The study is supported by US Public Health Service Grant DK-081527, DK-072473 and DK-20595 to the University of Chicago Diabetes Research and Training Center (Animal Models Core), and a gift from the Kovler Family Foundation.

Part 1: Preparation of Specimens 
<ol>
<li>Place a mouse under a dissection microscope, remove the entire pancreas along with the duodenum and spleen still attached, and place the organs on a pre-weighed glass slide. Remove the duodenum by cutting its connective tissue along the side where it is bound to the pancreas. Cut and remove the spleen and excess fat on the pancreas until the pancreas is completely isolated on the slide. (Pancreatic fat is distinguishable by its white color, as differentiated from the slightly darker and tanner color of pancreatic tissue.)</li>
<li>Place a coverslip (large cover glass 50x75mm; standard cover glass 25x75mm) over the pancreas so that it is entirely covered. Use a weight (e.g. a heavy book) to flatten the pancreas between the slide and its cover. Depending on the weight, flattening the pancreas takes approximately five minutes.</li>
<li>Take off the weight. If the pancreas is well-flattened against the slide, place it in 4% paraformaldehyde (PFA) at 4&deg;C overnight. In the morning, remove the coverslips and well expose the whole pancreas to PFA during the day (6-8 hours). If the pancreas is not well-fixed, allow it to remain in the PFA longer, possibly overnight. Transfer the slides to the container with 1% Triton x-100 in phosphate buffered saline (PBS) overnight. Next day, transfer the slides to the container of saturated sucrose for 1-2 days. Then transfer the slides to a container of 100% glycerol until the tissue is cleared, which allows for the optimal resolution of fluorescent signals; tissue clearing takes approximately 1-3 days. (The fluorescent signals may persist for weeks, and even months, but imaging should be performed soon after the tissue is cleared for optimum resolution.) </li>
<li>Store the pancreas in a dark and cool area in order to preserve the organ and its fluorescent signals.</li></ol>
Part 2: Imaging and quantifying the beta-cell area in the intact pancreas
<ol>
<li>Using forceps or gloved hands, take the slide out of the container with 100% glycerol. Prepare the slide for imaging by wiping off excess glycerol and exclusively cleaning the back of the cover glass with ethanol.</li>
<li>Open the StereoInvestigator software (MicroBrightField, Williston, VT) and select the 2x objective lens for imaging mice pancreata older than 3 weeks on large glass slides, or the 10x objective lens for imaging mice pancreata younger than 3 weeks pressed between two 25mm coverslips. Visualize the image by setting it to live image (Image &rarr; Live Image). Select an exposure time that clearly shows the GFP-tagged beta-cells. (Underexposing the image excludes smaller islets and beta-cells, while overexposing the image creates additional false signals.)</li>
<li>Click anywhere on the screen to establish a reference point and proceed to draw a contour around the entire pancreas. Initiate the Virtual Slice process (Image &rarr; Acquire Virtual Slice). Determine and select the best focal plane i.e., the plane with the highest number of visible and focused islets and beta-cells on the Z-axis by scrolling the focus knob. Once chosen, StereoInvestigator automatically captures the image displayed on the screen. With the motorized stage, the Virtual Slice feature sequentially captures each optical panel as a distinct image within the drawn contour (Fig. 1A) and then combines all of them as one merged image (Fig. 1B). Virtual Slice imaging uses an epifluorescent configuration i.e., widefield filters that allows the camera to capture all signals present at a certain depth, including those not perfectly in focus, so that the final Virtual Slice is an integrated two-dimensional image that is not a maximum projection from the three-dimensional reconstruction of the whole pancreas. Average Virtual Slice scanning time is 30 min per sample, but can take up to an hour for a large pancreas.</li> 
<li>After saving the image, begin its analysis by opening up the image with ImageJ. When the image finishes loading and appears on the screen, open and run the Virtual Slice analysis macro (<a href="https://www.jove.com/files/ftp_upload/1970/Supplementary_material 1.pdf">Supplementary material 1</a>).</li>
<li>Follow the step-by-step instructions provided by the macro. Eliminate undesired artifacts created by light scatter with the "Magic Wand" and "Select Area" tools. Check and subtract unnecessary background from the image. Determine the radius of the largest islet with the "Line" tool so that the ensuing Rolling Ball feature can effectively remove autofluorescence and scattered light. Test and select the most appropriate "Low Threshold" to capture the fluorescent signals of small islets and clusters of beta-cells (&lt;3x104 &mu;m2). Test and select the most appropriate "High Threshold" to capture the fluorescent signals of islets. Run the quantification of the Virtual Slice, which will measure and produce a list of islet area, perimeter, circularity, and Feret's diameter.</li></ol>
<img src="/files/ftp_upload/1970/1970Fig1A.jpg" alt="figure 1a" /> 
Figure 1A Virtual Slice image analysis of the entire distribution of beta-cells in an intact adult pancreas Images of individual optical panels of a male mouse pancreas at 10-wk taken under a 2x objective. The images include the entire distribution of islets, even small clusters of beta-cells (&lt;10 cells).
<img src="/files/ftp_upload/1970/1970Fig1B.jpg" alt="figure 1b" /> 
Figure 1B Virtual Slice image analysis of the entire distribution of beta-cells in an intact adult pancreas A unified virtual slice with the dorsal pancreas on the right and the ventral pancreas on the left. Scale bar is 5 mm.
Representative Results
Proficient preparation of a pancreas for Virtual Slice imaging will allow for an effective quantification of all GFP-tagged beta-cells in an entire pancreas as a Virtual Slice image with clear and distinct islets. Successful Virtual Slice imaging of the whole pancreas in situ provides the means to examine and quantify the beta-cells, not only individual and total islet area, but also islet size distribution, regional analysis, and growth patterns as well. While ImageJ maintains the capacity to detect all beta-cells simultaneously in the analysis of Virtual Slice images, it can also control which beta-cells to quantify by restricting the analysis to certain islet sizes (by area or diameter), or by location. A standard analysis excludes artifacts e.g., debris smaller than one single beta-cell (&lt;170 &mu;m2) and records the area, perimeter (the distance surrounding an area), circularity (a degree of roundness, where 1.0 represents a perfect circle), and Feret's diameter (the longest distance within an area) for each islet detected. Virtual Slice analysis is capable of enhancing virtual slice images by employing Watershed segmentation, which distinguishes and separates overlapping islets into individual islets according to their shapes. The analysis further produces a series of detailed images; this includes masks of the images under both low and high intensity (Fig. 1C), an outline of all presumed islets, which are each individually numbered and listed in a table of corresponding information (Fig. 1D), and the original Virtual Slice image (Fig. 1B). Note that potential technical bias when choosing threshold values can skew the quantification of islets by including gratuitous light surrounding large structures, or by reducing the total number of islets, especially faint signals from small particles.
<img src="/files/ftp_upload/1970/1970Fig1C.jpg" alt="figure 1c" /> 
Figure 1C Virtual Slice image analysis of the entire distribution of beta-cells in an intact adult pancreas A mask of the fluorescent particles in the virtual slice. Color codes: [1] blue: low intensity fluorescence; [2] green: intermediate intensity fluorescence; and [3] red: high intensity fluorescence.
<img src="/files/ftp_upload/1970/1970Fig1D.jpg" alt="figure 1d" /> 
Figure 1D Virtual Slice image analysis of the entire distribution of beta-cells in an intact adult pancreas Quantification of individual islets/clusters of beta-cells. Note that each islet (including small clusters of beta-cells) is numbered, with its information detailed in a corresponding chart. Four parameters were taken for each structure: (1) area; (2) perimeter; (3) circularity: a degree of roundness where the number 1.0 represents a perfect circle; and (4) Feret's diameter: the longest distance within an area. Note that #706 displays the analyses resolution with an area of only a few beta-cells. Watershed segmentation detects groups of adjacent islets, such as the one shown, and appropriately distinguishes them as distinct islets (islets 1554, 1555, and 1556).
<img src="/files/ftp_upload/1970/1970Fig1E.jpg" alt="figure 1e" /> 
Figure 1E Virtual Slice image analysis of the entire distribution of beta-cells in an intact adult pancreas 3-dimensional plot of the virtual slice analysis, with axes of area, perimeter, and Feret's diameter. Each dot represents an islet.

<ol>
	<li>Miller, K., Kim, A., Kilimnik, G., Moka, U., Jo, J., Periwal, V., Hara, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Islet+formation+during+the+neonatal+development+in+mice.">Islet formation during the neonatal development in mice.</a> PloS One. 4, E7739-E7739 (2009).</li><li>Kilimnik, G., Kim, A., Jo, J., Miller, K., Hara, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+pancreatic+islet+distribution+in+situ+in+mice.">Quantification of pancreatic islet distribution in situ in mice.</a> Am J Physiol Endocrinol Metab. 297, E1331-E1338 (2009).</li><li>Hara, M., Wang, X., Kawamura, T., Bindokas, V. P., Dizon, R. F., Alcoser, S. Y., Magnuson, M. A., Bell, G. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transgenic+mice+with+green+fluorescent+protein-labeled+pancreatic+beta+-cells.">Transgenic mice with green fluorescent protein-labeled pancreatic beta -cells.</a> Am J Physiol Endocrinol Metab. 284, E177-E183 (2003).</li><li>Hara, M., Dizon, R. F., Glick, B. S., Lee, C. S., Kaestner, K. H., Piston, D. W., Bindokas, V. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+pancreatic+beta-cells+in+the+intact+pancreas.">Imaging pancreatic beta-cells in the intact pancreas.</a> Am J Physiol Endocrinol Metab. 290, E1041-E1047 (2006).</li></ol>

No conflicts of interest declared.

The analysis of Virtual Slice images of islets and beta-cell clusters in the intact pancreas provides a large-scale view of the entire distribution of islets. Developments and changes in total islet distribution over time can thus be studied and compared. Such an example is demonstrated in our analysis of pancreatic islet formation (1). A comprehensive analysis of neonatal mice pancreata at various time points (P1-P21) has demonstrated that islets are formed by fission. While beta-cell proliferation fits with a lognormal...

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		<div>
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		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
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<td>Forceps</td>
<td>&nbsp;</td>
<td>Miltex</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
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<td>Scissors</td>
<td>&nbsp;</td>
<td>F.S.T</td>
<td>14001-13</td>
<td>01n2</td>
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<td>Scissors</td>
<td>&nbsp;</td>
<td>F.S.T</td>
<td>14072-10</td>
<td>02s5	</td>
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<tr>
<td>Large glass slide</td>
<td>&nbsp;</td>
<td>Electron Microscopy Sciences</td>
<td>71862-01</td>
<td>75x51x1.2mm</td>
</tr>
<tr>
<td>Large cover glass</td>
<td>&nbsp;</td>
<td>Ted Pella, Inc</td>
<td>260462</td>
<td>50x75mm</td>
</tr>
<tr>
<td>Glass Slide</td>
<td>&nbsp;</td>
<td>Fisher Scientific</td>
<td>12-550-15</td>
<td>25x75x1.0mm</td>
</tr>
<tr>
<td>Cover glass</td>
<td>&nbsp;</td>
<td>Fisher Scientific</td>
<td>12-458-5M</td>
<td>75x25mm</td>
</tr>
<tr>
<td>Cover glass</td>
<td>&nbsp;</td>
<td>Erie Scientific</td>
<td>&nbsp;</td>
<td>25mm circle</td>
</tr>
<tr>
<td>Fluorescent microscope</td>
<td>&nbsp;</td>
<td>Olympus IX-81</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Dissection microscope</td>
<td>&nbsp;</td>
<td>Olympus SZX12</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Stereo Investigator</td>
<td>&nbsp;</td>
<td>MicroBrightField</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>MIP-GFP mice</td>
<td>&nbsp;</td>
<td>Jackson Laboratory</td>
<td>&nbsp;</td>
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in situ quantification of pancreatic beta-cell mass in mice

Tracing changes of specific cell populations in health and disease is an important goal of biomedical research. The process of monitoring pancreatic beta-cell proliferation and islet growth is particularly challenging. We have developed a method to capture the distribution of beta-cells in the intact pancreas of transgenic mice with fluorescence-tagged beta-cells with a macro written for ImageJ (rsb.info.nih.gov/ij/). Following pancreatic dissection and tissue clearing, the entire pancreas is captured as a virtual slice, after which the GFP-tagged beta-cells are examined. The analysis includes the quantification of total beta-cell area, islet number and size distribution with reference to specific parameters and locations for each islet and for small clusters of beta-cells. The entire distribution of islets can be plotted in three dimensions, and the information from the distribution on the size and shape of each islet allows a quantitative and qualitative comparison of changes in overall beta-cell area at a glance.

Watch this Scientific Journal Video about In situ Quantification of Pancreatic Beta-cell Mass in Mice at JoVE.com

In situ Quantification of Pancreatic Beta-cell Mass in Mice

The following protocol outlines the process of pancreatic dissection for virtual slice imaging, and the subsequent quantification of all GFP-tagged beta-cells in the entire pancreas.

In situ Quantification of Pancreatic Beta-cell Mass in Mice

Tracing changes of specific cell populations in health and disease is an important goal of biomedical research. The process of monitoring pancreatic ...

in-situ-quantification-of-pancreatic-beta-cell-mass-in-mice

Research

JoVE Journal

Biology

12.1K Views.  University of Chicago. Следующий протокол описывает процесс поджелудочной рассечение для виртуальных изображений ломтик, и последующего количественного всех GFP-меткой бета-клеток в поджелудочной железе все.

Video: In situ Quantification of Pancreatic Beta-cell Mass in Mice

Transplantation of Pancreatic Islets Into the Kidney Capsule of Diabetic Mice

Our protocol was developed to cleanly and easily deliver islets or cells under the kidney capsule of diabetic or normal mice. We found that it was easier to concentrate the islets or cells into pellets in the final delivery tubing (PE50) used to transplant the cells under the kidney capsule. This technique provides both speed and ease while reducing any undue stress to the cells or to the mouse.

Loading: Settled, hand picked, islets or pelleted cells are carefully aspirated off the bottom of a 1.5 mL microcentrifuge tube using a p200 pipetteman and a straight, thin-wall pipette tip. A length of PE50 tubing is attached to the pipette tip using a small silicone adapter tubing. Cells are allowed to settle, in the tip, and then are transferred to the PE50 tubing by slowly dialing the pipetteman. Once the cells are near the end of the PE50 tubing, a kink is made and the silicone adaptor tubing is placed over the kink. The PE50 tubing is transferred to a 15 mL conical containing a cut 5 mL pipet, and the PE50 tubing is taped over the side of the 5 mL pipet to prevent curling during centrifuging. Cells are allowed to reach 1,000 rpm and stopped.
Transplantation: Recipient mice are anesthetized, shaved, and cleaned. A small incision is made on the left flank of the mouse and the kidney is exposed. The kidney, fat, and tissue are kept moist with normal saline swab. The distal end of the PE50 is attached to a Hamilton screw drive syringe, containing a pipette tip, using the silicone adaptor tubing. A small nick is made on the right flank side of the kidney, not too large nor too deep. The beveled end of the PE50 tubing, nearest the cells, is carefully placed under the capsule, the tubing is moved around gently to make space while swabbing normal saline; a dry capsule can tear easily. A small air bubble is delivered under the capsule by slowly dialing the syringe screw drive. Islets are then slowly delivered behind the air bubble. Once the islets have been delivered kidney homeostasis is maintained and the knick is cauterized with low heat. The kidney is placed back into the cavity and the peritoneum and skin are sutured and stapled. Mice are immediately treated with Flunixin and Buprenorphine s.q. and placed in a cage on a heating pad.

Our protocol was developed to cleanly and easily deliver islets or cells under the kidney capsule of mice. Cells are concentrated into pellets in the final tubing used for transplanting the cells under the kidney capsule. The ease of this technique reduces stress to the cells and the mouse.

Our protocol was developed to cleanly and easily deliver islets or cells under the kidney capsule of diabetic or normal mice.  We found that it was easier ...

Quantification of &gamma;H2AX Foci in Response to Ionising Radiation

DNA double-strand breaks (DSBs), which are induced by either endogenous metabolic processes or by exogenous sources, are one of the most critical DNA lesions with respect to survival and preservation of genomic integrity. An early response to the induction of DSBs is phosphorylation of the H2A histone variant, H2AX, at the serine-139 residue, in the highly conserved C-terminal SQEY motif, forming &gamma;H2AX1. Following induction of DSBs, H2AX is rapidly phosphorylated by the phosphatidyl-inosito 3-kinase (PIKK) family of proteins, ataxia telangiectasia mutated (ATM), DNA-protein kinase catalytic subunit and ATM and RAD3-related (ATR)2. Typically, only a few base-pairs (bp) are implicated in a DSB, however, there is significant signal amplification, given the importance of chromatin modifications in DNA damage signalling and repair. Phosphorylation of H2AX mediated predominantly by ATM spreads to adjacent areas of chromatin, affecting approximately 0.03% of total cellular H2AX per DSB2,3. This corresponds to phosphorylation of approximately 2000 H2AX molecules spanning ~2 Mbp regions of chromatin surrounding the site of the DSB and results in the formation of discrete &gamma;H2AX foci which can be easily visualized and quantitated by immunofluorescence microscopy2. The loss of &gamma;H2AX at DSB reflects repair, however, there is some controversy as to what defines complete repair of DSBs; it has been proposed that rejoining of both strands of DNA is adequate however, it has also been suggested that re-instatement of the original chromatin state of compaction is necessary4-8. The disappearence of &gamma;H2AX involves at least in part, dephosphorylation by phosphatases, phosphatase 2A and phosphatase 4C5,6. Further, removal of &gamma;H2AX by redistribution involving histone exchange with H2A.Z has been implicated7,8. Importantly, the quantitative analysis of &gamma;H2AX foci has led to a wide range of applications in medical and nuclear research. Here, we demonstrate the most commonly used immunofluorescence method for evaluation of initial DNA damage by detection and quantitation of &gamma;H2AX foci in &gamma;-irradiated adherent human keratinocytes9.

Quantification of &amp;#947;H2AX Foci in Response to Ionising Radiation

Quantification of DNA double-strand streaks using &gamma;H2AX formation as a molecular marker has become an invaluable tool in radiation biology. Here we demonstrate the use of an immunofluorescence assay for quantification of &gamma;H2AX foci after exposure of cells to radiation.

DNA double-strand breaks (DSBs), which are induced by either endogenous metabolic processes or by exogenous sources, are one of the most critical DNA ...

Computer-assisted Large-scale Visualization and Quantification of Pancreatic Islet Mass, Size Distribution and Architecture

The pancreatic islet is a unique micro-organ composed of several hormone secreting endocrine cells such as beta-cells (insulin), alpha-cells (glucagon), and delta-cells (somatostatin) that are embedded in the exocrine tissues and comprise 1-2% of the entire pancreas. There is a close correlation between body and pancreas weight. Total beta-cell mass also increases proportionately to compensate for the demand for insulin in the body. What escapes this proportionate expansion is the size distribution of islets. Large animals such as humans share similar islet size distributions with mice, suggesting that this micro-organ has a certain size limit to be functional. The inability of large animal pancreata to generate proportionately larger islets is compensated for by an increase in the number of islets and by an increase in the proportion of larger islets in their overall islet size distribution. Furthermore, islets exhibit a striking plasticity in cellular composition and architecture among different species and also within the same species under various pathophysiological conditions. In the present study, we describe novel approaches for the analysis of biological image data in order to facilitate the automation of analytic processes, which allow for the analysis of large and heterogeneous data collections in the study of such dynamic biological processes and complex structures. Such studies have been hampered due to technical difficulties of unbiased sampling and generating large-scale data sets to precisely capture the complexity of biological processes of islet biology. Here we show methods to collect unbiased "representative" data within the limited availability of samples (or to minimize the sample collection) and the standard experimental settings, and to precisely analyze the complex three-dimensional structure of the islet. Computer-assisted automation allows for the collection and analysis of large-scale data sets and also assures unbiased interpretation of the data. Furthermore, the precise quantification of islet size distribution and spatial coordinates (i.e. X, Y, Z-positions) not only leads to an accurate visualization of pancreatic islet structure and composition, but also allows us to identify patterns during development and adaptation to altering conditions through mathematical modeling. The methods developed in this study are applicable to studies of many other systems and organisms as well.

Novel computer-assisted methods of large-scale procurement and analysis of immunohistochemically stained pancreatic specimens are described: (1) Virtual Slice capture of the entire section; (2) Mass analysis of large-scale data; (3) Reconstruction of 2D Virtual Slices; (4) 3D islet mapping; and (5) Mathematical analysis.

The pancreatic islet is a unique micro-organ composed of several hormone secreting endocrine cells such as beta-cells (insulin), alpha-cells (glucagon), ...

Quantification of Proteins Using Peptide Immunoaffinity Enrichment Coupled with Mass Spectrometry

There is a great need for quantitative assays in measuring proteins. Traditional sandwich immunoassays, largely considered the gold standard in quantitation, are associated with a high cost, long lead time, and are fraught with drawbacks (e.g. heterophilic antibodies, autoantibody interference, 'hook-effect').1 An alternative technique is affinity enrichment of peptides coupled with quantitative mass spectrometry, commonly referred to as SISCAPA (Stable Isotope Standards and Capture by Anti-Peptide Antibodies).2 In this technique, affinity enrichment of peptides with stable isotope dilution and detection by selected/multiple reaction monitoring mass spectrometry (SRM/MRM-MS) provides quantitative measurement of peptides as surrogates for their respective proteins. SRM/MRM-MS is well established for accurate quantitation of small molecules 3, 4 and more recently has been adapted to measure the concentrations of proteins in plasma and cell lysates.5-7 To achieve quantitation of proteins, these larger molecules are digested to component peptides using an enzyme such as trypsin. One or more selected peptides whose sequence is unique to the target protein in that species (i.e. "proteotypic" peptides) are then enriched from the sample using anti-peptide antibodies and measured as quantitative stoichiometric surrogates for protein concentration in the sample. Hence, coupled to stable isotope dilution (SID) methods (i.e. a spiked-in stable isotope labeled peptide standard), SRM/MRM can be used to measure concentrations of proteotypic peptides as surrogates for quantification of proteins in complex biological matrices. The assays have several advantages compared to traditional immunoassays. The reagents are relatively less expensive to generate, the specificity for the analyte is excellent, the assays can be highly multiplexed, enrichment can be performed from neat plasma (no depletion required), and the technique is amenable to a wide array of proteins or modifications of interest.8-13 In this video we demonstrate the basic protocol as adapted to a magnetic bead platform.

Stable Isotope Standards and Capture by Anti-Peptide Antibodies (SISCAPA) couples affinity enrichment of peptides with stable isotope dilution mass spectrometry (MRM-MS) to provide quantitative measurement of peptides as surrogates for their respective proteins. Here we describe the protocol using magnetic particles in a partially automated format.

There is a great need for quantitative assays in measuring proteins. Traditional sandwich immunoassays, largely considered the gold standard in ...

Evaluation of Muscle Function of the Extensor Digitorum Longus Muscle Ex vivo and Tibialis Anterior Muscle In situ in Mice

Body movements are mainly provided by mechanical function of skeletal muscle. Skeletal muscle is composed of numerous bundles of myofibers that are sheathed by intramuscular connective tissues. Each myofiber contains many myofibrils that run longitudinally along the length of the myofiber. Myofibrils are the contractile apparatus of muscle and they are composed of repeated contractile units known as sarcomeres. A sarcomere unit contains actin and myosin filaments that are spaced by the Z discs and titin protein. Mechanical function of skeletal muscle is defined by the contractile and passive properties of muscle. The contractile properties are used to characterize the amount of force generated during muscle contraction, time of force generation and time of muscle relaxation. Any factor that affects muscle contraction (such as interaction between actin and myosin filaments, homeostasis of calcium, ATP/ADP ratio, etc.) influences the contractile properties. The passive properties refer to the elastic and viscous properties (stiffness and viscosity) of the muscle in the absence of contraction. These properties are determined by the extracellular and the intracellular structural components (such as titin) and connective tissues (mainly collagen) 1-2. The contractile and passive properties are two inseparable aspects of muscle function. For example, elbow flexion is accomplished by contraction of muscles in the anterior compartment of the upper arm and passive stretch of muscles in the posterior compartment of the upper arm. To truly understand muscle function, both contractile and passive properties should be studied.
The contractile and/or passive mechanical properties of muscle are often compromised in muscle diseases. A good example is Duchenne muscular dystrophy (DMD), a severe muscle wasting disease caused by dystrophin deficiency 3. Dystrophin is a cytoskeletal protein that stabilizes the muscle cell membrane (sarcolemma) during muscle contraction 4. In the absence of dystrophin, the sarcolemma is damaged by the shearing force generated during force transmission. This membrane tearing initiates a chain reaction which leads to muscle cell death and loss of contractile machinery. As a consequence, muscle force is reduced and dead myofibers are replaced by fibrotic tissues 5. This later change increases muscle stiffness 6. Accurate measurement of these changes provides important guide to evaluate disease progression and to determine therapeutic efficacy of novel gene/cell/pharmacological interventions. Here, we present two methods to evaluate both contractile and passive mechanical properties of the extensor digitorum longus (EDL) muscle and the contractile properties of the tibialis anterior (TA) muscle.

Evaluation of Muscle Function of the Extensor Digitorum Longus Muscle Ex vivo and Tibialis Anterior Muscle In situ in Mice

Changes in limb muscle contractile and passive mechanical properties are important biomarkers for muscle diseases. This manuscript describes physiological assays to measure these properties in the murine extensor digitorum longus and tibialis anterior muscles.

Body  movements are mainly provided by mechanical function of skeletal muscle. Skeletal  muscle is composed of numerous bundles of myofibers that are ...

Visualization and Analysis of mRNA Molecules Using Fluorescence In Situ Hybridization in Saccharomyces cerevisiae

The Fluorescence in situ Hybridization (FISH) method allows one to detect nucleic acids in the native cellular environment. Here we provide a protocol for using FISH to quantify the number of mRNAs in single yeast cells. Cells can be grown in any condition of interest and then fixed and made permeable. Subsequently, multiple single-stranded deoxyoligonucleotides conjugated to fluorescent dyes are used to label and visualize mRNAs. Diffraction-limited fluorescence from single mRNA molecules is quantified using a spot-detection algorithm to identify and count the number of mRNAs per cell. While the more standard quantification methods of northern blots, RT-PCR and gene expression microarrays provide information on average mRNAs in the bulk population, FISH facilitates both the counting and localization of these mRNAs in single cells at single-molecule resolution.

Visualization and Analysis of mRNA Molecules Using Fluorescence In Situ Hybridization in Saccharomyces cerevisiae

This protocol describes an experimental procedure for performing Fluorescence in situ Hybridization (FISH) for counting mRNAs in single cells at single-molecule resolution.

The Fluorescence in situ Hybridization (FISH) method allows one to detect nucleic acids in the native cellular environment. Here we provide a protocol for ...

High Resolution Quantification of Crystalline Cellulose Accumulation in Arabidopsis Roots to Monitor Tissue-specific Cell Wall Modifications

Plant cells are surrounded by a cell wall, the composition of which determines their final size and shape. The cell wall is composed of a complex matrix containing polysaccharides that include cellulose microfibrils that form both crystalline structures and cellulose chains of amorphous organization. The orientation of the cellulose fibers and their concentrations dictate the mechanical properties of the cell. Several methods are used to determine the levels of crystalline cellulose, each bringing both advantages and limitations. Some can distinguish the proportion of crystalline regions within the total cellulose. However, they are limited to whole-organ analyses that are deficient in spatiotemporal information. Others relying on live imaging, are limited by the use of imprecise dyes. Here, we report a sensitive polarized light-based system for specific quantification of relative light retardance, representing crystalline cellulose accumulation in cross sections of Arabidopsis thaliana roots. In this method, the cellular resolution and anatomical data are maintained, enabling direct comparisons between the different tissues composing the growing root. This approach opens a new analytical dimension, shedding light on the link between cell wall composition, cellular behavior and whole-organ growth.

High Resolution Quantification of Crystalline Cellulose Accumulation in Arabidopsis Roots to Monitor Tissue-specific Cell Wall Modifications

Crystalline cellulose is an important constituent of the plant cell wall. However, its quantification at a cellular resolution is technically challenging. Here, we report the use of polarized light technology and root cross sections to obtain information of cell wall composition at a spatiotemporal resolution.

Plant cells are surrounded by a cell wall, the composition of which determines their final size and shape. The cell wall is composed of a complex matrix ...

Observation and Quantification of Telomere and Repetitive Sequences Using Fluorescence In Situ Hybridization (FISH) with PNA Probes in Caenorhabditis elegans

Telomere is a ribonucleoprotein structure that protects chromosomal ends from aberrant fusion and degradation. Telomere length is maintained by telomerase or an alternative pathway, known as alternative lengthening of telomeres (ALT)1. Recently, C. elegans has emerged as a multicellular model organism for the study of telomere and ALT2. Visualization of repetitive sequences in the genome is critical in understanding the biology of telomeres. While telomere length can be measured by telomere restriction fragment assay or quantitative PCR, these methods only provide the averaged telomere length. On the contrary, fluorescence in situ hybridization (FISH) can provide the information of the individual telomeres in cells. Here, we provide protocols and representative results of the method to determine telomere length of C. elegans by fluorescent in situ hybridization. This method provides a simple, but powerful, in situ procedure that does not cause noticeable damage to morphology. By using fluorescently labeled peptide nucleic acid (PNA) and digoxigenin-dUTP-labeled probe, we were able to visualize two different repetitive sequences: telomere repeats and template of ALT (TALT) in C. elegans embryos and gonads.

Observation and Quantification of Telomere and Repetitive Sequences Using Fluorescence In Situ Hybridization FISH with PNA Probes in Caenorhabditis elegans

We report a concise procedure of fluorescence in situ hybridization (FISH) in the gonad and embryos of Caenorhabditis elegans for observing and quantifying repetitive sequences. We successfully observed and quantified two different repetitive sequences, telomere repeats and template of alternative lengthening of telomeres (TALT).

Telomere is a ribonucleoprotein structure that protects chromosomal ends from aberrant fusion and degradation. Telomere length is maintained by telomerase ...

Analysis of Beta-cell Function Using Single-cell Resolution Calcium Imaging in Zebrafish Islets

Pancreatic beta-cells respond to increasing blood glucose concentrations by secreting the hormone insulin. The dysfunction of beta-cells leads to hyperglycemia and severe, life-threatening consequences. Understanding how the beta-cells operate under physiological conditions and what genetic and environmental factors might cause their dysfunction could lead to better treatment options for diabetic patients. The ability to measure calcium levels in beta-cells serves as an important indicator of beta-cell function, as the influx of calcium ions triggers insulin release. Here we describe a protocol for monitoring the glucose-stimulated calcium influx in zebrafish beta-cells by using GCaMP6s, a genetically encoded sensor of calcium. The method allows monitoring the intracellular calcium dynamics with single-cell resolution in ex vivo mounted islets. The glucose-responsiveness of beta-cells within the same islet can be captured simultaneously under different glucose concentrations, which suggests the presence of functional heterogeneity among zebrafish beta-cells. Furthermore, the technique provides high temporal and spatial resolution, which reveals the oscillatory nature of the calcium influx upon glucose stimulation. Our approach opens the doors to use the zebrafish as a model to investigate the contribution of genetic and environmental factors to beta-cell function and dysfunction.

Beta-cell functionality is important for blood-glucose homeostasis, which is evaluated at single-cell resolution using a genetically encoded reporter for calcium influx.

Pancreatic beta-cells respond to increasing blood glucose concentrations by secreting the hormone insulin. The dysfunction of beta-cells leads to ...

Establishing a Diaphyseal Femur Fracture Model in Mice

Bones have a significant regenerative capacity. However, fracture healing is a complex process, and depending on the severity of the lesions and the age and overall health status of the patient, failures can occur, leading to delayed union or nonunion. Due to the increasing number of fractures resulting from high-energy trauma and aging, the development of innovative therapeutic strategies to improve bone repair based on the combination of skeletal/mesenchymal stem/stromal cells and biomimetic biomaterials is urgently needed. To this end, the use of reliable animal models is fundamental to better understanding the key cellular and molecular mechanisms that determine the healing outcomes. Of all the models, the mouse is the preferred research model because it offers a wide variety of transgenic strains and reagents for experimental analysis. However, the establishment of fractures in mice may be technically challenging due to their small size. Therefore, this article aims to demonstrate the procedures for the surgical establishment of a diaphyseal femur fracture in mice, which is stabilized with an intramedullary wire and resembles the most common bone repair process, through cartilaginous callus formation.

This protocol describes a surgical procedure for the establishment of a diaphyseal fracture in the femur of mice, which is stabilized with an intramedullary wire, for fracture healing studies.

Bones have a significant regenerative capacity. However, fracture healing is a complex process, and depending on the severity of the lesions and the age ...