Este protocolo permite el aislamiento axoplasma con la minimización de la contaminación de los tejidos gliales y vasculares. El método de producción de aproximadamente 70-100 mg de proteína total por axoplasma un 80-10 semanas de edad, la rata Wistar. 1. Disecar los nervios ciáticos <ol><li> La eutanasia a dos ratas por inhalación de CO 2 seguido por dislocación cervical. Confirmar la muerte mediante la palpación de la falta de ritmo cardíaco antes de la disección principio. </li><li> Limpie el área de disección con etanol al 70%. </li><li> Cortar la piel, los músculos separar y aislar el nervio ciático con tijeras y pinzas con cuidado, sin dañar los vasos sanguíneos. Diseccionar los nervios ciáticos (alrededor de 1,5 cm cada uno) de cada animal y recoger los cuatro nervios en un eppendorf con 500 l de PBS 0,2 X + inhibidores, se mantuvo en hielo. </li><li> La transferencia de los segmentos de los nervios a los platos de plástico que contienen al menos 2 ml de PBS 0,2 X + inhibidores de la proteasa. </li><li> Retire el epineuro de los nervios usando unas pinzas finas en el ámbito binocular. Separar los fascículos con mucho cuidado hasta que se enturbie y comienzan a flotar en la superficie de la solución. Este paso debe ser practicado hasta que pueda llevarse a cabo con rapidez y precisión (no tomar más de 10 minutos por los nervios). </li></ol> 2. Incubación, lavado y elución <ol><li> Transferencia de fascículos separados a un tubo Eppendorf con 500 l de PBS 0,2 X contiene inhibidores de la proteasa para la incubación durante 2 horas a temperatura ambiente. </li><li> Lavado por lo menos 3 veces con 1 ml del mismo tampón mediante la transferencia de los fascículos del tubo eppendorf al tubo eppendorf y agitar durante 5 min después de la transferencia. </li><li> Para eliminar el exceso de fluido que los fascículos en un nuevo tubo eppendorf vacío y luego transferir los fascículos a un nuevo tubo eppendorf con 300 L de PBS 1X que contiene inhibidor de la proteasa para la incubación durante 20-30 minutos a temperatura ambiente. </li><li> Centrifugar 10 minutos a 10.000 xga 4 ° C. </li><li> Tomar el sobrenadante y medir la concentración de proteínas. Esta es su preparación axoplasma. </li></ol> 3. Resultados representante <img src="/files/ftp_upload/2087/2087fig1.jpg" alt="Figura 1" /> Figura 1. Axoplasma Western blot comparar aislados por el método de apriete manual con las muestras de axoplasma aislado como se muestra en este protocolo. Tenga en cuenta la reducción de los niveles de albúmina y GFAP, en representación de proteína de la sangre y la contaminación de células gliales, respectivamente. Por el contrario, axonal tubulina b3 se enriquece en esta preparación, lo que indica un alto nivel de proteínas axonal.

<ol>
	<li>Hanz, S., Perlson, E., Willis, D., Zheng, J. Q., Massarwa, R., Huerta, J. J., Koltzenburg, M., Kohler, M., van-Minnen, J., Twiss, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Axoplasmic+importins+enable+retrograde+injury+signaling+in+lesioned+nerve.">Axoplasmic importins enable retrograde injury signaling in lesioned nerve.</a> Neuron. 40, 1095-1104 (2003).</li><li>Michaelevski, I., Medzihradszky, K. F., Lynn, A., Burlingame, A. L., Fainzilber, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Axonal+transport+proteomics+reveals+mobilization+of+translation+machinery+to+the+lesion+site+in+injured+sciatic+nerve.">Axonal transport proteomics reveals mobilization of translation machinery to the lesion site in injured sciatic nerve.</a> Mol Cell Proteomics. 9 (5), 976-987 (2010).</li><li>Rishal, I., Michaelevski, I., Rozenbaum, M., Shinder, V., Medzihradszky, K. F., Burlingame, A. L., Fainzilber, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Axoplasm+isolation+from+peripheral+nerve.">Axoplasm isolation from peripheral nerve.</a> Dev Neurobiol. 70, 126-133 (2010).</li><li>Twiss, J. L., Fainzilber, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ribosomes+in+axons--scrounging+from+the+neighbors.">Ribosomes in axons--scrounging from the neighbors.</a> Trends Cell Biol. 19, 236-243 (2009).</li></ol>

Los análisis bioquímicos y proteómica han confirmado que este procedimiento reduce la contaminación de células gliales en suero y 3 en comparación con los métodos descritos anteriormente para el aislamiento de axoplasma por presión mecánica 1. Hemos utilizado este protocolo de aislamiento para explorar axoplasma dineína basado en la señalización retrógrada después de la lesión del nervio ciático 2, y esperamos que tenga utilidad en la exploración de muchos otros procesos...

<ul><li> Ratas Wistar macho (8-10 semanas de edad) </li><li> PBS 0,2 X y PBS 1X soluciones que contienen inhibidores de la proteasa (Roshe) 2 comprimidos por 50 ml </li><li> Eppendorfs de 1,5 ml </li><li> Esterilizados platos de plástico de 35 mm </li><li> Herramientas de disección como: tijeras y unas pinzas finas </li><li> Binocular y mesa de luz </li></ul> Anticuerpos Mouse anti-GFAP clon GA-5 fue de Sigma (G6171). Conejo anti-albúmina fue de Cedarlane (CLAG5140). Mouse anti-tubulina β3 y de conejo anti-Gerk fueron de Sigma (T2200 y M5670, respectivamente).

axoplasm isolation from rat sciatic nerve

El aislamiento de citoplasma pura axonal (axoplasma) de los nervios periféricos es crucial para los estudios bioquímicos de muchos procesos biológicos. En este artículo, demostrar y describir un protocolo para el aislamiento de axoplasma del nervio ciático de rata adulta sobre la base de los siguientes pasos: (1) la disección de los fascículos nerviosos y la separación del tejido conectivo, (2) la incubación de segmentos cortos de fascículos nerviosos en medio hipotónico para liberar la mielina y la lisis no axonal estructuras, y (3) la extracción del resto del axón material enriquecido. Caracterización proteómica y bioquímica de esta preparación ha confirmado un alto grado de enriquecimiento para los componentes axonal.

Watch this Scientific Journal Video about Axoplasm Isolation from Rat Sciatic Nerve at JoVE.com

Axoplasm Isolation from Rat Sciatic Nerve

Demostramos un protocolo para el aislamiento de axoplasma del nervio ciático de rata adulta basada en la disección de los fascículos nerviosos y la incubación en un medio hipotónico para liberar la mielina y la lisis no axonal estructuras, seguido de la extracción del resto del axón material enriquecido.

Axoplasma de aislamiento de nervio ciático de rata

Isolation of pure axonal cytoplasm (axoplasm) from peripheral nerve is crucial for biochemical studies of many biological processes. In this article, we ...

axoplasm-isolation-from-rat-sciatic-nerve

Research

JoVE Journal

Neuroscience

13.6K vistas.  Weizmann Institute of Science. Demostramos un protocolo para el aislamiento de axoplasma del nervio ciático de rata adulta basada en la disección de los fascículos nerviosos y la incubación en un medio hipotónico para liberar la mielina y la lisis no axonal estructuras, seguido de la extracción del resto del axón material enriquecido.

Video: Axoplasm Isolation from Rat Sciatic Nerve

Reproducible Mouse Sciatic Nerve Crush and Subsequent Assessment of Regeneration by Whole Mount Muscle Analysis

Regeneration in the peripheral nervous system (PNS) is widely studied both for its relevance to human disease and to understand the robust regenerative response mounted by PNS neurons thereby possibly illuminating the failures of CNS regeneration1. Sciatic nerve crush (axonotmesis) is one of the most common models of peripheral nerve injury in rodents2. Crushing interrupts all axons but Schwann cell basal laminae are preserved so that regeneration is optimal3,4. This allows the investigator to study precisely the ability of a growing axon to interact with both the Schwann cell and basal laminae4. Rats have generally been the preferred animal models for experimental nerve crush. They are widely available and their lesioned sciatic nerve provides a reasonable approximation of human nerve lesions5,4. Though smaller in size than rat nerve, the mouse nerve has many similar qualities. Most importantly though, mouse models are increasingly valuable because of the wide availability of transgenic lines now allows for a detailed dissection of the individual molecules critical for nerve regeneration6, 7. Prior investigators have used multiple methods to produce a nerve crush or injury including simple angled forceps, chilled forceps, hemostatic forceps, vascular clamps, and investigator-designed clamps8,9,10,11,12. Investigators have also used various methods of marking the injury site including suture, carbon particles and fluorescent beads13,14,1. We describe our method to obtain a reproducibly complete sciatic nerve crush with accurate and persistent marking of the crush-site using a fine hemostatic forceps and subsequent carbon crush-site marking. As part of our description of the sciatic nerve crush procedure we have also included a relatively simple method of muscle whole mount we use to subsequently quantify regeneration.

In this report we describe a method to crush mouse sciatic nerve. This method uses readily available hemostatic forceps and easily and reproducibly produces complete sciatic nerve crush. In addition, we describe a method to prepare muscle whole mounts suitable for analysis of nerve regeneration after sciatic nerve crush.

Ratón reproducible aplastamiento del nervio ciático y posterior evaluación de la regeneración mediante el análisis de músculo entero Monte

Regeneration in the peripheral nervous system (PNS) is widely studied both for its relevance to human disease and to understand the robust regenerative ...

Investigación

Neurociencias

In Vivo Electrophysiological Measurements on Mouse Sciatic Nerves

Electrophysiological studies allow a rational classification of various neuromuscular diseases and are of help, together with neuropathological techniques, in the understanding of the underlying pathophysiology1. Here we describe a method to perform electrophysiological studies on mouse sciatic nerves in vivo.
The animals are anesthetized with isoflurane in order to ensure analgesia for the tested mice and undisturbed working environment during the measurements that take about 30 min/animal. A constant body temperature of 37 &#176;C is maintained by a heating plate and continuously measured by a rectal thermo probe2. Additionally, an electrocardiogram (ECG) is routinely recorded during the measurements in order to continuously monitor the physiological state of the investigated animals.
Electrophysiological recordings are performed on the sciatic nerve, the largest nerve of the peripheral nervous system (PNS), supplying the mouse hind limb with both motoric and sensory fiber tracts. In our protocol, sciatic nerves remain in situ and therefore do not have to be extracted or exposed, allowing measurements without any adverse nerve irritations along with actual recordings. Using appropriate needle electrodes3 we perform both proximal and distal nerve stimulations, registering the transmitted potentials with sensing electrodes at gastrocnemius muscles. After data processing, reliable and highly consistent values for the nerve conduction velocity (NCV) and the compound motor action potential (CMAP), the key parameters for quantification of gross peripheral nerve functioning, can be achieved.

In Vivo Electrophysiological Measurements on Mouse Sciatic Nerves

Measurements of nerve conduction properties in vivo exemplify a powerful tool to characterize various animal models of neuromuscular diseases. Here, we present an easy and reliable protocol by which electrophysiological analysis on sciatic nerves of anesthetized mice can be performed.

En Vivo electrofisiológicos mediciones sobre los nervios ciáticos de ratones

Electrophysiological studies allow a rational classification of various neuromuscular diseases and are of help, together with neuropathological ...

Minimally-invasive Technique for Injection into Rat Optic Nerve

The rat optic nerve is a useful model for stem cell regeneration research. Direct injection into the rat optic nerve allows delivery into the central nervous system in a minimally-invasive surgery without bone removal. This technique describes an approach to visualization and direct injection of the optic nerve following minor fascial dissection from the orbital ridge, using a conjunctival traction suture to gently pull the eye down and out. Representative examples of an injected optic nerve show successful injection of dyed beads.

Direct injection into the rat optic nerve is useful for regenerative research. We demonstrate a minimally-invasive technique for direct injection into a rat optic nerve that does not involve opening the skull. Using this method, surgical complications are minimized and recovery is more rapid.

Técnica mínimamente invasiva para la inyección en nervio óptico de la rata

The rat optic nerve is a useful model for stem cell regeneration research. Direct injection into the rat optic nerve allows delivery into the central ...

Visual Evoked Potential Recording in a Rat Model of Experimental Optic Nerve Demyelination

The visual evoked potential (VEP) recording is widely used in clinical practice to assess the severity of optic neuritis in its acute phase, and to monitor the disease course in the follow-up period. Changes in the VEP parameters closely correlate with pathological damage in the optic nerve. This protocol provides a detailed description about the rodent model of optic nerve microinjection, in which a partial demyelination lesion is produced in the optic nerve. VEP recording techniques are also discussed. Using skull implanted electrodes, we are able to acquire reproducible intra-session and between-session VEP traces. VEPs can be recorded on individual animals over a period of time to assess the functional changes in the optic nerve longitudinally. The optic nerve demyelination model, in conjunction with the VEP recording protocol, provides a tool to investigate the disease processes associated with demyelination and remyelination, and can potentially be employed to evaluate the effects of new remyelinating drugs or neuroprotective therapies.

Focal demyelination is induced in the optic nerve using lysolecithin microinjection. Visual evoked potentials are recorded via skull electrodes implanted over the visual cortex to examine the signal conduction along the visual pathway in vivo. This protocol details the surgical procedures underlying electrode implantation and optic nerve microinjection.

Grabación de potencial evocado visual en un modelo de rata de Experimental del Nervio Óptico Desmielinización

The visual evoked potential (VEP) recording is widely used in clinical practice to assess the severity of optic neuritis in its acute phase, and to ...

In Vivo Gene Transfer to Schwann Cells in the Rodent Sciatic Nerve by Electroporation

The formation of the myelin sheath by Schwann cells (SCs) is essential for rapid conduction of nerve impulses along axons in the peripheral nervous system. SC-selective genetic manipulation in living animals is a powerful technique for studying the molecular and cellular mechanisms of SC myelination and demyelination in vivo. While knockout/knockin and transgenic mice are powerful tools for studying SC biology, these methods are costly and time consuming. Viral vector-mediated transgene introduction into the sciatic nerve is a simpler and less laborious method. However, viral methods have limitations, such as toxicity, transgene size constraints, and infectivity restricted to certain developmental stages. Here, we describe a new method that allows selective transfection of myelinating SCs in the rodent sciatic nerve using electroporation. By applying electric pulses to the sciatic nerve at the site of plasmid DNA injection, genes of interest can be easily silenced or overexpressed in SCs in both neonatal and more mature animals. Furthermore, this in vivo electroporation method allows for highly efficient simultaneous expression of multiple transgenes. Our novel technique should enable researchers to efficiently manipulate SC gene expression, and facilitate studies on SC development and function.

In Vivo Gene Transfer to Schwann Cells in the Rodent Sciatic Nerve by Electroporation

Here, we present an in vivo technique for gene transfer to Schwann cells (SCs) in the rodent sciatic nerve. This simple technique is useful for investigating signaling mechanisms involved in the development and maintenance of myelinating SCs.

En Vivo Transferencia de genes a células de Schwann en el nervio ciático de roedores mediante electroporación

The formation of the myelin sheath by Schwann cells (SCs) is essential for rapid conduction of nerve impulses along axons in the peripheral nervous ...

In Vivo Electrophysiological Measurement of the Rat Ulnar Nerve with Axonal Excitability Testing

Electrophysiology enables the objective assessment of peripheral nerve function in vivo. Traditional nerve conduction measures such as amplitude and latency detect chronic axon loss and demyelination, respectively. Axonal excitability techniques &#34;by threshold tracking&#34; expand upon these measures by providing information regarding the activity of ion channels, pumps and exchangers that relate to acute function and may precede degenerative events. As such, the use of axonal excitability in animal models of neurological disorders may provide a useful in vivo measure to assess novel therapeutic interventions. Here we describe an experimental setup for multiple measures of motor axonal excitability techniques in the rat ulnar nerve.
The animals are anesthetized with isoflurane and carefully monitored to ensure constant and adequate depth of anesthesia. Body temperature, respiration rate, heart rate and saturation of oxygen in the blood are continuously monitored. Axonal excitability studies are performed using percutaneous stimulation of the ulnar nerve and recording from the hypothenar muscles of the forelimb paw. With correct electrode placement, a clear compound muscle action potential that increases in amplitude with increasing stimulus intensity is recorded. An automated program is then utilized to deliver a series of electrical pulses which generate 5 specific excitability measures in the following sequence: stimulus response behavior, strength duration time constant, threshold electrotonus, current-threshold relationship and the recovery cycle.
Data presented here indicate that these measures are repeatable and show similarity between left and right ulnar nerves when assessed on the same day. A limitation of these techniques in this setting is the effect of dose and time under anesthesia. Careful monitoring and recording of these variables should be undertaken for consideration at the time of analysis.

In Vivo Electrophysiological Measurement of the Rat Ulnar Nerve with Axonal Excitability Testing

Axonal excitability techniques provide a powerful tool to examine pathophysiology and biophysical changes that precede irreversible degenerative events. This manuscript demonstrates the use of these techniques on the ulnar nerve of anesthetized rats.

En Vivo Medición electrofisiológica del nervio cubital con la excitabilidad Axonal prueba rata

Electrophysiology enables the objective assessment of peripheral nerve function in vivo. Traditional nerve conduction measures such as amplitude and ...

Analysis of Immune Cells in Single Sciatic Nerves and Dorsal Root Ganglion from a Single Mouse Using Flow Cytometry

Nerve-resident immune cells in the peripheral nervous system (PNS) are essential to maintaining neuronal integrity in a healthy nerve. The immune cells of the PNS are affected by injury and disease, affecting the nerve function and the capacity for regeneration. Neuronal immune cells are commonly analyzed by immunofluorescence (IF). While IF is essential for determining the location of the immune cells in the nerve, IF is only semi-quantitative and the method is limited to the number of markers that can be analyzed simultaneously and the degree of surface expression. In this study, flow cytometry was used for quantitative analysis of leukocyte infiltration into sciatic nerves or dorsal root ganglions (DRGs) of individual mice. Single cell analysis was performed using DAPI and several proteins were analyzed simultaneously for either surface or intracellular expression. Both sciatic nerves from one mouse that were treated according to this protocol generated &#8805; 30,000 single nucleated events. The proportion of leukocytes in the sciatic nerves, determined by expression of CD45, was approximately 5% of total cell content in the sciatic nerve and approximately 5-10% in the DRG. Although this protocol focuses primarily on the immune cell population within the PNS, the flexibility of flow cytometry to measure a number of markers simultaneously means that the other cells populations present within the nerve, such as Schwann cells, pericytes, fibroblasts, and endothelial cells, can also be analyzed using this method. This method therefore provides a new means for studying systemic effects on the PNS, such as neurotoxicology and genetic models of neuropathy or in chronic diseases, such as diabetes.

Quantitative analysis of cell content within the murine sciatic nerve is difficult due to the scarcity of the tissue. This protocol describes a method for tissue digestion and preparation that provides sufficient cells for flow cytometry analysis of immune cell populations from nerves of individual mice.

Análisis de las células inmunes en solo de los nervios ciático y de ganglio de raíz Dorsal de un ratón mediante citometría de flujo

Nerve-resident immune cells in the peripheral nervous system (PNS) are essential to maintaining neuronal integrity in a healthy nerve. The immune cells of ...

Facial Nerve Surgery in the Rat Model to Study Axonal Inhibition and Regeneration

This protocol describes consistent and reproducible methods to study axonal regeneration and inhibition in a rat facial nerve injury model. The facial nerve can be manipulated along its entire length, from its intracranial segment to its extratemporal course. There are three primary types of nerve injury used for the experimental study of regenerative properties: nerve crush, transection, and nerve gap. The range of possible interventions is vast, including surgical manipulation of the nerve, delivery of neuroactive reagents or cells, and either central or end-organ manipulations. Advantages of this model for studying nerve regeneration include simplicity, reproducibility, interspecies consistency, reliable survival rates of the rat, and an increased anatomic size relative to murine models. Its limitations involve a more limited genetic manipulation versus the mouse model and the superlative regenerative capability of the rat, such that the facial nerve scientist must carefully assess time points for recovery and whether to translate results to higher animals and human studies. The rat model for facial nerve injury allows for functional, electrophysiological, and histomorphometric parameters for the interpretation and comparison of nerve regeneration. It thereby boasts tremendous potential toward furthering the understanding and treatment of the devastating consequences of facial nerve injury in human patients.

This protocol describes a reproducible approach to facial nerve surgery in the rat model, including descriptions of various inducible patterns of injury.

Cirugía de nervios faciales en el modelo de rata para estudiar la inhibición y regeneración axonal

This protocol describes consistent and reproducible methods to study axonal regeneration and inhibition in a rat facial nerve injury model. The facial ...

Use of In Vivo Single-fiber Recording and Intact Dorsal Root Ganglion with Attached Sciatic Nerve to Examine the Mechanism of Conduction Failure

Single-fiber recording has been a classical and effective electrophysiological technique over the last few decades because of its specific application for nerve fibers in the central and peripheral nervous systems. This method is particularly applicable to dorsal root ganglia (DRG), which are primary sensory neurons that exhibit a pseudo-unipolar structure of nervous processes. The patterns and features of the action potentials passed along axons are recordable in these neurons. The present study uses in vivo single-fiber recordings to observe the conduction failure of sciatic nerves in complete Freund&#8217;s adjuvant (CFA)-treated rats. As the underlying mechanism cannot be studied using in vivo single-fiber recordings, patch-clamp-recordings of DRG neurons are performed on preparations of intact DRG with the attached sciatic nerve. These recordings reveal a positive correlation between conduction failure and the rising slope of the after-hyperpolarization potential (AHP) of DRG neurons in CFA-treated animals. The protocol for in vivo single fiber-recordings allows the classification of nerve fibers via the measurement of conduction velocity and monitoring of abnormal conditions in nerve fibers in certain diseases. Intact DRG with attached peripheral nerve allows observation of the activity of DRG neurons in most physiological conditions. Conclusively, single-fiber recording combined with electrophysiological recording of intact DRGs is an effective method to examine the role of conduction failure during the analgesic process.

Single-fiber recording is an effective electrophysiological technique that is applicable to the central and peripheral nervous systems. Along with the preparation of intact DRG with the attached sciatic nerve, the mechanism of conduction failure is examined. Both protocols improve the understanding of the peripheral nervous system&#39;s relationship with pain.

Uso de la grabación de una sola fibra In Vivo y el ganglio de raíz dorsal intacto con nervio ciático adjunto para examinar el mecanismo de falla de conducción

Single-fiber recording has been a classical and effective electrophysiological technique over the last few decades because of its specific application for ...

3D Kinematic Analysis for the Functional Evaluation in the Rat Model of Sciatic Nerve Crush Injury

Compared to the Sciatic Functional Index (SFI), kinematic analysis is a more reliable and sensitive method for performing functional evaluations of sciatic nerve injury rodent models. In this protocol, we describe a novel kinematic analysis method that uses a three-dimensional (3D) motion capture apparatus for functional evaluations using a rat sciatic nerve crush injury model. First, the rat is familiarized with treadmill walking. Markers are then attached to the designated bone landmarks and the rat is made to walk on the treadmill at the desired speed. Meanwhile, the posterior limb movements of the rat are recorded using four cameras. Depending on the software used, marker tracings are created using both automatic and manual modes and the desired data are produced after subtle adjustments. This method of kinematic analysis, which uses a 3D motion capture apparatus, offers numerous advantages, including superior precision and accuracy. Many more parameters can be investigated during the comprehensive functional evaluations. This method has several shortcomings that require consideration: The system is expensive, can be complicated to operate, and may produce data deviations due to skin shifting. Nevertheless, kinematic analysis using a 3D motion capture apparatus is useful for performing functional anterior and posterior limb evaluations. In the future, this method may become increasingly useful for generating accurate assessments of various traumas and diseases.

We introduce a kinematic analysis method that uses a three-dimensional motion capture apparatus containing four cameras and data processing software for performing functional evaluations during fundamental research involving rodent models.

Análisis cinemático 3D para la evaluación funcional en el modelo de rata de lesión de aplastamiento de nervios ciáticos

Compared to the Sciatic Functional Index (SFI), kinematic analysis is a more reliable and sensitive method for performing functional evaluations of ...