1,061 research outputs found

    A density functional study of open-shell cyclopentadienyl-molybdenum(II) complexes. A comparison of stabilizing factors: Spin-pairing, Mo-X π bonding, and release of steric pressure

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    The dissociation of PH3 from the 18-electron system CpMoX(PH3)3 to afford the corresponding 16-electron CpMoX(PH3)2 fragment has been investigated theoretically by density functional theory for X = H, CH3, F, Cl, Br, I, OH, and PH2. The product is found to prefer a triplet spin state for all X ligands except PH2, the singlet-triplet gap varying between 1.7 kcal/mol for OH to 8.7 kcal/mol for F. The Mo-PH3 bond dissociation energy to the 16-electron ground state varies dramatically across the series, from 4.5 kcal/mol for OH to 23.5 kcal/mol for H, and correlates with experimental observations on trisubstituted phosphine derivatives. Geometry-optimized spin doublet CpMo(PH3)3, on the other hand, has a Mo-PH3 bond dissociation energy of 24.3 kcal/mol. The modulation of the Mo-PH3 bond dissociation energy by the introduction of X is analyzed in terms of three effects that stabilize the 16-electron product relative to the 18-electron starting complex: (i) adoption of the higher (triplet) spin state by release of pairing energy; (ii) Mo-X π interactions; (iii) release of steric pressure. A computational model for the approximate separation and evaluation of these three stabilizing effects is presented. According to the results of these calculations, the relative importance of the three effects depends on various factors related to the nature of X. For double-sided π-donor X ligands, the larger triplet-singlet gap is provided by the more electronegative atoms (F \u3e CL \u3e Br \u3e I), whereas single-sided π donors favor the singlet state. The π-stabilization ability goes in the order PH2 \u3e OH \u3e F \u3e other halogens \u3e H. Finally, the major steric interaction appears to be associated with the presence of inactive lone pairs and by their orientation/proximity to the PH3 ligands (Cl, Br \u3e I, OH \u3e F, PH2, H, CH3). The 16-electron methyl system establishes a marked α-agostic interaction in the singlet state, which nevertheless remains unfavored relative to an undistorted triplet configuration

    Analysis of the clinical relevance of histological classification of benign epithelial salivary gland tumours

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    IntroductionA vast increase in knowledge of numerous aspects of malignant salivary gland tumours has emerged during the last decade and, forseveral reasons, thishas not been the case in benign epithelial salivary gland tumours. We have performed a literature review to investigate whether an accurate histological diagnosis of the 11 different types of benign epithelial salivary gland tumours is correlated to any differences in their clinical behaviour.MethodsA search was performed for histological classifications, recurrence rates and risks for malignant transformation, treatment modalities, and prognosis of these tumours. The search was performed primarily through PubMed, Google Scholar, and all versions of WHO classifications since 1972, as well as numerous textbooks on salivary gland tumours/head and neck/pathology/oncology. A large number of archival salivary tumours were also reviewed histologically.ResultsPleomorphic adenomas carry a considerable risk (5-15%) for malignant transformation but, albeit to a much lesser degree, so do basal cell adenomas and Warthin tumours, while the other eight types virtually never develop into malignancy. Pleomorphic adenoma has a rather high risk for recurrence while recurrence occurs only occasionally in sialadenoma papilliferum, oncocytoma, canalicular adenoma, myoepithelioma and the membranous type of basal cell adenoma. Papillomas, lymphadenoma, sebaceous adenoma, cystadenoma, basal cell adenoma (solid, trabecular and tubular subtypes) very rarely, if ever, recur.ConclusionsA correct histopathological diagnosis of these tumours is necessary due to (1) preventing confusion with malignant salivary gland tumours; (2) only one (pleomorphic adenoma) has a considerable risk for malignant transformation, but all four histological types ofbasal cell adenoma canoccasionally develop into malignancy, as does Warthin tumour; (3) sialadenoma papilliferum, oncocytoma, canalicular adenoma, myoepithelioma and Warthin tumour only occasionally recur; while (4) intraductal and inverted papilloma, lymphadenoma, sebaceous adenoma, cystadenoma, basal cell adenoma (apart from the membranous type) virtually never recur. No biomarker was found to be relevant for predicting recurrence or potential malignant development. Guidelines for appropriate treatment strategies are given.info:eu-repo/semantics/publishedVersio

    Prognostic factors in laryngeal squamous cell carcinoma

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    Background The current treatment results of laryngeal squamous cell carcinoma still remain modest. Various prognostic factors have been investigated and need to be included in the management decision making. Methods We reviewed the pertinent literature regarding host, tumor, and treatment factors as prognostic indicators that influence outcome in patients diagnosed with laryngeal squamous cell carcinoma. Results Host, tumor, and treatment factors all have an important impact upon an individual patient's prognosis with laryngeal squamous cell carcinoma, whereas staging systems only take into account tumor factors. There is much work yet to be done to establish reliable, independent biomarkers that predict survival and response to treatment. Conclusions Optimal outcomes for an individual patient can be achieved when taking into account tumor, host, and treatment factors.Peer reviewe

    Evaluation of a rapid dipstick test, Malar-CheckTM, for the diagnosis of Plasmodium falciparum malaria in Brazil

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    The present study was carried out to evaluate the Malar-CheckTM Pf test, an immunochromatographic assay that detects Plasmodium falciparum Histidine Rich Protein II, does not require equipment, and is easy and rapid to perform. In dilution assays performed to test sensitivity against known parasite density, Malar-CheckTMwere compared with thick blood smear (TBS), the gold standard for diagnosis. Palo Alto isolate or P. falciparum blood from patients with different parasitemias was used. The average cut-off points for each technique in three independent experiments were 12 and 71 parasites/mm³ (TBS and Malar-CheckTM, respectively). In the field assays, samples were collected from patients with fever who visited endemic regions. Compared to TBS, Malar-CheckTMyielded true-positive results in 38 patients, false-positive results in 3, true-negative results in 23, and false-negative result in 1. Malar-CheckTMperformed with samples from falciparum-infected patients after treatment showed persistence of antigen up to 30 days. Malar-CheckTM should aid the diagnosis of P. falciparum in remote areas and improve routine diagnosis even when microscopy is available. Previous P. falciparum infection, which can determine a false-positive test in cured individuals, should be considered. The prompt results obtained with the Malar-CheckTM for early diagnosis could avoid disease evolution to severe cases.Este trabalho avaliou o Malar-CheckTM Pf test, ensaio imunocromatográfico que detecta a proteína rica em histidina de Plasmodium falciparum, dispensa uso de equipamentos, é rápido e de fácil execução. Ensaios de diluição com o isolado Palo Alto ou sangue de pacientes com P. falciparum, foram realizados para testar a sensibilidade em diferentes densidades do parasita. Malar-CheckTM foi comparado à gota espessa (GE), padrão ouro para diagnóstico de malária. A média do limiar de sensibilidade para cada técnica em três experimentos independentes foi de 12 e 71 parasitas/mm³ (GE e Malar-CheckTM, respectivamente). Em ensaios de campo, amostras foram coletadas de pacientes febris de áreas endêmicas. Comparado à GE, Malar-CheckTM foi verdadeiramente positivo em 38 pacientes, falso positivo em 3, verdadeiramente negativo em 23 e falso negativo em um. Malar-CheckTMrealizado com sangue de pacientes com P. falciparum após tratamento mostrou persistência do antígeno durante 30 dias. Malar-CheckTM pode ser útil no diagnóstico de P. falciparum em áreas remotas e auxiliar a rotina diagnóstica, mesmo quando a microscopia está disponível. Deve ser considerada infecção pregressa por P. falciparum, que pode determinar testes positivos em indivíduos curados. A rapidez do Malar-CheckTM para o diagnóstico precoce pode evitar evolução para casos graves

    Management of extracranial arteriovenous malformations of the head and neck

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    The purpose of this study was to review the outcomes of the different therapies for extracranial head and neck arteriovenous malformations (AVMs). AVMs are high-flow congenital vascular anomalies. They are composed of a complex system of vessels directly connecting feeding arteries to draining veins forming a nidus. They may be potentially life-threatening due to progressive symptoms and infiltrative disease. Extracranial AVMs most commonly affect the head and neck area (47.4%) followed by the extremities (28.5%). AVMs are best characterized as being either focal or diffuse. Focal AVMs have good outcomes following adequate treatment. Diffuse lesions have multiple feeding vessel, which results in high rates of recurrence despite treatment. The management of AVMs includes conventional surgery and endovascular techniques. A combination of embolization and surgical resection has become the treatment of choice over the last years. The main goal of both forms of treatment being the complete blockage or resection of the nidus. Transcatheter embolization of vessels has evolved over the years and new embolic agents have emerged. The types of materials available for embolization are classified into mechanical devices, liquid agents and particulates. Efficacy, rate of recurrence and most common complications were evaluated. AVMs recurrence after embolization or resection is reported in up to 80% of cases. Incomplete resection and embolization can induce aggressive growth of the remaining nidus and the risk of progression is up to 50% within the first 5 years and recurrences can occur up to 10 years later. Although ethanol seems to be associated with the highest degree of cure and permanent occlusion, the overall complication rate reported was 48%. Other materials, such as cyanoacrylate, have obtained modest rates of complete remission, while the reported rates of complete regression of AVMs with Fibrin glue and Polyvinyl alcohol are above 50%. At present, there are no unified agreement on the ideal embolic agent. Therefore, a multidisciplinary approach is recommended to support decision making about the best therapeutic approach and to achieve optimal outcome. A long-term post-treatment follow-up is recommended to recognize early recurrence.Peer reviewe

    OBESITY AND PERIODONTAL DISEASE ARE INVERSELY ASSOCIATED IN A POPULATION OF ADULTS IN SOUTHERN BRAZIL

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    Objective: Investigate the association between obesity (measured using the body mass index and abdominal circumference) and periodontal disease in adults.Methods: A cross-sectional study was conducted with 280 adults (102 men and 178 women) who sought dental care at the clinic of the dentistry course of the Lutheran University of Brazil (Cachoeira do Sul campus). The participants answered a questionnaire addressing socioeconomic, demographic, behavioral and health-related characteristics. Height, body weight and waist measurements were determined in a standardized way for the calculation of the variables used to define obesity: body mass index (BMI) and abdominal circumference (AC). Oral clinical examinations were performed by two examiners who had undergone training and calibration exercises. Periodontal disease was recorded when clinical attachment loss was ≥ 5 mm in ≥ 30% of the teeth. Statistical analysis involved simple and multivariate Poisson regression with robust variance.Results: The prevalence of periodontal disease was 49.6% (139/280). The multivariate models indicated a lower likelihood of periodontal disease in individuals considered obese based on BMI (PR=0.64; 95% CI: 0.47-0.88) and AC (PR=0.72; 95% CI: 0.55-0.93). Moreover, the prevalence of the outcome was significantly higher in older individuals, those with less schooling, smokers and individuals with diabetes.Conclusion: An inverse association was found between obesity measured using both criteria and periodontal disease. The present data suggest that care and counseling for the prevention and control of periodontal disease should be equally directed at individuals in the ideal weight range as well as those with overweight or obesity

    Staging and grading of oral squamous cell carcinoma : An update

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    Oral squamous cell carcinoma (OSCC) is a common malignancy of the head and neck region. OSCC has a relatively low survival rate and the incidence of the disease is increasing in some geographic areas. Staging and grading of OSCC are established prerequisites for management, as they influence risk stratification and are the first step toward personalized treatment. The current AJCC/UICC TNM staging (8th edition, 2017) of OSCC has included significant modifications through the incorporation of depth of invasion in the T stage and extracapsular spread/extranodal extension in the N stage. Further modifications for AJCC 8 have been suggested. On the other hand, the World Health Organization (WHO) classification (4th edition, 2017) still endorses a simple, differentiation-based histopathologic grading system of OSCC (despite its low prognostic value) and ignores factors such as tumor growth pattern and dissociation, stromal reactions (desmoplasia, local immune response), and tumor-stroma ratio. The various controversies and possible developments of the current staging and grading criteria of OSCC are briefly discussed in this update together with possible applications of artificial intelligence in the context of screening and risk stratification.Peer reviewe

    Value and Quality of Care in Head and Neck Oncology

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    Purpose of ReviewThe concept of value-based health care (VBHC) was articulated more than a decade ago. However, its clinical implementation remains an on-going process and a particularly demanding one for the domain of head and neck cancer (HNC). These cancers often present with fast growing tumors in functionally and cosmetically sensitive sites and afflict patients with differing circumstances and comorbidity. Moreover, the various treatment modalities and protocols have different effects on functional outcomes. Hence, the interpretation of what constitutes VBHC in head and neck oncology remains challenging.Recent FindingsThis monograph reviews developments in specific aspects of VBHC for HNC patients, including establishment of registries and quality indices (such as infrastructure, process, and outcome indicators). It emphasizes the importance of the multidisciplinary team, "time to treatment intervals," and adherence to guidelines. The discussion addresses major indicators including survival, quality of life and functional outcomes, and adverse events. Also, strengths and weaknesses of nomograms, prognostic and decision models, and variation of care warrant attention.SummaryHealth care professionals, together with patients, must properly define quality and relevant outcomes, both for the individual patient as well as the HNC population. It is essential to capture and organize the relevant data so that they can be analyzed and the results used to improve both outcomes and value.Peer reviewe
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