KO and AC are supported by a grant and a fellowship from the American Heart Association. SIB and RB are supported by grants from NIH.

<a href="https://www.jove.com/files/ftp_upload/1435/SOHA_overview.pdf">Click here to view an overview of the semi automated heartbeat analysis (SOHA) procedure.</a>
Semi-automated optical heartbeat analysis
1. Preprocess -
This step provides information on the diastolic and systolic heart diameters.
Heart edges are identified and marked during maximum diastole and systole. Optical recordings can be advanced at slow speeds and even one frame at a time allowing precise identification of the frames where maximal contraction and relaxation of the heart occur. One pair of marks identifying the diastolic edges and one pair identifying the systolic edges are made. Marks can also be made in duplicate at different horizontal locations along the heart.
The heart diameters obtained in this step are also used to calculate an additional measurement that provides an estimate of the contractility of the heart. This measure is the percent fractional shortening (%FS) and it represents the extent to which the heart edges move toward each other during a contraction. The formula used to calculate %FS is:
(((Diastolic diameter - Systolic diameter)/Diastolic diameter) x 100)
Note - The points identified in this set are used only for diameter and fractional shortening measurements and are not used for movement detection.
Example: In Drosophila, point mutations in myosin heavy chain's transducer domain, a region known to modulate the motor's enzymatic activity, result in hearts that are dilated or restricted depending upon whether they suppress or enhance myosin's ATPase activity (Cammarato, et al. 2008). These types of measurements cannot be made in intact flies as it is usually not possible to identify heart edges along the entire length of the heart tube through the cuticle and the fat, (compare Wildtype, D45 and Mhc5 M-modes in "M-mode Figure" below) which normally surround the heart. Measurements made when visualizing the heart in intact flies with other commonly employed methods are usually restricted to the most anterior portion of the heart, the conical chamber region. It is also not possible to obtain this dynamic measurement in fixed tissue.
2. Movement Detection-
This step is done automatically by the program and uses two different algorithms to analyze movement in each movie. Briefly, the first algorithm, the "Average Frame Darkness" algorithm uses a frame by frame approach. This algorithm averages the darkness intensity for an entire movie frame, normalizes the value to an interval between 0 and 1, and plots the normalized average for every frame in the movie over time. The second approach, the "Pixel by Pixel" algorithm, analyzes the change in darkness of all the individual pixels from one frame to the next. Pixels that exhibit intensity changes above a preset threshold are summed for each frame and plotted for every frame in the movie over time.
3. Check Intervals-
The output from the two movement detection algorithms is displayed in this module with the "Average Darkness" output displayed in a window above the "Pixel by pixel" output window. In order to be sure that the detection intervals agree with movement in the actual movie we display an edge-trace or M-mode made from the frames being analyzed directly below the algorithm output windows. The M-mode is made by digitally cutting slices one pixel wide through the heart from each frame in the movie and aligning them horizontally to provide a snapshot of the heart edge movements over time. In the "Pixel by pixel" window the identified diastolic intervals are indicated by a horizontal green line with the number of frames contributing to that interval directly above. Systolic intervals are identified as the interval between two successive diastoles. The beginning of a systole is indicated in the M-mode by a vertical blue line and the end is indicated by a vertical red line. With this display it is relatively easy to see if the algorithm output agrees with the actual heart movements.
Although movement detection is performed automatically the output must be checked for accuracy. There are several reasons for this; one is that there is often an underlying, slow wave fluctuation in light levels not related to the heart movement. This can usually be eliminated by use of a built in high pass filter. A second reason has to do with the sensitivity of the "Pixel by pixel" approach. The output from this algorithm is typically two movement traces, one for the contraction movement and one for the relaxation movement. In older flies and in some mutants the length of time between these two movements becomes relatively long and the program tries to interpret the two movements as two separate beats. This can be corrected by asking the program to compare the output of the Pixel by Pixel algorithm with that of the Average Frame Darkness algorithm, by clicking on the "Use darkness" box.
Example (refer to Video): In 5 to 7 week old flies the systolic intervals are typically much longer than in young flies. These long intervals are initially detected as two separate contractions separated by a short diastole. This can be corrected by selecting the "Use darkness" check box. In this case the program will compare the diastolic interval identified by the Pixel by Pixel algorithm with the Average Frame Darkness output. If the Average Frame Darkness output has a positive value, then any diastolic interval identified in the Pixel by Pixel algorithm will be ignored and the intervals will be correctly specified. The entire movie can be scanned in 10 second segments and accepted (click "Data OK") or rejected (click "Discard Data"). The Hi and Lo pass filter sensitivities can be manually adjusted to help more accurately define contraction intervals when employing the Darkness algorithm.
4. Output Statistics-
Once the output for a given movie has been accepted the program will use that information to automatically calculate a number of parameters. These include diastolic and systolic interval, heart period and heart rate, direction and velocity of the contraction wave, heart diameters, and %FS. In addition, the program has multiple methods for quantifying arrhythmicity reflecting non-uniform contraction and relaxation cycles (see Fink et al, 2009). Statistical output is provided for each movie individually and for the entire data set in the form of a comma separated value (.csv) file which can be opened in spreadsheet programs such as Microsoft Excel.
Table 1- 
<img src="/files/ftp_upload/1435/1435table1.jpg" alt="table1" /> An example of the output generated by the Semi-automated Optical Heart Analysis program.
5. Update Histograms- 
This portion of the program displays all of the data on heart intervals for a dataset in histogram format. Since heart rates are variable we normalize the histogram output data. However, because the distribution of the intervals is not symmetric around a mean we use the median interval value for our normalization.
Example (refer to Video): Flies that are mutant for the KCNQ potassium channel show extremely irregular diastolic and systolic intervals. Typically the systolic intervals are much longer and more irregular than in age-matched wildtype flies. This can clearly be seen by displaying the data in histogram format (see also Ocorr et al. 2007).
6. M-mode-
This module generates M-modes that can be made from any position along the heart in the movie frame. The length of the M-mode can also be specified. M-modes are useful to show qualitatively what the heart is doing in a movie.
Example (refer to Video): Movie of a 3 day old zebrafish larval heart showing the anterior ventricle that is used to generate an M-mode. The vertical slice of pixels that will be electronically excised from each movie frame is indicated by a red line.
M-mode Figure: Examples of M-modes from Drosophila and zebrafish. One of the myosin mutations discussed in the Preprocess step results in a molecular motor with faster enzyme kinetics resulting in heart restriction and occasionally a conduction block. Both parameters can be shown qualitatively using M-modes. <img src="/files/ftp_upload/1435/1435fig1.jpg" alt="M-modes Examples" /> M-modes made in the same portion of the heart in both wildtype and mutant flies clearly show the restricted phenotype in the Mhc5 mutant and the dilated diameters and arrhythmic contraction cycles of the D45 mutant (which expresses myosin with depressed enzyme kinetics) (modified from Cammarato et. al, 2008).
M-mode made from a Zebrafish larval heart showing the anterior ventricle (same heart movie as shown in the demonstration, Fink et.al. 2009).
7. Red Dot Movie-
This module automatically produces a slowed (1:4), 20 second version of an analyzed movie showing all the pixels that are identified as changing in red. This feature is primarily used for illustration purposes.
Movie 1 - A "red dot movie" showing the pixels that are identified as having darkness intensity changes by the program algorithms in red. The movie speed is slowed from the original by a factor of 4. <a href="https://www.jove.com/files/ftp_upload/1435/redmove.avi">Click here to download Movie 1.</a>
8. Additional Applications-
We have begun to apply this analytical system to high speed movies of other models with small hearts which are often difficult to analyze using traditional methodology. We have successfully applied this analysis to both zebrafish larval hearts and embryonic mouse hearts (Fink et al, 2009).
Movie 2 - Mouse heart movie plus figure with check intervals with data output. <a href="https://www.jove.com/files/ftp_upload/1435/Mouse%20heart%20clip%201.avi">Click here to download Movie 2.</a> <img src="/files/ftp_upload/1435/1435fig2.jpg" alt="Check Mouse Heart Intervals" />

<ol>
	<li>Cammarato, A., Dambacher, C. M., Reedy, M. C., Knowles, A. F., Kronert, W. A., Bodmer, R., Ocorr, K., Bernstein, S. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myosin+Transducer+mutations+differentially+affect+motor+function,+myofibril+structure,+and+the+performance+of+skeletal+and+cardiac+muscles.">Myosin Transducer mutations differentially affect motor function, myofibril structure, and the performance of skeletal and cardiac muscles.</a> Mol Biol Cell. 19 (2), 553-562 (2008).</li><li>Ocorr, K., Reeves, N., Wessells, R. J., Fink, M., Chen, H. -. S. V., Akasaka, T., Yasuda, S., Metzger, J., Giles, W., Posakony, J. W., Bodmer, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=KCNQ+potassium+channel+mutations+cause+cardiac+arrhythmias+in+Drosophila+that+mimic+the+effects+of+aging.">KCNQ potassium channel mutations cause cardiac arrhythmias in Drosophila that mimic the effects of aging.</a> Proc Natl Acad Sci U S A. 104, 3943-3948 (2007).</li><li>Fink, M., Callol-Massot, C., Chu, A., Ruiz-Lozano, P., Izpisua Belmonte, J. C., Giles, W., Bodmer, R., Ocorr, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+method+for+the+detection+and+quantification+of+heartbeat+parameters+in+Drosophila,+zebrafish+and+embryonic+mouse+hearts.">A new method for the detection and quantification of heartbeat parameters in Drosophila, zebrafish and embryonic mouse hearts.</a> Biotechniques. 46, 101-113 (2009).</li></ol>

The authors have nothing to disclose.

The Drosophila model has proven to be a powerful genetic tool that has been used to address a variety of scientific questions ranging from embryological development to learning and memory. Recently this versatile model organism has been used to investigate the genetics of heart function. A number of attempts to quantify heart physiology in adult Drosophila have relied on observations made in intact flies through the abdominal cuticle. Most of these approaches depend upon visual observation or recordings of changes in li...

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		<th>Material Name</th>
		<th>Type</th>
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		<th>Catalogue Number</th>
		<th>Comment</th>
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<td>MatLab software</td>
<td>&nbsp;</td>
<td>Math Works, Inc</td>
<td>&nbsp;</td>
<td>Required environment for the analysis software.</td>
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<td>EM-CCD digital camera</td>
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<td>Hamamatsu Corp.</td>
<td>9100 or 9300</td>
<td>Other high speed digital cameras will also work.</td>
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<td>HC image data capture software</td>
<td>&nbsp;</td>
<td>Hamamatsu Corp.</td>
<td>&nbsp;</td>
<td>Other image capture software that produces movies in avi format will also work.</td>
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<td>Light Microscope with 10x objective </td>
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<td>Leica</td>
<td>&nbsp;</td>
<td>A dipping lens that eliminates the air water interface greatly improves resolution</td>
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semi-automated optical heartbeat analysis of small hearts

We have developed a method for analyzing high speed optical recordings from Drosophila, zebrafish and embryonic mouse hearts (Fink, et. al., 2009). Our Semi-automatic Optical Heartbeat Analysis (SOHA) uses a novel movement detection algorithm that is able to detect cardiac movements associated with individual contractile and relaxation events. The program provides a host of physiologically relevant readouts including systolic and diastolic intervals, heart rate, as well as qualitative and quantitative measures of heartbeat arrhythmicity. The program also calculates heart diameter measurements during both diastole and systole from which fractional shortening and fractional area changes are calculated. Output is provided as a digital file compatible with most spreadsheet programs. Measurements are made for every heartbeat in a record increasing the statistical power of the output. We demonstrate each of the steps where user input is required and show the application of our methodology to the analysis of heart function in all three genetically tractable heart models.

Watch this Scientific Journal Video about Semi-automated Optical Heartbeat Analysis of Small Hearts at JoVE.com

Semi-automated Optical Heartbeat Analysis of Small Hearts

We have developed a Semi-automated Optical Heartbeat Analysis method (SOHA) for analyzing high speed optical recordings from Drosophila, zebrafish and embryonic mouse hearts. We demonstrate the application of our methodology to the analysis of heart function in fruit fly and embryonic mouse hearts.

We have developed a method for analyzing high speed optical recordings from Drosophila, zebrafish and embryonic mouse hearts (Fink, et. al., 2009). Our ...

semi-automated-optical-heartbeat-analysis-of-small-hearts

Research

JoVE Journal

Biology

12.1K Views.  The Sanford Burnham Institute for Medical Research. We have developed a Semi-automated Optical Heartbeat Analysis method (SOHA) for analyzing high speed optical recordings from Drosophila, zebrafish and embryonic mouse hearts. We demonstrate the application of our methodology to the analysis of heart function in fruit fly and embryonic mouse hearts.

Video: Semi-automated Optical Heartbeat Analysis of Small Hearts

Proper Care and Cleaning of the Microscope

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a microscope causes reduction in contrast and resolution. DIC is especially sensitive to contamination and scratches on the lens surfaces. This protocol details the procedure for keeping the microscope clean.

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a microscope causes reduction in contrast and resolution. DIC is especially sensitive to contamination and scratches on the lens surfaces. This protocol details the procedure for keeping the microscope clean.

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a ...

Major Components of the Light Microscope

The light microscope is a basic tool for the cell biologist, who should have a thorough understanding of how it works, how it should be aligned for different applications, and how it should be maintained as required to obtain maximum image-forming capacity and resolution. The components of the microscope are described in detail here.

The light microscope is a basic tool for the cell biologist, who should have a thorough understanding of how it works, how it should be aligned for different applications, and how it should be maintained as required to obtain maximum image-forming capacity and resolution. The components of the microscope are described in detail here.

The light microscope is a basic tool for the cell biologist, who should have a thorough understanding of how it works, how it should be aligned for ...

Phase Contrast and Differential Interference Contrast (DIC) Microscopy

Phase-contrast microscopy is often used to produce contrast for transparent, non light-absorbing, biological specimens. The technique was discovered by Zernike, in 1942, who received the Nobel prize for his achievement. DIC microscopy, introduced in the late 1960s, has been popular in biomedical research because it highlights edges of specimen structural detail, provides high-resolution optical sections of thick specimens including tissue cells, eggs, and embryos and does not suffer from the  phase halos  typical of phase-contrast images. This protocol highlights the principles and practical applications of these microscopy techniques.

Phase Contrast and Differential Interference Contrast DIC Microscopy

This protocol highlights the principles and practical applications of Phase and Differential Interference Contrast (DIC) Microscopy

Phase-contrast microscopy is often used to produce contrast for transparent, non light-absorbing, biological specimens. The technique was discovered by ...

Optical Mapping of Langendorff-perfused Rat Hearts

Optical mapping of the cardiac surface with voltage-sensitive fluorescent dyes has become an important tool to investigate electrical excitation in experimental models that range in scale from cell cultures to whole-organs[1, 2]. Using state-of-the-art optical imaging systems, generation and propagation of action potentials during normal cardiac rhythm or throughout initiation and maintenance of arrhythmias can be visualized almost instantly[1]. The latest commercially-available systems can provide information at exceedingly high spatiotemporal resolutions and were based on custom-built equipment initially developed to overcome the obstacles imposed by more conventional electrophysiological methods[1]. Advancements in high-resolution and high-speed complementary metal-oxide-semiconductor (CMOS) cameras and intensely-bright, light-emitting diodes (LEDs) as well as voltage-sensitive dyes, optics, and filters have begun to make electrical signal acquisition practical for cardiovascular cell biologists who are more accustomed to working with microscopes. Although the newest generation of CMOS cameras can acquire 10,000 frames per second on a 16,384 pixel array, depending on the type of sample preparation, long-established fluorescence acquisition technologies such as photodiode arrays, laser scanning systems, and cooled charged-coupled device (CCD) cameras still have some distinct advantages with respect to dynamic range, signal-to-noise ratio, and quantum efficiency[1, 3]. In the present study, Lewis rat hearts were perfused ex vivo with a crystalloid perfusate (Krebs-Henseleit solution) at 37&deg;C on a modified Langendorff apparatus. After a 20 minute stabilization period, the hearts were intermittently perfused with 11 mMol/L 2,3-butanedione monoxime to eliminate contraction-associated motion during image acquisition. For optical mapping, we loaded hearts with the fast-response potentiometric probe di-8-ANEPPS[4] (5 &mu;Mol/L) and briefly illuminated the preparation with 475&plusmn;15 nm excitation light. During a typical 2 second period of illumination, &gt;605 nm light emitted from the cardiac preparation was imaged with a high-speed CMOS camera connected to a horizontal macroscope. For this demonstration, hearts were paced at 300 beats per minute with a coaxial electrode connected to an isolated electrical stimulation unit. Simultaneous bipolar electrographic recordings were acquired and analyzed along with the voltage signals using readily-available software. In this manner, action potentials on the surface of Langendorff-perfused rat hearts can be visualized and registered with electrographic signals.

This article describes a high temporal and spatial resolution technique to optically image action potential movement on the surface of Langendorff-perfused rat hearts using a potentiometric dye (di-8-ANEPPS).

Optical mapping of the cardiac surface with voltage-sensitive fluorescent dyes has become an important tool to investigate electrical excitation in ...

Substrate Generation for Endonucleases of CRISPR/Cas Systems

The interaction of viruses and their prokaryotic hosts shaped the evolution of bacterial and archaeal life. Prokaryotes developed several strategies to evade viral attacks that include restriction modification, abortive infection and CRISPR/Cas systems. These adaptive immune systems found in many Bacteria and most Archaea consist of clustered regularly interspaced short palindromic repeat (CRISPR) sequences and a number of CRISPR associated (Cas) genes (Fig. 1) 1-3. Different sets of Cas proteins and repeats define at least three major divergent types of CRISPR/Cas systems 4. The universal proteins Cas1 and Cas2 are proposed to be involved in the uptake of viral DNA that will generate a new spacer element between two repeats at the 5' terminus of an extending CRISPR cluster 5. The entire cluster is transcribed into a precursor-crRNA containing all spacer and repeat sequences and is subsequently processed by an enzyme of the diverse Cas6 family into smaller crRNAs 6-8. These crRNAs consist of the spacer sequence flanked by a 5' terminal (8 nucleotides) and a 3' terminal tag derived from the repeat sequence 9. A repeated infection of the virus can now be blocked as the new crRNA will be directed by a Cas protein complex (Cascade) to the viral DNA and identify it as such via base complementarity10. Finally, for CRISPR/Cas type 1 systems, the nuclease Cas3 will destroy the detected invader DNA 11,12 .
These processes define CRISPR/Cas as an adaptive immune system of prokaryotes and opened a fascinating research field for the study of the involved Cas proteins. The function of many Cas proteins is still elusive and the causes for the apparent diversity of the CRISPR/Cas systems remain to be illuminated. Potential activities of most Cas proteins were predicted via detailed computational analyses. A major fraction of Cas proteins are either shown or proposed to function as endonucleases 4.
Here, we present methods to generate crRNAs and precursor-cRNAs for the study of Cas endoribonucleases. Different endonuclease assays require either short repeat sequences that can directly be synthesized as RNA oligonucleotides or longer crRNA and pre-crRNA sequences that are generated via in vitro T7 RNA polymerase run-off transcription. This methodology allows the incorporation of radioactive nucleotides for the generation of internally labeled endonuclease substrates and the creation of synthetic or mutant crRNAs. Cas6 endonuclease activity is utilized to mature pre-crRNAs into crRNAs with 5'-hydroxyl and a 2',3'-cyclic phosphate termini.

CRISPR/Cas systems mediate adaptive immunity in Bacteria and Archaea. Many Cas proteins are proposed to act as endoribonucleases acting on crRNA precursors of varying length. Here we illustrate three different approaches to generate pre-crRNA substrates for the biochemical analysis of Cas endonuclease activity.

The  interaction of viruses and their prokaryotic hosts shaped the evolution of  bacterial and archaeal life. Prokaryotes developed several strategies to ...

LeafJ: An ImageJ Plugin for Semi-automated Leaf Shape Measurement

High throughput phenotyping (phenomics) is a powerful tool for linking genes to their functions (see review1 and recent examples2-4). Leaves are the primary photosynthetic organ, and their size and shape vary developmentally and environmentally within a plant. For these reasons studies on leaf morphology require measurement of multiple parameters from numerous leaves, which is best done by semi-automated phenomics tools5,6. Canopy shade is an important environmental cue that affects plant architecture and life history; the suite of responses is collectively called the shade avoidance syndrome (SAS)7. Among SAS responses, shade induced leaf petiole elongation and changes in blade area are particularly useful as indices8. To date, leaf shape programs (e.g. SHAPE9, LAMINA10, LeafAnalyzer11, LEAFPROCESSOR12) can measure leaf outlines and categorize leaf shapes, but can not output petiole length. Lack of large-scale measurement systems of leaf petioles has inhibited phenomics approaches to SAS research. In this paper, we describe a newly developed ImageJ plugin, called LeafJ, which can rapidly measure petiole length and leaf blade parameters of the model plant Arabidopsis thaliana. For the occasional leaf that required manual correction of the petiole/leaf blade boundary we used a touch-screen tablet. Further, leaf cell shape and leaf cell numbers are important determinants of leaf size13. Separate from LeafJ we also present a protocol for using a touch-screen tablet for measuring cell shape, area, and size. Our leaf trait measurement system is not limited to shade-avoidance research and will accelerate leaf phenotyping of many mutants and screening plants by leaf phenotyping.

Demonstration of key methods for high throughput leaf measurements. These methods can be used to accelerate leaf phenotyping when studying many plant mutants or otherwise screening plants by leaf phenotype.

High throughput phenotyping (phenomics) is a powerful tool for linking genes to their functions (see review1 and recent examples2-4). Leaves are the ...

Semi-automated Imaging of Tissue-specific Fluorescence in Zebrafish Embryos

Zebrafish embryos are a powerful tool for large-scale screening of small molecules. Transgenic zebrafish that express fluorescent reporter proteins are frequently used to identify chemicals that modulate gene expression. Chemical screens that assay fluorescence in live zebrafish often rely on expensive, specialized equipment for high content screening. We describe a procedure using a standard epifluorescence microscope with a motorized stage to automatically image zebrafish embryos and detect tissue-specific fluorescence. Using transgenic zebrafish that report estrogen receptor activity via expression of GFP, we developed a semi-automated procedure to screen for estrogen receptor ligands that activate the reporter in a tissue-specific manner. In this video we describe procedures for arraying zebrafish embryos at 24-48 hours post fertilization (hpf) in a 96-well plate and adding small molecules that bind estrogen receptors. At 72-96 hpf, images of each well from the entire plate are automatically collected and manually inspected for tissue-specific fluorescence. This protocol demonstrates the ability to detect estrogens that activate receptors in heart valves but not in liver.

Described here is a protocol for semi-automated imaging of tissue-specific fluorescence in zebrafish embryos.

Zebrafish embryos are a powerful tool for large-scale screening of small molecules. Transgenic zebrafish that express fluorescent reporter proteins are ...

Isolation of Cardiomyocytes from Fixed Hearts for Immunocytochemistry and Ploidy Analysis

The adult mammalian heart is composed of various cell types including cardiomyocytes, endothelial cells and fibroblasts. Since it is difficult to reliably identify nuclei of cardiomyocytes on histological sections, many groups rely on isolating viable cardiomyocytes prior to fixation to perform immunostaining. However, these live cardiomyocyte isolation techniques require optimization to maximize the yield, viability and quality of the samples, with inherent fluctuations from sample to sample despite maximum optimization. Here, we report a reproducible protocol, involving fixation prior to enzymatic digestion of the heart, which leads to maximum yield while preserving the in vivo morphology of individual cardiomyocytes. We further developed an automated analysis platform to determine the number of nuclei and DNA content per nucleus for individual cardiomyocytes. After exposing the chest cavity, the heart was arrested in diastole by perfusion with 60 mM KCl in PBS. Next, the heart was fixed in 4% paraformaldehyde (PFA) solution, and then digested with 60 mg/mL collagenase solution. After digestions, cells were singularized by trituration, and the cardiomyocyte fraction was enriched via differential centrifugation. Isolated cardiomyocytes were stained for Troponin T and &#945;-actinin to assess purity of the obtained population. Furthermore, we developed an image analysis platform to determine cardiomyocyte nucleation and ploidy status following DAPI staining. Image based ploidy assessments led to consistent and reproducible results. Thus, with this protocol, it is possible to preserve native morphology of individual cardiomyocytes to allow immunocytochemistry and DNA content analysis while achieving maximum yield.

The goal of this work is to develop a method to reproducibly isolate cardiomyocytes from the adult heart and measure DNA content and nucleation.

The adult mammalian heart is composed of various cell types including cardiomyocytes, endothelial cells and fibroblasts. Since it is difficult to reliably ...

Quantitative Analysis of Viscoelastic Properties of Red Blood Cells Using Optical Tweezers and Defocusing Microscopy

The viscoelastic properties of erythrocytes have been investigated by a range of techniques. However, the reported experimental data vary. This is not only attributed to the normal variability of cells, but also to the differences in methods and models of cell response. Here, an integrated protocol using optical tweezers and defocusing microscopy is employed to obtain the rheological features of red blood cells in the frequency range of 1 Hz to 35 Hz. While optical tweezers are utilized to measure the erythrocyte-complex elastic constant, defocusing microscopy is able to obtain the cell height profile, volume, and its form factor a parameter that allows conversion of complex elastic constant into complex shear modulus. Moreover, applying a soft glassy rheology model, the scaling exponent for both moduli can be obtained. The developed methodology allows to explore the mechanical behavior of red blood cells, characterizing their viscoelastic parameters, obtained under well-defined experimental conditions, for several physiological and pathological conditions.

Here, an integrated protocol based on optical tweezers and defocusing microscopy is described to measure the rheological properties of cells. This protocol has wide applicability in studying the viscoelastic properties of erythrocytes under variable physio-pathological conditions.

The viscoelastic properties of erythrocytes have been investigated by a range of techniques. However, the reported experimental data vary. This is not ...

Semi-Automated Isolation of Murine White Adipose Tissue

Semi-Automated Isolation of the Stromal Vascular Fraction from Murine White Adipose Tissue Using a Tissue Dissociator

The in vitro study of white, brown, and beige adipocyte differentiation enables the investigation of cell-autonomous functions of adipocytes and their mechanisms. Immortalized white preadipocyte cell lines are publicly available and widely used. However, the emergence of beige adipocytes in white adipose tissue in response to external cues is difficult to recapitulate to the full extent using publicly available white adipocyte cell lines. Isolation of the stromal vascular fraction (SVF) from murine adipose tissue is commonly executed to obtain primary preadipocytes and perform adipocyte differentiation. However, mincing and collagenase digestion of adipose tissue by hand can result in experimental variation and is prone to contamination. Here, we present a modified semi-automated protocol that utilizes a tissue dissociator for collagenase digestion to achieve easier isolation of the SVF, with the aim of reducing experimental variation, reducing contamination, and increasing reproducibility. The obtained preadipocytes and differentiated adipocytes can be used for functional and mechanistic analyses.

Author Spotlight: Semi-Automated Isolation of the Stromal Vascular Fraction from Murine White Adipose Tissue Using a Tissue Dissociator  

This protocol describes the semi-automated isolation of the stromal vascular fraction (SVF) from murine adipose tissue to obtain preadipocytes and achieve adipocyte differentiation in vitro. Using a tissue dissociator for collagenase digestion reduces experimental variation and increases reproducibility.

The in vitro study of white, brown, and beige adipocyte differentiation enables the investigation of cell-autonomous functions of adipocytes and their ...