Levels of leaf Herbivory in Amazonian trees from different stages In forest regeneration

Leaves from 120 canopy trees and 60 understory tree saplings growing in primary and secondary forests near Manaus, Brazil, were collected for determination of standing levels of herbivory (percent leaf area lost). Overall, levels of herbivory on leaves of central Amazonian trees were low. About one quarter of the leaves examined (n = 855) had no damage at all. In most other Neotropical sites studied the mean percentage of herbivory was found to vary between 5.7 and 13.1%, whereas in Manaus it was only 3.1%. The data presented here support the contention that levels of herbivore damage are positively related to soil fertility. No significant difference was found in herbivory levels between canopy trees and understory saplings. Also, there was no difference in damage between leaves from pioneer and late successional trees. Field assays of preference, however, revealed that leaves from pioneer trees are more palatable to leaf-cutting ants (Atta laevigata). This effect was dependent upon leaf age, being observed in mature leaves, but not in young leaves. The greater rate of leaf production in secondary forests may be a factor accounting for the greater abundance of leaf-cutting ants in secondary compared to primary forests.

Physiological responses of matrinxã (Brycon amazonicus) fed different levels of vitamin C and submitted to air exposure

The role of vitamin C on physiological responses of matrinxã (Brycon amazonicus) submitted to air exposure was analyzed. Nine hundred fish (70.15 g) were distributed in fifteen 500 l boxes (60 fish.box-1) and fed five rations (treatments): Control (no vitamin C); T100 (100 mg); T200 (200 mg); T400 (400 mg) and T800 (800 mg of vitamin C kg.ration-1). Each ration was offered to fish of three boxes during 60 days before the stress challenge that consisted of exposing fish to air for two minutes. Samplings were carried out for 5, 15, 30 and 60 minutes after the air exposure. Blood was collected for glucose, cortisol, total protein, sodium, chloride, hematocrit, hemoglobin determination, and white and red cell count. Liver was removed for hepatosomatic index (HSI) calculation and glycogen determination. Vitamin C did not affect the levels of cortisol, chloride, total protein, hemoglobin, leukocytes, hepatic glycogen or HSI in air exposed fish. Blood glucose levels elevation observed 60 minutes after the challenge did not depend on the levels of vitamin C, nor did the drop in serum sodium levels verified 60 minutes after stressor. In general, hematocrit did not change by effect of vitamin C but it was lower at 15 and 30 minutes after the challenge. The number of erythrocytes decreased in fish after 5 minute sampling in all treatments, especially at 30 and 60 minutes. The air exposure evoked alterations in stress indicators of matrinxã, and the vitamin C did not alter the responses.

High levels of Mercury and Lead detected by hair analysis in two Venezuelan environments

Mercury and Lead concentrations obtained by ICP-OAS analysis of human hair from riverside communities along the Orinoco river in the Amazon state (Venezuela) were compared with those from Caracas, Venezuela. Taking into account the characteristics of these two environments and the values of the average concentrations of Mercury and Lead, baselines were established suggesting that gold mining activity near the Orinoco river is responsible for the high levels of Mercury in hair from the Amazon state, whereas automobile activity is responsible for high levels of Lead in hair in Caracas.

Flowering levels, harvest season and yields of cupuassu (Theobroma grandiflorum)

Cupuassu (Theobroma grandiflorum), a specie native to Amazonia, has been planted commercially in Brazil to satisfy the demand for the flavorful juice obtained from the pulp around its seeds. The trees are notorious for low and irregular fruit production. Data gathered over two seasons from trees in a germplasm collection in Pará, Brazil, showed that some of them fruited more regularly than others. Differences in fruit production correlated to differences in flower production. Tree-to-tree variation in flower production, fruit production, and consistency of both over time suggest considerable scope for improving yields by selection. Hand pollinations resulted in a much higher frequency of fruit set than open pollinations, indicating that lack of effective pollination is also a reason for low yield. However, attempts to increase the level of effective pollination are handicapped by low knowledge about the pollinators of cupuassu and their behavior.

Prevalence of excessive daytime sleepiness in Brazilian community-dwelling older adults with very low levels of schooling, and its association with sociodemographic characteristics and lifestyle: the Bambuí Health and Ageing Study (BHAS)

OBJECTIVE: Population-based studies on excessive daytime sleepiness (EDS) in older adults living in less developed countries are scarce. The purpose of this paper was to estimate the prevalence of EDS and its association with sociodemographic characteristics and lifestyle factors in Brazilian community-dwelling older adults. METHODS: The study was carried out in Bambuí, a city in the state of Minas Gerais, Brazil. EDS was defined as the presence of sleepiness in the last month occurring three or more times per week, with any interference in usual activities. The exploratory variables were: gender, age, skin color, marital status, schooling level, current employment status, religion, recent migration, smoking, binge drinking and physical activities during leisure time. RESULTS: Of 1,742 residents aged > 60 years, 1,514 (86.9%) participated. The prevalence of EDS was 13%. After adjustment for confounders, female gender and low schooling level remained positively and independently associated with EDS. CONCLUSIONS: The prevalence of EDS in the study population was within the range observed in studies carried out in developed countries. The most impressive finding was the association of EDS with schooling, indicating that even in a population with low levels of schooling, this was an important factor to explain the distribution of EDS.

Nanocomposites: the contribution of multiscale modelling to improve the dispersion levels

Tese de Doutoramento em Ciência e Engenharia de Polímeros e Compósitos

Plasma levels of immunoinflammatory markers in De Novo coronary atherosclerosis and coronary restenosis postangioplasty

OBJECTIVE: To compare circulating plasma levels of immunoinflammatory markers in patients with known de novo coronary artery disease and patients with postangioplasty restenosis. METHODS: Using enzymatic immunoabsorbent assay, we measured plasma levels of soluble interleukin-2 receptosr, tumor necrosis factor alpha, and soluble tumor necrosis alpha receptors I and II in 11 patients with restenosis postcoronary angioplasty (restenosis group), in 10 patients with primary atherosclerosis (de novo group) who were referred for coronary angiography because of stable or unstable angina, and in 9 healthy volunteers (control group). Levels of soluble interleukin-2 receptors were significantly higher in the de novo group compared with that in the restenosis and control groups. Levels were also higher in the restenosis group compared with that in the control group. Plasma levels of tumor necrosis alpha and receptor levels were significantly higher in the de novo group compared to with that in the restenosis and control groups, but levels in the restenosis group were not different from that in the controls. CONCLUSION: Coronary artery disease, either primary or secondary to restenosis, is associated with significant immunoinflammatory activity, which can be assessed by examining the extent of circulating plasma levels of inflammatory markers. Moreover, patients with de novo lesions appear to have increased inflammatory activity compared with patients with restenosis.

Analysis of Plasma Homocysteine Levels in Patients with Unstable Angina

OBJECTIVE - To determine the prevalence of hyperhomocystinemia in patients with acute ischemic syndrome of the unstable angina type. METHODS - We prospectively studied 46 patients (24 females) with unstable angina and 46 control patients (19 males), paired by sex and age, blinded to the laboratory data. Details of diets, smoking habits, medication used, body mass index, and the presence of hypertension and diabetes were recorded, as were plasma lipid and glucose levels, C-reactive protein, and lipoperoxidation in all participants. Patients with renal disease were excluded. Plasma homocysteine was estimated using high-pressure liquid chromatography. RESULTS - Plasma homocysteine levels were significantly higher in the group of patients with unstable angina (12.7±6.7 µmol/L) than in the control group (8.7±4.4 µmol/L) (p<0.05). Among males, homocystinemia was higher in the group with unstable angina than in the control group, but this difference was not statistically significant (14.1±5.9 µmol/L versus 11.9±4.2 µmol/L). Among females, however, a statistically significant difference was observed between the 2 groups: 11.0±7.4 µmol/L versus 6.4±2.9 µmol/L (p<0.05) in the unstable angina and control groups, respectively. Approximately 24% of the patients had unstable angina at homocysteine levels above 15 µmol/L. CONCLUSION - High homocysteine levels seem to be a relevant prevalent factor in the population with unstable angina, particularly among females.

Thiamin, selenium, and copper levels in patients with idiopathic dilated cardiomyopathy taking diuretics

OBJECTIVE: To analyze the association of thiamin, selenium, and copper serum levels with cardiac function in patients with idiopathic dilated cardiomyopathy using diuretics, and also to compare them with levels in control patients with no evidence of disease. METHODS: The study comprised 30 patients with heart disease and 30 healthy control individuals. Thiamin was analyzed by measuring the activity of erythrocytic transketolase and the effect of thiamin pyrophosphate. Selenium and copper serum levels were measured by hydride generation and flame atomic absorption spectrophotometry, respectively. RESULTS: Thiamin deficiency was observed in 10% of the control individuals and in 33% of the patients with heart disease (p=0.02). The mean selenium and copper serum levels in control individuals and patients with heart disease were, respectively, 73.2±9.9 µg/L (56.5 to 94.5 µg/L) and 72.3±14.3 µg/L (35.5 to 94 µg/L) (p=0.77); 1.1±0.4mg/L (0.6 to 1.8mg/L) and 1.2± 0.4mg/L (0.6 to 2.2mg/L) (p=0.27). No association between the levels of these nutrients and cardiac function was observed. CONCLUSION: Thiamin deficiency was significantly more frequent in patients with heart disease. No significant difference was observed between the mean selenium and copper serum levels in control individuals and in patients with heart disease. The results suggest possible benefits with thiamin replacement in patients taking diuretics.

National alert campaign about increased cholesterol: determination of cholesterol levels in 81,262 Brazilians

OBJECTIVE: To determine the levels of total cholesterol in a significant sample of the Brazilian population. METHODS: Blood cholesterol was determined in 81.262 individuals > 18 years old (51% male, 44.7 ± 15.7 years), using Accutrend equipment, in the cities São Paulo, Campinas, Campos do Jordão, São José dos Campos, Santos, Santo André, Ribeirão Preto, Porto Alegre, Rio de Janeiro, Belo Horizonte, Curitiba, Brasília, Salvador and documented in the presence of other risk factors (RF) for coronary artery disease (CAD) (systemic hypertension, CAD in the family, smoking, and diabetes). Participants were classified according to sex, age, and the presence or absence of RF, respectively, as 0 RF, 1 RF and > 2 RF. The percentage of individuals with cholesterol > 200 mg/dL and > 240 mg/dL was evaluated. RESULTS: The prevalence of individuals with 0, 1, and > 2 risk factors was 30% (n = 24,589), 36% (n =29,324), and 34% (n = 27,349) respectively, (P=0.657), and the mean total cholesterol of the population was 199.0 ± 35.0 mg/dL. Cholesterol levels above 200 and 240 mg/dL were found, respectively, in 40% (n = 32,515) and 13% (10.942) of individuals. The greater the number of risk factors the higher the levels of cholesterol (P<0.0001) and the greater the proportion of individuals with cholesterol > 200 mg/dL (P=0.032). No difference existed in the proportion of individuals with cholesterol > 240 mg/dL (P=0.11). CONCLUSION: A great percentage of individuals with cholesterol levels above those recommended to prevent coronary artery disease was found.

Cellular cholesterol efflux mediated by HDL isolated from subjects with low HDL levels and coronary artery disease

OBJECTIVE: The aim of this study was to verify whether HDL particles isolated from patients with coronary artery disease (CAD) and low HDL-C had diminished ability to promote cholesterol efflux from cultured cells compared with HDL isolated from subjects without CAD and with normal HDL-C. METHODS: Smooth muscle cells isolated from human aortas cultured and radiolabeled with ³H-cholesterol were loaded with cholesterol and incubated with increasing concentrations of HDL isolated from 13 CAD patients with low HDL-C (CAD group) or from 5 controls without CAD (C group). Efflux of cellular cholesterol was measured by cellular depletion of radiolabeled cholesterol and by the appearance of ³H-cholesterol into experimental medium expressed as a percentage of total labeled cholesterol. RESULTS: Cholesterol efflux increased with the amount of HDL present in the medium, and no difference was found between groups at various HDL protein concentrations: efflux was 28 ± 6.3% (C) and 25.5 ± 8.9% (CAD) with 25 mg/mL; 34 ± 4.3% (C) and 31.9 ± 6.6% (CD) with 50 mg/mL and 39.5 ± 3.5% (C) and 37.1 ± 4.4% (CAD) with 100 mg/mL, HDL. CONCLUSION: Because the HDL fraction of CAD patients with low HDL-C have normal ability to extract cholesterol from cells of the vessel wall, it is suggested that low HDL-C atherogenicity should be ascribed to diminished concentrations of HDL particles rather than to the qualitative properties of the HDL fraction.

Acciones tróficas de GABA: implicancias en la diferenciación sexual del cerebro. Trophic actions of GABA: Implications for sexual differentiation of the brain.

En el hipotálamo en desarrollo, el ácido gamma-amino butírico (GABA) produce depolarización neuronal, pudiendo incluso disparar potenciales de acción y causar la apertura de canales de calcio dependientes de voltaje. Esto se debe a que la concentración intracelular de Cl- es alta respecto al medio extracelular, por lo que en reposo el potencial de equilibrio de GABA es más positivo que el potencial de membrana. A medida que el desarrollo transcurre, la concentración intracelular de Cl- disminuye y se produce un cambio en la respuesta de depolarizante (etapa excitatoria) a hiperpolarizante (etapa inhibitoria). Se ha demostrado que este cambio ocurre también en neuronas hipotalámicas in vitro. El dimorfismo sexual del cerebro de los vertebrados es consecuencia de la acción del estrógeno aromatizado a partir de andrógenos segregados por el testículo durante el "periodo crítico" del desarrollo cerebral. Evidencias previas de nuestro y otros laboratorios pusieron de manifiesto diferencias en el crecimiento y diferenciación de neuronas que no podían atribuirse a la acción hormonal, ya que ocurren antes que se inicie el brusco aumento de la secreción gonadal, alrededor del día 18 de desarrollo embrionario en la rata (E18). Además de las diferencias morfológicas, encontramos diferencias sexuales en la forma que las neuronas hipotalámicas responden a muscimol, un agonista específico del receptor GABAA. A los 9 días in vitro (9 DIV) la respuesta a muscimol fue hiperpolarizante (etapa inhibitoria) y además fue de mayor amplitud, área y duración en machos respecto a hembras. Esto nos indica que las neuronas provenientes de embriones machos son intrínsecamente diferentes a las de embriones hembra aún antes de la acción organizadora de los esteroides sexuales. En base a estas evidencias nos propusimos continuar nuestros estudios sobre la participación de GABA en la determinación de diferencias sexuales en el cerebro antes de la acción organizadora de los esteroides gonadales. Para ello, en cultivos de neuronas hipotalámicas de E16 separados por sexos, estudiaremos:- la respuesta a muscimol de las neuronas, en la etapa excitatoria (2 DIV) de la acción de GABA.- las composición de subunidades de los receptores GABAA en la etapa excitatoria/inhibitoria de la acción de GABA.- la participación de los receptores GABAA sobre el crecimiento neurítico.- la activación de la vía de las MAP quinasas por muscimol.- la participación de los receptores GABAA sobre el crecimiento axonal inducido por estradiol in vitro.Toda la metodología propuesta es de uso habitual en nuestro laboratorio e involucra herramientas de la electrofisiología y la biología celular-molecular; como patch-clamp, cultivo de neuronas hipotalámicas, Western blot, RT-PCR, entre otras. Esperamos encontrar diferencias sexuales en la amplitud, área y duración de la respuesta de las neuronas hipotalámicas al muscimol a los 2 DIV, y que éstas se deban a una diferente composición de subunidades del receptor GABAA. En cuanto a la participación del receptor GABAA en la neuritogenesis, esperamos encontrar mayor longitud neurítica en neuronas macho como así también una activación sexualmente dimórfica de la vía de las MAP quinasas. Además esperamosque la acción de un antagonista del receptor GABAA interfiera con la axogénesis inducida por estradiol in vitro, característica que muestra diferencia sexual también a favor de los machos, lo que reforzaría nuestra hipótesis. La importancia y originalidad de este proyecto reside en la evaluación de la participación del sistema GABAérgico en la determinación de características que durante el desarrollo, podrían estar involucradas en la determinación de diferencias sexuales permanentes en el cerebro adulto independientemente de la acción de los esteroides sexuales. Hasta la fecha, no ha sido evaluada la influencia de los receptores GABAA en la diferenciación sexual del cerebro antes de la acción organizadora de los esteroides gonadales.

Comprensión en resolución de problemas en Física: niveles de representación e inferencias basadas en el conocimiento. Comprehension in Physics Problem-Solving: levels of representation and knowledge-based inferences.

Se propone desarrollar e integrar estudios sobre Modelado y Resolución de Problemas en Física que asumen como factores explicativos: características de la situación planteada, conocimiento de la persona que resuelve y proceso puesto en juego durante la resolución. Interesa comprender cómo los estudiantes acceden al conocimiento previo, qué procedimientos usan para recuperar algunos conocimientos y desechar otros, cuáles son los criterios que dan coherencia a sus decisiones, cómo se relacionan estas decisiones con algunas características de la tarea, entre otras. Todo ello con miras a estudiar relaciones causales entre las dificultades encontradas y el retraso o abandono en las carreras.Se propone organizar el trabajo en tres ejes, los dos primeros de construcción teórica y un tercero de implementación y transferencia. Se pretende.1.-Estudiar los procesos de construcción de las representaciones mentales en resolución de problemas de física, tanto en expertos como en estudiantes de diferentes niveles académicos.2.-Analizar y clasificar las inferencias que se producen durante las tareas de comprensión en resolución de problemas de física. Asociar dichas inferencias con procesos de transición entre representaciones mentales de diferente naturaleza.3.-Desarrollar materiales y diseños instruccionales en la enseñanza de la Física, fundamentado en un conocimiento de los requerimientos psicológicos de los estudiantes en diversas tareas de aprendizaje.En términos generales se plantea un enfoque interpretativo a la luz de marcos de la psicología cognitiva y de los desarrollos propios del grupo. Se trabajará con muestras intencionales de alumnos y profesores de física. Se utilizarán protocolos verbales y registros escritos producidos durante la ejecución de las tareas con el fin de identificar indicadores de comprensión, inferencias, y diferentes niveles de representación. Se prevé analizar material escrito de circulación corriente sea comercial o preparado por los docentes de las carreras involucradas.Las características del objeto de estudio y el distinto nivel de desarrollo en que se encuentran los diferentes ojetivos específicos llevan a que el abordaje contemple -según consideracion de Juni y Urbano (2006)- tanto la lógica cualitativa como la cuantitativa.

Effects of Ischemic Postconditioning on the Hemodynamic Parameters and Heart Nitric Oxide Levels of Hypothyroid Rats

Background: Ischemic postconditioning (IPost) is a method of protecting the heart against ischemia-reperfusion (IR) injury. However, the effectiveness of IPost in cases of ischemic heart disease accompanied by co-morbidities such as hypothyroidism remains unclear. Objective: The aim of this study was to determine the effect of IPost on myocardial IR injury in hypothyroid male rats. Methods: Propylthiouracil in drinking water (500 mg/L) was administered to male rats for 21 days to induce hypothyroidism. The hearts from control and hypothyroid rats were perfused in a Langendorff apparatus and exposed to 30 min of global ischemia, followed by 120 min of reperfusion. IPost was induced immediately following ischemia. Results: Hypothyroidism and IPost significantly improved the left ventricular developed pressure (LVDP) and peak rates of positive and negative changes in left ventricular pressure (±dp/dt) during reperfusion in control rats (p < 0.05). However, IPost had no add-on effect on the recovery of LVDP and ±dp/dt in hypothyroid rats. Furthermore, hypothyroidism significantly decreased the basal NO metabolite (NOx) levels of the serum (72.5 ± 4.2 vs. 102.8 ± 3.7 μmol/L; p < 0.05) and heart (7.9 ± 1.6 vs. 18.8 ± 3.2 μmol/L; p < 0.05). Heart NOx concentration in the hypothyroid groups did not change after IR and IPost, whereas these were significantly (p < 0.05) higher and lower after IR and IPost, respectively, in the control groups. Conclusion: Hypothyroidism protects the heart from IR injury, which may be due to a decrease in basal nitric oxide (NO) levels in the serum and heart and a decrease in NO after IR. IPost did not decrease the NO level and did not provide further cardioprotection in the hypothyroid group.

Serum Potassium Levels Inversely Correlate with D-Dimer In Patients with Acute-Onset Atrial Fibrillation

Background: D-dimer values are frequently increased in patients with atrial fibrillation (AF) compared to subjects in sinus rhythm. Hypokalemia plays a role in several cardiovascular diseases, but little is known about the association with AF. Objective: D-dimer values are frequently increased in patients with atrial fibrillation (AF) compared with subjects in sinus rhythm. Hypokalemia plays a role in several cardiovascular diseases, but little is known about the association with AF. The aim of this study was to investigate correlations between D-dimer and serum potassium in acute-onset AF (AAF). Methods: To investigate the potential correlation between the values of serum potassium and D-dimer in patients with AAF, we retrospectively reviewed clinical and laboratory data of all emergency department visits for AAF in 2013. Results: Among 271 consecutive AAF patients with D-dimer assessments, those with hypokalemia (n = 98) had significantly higher D-dimer values than normokalemic patients (139 versus 114 ng/mL, p = 0.004). The rate of patients with D-dimer values exceeding the diagnostic cut-off was higher in the group of patients with hypokalemia than in those with normal serum potassium (26.5% versus 16.2%; p = 0.029). An inverse and highly significant correlation was found between serum potassium and D-dimer (r = −0.21; p < 0.001), even after adjustments for age and sex (beta coefficient −94.8; p = 0.001). The relative risk for a positive D-dimer value attributed to hypokalemia was 1.64 (95% CI, 1.02 to 2.63; p = 0.040). The correlation remained statistically significant in patients free from antihypertensive drugs (r = −0.25; p = 0.018), but not in those taking angiotensin-receptor blockers, angiotensin-converting enzyme inhibitors, or diuretics. Conclusions: The inverse correlation between values of potassium and D-dimer in patients with AAF provides important and complementary information about the thromboembolic risk of these patients.