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Background: Some researchers have achieved favorable efficacy in the treatment of primary papillary thyroid microcarcinoma (PTMC) using microwave ablation (MWA). However, as PTMC is a slowly progressing disease, a long follow-up period is required to confirm treatment efficacy. Our study aim was to investigate the long-term efficacy and safety of ultrasound (US)-guided MWA in PTMC. Methods: In this study, 41 patients with thyroid masses (41 nodules) were diagnosed with PTMC by fine-needle aspiration or core needle biopsy. They underwent US-guided MWA. Preablation ultrasonic images of the thyroid nodules were collected, and the volumes were measured. The patients had follow-up at 1, 3, 6, and 12 months in the first year and every 6 months from the second year on, after MWA. The volume reduction rates (VRRs) of the thyroid nodules were analyzed. Results: In total, 40 of 41 nodules were completely ablated by MWA. After 60 months of follow-up, the volume significantly decreased from a median of 55.78 mm3 (quartile: 21.50, 112.20 mm3) to 0 mm3 (0, 0 mm3) (p < 0.001), with a VRR of 99.37% ± 4.02%. Two patients developed hoarseness after ablation; one recovered within 10 minutes, and the hoarseness in the other patient resolved 2 months after the ablation. No recurrence, metastatic cervical lymph nodes, or distal metastasis was found during the follow-up period. Conclusions: In this five-year follow-up, MWA presented favorable efficacy with satisfactory safety for the treatment of PTMC. It should be considered an alternative therapy to surgery and active surveillance for solitary PTMC.
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Técnicas de Ablação , Carcinoma Papilar/cirurgia , Micro-Ondas/uso terapêutico , Neoplasias da Glândula Tireoide/cirurgia , Técnicas de Ablação/efeitos adversos , Adulto , Biópsia por Agulha , Carcinoma Papilar/diagnóstico por imagem , Carcinoma Papilar/patologia , Progressão da Doença , Feminino , Seguimentos , Humanos , Metástase Linfática , Masculino , Micro-Ondas/efeitos adversos , Pessoa de Meia-Idade , Recidiva Local de Neoplasia , Estudos Retrospectivos , Medição de Risco , Fatores de Risco , Neoplasias da Glândula Tireoide/diagnóstico por imagem , Neoplasias da Glândula Tireoide/patologia , Fatores de Tempo , Resultado do Tratamento , Ultrassonografia de IntervençãoRESUMO
Based on the concentrations of 21 inorganic elements in particulate matter with diameters less than 10 µm (PM10) in 2004, and PM2.5 in 2004 and 2013 of representative road dust in Beijing, the pollution characteristics and potential ecological risks of heavy metals in this dust were analyzed and discussed. The results showed that the six main elements in road dust in Beijing were Si, Ca, Al, Fe, Mg, and K, and the proportions of the total content of the six elements in PM10 in 2004, PM2.5 in 2004, and PM2.5 in 2013 accounted for 96.51%, 96.42%, and 96.53% of the total content of all elements tested, respectively. The elemental enrichment level and the pollution degree and the potential ecological risk of heavy metal in road dust in Beijing in 2004 were PM2.5>PM10. Se, a characteristic element of coal dust, was highly enriched in PM2.5 in 2004, and Cd was high in PM10 and PM2.5 in 2004 with enrichment factors of 1024.03, 68.15, and 871.55, respectively. Co, Zn, Ca, and Cu were significantly enriched in PM10 and PM2.5 in 2004 with enrichment factors of 12.93, 12.33, 8.30, and 8.07 in PM10 and 17.41, 21.80, 12.83, and 19.73 in PM2.5, respectively; Na and Si were not enriched in the road dust. The pollution load index (PLI) of heavy metals was 3.95 in PM10 and 7.71 in PM2.5 in 2004. Owing to the implementation of dust, motor vehicles, and combustion source control measures in Beijing and the relocation of the Shougang corporation, the elemental enrichment level, pollution degree, and potential ecological risk of heavy metals in road dust PM2.5 in 2013 were significantly lower than those in 2004. The enrichment factors of Cd and Se in PM2.5 in 2013 decreased to 98.47 and 0.95, respectively; those of Cu, Ca, and Zn decreased to 11.90, 8.84, and 8.20, respectively; and PLI decreased to 2.56. The results showed that the total potential ecological risk of heavy metals in road dust in Beijing was extremely strong. Heavy metal Cd was the most significant pollution factor and the main potential ecological risk source; its potential ecological risk index (RI) contribution to the total RI of heavy metals was more than 85%. In 2004, the pollution degree of heavy metals in road dust of main roads was significantly higher than that for other road types. The pollution degree of heavy metals in PM10 was main road > expressway entrance to Beijing > secondary main road > ring road; that for PM2.5 was main road > ring road > expressway entrance to Beijing > secondary main road. For PM2.5 in 2013, however, the order was expressway entrance to Beijing > main road > ring road > secondary main road. The pollution degree of heavy metals in road dust of secondary main roads was significantly lower than that for other road types. In 2013, for road dust PM2.5 in Beijing, the correlation of heavy metals Ti, Zn, V, Cr, Cu, Pb, and Ni was significant owing mainly to traffic-related emissions.
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Poluentes Atmosféricos , Metais Pesados , Medição de Risco , Pequim , Poeira , Ecologia , Monitoramento AmbientalRESUMO
OBJECTIVES: (1) To compare the American College of Radiology (ACR) thyroid imaging reporting and data system (TIRADS) and American Thyroid Association (ATA) guidelines for thyroid nodules with regard to diagnostic performance and effectiveness at reducing the number of fine-needle aspiration (FNA) biopsies and to preliminarily discuss the reasons for the differences and (2) to compare the diagnostic performance of the two guidelines in the subgroup of nodules <1 cm in diameter. MATERIALS AND METHODS: In the present study, 1000 thyroid nodules in 894 consecutive patients with final diagnoses were included; these thyroid nodules were investigated via FNA biopsies in our hospital. The ultrasound (US) features of the thyroid nodules were reviewed and stratified according to the categories defined by the ACR TIRADS and ATA guidelines. RESULTS: Compared with the ACR TIRADS guidelines, the ATA guidelines had a higher sensitivity (93.4% (P < 0.001)) and a larger negative predictive value (NPV) (85.3% (P= 0.034)). Compared with the ATA guidelines, the ACR TIRADS guidelines had a higher specificity (66.0% (P < 0.001)), a greater PPV (73.6% (P= 0.001)), and greater accuracy (75.5% (P= 0.017)). Compared with the ATA guidelines, the ACR TIRADS guidelines resulted in significantly fewer unnecessary FNA biopsies (P= 0.007). CONCLUSIONS: This study suggests that both the ACR TIRADS and ATA guidelines have unique strengths with regard to their diagnostic performance. In terms of reducing the number of FNA biopsies, the ACR TIRADS guidelines were superior to the ATA guidelines.
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Técnicas de Diagnóstico Endócrino/normas , Guias de Prática Clínica como Assunto , Glândula Tireoide/patologia , Neoplasias da Glândula Tireoide/patologia , Nódulo da Glândula Tireoide/patologia , Biópsia por Agulha Fina/normas , China/epidemiologia , Estudos de Coortes , Diagnóstico Diferencial , Humanos , Guias de Prática Clínica como Assunto/normas , Valor Preditivo dos Testes , Dados Preliminares , Estudos Retrospectivos , Sensibilidade e Especificidade , Sociedades Médicas/normas , Neoplasias da Glândula Tireoide/diagnóstico , Neoplasias da Glândula Tireoide/epidemiologia , Nódulo da Glândula Tireoide/diagnóstico , Nódulo da Glândula Tireoide/epidemiologia , Carga Tumoral , Ultrassonografia/métodos , Estados UnidosRESUMO
3,4-Dichloroisothiazoles can induce systemic acquired resistance (SAR) to enhance plant resistance against a subsequent pathogen attack, and oxathiapiprolin exhibits excellent anti-fungal activity against oomycetes targeting at the oxysterol-binding protein. To discover novel chemicals with systemic acquired resistance and fungicidal activity, 21 novel isothiazole-thiazole derivatives were designed, synthesized and characterized according to the active compound derivatization method. Compound 6u, with EC50 values of 0.046 mg L-1 and 0.20 mg L-1 against Pseudoperonospora cubensis (Berk. et Curt.) Rostov and Phytophthora infestans in vivo, might act at the same target as oxysterol binding protein (PcORP1) of oxathiapiprolin; this result was validated by cross-resistance and molecular docking studies. The expression of the systemic acquired resistance gene pr1 was significantly up-regulated after treating with compound 6u for 24 h (43-fold) and 48 h (122-fold). These results can help the development of isothiazole-thiazole-based novel fungicides.
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BACKGROUND: Neonicotinoids, among the most important pesticides in recent decades, have played pivotal roles in controlling agricultural pests. However, the toxicity to some environmentally beneficial insects is a cause of concern. The development of novel insecticides safer to these insects is increasingly urgent. RESULTS: A novel series of hydrocarbylidene nitrohydrazinecarboximidamides were designed and synthesised, starting from S-methylisothiourea sulphate. Preliminary bioassays showed that the target molecules exhibited good activities against Lipaphis erysimi (turnip aphid) and Myzus persicae. As shown by initial insecticidal activity data, most of the target compounds had moderate to excellent activities at a concentration of 600 mg L-1 against L. erysimi, and the lethal rate of most compounds exceeded 90%. They were also highly effective against M. persicae. Some of them have shown excellent insecticidal activities, for example, the LC50 values of compounds Ie-02 to Ie-07 were found to be 3.8, 3.0, 2.5, 3.1, 4.1 and 4.0 mg L-1 respectively. CONCLUSION: Structure-activity relationship analysis indicated that a suitable flexible alkyl chain at the imine point and a Cl-substituted pyridine ring are the most crucial factors affecting the activity. © 2017 Society of Chemical Industry.
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Amidas/química , Amidas/síntese química , Afídeos , Inseticidas/química , Inseticidas/síntese química , Animais , Bioensaio , Técnicas de Química Sintética , Desenho de FármacosRESUMO
Simultaneous measurements of precursor gases NH3,NO,NO2,SO2 and the main water-soluble ions in PM2.5 such as sulphate (SO42-),nitrate (NO3-) and ammonium (NH4+) (collectively called SNA)were carried out in the urban area of Beijing during 2015-01 to 2015-12,which obtained 325 groups of samples. PTFE membrane filters were used to collect particulate NH4+, NO3- and SO42-, followed by the online instruments to collect precursor gases. The pollution characteristics of the precursor gases and SNA were analyzed and their correlation was studied. The mean concentrations of NH3, NO, NO2, SO2, NH4+,NO3- and SO42- were 21.5, 17.7, 54.3, 14.2, 8.1, 13.5 and 12.7 µg·m-3 respectively during the period of monitoring, and SNA accounted for 43.4% of PM2.5. The concentrations of SO2,NOx and SNA declined compared to 2014. The concentrations of NO,NO2 and SO2 were highest in winter and lowest in summer. The concentration of NH3 was higher in summer and lower in autumn; The concentration and the percentage of NH4+ were stable during the four seasons,both the concentrations and the percentage of NO3- were lowest in summer. The concentrations of SO42- was highest in winter and the percentage was lowest in summer. The ratio of ([NO3-]+2[SO42-]) and NH4+ was 0.97 during the whole year, showing that anions mainly existed in the form of NO3- and SO42-. In summer, the ratio of[NO3-]+2[SO42-] and[NH4+] was slightly higher than 1.0, which was the reason why NO3- was bound to Ca2+, Mg2+ and Na+besides NH4+. With the increase of pollution, the mass concentration of precursor gases and SNA increased dramatically, among which NOx increased most rapidly, and SO2 decreased from severe pollution to serious pollution. The contribution rate of NH4+ was maintained at a relatively stable level. SO42- had a higher contribution when the pollution level was lower, whereas the concentration of NO3- was higher than others and contributed most to PM2.5 in heavy pollution. Heterogeneous transformation on the surface of particulate matter played a more important role in the formation of SO42- and NO3-. The correlations between NO3-, NO2 and NO,NH4+ and NH3,SO42- and SO2 were significant at the confidence level of 0.01. SO42- had negative correlation with SO2, and NO3- had positive correlation with NO2. Compared with NH3, the NH4+ concentration was more obviously affected by acid gases NO2, SO2.
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OBJECTIVE: To study the value of digital tomosynthesis (DTS) applied in diagnosing spinal tuberculosis. METHODS: Images of digital radiology (DR) and DTS were retrospectively analyzed in patients with spinal tuberculosis, and image quality and ratio of detection of lesions were compared. RESULTS: Excellent ratio was higher for DTS images than DR images; ratios of detection of bone destruction, sequestration, and paraspinal abscess were higher for DTS than DR. CONCLUSIONS: DTS had better image quality and ratios of detection of lesions and could be applied in diagnosing and following spinal tuberculosis and other spinal conditions such as infections or suspected tumors.
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Intensificação de Imagem Radiográfica/métodos , Tomografia Computadorizada por Raios X/métodos , Tuberculose da Coluna Vertebral/diagnóstico , Adolescente , Adulto , Vértebras Cervicais/diagnóstico por imagem , Criança , Feminino , Humanos , Vértebras Lombares/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Vértebras Torácicas/diagnóstico por imagem , Adulto JovemRESUMO
Concentrations of water-soluble ions were measured in Beijing during 2014 for comparison of URG online monitoring systems and filter-based manual methods. The differences of four main ions components in spring, summer, autumn and winter were compared. The total concentrations of eight ions measured by URG online were higher than those of filter-based manual method. There was no significant differences among the annual concentrations of Cl-,NO3-,Mg2+ and Ca2+ obtained by the two methods, while the concentrations of SO42-,NH4+,Na+,K+ from online were higher than those from filter. NO3-,SO42-,Cl- had good correlations in autumn and winter, and NH4+ only had better fitting performance in winter.
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From August 2012 to July 2013, 220 groups of PM2.5 samples were continuously collected at four locations in the urban area of Beijing (Shijingshan, Chegongzhuang, Dongsi, and Tongzhou), and the primary chemical species of PM2.5 were analysed by the chemical mass balance method. It was found that the mass of PM2.5 obtained from chemical mass balance method agreed well with the value from gravimetric measurement, with a good correlation of 0. 95 in spring, autumn, and winter. However, the correlation seasonally changed in summer, with a relatively lower correlation coefficient of 0. 77. The concentrations of OM, EC, SO(4)2-, NO3-, NH4+, Cl-, crustal matter, and trace species were 31. 4, 3. 8, 19. 9, 21. 6, 14. 4, 4. 0, 15. 4, and 2. 9 µg.m-3, which accounted for 25. 1%, 3. 0% , 15. 9%, 17. 2%, 11. 5%, 3. 2%, 12. 3%, and 2. 3% of PM2, , respectively. Besides crustal matter, concentrations of the primary chemical species in PM2.5 from the west to the east gradually increased. The most serious PM pollution occurred between 11 and 14 February 2013, during which concentrations of OM, SO2-, NO3-, NH4+ were 1. 9, 5. 0, 3.2 and 4. 2 times as high as the annual average. SO(4)2- was recognized as the most important species for the pollution in the process. OM was the largest component of urban PM2.5 during both heating and non-heating periods. Comparing to non-heating period, the concentrations of OM, NH4+, NO3-, and SO(4)2- all increased during the heating period, except for the component of crust and EC. The biggest difference between the two periods was the component of Cl- (4. 4 fold), which can be attributed to the burning of coal. For unknown components, the main component was moisture, which accounted for about 6.0% in urban PM2.5. The highest moisture appeared in summer (6. 5%), followed by spring and winter, and the least appeared in fall (3. 7% ).
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Poluentes Atmosféricos/análise , Monitoramento Ambiental , Material Particulado/análise , China , Cidades , Carvão Mineral , Estações do AnoRESUMO
A total of 486 daily PM2.5 samples were collected at a background site, 3 urban sites, 4 suburban sites and a boundary transfer site during August 2012-July 2013. Mass concentrations of 9 water-soluble ions were obtained. The average mass concentration of the 9 ions was 60.5 µg x m(-3), and the order of concentration of ions was NO3- > SO4(2-) > NH4(+)- > Cl- > Na+ > K+ > Ca2+ > F- > Mg2+; Secondary inorganic species NO3-, SO4(2-) and NH4+ were the major components of water-soluble ions in PM2.5, with a contribution of 88% to the total ions of PM2.5. NO3- was the most fluctuated anion during the sampling period. With the increase of pollution level, the accumulation of SNA was obvious, the components that contained nitrogen, NO3- and NH4+, occupied the dominant position in the formation of the secondary components. NO3- had a relatively higher contribution to the accumulation of heavy pollution.
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Poluentes Atmosféricos/análise , Monitoramento Ambiental , Material Particulado/análise , Estações do Ano , Queixo , Cidades , Íons , ÁguaRESUMO
Integrin ß1 subunit and its downstream molecule integrin-linked kinase and focal adhesion kinase have been confirmed to be essential to cell survival and inhibition of apoptosis and hypoxia/reoxygenation (H/R)-induced injuries in cardiomyocytes. However, it is still unclear whether CrkL [v-crk avian sarcoma virus CT-10 oncogene homolog (Crk)-like], which acts also as a component of the integrin pathway, could also affect H/R-induced injuries in the cardiomyocytes. The rat-derived H9C2 cardiomyocytes were infected with a CrkL small hairpin RNA interference recombinant lentivirus, which knockdowns the endogenous CrkL expression in the cardiomyocytes. Apoptosis, cell proliferation and survival were examined in the H9C2 cardiomyocytes treated with either H/R or not. Results showed that knockdown of CrkL could significantly increase apoptosis and inhibition of the cell proliferation and survival and deteriorate the previously mentioned injuries induced by H/R. In contrast, overexpression of human CrkL could relieve the exacerbation of the previously mentioned injuries induced by CrkL knockdown in the H9C2 cardiomyocytes via regulation of Bax and extracellular signal-regulated kinase1/2 (p-ERK1/2). In conclusion, these results confirmed that knockdown of CrkL could deteriorate H/R-induced apoptosis and cell survival inhibition in rat-derived H9C2 cardiomyocytes via Bax and downregulation of p-ERK1/2. It implies that CrkL could mitigate H/R-induced injuries in the cardiomyocytes.
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Hipóxia Celular , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Miócitos Cardíacos/metabolismo , Proteínas Proto-Oncogênicas c-crk/genética , Proteínas Proto-Oncogênicas c-crk/metabolismo , RNA Interferente Pequeno/metabolismo , Proteína X Associada a bcl-2/metabolismo , Sequência de Aminoácidos , Animais , Apoptose , Sobrevivência Celular , Regulação para Baixo , Técnicas de Silenciamento de Genes , Humanos , Dados de Sequência Molecular , RatosRESUMO
The mass concentration of PM2.5 associated with its online and off-line water-soluble ions were obtained during 2014- 10- 2014-11. Secondary inorganic species NO3â», SO4²â» and NH4⺠were the major components of PM2.5 during different observation periods. The total concentration of NO3â», SO4²â» and NH4⺠was (26.8 ± 22.5) µg · m⻳, which contributed (41.7 ± 8.5)% to PM2.5. The concentration of NO3â» was higher than those of others and contributed most to PM2.5. The ions of NO3â», SO4²â» NH4⺠and Clâ» all showed three different periods during 2014 Beijing APEC, besides the different meteorological condition, the cumulative effect caused by local emissions and regional pollution could also not be ignored. Although the characteristics of water-soluble ions was different during different observation periods, there was no obvious acidification of PM2.5 in Beijing at the end of autumn and beginning of winter.
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Poluentes Atmosféricos/química , Íons/química , Material Particulado/química , Aerossóis , Pequim , Monitoramento Ambiental , Tamanho da Partícula , Estações do Ano , ÁguaRESUMO
Based on the environment monitoring data and the ambient air quality data during the period of 1997-2011 from Beijing municipal environmental monitoring center, the correlations between primary pre-cursors of acid deposition, acidic materials and precipitation in Beijing area were analyzed in detail by taking economic development and energy mix into account. These results will be helpful for assessing the performance of environment quality improvement, as well as supplying scientific supporting information to make policies for national and local environment protection authorities. The main findings included as follows: there are significant correlations between the concentrations of NO2, NOx, and SO2 in the atmosphere, which indicated that both N and S in ambient air of Beijing came from fossil fuels combustion; acidic pollutants in the air are mainly discharged from local emission sources in Beijing, while there is no obvious correlation between S and N in wet deposition and concentrations of SO2, NO2 and NOx in the atmosphere, which demonstrated that concentrations of different ions in the acid deposition were influenced by both local sources as well as the inputs from other surrounding districts. Besides, the concentration of NO3- appeared to be correlative with the amount of motor vehicles, implying that the NOx from motor vehicles have contributed the increase of NO3- concentration of substantially.
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Chuva Ácida , Poluentes Atmosféricos/química , Monitoramento Ambiental/métodos , Poluentes Atmosféricos/análise , Atmosfera/análise , China , Dióxido de Nitrogênio/análise , Óxidos de Nitrogênio/análise , Dióxido de Enxofre/análiseRESUMO
The microbiological transformation of the triterpene nigranoic acid (3,4-secocycloarta-4(28),24(Z)-diene-3,26-dioic acid) (1) to 3,4-secocycloarta-4(28),17(20),24(Z)-triene-7ß-hydroxy-16ß,26-lactone-3-oic acid (2) and 3,4-secocycloarta-4(28),17(20)(Z),24(Z)-triene-7ß-hydroxy-16ß-methoxy-3,26-dioic acid (3) by the freshwater fungus Dictyosporium heptasporum YMF1.01213 has been demonstrated. The structures of the biotransformation products were determined by spectroscopic and MS analyses. Compound 2, characterized by the presence of a formed C-16/C-26 ester bridge, provided a novel nine-membered lactone ring structural skeleton for 3,4-secocycloartane triterpenoid derivatives. In addition, Compounds 1-3 exhibited weak anti-HIV activity in vitro. Compounds 2 and 3 were reported for the first time as natural product derivatives.
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Fármacos Anti-HIV/metabolismo , Fungos/metabolismo , Triterpenos/metabolismo , Fármacos Anti-HIV/química , Biotransformação , Água Doce/microbiologia , Humanos , Ressonância Magnética Nuclear Biomolecular , Triterpenos/química , Triterpenos/farmacologiaRESUMO
Characteristics of chemical compositions of precipitation in Beijing were analyzed. The average value of pH was 5.19 from 2005 to 2009, showing stable characteristics of acidification with precipitation. The lowest annual average pH was 4. 87 in 2008 with the highest acidification frequency of 42% and 23% in Chegongzhuang and Daxing districts respectively. The inorganic ion concentrations declined in 5a, indicating an increasing improvement of air quality in Beijing. The concentrations of NH4+ and NO3- were found to increase and contributed to the high nitrogen amount in precipitation. Different seasons have influence on composition concentrations. Generally speaking, the ion concentrations in winter were higher that that in summer. SO4(2-) was the main factor responsible for the acidification of snow in winter, SO4(2-) and NO3- had similar contributions to the acidification of precipitation in summer. It was also found that the local pollutants of SO2, NO(x) and NH3 were major contributors to the acidification of precipitation in Beijing area, local geological conditions and long-distance transfers have important effects on the neutralization of the precipitation.
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Poluentes Atmosféricos/análise , Compostos de Amônio Quaternário/análise , Chuva/química , Neve/química , Dióxido de Enxofre/análise , Chuva Ácida/análise , China , Cidades , Monitoramento Ambiental , Concentração de Íons de Hidrogênio , Estações do Ano , Movimentos da ÁguaRESUMO
Hybridization-based and sequencing-based technologies have found a widespread application in gene expression profiling analysis but much ambiguity exists regarding their reliability. This study developed a framework based on three parameters: detection ability, repeatability, and accuracy to evaluate the reliability of gene expression profiling technologies. The fraction of coverage of detected transcript category, the degree of variance for the number of differentially expressed genes (DEGs), the consistency of DEG category, and suspected false discovery rate (sFDR) were first introduced as statistical indices. In order to validate the availability of these indices, based on the same RNA extract, the analysis was performed by comparing gene expression differences between wild-type and transgenic rice using deep sequencing and microarray. The results suggested that the parameters were available and showed advances in the determination of gene expression differences. Based on relative self-comparison design, suspected false positive genes were easily identified from all DEGs detected, which was difficult for quantitative real-time polymerase chain reaction (qRT-PCR) validation when the count of DEGs was enormous. In addition, sFDRs had advantages in the accuracy evaluation for previous datasets.
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Perfilação da Expressão Gênica/métodos , Hibridização Genética/genética , Análise de Sequência com Séries de Oligonucleotídeos/métodos , Genoma de Planta/genética , Oryza/genética , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
BACKGROUND: C-Myc is a short-lived oncoprotein that is destroyed by ubiquitin-mediated proteolysis. Dysregulated accumulation of c-Myc commonly occurs in human cancers. Some of those cases with the dysregulated c-Myc protein accumulation are attributed to gene amplification or increased mRNA expression. However, the abnormal accumulation of c-Myc protein is also a common finding in human cancers with normal copy number and transcription level of c-Myc gene. It seems that the mechanistic dysregulation in the control of c-Myc protein stabilization is another important hallmark associated with c-Myc accumulation in cancer cells. Here we report a novel mechanistic pathway through which DNA-dependent protein kinase catalytic subunit (DNA-PKcs) modulates the stability of c-Myc protein. RESULTS: Firstly, siRNA-mediated silencing of DNA-PKcs strikingly downregulated c-Myc protein levels in HeLa and HepG2 cells, and simultaneously decreased cell proliferation. The c-Myc protein level in DNA-PKcs deficient human glioma M059J cells was also found much lower than that in DNA-PKcs efficient M059K cells. ATM deficiency does not affect c-Myc expression level. Silencing of DNA-PKcs in HeLa cells resulted in a decreased stability of c-Myc protein, which was associated the increasing of c-Myc phosphorylation on Thr58/Ser62 and ubiquitination level. Phosphorylation of Akt on Ser473, a substrate of DNA-PKcs was found decreased in DNA-PKcs deficient cells. As the consequence, the phosphorylation of GSK3 beta on Ser9, a negatively regulated target of Akt, was also decreased, and which led to activation of GSK 3beta and in turn phosphorylation of c-Myc on Thr58. Moreover, inhibition of GSK3 activity by LiCl or specific siRNA molecules rescued the downregulation of c-Myc mediated by silencing DNA-PKcs. Consistent with this depressed DNA-PKcs cell model, overexpressing DNA-PKcs in normal human liver L02 cells, by sub-chronically exposing to very low dose of carcinogen 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), increased c-Myc protein level, the phosphorylation of Akt and GSK3 beta, as well as cell proliferation. siRNA-mediated silencing of DNA-PKcs in this cell model reversed above alterations to the original levels of L02 cells. CONCLUSION: A suitable DNA-PKcs level in cells is necessary for maintaining genomic stability, while abnormal overexpression of DNA-PKcs may contribute to cell proliferation and even oncogenic transformation by stabilizing the c-Myc oncoprotein via at least the Akt/GSK3 pathway. Our results suggest DNA-PKcs a novel biological role beyond its DNA repair function.