms involved in the root architecture of apple trees under drought conditions. We previously observed that MdMYB88 and its paralog MdMYB124 regulate apple tree root morphology. In this study, we found that MdMYB88 and MdMYB124 play important roles in maintaining root hydraulic conductivity under long-term drought conditions and therefore contribute toward adaptive drought tolerance. Further investigation revealed that MdMYB88 and MdMYB124 regulate root xylem development by directly binding MdVND6 and MdMYB46 promoters and thus influence expression of their target genes under drought conditions. In addition, MdMYB88 and MdMYB124 were shown to regulate the deposition of cellulose and lignin root cell walls in response to drought. Taken together, our results provide novel insights into the importance of MdMYB88 and MdMYB124 in root architecture, root xylem development, and secondary cell wall deposition in response to drought in apple trees.

Stealth microplastics pollutants: Toxicological evaluation of polyethylene terephthalate-based glitters on the microalga Desmodesmus sp. and its color effect.

Polyethylene terephthalate-based glitters (PET glitters) are a potential source of primary microplastics in the environment. However, the bioeffects of PET glitters and the associated leachates remain largely unknown. In this study, we investigated the individual and combined toxicity of five colors (silver, black, red, green, and blue) of PET glitters and their corresponding leachates on the cellular responses of Desmodesmus sp. The results indicated that the photosynthesis of Desmodesmus sp. could be partly affected by PET glitters through the shading effect, but not that of growth. Conversely, the leachates of red and green PET glitters significantly inhibited the growth of the microalga, suggesting a higher risk associated with additives leached from these colors of PET glitters. Furthermore, the adverse effects of the co-occurrence of PET glitters and leachates were closely related to oxidative stress responses in the microalgal cells, along with a color effect, which could be mainly attributed to variations in the composition and abundance of toxic additives in different colors of PET glitters. Overall, our findings provide insights into the ecological risks posed by glitters in aquatic environments and emphasize the importance of considering color factors in assessing microplastics toxicity.

Autochthonous DOM had solar disinfection effect but nitrate counteracted with them.

Pathogens in natural water can pose great threat to public health and challenge water quality. In sunlit surface water, dissolved organic matters (DOMs) can inactivate pathogens due to their photochemical activity. However, the photoreactivity of autochthonous DOM derived from different source and their interaction with nitrate on photo-inactivation remained limited understood. In this study, the composition and photoreactivity of DOM extracted from Microcystis (ADOM), submerged aquatic plant (PDOM) and river water (RDOM) were studied. Results revealed that lignin and tannin-like polyphenols and polymeric aromatic compounds negatively correlated with quantum yield of 3DOM*, whilst lignin like molecules positively correlated with •OH generation. ADOM had highest photoinactivation efficiency of E. coli, followed by RDOM and PDOM. Both the photogenerated •OH and low energy 3DOM* could inactivate bacteria damaging cell membrane and causing increase of intracellular reactive species. PDOM with more phenolic or polyphenols compounds not only weaken its photoreactivity, also increase regrowth potential of bacteria after photodisinfection. The presence of nitrate counteracted with autochthonous DOMs on photogeneration of •OH and photodisinfection activity, as well as increased the reactivation rate of PDOM and ADOM, which might be attributed to the increase of survival bacteria and more bioavailable fractions provided in systems.

Light availability modulates the responses of the microalgae Desmodesmus sp. to micron-sized polyvinyl chloride microplastics.

The vertical movement of large-size and high-density MPs in the water column is usually along with dynamic changes in light intensity. However, whether the change in light availability affects the bioeffects of MPs on surrounding microalgae is currently unknown. This study investigated the effects of micron-sized polyvinyl chloride (mPVC, 143.5 µm) microplastics, alone and in combination with light intensity (from 7.5 to 162.5 µmol·m-2·s-1) on the growth and physiology of Desmodesmus sp. Although mPVC did not impact microalgal growth under optimal light (40 and 93.8 µmol·m-2·s-1), it could induce a no-contact shading effect, thereby significantly affecting the physiology of Desmodesmus sp. The growth of Desmodesmus sp. exposed to mPVC was enhanced under a high light intensity of 162.5 µmol·m-2·s-1 which can induce growth inhibition but was retarded when under a light inadequacy condition (20 µmol·m-2·s-1), along with a dose-dependent effect. Significantly, the photosynthesis of Desmodesmus sp. was a highly sensitive metabolic pathway to mPVC stress and largely influenced by the plastic particles under different light conditions. Additionally, mPVC modulated the energy metabolism strategy of Desmodesmus sp., depending on exposure dose and external light availability. Our findings provided a critical basis for the risk assessment of MPs in fluctuating light conditions.

Size-dependent toxic effects of polystyrene microplastic exposure on Microcystis aeruginosa growth and microcystin production.

Due to increasingly severe microplastic pollution in freshwaters, the interaction between these contaminants and cyanobacteria warrants study. In this study, we expose the freshwater cyanobacterium Microcystis aeruginosa to different sizes (1 µm and 100 nm) of polystyrene (PS) microplastics of 5 mg/L. Results indicate 1 µm microplastics promote algal growth (12.42% ± 0.94%) at 96 h, and have greater potential to aggregate on algal cell surfaces and inhibit photosynthesis. But no significance was observed in 100 nm microplastics treatment on algal growth and photosynthetic activity after 96 h exposure. Especially, 1 µm microplastics increased the content of intracellular microcystins (MCs) (18.42% ±0.33%) after 72 h and inhibit MCs release (23.87% ±8.79%) at 72 h, while 100 nm PS microplastics promote MCs production only at 48 h (14.83% ± 7.07%). Results indicate that smaller size does not necessarily mean greater toxicity, 1 µm microplastics showing more adverse effects than 100 nm microplastics to M. aeruginosa, improving understanding of the toxicity of microplastics in freshwater ecosystems, and challenging the conventionally held belief that smaller microplastics are more toxic.

Comprehensive assessment of factors influencing Nile red staining: Eliciting solutions for efficient microplastics analysis.

Monitoring microplastics in the environment based on the Nile red staining protocol has proven to be a newly emerged method in several instances. However, the methodology is still having the limitations of susceptibility, indiscrimination, and complexity, etc. The objectives of this paper are to explore the effects of wavelength, temperature, H2O2 and NaCl addition, plastic property, and fluorescent index on the Nile red staining in microplastics analysis and propose solutions to these inadequacies. Sample co-stained with H2O2 (ωfinal = 10%) and NaCl (ωfinal = 8.8%) will lower the fluorescence intensity of biogenic materials and reduce their interferences. Based on the fluorescence color and intensity of fused fluorographs, the combined fluorescent index for twelve microplastics was significantly different, thus could be preliminarily distinguished. An elevated staining temperature is propitious to fluorescent tagging with Nile Red. Finally, an improved protocol was proposed, which made the methodology streamlined in microplastics analysis.

[Effects of Microplastics on the Growth, Physiology, and Biochemical Characteristics of Wheat (Triticum aestivum)].

The toxicological effects of microplastics in the soil environment have gradually attracted widespread attention, while less is known about the influence of microplastics on plants. The growth of wheat, photosynthetic pigment content, soluble protein content, and the antioxidant enzyme activities of leaves were investigated to explore the toxic effects of microplastics on wheat (Triticum aestivum). In this study, 100 nm and 5 µm polystyrene microplastics (PS-MPs) were used for soil culture treatment combined with hydroponic growth. The results showed that in hydroponic experiment, high concentrations (200 mg·L-1) of PS-MPs significantly inhibited the elongation of wheat roots and stems, and 5 µm PS-MPs showed a greater toxicity effect than 100 nm PS-MPs. Roots and stem length inhibition rates were 67.15% and 56.45%, respectively. In the soil culture tests, 10 mg·kg-1 PS-MPs had the most significant effect on wheat growth. Within the test content range (0-100 mg·kg-1), with an increase in PS-MPs exposure, the content of photosynthetic pigment and soluble protein in wheat leaves increased first and then decreased. This indicated that PS-MPs damaged the photosynthetic pathway of wheat leaves and inhibited protein synthesis. SOD activity decreased, and CAT decreased first and then increased, indicating that the possible mechanism of toxicity to wheat involves oxidative stress. The results provide a basis for the ecological risk assessment of microplastics in the soil environment.

Novel Simvastatin-Loaded Nanoparticles Based on Cholic Acid-Core Star-Shaped PLGA for Breast Cancer Treatment.

A novel nanocarrier system of cholic acid (CA) core, star-shaped polymer consisting of poly(D,L-lactide-co-glycolide) (PLGA) was developed for sustained and controlled delivery of simvastatin for chemotherapy of breast adenocarcinoma. The star-shaped polymer CA-PLGA with three branch arms was synthesized successfully through the core-first approach. The simvastatin-loaded star-shaped CA-PLGA nanoparticles were prepared through a modified nanoprecipitation method. The data showed that the fluorescence star-shaped CA-PLGA nanoparticles could be internalized into MDA-MB-231 and MDA-MB-468 human breast cancer cells. The simvastatin-loaded star-shaped CA-PLGA nanoparticles achieved significantly higher level of cytotoxicity than pristine simvastatin and simvastatin-loaded linear PLGA nanoparticles. Moreover, the expression of the cell cycle protein cyclin D1 was dramatically inhibited by simvastatin in both cells, with simvastatin-loaded star-shaped CA-PLGA nanoparticles having the greatest effect. MDA-MB-231 xenograft tumor model on BALB/c nude mice showed that simvastatin-loaded star-shaped CA-PLGA nanoformulations could effectively inhibit the growth of tumor over a longer period of time than pristine simvastatin and simvastatin-loaded linear PLGA nanoformulations at the same dose. In agreement with these, the nuclear expression of proliferation marker Ki-67 in simvastatin-loaded star-shaped CA-PLGA nanoparticles group was reduced to a most extent among four groups through tumor frozen section immunohistochemistry. In conclusion, the star-shaped CA-PLGA polymers could serve as a novel polymeric nanocarrier for breast cancer chemotherapy.

[Field epidemiological study on news reports that related to public health emergencies].

OBJECTIVE: All news reports (NR) that were related to public health emergency (PHE) were collected from the Southern Metropolis Daily (SMD) to explore the characteristics of epidemiology in the fields. METHODS: Based on the theory of communication that including both case and text analysis, qualitative analysis on all the NR regarding PHE published in SMD from the years of 2008 to 2012, was carried out and input to database using the EpiData. Numbers of articles as indicators were compared to show the yearly change of different types of events. Various features of the NR including coverage, source of information, location of the incident, style and size of news, with or without editorials etc. were statistically analyzed by SPSS version 18.0. RESULTS: Among all the 998 reports related to PHE, higher proportion was found in the events of Infectious diseases (35.3%) and food safety (34.1%)respectively. Events on vaccines and drugs used for disease prevention and control (8.9%), environmental pollution caused incidents (8.0%)appeared to be less frequent. Events related to occupational disease, poisoning, bioterrorism and biochemical events were rare. Looking at the monthly distribution of reports, we noticed that the peaks occurred in 2008 and in 2009, which were caused by the Melamine-contamination events and the 2009 H1N1 pandemic. Between 2010 and 2012, figures of monthly reports were smooth, including some critical events from the interests of the media. Most events took place in Guangdong province (34.3%) and other provinces (50.9%), with some were from Hong Kong, Macao and Taiwan regions (9.5%). However, international events (5.2%)were less seen. Extensive coverage accounted for 17.6% of all of reports, and 11.5% allotted the editorials or other forms of in-depth reports. Most of the source of reports on infectious diseases and food safety were from the official release, however. The main sources of occupational diseases and poisoning, vaccines and drug incidents, environmental pollution related incidents were reported by active journalists through interview. Reports on hand, foot and mouth disease, influenza, milk safety, AIDS and lead pollution showed continued concern in the past five years by SMD. CONCLUSION: NR on public health emergencies by SM had encompassed all 10 categories-related events formulated by the Ministry of Health. Sustained and in-depth coverage were more commonly seen. Field-epidemiologists should learn interdisciplinary sciences on the theory and methodology of communication. They also need to interact with media people during the whole processes of public health emergency preparedness and responses.