Agradecemos a los Dres Karl-Heinz Krause y Vincent Jaquet ayuda y consejo para establecer estos protocolos, y también gracias a Christoph Bauer y Jérôme Bosset de la Plataforma Bioimaging del NCCR y el Dr. Navin Gopaldass por su apoyo técnico. La investigación es apoyada por una beca ProDoc de la Fundación Nacional de Ciencia de Suiza.

1. La visualización y valoración cualitativa de ROS producción en Fagosomas Las perlas recubiertas con OBG deben estar preparados de antemano. Los procedimientos de revestimiento cuentas y técnica de superposición de agar fueron adaptadas de referencias publicadas 5,14. <ol><li> Añadir 1 ml de suspensión de 3,0 micras perlas de sílice carboxilados (alrededor de 1,8 x 10 9 bolas) a un tubo de 1,5 ml, se lavan las perlas 3 veces con 1 ml de PBS por vuelta rápida y vórtex. </li><li> Resuspender las perlas en 1 ml de PBS que contenía 25 mg / ml de cianamida (para activar las perlas de sílice carboxilados unen covalentemente a premarcan BSA), incubar en una rueda durante 15 min. </li><li> Lave 3 veces con 1 ml de tampón de acoplamiento (0,1 M de borato de sodio, pH 8,0) por vuelta rápida (centrifugar a toda velocidad en una mini centrífuga de sobremesa durante 5 segundos o bien se centrifuga a 2000 × g durante 1 min en una centrífuga de mesa) y vortex para eliminar el exceso de cianamida. </li><li> Mezclar las perlas lavadas con 500 l de coupling tampón que contiene 1 mg de OxyBurst Green (OBG) H2HFF (dihidro-2 &#39;, 4,5,6,7,7&#39;-hexafluorofluorescein)-BSA, llenar el tubo con gas nitrógeno a partir de un estándar de gas-can antes de la limitación, y incubar en una rueda de 14 horas (durante la noche) a TA en la oscuridad. </li><li> Lavar las perlas 2X con 1 ml de tampón de enfriamiento (250 mM de glicina en PBS) para eliminar sin reaccionar OBG, y dos veces con tampón de acoplamiento para eliminar el tampón de enfriamiento rápido por vuelta rápida y agitación en vórtex. </li><li> Añadir 1 ml de tampón de acoplamiento que contienen 50 g de Alexa Fluor 594 éster de succinimidilo para conjugar a BSA. Llenar el tubo con nitrógeno antes de la limitación, e incubar en una rueda durante 1,5 horas a temperatura ambiente en la oscuridad. </li><li> Lave las perlas 3 veces con 1 ml de tampón de extinción por vuelta rápida y un vórtex para detener la reacción, después se lavan las perlas 3 veces con 1 ml de PBS por vuelta rápida y vórtex. </li><li> Finalmente, resuspender las perlas en 1 ml de PBS con 2 l de 10% w / v de azida para el almacenamiento a largo plazo. Mida la concentration de cuentas en la suspensión con un hemocitómetro (generalmente alrededor de 1-2 x 10 9 cuentas / ml), llenar el tubo con nitrógeno antes de la limitación, y se almacena a 4 ° C en la oscuridad. </li><li> La eficacia del recubrimiento de la fluoresceína OBG se puede probar mediante la comprobación del espectro de emisión usando excitación a 500 nm. Cuando se oxida por H 2 O 2 en la presencia de peroxidasa de rábano picante (HRP), la intensidad de fluorescencia de perlas oxidados, en el pico de emisión (538 nm), es 11-12x mayor que el de perlas recubiertas no oxidado. </li><li> Cosecha en crecimiento exponencial Dictyostelium células de una placa de Petri de 10 cm, la placa de diferentes densidades de células de 3 cm de platos con un plástico ópticamente transparente o con fondo de cristal, y crecer durante la noche. Elija los platos que son aproximadamente el 80% de confluencia para el experimento. Un protocolo detallado para el cultivo de células de Dictyostelium ha sido publicada 15. </li><li> Sustituya el medio de cultivo con medio LoFlo (medio LF), incubar2 horas antes del experimento con el fin de disminuir la autofluorescencia extracelular y intraendosomal del medio de cultivo HL5C. </li><li> En paralelo, derretir 10 ml de 1,5% de agar Bacto en medio LF, verter el agar en una superficie plana (es decir, una placa de vidrio de 10 cm x 10 cm) con el fin de formar una capa de agar sobre 1 mm de espesor, esperar a 10-15 min se solidifique. Cortar la capa de agar en 2 cm x 2 cm cuadrados y colocar en medio de LF para su uso posterior. </li><li> Mientras tanto, preparar el hilado de disco o ancho microscopio de campo, ajuste la temperatura de la cámara climática a 22 ° C y ajuste la configuración para este experimento. (Ver comentarios adicionales en la discusión). </li><li> Después de 2 horas de incubación, aspirar el medio de LF desde el plato de 3 cm, pero la monocapa de células todavía debería estar cubierta por una película fina de medio. Diluir las perlas recubiertas con 1,5 x 10 7 perlas / ml, y añadir 10 l en la capa de células. </li><li> Tome una hoja de agar cuadrado, drenar el exceso de líquido, pero mantener húmeda. Coloque cuidadosamente the cuadrada de agar en la parte superior de la capa de células. No mueva la plaza agar cuando se está tumbado en las células. La capa de agar se utiliza para aumentar el contacto entre los granos y las células, mejorando de este modo la absorción, y también comprime ligeramente las células, manteniéndolos mejor en el plano focal del objetivo. </li><li> Coloque la tapa sobre el plato, colóquelo en la platina del microscopio, y automáticamente tomar fotos en los canales rojo, verde y fase cada 1 min durante 2 horas o más. </li><li> Seleccione y centrarse en los eventos celulares que contienen todo el proceso de fagocitosis. Combinar los 3 canales optimizados y montar las imágenes en una película utilizando el software profesional de procesamiento de imágenes. Cuantificar intensidades de fluorescencia de cada uno de los granos seleccionados en los canales rojo y verde, y la proporción de verde / rojo reflejará la phagosomal dinámica de ROS producción de las células. </li></ol> 2. Cuantitativa y Medianas rendimiento Medición de la Producción intracelular superóxido <ol><li> Recoger oNE 80% plato confluente de Dictyostelium en 10 ml de medio HL5C. Centrifugar las células de Dictyostelium a 850 xg durante 5 min, con cuidado y exceso de medio completamente aspirado. Resuspender las células en tampón de SS6.4 [sorbitol 0,12 M en tampón de Sorensen (14,69 mM KH 2 PO 4 y 6,27 mM de Na 2 HPO 4), pH 6,4], contar las células y diluir hasta una densidad final de 6 x 10 6 células / ml (ver comentarios adicionales en la discusión). </li><li> Añadir 50 l de suspensión celular en cada pocillo de una placa de 96 pocillos no transparente blanco (ver comentarios adicionales en la discusión). </li><li> Diluir DHE de stock (30 mM en DMSO) 500 veces con SS6.4, pipeta de 50 l de DHE diluido en cada pocillo usando una pipeta multicanal si es necesario. La concentración final de DHE es 30 mM. La reacción se inicia inmediatamente. </li><li> Los estímulos o inhibidores se pueden añadir en este punto, o en otros puntos de tiempo de acuerdo a las necesidades específicas. </li><li> Utilice el punto de &quot;la lectura y # top final34; modo de un lector de microplacas de fluorescencia, con excitación de fluorescencia / emisión a 522 nm/605 nm, leer cada 2 min durante 1 h, medio batido de 5 seg / min, a 22 º C. </li></ol> 3. Cuantitativa y de alto rendimiento La medición de extracelular H 2 O 2 de producción <ol><li> Siga los mismos pasos que se describen en el punto 2.1 y 2.2. </li><li> Preparar HRP diluido añadiendo 5 l de HRP de valores (100 U / ml en agua destilada) en 10 ml de SS6.4, vórtice o invertir el tubo para mezclar bien y mantener en hielo para su uso posterior. La solución de HRP diluida es a 0,05 U / ml. </li><li> Preparar la mezcla de reacción AUR mediante la mezcla de la población de AUR (mM AUR 10 en DMSO) y la solución de HRP diluida en tampón de SS6.4 a las concentraciones finales de 6,25 mM, y 0,005 U / ml, respectivamente. Como un ejemplo, para preparar la mezcla de reacción para 40 reacciones, mezclar 1,600 l de SS6.4 con 400 l de HRP diluido y 2,5 l de solución madre de AUR. </li><li> Añadir 50 l de mezcla AURtura en cada pocillo usando una pipeta multicanal si es necesario. Ahora comienza la reacción. </li><li> Los estímulos o inhibidores se pueden añadir en este punto, o en otros puntos de tiempo de acuerdo a las necesidades específicas. </li><li> Utilice el punto de modo extremo &quot;top lectura&quot; de un lector de placas de micro fluorescencia, con la excitación de fluorescencia / emisión a 530 nm/590 nm, leer cada 2 min durante 1 hora, medio batido 5 s / min, a 22 º C. </li></ol>

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No hay conflictos de interés declarado.

En comparación con los métodos descritos anteriormente, el ensayo de OBG visualiza dinámicamente el proceso de phagosomal la generación de ROS en el nivel de células individuales, en lugar de medir una señal promedio de ROS de una población de células. Tales métodos población de promediación tienden a oscurecer la información crítica causada por la fagocitosis no sincrónico. Se adaptó con éxito los ensayos DHE y AUR a Dictyostelium y optimizado los protocolos. Lo más importante es que hemos esp...

Especies reactivas de oxígeno (ROS) están involucrados en una amplia variedad de procesos biológicos tales como la defensa del huésped, señalización, el desarrollo del tejido y la respuesta a la lesión, así como la hipertensión y el cáncer. La maquinaria de la oxidasa NADPH phagosomal bien estudiado se dedica a la generación de ROS rápida, conocida como la explosión oxidativa, para matar las bacterias ingeridas en los fagosomas neutrófilos &#39;1. Además, la fuga de electrones como un subproducto de la cadena respiratoria mitocondrial se pensaba que ser responsable sólo de una fuente no regulada de ROS. Sin embargo, recientemente, se identificó como un importante mecanismo para contribuir a la muerte intraphagosomal de bacterias en macrófagos de ratón 2. En los últimos años, la ameba sociales, Dictyostelium, se ha convertido en un modelo de gran alcance y popular para estudiar mecanismos celulares intrínsecas de la respuesta inmune innata. De hecho, Dictyostelium y fagocitos humanos comparten un sorprendente alto nivel de conservación en moleculamaquinarias r responsables de las bacterias de detección, inmersión y matando a 3,4. Los homólogos de proteínas y enzimas relacionadas con la producción o la desintoxicación de ROS, tales como NADPH oxidasas, catalasas, superóxido dismutasas, se pueden encontrar en humanos y Dictyostelium. A medida que la ameba mejor estudiado, Dictyostelium presenta varias ventajas únicas sobre modelo de sistema de los mamíferos. Crecen a temperatura ambiente sin la necesidad de CO 2, con un tiempo de duplicación de 8-10 horas. Se pueden mantener fácilmente como cultivos adherentes o de suspensión. Además, gracias a su genoma haploide totalmente secuenciado y anotado, y a la manipulación genética fácil, Dictyostelium se ha convertido en un muy atractivo organismo modelo experimental. En estudios anteriores, diversos derivados clorados y fluorados de fluoresceína (conocidos colectivamente como OxyBurst verde, OBG) que emite fluorescencia después de la oxidación por ROS, se han utilizado como un reportero de ROS. Est Cell-permeantderivados erified se utilizan para medir citoplasmática de ROS, mientras que o dextrano-derivados de células impermeable acoplados a proteínas se utilizan para medir extracelular ROS. En particular, perlas recubiertas con BSA OBG ya han sido utilizados para detectar la producción de ROS en células de mamífero phagosomal 5. Sin embargo, el enfoque basado en el lector de microplacas sólo puede dar una curva de generación de ROS promedio de una población de células. Con el presente protocolo, mediante el uso de Dictyostelium, un fagocito profesional, y condiciones experimentales optimizadas, obtenemos la fagocitosis estable y eficiente, sin conjugar cualquier opsonina sobre las perlas. DHE se ha utilizado en diversos sistemas modelo, como los neutrófilos y los macrófagos de mamíferos, para detectar la producción de ROS 6-9. Mientras tanto, existen algunas controversias acerca de la especificidad y sensibilidad del método de 8,10. Como una versión mejorada de Amplex Red, la intensidad de fluorescencia de AUR es menos sensible al pH, que lo hace más adecuado para medirROS en ambientes no neutrales o ligeramente ácidos. AUR se ha aplicado recientemente en varios sistemas de mamíferos 11,12, pero su uso en modelos no mamíferos, que muy a menudo requieren medios de crecimiento débilmente ácido, no se ha informado todavía. Además, no hay ningún protocolo publicado para medir cuantitativamente y dinámicamente la producción de ROS y la localización en la ameba social de Dictyostelium. El objetivo del conjunto de protocolos presentado es proporcionar una solución sencilla y versátil para controlar diversos ROS y su localización, y además dar una visión de los mecanismos celulares relacionados con el ROS. Para el ensayo de OBG, se utilizó la microscopía en vivo para supervisar todo el proceso de generación de ROS phagosomal después de la absorción de perlas revestidas de OBG por células de Dictyostelium, y nos proporcionó un nuevo enfoque para estudiar el mecanismo de la muerte intraphagosomal de bacterias. Hemos optimizado DHE y AUR ensayos de mediano rendimiento en Dictyostelium, para medir superóxido intracelularIDE y H extracelular 2 O 2 de producción, respectivamente, mediante el uso de LPS como un estimulador potente de ROS. Tenga en cuenta que el LPS se demostró recientemente para aumentar la actividad bactericida de Dictyostelium hacia bacterias fagocitadas 13. Además, el tratamiento con DEDTC y catalasa confirmó explícitamente que estos dos métodos de medir específicamente los diferentes tipos y localizaciones subcelulares de ROS en Dictyostelium. Por último, el ensayo de OBG se puede adaptar a cualquier célula fagocítica adherente, por opsonizantes aún más las perlas con ligandos para receptores de células fagocíticas animales. En principio, los ensayos DHE y AUR también puede ser ajustado para mediciones en cualquier celular adherente o no adherente en condiciones experimentales adecuadas.

<table border="1">
	<tbody>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>REAGENTS</td>
		</tr>
		<tr>
			<td>OxyBURST Green H2HFF BSA</td>
			<td>Invitrogen</td>
			<td>O-13291</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluor 594</td>
			<td>Invitrogen</td>
			<td>A-20004</td>
			<td></td>
		</tr>
		<tr>
			<td>Carboxylated silica beads</td>
			<td>Kisker Biotech</td>
			<td>PSi-3.0COOH</td>
			<td></td>
		</tr>
		<tr>
			<td>HL5C medium</td>
			<td>ForMedium</td>
			<td>HLC0102</td>
			<td></td>
		</tr>
		<tr>
			<td>LoFlo medium</td>
			<td>ForMedium</td>
			<td>LF1001</td>
			<td></td>
		</tr>
		<tr>
			<td>Bacto agar</td>
			<td>BD</td>
			<td>204010</td>
			<td></td>
		</tr>
		<tr>
			<td>Dihydroethidium</td>
			<td>Sigma</td>
			<td>37291-25MG</td>
			<td></td>
		</tr>
		<tr>
			<td>Amplex UltraRed</td>
			<td>Invitrogen</td>
			<td>A36006</td>
			<td></td>
		</tr>
		<tr>
			<td>Horseradish peroxidase</td>
			<td>Roche</td>
			<td>10108090001</td>
			<td></td>
		</tr>
		<tr>
			<td>Diethyldithiocarbamate (DEDTC)</td>
			<td>Sigma</td>
			<td>D3506-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Catalase</td>
			<td>Sigma</td>
			<td>C9322-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>Cyanamide</td>
			<td>Sigma</td>
			<td>187364-25G</td>
			<td></td>
		</tr>
		<tr>
			<td>Lipopolysaccharides</td>
			<td>Sigma</td>
			<td>L2630-25G</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>EQUIPMENT</td>
		</tr>
		<tr>
			<td>ibidi &#956;-Dish 35 mm, high</td>
			<td>ibidi</td>
			<td>81156</td>
			<td>Bottom made of optically clear plastic</td>
		</tr>
		<tr>
			<td>MatTek dish 35 mm</td>
			<td>MatTek corporation</td>
			<td>P35G-1.5-14-C</td>
			<td>Bottom made of a glass coverslip</td>
		</tr>
		<tr>
			<td>Scepter Cell Counter</td>
			<td>Merck Millipore</td>
			<td>PHCC00000</td>
			<td></td>
		</tr>
		<tr>
			<td>White 96 well plate</td>
			<td>Nunc</td>
			<td>236108</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>SORVALL</td>
			<td>Legend RT</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate reader</td>
			<td>BioTek</td>
			<td>Synergy Mx</td>
			<td></td>
		</tr>
	</tbody>
</table>

detecting, visualizing and quantitating the generation of reactive oxygen species in an amoeba model system

Especies reactivas de oxígeno (ROS) comprenden una gama de, moléculas que contienen oxígeno reactivas y de corta duración, que se interconvertir o eliminarse ya sea catalíticamente o espontáneamente dinámicamente. Debido a los cortos ciclos de vida de la mayoría de ROS y la diversidad de sus fuentes y localizaciones subcelulares, una imagen completa se puede obtener sólo por medio de mediciones cuidadosas usando una combinación de protocolos. A continuación, presentamos un conjunto de tres protocolos diferentes utilizando OxyBurst Green (OBG) recubierto con perlas, o dihydroethidium (DHE) y Amplex UltraRed (AUR), para controlar cualitativa y cuantitativamente diferentes ROS en fagocitos profesionales como Dictyostelium. Hemos optimizado los procedimientos de revestimiento cuentas y perlas revestidas de OBG usados ​​y microscopía en vivo para visualizar dinámicamente intraphagosomal la generación de ROS en el nivel de células individuales. Se identificaron lipopolisacárido (LPS) de E. coli como un potente estimulador de la generación de ROS en Dictyostelium. Además, Dtiempo real eveloped, ensayos de mediano rendimiento utilizando DHE y AUR para medir cuantitativamente superóxido intracelular y extracelular H 2 O 2 de producción, respectivamente.

La generación de ROS en los fagosomas se puede visualizar cualitativa y dinámicamente por microscopía (S1 del archivo). La fluorescencia roja emitida por Alexa Fluor 594-es insensible al pH y se mantiene constante en el medio ambiente phagosomal, mientras que la oxidación de OBG aumenta su fluorescencia en el canal verde. Los espectros de emisión de in vitro oxida y perlas recubiertas con OBG no oxidado se comparan en la Figura 1B, que muestra un aumento significativo de l...

Watch this Scientific Journal Video about Detecting, Visualizing and Quantitating the Generation of Reactive Oxygen Species in an Amoeba Model System at JoVE.com

Detecting, Visualizing and Quantitating the Generation of Reactive Oxygen Species in an Amoeba Model System

Se adaptó un conjunto de protocolos para la medición de especies reactivas de oxígeno (ROS) que se pueden aplicar en varios modelos celulares de ameba y de mamíferos para estudios cualitativos y cuantitativos.

La detección, la visualización y cuantificación de la generación de especies reactivas de oxígeno en un sistema modelo de la ameba

Reactive oxygen species (ROS) comprise a range of reactive and short-lived, oxygen-containing molecules, which are dynamically interconverted or ...

detecting-visualizing-quantitating-generation-reactive-oxygen-species

Research

JoVE Journal

Biology

16.0K vistas.  University of Geneva.  Se adaptó un conjunto de protocolos para la medición de especies reactivas de oxígeno (ROS) que se pueden aplicar en varios modelos celulares de ameba y de mamíferos para estudios cualitativos y cuantitativos. 

Video: Detecting, Visualizing and Quantitating the Generation of Reactive Oxygen Species in an Amoeba Model System

Visualizing the Beating Heart in Drosophila

The Drosophila heart has recently emerged as a good model system for examining the genetic, cellular, and molecular mechanisms underlying function in myogenic hearts. A key step in examining heart function in the fly is finding a way to access the heart in a manner that preserves its myogenic function while still allowing the beating heart organ to be observed and recorded. Two different methods for observing and recording the beating heart in both larva and adult Drosophila are described here. Our semi-intact preparation using adult flies allows clear visualization of the abdominal heart without interference from the pigmented cuticle and overlying fat bodies. To record larval heart beats it is necessary to immobilize the larva, which minimizes body wall movements thereby reducing heart movements that are not associated with myocardial contractions. Our methodologies produce stable adult and larval heart preparations that can beat for hours at rates of 1-3 Hz.

Visualizing the Beating Heart in Drosophila

Technique required for visualizing the beating heart in larval and adult Drosophila are presented. Each life stage requires a different methodology.

Visualizar el corazón latiendo en Drosophila</em

The Drosophila heart has recently emerged as a good model system for examining the genetic, cellular, and molecular mechanisms underlying function in ...

Investigación

Biología

Electron Spin Resonance Micro-imaging of Live Species for Oxygen Mapping

This protocol describes an electron spin resonance (ESR) micro-imaging method for three-dimensional mapping of oxygen levels in the immediate environment of live cells with micron-scale resolution1. Oxygen is one of the most important molecules in the cycle of life. It serves as the terminal electron acceptor of oxidative phosphorylation in the mitochondria and is used in the production of reactive oxygen species. Measurements of oxygen are important for the study of mitochondrial and metabolic functions, signaling pathways, effects of various stimuli, membrane permeability, and disease differentiation. Oxygen consumption is therefore an informative marker of cellular metabolism, which is broadly applicable to various biological systems from mitochondria to cells to whole organisms. Due to its importance, many methods have been developed for the measurements of oxygen in live systems. Current attempts to provide high-resolution oxygen imaging are based mainly on optical fluorescence and phosphorescence methods that fail to provide satisfactory results as they employ probes with high photo-toxicity and low oxygen sensitivity. ESR, which measures the signal from exogenous paramagnetic probes in the sample, is known to provide very accurate measurements of oxygen concentration. In a typical case, ESR measurements map the probe's lineshape broadening and/or relaxation-time shortening that are linked directly to the local oxygen concentration. (Oxygen is paramagnetic; therefore, when colliding with the exogenous paramagnetic probe, it shortness its relaxation times.) Traditionally, these types of experiments are carried out with low resolution, millimeter-scale ESR for small animals imaging. Here we show how ESR imaging can also be carried out in the micron-scale for the examination of small live samples. ESR micro-imaging is a relatively new methodology that enables the acquisition of spatially-resolved ESR signals with a resolution approaching 1 micron at room temperature2. The main aim of this protocol-paper is to show how this new method, along with newly developed oxygen-sensitive probes, can be applied to the mapping of oxygen levels in small live samples. A spatial resolution of ~30 x 30 x 100 &mu;m is demonstrated, with near-micromolar oxygen concentration sensitivity and sub-femtomole absolute oxygen sensitivity per voxel. The use of ESR micro-imaging for oxygen mapping near cells complements the currently available techniques based on micro-electrodes or fluorescence/phosphorescence. Furthermore, with the proper paramagnetic probe, it will also be readily applicable for intracellular oxygen micro-imaging, a capability which other methods find very difficult to achieve.

This protocol describes a method for micron-scale three-dimensional imaging of oxygen concentration in the immediate environment of live cells by electron spin resonance microscopy.

Resonancia de spin electrónico micro imágenes en vivo de las especies para la asignación de oxígeno

This protocol describes an electron spin resonance (ESR) micro-imaging method for three-dimensional mapping of oxygen levels in the immediate environment ...

Do-It-Yourself Device for Recovery of Cryopreserved Samples Accidentally Dropped into Cryogenic Storage Tanks

Liquid nitrogen is colorless, odorless, extremely cold (-196 &deg;C) liquid kept under pressure. It is commonly used as a cryogenic fluid for long term storage of biological materials such as blood, cells and tissues 1,2. The cryogenic nature of liquid nitrogen, while ideal for sample preservation, can cause rapid freezing of live tissues on contact - known as 'cryogenic burn'2, which may lead to severe frostbite in persons closely involved in storage and retrieval of samples from Dewars. Additionally, as liquid nitrogen evaporates it reduces the oxygen concentration in the air and might cause asphyxia, especially in confined spaces2.
In laboratories, biological samples are often stored in cryovials or cryoboxes stacked in stainless steel racks within the Dewar tanks1. These storage racks are provided with a long shaft to prevent boxes from slipping out from the racks and into the bottom of Dewars during routine handling. All too often, however, boxes or vials with precious samples slip out and sink to the bottom of liquid nitrogen filled tank. In such cases, samples could be tediously retrieved after transferring the liquid nitrogen into a spare container or discarding it. The boxes and vials can then be relatively safely recovered from emptied Dewar. However, the cryogenic nature of liquid nitrogen and its expansion rate makes sunken sample retrieval hazardous. It is commonly recommended by Safety Offices that sample retrieval be never carried out by a single person. Another alternative is to use commercially available cool grabbers or tongs to pull out the vials3. However, limited visibility within the dark liquid filled Dewars poses a major limitation in their use.
In this article, we describe the construction of a Cryotolerant DIY retrieval device, which makes sample retrieval from Dewar containing cryogenic fluids both safe and easy.

Here we present a low cost, durable cryotolerant device for sample retrieval from Dewar tanks filled with liquid nitrogen. The ease of construction and modular design of the device makes the process of sample retrieval from cryogenic tanks safe and easy.

Do-It-Yourself de dispositivos para la recuperación de las muestras criopreservadas de caída accidental en los tanques de almacenamiento criogénicos

Liquid nitrogen is colorless, odorless, extremely cold (-196 &deg;C) liquid kept under pressure. It is commonly used as a cryogenic fluid for long term ...

Generation, Purification, and Characterization of Cell-invasive DISC1 Protein Species

Protein aggregation is seen as a general hallmark of chronic, degenerative brain conditions like, for example, in the neurodegenerative diseases Alzheimer's disease (A&beta;, tau), Parkinson's Disease (&alpha;-synuclein), Huntington's disease (polyglutamine, huntingtin), and others. Protein aggregation is thought to occur due to disturbed proteostasis, i.e. the imbalance between the arising and degradation of misfolded proteins. Of note, the same proteins are found aggregated in sporadic forms of these diseases that are mutant in rare variants of familial forms.
Schizophrenia is a chronic progressive brain condition that in many cases goes along with a permanent and irreversible cognitive deficit. In a candidate gene approach, we investigated whether Disrupted-in-schizophrenia 1 (DISC1), a gene cloned in a Scottish family with linkage to chronic mental disease1, 2, could be found as insoluble aggregates in the brain of sporadic cases of schizophrenia3. Using the SMRI CC, we identified in approximately 20 % of cases with CMD but not normal controls or patients with neurodegenerative diseases sarkosyl-insoluble DISC1 immunoreactivity after biochemical fractionation. Subsequent studies in vitro revealed that the aggregation propensity of DISC1 was influenced by disease-associated polymorphism S704C4, and that DISC1 aggresomes generated in vitro were cell-invasive5, similar to what had been shown for A&beta;6, tau7-9, &alpha;-synuclein10, polyglutamine11, or SOD1 aggregates12. These findings prompted us to propose that at least a subset of cases with CMD, those with aggregated DISC1 might be protein conformational disorders.
 Here we describe how we generate DISC1 aggresomes in mammalian cells, purify them on a sucrose gradient and use them for cell-invasiveness studies. Similarly, we describe how we generate an exclusively multimeric C-terminal DISC1 fragment, label and purify it for cell invasiveness studies. Using the recombinant multimers of DISC1 we achieve similar cell invasiveness as for a similarly labeled synthetic &alpha;-synuclein fragment. We also show that this fragment is taken up in vivo when stereotactically injected into the brain of recipient animals.

The generation, purification and cell invasion of intracellular, cytoplasmic full length DISC1 protein aggresomes from cell cultures and of a labeled, multimeric recombinant DISC1 protein fragment in E. coli are described. Cell invasiveness is shown for recipient cells in cell culture and for neurons in vivo after stereotactical brain inoculation.

Generación, purificación y caracterización de especies invasivas en células de proteína DISC1

Protein aggregation is seen as a general hallmark of chronic, degenerative brain conditions like, for example, in the neurodegenerative diseases ...

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the function and regulation of protein folding was studied in vitro, in isolated tissue culture cells and in unicellular organisms. Recent studies have uncovered links between protein homeostasis (proteostasis), metabolism, development, aging, and temperature-sensing. These findings have led to the development of new tools for monitoring protein folding in the model metazoan organism Caenorhabditis elegans. In our laboratory, we combine behavioral assays, imaging and biochemical approaches using temperature-sensitive or naturally occurring metastable proteins as sensors of the folding environment to monitor protein misfolding. Behavioral assays that are associated with the misfolding of a specific protein provide a simple and powerful readout for protein folding, allowing for the fast screening of genes and conditions that modulate folding. Likewise, such misfolding can be associated with protein mislocalization in the cell. Monitoring protein localization can, therefore, highlight changes in cellular folding capacity occurring in different tissues, at various stages of development and in the face of changing conditions. Finally, using biochemical tools ex vivo, we can directly monitor protein stability and conformation. Thus, by combining behavioral assays, imaging and biochemical techniques, we are able to monitor protein misfolding at the resolution of the organism, the cell, and the protein, respectively.

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

To study the relationship between protein homeostasis, stress and aging, we monitored changes in protein folding by following protein dysfunction, protein localization in the cell and protein stability at the organismal, cellular and protein levels, using the genetically tractable metazoan Caenorhabditis elegans as a model system.

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the ...

Generation of Marked and Markerless Mutants in Model Cyanobacterial Species

Cyanobacteria are ecologically important organisms and potential platforms for production of biofuels and useful industrial products. Genetic manipulation of cyanobacteria, especially model organisms such as Synechocystis sp. PCC6803 and Synechococcus sp. PCC7002, is a key tool for both basic and applied research. Generation of unmarked mutants, whereby chromosomal alterations are introduced into a strain via insertion of an antibiotic resistance cassette (a manipulatable fragment of DNA containing one or more genes), followed by subsequent removal of this cassette using a negative selectable marker, is a particularly powerful technique. Unmarked mutants can be repeatedly genetically manipulated, allowing as many alterations to be introduced into a strain as desired. In addition, the absence of genes encoding antibiotic resistance proteins in the mutated strain is desirable, as it avoids the possibility of 'escape' of antibiotic resistant organisms into the environment. However, detailed methods for repeated rounds of genetic manipulation of cyanobacteria are not well described in the scientific literature. Here we provide a comprehensive description of this technique, which we have successfully used to generate mutants with multiple deletions, single point mutations within a gene of interest and insertion of novel gene cassettes.

Introducing multiple genomic alterations into cyanobacteria is an essential tool in the development of strains for industrial and basic research purposes. We describe a system for generating unmarked mutants in the model cyanobacterial species Synechocystis sp. PCC6803 and marked mutants in Synechococcus sp. PCC7002.

Generación de mutantes sin marcadores marcados y en el modelo de especies de cianobacterias

Cyanobacteria are ecologically important organisms and potential platforms for production of biofuels and useful industrial products. Genetic manipulation ...

Rodent Working Heart Model for the Study of Myocardial Performance and Oxygen Consumption

Isolated working heart models have been used to understand the effects of loading conditions, heart rate and medications on myocardial performance in ways that cannot be accomplished in vivo. For example, inotropic medications commonly also affect preload and afterload, precluding load-independent assessments of their myocardial effects in vivo. Additionally, this model allows for sampling of coronary sinus effluent without contamination from systemic venous return, permitting assessment of myocardial oxygen consumption. Further, the advent of miniaturized pressure-volume catheters has allowed for the precise quantification of markers of both systolic and diastolic performance. We describe a model in which the left ventricle can be studied while performing both volume and pressure work under controlled conditions. 
In this technique, the heart and lungs of a Sprague-Dawley rat (weight 300-500 g) are removed en bloc under general anesthesia. The aorta is dissected free and cannulated for retrograde perfusion with oxygenated Krebs buffer. The pulmonary arteries and veins are ligated and the lungs removed from the preparation. The left atrium is then incised and cannulated using a separate venous cannula, attached to a preload block. Once this is determined to be leak-free, the left heart is loaded and retrograde perfusion stopped, creating the working heart model. The pulmonary artery is incised and cannulated for collection of coronary effluent and determination of myocardial oxygen consumption. A pressure-volume catheter is placed into the left ventricle either retrograde or through apical puncture. If desired, atrial pacing wires can be placed for more precise control of heart rate. This model allows for precise control of preload (using a left atrial pressure block), afterload (using an afterload block), heart rate (using pacing wires) and oxygen tension (using oxygen mixtures within the perfusate).

Isolated working heart models can be used to measure the effect of loading conditions, heart rate, and medications on myocardial performance and oxygen consumption. We describe methods for preparation of a rodent left heart working model that permits study of systolic and diastolic performance and oxygen consumption under various conditions.

Roedor de Trabajo Modelo del corazón para el estudio sobre los resultados de miocardio y el consumo de oxígeno

Isolated working heart models have been used to understand the effects of loading conditions, heart rate and medications on myocardial performance in ways ...

Visualizing the Early Stages of Phagocytosis

The mammalian body is equipped with various layers of mechanisms that help to defend itself from pathogen invasions. Professional phagocytes of the immune system &#8212; such as neutrophils, dendritic cells, and macrophages &#8212; retain the innate ability to detect and clear such invading pathogens through phagocytosis1. Phagocytosis involves choreographed events of membrane reorganization and actin remodeling at the cell surface2,3. Phagocytes successfully internalize and eradicate foreign molecules only when all stages of phagocytosis are fulfilled. These steps include recognition and binding of the pathogen by pattern recognition receptors (PRRs) residing at the cell surface, formation of phagocytic cup through actin-enriched membranous protrusions (pseudopods) to surround the particulate, and scission of the phagosome followed by phagolysosome maturation that results in the killing of the pathogen3,4.
Imaging and quantification of various stages of phagocytosis is instrumental for elucidating the molecular mechanisms of this cellular process. The present manuscript reports methods to study the different phases of phagocytosis. We describe a microscope-based approach to visualize and quantify the binding, phagocytic cup formation, and the internalization of particulate by phagocytes. As phagocytosis occurs when innate receptors on phagocytic cells encounter ligands on a target particle bigger than 0.5 &#181;m, the assays we present here comprise the use of pathogenic fungi Candida albicans and other particulates such as zymosan and IgG-coated beads.

Here we describe a microscope-based technique to visualize and quantify the early cascades of events during phagocytosis of pathogens such as the fungi Candida albicans and particulates that are larger than 0.5 &#181;m including zymosan and IgG-coated beads.

La visualización de las primeras etapas de la fagocitosis

The mammalian body is equipped with various layers of mechanisms that help to defend itself from pathogen invasions. Professional phagocytes of the immune ...

Establishment of an Extracellular Acidic pH Culture System

Conditions of the tumor microenvironment, such as hypoxia or nutrient starvation, play critical roles in cancer progression and malignancy. However, the role of acidic extracellular pH in tumor aggressiveness and its underlying mechanism has not been extensively studied compared to hypoxic or nutrient starvation conditions. In addition, a well-defined culture method to mimic the acidic extracellular tumor microenvironment has not been fully reported.
Here we present a simple in vitro culture method to maintain acidic extracellular pH using reduced bicarbonate and increased lactate or HCl concentrations in the culture medium. The medium pH was sustained for at least 24 h and gradually decreased by 72 h following culture of PANC-1 and AsPC-1 pancreatic cancer cells. Three distinct acidic media conditions in this study highly upregulated pH-responsive genes such as MSMO1, INSIG1, and IDI1 compared to hypoxia or nutrient starvation. The upregulation of these genes can be used as a marker of acidic pH. These simple techniques are beneficial to elucidate underlying mechanisms of tumor malignancy under acidic tumor microenvironment. Therefore, our extracellular acidic pH culture system enables discovery of cellular acidic pH responses not only in cancer cells but also in primary cells, such as renal tubular cells, in relation to the other acidic disorders including, diabetic ketoacidosis, lactic acidosis, renal tubular acidosis, and respiratory acidosis.

The acidic tumor microenvironment plays critical roles in tumor progression. To assess the effects of acidic extracellular pH on cancer cells in vitro, we established simple acidic culture systems.

Establecimiento de un pH extracelular ácido sistema de cultivo

Conditions of the tumor microenvironment, such as hypoxia or nutrient starvation, play critical roles in cancer progression and malignancy. However, the ...

Stimulation of Stem Cell Niches and Tissue Regeneration in Mouse Skin by Switchable Protoporphyrin IX-Dependent Photogeneration of Reactive Oxygen Species In Situ

Here, we describe a protocol to induce switchable in vivo photogeneration of endogenous reactive oxygen species (ROS) in mouse skin. This transient production of ROS in situ efficiently activates cell proliferation in stem cell niches and stimulates tissue regeneration as strongly manifested through the acceleration of burn healing and hair follicle growth processes. The protocol is based on a regulatable photodynamic treatment that treats the tissue with precursors of the endogenous photosensitizer protoporphyrin IX and further irradiates the tissue with red light under tightly controlled physicochemical parameters. Overall, this protocol constitutes an interesting experimental tool to analyze ROS biology.

The aim of this protocol is to induce transient in vivo production of nonlethal levels of reactive oxygen species (ROS) in mouse skin, further promoting physiological responses in the tissue.

Estimulación de nichos de células madre y regeneración de tejidos en piel de ratón mediante fotogeneración in situ dependiente de protoporfirina IX conmutable de especies reactivas de oxígeno

Here, we describe a protocol to induce switchable in vivo photogeneration of endogenous reactive oxygen species (ROS) in mouse skin. This transient ...