Cooperative cell motility during tandem locomotion of amoeboid cells.

Streams of migratory cells are initiated by the formation of tandem pairs of cells connected head to tail to which other cells subsequently adhere. The mechanisms regulating the transition from single to streaming cell migration remain elusive, although several molecules have been suggested to be involved. In this work, we investigate the mechanics of the locomotion ofDictyosteliumtandem pairs by analyzing the spatiotemporal evolution of their traction adhesions (TAs). We find that in migrating wild-type tandem pairs, each cell exerts traction forces on stationary sites (∼80% of the time), and the trailing cell reuses the location of the TAs of the leading cell. Both leading and trailing cells form contractile dipoles and synchronize the formation of new frontal TAs with ∼54-s time delay. Cells not expressing the lectin discoidin I or moving on discoidin I-coated substrata form fewer tandems, but the trailing cell still reuses the locations of the TAs of the leading cell, suggesting that discoidin I is not responsible for a possible chemically driven synchronization process. The migration dynamics of the tandems indicate that their TAs' reuse results from the mechanical synchronization of the leading and trailing cells' protrusions and retractions (motility cycles) aided by the cell-cell adhesions

General behavior of the effective nucleon-nucleon interaction as a function of the relative velocity

We have studied volume integrals of the central part of optical potentials extracted from data analyses for a variety of light and heavy systems. The data-extracted integrals present a quite simple behavior as a function of the relative velocity between target and projectile. This behavior is system independent and, therefore, it reflects a feature of the effective nucleon-nucleon interaction itself. The overall results are in good agreement with the predictions of the São Paulo potential, which is a model for the nuclear interaction that so far has been employed mostly in analyses of heavy-ion reactions

Estrategias de intervención tutorial en la universidad: una experiencia para la formación integral del alumnado de nuevo ingreso

The requirements that the university education raises in the frame of the EEES make the putting necessary in practice of strategies that allow to achieve a more integral vision of the formation of the student. The university tutoring allows an approximation the budgets that define the process of European Convergence, since across the same one there is reached a more integral vision of the formative process, a major autonomy of the student body and a better preparation along the life. In this article there is defined the model of action who follows in the Faculty of Education of the University of La Laguna (Spain) and there are described the results obtained in a program with students of the first course.Las exigencias que plantea la enseñanza universitaria en el marco del EEES hacen necesario la puesta en práctica de estrategias que permitan lograr una visión más integral de la formación del alumnado. La tutoría universitaria permite un acercamiento a los presupuestos que definen el proceso de Convergencia Europea, puesto que a través de la misma se alcanza una visión más integral del proceso formativo, una mayor autonomía del alumnado y una mejor preparación a lo largo de la vida. En este artículo se define el modelo de actuación que se sigue en la Facultad de Educación de la Universidad de La Laguna (España) y se describen los resultados obtenidos en un programa con estudiantes de primer curso

El asesoramiento y la tutoría de carrera en la Enseñanza Superior : resultados de un programa de atención al alumnado en la Universidad de la Laguna

El Espacio Común Europeo de Educación Superior ha traído consigo cambios sustanciales en los fines y en la forma de organizar la enseñanza, ya que se intenta ahora que sea el alumnado el verdadero protagonista de su proceso formativo y que esta formación tenga una dimensión profesionalizadora. Con ello la función tutorial del profesorado universitario se ha revalorizado debido a su importante contribución como guía de aprendizaje y estimulador del desarrollo integral del alumnado. En este trabajo se define un modelo de actuación y los resultados de una experiencia con la que se potencia desde la tutoría de carrera la adaptación de los estudiantes a la enseñanza universitaria y el desarrollo de las competencias trasferibles para su futuro profesional.The European Higher Education Area brings with it substantial change in the purposes and organization of education. Those changes flow from the recognition of the student as the centre of the learning process, and the pursuing of a training that educate students not only in the academic field but as professionals. All these have supposed the revaluation of the tutorial functions of university teaching, because of its contribution as a guide of learning and animator of the integral development of students. In this article we define a model of performance, and the results of an experience of career tutoring which promoted the adjustment of the students to university education and the development of competences transferable for her professional future

A preliminary study on the use of jenny colostrum to improve quality in extenders for freezing donkey semen

Sperm quality in donkeys (Equus asinus) after freezing thawing is still considered lower than that from other animals, including horses. The aim of this study was to test a new freezing extender supplemented with jenny colostrum on donkey sperm. After thawing, we evaluated sperm motility by means of computer-assisted analysis, viability by SYBR-14 and propidium iodide (PI), membrane functional integrity by HOS-test and acrosome integrity by isothiocyanate conjugated with peanut agglutinin (FITC-PNA) and PI. Ejaculates were collected from five fertile Donkeys. Sperm samples were pooled, diluted and cryopreserved into three experimental extender groups: BotuCrio®, lactose-extender supplemented with egg yolk (20%) and lactose-extender supplemented with jenny colostrum (20%). The results demonstrated that lactose-jenny colostrum samples displayed significantly higher values in almost all parameters evaluated (p < 0.05) compared with the other two extenders after thawing (BotuCrio® and lactose-egg yolk based extender, respectively) –Total Motility, Viability, HOS test, VCL, VSL and VAP. Acrosome status, LIN, STR and WOB despite showing lower values, none of them were statistically significant (p > 0.05). In conclusion, the extender containing jenny colostrum can be successfully used for donkey semen crypreservation and could effectively improve donkey sperm qualities after freezing -thawing

Effect of Mare Colostrum in Extenders for Freezing Stallion Semen

This study aimed to evaluate the addition of mare colostrum in stallion freezing extenders to improve sperm quality. First, colostrum samples were collected from four mares after the foal''s birth and their composition was determined. Ejaculates were collected from nine fertile stallions. Sperm samples were pooled, diluted, and cryopreserved into three experimental extender groups: Lactose-based extender supplemented with mare colostrum (20%), lactose-based extender supplemented with egg yolk (20%), and BotuCrio. The quality of the post-thaw semen samples were evaluated assessing sperm motility by means of computer-assisted analysis, viability by SYBR-14 and propidium iodine (PI) stain, acrosome integrity by fluorescein isothiocyanate and peanut agglutinine (FITC-PNA) and PI stain, plasma membrane functionality by hypo-osmotic swelling (HOS) test, and DNA denaturation by acridine orange (AO) test. There were no significant differences in the percentages of total motility, acrosome integrity, and DNA fragmentation among the extenders after thawing. Kinematics parameters showed significantly higher values in BotuCrio than in lactose extenders (P < .05). BotuCrio and lactose colostrum extender yielded significantly better rates for HOS-test, linearity, straightness, and wobble than egg-yolk extender (P < .05). However, in relation to sperm viability, lactose egg yolk extender showed significantly better results in comparison to the others seminal experimental media (P < .05). In conclusion, the incorporation of mare colostrum into cryopreservation media protected the sperm against cold-shock; therefore, it may be a good cryoprotectant agent alternative in extenders for freezing stallion semen

Investigation of Coulomb dipole polarization effects on reactions involving exotic nuclei

We have analyzed elastic scattering angular distributions and total reaction cross sections of the exotic nuclei Li9,11 on Pb208, at energies below and above the Coulomb barrier. For this purpose, we have used an optical potential with no adjustable parameters, composed by the nuclear São Paulo potential, derived from the nonlocal nature of the interaction, and the Coulomb dipole polarization potential, derived from the semiclassical theory of Coulomb excitation. Within this formalism, we identified an unusual long-range absorption for the Li11+Pb208 system, which is dominated by the Coulomb interaction. We compare it to the absorption mechanisms observed for He6+Pb208 which, unlike those of Li11+Pb208, take place at small interacting distances, where both Coulomb and nuclear interactions are important. The proposed approach shows to be a fundamental basis to study reactions involving exotic nuclei

Dimension and support of underground slate mines

[Abstract] We've studied the conditions about dimensions and support ofan underground mine of roofing slate in Galice, worked by rooms with continuous pillars. The rock mass was characterized by the empiric and analitic methods, calculating the stable pillar wide along the mine by the theory of attributed area and by a model of finite elements, where the breaking criterion ofHoek and Brown was applied. The result was a parabolic relationship between pillar wide and mine length. Stability studies in an isolated stope give an elastic performance on the periphery of the room, without tractions. Although the stability ofthe mine is good, a systematic support is recommended on the basis of bolts, that will be reinforced with projected concret at the top, and a singular treatment of the detected wedges

EU Polluting Emissions: an empirical analysis

We provide an empirical study of the evolution of emissions of some specific air pollutants on a panel of EU member states from 1990 to 2000, and we relate observed patterns to macroeconomic performance. The ratio pollution emission to GDP, so-called emission intensity, has decreased over the period considered in most EU member states. However, a non-parametric analysis reveals that the relative positions of different countries in terms of GDP growth and reduction of emissions have remained basically unchanged. More specifically, remarkable differences can be detected between the richest and the poorest EU members notwithstanding. Also, more dispersion in emissions levels can be found in those countries with lower per capita GDP.Polluting emissions, European Union