Cellular Process of Polystyrene Nanoparticles Entry into Wheat Roots.

Nanoscale plastic particles are widely found in the terrestrial environment and being increasingly studied in recent years. However, the knowledge of their translocation and accumulation mechanism controlled by nanoplastic characterizations in plant tissues is limited, especially in plant cells. Here, 20 mg L-1 polystyrene nanoparticles (PS NPs) with different sizes and amino/carboxy groups were employed to investigate the internalization process in wheat roots and cells. From the results, we found that the uptake of small-size PS NPs in the root tissues was increased compared to that of large-size ones, but no PS NPs were observed in the vascular cylinder. Similar results were observed in their cellular uptake process. Besides, the cell wall could block the entry of large-size PS NPs while the cell membrane could not. The -NH2 group on the PS NPs surface could benefit their tissular/cellular translocation compared to the -COOH group. The internalization of PS NPs was controlled by both particle size and surface functional group, and the size should be the primary factor. Our findings offer important information for understanding the PS NPs behaviors in plant tissues, especially at the cellular level, and assessing their potential risk to food safety, quality, and agricultural sustainability.

In vitro wheat protoplast cytotoxicity of polystyrene nanoplastics.

Nanoplastics are an emerging environmental pollutant, having a potential risk to the terrestrial ecosystem. In the natural environment, almost all the micro-or nano-plastics will be aged by many factors and their characterizations of the surface will be modified. However, the toxicity and mechanism of the modified polystyrene nanoparticles (PS-NPs) to plant cells are not clear. In the study, the amino- and carboxyl-modified PS-NPs with different sizes (20 and 200 nm) were selected as the typical representatives to investigate their effects on protoplast cell viability, reactive oxygen species (ROS) production in the cell and the leakage of cell-inclusion and apoptosis. The results indicated that the 20 nm amino-modified PS-NPs (PS-20A) could significantly damage the structure of the cell, especially the cell membrane, chloroplast and mitochondrion. After being modified by amino group, smaller size nanoplastics had the potential to cause more severe damage. In addition, compared with carboxyl-modified PS-NPs, the amino-modified PS-NPs induced more ROS production and caused higher membrane permeability/lactate dehydrogenase (LDH) leakage. Apoptosis assay indicated that the proportion of viable cells in the PS-20A treatment decreased significantly, and the proportion of necrotic cells increased by four times. This study provides new insights into the toxicity and damage mechanism of PS-NPs to terrestrial vascular plants at the cellular level, and guides people to pay attention to the quality and safety of agricultural products caused by nanoplastics.

Microplastics lag the leaching of phenanthrene in soil and reduce its bioavailability to wheat.

Microplastics wildly occur in soil and they can become the carriers of persistent contaminants. However, the influence of microplastics on polycyclic aromatic hydrocarbons vertical translocation in the soil system after rainfall is limitedly understood. Here, experiments were conducted to study the influence of polyethylene (PE), polystyrene (PS) and polyvinyl chloride (PVC) microplastics on the leaching behavior and bioavailability of phenanthrene (Phe). The adsorption capacity of phenanthrene on the microplastics followed the order of PS > PE > PVC. The Phe concentrations in the top soil layer after 15 days of leaching with water were 30.25, 28.32 and 27.25 mg kg-1 for the treatments of Phe-PS, Phe-PE and Phe-PVC respectively, which is consistent with the adsorption capacities of microplastics. The concentrations of Phe were correlated with the microplastic adsorption capacities at soil depths of 5-45 cm. Under long-term leaching, Phe could reach the deeper soil layer. Phe concentrations significantly decreased in the leachate over time. Phe concentrations in wheat had a positive correlation with that in leachate/leached top soil layer. Our findings are beneficial to accurately evaluate the ecological risk of the combined contamination of PAHs and microplastics, and improve the understanding of the environmental behaviors of different microplastics.

Microplastic particles alter wheat rhizosphere soil microbial community composition and function.

The wide existence of microplastics (MPs) in the terrestrial systems is proved by -many studies, and their presence could potentially change the soil chem-physical properties and processes. Various types of microplastics may have different behaviors, inducing distinct effects on the soil ecosystems. However, the knowledge of microplastic impacts on rhizosphere soil bacterial community structure is limited. In our study, three types of microplastics, i.e., polyethylene (PE), polyvinylchloride (PVC) and polystyrene (PS), with the same particle size (200 µm) and concentration (2%) were used to investigate their influences on the rhizosphere soil bacterial communities. Results revealed that the alpha diversities (richness, evenness and diversity) of microbiota in the rhizosphere soil were variously decreased by the microplastics, especially the PE MPs. The relative abundance of some various phyla and genera related to pollution degradation was miscellaneously increased, indicating that the MPs with different characterizations may have miscellaneous biodegradation pathways. Moreover, the PICRUSt2 analysis demonstrated that PS decreased most functional category levels and led to a decrease of bacterial genus number, however, PE and PVC improved metabolic pathways and xenobiotics biodegradation and metabolism. Our findings offer important knowledge of how the microplastics with different characterizations influence rhizosphere soil bacterial communities and their related function.

The joint toxicity of polyethylene microplastic and phenanthrene to wheat seedlings.

Due to wide distribution, easy production, and difficult degradation, microplastic pollution has become a new environmental problem that has attracted worldwide attention. However, there is little information about the effects of microplastics in soil and their combined pollution with other organic pollutants on crop growth. In this study, we conducted soil culture experiments to evaluate the effects of polyethylene microplastics (PE-MPs) (0.5%, 1%, 2%, 5%, 8% w/w) individual and combined with phenanthrene (100 mg kg-1) on wheat growth for 15 days. Under PE-MPs alone and combined with phenanthrene exposure, dose-dependent toxicities in biomass, shoot height and root length were observed. Over 1% PE-MPs stimulate wheat root elongation. Compared with single phenanthrene treatment, the co-contamination of PE-MPs and phenanthrene reduces the accumulation of phenanthrene in wheat roots and leaves. In the range of 0-5%, the activity of wheat root antioxidant enzymes increases with increasing PE-MP concentration; but both phenanthrene and high concentrations (8%) of PE-MPs cause damage to the antioxidant system in wheat roots. In the presence or absence of phenanthrene, the photosynthetic pigment concentration of wheat leaves shows a dual concentration effect of low promotion and high inhibition under PE-MPs stress. The single pollution of PE-MPs destroys the photosynthetic system of wheat leaves, while the co-contamination of PE-MPs and phenanthrene exacerbates this destruction. Therefore, the co-contamination of PE-MPs and phenanthrene causes greater damage to wheat growth. Our findings can help to evaluate the individual and comprehensive toxicity of microplastics and polycyclic aromatic hydrocarbons to crops.

[Repair of cervicofacial scar by forehead expansive skin flap double-pedicled with superficial temporal vessels].

OBJECTIVE: To explore the clinical efficacy of using forehead expansive skin flap double-pedicled with superficial temporal vessels for repairing male cervicofacial scar. METHODS: From July 2005 to June 2009, 13 male patients with an average age of 27 years old (range: 21 - 38) were operated by the above method. The scar-repairing area was from 14 cm × 5 cm to 32 cm × 15 cm. The procedure was carried out in three stages. Firstly, ultrasound Doppler was used to detect and mark the location and orientation of superficial temporal artery. A proper cavity was created under the forehead muscle and then the appropriate expander embedded through the scalp incision. The expander was expanded first by injecting normal saline at 1 or 2 weeks post-operation. After that, the injection was repeated by 3 or 5 days. The volume ratio of injection to expander was (1.5-3.5):1. Secondly the forehead expansive skin flap was designed with proper hair follicle scalp pedicled by bilateral superficial temporal artery when the expansion was completed. After removal of the expander, the rectangle expansive skin flap with hair follicle scalp was transferred through the double pedicle. The cervicofacial scar was excised according to the size of the transferred expansive skin flap (25 cm × 6 cm to 32 cm × 9 cm). And the flap was adjusted with hair follicle scalp to the middle of the chin area in order to obtain the normal beard appearance. Donor site were closed directly. Thirdly, the pedicle skin flap were cut and restored after one month. RESULTS: The volume expanded for each expander ranged from 420 to 800 ml (mean: 660). The average expansion time was 4 months (range: 3 - 5). All flaps survived well. Donor site were closed directly. Both chin and beard looked normal. CONCLUSIONS: Repairing hypertrophic scar and reconstructing beard in cervicofacial area with forehead expansive skin flap pedicled by bilateral superficial temporal artery is a valuable and safe method. The donor site is scarless. And the reconstructed chin and beard are normal both functionally and aesthetically.

Elevating microRNA-122 in blood improves outcomes after temporary middle cerebral artery occlusion in rats.

Because our recent studies have demonstrated that miR-122 decreased in whole blood of patients and in whole blood of rats following ischemic stroke, we tested whether elevating blood miR-122 would improve stroke outcomes in rats. Young adult rats were subjected to a temporary middle cerebral artery occlusion (MCAO) or sham operation. A polyethylene glycol-liposome-based transfection system was used to administer a miR-122 mimic after MCAO. Neurological deficits, brain infarction, brain vessel integrity, adhesion molecule expression and expression of miR-122 target and indirect-target genes were examined in blood at 24 h after MCAO with or without miR-122 treatment. miR-122 decreased in blood after MCAO, whereas miR-122 mimic elevated miR-122 in blood 24 h after MCAO. Intravenous but not intracerebroventricular injection of miR-122 mimic decreased neurological deficits and brain infarction, attenuated ICAM-1 expression, and maintained vessel integrity after MCAO. The miR-122 mimic also down-regulated direct target genes (e.g. Vcam1, Nos2, Pla2g2a) and indirect target genes (e.g. Alox5, Itga2b, Timp3, Il1b, Il2, Mmp8) in blood after MCAO which are predicted to affect cell adhesion, diapedesis, leukocyte extravasation, eicosanoid and atherosclerosis signaling. The data show that elevating miR-122 improves stroke outcomes and we postulate this occurs via downregulating miR-122 target genes in blood leukocytes.

[Repair of scars in submaxillary region using expanded forehead axial flaps with fascia pedicles carrying bilateral frontal branches of superficial temporal artery and vein].

OBJECTIVE: To study the feasibility of applying expanded forehead axial flaps with fascia pedicles carrying bilateral frontal branches of superficial temporal artery and vein (expanded forehead axial flap with double pedicles in brief, EFAF-DP) in repairing scars in submaxillary region. METHODS: Sixteen patients with mandibular scars hospitalized in Department of Burns and Plastic Surgery of the First Hospital Affiliated to Fuzhou General Hospital in Nanjing Military Area Command from July 2005 to December 2009 were repaired with EFAF-DP. The operation consisted of 3 stages. Before operation, the location and course of superficial temporal arteries and veins (STAV) and their frontal and parietal branches were identified with Ultrasonic Doppler blood flow detector. In stage I, STAV were dissected from the frontalis muscle as a pedicle to form a skin soft tissue space to hold the dilator of a proper size. In stage II, after gradual dilation by repeated filling with saline, the dilator was removed. EFAF-DP was dissected to repair mandibular scar. Donor site was closed with sutures. In stage III, flap pedicles were divided and pruned. RESULTS: Flap sizes ranged from 25 cm × 6 cm to 33 cm × 16 cm. The duration of dilation was 3-5 months, with 3.6 months in average. Ten patients underwent the operation of EFAF-DP transplantation and cervical skin dilatation. All flaps survived with healing of wounds. Disorder of venous return at the distal end of one flap was seen after second stage surgery, and it was corrected after comprehensive treatment including relieving spasm and improving venous return. Donor site wounds healed with normally grown hair without cicatricial alopecia along the hairline. Few hairs grew around mandible in one female patient out of the three (no hair grew on flaps of other two patients). This female patient and two male patients requesting for beard plasty received laser depilation treatment 1 to 3 months after discharge, with good result. Other male patients received no special treatment for their beard, and they shaped their beard with shaver. Sixteen patients were followed up for 6 to 24 months, and the shape of the flaps and beard (excluding female patients) were satisfactory with good appearance, satisfactory skin color and texture. The mobility of neck was obviously improved. CONCLUSIONS: EFAF-DP provides bigger areas of a thin flap besides promoting vascularization of new vessels of flap. Extra expanded skin can be directly sutured at the fringe of hairline, which makes skin grafting unnecessary, and decreases the incidence of secondary deformity in donor sites. Some hair carried by the flaps can be directly used for beard reconstruction after rotation to help the male patients have a better appearance.