Expression of spidroin proteins in the silk glands of golden orb-weaver spiders.

The expression of spidroins in the major ampullate, minor ampullate, flagelliform, and tubuliform silk glands of Trichonephila clavipes spiders was analyzed using proteomics analysis techniques. Spidroin peptides were identified and assigned to different gene products based on sequence concurrence when compared with the whole genome of the spider. It was found that only a relatively low proportion of the spidroin genes are expressed as proteins in any of the studied glands. In addition, the expression of spidroin genes in different glands presents a wide range of patterns, with some spidroins being found in a single gland exclusively, while others appear in the content of several glands. The combination of precise genomics, proteomics, microstructural, and mechanical data provides new insights both on the design principles of these materials and how these principles might be translated for the production of high-performance bioinspired artificial fibers.

Preservation of muscular and elastic artery distensibility after an intercontinental cryoconserved exchange: theoretical advances in arterial homograft generation and utilization.

While the situation of tissue donation and transplantation differs between Latin American and European countries, a common problem is tissue deficiency. Hence, at present, there is a pressing need to generate alternatives so as to increase the possibilities of obtaining the requested materials. Consequently, it would be of significant interest to establish an intercontinental network for tissue exchange, to improve international cooperation, and to help patients that need tissue transplantation, and to evaluate the feasibility of using an intercontinental network for the exchange of cryopreserved arteries (cryografts), preserving the arterial distensibility and ensuring a reduced native artery-cryograft biomechanical mismatch. Distensibility was studied in ovine arteries divided into three groups: intact (in vivo tests, conscious animals), fresh control (in vitro tests immediately after the artery excision, Uruguay), and cryografts (in vitro tests of cryopreserved-transported-defrosted arteries, Spain). Histological studies were performed so as to analyze changes in the endothelial layer and elastic components. The comparison between fresh control and cryografts showed that neither the cryopreservation nor the exchange network impaired the distensibility, despite the expected histological changes found in the cryografts. The comparison between intact and cryografts showed that the cryografts would be capable of ensuring a reduced biomechanical mismatch. The cryopreservation and the intercontinental network designed for artery exchange preserved the arterial distensibility. It could be possible to transfer cryografts between Latin America and Europe to be used in cardiovascular surgeries and/or for tissue banking reprocessing, with basic biomechanical properties similar to those of the fresh and/or native arteries.

How cognitive reserve influences older adults' cognitive state, executive functions and language comprehension: A structural equation model.

Cognitive reserve has been defined as the individuals' ability to tolerate age-related and neurodegenerative changes in the brain without developing clinical symptoms or signs of disease. Formal education, occupational attainment, and knowledge of other languages have been assessed as the most relevant factors determining cognitive reserve. The main objective of this study was to develop a structural equation model that reflects the direct influence of cognitive reserve on old adults' general cognitive status and executive functioning, and indirectly on sentence comprehension performance through executive functions mediation. One hundred and fifty eight Spanish-speaking older adults, cognitively intact, were assessed to obtain cognitive reserve data, general cognitive status, executive functioning (inhibitory control, working memory and cognitive flexibility), and sentence comprehension measures. High indicators of adjustment of the proposed model were obtained. The most related factors to cognitive reserve were education and occupational attainment. As we hypothesize, cognitive reserve had a higher direct significant relation to cognitive status and, in a lesser extent, to executive functioning. Participants' general cognitive status and executive function were high and directly related. Furthermore, cognitive reserve has an indirect positive relation to sentence comprehension via executive functions' mediation.

Optimal selection of biological tissue using the energy dissipated in the first loading cycle.

Calf pericardium, similar to that used in the manufacturing of prosthetic valve cusps, was fatigue tested. After six batches of 100 cycles of 1 MPa of loading pressure, half of the samples broke. The mean energy dissipated in the first cycle by the surviving samples was 0.16 J, which is lower than the 0.28 J dissipated by the specimens that broke (p = 0.005). The hysteresis of the first cycle was characteristic and different from the following ones and correlated superbly with fatigue resistance. Setting a threshold value for the energy of the first cycle of 0.20 J, the performance index (the percentage of true predictions) was almost 80%, and the area under the ROC curve was 0.823 (maximum value is 1). When including the mean thickness in the selection parameters, as an indirect measure of the specimen mass, the performance index grew over 95%, meaning that the error of the predictions was less than 5%. Combining both parameters in one, a high performance index is maintained at 87.5% and the area under the ROC curve increases to 0.917. This non-destructive method should help optical methods in the process of selecting the most appropriate and homogenous biological material.

Factors influencing the mechanical behaviour of healthy human descending thoracic aorta.

In recent times, significant effort has been made to understand the mechanical behaviour of the arterial wall and how it is affected by the different vascular pathologies. However, to be able to interpret the results correctly, it is essential that the influence of other factors, such as aging or anisotropy, be understood. Knowledge of mechanical behaviour of the aorta has been customarily constrained by lack of data on fresh aortic tissue, especially from healthy young individuals. In addition, information regarding the point of rupture is also very limited. In this study, the mechanical behaviour of the descending thoracic aorta of 28 organ donors with no apparent disease, whose ages vary from 17 to 60 years, is evaluated. Tensile tests up to rupture are carried out to evaluate the influence of age and wall anisotropy. Results reveal that the tensile strength and stretch at failure of healthy descending aortas show a significant reduction with age, falling abruptly beyond the age of 30. This fact places age as a key factor when mechanical properties of descending aorta are considered.

Increases of corporal temperature as a risk factor of atherosclerotic plaque instability.

BACKGROUND: This work explores for the first time the effects of temperature increments on the development of high shear stresses between plaque and arterial wall due to their different dilatational properties. Data from the literature report febrile reactions prior to myocardial infarction in patients with normal coronary arteries and that coronary syndromes seem to be triggered by bacterial and viral infections, being fever the common symptom. METHODS: The thermo-mechanical behavior of thoracic aortas of New Zealand White rabbits with different degrees of atherosclerosis was measured by means of pressure-diameter tests at different temperatures. In addition, specific measurements of the thermal dilatation coefficient of atheroma plaques and of healthy arterial walls were performed by means of tensile tests at different temperatures. RESULTS: Results show a different thermo-mechanical behavior, the dilatation coefficient of atheroma plaque being at least twice that of the arterial wall. The calculation of temperature-induced mechanical stress at the plaque-vessel interface yielded shear stress levels enough to promote plaque rupture. CONCLUSIONS: Increases of corporal temperature either local--produced by the inflammatory processes associated with atherosclerosis--or systemic--by febrile reactions--can play a role in increasing the risk of acute coronary syndromes, and they deserve a more comprehensive study.

[The influence of pressure and temperature on the behavior of the human aorta and carotid arteries]. / Influencia de la presión y la temperatura en el comportamiento de la aorta y las carótidas humanas.

INTRODUCTION AND OBJECTIVES: The thermomechanical behavior of human arteries is still not well characterized despite its importance for understanding arterial physiology, and for evaluating and improving surgical procedures. The aim of this study was to provide, for the first time, experimental data illustrating how the mechanical responses of two types of human artery -the carotid artery and the aorta- are affected by changes in temperature. METHODS: The mechanical properties of the arteries were derived in vitro from internal pressure-external diameter curves measured at four different temperatures (i.e., 17, 27, 37 and 42 degree C). Coefficients of expansion and stiffness were obtained by thermomechanical analysis. The condition of the arterial wall was determined histologically. RESULTS: The aorta and the carotid artery became slightly more compliant as the temperature increased. In both vessels, the coefficient of expansion depended critically on internal pressure. At low pressures, the coefficient of expansion was negative (i.e., the vessel contracted when heated), whereas close to a specific threshold pressure, which is different for each type of artery, the coefficient became positive. CONCLUSIONS: The mechanical behavior of arteries is affected by the combination of internal pressure and temperature. Consequently, the effect of this combination should be taken into account in clinical situations involving a change in temperature. Moreover, the strength of the effect depends on the type of artery under study. As a result, more detailed experimental data focusing on vessels of clinical interest are required.

Reserva cognitiva y habilidades lingüísticas en mayores sanos / Cognitive reserve and linguistic skills in healthy elderly persons

Introducción. Una estrategia de investigación en relación con la reserva cognitiva supone establecer grupos de mayores que difieren en variables clave que afectan a la reserva cognitiva y comparar su rendimiento en pruebas de carácter cognitivo. Objetivo. Determinar qué variables de las que influyen en la reserva cognitiva (medidas mediante el cuestionario de reserva cognitiva) se relacionan con el rendimiento en el test de denominación de Boston, y en las pruebas de vocabulario y comprensión gramatical de la batería ECCO_Senior. Sujetos y métodos. Participaron en el estudio 83 mayores de edades comprendidas entre los 60 y los 75 años. Resultados y conclusiones. La escolaridad, la escolaridad de los padres, la ocupación laboral y la actividad lectora se relacionan estrechamente con el rendimiento de los mayores en denominación, comprensión gramatical y vocabulario. La escolaridad afecta a la comprensión de las oraciones con mayor densidad proposicional, y los hábitos de lectura parecen estar estrechamente relacionados con la comprensión de oraciones de mayor complejidad sintáctica. La escolaridad y la ocupación laboral afectan al rendimiento obtenido ante los verbos en la prueba de vocabulario (AU)

Introduction. One research strategy that can be used with the cognitive reserve is to establish groups of elderly persons who differ in key variables that affect the cognitive reserve and then compare their performance in cognitive tests. Aims. To determine which of the variables that have an influence on the cognitive reserve (measured by means of the cognitive reserve questionnaire) are related with performance in the Boston Naming Test, and in the vocabulary and grammar comprehension tests from the ECCO_Senior battery. Subjects and methods. The sample consisted of 83 elderly persons aged between 60 and 75 years. Results and conclusions. Schooling, parents’ schooling, job and reading habits are closely related to the performance of the elderly in naming, grammar comprehension and vocabulary. Schooling affects the comprehension of sentences with a higher propositional density, and reading habits seem to be closely related with the comprehension of sentences that are more complex in terms of their syntax. Schooling and job affect the performance obtained when dealing with verbs in the vocabulary test (AU)

Influencia de la presión y la temperatura en el comportamiento de la aorta y las carótidas humanas / The influence of pressure and temperature on the behavior of the human aorta and carotid arteries

Introducción y objetivos. La respuesta termomecánica de las arterias humanas es poco conocida a pesar de su importancia para la comprensión de la fisiología arterial, y para la evaluación y mejora de los procedimientos quirúrgicos. El objetivo de este trabajo es aportar por vez primera datos experimentales que muestren cómo se ve afectada la respuesta mecánica de dos tipos de arterias humanas ­aorta y carótida­ por los cambios de temperatura. Métodos. La respuesta mecánica de las arterias se ha obtenido in vitro a través de la medición de las curvas presión interior-diámetro exterior para 4 temperaturas (17, 27, 37 y 42 oC). Se ha realizado un análisis termomecánico para obtener los coeficientes de dilatación y la rigidez del material. El estado de la pared arterial se ha evaluado mediante análisis histológico. Resultados. Las arterias aorta y carótida aumentan ligeramente su flexibilidad con la temperatura. El coeficiente de dilatación de ambos vasos depende críticamente de la presión interior aplicada. A bajas presiones, el coeficiente de dilatación es negativo (el vaso se contrae cuando se calienta), mientras que por encima de cierta presión umbral ­distinta para cada tipo de arteria­ el coeficiente de dilatación se hace positivo. Conclusiones. El efecto combinado de la presión interior y la temperatura afecta al comportamiento de las arterias y, por ello, debe ser tenido en cuenta al abordar situaciones clínicas que impliquen cambios de temperatura. La intensidad de este efecto depende del tipo de arteria estudiada, lo que requiere la obtención de datos más detallados, centrados en los vasos de interés clínico

Introduction and objectives. The thermomechanical behavior of human arteries is still not well characterized despite its importance for understanding arterial physiology, and for evaluating and improving surgical procedures. The aim of this study was to provide, for the first time, experimental data illustrating how the mechanical responses of two types of human artery ­the carotid artery and the aorta­ are affected by changes in temperature. Methods. The mechanical properties of the arteries were derived in vitro from internal pressure­external diameter curves measured at four different temperatures (i.e., 17, 27, 37 and 42 oC). Coefficients of expansion and stiffness were obtained by thermomechanical analysis. The condition of the arterial wall was determined histologically. Results. The aorta and the carotid artery became slightly more compliant as the temperature increased. In both vessels, the coefficient of expansion depended critically on internal pressure. At low pressures, the coefficient of expansion was negative (i.e., the vessel contracted when heated), whereas close to a specific threshold pressure, which is different for each type of artery, the coefficient became positive. Conclusions. The mechanical behavior of arteries is affected by the combination of internal pressure and temperature. Consequently, the effect of this combination should be taken into account in clinical situations involving a change in temperature. Moreover, the strength of the effect depends on the type of artery under study. As a result, more detailed experimental data focusing on vessels of clinical interest are required