Actividades prácticas en anatomía: factor nivelador de los contrastes de origen entre los alumnos de medicina / Practical activities in anatomy: leveling factor for the origin related contrasts among medical students

Las mediciones de los logros educacionales y las pruebas de selección de ingreso a la educación superior están fuertemente correlacionadas con los antecedentes socioeconómicos y el tipo de establecimiento educacional del postulante, situación que representaría un factor predictor del rendimiento para los alumnos de primer año universitario. Considerando que los puntajes de ingreso para la carrera de medicina presentan una diferencia significativa entre los primeros y últimos seleccionados, nos preguntamos si existe algún factor nivelador que reduzca esa brecha de origen. Se analiza el rendimiento en las evaluaciones prácticas y pruebas teóricas, al comienzo y al final del año académico 2009 comparando los primeros y últimos seleccionados de acuerdo al puntaje de ingreso PSU a la carrera de medicina de la Pontificia Universidad Católica de Chile. Se observan diferencias significativas en el rendimiento de la primera evaluación Teórica de Anatomía y en la Nota Final obtenida en el curso, en cambio, no se encuentran diferencias significativas tanto en la primera Evaluación Práctica cómo en el examen final práctico del curso. Nuestros resultados sugieren que la única evaluación niveladora, que logra superar las diferencias de origen de los examinados, la constituyen nuestras pruebas prácticas; evaluaciones en las cuales el rendimiento de los primeros y de los últimos seleccionados de medicina es más homogéneo. Este tipo de evaluaciones prácticas, realizadas sobre preparaciones cadavéricas, demandan fundamentalmente experiencias vividas en nuestras actividades prácticas, colocándose por sobre la mayor o menor habilidad o experiencia que posea el estudiante relacionada con su establecimiento educacional de origen.

Level of educational achievement and screening tests for admission to higher education are strongly correlated with socioeconomic background and the type of school of the applicant, these situations would be a performance predictor for college freshmen students. Whereas the scores to be accepted into the medical career have a significant difference between the first and last selected, we wonder if there is a leveling factor that reduces the gap of origin. We analyze the performance in practical assessments and theory tests at the beginning and end of the academic year 2009 comparing the first and last selected according to the PSU score admission to medical studies at the Pontificia Universidad Catolica de Chile. Significant differences were observed in the performance of the first assessment of the theory of Anatomy and the final score obtained in the course, however, no significant differences in both the first practical test and practical final exam of the course. Our results suggest that the only evaluation level, which overcomes the differences of origin of the examined, are our practical tests; assessments in which the performance of the first and the last selected medical student is more homogenous. This type of practical assessments, performed on cadavers, primarily demanded experiences in our practical segment, standing by on the degree of skill or experience held by the students related to their educational institution of origin.

Ausencia congénita de la vena porta hepática asociada a malrotación intestinal y a vena cava inferior izquierda: reporte de caso / Congenital absence of the hepatic portal vein associated to intestinal malrotation and left-sided inferior vena cava: a case report

La ausencia congénita de la vena porta hepática es una malformación en extremo rara, fue descrita por primera vez en 1793 por John Abernethy y a la fecha se han reportado sólo 101 casos. Afecta con mayor frecuencia a mujeres y determina que el drenaje venoso intestinal sea derivado hacia el territorio de las venas sistémicas. Es también conocida como derivación porto-sistémica extra hepática congénita (CEPS), por su sigla en inglés, y se asocia a otras alteraciones congénitas,incluyendo anomalías cardíacas, de las vías biliares, enfermedades metabólicas y retardo mental. En este trabajo presentamos el hallazgo de esta malformación en el cadáver de un niño de dos años de edad, donde la vena porta seguía un trayecto anómalo y se unía a la vena renal derecha. El confluente venoso "mesentérico-esplénico-renal" así formado presentaba un trayecto descendente, recibía a la vena gonadal derecha, y desembocando en la confluencia de las venas ilíacas comunes. Esto se asociaba a mal rotación intestinal, arteria hepática aberrante y a vena cava inferior izquierda, situación descrita sólo una vez en la literatura. El hallazgo de estas anomalías anatómicas en los cadáveres disecados con fines docentes en nuestro Departamento de Anatomía, tiene un valor formativo indiscutible para nuestros alumnos de pre y postgrado, quienes pueden valorar las implicancias de este conocimiento anatómico en la clínica diaria.

Congenital absence of the hepatic portal vein is an extremely rare malformation that was first described by John Abernethy in 1793. Only 101 cases had been described in the literature until 2015 and most affected females. In this anomaly, also known as congenital extrahepatic porto-systemic shunt (CEPS), intestinal venous drainage is derived towards the territory of the systemic veins and could be associated with other birth defects, including heart and biliary tract anomalies, metabolic diseases, mental retardation. We present the case of a 2-year-old boy who died because of multifocal pneumonia and necropsy showed anatomical findings consistent with this malformation as an incidental finding. The portal vein followed an anomalous course and joined the right renal vein, forming the "mesenteric-splenic-renal" venous collector, which then received the right gonadal vein and ended at the confluence of the common iliac veins. In our case this anomaly was associated to intestinal malrotation, aberrant hepatic artery and persistent left inferior vena cava, situation described once in the literature. The finding of these anatomical abnormalities in cadavers has a great teaching value for our undergraduate and graduate students who are learning anatomy and they can also assess the associated clinical.

Specificity of Collybistin-Phosphoinositide Interactions: IMPACT OF THE INDIVIDUAL PROTEIN DOMAINS.

The regulatory protein collybistin (CB) recruits the receptor-scaffolding protein gephyrin to mammalian inhibitory glycinergic and GABAergic postsynaptic membranes in nerve cells. CB is tethered to the membrane via phosphoinositides. We developed an in vitro assay based on solid-supported 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine membranes doped with different phosphoinositides on silicon/silicon dioxide substrates to quantify the binding of various CB2 constructs using reflectometric interference spectroscopy. Based on adsorption isotherms, we obtained dissociation constants and binding capacities of the membranes. Our results show that full-length CB2 harboring the N-terminal Src homology 3 (SH3) domain (CB2SH3+) adopts a closed and autoinhibited conformation that largely prevents membrane binding. This autoinhibition is relieved upon introduction of the W24A/E262A mutation, which conformationally "opens" CB2SH3+ and allows the pleckstrin homology domain to properly bind lipids depending on the phosphoinositide species with a preference for phosphatidylinositol 3-monophosphate and phosphatidylinositol 4-monophosphate. This type of membrane tethering under the control of the release of the SH3 domain of CB is essential for regulating gephyrin clustering.

A conformational switch in collybistin determines the differentiation of inhibitory postsynapses.

The formation of neuronal synapses and the dynamic regulation of their efficacy depend on the assembly of the postsynaptic neurotransmitter receptor apparatus. Receptor recruitment to inhibitory GABAergic and glycinergic synapses is controlled by the scaffold protein gephyrin and the adaptor protein collybistin. We derived new insights into the structure of collybistin and used these to design biochemical, cell biological, and genetic analyses of collybistin function. Our data define a collybistin-based protein interaction network that controls the gephyrin content of inhibitory postsynapses. Within this network, collybistin can adopt open/active and closed/inactive conformations to act as a switchable adaptor that links gephyrin to plasma membrane phosphoinositides. This function of collybistin is regulated by binding of the adhesion protein neuroligin-2, which stabilizes the open/active conformation of collybistin at the postsynaptic plasma membrane by competing with an intramolecular interaction in collybistin that favors the closed/inactive conformation. By linking trans-synaptic neuroligin-dependent adhesion and phosphoinositide signaling with gephyrin recruitment, the collybistin-based regulatory switch mechanism represents an integrating regulatory node in the formation and function of inhibitory postsynapses.

The Drosophila p21 activated kinase Mbt regulates the actin cytoskeleton and adherens junctions to control photoreceptor cell morphogenesis.

The p21 activated kinase (Pak) family of protein kinases are involved in many cellular functions like re-organisation of the cytoskeleton, transcriptional control, cell division, and survival. These pleiotropic actions are reflected in a plethora of known interacting proteins and phosphorylation substrates. Yet, the integration of a single Pak protein into signalling pathways controlling a particular developmental process are less well studied. For two of the three known Pak proteins in Drosophila melanogaster, D-Pak and Mbt, distinct functions during eye development have been established. In this study we undertook a genetic approach to identify proteins acting in the Mbt signalling pathway during photoreceptor cell morphogenesis. The genetic screen identified the actin depolymerisation factor Twinstar/Cofilin as one target of Mbt signalling. Twinstar/Cofilin becomes phosphorylated upon activation of Mbt. However, biochemical and genetic experiments question the role of the LIM domain protein kinase (Limk) as a major link between Mbt and Twinstar/Cofilin as it has been suggested for other PAK proteins. Constitutive activation of Mbt not only disturbs the actin cytoskeleton but also affects adherens junction organisation indicating a requirement of the protein in cell adhesion dependent processes during photoreceptor cell differentiation.

Mbt, a Drosophila PAK protein, combines with Cdc42 to regulate photoreceptor cell morphogenesis.

The Drosophila gene mushroom bodies tiny (mbt) encodes a putative p21-activated kinase (PAK), a family of proteins that has been implicated in a multitude of cellular processes including regulation of the cytoskeleton, cell polarisation, control of MAPK signalling cascades and apoptosis. The mutant phenotype of mbt is characterised by fewer neurones in the brain and the eye, indicating a role of the protein in cell proliferation, differentiation or survival. We show that mutations in mbt interfere with photoreceptor cell morphogenesis. Mbt specifically localises at adherens junctions of the developing photoreceptor cells. A structure-function analysis of the Mbt protein in vitro and in vivo revealed that the Mbt kinase domain and the GTPase binding domain, which specifically interacts with GTP-loaded Cdc42, are important for Mbt function. Besides regulation of kinase activity, another important function of Cdc42 is to recruit Mbt to adherens junctions. We propose a role for Mbt as a downstream effector of Cdc42 in photoreceptor cell morphogenesis.