Ilustraciones de procesos de tejidos con fibra de palma tetera.

15 hojas : ilustraciones, fotografías a color

Characterization of the degradation of wild-type and mutant HFE proteins during stress signalling in the endoplasmic reticulum

HFE is a transmembrane protein that becomes N-glycosylated during transport to the cell membrane. It acts to regulate cellular iron uptake by interacting with the Type 1 transferrin receptor and interfering with its ability to bind iron-loaded transferrin. There is also evidence that HFE regulates systemic iron levels by binding to the Type II transferrin receptor although the mechanism by which this occurs is still not well understood. Mutations to HFE that disrupt this function, or physiological conditions that decrease HFE protein levels, are associated with increased iron uptake, and its accumulation in tissues and organs. This is exemplified by the point mutation that results in conversion of cysteine residue 282 to tyrosine (C282Y), and gives rise to the majority of HFE-related hemochromatoses. The C282Y mutation prevents the formation of a disulfide bridge and disrupts the interaction with its co-chaperone β2-microglobulin. The resulting misfolded protein is retained within the endoplasmic reticulum (ER) where it activates the Unfolded Protein Response (UPR) and is subjected to proteasomal degradation. The absence of functional HFE at the cell surface leads to unregulated iron uptake and iron loading. While the E3 ubiquitin ligase involved in the degradation of HFE-C282Y has been identified, the mechanism by which it is targeted for degradation remains relatively obscure. The primary objective of this project was to further our understanding of how the iron regulatory HFE protein is targeted for degradation. Our studies suggest that the glycosylation status, and the active process of deglycosylation, are central to this process. We identified a number of additional factors that can contribute towards degradation and explored their regulation during ER stress conditions.

Endogenous interleukin-10 modulates fibrosis and regeneration in experimental chronic pancreatitis.

Interleukin (IL)-10, a potent anti-inflammatory cytokine, limits the severity of acute pancreatitis and downregulates transforming growth factor (TGF)-beta release by inflammatory cells on stimulation. Proinflammatory mediators, reactive oxygen species, and TGF-beta can activate pancreatic stellate cells and their synthesis of collagen I and III. This study evaluates the role of endogenous IL-10 in the modulation of the regeneration phase following acute pancreatitis and in the development of pancreatic fibrosis. IL-10 knockout (KO) mice and their C57BL/6 controls were submitted to repeated courses (3/wk, during 6 wk, followed by 1 wk of recovery) of cerulein-induced acute pancreatitis. TGF-beta(1) release was measured on plasma, and its pancreatic expression was assessed by quantitative RT-PCR and immunohistochemistry. Intrapancreatic IL-10 gene expression was assessed by semiquantitative RT-PCR, and intrapancreatic collagen content was assessed by picrosirius staining. Activated stellate cells were detected by immunohistochemistry. S phase intrapancreatic cells were marked using tritiated thymidine labeling. After repeated acute pancreatitis, IL-10 KO mice had more severe histological lesions and fibrosis (intrapancreatic collagen content) than controls. TGF-beta(1) plasma levels, intrapancreatic transcription, and expression by ductal and interstitial cells, as well as the number of activated stellate cells, were significantly higher. IL-10 KO mice disclosed significantly fewer acinar cells in S phase, whereas the opposite was observed for pseudotubular cells. Endogenous IL-10 controls the regeneration phase and limits the severity of fibrosis and glandular atrophy induced by repeated episodes of acute pancreatitis in mice.

Mainland size variation informs predictive models of exceptional insular body size change in rodents.

The tendency for island populations of mammalian taxa to diverge in body size from their mainland counterparts consistently in particular directions is both impressive for its regularity and, especially among rodents, troublesome for its exceptions. However, previous studies have largely ignored mainland body size variation, treating size differences of any magnitude as equally noteworthy. Here, we use distributions of mainland population body sizes to identify island populations as 'extremely' big or small, and we compare traits of extreme populations and their islands with those of island populations more typical in body size. We find that although insular rodents vary in the directions of body size change, 'extreme' populations tend towards gigantism. With classification tree methods, we develop a predictive model, which points to resource limitations as major drivers in the few cases of insular dwarfism. Highly successful in classifying our dataset, our model also successfully predicts change in untested cases.

Freezing behaviour facilitates bioelectric crypsis in cuttlefish faced with predation risk.

Cephalopods, and in particular the cuttlefish Sepia officinalis, are common models for studies of camouflage and predator avoidance behaviour. Preventing detection by predators is especially important to this group of animals, most of which are soft-bodied, lack physical defences, and are subject to both visually and non-visually mediated detection. Here, we report a novel cryptic mechanism in S. officinalis in which bioelectric cues are reduced via a behavioural freeze response to a predator stimulus. The reduction of bioelectric fields created by the freeze-simulating stimulus resulted in a possible decrease in shark predation risk by reducing detectability. The freeze response may also facilitate other non-visual cryptic mechanisms to lower predation risk from a wide range of predator types.

Aspectos morfológicos y biológicos de la oruga militar verdadera (Pseudaletia adultera (Schaus) ) (Lep. Noctuidae)

p.39-46

Resultados económicos de la producción comercial de jabalíes cruza en la Argentina

p.139-145

Descripción y caracterización del razonamiento inductivo utilizado por estudiantes de educación secundaria al resolver tareas relacionadas con sucesiones lineales y cuadráticas

El objetivo general de la investigación es describir y caracterizar el razonamiento inductivo empleado por estudiantes de tercero y cuarto de Educación Secundaria Obligatoria en la resolución de problemas que pueden ser modelizados mediante una progresión aritmética de números naturales cuyo orden sea 1 o 2. El principal aporte teórico de este trabajo es la elaboración de un modelo de razonamiento inductivo que ha permitido describir el proceso seguido por los estudiantes. El procedimiento para la identificación y descripción de las estrategias en la resolución de problemas en los que se puede utilizar el razonamiento inductivo es un aporte metodológico destacado. Los 359 estudiantes participantes resolvieron una prueba individual escrita compuesta por seis problemas. El análisis de las producciones de los estudiantes permite obtener resultados sobre los pasos de razonamiento inductivo que emplean y las estrategias que utilizan.

Pensamiento variacional: El estudio de las relaciones trigonometricas en contextos dinámicos

Este documento se elabora a partir de una revisión inicial de literatura donde se analizaron los Lineamientos Curriculares, los Estándares Básicos de Competencia y algunos estudios e investigaciones en el campo de la variación y la trigonometría. Desde los elementos teóricos observados en la literatura se hizo indispensable un análisis de algunos libros de texto frente al tipo de ejercicios que se proponía para abordar la trigonometría plana; de este análisis surgió la necesidad de diseñar propuestas alternativas en las cuales se haga hincapié en la visualización de relaciones funcionales entre los ángulos y los lados de un triángulo; de este modo, se espera aportar elementos para superar la idea de que las relaciones trigonométricas son “fórmulas” para calcular datos fijos y desconocidos de un triángulo.

Beneficial entitlement after Stack

Reviews the approach adopted in Stack v Dowden to determination of beneficial interests in a property purchased in the joint names of cohabitees. Considers two cases which extended the Stack v Dowden approach to encompass the beneficial entitlement of family members, namely: (1) Adekunle v Ritchie on beneficial entitlement in a property jointly purchased by a mother and son, where the transfer document contained no express declaration of trust; and (2) Abbott v Abbott on the impact of a wife's indirect financial contributions in determining her beneficial entitlement in the matrimonial home.

Chattels: I have bought it all for you

Outlines the ways by which personal property can be acquired through the gift of chattels, referring to case law including the Court of Appeal rulings in Re Cole (A Bankrupt) and Re Kirkland, and through the declaration of trust, with reference to the Chancery Division ruling in Rowe v Prance. Compares this to the use of constructive trusts or proprietary estoppel to secure assets and considers the need to prove detrimental reliance.

Giving credit where it's due

Discusses the entitlement to occupation rent where one party to a relationship no longer lives in the matrimonial or family home in which he/she has an interest and a right of occupation. Describes the case law illustrating that forceful exclusion of the non-occupying party is not a prerequisite to entitlement to an occupation rent. Considers the calculation of the parties' respective credits where the occupying party has made mortgage repayments since the separation and the other is entitled to an occupation rent.

Patch me if you can

Considers the circumstances in which repair works may be more appropriate than replacement where a landlord is attempting to claim under a repair covenant. Examines case law on which method is more appropriate and on the standard of remedial work to be undertaken. Reflects on the situation where performance of remedial works would be futile. Comments on the Technology and Construction Court ruling in Carmel Southend Ltd v Strachan & Henshaw Ltd on whether a landlord had been correct to carry out overcladding works to a roof where surveyors had agreed that patch repairs would be adequate.