[Analyzing the Pollution Sources and Mechanisms of Urban Rivers Based on Identifying the Molecular Signature of Dissolved Organic Matter].

Dissolved organic matter (DOM) is an essential component of river pollutants. Under the new situation of black water treatment in urban areas of China, in view of the widespread problem of unclear sources of multiple pollutants, further analysis of DOM components in urban rivers from the molecular level is a key link to deeply explore the sources, causes, and mechanism of river pollution so as to achieve efficient management. In this study, the urban rivers in the central city were selected as the research object, and a total of five rivers were selected that were seriously affected by the discharge sewage of four combined and separated sewer systems, respectively. Using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), this study identified the molecular formulae and analyzed the elemental composition and compound groups of DOM in water and sediment samples at each site in dry and wet weather. The results showed that:①although CHO molecules and lignins were the main compounds in the urban river DOM, the high proportion of lipids, proteins, and heteroatomic compounds (especially CHOS molecules) revealed the anthropogenic pollution in rivers, which also led to the increase in DOC, TN, and NH+4-N. ②Surfactants such as C17H28O3S and C18H30O3S were ubiquitous in all urban rivers, which could be used as markers of domestic wastewater pollution. ③In wet weather, the rainfall inputs, storm runoffs, and hydraulic disturbance jointly led to the increase in the proportion of CHO molecules and lignin compounds; the decrease in proteins and lipids; the rise of DOC, TN, and NH+4-N concentrations in river water; and the decrease in DOC, TN, and NH+4-N concentrations and proteins and lipids in river sediments. ④The abundance of multi-heteroatomic compounds and condensed aromatics in the combined sewer system was higher than that in the separated sewer system, which may have been more severely polluted by domestic wastewater and storm runoff, especially kitchen wastewater. This study provides new insight for clarifying the critical causes of pollution in the new stage and provides an essential basis for further precision prevention and control of water pollution.

[Ecological Risk Assessment of Microplastics Occurring in Surface Water of Terrestrial Water Systems across China].

To assess the ecological risk of microplastics (MPs) occurring in the surface water of terrestrial water systems across China, this study obtained relevant literature and data by searching keywords including microplastics, urban, and river on websites such as Science Direct and Web of Science. We constructed an evaluation method of ecological risk characterization ratio (RCR) based on chemical hazard data, as well as data of MPs abundance and polymer proportion originating in studies from 2017 to 2021 that covered 33 water bodies in 15 provinces. The results showed that the average abundance of MPs in natural water bodies in China reached (3604.2±5926.4) n·m-3, and the average abundance of MPs in urban water bodies was (7722.6±9505.7) n·m-3. The corresponding average RCR of natural water bodies was 22.09±45.2, and the average RCR of urban water bodies was 15.67±34.8. Therefore, according to the value of RCR, the ecological risk could be rated as four levels. Of these, no significant risk (RCR ≤ 1) was found in 17 water bodies, accounting for 42.5%; low ecological risks (RCR 1-10) were found in 12 water bodies (30%); medium ecological risks (RCR 10-100) were found in 9 water bodies (22.5%); and high ecological risks (RCR>100) were found in 2 water bodies (5%). Data analysis showed a significant correlation between MPs abundance and RCR values in natural water bodies (R2=0.875, P<0.01), though not in urban water bodies. This suggested that the high abundance of MPs could not precisely indicate a high degree of ecological risk in the area. In addition, RCR values were observed to be positively correlated with the watershed area (R2=0.864, P<0.01), and MPs abundance was correlated with GDP (R2=0.679, P<0.05) and watershed resident population (R2=0.922, P<0.05). This study provides baseline data for evaluating the ecological risk of MPs and a feasible method for evaluating the ecological risk of MPs in surface water of terrestrial water systems.

[Distribution and Influencing Factors of DOM Components in Urban and Suburban Polluted Rivers].

Dissolved organic matter(DOM) in water environments is an important component of the global carbon cycle. Under the current urgency to control the pollution of urban rivers in China, exploring the influence of different exogenous and endogenous secondary pollution and weather patterns on river DOM is the premise to better understand the causes of the pollution. In this study, a large city in China was established as the research area, and the underlying water and sediments from 21 sites along urban and suburban rivers, and other water sources were evaluated. The excitation-emission matrix-parallel factor analysis(EEM-PARAFAC) was used to analyze the difference in DOM composition and equivalent in urban rivers polluted by domestic sewage and suburban rivers polluted by aquaculture, agriculture, and livestock breeding. The results showed that:① DOM components in urban and suburban river waters were mainly protein compounds(tyrosine-and tryptophan-like), containing a small amount of humic acid. Humic acid components of anthropogenic origin were found in urban river water; ② The reasons for the formation of DOM components in urban and suburban rivers were completely different. Urban rivers are mainly polluted by domestic sewage and endogenous secondary pollution, resulting in an increase in anthropogenic humic acid components. Suburban rivers are mainly polluted by agricultural wastewater rich in N and P, which promotes endogenous metabolism of autotrophic bacteria and increases protein components, which may be related to the formation of existing DOM characteristics. ③ Rainfall runoff and urban overflow transported exogenous pollutants into rivers, while hydrodynamic factors such as hydraulic agitation affect the distribution of DOM components in underlying water and sediments through physical effects such as dilution.

[Pollution Status and Pollution Behavior of Microplastic in Surface Water and Sediment of Urban Rivers].

Rivers have been a subject of great concern in recent years as they have been found to be the critical path for the transmission of microplastics from terrestrial land to the ocean. However, the pollution status of microplastics and their behavior in the surface waters and sediments of urban rivers located in different urban areas remain unclear. In this study, 16 samples of surface water and sediment from eight rivers in the central and suburban areas of Shanghai Megacity were obtained and analyzed. High-speed cameras and Fourier transform infrared spectrometers were used to identify the abundance, size, color, shape, type, and other characteristics of microplastics in these samples. The results showed that the average abundance of microplastics in the surface waters of urban rivers in Shanghai Megacity was (7.5±2.8) pieces·L-1, while the corresponding average abundance in the sediment reached (1575.5±758.4)pieces·kg-1 (wet weight). The abundance of microplastics was found to increase with the decreasing particle diameter. Among which, microplastics with a size of less than 500 µm, as well as the fibrous shape, transparent color, and Polyester composition, have always dominated in the urban rivers in Shanghai megacity. Comparably, microplastics in the sediments were more diverse in their morphology features and polymer compositions. Microplastic pollution in the urban rivers in Shanghai megacity was severe in comparison to that in other urban rivers worldwide. Among various urban rivers, the distribution of microplastics with different morphology features and polymer compositions is greatly influenced by a number of factors including the source (e.g., mainly laundry wastewater, personal care products, and refuse plastic waste), hydrodynamic conditions, and the physical and chemical properties of plastics. Furthermore, the pollution behavior (i.e., source, transmission, and fate) of microplastics occurring in urban rivers is discussed, and the potential impacts of various environmental factors are explained.

[Molecular Chemo-diversity of the Dissolved Organic Matter Occurring in Urban Stormwater Runoff].

Stormwater runoff pollution occurring in urban areas can be a notable threat to the ecological environments of receiving water bodies. Dissolved organic matter (DOM) constitutes the primary type of pollutant in stormwater runoff, and tracking of its components and sources can provide valuable scientific bases for the future abatement of stormwater runoff pollution. In this study, aiming to demonstrate the characteristics and sources of the contained DOM in both pavement runoff (PR) and greenland runoff (GR), we applied ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to analyze the molecular chemo-diversity of their DOM, as well as Spearman rank correlations between the molecular chemo-diversity and water quality indicators including suspended solids (SS), total nitrogen (TN), dissolved organic carbon (DOC), and dissolved lead (Pb). The results show:① When the molecular accumulation reaches a saturated state, the cumulative number of molecules of PR-DOM (12498) is much larger than that of GR-DOM (7015). The molecular distribution of PR-DOM (150-750) is smaller yet more concentrated than that of GR-DOM (150-850). ② According to the molecular composition characterization and Spearman rank correlation analysis, the sources of the components of PR-DOM and GR-DOM are remarkably different. PR-DOM can be greatly influenced by human activities, and its primary element component (CHOS) contains a large number of substances that were recognized to be from the surfactant sulfonic acid. Additionally, the significant aliphatic components that emerged were from traffic pollution. In contrast, GR-DOM is less affected by human activities, and its primary element component (CHO) gives priority to natural organic matter (NOM). The most abundant substance component that occurred in GR-DOM, i.e., the highly unsaturated and phenolic compound that generally originates in the degraded humus, is initially formed by the plant residue and flushed by rainfall runoff.

[Relationship Between CO2 and CH4 Emissions in Urban Rivers and Sewage Discharging from a Municipal Drainage Network].

The increasing carbon emission of polluted rivers in urban areas is an environmental problem commonly faced by many cities in China, especially the megacities with vast populations. In this study, two typical rivers located in the megacity of Shanghai, including the suburban river network R1 and urban river R2 (in the central city), were investigated for their emission characteristics of CO2 and CH4 in dry and wet weather. We also analyzed the relationship between the state and type of river pollution and CO2 and CH4 emissions, and further explained the mechanisms of CO2 and CH4 emissions in urban rivers impacted by sewage discharged from the municipal drainage network. The results show that:① In dry weather, the average fluxes of CO2 and CH4 emitted from the river in the central city (R2) were (2.48±1.02) mmol·(m2·h)-1 and (1.21×10-2±0.71×10-2) mmol·(m2·h)-1, respectively. The average fluxes of CO2 and CH4 from the suburban river (R1) network were (1.53±0.39) mmol·(m2·h)-1 and (9.26×10-3±9.18×10-3) mmol·(m2·h)-1, respectively. In wet weather, affected by sewage from the municipal drainage network, CH4 flux emitted from the surface water of the R2 river downstream of the pump station P increased by up to 119 times that in dry weather. ② Global carbon emission statistics, involving the data from our study and from other rivers around the world, seemed to imply a relationship between the carbon emission flux and the pollution state of an urban river, i.e., the rivers with high pollution showed significant carbon emission intensity. ③ According to the results of PCA, organic matter can be an essential factor in driving the variation of carbon emissions, and this trend is evident in all the rivers in urban and suburban areas. The relationship between carbon emissions and nitrogen pollution in a river varies with different types of underlying riparian surface. In the less polluted urban rivers, the aquatic physical factor can also be an essential factor. ④ In the short term, with massive quantities of sewage discharged into urban rivers, a large amount of CH4 flux can be emitted. In contrast, in the long run, the carbon cycle can be strengthened when the carbon storage is increased, and thus the emission potential of CO2 and CH4 is improved.

[Removal of Microplastics by Different Treatment Processes in Shanghai Large Municipal Wastewater Treatment Plants].

Wastewater treatment plants are important sources of microplastics (MPs) in aquatic environments. The present study was conducted to investigate the number concentration, removal rate, and fate of MPs in two large municipal treatment plants in Shanghai. The MPs number concentration in the influent water of WWTP1 and WWTP2 were (226.27±83.00) piece·L-1 and (171.89±62.98) piece·L-1, respectively. WWTP1 had a MPs removal efficiency of 63.25%, which is slightly higher than that of WWTP2, at 59.84%. The removal efficiency during the primary treatment process of the two sewage treatment plants on MPs accounted for 70%-80% of the whole treatment process. The primary treatment process and secondary treatment process transferred (48.10%±1.62%) and (12.97%±0.05%) of MPs in the sewage to the sludge, respectively. As a whole, (38.82%±1.55%) of MPs in the sewage treatment plants were finally discharged into natural waters, and the remaining (61.18%±1.55%) entered the sludge. This study shows that the removal rate of MPs in Shanghai's municipal treatment plants is low and that after treatment, large amounts still enter the natural waters with the final effluent, which causes significant ecological risks. This study provides basic data of MPs removal and trends of large urban sewage treatment plants in a plain river network area, which can provide reference for further design of MPs removal processes.

A simple risk score model for predicting contrast-induced nephropathy after coronary angiography in patients with diabetes.

BACKGROUND: Contrast-induced nephropathy (CIN) is a common complication in patients undergoing coronary angiography (CAG) or percutaneous coronary intervention (PCI) and associated with poor outcome. Some previous studies have already set up models to predict CIN, but there is no model for patients with diabetes mellitus (DM) especially. Therefore, we aim to develop and validate a simple risk score for predicting the risk of CIN in patients with DM undergoing CAG/PCI. METHODS: A total of 1157 consecutive patients with DM undergoing CAG/PCI were randomly assigned to a development cohort (n = 771) and a validation cohort (n = 386). The primary endpoint was CIN, which was defined as an absolute increase in serum creatinine (SCr) by 0.5 mg/dL from the baseline within 48-72 h after contrast exposure. The independent predictors for CIN were identified by multivariate logistic regression, and the discrimination and calibration of the risk score were assessed by ROC curve and Hosmer-Lemeshow test, respectively. RESULTS: The overall incidence of CIN was 45 (3.9%). The new simple risk score (Chen score), which included four independent variables (age > 75 years, acute myocardial infarction, SCr > 1.5 mg/dL, the use of intra-aortic balloon pump), exhibited a similar discrimination and predictive ability on CIN (AUC 0.813, 0.843, 0.796, P > 0.05, respectively), mortality (AUC 0.735, 0.771, 0.826, respectively) and MACEs when being compared with the classical Mehran or ACEF risk score. CONCLUSION: Our data suggest that the new simple risk score might be a good tool for predicting CIN in patients with DM undergoing CAG/PCI.

Stenosing tenosynovitis : Evaluation of percutaneous release with a specially designed needle vs. open surgery.

PURPOSE: The purpose of this study was to evaluate the effectiveness of conventional open surgery and percutaneous release with a specially designed needle for treating stenosing tenosynovitis in terms of cure, relapse and complication rates. METHODS: In this study 89 fingers from 76 patients were randomly assigned and allocated to one of the treatment groups. A total of 37 patients were treated with open surgery in group 1 and 39 patients with percutaneous release using a specially designed needle in group 2. A patient-based 4-inch visual analogue scale (VAS), Quinnell grading (QG), disability of arm shoulder and hand (DASH) score and finger total joint range of motion (FTROM) score were evaluated before treatment and after 7, 30 and 180 days. When finger QG scores were equal or greater than 2 points at follow-up at 180 days this was defined as recurrence.. RESULTS: There were no significant differences between the two groups (P > 0.05) in terms of VAS, DASH and QG scores and the degree of FTROM. At 7 days all the data were significantly different (p < 0.05) compared with preoperative data, 30 days was significantly different (p < 0.05) compared with 7 days while at 180 days no significant differences could be found (p > 0.05) compared with 30 days. The recurrence rate in group 1 was 4.65% and 6.55% in group 2. CONCLUSION: The percutaneous release and open surgery methods displayed similar effectiveness regarding the cure and recurrence of trigger finger disorder. The use of a specially designed needle for release is a safe and reliable method.

Luteolin is a rare substrate of human catechol-O-methyltransferase favoring a para-methylation.

SCOPE: The study aimed to investigate the regioselectivity of methylation of luteolin (3',4',5,7-tetrahydroxyflavone) in human in vitro and in vivo. METHODS AND RESULTS: Recombinant human catechol-O-methyltransferase (COMT) and human liver S9 were utilized to study the kinetics of meta (3')- and para (4')- methylation of luteolin, and urine samples from volunteers after giving a luteolin-containing formulation were collected to determine the ratio of para-/meta-production. The results showed luteolin favored a para-methylation, with a ratio of of para-/meta-production in CLint (1.43 in recombinant human COMT and 1.47 in human liver S9), which was contrary to the known substrates of COMT. However, the result of urine sample assay showed a preference of meta-methylation with a ratio of of para-/meta-production (0.460 ± 0.126). To elucidate the mechanism for different preference of methylation of luteolin in vitro and in vivo, metabolism stability of the meta- and para-methylated luteolin was evaluated in human liver microsomes and recombinant human CYP450s, which revealed that para-methylated luteolin was more easily demethylated by human CYP1A2 and CYP3A4/5 than meta-methylated luteolin. CONCLUSION: Luteolin was a rare substrate of human COMT favoring a para-methylation, but further demethylation by human CYP1A2 and CYP3A4/5 caused a preference of accumulation in meta-methylated luteolin in vivo.

Uricosuric and nephroprotective properties of Ramulus Mori ethanol extract in hyperuricemic mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Ramulus Mori, the branch of Morus alba, is widely used in traditional Chinese medicine prescriptions to treat gout and hyperuricemia. AIM OF THIS STUDY: To evaluate the uricosuric and nephroprotective effects of ethanol extract of Ramulus Mori (ERM) and explore its possible mechanisms in hyperuricemic mice. MATERIALS AND METHODS: HPLC analysis was employed to determine the main constituents. Hyperuricemia was induced by potassium oxonate (250 mg/kg) in male mice. ERM (10, 20 and 40 mg/kg) was orally administered to hyperuricemic and normal mice for 7 days. Serum and urine levels of uric acid, creatinine and blood urea nitrogen (BUN) were measured. Simultaneously, renal mRNA and protein levels of mouse urate transporter 1 (mURAT1), glucose transporter 9 (mGLUT9), organic anion transporter 1 (mOAT1) and organic cation/carnitine transporters (mOCT1/2, mOCTN1/2) were analyzed by RT-PCR and Western blotting methods. RESULTS: ERM mainly contained mulberroside A, oxyresveratrol, 4-hydroxycinnamic acid, resveratrol, 7-hydroxycumarin and morin. ERM significantly reduced serum urate levels and increased 24h-urine urate excretion and fractional excretion of uric acid in hyperuricemic mice. It effectively restored oxonate-induced expression alteration of renal mURAT1, mGLUT9 and mOAT1, resulting in urate excretion enhancement. Moreover, ERM decreased serum creatinine and BUN levels and increased creatinine clearance, and up-regulated expression of mOCT1/2 and mOCTN1/2, contributing to kidney function improvement in this model. CONCLUSION: These results suggest that ERM exerts the uricosuric and nephroprotective actions by the regulation of these renal organic ion transporters in hyperuricemic mice, and provide scientific support for the empirical use of Ramulus Mori.

Mulberroside a possesses potent uricosuric and nephroprotective effects in hyperuricemic mice.

Mulberroside A is a major stilbene glycoside of MORUS ALBA L. (Moraceae), which is effectively used for the treatment of hyperuricemia and gout in traditional Chinese medicine. We examined whether mulberroside A had effects on renal urate underexcretion and dysfunction in oxonate-induced hyperuricemic mice and investigated the potential uricosuric and nephroprotective mechanisms involved. Mulberroside A at 10, 20, and 40 mg/kg decreased serum uric acid levels and increased urinary urate excretion and fractional excretion of uric acid in hyperuricemic mice. Simultaneously, it reduced serum levels of creatinine and urea nitrogen (10-40 mg/kg), urinary N-acetyl- ß-D-glucosaminidase activity (10-40 mg/kg), ß2-microglobulin (10-40 mg/kg) and albumin (20-40 mg/kg), and increased creatinine clearance (10-40 mg/kg) in hyperuricemic mice. Furthermore, mulberroside A downregulated mRNA and protein levels of renal glucose transporter 9 (mGLUT9) and urate transporter 1 (mURAT1), and upregulated mRNA and protein levels of renal organic anion transporter 1 (mOAT1) and organic cation and carnitine transporters (mOCT1, mOCT2, mOCTN1, and mOCTN2) in hyperuricemic mice. This is the first study demonstrating that mulberroside A exhibits uricosuric and nephroprotective effects mediated in part by cooperative attenuation of the expression alterations of renal organic ion transporters in hyperuricemic mice. These data suggest that mulberroside A may be a new drug candidate for the treatment of hyperuricemia with renal dysfunction.

[Dynamic rule of organic matter removal in vertical-flow constructed wetland].

Based upon the analysis of the removal rate and form change of the organic pollutants with the different height of the vertical-flow constructed wetland, it comes to the conclusion of the average longitudinal removal rate of variant forms organics and presents the influent concentration and the hydraulic load curve. The results indicated that: Under this experimental condition, the reduction of the organics in the vertical subsurface flow constructed wetland mainly occurred within the 0-10 cm substrate below the pipe distributor. In the meantime, the smaller the hydraulic load of influent, the higher the removal ratio of the organic pollutants in the substrate section. Under the condition that the vertical subsurface flow constructed wetland used the coarse sands as the substrate and kept the influent hydraulic load less than or equal to 0.5 m3/(m2 x d), the effective height of the organics removal was 60 cm. It also showed that the average degradation rate of different kinds of the organic pollutants has a maximum value in the 0-10 cm substrate section below the pipeline. Moreover, the degradation ratio of different kinds of the organics is in significant decreasing tendency with increasing the depth of the longitudinal direction along the pipe. Using sands as the substrate in the vertical subsurface flow constructed wetland, the relationship of the influent concentration and influent hydraulic load can be expressed by formula:(c(in) - c(out)) x q = 1107.02-2.96 c(in) x q.

[Clogging mechanism in vertical-flow constructed wetland: clogging cause and accumulation distribution characteristics].

In order to solve the problem of clogging in the vertical-flow constructed wetland, the reason of clogging and the distribution rule of clogging substance in the vertical-flow constructed wetland was investigated first. Based on the correlativity of accumulation quantity and banked-up water area or lacuna rate in constructed wetland systems, the results show that the accumulation of non-filter materials is the main reason of clogging. The banked-up phenomenon will occur when the accumulation of non-filter materials is more than 18.23 mg in the per milliliter substrate. Under the condition of this experiment, the clogging phenomenon is easy to take place around current outlet, and accumulation materials mainly distribute in the 10-20 cm upper layer under water pipe. In the substrate, the accumulation degree of that of non-filter inorganic is more obvious than non-filter organic, with the trend of migrating along the water direction. The accumulation of organic and the depth of substrate is negatively correlated, i.e. deeper substrate,less organic content. The organic content in the surface layer of substrate is higher than that in other layers after banking up.

[Effects of benazepril combined with valsartan on congestive heart failure].

OBJECTIVE: To observe the effects of routine doses of benazepril combined with valsartan on congestive heart failure. METHODS: Totally 203 patients with congestive heart failure were randomized into Group A (receiving benazepril 20 mg/day), Group B (benazepril,10 mg/day plus valsartan, 80 mg/day), and group C (valsartan 160 mg/day) for different treatment protocols on the basis of routine therapy for heart failure with digitalis, diuretics and beta blockers. The cardiac functions and echocardiographical findings were evaluated before and after the treatments. RESULTS: All the patients showed improvement of NYHA class, left ventricular end-diastolic dimension (LVEDd), left ventricular end-systolic dimension (LVESd) and left ventricular ejection fraction (LVEF) (P<0.01), and the effect was better in group B than in group A (P>0.05), and both groups A and B had better results than group C (P<0.05). No serious adverse effects were found. CONCLUSION: The combination of benazepril and valsartan at routine doses can be effective for treating congestive heart failure.

Dynamic investigation of leukocyte-endothelial cell adhesion interaction under fluid shear stress in vitro.

To establish a method to investigate the dynamic adhesion between leukocytes and human umbilical vein endothelial cells (HUVECs) under definite shear stress. A parallel plate flow chamber system was developed to produce the definite shear stress in vitro. After the cultured HUVECs were loaded in the flow chamber, the circulation solution containing acridine orange (AO)-labeled leukocytes was perfused to flow through chamber at 0.71 dynes/cm(2). In this case, leukocyte-endothelial cell adhesion process was induced. Lipopolysaccharide(LPS) was used as the chemical stimulus and dexamethasone(DXM) was used as the anti-inflammatory reagent. The adhesion process was recorded in videotape by Olympus IX70 fluorescence microscope and CCD-camera. Then the number of adhesion leukocyte, slow and fast rolling velocities of leukocytes on the surface of HUVECs were measured based on the captured images. The number of static adhering and slow rolling leukocytes on the HUVECs treated with LPS was significantly increased by 23.7-fold and 4.1-fold compared with that of the control group. Meanwhile, both the slow and fast rolling velocities of the leukocytes on HUVECs treated with LPS were significantly decreased by 25.6% and 26.1%. When HUVECs were treated with both LPS and DXM, the effect of LPS was inhibited obviously. This developed method can be used in studying ECs adhesion function affected by different chemical and physical stimulus and evaluating the various compounds interfering with cell adhesion.

Real-time detection of nitric oxide in cultured rat aorta endothelial cells induced by shear stress.

To establish a stable and real-time method to detect the production of intracellular nitric oxide (NO) of endothelial cells under different shear stresses. After the cultured endothelial cells were loaded with DAF-FM, the relative NO production was determined by fluorescence intensity, which was detected using Zeiss Axioskop 2 fluorescence microscope and ICCD-camera. The fluorescence of DAF-FM can reflect NO production. Shear stress can induce a dose-dependent increase of NO production, and the increase can be totally inhibited by L-NAME and partly inhibited by Ca(2+)-free buffer. The method can be used to detect the change of NO production in real time, and it can also be used to study the mechanism related to NO increase induced by shear stress.