Rhizosphere bacteria regulated arsenic bioavailability and accumulation in the soil-Chinese cabbage system.

The accumulation of arsenic (As) in Chinese cabbage (Brassica rapa ssp. pekinensis) has recently been a source of concern for a potential risk to human health. It is unknown whether natural variations of As accumulation in different genotypes of Chinese cabbage are related to rhizobacterial characteristics. Experiments were conducted to investigate the mechanisms of rhizobacteria involving in As fates in a soil-Chinese cabbage system using various genotypes using high-throughput sequencing and quantitative PCR. There were significant differences in As accumulation in cabbage leaves between 32 genotypes, and genotypes of low-As-accumulation (LSA) and high-As-accumulation (HSA) were identified. The As concentrations in the shoots of LSA were 23.25 %, 24.19 %, 15.05 %, and 70.69 % lower than those of HSA in seedling stage (SS), rosette stage (RS), heading stage (HS), and mature stage (MS), respectively. Meanwhile, the relative abundances of phyla Patescibacteria (in RS), Acidobacteria and Rokubacteria (in HS) in the rhizosphere of LSA were 60.18 %, 28.19 %, and 45.38 % less than those of HSA, respectively. Additionally, both shoot-As and As translocation factor had significantly positive or negative correlations with the relative abundances of Rokubacteria or Actinobacteria. In LSA rhizosphere, the relative abundances of genera Flavobacterium (in SS), Ellin6055 and Sphingomonas (in HS) were 128.12 %, 83.69 % and 79.50 % higher than those of HSA, respectively. This demonstrated that rhizobacteria contribute to the accumulation and translocation of As in HSA and LSA. Furthermore, the gene copies of aioA and arsM in LSA rhizosphere were 25.54 % and 16.13 % higher than those of HSA, respectively, whereas the gene copies of arsC in LSA rhizosphere were 26.36 % less than those of HSA in MS, indicating that rhizobacteria are involved in As biotransformation in the soil. These results provide a comprehensive understanding of the relationship between characteristics of rhizobacterial communities and As variations in Chinese cabbage genotypes.

Remediation of organic amendments on soil salinization: Focusing on the relationship between soil salts and microbial communities.

Soil salinization has emerged as a major factor with an adverse influence on agricultural green development worldwide. It is necessary to develop high-efficiency and ecologically beneficial management measures for alleviating soil salinization. The experiment of application for cow manure (CM), biochar (BC), and bio-organic fertilizer (BIO) in soil with light salinity was conducted to investigate the remediation of organic materials on soil salinization with melon (Cucumis melo L.) by reducing the availability of saline ions and shifting the soil microbial community. Results showed that BC treatment significantly decreased the EC values of the soil and soil solution by 19.23% and 27.02% and the concentrations of Na+, K+, and Cl- by 13.28%, 13.08%, and 15.21%, respectively, followed by CM and BIO treatments. High-throughput sequencing identified that organic amendments significantly improved the richness of the soil bacterial community and increased the relative abundances of Acidobacteria and Firmicutes by 33.11% and 111.2%, respectively, and the beneficial salt-tolerant bacterial genera Flavobacterium, Bacillus and Arthrobacter by 32.04%, 38.92% and 35.67%, respectively. Additionally, soil Na+, Ca2+, K+ and Cl- were significantly negatively correlated with Acidobacteria and Flavobacterium and were also the most important factors driving the changes in the structure of the soil bacterial communities. The bacterial networks were more complex in the organic amendments treatments than in CK, reflecting through more nodes and links and a higher average clustering coefficient, density and modularity. This study provided a comprehensive understanding of the application of organic amendments in alleviating soil salinization and improving soil bacterial and fungal communities and provides scientific support for agriculture green development.

Photoelectrochemical aptasensing of ofloxacin based on the use of a TiO2 nanotube array co-sensitized with a nanocomposite prepared from polydopamine and Ag2S nanoparticles.

A photoelectrochemical (PEC) method is described for aptamer-based detection of ofloxacin (OFL). It is making use of a TiO2 nanotube array (NTA) that is sensitized with a structure composed of polydopamine and silver sulfide nanoparticles. The NTA were prepared by a two-step synthetic method. First, the TiO2 nanotube electrode was covered with Ag2S nanoparticles via successive ionic layer adsorption and reaction strategy. Next, they were coated with a thin film of polydopamine (PDA) by in-situ polymerization. The inorganic/organic nanocomposites exhibit distinctly enhanced visible-light PEC activity. This was exploited to fabricate a PEC aptasensor. The PDA film serves as both the sensitizer for charge separation and as a support to bind the aptamer against OFL. The aptasensor undergoes a decrease in photocurrent due to the formation of the aptamer-OFL complex. Under the optimized conditions and at a typical working potential of 0 V (vs. Hg/Hg2Cl2), the NTA has a linear response in the 5.0 pM to 100 nM OFL concentration range and a 0.75 pM detection limit (at S/N = 3). The aptasensor was successfully applied to the determination of OFL in spiked milk samples. Graphical abstract Schematic illustration for the preparation and mechanism of the photoelectrochemical aptasensor for ofloxacin. TiO2 NTs: TiO2 nanotube arrays; PDA: polydopamine; MCH: 6-mercapto-1-hexanol; OFL: ofloxacin; PEC: photoelectrochemistry; CB: conduction band; VB: valence band; LUMO: the lowest unoccupied molecular orbital; HOMO: the highest occupied molecular orbital; AA: ascorbic acid.

γδ T cells are essential effectors of type 1 diabetes in the nonobese diabetic mouse model.

γδ T cells, a lineage of innate-like lymphocytes, are distinguished from conventional αß T cells in their Ag recognition, cell activation requirements, and effector functions. γδ T cells have been implicated in the pathology of several human autoimmune and inflammatory diseases and their corresponding mouse models, but their specific roles in these diseases have not been elucidated. We report that γδ TCR(+) cells, including both the CD27(-)CD44(hi) and CD27(+)CD44(lo) subsets, infiltrate islets of prediabetic NOD mice. Moreover, NOD CD27(-)CD44(hi) and CD27(+)CD44(lo) γδ T cells were preprogrammed to secrete IL-17, or IFN-γ upon activation. Adoptive transfer of type 1 diabetes (T1D) to T and B lymphocyte-deficient NOD recipients was greatly potentiated when γδ T cells, and specifically the CD27(-) γδ T cell subset, were included compared with transfer of αß T cells alone. Ab-mediated blockade of IL-17 prevented T1D transfer in this setting. Moreover, introgression of genetic Tcrd deficiency onto the NOD background provided robust T1D protection, supporting a nonredundant, pathogenic role of γδ T cells in this model. The potent contributions of CD27(-) γδ T cells and IL-17 to islet inflammation and diabetes reported in this study suggest that these mechanisms may also underlie human T1D.

Roots recruited distinct rhizo-microbial communities to adapt to long-term Cd and As co-contaminated soil in wheat-maize rotation.

Cd and As accumulation in staple crops poses potential risks to food safety and human health. Rhizo-microbial communities are involved in their behaviors from soil to crops. However, the responses of rhizo-microbial communities to different Cd and As co-contaminated soils in wheat‒maize rotation are still unclear. This study explored whether wheat or maize could recruit distinct rhizo-microbial communities to adapt to long-term co-contaminated soils with low or high levels of Cd and As (LS or HS). It was apparent that the average wheat grain-Cd/As concentrations were 17.96-fold/4.81-fold in LS and 5.64-fold/7.70-fold in HS higher than those in maize grains, significantly depending on the mobility of Cd/As in soil-crop system, especially from soil to root and from straw to grain. Meanwhile, wheat or maize roots recruited specific bacteria and fungi in LS and HS, which were substantially associated with Cd/As bioavailability in rhizosphere. Wheat roots recruited specific bacterial genera norank_c__MB-A2-108 (Actinobacteria), norank_f__JG30-KF-CM45 (Chloroflexi), and norank_o__Rokubacteriales (Methylomirabilota) and fungal genera Metarhizium and Olpidium under HS, and their relative abundances were positively correlated with soil Cd/As bioavailability and were resistant to Cd and As co-contamination. However, bacterial genera Arthrobacter, Nocardioides, Devosia, Skermanella, and Pedobacter were sensitive to Cd and As co-contamination and were specifically enriched in wheat rhizospheres under LS. Meanwhile, the bacterial genus norank_c__KD4-96 (Chloroflexi) was resistant to Cd and As co-contamination under HS and was distinctly enriched in maize rhizosphere. Furthermore, the roots of wheat and maize recruited the bacterial genus Marmoricola in LS, which was sensitive to Cd and As co-contamination, and recruited specific fungal genus Fusicolla in HS, which was tolerant to Cd and As co-contamination. These results confirmed that HS and LS shifted the composition and structure of the rhizo-microbial communities in the wheat-maize rotation to promote crops survival in different long-term Cd and As co-contaminated soils.

Trade-offs of reproductive growth and Cd remobilization regulated Cd accumulation in wheat grains (Triticum aestivum L.).

Minimization of cadmium (Cd) accumulation in wheat grain (Triticum aestivum L.) is an important way to prevent Cd hazards to humans. However, little is known about the mechanisms of varietal variation of Cd accumulation in wheat grain. This study explores the physiological mechanisms of Cd bioaccumulation through field and hydroponic experiments on two wheat varieties of low-Cd-accumulating variety (L-6331) and high-Cd-accumulating variety (H-6049). Field study showed that average Cd accumulative rates in spikes of H-6049 were 1.57-fold of L-6331 after flowering, ultimately grain-Cd of H-6049 was 1.70-fold of L-6331 in Cd-contaminated farmland. The hydroponic experiment further confirmed that more vegetative tissues of L-6331 were involved in the remobilization of Cd, which jointly mitigated the process of Cd loaded to grains when leaf-cutting conducted after Cd stress. Additionally, the L1 and N1 of L-6331 play an especially important role in regulating Cd remobilization, and the larger EVB areas in N1 have the morphological feature that facilitates the transfer of Cd to L1. Overall results implied that low-Cd-accumulating variety initiated more trade-offs of reproductive growth and Cd remobilizatoin under Cd-stress after flowering compared with high-Cd-accumulating variety, and provided new insights into the processes of Cd loaded into wheat grains among different varieties.

Foliar uptake screening: A promising strategy for identifying wheat varieties with low lead accumulation.

Lead (Pb) contamination in wheat grain is of great concern, especially in North China. Atmospheric deposition is a major contributor to Pb accumulation in wheat grain. Screening low Pb accumulating wheat varieties has been an effective method for addressing Pb contamination in wheat grain. However, identifying wheat varieties with low Pb accumulation based on foliar uptake of atmospheric Pb has been neglected. Therefore, two field trials with distinct atmospheric Pb deposition were conducted to screen for stable varieties with low Pb accumulation. It was verified that YB700 and CH58, which have high thousand-grain weights and stable low Pb accumulation in field 1 (0.19 and 0.13 mg kg-1) and field 2 (0.17 and 0.20 mg kg-1), respectively, were recommended for cultivation in atmospheric Pb contaminated farmlands in North China. Furthermore, indoor experiments were conducted to investigate Pb uptake by the roots and leaves of different wheat varieties. Our findings indicate that Pb accumulation in different wheat varieties is primarily influenced by foliar Pb uptake rather than root Pb uptake. Interestingly, there was a positive correlation (p < 0.05) between the Pb concentrations in leaves and the stomatal width and trichome length of the adaxial epidermal surface. Additionally, there is a positive correlation (p < 0.01) between the Pb concentration in the wheat grain and trichome length. In conclusion, the screening of wheat varieties with narrower stomatal widths or shorter trichomes based on foliar uptake pathways is an effective strategy for ensuring food safety in areas contaminated by atmospheric Pb.

[Distribution and Transport of Cadmium and Arsenic in Different Aboveground Parts of Wheat After Flowering].

To investigate the effects of leaves and stems on the accumulation and transport of cadmium(Cd) and arsenic(As) in wheat shoots after flowering, a field experiment was conducted in a typical Cd and As co-contaminated agricultural land to explore the distribution and translocation of Cd and As in the different parts of two wheat cultivars after flowering. The results showed that Cd was mainly distributed in the nodes of two varieties, and the translocation factors of Cd from internode 3 to node 2, from internode 2 to node 1, and from sheath 1 to node 1 were markedly higher than those of other aboveground parts during the grain-filling stage. However, Cd was mainly distributed in the leaves, and the translocation factors of Cd from sheath to leaf and from node 1 to rachis was significantly higher than those of other parts at the mature stage. In addition, the transport capacity of Cd from glume to rachis and from rachis to grain in JM22 was significantly lower than that in SN28, which significantly reduced Cd concentrations in the rachis, glume, and grain of JM22 by 22.3%, 40.8%, and 44.4%, respectively. Meanwhile, As was mainly distributed in the wheat leaves from the grain-filling stage to the mature stage, and As concentrations in the glume and grain of JM22 were 25.8% and 33.3% lower than those of SN28, respectively. Additionally, the translocation factors of As from the sheath to the node were significantly 438% and 190% higher than that from leaf to sheath and from node to internode during the whole grain filling stage and mature stage. Moreover, the translocation factors of As from glumes to grains and from rachis to grains in JM22 were 40.6% and 44.4% lower than that in SN28, respectively. In summary, flag leaf, node 1, and the rachis had regulated Cd transport and accumulation in wheat grains, whereas leaf 3, flag leaf, node 1, the glumes, and the rachis were mainly responsible for As transport and accumulation in wheat grains.

Mechanism of Pb accumulation in Chinese cabbage leaves: Stomata and trichomes regulate foliar uptake of Pb in atmospheric PM2.5.

Chinese cabbage (Brassica rapa ssp. pekinensis) is one of the most popular and frequently consumed leafy vegetables. It was found that atmospheric PM2.5-Pb contributes to Pb accumulation in the edible leaves of Chinese cabbage via stomata in North China during haze seasons with high concentrations of fine particulate matter in autumn and winter. However, it is unclear whether both stomata and trichomes co-regulate foliar transfer of PM2.5-Pb from atmospheric deposition to the leaf of Chinese cabbage genotypes with trichomes. Field and hydroponic experiments were conducted to investigate the effects of foliar uptake of PM2.5-Pb on Pb accumulation in leaves using two genotypes of Chinese cabbage, one without trichomes and one with trichomes. It was verified that open stoma is a prominent pathway of foliar PM2.5-Pb transfer in the short-term exposure for 6 h, contributing 74.5% of Pb accumulation in leaves, whereas Pb concentrations in the leaves of with-trichome genotype in the rosette stage were 6.52- and 1.04-fold higher than that of without-trichome genotype in greenhouse and open field, respectively, which suggests that stomata and trichomes co-regulate foliar Pb uptake of from atmospheric PM2.5. Moreover, subcellular Pb in the leaves was distributed in the following order of cytoplasm (53.8%) > cell wall (38.5%)> organelle (7.8%), as confirmed through high-resolution secondary ion mass spectrometry (NanoSIMS). The Leadmium™ Green AM dye manifested that Pb in PM2.5 entered cellular space of trichomes and accumulated in the basal compartment, enhancing foliar Pb uptake in the edible leaves of cabbage. The results of these experiments are evidence that both stomata and trichomes are important pathways in the regulation of foliar Pb uptake and translocation in Chinese cabbage.

Bioimaging of Pb by LA-ICP-MS and Pb isotopic compositions reveal distributions and origins of Pb in wheat grain.

Atmospheric heavy metal deposition in agroecosystems has increased recently, especially in northern China, which poses serious risks to crop safety and human health via food chain. Wheat grains can accumulate high levels of Pb even when wheat is planted in soils with low levels of Pb. However, the influence of atmospheric deposition on the accumulation and distribution of Pb in wheat grain is still unclear. A field survey was conducted in three districts (A: a district with industrial and traffic pollution; B: a district with traffic pollution; and C: an unpolluted district) in Hebei Province, North China. The grain of wheat cultivated in district A accumulated more Pb from soil and atmospheric deposition than those in other districts, and the bran from district A contained 3.50 and 2.04 times more Pb than those from districts B and C, respectively. The Pb distribution pattern in wheat grain detected by laser ablation inductively coupled mass spectrometry (LA-ICP-MS) was characterized by accumulation mostly in the pericarp and seed coat rather than in the crease, embryo and endosperm. Furthermore, Pb isotopic data showed that airborne Pb was the major source (>50%) of Pb in wheat grain. Interestingly, average contributions of Pb from atmospheric deposition to white flour (78.22%) were higher than its contributions to bran (56.27%). In addition, wheat flag leaves were exposed to PbSO4 at the booting stage, and much greater Pb accumulation (0.33-0.48 mg/kg) was observed in exposed wheat grain than in the control (P < 0.05), PbSO4 constituted most (82.80-100%) of the Pb in the wheat grain. In summary, the results confirmed the efficient foliar Pb uptake and transfer from atmospheric deposition into wheat grain. It would be a new sight for understanding the contribution of airborne Pb to Pb accumulation in wheat grains.

Contribution of PM2.5-Pb in atmospheric fallout to Pb accumulation in Chinese cabbage leaves via stomata.

Foliar uptake of Pb is especially important when Chinese cabbage (Brassica rapa spp. pekinensis), having a large leaf surface area, is cultivated in North China during seasons with heavy haze. However, the mechanisms of foliar Pb uptake via stomata by Chinese cabbage exposed to atmospheric fallout are unclear. A field experiment was conducted to explore the impacts of Pb in particulate matter with sizes ≤ 2.5 µm (PM2.5-Pb) from atmospheric fallout to Pb accumulation in cabbage leaves through stomata. Cabbage varieties with low-Pb-accumulation (LPA) and high-Pb-accumulation (HPA) were examined using inductively coupled plasma-mass spectrometry and scanning electron microscopy/energy-dispersive X-ray analysis. The 206Pb/207Pb and 208Pb/207Pb ratios of PM2.5, plants, and soil demonstrated that the major source of Pb in cabbage leaves was PM2.5. The average width and length of the stomatal apertures were 7.14 and 15.61 µm for LPA cabbage and 8.10 and 16.64 µm for HPA cabbage, which are large enough for PM2.5-Pb to enter the leaves. The HPA cabbage had significantly higher stomatal width-to-length ratios than the LPA cabbage, indicating that the former trapped much more PM2.5-Pb and accumulated more Pb. These results clarify the contributions of the stomatal characteristics to PM2.5-Pb accumulation in the edible parts of Chinese cabbage.

Resident skin-specific gammadelta T cells provide local, nonredundant regulation of cutaneous inflammation.

The function of the intraepithelial lymphocyte (IEL) network of T cell receptor (TCR) gammadelta(+) (Vgamma5(+)) dendritic epidermal T cells (DETC) was evaluated by examining several mouse strains genetically deficient in gammadelta T cells (delta(-/-) mice), and in delta(-/-) mice reconstituted with DETC or with different gammadelta cell subpopulations. NOD.delta(-/-) and FVB.delta(-/-) mice spontaneously developed localized, chronic dermatitis, whereas interestingly, the commonly used C57BL/6.delta(-/-) strain did not. Genetic analyses indicated a single autosomal recessive gene controlled the dermatitis susceptibility of NOD.delta(-/-) mice. Furthermore, allergic and irritant contact dermatitis reactions were exaggerated in FVB.delta(-/-), but not in C57BL/6.delta(-/-) mice. Neither spontaneous nor augmented irritant dermatitis was observed in FVB.beta(-/-) delta(-/-) mice lacking all T cells, indicating that alphabeta T cell-mediated inflammation is the target for gammadelta-mediated down-regulation. Reconstitution studies demonstrated that both spontaneous and augmented irritant dermatitis in FVB.delta(-/-) mice were down-regulated by Vgamma5(+) DETC, but not by epidermal T cells expressing other gammadelta TCRs. This study demonstrates that functional impairment at an epithelial interface can be specifically attributed to absence of the local TCR-gammadelta(+) IEL subset and suggests that systemic inflammatory reactions may more generally be subject to substantial regulation by local IELs.

Spraying silicon to decrease inorganic arsenic accumulation in rice grain from arsenic-contaminated paddy soil.

Addition of Si to soil can reduce As uptake and accumulation in rice, while also enhancing As release from soil particles via competing sorption sites in soil minerals with As. Foliar application of Si might be an alternative pathway to reduce As accumulation in rice. It is not clear which growing stage would be better for spraying different types of Si solution to reduce inorganic As in edible parts of rice. Soil pot experiments were conducted to investigate whether total As and inorganic As accumulation in rice grains was alleviated via spraying Si in As-contaminated paddy soil. The results showed that foliar Si application at the tillering or jointing stage significantly reduced As concentrations in rice husks and grain via inhibiting the translocation of As from straw to husk or grain compared with other growing stages. Spraying of Si at the tillering stage markedly decreased the concentrations of inorganic As in rice bran and polished rice, accounting for 27.3% and 61.4% respectively. Furthermore, spraying Si solution mixed with surfactant-Tween 80 not only dramatically reduced the total As in rice tissues by 48.8%, but also significantly alleviated the accumulation of inorganic As in rice grain by 49.2%. Spraying Si restricted inorganic As in rice grain through the mechanism by which foliar Si application at tillering stage increased the Si concentrations in shoot and root, which downregulated Si transporters of Lsi1 and Lsi2 in the root and Lsi6 in the blade and sheath significantly, and finally decreased As uptake and transport. Therefore, spraying Si is an alternative and efficient pathway to reduce inorganic As accumulation of rice grain in As-contaminated soil.

Label-Free Electrochemical Aptasensor for Sensitive Detection of Malachite Green Based on Au Nanoparticle/Graphene Quantum Dots/Tungsten Disulfide Nanocomposites.

A label-free electrochemical aptasensor was fabricated to sensitively determine malachite green (MG) based on Au nanoparticles/graphene quantum dots-tungsten disulfide nanosheet composite film modified glassy carbon electrode (AuNPs/GQDs-WS2/GCE). A facial strategy for the self-assembly of graphene quantum dots (GQDs) on tungsten disulfide nanosheets (WS2) was developed to fabricate 0D/2D nanocomposites. As-prepared GQDs-WS2 hybrids exhibited significantly enhanced electrocatalytic properties, and were first used as electroactive materials to construct electrochemical aptasensor. The AuNPs/GQDs-WS2/GCE was prepared through depositing Au nanoparticles on the surface of the GQDs-WS2 film, which acted as the electrochemical sensing matrix to covalently immobilize the aptamers of MG via the Au⁻S bond. In this label-free proposal, the aptasensor was applied to detect MG by monitoring voltammetric signal resulted from electrochemical oxidation of the MG captured by the aptamer. Under the optimized conditions, the aptasensor showed a wide linear range from 0.01 to 10 µM for MG detection with a low detection limit of 3.38 nM (S/N = 3). The method was applied to determination of MG in spiked fish samples and gave satisfactory results.

A "signal-on" photoelectrochemical aptasensor based on graphene quantum dots-sensitized TiO2 nanotube arrays for sensitive detection of chloramphenicol.

An ultrasensitive photoelectrochemical (PEC) aptasensor was designed for detection of chloramphenicol (CAP) based on graphene quantum dots-sensitized TiO2 nanotube arrays (GQDs/TiO2 NTs). The GQDs/TiO2 NTs nanohybrids were prepared by a coupling technique of linker molecule binding and electrophoretic deposition. It exhibited significantly enhanced visible-light photoelectrochemical activity, which was firstly employed as the photoactive material for fabrication of PEC aptasensor. As the recognition unit, the aptamers of CAP were immobilized on GQDs/TiO2 NTs photoelectrode via π-π stacking interaction between GQDs and the nucleobases of the aptamer. In this signal-on proposal, the aptasensor was used for the label-free analysis of CAP by monitoring the increase in photocurrent that resulted from the formation of aptamer-CAP bioaffinity complexes with ascorbic acid as an efficient electron donor for scavenging photogenerated holes. Under the optimized conditions, the aptasensor showed a wide linear range from 0.5 nM to 100 nM for CAP detection with a low detection limit of 57.9 pM (S/N = 3). With good selectivity and sensitivity, the PEC aptasensor was applied to the determination of CAP in spiked honey samples with satisfactory results, suggesting that the GQDs/TiO2 NTs photoelectrode has a promising application in constructing PEC sensor platform.

Characteristics of heavy metals in soils and grains of wheat and maize from farmland irrigated with sewage.

The farmland irrigation with the sewage is a common and better pathway to save the resource of groundwater in Northern China. The investigation was conducted in the farmland along the Fuhe River to explore characteristics of heavy metals in soils and grains of wheat and maize from a long-term sewage-irrigated area of Baoding region. The results showed that the topsoil with long-term sewage irrigation accumulated more Cd, Pb, and Hg compared with that of soil irrigated with groundwater and their corresponding natural background values. Cd concentrations in 48% of sewage-irrigated soil samples exceeded the Chinese safety limitation at 0.6 mg/kg, but less Cd accumulated in crop grains and did not pose the potential health risk. On the contrary, Pb levels in soils irrigated with sewage were lower than the safety limitation but Pb concentrations in 24% of wheat grain samples exceeded the Chinese national safety limit. Long-term sewage irrigation did not increase As, Cr, and Ni concentrations in soils or crop grains. The target hazard quotient (THQ) of heavy metals in edible grains of crops was selected to assess their risk to human health. Total THQ values were higher than 1.0 for the wheat samples from sewage-irrigated area and both sewage-irrigated and smelter-impacted areas, and As is the main contributor to the total THQ and posed the potential risk to human health. Therefore, the accumulation of Cd, Pb, Hg, and As in soils and crops in sewage-irrigated area should be monitored continuously to ensure food safety and security.

[The prognostic role of electromyography in vocal cord paralysis].

OBJECTIVE: To predict the recovery of vocal cord paralysis (VCP) by using electromyography (EMG). METHOD: The characteristics of EMG of 46 patients with unilateral VCP were assessed to determine the most useful factors in determining prognosis. The factors include the duration, amplitude, waveform morphology, root-mean-square, and time interval. RESULT: A positive prognosis for laryngeal recovery was indicated when the following EMG features were present in the immobile vocal fold during voluntary tasks if EMG was performed during 6 months of the onset of VCP: normal motor unit waveform morphology; no electrical silence. This predictive rate is 76%. When the root-mean-square value is greater than 26 microV, the predictive rate is 80%. On the basis of the criteria, all the prognostic rate is 84%. CONCLUSION: The results support the concept that EMG record is valuable in determining prognosis performed during 6 months of the onset of VCP.

[Glottic measurement and vocal evaluation before and after adult arytenoidectomy].

OBJECTIVE: To study minimal glottic area which can acquire sufficient airway for decannulation and maximal glottic area which can maintain preoperative vocal function on adult bilateral vocal cord paralysis with unilateral arytenoidectomy. METHODS: Sixteen adult received microscopic right arytenoidectomy with Diomed-25 laser under general anaesthesia and sustained laryngoscope from September 1998 to February 2003. The pre-postoperative glottic measurement and vocal acoustic parameters were analyzed. RESULTS: The postoperative maximal glottic area, maximal posterior glottic width and maximal opening angle between bilateral vocal cords of the 15 decannulated cases were (45.93 +/- 6.56) mm2, (4.97 +/- 0.73) mm and (24.34 +/- 4.74) degrees respectively. Compared with preoperative period, there were significant difference. Pre-postoperative acoustic parameters (Jitter, Shimmer, harmonics-noise ratio) were analyzed and no significant difference were found (P > 0.05, but there are significant difference in NNE (normalized noise energy) and MPT (maximum phonation time) (P < 0.05). Except for three cases whose postoperative glottic area were more than 50. 1 mm2, there were no significant difference in pre and postoperative NNE (P > 0.05). The minimal glottic area decannulated was 38.0 mm2. The more opening maximal glottic area, the greater of NNE because of bigger closing gap. Noticeable increase of NNE was observed when maximal opening glottic area was up to 50.1 mm2. CONCLUSIONS: The minimal glottic area for decannulation should be 38.0 mm2, and the maximal glottic area for maintaining preoperation vocal function should be 50.1 mm2 on adult bilateral voca cord paralysis with laser aryntenoidectomy.

[Reinnervation of the posterior cricoarytenoid muscle by the phrenic nerve for bilateral vocal cord paralysis in humans].

OBJECTIVE: To reestablish the respiratory abduction of the paralyzed vocal cord through reinnervation of the posterior cricoarytenoid(PCA) muscle by the phrenic nerve in humans. METHODS: In six cases with bilateral recurrent laryngeal nerve paralysis, the phrenic nerve was anastomosed to the anterior branch of recurrent laryngeal nerve, while the adductor branch of recurrent laryngeal nerve was severed and its proximal end was implanted into the PCA muscle belly in one side, for the other side nerve-muscle pedicle technique was used. All cases had been subjected to preoperative and postoperative video laryngoscopy, stroboscopy, electromyography, voice recording and acoustic analysis. RESULTS: Among the 6 patients, it is observed in five cases' phrenic nerve reinnervation side the inspiratory abducent motion evidently recovered, and the abducent range was from 3 to 5 mm, While only slight abductent motion or no motion could be recorded on the other side reinnervated with nerve-muscle pedicle technique, and the vocal cord excursion on this side was less than 1 mm in all cases. It is because the glottis is broad enough for the patients to have daily activities without short of breath, so all of them were decannulated postoperatively. The reinnervated PCA muscle by the phrenic nerve showed typical inspiratory high frequency discharge with 100-200 ms delay as compared with the other side, indicating the phrenic motoneuron pattern. No long-term diaphragmatic paralysis and lesion of respiratory function was found. All cases' voice was not weakened, and no aspiration occurred. CONCLUSION: The phrenic reinnervation is feasible clinically for treating vocal cord paralysis, and it is found to be more effective for restoring inspiratory abducent function than the nerve-muscle pedicle technique.

[Laryngeal reinnervation for unilateral traumatic recurrent laryngeal nerve injuries].

OBJECTIVE: To investigate 5 procedures of laryngeal reinnervation for unilateral vocal cord paralysis induced by traumatic recurrent laryngeal nerve injury. METHODS: 35 cases were selected for our study, all patients had unilateral recurrent laryngeal nerve injury, including 8 for nerve decompression, 6 for end to end anastomosis of recurrent laryngeal nerve, 16 for main branch of ansa cervicalis anastomosis to recurrent laryngeal nerve, 3 for nerve muscular pedicle and 2 for nerve implantation. All cases have been subjected to preoperative and postoperative voice recording, acoustic analysis, videolaryngoscopy, strobscopy and electromyography. RESULTS: It is found the adductory and abductory motion of the vocal cord restored in 5 cases with less than 4 months course who received nerve decompression. Although functional motion of vocal cord was not seen in two patients who received nerve decompression with a course longer than 4 months and one less than 4 months, and in all cases who received ansa cervicalis anastomosis and end to end anastomosis of recurrent laryngeal nerve, these procedures resulted in medialization of vocal cord and the mass and tension of the reinnervated vocal cord may become much the same as the contralateral normal vocal cord, thus resuming symmetric vibration of the vocal cords and physiological phonation. Nerve muscular pedicle technique and nerve implantation enabled adductory muscles to be reinnervated, thus improving severe hoarseness, but they didn't restore normal voice. CONCLUSIONS: (1) Nerve decompression seems to be the best procedure in laryngeal reinnervation; (2) Main branch of ansa cervicalis technique raises satisfactory reinnervation of adductor muscles; (3) Selection of the laryngeal reinnervation protocols should depend on the course, severity and type of nerve injury.