<h2 class="jove_title"><a href="https://www.jove.com/video/3524">Doppler Optical Coherence Tomography of Retinal Circulation</a></h2>
Ou Tan1, Yimin Wang1, Ranjith K. Konduru2, Xinbo Zhang1, SriniVas R. Sadda2, David Huang1 1Department of Ophthalmology, Oregon Health and Science University , 2Department of Ophthalmology, University of Southern California
Total retinal blood flow is measured by Doppler optical coherence tomography and semi-automated grading software.
<h2 class="jove_title"><a href="https://www.jove.com/video/3886">Micropipette Aspiration of substrate-attached cells to estimate cell stiffness</a></h2>
Myung-Jin Oh1, Frank Kuhr1, Fitzroy Byfield2, Irena Levitan1 1Section of Respiratory, Critical Care and Sleep Medicine, Department of Medicine, University of Illinois, 2Institute for Medicine and Engineering, University of Pennsylvania 
Here we describe a quick and simple method to measure cell stiffness. The general principle of this approach is to measure membrane deformation in response to well-defined negative pressure applied through a micropipette to the cell surface. This method provides a powerful tool to study biomechanical properties of substrate-attached cells.
<h2 class="jove_title"><a href="https://www.jove.com/video/4061">Time-lapse imaging of neuroblast migration in the mouse forebrain</a></h2>
Jivan Khlghatyan, Armen Saghatelyan The Cellular Neurobiology Unit, Centre de Recherche Universit&#233; Laval Robert-Giffard
We describe a protocol for real-time videoimaging of neuronal migration in the mouse forebrain. The migration of virally-labeled or grafted neuronal precursors was recorded in acute live slices using wide-field fluorescent imaging with a relatively rapid acquisition interval to study the different phases of cell migration, including the durations of the stationary and migration phases and the speed of migration.
<h2 class="jove_title"><a href="https://www.jove.com/video/4215">Fluorescent in situ Hybridization on Mitotic Chromosomes of Mosquitoes</a></h2>
Vladimir A. Timoshevskiy, Atashi Sharma, Igor V. Sharakhov, Maria V. Sharakhova Department of Entomology, Virginia Tech
Among the three mosquito genera, namely Anopheles, Aedes, and Culex, physical genome mapping techniques were established only for Anopheles, whose members possess readable polytene chromosomes. For the genera of Aedes and Culex, however, cytogenetic mapping remains challenging because of the poor quality of polytene chromosomes. Here we present a universal protocol for obtaining high-quality preparations of mitotic chromosomes and an optimized FISH protocol for all three genera of mosquitoes.
<h2 class="jove_title"><a href="https://www.jove.com/video/4251">Two- and Three-Dimensional Live Cell Imaging of DNA Damage Response Proteins</a></h2>
Jason M. Beckta1, 2, Scott C. Henderson3, Kristoffer Valerie1, 2, 4 1Department of Radiation Oncology, Virginia Commonwealth University, 2Department of Biochemistry &#38; Molecular Biology, Virginia Commonwealth University, 3Department of Anatomy &#38; Neurobiology, Virginia Commonwealth University, 4Massey Cancer Center, Virginia Commonwealth University
This protocol describes a method for visualizing a DNA double-strand break signaling protein activated in response to DNA damage as well as its localization during mitosis.
<h2 class="jove_title"><a href="https://www.jove.com/video/4350">Cell tracking using photoconvertible proteins during zebrafish development</a></h2>
Ver&#243;nica A. Lombardo, Anje Sporbert, Salim Abdelilah-Seyfried Max Delbr&#252;ck Center for Molecular Medicine
Here, we present a method for the photoactivated switch of photoconvertible fluorescent proteins (PCFPs) in the living zebrafish embryo and further tracking of photoconverted protein at specific time points during development. This methodology allows monitoring of cell biological events underlying different developmental processes in a live vertebrate organism.
<h2 class="jove_title"><a href="https://www.jove.com/video/4427">Driving Simulation in the Clinic: Testing visual exploratory behavior in daily life activities in patients with visual field defects </a></h2>
Johanna Hamel1, 2, Antje Kraft1, Sven Ohl3, Sophie De Beukelaer1, Heinrich J. Audebert1, 2, Stephan A. Brandt1 1Department of Neurology, Universit&#228;tsmedizin Charit&#233;, 2Center for Stroke Research Berlin (CSB), Universit&#228;tsmedizin Charit&#233;, 3Berlin School of Mind and Brain, Humboldt Universit&#228;t zu Berlin
Patients with visual deficits after stroke report about different constraints in daily life most likely due to variable compensatory strategies, which are difficult to differentiate in clinical routine. We present a clinical set-up which allows measurement of different compensatory head- and eye-movement-strategies and evaluating their effects on driving performance.

No conflicts of interest declared.

september 2012: this month in jove

This September in JoVE, researchers from the School of Medicine at the Free University of Berlin demonstrate a novel method for studying how stroke patients compensate for visual field defects. To do this, our authors make use of a driving simulator complete with brakes, a steering wheel, and turn signals. Using driving simulation software and sophisticated eye tracking, researchers can compare the gaze behavior of stroke patients as they navigate through virtual driving courses with varying degrees of complexity. Though posterior cerebral artery infarction can lead to similar visual deficits in patients, some are able to navigate through the driving courses by developing compensatory eye movements, while others crash into dangerous obstacles, like wild boars. Through the analysis of compensatory gaze behavior employed by patients, our authors see great potential for using driving simulation as a tool to rehabilitate stroke patients trying to overcome the blind spots in their visual fields.
In collaboration with the University of Southern California, researchers in the Department of Ophthalmology at Oregon Health and Science University present a method for measuring total blood flow in the retina using Doppler optical coherence tomography (OCT). The retina contains millions of neurons that capture visual images and convert them into electrical signals, which travel through the optic nerve to the brain. Blood vessels enter the retina at the optic disk, where the optic nerve connects to the retina. These vessels supply oxygen and nutrients, and also remove waste. In some retinal diseases (such as diabetic retinopathy) or glaucoma (which affects the optic nerve), the retinal vasculature may be abnormal. Because these diseases are leading causes of irreversible vision loss, measurements of retinal blood flow can be very useful in clinical practice and research. Unlike traditional optical imaging methods, like laser Doppler and ultrasound color Doppler, laser Doppler OCT can provide absolute measurements of retinal blood flow; these are based on Doppler-shifted light, which is backscattered from red blood cells as they flow through vessels. Our authors demonstrate how to scan the retina and optic disc with Doppler OCT; the scans are then graded and analyzed with DOCTORC software, which our authors developed. This method shows good reproducibility between graders and methods. Furthermore, in eyes with glaucoma, retinal blood flow measurements are highly correlated with vision loss. Thus, Doppler OCT represents a powerful tool that can be used in ophthalmology research and clinical practice.
Coinciding with mosquito season, researchers in the Department of Entomology at Virginia Tech demonstrate a simple and robust technique for chromosome mapping of mosquito genomes. Out of more than 40 mosquito genera containing thousands of species, researchers are particularly interested in the genera Anopheles, Aedes, and Culex because they contain species that transmit harmful human diseases. About 90% of the Anopheles gambia genome has been mapped to chromosomal locations; however, it is extremely difficult to prepare suitable chromosome spreads for the Aedes genus or the Culex genus using cell lines and standard techniques. To overcome this problem, our authors use 4th instar mosquito larvae, which have imaginal discs that produce high-quality chromosomal spreads. The researchers show how to dissect the imaginal discs and prepare suitable chromosome preparations for fluorescence in situ hybridization (FISH). Genome mapping is thus possible for mosquitoes in the Aedes, Culex, and Anopheles genera. This technique paved the way for entomologists to make precise chromosomal maps for not only mosquitoes, but also for other insects.
In the Center for Research at Quebec's University of Laval, researchers demonstrate a method for tracking neuronal migration in the murine forebrain. One important site of neurogenesis in the mammalian brain is the subventricular zone, and newly born neurons migrate away from this area via the rostral migratory stream to the olfactory bulb. The cells are labeled with a stereotaxically injected retrovirus encoding a green fluorescent protein; then, using a combination of acute slice preparation, timelapse imaging, and image analysis, our authors can calculate the migration speed of labeled neuroblasts. Through careful tracking of cell trajectories along blood vessels, this method can help elucidate the different molecular cues and cellular mechanisms that influence cell migration.
This brief summary highlights just a few notable video-articles that will be released this September in JoVE. We also feature methods for tracking cell fate in zebrafish with photoconvertible fluorescent proteins, using micropipettes to test cell stiffness, and imaging the behavior of proteins that respond to DNA damage.

Watch this Scientific Journal Video about September 2012: This Month in JoVE at JoVE.com

September 2012: This Month in JoVE

This September in JoVE, researchers from the School of Medicine at the Free University of Berlin demonstrate a novel method for studying how stroke patients compensate for visual field defects. To do this, our authors make use of a driving simulator complete with brakes, a steering wheel, and turn signals. Using driving simulation software and sophisticated eye tracking, researchers can compare the gaze behavior of stroke patients as they navigate through virtual driving courses with varying degrees of complexity. Though posterior cerebral artery infarction can lead to similar visual deficits in patients, some are able to navigate through the driving courses by developing compensatory eye movements, while others crash into dangerous obstacles, like wild boars. Through the analysis of compensatory gaze behavior employed by patients, our authors see great potential for using driving simulation as a tool to rehabilitate stroke patients trying to overcome the blind spots in their visual fields.

This September in JoVE, researchers from the School of Medicine at the Free University of Berlin demonstrate a novel method for studying how stroke ...

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7.9K Views.  Massachusetts Eye and Ear. This September in JoVE, researchers from the School of Medicine at the Free University of Berlin demonstrate a novel method for studying how stroke patients compensate for visual field defects. To do this, our authors make use of a driving simulator complete with brakes, a steering wheel, and turn signals. Using driving simulation software and sophisticated eye tracking, researchers can compare the gaze behavior of stroke patients as they navigate through virtual driving ...

Video: September 2012: This Month in JoVE

December 2011: This Month in JoVE

The Journal of Visualized Experiments (JoVE) closes 2011 with a December issue that begins by honoring World's AIDS Day with an article that deals with visualizing the structure of HIV envelope glycoproteins, which are a critical component of the viral infection pathway.
One key method for determining virion envelope structure is cryo-electron tomography. Prior to using this technique, soluble virus must be vitrified on a gold grid - a process that involves adding gold to a viral suspension, transferring that suspension to the grid, and plunging the grid into liquid ethane. The virus particles, present in a thin film of liquid atop the grid, are frozen at a rate greater than 100,000 K per second. Following vitrification, collected samples are loaded into the electron microscope and precisely defined regions on the grid are hit with a focused electron beam, while the grid is tilted. The tilt series that results from these imaging sessions is comprised of hundreds of individual images, which must be aligned and averaged to resolve individual envelope proteins. This computationally intense process often requires computer clusters, capable of remote-access parallel processing, like NIH's Biowulf.
Once completed, 3D models can not only provide insight into the structure of envelope glycoproteins themselves, but can also reveal the manner in which they interact other proteins, like the neutralizing antibody B12, which is information that can greatly influence vaccine design.
This article, from the laboratory of Dr. Sriram Subramaniam involves contributions from twenty authors, including not only graduates students and postdocs, but also middle and highschool students, showing that you are never too young to make an impact in the fight against a disease that has infected over 60 million people, worldwide.
In Clinical and Translational Medicine, JoVE presents an article from the University College London and the University of Oxford that investigates the physiological correlates of nociception, or pain sensation, in infants. Typically, infants respond to noxious stimuli by crying and changing their facial expressions - reactions considered to be autonomic and reliant on subcortical regions of the brain.
In order to understand the involvement of the cerebral cortex and spinal cord in infant nociception our authors first prepare infants for EEG and EMG recordings. They also set up physiological monitoring and video recording, so that the infant's facial expressions can be linked to physiological data. Following assessment of infant responses to neutral tactile stimuli, the baby is subjected to heel lancing - a clinical procedure used to obtain blood samples from infants. After data processing, electrical potentials can be compared between noxious and non-noxious stimuli in these infants, which will hopefully lead to meaningful conclusions, regarding how nociceptive information is interpreted by newborns.
JoVE's Bioengineering section takes a more clinical focus in December with an article from the University of Wisconsin, Madison, which involves the fabrication of a compartmentalized microfluidic device for studying cancer stem cell migration. Following device design, master molds are created by photolithography for the application of poly dimethyl siloxane (PDMS)- an organosilicon compound that is transparent and biologically inert - making it suitable for microfluidics applications with live cells. Specifically, our authors load tumor stem cells derived from multiform glioblastoma, a highly malignant brain cancer, into the compartmentalized devices and then place them in a specialized imaging system that acquires data over a few days. 
Time lapse video from these authors show that cancer stem cells are able to regulate their morphology in the size-constrained microfluidic channels much like they would in the interstitial space, and fluidic isolation made possible by chambers like these facilitates drug screening for potential therapeutics that can affect cancer stem cell migration.
Late on in the month, JoVE travels to France, where investigators from the Institute Pasteur and the Centre National de la Recherche Scientifique, illustrate a method for inducing expression of channel-rhodopsin, a light-activated ion channel, into the olfactory bulb of mice, as well as subsequent neuronal stimulation using a miniature light emitting diode (LED).
Our authors give detailed step-by-step instructions for preparing injection needles, and for precise injection of virus into the rostral migratory stream, a site of migration for adult born neuroblasts. Furthermore, they show how miniature LED stimulation devices are fabricated, calibrated, and implanted atop a cranial window prepared over the bulb. In particular, our authors are interested in the way that adult born neurons integrate into existing olfactory neuronal circuits, and they show that LED stimulation in awake behaving animals, can lead to activation of virally-tranduced neuroblasts in the olfactory bulb, which have migrated from the rostral migratory stream.
These video-articles comprise JoVE's highlights for the month of December. Other noteworthy upcoming articles illustrate methods for patterning conductive inks into microelectrodes, measuring cytosolic calcium in contractile lymphatics, and imaging neuronal responses to pheromones in the vomeronasal organ.

Here are some highlights from the December 2011 Issue of Journal of Visualized Experiments (JoVE).

The Journal of Visualized Experiments (JoVE) closes 2011 with a December issue that begins by honoring World's AIDS Day with an article that deals with ...

August 2012: This Month in JoVE

Traditional microscopy requires lens objectives to magnify specimens, and can involve numerous optical components like additional objectives, filters, and mirrors to refract and direct light to optical sensors. The August 2012 issue of JoVE (Journal of Visualized Experiments) is marked by the third publication from the Ozcan Lab (University of California, Los Angeles) on their lens free lens-free "on-chip" microscopy platform, which they have pioneered.
Back in 2009, the Ozcan lab published their first article, which demonstrated the use of a lens-free imaging platform that could image cells within whole blood. This imaging technique involves placing a sample directly on an optoelectric sensor array, like the CCD or CMOS chips found in the standard camcorder. Then, LED illumination from above the sample casts shadows on the chip, which are recorded as digital holograms that can be subjected to image processing. Not only does this lensless imaging system allow for an extremely large field of view (FOV of 0.6-8 cm2), the lack of bulky optical components makes it excellent for microfluidic applications. The Ozcan group demonstrates this in their follow-up 2011 JoVE article, in which fluorescently labeled white blood cells are imaged within a microfluidic chip.
This August in JoVE, the Ozcan group demonstrates further advancements to their lens-free microscopy platform by applying it to tomographic imaging of the nematode, C. elegans. By changing the angle of illumination, using a motorized rotation stage, the Ozcan group shows how multiple holographic slices may be generated for a sample-which, following processing, can be combined into tomograms. The Ozcan group confirms that their 3D reconstruction of the worm is successful by citing that the pharyngeal tube, a 5-micron-thick structure, is only visible in a single slice and in a 3D reconstructed cross section.
The compact and inexpensive nature of the lens-free imaging systems - designed and assembled by the Ozcan group - make them well suited for point-of-care diagnostic applications, or even cell phone based microscopy that can be performed in the field.
At the Ernest Gallo Clinic and Research Center at University of California, San Francisco JoVE learns how to visualize morphological changes in single cells using three-dimensional fluorescence microscopy and computer analysis. In this procedure, cells are given agonist, antagonist plus agonist, or no treatment, and prepared for immunofluorescence microscopy. Three-dimensional images are acquired with the help of a two-photon laser system, and the fluorescence data are processed on the computer using Imaris and Matlab.
To demonstrate the power of this technique, our authors quantify single-cell phenotypic changes in transfected HEK293 cells. Three-dimensional morphometric analysis shows dramatic changes in cells treated with agonist. These changes are not always apparent when using conventional 2D analysis. This technique allows morphological changes in single cells to be quantified and characterized in response to pharmacologic stimuli, offering a powerful new assessment tool to the arsenal of drug discovery research.
This month, in JoVE Applied Physics, we travel to South Carolina to visit the School of Materials Science and Engineering at Clemson University. Here, researchers show us how to construct lithium batteries for laboratory research.
The basic components of a lithium coin cell are the working electrode, the lithium electrolyte, and a lithium foil counter electrode. The different components of the coin cell are carefully assembled and sealed with a crimping machine. The finished coin cell can then be characterized in a battery tester. Using their homemade coin cells, our researchers can experiment with using different materials to make the cathodes of lithium coin cells.
This month in JoVE Immunology and Infection, we head to Basel, Switzerland to witness two techniques for diagnosing helminth infections. We also see how investigators perform the shuttle run test in children, in order to assess the effects of these infections on physical fitness.
Helminths are parasitic worms that can live inside humans and animals. Many species infect the intestinal tract, and may be transmitted through soil. Our authors demonstrate the Kato-Katz technique, which is used for diagnosing several common soil-transmitted helminths. They also demonstrate the Baermann technique, which uses light to stimulate the migration of certain types of phototactic helminths out of sample preparations. The various types of helminth species can subsequently be determined based on morphology.
Our authors then demonstrate how to set up and perform a 20-meter shuttle run test for children, and to measure the impact of helminth infections on physical fitness. This method can help determine the true burden of soil-transmitted helminth infections on overall health.
This brief summary highlights but a few notable video-articles that will be released in August. We'll also feature articles that demonstrate how to express genes in the midbrain of the chick embryo, study neutrophil transmigration in parallel flow chambers lined with endothelial cells, and precisely measure proteolytic degradation of the extracellular matrix.

Traditional microscopy requires lens objectives to magnify specimens, and can involve numerous optical components like additional objectives, filters, and mirrors to refract and direct light to optical sensors. The August 2012 issue of JoVE (Journal of Visualized Experiments) is marked by the third publication from the Ozcan Lab (University of California, Los Angeles) on their lens-free "on-chip" microscopy platform, which they have pioneered.

Traditional microscopy requires lens objectives to magnify specimens, and can involve numerous optical components like additional objectives, filters, and ...

2012: A Year In Review

Here's a look at some of the milestones and highlights of the year 2012 in Journal of Visualized Experiments (JoVE).
At the start of 2012, JoVE reached a major milestone by publishing our 1500th article. In this publication, in JoVE Bioengineering, Yu et al. described a method for analyzing the free radical composition of cigarette smoke. This method simulated cigarette puffing with a single-port smoking device, and combined it with electron spin resonance (ESR) spectroscopy to measure the degree to which antioxidant compounds can scavenge free radicals in cigarette smoke. A possible outcome of this research is the creation of less harmful cigarettes.
JoVE Bioengineering also contained the most-viewed article of 2012. Owczarczak et al. described a method for hacking a standard inkjet printer, loading ink cartridges with a cell-suspension "bioink," and printing lines of live cells onto glass slides. The thermal inkjet printing process creates temporary pores in the cell membrane, visualized by the incorporation of fluorescently labeled actin monomers. This concept, called "bioprinting," has many potential applications in cell and tissue engineering.
Also in 2012, JoVE Bioengineering featured a protocol by Hsia et al. for isolating and purifying spider silk protein, spinning it into fibers, and assessing the fiber strength. This protocol for laboratory-scale production of spider silk, which is stronger than tensile steel, can potentially be extended to large-scale manufacturing.
In JoVE Clinical and Translational Medicine, we featured a number of articles related to stroke, one of which. In one article, M&ouml;bius-Winkler et al. demonstrated placement of the WATCHMAN left atrial appendage occlusion device from Boston Scientific. This device is designed to prevent strokes by trapping clots within the left atrial appendage of the heart before they exit. Our authors demonstrated how to insert the guide wire through the femoral artery into the heart, advance the device into the left atrium, and deploy the device in the left atrial appendage.
Another article focused on stroke, Hamel et al. described the use of a driving simulator to study how patients compensate for visual field defects following stroke. By analyzing the compensatory gaze behavior of patients as they navigated through virtual driving courses with varying degrees of complexity, our authors see great potential for the use of driving simulators in stroke rehabilitation.
In JoVE Immunology and Infection, we published an article by Keyel et al. describing the real-time kinetics of immune cell responses to bacterial toxins using live cell microscopy. Combined with high-speed 3D confocal microscopy, this technique can also visualize the cellular repair response.
Also in JoVE Immunology and Infection, we featured an article by Yap et al. describing methods for diagnosing helminth infections in children. Helminths are parasitic worms that can infect the intestinal tract of humans and animals, and may be distinguished based on their morphology. The same article demonstrated how to measure the impact of helminth infections on physical fitness in children, which is a measure of overall health.
In JoVE Neuroscience, we featured a method by Hoffmann et al., who used tiny headphones to alter the auditory feedback in songbirds, and analyzed the computational and neurophysiological basis of vocal learning in birds when they adjust their singing in response to altered acoustic signals.
Also in JoVE Neuroscience, we moved from birds to bees with a method that assesses associative and non-associative tactile learning in honeybees. This method, by Mujagi&#263; et al., allowed bees to scan different metal surfaces with their antennae, then conditioned them to expect sugar water when their antennae touched particular surfaces, and analyzed the corresponding changes in antennal movement.
In 2012, we launched a brand-new section: JoVE Applied Physics, which features articles on subjects ranging from plasma physics to material science. The Applied Physics section also contained JoVE's 2000th video article, filmed in a synchrotron radiation facility, where Borisenko et al. showed how to determine the electronic structure of complex materials using angle-resolved photoemission spectroscopy.
In the JoVE General section, we published an article by Artioli et al. demonstrating the use of a portable gas analyzer to measure oxygen consumption during complex exercise - such as judo. By analyzing oxygen consumption and collecting blood for measuring plasma lactate concentration, this method can determine the relative contributions of different energy systems to specific aspects of complex exercise.
Finally, JoVE followed Dolhi et al. to a permanently ice-covered saline lake in Antarctica. There, scientists drilled through the ice to study single-celled microorganisms called protists that live in the harsh conditions of Antarctica.
This Year in Review was just a brief glimpse of a few of over 600 video articles that JoVE offered in 2012. Browse the JoVE archives to see thousands of other videos, and stay tuned for what's coming up this year in JoVE: The Journal of Visualized Experiments.

Here's a look at some of the milestones and highlights of the year 2012 in Journal of Visualized Experiments (JoVE).

 
 
Here's a look at some of the milestones and highlights of the year 2012 in Journal of Visualized Experiments (JoVE).
At the start of 2012, JoVE ...