This work was supported by National Institutes of Health Grants K08 NS061039-01A2, The Program for Neurology Research &#38; Discovery, and The A. Alfred Taubman Medical Research Institute at the University of Michigan. This work used the Morphology and Image Analysis Core of the Michigan Diabetes Research Center, funded by National Institutes of Health Grant 5P90 DK-20572 from the National Institute of Diabetes and Digestive and Kidney Diseases. The authors would like to thank J. Robinson Singleton and A. Gordon Smith (University of Utah) for their generous donation of human skin samples.

Skin punch biopsies were obtained from subjects that were recruited from a large community-based primary care network at the University of Utah Diabetes Center (Salt Lake City, UT). This study was approved by the University of Michigan Institutional Review Board and complied with the tenets of the Declaration of Helsinki. Written informed consent was obtained from each subject prior to testing.
1. Fluorescence Immunohistochemistry
<ol>
	<li>Prepare punch biopsies for intraepidermal nerve fiber immunohistochemistry:
	<ol>
		<li>Perform 3 mm skin biopsies by medical staff and place the whole biopsy in 1.5 mL Zamboni&#39;s fixative solution (2% paraformaldehyde, 0.3% saturated picric acid in phosphate buffered saline (PBS), pH 7.4) at 4 &#176;C overnight.</li>
		<li>Rinse samples with a solution of 30% sucrose in PBS at 4 &#176;C for 16-24 h or until the sample sinks.</li>
		<li>Embed samples in optimal cutting temperature compound (OCT) using a cryomold. Place the whole 3 mm biopsy with the epidermis facing down in the mold and fill the mold with approximately 2 mL of OCT. Freeze the mold on crushed dry ice. Store at -80 &#176;C until ready to use.</li>
		<li>Cut 50 &#181;m thick cross sections using a cryostat and store in individual wells of a 96-well plate using 180 &#181;L antifreeze storage solution per well (30% ethylene glycol, 30% glycerol in PBS). The following directions are for 8 wells of a 96 well plate. Stain sections from each biopsy site that are 200 - 300 &#181;m away from each other.</li>
	</ol>
	</li>
</ol>
DAY 1:
<ol start="2">
	<li>Quench non-specific labeling of the stratum corneum:
	<ol>
		<li>Label 96-well plate as shown in Figure 1.</li>
		<li>Pipet 150 &#181;L of stock signal enhancer solution to reduce nonspecific binding of secondary antibodies34,35 into each well. Transfer sections into signal enhancer solution using an inoculating loop. 
		NOTE: Take care while working with the tissue to avoid damaging or tearing the tissue sections. Keep in signal enhancer solution for 30 minutes at room temperature on a flat rocker.</li>
		<li>Prepare rinse wells in rows 2 and 3 of the 96-well plate by adding 150 &#181;L of 1x phosphate buffered saline (PBS) into each well.</li>
		<li>Carefully transfer sections into row 2 and rinse in 1x PBS for 10 min at room temperature.</li>
		<li>Rinse a second time in 1x PBS for 10 min at room temperature (row 3).</li>
	</ol>
	</li>
	<li>Prepare 5% bovine serum albumin (BSA) blocking solution:
	<ol>
		<li>Prepare 5% blocking solution that contains 5% BSA and 0.3% Triton X 100 (TX-100) in 0.1 M PBS (see Table 1) while sections are incubating in signal enhancer solution. BSA does not go into solution easily. Vortex solution until BSA completely dissolves.</li>
		<li>Prepare blocking wells in row 4 of the 96-well plate by adding 150 &#181;L of 5% BSA blocking solution into each well.</li>
		<li>Transfer sections into individual wells of 5% BSA blocking solution and incubate sections in 5% BSA blocking solution for 1 - 2 h at room temperature on a flat rocker.</li>
	</ol>
	</li>
	<li>Prepare 1% BSA rinsing solution and dilution of primary antibodies:
	<ol>
		<li>Prepare 1% rinsing solution that contains 1% BSA and 0.3% TX-100 in 0.1 M PBS (see Table 2) while sections are incubating in 5% BSA blocking solution. BSA does not go into solution easily. Vortex solution until BSA completely dissolves.</li>
		<li>Dilute primary antibodies in 1% BSA rinsing solution while sections are incubating in 5% BSA blocking solution.
		<ol>
			<li>Make 1,500 &#181;L of primary antibody solution and add to each well in row 5.</li>
			<li>Dilute the primary antibodies: Use the nerve-specific label, rabbit polyclonal anti-protein gene product 9.5 (PGP9.5) at 1:1,000. Use the mitochondria-specific label, mouse monoclonal anti-pyruvate dehydrogenase E2/E3bp antibody (PDH) at 1:100 in 1% BSA rinsing solution.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Prepare primary antibody:
	<ol>
		<li>Pipet 150 &#181;L of primary antibody into each well in row 5 of the 96-well plate.</li>
		<li>Using the loop tool, transfer sections from the blocking solution (row 4) into the row 5 containing the primary antibody.</li>
		<li>Wrap the plate tightly with parafilm to keep it from drying out.</li>
		<li>Place samples on flat rocker at room temperature for 1 h, and then incubate samples at 4 &#186;C on a flat rocker overnight.</li>
	</ol>
	</li>
</ol>
DAY 2:
<ol start="6">
	<li>Rinse samples:
	<ol>
		<li>Prepare rinse wells in rows 6, 7 and 8 of the 96-well plate by adding 150 &#181;L of 1% BSA rinsing solution into each well.</li>
		<li>Transfer sections into first 1% BSA rinsing solution (row 6) and incubate for 1 h at room temperature. Repeat rinses twice more by incubating sections in 1% BSA rinsing solution in rows 7 and 8 for 1 h each at room temperature.</li>
	</ol>
	</li>
	<li>Dilute secondary antibodies in 1% BSA rinsing solution:
	<ol>
		<li>Make 1,500 &#181;L of secondary antibody solution while sections are incubating in the last rinse of 1% BSA rinsing solution (row 8).</li>
		<li>Dilute secondary antibodies: for PGP9.5 (green-fluorescent conjugated goat anti-rabbit antibody, 1:1000), for PDH (red-fluorescent conjugated goat anti-mouse, 1:1,000) in 1% BSA rinsing solution.</li>
	</ol>
	</li>
	<li>Prepare secondary antibody:
	<ol>
		<li>Pipet 150 &#181;L of secondary antibody into row 9 of the 96-well plate.</li>
		<li>Gently transfer the sections from 1% BSA rinsing solution (row 8) into secondary antibody wells (row 9).</li>
		<li>Using parafilm, wrap the plate tightly to keep it from drying out. Cover with aluminum foil. Place samples on flat rocker at room temperature for 1 h, and then incubate samples at 4 &#730;C on a flat rocker overnight.</li>
	</ol>
	</li>
</ol>
DAY 3:
<ol start="9">
	<li>Prepare clean 1x PBS by filtering through a 0.22 &#181;m filter:
	<ol>
		<li>Pipet 150 &#181;L of filtered 1x PBS into row 10, 11, and 12.</li>
		<li>Transfer samples to row 10 and rinse in 1x PBS for 1 h at room temperature. Cover the 96-well plate with aluminum foil and place on a flat rocker during rinse. Repeat filtered 1x PBS rinse two more times for 1 h each at room temperature in rows 11 and 12.</li>
	</ol>
	</li>
	<li>Prepare microscope slides for mounting tissue sections:
	<ol>
		<li>Place 50 &#181;L of filtered 1x PBS on a slide.</li>
		<li>Transfer section from 1x PBS (row 12) into the 50 &#181;L drop. Carefully position the section in the drop of PBS by unfolding the tissue and gently flattening it onto the glass slide. Remove excess PBS with a glass pipette to avoid diluting the mounting reagent. Do not touch sections with the glass bulb.</li>
		<li>Pipet 1 - 2 drops of mounting reagent containing DAPI directly on top of the section on the microscope slide using care to not disturb the orientation of the section. Gently place a 50 mm x 24 mm #1.5 microscope glass coverslip over the section.</li>
		<li>Clear any air bubbles that formed while placing the coverslip and wipe excess liquid off the edges of the coverslip. Prepare a new slide and repeat the mounting process for each section.</li>
		<li>Cure/dry the mounting media by placing the slides in the dark overnight at room temperature. Transfer the slides to 4 &#176;C for short-term (1 - 2 weeks) or -20 &#176;C for long-term storage (greater than 2 weeks). 
		NOTE: Negative controls omitted primary antibodies for PGP9.5 or PDH in step 1.4.2.2 and displayed no distinguishable labeling of nerves or mitochondria in the epidermis. Positive controls were performed for the PDH antibody to prove it labels all mitochondria (data not shown). Positive controls were performed on cultured primary mouse dorsal root ganglion neurons that were transduced with a baculovirus to label mitochondria with a Green Fluorescent Protein (GFP) signal and then fixed and stained with the PDH antibody and red fluorescent secondary antibody. All mitochondria that were expressing GFP were co-labeled with the red label for PDH immunohistochemistry (data not shown).</li>
	</ol>
	</li>
</ol>
2. Confocal Imaging
<ol>
	<li>Perform confocal imaging:
	<ol>
		<li>Collect images using a laser scanning confocal microscope with a 40X oil-immersion (1.25 numerical aperture (N.A.)) objective on an inverted microscope.
		<ol>
			<li>At each focal plane sequentially acquire fluorescent signals: 
			Nuclei: excitation &#955; = 405 nm, spectral emission filter &#955; = 420 - 480 nm 
			Nerve fibers: excitation &#955;= 488 nm, spectral emission filter &#955; = 505 - 560 nm 
			Mitochondria: excitation &#955; = 543 nm, spectral emission filter &#955;= 606 - 670 nm</li>
		</ol>
		</li>
		<li>Enter the following scan parameters into the microscope software: scan rate of 600 Hz with 2 frame averaging and zoom of 2.2; 12-bit intensity resolution (4096 gray levels).
		<ol>
			<li>Set the microscope software for optimized lateral resolution (scan resolution = 1,024 x 1,024) and axial resolution/optical sectioning (confocal aperture = 1 airy unit (AU) with z-step size of 210 nm). 
			NOTE: The resulting XYZ resolution is 172.2 nm x 172.2 nm x 210 nm with an image size of 176.1 &#181;m x 176.1 &#181;m x 30-50 &#181;m.</li>
		</ol>
		</li>
		<li>Activate a live scan for the nerve signal (green-fluorescence) and adjust the z-focus control to find and set the upper and lower focal planes in the microscope software that encompass the nerve signal within the tissue section. The total z-range is typically 30-50 &#181;m for a 50 &#181;m tissue section.</li>
		<li>Rotate the scan field with the microscope software during a live scan so that the epidermis is horizontally or vertically positioned in the image.</li>
		<li>Scan each signal separately and adjust the detector (photomultiplier tube, PMT) voltage and offset to minimize/remove any over and under saturated pixels. 
		NOTE: Scan times with the above parameters take approximately 20 - 40 min depending on the number of z slices.</li>
	</ol>
	</li>
</ol>
3. 3D Visualization and Analysis of Mitochondria within Human Intraepidermal Nerve Fibers
<ol>
	<li>Isolate the 3D epidermis:
	<ol>
		<li>Duplicate the original image and use the maximum intensity projection (extended focus view) of the image to identify and isolate the epidermis.</li>
		<li>Use a region of interest tool to trace along the upper and lower edges of the epidermis to remove unwanted areas such as the stratum corneum and dermis that are absent of intraepidermal nerve fibers. Crop to this selection.</li>
	</ol>
	</li>
	<li>Use deconvolution on the nerve and mitochondrial fluorescent signals: 
	NOTE: Deconvolution helps to restore the integrity of the fluorescent signals. The restoration used in this protocol is called blind deconvolution because it uses the fluorescent signals in the images to determine how much the signals spread from their original source (point spread function). The process improves signal resolution by reassigning the signal spread back to its origin location.
	<ol>
		<li>Calculate a point spread function (PSF) for the green fluorescent nerve signal (green-fluorescence) with the following parameters:
		<ol>
			<li>Set calculated PSF to confocal. Set medium refractive index to 1.515 and numerical aperture to 1.25. Set detector pinhole to 1 Airy unit (A.U.). Set laser excitation wavelength to 488 nm and emission wavelength to 515 nm.</li>
		</ol>
		</li>
		<li>Calculate a PSF for the red fluorescent mitochondrial signal (red-fluorescence) with the following parameters:
		<ol>
			<li>Set calculated PSF to confocal. Set medium refractive index to 1.515 and numerical aperture to 1.25. Set detector pinhole to 1 AU. Set laser excitation wavelength to 543 nm and emission wavelength to 617 nm.</li>
		</ol>
		</li>
		<li>Optimize the nerve and mitochondria fluorescent signals by deconvolution using the corresponding PSFs listed above and iterative restoration feature set at 100% confidence and an iteration limit of 10 cycles.</li>
	</ol>
	</li>
	<li>Create nerve-specific surfaces:
	<ol>
		<li>Use the &#34;create surface&#34; tool to make a solid surface of the nerves from the deconvolved green- fluorescent secondary labeling of the PGP9.5 identified nerves.</li>
		<li>Uncheck the &#34;smooth&#34; feature and use the absolute intensity feature to set the threshold for the nerve signal since it is significantly brighter than background fluorescence.</li>
		<li>Use the absolute intensity feature to set the threshold for the nerve signal since it is significantly brighter than background fluorescence. Set threshold value low enough to accurately identify the nerves.</li>
		<li>Filter out small, non-nerve surfaces based on size. 
		NOTE: If necessary, manually edit out additional non-nerve surfaces within the &#34;Edit&#34; tab by holding the CONTROL key to highlight multiple objects and then deleting them with the Delete key.</li>
	</ol>
	</li>
	<li>Isolate nerve-specific fluorescent mitochondrial signal:
	<ol>
		<li>Select the Edit tab of the nerve surface to view the &#34;Mask Properties&#34; feature. The nerve surface created in steps 3.3 is used to isolate mitochondria within those nerves away from mitochondrial signals associated with the keratinocytes.</li>
		<li>As the &#34;Mask All&#39; button opens a &#34;Mask Channel&#34; window, choose the deconvolved red-fluorescent signal from the pull down menu under &#34;Channel Selection&#34; for the mitochondrial signal.</li>
		<li>Click in the box to put a check mark in the &#34;duplicate channel before applying mask&#34; option.</li>
		<li>Click on the radio button in front of the &#34;Constant inside/outside&#34; option of the Mask Settings and click in the box to put a check mark in the &#34;Set voxel outside surface to&#34; option and type in 0.00 for the value. Click OK button to create the new channel that represents mitochondrial signals within the nerve surface.</li>
	</ol>
	</li>
	<li>Create mitochondria-specific surfaces:
	<ol>
		<li>Use the &#34;create surface&#34; tool to make a solid surface of the mitochondria from the newly created fluorescent channel of the nerve-specific mitochondrial signals from steps 3.4.</li>
		<li>Uncheck the &#34;smooth&#34; feature and select the &#34;background subtraction&#34; feature to set the threshold. This feature uses local contrast around the mitochondrial signal to identify mitochondria from background.</li>
		<li>Set threshold value low enough to accurately identify mitochondria. In this example the lower threshold was set at 2,000 for a 16-bit (65,536) scale.</li>
		<li>Filter mitochondrial surfaces based on size. In this example the voxel limit was set to 1.0 voxels, which is the lowest limit possible. If necessary, manually edit out non-mitochondria surfaces within the &#34;Edit&#34; tab by holding the CONTROL key to select multiple objects and then deleting them with the Delete key. 
		NOTE: Occasionally, the software will create surfaces that are not associated with a distinguishable fluorescent mitochondrial signal. In these cases, it is possible to remove them with the &#34;Edit&#34; tab.</li>
	</ol>
	</li>
	<li>Export and calculate morphometric values for analysis:
	<ol>
		<li>Export values for nerve and mitochondrial surfaces from the &#34;Statistics&#34; tab for further analysis with electronic spreadsheet software.</li>
		<li>Export the volume values for both the nerve and mitochondrial surfaces.</li>
		<li>Count the number of individual nerve fibers present in each image and record the value in the electronic spreadsheet.</li>
		<li>For each image, calculate the following potential values for analysis in the electronic spreadsheet:
		<ol>
			<li>Sum the volumes for all nerve surfaces.</li>
			<li>Filter out nerve-specific mitochondrial surfaces below a volume of less than 0.02 &#181;m3 and bin the surfaces by size. For example, use bins such as 0.02 - 0.04, 0.04 - 0.08, 0.08 - 0.16, 0.16 - 0.32, 0.32 - 0.64, 0.64 - 1.28, 1.28 - 2.56, greater than 2.56 &#181;m3. 
			NOTE: The lower limit of mitochondrial volume was set to 0.02 &#181;m3 based on previously published volumes of mitonchodria36,37,38.</li>
			<li>Count the number of nerve-specific mitochondrial surfaces within each bin and the total number of surfaces over the bins (0.02 - greater than 2.56 &#181;m3).</li>
			<li>Calculate the proportion of nerve-specific mitochondrial surfaces in each bin. Use the count per bin divided by the total number of mitochondria surfaces.</li>
			<li>Sum the volumes for all nerve-specific mitochondrial surfaces.</li>
			<li>Calculate the proportion of nerve with mitochondrial signal by dividing the total nerve surface volume by the sum of all mitochondrial surface volumes.</li>
			<li>Calculate the number of mitochondria per nerve volume by dividing the total nerve surface volume by the count of all mitochondrial surfaces.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>

No conflicts of interest to declare.

This protocol is designed to isolate, quantify and analyze the size and distribution of nerve-specific mitochondria within IENFs in 3D from human skin biopsies. There are several critical steps in the protocol. The free-floating fluorescence immunohistochemistry is designed to stain and analyze multiple signals in each sample, providing a more versatile methodology for explorative research44,45. This procedure allows for penetration of the antibodies into the tis...

Mitochondria serve vital cellular functions that include producing cell energy, buffering calcium, and regulating necrotic and apoptotic cell death1,2,3. The nervous system has a high metabolic rate compared to the body4 suggesting that neurons generate a high degree of cellular energy in the form of adenosine triphosphate (ATP) through mitochondrial respiration. A lot of evidence documents that neuronal functions are dependent on ATP5, especially at the synapses6. Therefore, the distribution of mitochondria within neurons is important.
Over the last 10 years a lot of information has shown that the trafficking and docking of neuronal mitochondria is highly regulated. Motor proteins are involved in distributing mitochondria to specific cellular compartments throughout the neuron. Trafficking of mitochondria is particularly important because neurons project axons and dendrites far away from the soma. Kinesin motor proteins primarily direct anterograde (away from the soma) trafficking of mitochondria along microtubules while dynein motor proteins direct retrograde (toward the soma) motility7,8,9,10. There are cellular signals such a mitochondrial membrane potential and impulse conduction that influence the presence and direction of mitochondrial trafficking11,12,13.
In addition to transporting mitochondria, there are specialized proteins to localize mitochondria to specific cellular compartments that have high energy demands, such as nodes of Ranvier and synapses8,14,17. In fact, the majority of mitochondria within axons are non-motile9,13,18. Specialized proteins like syntaphilin anchor mitochondria to microtubules along axons while other proteins anchor mitochondria to the actin cytoskeleton19-21. Growth factors and ions such as calcium have been reported to support the cessation of mitochondria movement to localize them to regions where they are needed21,22,23.
Taken together, the trafficking and docking of mitochondria are vital for proper function of neurons. In support of this, disruption in mitochondrial trafficking has been associated with several neurological conditions including Alzheimer&#39;s disease, amyotrophic lateral sclerosis, Charcot-Marie-Tooth disease, Huntington&#39;s disease, hereditary spastic paraparesis, and optic atrophy15,24,25,26,27. Recent studies have focused on mitochondrial dysfunction and pathology as a potential mechanism for diabetic neuropathy, the sensory loss associated with diabetes28,29,30,31,32,33. The hypothesis is that diabetes alters the distribution of mitochondria within the sensory projections of cutaneous nerve ending. Therefore, a technique was developed to visualize and quantify mitochondria within the intraepidermal nerve fibers (IENFs), the distal tips of dorsal root ganglion sensory afferents. The technique combines fluorescence immunohistochemistry of specific mitochondrial and nerve fiber labels with confocal microscopy z-series acquisition of signals with powerful 3D image analysis software to measure the distribution of nerve-specific mitochondria from human cutaneous punch biopsies to achieve this goal.

<table border="0" cellpadding="0" cellspacing="0" width="1027">
	<tbody>
		<tr height="69">
			<td height="69" style="height:69px;width:267px;">2% Zamboni&#39;s Fixative</td>
			<td style="width:200px;">Newcomer Supply, Middleton, WI&#160;</td>
			<td style="width:199px;">1459A</td>
			<td style="width:363px;">2% paraformaldehyde, 0.2% saturated picric acid in phosphate buffered saline (PBS), pH 7.4</td>
		</tr>
		<tr height="48">
			<td height="48" style="height:48px;width:267px;">10X Phosphate Buffered Saline (PBS)&#160;</td>
			<td style="width:200px;">Fisher Scientific, Pittsburgh, PA</td>
			<td style="width:199px;">BP399-4</td>
			<td style="width:363px;">To make up 1X PBS</td>
		</tr>
		<tr height="47">
			<td height="47" style="height:47px;width:267px;">Image-iT FX Signal Enhancer</td>
			<td style="width:200px;">ThermoFisher Scientific, Waltham, Massachusetts</td>
			<td style="width:199px;">I36933</td>
			<td style="width:363px;">enhances Alexa Fluor dye signals by reducing nonspecific binding</td>
		</tr>
		<tr height="73">
			<td height="73" style="height:73px;width:267px;">Anti-Protein Gene Product 9.5 Antibody (Rabbit Polyclonal)</td>
			<td style="width:200px;">Proteintech Group Inc. Rosemont, IL</td>
			<td style="width:199px;">14730-1-AP</td>
			<td style="width:363px;">abbreviated as PGP9.5, replaces discontinued AbD Serotec (Cat. No. 7863-0504) antibody</td>
		</tr>
		<tr height="66">
			<td height="66" style="height:66px;width:267px;">Anti-Pyruvate Dehydrogenase E2/E3bp Antibody (Mouse Monoclonal)</td>
			<td style="width:200px;">abcam, Cambridge, MA</td>
			<td style="width:199px;">ab110333</td>
			<td style="width:363px;">abbreviated as PDH</td>
		</tr>
		<tr height="50">
			<td height="50" style="height:50px;width:267px;">Goat anti-mouse Secondary antibody Alexa Fluor 594 conjugate</td>
			<td style="width:200px;">ThermoFisher Scientific, Waltham, Massachusetts</td>
			<td style="width:199px;">A-11034</td>
			<td style="width:363px;">red-fluorescent conjugated secondaryantibody</td>
		</tr>
		<tr height="51">
			<td height="51" style="height:51px;width:267px;">Goat anti-rabbit Secondary antibody Alexa Fluor 488 conjugate</td>
			<td style="width:200px;">ThermoFisher Scientific, Waltham, Massachusetts</td>
			<td style="width:199px;">A-11032</td>
			<td style="width:363px;">green-fluorescent conjugated secondaryantibody</td>
		</tr>
		<tr height="44">
			<td height="44" style="height:44px;width:267px;">Albumin, from Bovine Serum</td>
			<td style="width:200px;">Sigma-Aldrich, St. Louis, MO</td>
			<td style="width:199px;">A7906-100</td>
			<td style="width:363px;">abbreviated as BSA</td>
		</tr>
		<tr height="48">
			<td height="48" style="height:48px;width:267px;">Triton X- 100</td>
			<td style="width:200px;">Sigma-Aldrich, St. Louis, MO</td>
			<td style="width:199px;">T9284</td>
			<td style="width:363px;">abbreviated as TX-100</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:267px;">0.22 &#181;m Filter</td>
			<td style="width:200px;">EMD Millipore, Billerica 
			MA</td>
			<td style="width:199px;">MILLEX GP SLGP 033NS</td>
			<td style="width:363px;">0.22 &#181;m Millipore filter</td>
		</tr>
		<tr height="51">
			<td height="51" style="height:51px;width:267px;">Parafilm M</td>
			<td style="width:200px;">Fisher Scientific, Pittsburgh, PA</td>
			<td style="width:199px;">13-374-10</td>
			<td style="width:363px;">Curwood Wisconsin LLC Parafilm M (PM-996)</td>
		</tr>
		<tr height="51">
			<td height="51" style="height:51px;width:267px;">Non-calibrated Loop</td>
			<td style="width:200px;">Fisher Scientific, Pittsburgh, PA</td>
			<td style="width:199px;">22-032092</td>
			<td style="width:363px;">inoculating Loop by Decon LeLoop (MP 199-25)</td>
		</tr>
		<tr height="52">
			<td height="52" style="height:52px;width:267px;">96-well Assay Plate</td>
			<td style="width:200px;">Corning Incorporated, Corning, NY</td>
			<td style="width:199px;">3603</td>
			<td style="width:363px;">96-well flat bottom plate</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:267px;">Prolong Gold antifade reagent with DAPI</td>
			<td style="width:200px;">ThermoFisher Scientific, Waltham, Massachusetts</td>
			<td style="width:199px;">P-36931</td>
			<td style="width:363px;">DAPI staining of nuclei</td>
		</tr>
		<tr height="46">
			<td height="46" style="height:46px;width:267px;">Microscope Cover Glass 50 x 24 mm</td>
			<td style="width:200px;">Fisher Scientific, Pittsburgh, PA</td>
			<td style="width:199px;">12-544E</td>
			<td style="width:363px;">Coverslips</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:267px;">Superfrost Plus Microscope Slides</td>
			<td style="width:200px;">Fisher Scientific, Pittsburgh, PA</td>
			<td style="width:199px;">12-550-15</td>
			<td style="width:363px;">Microscope Slides</td>
		</tr>
		<tr height="45">
			<td height="45" style="height:45px;width:267px;">Leica SP5 Laser Scanning Confocal Microscope</td>
			<td style="width:200px;">Leica Microsystems, Buffalo Grove, IL</td>
			<td style="width:199px;">SP5</td>
			<td style="width:363px;">Confocal Microscope</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:267px;">Volocity x64 Software&#160;</td>
			<td style="width:200px;">Perkin Elmer, Waltham , MA</td>
			<td style="width:199px;">version 4.4.0</td>
			<td style="width:363px;">Volocity software is used for Steps 3.1 and 3.2 in the protocol for image processing</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:267px;">Imaris x64 3 Dimensional Analysis Software</td>
			<td style="width:200px;">Bitplane, Concord, MA</td>
			<td style="width:199px;">version 7.7.1</td>
			<td style="width:363px;">Imaris software is used for Steps 3.3 through 3.5 in the protocol for image analysis</td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:267px;">Excel</td>
			<td style="width:200px;">Microsoft, Redmond, WA</td>
			<td style="width:199px;">version Office 2013</td>
			<td style="width:363px;">Excel spreadsheet software is used for Step 3.6 in the protocol to summarize morphometric features</td>
		</tr>
		<tr height="52">
			<td height="52" style="height:52px;width:267px;">Optimum Cutting Temperature Compound</td>
			<td style="width:200px;">Sakura Finetek USA, Inc., Torrance, CA</td>
			<td style="width:199px;">4583</td>
			<td style="width:363px;">abbreviated as OCT</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:267px;">Leica Cryostat</td>
			<td style="width:200px;">Leica Biosystems, Buffalo Grove, IL</td>
			<td style="width:199px;">CM1850</td>
			<td style="width:363px;">Cryostat for cutting 50 &#181;m sections</td>
		</tr>
		<tr height="50">
			<td height="50" style="height:50px;width:267px;">CellLight Mitochondria-GFP, BacMam 2.0</td>
			<td style="width:200px;">ThermoFisher Scientific, Waltham, Massachusetts</td>
			<td style="width:199px;">C10600</td>
			<td style="width:363px;">Used as a postive control to label mitochondria with a green fluorescent signal</td>
		</tr>
	</tbody>
</table>

three-dimensional imaging and analysis of mitochondria within human intraepidermal nerve fibers

The goal of this protocol is to study mitochondria within intraepidermal nerve fibers. Therefore, 3D imaging and analysis techniques were developed to isolate nerve-specific mitochondria and evaluate disease-induced alterations of mitochondria in the distal tip of sensory nerves. The protocol combines fluorescence immunohistochemistry, confocal microscopy and 3D image analysis techniques to visualize and quantify nerve-specific mitochondria. Detailed parameters are defined throughout the procedures in order to provide a concrete example of how to use these techniques to isolate nerve-specific mitochondria. Antibodies were used to label nerve and mitochondrial signals within tissue sections of skin punch biopsies, which was followed by indirect immunofluorescence to visualize nerves and mitochondria with a green and red fluorescent signal respectively. Z-series images were acquired with confocal microscopy and 3D analysis software was used to process and analyze the signals. It is not necessary to follow the exact parameters described within, but it is important to be consistent with the ones chosen throughout the staining, acquisition and analysis steps. The strength of this protocol is that it is applicable to a wide variety of circumstances where one fluorescent signal is used to isolate other signals that would otherwise be impossible to study alone.

Visualization and quantification of mitochondria within human IENFs
Fluorescence immunohistochemistry allows for the simultaneous labeling of multiple signals within human skin biopsies to visualize nerves, mitochondria, and nuclei. A 96-well plate is a convenient way to organize the steps in the immunohistochemistry procedure. Figure 1 shows that this configuration accounts for up ...

Watch this Scientific Journal Video about Three-dimensional Imaging and Analysis of Mitochondria within Human Intraepidermal Nerve Fibers at JoVE.com

Three-dimensional Imaging and Analysis of Mitochondria within Human Intraepidermal Nerve Fibers

This protocol uses three-dimensional (3D) imaging and analysis techniques to visualize and quantify nerve-specific mitochondria. The techniques are applicable to other situations where one fluorescent signal is used to isolate a subset of data from another fluorescent signal.

The goal of this protocol is to study mitochondria within intraepidermal nerve fibers. Therefore, 3D imaging and analysis techniques were developed to ...

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Research

JoVE Journal

Neuroscience

10.1K Views.  University of Michigan Medical School. This protocol uses three-dimensional (3D) imaging and analysis techniques to visualize and quantify nerve-specific mitochondria. The techniques are applicable to other situations where one fluorescent signal is used to isolate a subset of data from another fluorescent signal. 

Video: Three-dimensional Imaging and Analysis of Mitochondria within Human Intraepidermal Nerve Fibers

Tissue Preparation and Immunostaining of Mouse Sensory Nerve Fibers Innervating Skin and Limb Bones

Detection and primary processing of physical, chemical and thermal sensory stimuli by peripheral sensory nerve fibers is key to sensory perception in animals and humans. These peripheral sensory nerve fibers express a plethora of receptors and ion channel proteins which detect and initiate specific sensory stimuli. Methods are available to characterize the electrical properties of peripheral sensory nerve fibers innervating the skin, which can also be utilized to identify the functional expression of specific ion channel proteins in these fibers. However, similar electrophysiological methods are not available (and are also difficult to develop) for the detection of the functional expression of receptors and ion channel proteins in peripheral sensory nerve fibers innervating other visceral organs, including the most challenging tissues such as bone. Moreover, such electrophysiological methods cannot be utilized to determine the expression of non-excitable proteins in peripheral sensory nerve fibers. Therefore, immunostaining of peripheral/visceral tissue samples for sensory nerve fivers provides the best possible way to determine the expression of specific proteins of interest in these nerve fibers. So far, most of the protein expression studies in sensory neurons have utilized immunostaining procedures in sensory ganglia, where the information is limited to the expression of specific proteins in the cell body of specific types or subsets of sensory neurons. Here we report detailed methods/protocols for the preparation of peripheral/visceral tissue samples for immunostaining of peripheral sensory nerve fibers. We specifically detail methods for the preparation of skin or plantar punch biopsy and bone (femur) sections from mice for immunostaining of peripheral sensory nerve fibers. These methods are not only key to the qualitative determination of protein expression in peripheral sensory neurons, but also provide a quantitative assay method for determining changes in protein expression levels in specific types or subsets of sensory fibers, as well as for determining the morphological and/or anatomical changes in the number and density of sensory fibers during various pathological states. Further, these methods are not confined to the staining of only sensory nerve fibers, but can also be used for staining any types of nerve fibers in the skin, bones and other visceral tissue.

Immunocytochemical identification of peripheral sensory nerve fiber subtypes (and detection of protein expression therein) are key to the understanding of molecular mechanisms underlying peripheral sensation. Here we describe methods for preparation of peripheral/visceral tissue samples, such as skin and limb bones, for specific immunostaining of peripheral sensory nerve fibers.

Detection and primary processing of physical, chemical and thermal sensory stimuli by peripheral sensory nerve fibers is key to sensory perception in ...

Three Dimensional Vestibular Ocular Reflex Testing Using a Six Degrees of Freedom Motion Platform

The vestibular organ is a sensor that measures angular and linear accelerations with six degrees of freedom (6DF). Complete or partial defects in the vestibular organ results in mild to severe equilibrium problems, such as vertigo, dizziness, oscillopsia, gait unsteadiness nausea and/or vomiting. A good and frequently used measure to quantify gaze stabilization is the gain, which is defined as the magnitude of compensatory eye movements with respect to imposed head movements. To test vestibular function more fully one has to realize that 3D VOR ideally generates compensatory ocular rotations not only with a magnitude (gain) equal and opposite to the head rotation but also about an axis that is co-linear with the head rotation axis (alignment). Abnormal vestibular function thus results in changes in gain and changes in alignment of the 3D VOR response.
Here we describe a method to measure 3D VOR using whole body rotation on a 6DF motion platform. Although the method also allows testing translation VOR responses 1, we limit ourselves to a discussion of the method to measure 3D angular VOR. In addition, we restrict ourselves here to description of data collected in healthy subjects in response to angular sinusoidal and impulse stimulation.
Subjects are sitting upright and receive whole-body small amplitude sinusoidal and constant acceleration impulses. Sinusoidal stimuli (f = 1 Hz, A = 4&deg;) were delivered about the vertical axis and about axes in the horizontal plane varying between roll and pitch at increments of 22.5&deg; in azimuth. Impulses were delivered in yaw, roll and pitch and in the vertical canal planes. Eye movements were measured using the scleral search coil technique 2. Search coil signals were sampled at a frequency of 1 kHz.
The input-output ratio (gain) and misalignment (co-linearity) of the 3D VOR were calculated from the eye coil signals 3.
Gain and co-linearity of 3D VOR depended on the orientation of the stimulus axis. Systematic deviations were found in particular during horizontal axis stimulation. In the light the eye rotation axis was properly aligned with the stimulus axis at orientations 0&deg; and 90&deg; azimuth, but gradually deviated more and more towards 45&deg; azimuth.
The systematic deviations in misalignment for intermediate axes can be explained by a low gain for torsion (X-axis or roll-axis rotation) and a high gain for vertical eye movements (Y-axis or pitch-axis rotation (see Figure 2). Because intermediate axis stimulation leads a compensatory response based on vector summation of the individual eye rotation components, the net response axis will deviate because the gain for X- and Y-axis are different.
In darkness the gain of all eye rotation components had lower values. The result was that the misalignment in darkness and for impulses had different peaks and troughs than in the light: its minimum value was reached for pitch axis stimulation and its maximum for roll axis stimulation.
Case Presentation
Nine subjects participated in the experiment. All subjects gave their informed consent. The experimental procedure was approved by the Medical Ethics Committee of Erasmus University Medical Center and adhered to the Declaration of Helsinki for research involving human subjects.
Six subjects served as controls. Three subjects had a unilateral vestibular impairment due to a vestibular schwannoma. The age of control subjects (six males and three females) ranged from 22 to 55 years. None of the controls had visual or vestibular complaints due to neurological, cardio vascular and ophthalmic disorders.
The age of the patients with schwannoma varied between 44 and 64 years (two males and one female). All schwannoma subjects were under medical surveillance and/or had received treatment by a multidisciplinary team consisting of an othorhinolaryngologist and a neurosurgeon of the Erasmus University Medical Center. Tested patients all had a right side vestibular schwannoma and underwent a wait and watch policy (Table 1; subjects N1-N3) after being diagnosed with vestibular schwannoma. Their tumors had been stabile for over 8-10 years on magnetic resonance imaging.

A method is described to measure three-dimensional vestibulo ocular reflexes (3D VOR) in humans using a six degrees of freedom (6DF) motion simulator. The gain and misalignment of the 3D angular VOR provide a direct measure of the quality of vestibular function. Representative data on healthy subjects are provided

The vestibular organ is a sensor that measures angular and linear accelerations with six degrees of freedom (6DF). Complete or partial defects in the ...

Selective Tracing of Auditory Fibers in the Avian Embryonic Vestibulocochlear Nerve

The embryonic chick is a widely used model for the study of peripheral and central ganglion cell projections. In the auditory system, selective labeling of auditory axons within the VIIIth cranial nerve would enhance the study of central auditory circuit development. This approach is challenging because multiple sensory organs of the inner ear contribute to the VIIIth nerve 1. Moreover, markers that reliably distinguish auditory versus vestibular groups of axons within the avian VIIIth nerve have yet to be identified. Auditory and vestibular pathways cannot be distinguished functionally in early embryos, as sensory-evoked responses are not present before the circuits are formed. Centrally projecting VIIIth nerve axons have been traced in some studies, but auditory axon labeling was accompanied by labeling from other VIIIth nerve components 2,3. Here, we describe a method for anterograde tracing from the acoustic ganglion to selectively label auditory axons within the developing VIIIth nerve. First, after partial dissection of the anterior cephalic region of an 8-day chick embryo immersed in oxygenated artificial cerebrospinal fluid, the cochlear duct is identified by anatomical landmarks. Next, a fine pulled glass micropipette is positioned to inject a small amount of rhodamine dextran amine into the duct and adjacent deep region where the acoustic ganglion cells are located. Within thirty minutes following the injection, auditory axons are traced centrally into the hindbrain and can later be visualized following histologic preparation. This method provides a useful tool for developmental studies of peripheral to central auditory circuit formation.

Here we describe a microdissection technique followed by fluorescent dye injection into the acoustic ganglion of early chick embryos for selective tracing of auditory axon fibers in the nerve and hindbrain.

The embryonic chick is a widely used model for the study of peripheral and central ganglion cell projections. In the auditory system, selective labeling ...

Three-dimensional Confocal Analysis of Microglia/macrophage Markers of Polarization in Experimental Brain Injury

After brain stroke microglia/macrophages (M/M) undergo rapid activation with dramatic morphological and phenotypic changes that include expression of novel surface antigens and production of mediators that build up and maintain the inflammatory response. Emerging evidence indicates that M/M are highly plastic cells that can assume classic pro-inflammatory (M1) or alternative anti-inflammatory (M2) activation after acute brain injury. However a complete characterization of M/M phenotype marker expression, their colocalization and temporal evolution in the injured brain is still missing.	
	Immunofluorescence protocols specifically staining relevant markers of M/M activation can be performed in the ischemic brain. Here we present immunofluorescence-based protocols followed by three-dimensional confocal analysis as a powerful approach to investigate the pattern of localization and co-expression of M/M phenotype markers such as CD11b, CD68, Ym1, in mouse model of focal ischemia induced by permanent occlusion of the middle cerebral artery (pMCAO). Two-dimensional analysis of the stained area reveals that each marker is associated to a defined M/M morphology and has a given localization in the ischemic lesion. Patterns of M/M phenotype marker co-expression can be assessed by three-dimensional confocal imaging in the ischemic area. Images can be acquired over a defined volume (10 &mu;m z-axis and a 0.23 &mu;m step size, corresponding to a 180 x 135 x 10 &mu;m volume) with a sequential scanning mode to minimize bleed-through effects and avoid wavelength overlapping. Images are then processed to obtain three-dimensional renderings by means of Imaris software. Solid view of three dimensional renderings allows the definition of marker expression in clusters of cells. We show that M/M have the ability to differentiate towards a multitude of phenotypes, depending on the location in the lesion site and time after injury.

A way to gain new insights into the complexity of the brain inflammatory response is presented. We describe immunofluorescence-based protocols followed by three-dimensional confocal analysis to investigate the pattern of co-expression of microglia/macrophage phenotype markers in a mouse model of focal ischemia.

After brain stroke microglia/macrophages (M/M) undergo  rapid activation with dramatic morphological and phenotypic changes that  include expression of ...

Protocol for Three-dimensional Confocal Morphometric Analysis of Astrocytes

As glial cells in the brain, astrocytes have diverse functional roles in the central nervous system. In the presence of harmful stimuli, astrocytes modify their functional and structural properties, a condition called reactive astrogliosis. Here, a protocol for assessment of the morphological properties of astrocytes is presented. This protocol includes quantification of 12 different parameters i.e. the surface area and volume of the tissue covered by an astrocyte (astrocyte territory), the entire astrocyte including branches, cell body, and nucleus, as well as total length and number of branches, the intensity of fluorescence immunoreactivity of antibodies used for astrocyte detection, and astrocyte density (number/1,000 &#181;m2). For this purpose three-dimensional (3D) confocal microscopic images were created, and 3D image analysis software such as Volocity 6.3 was used for measurements. Rat brain tissue exposed to amyloid beta1-40 (A&#946;1-40) with or without a therapeutic&#160;intervention was used to present the method. This protocol can also be used for 3D morphometric analysis of other cells from either in vivo or in vitro conditions.

Astrocytes in the CNS change their functional and structural properties in response to harmful stimuli. This report presents a protocol for assessment of three-dimensional astrocyte morphology in diseased conditions or after therapeutic interventions.

As glial cells in the brain, astrocytes have diverse functional roles in the central nervous system. In the presence of harmful stimuli, astrocytes modify ...

Analysis of Brain Mitochondria Using Serial Block-Face Scanning Electron Microscopy

Human brain is a high energy consuming organ that mainly relies on glucose as a fuel source. Glucose is catabolized by brain mitochondria via glycolysis, tri-carboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) pathways to produce cellular energy in the form of adenosine triphosphate (ATP). Impairment of mitochondrial ATP production causes mitochondrial disorders, which present clinically with prominent neurological and myopathic symptoms. Mitochondrial defects are also present in neurodevelopmental disorders (e.g. autism spectrum disorder) and neurodegenerative disorders (e.g. amyotrophic lateral sclerosis, Alzheimer&#39;s and Parkinson&#39;s diseases). Thus, there is an increased interest in the field for performing 3D analysis of mitochondrial morphology, structure and distribution under both healthy and disease states. The brain mitochondrial morphology is extremely diverse, with some mitochondria especially those in the synaptic region being in the range of &#60;200 nm diameter, which is below the resolution limit of traditional light microscopy. Expressing a mitochondrially-targeted green fluorescent protein (GFP) in the brain significantly enhances the organellar detection by confocal microscopy. However, it does not overcome the constraints on the sensitivity of detection of relatively small sized mitochondria without oversaturating the images of large sized mitochondria. While serial transmission electron microscopy has been successfully used to characterize mitochondria at the neuronal synapse, this technique is extremely time-consuming especially when comparing multiple samples. The serial block-face scanning electron microscopy (SBFSEM) technique involves an automated process of sectioning, imaging blocks of tissue and data acquisition. Here, we provide a protocol to perform SBFSEM of a defined region from rodent brain to rapidly reconstruct and visualize mitochondrial morphology. This technique could also be used to provide accurate information on mitochondrial number, volume, size and distribution in a defined brain region. Since the obtained image resolution is high (typically under 10 nm) any gross mitochondrial morphological defects may also be detected.

Mitochondrial visualization and analysis from mammalian brain tissue is a challenging task. Here, we describe how three dimensional (3D) reconstruction analysis from the serial block-face scanning electron microscopy (SBFSEM) can be used to gain insights on the morphological and volumetric analysis of this critical energy generating organelle.

Human brain is a high energy consuming organ that mainly relies on glucose as a fuel source. Glucose is catabolized by brain mitochondria via glycolysis, ...

Large-scale Three-dimensional Imaging of Cellular Organization in the Mouse Neocortex

The mammalian neocortex is composed of many types of excitatory and inhibitory neurons, each with specific electrophysiological and biochemical properties, synaptic connections, and in vivo functions, but their basic functional and anatomical organization from cellular to network scale is poorly understood. Here we describe a method for the three-dimensional imaging of fluorescently-labeled neurons across large areas of the brain for the investigation of the cortical cellular organization. Specific types of neurons are labeled by the injection of fluorescent retrograde neuronal tracers or expression of fluorescent proteins in transgenic mice. Block brain samples, e.g., a hemisphere, are prepared after fixation, made transparent with tissue clearing methods, and subjected to fluorescent immunolabeling of the specific cell types. Large areas are scanned using confocal or two-photon microscopes equipped with large working distance objectives and motorized stages. This method can resolve the periodic organization of the cell type-specific microcolumn functional modules in the mouse neocortex. The procedure can be useful for the study of three-dimensional cellular architecture in the diverse brain areas and other complex tissues.

Here we describe a procedure for tissue clearing, fluorescent labeling, and large-scale imaging of mouse brain tissue which, thereby, enables visualization of the three-dimensional organization of cell types in the neocortex.

The mammalian neocortex is composed of many types of excitatory and inhibitory neurons, each with specific electrophysiological and biochemical ...

Three-Dimensional Shape Modeling and Analysis of Brain Structures

Statistical shape analysis of brain structures has been used to investigate the association between their structural changes and pathological processes. We have developed a software package for accurate and robust shape modeling and group-wise analysis. Here, we introduce an pipeline for the shape analysis, from individual 3D shape modeling to quantitative group shape analysis. We also describe the pre-processing and segmentation steps using open software packages. This practical guide would help researchers save time and effort in 3D shape analysis on brain structures.

We introduce a semi-automatic protocol for shape analysis on brain structures, including image segmentation using open software, and further group-wise shape analysis using an automated modeling package. Here, we demonstrate each step of the 3D shape analysis protocol with hippocampal segmentation from brain MR images.

Statistical shape analysis of brain structures has been used to investigate the association between their structural changes and pathological processes. ...

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.

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

Imaging and Analysis of Neurofilament Transport in Excised Mouse Tibial Nerve

Neurofilament protein polymers move along axons in the slow component of axonal transport at average speeds of ~0.35-3.5 mm/day. Until recently the study of this movement in situ was only possible using radioisotopic pulse-labeling, which permits analysis of axonal transport in whole nerves with a temporal resolution of days and a spatial resolution of millimeters. To study neurofilament transport in situ with higher temporal and spatial resolution, we developed a hThy1-paGFP-NFM transgenic mouse that expresses neurofilament protein M tagged with photoactivatable GFP in neurons. Here we describe fluorescence photoactivation pulse-escape and pulse-spread methods to analyze neurofilament transport in single myelinated axons of tibial nerves from these mice ex vivo. Isolated nerve segments are maintained on the microscope stage by perfusion with oxygenated saline and imaged by spinning disk confocal fluorescence microscopy. Violet light is used to activate the fluorescence in a short axonal window. The fluorescence in the activated and flanking regions is analyzed over time, permitting the study of neurofilament transport with temporal and spatial resolution on the order of minutes&#160;and microns, respectively. Mathematical modeling can be used to extract kinetic parameters of neurofilament transport including the velocity, directional bias and pausing behavior from the resulting data. The pulse-escape and pulse-spread methods can also be adapted to visualize neurofilament transport in other nerves. With the development of additional transgenic mice, these methods could also be used to image and analyze the axonal transport of other cytoskeletal and cytosolic proteins in axons.

We describe fluorescence photoactivation methods to analyze the axonal transport of neurofilaments in single myelinated axons of peripheral nerves from transgenic mice that express a photoactivatable neurofilament protein.

Neurofilament protein polymers move along axons in the slow component of axonal transport at average speeds of ~0.35-3.5 mm/day. Until recently the study ...