Esta investigación fue apoyada por las subvenciones F31DC017053-01A1 (Lenell, PI) y K23DC014517 (Johnson, PI) del Instituto Nacional de Sordera y otros Trastornos de la Comunicación de los Institutos Nacionales de Salud.

Este estudio se realizó de conformidad con el Comité Institucional de Cuidado y Uso de Animales de la Facultad de Medicina de la Universidad de Nueva York.
1. Diseccionar la laringe de la rata
<ol><li>Eutanasia de rata de acuerdo con el protocolo aprobado institucionalmente. Afeitar el cuello ventral desde la mandíbula hasta el manubrium e hisopo con alcohol para evitar la contaminación del pelaje en las muestras de tejido.</li>
	<li>Bajo un endoscopio de disección con aumento de 10x extirpar toda la laringe creando una incisión en la línea media del cuello con un bisturí hasta que la tráquea esté expuesta.</li>
	<li>Separe los músculos laríngeos extrínsecos ventrales en la línea media para exponer la laringe usando fórceps y diseccionando tijeras o un bisturí.</li>
	<li>Corte la tráquea caudal hasta el tercer anillo traqueal y haga una incisión rostral en el hueso hioides para extirpar toda la laringe con tijeras de disección.</li>
	<li>Extraiga los tejidos laríngeos extrínsecos (esófago, glándula tiroides y músculos laríngeos extrínsecos) de la laringe utilizando herramientas de microdisección (pinzas, alfileres y microescisores) bajo aumento.</li>
	<li>Con microscisores, divida la laringe dorsalmente entre los aritenoides utilizando la línea media entre los músculos cricoaritenoides posteriores como punto de referencia. Pin paredes laterales de la laringe para exponer las cuerdas vocales y luego dividir ventralmente a través de la línea media del cartílago tiroideo entre la comisura anterior de las cuerdas vocales con microscisores (Figura 1). NOTA: Este paso puede ser opcional; se puede omitir para mantener la laringe entera. La bisección de las laringes permite múltiples técnicas de inmunotinción utilizando por separado los lados derecho e izquierdo de la misma laringe.</li>
	<li>Enjuague cada hemilacinge en solución tamponada con fosfato (PBS) durante ~ 10 s y seque delicadamente con un limpiaparabrisas de tareas para reducir la formación de cristales de hielo durante la congelación.</li>
</ol>2. Fijar y/o congelar el tejido laríngeo
NOTA: La fijación puede no ser ideal para todos los protocolos de inmunotinción. A menudo, los tejidos laríngeos se congelan frescos inmediatamente después de la disección. Omita el paso 2.1 para congelar el tejido laríngeo sin fijación.
<ol><li>Para fijar hemilaringes, coloque los tejidos en un tubo de centrífuga lleno de formaldehído al 4% en PBS durante 1 h a temperatura ambiente en un agitador orbital a 70 rpm. Transfiera los tejidos a un tubo de centrífuga limpio y enjuague 3 veces durante 20 minutos en PBS. Luego transfiera a un tubo de centrífuga limpio y sumérjalo en una solución de sacarosa al 20% / glicerol al 5% (~ 18 h o hasta que el tejido se hunda) a 4 ° C. PRECAUCIÓN: El formaldehído es peligroso y debe usarse en una campana extractora de humos junto con el equipo de protección personal adecuado.</li>
	<li>Coloque todos los hemi-laringnges en una posición uniforme en un criomolde lleno de compuesto de temperatura de corte óptima (OCT). Para una hemilaringe, coloque el tejido con la superficie medial de la cuerda vocal mirando hacia la parte inferior del criomold y el aspecto longitudinal del pliegue vocal paralelo al borde inferior de la abertura criomold. Para laringes enteros, coloque el tejido con los cricoaritenoides posteriores mirando hacia la parte inferior del criomold y el aspecto longitudinal de la cuerda vocal paralelo al borde inferior de la abertura criomal. NOTA: La orientación laríngea consistente dentro del compuesto oct es fundamental para la criosecciona de la cuerda vocal de la rata. Una vez que la hemilinge está incrustada y congelada, debe descongelarse para cambiar su orientación, introduciendo así riesgos de daño tisular por múltiples ciclos de descongelación-congelación.</li>
	<li>Tejidos de congelación instantánea utilizando isopentano (2-metilbutano) refrigerados en un vaso de precipitados de acero rodeado de nitrógeno líquido. NOTA: El isopentano alcanza la temperatura óptima para la congelación del tejido cuando los precipitados blancos comienzan a formarse en los lados y la parte inferior del vaso de precipitados13. El isopentano se usa porque tiene una conductividad térmica más alta que el nitrógeno líquido, lo que ayuda a prevenir el agrietamiento del bloque de tejido durante la congelación rápida. Para una descripción más detallada del tejido congelado en OTC, consulte Kumar et al.13.</li>
	<li>Envuelva cada molde en papel de aluminio preetiquetado y colóquelo en una bolsa de congelador individual para evitar la deshidratación y guárdelo inmediatamente en hielo seco hasta que se transfiera para su almacenamiento en un congelador de -80 ° C.</li>
</ol>3. Hemilaringe criosectante en plano transversal
<ol><li>Ajuste la temperatura de la cámara en el criostato a -20 ° C, que se encuentra en el medio del rango de temperatura (15-25 ° C) recomendado para la sección del tejido muscular por el manual del fabricante.</li>
	<li>Ajuste el grosor de la sección del criostato a secciones de 10 μm de espesor. NOTA: Para el análisis transversal de fibras musculares, las secciones de 10 μm de espesor son óptimas para permitir una tinción completa y una intensidad de imagen robusta de las fibras musculares marcadas para el análisis de tipificación de fibras14,15,16. Algunos protocolos pueden requerir diferentes grosores de sección dependiendo de los objetivos neuromusculares.</li>
	<li>Transfiera los tejidos a la cámara de criostato, agregue una capa uniforme de compuesto de OCT en el disco de muestra de criostato (chuck) y coloque el bloque de tejido incrustado encima del compuesto de OCT en el disco de muestra. Para obtener secciones transversales de la cuerda vocal para el análisis de la fibra muscular tiroaritenoide (TA), coloque la muestra en el mandril de modo que el cartílago tiroideo ventral se enfrente a la hoja del criostato y el cartílago aritenoide se enfrente al disco de la muestra. NOTA: Es fundamental tener en cuenta que estos puntos de referencia no son visibles en esta etapa, debido a que el compuesto OCT se vuelve blanco y opaco cuando se congela. Esta falta de visibilidad es la razón por la que es fundamental tener en cuenta la orientación de la hemilinge durante la etapa de congelación del flash.</li>
	<li>Recorte el compuesto oct haciendo avanzar la cabeza de la muestra en 100 μm hasta que aparezca la porción ventral del cartílago tiroideo.</li>
	<li>Luego recorte y rastree secciones de 30 μm desde el inicio del cartílago tiroideo hasta que se expongan la lámina propia, los músculos medial TA y el músculo TA lateral. NOTA: Los puntos de referencia laríngeos deben rastrearse y anotarse desde el inicio del cartílago tiroideo cada 100 μm para garantizar que el ángulo de seccionamiento no sea oblicuo. La Figura 2 representa los dos conjuntos de puntos de referencia laríngeos en el plano de la sección transversal con un aumento de 10x.</li>
	<li>Una vez que se alcanza el músculo TA objetivo, recoja secciones en diapositivas cargadas positivamente a 10 μm.</li>
	<li>Guarde las secciones en PBS a 4 °C para retener la humedad hasta que estén listas para teñirse. NOTA: El tejido fijo se puede almacenar en PBS hasta una semana dependiendo del objetivo de IHC, mientras que el tejido no fijo debe procesarse de inmediato.</li>
</ol>4. Criosectación hemilaríngea en plano longitudinal
<ol><li>Con la cámara de criostato nuevamente ajustada a -20 °C, cambie el grosor de la sección a 30 μm. NOTA: Para el análisis de NMJ, se puede utilizar un espesor tisular entre 30-60 μm para capturar varios NMJ completos dentro de los músculos laríngeos sin fragmentación de la terminal nerviosa o la placa terminal motora11,12,17.</li>
	<li>Para obtener secciones longitudinales de las cuerdas vocales para el análisis NMJ del músculo TA, fije las muestras al mandril de modo que la epiglotis esté orientada hacia la hoja del criostato y la luz traqueal mire hacia abajo hacia el disco de la muestra.</li>
	<li>Recorte el compuesto oct haciendo avanzar la cabeza de la muestra en 100 μm hasta que aparezca el cartílago tiroideo.</li>
	<li>Recorte y rastree secciones de 30 μm desde el inicio de la tiroides hasta que la lámina propia y las divisiones medial y lateral del músculo TA estén expuestas. NOTA: Se recomiendan cinco conjuntos de puntos de referencia laríngeos en el plano longitudinal para rastrear la progresión de la profundidad del tejido hacia el músculo TA objetivo. La Figura 3 representa los puntos de referencia laríngeos en el plano longitudinal a un aumento de 10x.</li>
	<li>Una vez que se alcanza el músculo TA objetivo, recoja secciones en diapositivas cargadas positivamente a 30 μm.</li>
	<li>Guarde las secciones en PBS a 4 °C para retener la humedad hasta que estén listas para teñirse.</li>
</ol>

<ol>
	<li>Connor, N. P., Suzuki, T., Lee, K., Sewall, G. K., Heisey, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuromuscular+junction+changes+in+aged+rat+thyroarytenoid+muscle.">Neuromuscular junction changes in aged rat thyroarytenoid muscle.</a> Annals of Otology, Rhinology and Laryngology. 111 (7), 579-586 (2002).</li><li>Suzuki, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Age-Related+Alterations+in+Myosin+Heavy+Chaing+Isoforms+in+Rat+Intrinsic+Laryngeal+Muscles.">Age-Related Alterations in Myosin Heavy Chaing Isoforms in Rat Intrinsic Laryngeal Muscles.</a> Annals of Otology, Rhinology and Laryngology. 111 (11), 962 (2002).</li><li>Johnson, A. M., Grant, L. M., Schallert, T., Ciucci, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+Rat+50-kHz+Ultrasonic+Vocalizations+During+Dopamine+Denervation+and+Aging:+Relevance+to+Neurodegeneration.">Changes in Rat 50-kHz Ultrasonic Vocalizations During Dopamine Denervation and Aging: Relevance to Neurodegeneration.</a> Current Neuropharmacology. 13 (2), 211-219 (2015).</li><li>Wright, J. M., Gourdon, J. C., Clarke, P. 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R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduction+of+dopamine+synaptic+activity:+degradation+of+50-kHz+ultrasonic+vocalization+in+rats.">Reduction of dopamine synaptic activity: degradation of 50-kHz ultrasonic vocalization in rats.</a> Behavioral Neuroscience. 123 (2), 328-336 (2009).</li><li>Ciucci, M. R., Vinney, L., Wahoske, E. J., Connor, N. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+translational+approach+to+vocalization+deficits+and+neural+recovery+after+behavioral+treatment+in+Parkinson+disease.">A translational approach to vocalization deficits and neural recovery after behavioral treatment in Parkinson disease.</a> Journal of Communication Disorders. 43 (4), 319-326 (2010).</li><li>Nagai, H., Ota, F., Konopacki, R., Connor, N. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Discoordination+of+laryngeal+and+respiratory+movements+in+aged+rats.">Discoordination of laryngeal and respiratory movements in aged rats.</a> American Journal of Otolaryngology. 26 (6), 377-382 (2005).</li><li>Ma, S. T., Maier, E. Y., Ahrens, A. M., Schallert, T., Duvauchelle, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Repeated+intravenous+cocaine+experience:+development+and+escalation+of+pre-drug+anticipatory+50-kHz+ultrasonic+vocalizations+in+rats.">Repeated intravenous cocaine experience: development and escalation of pre-drug anticipatory 50-kHz ultrasonic vocalizations in rats.</a> Behavioural Brain Research. 212 (1), 109-114 (2010).</li><li>Inagi, K., Schultz, E., Ford, C. 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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laryngeal+Neuromuscular+Response+to+Short-+and+Long-Term+Vocalization+Training+in+Young+Male+Rats.">Laryngeal Neuromuscular Response to Short- and Long-Term Vocalization Training in Young Male Rats.</a> Journal of Speech, Language, and Hearing Research. 62 (2), 247-256 (2019).</li><li>Kumar, A., Accorsi, A., Rhee, Y., Girgenrath, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Do's+and+don'ts+in+the+preparation+of+muscle+cryosections+for+histological+analysis.">Do's and don'ts in the preparation of muscle cryosections for histological analysis.</a> Journal of Visualized Experiments. (99), e52793 (2015).</li><li>McMullen, C. A., Andrade, F. 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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sexual+dimorphism+in+laryngeal+muscle+fibers+and+ultrasonic+vocalizations+in+the+adult+rat.">Sexual dimorphism in laryngeal muscle fibers and ultrasonic vocalizations in the adult rat.</a> Laryngoscope. 127 (8), 270-276 (2017).</li><li>Johnson, A. M., Ciucci, M. R., Connor, N. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vocal+training+mitigates+age-related+changes+within+the+vocal+mechanism+in+old+rats.">Vocal training mitigates age-related changes within the vocal mechanism in old rats.</a> Journals of Gerontology. Series A: Biological Sciences and Medical Sciences. 68 (12), 1458-1468 (2013).</li><li>Feng, X., Zhang, T., Ralston, E., Ludlow, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differences+in+neuromuscular+junctions+of+laryngeal+and+limb+muscles+in+rats.">Differences in neuromuscular junctions of laryngeal and limb muscles in rats.</a> Laryngoscope. 122 (5), 1093-1098 (2012).</li></ol>

Los autores no tienen nada que revelar.

La preparación de las cuerdas vocales de las ratas para el análisis neuromuscular puede presentar varios desafíos. Los músculos laríngeos no solo son pequeños y están rodeados de cartílago, lo que dificulta la extracción directa del músculo objetivo, sino que también se encontró una alta variabilidad entre los animales en la profundidad de los puntos de referencia anatómicos laríngeos. Para el protocolo del plano de sección transversal muscular, las secciones completas de las cuerdas vocales aparecieron en...

La laringe de rata es un modelo bien establecido para investigar las adaptaciones laríngeas neuromusculares estructurales y funcionales al desarrollo, el envejecimiento, la enfermedad y los agentes farmacológicos1,2,3,4,5. La consistencia de los métodos histológicos es fundamental para esta línea de trabajo, ya que existen múltiples complejidades involucradas en la preparación y el análisis muscular, así como desafíos asociados con el tamaño, la forma y la topografía de la laringe de los músculos encapsulados dentro de los cartílagos laríngeos1,6,7,8,9,10,11 . Debido al pequeño tamaño de los músculos laríngeos intrínsecos de la rata, la incrustación sistemática, la congelación y la crioseccionación son fundamentales para lograr resultados consistentes y precisos. Por ejemplo, al seccionar la cuerda vocal de la rata en el plano coronal, las uniones neuromusculares (NMJ) de cuatro de los músculos laríngeos intrínsecos se encuentran a menos de 1,8 mm de profundidad tisular11. Por lo tanto, el monitoreo preciso de la anatomía del músculo laríngeo durante la criosecciona es imperativo para identificar con precisión la (s) sección (s) de interés y evitar la sobreseccionamiento del tejido. La sobresección del músculo objetivo puede dar lugar a una identificación inexacta del número y la topografía de nmJs11 o puede dar lugar a reducciones generales en el tamaño de la muestra si el músculo objetivo se descarta debido a la confusión de orientación de punto de referencia12. A medida que se desarrollan nuevos modelos para el estudio del músculo laríngeo y sus respectivas adaptaciones, los procedimientos operativos estándar son esenciales para garantizar que los resultados sean precisos, confiables y reproducibles en todos los estudios.
El objetivo de este artículo es detallar la preparación de la cuerda vocal de la rata para un análisis longitudinal y transversal óptimo. Se describen métodos detallados utilizados regularmente en nuestro laboratorio para identificar puntos de referencia musculares objetivo durante la crioseccionación. Aunque se utilizan métodos similares en varios laboratorios, aquí se proporciona un mayor detalle que en la literatura para garantizar una replicación confiable y precisa cuando es implementada por investigadores novatos. El objetivo de este tutorial es proporcionar una metodología estándar para la evaluación inmunohistoquímica (IHC) de la cuerda vocal de la rata para mejorar la consistencia en los laboratorios e investigaciones.

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			<td>Timer</td>
			<td>Fisherbrand</td>
			<td>2261840</td>
			<td></td>
		</tr>
		<tr>
			<td>Vannas Pattern Scissors</td>
			<td>Assi</td>
			<td>ASSI.SAS15RV</td>
			<td></td>
		</tr>
		<tr>
			<td colspan="4">NOTE: For all supplies, these are examples of equipment to purchase. The exact model is not necessary to complete our methods.</td>
		</tr>
	</tbody>
</table>

preparation of the rat vocal fold for neuromuscular analyses

El propósito de este tutorial es describir la preparación de la cuerda vocal de la rata para el estudio neuromuscular histoquímico. Este protocolo describe los procedimientos para la disección laríngea de ratas, la congelación por flash y la crioseccionación de las cuerdas vocales. Este estudio describe cómo crioseccionar las cuerdas vocales tanto en planos longitudinales como transversales. Una novedad de este protocolo es el seguimiento laríngeo durante la crioseccionación que garantiza la identificación precisa de los músculos laríngeos intrínsecos y reduce la posibilidad de pérdida de tejido. Las cifras demuestran la crioseccionación progresiva en ambos planos. Veintinueve hemi-laringes de rata fueron crioseccionados y rastreados desde la aparición del cartílago tiroideo hasta la aparición de la primera sección que incluía el pliegue vocal completo. La cuerda vocal completa se visualizó para todos los animales en ambos planos. Hubo una alta variabilidad en la distancia desde la aparición del cartílago tiroideo hasta la aparición de la cuerda vocal completa en ambos planos. El peso no se correlacionó con la profundidad de los puntos de referencia laríngeos, lo que sugiere que la variabilidad individual y otros factores relacionados con la preparación del tejido pueden ser responsables de la alta variabilidad en la aparición de puntos de referencia durante la sección. Este estudio detalla una metodología y presenta datos morfológicos para la preparación de la cuerda vocal de la rata para la investigación neuromuscular histoquímica. Debido a la alta variabilidad individual, los puntos de referencia laríngeos deben rastrearse de cerca durante la criosecciona para evitar la sobresección del tejido y la pérdida de tejido. El uso de una metodología consistente, incluida la preparación adecuada del tejido y el conocimiento de los puntos de referencia dentro de la laringe de la rata, ayudará con resultados consistentes en todos los estudios y ayudará a los nuevos investigadores interesados en usar el pliegue vocal de la rata como modelo para investigar los mecanismos neuromusculares laríngeos.

Los resultados representativos fueron parte de una investigación en curso de los efectos del ejercicio vocal en el sistema neuromuscular laríngeo. Veintinueve machos de ratas Fischer 344/brown Norway (12 de 9 meses de edad, 17 de 24 meses de edad) fueron pesadas y sacrificadas con inhalación de CO2 seguida de una toracotomía bilateral.
Los procedimientos siguieron el protocolo descrito para etiquetar nmj y el tamaño de la fibra de los músculos LATERALES y mediales de la AT. La...

Watch this Scientific Journal Video about Preparation of the Rat Vocal Fold for Neuromuscular Analyses at JoVE.com

Preparation of the Rat Vocal Fold for Neuromuscular Analyses

Este protocolo describe los métodos utilizados para preparar las cuerdas vocales de las ratas para el estudio neuromuscular histoquímico.

Preparación de la cuerda vocal de la rata para análisis neuromusculares

The purpose of this tutorial is to describe the preparation of the rat vocal fold for histochemical neuromuscular study. This protocol outlines procedures ...

preparation-of-the-rat-vocal-fold-for-neuromuscular-analyses

Research

JoVE Journal

Neuroscience

2.6K vistas.  New York University School of Medicine. Este protocolo describe los métodos utilizados para preparar las cuerdas vocales de las ratas para el estudio neuromuscular histoquímico.

Video: Preparation of the Rat Vocal Fold for Neuromuscular Analyses

Morphometric Analyses of Retinal Sections

Morphometric analyses of retinal sections have been used in examining retinal diseases. For examples, neuronal cells were significantly lost in the retinal ganglion cell layer (RGCL) in rat models with N-methyl-D-aspartate (NMDA)&#x2013;induced excitotoxicity1, retinal ischemia-reperfusion injury2 and glaucoma3. Reduction of INL and inner plexiform layer (IPL) thicknesses were reversed with citicoline treatment in rats' eyes subjected to kainic acid-mediated glutamate excitotoxicity4. Alteration of RGC density and soma sizes were observed with different drug treatments in eyes with elevated intraocular pressure3,5,6. Therefore, having objective methods of analyzing the retinal morphometries may be of great significance in evaluating retinal pathologies and the effectiveness of therapeutic strategies.
The retinal structure is multi-layers and several different kinds of neurons exist in the retina. The morphometric parameters of retina such as cell number, cell size and thickness of different layers are more complex than the cell culture system. Early on, these parameters can be detected using other commercial imaging software. The values are normally of relative value, and changing to the precise value may need further accurate calculation. Also, the tracing of the cell size and morphology may not be accurate and sensitive enough for statistic analysis, especially in the chronic glaucoma model. The measurements used in this protocol provided a more precise and easy way. And the absolute length of the line and size of the cell can be reported directly and easy to be copied to other files. For example, we traced the margin of the inner and outer most nuclei in the INL and formed a line then using the software to draw a 90 degree angle to measure the thickness. While without the help of the software, the line maybe oblique and the changing of retinal thickness may not be repeatable among individual observers. In addition, the number and density of RGCs can also be quantified. This protocol successfully decreases the variability in quantitating features of the retina, increases the sensitivity in detecting minimal changes.
 	This video will demonstrate three types of morphometric analyses of the retinal sections. They include measuring the INL thickness, quantifying the number of RGCs and measuring the sizes of RGCs in absolute value. These three analyses are carried out with Stereo Investigator (MBF Bioscience &mdash; MicroBrightField, Inc.). The technique can offer a simple but scientific platform for morphometric analyses.

This video demonstrates three types of morphometric analyses of the retina, which include measuring the inner nuclear layer thickness, quantifying the number of retinal ganglion cells (RGCs) and measuring the sizes of RGCs. The technique can offer a simple but scientific platform for morphometric analyses.

Los análisis morfométricos de las Secciones de retina

Morphometric analyses of retinal sections have been used in examining retinal diseases. For examples, neuronal cells were significantly lost in the ...

Investigación

Neurociencias

Sequential Photo-bleaching to Delineate Single Schwann Cells at the Neuromuscular Junction

Sequential photo-bleaching provides a non-invasive way to label individual SCs at the NMJ. The NMJ is the largest synapse of the mammalian nervous system and has served as guiding model to study synaptic structure and function. In mouse NMJs motor axon terminals form pretzel-like contact sites with muscle fibers. The motor axon and its terminal are sheathed by SCs. Over the past decades, several transgenic mice have been generated to visualize motor neurons and SCs, for example Thy1-XFP1 and Plp-GFP mice2, respectively.
Along motor axons, myelinating axonal SCs are arranged in non-overlapping internodes, separated by nodes of Ranvier, to enable saltatory action potential propagation. In contrast, terminal SCs at the synapse are specialized glial cells, which monitor and promote neurotransmission, digest debris and guide regenerating axons. NMJs are tightly covered by up to half a dozen non-myelinating terminal SCs - these, however, cannot be individually resolved by light microscopy, as they are in direct membrane contact3.
Several approaches exist to individually visualize terminal SCs. None of these are flawless, though. For instance, dye filling, where single cells are impaled with a dye-filled microelectrode, requires destroying a labelled cell before filling a second one. This is not compatible with subsequent time-lapse recordings3. Multi-spectral "Brainbow" labeling of SCs has been achieved by using combinatorial expression of fluorescent proteins4. However, this technique requires combining several transgenes and is limited by the expression pattern of the promoters used. In the future, expression of "photo-switchable" proteins in SCs might be yet another alternative5. Here we present sequential photo-bleaching, where single cells are bleached, and their image obtained by subtraction. We believe that this approach - due to its ease and versatility - represents a lasting addition to the neuroscientist's technology palette, especially as it can be used in vivo and transferred to others cell types, anatomical sites or species6.
In the following protocol, we detail the application of sequential bleaching and subsequent confocal time-lapse microscopy to terminal SCs in triangularis sterni muscle explants. This thin, superficial and easily dissected nerve-muscle preparation7,8 has proven useful for studies of NMJ development, physiology and pathology9. Finally, we explain how the triangularis sterni muscle is prepared after fixation to perform correlated high-resolution confocal imaging, immunohistochemistry or ultrastructural examinations.

Visualizing individual cells in densely packed tissues, such as terminal Schwann cells (SCs) at neuromuscular junctions (NMJs), is challenging. "Sequential photo-bleaching" allows delineating single terminal SCs, for instance in the triangularis sterni muscle explant, a convenient nerve-muscle preparation, where sequential bleaching can be combined with time-lapse imaging and post-hoc immunostainings.

Secuencial Foto-blanqueamiento para Precisar las células individuales de Schwann en la unión neuromuscular

Sequential photo-bleaching provides a non-invasive way to label individual SCs at the NMJ. The NMJ is the largest synapse of the mammalian nervous system ...

Dissection of the Transversus Abdominis Muscle for Whole-mount Neuromuscular Junction Analysis

Analysis of neuromuscular junction morphology can give important insight into the physiological status of a given motor neuron. Analysis of thin flat muscles can offer significant advantage over traditionally used thicker muscles, such as those from the hind limb (e.g. gastrocnemius). Thin muscles allow for comprehensive overview of the entire innervation pattern for a given muscle, which in turn permits identification of selectively vulnerable pools of motor neurons. These muscles also allow analysis of parameters such as motor unit size, axonal branching, and terminal/nodal sprouting. A common obstacle in using such muscles is gaining the technical expertise to dissect them. In this video, we detail the protocol for dissecting the transversus abdominis (TVA) muscle from young mice and performing immunofluorescence to visualize axons and neuromuscular junctions (NMJs). We demonstrate that this technique gives a complete overview of the innervation pattern of the TVA muscle&#160;and can be used to investigate NMJ pathology in a mouse model of the childhood motor neuron disease, spinal muscular atrophy.

Dissection of the Transversus Abdominis Muscle for Whole-mount Neuromuscular Junction Analysis

In this video we demonstrate a protocol for dissection of the transversus abdominis muscle of the mouse and use immunofluorescence and microscopy to visualize neuromuscular junctions.

Disección Del Músculo Transverso Abdominis Para El Análisis De La Unión Neuromuscular De Montaje Completo

Analysis of neuromuscular junction morphology can give important insight into the physiological status of a given motor neuron. Analysis of thin flat ...

Why Quantification Matters: Characterization of Phenotypes at the Drosophila Larval Neuromuscular Junction

Most studies on morphogenesis rely on qualitative descriptions of how anatomical traits are affected by the disruption of specific genes and genetic pathways. Quantitative descriptions are rarely performed, although genetic manipulations produce a range of phenotypic effects and variations are observed even among individuals within control groups.&#160;Emerging evidence shows that morphology, size and location of organelles play a previously underappreciated, yet fundamental role in cell function and survival. Here we provide step-by-step instructions for performing quantitative analyses of phenotypes at the Drosophila larval neuromuscular junction (NMJ). We use several reliable immuno-histochemical markers combined with bio-imaging techniques and morphometric analyses to examine the effects of genetic mutations on specific cellular processes. In particular, we focus on the quantitative analysis of phenotypes affecting morphology, size and position of nuclei within the striated muscles of Drosophila larvae. The Drosophila larval NMJ is a valuable experimental model to investigate the molecular mechanisms underlying the structure and the function of the neuromuscular system, both in health and disease. However, the methodologies we describe here can be extended to other systems as well.

Why Quantification Matters: Characterization of Phenotypes at the Drosophila Larval Neuromuscular Junction

Morphology, size and location of intracellular organelles are evolutionarily conserved and appear to directly affect their function. Understanding the molecular mechanisms underlying these processes has become an important goal of modern biology. Here we show how these studies can be facilitated by the application of quantitative techniques.

¿Por qué importa la cuantificación: Caracterización de fenotipos en el<em&gt; Drosophila</em&gt; Larval unión neuromuscular

Most studies on morphogenesis rely on qualitative descriptions of how anatomical traits are affected by the disruption of specific genes and genetic ...

Microstate and Omega Complexity Analyses of the Resting-state Electroencephalography

Microstate and omega complexity are two reference-free electroencephalography (EEG) measures that can represent the temporal and spatial complexities of EEG data and have been widely used to investigate the neural mechanisms in some brain disorders. The goal of this article is to describe the protocol underlying EEG microstate and omega complexity analyses step by step. The main advantage of these two measures is that they could eliminate the reference-dependent problem inherent to traditional spectrum analysis. In addition, microstate analysis makes good use of high time resolution of resting-state EEG, and the four obtained microstate classes could match the corresponding resting-state networks respectively. The omega complexity characterizes the spatial complexity of the whole brain or specific brain regions, which has obvious advantage compared with traditional complexity measures focusing on the signal complexity in a single channel. These two EEG measures could complement each other to investigate the brain complexity from the temporal and spatial domain respectively.

This article describes the protocol underlying electroencephalography (EEG) microstate analysis and omega complexity analysis, which are two reference-free EEG measures and highly valuable to explore the neural mechanisms of brain disorders.

Según los Estados y análisis de complejidad de Omega de la electroencefalografía de estado descansando

Microstate and omega complexity are two reference-free electroencephalography (EEG) measures that can represent the temporal and spatial complexities of ...

Levator Auris Longus Preparation for Examination of Mammalian Neuromuscular Transmission Under Voltage Clamp Conditions

This protocol describes a technique to record synaptic transmission from the neuromuscular junction under current-clamp and voltage-clamp conditions. An ex vivo preparation of the levator auris longus (LAL) is used because it is a thin muscle that provides easy visualization of the neuromuscular junction for microelectrode impalement at the motor endplate. This method allows for the recording of spontaneous miniature endplate potentials and currents (mEPPs and mEPCs), nerve-evoked endplate potentials and currents (EPPs and EPCs), as well as the membrane properties of the motor endplate. Results obtained from this method include the quantal content (QC), number of vesicle release sites (n), probability of vesicle release (prel), synaptic facilitation and depression, as well as the muscle membrane time constant (&#964;m) and input resistance. Application of this technique to mouse models of human disease can highlight key pathologies in disease states and help identify novel treatment strategies. By fully voltage-clamping a single synapse, this method provides one of the most detailed analyses of synaptic transmission currently available.

Levator Auris Longus Preparation for Examination of Mammalian Neuromuscular Transmission Under Voltage Clamp Conditions

The protocol described in this paper uses the mouse levator auris longus (LAL) muscle to record spontaneous and nerve-evoked postsynaptic potentials (current-clamp) and currents (voltage-clamp) at the neuromuscular junction. Use of this technique can provide key insights into mechanisms of synaptic transmission under normal and disease conditions.

Del levator Auris Longus Preparación para examen de la transmisión Neuromuscular mamífero bajo condiciones de fijación de voltaje

This protocol describes a technique to record synaptic transmission from the neuromuscular junction under current-clamp and voltage-clamp conditions. An ...

Dissection of Single Skeletal Muscle Fibers for Immunofluorescent and Morphometric Analyses of Whole-Mount Neuromuscular Junctions

The neuromuscular junction (NMJ) is a specialized point of contact between the motor nerve and the skeletal muscle. This peripheral synapse exhibits high morphological and functional plasticity. In numerous nervous system disorders, NMJ is an early pathological target resulting in neurotransmission failure, weakness, atrophy, and even in muscle fiber death. Due to its relevance, the possibility to quantitatively assess certain aspects of the relationship between NMJ components can help to understand the processes associated with its assembly/disassembly. The first obstacle when working with muscles is to gain the technical expertise to quickly identify and dissect without damaging their fibers. The second challenge is to utilize high-quality detection methods to obtain NMJ images that can be used to perform quantitative analysis. This article presents a step-by-step protocol for dissecting extensor digitorum longus and soleus muscles from rats. It also explains the use of immunofluorescence to visualize pre and postsynaptic elements of whole-mount NMJs. Results obtained demonstrate that this technique can be used to establish the microscopic anatomy of the synapsis and identify subtle changes in the status of some of its components under physiological or pathological conditions.

The ability to accurately detect neuromuscular junction components is crucial in evaluating modifications in its architecture because of pathological or developmental processes. Here we present a complete description of a straightforward method to obtain high-quality images of whole-mount neuromuscular junctions that can be used to perform quantitative measurements.

Disección De Fibras Musculares Esqueléticas Individuales Para Análisis Inmunofluorescentes Y Morfométricos De Las Uniones Neuromusculares De Montaje Completo

The neuromuscular junction (NMJ) is a specialized point of contact between the motor nerve and the skeletal muscle. This peripheral synapse exhibits high ...

Expanding the Toolkit for In Vivo Imaging of Axonal Transport

Axonal transport maintains neuronal homeostasis by enabling the bidirectional trafficking of diverse organelles and cargoes. Disruptions in axonal transport have devastating consequences for individual neurons and their networks, and contribute to a plethora of neurological disorders. As many of these conditions involve both cell autonomous and non-autonomous mechanisms, and often display a spectrum of pathology across neuronal subtypes, methods to accurately identify and analyze neuronal subsets are imperative.
This paper details protocols to assess in vivo axonal transport of signaling endosomes and mitochondria in sciatic nerves of anesthetized mice. Stepwise instructions are provided to 1) distinguish motor from sensory neurons in vivo, in situ, and ex vivo by using mice that selectively express fluorescent proteins within cholinergic motor neurons; and 2) separately or concurrently assess in vivo axonal transport of signaling endosomes and mitochondria. These complementary intravital approaches facilitate the simultaneous imaging of different cargoes in distinct peripheral nerve axons to quantitatively monitor axonal transport in health and disease.

Expanding the Toolkit for In Vivo Imaging of Axonal Transport

Using transgenic fluorescent mice, detailed protocols are described to assess in vivo axonal transport of signaling endosomes and mitochondria within motor and sensory axons of the intact sciatic nerve in live animals.

Ampliación del kit de herramientas para imágenes in vivo del transporte axonal

Axonal transport maintains neuronal homeostasis by enabling the bidirectional trafficking of diverse organelles and cargoes. Disruptions in axonal ...

Preparation of Rat Sciatic Nerve for Ex Vivo Neurophysiology

Ex vivo preparations enable the study of many neurophysiological processes in isolation from the rest of the body while preserving local tissue structure. This work describes the preparation of rat sciatic nerves for ex vivo neurophysiology, including buffer preparation, animal procedures, equipment setup and neurophysiological recording. This work provides an overview of the different types of experiments possible with this method. The outlined method aims to provide 6 h of stimulation and recording on extracted peripheral nerve tissue in tightly controlled conditions for optimal consistency in results. Results obtained using this method are A-fibre compound action potentials (CAP) with peak-to-peak amplitudes in the millivolt range over the entire duration of the experiment. CAP amplitudes and shapes are consistent and reliable, making them useful to test and compare new electrodes to existing models, or the effects of interventions on the tissue, such as the use of chemicals, surgical alterations, or neuromodulatory stimulation techniques. Both conventional commercially available cuff electrodes with platinum-iridium contacts and custom-made conductive elastomer electrodes were tested and gave similar results in terms of nerve stimulus strength-duration response.

Preparation of Rat Sciatic Nerve for Ex Vivo Neurophysiology

This protocol describes the preparation of rat whole sciatic nerve tissue for ex vivo electrophysiological stimulation and recording in an environmentally-regulated, two-compartment, perfused saline bath.

Preparación del nervio ciático de rata para neurofisiología ex vivo

Ex vivo preparations enable the study of many neurophysiological processes in isolation from the rest of the body while preserving local tissue structure. ...

Visualizing the Morphological Characteristics of Neuromuscular Junction in Rat Medial Gastrocnemius Muscle

The neuromuscular junction (NMJ) is a complex structure serving for the signal communication from the motor neuron to the skeletal muscle and consists of three essential histological components: the pre-synaptic motor axon terminals, post-synaptic nicotinic acetylcholine receptors (AchRs), and peri-synaptic Schwann cells (PSCs). In order to demonstrate the morphological characteristics of NMJ, the rat medial gastrocnemius muscle was selected as the target-tissue and examined by using multiple fluorescent staining with various kinds of biomarkers, including neurofilament 200 (NF200) and vesicular acetylcholine transporter (VAChT) for the motor nerve fibers and their pre-synaptic terminals, alpha-bungarotoxin (&#945;-BTX) for the post-synaptic nicotinic AchRs, and S100 for the PSCs. In this study, staining was performed in two groups: in the first group, samples were stained with NF200, VAChT, and &#945;-BTX, and in the second group, samples were stained with NF200, &#945;-BTX, and S100. It was shown that both protocols can effectively demonstrate the detailed structure of NMJ. Using the confocal microscope, morphological characteristics of the pre-synaptic terminals, post-synaptic receptors, and PSC were seen, and their Z-stacks images were reconstructed in a three-dimensional pattern to further analyze the spatial correlation among the different labeling. From the perspective of methodology, these protocols provide a valuable reference for investigating the morphological characteristics of NMJ under physiological conditions, which may also be suitable to evaluate the pathological alteration of NMJ, such as peripheral nerve injury and regeneration.

The protocol shows a method to examine spatial correlation among the pre-synaptic terminals, post-synaptic receptors, and peri-synaptic Schwann cells in the rat medial gastrocnemius muscle using fluorescent immunohistochemistry with different biomarkers, namely, neurofilament 200, vesicular acetylcholine transporter, alpha-bungarotoxin, and S100.

Visualización de las características morfológicas de la unión neuromuscular en el músculo gastrocnemio medial de rata

The neuromuscular junction (NMJ) is a complex structure serving for the signal communication from the motor neuron to the skeletal muscle and consists of ...