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AIMS: This study aims to establish a population pharmacokinetic (PK) model of teicoplanin in Chinese adult patients to evaluate the dosing regimen in the label sheet and optimize it. METHODS: Nonlinear mixed-effects modelling was used to estimate PK parameters. Monte Carlo simulations were used to evaluate the attainment of various dosing regimens in achieving the target trough concentrations in patients with normal or decreased renal function. RESULTS: A total of 115 patients were enrolled in this retrospective study. Creatinine clearance (CrCL) and albumin (ALB) were identified as covariates on the clearance of teicoplanin. For the treatment of non-complicated methicillin-resistant Staphylococcus aureus (MRSA) infections in patients with normal renal function and serum ALB concentration, the recommended dosing regimen was 600 mg q12h with five administrations as the loading dose followed by 600 mg qd as the maintenance dose; for the treatment of serious and/or complicated MRSA infections, the recommended dosing regimen was 800 mg q12h with five administrations as the loading dose followed by 800 mg qd as the maintenance dose. It is worth noting that both the loading and maintenance doses ought to be modified based on the patient's renal function and serum ALB concentration. In addition, trough concentrations of teicoplanin were significantly increased every other week. CONCLUSIONS: Both loading dosing and maintenance dosing regimens were recommended to be adjusted according to patient's renal function and serum ALB concentration. In addition, it is necessary to perform follow-up therapeutic drug monitoring of teicoplanin at least once every week.
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Staphylococcus aureus Resistente à Meticilina , Infecções Estafilocócicas , Adulto , Humanos , Teicoplanina/uso terapêutico , Antibacterianos , Estudos Retrospectivos , Monitoramento de Medicamentos , Albumina Sérica , Infecções Estafilocócicas/tratamento farmacológicoRESUMO
Limited therapeutic options exist for multidrug-resistant/extensively drug-resistant Acinetobacter baumannii (MDR/XDR-Ab) meningitis/ventriculitis. A combination of intravenous and intraventricular (IVT)/intrathecal (IT) polymyxins achieves good therapeutic outcomes for cases of healthcare-associated MDR/XDR-Ab meningitis/ventriculitis. Colistin is commercially available as colistin sulphate and its sulphomethylated derivative. However, the effect and safety of colistin sulphate in the treatment of MDR/XDR-Ab meningitis/ventriculitis has not been reported. We report on a 66-year-old male patient who developed post-neurosurgical ventriculitis caused by MDR-Ab. IVT concomitant intravenous colistin sulphate was used as a last-resort antimicrobial therapy, the patient's ventriculitis was dramatically improved, and the concentrations of CSF colistin were higher than the MIC breakpoint throughout the treatment. Meanwhile, no nephrotoxicity or neurotoxicity was observed during the treatment.
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Infecções por Acinetobacter , Acinetobacter baumannii , Ventriculite Cerebral , Meningite , Infecções por Acinetobacter/tratamento farmacológico , Idoso , Antibacterianos , Ventriculite Cerebral/tratamento farmacológico , Ventriculite Cerebral/etiologia , Colistina/farmacologia , Colistina/uso terapêutico , Farmacorresistência Bacteriana Múltipla , Humanos , Masculino , Meningite/tratamento farmacológico , Meningite/etiologiaRESUMO
AIMS: Data regarding clinical pharmacokinetic/toxicodynamic (PK/TD) of polymyxin B is short of direct quantitative data. This study aims to investigate the risk factors of polymyxin B associated acute kidney injury (AKI) and to assess the relationship between polymyxin B plasma levels and its nephrotoxicity. METHODS: A retrospective study was performed in adult patients treated with polymyxin B. Risk factors associated with AKI and plasma trough concentrations of polymyxin B were identified via medical record review. A multivariate logistic regression model was established and the risk of polymyxin B-associated AKI were predicted by a receiver operating characteristic curve, with maximal Youden index used to identify safety thresholds among the study population. RESULTS: Fifty-four adult patients were included in the study. AKI was detected in 14 patients during polymyxin B treatment (25.9%, 14 out of 54). Cmin (odds ratio [OR] 2.071; 95% confidence interval [CI] 1.235-3.472) and baseline serum creatinine (OR 1.024; 95% CI 1.005-1.043) were significant independent risk factors for developing AKI. The area under the ROC curve of the combined predictor was larger based on the above factors. When the Youden index was at maximum, the optimal cut-off point was 6.678 of the ROC curve. When Cmin ≥ 3.13 mg/L, the probability of AKI was more than 50%. CONCLUSION: In this study, when the calculated combined predictor value was >6.678, there was an increased risk of AKI. Maintaining a polymyxin B Cmin level below 3.13 mg/L may be helpful in reducing the incidence of polymyxin B associated nephrotoxicity.
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Injúria Renal Aguda , Polimixina B , Injúria Renal Aguda/induzido quimicamente , Injúria Renal Aguda/epidemiologia , Adulto , Antibacterianos/efeitos adversos , Feminino , Humanos , Masculino , Polimixina B/efeitos adversos , Estudos Retrospectivos , Fatores de RiscoRESUMO
Through literature analysis of Pheretima and its origin-related earthworm,this study summarized the progress on Pheretima in textual criticism of origin,origin identification,effective components,detection of harmful components,and pharmacological effects,which can lay a basis for further research on Pheretima. Through literature research,the authors found that Pheretima was first recorded in Secret Formulary for Traumatology and Fracture Taught by Immortal written by LIN Daoren in Tang Dynasty rather than the Taiping Holy Prescriptions for Universal Relief in Song Dynasty. The latest techniques for origin identification include microscopic trait identification,DNA barcoding,and HPLC. The main effective components of Pheretima are proteins,polypeptides,enzymes,nucleotides,amino acids,and trace elements. According to recent studies,Pheretima has anti-pulmonary and anti-renal interstitial fibrosis,respiratory syncytial virus-inhibiting,human hypertrophic scar fibroblast proliferation-suppressing,and mouse embryonic fibroblast proliferation-promoting effects. Moreover,Pheretima can prevent colitis-induced colon cancer by inhibiting the activation of COX-2/PGE2/ß-catenin signaling pathway. METHODS:: for detecting the harmful components and their residues( organic pollutant polychlorinated biphenyl,heavy metals) and bacteria in Pheretima,have been established. Pheretima,mainly derived from wild earthworms,has remarkable clinical efficacy. However,the wild resource is in short supply and artificial culture is expected to be a promising solution.
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Oligoquetos , Animais , Cromatografia Líquida de Alta Pressão , Ciclo-Oxigenase 2 , DNA , Fibroblastos , CamundongosRESUMO
Alternative pre-mRNA splicing plays important roles in regulating self-renewal and differentiation of embryonic stem cells (ESCs). However, how specific alternative splicing programs are established in ESCs remains elusive. Here, we show that a subset of alternative splicing events in ESCs is dependent on miR-294 expression. Remarkably, roughly 60% of these splicing events are affected by the depletion of Muscleblind-Like Splicing Regulator 1 and 2 (Mbnl1/2). Distinct from canonical miRNA function, miR-294 represses Mbnl1/2 through both posttranscriptional and epigenetic mechanisms. Furthermore, we uncover non-canonical functions of MBNL proteins that bind and promote the expression of miR-294 targets, including Cdkn1a and Tgfbr2, thereby opposing the role of miR-294 in regulating cell proliferation, apoptosis, and epithelial-mesenchymal transition (EMT). Our study reveals extensive interactions between miRNAs and splicing factors, highlighting their roles in regulating cell type-specific alternative splicing and defining gene expression programs during development and cellular differentiation.
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Proteínas de Ligação a DNA/fisiologia , Células-Tronco Embrionárias/fisiologia , MicroRNAs/fisiologia , Proteínas de Ligação a RNA/fisiologia , Processamento Alternativo , Animais , Apoptose/genética , Linhagem Celular , Proliferação de Células/genética , Transição Epitelial-Mesenquimal/genética , Regulação da Expressão Gênica no Desenvolvimento , Redes Reguladoras de Genes , MicroRNAs/genéticaRESUMO
Carbon nanotube (CNT) fibers are promising reinforcements in ceramic matrix composites where the service environments involve extremely high temperatures that are generally beyond 1000 °C. This work focuses on the thermal stability of a direct spun CNT fiber in vacuum and in a wide temperature (25-2000 °C). The microstructure, mechanical and electrical properties of the fibers as a function of the heat-treatment temperature were investigated. The results show that high temperature exposure could increase the defect density and loosen the packing state of the fiber, but enhance the graphitization degree of the CNTs. Accordingly, there was a ductile-to-brittle transition in the uniaxial tensile response as the heat-treatment temperature increased, and this was mainly a consequence of the failure mode transitions from localized shear to defect dominant fracture. The tensile modulus was enhanced, but the tensile strength was decreased after the heat-treatment. The former can be explained by the enhanced graphitization degree of CNT and the latter should be a result of the increased defect density. Finally, the electrical property of the fiber was degraded, due to the increased contact resistance of mutual CNTs.
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OBJECTIVE: To evaluate the efficacy and safety of a hospital-made resuscitation pack, a Chinese medicinal herbal compound formula designed to enhance recovery in post-bronchoscopy patients. METHODS: In this randomized, single-blind, placebo-controlled clinical trial, eligible patients were randomly assigned 1:1 to either the treatment or control groups. The patients in the treatment group applied the resuscitation pack, which contained aromatic compounded Chinese herbs. The patients in the control group applied a hospital-made, single herb placebo pack. Packs were placed on the Tiantu (CV 22) acupuncture point for 4 h as soon as the bronchoscopy finished. Efficacy indicators, such as recovery time, patients' symptoms including nausea and dizziness, and adverse events (AEs) were observed and compared. The outcome indices were evaluated at baseline, 1 and 24 h after the bronchoscopy. Subgroup analysis was further performed by patients' age and depth of sedation. RESULTS: When applying generalized estimating equations (GEE) to evaluate the intensity of post-bronchoscopy nausea and vomiting, the intensity was lower in the treatment group (163 cases) compared with the control group (162 cases; 95% CI: 0.004, 0.099, P=0.03]. Also, significantly lower intensity of nausea was observed in the 60-70 years of age subgroup (95% CI: 0.029, 0.169, P=0.006) and deep sedation subgroup (95% CI: 0.002, 0.124; P=0.04). There was no significant difference in dizziness between two groups by GEE (95% CI: -0.134, 0.297; P=0.459). In addition, no serious AEs were observed in either group. CONCLUSIONS: Our study found that the resuscitation pack markedly improved patients' symptoms by reducing nausea and vomiting after bronchoscopy without AEs, compared with placebo in the perioperative period. (Trial registration No. ChiCTR2000038299).
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Objective: To develop a highly sensitive and rapid nucleic acid detection method for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods: We designed, developed, and manufactured an integrated disposable device for SARS-CoV-2 nucleic acid extraction and detection. The precision of the liquid transfer and temperature control was tested. A comparison between our device and a commercial kit for SARS-Cov-2 nucleic acid extraction was performed using real-time fluorescence reverse transcription polymerase chain reaction (RT-PCR). The entire process, from SARS-CoV-2 nucleic acid extraction to amplification, was evaluated. Results: The precision of the syringe transfer volume was 19.2 ± 1.9 µL (set value was 20), 32.2 ± 1.6 (set value was 30), and 57.2 ± 3.5 (set value was 60). Temperature control in the amplification tube was measured at 60.0 ± 0.0 °C (set value was 60) and 95.1 ± 0.2 °C (set value was 95) respectively. SARS-Cov-2 nucleic acid extraction yield through the device was 7.10 × 10 6 copies/mL, while a commercial kit yielded 2.98 × 10 6 copies/mL. The mean time to complete the entire assay, from SARS-CoV-2 nucleic acid extraction to amplification detection, was 36 min and 45 s. The detection limit for SARS-CoV-2 nucleic acid was 250 copies/mL. Conclusion: The integrated disposable devices may be used for SARS-CoV-2 Point-of-Care test (POCT).
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COVID-19 , Equipamentos Descartáveis , RNA Viral , SARS-CoV-2 , SARS-CoV-2/isolamento & purificação , COVID-19/diagnóstico , COVID-19/virologia , Humanos , RNA Viral/isolamento & purificação , RNA Viral/análise , Teste de Ácido Nucleico para COVID-19/instrumentação , Teste de Ácido Nucleico para COVID-19/métodos , Técnicas de Amplificação de Ácido Nucleico/instrumentação , Técnicas de Amplificação de Ácido Nucleico/métodos , Reação em Cadeia da Polimerase em Tempo Real/métodos , Reação em Cadeia da Polimerase em Tempo Real/instrumentaçãoRESUMO
Organoid technology offers sophisticatedin vitrohuman models for basic research and drug development. However, low batch-to-batch reproducibility and high cost due to laborious procedures and materials prevent organoid culture standardization for automation and high-throughput applications. Here, using a novel platform based on the findings that Pluronic F-127 (PF-127) could trigger highly uniform spheroid assembly through a mechanism different from plate coating, we develop a one-pot organoid differentiation strategy. Using our strategy, we successfully generate cortical, nephron, hepatic, and lung organoids with improved reproducibility compared to previous methods while reducing the original costs by 80%-95%. In addition, we adapt our platform to microfluidic chips allowing automated culture. We showcase that our platform can be applied to tissue-specific screening, such as drug toxicity and transfection reagents testing. Finally, we generateNEAT1knockout tissue-specific organoids and showNEAT1modulates multiple signaling pathways fine-tuning the differentiation of nephron and hepatic organoids and suppresses immune responses in cortical organoids. In summary, our strategy provides a powerful platform for advancing organoid research and studying human development and diseases.
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Organoides , Poloxâmero , Humanos , Poloxâmero/farmacologia , Reprodutibilidade dos Testes , Análise Custo-Benefício , FígadoRESUMO
This study aims to assess the risk factors for insufficient vancomycin concentrations for its prophylactic use in adult patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) and to modify the dosing regimen to achieve appropriate plasma concentrations. A total of 27 patients with vancomycin dosing of 1 to 1.5 g based on a weight cutoff of 67 kg were included, of which only 13 (48.15%) had vancomycin plasma concentration >15 mg/L at surgical closure. Risk factors of vancomycin concentration <15 mg/L at surgical-site closure were confirmed by multivariate logistic regression analysis, which showed that CPB duration was an independent predictor. Patients with CPB duration >4 hours had significantly lower vancomycin concentrations and lower proportion in achieving target vancomycin concentration at the end of CPB and surgical closure. For patients with CPB >4 hours, the modified dosing regimen that a second dose of 0.5 to 0.75 g added at 4 hours since the onset of CPB improved the target achievement of vancomycin concentration at surgical closure. Taken together, CPB duration >4 hours was the risk factor for insufficient vancomycin concentration at surgical closure, while our modified dosing could improve the vancomycin concentrations for its prophylactic use in patients undergoing cardiac surgery with CPB.
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Procedimentos Cirúrgicos Cardíacos , Vancomicina , Adulto , Humanos , Antibacterianos , Ponte CardiopulmonarRESUMO
Background: Linezolid is associated with myelosuppression, which may cause failure in optimally treating bacterial infections. The study aimed to define the pharmacokinetic/toxicodynamic (PK/TD) threshold for critically ill patients and to identify a dosing strategy for critically ill patients with renal insufficiency. Methods: The population pharmacokinetic (PK) model was developed using the NONMEM program. Logistic regression modeling was conducted to determine the toxicodynamic (TD) threshold of linezolid-induced myelosuppression. The dosing regimen was optimized based on the Monte Carlo simulation of the final model. Results: PK analysis included 127 linezolid concentrations from 83 critically ill patients at a range of 0.25-21.61 mg/L. Creatinine clearance (CrCL) was identified as the only covariate of linezolid clearance that significantly explained interindividual variability. Thirty-four (40.97%) of the 83 patients developed linezolid-associated myelosuppression. Logistic regression analysis showed that the trough concentration (Cmin) was a significant predictor of myelosuppression in critically patients, and the threshold for Cmin in predicting myelosuppression with 50% probability was 7.8 mg/L. The Kaplan-Meier plot revealed that the overall median time from the initiation of therapy to the development of myelosuppression was 12 days. Monte Carlo simulation indicated an empirical dose reduction to 600 mg every 24 h was optimal to balance the safety and efficacy in critically ill patients with CrCL of 30-60 ml/min, 450 mg every 24 h was the alternative for patients with CrCL <30 ml/min, and 600 mg every 12 h was recommended for patients with CrCL ≥60 ml/min. Conclusion: Renal function plays a significant role in linezolid PKs for critically ill patients. A dose of 600 mg every 24 h was recommended for patients with CrCL <60 ml/min to minimize linezolid-induced myelosuppression.
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Objectives: This study aims to characterize the population pharmacokinetics of polymyxin B in lung transplant recipients and optimize its dosage regimens. Patients and methods: This prospective study involved carbapenem-resistant organisms-infected patients treated with polymyxin B. The population pharmacokinetic model was developed using the NONMEM program. The clinical outcomes including clinical treatment efficacy, microbiological efficacy, nephrotoxicity, and hyperpigmentation were assessed. Monte Carlo simulation was performed to calculate the probability of target attainment in patients with normal or decreased renal function. Results: A total of 34 hospitalized adult patients were included. 29 (85.29%) patients were considered of clinical cure or improvement; 14 (41.18%) patients had successful bacteria elimination at the end of the treatment. Meanwhile, 5 (14.71%) patients developed polymyxin B-induced nephrotoxicity; 19 (55.88%) patients developed skin hyperpigmentation. A total of 164 concentrations with a range of 0.56-11.66 mg/L were obtained for pharmacokinetic modeling. The pharmacokinetic characteristic of polymyxin B was well described by a 1-compartment model with linear elimination, and only creatinine clearance was identified as a covariate on the clearance of polymyxin B. Monte Carlo simulations indicated an adjusted dosage regimen might be needed in patients with renal insufficiency and the currently recommended dose regimens by the label sheet of polymyxin B may likely generate a subtherapeutic exposure for MIC = 2 mg/L. Conclusion: Renal function has a significant effect on the clearance of polymyxin B in lung transplant recipients, and an adjustment of dosage was needed in patients with renal impairments.
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Limited data are available for ceftazidime-avibactam (CZA) dosing in patients receiving renal replacement therapy, especially the data on the dosing in patients receiving intermittent hemodialysis (IHD). In this report, we firstly described a case in which CZA was administered as 2.5 g after each time of IHD, and a dose of 1.25 g was added on the 48th-hour for the 72-h interdialytic interval. Plasma concentrations of CZA measured at different time indicated that > 50% of administered ceftazidime and avibactam were removed during the 4-h hemodialysis. In addition, we described another case on continuous venovenous hemodialysis (CVVHD), in which CZA was administered as 2.5 g q12h in 2-h infusions. The dose regimen for these two cases could achieve trough concentration of ceftazidime higher than fourfold of the MIC and trough concentration of avibactam higher than the threshold of 1 µg/mL during the treatment, and exert efficient antimicrobial effect.
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Background: Presently, colistin is commercially available in two different forms, namely, colistin sulfate and its sulphomethylated derivative, colistimethate sodium (CMS). However, in the currently reported studies, most of the clinical studies on colistin for parenteral use are referred to as CMS. Data on the pharmacokinetics (PK), clinical efficacy, and side effects of colistin sulfate in clinical use have not been reported. Methods: This retrospective study was performed on carbapenem-resistant organism (CRO)-infected patients treated with colistin sulfate for more than 72 h. The population pharmacokinetic model was developed using the NONMEM program. The clinical outcomes including clinical treatment efficacy, microbiological eradication, and nephrotoxicity were assessed. Monte Carlo simulation was utilized to calculate the probability of target attainment (PTA) in patients with normal or decreased renal function. Results: A total of 42 patients were enrolled, of which 25 (59.52%) patients were considered clinical treatment success and 29 (69.06%) patients had successful bacteria elimination at the end of treatment. Remarkably, no patient developed colistin sulfate-related nephrotoxicity. A total of 112 colistin concentrations with a range of 0.28-6.20 mg/L were included for PK modeling. The PK characteristic of colistin was well illustrated by a one-compartment model with linear elimination, and creatinine clearance (CrCL) was identified as a covariate on the clearance of colistin sulfate that significantly explained inter-individual variability. Monte Carlo simulations showed that the recommended dose regimen of colistin sulfate, according to the label sheet, of a daily dose of 1-1.5 million IU/day, given in 2-3 doses, could attain PTA > 90% for MICs ≤ 0.5 µg/mL, and that a daily dose of 1 million IU/day could pose a risk of subtherapeutic exposure for MIC ≥1 µg/ml in renal healthy patients. Conclusion: Renal function significantly affects the clearance of colistin sulfate. A dose of 750,000 U every 12 h was recommended for pathogens with MIC ≤1 µg/ml. The dosage recommended by the label inserts had a risk of subtherapeutic exposure for pathogens with MIC ≥2 µg/ml. Despite higher exposure to colistin in patients with acute renal insufficiency, dose reduction was not recommended.
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Evidence supports linezolid therapeutic drug monitoring as the exposure-response relationship has been identified for toxicity among patients receiving linezolid, but the data to establish the upper limit are limited and the published toxicity thresholds range widely. The purpose of this study was to determine the linezolid exposure-toxicity thresholds to improve the safety of linezolid. This is a multicenter retrospective study of adult patients treated with linezolid from 2018 to 2019. The population pharmacokinetic model of linezolid was established based on 270 plasma concentrations in 152 patients, which showed creatinine clearance and white cell count are covariates affecting the clearance of linezolid, and serum albumin is the covariate affecting the volume of distribution. Classification and regression tree analysis was used to determine the linezolid exposure thresholds associated with an increased probability of toxicity. Among 141 patients included for toxicity analysis, the rate of occurring toxicity was significantly higher among patients with an AUC0-24, d1 ≥163 mg h/L, AUC0-24, d2 ≥207 mg h/L, AUC0-24, ss ≥210 mg h/L, and Cmin,d2 ≥6.9 mg/L, Cmin,ss ≥6.9 mg/L, while no threshold was discovered for Cmin, d1. Those exposure thresholds and duration of linezolid treatment were independently associated with linezolid-related toxicity in the logistic regression analyses. In addition, the predictive performance of the AUC0-24 and Cmin thresholds at day 2 and steady state were close. Considering that the AUC estimation is cumbersome, Cmin threshold at 48 h and steady state with a value of ≥6.9 mg/L is recommended to improve safety, especially for patients with renal insufficiency and patients with low serum albumin.
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The morphological and functional integrity of the endothelial cell (EC) is compromised in many cardiovascular diseases such as atherosclerosis, hypertension, and diabetes. Angiotensin II (Ang II) plays important roles in the initiation and progression of these diseases. 3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins) may have cholesterol-independent pleiotropic effects on preventing the EC injury and dysfunction that occurs in these diseases, and the protective effects may relate to bradykinin 2 receptors (B2Rs). Our study was designed to test the hypothesis that atorvastatin, via B2Rs, protects the viability and function of EC exposed to Ang II independent of hemodynamics. The experimental results showed that the cytotoxic effects of Ang II on human umbilical vein endothelial cells were significantly ameliorated by atorvastatin pretreatment (LDH tests, MTT assay, and propdium iodide (PI)/Annexin V-stating analysis), and atorvastatin treatment simultaneously enhanced expression of endothelial nitric oxide synthase and yielded of nitric oxide (NO) and cyclic guanosine monophosphate, but both effects were attenuated by the B2Rs antagonist HOE-140. This study proves the hypothesis and may be pertinent to the complex mechanism of action of statins explaining their long-term beneficial effects in maintaining the morphological and functional integrity of vascular ECs.
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Angiotensina II/farmacologia , Células Endoteliais/efeitos dos fármacos , Ácidos Heptanoicos/farmacologia , Pirróis/farmacologia , Receptor B2 da Bradicinina/fisiologia , Veias Umbilicais/metabolismo , Angiotensina II/fisiologia , Apoptose , Atorvastatina , Linhagem Celular , Células Endoteliais/metabolismo , Humanos , Inibidores de Hidroximetilglutaril-CoA Redutases/farmacologia , Óxido Nítrico Sintase Tipo III/metabolismo , Veias Umbilicais/citologiaRESUMO
Nitrogen is essential for forest growth and forest stand development. It is commonly a limited factor for forest productivity. We examined delta (15)N values in soils and plants by studying the sources of N used by vegetation and cycles of N in a 43-year-old plantation of the TieShanPing forest ecosystem in southwestern China, dominated by massone pine (Pinus massoniana). The N concentration of plant materials ranges from 1.1% to 2.2%. The nitrogen concentration of P. massoniana was 1.3% while soils showed the concentration of 0.04-0.15%. Regarding natural abundance of (15)N, large significant variation (-6.0 per thousand to -3.8 per thousand) in delta (15)N values was observed among shrub and tree leaves. delta (15)N values were also significantly varied from -4.7 per thousand to -3.8 per thousand among the pioneer species in the plantation. Soil delta (15)N values (3.1-6.3 per thousand) were significantly enriched compared to those values in plant samples. Despite the negative delta (15)N values of the vegetation cover, the high delta (15)N values in the topsoil indicate that return of N to soils by litter-fall is minimal on TieShanPing and the present forests do not change very much the soil (15)N signals at the surface layer. The positive delta (15)N values may also indicate large N losses from the soil system vial leaching, volatilization and plant uptake.
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Ecossistema , Isótopos de Nitrogênio/análise , Nitrogênio/análise , Nitrogênio/metabolismo , Árvores/metabolismo , ChinaRESUMO
An investigation of gaseous elemental mercury concentration in atmosphere was conducted at Beijing and Guangzhou urban, Yangtze Delta regional sites and China Global Atmosphere Watch Baseline Observatory (CGAWBO) in Mt. Waliguan of remote continental area of China. High temporal resolved data were obtained using automated mercury analyzer RA-915+. Results showed that the overall hourly mean Hg0 concentrations in Mt. Waliguan were 1.7+/-1.1 ng/m3 in summer and 0.6+/-0.08 ng/m3 in winter. The concentration in Yangtze Delta regional site was 5.4+/-4.1 ng/m3, which was much higher than those in Waliguan continental background area and also higher than that found in North America and Europe rural areas. In Beijing urban area the overall hourly mean Hg0 concentrations were 8.3+/-3.6 ng/m3 in winter, 6.5+/-5.2 ng/m3 in spring, 4.9+/-3.3 ng/m3 in summer, and 6.7+/-3.5 ng/m3 in autumn, respectively, and the concentration was 13.5+/-7.1 ng/m3 in Guangzhou site. The mean concentration reached the lowest value at 14:00 and the highest at 02:00 or 20:00 in all monitoring campaigns in Beijing and Guangzhou urban areas, which contrasted with the results measured in Yangtze Delta regional site and Mt. Waliguan. The features of concentration and diurnal variation of Hg0 in Beijing and Guangzhou implied the importance of local anthropogenic sources in contributing to the high Hg0 concentration in urban areas of China. Contrary seasonal variation patterns of Hg0 concentration were found between urban and remote sites. In Beijing the highest Hg0 concentration was in winter and the lowest in summer, while in Mt. Waliguan the Hg0 concentration in summer was higher than that in winter. These indicated that different processes and factors controlled Hg0 concentration in urban, regional and remote areas.
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Poluentes Atmosféricos/análise , Mercúrio/análise , Atmosfera , China , Cidades , Monitoramento Ambiental , Estações do AnoRESUMO
Headspace solid-phase microextraction HS-SPME) technique was employed to extract the volatile compounds from Pollen Pini. The volatile components were isolated and identified successfully by gas chromatography-mass spectrometry (GC-MS). The volatiles were collected using several SPME parameters (including extraction time and temperature). The best response was obtained using a PA fiber by when the extraction temperature was 70 degrees C, extraction time was 30 minutes and desorption time was 10 time. Analysis was performed by GC-MS. Seventy components were identified by HS-SPME. The main components were fatty compounds. The results showed that the HS-SPME technique could be used to extract the volatile components from HS-SPME-GC-MS.