USP17 is required for peripheral trafficking of lysosomes.

Expression of the deubiquitinase USP17 is induced by multiple stimuli, including cytokines (IL-4/6), chemokines (IL-8, SDF1), and growth factors (EGF), and several studies indicate it is required for cell proliferation and migration. However, the mechanisms via which USP17 impacts upon these cellular functions are unclear. Here, we demonstrate that USP17 depletion prevents peripheral lysosome positioning, as well as trafficking of lysosomes to the cell periphery in response to EGF stimulation. Overexpression of USP17 also increases secretion of the lysosomal protease cathepsin D. In addition, USP17 depletion impairs plasma membrane repair in cells treated with the pore-forming toxin streptolysin O, further indicating that USP17 is required for lysosome trafficking to the plasma membrane. Finally, we demonstrate that USP17 can deubiquitinate p62, and we propose that USP17 can facilitate peripheral lysosome trafficking by opposing the E3 ligase RNF26 to untether lysosomes from the ER and facilitate lysosome peripheral trafficking, lysosome protease secretion, and plasma membrane repair.

Axo-myelinic neurotransmission: a novel mode of cell signalling in the central nervous system.

It is widely recognized that myelination of axons greatly enhances the speed of signal transmission. An exciting new finding is the dynamic communication between axons and their myelin-forming oligodendrocytes, including activity-dependent signalling from axon to myelin. The oligodendrocyte-myelin complex may in turn respond by providing metabolic support or alter subtle myelin properties to modulate action potential propagation. In this Opinion, we discuss what is known regarding the molecular physiology of this novel, synapse-like communication and speculate on potential roles in disease states including multiple sclerosis, schizophrenia and Alzheimer disease. An emerging appreciation of the contribution of white-matter perturbations to neurological dysfunction identifies the axo-myelinic synapse as a potential novel therapeutic target.

Axo-myelinic neurotransmission: a novel mode of cell signalling in the central nervous system.

This corrects the article DOI: 10.1038/nrn.2017.128.

Real-time measurement of free Ca2+ changes in CNS myelin by two-photon microscopy.

Here we describe a technique for measuring changes in Ca2+ in the cytosolic domain of mature compact myelin of live axons in the central nervous system (CNS). We label the myelin sheath of optic nerve and dorsal column axons by using the Ca2+ indicator X-rhod-1 coupled with DiOC6(3) to produce bright myelin counterstaining, thereby providing unambiguous identification of the myelin sheath for analysis of two-photon excited fluorescence. We present evidence for localization of the Ca2+ reporter to the cytosolic domain of myelin, obtained by using fluorescence lifetime, spectral measurements and Mn2+ quenching. Chemical ischemia increased myelinic X-rhod-1 fluorescence (approximately 50% after 30 min) in a manner dependent on extracellular Ca2+. Inhibiting Na+-dependent glutamate transporters (with TBOA) or glycine transporters (with sarcosine and ALX-1393) reduced the ischemia-induced increase in Ca2+. We show that myelinic N-methyl-D-aspartate (NMDA) receptors are activated by the two conventional coagonists glutamate and glycine, which are released by specific transporters under conditions of cellular Na+ loading and depolarization in injured white matter. This new technique facilitates detailed studies of living myelin, a vital component of the mammalian CNS.

Excitatory glycine responses of CNS myelin mediated by NR1/NR3 "NMDA" receptor subunits.

NMDA receptors are typically excited by a combination of glutamate and glycine. Here we describe excitatory responses in CNS myelin that are gated by a glycine agonist alone and mediated by NR1/NR3 "NMDA" receptor subunits. Response properties include activation by d-serine, inhibition by the glycine-site antagonist CNQX, and insensitivity to the glutamate-site antagonist d-APV. d-Serine responses were abrogated in NR3A-deficient mice. Our results suggest the presence of functional NR1/NR3 receptors in CNS myelin.

CAMKII as a therapeutic target for growth factor-induced retinal and choroidal neovascularization.

While anti-VEGF drugs are commonly used to inhibit pathological retinal and choroidal neovascularization, not all patients respond in an optimal manner. Mechanisms underpinning resistance to anti­VEGF therapy include the upregulation of other proangiogenic factors. Therefore, therapeutic strategies that simultaneously target multiple growth factor signaling pathways would have significant value. Here, we show that Ca2+/calmodulin-dependent kinase II (CAMKII) mediates the angiogenic actions of a range of growth factors in human retinal endothelial cells and that this kinase acts as a key nodal point for the activation of several signal transduction cascades that are known to play a critical role in growth factor-induced angiogenesis. We also demonstrate that endothelial CAMKIIγ and -δ isoforms differentially regulate the angiogenic effects of different growth factors and that genetic deletion of these isoforms suppresses pathological retinal and choroidal neovascularization in vivo. Our studies suggest that CAMKII could provide a novel and efficacious target to inhibit multiple angiogenic signaling pathways for the treatment of vasoproliferative diseases of the eye. CAMKIIγ represents a particularly promising target, as deletion of this isoform inhibited pathological neovascularization, while enhancing reparative angiogenesis in the ischemic retina.

Effects of laser polarization on responses of the fluorescent Ca2+ indicator X-Rhod-1 in neurons and myelin.

Laser-scanning optical microscopes generally do not control the polarization of the exciting laser field. We show that laser polarization and imaging mode (confocal versus two photon) exert a profound influence on the ability to detect [Formula: see text] changes in both cultured neurons and living myelin. With two-photon excitation, increasing ellipticity resulted in a [Formula: see text] reduction in resting X-Rhod-1 fluorescence in homogeneous bulk solution, cell cytoplasm, and myelin. In contrast, varying the angle of a linearly polarized laser field only had appreciable effects on dyes that partitioned into myelin in an ordered manner. During injury-induced [Formula: see text] increases, larger ellipticities resulted in a significantly greater injury-induced signal increase in neurons, and particularly in myelin. Indeed, the traditional method of measuring [Formula: see text] changes using one-photon confocal mode with linearly polarized continuous wave laser illumination produced no appreciable X-Rhod-1 signal increase in ischemic myelin, compared to a robust [Formula: see text] fluorescence increase with two-photon excitation and optimized ellipticity with the identical injury paradigm. This underscores the differences in one- versus two-photon excitation and, in particular, the under-appreciated effects of laser polarization on the behavior of certain [Formula: see text] reporters, which may lead to substantial underestimates of the real [Formula: see text] fluctuations in various cellular compartments.

A T-type channel-calmodulin complex triggers αCaMKII activation.

Calmodulin (CaM) is an important signaling molecule that regulates a vast array of cellular functions by activating second messengers involved in cell function and plasticity. Low voltage-activated calcium channels of the Cav3 family have the important role of mediating low threshold calcium influx, but were not believed to interact with CaM. We find a constitutive association between CaM and the Cav3.1 channel at rest that is lost through an activity-dependent and Cav3.1 calcium-dependent CaM dissociation. Moreover, Cav3 calcium influx is sufficient to activate αCaMKII in the cytoplasm in a manner that depends on an intact Cav3.1 C-terminus needed to support the CaM interaction. Our findings thus establish that T-type channel calcium influx invokes a novel dynamic interaction between CaM and Cav3.1 channels to trigger a signaling cascade that leads to αCaMKII activation.

The molecular physiology of the axo-myelinic synapse.

Myelinated axons efficiently transmit information over long distances. The apposed myelin sheath confers favorable electrical properties, but restricts access of the axon to its extracellular milieu. Therefore, axonal metabolic support may require specific axo-myelinic communication. Here we explored activity-dependent glutamate-mediated signaling from axon to myelin. 2-Photon microscopy was used to image Ca(2+) changes in myelin in response to electrical stimulation of optic nerve axons ex vivo. We show that optic nerve myelin responds to axonal action potentials by a rise in Ca(2+) levels mediated by GluN2D and GluN3A-containing NMDA receptors. Glutamate is released from axons in a vesicular manner that is tetanus toxin-sensitive. The Ca(2+) source for vesicular fusion is provided by ryanodine receptors on axonal Ca(2+) stores, controlled by L-type Ca(2+) channels that sense depolarization of the internodal axolemma. Genetic ablation of GluN2D and GluN3A subunits results in greater lability of the compact myelin. Our results support the existence of a novel synapse between the axon and its myelin, suggesting a means by which traversing action potentials can signal the overlying myelin sheath. This may be an important physiological mechanism by which an axon can signal companion glia for metabolic support or adjust properties of its myelin in a dynamic manner. The axo-myelinic synapse may contribute to learning, while its disturbances may play a role in the pathophysiology of central nervous system disorders such as schizophrenia, where subtle abnormalities of myelinated white matter tracts have been shown in the human, or to frank demyelinating disorders such as multiple sclerosis.

Sources of axonal calcium loading during in vitro ischemia of rat dorsal roots.

A detailed understanding of injury mechanisms in peripheral nerve fibers will help guide successful design of therapies for peripheral neuropathies. This study was therefore undertaken to examine the ionic mechanisms of Ca2+ overload in peripheral myelinated fibers subjected to chemical inhibition of energy metabolism. Myelinated axons from rat dorsal roots were co-loaded with Ca2+-sensitive (Oregon Green BAPTA-1) and Ca2+-insensitive (Alexa Fluor 594) dextran-conjugated fluorophores and imaged using confocal laser scanning microscopy. Axoplasmic regions were clearly outlined by the Ca2+-insensitive dye, from which axonal Ca2+-dependent fluorescence changes (FCa.ax) were measured. Block of Na+-K+ ATPase (ouabain), opening of Na+ channels (veratridine), and inhibiting energy metabolism (iodoacetate + NaN3) caused a rapid rise in FCa.ax to 96% above control after 30 min. Chemical ischemia (iodoacetate + NaN3) caused a more gradual increase in FCa.ax (54%), which was almost completely dependent on bath Ca2+, indicating that most of the Ca2+ accumulation occurred via influx across the axolemma. Na+ channel block (tetrodotoxin) reduced ischemic FCa.ax rise (14%); however, inhibition of L-type Ca2+ channels (nimodipine) had no effect (60%). In contrast, Na+-Ca2+ exchange inhibition (KB-R7943) significantly reduced ischemic FCa.ax rise (18%). Together our results indicate that the bulk of Ca2+ overload in injured peripheral myelinated axons occurs via reverse Na+-Ca2+ exchange, driven by axonal Na+ accumulation through voltage-gated tetrodotoxin-sensitive Na+ channels. This mechanism may represent a viable therapeutic target for peripheral neuropathies.

Conversion of the Nikon C1 confocal laser-scanning head for multiphoton excitation on an upright microscope.

Most commercial laser-scanning imaging systems used for confocal fluorescence microscopy can be readily adapted for use with two-photon fluorescence excitation. We report here on the details of the conversion of the Nikon C1 (product released November 2001) with two channels of nondescanned detection of two-photon-excited fluorescence. One of the goals of the design was to utilize off-the-shelf components as much as possible to minimize the use of custom machining and electronics assembly. We also give some initial characterization of the imaging properties of the system.

Red semántica del término alumno elaborado por docentes de medicina / The semantic network of the term student, carried out by teachers of medicine

El objetivo de la investigación fue conocer cuál es el concepto de 31 profesores de medicina respecto al término alumno, considerando que lo construyen con los conocimientos y experiencias de su ejercicio docente y sus propias vivencias como alumnos. Se aplicó la técnica de redes semánticas naturales, pidiendo a cada uno que elaborara un listado de palabras definidoras asociadas con el término y las jerarquizaran. Se obtuvieron 202 conceptos definidores. Los más frecuentemente mencionados y con mayor peso semántico fueron: estudiar, receptor, aprender, responsable e interés. Del consenso conceptual se acordaron diez categorías, tres generales: funciones mentales, valores y ser humano; y siete específicas: actitudes y conductas, funciones, comunicación, sentimientos, contexto del alumno, sinónimos y metáforas, y otras palabras. Se esquematizó la red semántica con los veinte definidores del conjunto SAM. Los resultados fueron comparados con tres de las teorías que más han influido en la educación médica: la tradicional, la tecnología educativa y la cognoscitiva, mostrando que los profesores básicamente emplean los dos primeros enfoques y empiezan a considerar el cognoscitivismo.

Factores de no acreditación referidos por los alumnos afectados / Causes of failure refered by the students

El alto índice de reprobación en las materias de los primeros ciclos de la carrera, despertó nuestro interés por investigar los factores que pudieran estar involucrados. Se diseñó una encuesta con 51 reactivos y se aplicó a 238 sujetos que presentaron exámenes extraordinarios de embriología, psicología médica y medicina humanística. De estos alumnos 482 sintieron la necesidad de explicar, en la pregunta abierta los motivos que consideraron los condujeron a reprobar. Estas opiniones fueron clasificadas en tres categorías: problemas personales, causas atribuibles a los profesores y situaciones imputables al proceso académico y administrativo.

La construcción semántica del concepto de psicología médica en alumnos de primer año medicina, UNAM / Evaluation of the medical psychology concept on first-year medical students

El estudio se centra en los aspectos cognoscitivos presentes en los alumnos del primer año de la carrera de Médico Cirujano en la UNAM antes y después de un curso de psicología Médica en relación a este concepto. Se utiliza la prueba de Redes Semánticas naturales en siete grupos seleccionados aleatoriamente. Los resultados muestran que los alumnos adquieren en la preparatoria un concepto adecuado de este término y la materia modifica poco la estructura, aunque existe la tendencia a reforzar las definidoras empleadas

Caracterización de las opiniones y experiencias sexuales de los alumnos de primer ingreso a la carrera de médico cirujano / Characterization of the opinions and sexual experiences in pupils of first ingress in surgeen physician career

A partir de los datos obtenidos por medio de una encuesta aplicada a 521 alumnos de primer ingreso a la facultad de medicina de la UNAM, se presenta un panorama descriptivo de las opiniones sobre diversos aspectos de la sexualidad, así como sobre las experiencias sexuales reportadas por los participantes. La información sobre las opiniones se organizó en seis áreas: masturbación, relaciones sexuales premaritales, relaciones sexuales extramaritales, roles sexuales, estructura familiar y homosexualidad. En general, el perfil encontrado tiene a la liberalidad. La mayoria de los sujetos sometidos a la encuesta rechazan la afirmación de que la masturbación es una práctica dañina, aunque sólo una minoria de los participantes aceptó dicha forma de conducta sexual como algo digno de alentarse durante el desarrollo. La mayoria de los sujetos de la encuesta (59.6%) indicó aceptar la relación sexual premarital. Ante las relaciones extramaritales, las opiniones no muestran una tendencia definida, pues casi igual proporción de participantes indicaron su creencia de que éstas son dañinas para el matrimonio (43.2%), que los que lo negaron (41.7%). Ante los reactivos que investigaron los papeles sexuales, la mayoria de las opiniones fueron en contra de los roles sexuales estereotipados, especialmente en lo que concierne a las áreas de la igualdad y el derecho al goce sexual y de la igualdad de derechos a la educación universitaria. La mayoria de los participantes (89.7%) de ambos sexos puso en duda la estructura patriarcal de la familia. Ante la homosexualidad, el 58.75% se manifestó contrario a tomar medidas legales en contra de los individuos homosexuales. Las perguntas sobre la experiencia sexual incluyeron noviazgos, relaciones sexuales y masturbación. La mayoría de los jóvenes (81.1%) reportó haber tenido novio (a). Un 45.5% de los participantes reportó haber tenido relaciones sexuales (59.15% de los hombres y 30.5% de las mujeres), mientras que el 65.7% reportó haberse masturbado (88.1% de los hombres y 39.3% de las mujeres). Se investigó la vigencia del doble código de mortalidad sexual probando tres hipótess formuladas a partir de la conceptualización de Ira Reiss del "doble estándar" de la mortalidad sexual, que afirma que se concede un mayor derecho al coito premarital a los hombres que a las mujeres...

Construcción semántica del concepto relación médico-paciente, por alumnos del primer año de la carrera de médico cirujano / Semantic construction of the concept doctor-patient relationship by first year students of medical school

La relación médico-paciente, es una transacción, un sistema de interacción recíproca, tanto intelectual como emocional, que incorpora lo que el médico y el enfermo piensan, sienten, hacen y reciben, el uno del otro. El presente estudio pretende conocer los cambios de que desarrollan los alumnos del primer año de la carrera de médico cirujano en la UNAM antes y después de un curso de psicología médica en conexión al concepto "relación médico-paciente", con el fin de vislumbrar las modificaciones congnocitivas que el proceso enseñanza-aprendizaje del tema efectúa en su construcción semántica del concepto. Se utiliza la prueba de Redes Semánticas Naturales en 7 grupos de alumnos seleccionados aleatoriamente. Los resultados muestran que las mujeres tuvieron una mayor asimilación de nuevos términos que el hombre y que ambos sexos mantuvieron un 40 por ciento de sus conocimientos previos a su entrada a la carrera. Se mostraron mayores cambios en consistencia interna que afirma la influencia del proceso de enseñanza de la materia de psicología médica sobre su memoria semántica

La red semántica natural de la relación profesor-alumno expresada por profesores de medicina / Analysis of the natural semantic net on the teacher student relationship expressed by professors of medical courses

La investigación tiene como propósito conocer la concepción de la relación que guardan el profesor y el alumno de medicina en el proceso educativo, en el entendido de que es una forma de convivencia social y se considera uno de los elementos de mayor jerarquía sociopeda-gógica. Se solicitó a 31 profesores de medicina que formularan un listado de palabras definidoras asociadas con el término relación profesor-alumno y las organizaran en orden de importancia. Se obtuvieron 168 palabras diferentes. Las más mencionadas, y por lo tanto con mayor peso semántico, fueron respeto, amistad, dinámica, confianza y afecto. Se acordaron 10 categorías por consenso conceptual, siendo dos de ellas genéricas: valores y funciones mentales; y ocho específicas: vínculo humano, vínculo de interacción, comunicación, factores desventajosos de la relación, sentimientos, protagonistas, duración y otras. Se elaboró la red semántica con las diez primeras. Los resultados fueron comparados con los puntos de vista de expertos de diversas tendencias. Los profesores mostraron una tendencia hacia las relaciones humanas en donde el respeto y la honestidad eran tan importantes como la amistad y la confianza.