Prediciendo la Actividad Cardíaca de la Almeja Tivela stultorum con Digoxina Utilizando Redes Neuronales Artificiales / Predicting the Cardioactivity of Tivela stultorum clam with Digoxin Using Artificial Neural Networks

Resumen: Las redes neuronales artificiales (RNA) son un método computacional extensamente utilizado para resolver problemas complejos y realizar predicciones en sistemas de relación no lineal. En este trabajo se utilizaron RNA para predecir la respuesta fisiológica obtenida al adicionar una concentración específica de digoxina a corazones de Tivela stultorum, un organismo modelo para probar fármacos cardíacos que se pretenden utilizar en humanos. Las entradas de la RNA fueron el peso, volumen, largo y ancho del corazón, la concentración de digoxina, el volumen utilizado para la dilución de digoxina, el máximo y mínimo de contracción, tiempo de llenado, y frecuencia cardíaca antes de adicionar la digoxina, las salidas fueron el máximo y mínimo de contracción, tiempo de llenado y frecuencia cardíaca esperados después de agregar digoxina al corazón. Las RNA se entrenaron, validaron y probaron con los resultados de experimentos in vivo. Para elegir la red óptima se utilizó el valor más pequeño del error medio cuadrado. Se obtuvo una correlación alta entre los valores predichos y calculados, excepto en el caso del tiempo de llenado. Se lograron obtener predicciones acertadas de la cardioactividad de la almeja T. stultorum cuando se les agrega una concentración específica de digoxina haciendo uso de RNA; esto con el fin de utilizarse como una herramienta para facilitar las pruebas en el laboratorio de los efectos de la digoxina.

Abstract: Artificial neural networks (ANN) are a computational method that has been widely used to solve complex problems and carry out predictions on nonlinear systems. Multilayer perceptron artificial neural networks were used to predict the physiological response that would be obtained by adding a specific concentration of digoxin to Tivela stultorum hearts, this organism is a model for testing cardiac drugs that pretends to be used in humans. The MLP-ANN inputs were weight, volume, length, and width of the heart, digoxin concentration and volume used for diluting digoxin, and maximum contraction, minimum contraction, filling time, and heart rate before adding digoxin, and the outputs were the maximum contraction, minimum contraction, filling time, and heart rate that would be obtained after adding digoxin to the heart. ANNs were trained, validated, and tested with the results obtained from the in vivo experiments. To choose the optimal network, the smallest square mean error value was used. Perceptrons obtained a high performance and correlation between predicted and calculated values, except in the case of the filling time output. Accurate predictions of the T. stultorum clams cardioactivity were obtained when a specific concentration of digoxin was added using ANNs with one hidden layer; this could be useful as a tool to facilitate laboratory experiments to test digoxin effects.

Quantification of Carbon Nanotubes in Environmental Matrices: Current Capabilities, Case Studies, and Future Prospects.

Carbon nanotubes (CNTs) have numerous exciting potential applications and some that have reached commercialization. As such, quantitative measurements of CNTs in key environmental matrices (water, soil, sediment, and biological tissues) are needed to address concerns about their potential environmental and human health risks and to inform application development. However, standard methods for CNT quantification are not yet available. We systematically and critically review each component of the current methods for CNT quantification including CNT extraction approaches, potential biases, limits of detection, and potential for standardization. This review reveals that many of the techniques with the lowest detection limits require uncommon equipment or expertise, and thus, they are not frequently accessible. Additionally, changes to the CNTs (e.g., agglomeration) after environmental release and matrix effects can cause biases for many of the techniques, and biasing factors vary among the techniques. Five case studies are provided to illustrate how to use this information to inform responses to real-world scenarios such as monitoring potential CNT discharge into a river or ecotoxicity testing by a testing laboratory. Overall, substantial progress has been made in improving CNT quantification during the past ten years, but additional work is needed for standardization, development of extraction techniques from complex matrices, and multimethod comparisons of standard samples to reveal the comparability of techniques.

Slow biotransformation of carbon nanotubes by horseradish peroxidase.

Due to steady increase in use and mass production carbon nanotubes (CNTs) will inevitably end up in the environment. Because of their chemical nature CNTs are expected to be recalcitrant and biotransform only at very slow rates. Degradation of CNTs within days has recently been reported, but excluding one study, conclusions relied solely on qualitative results. We incubated 13 different types of CNTs and subjected them to enzymatic oxidation with horseradish peroxidase and concluded that the analytical methods commonly employed for studying degradation of CNTs did not have the sensitivity to unequivocally demonstrate degradation of these materials. To obtain unambiguous results with regard to the biotransformability of CNTs in the horseradish peroxidase system we incubated: (a) (14)C-labeled multiwalled CNTs, homologous to Baytubes CNTs; and (b) (13)C-depleted single-walled CNTs, used in previous studies. Our results show that (14)C-CO2 evolved linearly at a rate of about 0.02‰ per day, and at the end of the 30-day incubations the CO2 evolved amounted to about 0.5‰ of both initial substrates, the (14)C-labeled multiwalled and (13)C-depleted single-walled CNTs. These results clearly show that CNT material is oxidized in the horseradish peroxidase system but with half-lives of about 80 years and not a few days as has been reported before. Adequately addressing biotransformation rates of CNTs is key toward a better understanding of the fate of these materials in the environment.

Testing the resistance of fullerenes to chemothermal oxidation used to isolate soots from environmental samples.

We tested the resistance of five different fullerenes (C(60), C(70), C(76/78) mix, and C(84)) to chemothermal oxidation at 375 °C (CTO-375), a method that has been used and tested for quantifying black carbon (BC) and CNTs in soils and sediments. C(60) survived CTO-375 the most (50%), while C(70) was the fullerene with the lowest survival rate (<1%). Standard additions of C(60) to soil and sediment reference materials yielded recoveries between 18 and 36%. Although lower than recoveries previously observed for soot and CNTs, these results demonstrate the capability of CTO-375 to partially isolate C(60) from solid environmental matrices. Standard additions of C(70), C(76/78), and C(84) yielded slightly higher survival rates when added to soil and sediment than in their pure form. These results indicate that the mineral matrices of these samples probably had a catalytic effect towards C(60) and a protective effect towards C(70), C(76/78), and C(84) during CTO-375.

Inferring black carbon concentrations in particulate organic matter by observing pyrene fluorescence losses.

Black carbon (BC), the soot and char formed during incomplete combustion of fossil and biomass fuels, is ubiquitous, participates in diverse environmental processes, and has adverse effects on human health. However, uncertainty persists regarding how accurately the present measurement methods quantify total BC or even defined subportions of the BC continuum. Hence, we sought to improve this situation by developing a new, low-sample manipulation methodology that does not require any oxidative or pyrolytic treatments but rather differentiates BC from other non-BC organic carbon (OC) using its sorbent properties. The procedure, referred to as the pyrene fluorescence loss (PFL) method, infers BC concentrations in particulate organic matter (POM) by observing the decrease in fluorescence from pyrene spiked into aqueous POM suspensions. The method was first tested using diverse materials previously utilized in an international BC method intercomparison study, and then its effectiveness (e.g., sensitivity and geochemical reasonableness) was tested by applying itto sediment and seawater POM samples collected from a coastal area downwind of important BC sources. Parallel evaluation of BC, using the PFL method and CTO-375 procedure, suggested we can characterize the predominant BC in a given sample as (i) thermally recalcitrant and highly sorptive per mass (e.g., soot), (ii) thermally labile and highly sorptive per mass (e.g., char), or (iii) thermally recalcitrant but not highly sorptive (e.g., lignite coal).

Superoxide dismutase, catalase, and glutathione peroxidase in the testis of the Mexican big-eared bat (Corynorhinus mexicanus) during its annual reproductive cycle.

The reproductive physiology of Corynorhinus mexicanus includes a testes growth-involution cycle. Testis recrudescence begins in May-June, peaks in August and then undergoes a profound involution being totally regressed in November. Adult, male individuals were captured monthly during one year and ROS scavenging enzyme activities were measured in testes and expressed per total wet-weight and per mg protein. SOD total activity is very low from October to February; increases sharply one full month before testes recrudescence starts, and in August, when testis activity was at its peak, SOD is 3-4 times lower than in July. Catalase total activity is bimodal. The main peak of activity occurs during testicular recrudescence with an additional smaller peak, two months before the onset of recrudescence. Glutathione peroxidase total activity parallels almost exactly the testis growth cycle, increases in July, reaches a peak in August and decreases through September to almost disappear in October. SOD specific activity shows a pre-testicular increase of activity, maintains its activity from March to July and then descends drastically to almost nil in August, maintaining these low values until February. Catalase specific activity is particularly important during the period of testicular regression. GPX specific activity is low from March to July, months of testicular recrudescence; whereas its activity increases in August and peaks in November, when testes regression occurs. Our data show that ROS-scavenging enzymes may play a very important role during testes involution-recrudescence in C. mexicanus, and we believe their participation could be equally important in all seasonally breeding mammals.

Starch-based plastic polymer degradation by the white rot fungus Phanerochaete chrysosporium grown on sugarcane bagasse pith: enzyme production.

In this study, starch metabolites and enzymes were determined during starch-based plastic polymer biodegradation by the white rot fungus Phanerochaete chrysosporium, grown in sugarcane bagasse pith in tubular reactors. Various metabolites, amylase, ligninase and cellulase production were measured during P. chrysosporium growth on sugarcane bagasse pith with added glucose and starch polymer. On-line respirometric analyses followed during 32 days confirmed the P. chrysosporium capability of growing on sugarcane bagasse pith with starch polymer degradation. Enzyme activity during secondary metabolism increased, and a 70% and 74% starch degradation was reached with and without glucose addition, generating low molecular weight metabolites (e.g.) dextrin, maltotriose, maltose and glucose that were detected by high performance liquid chromatography.

[Isolated pulmonary endocarditis on native valve in elderly patient without predisposing factors]. / Endocarditis pulmonar aislada sobre válvula nativa en un paciente anciano sin factores predisponentes.

Isolated infective endocarditis in the native pulmonary valve is an unusual clinical entity in patients without predisposing factors and in non-intravenous drugs users. We present the case of a 75-year-old patient, with a subacute clinical picture of fever and pulmonary cavity nodules, admitted to our hospital with an initial suspected diagnosis of pulmonary tuberculosis. The presence of Enterococcal bacteremia in hemocultive and the documentation of a large vegetation in pulmonary valve by transtoracic and transesophageal echocardiography were key factors for final diagnosis.

Rating of breathlessness at rest during acute asthma: correlation with spirometry and usefulness of breath-holding time.

We studied 13 patients with acute attacks of asthma to test the hypothesis that magnitude of dyspnea at rest correlates well with spirometry and with breath-holding time. Dyspnea ("falta de aire" in Spanish) was quantitated with a linear numerical scale from 0 to 10. We measured breath-holding time, breathing frequency (f), and FEV1 and FVC both expressed as percent of normal. Measurements were done on the patient's arrival and were repeated 3 to 6 times until dyspnea at rest disappeared or was minimal. Dyspnea magnitude, f, and breath-holding time correlated well with FEV1% and FVC% (r between 0.65 and 0.78), and better with changes in FEV1% and FVC% with respect to initial values (delta FEV1 y delta FVC; r between 0.80 and 0.89). Breath-holding time and f changed in proportion to magnitude of dyspnea (r = -0.85 and 0.87 respectively). Regression equations were: dyspnea = 6.34 -0.16 (delta FEV1) r = 0.80, and dyspnea = 7.82-0.105 (FEV1%) r = 0.62. Using multiple regression we improved prediction of FEV1% with easily obtained variables (R = 0.76). These results suggest that: 1) magnitude of dysnea, f, and breath-holding time correlate with severity of airflow obstruction in acute asthma attacks associated with dyspnea at rest; and 2) breath-holding time varies inversely with dyspnea magnitude when it is present at rest.

La familia, la residencia y la alimentación de los niños con anemia aplástica / Family, residence and feeding of the children with aplastic anemia

En un estudio previo se encontró en las familias de los niños con anemia aplástica, predominio de hogares no integrados, pobreza y alimentación deficiente, por lo que se planteó confirmar o rechazar estos hallazgos mediante un muestro más adecuado, de las familias testigo. Por cada paciente que ingresó al hospital con anemia aplástica, se eligió uno por azar que hubiera ingresado al mismo tiempo, con otro diagnóstico y que comparable en cuanto a sexo y edad. Se explicó a las dos familias el objeto del estudio y los autores investigaron en las dos, características de residencias respectivas, de los padres y de su unión, de la alimentación y de los enfermos desde el punto de vista nutricional. Se estudiaron 30 familias de cada grupo y en los de anemia aplástica se encontró predominio significativo de: residencia proletaria en área no urbana; ausencia de drenaje y de baño individual; fecalismo y convivencia con animales; padres analfabetos; padres que trabajan como campesinos o albañiles; ingestión deficiente de carne, leche, huevo, plátano, naranja, otras frutas y verduras; retraso en la edad ósea y albúmina sérica baja; calificaciones inferiores a 8 y frecuencia de reprobados (paciente y hermanos) y exposición a agentes químicos. Estos datos sugieren que la anemia aplástica en México tiene una etiología multifactorial