This work was supported by grants from the National Institutes of Health [R01 AR048179 and R01 HL126204 to R.C.W, T32 AR059033 and F32 AR069469to E.M.G] and the Muscular Dystrophy Association USA [274143 and 416364 to R.C.W.].

The methods described here were approved by the Institutional Animal Care and Use Committee at the University of California, Los Angeles. Wild-type (C57BL/6J) and mdx mice (C57Bl/10ScSn background) were purchased from a commercial source. mdx:utrophin-Tg mice were a gift from James Ervasti, with permission from Kay Davies, and were maintained on the mdx background. Ambulation assays were performed on male mice at 6 months of age. Mice were maintained in the Terasaki Life Sciences Vivarium following guidelines established by the Institutional Animal Care and Use Committee at the University of California, Los Angeles (approval #2000-029-43) and approval for these studies was granted by the UCLA Animal Welfare Assurance (approval #A3196-01).
1. Preparation of Chamber
<ol>
	<li>Perform data collection in a quiet, temperature controlled room at a consistent time of day9. Perform the tests blinded to the genotype and treatment of the mouse being tested.</li>
	<li>Adapt any open field chamber system for this analysis. 
	NOTE: In this study, we use an inexpensive and easily transportable recording chamber constructed from a large trash bin. The open field arena is a tray set on a cage or similar elevated platform.</li>
	<li>Place the camera on a wire mesh above the chamber to record across the full arena.</li>
	<li>Clean the recording chamber with disinfectant before each trial.</li>
</ol>
2. Pre-exercise Protocol and Data Collection
<ol>
	<li>Optionally, immediately prior to activity recording, challenge each mouse with a muscle activation protocol. 
	NOTE: This is optional but recommended in experiments involving mdx mice.
	<ol>
		<li>Allow the mouse to grip the pull bar of a digital force gauge and gently pull back until the pull bar is released. Repeat this procedure five times per trial.</li>
		<li>Record peak tension (N) for each trial. 
		NOTE: In addition to serving as an exercise challenge for the ambulation assay, the force exerted by the animal during this grip strength assay can be used as an additional functional outcome measure2,10.</li>
		<li>Perform five total trials for each mouse with 1 min of rest between each trial.</li>
	</ol>
	</li>
	<li>Immediately following the grip strength assay or other exercise protocol, place the mouse in the activity chamber.</li>
	<li>Start the video recording of the movement of the mouse in the chamber arena. Allow the mouse to freely explore for 6 min.</li>
	<li>Stop the recording at 6 min and return the mouse to its home cage.</li>
</ol>
3. Video Analysis
<ol>
	<li>Optionally, prepare video for analysis by reducing the frame rate. In order to reduce the frame rate for tracking analysis, use the following protocol in a video editing software (e.g., iMovie or similar program) to decimate the video frame rate by a factor of 2. 
	NOTE: Depending on length and frame rate of the video, it may be useful to reduce the video frame rate prior to analysis. In this study, video was recorded at 30 frames/s (6 min recording, approximately 10,800 frames total).
	<ol>
		<li>Load the video into the software.</li>
		<li>Under the &#39;Speed&#39; menu, select &#39;Speed: Fast&#39; and set speed to 2x.</li>
		<li>Export the decimated video in .mp4 file format for tracking analysis.</li>
	</ol>
	</li>
	<li>Open the video for analysis in the software program. Set the calibration for the video recording by using the line tool. Draw a line along one side of the chamber. Right click on the line and select &#34;Calibrate measure&#8230;&#34; Enter the actual size of the chamber side in centimeters.</li>
	<li>To begin semi-automated tracking of the mouse position, click on the &#39;move&#39; cursor. 
	Starting at the initial frame in the video, right click on the point to be tracked; the tracking point is marked with a blue circle. 
	NOTE: In the present study, the position of each animal was tracked by tracing the base of the tail.</li>
	<li>Advance the frame by clicking the right arrow on the keyboard; the tracking point should automatically move based on the position of the tail base.
	<ol>
		<li>If the tracking position is not aligned with the point of interest in a given frame, manually align the blue circle to the base of the tail. 
		NOTE: Depending on the quality of the video and the speed of the mouse, the tracking may require variable levels of user input to maintain alignment with the point of interest. The path of the mouse should advance through the course of the video.</li>
	</ol>
	</li>
	<li>When tracking of the full video is complete, save the video and tracing overlay. Export the positional data of the tracing by selecting &#34;Export to Spreadsheet&#34;.</li>
</ol>
4. Data Analysis
<ol>
	<li>Open the positional data in a spreadsheet software program. The movement analysis software reports the X,Y coordinate position of the mouse in each frame.</li>
	<li>To calculate distance traveled by frame, use the following equation (where position in frame one is x1,y1 and frame two is x2,y2): 
	<img alt="Equation" src="/files/ftp_upload/56772/56772eq1.jpg" /> 
	NOTE: Cumulative distance over time can be calculated by adding the distance traveled between each frame.</li>
</ol>

<ol>
	<li>Nagaraju, K., Carlson, G., De Luca, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Behavioral+and+locomotor+measurements+using+open+field+animal+activity+monitoring+system.">Behavioral and locomotor measurements using open field animal activity monitoring system.</a> TREAT-NMD SOP Number M2.1.002. 2. 2, (2010).</li><li>Tatem, K. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Behavioral+and+locomotor+measurements+using+an+open+field+activity+monitoring+system+for+skeletal+muscle+diseases.">Behavioral and locomotor measurements using an open field activity monitoring system for skeletal muscle diseases.</a> J Vis Exp. (91), e51785 (2014).</li><li>Kobayashi, Y. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sarcolemma-localized+nNOS+is+required+to+maintain+activity+after+mild+exercise.">Sarcolemma-localized nNOS is required to maintain activity after mild exercise.</a> Nature. 456 (7221), 511-515 (2008).</li><li>Belanto, J. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microtubule+binding+distinguishes+dystrophin+from+utrophin.">Microtubule binding distinguishes dystrophin from utrophin.</a> Proc Natl Acad Sci U S A. 111 (15), 5723-5728 (2014).</li><li>McDonald, C. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+6-minute+walk+test+in+Duchenne/Becker+muscular+dystrophy:+longitudinal+observations.">The 6-minute walk test in Duchenne/Becker muscular dystrophy: longitudinal observations.</a> Muscle Nerve. 42 (6), 966-974 (2010).</li><li>Mazzone, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Star+Ambulatory+Assessment,+6-minute+walk+test+and+timed+items+in+ambulant+boys+with+Duchenne+muscular+dystrophy.">Star Ambulatory Assessment, 6-minute walk test and timed items in ambulant boys with Duchenne muscular dystrophy.</a> Neuromuscul Disord. 20 (11), 712-716 (2010).</li><li>Kobayashi, Y. M., Rader, E. P., Crawford, R. W., Campbell, K. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endpoint+measures+in+the+mdx+mouse+relevant+for+muscular+dystrophy+pre-clinical+studies.">Endpoint measures in the mdx mouse relevant for muscular dystrophy pre-clinical studies.</a> Neuromuscul Disord. 22 (1), 34-42 (2012).</li><li>Acosta, A. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+the+six-minute+walk+test+to+characterize+golden+retriever+muscular+dystrophy.">Use of the six-minute walk test to characterize golden retriever muscular dystrophy.</a> Neuromuscul Disord. 26 (12), 865-872 (2016).</li><li>Sousa, N., Almeida, O. F., Wotjak, C. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+hitchhiker's+guide+to+behavioral+analysis+in+laboratory+rodents.">A hitchhiker's guide to behavioral analysis in laboratory rodents.</a> Genes Brain Behav. 5, 5-24 (2006).</li><li>Gibbs, E. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+levels+of+sarcospan+are+well+tolerated+and+act+as+a+sarcolemmal+stabilizer+to+address+skeletal+muscle+and+pulmonary+dysfunction+in+DMD.">High levels of sarcospan are well tolerated and act as a sarcolemmal stabilizer to address skeletal muscle and pulmonary dysfunction in DMD.</a> Hum Mol Genet. 25 (24), 5395-5406 (2016).</li><li>Gillis, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multivariate+evaluation+of+the+functional+recovery+obtained+by+the+overexpression+of+utrophin+in+skeletal+muscles+of+the+mdx+mouse.">Multivariate evaluation of the functional recovery obtained by the overexpression of utrophin in skeletal muscles of the mdx mouse.</a> Neuromuscul Disord. 12, S90-S94 (2002).</li><li>Tinsley, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+of+full-length+utrophin+prevents+muscular+dystrophy+in+mdx+mice.">Expression of full-length utrophin prevents muscular dystrophy in mdx mice.</a> Nat Med. 4 (12), 1441-1444 (1998).</li><li>Song, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Suite+of+clinically+relevant+functional+assays+to+address+therapeutic+efficacy+and+disease+mechanism+in+the+dystrophic+mdx+mouse.">Suite of clinically relevant functional assays to address therapeutic efficacy and disease mechanism in the dystrophic mdx mouse.</a> J Appl Physiol. 122 (3), 593-602 (2017).</li><li>Bolivar, V. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intrasession+and+intersession+habituation+in+mice:+from+inbred+strain+variability+to+linkage+analysis.">Intrasession and intersession habituation in mice: from inbred strain variability to linkage analysis.</a> Neurobiol Learn Mem. 92 (2), 206-214 (2009).</li></ol>

The authors have nothing to disclose.

The open field assay provides an effective and non-invasive way to test motor function in mouse models of muscle disease, and variations of this assay can serve as a valuable endpoint measure for pre-clinical studies. One major limitation with this type of assay is the high-cost and limited accessibility of activity monitoring systems. In this study, we demonstrate a low-cost system for open field activity analysis that can generate similar results to existing commercial software and equipment. This system can be used within vivaria where mice are housed, eliminating the need to transfer animals to core facilities. The versatility of this assay also enables the use of video tracking in a wide variety of research and educational settings, including undergraduate laboratory courses focused on animal physiology and behavior.
In this study, we found that differences in voluntary movement between wild-type and mdx mice can be readily detected following exacerbation by exercise. This robust difference has been reported by other groups looking at similar activity outcomes, including hour-long open field assays and overnight rearing assays. While we observed no difference in voluntary ambulation between unexercised wild-type and mdx mice, this is consistent with results from other groups13. Some researchers have reported a modest difference in voluntary ambulation distance between unexercised wild-type and mdx mice7, while others report no difference13. Our findings support the use of muscle activation prior to testing in order to reliably detect a statistically significant difference in mdx activity.
In this study, we presented mice with a novel open field environment. Using this novel environment protocol, we observed very little variability within groups. However, when mice are placed in an unfamiliar environment, they tend to have heightened activity14. If the same animals are to be tested across multiple sessions, animals should be habituated to the recording chamber and undergo the full test protocol multiple times before recording data.
One important consideration in evaluating data from open field assays is that it is highly sensitive to animal behavior and emotional conditions, particularly anxiety-like behaviors. It is possible that the mdx may have a different behavioral response to the novel environment than the wild-type control animals. However, we additionally tested a muscle-specific rescue, the mdx:utr-Tg mouse, which expresses utrophin under a muscle-specific promoter. These mice performed as well as wild-type animals, suggesting that any behavioral differences in mdx mice are not driving the changes in voluntary ambulation.
Open field assays are widely used in behavioral paradigms as well as in studies of motor function, and there are a variety of parameters that can be recorded from activity monitoring systems. Some of these measurements commonly used in commercial activity analysis software include the automated detection of specific behaviors, turn frequencies, vertical movement, and preferences for specific regions of interest. For the 6-minute ambulation distance assay used in this study, the output is largely limited to distance and speed of horizontal ambulation.
Additionally, due to the level of user input required for semi-automated tracking in this protocol, this assay would likely not be well suited for activity monitoring for longer periods of time or measuring multiple animals in parallel. In this study, we found that a trained user could process and extract data from videos in approximately 15-30 min per recording. While this represents only a moderate time burden for small-scale experiments, this level of analysis would rapidly become prohibitive for studies looking at large sample sets over a longer time period. While more fully automated commercial tracking systems typically cost more than 20,000 USD, these solutions may be more cost- and time-effective for laboratories where ambulation is frequently tested. However, for laboratory and educational settings that only test small numbers of animals, the simple set-up and reproducibility of this assay provides a valuable tool for assessing motor behavior.
The types of data analyses available are an important consideration in determining appropriate endpoint assays for a pre-clinical study. While we were able to consistently detect differences between three genotypes using 6 minute ambulation distance (wild-type, mdx, and mdx:utr-tg), a more complex analysis of longer-term activity may be desirable when looking at subtle changes in voluntary movement. However, the accessibility and simplicity of this low-cost set-up make it a useful and highly relevant functional test for pre-clinical studies in the mdx mouse model.

Reliable and reproducible measurements of muscle function are critical for evaluating the efficacy of potential therapies for DMD. DMD is a genetic disorder caused by mutations in the dystrophin gene, leading to progressive muscle weakness, loss of ambulation, and eventual cardiorespiratory failure. The most widely used animal model of DMD is the dystrophin-null mdx mouse. A battery of functional tests have emerged as routine assays for evaluating disease progression in the mdx mouse as well as in similar animal models of other dystrophies and myopathies. Commonly used in vivo assays include measurements of forelimb grip strength, wire hanging time, rotarod maximum, time to exhaustion during treadmill running, and motor activity tracking. There has been a substantial effort in the field to standardize these tests, with the goal of reducing variability between preclinical studies and increasing the translational potential of therapeutics tested in mice1,2.
One important category of preclinical testing is the measurement of voluntary movement, a parameter that is frequently altered in murine models of muscular dystrophy. This is usually tested by assays based on open field activity monitoring, and may evaluate either horizontal (walking) or vertical (rearing) movements over a course of minutes or hours2,3,4. A number of studies have shown voluntary movement to be altered in mdx mice, particularly after exercise, and these measurements have been shown to be sensitive to drug treatment and disease progression. One major limitation in performing these assays is the need for specialized, high-cost equipment. Here, a low-cost method that tracks mouse ambulation using readily available resources is presented.
The 6-minute walk distance is a metric commonly used as a clinical assessment tool in individuals with Duchenne muscular dystrophy5,6. Modifications of this measure have been used to assess outcomes in animal models of Duchenne, including mdx mice7 and golden retriever muscular dystrophy (GRMD) dogs8. In this study, we record voluntary open field movement in the 6 minutes immediately following a mild exercise challenge. Ambulation distance was then calculated using free open-source software to measure horizontal movement over time.
The main advantage of this method is that animals can be tested in a variety of settings without needing specialized equipment or high-cost commercial software for analysis. One important aspect of this analysis is that it can be performed in a basic laboratory setting without needing to move or transfer mice out of the vivarium to a specialized core facility. The video-tracking protocol described here is well-suited to the assessment of ambulation over relatively short time-periods and can detect activity differences between wild-type and mdx mice, as well as reveal functional improvement in a rescue model of DMD.

<table>
	<tbody>
		<tr>
			<td>Video camera</td>
			<td>Apple Inc.</td>
			<td>ME553LL/A</td>
			<td>For recording ambulation video, iPhone 5S Plus (or equivalent)</td>
		</tr>
		<tr>
			<td>Kinovea software (version 0.8.15)</td>
			<td>Kinovea Association</td>
			<td></td>
			<td>Open source video analysis software. Free download, PC compatible (Version 0.8.15, www.kinovea.org)</td>
		</tr>
		<tr>
			<td>iMovie (version 10.0.6)</td>
			<td>Apple Inc.</td>
			<td></td>
			<td>Any similar software can be used to reduce video frame rate (optional)</td>
		</tr>
		<tr>
			<td>Roughneck 32 Gallon Black Round Trash Bin (Open field chamber)</td>
			<td>Rubbermaid</td>
			<td># 1778013</td>
			<td>Any open field chamber system can be adapted for recording. This study uses a recording chamber constructed out of a tray on a platform, at the bottom of a large trash bin.</td>
		</tr>
		<tr>
			<td>Avant White Plastic Tray 15&#34;W x 10&#34;D x 1.45&#34;H (Open field chamber)</td>
			<td>US Acrylic, LLC</td>
			<td></td>
			<td>Any open field chamber system can be adapted for recording. This study uses a recording chamber constructed out of a tray on a platform, at the bottom of a large trash bin.</td>
		</tr>
		<tr>
			<td>C57BL/6J</td>
			<td>Jackson Laboratory</td>
			<td>#000664</td>
			<td>Male 6 month mice</td>
		</tr>
		<tr>
			<td>C57BL/10ScSn-Dmd/J (mdx)</td>
			<td>Jackson Laboratory</td>
			<td>#001801</td>
			<td>Male 6 month mice</td>
		</tr>
		<tr>
			<td>mdx: utrophin-Tg (fiona)</td>
			<td>Gift from from James Ervasti, with permission from Kay Davies</td>
			<td></td>
			<td>Male 6 month mice</td>
		</tr>
	</tbody>
</table>

a simple and low-cost assay for measuring ambulation in mouse models of muscular dystrophy

Measuring functional outcomes in the treatment of muscular dystrophy is an essential aspect of preclinical testing. The assessment of voluntary ambulation in mouse models is a non-invasive and reproducible activity assay that is directly analogous to measures of patient ambulation such as the 6-minute walk test and related mobility scores. Many common methods for testing mouse ambulation speed and distance are based on the open field test, where an animal&#39;s free movement within an arena is measured over time. One major downside to this approach is that commercial software and equipment for high-resolution motion tracking is expensive and may require transferring mice to specialized facilities for testing. Here, we describe a low-cost, video-based system for measuring mouse ambulation that utilizes free and open-source software. Using this protocol, we demonstrate that voluntary ambulation in the dystrophin-null mdx mouse model for Duchenne muscular dystrophy (DMD) is decreased relative to wild-type mouse activity. In mdx mice expressing the utrophin transgene, these activity deficits are not observed and the total distance traveled is indistinguishable from wild-type mice. This method is effective for measuring changes in voluntary ambulation associated with dystrophic pathology, and provides a versatile platform that can be readily adapted to diverse research settings.

Variations of the open field assay have been shown to be an effective method to test the disease progression in models of muscular dystrophy. Here, we demonstrate a versatile video tracking method for the analysis of two-dimensional mouse movement using readily available recording equipment and open source software (Figure 1A-B). Consistent with results reported from similar assays, we show that mdx mice challenged with an exercise protocol immediately before testing show significantly less voluntary movement in a 6-minute open field task than wild-type mice (Figure 1C, Figure 2). Following the mild exertion of a grip strength challenge, mdx mice typically remain still for the first few minutes of the ambulation protocol, with a modest increase in movement by minute 4 to 5 (Figure 3A). When testing wild-type and mdx animals without an exercise challenge, we detected no difference in total distance traveled (Figure 2).
This is consistent with reports from other groups looking at similar movement assays, with unexercised mdx showing no difference or small decreases relative to wild-type mice. We additionally evaluated transgenic mice expressing high levels of utrophin in order to test the sensitivity of our assay (mdx:utr-tg, Fiona line)11,12. The mdx:utr-tg is a robust rescue model of the mdx phenotype with few dystrophic features. Following exercise, mdx mice expressing utrophin were indistinguishable from wild-type, with no significant difference in the total distance traveled (Figure 3B) or at any of the cumulative time points measured (Figure 3A).
Video-based tracking relies on frame-to-frame variability, measured by either manual observer scoring or by automated software detection. Free and open source movement analysis software allows for semi-automated detection of animal movement, in which undetected or overestimated movements can be manually corrected as the activity trace is generated. To minimize the data processing in this assay, we downsampled the original videos from the recorded 30 fps to 15 fps. To determine the effect of decreasing the sampling rate, we measured the total distance traveled from 1 min of full frame rate video and then compared distance measurements derived from downsampled versions of the data set (Figure 4A). We found that reducing the frame rate by half (decimation by 2) decreased the measured distance by 5.0%, and reducing the frame rate as low as 7.5 fps retained nearly 90% of the original distance calculated (89.2% of distance from 30 fps video). The accuracy of measured distance dropped off sharply after this point, although even highly-decimated datasets still closely approximated the path of the animal (Figure 4B). These observations highlight the importance of considering frame rate and signal processing in assessing animal activity, and demonstrate that high spatial resolution can be retained in downsampled video data.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56772/56772fig1.jpg" /> 
Figure 1: Representative open field traces of 6-minute ambulation distance. (A) Set-up of activity recording chamber used in this study. Grip meter was used for exercise challenge prior to assay, then free ambulation was recorded on the open field platform. (B) Composite image of 6 min video recording with tracing analysis in movement tracking software. (C) Overlay of two representative traces (WT, grey, n = 1; mdx, red, n = 1). <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56772/56772fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56772/56772fig2.jpg" /> 
Figure 2: Effect of exercise on mdx ambulation. 6-minute ambulation distances were recorded at 6 months of age with or without prior exercise (non-exercised mdx n = 5, WT n = 4; exercised mdx n = 5, WT n = 5). No significant difference was observed between WT and mdx when unexercised, but a significant difference was seen in mice exercised prior to assay (no exercise: WT 1077.0&#177; 106.4 cm, mdx&#160;971.0 &#177; 36.16 cm; post-exercise: WT 770.2 &#177; 30.75 cm, mdx&#160;127.8 &#177; 36.16 cm). Data represent means &#177; SEM. Statistics calculated using two-way ANOVA followed by Tukey&#39;s multiple comparison&#39;s test (*p &#60; 0.05, **p &#60; 0.01, *** p &#60; 0.001 and ****p &#60; 0.0001). <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56772/56772fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56772/56772fig3.jpg" /> 
Figure 3: Transgenic expression of utrophin improves ambulation in mdx mice. 6-minute ambulation distances were recorded at 6 months of age using an open field activity chamber (WT n = 5, mdx n = 5, mdx:utr-Tg n = 4). (A) Cumulative distance traveled by minute. No significant difference was detected between WT and mdx:utr-tg at any point. Statistics calculated using two-way ANOVA followed by Tukey&#39;s multiple comparison&#39;s test (*p &#60; 0.05, **p &#60; 0.01, ***p &#60; 0.001 and ****p &#60; 0.0001). (B) Total open field distance traveled over 6 min (WT 770.2 &#177; 30.75 cm, mdx&#160;127.8 &#177; 36.16 cm, mdx:utr-Tg 701.3 &#177; 33.54 cm). Data represent means &#177; SEM. Statistics calculated using one-way ANOVA followed by Tukey&#39;s multiple comparison&#39;s test (*p &#60; 0.05, **p &#60; 0.01, ***p &#60; 0.001 and ****p &#60; 0.0001). <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56772/56772fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/56772/56772fig4.jpg" /> 
Figure 4: Effect of sampling rate on ambulation tracking. In a wild-type mouse, 1 min of ambulation distance was recorded and tracked using movement tracking software at full frame rate (30.0 fps, 1,819 total frames). The two-dimensional position of the mouse in each frame was determined, and these data were then decimated to simulate tracking in lower frame rate video (30, 22.5, 20, 15, 10, 7.5, 6, 3, 1.5, and 0.75 fps). (A) Total distance calculated from coordinates in each downsampled data set. Dotted lines show values within 5% of the distance calculated from the full frame rate video. Data in this study were obtained from video decimated to 15 fps (red arrow). (B) Overlays of traces comparing full frame rate tracing with 1.5 fps (above) and 15 fps (below). <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56772/56772fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about A Simple and Low-cost Assay for Measuring Ambulation in Mouse Models of Muscular Dystrophy at JoVE.com

A Simple and Low-cost Assay for Measuring Ambulation in Mouse Models of Muscular Dystrophy

This protocol describes a flexible, low-cost system for measuring mouse ambulation in an open field activity assay. We show that a 6-minute ambulation assay based on this system detects a decrease in voluntary movement in mdx mice, and accurately distinguishes improvement in a muscle-specific rescue of these animals.

Measuring functional outcomes in the treatment of muscular dystrophy is an essential aspect of preclinical testing. The assessment of voluntary ambulation ...

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Nanyang Technological University

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9.8K Views.  University of California. This protocol describes a flexible, low-cost system for measuring mouse ambulation in an open field activity assay. We show that a 6-minute ambulation assay based on this system detects a decrease in voluntary movement in mdx mice, and accurately distinguishes improvement in a muscle-specific rescue of these animals.

Video: A Simple and Low-cost Assay for Measuring Ambulation in Mouse Models of Muscular Dystrophy

Nest Building as an Indicator of Health and Welfare in Laboratory Mice

The minimization and alleviation of suffering has moral and scientific implications. In order to mitigate this negative experience one must be able to identify when an animal is actually in distress. Pain, illness, or distress cannot be managed if unrecognized. Evaluation of pain or illness typically involves the measurement of physiologic and behavioral indicators which are either invasive or not suitable for large scale assessment. The observation of nesting behavior shows promise as the basis of a species appropriate cage-side assessment tool for recognizing distress in mice. Here we demonstrate the utility of nest building behavior in laboratory mice as an ethologically relevant indicator of welfare. The methods presented can be successfully used to identify thermal stressors, aggressive cages, sickness, and pain. Observation of nest building behavior in mouse colonies provides a refinement to health and well-being assessment on a day to day basis.

We demonstrate the utility of nest building behavior in laboratory mice as an indicator of welfare. Nest scoring is a sensitive technique that is altered by temperature, illness, and aggression. The time to integrate into nest test (TINT) is a simple cage-side assessment that can detect postoperative pain.

The minimization and alleviation of  suffering has moral and scientific implications. In order to mitigate this  negative experience one must be able to ...

Barnes Maze Testing Strategies with Small and Large Rodent Models

Spatial learning and memory of laboratory rodents is often assessed via navigational ability in mazes, most popular of which are the water and dry-land (Barnes) mazes. Improved performance over sessions or trials is thought to reflect learning and memory of the escape cage/platform location. Considered less stressful than water mazes, the Barnes maze is a relatively simple design of a circular platform top with several holes equally spaced around the perimeter edge. All but one of the holes are false-bottomed or blind-ending, while one leads to an escape cage. Mildly aversive stimuli (e.g.&#160;bright overhead lights) provide motivation to locate the escape cage. Latency to locate the escape cage can be measured during the session; however, additional endpoints typically require video recording. From those video recordings, use of automated tracking software can generate a variety of endpoints that are similar to those produced in water mazes (e.g.&#160;distance traveled, velocity/speed, time spent in the correct quadrant, time spent moving/resting, and confirmation of latency). Type of search strategy (i.e.&#160;random, serial, or direct) can be categorized as well. Barnes maze construction and testing methodologies can differ for small rodents, such as mice, and large rodents, such as rats. For example, while extra-maze cues are effective for rats, smaller wild rodents may require intra-maze cues with a visual barrier around the maze. Appropriate stimuli must be identified which motivate the rodent to locate the escape cage. Both Barnes and water mazes can be time consuming as 4-7 test trials are typically required to detect improved learning and memory performance (e.g.&#160;shorter latencies or path lengths to locate the escape platform or cage) and/or differences between experimental groups. Even so, the Barnes maze is a widely employed behavioral assessment measuring spatial navigational abilities and their potential disruption by genetic, neurobehavioral manipulations, or drug/ toxicant exposure.

The dry-land Barnes maze is widely used to measure spatial navigation ability in response to mildly aversive stimuli. Over consecutive days, performance (e.g.&#160;latency to locate escape cage) of control subjects improves, indicative of normal learning and memory. Differences between rats and mice necessitate apparatus and methodology changes that are detailed here.

Spatial learning and memory of laboratory rodents is often assessed via navigational ability in mazes, most popular of which are the water and dry-land ...

The Modified Hole Board - Measuring Behavior, Cognition and Social Interaction in Mice and Rats

This protocol describes the modified hole board (mHB), which combines features from a traditional hole board and open field and is designed to measure multiple dimensions of unconditioned behavior in small laboratory mammals (e.g., mice, rats, tree shrews and small primates). This paradigm is a valuable alternative for the use of a behavioral test battery, since a broad behavioral spectrum of an animal&#8217;s behavioral profile can be investigated in one single test.
The apparatus consists of a box, representing the &#8216;protected&#8217; area, separated from a group compartment. A board, on which small cylinders are staggered in three lines, is placed in the center of the box, representing the &#8216;unprotected&#8217; area of the set-up. The cognitive abilities of the animals can be measured by baiting some cylinders on the board and measuring the working and reference memory. Other unconditioned behavior, such as activity-related-, anxiety-related- and social behavior, can be observed using this paradigm. Behavioral flexibility and the ability to habituate to a novel environment can additionally be observed by subjecting the animals to multiple trials in the mHB, revealing insight into the animals&#8217; adaptive capacities.
Due to testing order effects in a behavioral test battery, na&#239;ve animals should be used for each individual experiment. By testing multiple behavioral dimensions in a single paradigm and thereby circumventing this issue, the number of experimental animals used is reduced. Furthermore, by avoiding social isolation during testing and without the need to food deprive the animals, the mHB represents a behavioral test system, inducing if any, very low amount of stress.

This protocol describes the modified hole board, which is a behavioral test set-up that comprises the characteristics of an open field and a traditional hole board. This set-up enables the differential analysis of unconditioned behavior of small laboratory mammals as well as the analysis of cognitive abilities.

This protocol describes the modified hole board (mHB), which combines features from a traditional hole board and open field and is designed to measure ...

The Treadmill Fatigue Test: A Simple, High-throughput Assay of Fatigue-like Behavior for the Mouse

Fatigue is a prominent symptom in many diseases and disorders and reduces quality of life for many people. The lack of clear pathogenesis and failure of current interventions to adequately treat fatigue in all patients leaves a need for new treatment options. Despite the therapeutic need and importance of preclinical research in helping identify promising novel treatments, few preclinical assays of fatigue are available. Moreover, the most common preclinical assay used to assess fatigue-like behavior, voluntary wheel running, is not suitable for use with some strains of mice, may not be sensitive to drugs that reduce fatigue, and has relatively low throughput. The current protocol describes a novel, non-voluntary preclinical assay of fatigue-like behavior, the treadmill fatigue test, and provides evidence of its efficacy in detecting fatigue-like behavior in mice treated with a chemotherapy drug known to cause fatigue in humans and fatigue-like behavior in animals. This assay may be a beneficial alternative to wheel running, as fatigue-like behavior and potential interventions can be assessed in a greater number of mice over a shorter time frame, thus permitting faster discovery of new therapeutic options.

Fatigue is a common, undertreated and frequently poorly-understood symptom in many diseases and disorders. New preclinical assays of fatigue may help to improve current understanding and future treatment of fatigue. To that end, the current protocol provides a novel means of measuring fatigue-like behavior in the mouse.

Fatigue is a prominent symptom in many diseases and disorders and reduces quality of life for many people. The lack of clear pathogenesis and failure of ...

Battery of Behavioral Tests Assessing General Locomotion, Muscular Strength, and Coordination in Mice

Behavioral testing is used in pre-clinical trials to assess the phenotypic effects and outcomes that a particular disease or treatment has on the animal&#39;s wellbeing and health. There are numerous behavioral tests that may be applied. We selected a test for general locomotion, the open field test (OFT); a test for muscular strength, the mesh test (MT); and a test for coordination, the rotarod test (RR). Testing can be accomplished on a weekly or monthly basis. As a test for general locomotion, the OFT works by objectively monitoring movement parameters while the mouse is in an open field apparatus. The field is generally a 2&#39; x 2&#39; box, and the movements are recorded through laser sensing or through video capture. The mouse is placed in the center of the open field and allowed to move freely for the test. The MT uses the latency for a mouse to fall off an inverted screen as a measure of muscular strength. A mouse is placed on a screen, which is inverted over a clear box, and is timed for their latency to fall. Three trials are performed, with the best of the three trials scored for that day. A score of 60 s is the maximum time a mouse is left inverted. Mice are given a 5-min rest period between mesh test trials. Lastly, an accelerated protocol on the RR assesses motor coordination and endurance. During a trial, a mouse walks on a rotating rod as it increases in speed from 4 rpm to 40 rpm over 5 min. The trial ends when the mouse touches the magnetized pressure sensor upon falling. Each mouse undergoes three trials, and the best trial is scored for that day. This combined behavioral data allows for the global assessment of mobility, coordination, strength, and movement of the test animals. At least two out of the three behavioral testing measures must show improvement for an animal to qualify as having overall improved motor function.

Behavioral testing is used in pre-clinical trials to assess the phenotypic effects of a disease or treatment on an animal's wellbeing. In order to globally assess motor functioning, we selected tests for general locomotion, muscular strength, and coordination: the open field test, the mesh test, and the rotarod test, respectively.

Behavioral testing is used in pre-clinical trials to assess the phenotypic effects and outcomes that a particular disease or treatment has on the ...

Automated, Long-term Behavioral Assay for Cognitive Functions in Multiple Genetic Models of Alzheimer's Disease, Using IntelliCage

Multiple factors&#8212;such as aging and genes&#8212;are frequently associated with cognitive decline. Genetically modified mouse models of cognitive decline, such as Alzheimer&#39;s disease (AD), have become a promising tool to elucidate the underlying mechanisms and promote the therapeutic advances. An important step is the validation and characterization of expected behavioral abnormality in the models, in the case of AD, cognitive decline. The long-term behavioral investigations of laboratory animals to study the effect of aging demand substantial efforts from researchers. The IntelliCage system is a high-throughput and cost-effective test battery for mice that eliminates the need for daily human handling. Here, we describe how the system is utilized in the long-term phenotyping of a genetic Alzheimer&#39;s disease model, specifically focusing on the cognitive functions. The experiment employs repeated battery of tests that assess spatial learning and executive functions. This cost-effective age-dependent phenotyping allows us to identify the transient and/or permanent effects of genes on various cognitive aspects.

This paper describes a protocol for cognitive assessments for genetic models of the Alzheimer&#39;s disease using the IntelliCage system, which is a high throughput automated behavioral monitoring system with operant conditioning.

Multiple factors&#8212;such as aging and genes&#8212;are frequently associated with cognitive decline. Genetically modified mouse models of cognitive ...

Measuring Active and Passive Tameness Separately in Mice

Domesticated animals such as dogs and laboratory mice show a high level of tameness, which is important for humans to handle them easily. Tameness has two behavioral components: a reluctance to avoid humans (passive tameness) and a motivation to approach humans (active tameness). To quantify these components in mice, we previously developed behavioral tests for active tameness, passive tameness, and the willingness to stay on a human hand, each designed to be completed within 3 min. The data obtained were used for selective breeding, with a large number of mice analyzed per generation. The active tameness test measures the movement of the mouse toward a human hand and the contact it engages in. The passive tameness test measures the duration of time that a mouse tolerates human touch. In the stay-on-hand test, a mouse is placed on a human hand and touched slowly using the thumb of that hand; the duration of time that the animal remains on the hand is measured. Here, we describe the test set-up and apparatus, explain the procedures, and discuss the appropriate data analysis. Finally, we explain how to interpret the results.

Tameness in animals includes a reduction of avoidance responses to humans (passive tameness) and an increase in active approaches to humans (active tameness). Here, we describe detailed protocols for three behavioral tests (active tameness, passive tameness, and stay-on-hand tests) to separately measure the active and passive tameness of mice.

Domesticated animals such as dogs and laboratory mice show a high level of tameness, which is important for humans to handle them easily. Tameness has two ...

Continuous Noninvasive Measuring of Crayfish Cardiac and Behavioral Activities

A crayfish is a pivotal aquatic organism that serves both as a practical biological model for behavioral and physiological studies of invertebrates and as a useful biological indicator of water quality. Even though crayfish cannot directly specify the substances that cause water quality deterioration, they can immediately (within a few seconds) warn humans of water quality deterioration via acute changes in their cardiac and behavioral activities.
In this study, we present a noninvasive method that is simple enough to be implemented under various conditions due to a combination of simplicity and reliability in one model.
This approach, in which the biological organisms are implemented into environmental evaluation processes, provides a reliable and timely alarm for warning of and preventing acute water deterioration in an ambient environment. Therefore, this noninvasive system based on crayfish physiological and ethological parameter recordings was investigated for the detection of changes in an aquatic environment. This system is now applied at a local brewery for controlling&#160;quality of the water used for beverage production, but it can be used at any water treatment and supply facility for continuous, real-time water quality evaluation and for regular laboratory investigations of crayfish cardiac physiology and behavior.

This article presents a noninvasive biomonitoring system for the continuous recording and analyses of crayfish cardiac and locomotor activities. This system consists of a near-infrared optical sensor, a video-tracking module, and software for evaluating crayfish heartbeats that reflects its physiological condition and characterizes crayfish behavior during heartbeat fluctuations.

A crayfish is a pivotal aquatic organism that serves both as a practical biological model for behavioral and physiological studies of invertebrates and as ...

Low-cost Protocol of Footprint Analysis and Hanging Box Test for Mice Applied the Chronic Restraint Stress

Gait disturbance is frequently observed in patients with movement disorders. In mouse models used for movement disorders, gait analysis is important behavioral test to determine whether the mice mimic the symptoms of patients. Motor deficits are often induced by stress when no spontaneous motor phenotype is observed in the mouse models. Therefore, gait analysis followed by stress loading would be a sensitive method for evaluating the motor phenotype in mouse models. However, researchers face the requirement of an expensive apparatus to obtain quantitative results automatically from gait analysis. For stress, stress loading by simple methods without expensive apparatuses required for electric shock and forced running is desirable. Therefore, we introduce a simple and low-cost protocol consisting of footprint analysis with paper and ink, hanging box test to evaluate motor function, and stress loading defined by restraint with a conical tube. The motor deficits of mice were successfully detected by this protocol.

The low-cost protocol consisting of footprint analysis and hanging box test after restraint stress is useful for evaluating the movement disorders of mouse model.

Gait disturbance is frequently observed in patients with movement disorders. In mouse models used for movement disorders, gait analysis is important ...

Paw-Print Analysis of Contrast-Enhanced Recordings (PrAnCER): A Low-Cost, Open-Access Automated Gait Analysis System for Assessing Motor Deficits

Gait analysis is used to quantify changes in motor function in many rodent models of disease. Despite the importance of assessing gait and motor function in many areas of research, the available commercial options have several limitations such as high cost and lack of accessible, open code. To address these issues, we developed PrAnCER, Paw-Print Analysis of Contrast-Enhanced Recordings, for automated quantification of gait. The contrast-enhanced recordings are produced by using a translucent floor that obscures objects not in contact with the surface, effectively isolating the rat&#8217;s paw prints as it walks. Using these videos, our simple software program reliably measures a variety of spatiotemporal gait parameters. To demonstrate that PrAnCER can accurately detect changes in motor function, we employed a haloperidol model of Parkinson&#8217;s disease (PD). We tested rats at two doses of haloperidol: high dose (0.30 mg/kg) and low dose (0.15 mg/kg). Haloperidol significantly increased stance duration and hind paw contact area in the low dose condition, as might be expected in a PD model. In the high dose condition, we found a similar increase in contact area but also an unexpected increase in stride length. With further research, we found that this increased stride length is consistent with the bracing-escape phenomenon commonly observed at higher doses of haloperidol. Thus, PrAnCER was able to detect both expected and unexpected changes in rodent gait patterns. Additionally, we confirmed that PrAnCER is consistent and accurate when compared with manual scoring of gait parameters.

Paw-Print Analysis of Contrast-Enhanced Recordings PrAnCER: A Low-Cost, Open-Access Automated Gait Analysis System for Assessing Motor Deficits

We describe a novel gait analysis system, Paw-Print Analysis of Contrast-Enhanced Recordings (PrAnCER), an open-access automated system for the quantification of gait characteristics in rats that utilizes a novel semitransparent floor to automatically quantify gait. This system was validated using the haloperidol model of Parkinson&#8217;s Disease.

Gait analysis is used to quantify changes in motor function in many rodent models of disease. Despite the importance of assessing gait and motor function ...