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Background/purpose: With the development of computer-assisted surgery, digital guide plate was widely used in vascularized bone flap grafts for mandibular reconstruction. The purpose of this study was to design and manufacture a digital guide plate with drill-hole sharing for mandibular reconstruction and assess for surgical accuracy. Materials and methods: 17 patients that required mandibular reconstruction using fibula free flap or iliac crest free flap were included in the study. The computed tomography (CT) data of the patient's mandible and pelvis or fibula were acquired preoperatively. A surgical simulation was then performed using computer-aided surgical simulation (CASS) technology based on above date, which allowed the design of two cutting guide and a repositioning guide for mandibular reconstruction. After surgery, the accuracy of reconstruction was evaluated by superimposing the postoperative image onto the preoperative image of mandible, recording the linear and angular deviation of landmarks, measuring the differences between the planned and actual outcomes. Results: The osteotomy and repositioning of fibula or iliac crest segments were successfully performed as planned using surgical guides. The digital guide plate with drill-hole sharing showed excellent accuracy, When the iliac crest or the fibula free flap were used for mandibular reconstruction, the largest mean differences between the preoperative and postoperative were 1.11 mm and 2.8° or 1.3 mm and 3.87°. Conclusion: The digital guide plate with drill-hole sharing designed preoperatively provides a reliable method of for the mandibular reconstruction. This can assist surgeons in accurately performing osteotomy and repositioning fibula or iliac crest segments during the mandibular reconstruction.
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BACKGROUND: Elymus breviaristatus and Elymus sinosubmuticus are perennial herbs, not only morphologically similar but also sympatric distribution. The genome composition of E. sinosubmuticus has not been reported, and the relationship between E. sinosubmuticus and E. breviaristatus is still controversial. We performed artificial hybridization, genomic in situ hybridization, and phylogenetic analyses to clarify whether the two taxa were the same species. RESULTS: The high frequency bivalent (with an average of 20.62 bivalents per cell) at metaphase I of pollen mother cells of the artificial hybrids of E. breviaristatus (StYH) × E. sinosubmuticus was observed. It illustrated that E. sinosubmuticus was closely related to E. breviaristatus. Based on genomic in situ hybridization results, we confirmed that E. sinosubmuticus was an allohexaploid, and the genomic constitution was StYH. Phylogenetic analysis results also supported that this species contained St, Y, and H genomes. In their F1 hybrids, pollen activity was 53.90%, and the seed setting rate was 22.46%. Those indicated that the relationship between E. sinosubmuticus and E. breviaristatus is intersubspecific rather than interspecific, and it is reasonable to treated E. sinosubmuticus as the subspecies of E. breviaristatus. CONCLUSIONS: In all, the genomic constitutions of E. sinosubmuticus and E. breviaristatus were StYH, and they are species in the genus Campeiostachys. Because E. breviaristatus was treated as Campeistachys breviaristata, Elymus sinosubmuticus should be renamed Campeiostachys breviaristata (Keng) Y. H. Zhou, H. Q. Zhang et C. R. Yang subsp. sinosubmuticus (S. L. Chen) Y. H. Zhou, H. Q. Zhang et L. Tan.
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Quimera/genética , Classificação , Elymus/classificação , Elymus/genética , Genoma de Planta , Hibridização Genética , Filogenia , China , Variação Genética , Especificidade da EspécieRESUMO
We focus on a fundamental task of detecting meaningful line structures, a.k.a., semantic line, in natural scenes. Many previous methods regard this problem as a special case of object detection and adjust existing object detectors for semantic line detection. However, these methods neglect the inherent characteristics of lines, leading to sub-optimal performance. Lines enjoy much simpler geometric property than complex objects and thus can be compactly parameterized by a few arguments. To better exploit the property of lines, in this paper, we incorporate the classical Hough transform technique into deeply learned representations and propose a one-shot end-to-end learning framework for line detection. By parameterizing lines with slopes and biases, we perform Hough transform to translate deep representations into the parametric domain, in which we perform line detection. Specifically, we aggregate features along candidate lines on the feature map plane and then assign the aggregated features to corresponding locations in the parametric domain. Consequently, the problem of detecting semantic lines in the spatial domain is transformed into spotting individual points in the parametric domain, making the post-processing steps, i.e., non-maximal suppression, more efficient. Furthermore, our method makes it easy to extract contextual line features that are critical for accurate line detection. In addition to the proposed method, we design an evaluation metric to assess the quality of line detection and construct a large scale dataset for the line detection task. Experimental results on our proposed dataset and another public dataset demonstrate the advantages of our method over previous state-of-the-art alternatives. The dataset and source code is available at https://mmcheng.net/dhtline/.
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Label smoothing is an effective regularization tool for deep neural networks (DNNs), which generates soft labels by applying a weighted average between the uniform distribution and the hard label. It is often used to reduce the overfitting problem of training DNNs and further improve classification performance. In this paper, we aim to investigate how to generate more reliable soft labels. We present an Online Label Smoothing (OLS) strategy, which generates soft labels based on the statistics of the model prediction for the target category. The proposed OLS constructs a more reasonable probability distribution between the target categories and non-target categories to supervise DNNs. Experiments demonstrate that based on the same classification models, the proposed approach can effectively improve the classification performance on CIFAR-100, ImageNet, and fine-grained datasets. Additionally, the proposed method can significantly improve the robustness of DNN models to noisy labels compared to current label smoothing approaches. The source code is available at our project page: https://mmcheng.net/ols/.
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Aprendizado Profundo , Processamento de Imagem Assistida por Computador/métodos , Algoritmos , Bases de Dados Factuais , HumanosRESUMO
The class activation maps are generated from the final convolutional layer of CNN. They can highlight discriminative object regions for the class of interest. These discovered object regions have been widely used for weakly-supervised tasks. However, due to the small spatial resolution of the final convolutional layer, such class activation maps often locate coarse regions of the target objects, limiting the performance of weakly-supervised tasks that need pixel-accurate object locations. Thus, we aim to generate more fine-grained object localization information from the class activation maps to locate the target objects more accurately. In this paper, by rethinking the relationships between the feature maps and their corresponding gradients, we propose a simple yet effective method, called LayerCAM. It can produce reliable class activation maps for different layers of CNN. This property enables us to collect object localization information from coarse (rough spatial localization) to fine (precise fine-grained details) levels. We further integrate them into a high-quality class activation map, where the object-related pixels can be better highlighted. To evaluate the quality of the class activation maps produced by LayerCAM, we apply them to weakly-supervised object localization and semantic segmentation. Experiments demonstrate that the class activation maps generated by our method are more effective and reliable than those by the existing attention methods. The code will be made publicly available.
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BACKGROUND/PURPOSE: Genioplasty were used widely to correct chin deformities. The purpose of this study was to design and manufacture a dental-supported surgical guide for genioplasty surgery and assess for surgical accuracy. MATERIALS AND METHODS: eleven patients with chin deformities were treated in this study. The computed tomography (CT) data of the patient's skull and the digital dental models of stone dental models were acquired preoperatively. For each patient, a virtual three-dimensional (3D) model of the skull was constructed and enhanced with digital dental models. A surgical simulation was then performed using computer-aided surgical simulation (CASS) technology based on clinical examination and 3D cephalometry. The surgery was simulated preoperatively which allowed the design of a cutting guide and a dental-supported repositioning guide for genioplasty, which was then 3D-printed and used during operation after disinfection. After surgery, the outcome was evaluated by superimposing the postoperative CT model onto the preoperative model, recording the linear and angular deviation of landmarks and plane, then measuring the differences between the planned and actual outcomes. RESULTS: The osteotomy and repositioning were successfully performed as planned using surgical guides. No inferior alveolar nerve damage was seen in this study. The dental-supported surgical guide showed excellent accuracy, with the largest differences between the planned and the postoperative chin segment being 0.9â¯mm and 3.2°. CONCLUSION: The dental-supported surgical guide designed preoperatively provided a reliable method of transfer genioplasty planning. This can assist surgeons in accurately performing osteotomy and repositioning bone segments during a genioplasty.
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BACKGROUND: Hand, foot, and mouth disease (HFMD) is a common infectious disease occurring in children under 5 years of age worldwide, and Enterovirus A71 (EV-A71) and Coxsackievirus A16 (CVA-16) are identified as the predominant pathogens. In recent years, Coxsackievirus A6 (CVA-6) and Coxsackievirus A10 (CVA-10) have played more and more important role in a series of HFMD outbreaks. This study aimed to understand the epidemic characteristics associated with HFMD outbreak in Guangzhou, 2018. METHODS: The clinical and laboratory data of 1220 enterovirus-associated HFMD patients in 2018 were analysed in this study. Molecular diagnostic methods were performed to identify its serotypes. Phylogenetic analyses were depicted based on the complete VP1 gene. RESULTS: There were 21 enterovirus serotypes detected in Guangzhou in 2018. Three serotypes of enterovirus, CVA-6 (364/1220, 29.8%), CVA-10 (305/1220, 25.0%), and CVA-16 (397/1220, 32.5%), were identified as the causative pathogens and accounted for 87.3% among all 1220 HFMD patients. In different seasons, CVA-6 was the predominant pathogen of HFMD during autumn, and CVA-10 as well as CVA-16 were more prevalent in summer. Patients infected by CVA-6, CVA-10 or CVA-16 showed similar clinical features and laboratory characteristics, and the ratios of severe HFMD were 5.8, 5.9, and 1.5% in the three serotypes. Phylogenetic analyses of VP1 sequences showed that the CVA-6, CVA-10, and CVA-16 sequences belonged to the sub-genogroup E2, genogroup E, and genogroup B1, respectively. CONCLUSIONS: CVA-6, CVA-10, and CVA-16 were the predominant and co-circulated serotypes in Guangzhou China, 2018, which should be the new target for prevention and control of HFMD. Our findings provide useful information for diagnosis, treatment, and prevention of HFMD.
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Enterovirus Humano A/classificação , Enterovirus Humano A/genética , Epidemias , Doença de Mão, Pé e Boca/epidemiologia , Sequência de Bases/genética , Proteínas do Capsídeo/genética , Criança , Pré-Escolar , China/epidemiologia , Feminino , Genótipo , Doença de Mão, Pé e Boca/virologia , Humanos , Lactente , Masculino , Filogenia , Prevalência , Estações do Ano , SorogrupoRESUMO
BACKGROUND: Respiratory tract infection (RTI) in young children is a leading cause of morbidity and hospitalization worldwide. There are few studies assessing the performance for bronchoalveolar lavage fluid (BALF) versus oropharyngeal swab (OPS) specimens in microbiological findings for children with RTI. The primary purpose of this study was to compare the detection rates of OPS and paired BALF in detecting key respiratory pathogens using suspension microarray. METHODS: We collected paired OPS and BALF specimens from 76 hospitalized children with respiratory illness. The samples were tested simultaneously for 8 respiratory viruses and 5 bacteria by suspension microarray. RESULTS: Of 76 paired specimens, 62 patients (81.6%) had at least one pathogen. BALF and OPS identified respiratory pathogen infections in 57 (75%) and 49 (64.5%) patients, respectively (P > 0.05). The etiology analysis revealed that viruses were responsible for 53.7% of the patients, whereas bacteria accounted for 32.9% and Mycoplasma pneumoniae for 13.4%. The leading 5 pathogens identified were respiratory syncytial virus, Streptococcus pneumoniaee, Haemophilus influenzae, Mycoplasma pneumoniae and adenovirus, and they accounted for 74.2% of etiological fraction. For detection of any pathogen, the overall detection rate of BALF (81%) was marginally higher than that (69%) of OPS (p = 0.046). The differences in the frequency distribution and sensitivity for most pathogens detected by two sampling methods were not statistically significant. CONCLUSIONS: In this study, BALF and OPS had similar microbiological yields. Our results indicated the clinical value of OPS testing in pediatric patients with respiratory illness.
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Líquido da Lavagem Broncoalveolar/microbiologia , Líquido da Lavagem Broncoalveolar/virologia , Criança Hospitalizada , Testes Diagnósticos de Rotina/métodos , Orofaringe/microbiologia , Orofaringe/virologia , Infecções Respiratórias/diagnóstico , Criança , Pré-Escolar , Feminino , Hospitalização , Humanos , Lactente , Recém-Nascido , Masculino , Infecções Pneumocócicas/diagnóstico , Infecções Pneumocócicas/microbiologia , Infecções por Vírus Respiratório Sincicial/diagnóstico , Infecções por Vírus Respiratório Sincicial/virologia , Vírus Sincicial Respiratório Humano/genética , Vírus Sincicial Respiratório Humano/isolamento & purificação , Infecções Respiratórias/microbiologia , Infecções Respiratórias/virologia , Streptococcus pneumoniae/genética , Streptococcus pneumoniae/isolamento & purificaçãoRESUMO
OBJECTIVE: To study the distribution of peripheral blood lymphocyte subsets in healthy children aged 0-6 years. METHODS: A total of 826 healthy Han children aged 0-6 years were recruited. According to their age, the children were divided into four groups: newborn, infant, toddler and preschool. Their peripheral blood samples were collected to measure the percentages of lymphocyte subsets by flow cytometry. RESULTS: There were significant differences in the percentages of CD3+ T cells, CD3+CD4+ T cells and CD3-CD19+ B cells and the CD4+/CD8+ ratio between boys and girls (P<0.05). The girls had a lower percentage of CD3-CD19+ B cells, higher percentages of CD3+ T cells and CD3+CD4+ T cells and a higher CD4+/CD8+ ratio than the boys. The newborn group had the highest percentages of CD3+ T cells and CD3+CD4+ T cells and the highest CD4+/CD8+ ratio (P<0.05). The percentage of CD3+CD4+ T cells and the CD4+/CD8+ ratio gradually decreased with age and the preschool group had the lowest values (P<0.05). The newborn group had the lowest percentages of CD3-CD19+ B cells and CD3-CD16+CD56+ NK cells (P<0.05). The percentage of CD3-CD16+CD56+ NK cells gradually increased with age and the preschool group had the highest percentage (P<0.05). The percentage of CD3-CD19+ B cells reached the peak in the toddler period and then decreased with age (P<0.05). The preschool group had the highest percentage of CD3+CD8+ T cells (P<0.05). The variation trend of distribution of lymphocyte subsets in boys from different age groups was consistent with that in children from different age groups. For girls, the newborn group had the highest percentage of CD3+CD4+ T cells and CD4+/CD8+ ratio (P<0.05). CONCLUSIONS: The distribution of peripheral blood lymphocyte subsets in healthy children is significantly different across ages and sexes. Therefore, the reference values should be established according to age and sex.
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Linfócitos B , Subpopulações de Linfócitos , Antígenos CD19 , Criança , Pré-Escolar , Feminino , Citometria de Fluxo , Humanos , Lactente , Recém-Nascido , Células Matadoras Naturais , Contagem de Linfócitos , MasculinoRESUMO
OBJECTIVE: This study aims to understand the current status and analyze the influencing factors of tooth extraction anxiety of dental patients. METHODS: The General Factor Questionnaire and Modified Dental Anxiety Scale (MDAS) were used to survey and analyze tooth extraction anxiety of 800 dental patients. Single-factor and multi-factor analyses were used for statistical data analysis. RESULTS: A total of 768 qualified questionnaires were received out of 800, the efficiency was 96%. The mean MDAS score was 10.21±3.29. The prevalence percentage of dental anxiety was 14.7%. Significant statistical differences of the incidence of dental anxiety were observed with regard to sex, age, tooth extraction time, accompanying relatives and friends, before tooth extraction, tooth extraction experience for family and friends, pain tolerance, mental health state before tooth extraction, and self-reported oral health status (P<0.05. By contrast, no significant statistical differences in the incidence of dental anxiety were observed with regard to educational level, tooth extraction type, national life experience, profession, and personality (P>0.05). Logistic regression analysis indicated that the risk factors of dental anxiety were sex, accompanying relatives and friends, mental health state before tooth extraction, and self-rated oral health status. CONCLUSIONS: The prevalence percentage of tooth extraction anxiety is high for dental patients. Gender, age, health satisfaction, tooth extraction time, accompanying relatives and friends, before tooth extraction, tooth extraction experience for family and friends, pain tolerance, mental health state before tooth extraction, and self-reported oral health status are the influencing factors of dental anxiety.
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Ansiedade ao Tratamento Odontológico , Extração Dentária , Transtornos de Ansiedade , Assistência Odontológica , Feminino , Humanos , Masculino , Fatores Sexuais , Inquéritos e QuestionáriosRESUMO
Emodin is a principle ingredient isolated from rhubarb rhizome, which is commonly used for constipation or pain-related diseases in traditional Chinese medicine (TCM) practice. The transient receptor potential vanilloid 1 ion channel proteins (TRPV1) are abundantly expressed in the peripheral sensory neurons and are assumed to act as a kind of nociceptor involved in the perception of pain and development of hyperalgesia. The aim of this study was to further unravel the analgesic mechanisms of rhubarb through investigating the effects of its main constitutive ingredient emodin on the expression of TRPV1 mRNA as well as on its calcium- mediating functions in vitro. The primary DRG neurons with a high purity and viability were obtained, and the TRPV1 mRNA expression levels were examined by using real-time RT-PCR and the elevated amplitudes of intracellular [Ca(2+)]i in the DRG neurons evoked by TRPV1 agonist capsaicin were examined by confocal microscopy. The results showed that emodin could significantly down-regulate both the mRNA expression of TRPV1 and the capsaicin-evoked intracellular fluorescent intensity in the DRG neurons under both 37 degrees C and 39 degrees C in vitro. Concomitantly, all of the changes induced by emodin could not be blocked by pretreatment of the primary neurons with capsazepine, an antagonist of TRPV1. In conclusion, we established that the mRNA expression level of TRPV1 and its calcium-mediating function in naive DRG neurons could be down-regulated by emodin through perhaps the non-TRPV1 channel pathways, and this might be the molecular mechanisms for rhubarb to inhibit hyperalgesia induced by inflammatory stimuli.
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Analgésicos/farmacologia , Emodina/farmacologia , Gânglios Espinais/efeitos dos fármacos , Expressão Gênica/efeitos dos fármacos , Extratos Vegetais/farmacologia , Rheum/química , Canais de Cátion TRPV/metabolismo , Animais , Cálcio/metabolismo , Capsaicina/análogos & derivados , Capsaicina/farmacologia , Células Cultivadas , Regulação para Baixo/efeitos dos fármacos , Gânglios Espinais/citologia , Neurônios/metabolismo , Extratos Vegetais/química , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Rizoma , Canais de Cátion TRPV/genéticaRESUMO
ETHNOPHARMACOLOGICAL RELEVANCE: Scutellaria baicalensis Georgi (Lamiaceae) is often included as an ingredient in traditional Chinese compound prescriptions for the treatment of fever-related or inflammatory conditions. AIM OF THE STUDY: The present work was to further uncover the analgesic mechanisms of baicalin (a known principal constituent of Scutellaria baicalensis) by investigating its effects on the expression of TRPV1 mRNA as well as on its functions as mediators of calcium entrance into the cytoplasm of dorsal root ganglion (DRG) neurons in vitro. MATERIALS AND METHODS: By using CPT as an agent to eliminate the non-neuronal cells and using serum-free neurobasal as culture medium, primary cultures of rat DRG neurons with high purity and viability were established. On this basis, effects of baicalin on both the expression of TRPV1 mRNA and on the function of TRPV1 in vitro under two various temperature conditions were studied. The TRPV1 mRNA expression levels were examined by using qRT-PCR and analyzed by the method of 2(-DeltaDeltaCT). The elevation amplitudes of intracellular [Ca(2+)]i evoked by TRPV1 agonist capsaicin in DRG neurons were examined by the calcium fluorescence imaging method under confocal microscopy. RESULTS: Baicalin was shown to down-regulate the mRNA expression levels of TRPV1 at both 37 and 39 degrees C, and under the latter temperature, the intracellular fluorescent intensity evoked by capsaicin was significantly decreased following incubation with baicalin in vitro. We also demonstrated that the actions of baicalin to TRPV1 were not achieved through pathways of TRPA1 or TRPV subfamily members. CONCLUSIONS: Collectively, these results provide compelling evidence that the down-regulated actions of baicalin to TRPV1 in DRG neurons might account for part of the anti-nociceptive mechanism of baicalin.
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Anti-Inflamatórios não Esteroides/farmacologia , Flavonoides/farmacologia , Gânglios Espinais/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Canais de Cátion TRPV/biossíntese , Animais , Animais Recém-Nascidos , Anti-Inflamatórios não Esteroides/isolamento & purificação , Cálcio/metabolismo , Capsaicina/farmacologia , Técnicas de Cultura de Células , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Meios de Cultura Livres de Soro , Regulação para Baixo , Flavonoides/isolamento & purificação , Gânglios Espinais/citologia , Gânglios Espinais/metabolismo , Microscopia Confocal , Estrutura Molecular , Neurônios/metabolismo , Ratos , Ratos Sprague-Dawley , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Scutellaria baicalensis/química , Canais de Cátion TRPV/agonistas , Canais de Cátion TRPV/antagonistas & inibidoresRESUMO
Cinnamaldehyde (1) is a pharmacologically active ingredient isolated from cassia twig (Ramulus Cinnamomi), which is commonly used in herbal remedies to treat fever-related diseases. Both TRPV1 and TRPM8 ion channel proteins are abundantly expressed in sensory neurons, and are assumed to act as a thermosensor, with the former mediating the feeling of warmth and the latter the feeling of cold in the body. Both of them have recently been reported to be involved in thermoregulation. The purpose of this paper is to further uncover the antipyretic mechanisms of 1 by investigating its effects on the mRNA expression levels and functions of both TRPV1 and TRPM8. The results showed that 1 could up-regulate the mRNA expression levels of TRPV1 at both 37 and 39 degrees C, and its calcium-mediating function was significantly increased at 39 degrees C, all of which could not be blocked by pretreatment of the neuronal cells with ruthenium red, a general transient receptor potential (TRP) blocker, indicating that the action of 1 was achieved through a non-TRPA1 channel pathway. In conclusion, the findings in our in vitro studies might account for part of the peripheral molecular mechanisms for the antipyretic action of 1.
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Acroleína/análogos & derivados , Cassia/química , Canais Iônicos/metabolismo , Neurônios/metabolismo , Canais de Cátion TRPV/genética , Acroleína/química , Acroleína/isolamento & purificação , Acroleína/farmacologia , Animais , Animais Recém-Nascidos , Capsaicina/farmacologia , Caules de Planta/química , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Canais de Cátion TRPM/metabolismo , Canais de Cátion TRPV/metabolismoRESUMO
Angiogenesis is crucial for tumor metastasis, with many compounds that inhibit tumor metastasis acting through suppression of angiogenesis. We investigated anti-angiogenic properties of Ligustrazine in a series of in vitro and in vivo models. Ligustrazine inhibited VEGF-induced HUVECs migration and tube formation in a dose-dependent manner in vitro, and had limited cytotoxicity to HUVECs and normal fibroblasts even at a dose up to 100 microg/ml. Ligustrazine also suppressed VEGF-induced rat aortic ring sprouting dose-dependently. Invivo, Ligustrazine reduced the Hb content in a Matrigel plug implanted in mice and inhibited new vessel formation in CAM. In addition, in a B16F10 spontaneous metastasis model, Ligustrazine decreased the expression of CD34 and VEGF in primary tumor tissue and reduced the number of metastasis nodi on the lung surface. Our data suggests that Ligustrazine may inhibit tumor metastasis, at least in part, through its anti-angiogenic activity.
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Inibidores da Angiogênese/uso terapêutico , Neoplasias Pulmonares/prevenção & controle , Melanoma Experimental/tratamento farmacológico , Neovascularização Patológica/tratamento farmacológico , Pirazinas/uso terapêutico , Inibidores da Angiogênese/farmacologia , Animais , Movimento Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Feminino , Fibroblastos/efeitos dos fármacos , Humanos , Neoplasias Pulmonares/secundário , Melanoma Experimental/irrigação sanguínea , Melanoma Experimental/patologia , Camundongos , Camundongos Endogâmicos C57BL , Microvasos/efeitos dos fármacos , Neovascularização Patológica/induzido quimicamente , Neovascularização Patológica/patologia , Pirazinas/farmacologia , Ratos , Fator A de Crescimento do Endotélio Vascular/farmacologiaRESUMO
Catalytic elimination of formaldehyde (HCHO) was investigated over Cu-Al2O3 catalyst at room temperature. The results indicated that no oxidation of HCHO into CO2 occurs at room temperature, but the adsorption of HCHO occurs on the catalyst surface. With the increase of gas hourly space velocity (GHSV) and inlet HCHO concentration, the time to reach saturation was shortened proportionally. The results of the in situ DRIFTS, Density functional theory calculations and temperature programmed desorption(TPD) showed that HCHO was completely oxidized into HCOOH over Cu-Al2O3 at room temperature. With increasing the temperature in a flow of helium, HCOOH was completely decomposed into CO2 over the catalyst surface, and the deactivated Cu-Al2O3 is regenerated at the same time. In addition, although Cu had no obvious influence on the adsorption of HCHO on Al2O3, Cu dramatically lowered the decomposition temperature of HCOOH into CO2. It was shown that Cu-Al2O3 catalyst had a good ability for the removal of HCHO, and appeared to be promising for its application in destroying HCHO at room temperature.
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Poluição do Ar em Ambientes Fechados/análise , Óxido de Alumínio/química , Cobre/química , Formaldeído/química , Modelos Químicos , Adsorção , Catálise , Espectrometria de Massas , Oxirredução , TemperaturaRESUMO
The preparation of ethanol-diesel fuel blends and their emission characteristics were investigated. Results showed the absolute ethanol can dissolve in diesel fuel at an arbitrary ratio and a small quantity of water(0.2%) addition can lead to the phase separation of blends. An organic additive was synthesized and it can develop the ability of resistance to water and maintain the stability of ethanol-diesel-trace amounts of water system. The emission characteristics of 10%, 20%, and 30% ethanol-diesel fuel blends, with or without additives, were compared with those of diesel fuel in a direct injection (DI) diesel engine. The experimental results indicated that the blend of ethanol with diesel fuel significantly reduced the concentrations of smoke, hydrocarbon (HC), and carbon monoxide (CO) in exhaust gas. Using 20% ethanol-diesel fuel blend with the additive of 2% of the total volume, the optimum mixing ratio was achieved, at which the bench diesel engine testing showed a significant decrease in exhaust gas. Bosch smoke number was reduced by 55%, HC emission by 70%, and CO emission by 45%, at 13 kW/1540 r/min. However, ethanol-diesel fuel blends produced a few ppm acetaldehydes and more ethanol in exhaust gas.