The authors wish to thank Drs. Sung-wan An and Mike O&#8217;Donnell for practical advice on establishing this assay, Dr. Chih-Jen Cheng for helpful discussions on the use of ion-specific electrodes, and Dr. Chou-Long Huang for his mentorship and support. This work was supported by the National Institutes of Health (K08DK091316 to ARR) and the American Society of Nephrology Gottschalk Award to ARR.

<ol>
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The authors have nothing to disclose.

El uso del ensayo Ramsay, junto con electrodos de ión específico, permite la medición de tasas de secreción de fluidos y los flujos de iones en el aislado de insectos de Malpighi (renales) túbulos. Veinte o más túbulos se pueden ensayar a la vez, lo que permite un mayor rendimiento en comparación con el ensayo de individuo en túbulos in vitro microperfused. Además, los electrodos de ión específico permiten la determinación de las concentraciones de iones dentro del fluido secretado in ...

<html> Transporte iónico epitelial renal subyace ionosfera del organismo y la osmorregulación. La Drosophila melanogaster Malpighi (renal) túbulo ofrece una oportunidad sin precedentes para estudiar los mecanismos moleculares de transporte iónico epitelial. Esto es debido a la combinación de las poderosas genética de Drosophila, emparejado con la accesibilidad de sus túbulos renales a estudio fisiológico. El ensayo de Ramsay, el nombre del investigador que fue pionero en la técnica 1, mide las tasas de secreción de líquido de los túbulos de Malpighi aislados, y se constituyó en Drosophila en 1994 por Dow y colegas 2. Esto allanó el camino para más estudios utilizando Drosophila herramientas genéticas, tales como el sistema GAL4-UAS 3,4, para definir las vías de señalización de células específicas que regulan la secreción de fluidos. Un ejemplo incluye la señalización del calcio en respuesta a una hormona peptídica 5, entre muchos otros 6,7. ve_content &quot;&gt; Una combinación de técnicas genéticas y estudio fisiológico clásica ha demostrado que la generación de la orina en el se produce la marcha a través de la secreción de un cloruro de potasio rica en líquido de la principal segmento del túbulo. Esto ocurre a través de la secreción transepitelial paralelo de cationes, principalmente K + Na +, sino también, a través de la célula principal, y Cl -. a través de la secreción de las células estrelladas 8-12 La capacidad de medir por separado transepiteliales flujos de K + y Na + permite una caracterización más detallada de los mecanismos de transporte que la medición de la secreción de fluidos solo. Por ejemplo, en los túbulos de Drosophila no estimuladas, el Na + / K + -ATPasa ouabaína no tiene ningún efecto sobre la secreción de fluido 2, incluso cuando su captación en las células principales se inhibe por el transportador de aniones orgánicos inhibidor de taurocolato 13. Sin embargo, Linton y O&#39;Donnell mostró que ouabaína despolarizael potencial de membrana basolateral, y aumenta Na + flujo 9. Como se muestra en los resultados representativos, replicamos estos hallazgos, y demostramos que K + flujo es concomitante disminución de 14; el aumento del flujo de Na + y la disminución de K + flujo tener efectos opuestos sobre la secreción de fluidos, lo que resulta en ningún cambio neto en la secreción. Por lo tanto, hay dos resoluciones a la &quot;paradoja ouabaína&quot;, es decir, la observación inicial de que ouabaína no tiene ningún efecto sobre la secreción de fluido en el túbulo Drosophila:. Primero, en los túbulos estimulados, el efecto de ouabaína sobre la secreción de fluido no es evidente debido a la su absorción por el transportador de aniones orgánicos 13; y en segundo lugar, en los túbulos no estimuladas, ouabaina ha oponerse efectos sobre transepitelial Na + y K + flujo, lo que resulta en ningún cambio neto en la secreción de fluidos (ver resultados representativos y ref. 9). Por lo tanto, la función principal de la Na + / K + -ATPase en los túbulos no estimuladas es disminuir la concentración intracelular de Na + para generar un gradiente de concentración favorable para Na + -junto procesos de transporte a través de la membrana basolateral. En efecto, mediante la medición por separado de Na + y K + fundentes, hemos demostrado que los túbulos que carece del cotransportador sodio-potasio-2-cloruro de mosca (NKCC) han disminuido K transepitelial + fundente, sin mayor descenso después de la adición ouabaina, y ningún cambio en transepitelial Na + Flujo 14. Estos resultados apoyan nuestra conclusión de que Na + entrar en la célula a través de la NKCC se recicla a través de la Na + / K + -ATPasa. En otro ejemplo, Ianowski et al. Observaron que la reducción de baño de K + concentración de 10 mM a 6 mM disminuyó transepitelial K + y el aumento de flujo transepitelial Na + en los túbulos flujo de Rhodnius prolixus, sin cambio neto en la secreción de fluidos <sup&gt; 15. Efectos diferenciales sobre Na + y K + flujo flujo a través de los túbulos de larvas se han observado también en los túbulos de Drosophila en respuesta a diferentes dietas de sal 16 y en dos especies de mosquitos en respuesta a la cría de salinidad 17. El mayor reto en la medición del flujo de iones transepitelial en la preparación de ensayo Ramsay es la determinación de las concentraciones de iones dentro del fluido secretado. Este reto se ha cumplido con soluciones diferentes, incluyendo photometery llama 18, el uso de iones radiactivos 19, y el electrón sonda de longitud de onda de la espectroscopía dispersiva 20. Estas técnicas requieren la transferencia de la gota de líquido secretado a un instrumento para la medición de concentraciones de iones. Dado que el volumen de líquido secretado por el túbulo Drosophila no estimulada es pequeño, típicamente ~ 0,5 nl / min, esto plantea un reto técnico y también introduce error si algo del fluido es secretadaperdido en la transferencia. En contraste, el uso de electrodos de ión específico permite la medición de la actividad de iones (a partir del cual se puede calcular la concentración de iones) in situ. El protocolo actual fue adaptado de la utilizada por Maddrell y sus colegas para medir transepitelial K + flujo a través de los túbulos Rhodnius usando valinomicina como el K + ionóforo 21, y también describe el uso de un -butylcalix 4- terc [4] areno-ácido tetraacético Na base de éster de tetraetilo + específico de electrodo específico de iones caracterizado por Messerli et. al., 22. Ion-electrodos específicos también se han utilizado para medir las concentraciones de iones en el fluido secretado por los túbulos de Malpighi en el ensayo de Ramsay en adulto y larval 9,23 16 Drosophila melanogaster, la Nueva Zelanda Alpine Weta (Hemideina maori) 24 y 17 en los mosquitos. Aquí se describe en detalle el uso del Ramsay comodecir para medir las tasas de secreción de fluidos en los túbulos de Malpighi de Drosophila melanogaster, así como el uso de electrodos de ión específico para determinar las concentraciones de K + y Na + en el fluido secretado y por lo tanto el cálculo de los flujos de iones transepitelial. Una visión general del ensayo se proporciona en la Figura 1. <img alt="Figura 1" src="/files/ftp_upload/53144/53144fig1.jpg" /> Figura 1. Esquema del Malpighi túbulos y el ensayo de Ramsay con uso de iones específicos electrodos para medir concentraciones de iones. Esta figura ilustra la configuración para el ensayo de Ramsay. (A) Cada mosca tiene cuatro túbulos, un par de túbulos anterior y un par de túbulos posteriores, que flotan en la cavidad abdominal rodeado de hemolinfa. En cada par, los dos túbulos se unen en el uréter, que luego se vacía la orina en la unión del intestino medio y hindgut. Los túbulos son ciego terminado. La orina se genera por el segmento principal de fluido que secretan (mostrado en rojo), y fluye hacia el uréter y hacia fuera en el intestino. Después de la disección, el par túbulo se disocia desde el intestino por transección el uréter. (B) El par de túbulos se transfiere a continuación en una gota de solución salina de baño dentro de un pocillo de la placa de ensayo. Uno de los dos túbulos, que se refiere aquí como el &quot;túbulo ancla,&quot; se envuelve alrededor de un pasador de metal y es inerte. El otro es el túbulo túbulo secretor. El segmento inicial (que no secretar fluido) y el segmento principal de los túbulos secretores se mantienen dentro de la gota de solución salina de baño. Iones y movimiento de agua de la solución salina de baño y en el lumen de los túbulos del segmento principal, y luego se mueven hacia el uréter, como ocurriría en vivo. El segmento inferior (azul) está fuera de la solución salina de baño y por lo tanto inerte. Desde el uréter se corta, el fluido secretado emerge como una gotita desde el extremo cortado del uréter. Tél secretada gotita de fluido aumenta con el tiempo como la secreción continúa, y su diámetro se mide utilizando un micrómetro ocular. Una capa de aceite mineral evita la evaporación del fluido secretado. Los iones de referencia y electrodos específicos miden la concentración de iones del líquido secretado. <a href="https://www.jove.com/files/ftp_upload/53144/53144fig1large.jpg" target="_blank">Por favor haga clic aquí para ver una versión más grande de esta figura.</a>

<table>
	<tbody>
		<tr>
			<td>Sylgard 184 Silicone Elastomer Kit</td>
			<td>Ellsworth Adhesives</td>
			<td>http://www.ellsworth.com/dow-corning-sylgard-184-silicone-encapsulant-0-5kg-kit-clear/</td>
			<td>May be purchased from multiple distributors</td>
		</tr>
		<tr>
			<td>Petri dish, polystyrene, 100 mm x 15 mm</td>
			<td>Fisher</td>
			<td>FB0875712</td>
			<td>Specific brand is not important</td>
		</tr>
		<tr>
			<td>Petri dish, polystyrene, 35 mm x 10 mm</td>
			<td>Corning Life Sciences</td>
			<td>Fisher 08-757-100A</td>
			<td>Specific brand is not important</td>
		</tr>
		<tr>
			<td>Scalpel Handle #3</td>
			<td>Fine Science Tools</td>
			<td>10003-12</td>
			<td>Specific brand is not important</td>
		</tr>
		<tr>
			<td>Scalpel Blades #1</td>
			<td>Fine Science Tools</td>
			<td>10011-00</td>
			<td>Specific brand is not important; use appropriate sharps precautions</td>
		</tr>
		<tr>
			<td>Needle, 30G x 1/2</td>
			<td>Becton Dickinson</td>
			<td>305106</td>
			<td>Use appropriate sharps precautions</td>
		</tr>
		<tr>
			<td>Minutien pins, black anodized, 0.15 mm</td>
			<td>Fine Science Tools</td>
			<td>26002-15</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereomicroscope with ocular micrometer</td>
			<td>Nikon</td>
			<td>SMZ800</td>
			<td>Specific brand is not important; this is given as an example</td>
		</tr>
		<tr>
			<td>Sheet of black stained glass, 3 mm (1/8 inch) thick</td>
			<td>Hobby shop</td>
			<td></td>
			<td>Example includes Spectrum Black Opal by Spectrum Glass (http://www.delphiglass.com/spectrum-glass/opalescent/spectrum-black-opal)</td>
		</tr>
		<tr>
			<td>Glass cutting tools (glass cutter, glass cutting pliers)</td>
			<td>Hobby shop</td>
			<td></td>
			<td>Examples include the Studio Pro Lightweight Running Pliers by Diamond Tech (http://www.delphiglass.com/glass-cutters-tools/pliers-nippers/studio-pro-lightweight-running-pliers) and the Studio Pro Brass Glass Cutter by Diamond Tech (http://www.delphiglass.com/glass-cutters-tools/glass-cutters/studio-pro-brass-glass-cutter). Use appropriate safety precautions when cutting glass</td>
		</tr>
		<tr>
			<td>Borosilicate glass capillary tube, unfilamented, GC120-10, OD 1.2 mm, ID 0.69 mm, length 10 cm</td>
			<td>Warner Instruments</td>
			<td>30-0042</td>
			<td></td>
		</tr>
		<tr>
			<td>Borosilicate glass capillary tube, filamented, GC120F-10, OD 1.2 mm, ID 0.69 mm, length 10 cm</td>
			<td>Warner Instruments</td>
			<td>30-0044</td>
			<td></td>
		</tr>
		<tr>
			<td>Nitric acid, 70%</td>
			<td>Sigma</td>
			<td>438073</td>
			<td>CAUTION: see Material Data Safety Sheet for appropriate storage and handling guidelines. Specific brand is not important</td>
		</tr>
		<tr>
			<td>Cimarec 7 in x 7 in hotplate</td>
			<td>Fisher</td>
			<td>11675911Q</td>
			<td>Specific brand is not important; caution when heated</td>
		</tr>
		<tr>
			<td>Selectophore dichlorodimethylsilane</td>
			<td>Sigma</td>
			<td>40136-1ML</td>
			<td>CAUTION: see Material Data Safety Sheet for appropriate storage and handling guidelines</td>
		</tr>
		<tr>
			<td>Two-step vertical pipet puller</td>
			<td>Narishige</td>
			<td>PC-10</td>
			<td>Other pipet pullers can be used; this is given as an example</td>
		</tr>
		<tr>
			<td>Glass petri dish, 150 mm diameter x 15 mm height</td>
			<td>Fisher</td>
			<td>08-748E</td>
			<td>Specific brand is not important; only one dish needed</td>
		</tr>
		<tr>
			<td>World Precision Instruments E210 1 mm micropipette storage jar</td>
			<td>Fisher</td>
			<td>50-821-852</td>
			<td>May be available from other distributors. Useful to have two jars. Note that although this jar is specified for 1 mm pipets, and the pipets used here are 1.2 mm, in our experience the 1 mm jar works best for the 1.2 mm pipets.</td>
		</tr>
		<tr>
			<td>Silica Gel, Tel-Tale Desiccant, indicating, 10-18 mesh</td>
			<td>Fisher</td>
			<td>S161-500</td>
			<td>Indicating silica useful for determining whether silica gel retains desiccating ability</td>
		</tr>
		<tr>
			<td>World Precision Instruments MicroFil, 34G</td>
			<td>Fisher</td>
			<td>50-821-914</td>
			<td>May be available from other distributors.</td>
		</tr>
		<tr>
			<td>1 ml syringe with luer lock</td>
			<td>Becton Dickinson</td>
			<td>309659</td>
			<td>May be available from other distributors.</td>
		</tr>
		<tr>
			<td>3 ml syringe with luer lock</td>
			<td>Becton Dickinson</td>
			<td>309657</td>
			<td>May be available from other distributors.</td>
		</tr>
		<tr>
			<td>D300 3-way stopcock with female luer lock inlet port, male luer outlet port with rotating collar and guard</td>
			<td>Cole-Parmer</td>
			<td>UX-30600-02</td>
			<td>Specific brand is not important</td>
		</tr>
		<tr>
			<td>Female Luer Locking Connector</td>
			<td>4 Medical Solutions</td>
			<td>ADC 9873-10</td>
			<td>Specific brand is not important; barbed end is ~4 mm at narrowest point and ~7 mm at widest point.</td>
		</tr>
		<tr>
			<td>Silicone Tubing I.D. x O.D. x Wall: 1/16 x 1/8 x 1/32 in. (1.59 x 3.18 x 0.79 mm)</td>
			<td>Fisher</td>
			<td>14-179-110</td>
			<td>Specific brand is not important</td>
		</tr>
		<tr>
			<td>E-3603 tubing, I.D. x O.D.: 1/32 x 3/32 in</td>
			<td>Fisher</td>
			<td>14171208</td>
			<td>Specific brand is not important</td>
		</tr>
		<tr>
			<td>Modeling clay</td>
			<td></td>
			<td></td>
			<td>Specific brand is not important</td>
		</tr>
		<tr>
			<td>Selectophore potassium ionophore I, cocktail B</td>
			<td>Sigma</td>
			<td>99373</td>
			<td>CAUTION: see Material Data Safety Sheet for appropriate storage and handling guidelines</td>
		</tr>
		<tr>
			<td>Selectophore sodium ionophore X</td>
			<td>Sigma</td>
			<td>71747</td>
			<td>Sodium ionphore X = 4-tert-butylcalix[4]arene-tetraacetic acid tetraethylester</td>
		</tr>
		<tr>
			<td>Selectophore 2-nitrophenyl octyl ether</td>
			<td>Sigma</td>
			<td>73732</td>
			<td></td>
		</tr>
		<tr>
			<td>Selectophore sodium tetraphenylborate</td>
			<td>Sigma</td>
			<td>72018</td>
			<td></td>
		</tr>
		<tr>
			<td>Schneider&#39;s Drosophila medium</td>
			<td>Life Technologies</td>
			<td>21720024</td>
			<td></td>
		</tr>
		<tr>
			<td>High impedance electrometer</td>
			<td>World Precision Instruments</td>
			<td>FD223a</td>
			<td></td>
		</tr>
		<tr>
			<td>Microelectrode holder 1 mm with 45&#176; body, vented, with handle</td>
			<td>Warner Instruments</td>
			<td>64-1051</td>
			<td></td>
		</tr>
		<tr>
			<td>Microelectrode holder 1 mm with straight body, vented</td>
			<td>Warner Instruments</td>
			<td>64-1007</td>
			<td></td>
		</tr>
		<tr>
			<td>Silver wire</td>
			<td>Warner Instruments</td>
			<td>64-1318</td>
			<td></td>
		</tr>
		<tr>
			<td>Micromanipulators, pair</td>
			<td>Leitz</td>
			<td></td>
			<td>Various brands/models will work; this is an example</td>
		</tr>
		<tr>
			<td>Faraday cage</td>
			<td>Technical Manufacturing Corporation</td>
			<td>81-334-03</td>
			<td>This is an example; any Faraday cage will work</td>
		</tr>
		<tr>
			<td>Single gooseneck fiberoptic light</td>
			<td>Nikon</td>
			<td></td>
			<td>Specific brand is not important</td>
		</tr>
		<tr>
			<td>mineral oil</td>
			<td>Fisher</td>
			<td>BP-2629</td>
			<td>Specific brand is not important</td>
		</tr>
		<tr>
			<td>forceps, Dumont #5 with Biologie tip</td>
			<td>Fine Science Tool</td>
			<td>11295-10</td>
			<td>May be available from other distributors.</td>
		</tr>
	</tbody>
</table>

use of the ramsay assay to measure fluid secretion and ion flux rates in the drosophila melanogaster malpighian tubule

La modulación de transporte de iones epiteliales renales permite a los organismos para mantener la homeostasis iónica y osmótica en la cara de la variación de las condiciones externas. La Drosophila melanogaster Malpighi (renal) túbulo ofrece una oportunidad sin precedentes para estudiar los mecanismos moleculares de transporte iónico epitelial, debido a los poderosos genética de este organismo y la accesibilidad de sus túbulos renales al estudio fisiológico. Aquí se describe el uso del ensayo de Ramsay para medir las tasas de secreción de líquido de los túbulos renales aislados de moscas, con el uso de electrodos de iones específicos para medir las concentraciones de sodio y potasio en el líquido secretado. Este ensayo permite el estudio de fluido transepitelial de iones y los flujos de ~ 20 túbulos a la vez, sin la necesidad de transferir el fluido secretado a un aparato separado para medir las concentraciones de iones. Genéticamente túbulos distintas se pueden analizar para evaluar el papel de genes específicos en procesos de transporte. Además, el bsolución salina athing puede ser modificado para examinar los efectos de sus características químicas o fármacos u hormonas añadidas. En resumen, esta técnica permite la caracterización molecular de los mecanismos básicos de transporte epitelial de iones en el túbulo Drosophila, así como la regulación de estos mecanismos de transporte.

Las Figuras 7 y 8 demuestran que el uso del ensayo de Ramsay con electrodos de ión específico para medir las concentraciones de K + y Na + puede distinguir genéticamente y farmacológicamente distintas K + y los flujos de Na +, la información que no se captura mediante la medición de las tasas de secreción de líquido solo. Figura 7 muestra que la disminución de la secreción de fluidos en los túbulos de las moscas que llevan una mutac...

Watch this Scientific Journal Video about Use of the Ramsay Assay to Measure Fluid Secretion and Ion Flux Rates in the Drosophila melanogaster Malpighian Tubule at JoVE.com

Use of the Ramsay Assay to Measure Fluid Secretion and Ion Flux Rates in the Drosophila melanogaster Malpighian Tubule

Este protocolo describe el uso del ensayo de Ramsay para medir las tasas de secreción de fluidos aislados de Malpighi (renal) túbulos de Drosophila melanogaster. Además, el uso de electrodos de ión específico para medir las concentraciones de sodio y potasio en el líquido secretado, lo que permite el cálculo del flujo de iones transepitelial, se describe.

El uso del ensayo de Ramsay medir la secreción de fluidos y de iones Flux tarifas en el<em&gt; Drosophila melanogaster</em&gt; Túbulo de Malpighi

Modulation of renal epithelial ion transport allows organisms to maintain ionic and osmotic homeostasis in the face of varying external conditions. The ...

use-ramsay-assay-to-measure-fluid-secretion-ion-flux-rates-drosophila

Research

JoVE Journal

Biology

Use of the Ramsay Assay to Measure Fluid Secretion and Ion Flux Rates in the Drosophila melanogaster Malpighian Tubule

11.7K vistas.  University of Texas Southwestern Medical Center.  Este protocolo describe el uso del ensayo de Ramsay para medir las tasas de secreción de fluidos aislados de Malpighi (renal) túbulos de Drosophila melanogaster. Además, el uso de electrodos de ión específico para medir las concentraciones de sodio y potasio en el líquido secretado, lo que permite el cálculo del flujo de iones transepitelial, se describe. 

Video: Use of the Ramsay Assay to Measure Fluid Secretion and Ion Flux Rates in the Drosophila melanogaster Malpighian Tubule

Microinjection Techniques for Studying Mitosis in the Drosophila melanogaster Syncytial Embryo

This protocol describes the use of the Drosophila melanogaster syncytial embryo for studying mitosis1. Drosophila has useful genetics with a sequenced genome, and it can be easily maintained and manipulated. Many mitotic mutants exist, and transgenic flies expressing functional fluorescently (e.g. GFP) - tagged mitotic proteins have been and are being generated. Targeted gene expression is possible using the GAL4/UAS system2. 

The Drosophila early embryo carries out multiple mitoses very rapidly (cell cycle duration, &asymp;10 min). It is well suited for imaging mitosis, because during cycles 10-13, nuclei divide rapidly and synchronously without intervening cytokinesis at the surface of the embryo in a single monolayer just underneath the cortex. These rapidly dividing nuclei probably use the same mitotic machinery as other cells, but they are optimized for speed; the checkpoint is generally believed to not be stringent, allowing the study of mitotic proteins whose absence would cause cell cycle arrest in cells with a strong checkpoint. Embryos expressing GFP labeled proteins or microinjected with fluorescently labeled proteins can be easily imaged to follow live dynamics (Fig. 1). In addition, embryos can be microinjected with function-blocking antibodies or inhibitors of specific proteins to study the effect of the loss or perturbation of their function3. These reagents can diffuse throughout the embryo, reaching many spindles to produce a gradient of concentration of inhibitor, which in turn results in a gradient of defects comparable to an allelic series of mutants. Ideally, if the target protein is fluorescently labeled, the gradient of inhibition can be directly visualized4. It is assumed that the strongest phenotype is comparable to the null phenotype, although it is hard to formally exclude the possibility that the antibodies may have dominant effects in rare instances, so rigorous controls and cautious interpretation must be applied. Further away from the injection site, protein function is only partially lost allowing other functions of the target protein to become evident.

Microinjection Techniques for Studying Mitosis in the Drosophila melanogaster Syncytial Embryo

This protocol describes the use of microinjection and high resolution imaging in the Drosophila melanogaster syncytial embryo to study mitosis.

Técnicas de microinyección para el estudio de la mitosis en el Drosophila melanogaster Embrión sincitial

This protocol describes the use of the Drosophila melanogaster syncytial embryo  for studying mitosis1.  Drosophila has useful genetics with a sequenced ...

Investigación

Biología

Photobleaching Assays (FRAP &amp; FLIP) to Measure Chromatin Protein Dynamics in Living Embryonic Stem Cells

Fluorescence Recovery After Photobleaching (FRAP) and Fluorescence Loss In Photobleaching (FLIP) enable the study of protein dynamics in living cells with good spatial and temporal resolution. Here we describe how to perform FRAP and FLIP assays of chromatin proteins, including H1 and HP1, in mouse embryonic stem (ES) cells. In a FRAP experiment, cells are transfected, either transiently or stably, with a protein of interest fused with the green fluorescent protein (GFP) or derivatives thereof (YFP, CFP, Cherry, etc.). In the transfected, fluorescing cells, an intense focused laser beam bleaches a relatively small region of interest (ROI). The laser wavelength is selected according to the fluorescent protein used for fusion. The laser light irreversibly bleaches the fluorescent signal of molecules in the ROI and, immediately following bleaching, the recovery of the fluorescent signal in the bleached area - mediated by the replacement of the bleached molecules with the unbleached molecules - is monitored using time lapse imaging. The generated fluorescence recovery curves provide information on the protein's mobility. If the fluorescent molecules are immobile, no fluorescence recovery will be observed. In a complementary approach, Fluorescence Loss in Photobleaching (FLIP), the laser beam bleaches the same spot repeatedly and the signal intensity is measured elsewhere in the fluorescing cell. FLIP experiments therefore measure signal decay rather than fluorescence recovery and are useful to determine protein mobility as well as protein shuttling between cellular compartments. Transient binding is a common property of chromatin-associated proteins. Although the major fraction of each chromatin protein is bound to chromatin at any given moment at steady state, the binding is transient and most chromatin proteins have a high turnover on chromatin, with a residence time in the order of seconds. These properties are crucial for generating high plasticity in genome expression1. Photobleaching experiments are therefore particularly useful to determine chromatin plasticity using GFP-fusion versions of chromatin structural proteins, especially in ES cells, where the dynamic exchange of chromatin proteins (including heterochromatin protein 1 (HP1), linker histone H1 and core histones) is higher than in differentiated cells2,3.

Photobleaching Assays FRAP &amp; FLIP to Measure Chromatin Protein Dynamics in Living Embryonic Stem Cells

We describe photobleaching methods including Fluorescence Recovery After Photobleaching (FRAP) and Fluorescence Loss In Photobleaching (FLIP) to monitor chromatin protein dynamics in embryonic stem (ES) cells. Chromatin protein dynamics, which is considered to be one of the means to study chromatin plasticity, is enhanced in pluripotent cells.

Photobleaching ensayos (FRAP y FLIP) para medir la dinámica de la cromatina de proteínas en células vivas madre embrionarias

Fluorescence Recovery After Photobleaching (FRAP) and Fluorescence Loss In Photobleaching (FLIP) enable the study of protein dynamics in living cells with ...

Insulin Injection and Hemolymph Extraction to Measure Insulin Sensitivity in Adult Drosophila melanogaster

Conserved nutrient sensing mechanisms exist between mammal and fruit fly where peptides resembling mammalian insulin and glucagon, respectively function to maintain glucose homeostasis during developmental larval stages 1,2. Studies on largely post-mitotic adult flies have revealed perturbation of glucose homeostasis as the result of genetic ablation of insulin-like peptide (ILP) producing cells (IPCs) 3. Thus, adult fruit flies hold great promise as a suitable genetic model system for metabolic disorders including type II diabetes. To further develop the fruit fly system, comparable physiological assays used to measure glucose tolerance and insulin sensitivity in mammals must be established. To this end, we have recently described a novel procedure for measuring oral glucose tolerance response in the adult fly and demonstrated the importance of adult IPCs in maintaining glucose homeostasis 4,5. Here, we have modified a previously described procedure for insulin injection 6 and combined it with a novel hemolymph extraction method to measure peripheral insulin sensitivity in the adult fly. Uniquely, our protocol allows direct physiological measurements of the adult fly's ability to dispose of a peripheral glucose load upon insulin injection, a methodology that makes it feasible to characterize insulin signaling mutants and potential interventions affecting glucose tolerance and insulin sensitivity in the adult fly.

Insulin Injection and Hemolymph Extraction to Measure Insulin Sensitivity in Adult Drosophila melanogaster

Conserved insulin signaling pathways found in the fruit fly Drosophila melanogaster make this organism a potential tool for modeling metabolic disorders including type II diabetes. To this end, it is critical to establish physiological assays to effectively measure systemic insulin action in peripheral glucose disposal in the adult fly.

Inyección de insulina y extracción hemolinfa para medir la sensibilidad a la insulina en adultos Drosophila melanogaster</em

Conserved nutrient sensing mechanisms exist between mammal and fruit fly where peptides resembling mammalian insulin and glucagon, respectively function ...

Measurement of Lifespan in Drosophila melanogaster

Aging is a phenomenon that results in steady physiological deterioration in nearly all organisms in which it has been examined, leading to reduced physical performance and increased risk of disease. Individual aging is manifest at the population level as an increase in age-dependent mortality, which is often measured in the laboratory by observing lifespan in large cohorts of age-matched individuals. Experiments that seek to quantify the extent to which genetic or environmental manipulations impact lifespan in simple model organisms have been remarkably successful for understanding the aspects of aging that are conserved across taxa and for inspiring new strategies for extending lifespan and preventing age-associated disease in mammals.
The vinegar fly, Drosophila melanogaster, is an attractive model organism for studying the mechanisms of aging due to its relatively short lifespan, convenient husbandry, and facile genetics. However, demographic measures of aging, including age-specific survival and mortality, are extraordinarily susceptible to even minor variations in experimental design and environment, and the maintenance of strict laboratory practices for the duration of aging experiments is required. These considerations, together with the need to practice careful control of genetic background, are essential for generating robust measurements. Indeed, there are many notable controversies surrounding inference from longevity experiments in yeast, worms, flies and mice that have been traced to environmental or genetic artifacts1-4. In this protocol, we describe a set of procedures that have been optimized over many years of measuring longevity in Drosophila using laboratory vials. We also describe the use of the dLife software, which was developed by our laboratory and is available for download (<a href="http://sitemaker.umich.edu/pletcherlab/software">http://sitemaker.umich.edu/pletcherlab/software</a>). dLife accelerates throughput and promotes good practices by incorporating optimal experimental design, simplifying fly handling and data collection, and standardizing data analysis. We will also discuss the many potential pitfalls in the design, collection, and interpretation of lifespan data, and we provide steps to avoid these dangers.

Measurement of Lifespan in Drosophila melanogaster

Drosophila melanogaster is a powerful model organism for exploring the molecular basis of longevity regulation. This protocol will discuss the steps involved in generating a reproducible, population-based measurement of longevity as well as potential pitfalls and how to avoid them.

Medición de la esperanza de vida en<em&gt; Drosophila melanogaster</em

Aging is a phenomenon that results in steady physiological deterioration in nearly all organisms in which it has been examined, leading to reduced ...

Live Imaging of Apoptotic Cell Clearance during Drosophila Embryogenesis

The proper elimination of unwanted or aberrant cells through apoptosis and subsequent phagocytosis (apoptotic cell clearance) is crucial for normal development in all metazoan organisms. Apoptotic cell clearance is a highly dynamic process intimately associated with cell death; unengulfed apoptotic cells are barely seen in vivo under normal conditions. In order to understand the different steps of apoptotic cell clearance and to compare 'professional' phagocytes - macrophages and dendritic cells to 'non-professional' - tissue-resident neighboring cells, in vivo live imaging of the process is extremely valuable. Here we describe a protocol for studying apoptotic cell clearance in live Drosophila embryos. To follow the dynamics of different steps in phagocytosis we use specific markers for apoptotic cells and phagocytes. In addition, we can monitor two phagocyte systems in parallel: 'professional' macrophages and 'semi-professional' glia in the developing central nervous system (CNS). The method described here employs the Drosophila embryo as an excellent model for real time studies of apoptotic cell clearance.

Live Imaging of Apoptotic Cell Clearance during Drosophila Embryogenesis

Here we describe an effective method for studying dynamics of apoptotic cell clearance in vivo. This method employs live Drosophila embryos as a powerful model for monitoring phagocytosis of apoptotic cells using specific labeling of apoptotic cells and phagocytes.

Imágenes de Apoptotic Liquidación de células vivas durante<em&gt; Drosophila</em&gt; Embriogénesis

The  proper elimination of unwanted or aberrant cells through apoptosis and  subsequent phagocytosis (apoptotic cell clearance) is crucial for normal  ...

Imaging Through the Pupal Case of Drosophila melanogaster

The longstanding use of Drosophila as a model for cell and developmental biology has yielded an array of tools. Together, these techniques have enabled analysis of cell and developmental biology from a variety of methodological angles. Live imaging is an emerging method for observing dynamic cell processes, such as cell division or cell motility. Having isolated mutations in uncharacterized putative cell cycle proteins it became essential to observe mitosis in situ using live imaging. Most live imaging studies in Drosophila have focused on the embryonic stages that are accessible to manipulation and observation because of their small size and optical clarity. However, in these stages the cell cycle is unusual in that it lacks one or both of the gap phases. By contrast, cells of the pupal wing of Drosophila have a typical cell cycle and undergo a period of rapid mitosis spanning about 20 hr of pupal development. It is easy to identify and isolate pupae of the appropriate stage to catch mitosis in situ. Mounting intact pupae provided the best combination of tractability and durability during imaging, allowing experiments to run for several hours with minimal impact on cell and animal viability. The method allows observation of features as small as, or smaller than, fly chromosomes. Adjustment of microscope settings and the details of mounting, allowed extension of the preparation to visualize membrane dynamics of adjacent cells and fluorescently labeled proteins such as tubulin. This method works for all tested fluorescent proteins and can capture submicron scale features over a variety of time scales. While limited to the outer 20 &#181;m of the pupa with a conventional confocal microscope, this approach to observing protein and cellular dynamics in pupal tissues in vivo may be generally useful in the study of cell and developmental biology in these tissues.

Imaging Through the Pupal Case of Drosophila melanogaster

This paper demonstrates the use of a fast scanning confocal microscope to image cell behavior directly through the puparium. By leaving the pupal case intact, this method allows observation and measurement of dynamic cell processes at a stage of Drosophila development that is difficult to study directly.

Imaging A través de la envoltura pupal de<em&gt; Drosophila melanogaster</em

The longstanding use of Drosophila as a model for cell and developmental biology has yielded an array of tools. Together, these techniques have enabled ...

Quantitative Immunofluorescence Assay to Measure the Variation in Protein Levels at Centrosomes

Centrosomes are small but important organelles that serve as the poles of mitotic spindle to maintain genomic integrity or assemble primary cilia to facilitate sensory functions in cells. The level of a protein may be regulated differently at centrosomes than at other .cellular locations, and the variation in the centrosomal level of several proteins at different points of the cell cycle appears to be crucial for the proper regulation of centriole assembly. We developed a quantitative fluorescence microscopy assay that measures relative changes in the level of a protein at centrosomes in fixed cells from different samples, such as at different phases of the cell cycle or after treatment with various reagents. The principle of this assay lies in measuring the background corrected fluorescent intensity corresponding to a protein at a small region, and normalize that measurement against the same for another protein that does not vary under the chosen experimental condition. Utilizing this assay in combination with BrdU pulse and chase strategy to study unperturbed cell cycles, we have quantitatively validated our recent observation that the centrosomal pool of VDAC3 is regulated at centrosomes during the cell cycle, likely by proteasome-mediated degradation specifically at centrosomes.

Here, a novel quantitative fluorescence assay is developed to measure changes in the level of a protein specifically at centrosomes by normalizing that protein&#8217;s fluorescence intensity to that of an appropriate internal standard.

Cuantitativa inmunofluorescencia Ensayo para medir la variación en los niveles de proteína en centrosomas

Centrosomes are small but important organelles that serve as the poles of mitotic spindle to maintain genomic integrity or assemble primary cilia to ...

Optical Quantification of Intracellular pH in Drosophila melanogaster Malpighian Tubule Epithelia with a Fluorescent Genetically-encoded pH Indicator

Epithelial ion transport is vital to systemic ion homeostasis as well as maintenance of essential cellular electrochemical gradients. Intracellular pH (pHi) is influenced by many ion transporters and thus monitoring pHi is a useful tool for assessing transporter activity. Modern Genetically Encoded pH-Indicators (GEpHIs) provide optical quantification of pHi in intact cells on a cellular and subcellular scale. This protocol describes real-time quantification of cellular pHi regulation in Malpighian Tubules (MTs) of Drosophila melanogaster through ex vivo live-imaging of pHerry, a pseudo-ratiometric GEpHI with a pKa well-suited to track pH changes in the cytosol. Extracted adult fly MTs are composed of morphologically and functionally distinct sections of single-cell layer epithelia, and can serve as an accessible and genetically tractable model for investigation of epithelial transport. GEpHIs offer several advantages over conventional pH-sensitive fluorescent dyes and ion-selective electrodes. GEpHIs can label distinct cell populations provided appropriate promoter elements are available. This labeling is particularly useful in ex vivo, in vivo, and in situ preparations, which are inherently heterogeneous. GEpHIs also permit quantification of pHi in intact tissues over time without need for repeated dye treatment or tissue externalization. The primary drawback of current GEpHIs is the tendency to aggregate in cytosolic inclusions in response to tissue damage and construct over-expression. These shortcomings, their solutions, and the inherent advantages of GEpHIs are demonstrated in this protocol through assessment of basolateral proton (H+) transport in functionally distinct principal and stellate cells of extracted fly MTs. The techniques and analysis described are readily adaptable to a wide variety of vertebrate and invertebrate preparations, and the sophistication of the assay can be scaled from teaching labs to intricate determination of ion flux via specific transporters.

Optical Quantification of Intracellular pH in Drosophila melanogaster Malpighian Tubule Epithelia with a Fluorescent Genetically-encoded pH Indicator

Cellular ion transport can often be assessed by monitoring intracellular pH (pHi). Genetically Encoded pH-Indicators (GEpHIs)&#160;provide optical quantification of intracellular pH in intact cells. This protocol details the quantification of intracellular pH through cellular ex vivo live-imaging of Malpighian tubules of Drosophila melanogaster with pHerry, a pseudo-ratiometric genetically encoded pH-indicator.

Óptica pH cuantificación de intracelular en epitelios de túbulos de Malpighi de Drosophila melanogaster con fluorescentes genéticamente codificado pH indicador

Epithelial ion transport is vital to systemic ion homeostasis as well as maintenance of essential cellular electrochemical gradients. Intracellular pH ...

Oral Bacterial Infection and Shedding in Drosophila melanogaster

The fruit fly Drosophila melanogaster is one of the best developed model systems of infection and innate immunity. While most work has focused on systemic infections, there has been a recent increase of interest in the mechanisms of gut immunocompetence to pathogens, which require methods to orally infect flies. Here we present a protocol to orally expose individual flies to an opportunistic bacterial pathogen (Pseudomonas aeruginosa) and a natural bacterial pathogen of D. melanogaster (Pseudomonas entomophila). The goal of this protocol is to provide a robust method to expose male and female flies to these pathogens. We provide representative results showing survival phenotypes, microbe loads, and bacterial shedding, which is relevant for the study of heterogeneity in pathogen transmission. Finally, we confirm that Dcy mutants (lacking the protective peritrophic matrix in the gut epithelium) and Relish mutants (lacking a functional immune deficiency (IMD) pathway), show increased susceptibility to bacterial oral infection. This protocol, therefore, describes a robust method to infect flies using the oral route of infection, which can be extended to the study of a variety genetic and environmental sources of variation in gut infection outcomes and bacterial transmission.

Oral Bacterial Infection and Shedding in Drosophila melanogaster

This protocol describes methods to orally expose and infect the fruit fly Drosophila melanogaster with bacterial pathogens, and to measure the number of infectious bacteria shed following gut infection. We further describe the effect of immune mutants on fly survival following oral bacterial infection.

Oral infección bacteriana y vertimiento en Drosophila melanogaster

The fruit fly Drosophila melanogaster is one of the best developed model systems of infection and innate immunity. While most work has focused on systemic ...

Visualizing and Tracking Endogenous mRNAs in Live Drosophila melanogaster Egg Chambers

Fluorescence-based imaging techniques, in combination with developments in light microscopy, have revolutionized how cell biologists conduct live cell imaging studies. Methods for detecting RNAs have expanded greatly since seminal studies linked site-specific mRNA localization to gene expression regulation. Dynamic mRNA processes can now be visualized via approaches that detect mRNAs, coupled with microscopy set-ups that are fast enough to capture the dynamic range of molecular behavior. The molecular beacon technology is a hybridization-based approach capable of direct detection of endogenous transcripts in living cells. Molecular beacons are hairpin-shaped, internally quenched, single-nucleotide discriminating nucleic acid probes, which fluoresce only upon hybridization to a unique target sequence. When coupled with advanced fluorescence microscopy and high-resolution imaging, they enable one to perform spatial and temporal tracking of intracellular movement of mRNAs. Although this technology is the only method capable of detecting endogenous transcripts, cell biologists have not yet fully embraced this technology due to difficulties in designing such probes for live cell imaging. A new software application, PinMol, allows for enhanced and rapid design of probes best suited to efficiently hybridize to mRNA target regions within a living cell. In addition, high-resolution, real-time image acquisition and current, open source image analysis software allow for a refined data output, leading to a finer evaluation of the complexity underlying the dynamic processes involved in the mRNA&#39;s life cycle.
Here we present a comprehensive protocol for designing and delivering molecular beacons into Drosophila melanogaster egg chambers. Direct and highly specific detection and visualization of endogenous maternal mRNAs is performed via spinning disc confocal microscopy. Imaging data is processed and analyzed using object detection and tracking in Icy software to obtain details about the dynamic movement of mRNAs, which are transported and localized to specialized regions within the oocyte.

Visualizing and Tracking Endogenous mRNAs in Live Drosophila melanogaster Egg Chambers

Here, we present a protocol for the visualization, detection, analysis and tracking of endogenous mRNA trafficking in live Drosophila melanogaster egg chamber using molecular beacons, spinning disc confocal microscopy, and open-source analysis software.

Visualización y seguimiento de ARNm endógenos en cámaras de huevo Drosophila melanogaster en vivo

Fluorescence-based imaging techniques, in combination with developments in light microscopy, have revolutionized how cell biologists conduct live cell ...