Project based learning activities as a means of adapting conventional curricula to the demands of the 21st century aeronautical engineer: The design and building of the EYEFLY 1.

In this paper we report the process of designing and building the EYEFLY 1, a real UAS platform which has just performed its maiden flight. For the development of this aircraft, 30 groups of students from successive years at the Escuela Universitaria de Ingeniería Técnica Aeronáutica (EUITA) of the Universidad Politécnica de Madrid (UPM) carried out their compulsory End of Degree Project as a coordinated Project Based learning activity. Our conclusions clearly indicate that Project Based Learning activities can provide a valid complement to more conventional, theoretically-based, teaching methods. The combination of both approaches will allow us to maintain traditional but well-tested methods for providing our students with a sound knowledge of fundamental engineering disciplines and, at the same time, to introduce our students to exciting and relevant engineering situations and sceneries where social and business skills, such as communication skills, team-working or decision-taking, can be put into practice.

Supporting the design and development of Project Based Learning courses.

The use of Project Based Learning has spread widely over the last decades, not only throughout countries but also among disciplines. One of the most significant characteristics of this methodology is the use of ill-structured problems as central activity during the course, which represents an important difficulty for both teachers and students. This work presents a model, supported by a tool, focused on helping teachers and students in Project Based Learning, overcoming these difficulties. Firstly, teachers are guided in designing the project following the main principles of this methodology. Once the project has been specified at the desired level of depth, the same tool helps students to finish the project specification and organize the implementation. Collaborative work among different users is allowed in both phases. This tool has been satisfactorily tested designing two real projects used in Computer Engineering and Software Engineering degrees.

iCarer Project: Intelligent Care Guidance and Learning Services Platform for Informal Carers of the Elderly

The increasing ageing population is demanding new care approaches to maintain the quality of life of elderly people. Informal carers are becoming crucial agents in the care and support of elderly people, which can lead to those carers suffering from additional stress due to competing priorities with employment or due to lack of knowledge about elderly people?s care needs. Thus, support and stress relief in carers should be a key issue in the home-care process of these older adults. Considering this context, this work presents the iCarer project aimed at developing a personalized and adaptive platform to offer informal carers support by means of monitoring their activities of daily care and psychological state, as well as providing an orientation to help them improve the care provided. Additionally, iCarer will provide e-Learning services and an informal carers learning network. As a result, carers will be able to expand their knowledge, supported by the experience provided by expert counsellors and fellow carers. Additionally, the coordination between formal and informal carers will be improved, offering the informal carers flexibility to organize and combine their assistance and social activities.

Machine Learning in Scientometrics

El aprendizaje automático y la cienciometría son las disciplinas científicas que se tratan en esta tesis. El aprendizaje automático trata sobre la construcción y el estudio de algoritmos que puedan aprender a partir de datos, mientras que la cienciometría se ocupa principalmente del análisis de la ciencia desde una perspectiva cuantitativa. Hoy en día, los avances en el aprendizaje automático proporcionan las herramientas matemáticas y estadísticas para trabajar correctamente con la gran cantidad de datos cienciométricos almacenados en bases de datos bibliográficas. En este contexto, el uso de nuevos métodos de aprendizaje automático en aplicaciones de cienciometría es el foco de atención de esta tesis doctoral. Esta tesis propone nuevas contribuciones en el aprendizaje automático que podrían arrojar luz sobre el área de la cienciometría. Estas contribuciones están divididas en tres partes: Varios modelos supervisados (in)sensibles al coste son aprendidos para predecir el éxito científico de los artículos y los investigadores. Los modelos sensibles al coste no están interesados en maximizar la precisión de clasificación, sino en la minimización del coste total esperado derivado de los errores ocasionados. En este contexto, los editores de revistas científicas podrían disponer de una herramienta capaz de predecir el número de citas de un artículo en el fututo antes de ser publicado, mientras que los comités de promoción podrían predecir el incremento anual del índice h de los investigadores en los primeros años. Estos modelos predictivos podrían allanar el camino hacia nuevos sistemas de evaluación. Varios modelos gráficos probabilísticos son aprendidos para explotar y descubrir nuevas relaciones entre el gran número de índices bibliométricos existentes. En este contexto, la comunidad científica podría medir cómo algunos índices influyen en otros en términos probabilísticos y realizar propagación de la evidencia e inferencia abductiva para responder a preguntas bibliométricas. Además, la comunidad científica podría descubrir qué índices bibliométricos tienen mayor poder predictivo. Este es un problema de regresión multi-respuesta en el que el papel de cada variable, predictiva o respuesta, es desconocido de antemano. Los índices resultantes podrían ser muy útiles para la predicción, es decir, cuando se conocen sus valores, el conocimiento de cualquier valor no proporciona información sobre la predicción de otros índices bibliométricos. Un estudio bibliométrico sobre la investigación española en informática ha sido realizado bajo la cultura de publicar o morir. Este estudio se basa en una metodología de análisis de clusters que caracteriza la actividad en la investigación en términos de productividad, visibilidad, calidad, prestigio y colaboración internacional. Este estudio también analiza los efectos de la colaboración en la productividad y la visibilidad bajo diferentes circunstancias. ABSTRACT Machine learning and scientometrics are the scientific disciplines which are covered in this dissertation. Machine learning deals with the construction and study of algorithms that can learn from data, whereas scientometrics is mainly concerned with the analysis of science from a quantitative perspective. Nowadays, advances in machine learning provide the mathematical and statistical tools for properly working with the vast amount of scientometrics data stored in bibliographic databases. In this context, the use of novel machine learning methods in scientometrics applications is the focus of attention of this dissertation. This dissertation proposes new machine learning contributions which would shed light on the scientometrics area. These contributions are divided in three parts: Several supervised cost-(in)sensitive models are learned to predict the scientific success of articles and researchers. Cost-sensitive models are not interested in maximizing classification accuracy, but in minimizing the expected total cost of the error derived from mistakes in the classification process. In this context, publishers of scientific journals could have a tool capable of predicting the citation count of an article in the future before it is published, whereas promotion committees could predict the annual increase of the h-index of researchers within the first few years. These predictive models would pave the way for new assessment systems. Several probabilistic graphical models are learned to exploit and discover new relationships among the vast number of existing bibliometric indices. In this context, scientific community could measure how some indices influence others in probabilistic terms and perform evidence propagation and abduction inference for answering bibliometric questions. Also, scientific community could uncover which bibliometric indices have a higher predictive power. This is a multi-output regression problem where the role of each variable, predictive or response, is unknown beforehand. The resulting indices could be very useful for prediction purposes, that is, when their index values are known, knowledge of any index value provides no information on the prediction of other bibliometric indices. A scientometric study of the Spanish computer science research is performed under the publish-or-perish culture. This study is based on a cluster analysis methodology which characterizes the research activity in terms of productivity, visibility, quality, prestige and international collaboration. This study also analyzes the effects of collaboration on productivity and visibility under different circumstances.

Automatic physical activity pattern recognition and meal intake modelling in type 1 diabetes for their inclusion in artificial pancreas systems

La diabetes comprende un conjunto de enfermedades metabólicas que se caracterizan por concentraciones de glucosa en sangre anormalmente altas. En el caso de la diabetes tipo 1 (T1D, por sus siglas en inglés), esta situación es debida a una ausencia total de secreción endógena de insulina, lo que impide a la mayoría de tejidos usar la glucosa. En tales circunstancias, se hace necesario el suministro exógeno de insulina para preservar la vida del paciente; no obstante, siempre con la precaución de evitar caídas agudas de la glucemia por debajo de los niveles recomendados de seguridad. Además de la administración de insulina, las ingestas y la actividad física son factores fundamentales que influyen en la homeostasis de la glucosa. En consecuencia, una gestión apropiada de la T1D debería incorporar estos dos fenómenos fisiológicos, en base a una identificación y un modelado apropiado de los mismos y de sus sorrespondientes efectos en el balance glucosa-insulina. En particular, los sistemas de páncreas artificial –ideados para llevar a cabo un control automático de los niveles de glucemia del paciente– podrían beneficiarse de la integración de esta clase de información. La primera parte de esta tesis doctoral cubre la caracterización del efecto agudo de la actividad física en los perfiles de glucosa. Con este objetivo se ha llevado a cabo una revisión sistemática de la literatura y meta-análisis que determinen las respuestas ante varias modalidades de ejercicio para pacientes con T1D, abordando esta caracterización mediante unas magnitudes que cuantifican las tasas de cambio en la glucemia a lo largo del tiempo. Por otro lado, una identificación fiable de los periodos con actividad física es un requisito imprescindible para poder proveer de esa información a los sistemas de páncreas artificial en condiciones libres y ambulatorias. Por esta razón, la segunda parte de esta tesis está enfocada a la propuesta y evaluación de un sistema automático diseñado para reconocer periodos de actividad física, clasificando su nivel de intensidad (ligera, moderada o vigorosa); así como, en el caso de periodos vigorosos, identificando también la modalidad de ejercicio (aeróbica, mixta o de fuerza). En este sentido, ambos aspectos tienen una influencia específica en el mecanismo metabólico que suministra la energía para llevar a cabo el ejercicio y, por tanto, en las respuestas glucémicas en T1D. En este trabajo se aplican varias combinaciones de técnicas de aprendizaje máquina y reconocimiento de patrones sobre la fusión multimodal de señales de acelerometría y ritmo cardíaco, las cuales describen tanto aspectos mecánicos del movimiento como la respuesta fisiológica del sistema cardiovascular ante el ejercicio. Después del reconocimiento de patrones se incorpora también un módulo de filtrado temporal para sacar partido a la considerable coherencia temporal presente en los datos, una redundancia que se origina en el hecho de que en la práctica, las tendencias en cuanto a actividad física suelen mantenerse estables a lo largo de cierto tiempo, sin fluctuaciones rápidas y repetitivas. El tercer bloque de esta tesis doctoral aborda el tema de las ingestas en el ámbito de la T1D. En concreto, se propone una serie de modelos compartimentales y se evalúan éstos en función de su capacidad para describir matemáticamente el efecto remoto de las concetraciones plasmáticas de insulina exógena sobre las tasas de eleiminación de la glucosa atribuible a la ingesta; un aspecto hasta ahora no incorporado en los principales modelos de paciente para T1D existentes en la literatura. Los datos aquí utilizados se obtuvieron gracias a un experimento realizado por el Institute of Metabolic Science (Universidad de Cambridge, Reino Unido) con 16 pacientes jóvenes. En el experimento, de tipo ‘clamp’ con objetivo variable, se replicaron los perfiles individuales de glucosa, según lo observado durante una visita preliminar tras la ingesta de una cena con o bien alta carga glucémica, o bien baja. Los seis modelos mecanísticos evaluados constaban de: a) submodelos de doble compartimento para las masas de trazadores de glucosa, b) un submodelo de único compartimento para reflejar el efecto remoto de la insulina, c) dos tipos de activación de este mismo efecto remoto (bien lineal, bien con un punto de corte), y d) diversas condiciones iniciales. ABSTRACT Diabetes encompasses a series of metabolic diseases characterized by abnormally high blood glucose concentrations. In the case of type 1 diabetes (T1D), this situation is caused by a total absence of endogenous insulin secretion, which impedes the use of glucose by most tissues. In these circumstances, exogenous insulin supplies are necessary to maintain patient’s life; although caution is always needed to avoid acute decays in glycaemia below safe levels. In addition to insulin administrations, meal intakes and physical activity are fundamental factors influencing glucose homoeostasis. Consequently, a successful management of T1D should incorporate these two physiological phenomena, based on an appropriate identification and modelling of these events and their corresponding effect on the glucose-insulin balance. In particular, artificial pancreas systems –designed to perform an automated control of patient’s glycaemia levels– may benefit from the integration of this type of information. The first part of this PhD thesis covers the characterization of the acute effect of physical activity on glucose profiles. With this aim, a systematic review of literature and metaanalyses are conduced to determine responses to various exercise modalities in patients with T1D, assessed via rates-of-change magnitudes to quantify temporal variations in glycaemia. On the other hand, a reliable identification of physical activity periods is an essential prerequisite to feed artificial pancreas systems with information concerning exercise in ambulatory, free-living conditions. For this reason, the second part of this thesis focuses on the proposal and evaluation of an automatic system devised to recognize physical activity, classifying its intensity level (light, moderate or vigorous) and for vigorous periods, identifying also its exercise modality (aerobic, mixed or resistance); since both aspects have a distinctive influence on the predominant metabolic pathway involved in fuelling exercise, and therefore, in the glycaemic responses in T1D. Various combinations of machine learning and pattern recognition techniques are applied on the fusion of multi-modal signal sources, namely: accelerometry and heart rate measurements, which describe both mechanical aspects of movement and the physiological response of the cardiovascular system to exercise. An additional temporal filtering module is incorporated after recognition in order to exploit the considerable temporal coherence (i.e. redundancy) present in data, which stems from the fact that in practice, physical activity trends are often maintained stable along time, instead of fluctuating rapid and repeatedly. The third block of this PhD thesis addresses meal intakes in the context of T1D. In particular, a number of compartmental models are proposed and compared in terms of their ability to describe mathematically the remote effect of exogenous plasma insulin concentrations on the disposal rates of meal-attributable glucose, an aspect which had not yet been incorporated to the prevailing T1D patient models in literature. Data were acquired in an experiment conduced at the Institute of Metabolic Science (University of Cambridge, UK) on 16 young patients. A variable-target glucose clamp replicated their individual glucose profiles, observed during a preliminary visit after ingesting either a high glycaemic-load or a low glycaemic-load evening meal. The six mechanistic models under evaluation here comprised: a) two-compartmental submodels for glucose tracer masses, b) a single-compartmental submodel for insulin’s remote effect, c) two types of activations for this remote effect (either linear or with a ‘cut-off’ point), and d) diverse forms of initial conditions.

Motivación, flow e intención de práctica físico-deportiva en estudiantes de educación física de España y Latinoamérica

A pesar de los innegables beneficios físicos y psicosociales que la práctica de actividad física tiene para la población en las últimas décadas se observa un importante descenso en el nivel de práctica de actividad física durante la adolescencia. La Educación Física (EF) es una asignatura presente en las primeras etapas educativas de los currículums de todos los países y supone para la población infantil y adolescente, durante el periodo de escolarización obligatoria, un entorno de contacto cotidiano con la actividad física y deportiva lo que explica el creciente interés que existe por investigar en este contexto y extraer conclusiones que puedan ayudar a revertir el proceso de progresivo abandono de la práctica en estas edades. El presente trabajo se centra en un periodo, la adolescencia, especialmente sensible al abandono de la práctica de actividad física. Apoyándonos en tres de los marcos teóricos más importantes de los últimos años - Teoría de Metas de Logro, Teoría de la Autodeterminación y Teoría del Flow - hemos realizado un diseño con tres estudios complementarios que nos permitan avanzar en el conocimiento de las variables que afectan a esta realidad. En el primero de los estudios, en el que participaron 3990 estudiantes de EF de España, Argentina, Colombia y Ecuador con edades comprendidas entre 12 y 18 años, se fijaron como objetivos el establecimiento de perfiles motivacionales en estudiantes de EF considerando las orientaciones motivacionales, la motivación intrínseca y el flow disposicional; la comprobación de la posible estabilidad de los perfiles establecidos en cuatro países diferentes; y el análisis de la relación entre los perfiles motivacionales establecidos con la práctica de actividad física realizada en la actualidad y la intención de ser activo en el futuro. Los resultados revelaron la existencia de tres perfiles motivacionales en los estudiantes: perfil de motivación baja-moderada, perfil de motivación de alta motivación con bajo ego y perfil de alta motivación. Se encontraron similitudes en los perfiles motivacionales obtenidos en los cuatro países analizados, sugiriéndose la posibilidad de que la lengua materna compartida pueda ser una variable de influencia en la existencia de patrones conductuales similares. La orientación al ego resultó ser un elemento diferenciador en la relación de los dos perfiles que mostraron niveles más altos de motivación intrínseca, flow disposicional y orientación a la tarea con las variables de práctica. Mayores niveles de orientación al ego determinaron mayores valores de práctica e intención de práctica. En el segundo estudio, en el que participaron 365 estudiantes de EF de España, Argentina y Colombia con edades comprendidas entre 12 y 16 años, se testó un modelo explicativo de la intención de ser físicamente activo en el futuro en estudiantes de EF poco motivados introduciendo el flow disposicional como variable explicativa junto a las orientaciones motivacionales y la motivación intrínseca. El modelo de ecuaciones estructurales testado muestra que tanto la orientación al ego como la orientación a la tarea y la motivación intrínseca predijeron el flow disposicional. No se encontró un efecto significativo de la orientación a la tarea sobre la motivación intrínseca, ni de esta sobre la intención de práctica de AFD en el futuro. El flow disposicional resultó ser un mediador entre ambas orientaciones motivacionales y dicha intención, adquiriendo un papel relevante en la predicción de la intención de realizar actividad física en el futuro en los sujetos con poca motivación hacia la clase de EF. En el último estudio, con una muestra de 53 estudiantes de EF pertenecientes a dos clases de segundo curso de ESO con edades comprendidas entre 13 y 15 años, se analizó el efecto de una intervención de apoyo a las NPB sobre la satisfacción de las mismas, la motivación intrínseca, la disposición a experimentar flow y la intención de ser físicamente activo en el futuro; estudiándose también el efecto de la misma sobre ciertas variables presentes en el proceso de enseñanza-aprendizaje tales como la diversión, el aprendizaje y el gusto hacia el contenido y la metodología empleada. La intervención resultó efectiva en la mejora de todas las variables motivacionales analizadas a excepción de la satisfacción de la necesidad de relaciones sociales, variable que podría ser más difícilmente modificable en tanto que los grupos de clase suelen permanecer estables a lo largo de esta etapa educativa. Los alumnos de la condición experimental presentaron niveles más elevados de diversión, aprendizaje y gusto hacia el contenido y la metodología empleada. ABSTRACT Despite the undeniable physical and psychological benefits that physical activity has on health, a significant drop in the level of physical activity during adolescence has been observed over the last few decades. Physical education (PE) is present in the early stages of educational curricula of all countries, creating an environment in which children and adolescents can maintain daily contact with sport and physical activity during the period of compulsory education. There is thus a growing interest in research within this context, helping to draw conclusions aimed at reversing the progressive decline of physical activity in this age bracket. The work presented here focuses on adolescence – a period particularly sensitive when faced with declining rates of physical activity. Relying on three of the most important recent theoretical frameworks – Achievement Goal Theory, Self-Determination Theory and Flow Theory – we have carried out a design using three complementary studies that allow us to advance the understanding of variables affecting this reality. The first two studies employ a correlational methodology while the third follows a quasi-experimental design. The objectives of the first study, with the participation of 3990 PE students aged 12 to 18 from Spain, Argentina, Colombia and Ecuador, were: a) to establish motivational profiles in physical education students taking into consideration motivational orientations, intrinsic motivation and dispositional flow; b) to check the possible stability of the established profiles in the four countries; and c) to analyze the relationship between motivational profiles and both current levels of physical activity and intention to be physically active in the future. Results revealed the existence of three motivational profiles: low-moderate motivation profile, high motivation and low ego profile and high motivation profile. Similarities were found across the four countries, which presents the possibility that sharing the same mother tongue might influence the existence of similar behavioral patterns. Amongst the profiles that showed the highest levels of intrinsic motivation, dispositional flow and task orientation with practice variables, ego orientation became apparent as a differentiating element. Higher levels of ego orientation correlated with higher levels both in current level of physical activity and intention to be physically active in the future. In the second study, with the participation of 365 PE students aged 12 to 16 from Spain, Argentina and Colombia, an explanatory model of the intention to be physically active within the low-moderate motivation profile was tested, including dispositional flow as an influence variable together with motivational orientations and intrinsic motivation. The structural model equation in the low-moderate motivation profile shows some differences with respect to findings of similar studies using heterogeneous samples in motivational profiles. It was found that ego orientation, task orientation and intrinsic motivation predicted dispositional flow. No significant effects of task orientation on intrinsic motivation, or of intrinsic motivation on intention to be physically active in the future were found. Dispositional flow emerged as a mediator between both motivational orientations and intention, acquiring an important role in the prediction of future intentions to be physically active in adolescents who show low levels of motivation towards physical education. In the last of the three studies, with the participation of 53 PE students drawn from two classes in the second year of secondary education aged 13 to 15, the effect of an intervention to support basic psychological needs was tested against the satisfaction of these needs, intrinsic motivation, disposition to experience flow and intention to be physically active in the future. Alongside this, the aforementioned intervention was tested on certain variables present in the teaching-learning process such as fun, learning and taste for the activity and methodology. Supportive intervention was effective in improving all the motivational variables, except for the satisfaction of the relatedness variable, which may be more difficult to modify as class groups tend to remain stable throughout this educational state. Students in the experimental condition showed higher levels of fun, learning and taste for the content and methodology.

Neural systems underlying learning and representation of global motion

We demonstrate performance-related changes in cortical and cerebellar activity. The largest learning-dependent changes were observed in the anterior lateral cerebellum, where the extent and intensity of activation correlated inversely with psychophysical performance. After learning had occurred (a few minutes), the cerebellar activation almost disappeared; however, it was restored when the subjects were presented with a novel, untrained direction of motion for which psychophysical performance also reverted to chance level. Similar reductions in the extent and intensity of brain activations in relation to learning occurred in the superior colliculus, anterior cingulate, and parts of the extrastriate cortex. The motion direction-sensitive middle temporal visual complex was a notable exception, where there was an expansion of the cortical territory activated by the trained stimulus. Together, these results indicate that the learning and representation of visual motion discrimination are mediated by different, but probably interacting, neuronal subsystems.

Running enhances neurogenesis, learning, and long-term potentiation in mice

Running increases neurogenesis in the dentate gyrus of the hippocampus, a brain structure that is important for memory function. Consequently, spatial learning and long-term potentiation (LTP) were tested in groups of mice housed either with a running wheel (runners) or under standard conditions (controls). Mice were injected with bromodeoxyuridine to label dividing cells and trained in the Morris water maze. LTP was studied in the dentate gyrus and area CA1 in hippocampal slices from these mice. Running improved water maze performance, increased bromodeoxyuridine-positive cell numbers, and selectively enhanced dentate gyrus LTP. Our results indicate that physical activity can regulate hippocampal neurogenesis, synaptic plasticity, and learning.

Perceptual learning reflects external noise filtering and internal noise reduction through channel reweighting

To investigate the nature of plasticity in the adult visual system, perceptual learning was measured in a peripheral orientation discrimination task with systematically varying amounts of external (environmental) noise. The signal contrasts required to achieve threshold were reduced by a factor or two or more after training at all levels of external noise. The strong quantitative regularities revealed by this novel paradigm ruled out changes in multiplicative internal noise, changes in transducer nonlinearites, and simple attentional tradeoffs. Instead, the regularities specify the mechanisms of perceptual learning at the behavioral level as a combination of external noise exclusion and stimulus enhancement via additive internal noise reduction. The findings also constrain the neural architecture of perceptual learning. Plasticity in the weights between basic visual channels and decision is sufficient to account for perceptual learning without requiring the retuning of visual mechanisms.

Folding and activity of circularly permuted forms of a polytopic membrane protein

The transmembrane subunit of the Glc transporter (IICBGlc), which mediates uptake and concomitant phosphorylation of glucose, spans the membrane eight times. Variants of IICBGlc with the native N and C termini joined and new N and C termini in the periplasmic and cytoplasmic surface loops were expressed in Escherichia coli. In vivo transport/in vitro phosphotransferase activities of the circularly permuted variants with the termini in the periplasmic loops 1 to 4 were 35/58, 32/37, 0/3, and 0/0% of wild type, respectively. The activities of the variants with the termini in the cytoplasmic loops 1 to 3 were 0/25, 0/4 and 24/70, respectively. Fusion of alkaline phosphatase to the periplasmic C termini stabilized membrane integration and increased uptake and/or phosphorylation activities. These results suggest that internal signal anchor and stop transfer sequences can function as N-terminal signal sequences in a circularly permuted α-helical bundle protein and that the orientation of transmembrane segments is determined by the amino acid sequence and not by the sequential appearance during translation. Of the four IICBGlc variants with new termini in periplasmic loops, only the one with the discontinuity in loop 4 is inactive. The sequences of loop 4 and of the adjacent TM7 and TM8 are conserved in all phosphoenolpyruvate-dependent carbohydrate:phosphotransferase system transporters of the glucose family.

A functional genetic screen identifies regions at the C-terminal tail and death-domain of death-associated protein kinase that are critical for its proapoptotic activity

Death-associated protein kinase (DAP-kinase) is a Ca+2/calmodulin-regulated serine/threonine kinase with a multidomain structure that participates in apoptosis induced by a variety of signals. To identify regions in this protein that are critical for its proapoptotic activity, we performed a genetic screen on the basis of functional selection of short DAP-kinase-derived fragments that could protect cells from apoptosis by acting in a dominant-negative manner. We expressed a library of randomly fragmented DAP-kinase cDNA in HeLa cells and treated these cells with IFN-γ to induce apoptosis. Functional cDNA fragments were recovered from cells that survived the selection, and those in the sense orientation were examined further in a secondary screen for their ability to protect cells from DAP-kinase-dependent tumor necrosis factor-α-induced apoptosis. We isolated four biologically active peptides that mapped to the ankyrin repeats, the “linker” region, the death domain, and the C-terminal tail of DAP-kinase. Molecular modeling of the complete death domain provided a structural basis for the function of the death-domain-derived fragment by suggesting that the protective fragment constitutes a distinct substructure. The last fragment, spanning the C-terminal serine-rich tail, defined a new regulatory region. Ectopic expression of the tail peptide (17 amino acids) inhibited the function of DAP-kinase, whereas removal of this region from the complete protein caused enhancement of the killing activity, indicating that the C-terminal tail normally plays a negative regulatory role. Altogether, this unbiased screen highlighted functionally important regions in the protein and revealed an additional level of regulation of DAP-kinase apoptotic function that does not affect the catalytic activity.

Diffusion of nitric oxide can facilitate cerebellar learning: A simulation study

The gaseous second messenger nitric oxide (NO), which readily diffuses in brain tissue, has been implicated in cerebellar long-term depression (LTD), a form of synaptic plasticity thought to be involved in cerebellar learning. Can NO diffusion facilitate cerebellar learning? The inferior olive (IO) cells, which provide the error signals necessary for modifying the granule cell–Purkinje cell (PC) synapses by LTD, fire at ultra-low firing rates in vivo, rarely more than 2–4 spikes within a second. In this paper, we show that NO diffusion can improve the transmission of sporadic IO error signals to PCs within cerebellar cortical functional units, or microzones. To relate NO diffusion to adaptive behavior, we add NO diffusion and a “volumic” LTD learning rule, i.e., a learning rule that depends both on the synaptic activity and on the NO concentration at the synapse, to a cerebellar model for arm movement control. Our results show that biologically plausible diffusion leads to an increase in information transfer of the error signals to the PCs when the IO firing rate is ultra-low. This, in turn, enhances cerebellar learning as shown by improved performance in an arm-reaching task.

Ts1Cje, a partial trisomy 16 mouse model for Down syndrome, exhibits learning and behavioral abnormalities

A mouse model for Down syndrome, Ts1Cje, has been developed. This model has made possible a step in the genetic dissection of the learning, behavioral, and neurological abnormalities associated with segmental trisomy for the region of mouse chromosome 16 homologous with the so-called “Down syndrome region” of human chromosome segment 21q22. Tests of learning in the Morris water maze and assessment of spontaneous locomotor activity reveal distinct learning and behavioral abnormalities, some of which are indicative of hippocampal dysfunction. The triplicated region in Ts1Cje, from Sod1 to Mx1, is smaller than that in Ts65Dn, another segmental trisomy 16 mouse, and the learning deficits in Ts1Cje are less severe than those in Ts65Dn. In addition, degeneration of basal forebrain cholinergic neurons, which was observed in Ts65Dn, was absent in Ts1Cje.

HCC-2, a human chemokine: Gene structure, expression pattern, and biological activity

Cloning and sequencing of the upstream region of the gene of the CC chemokine HCC-1 led to the discovery of an adjacent gene coding for a CC chemokine that was named “HCC-2.” The two genes are separated by 12-kbp and reside in a head-to-tail orientation on chromosome 17. At variance with the genes for HCC-1 and other human CC chemokines, which have a three-exon-two-intron structure, the HCC-2 gene consists of four exons and three introns. Expression of HCC-2 and HCC-1 as studied by Northern analysis revealed, in addition to the regular, monocistronic mRNAs, a common, bicistronic transcript. In contrast to HCC-1, which is expressed constitutively in numerous human tissues, HCC-2 is expressed only in the gut and the liver. HCC-2 shares significant sequence homology with CKβ8 and the murine chemokines C10, CCF18/MRP-2, and macrophage inflammatory protein 1γ, which all contain six instead of four conserved cysteines. The two additional cysteines of HCC-2 form a third disulfide bond, which anchors the COOH-terminal domain to the core of the molecule. Highly purified recombinant HCC-2 was tested on neutrophils, eosinophils, monocytes, and lymphocytes and was found to exhibit marked functional similarities to macrophage inflammatory protein 1α. It is a potent chemoattractant and inducer of enzyme release in monocytes and a moderately active attractant for eosinophils. Desensitization studies indicate that HCC-2 acts mainly via CC chemokine receptor CCR1.

Lack of tissue glucocorticoid reactivation in 11β-hydroxysteroid dehydrogenase type 1 knockout mice ameliorates age-related learning impairments

11β-hydroxysteroid dehydrogenase type 1 (11β-HSD-1) intracellularly regenerates active corticosterone from circulating inert 11-dehydrocorticosterone (11-DHC) in specific tissues. The hippocampus is a brain structure particularly vulnerable to glucocorticoid neurotoxicity with aging. In intact hippocampal cells in culture, 11β-HSD-1 acts as a functional 11β-reductase reactivating inert 11-DHC to corticosterone, thereby potentiating kainate neurotoxicity. We examined the functional significance of 11β-HSD-1 in the central nervous system by using knockout mice. Aged wild-type mice developed elevated plasma corticosterone levels that correlated with learning deficits in the watermaze. In contrast, despite elevated plasma corticosterone levels throughout life, this glucocorticoid-associated learning deficit was ameliorated in aged 11β-HSD-1 knockout mice, implicating lower intraneuronal corticosterone levels through lack of 11-DHC reactivation. Indeed, aged knockout mice showed significantly lower hippocampal tissue corticosterone levels than wild-type controls. These findings demonstrate that tissue corticosterone levels do not merely reflect plasma levels and appear to play a more important role in hippocampal functions than circulating blood levels. The data emphasize the crucial importance of local enzymes in determining intracellular glucocorticoid activity. Selective 11β-HSD-1 inhibitors may protect against hippocampal function decline with age.