蚯蚓在重金属污染土壤生物修复中的应用潜力

综述了不同生态类型的蚯蚓的特性及其土壤生态功能;总结了其对土壤重金属富集和有效性的作用及影响重金属活化的机理,并指出目前相关的生物化学机理研究的不足及其未来研究方向.同时,文章针对蚯蚓在农业和环境领域的应用现状,提出其应用于重金属污染土壤的植物提取技术的可能性,在未来工作中应加强真实污染土壤室内模拟和田间试验研究,进一步探索筛选和繁育本地蚯蚓品种以及添加有机物等相关技术.     

Effectiveness of soil N availability indices in predicting site productivity in the oil sands region of Alberta

Background and aims

Quantitative relationships between soil N availability indices and tree growth are lacking in the oil sands region of Alberta and this can hinder the development of guidelines for the reclamation of the disturbed landscape after oil sands extraction. The aim of this paper was to establish quantitative relationships between soil N availability indices and tree growth in the oil sands region of Alberta.

Methods

In situ N mineralization rates, in situ N availability measured in the field using Plant Root Simulators (PRS? probes), laboratory aerobic and anaerobic soil N mineralization rates, and soil C/N and N content were determined for both the forest floor and the 0–20?cm mineral soil in eight jack pine (Pinus banksiana Lamb.) stands in the oil sands region in northern Alberta. Tree growth rates were determined based on changes in tree ring width in the last 6?years and as mean annual aboveground biomass increment.

Results

Soil N availability indices across those forest stands varied and for each stand it was several times higher in the forest floor than in the mineral soil. The in situ and laboratory aerobic and anaerobic soil N mineralization rates, soil mineralized N, in situ N availability measured using PRS probes, soil C/N ratio and N content in both the forest floor and mineral soil, as well as stand age were linearly correlated with tree ring width of jack pine trees across the selected forest stands, consistent with patterns seen in other published studies and suggesting that N availability could be a limiting factor in the range of jack pine stands studied.

Conclusions

In situ and laboratory aerobic and anaerobic N mineralization rates and soil C/N ratio and N content can be used for predicting tree growth in jack pine forests in the oil sand region. Laboratory based measurements such as aerobic and anaerobic N mineralization rates and soil C/N ratio and N content would be preferable as they are more cost effective and equally effective for predicting jack pine growth.     

Identification and characterization of a xyloglucan-specific family 74 glycosyl hydrolase from Streptomyces coelicolor A3(2)

The sco6545 gene of Streptomyces coelicolor A3(2) was nominated as a putative cellulase with 863 mature-form amino acids (90.58 kDa). We overexpressed and purified Sco6545 and demonstrated that the protein is not a cellulase but a xyloglucan-specific glycosyl hydrolase which cleaves xyloglucan at unbranched glucose residues.     

Preparation and evaluation of antioxidant peptides from ethanol-soluble proteins hydrolysate of Sphyrna lewini muscle

To get high yield of ethanol-soluble proteins (EP) and the antioxidant peptides from Sphyrna lewini muscle, orthogonal experiments (L(9)(3)(4)) were applied to optimize the best extraction conditions and enzyme hydrolysis conditions. The yield of EP reached 5.903±0.053% under the optimum conditions of ethanol concentration 90%, solvent to material ratio 20:1, extraction temperature of 40°C and extraction time of 80min. The antioxidant SEPH (EP hydrolysate of S. lewini muscle) was prepared by using papain under the optimum conditions of enzymolysis time 2h, total enzyme dose 1.2%, enzymolysis temperature 50°C and pH 6, and its DPPH radical scavenging activity reached 21.76±0.42% at the concentration of 10mg/ml. Two peptides (F42-3 and F42-5) were isolated from SEPH by using ultrafiltration, anion-exchange chromatography, gel filtration chromatography and RP-HPLC. The structures of F42-3 and F42-5 were identified as Trp-Asp-Arg and Pro-Tyr-Phe-Asn-Lys with molecular weights of 475.50Da and 667.77Da, respectively. F42-3 and F42-5 exhibited good scavenging activity on hydroxyl radical (EC(50) 0.15mg/ml and 0.24mg/ml), ABTS radical (EC(50) 0.34mg/ml and 0.12mg/ml), and superoxide anion radical (EC(50) 0.09mg/ml and 0.11mg/ml), but moderate DPPH radical (EC(50) 3.63mg/ml and 4.11mg/ml). F42-3 and F42-5 were also effectively against lipid peroxidation in the model system and peroxyl free radical scavenging in β-carotene linoleic acid assay. Their high activities were due to the smaller size and the presence of antioxidative amino acids within the peptide sequences.     

Expression of the c-Met Proto-Oncogene and Integrin α5β1 in Human Gastric Cardia Adenocarcinoma

The hepatocyte growth factor receptor c-Met, a receptor tyrosine kinase, and Integrin α5β1, one of the main ECM receptors of hepatocytes have been reported to play important roles in tumor growth by activating mitogenic signaling pathways. In human gastric cardia adenocarcinoma, however, expression of the c-Met and Integrin α5β1 have not been reported. Here we examined the mRNA levels and protein expressions of these two genes and their relationship in human normal gastric cardia mucosa and primary carcinomas. Quantitative real-time PCR was used to analyze the mRNA expression of both c-Met and Integrin α5β1. The relationship between c-Met and Integrin α5β1 expression and the histologic characteristics of tumors were studied. Western blot analysis was performed to investigate the presence of c-Met and Integrin α5β1. The expression patterns of c-Met and Integrin α5β1 in 45 frozen slides of cardia adenocarcinoma were identified by immunohistochemistry. Our results indicate that the expression of c-Met and of Integrin α5β1 was significantly associated with tumor differentiation, TNM, and metastasis via the lymphogenic route. A significant positive correlation was also found between c-Met and Integrin α5β1 mRNA expression, suggesting that expression of c-Met and Integrin α5β1 has mechanical significance in the early stages of human gastric cardia adenocarcinoma.     

Stability and bioactivity studies on dipeptidyl peptidase IV resistant glucogan-like peptide-1 analogues

Glucagon-like peptide-1 (GLP-1) was once considered as an ideal anti-diabetic candidate for its important role in maintaining glucose homeostasis through the regulation of islet hormone secretion, as well as hepatic and gastric function. However, the major therapeutic obstacle for using native GLP-1 as a therapeutic agent is its very short half-life primarily due to their degradation by the enzyme dipeptidyl peptidase IV (DPP-IV). In this study, GLP-1 analogues with modifications in amino acid site 8, 22 and 23 were synthesized using solid phase peptide synthesis. Resistance of these analogues to DPP-IV cleavage was investigated in vitro by incubation of the peptides with DPP-IV or human plasma. Glucoregulating efficacy of the analogues was evaluated in normal Kunming mice using intraperitoneal glucose tolerance model. Glucose lowering effect of combination therapy (analogue plus Vildagliptin) has also been studied. In vitro studies showed that the modified analogues were much more stable than native GLP-1 (nearly 100% of the peptide keep intact after 4 h incubation). In vivo biological activity evaluation revealed that His8-EEE (the most potent GLP-1 analogues in this study) exhibited significantly improved glycemic control potency (approximately 4.1-fold over saline and 2.5-fold over GLP-1) and longer time of active duration (at least 5 h). Combination therapy also showed the trend of its superiority over mono-therapy. Modified analogues showed increased potency and biological half-time compared with the native GLP-1, which may help to understand the structure-activity relationship of GLP-1 analogues.     

Purification, characterization and gene cloning of the killer toxin produced by the marine-derived yeast Williopsis saturnus WC91-2

As the killer toxin produced by Williopsis saturnus WC91-2 could kill many sensitive yeast strains, including the pathogenic ones, the extracellular killer toxin in the supernatant of cell culture of the marine yeast strain was purified and characterized. The molecular mass of the purified killer toxin was estimated to be 11.0kDa according to the data from SDS-PAGE. The purified killer toxin had killing activity, but could not hydrolyze laminarin. The optimal conditions for action of the purified killer toxin against the pathogenic yeast Metschnikowia bicuspidate WCY were the assay medium with 10% NaCl, pH 3-3.5 and temperature 16°C. The gene encoding the killer toxin from the marine killer yeast WC91-2 was cloned and the ORF of the gene was 378bp. The deduced protein from the cloned gene encoding the killer toxin had 125 amino acids with calculated molecular weight of 11.6kDa. It was also found that the N-terminal amino acid sequence of the purified killer toxin had the same corresponding sequence deduced from the cloned killer toxin gene in this marine yeast, confirming that the purified killer toxin was indeed encoded by the cloned gene.     

Involvements of calcium channel and potassium channel in Danshen and Gegen decoction induced vasodilation in porcine coronary LAD artery

Danshen (Salviae Miltiorrhizae Radix) and Gegen (Puerariae Lobatae Radix) have been widely used in treating cardiovascular diseases for thousands of years in China. The present study was carried out to evaluate the effects of a Danshen and Gegen decoction (DG) on the vascular reactivity of a porcine isolated coronary artery and the underlying mechanisms involved. Porcine coronary rings were precontracted with 15nM U46619. The involvement of endothelium-dependent mechanisms was explored by removing the endothelium; the involvement of potassium channels was investigated by the pretreatment of the artery rings with various blockers, and the involvement of the calcium channels was investigated by incubating the artery rings with Ca(2+)-free buffer and priming them with high [K(+)] prior to adding CaCl(2) to elicit contraction. The involvement of Ca(2+) sensitization was explored by evaluating the Rho-activity expression. The results revealed that DG elicited a concentration-dependent relaxation on a U46619-precontracted coronary artery ring. These relaxation responses were not altered by the pretreatment of inhibitors of endothelium-related dilator synthases, cGMP and cAMP pathway inhibitors, potassium channel (BK(Ca), SK(Ca), K(V) and K(ATP)) blockers and endothelium removal. The K(IR) channel blocker BaCl(2) only slightly attenuated the DG-induced relaxation. However, the Ca(2+)-induced artery contraction was inhibited by DG. Additionally, the expression of the phosphorylated myosin light chain was inhibited by DG whereas the activity of RhoA was not affected. Therefore, DG could be a useful cardioprotective agent for vasodilation in patients who have hypertension.     

Borapetoside C from Tinospora crispa improves insulin sensitivity in diabetic mice

Diabetes mellitus (DM) often leads to disability from vascular complications and neurological complications. Tinospora crispa has been widely used in Asia and Africa as a remedy for diabetes and other diseases. In this study, we investigated the hypoglycemic actions of borapetoside C isolated from T. crispa, and the mechanisms underlying its actions. Acute treatment with borapetoside C (5mg/kg, i.p.) attenuated the elevated plasma glucose induced by oral glucose in normal and type 2 DM (T2DM) mice. Compared to the effect of injected insulin (0.5 IU/kg), borapetoside C caused a more prominent increase of glycogen content in skeletal muscle of T2DM mice, but a less increase in type 1 DM (T1DM) mice. Combined treatment of a low dose borapetoside C (0.1mg/kg, i.p.) plus insulin enhanced insulin-induced lowering of the plasma glucose level and insulin-induced increase of muscle glycogen content. Continuous treatment with 5mg/kg borapetoside C (twice daily) for 7 days increased phosphorylation of insulin receptor (IR) and protein kinase B (Akt) as well as the expression of glucose transporter-2 (GLUT2) in T1DM mice. Combined treatment of a low dose borapetoside C (0.1mg/kg, twice daily) plus insulin for 7 days enhanced insulin-induced IR and Akt phosphorylation and GLUT2 expression in the liver of T1DM mice. This study proved that borapetoside C can increase glucose utilization, delayed the development of insulin resistance and enhanced insulin sensitivity. The activation of IR-Akt-GLUT2 expression and the enhancement of insulin sensitivity may contribute to the hypoglycemic action of borapetoside C in diabetic mice.     

The Cold Awakening of <Emphasis Type="Italic">Doritaenopsis</Emphasis> ‘Tinny Tender’ Orchid Flowers: The Role of Leaves in Cold-induced Bud Dormancy Release

Massive flowering of tropical Phalaenopsis orchids is coordinated by the cold-induced release of reproductive bud dormancy. Light and temperature are the two key factors integrated by the dormancy mechanism to both stop and reactivate the meristem development of many other angiosperm species, including fruit trees and ornamental plants. It is well established that leaves and roots play a major role in inducing flower development; however, currently, knowledge of molecular events associated with reproductive bud dormancy release in organs other than the bud is limited. Using differential gene expression, we have shown that the leaves of a hybrid of Phalaenopsis species, Doritaenopsis ‘Tinny Tender’, undergo major metabolic modifications. These changes result in the production of sucrose and amino acids, both of which can sustain bud outgrowth, and auxin and ethylene, which may play important roles in awaking the dormant buds. Intake of abscisic acid and synthesis of the hormone jasmonate may also explain the inhibition of vegetative growth that coincides with bud growth. Interestingly, many genes that were upregulated by cold treatment are homologous for genes involved in flower induction and vernalization in Arabidopsis, indicating that processes regulating flowering induction and those regulating reproductive bud dormancy release may use similar pathways and effector molecules.