Consumo de substâncias psicoactivas na população estudantil da Escola Superior de Tecnologia da Saúde de Lisboa

O consumo de substâncias psicoactivas por estudantes do ensino superior tem sido objecto de estudo nos últimos anos em Portugal. Ao actuarem no Sistema Nervoso Central, produzindo alterações comportamentais, cognitivas, de consciência e de humor, as substâncias psicoactivas podem comprometer a capacidade de aprendizagem e futuro desempenho profissional. As prevalências de consumo em estudantes das áreas específicas da saúde (Medicina, Enfermagem, Farmácia) têm sido amplamente estudadas e caracterizadas. Considera-se que estes constituem um grupo vulnerável ao consumo de substâncias psicoactivas devido, em parte, ao esforço intelectual intenso, stress, ansiedade, insónias e depressão a que estão frequentemente sujeitos. Desconhecem-se dados específicos sobre o consumo de substâncias psicoactivas nos estudantes das Tecnologias de Saúde

The late endocytic Rab39a GTPase regulates the interaction between multivesicular bodies and chlamydial inclusions.

Given their obligate intracellular lifestyle, Chlamydia trachomatis ensure their access to multiple host sources of essential lipids by interfering vesicular transport. These bacteria hijack Rab6-, Rab11- and Rab14-controlled trafficking pathways to acquire sphingomyelin from the Golgi apparatus. Another important source of sphingolipids, phospholipids and cholesterol are multivesicular bodies (MVBs). Despite their participation in chlamydial inclusion development and bacterial replication, the molecular mechanisms mediating MVBs-inclusion interaction remain unknown. In the present study, we demonstrate that Rab39a labels a subset of late endocytic vesicles -mainly MVBs- that move along microtubules. Moreover, Rab39a is actively recruited to chlamydial inclusions throughout the pathogen life cycle by a bacterial-driven process and depending on its GTP/GDP binding state. Interestingly, Rab39a participates in the delivery of MVB and host sphingolipids to maturing chlamydial inclusions thereby promoting inclusion growth and bacterial development. Altogether, our findings indicate that Rab39a favours chlamydial replication and infectivity. This is the first report showing a late endocytic Rab GTPase involved in chlamydial infection development.Fil: Gambarte Tudela, Julian Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Capmany, Anahi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Romao, Maryse. Institute Curie; FranciaFil: Quintero, Cristian Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Miserey Lenkei, Stephanie. Institute Curie; FranciaFil: Raposo, Graça. Institute Curie; FranciaFil: Goud, Bruno. Institute Curie; FranciaFil: Damiani, Maria Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; Argentin

ADP ribosylation factor 6 is activated and controls membrane delivery during phagocytosis in macrophages

Engulfment of particles by phagocytes is induced by their interaction with specific receptors on the cell surface, which leads to actin polymerization and the extension of membrane protrusions to form a closed phagosome. Membrane delivery from internal pools is considered to play an important role in pseudopod extension during phagocytosis. Here, we report that endogenous ADP ribosylation factor 6 (ARF6), a small GTP-binding protein, undergoes a sharp and transient activation in macrophages when phagocytosis was initiated via receptors for the Fc portion of immunoglobulins (FcRs). A dominant-negative mutant of ARF6 (T27N mutation) dramatically affected FcR-mediated phagocytosis. Expression of ARF6-T27N lead to a reduction in the focal delivery of vesicle-associated membrane protein 3+ endosomal recycling membranes at phagocytosis sites, whereas actin polymerization was unimpaired. This resulted in an early blockade in pseudopod extension and accumulation of intracellular vesicles, as observed by electron microscopy. We conclude that ARF6 is a major regulator of membrane recycling during phagocytosis

Rab38 and Rab32 control post-Golgi trafficking of melanogenic enzymes

Amutation in the small GTPase Rab38 gives rise to the mouse coat color phenotype “chocolate” (cht), implicating Rab38 in the regulation of melanogenesis. However, its role remains poorly characterized. We report that cht Rab38G19V is inactive and that the nearly normal pigmentation in cht melanocytes results from functional compensation by the closely related Rab32. In cht cells treated with Rab32-specific small interfering RNA, a dramatic loss of pigmentation is observed. In addition to mature melanosomes, Rab38 and Rab32 localize to perinuclear vesicles carrying tyrosinase and tyrosinase-related protein 1, consistent with a role in the intracellular sorting of these proteins. In Rab38/Rab32-deficient cells, tyrosinase appears to be mistargeted and degraded after exit from the trans-Golgi network (TGN). This suggests that Rab38 and Rab32 regulate a critical step in the trafficking of melanogenic enzymes, in particular, tyrosinase, from the TGN to melanosomes. This work identifies a key role for the Rab38/Rab32 subfamily of Rab proteins in the biogenesis of melanosomes and potentially other lysosome-related organelles

Isolation and characterization of exosomes from cell culture supernatants and biological fluids

Exosomes are small membrane vesicles found in cell culture supernatants and in different biological fluids. Exosomes form in a particular population of endosomes, called multivesicular bodies (MVBs), by inward budding into the lumen of the compartment. Upon fusion of MVBs with the plasma membrane, these internal vesicles are secreted. Exosomes possess a defined set of membrane and cytosolic proteins. The physiological function of exosomes is still a matter of debate, but increasing results in various experimental systems suggest their involvement in multiple biological processes. Because both cell-culture supernatants and biological fluids contain different types of lipid membranes, it is critical to perform high-quality exosome purification. This unit describes different approaches for exosome purification from various sources, and discusses methods to evaluate the purity and homogeneity of the purified exosome preparations

Dynamics of Major Histocompatibility Complex Class II Compartments during B Cell Receptor–mediated Cell Activation

Antigen recognition by clonotypic B cell receptor (BcR) is the first step of B lymphocytes differentiation into plasmocytes. This B cell function is dependent on efficient major histocompatibility complex (MHC) class II–restricted presentation of BcR-bound antigens. In this work, we analyzed the subcellular mechanisms underlying antigen presentation after BcR engagement on B cells. In quiescent B cells, we found that MHC class II molecules mostly accumulated at the cell surface and in an intracellular pool of tubulovesicular structures, whereas H2-M molecules were mostly detected in distinct lysosomal compartments devoid of MHC class II. BcR stimulation induced the transient intracellular accumulation of MHC class II molecules in newly formed multivesicular bodies (MVBs), to which H2-M was recruited. The reversible downregulation of cathepsin S activity led to the transient accumulation of invariant chain–MHC class II complexes in MVBs. A few hours after BcR engagement, cathepsin S activity increased, the p10 invariant chain disappeared, and MHC class II–peptide complexes arrived at the plasma membrane. Thus, BcR engagement induced the transient formation of antigen-processing compartments, enabling antigen-specific B cells to become effective antigen-presenting cells

Proprotein convertase cleavage liberates a fibrillogenic fragment of a resident glycoprotein to initiate melanosome biogenesis

Lysosome-related organelles are cell type–specific intracellular compartments with distinct morphologies and functions. The molecular mechanisms governing the formation of their unique structural features are not known. Melanosomes and their precursors are lysosome-related organelles that are characterized morphologically by intralumenal fibrous striations upon which melanins are polymerized. The integral membrane protein Pmel17 is a component of the fibrils and can nucleate their formation in the absence of other pigment cell–specific proteins. Here, we show that formation of intralumenal fibrils requires cleavage of Pmel17 by a furin-like proprotein convertase (PC). As in the generation of amyloid, proper cleavage of Pmel17 liberates a lumenal domain fragment that becomes incorporated into the fibrils; longer Pmel17 fragments generated in the absence of PC activity are unable to form organized fibrils. Our results demonstrate that PC-dependent cleavage regulates melanosome biogenesis by controlling the fibrillogenic activity of a resident protein. Like the pathologic process of amyloidogenesis, the formation of other tissue-specific organelle structures may be similarly dependent on proteolytic activation of physiological fibrillogenic substrates