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1.
ACS Appl Mater Interfaces ; 16(17): 21877-21884, 2024 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-38648335

RESUMO

The hydrogen evolution reaction (HER) is a crucial electrochemical process for the proposed hydrogen economy since it has the potential to provide pure hydrogen for fuel cells. Nowadays, hydrogen electroproduction is considerably expensive, so promoting the development of new non-noble catalysts for the cathode of alkaline electrolyzers appears as a suitable way to reduce the costs of this technology. In this sense, a series of tungsten-based carbide materials have been synthesized by the urea-glass route as candidates to improve the HER in alkaline media. Moreover, two different pyridinium-based ionic liquids were employed to modify the surface of the carbide grains and control the amount and nature of their surface species. The main results indicate that the catalyst surface composition is modified in the hybrid materials, which are then distinguished by the appearance of tungsten suboxide structures. This implies the action of ionic liquids as reducing agents. Consequently, differential electrochemical mass spectrometry (DEMS) is used to precisely determine the onset potentials and rate-determining steps (RDS) for the HER in alkaline media. Remarkably, the modified surfaces show high catalytic performance (overpotentials between 45 and 60 mV) and RDS changes from Heyrovsky-Volmer to Heyrovsky as the surface oxide structures get reduced. H2O molecule reduction is then faster at tungsten suboxide, which allows the formation of the adsorbed hydrogen at the surface, boosting the catalytic activity and the kinetics of the alkaline HER.

2.
Radiologia (Engl Ed) ; 66(1): 70-77, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38365356

RESUMO

The universally accepted system for the transmission of scientific knowledge in the field of medicine has long been grounded in scientific publications. Social networks can be a useful alternative or complementary method of transmitting this knowledge. Social networks (e.g., Twitter, Instagram, Facebook, LinkedIn, YouTube, and TikTok) generate educational contents that enable quality training, despite their informality. Each of these networks has strengths and weaknesses that users should know about. These platforms are free and allow for real-time discussion. They make it easy to incorporate content and to contact experts or access sources of knowledge directly. Aware of their influence, publishers have incorporated metrics to measure the impact of their articles in social networks (Altmetrics). These networks should be incorporated into departmental training programs immediately. Nevertheless, navigating through social networks is complex, and the hashtag-based system of searching is inefficient, limiting their use in education. Despite the informality of the knowledge generated on social networks, the importance of these networks as a source of knowledge is growing. Radiology departments must design a strategy for using social networks for education rather than for propaganda, creating well-organized focal groups that search for contents through systematic, filtered review of information, digital repositories, and review sessions and for sharing this knowledge both inside and outside the department. Departments must also implement a strategy for communicating through these networks.


Assuntos
Educação Médica , Radiologia , Mídias Sociais , Humanos , Radiologia/educação , Rede Social
3.
Radiologia (Engl Ed) ; 65(6): 492-501, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38049248

RESUMO

OBJECTIVE: To evaluate the long-term outcomes of renal tumor ablation, analyzing efficacy, long-term survival, and factors associated with complications and therapeutic success. MATERIAL AND METHODS: We retrospectively reviewed 305 ablations (generally done with expandable electrodes) of 273 renal tumors between May 2005 and April 2019. We analyzed survival, primary and secondary efficacy, and complications according to various patient factors and tumor characteristics. RESULTS: Mean blood creatinine was 1.14 mg/dL before treatment and 1.30 mg/dL after treatment (p < 0.0001). Complications were observed in 13.25% of the ablations, including major complications in in 4.97%. Complications were associated with age (p = 0.013) and tumor diameter (p < 0.0001). Primary efficacy was 96.28%. Incomplete ablation was more common in lesions measuring > 4 cm in diameter (p = 0.002). Secondary efficacy was 95.28%. The only factor associated with the risk of recurrence was the size of the tumor (p = 0.02). Overall survival was 95.26% at 1 year, 77.01% at 5 years, and 51.78% at 10 years, with no differences between patients with malignant and benign lesions. Mortality was higher in patients with creatinine >1 (p = 0.05) or ASA > 2 (p = 0.0001). CONCLUSIONS: Percutaneous ablation is extremely efficacious for renal tumors; it improves the prognosis of renal carcinoma to the point where it does not differ from that of benign lesions. Complications are rare. Like survival, complications are associated with age and overall health status.


Assuntos
Carcinoma de Células Renais , Ablação por Cateter , Neoplasias Renais , Humanos , Estudos Retrospectivos , Creatinina , Neoplasias Renais/cirurgia , Neoplasias Renais/patologia , Carcinoma de Células Renais/cirurgia , Carcinoma de Células Renais/patologia
4.
Radiologia (Engl Ed) ; 65(2): 133-148, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37059579

RESUMO

Teleradiology is the electronic transmission of radiological images from one location to another with the main purpose of interpreting or consulting a diagnosis and must be subject to codes of conduct agreed upon by professional societies. The content of fourteen teleradiology best practice guidelines is analyzed. Their guiding principles are: the best interest and benefit of the patient, quality and safety standards homologous to the local radiology service, and use as a complement and support of the same. As legal obligations: guaranteeing rights by applying the principle of the patient's country of origin, establishing requirements in international teleradiology and civil liability insurance. Regarding the radiological process: integration with the local service process, guaranteeing the quality of images and reports, access to previous studies and reports and complying with the principles of radioprotection. Regarding professional requirements: compliance with the required registrations, licenses and qualifications, training and qualification of the radiologist and technician, prevention of fraudulent practices, respect for labor standards and remuneration of the radiologist. Subcontracting must be justified, managing the risk of commoditization. Compliance with the system's technical standards.


Assuntos
Radiologia , Telerradiologia , Humanos , Radiografia
5.
J Endocrinol Invest ; 46(11): 2269-2273, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37032399

RESUMO

INTRODUCTION: Radiofrequency ablation (RFA) has emerged as a minimally invasive approach to single parathyroid adenoma in primary hyperparathyroidism; however, there is limited evidence on its effectiveness. OBJECTIVE: To evaluate the effectiveness and safety of RFA to treat hyper-functioning parathyroid lesions suggestive of adenomas. MATERIAL AND METHODS: A prospective study was conducted in consecutive patients with primary hyperparathyroidism treated with RFA for single parathyroid lesions in our reference center between November 2017 and June 2021. Pre-treatment (baseline) and follow-up analytical data were gathered on total protein-adjusted calcium, parathyroid hormone [PTH], phosphorus, and 24-h urine calcium. Effectiveness was defined as complete response (normal calcium and PTH), partial response (reduced but not normalized PTH with normal serum calcium), or disease persistence (elevated calcium and PTH). SPSS 15.0 was used for statistical analysis. RESULTS: Four of thirty-three enrolled patients were lost to the follow-up. The final sample comprised 29 patients (22 females) with mean age of 60.93 ± 13.28 years followed up for a mean of 16.29 ± 7.23 months. Complete response was observed in 48.27%, partial response in 37.93%, and hyperparathyroidism persistence in 13.79%. Serum calcium and PTH levels were significantly lower at 1 and 2 years of post-treatment than at baseline. Adverse effects were mild, with two cases of dysphonia (self-limited in one patient) and no cases of hypocalcaemia or hypoparathyroidism. CONCLUSION: RFA may be a safe and effective technique to treat hyper-functioning parathyroid lesions in selected patients.


Assuntos
Adenoma , Hiperparatireoidismo Primário , Ablação por Radiofrequência , Feminino , Humanos , Pessoa de Meia-Idade , Idoso , Cálcio , Hiperparatireoidismo Primário/diagnóstico , Hiperparatireoidismo Primário/cirurgia , Estudos Prospectivos , Hormônio Paratireóideo , Adenoma/complicações , Adenoma/cirurgia
6.
Braz J Biol ; 84: e257470, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35416853

RESUMO

Lethal yellowing (LY) is a disease that affects coconut and other palm species. It is associated to phytoplasmas of the group 16SrIV and the only reported insect vector for this pathogen so far is Haplaxius crudus. H. crudus is present in Mexico and has been associated to 16SrIV phytoplasmas, however, it was not detectable during a LY outbreak in the coast of Yucatan, Mexico, suggesting the existence of other vector species. To test this hypothesis a survey of insects was carried out and a total of 3074 insects were captured during a year of monthly sampling. Ten taxonomic orders were identified in this sample, Hemiptera being the most abundant (N=2094), and these were classified into nine families. The leafhopper Colpoptera sp. from to the Nogodinidae family was de most abundant representing 56% of the total number of insects sampled and 23% of these samples resulted positive for LY phytoplasma by PCR detection. The BLAST comparison, virtual RFLP and phylogenetic analyses of the sequenced amplicons relate the detected phytoplasma to the subgroup 16SrIV-A. The findings presented herein suggest that Colpoptera sp. could be considered as a new putative vector of the LY-causing phytoplasmas in Mexico and a candidate for further research.


Assuntos
Hemípteros , Phytoplasma , Animais , DNA , Hemípteros/genética , Humanos , México , Filogenia , Phytoplasma/genética , Doenças das Plantas
7.
Actas Urol Esp (Engl Ed) ; 45(9): 569-575, 2021 Nov.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-34690104

RESUMO

INTRODUCTION AND OBJECTIVES: Currently, there are no established criteria regarding treatment for lumbar ureteral stones. The objective of this work is to present our results in the endourological treatment of this pathology, analyzing the variables associated with the use of the flexible ureterorenoscope. MATERIAL AND METHODS: Retrospective review of 103 patients who underwent retrograde URS with semi-rigid or flexible ureterorenoscope. Proximal location: L2-L3. Medial location: L4-L5. Semirigid URS was the initial treatment, with conversion to flexible URS when it was required to complete the procedure. Success was defined as absence of residual fragments (6 weeks). Demographic, surgical, immediate postoperative variables, and those related to the stone, were analyzed. Their correlation with the use of the flexible ureterorenoscope was evaluated. RESULTS: Mean age: 57.2 years (SD 15.6); there were 73 men (70.9%). Stone size: 8 mm (range 4-30; IQR 4.5). Proximal location: 58 (56.3%). Previous JJ: 44.7%. Previous nephrostomy: 10.7%. Semirigid URS with conversion to flexible URS: 51 (49.5%). Impacted stones: 28.2%. Intraoperative complications: 2 (1.9%). Postoperative JJ: 84.5%. Immediate postoperative complications: 23 (22.3%) (Clavien-Dindo I-II: 91.3%). Postoperative ureteral stricture: 5.8%. Success: 88.4%. Residual fragments: 12 (11.7%). Spontaneous passage: 6 (50%). Greater performance of flexible URS in proximal ureteral stones (p = 0.001) of more than 11 mm (p = 0.02) in univariate analysis, and in proximal stones [OR 3.5; 1.5-8.1; p = 0.004] in multivariate analysis. CONCLUSIONS: Endourological treatment obtained a high success rate in our sample. Size greater than 11 mm and proximal ureteral location in univariate and multivariate analysis, respectively, behaved as predictors of flexible URS.


Assuntos
Litotripsia , Cálculos Ureterais , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Resultado do Tratamento , Cálculos Ureterais/cirurgia , Ureteroscopia/efeitos adversos
8.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-34344584

RESUMO

INTRODUCTION AND OBJECTIVES: Currently, there are no established criteria regarding treatment for lumbar ureteral stones. The objective of this work is to present our results in the endourological treatment of this pathology, analyzing the variables associated with the use of the flexible ureterorenoscope. MATERIAL AND METHODS: Retrospective review of 103 patients who underwent retrograde URS with semi-rigid or flexible ureterorenoscope. Proximal location: L2-L3. Medial location: L4-L5. Semirigid URS was the initial treatment, with conversion to flexible URS when it was required to complete the procedure. Success was defined as absence of residual fragments (6 weeks). Demographic, surgical, immediate postoperative variables, and those related to the stone, were analyzed. Their correlation with the use of the flexible ureterorenoscope was evaluated. RESULTS: Mean age: 57.2 years (SD 15.6); there were 73 men (70.9%). Stone size: 8mm (range 4-30; IQR 4.5). Proximal location: 58 (56.3%). Previous JJ: 44.7%. Previous nephrostomy: 10.7%. Semirigid URS with conversion to flexible URS: 51 (49.5%). Impacted stones: 28.2%. Intraoperative complications: 2 (1.9%). Postoperative JJ: 84.5%. Immediate postoperative complications: 23 (22.3%) (Clavien-Dindo I-II: 91.3%). Postoperative ureteral stricture: 5.8%. Success: 88.4%. Residual fragments: 12 (11.7%). Spontaneous passage: 6 (50%). Greater performance of flexible URS in proximal ureteral stones (P=0.001) of more than 11mm (P=0.02) in univariate analysis, and in proximal stones [OR 3.5; 1.5-8.1; P=0.004] in multivariate analysis. CONCLUSIONS: Endourological treatment obtained a high success rate in our sample. Size greater than 11mm and proximal ureteral location in univariate and multivariate analysis, respectively, behaved as predictors of flexible URS.

9.
Clin Microbiol Infect ; 27(3): 428-434, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32311472

RESUMO

OBJECTIVES: The objective of this study was to analyse lung function decline over time in bronchiectasis, along with the factors associated with it. METHODS: Spirometry was measured every year in this observational, prospective study in 849 patients from the Spanish Bronchiectasis Registry (RIBRON). The main outcome was the decline in the rate of forced expiratory volume during the first second (FEV1). To be included in this study, patients needed a baseline assessment and at least one subsequent assessment. FEV1 decline was analysed using a mixed-effects linear regression model adjusted for clinically significant variables. RESULTS: We recruited 849 bronchiectasis patients with at least two annual lung function measurements (follow-up range 1-4 years). A total of 2262 lung function tests were performed (mean 2.66 per patient, range 2-5). Mean baseline FEV1 was 1.78 L (standard deviation (SD) 0.76; 71.3% predicted). Mean age was 69.1 (SD 15.4) years; 543 (64% women. The adjusted rates of FEV1 decline were -0.98% predicted/year (95% confidence interval (CI) -2.41 to -0.69) and -31.6 (95% CI -44.4 to -18.8) mL. The annual FEV1 decline was faster in those patients with chronic bronchial infection by Pseudomonas aeruginosa (-1.37% (52.1 mL) vs -0.37% (-24.6 mL); p < 0.001), greater age, increased number of severe exacerbations in the previous year and higher baseline FEV1 value. DISCUSSION: In patients with bronchiectasis, the annual rate of FEV1 decline was -31.6 mL/year and it was faster in older patients and those with chronic bronchial infection by P. aeruginosa, increased number of previous severe exacerbations and higher baseline FEV1 value.


Assuntos
Bronquiectasia/complicações , Bronquiectasia/microbiologia , Infecções por Pseudomonas/complicações , Infecções por Pseudomonas/microbiologia , Pseudomonas aeruginosa , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Testes de Função Respiratória
10.
IEEE J Biomed Health Inform ; 24(12): 3595-3605, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33170789

RESUMO

Currently, Coronavirus disease (COVID-19), one of the most infectious diseases in the 21st century, is diagnosed using RT-PCR testing, CT scans and/or Chest X-Ray (CXR) images. CT (Computed Tomography) scanners and RT-PCR testing are not available in most medical centers and hence in many cases CXR images become the most time/cost effective tool for assisting clinicians in making decisions. Deep learning neural networks have a great potential for building COVID-19 triage systems and detecting COVID-19 patients, especially patients with low severity. Unfortunately, current databases do not allow building such systems as they are highly heterogeneous and biased towards severe cases. This article is three-fold: (i) we demystify the high sensitivities achieved by most recent COVID-19 classification models, (ii) under a close collaboration with Hospital Universitario Clínico San Cecilio, Granada, Spain, we built COVIDGR-1.0, a homogeneous and balanced database that includes all levels of severity, from normal with Positive RT-PCR, Mild, Moderate to Severe. COVIDGR-1.0 contains 426 positive and 426 negative PA (PosteroAnterior) CXR views and (iii) we propose COVID Smart Data based Network (COVID-SDNet) methodology for improving the generalization capacity of COVID-classification models. Our approach reaches good and stable results with an accuracy of [Formula: see text], [Formula: see text], [Formula: see text] in severe, moderate and mild COVID-19 severity levels. Our approach could help in the early detection of COVID-19. COVIDGR-1.0 along with the severity level labels are available to the scientific community through this link https://dasci.es/es/transferencia/open-data/covidgr/.


Assuntos
COVID-19/diagnóstico por imagem , COVID-19/epidemiologia , COVID-19/virologia , Humanos , Modelos Teóricos , Pandemias , SARS-CoV-2/isolamento & purificação
11.
Chem Phys Lipids ; 232: 104968, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32896519

RESUMO

The Langmuir monolayer technique has long been known for its usefulness to study the interaction between molecules and mimic cellular membranes to understand the mechanism of action of biologically relevant molecules. In this review we summarize the results that provided insight into the potential mechanism for lowering the plasma level of cholesterol by hypocholesterolemic substances (unsaturated fatty acids (UFAs) and phytocompounds) - in the aspect of prevention of atherosclerosis - and their effects on model biomembranes. The results on UFAs/cholesterol (oxysterols) interactions indicate that these systems are miscible and strongly interacting, contrary to immiscible systems containing saturated fatty acids. Lowering of cholesterol plasma level by UFAs was attributed to the strong affinity between UFAs and sterols, resulting in the formation of high stability complexes, in which sterols were bound and eliminated from the body. Studies on the effect of UFAs and plant sterols/stanols on simplified biomembranes (modeled as cholesterol/DPPC system) indicated that the studied hypocholesterolemic substances modify the biophysical properties of model membrane, affecting its fluidity and interactions between membrane components. Both UFAs and plant sterols/stanols were found to loosen interactions between DPPC and cholesterol and decrease membrane rigidity caused by the excess cholesterol in biomembrane, thus compensating strong condensing effect of cholesterol and restoring proper membrane fluidity, which is of utmost importance for normal cells functioning. The agreement between model - in vitro - studies and biological results prove the usefulness of the Langmuir monolayer technique, which helps in understanding the mode of action of biologically relevant substances.


Assuntos
Membrana Celular/metabolismo , Ácidos Graxos Insaturados/metabolismo , Modelos Moleculares , Esteróis/sangue , Humanos
12.
Clin Radiol ; 75(11): 880.e5-880.e12, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32888653

RESUMO

AIM: To compare the performance of multi-echo chemical-shift-encoded (MECSE) magnetic resonance imaging (MRI) proton density fat fraction (PDFF) estimation, considering three different fat frequency peak combinations, for the quantification of steatosis in patients with non-alcoholic fatty liver disease (NAFLD). MATERIALS AND METHODS: The present study was a prospective cross-sectional research of 121 patients with metabolic syndrome and evidence of hepatic steatosis on ultrasound, who underwent a 3 T MRI examination. All patients were studied with a multifrequency MECSE sequence. The PDFF was calculated using six peaks (MECSEp123456), three peaks (MECSEp456), and a single peak (MECSEp5) model. The two simpler fat peak models were compared to the six peaks model, which was considered the reference standard. Linearity was evaluated using linear regression while agreement was described using Bland-Altman analysis. RESULTS: The mean age was 47 (±9) years and BMI was 29.9 (±2.9) kg/m2. Steatosis distribution was 15%/31%/54% (S1/S2/S3, respectively). Compared to MECSEp123456, both models provided linear PDFF measurements (R2= 0.99 and 0.97, MECSEp456 and MECSEp5 respectively). Regression slope (0.92; p<0.001) and mean Bland-Altman bias (-1.5%; 95% limits of agreement: -3.19%, 0.22%) indicated minimal underestimation by using PDFF-MECSEp456. Nonetheless, mean differences in PDFF estimations varied from -1.5% (MECSEp456,p=0.006) to -2.2% (MECSEp5,p<0.001) when compared to full six fat frequencies model. CONCLUSION: Although simpler spectral fat MECSE analysis shows a linear relationship with the standard six peaks model, their variation in estimated PDFF values introduces a low but clinically significant bias in fat quantification and steatosis grading in NAFLD patients.


Assuntos
Fígado/diagnóstico por imagem , Imageamento por Ressonância Magnética , Hepatopatia Gordurosa não Alcoólica/diagnóstico por imagem , Tecido Adiposo/diagnóstico por imagem , Tecido Adiposo/patologia , Estudos Transversais , Fígado Gorduroso/diagnóstico por imagem , Fígado Gorduroso/patologia , Feminino , Humanos , Fígado/patologia , Masculino , Pessoa de Meia-Idade , Hepatopatia Gordurosa não Alcoólica/patologia , Estudos Prospectivos
13.
J Prosthet Dent ; 123(3): 379-383, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31307796

RESUMO

This clinical report describes a chemical abrasive protocol and whitening techniques to quantify modifications to the color and volume produced when eliminating white spots associated with developmental defects in enamel. Chemical (oxidative-erosive) abrasive treatment (whitening + 6.6% hydrochloric acid) resolves white spots up to a depth of 0.2 mm. At greater depths, infiltration with 16% hydrochloric acid followed by composite resin infiltration is recommended.


Assuntos
Cárie Dentária , Clareamento Dental , Resinas Compostas , Esmalte Dentário , Humanos
14.
PLoS One ; 14(11): e0225053, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31710628

RESUMO

We report the results of a study on the learnability of haptic icons used as alerts or notifications in smartphones. The aim was to explore the feasibility of using haptic icons to create assistive technologies for people with visual impairments. We compared the performance and satisfaction of users with different visual capacities (visually impaired vs. sighted) and using different learning processes (with or without a reinforcement learning stage). The reinforcement learning stage improves the recognition rate in both types of users, although the improvement obtained by the visually impaired users is even better as their recognition rates become very similar to those obtained by the sighted users. Finally, it was observed that the better recognized haptic icons are those assigned to the most employed applications by the user.


Assuntos
Aprendizagem , Smartphone , Tato , Pessoas com Deficiência Visual , Humanos , Percepção , Vibração
15.
J Colloid Interface Sci ; 557: 777-792, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31580974

RESUMO

Positively charged elastin-like polypeptides (ELPs) were synthesized for the compaction of genetic material. A recombinant ELP (VPGXG)40 with X = V,M (3:1) was post-modified in two steps to introduce chemoselectively either primary or secondary amine pendant groups at each methionine residue. Positively charged ELPs were characterized by SDS-PAGE, size exclusion chromatography, 1H NMR, potentiometric titrations and dynamic light scattering to assess their purity and determine their degree of functionalization, molecular weight, isoelectric point and thermo-responsive behaviour. Electrostatic complexation between the different ELP derivatives and nucleic acids was studied to determine the stoichiometry of ELPS/nucleic acids complex formation, and to find optimal conditions leading to stable nanoparticles with controlled size and surface potential. The stability of these complexes was investigated in the presence of salts at physiological concentrations and in the presence of surfactant. This study revealed that two regimes of stable nanoparticles in terms of size and charge can be obtained from the electrostatic complexation between the primary amine containing ELP derivative, ELP(-NH2), and plasmid DNA. Resulting complexes were found to be stable to dissociation for charge ratios up to 2.5 under physiological salt concentrations (154 mM NaCl), showing that plasmid DNA was completely condensed by the polycationic ELP and protected against electrolyte-mediated dissociation.


Assuntos
Elastina/química , Nanopartículas/química , Ácidos Nucleicos/química , Peptídeos/química , Alquilação , Aminas/química , Cátions/química , Interações Hidrofóbicas e Hidrofílicas , Metionina/química , Conformação Molecular , Peso Molecular , Polieletrólitos/química , Multimerização Proteica , Eletricidade Estática
16.
Chem Phys Lipids ; 225: 104819, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31525379

RESUMO

Surface pressure (π) - molecular area (A) isotherms of cholesterol were precisely measured to get insight into the orientation of molecules in Langmuir monolayers, which allowed to obtain detailed information on their phase behaviour. This was possible from the detailed analysis of the interfacial compressibility modulus versus surface pressure (Cs-1- π) plots (obtained from the experimental surface pressure, π - area, A isotherms) and films thickness measurements (applying Brewster angle microscope, BAM) complemented with polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS). At first glance, the isotherm for cholesterol is characterized by the major slope change of surface pressure versus area per molecule. However, a more detailed analysis showed the presence of a discontinuity and slope change both upon the compression and expansion of the monolayer. This discontinuity is more accurately reflected in the Cs-1- π plot as a pseudo-plateau visible at π values between approximately 5 and 10 mN/m. This plateau was found to be temperature-dependent. Also, film thickness versus area plot (th-A) exhibits a pseudo-plateau in this region of surface pressures, in which the monolayer thickness increased gradually from 1.15 nm to 1.5 nm. Interestingly, although cholesterol has been intensively investigated in Langmuir monolayers, the existence of such a plateau have been overlooked previously. By linking experimental thickness values with theoretical molecular conformations, we have identified the presence of this plateau to the solid-solid (S-S') second-order transition. Using 2D analog of Clausius-Clapeyron equation, the thermodynamic functions (ΔH and ΔS) for this transition have been calculated. Based on monolayer experiments, the orientation of molecules in both solid phases was assumed to differ in the orientation of short alkyl chain attached to C17, which has additionally been confirmed with PM-IRRAS analysis.


Assuntos
Colesterol/química , Ar , Conformação Molecular , Tamanho da Partícula , Transição de Fase , Propriedades de Superfície , Água/química
17.
Radiologia (Engl Ed) ; 61(5): 351-356, 2019.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-31320205

RESUMO

The recent publication of the resolution through which the basic directives about the contents of the documents to accredit the assessments of specialists in training maintains the model but incorporates new elements that enable important changes in the assessment. The resolution has errors and is confusing because the rules are hidden in the instructions for filling out the forms and in footnotes. Nevertheless, the resolution is more than a simple change in the forms: it is a step toward a more current assessment based on the evaluation of residents' competence. The most significant changes are a stronger role for collaborating teachers, an increase in the number of possible reasons for negative assessments, and the establishment of the rotation as the basic unit of analysis.


Assuntos
Competência Clínica , Formulários como Assunto , Internato e Residência , Radiologia/educação , Internato e Residência/normas
18.
Biochim Biophys Acta Biomembr ; 1861(8): 1428-1436, 2019 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-31189076

RESUMO

Unsaturated fatty acids (UFAs) are known to lower the level of sterols in blood, which accounts for their cardioprotective effect. To understand the molecular basis of this effect, Langmuir monolayer studies have been performed. A series of UFAs differing in the length of the fatty acid chain and the number of double bonds (oleic acid, OA; linoleic acid, LA; stearidonic acid, SDA; eicosanoic acid, EA) were mixed with cholesterol and its more toxic oxidized derivative, 7­ketocholesterol (7-KC), abundantly present in atheroma plaques. Strong attractive UFA-sterol interactions were attributed to the formation of "surface complexes", in which sterol molecules are bound, thereby reducing the amount of free sterol molecules. It has been found that strength of interactions increases with the degree of unsaturation of the acyl chain in UFA molecule. The most attractive interactions correspond to mixtures with SDA containing 70 mol% of 7-KC and 50 mol% of cholesterol. In both cases, the formation of high stability complexes of, respectively, 2:1 and 1:1 sterol/SDA stoichiometry has been proposed. Other complexes of lower stability and 1:2 stoichiometry were postulated for chol (or 7-KC)/LA systems. The complexes of the lowest stability correspond to chol (or 7-KC) mixtures with OA and EA of 1:1 stoichiometry. In all the cases, the interactions of 7-KC with UFAs are more energetically favorable versus cholesterol. The elongation of the hydrophobic chain of UFAs decreased the interactions with the studied sterols. The obtained results can be related to different conformations of the fatty acids chains.


Assuntos
Colesterol/química , Ácidos Graxos Insaturados/química , Cetocolesteróis/química , Propriedades de Superfície , Termodinâmica
20.
Diabetes Metab ; 45(5): 473-479, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-30660761

RESUMO

AIM: The association of non-alcoholic fatty liver disease (NAFLD) with insulin resistance (IR) is well established, yet little is known of their possible relationship with intrahepatic iron and serum tumour necrosis factor (TNF)-α concentrations in adults without diabetes. Thus, this study looked at the relationship of intrahepatic iron and serum TNF-α with intrahepatic triglycerides and IR in non-diabetic adults. METHODS: In this cross-sectional study of 104 healthy non-diabetic Caucasians, a quantitative magnetic resonance (MR) imaging T2 gradient-echo technique was used to measure hepatic iron, with 1H-MR spectroscopy used to measure hepatic triglycerides. HOMA-IR was calculated to determine IR. RESULTS: The prevalence of hepatic iron overload (HIOL) was 26.6% in individuals with NAFLD vs. 0% in those without. IR was present in 87.5% of subjects with both NAFLD and HIOL, in 45.4% of those with NAFLD but not HIOL, and in 4.5% of those with neither. HOMA-IR was positively correlated with hepatic triglycerides (r = 0.56, P < 0.001) and hepatic iron (r = 0.52, P < 0.001), whereas serum TNF-α concentrations correlated with intrahepatic triglyceride levels (r = 0.28, P < 0.04), but not with intrahepatic iron. Hepatic triglycerides, serum TNF-α and age were the only significant determinants of IR in regression analyses. CONCLUSION: IR is closely associated with intrahepatic triglycerides and, to a lesser extent, intrahepatic iron, with some interplay between them. High serum TNF-α concentrations may contribute to the association between NAFLD and IR, while increased hepatic triglycerides appear to be a determinant of the development of HIOL in non-diabetic subjects without haemochromatosis.


Assuntos
Resistência à Insulina/fisiologia , Ferro/análise , Fígado/diagnóstico por imagem , Hepatopatia Gordurosa não Alcoólica/sangue , Fator de Necrose Tumoral alfa/sangue , Adulto , Fatores Etários , Idoso , Estudos Transversais , Feminino , Humanos , Imageamento por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Hepatopatia Gordurosa não Alcoólica/diagnóstico por imagem , Triglicerídeos/sangue
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