首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 93 毫秒
1.
The response of halophyte arrowleaf saltbush(Atriplex triangularis Willd)plants to a gradient of salt stress were investigatedwith hydroponically cultured seedlings.Under salt stress,both the Na~ uptake into root xylem and negative pressures inxylem vessels increased with the elevation of salinity(up to 500 mol/m~3)in the root environment.However,the increment innegative pressures in root xylem far from matches the decrease in the osmotic potential of the root bathing solutions,evenwhen the osmotic potential of xylem sap is taken into consideration.The total water potential of xylem sap in arrowleafsaltbush roots was close to the osmotic potential of root bathing solutions when the salt stress was low,but a progressivelyincreased gap between the water potential of xylem sap and the osmotic potential of root bathing solutions was observedwhen the salinity in the root environment was enhanced.The maximum gap was 1.4 MPa at a salinity level of 500 mol/m~3without apparent dehydration of the tested plants.This discrepancy could not be explained with the current theories inplant physiology.The radial reflection coefficient of root in arrowleaf saltbush decreased with the enhanced salt stress wasand accompanied by an increase in the Na~ uptake into xylem sap.However,the relative Na~ in xylem exudates based onthe corresponding NaCl concentration in the root bathing solutions showed a tendency of decrease.The results showedthat the reduction in the radial reflection coefficient of roots in the arrowleaf saltbush did not lead to a mass influx of NaClinto xylem when the radial reflection coefficient of the root was considerably small;and that arrowleaf saltbush could usesmall xylem pressures to counterbalance the salt stresses,either with the uptake of large amounts of salt,or with thedevelopment of xylem pressures dangerously negative.This strategy could be one of the mechanisms behind the highresistance of arrowleaf saltbush plants to salt stress.  相似文献   

2.
Summary. The levels of polyamines (putrescine, spermidine and spermine) and polyamine oxidase in plasma of patients with chronic renal failure were determined. The level of putrescine was increased but the level of spermine was decreased in the plasma of these patients. The patients also had increased plasma polyamine oxidase activity leading to increased degradation of spermine. As acrolein was a major toxic compound produced from spermine by polyamine oxidase, the levels of free and protein-conjugated acrolein in plasma were also measured. Acrolein levels were enhanced in plasma of patients with chronic renal failure. The accumulated acrolein found as protein conjugates was equivalent to 170 μM, which was about 5-fold higher than in plasma of normal subjects. It was found that acrolein is mainly produced by spermine oxidase in plasma. An increase in putrescine, spermine oxidase and acrolein in plasma was observed in all cases such as diabetic nephropathy, chronic glomerulonephritis and nephrosclerosis. After patients with chronic renal failure had undergone hemodialysis, their levels of plasma polyamines, spermine oxidase and acrolein returned towards normal. It is likely that acrolein produced from spermine accumulates in the blood due to decreased excretion into urine and may function as a uremic “toxin”.  相似文献   

3.
An investigation into the effects of Salmonella plasmid virulence genes (spv) on autophagy, apoptosis, and inflammation was carried out in mice, using a strain of Salmonella enterica serovar Typhimurium (S. typhimurium) SR-11 carrying spv. Strain BRD509 without spv was used as a control. Results showed that the expression of autophagy protein Beclin-1 in the livers and spleens in the SR-11 group was lower than that in the BRD509 group, while the apoptosis protein, Caspase-3, was higher in the SR-11 group. Inflammatory cytokine levels [interleukin 12 (IL-12) and interferon γ (IFN-γ)] were higher in the SR-11 group compared with those in the BRD509 group since 4 d post-infection. In addition, we found an increase in severe pathological changes and larger viable bacterial amounts in livers and spleens in the SR-11 group. After intervention with autophagy agonist rapamycin (RAPA), Beclin-1 expression increased in both groups, while Caspase-3 expression was different between the two groups: Caspase-3 decreased in the SR-11 group but increased in the BRD509 group. Moreover, RAPA decreased cytokine levels, bacterial quantity and organ-related injury in the SR-11 group whereas RAPA increased cytokine levels and aggravated organ injury in the BRD509 group. Results from these studies suggest that S. typhimurium with spv genes may exacerbate infection by inhibiting autophagy and affecting the production of inflammatory cytokines. RAPA-enhanced autophagy may improve the secretion of cytokines in order to protect the host from damaging by Salmonella infection. Our study suggests that the regulation of cellular autophagy may play a role in the prevention and control of certain infectious diseases.  相似文献   

4.
The aim of the present study was to determine the effect of environmental stresses (temperature, pH, osmotic pressure, high hydrostatic pressure (HHP)) on the antibiotic susceptibility of 12 different pathogenic Vibrio parahaemolyticus isolates. Isolates were subjected to growth at (30 ℃and 37 ℃), an osmotic pressure of (1% and 6% NaCl), a media at pH (6.0 and 9.0) and three different HHP treatment (180, 250, 300 MPa). The minimal inhibitory concentrations (MICs) of tested antibiotics used against unstressed (control), stressed or post-stressed isolates were determined using the broth microdilution method. The study found that incubation under increased salt (6%), reduced salt (1%) and increased pH (9.0) conditions were commonly associated with increased antibiotic resistance. Incubation at 30 ℃ temperature, reduced pH (6.0) and HHP treatment were commonly associated with decreased antibiotic resistance. Besides, both ciprofloxacin and cefotaxime kept a constant MIC during almost all stress challenges. Thus our data demonstrate that exposure of V. parahaemolyticus to some stress conditions may contribute on the rapid development of antibiotic resistance in this food borne pathogen.  相似文献   

5.
Pot experiments were conducted to evaluate the possible interaction of salinity (osmotic potential -0.3, -0.9 and -1.2 MPa) and occurrence of Azospirillum lipoferum or exogenous gibberellic acid (GA3) (100 μg g-1) on growth and some physiological parameters of maize. 15N-uptake as well as the percentage of nitrogen derived from 15N-fertilizer were decreased by increasing the NaCl concentrations and completely inhibited at concentrations corresponding to osmotic potentials -0.9 and -1.2 MPa. The percentage of nitrogen originating from N2 fixation was significantly correlated to the total counts of Azospirillum cells that colonized the histosphere. At high NaCl concentrations although no significant changes in N % in shoot dry mass either in inoculated or uninoculated plants were observed, the total N-yield [mg(N) pot-1] was decreased. Fresh and dry shoot mass significantly increased by Azospirillum inoculation. Azospirillum and GA3 treatments were positively correlated with most of the parameters analysed. Azospirillum inoculation or GA3 application at NaCl concentrations up to -1.2 MPa significantly increased the chlorophyll, K, Ca, soluble saccharides and protein contents as compared with control plants. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

6.
By means of single and mixed inoculation, this paper studied the interspecific competition between T. confusum and T. pretiosum on the factitious eggs of Corcyra cephaloica under different parasitoid densities, host densities and inoculated spaces. The results showed that for both singly and mixed inoculated groups, the parasitism increased with parasitoid density but decreased with host density, whereas the percentage of female progeny dropped with parasitoid density but enhanced with host density. No significant effect was observed on adult emergence for all parasitoid and host density treatments. In mixed inoculated group, the proportion of T. pretiosum in the progeny decreased with parasitoid density but increased with host density, and was more than 50% in all treatments, indicating that T. pretiosum had a stronger competitive ability than T. confusum. In the spaces ranging from 4cm^3 to 102cm^3, the parasitism decreased gradually in both singly and mixed inoculated groups. The percentage of female progeny and adult emergence had no significant difference among different inoculated spaces. In mixed inoculated group, the proportion of T. pretiosum in the progeny was more than 50% in all treatments except space 102 cm3, but decreased with space, which suggested that T. confusum could improve their competitive ability through increasing their search areas and looking for more hosts.  相似文献   

7.
The daily change in both percentage and absolute number of circulating major lymphocyte subset was determined with young Japanese monkeys and rhesus monkeys. The blood sample was collected at four hour-intervals beginning at 16:00 for 24 hours under the condition of applying tethering system by which blood samples could be collected without restraint. During the dark period (from 20:00 to 08:00), the number of peripheral lymphocytes increased and that of granulocytes decreased, resulting in no significant change in the number of total peripheral white blood cells. The absolute number of CD4 + T, CD8 + T, and CD20 + B cells showed the significant daily change similar to that in number of peripheral lymphocytes, indicating no proportional change in these subsets. The typical proportional change was observed in CD16 + natural killer (NK) cells and the percentage of CD16 + cells decreased during dark period (from 20:00 to 04:00) and increased in the morning (from 08:00 to 12:00). The NK activity determined by killing K562 target cells showed the same changing pattern as that of percentage in CD16+ NK cells. The changing pattern of both percentage and activity of NK cells was consistent with that of plasma cortisol levels. In addition, the intravenous injection of 300 μg/kg of cortisol induced increase in plasma cortisol levels and decrease in percentage of CD16 + NK cells during the first 60 min after cortisol injection. These results strongly suggest that the levels of peripheral functional CD16 + NK cells might be directly regulated by plasma cortisol level in macaque monkeys.  相似文献   

8.
The effects of dietary selenium on the immune system in healthy men   总被引:8,自引:0,他引:8  
Eleven men were fed foods naturally high or low in selenium for 120 d. Selenium intake was stabilized at 47 μg/d for 21 d, then changed to either 13 or 297 μg/d for 99 d, leading to significantly different blood selenium and glutathione peroxidase concentrations. Serum immunoglobulins, complement components, and primary antibody responses to influenza vaccine were unchanged. Antibody titers against diphtheria vaccine were 2.5-fold greater after reinoculation in the high selenium group. White blood cell counts decreased in the high-selenium group and increased in the low-selenium group, resulting primarily from changes in granulocytes. Apparent increases in cytotoxic T-lymphocytes and activated T-cells in the high-selenium group only approached statistical significance. Lymphocyte counts increased on d 45 in the high-selenium group. In vitro proliferation of peripheral lymphocytes in autologous serum in response to pokeweed mitogen was stimulated in the high-selenium group by d 45 and remained elevated throughout the study, whereas proliferation in the low selenium group did not increase until d 100. This study indicates that the immune-enhancing properties of selenium in humans are the result, at least in part, of improved activation and proliferation of B-lymphocytes and perhaps enhanced T-cell function.  相似文献   

9.
The glucose-lowering effect of vanadate, ammonium metavanadate (AMV), on diabetic KK mice was examined. Five-week-old male KK mice were administrated with a solution of AMV via drinking water at concentrations of vanadium (V) with 0.1, 1.0, 10 and 100 μg/mL for a period of 10 wk, respectively. Body weight, consumption of food and water, and blood glucose levels was measured every week for 10 wk. The results showed that food consumption and body weight in the experimental groups were similar to those in the control group. A statistically significant decrease of drinking water consumption and blood glucose levels in the group treated with 100 μg V/mL was observed. The glucose tolerance in the vanadate-treated mice with 10 and 100 μg V/mL was remarkably improved compared with the control group. Biochemical analyses at the end of experiments demonstrated that a distinct tendency for the glucose and hemoglobin A1c (HbA1c) levels to decrease with vanadate treatment in the blood was also observed. The glutamic pyruvic transaminase, glutamic oxaloacetate transaminase, blood urea nitrogen, triglyceride, high-density lipoprotein, and total cholesterol levels in plasma were lower in the higher vanadium groups than those in the control group. These results indicate that vanadium effectively produced the glucose-lowering effect at a higher dose than that at a low dose of vanadium in drinking water, without any overt signs of toxicity.  相似文献   

10.
Bioavailability and possible benefits of wheat intake naturally enriched with selenium and its products was tested. Wheat obtained by application of an original combination and procedure for foliar supplementation of plants with Se was characterized on the average by five times higher content of Se, the main form being l-(+)-selenomethionine (SeMet). Substitution of Se-deficient wheat by wheat naturally enriched with Se and its products contributed to the increase of daily intake on the average by 18 μg (12–35 μg) in volunteers, which is more than 50% of the average daily intake. Six weeks after the beginning of its application, increased daily intake of Se brought about the increase of its concentration in the plasma of the examined persons by 53%, in their erythrocytes by 37%, in their hair by 44%, and in their urine by 54%. This result was comparable to the effect obtained in the course of an 8-wk daily intake of supplements with 100 μg Se in the form of enriched bakery yeast. Analysis of glutathione peroxidase (GSH-Px) activity in blood, thiobarbituric acid reactive substances (TBARS) in plasma, lipid parameters (total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides), and glucose in serum of volunteers showed that the increased Se intake induced increased GSH-Px activity in blood and decreased concentrations of TBARS, lipid parameters, and glucose in blood. Using only one crop (wheat enriched with Se), the existing deficiency of Se in our population can be alleviated. In this way, one-fourth of our population with lower Se intake than 21 μg/d will satisfy basal requirements, whereas one-half will become moderately deficient in Se instead of distinctly deficient in Se.  相似文献   

11.
Codium decorticatum regulates its internal ionic composition and osmotic pressure in response to changes in external salinity. Over a salinity range of 23 to 37% (675 to 1120 mosmol/kg) Codium maintains a constant turgor pressure of 95 mosmol/kg (2.3 atm), observed as a constant difference between internal and external osmotic pressures. The changes in internal osmotic pressure are due to changes in intracellular inorganic ions. At 30 0/00 salinity the major intracellular ions are present in the following concentrations (mmol/kg cell H20): K+, 295; Na+, 255; Cl-, 450. At different salinities intracellular ion concentrations remain in constant proportion to the external ion concentrations, and thus the equilibrium potentials are approximately constant. The potential difference between the vacuole and seawater (-76 mV), whici is predominantly a K+ diffusion potential, is also constant with changing salinity. Comparison of the equilibrium potentials with the vacuole potential suggests that Cl- is actively absorbed and Na+ actively extruded, whereas K+ may be passively distributed between the vacuole and seawater. Turgor pressure does not change with environmental hydrostatic pressure, and increasing the external osmotic pressure with raffinose elicits a response similar to that obtained by increasing the salinity. These two results suggest that the stimulus for turgor regulation is a change in turgor pressure rather than a change in internal hydrostatic pressure or ion concentrations.  相似文献   

12.
13.
Species specificity of osmotic and ion regulation in five species of acipenserids connected in varying degrees with sea conditions is investigated. The objects of study were freshwater middle-Volga sterlet Acipenser ruthenus; Siberian sturgeon A. baerii, inhabiting the Lena River and migrating to the sea near the river mouth; and the following migratory acipenserids of the Volga-Caspian Basin (regular diadromous migrations): the Russian sturgeon A. gueldenstaedtii, the great sturgeon Huso huso, and the starred sturgeon A. stellatus. The study was carried out on immature specimens (of age 2+). The level of osmolarity and concentrations of cations (Na+, K+, Ca2+, and Mg2+) were determined in blood serum, urine, and liquid from the cavity of spiral valve in fish from the fresh water (control) and after their adaptation (period of seven to ten days) to sea water with salinity 12.5–12.7 and 18‰. The increase was found in the functional activity of the mechanism of osmotic and ion homeostasis in sturgeons according to the increase of the environmental salinity of a particular species. The freshwater sterlet adapted to the sea environment as osmoconformer. The other studied species were capable of maintaining a relative stability of osmolarity and ion concentration in blood serum at different levels while adapting to the sea environment; they changed from hyperosmotic (in fresh water) to hypoosmotic type of regulation. The kidney plays a more significant role in the removal of excessive Na+ in sturgeons than in bony fish. An increase in the sodium-reabsorption and magnesium-secretion functions of the kidney as well as the sodium-absorption function of the intestines was observed in sturgeons, relative to the increase of environmental salinity.  相似文献   

14.
Quantifying the three main components of salinity tolerance in cereals   总被引:3,自引:0,他引:3  
Salinity stress is a major factor inhibiting cereal yield throughout the world. Tolerance to salinity stress can be considered to contain three main components: Na+ exclusion, tolerance to Na+ in the tissues and osmotic tolerance. To date, most experimental work on salinity tolerance in cereals has focused on Na+ exclusion due in part to its ease of measurement. It has become apparent, however, that Na+ exclusion is not the sole mechanism for salinity tolerance in cereals, and research needs to expand to study osmotic tolerance and tissue tolerance. Here, we develop assays for high throughput quantification of Na+ exclusion, Na+ tissue tolerance and osmotic tolerance in 12 Triticum monococcum accessions, mainly using commercially available image capture and analysis equipment. We show that different lines use different combinations of the three tolerance mechanisms to increase their total salinity tolerance, with a positive correlation observed between a plant's total salinity tolerance and the sum of its proficiency in Na+ exclusion, osmotic tolerance and tissue tolerance. The assays developed in this study can be easily adapted for other cereals and used in high throughput, forward genetic experiments to elucidate the molecular basis of these components of salinity tolerance.  相似文献   

15.
Abstract. In a highly saline environment high rates of ion uptake are required to generate sufficient osmotic pressure to maintain the turgor that is needed for the continued growth of plants. We estimate the rates of net uptake of Cl and Na+ required by growing cells to sustain cell expansion at an external NaCl concentration of 500 mol m−3. We also estimate the ion fluxes required to regulate turgor of expanding and fully expanded cells during diurnal changes in transpiration. Passive fluxes could contribute significantly to osmotic regulation, but active fluxes are still essential and would consume a substantial amount of energy. We discuss whether a limitation to growth at high salinity would arise from lack of energy, or from insufficient capacity for ion uptake. There is insufficient evidence to choose between these possibilities.  相似文献   

16.
The effects of salinity on growth, water relations, glycinebetainecontent, and ion accumulation in the perennial halophyte Atriplexgriffithii var. stocksii were determined. The following questionswere addressed: (1) What effect does salinity have on growthresponses at different ages? (2) Is A. griffithii an ion accumulator?(3) Does A. griffithii accumulate glycinebetaine in responseto salinity? Atriplex griffithii plants were grown in pots at0, 90, 180 and 360  m M NaCl in sand culture in a plantgrowth chamber and plants were harvested after 30, 60 and 90d. Plant total dry weight was significantly inhibited at 360m M NaCl. Root growth showed a substantial promotion at 90 mM NaCl. The water potential and osmotic potential of shootsbecame more negative with increasing salinity and time of growth.The Na+and Cl-content in both shoots and roots increased withincreases in salinity. Increased treatment levels of NaCl induceddecreases in Ca+, K+and Mg2+in plants. Atriplex griffithii accumulateda large quantity of ions, with the ash content reaching 39%of the dry weight in leaves. Inorganic ion accumulation is significantin osmotic adjustment and facilitates water uptake along a soil-plantgradient. Glycinebetaine concentration was low in roots, andin stems it increased with increases in salinity. Total amountsof glycinebetaine in leaves increased with increases in salinity,and its concentration increased substantially at 360 m M NaCl.Copyright 2000 Annals of Botany Company Atriplex griffithii, glycinebetaine, growth, ions, water relations.  相似文献   

17.
Abstract Measurements of tissue ion contents (Na, K and Cl) were carried out at frequent intervals on plants of Aster tripolium L. grown at a range of salinities for 36 d. Aster tripolium behaved as a typical halophyte showing high levels of inorganic ion accumulation even at low salinities. As salinity increased Na replaced K to a large extent in the shoot but root K was unaffected up to 500 mol m?3 external NaCl. Shoot (Na + K) concentration on a tissue water basis was maintained constant in all treatments throughout the experiment, whereas shoot (Na + K) on a dry weight basis showed marked fluctuations in some treatments. An increase in (Na + K) per gram dry weight was, however, accompanied by a parallel increase in fresh weight: dry weight (FW : DW) ratio. Transport of (Na + K) to the shoot per unit root weight changed during the experiment in the manner expected, given the observed changes in shoot relative growth rate and FW : DW to result in a constant shoot (Na + K) concentration on a water basis. Chloride was the major balancing anion in the shoot at high salinity, but never accounted for more than 38% of the (Na + K) found in the root tissue. At all salinities (Na + K) salts accounted for the majority of the measured shoot sap osmotic potential. The interactions between salinity, growth, ion transport and osmotic adjustment are discussed.  相似文献   

18.
Swelling of articular cartilage depends on its fixed charge density and distribution, the stiffness of its collagen-proteoglycan matrix, and the ion concentrations in the interstitium. A theory for a tertiary mixture has been developed, including the two fluid-solid phases (biphasic), and an ion phase, representing cation and anion of a single salt, to describe the deformation and stress fields for cartilage under chemical and/or mechanical loads. This triphasic theory combines the physico-chemical theory for ionic and polyionic (proteoglycan) solutions with the biphasic theory for cartilage. The present model assumes the fixed charge groups to remain unchanged, and that the counter-ions are the cations of a single-salt of the bathing solution. The momentum equation for the neutral salt and for the intersitial water are expressed in terms of their chemical potentials whose gradients are the driving forces for their movements. These chemical potentials depend on fluid pressure p, salt concentration c, solid matrix dilatation e and fixed charge density cF. For a uni-uni valent salt such as NaCl, they are given by mu i = mu io + (RT/Mi)ln[gamma 2 +/- c(c + cF)] and mu w = mu wo + [p-RT phi (2c + cF) + Bwe]/pwT, where R, T, Mi, gamma +/-, phi, pwT and Bw are universal gas constant, absolute temperature, molecular weight, mean activity coefficient of salt, osmotic coefficient, true density of water, and a coupling material coefficient, respectively. For infinitesimal strains and material isotropy, the stress-strain relationship for the total mixture stress is sigma = - pI-TcI + lambda s(trE)I + 2 musE, where E is the strain tensor and (lambda s, mu s) are the Lamé constants of the elastic solid matrix. The chemical-expansion stress (-Tc) derives from the charge-to-charge repulsive forces within the solid matrix. This theory can be applied to both equilibrium and non-equilibrium problems. For equilibrium free swelling problems, the theory yields the well known Donnan equilibrium ion distribution and osmotic pressure equations, along with an analytical expression for the "pre-stress" in the solid matrix. For the confined-compression swelling problem, it predicts that the applied compressive stress is shared by three load support mechanisms: 1) the Donnan osmotic pressure; 2) the chemical-expansion stress; and 3) the solid matrix elastic stress. Numerical calculations have been made, based on a set of equilibrium free-swelling and confined-compression data, to assess the relative contribution of each mechanism to load support. Our results show that all three mechanisms are important in determining the overall compressive stiffness of cartilage.  相似文献   

19.
We show here that both salinity and osmotic stress trigger transient increases in intracellular free Ca2+ concentration ([Ca2+]i) in cells of the nitrogen‐fixing filamentous cyanobacterium Anabaena sp. PCC7120, which constitutively expresses apoaequorin. Isoosmolar concentrations of salt (NaCl) and osmoticum (sucrose) induced calcium transients of similar magnitude and shape, suggesting that cells sense, via Ca2+ signalling, mostly osmotic stress. The Ca2+ transients induced by NaCl and sucrose were completely blocked by the calcium chelator ethylene glycol‐bis(b‐aminoethylether)N,N,N¢,N¢‐tetraacetic acid (EGTA) and were partially inhibited by the calcium channel blocker verapamil. Increased external Ca2+ and the Ca2+ ionophore calcimycin (compound A23187) enhanced Ca2+ influx further, suggesting the involvement of extracellular Ca2+ in the observed response to salinity and osmotic stress. However, the plant hormone abscisic acid (ABA) did not provoke any effect on the Ca2+ transients induced by both stresses, indicating that it may not be acting upstream of Ca2+ in the signalling of salinity and/or osmotic stress in Anabaena sp. PCC7120.  相似文献   

20.
The effects of inorganic ions and of the hydrogen ion on oxygen-binding properties of most respiratory pigments are opposite. The addition of salt to the medium increases oxygen affinities, and the addition of H+ decreases oxygen affinities of crustacean hemocyanins. These oxygenation properties, as observed in vitro, suggest that the oxygen-transport system must adapt to ionic changes in the blood. In fact, decreases in the salt concentration of the blood of estaurine blue crabs are accompanied by increases in pH, probably resulting from the input of ammonia produced in deamination of the intracellular pool of free amino acids as the cells conform to osmotic changes in body fluids. The result is a stability of hemocyanin function until the blood becomes very dilute. As the acclimation salinity is reduced from 35 to 15 o/ooo, the ionic effects on respiratory transport are balanced and there is no change in total oxygen uptake. At 5 o/ooo salinity, however, the higher blood pH is manifested in an elevation of the total oxygen concentration of prebranchial blood, probably because the Bohr shift is no longer opposed by a critical level of salt in the blood. Under these conditions the role of hemocyanin in aerobic respiration is reduced at high environmental oxygen levels, but it may be enhanced in hypoxic uaters.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号