Foliar-selenium enhances plant growth and arsenic accumulation in As-hyperaccumulator Pteris vittata: Critical roles of GSH-GSSG cycle and arsenite antiporters PvACR3.

It is known that selenium (Se) enhances plant growth and arsenic (As) accumulation in As-hyperaccumulator Pteris vittata, but the associated mechanisms are unclear. In this study, P. vittata was exposed to 50 µM arsenate (AsV) under hydroponics plus 25 or 50 µM foliar selenate. After 3-weeks of growth, the plant biomass, As and Se contents, As speciation, malondialdehyde (MDA) and glutathione (GSH and GSSG) levels, and important genes related to As-metabolism in P. vittata were determined. Foliar-Se increased plant biomass by 17 - 30 %, possibly due to 9.1 - 19 % reduction in MDA content compared to the As control. Further, foliar-Se enhanced the As contents by 1.9-3.5 folds and increased arsenite (AsIII) contents by 64 - 136 % in the fronds. The increased AsV reduction to AsIII was attributed to 60 - 131 % increase in glutathione peroxidase activity, which mediates GSH oxidation to GSSG (8.8 -29 % increase) in the fronds. Further, foliar-Se increased the expression of AsIII antiporters PvACR3;1-3;3 by 1.6 - 2.1 folds but had no impact on phosphate transporters PvPht1 or arsenate reductases PvHAC1/2. Our results indicate that foliar-Se effectively enhances plant growth and arsenic accumulation by promoting the GSH-GSSG cycle and upregulating gene expression of AsIII antiporters, which are responsible for AsIII translocation from the roots to fronds and AsIII sequestration into the fronds. The data indicate that foliar-Se can effectively improve phytoremediation efficiency of P. vittata in As-contaminated soils.

Selenium alleviates chromium stress and promotes chromium uptake in As-hyperaccumulator Pteris vittata: Cr reduction and cellar distribution.

Arsenic-hyperaccumulator Pteris vittata exhibits remarkable absorption ability for chromium (Cr) while beneficial element selenium (Se) helps to reduce Cr-induced stress in plants. However, the effects of Se on the Cr uptake and the associated mechanisms in P. vittata are unclear, which were investigated in this study. P. vittata plants were grown for 14 days in 0.2-strength Hoagland solution containing 10 (Cr10) or 100 µM (Cr100) chromate (CrVI) and 1 µM selenate (Se1). The plant biomass, malondialdehyde contents, total Cr and Se contents, Cr speciation, expression of genes associated with Cr uptake, and Cr subcellular distribution in P. vittata were determined. P. vittata effectively accumulated Cr by concentrating 96-99% in the roots under Cr100 treatment. Further, Se substantially increased its Cr contents by 98% to 11,596 mg kg-1 in the roots, which may result from Se's role in reducing its oxidative stress as supported by 27-62% reduction in the malondialdehyde contents. Though supplied with CrVI, up to 98% of the Cr in the roots was reduced to insoluble chromite (CrIII), with 83-89% being distributed on root cell walls. Neither Cr nor Se upregulated the expression of sulfate transporters PvSultr1;1-1;2 or phosphate transporter PvPht1;4, indicating their limited role in Cr uptake. P. vittata effectively accumulates Cr in the roots mainly as CrIII on cell walls and Se effectively enhances its Cr uptake by reducing its oxidative stress. Our study suggests that Se can be used to enhance P. vittata Cr uptake and reduce its oxidative stress, which may have application in phytostabilization of Cr-contaminated soils.

Copper enhanced arsenic-accumulation in As-hyperaccumulator Pteris vittata by upregulating its gene expression for As uptake, translocation, and sequestration.

In contaminated soils, arsenic (As) often co-exists with copper (Cu). However, its effects on As accumulation and the related mechanisms in As-hyperaccumulator Pteris vittata remain unclear. In this study, P. vittata plants were exposed to 50 µM As and/or 50 µM Cu under hydroponics to investigate the effects of Cu on plant growth and As accumulation, as well as gene expression related to arsenic uptake (P transporters), reduction (arsenate reductases), and translocation and sequestration (arsenite antiporters). After 14 d of growth and compared to the As treatment, the As concentration in P. vittata fronds increased by 1.4-times from 793 to 1131 mg·kg-1 and its biomass increased by 1.2-fold from 18.0 to 21.1 g·plant-1 in the As+Cu treatment. Copper-enhanced As accumulation was probably due to upregulated gene expressions related to As-metabolisms including As uptake (1.9-fold in P transporter PvPht1;3), translocation (2.1-2.4 fold in arsenite antiporters PvACR3/3;2) and sequestration (1.5-2.0 fold in arsenite antiporters PvACR3;1/3;3). Our results suggest that moderate amount of Cu can help to increase the As accumulation efficiency in P. vittata, which has implication in its application in phytoremedation in As and Cu co-contaminated soils.

[Preliminary report of laryngeal preservation in the surgical salvage of recurrent laryngeal cancer].

OBJECTIVE: To explore the plausibility of laryngeal preservation in salvage surgery of recurrent laryngeal carcinoma. METHODS: Comprehensive clinical and radiological assessments on a specific group of patients with recurrent laryngeal cancer and their relapsed tumors were carried out to determine the methods and indications of salvage surgery for preservation of laryngeal functions. Salvage surgery with preservation of larynx was performed in a selective of 36 laryngeal cancer patients with relapsed tumors in their larynges after radiotherapy or partial laryngectomies. All patients were regularly followed up after discharge from the hospital. Postoperative survival was calculated by Kaplan-Meier's method. RESULTS: Among various laryngeal preservation regimens given, a second transoral laser surgery was carried out in 4 cases, horizontal hemilaryngectomy in 4 cases, vertical hemilaryngectomy in 13 cases and Majer-Piquet's operation in 15 cases, respectively. Simultaneous neck dissection was conducted in 18 cases. Postoperative complications were encountered in 6 cases, most common of which were local infection and laryngeal fistula with no hospital mortality and other major morbidities. Five cases with immediate postoperative complications were cured with proper management. The remained one case undergone vertical partial laryngectomy for recurrence after tumor resection via laryngeal fissure received postoperative radiation due to positive surgical margin, and complicated laryngeal atresia and obstruction with loss of his laryngeal functions. Local recurrence was observed in 5 cases and simultaneous locoregional recurrence was seen in 1 case, with the resulting local control rate of 83.3% (30/36). The 3-year postoperative survival rate was 80.6%. The cause of death was tumor recurrence in 3 cases, distant metastasis in 3 cases and non-tumor-associated disease (heart attack) in 1 case, respectively. CONCLUSIONS: Salvage surgery with laryngeal preservation can be carried out in the selected cases with early or locally-confined recurrent lesions within the larynx, on the condition that the recurrent tumors be assessed thoroughly and indications for associated surgical techniques be evaluated properly.

[Long-term results of one stage tracheoesophageal end-side anastomosis voice restoration after total laryngectomy].

OBJECTIVE: The purpose of this study is to discuss long-term results of one different kind of voice restoration after total laryngectomy with 10 years experience. METHOD: One stage tracheoesophageal end-side anastomosis after total laryngectomy was performed in 36 patients from 1991-1996. The key technique of this operation is to make a tongue-ship flap(1.5 cm x 1.5 cm-1.8 cm x 1.5 cm) with tracheal membranous part and dissect it from the esophagus to 1 cm below the upper incisal margin of trachea. Then a 0.8 cm middle vertical incision was made on the lowest anterior wall of the separated esophagus. Folding the tongue-ship flap posteriorly to approximate the esophagus incision and make an end-side anastomosis. Close the upper incisal margin of trachea with left to right direction suture. The follow up time is 5 - 10 year. One lost follow 2.5 years later and was judged as dead. RESULT: The short-term and long-term success rate were 69% (25/36) and 83% (30/36) respectively. The 3-, 5- and 10 year survival rate are 72%, 69%, 69%, respectively. CONCLUSION: This technique does not change the pattern of total laryngectomy and various neck dissections do not affect voice rehabilitation. Advantages of the operation: easy to operate and learn; the special form of tracheoesophageal shunt (high in the tracheal side and low in esophageal side) prevents the aspiration; high successful rate, excellent speech, fluent language, good acceptability and lower aspiration.