RESUMEN
Nanocomposites physical properties unexplainable by general mixture laws are usually supposed to be related to interphases, highly present at the nanoscale. The intrinsic dielectric constant of the interphase and its volume need to be considered in the prediction of the effective permittivity of nanodielectrics, for example. The electrostatic force microscope (EFM) constitutes a promising technique to probe interphases locally. This work reports theoretical finite-elements simulations and experimental measurements to interpret EFM signals in front of nanocomposites with the aim of detecting and characterizing interphases. According to simulations, we designed and synthesized appropriate samples to verify experimentally the ability of EFM to characterize a nanoshell covering nanoparticles, for different shell thicknesses. This type of samples constitutes a simplified electrostatic model of a nanodielectric. Experiments were conducted using either DC or AC-EFM polarization, with force gradient detection method. A comparison between our numerical model and experimental results was performed in order to validate our predictions for general EFM-interphase interactions.
RESUMEN
Regulation of food intake through modulation of gastrointestinal responses to ingested foods is an ever-growing component of the therapeutic approaches targeting the obesity epidemic. Alginates, viscous and gel-forming soluble fibers isolated from the cell wall of brown seaweeds and some bacteria, are recently receiving considerable attention because of their potential role in satiation, satiety, and food intake regulation in the short term. Enhancement of gastric distension, delay of gastric emptying, and attenuation of postprandial glucose responses may constitute the basis of their physiological benefits. Offering physical, chemical, sensorial, and physiological advantages over other viscous and gel-forming fibers, alginates constitute promising functional food ingredients for the food industry. Therefore, the current review explores the role of alginates in food intake and glycemic regulation, their underlying modes of action and their potential in food applications.
Asunto(s)
Alginatos/farmacología , Glucemia/efectos de los fármacos , Ingestión de Alimentos/efectos de los fármacos , Vaciamiento Gástrico/efectos de los fármacos , Saciedad/efectos de los fármacos , Alginatos/administración & dosificación , Industria de Alimentos , Humanos , Periodo Posprandial/fisiologíaRESUMEN
BACKGROUND/OBJECTIVES: Sodium alginate reduces appetite and glycemia, when consumed in water- and sugar-based drinks. But, its effects when added to other commonly consumed beverages have not been reported. Because chocolate milk (CM) is criticized for raising blood glucose more than unflavored milk, the aim of our study was to investigate the effect of adding a strong-gelling sodium alginate to CM on glycemia, insulinemia, appetite and food intake. SUBJECTS/METHODS: In a randomized crossover design, 24 men (22.9±0.4 years; 22.5±0.3 kg/m(2)) were provided with isovolumetric (325 ml) treatments of CM, 1.25% alginate CM, 2.5% alginate CM or 2.5% alginate solution. Sodium alginate had a ratio of 0.78:1 of mannuronic acid (M) to guluronic acid (G) residues, and was block distributed. Treatments were standardized for lactose, sucrose and calcium content, and provided 120 min before an ad libitum pizza meal during which food intake was measured. Appetite and blood glucose and insulin were measured at baseline and at intervals pre- and post-meal. RESULTS: Addition of 2.5% alginate to CM reduced peak glucose concentrations, at 30 min, by an average of 6% and 13% compared with 1.25% alginate CM (95% confidence intervals (CIs): 0.02-1.08; P=0.037) and CM alone (95% CIs: 0.49-1.55; P=0.000) respectively. Insulin peaks at 30 min were lower by 46% after 2.5% alginate CM relative to CM (95% CIs: 3.49-31.78; P=0.009). Pre-meal appetite was attenuated dose dependently by alginate addition to CM; CM with 2.5% alginate reduced mean appetite by an average of 134% compared with CM alone (95% CIs: 8.87-18.98; P=0.000). However, total caloric intake at the pizza meal did not differ among treatments. CONCLUSIONS: The addition of a strong-gelling sodium alginate to CM decreases pre-meal glycemia, insulinemia and appetite, but not caloric intake at a meal 2 h later, in healthy adult men.
Asunto(s)
Alginatos/administración & dosificación , Apetito/efectos de los fármacos , Glucemia/metabolismo , Productos Lácteos/análisis , Insulina/sangre , Adulto , Alginatos/análisis , Bebidas/análisis , Índice de Masa Corporal , Fenómenos Químicos , Estudios Cruzados , Ingestión de Energía/efectos de los fármacos , Ácido Glucurónico/administración & dosificación , Ácido Glucurónico/análisis , Voluntarios Sanos , Ácidos Hexurónicos/administración & dosificación , Ácidos Hexurónicos/análisis , Ácidos Hexurónicos/química , Humanos , Masculino , Comidas , Periodo Posprandial/efectos de los fármacos , Método Simple Ciego , Adulto JovenRESUMEN
The use of nutritional supplements among exercisers in gyms has been never investigated in the Middle East. The aim of the current study was to assess the prevalence intake of nutritional supplements and the potential influencing factors among people exercising in gyms in Beirut city. In this cross-sectional study, 512 exercisers, aged between 20 and 50 years, were randomly selected from gyms. The intake of nutritional supplements was reported among 36.3% (95% confidence interval 32.2-40.5) of participants, with a weak presence of medical supervision. Patterns of supplement use differed by gender and age. Men and younger exercisers were found to focus on supplements associated with performance enhancement and muscle building, while women and older exercisers were more concerned with health-promoting products such as vitamins, minerals, and herbal supplements. An appropriate dissemination of accurate and scientifically sound information regarding the benefits and side effects of nutritional supplements is highly recommended in the sports environment in Beirut city.
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Despite the lack of international agreement regarding the definition and classification of fiber, there is established evidence on the role of dietary fibers in obesity and metabolic syndrome. Beta glucan (ß-glucan) is a soluble fiber readily available from oat and barley grains that has been gaining interest due to its multiple functional and bioactive properties. Its beneficial role in insulin resistance, dyslipidemia, hypertension, and obesity is being continuously documented. The fermentability of ß-glucans and their ability to form highly viscous solutions in the human gut may constitute the basis of their health benefits. Consequently, the applicability of ß-glucan as a food ingredient is being widely considered with the dual purposes of increasing the fiber content of food products and enhancing their health properties. Therefore, this paper explores the role of ß-glucans in the prevention and treatment of characteristics of the metabolic syndrome, their underlying mechanisms of action, and their potential in food applications.
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Current data indicate that CD5 functions as an inhibitor of TCR signal transduction. Consistent with this role, thymocyte selection in TCR transgenic/CD5(-/-) mice is altered in a manner suggestive of enhanced TCR signaling. However, the impact of CD5 deletion on thymocyte selection varies depending on the transgenic TCR analyzed, ranging from a slight to a marked shift from positive toward negative selection. An explanation for the variable effect of CD5 on selection is suggested by the observation that CD5 surface expression is regulated by TCR signal intensity during development and CD5 surface levels on mature thymocytes and T cells parallel the avidity of the positively selecting TCR/MHC/ligand interaction. In this study, we generated mice that overexpress CD5 during thymocyte development (CD5-tg), and then examined the effect of CD5 overexpression or CD5 deletion (CD5(-/-)) on selection of thymocytes that express the same TCR transgenes. The results demonstrate that the effect on thymocyte selection of altering CD5 expression depends on the avidity of the selecting interaction and, consequently, the level of basal (endogenous) CD5 surface expression. Substitution of endogenous CD5 with a transgene encoding a truncated form of the protein failed to rescue the CD5(-/-) phenotype, demonstrating that the cytoplasmic domain of CD5 is required for its inhibitory function. Together, these results indicate that inducible regulation of CD5 surface expression during thymocyte selection functions to fine tune the TCR signaling response.
Asunto(s)
Antígenos CD5/fisiología , Receptores de Antígenos de Linfocitos T/fisiología , Transducción de Señal/inmunología , Animales , Antígenos CD5/biosíntesis , Antígenos CD5/genética , Diferenciación Celular/genética , Diferenciación Celular/inmunología , Membrana Celular/genética , Membrana Celular/inmunología , Membrana Celular/metabolismo , Citoplasma/inmunología , Regulación hacia Abajo/genética , Regulación hacia Abajo/inmunología , Femenino , Humanos , Ligandos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Transgénicos , Unión Proteica/genética , Unión Proteica/inmunología , Estructura Terciaria de Proteína/genética , Receptores de Antígenos de Linfocitos T/genética , Receptores de Antígenos de Linfocitos T/metabolismo , Transducción de Señal/genética , Linfocitos T/citología , Linfocitos T/inmunología , Linfocitos T/metabolismo , Timo/citología , Timo/inmunología , Timo/metabolismoRESUMEN
The T cell antigen receptor (TCR) and pre-TCR complexes are composed of multiple signal-transducing subunits (CD3 gamma, CD3 delta, CD3 epsilon, and zeta) that each contain one or more copies of a semiconserved functional motif, the immunoreceptor tyrosine-based activation motif (ITAM). Although biochemical studies indicate that individual TCR-ITAMs may bind selectively or with different affinity to various effector molecules, data from other experiments suggest that at least some ITAMs are functionally equivalent. In this study, we examined the role of CD3straightepsilon ITAM-mediated signals in T cell development by genetically reconstituting CD3 epsilon-deficient mice with transgenes encoding either wild-type or ITAM-mutant (signaling defective) forms of the protein. The results demonstrate that signals transduced by CD3 epsilon are not specifically required for T cell maturation but instead contribute quantitatively to TCR signaling in a manner similar to that previously observed for zeta chain. Unexpectedly, analysis of TCR-transgenic/CD3 epsilon-mutant mice reveals a potential role for CD3 epsilon signals in T cell survival.