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Compressed ultrafast photography (CUP) is a computational imaging technology capable of capturing transient scenes in picosecond scale with a sequence depth of hundreds of frames. Since the inverse problem of CUP is an ill-posed problem, it is challenging to further improve the reconstruction quality under the condition of high noise level and compression ratio. In addition, there are many articles adding an external charge-coupled device (CCD) camera to the CUP system to form the time-unsheared view because the added constraint can improve the reconstruction quality of images. However, since the images are collected by different cameras, slight affine transformation may have great impacts on the reconstruction quality. Here, we propose an algorithm that combines the time-unsheared image constraint CUP system with unsupervised neural networks. Image registration network is also introduced into the network framework to learn the affine transformation parameters of input images. The proposed algorithm effectively utilizes the implicit image prior in the neural network as well as the extra hardware prior information brought by the time-unsheared view. Combined with image registration network, this joint learning model enables our proposed algorithm to further improve the quality of reconstructed images without training datasets. The simulation and experiment results demonstrate the application prospect of our algorithm in ultrafast event capture.
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This paper present a novel, integrated compressed ultrafast photography system for comprehensive measurement of the aluminium planar wire array Z-Pinch evolution process. The system incorporates a large array streak camera and embedded encoding to improve the signal-to-noise ratio. Based on the "QiangGuang-I" pulsed power facility, we recorded the complete continuous 2D implosion process of planar wire array Z-Pinch for the first time. Our results contribute valuable understanding of imploding plasma instabilities and offer direction for the optimization of Z-Pinch facilities.
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AIM: This study aims to investigate the prevalence of intestinal pathogenic Escherichia coli (InPEC) in healthy pig-related samples and evaluate the potential virulence of the InPEC strains. METHODS AND RESULTS: A multiplex PCR method was established to identify different pathotypes of InPEC. A total of 800 rectal swab samples and 296 pork samples were collected from pig farms and slaughterhouses in Hubei province, China. From these samples, a total of 21 InPEC strains were isolated, including 19 enteropathogenic E. coli (EPEC) and 2 shiga toxin-producing E. coli (STEC) strains. By whole-genome sequencing and in silico typing, it was shown that the sequence types and serotypes were diverse among the strains. Antimicrobial susceptibility assays showed that 90.48% of the strains were multi-drug resistant. The virulence of the strains was first evaluated using the Galleria mellonella larvae model, which showed that most of the strains possessed medium to high pathogenicity. A moderately virulent EPEC isolate was further selected to characterize its pathogenicity using a mouse model, which suggested that it could cause significant diarrhea. Bioluminescence imaging (BLI) was then used to investigate the colonization dynamics of this EPEC isolate, which showed that the EPEC strain could colonize the mouse cecum for up to 5 days.
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Escherichia coli Enteropatogênica , Infecções por Escherichia coli , Proteínas de Escherichia coli , Escherichia coli Shiga Toxigênica , Humanos , Escherichia coli Enteropatogênica/genética , Infecções por Escherichia coli/epidemiologia , Infecções por Escherichia coli/veterinária , Virulência , Diarreia , Fatores de Virulência , Escherichia coli Shiga Toxigênica/genéticaRESUMO
Power line interference (PLI) is a major source of noise in sEMG signals. As the bandwidth of PLI overlaps with the sEMG signals, it can easily affect the interpretation of the signal. The processing methods used in the literature are mostly notch filtering and spectral interpolation. However, it is difficult for the former to reconcile the contradiction between completely filtering and avoiding signal distortion, while the latter performs poorly in the case of a time-varying PLI. To solve these, a novel synchrosqueezed-wavelet-transform (SWT)-based PLI filter is proposed. The local SWT was developed to reduce the computation cost while maintaining the frequency resolution. A ridge location method based on an adaptive threshold is presented. In addition, two ridge extraction methods (REMs) are proposed to fit different application requirements. Parameters were optimized before further study. Notch filtering, spectral interpolation, and the proposed filter were evaluated on the simulated signals and real signals. The output signal-to-noise ratio (SNR) ranges of the proposed filter with two different REMs are 18.53-24.57 and 18.57-26.92. Both the quantitative index and the time-frequency spectrum diagram show that the performance of the proposed filter is significantly better than that of the other filters.
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Cardiac shockwave therapy (CSWT) is a noninvasive treatment for patients with refractory angina or myocardial ischemia. This study aims to evaluate the potential beneficial effect and safety of CSWT in patients with severe coronary artery disease (CAD) who have undergone coronary artery bypass grafting (CABG).This was a single-arm prospective cohort study. A total of 30 patients with severe CAD who were not suitable for coronary revascularization and who had undergone CABG were enrolled. All patients received CSWT for nine sessions. Evaluation was performed before and after CSWT, including the Canadian Cardiovascular Society (CCS) classification, New York Heart Association (NYHA) classification, 6-minute walk test (6MWT), Seattle Angina Questionnaire (SAQ) score, nitroglycerin dosage, echocardiography, myocardial perfusion imaging (MPI), and safety parameters. All patients were followed up at both 1 month and 9 months after CSWT.After treatment, CSWT significantly improved CCS classification (P < 0.05), NYHA classification (P < 0.05), nitroglycerin dosage (P < 0.001), and 6MWT (P < 0.05) at 1 month and 9 months after CSWT. SAQ score (P < 0.05) and left ventricular ejection fraction (LVEF; P = 0.037) by echocardiography significantly improved at 1 month after CSWT. Significant decreases in summed stress score (SSS), summed difference score (SDS), ischemic area stress, and ischemic area difference by MPI were observed at 1 month and 9 months after CSWT (P < 0.01). There were no changes in safety parameters before and after CSWT.CSWT may have a beneficial effect on improving myocardial perfusion, clinical symptoms, exertional capacity, and quality of life and is a safe alternative treatment for patients with severe CAD who have undergone CABG.
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Doença da Artéria Coronariana , Ondas de Choque de Alta Energia , Humanos , Doença da Artéria Coronariana/cirurgia , Doença da Artéria Coronariana/diagnóstico , Nitroglicerina , Ondas de Choque de Alta Energia/uso terapêutico , Volume Sistólico , Estudos Prospectivos , Qualidade de Vida , Resultado do Tratamento , Função Ventricular Esquerda , Canadá , Ponte de Artéria CoronáriaRESUMO
BACKGROUND: Previous studies proved the efficacy of cardiac shock wave therapy (CSWT) for coronary artery disease (CAD) patients who are not candidate for reperfusion therapy. Randomized control trials are limited. We try to explore the efficacy and safety of CSWT for patients with severe CAD. METHODS: Thirty patients with severe CAD who had obvious ischemia on myocardial perfusion imaging (MPI) were enrolled and randomly assigned to the CSWT group or the control group. They had received optimal medication treatment for at least three months. Nine sessions of shock wave therapy were conducted over 3 months. CSWT group received the real treatment, while the control group received the pseudo-treatment. Clinical symptom, imaging outcomes and safety parameters were compared between two groups. RESULTS: After treatment, regional stress score (P = .023), improvement rate (IR) of ischemic area (IA) stress (P < .001) and IR of IA difference (P < .001) were significantly favor CSWT group. The interaction of summed rest score (P < .001), summed stress score (P = .004), summed difference score (P = .036) were significantly improved in the CSWT group compared to the control group. Seattle angina questionnaire, quality of life (QOL) and the distance of six-minute walking test (6MWT) were improved in both groups without significant difference between them. Hemodynamic parameters were stable during procedure. Myocardial injury markers showed no changes in two groups. CONCLUSIONS: Our study demonstrated CSWT could effectively and safely improve myocardial perfusion in patients with severe CAD. Clinical symptom, QOL and 6MWT were all improved after treatment, but no significant difference between two groups.
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Doença da Artéria Coronariana , Tratamento por Ondas de Choque Extracorpóreas , Ondas de Choque de Alta Energia , Imagem de Perfusão do Miocárdio , Doença da Artéria Coronariana/diagnóstico por imagem , Doença da Artéria Coronariana/terapia , Tratamento por Ondas de Choque Extracorpóreas/métodos , Ondas de Choque de Alta Energia/efeitos adversos , Humanos , Qualidade de Vida , Resultado do TratamentoRESUMO
As a promising feedstock, alkali-extracted xylan from lignocellulosic biomass is desired for producing xylose, which can be used for renewable biofuels production. In this study, an efficient pathway has been established for low-cost and high-yield production of xylose by hydrolysis of alkali-extracted xylan from agricultural wastes using an endo-1,4-xylanase (XYLA) from Bacillus safensis TCCC 111022 and a ß-xylosidase (XYLO) from B. pumilus TCCC 11573. The optimum activities of recombinant XYLA (rXYLA) and XYLO (rXYLO) were 60 â and pH 8.0, and 30 â and pH 7.0, respectively. They were stable over a broad pH range (pH 6.0-11.0 and 7.0-10.0). rXYLO showed a relatively high xylose tolerance up to 100 mM. Furthermore, the yield of xylose from wheat straw, rice straw, corn stover, corncob and sugarcane bagasse by rXYLA and rXYLO was 63.77%, 71.76%, 68.55%, 53.81%, and 58.58%, respectively. This study demonstrated a strategy to produce xylose from agricultural wastes by integrating alkali-extracted xylan and enzymatic hydrolysis.
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Bacillus , Saccharum , Xilosidases , Álcalis , Bacillus/metabolismo , Biocombustíveis , Celulose , Endo-1,4-beta-Xilanases/metabolismo , Hidrólise , Saccharum/metabolismo , Xilanos , Xilose/metabolismo , Xilosidases/metabolismoRESUMO
BACKGROUND: Estimated glomerular filtration rate (eGFR) equations can be inaccurate when applied to elderly patients. Newly, the full-age-spectrum (FAS) equation was developed for use in elderly patients. AIM: We compared the available eGFR equations in elderly Chinese patients with mGFRs < 60 mL/min/1.73 m2. METHODS: Measured glomerular filtration rates (mGFRs) were obtained using 99mTc-DTPA (diethylene-triamine-pentaacetic acid) scans, 220 patients ≥ 80 years with mGFRs < 60 mL/min/1.73 m2 were enrolled. Serum creatinine (SCr) levels were measured simultaneously, and eGFRs based on SCr were calculated using four formulas: the modification of diet in renal disease (MDRD), chronic kidney disease epidemiology collaboration (CKD-EPI-SCr), Berlin initiative study (BIS1), and the FAS-SCr equations. RESULTS: All the equations tended to overestimate GFR. The FAS-SCr equation provided the least bias (1.84), the highest proportion of eGFR within 30% of mGFR (P30, 72.7%), the bias and P30 of the BIS1 equation were 3.45 and 72.3%, respectively. In patients with mGFRs of 30-60 mL/min/1.73 m2, the BIS1 and FAS-SCr equations demonstrated better performances than the MDRD and CKD-EPI-SCr equations. While in patients with mGFR < 30 mL/min/1.73 m2, the accuracy of all equations was poor. DISCUSSION: In older patients with mGFRs of 30-60 mL/min/1.73 m2, the BIS1 and the FAS-SCr equations exhibited good performance, none of the equations based on SCr were suitable for older subjects with mGFRs < 30 mL/min/1.73 m2. CONCLUSIONS: The BIS1 and FAS-SCr equations may be optimal for older patients with moderately reduced kidney function.
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Taxa de Filtração Glomerular/fisiologia , Insuficiência Renal Crônica/fisiopatologia , Idoso de 80 Anos ou mais , Envelhecimento/fisiologia , Algoritmos , China , Creatinina/sangue , Feminino , Humanos , Masculino , Insuficiência Renal Crônica/sangueRESUMO
PURPOSE: To evaluate the clinical value of 18F-FDG-PET/CT for the diagnosis of fever of unknown origin (FUO) and inflammation of unknown origin (IUO) in Chinese population, as well as the characteristics of PET/CT in different category of etiological disease. METHODS: A total of 376 consecutive patients with FUO/IUO who underwent FDG-PET/CT at 12 hospitals were retrospectively studied. FDG uptake was quantitatively and visually evaluated, by using SUVmax and a 4-grade scale respectively. A questionnaire survey to the clinicians was used to evaluate the significance of PET/CT in diagnosing of FUO/IUO. Data analysis included the etiological distribution in the study population, image characteristics in different category of diseases, and clinical significance of PET/CT. RESULTS: In 376 studied patients, the infectious diseases accounted for 33.0% of patients, rheumatologic diseases for 32.4%, malignancies for 19.1%, miscellaneous causes for 6.6%, and cause unknown for 8.8%. However, the etiological distribution among hospitals was varied. In addition, the etiological disease composition ratio has changed over time in China. On PET/CT examinations, 358 (95.2%) of the patients had a positive finding. Within them, local high uptake lesion was found in 219 cases, and nonspecific abnormal uptake (NAU) was found in 187 cases. FDG uptake in malignant diseases was significantly higher than in other category diseases both on SUVmax and visual scores (t-value range from 4.098 to 5.612, all P value < 0.001). Based on a clinical questionnaire survey, PET/CT provided additional diagnostic information for 77.4% of patients, and 89.6% of patients benefited from PET/CT examination. CONCLUSIONS: FDG PET/CT is a valuable tool for clinical diagnosis of FUO/IUO, and it is of great significance in further investigating the usefulness of PET/CT in non-neoplastic diseases.
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Febre de Causa Desconhecida/diagnóstico por imagem , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada/normas , Adulto , Idoso , Feminino , Febre de Causa Desconhecida/etiologia , Fluordesoxiglucose F18 , Humanos , Masculino , Pessoa de Meia-Idade , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada/métodos , Compostos RadiofarmacêuticosRESUMO
Parkinson's Disease (PD) is a neurodegenerative disease that occurs in the middle-aged and elderly population and has dyskinesia as the main clinical symptom. Bradykinesia is a typical dyskinesia symptom of Parkinson's disease. The evaluation of bradykinesia based on wearable devices is an important support for individualized diagnosis and telemedicine. This paper focuses on the bradykinesia, expound the existing detection and evaluation techniques for wearable devices and data analysis methods. This paper also analyzes and discusses some current problems in the field and future research directions.
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Hipocinesia , Doença de Parkinson , Telemedicina , Dispositivos Eletrônicos Vestíveis , HumanosRESUMO
In order to detect freezing of gait of Parkinson's patients automatically, a system based on inertial measurement unit to detect freezing of gait for Parkinson's patients is established. The two inertial measurement units are respectively fixed on the left and right ankles of the patient to be measured, the freezing index is calculated by windowed Fourier transform, the freezing threshold is calculated based on the freezing index during normal walking, and the freezing index and the freezing threshold are compared to complete the detection of freezing of gait. The experimental results show that the number of freezing of gait occurrences in Parkinson's patients is accurately detected, and it has high sensitivity and specificity, which can assist doctors to objectively assess the patient's condition.
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Equipamentos para Diagnóstico , Transtornos Neurológicos da Marcha , Doença de Parkinson , Equipamentos para Diagnóstico/normas , Transtornos Neurológicos da Marcha/diagnóstico , Transtornos Neurológicos da Marcha/etiologia , Humanos , Doença de Parkinson/complicações , Sensibilidade e Especificidade , CaminhadaRESUMO
An all-optical framing camera has been developed which measures the spatial profile of photons flux by utilizing a laser beam to probe the refractive index change in an indium phosphide semiconductor. This framing camera acquires two frames with the time resolution of about 1.5 ns and the inter frame separation time of about 13 ns by angularly multiplexing the probe beam on to the semiconductor. The spatial resolution of this camera has been estimated to be about 140 µm and the spectral response of this camera has also been theoretically investigated in 5 eV-100 KeV range. This camera has been applied in investigating the imploding dynamics of the molybdenum planar wire array Z-pinch on the 1-MA "QiangGuang-1" facility. This framing camera can provide an alternative scheme for high energy density physics experiments.
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OBJECTIVE: We investigated the cardiac risk stratification value of adenosine triphosphate stress myocardial perfusion imaging (ATP-MPI) in patients aged 70 years and older with suspected coronary artery disease (CAD). METHODS: We identified a series of 415 consecutive patients aged 70 years and older with suspected CAD, who had undergone ATP-MPI with 99mTc-MIBI. The presence of a fixed and/or reversible perfusion defect was considered as an abnormal MPI. Follow-up was available in 399 patients (96.1%) over 3.45 ± 1.71 years after excluding 16 patients who underwent early coronary revascularization <60 days after MPI. The major adverse cardiac events (MACE), including cardiac death, nonfatal infarction, and late coronary revascularization, were recorded. RESULTS: One hundred twenty-five (31.3%) patients had abnormal MPI and the remaining had normal MPI. A multivariable analysis using Cox regression demonstrated that abnormal MPI was independently associated with MACE (hazard ratio 19.50 and 95% confidence interval 5.91-64.31, P value .000). The patients with SSS > 8 had significantly higher cumulative MACE rate than patients with SSS ≤ 8 had (37.8% vs 5.2%, respectively, P < .001). The Kaplan-Meier cumulative MACE-free survival in patients with abnormal MPI (57.0%) was significantly lower than that in patients with normal MPI (89.6%), P < .0001. Among patients with SSS > 8, the Kaplan-Meier cumulative MACE-free survival were 36.9% in patients ≥80 years old and 49.5% in patients 70-79 years old, respectively, P < .05. However, among patients with SSS ≤ 8, there was no difference between the Kaplan-Meier cumulative MACE-free survivals of these two age groups. CONCLUSIONS: ATP-MPI data are useful for the prediction of major adverse cardiac events in patients aged 70 years and older with suspected CAD.
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Trifosfato de Adenosina , Doença da Artéria Coronariana/diagnóstico por imagem , Doença da Artéria Coronariana/mortalidade , Morte Súbita Cardíaca/epidemiologia , Imagem de Perfusão do Miocárdio/métodos , Intervenção Coronária Percutânea/mortalidade , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Idoso , Idoso de 80 Anos ou mais , China/epidemiologia , Doença da Artéria Coronariana/cirurgia , Morte Súbita Cardíaca/prevenção & controle , Feminino , Avaliação Geriátrica/métodos , Avaliação Geriátrica/estatística & dados numéricos , Humanos , Estudos Longitudinais , Masculino , Imagem de Perfusão do Miocárdio/estatística & dados numéricos , Prevalência , Prognóstico , Reprodutibilidade dos Testes , Medição de Risco/métodos , Fatores de Risco , Sensibilidade e Especificidade , Taxa de Sobrevida , Tomografia Computadorizada de Emissão de Fóton Único/estatística & dados numéricos , VasodilatadoresRESUMO
At present, the somatic function assessment of the elderly mostly depends on the doctor's observation and the scale evaluation, and there isn't the objective and quantitative assessment criteria. In this paper, we design and construct a digital system for the geriatric somatic function assessment, which is based on digital ground, inertial unit, mobile terminal and PC terminal. The gait and balance parameters of the elderly were obtained by the Time Up and Go test and five postures test. Based on the linear regression model of gait and balance parameters, the system was used to evaluate the somatic function of the elderly. The experimental results show that the system not only can accurately distinguish elderly between fall and non-fall, but also has a high correlation between the score of the system and the score of clinical geriatric physical function scale.
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Acidentes por Quedas/prevenção & controle , Sistemas Computacionais , Marcha , Avaliação Geriátrica , Idoso , Humanos , Modalidades de Fisioterapia , Equilíbrio PosturalRESUMO
This study examines the frequency and spectrum of α- and ß-thalassemia (thal) mutations of the Li people in Hainan Province of China. We have analyzed by genotyping a sample of 8600 subjects of the Li people and found that 53.45% subjects have only α-thal mutations with high frequencies of -α(4.2) and -α(3.7), but fewer --(SEA) mutation; 3.83% have ß-thal mutations all identified to be 41/42 (-TCTT); whereas 7.99% carry both α-thal and ß-thal mutations. We also examined 9800 subjects of the Han people, and the result showed 12.16% subjects have only α-thal mutations with --(SEA) and -α(3.7) the most frequent mutation types, 6.11% have only ß-thal mutations of 7 types, whereas 4.85% carry both α-thal and ß-thal mutations. Our study demonstrated that the Li people in Hainan province have a high incidence of -α(4.2) and -α(3.7) thalassemia, low frequencies of α-thal -(SEA), and a novel ß mutation, 41/42 (-TCTT). We provide the complete spectrum of α-thal and ß-thal mutations and a strategy for accurate molecular diagnostic testing in the Li people in Hainan Province of Southern China.
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Etnicidade/genética , Mutação , Talassemia alfa/genética , Talassemia beta/genética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Alelos , Criança , Pré-Escolar , China/epidemiologia , Frequência do Gene , Genótipo , Geografia , Humanos , Incidência , Lactente , Pessoa de Meia-Idade , Fenótipo , Adulto Jovem , alfa-Globinas/genética , Talassemia alfa/epidemiologia , Globinas beta/genética , Talassemia beta/epidemiologiaRESUMO
Understanding of characteristics and transport of perfluoroalkyl acids (PFAAs) in heterogeneous estuarine environments is limited. Furthermore, the role of suspended particles (SPS) in different layers remains unclear. This study explores the multiphase distribution process and mechanism of PFAAs controlled by SPS across surface and bottom layers in five small estuaries. Peaks in PFAA concentrations are consistently observed at strongly stratified sites. Concentrations of the PFAAs in both surface and bottom SPS decreased as the degree of mixing increased from strongly stratified levels to well-mixed levels. The water-SPS partitioning of some short-chain PFAAs (PFBS, PFHxA, and PFHpA) is influenced by environmental factors (pH, depth, temperature, and salinity) due to electrostatic interactions, while the sorption of some long-chain PFAAs (PFOA, PFOS, and PFNA) is controlled by SPS and dissolved organic carbon (OC), driven by hydrophobic interactions. Additionally, SPS dominates OC transport in estuarine systems, except in sandy sediment environments. SPS plays a dominant role in PFAA partitioning in both surface and bottom water-SPS systems (p < 0.05), and salinity only significantly affects PFBS in bottom layer (p < 0.01). These findings are critical for understanding the drivers of PFAA partitioning and the roles of SPS in different layers, underscoring the necessity of considering particle-associated PFAA fractions in future coastal environmental management.
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OBJECTIVE: To assess the diagnostic accuracy of ventilation/perfusion (V/Q) single photon emission CT (SPECT) as compared to computed tomographic pulmonary angiography (CTPA) for pulmonary embolism (PE). METHODS: In this prospective multicenter study, 111 patients in whom acute or sub-acute PE was clinically confirmed or suspected were enrolled. The patients underwent one-day method V/Q lung scan (including SPECT and planar imaging) within 3 days before and after completion of CTPA. The European Association of Nuclear Medicine (EANM) guidelines for ventilation/perfusion scintigraphy (2009) reference was used as the evaluation criteria of V/Q SPECT imaging. The refined modified prospective investigation of pulmonary embolism diagnosis (RM-PIOPED) criteria was used for evaluation of planar imaging. According to the direct and indirect signs of PE, the imaging of CTPA was evaluated. All patients were followed for at least 6 months. A diagnosis was finally made by consensus of respiratory physicians, radiologists and nuclear medicine physicians based on the clinical data, laboratory tests, imaging features and follow-up results. The difference among diagnostic methods was evaluated for significance using chi-square test. The receiver operator characteristic (ROC) curve was drawn according to the results of the 3 diagnostic tests. The area under ROC curve (AUC) was calculated and compared. P < 0.05 was considered statistically significant. RESULTS: Among the 111 patients, PE was confirmed in 80, and excluded in 31. The diagnostic sensitivity/specificity/accuracy of V/Q SPECT, planar imaging, and CTPA were 85.9%/93.5%/88.1%, 75.7%/92.9%/81.4%, and 85.5%/90.0%/86.8%, respectively. By ROC curve analysis, the AUC values of V/Q SPECT, planar imaging and CTPA were 0.898, 0.838, and 0.877, respectively; with 95% confidence intervals [CI] 0.831 to 0.966, 0.759 to 0.917, and 0.801 to 0.954, respectively. The area of the fitted smooth ROC curve was statistically significant (P < 0.05) as compared with the area under the reference line. CONCLUSION: The results indicate that SPECT V/Q imaging is superior to V/Q planar scan and CTPA in the diagnosis of PE.
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Angiografia/métodos , Artéria Pulmonar/diagnóstico por imagem , Embolia Pulmonar/diagnóstico por imagem , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Processamento de Imagem Assistida por Computador/métodos , Pulmão/irrigação sanguínea , Pulmão/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Ventilação Pulmonar , Curva ROC , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Relação Ventilação-Perfusão , Adulto JovemRESUMO
Macrolides are currently a class of extensively used antibiotics in human and animal medicine. Tylosin is not only one of the most important veterinary macrolides but also an indispensable material for the bio- and chemo-synthesis of new generations of macrolide antibiotics. Thus, improving its production yield is of great value. As the key rate-limiting enzyme catalyzing the terminal step of tylosin biosynthesis in Streptomyces fradiae (S. fradiae), TylF methyltransferase's catalytic activity directly affects tylosin yield. In this study, a tylF mutant library of S. fradiae SF-3 was constructed based on error-prone PCR technology. After two steps of screening in 24-well plates and conical flask fermentation and enzyme activity assay, a mutant strain was identified with higher TylF activity and tylosin yield. The mutation of tyrosine to phenylalanine is localized at the 139th amino acid residue on TylF (TylFY139F), and protein structure simulations demonstrated that this mutation changed the protein structure of TylF. Compared with wild-type protein TylF, TylFY139F exhibited higher enzymatic activity and thermostability. More importantly, the Y139 residue in TylF is a previously unidentified position required for TylF activity and tylosin production in S. fradiae, indicating the further potential to engineer the enzyme. These findings provide helpful information for the directed molecular evolution of this important enzyme and the genetic modification of tylosin-producing bacteria.
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Tylosin is a potent veterinary macrolide antibiotic produced by the fermentation of Streptomyces fradiae; however, it is necessary to modify S. fradiae strains to improve tylosin production. In this study, we established a high-throughput, 24-well plate screening method for identifying S. fradiae strains that produce increased yields of tylosin. Additionally, we constructed mutant libraries of S. fradiae via ultraviolet (UV) irradiation and/or sodium nitrite mutagenesis. A primary screening of the libraries in 24-well plates and UV spectrophotometry identified S. fradiae mutants producing increased yields of tylosin. Mutants with tylosin yield 10% higher than the wild-type strain were inoculated into shake flasks, and the tylosin concentrations produced were determined by high-performance liquid chromatography (HPLC). Joint (UV irradiation and sodium nitrite) mutagenesis resulted in higher yields of mutants with enhanced tylosin production. Finally, 10 mutants showing higher tylosin yield were re-screened in shake flasks. The yield of tylosin A by strains UN-C183 (6767.64 ± 82.43 µg/ml) and UN-C137 (6889.72 ± 70.25 µg/ml) was significantly higher than that of the wild-type strain (6617.99 ± 22.67 µg/ml). These mutant strains will form the basis for further strain breeding in tylosin production.
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Nitrito de Sódio , Tilosina , Mutagênese , AntibacterianosRESUMO
Antimicrobial resistance (AMR) is a global concern threatening public health. Developing novel antibiotics is one of the effective strategies to tackle AMR. Serine/threonine kinases (STKs) have been recently shown to play critical roles in the physiology and pathogenesis of several important bacterial pathogens which are regarded as a promising antimicrobial drug target. We previously reported the roles of STK in the regulation of bacterial cell division, metabolism, and pathogenesis in Streptococcus suis, an important zoonotic bacterial pathogen. In this study, we firstly identified the Thr167 and Ser175 residues in the activation loop of S. suis STK (ssSTK) as the kinase autophosphorylation sites. Phenotyping results demonstrated that the autophosphorylation deficient strain resembled the stk deletion strain showing essentiality for bacterial growth in minimal medium, abnormal morphology, and decreased virulence when compared with the wild-type S. suis SC19 strain. Based on these findings, we established an ssSTK inhibitor screening approach by measuring the growth of S. suis in a minimal medium and testing the autophosphorylation inhibition by measuring the consumption of ATP in an enzymatic reaction by ssSTK. A series of inhibitors against ssSTK are identified from a commercial kinase inhibitors library, including Staurosporine, K252a, AT9283, and APY29. These inhibitors showed antimicrobial activity in vitro. Moreover, by using Galleria mellonella larvae infection assay, compound APY29 displayed in vivo efficacy against S. suis infection. Additionally, it was predicted by molecular docking that these inhibitors could interact with ssSTK. Collectively, our data illustrated the essential roles of ssSTK autophosphorylation in the physiology and pathogenicity of S. suis and consider these inhibitors as promising antimicrobial lead compounds.