<h2 class="jove_title"><a style="color:#3a74ba; text-decoration: none;" href="https://www.jove.com/video/4033">Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses</a></h2>
Wenqian Hu, Yung C. Shin, Galen B. King Mechanical Engineering, Purdue University
An experimental method to examine the early plasma evolution induced by ultrashort laser pulses is described. Using this method, high quality images of early plasma are obtained with high temporal and spatial resolutions. A novel integrated atomistic model is used to simulate and explain the mechanisms of early plasma.
<h2 class="jove_title"><a style="color:#3a74ba; text-decoration: none;" href="https://www.jove.com/video/3980">Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures</a></h2>
Davor Copic1, Sei Jin Park1, Sameh Tawfick1, Michael De Volder2, A. John Hart1 1Mechanosynthesis Group, Department of Mechanical Engineering, University of Michigan , 2IMEC, Belgium
We present methods for fabrication of patterned microstructures of vertically aligned carbon nanotubes (CNTs), and their use as master molds for production of polymer microstructures with organized nanoscale surface texture. The CNT forests are densified by condensation of solvent onto the substrate, which significantly increases their packing density and enables self-directed formation of 3D shapes.
<h2 class="jove_title"><a style="color:#3a74ba; text-decoration: none;" href="https://www.jove.com/video/4115">NADH Fluorescence Imaging of Isolated Bi-ventricular Working Rabbit Hearts</a></h2>
Huda Asfour1, Anastasia M. Wengrowski1, Rafael Jaimes III1, Luther M. Swift2, Matthew W. Kay1 1Electrical and Computer Engineering Department, The George Washington University, 2Pharmacology and Physiology Department, The George Washington University
The objective is to monitor the mitochondrial redox state of isolated hearts within the context of physiologic preload and afterload pressures. A biventricular working rabbit heart model is presented. High spatiotemporal resolution fluorescence imaging of NADH is used to monitor the mitochondrial redox state of epicardial tissue.
<h2 class="jove_title"><a style="color:#3a74ba; text-decoration: none;" href="https://www.jove.com/video/4191">Synthetic Spider Silk Production on a Laboratory Scale</a></h2>
Yang Hsia, Eric Gnesa, Ryan Pacheco, Kristin Kohler, Felicia Jeffery, Craig Vierra Department of Biological Sciences, University of the Pacific
Despite the outstanding mechanical and biochemical properties of spider silks, this material cannot be harvested in large quantities by conventional means. Here we describe an efficient strategy to spin artificial spider silk fibers, which is an important process for investigators studying spider silk production and their use as next-generation biomaterials.
<h2 class="jove_title"><a style="color:#3a74ba; text-decoration: none;" href="https://www.jove.com/video/4078">Gene Transfer into Older Chicken Embryos by ex ovo Electroporation</a></h2>
Jiankai Luo1, Xin Yan1, Juntang Lin2, Arndt Rolfs1 1Albrecht-Kossel-Institute for Neuroregeneration, School of Medicine University of Rostock, 2Institute of Anatomy I, School of Medicine University of Jena
A method of gene transfer into chicken embryos at later incubation stages (older than Hamburger and Hamilton stage (HH) 22) is described. This method overcomes disadvantages of in ovo electroporation applied to older chicken embryos and is a useful technique to study gene function and regulation at older developmental stages.
<h2 class="jove_title"><a style="color:#3a74ba; text-decoration: none;" href="https://www.jove.com/video/4041">A Convenient and General Expression Platform for the Production of Secreted Proteins from Human Cells</a></h2>
Halil Aydin*, Farshad C. Azimi*, Jonathan D. Cook*, Jeffrey E. Lee Department of Laboratory Medicine and Pathobiology, University of Toronto * These authors contributed equally.
In the post-human genomics era, the availability of recombinant proteins in native conformations is crucial to structural, functional and therapeutic research and development. Here, we describe a test- and large-scale protein expression system in human embryonic kidney 293T cells that can be used to produce a variety of recombinant proteins.
<h2 class="jove_title"><a style="color:#3a74ba; text-decoration: none;" href="https://www.jove.com/video/4270">Ex vivo Culturing of Whole, Developing Drosophila Brains</a></h2>
Ranjini Prithviraj1, 2, Svetlana Trunova1, 2, Edward Giniger1, 2 1National Institute of Neurological Disorders and Stroke, 2National Human Genome Research Institute, National Institutes of Health, Bethesda, MD
This article describes a method by which one can mimic in vivo development of the Drosophila mushroom body in an ex vivo culture system.

No conflicts of interest declared.

july 2012: this month in jove

Historically, JoVE, The Journal of Visualized Experiments, has focused primarily on biomedical research and has developed subsections for Bioengineering, Clinical and Translational Medicine, Immunology and Infection, and Neuroscience. This July, JoVE launches its Applied Physics section, which includes a range of content from Plasma Physics to Materials Science. We begin the new section with a notable article from Purdue University, where researchers in the Center for Laser-Based Manufacturing are studying.
Matter exists in three familiar states: solid, liquid, and gas. If a gas is hit with enough energy, atoms can lose electrons, or become ionized, to form a fourth state called plasma. Plasma is the most abundant form of matter; occupying about 99.999% of the visible universe. Using ultrashort laser pulses of 100 femtoseconds, or 100 quadrillionths of a second, our authors demonstrate a technique called pump probe shadowgraphy, which allows the early plasma to be visualized as it evolves from metal surfaces. By constructing a simulation model, these investigators are able to examine early plasma dynamics, enabling a better understanding of how matter becomes ionized.
For the materials science subcategory of applied physics, JoVE materializes at the University of Michigan, where researchers are developing new methods in microfabrication. Our authors demonstrate a method for growing complex, three-dimensional microstructures out of carbon nanotubes, which can be used as master molds to cast replicas out of polymers or biological materials. Scanning electron microscopy reveals that the carbon nanotube master molds are reproduced with high fidelity in microscale shape and nanoscale texture in the polymer replicas made from these molds. Microfabrication technology allows laboratory operations to be performed on small scales &#x2013; essentially putting a lab on a chip.
Shifting from Applied Physics to cardiac physiology, JoVE visits The George Washington University to capture a modified Langendorff preparation. JoVE has published several articles that demonstrate this physiological prep, which allows the heart to beat in isolation for hours at a time. The approach involves retrograde perfusion of the heart, via the aorta, which shuts the aortic valve and forces oxygenated perfusate through the coronary circulation, in order to sustain cardiac tissue.
Our authors present a modification to this preparation that involves cannulating the left atrial appendage, the inferior vena cava, and the pulmonary artery. In this state all four chambers of the heart are cannulated, thereby providing physiological load pressures to both ventricles, and eliminating the need to retrogradely-pefuse the heart through the aorta. Therefore, perfusion of the heart is in the normal direction, and the heart provides its own pressure for coronary perfusion. 
Once this biventricular working heart model is achieved, our authors proceed to set up imaging of nictonamide adenine dinucleoutide, or NADH, fluorescence. This coenzyme, which is found in mitochondria, emits fluorescence in its reduced state and provides a readout for local oxygen concentration, and therefore heart metabolism. These investigators demonstrate measurements of NADH fluorescence during different pacing rates and thereby illustrate the potential of this physiologically-relevant model to provide insight into cardiac pathologies. 
In our Bioengineering section, JoVE visits the University of the Pacific for an article dealing with synthetic spider silk production. Back in 2010, JoVE published an article from the Vierra lab, which demonstrated microdissection techniques to isolate the 12 silk producing glands from the Black Widow spider. Isolation of these glands allows for analytical techniques to be performed, in order to identify specific spider silk proteins. Because spiders are venomous and cannibalistic, rearing them for large scale production of spider silk is unrealistic. Therefore, the Vierra lab transforms bacteria with silk protein-containing plasmids and expresses recombinant spider silk proteins in bacteria.
This July in JoVE, the Vierra group takes us through a method for isolating and purifying spider silk protein from these bacteria. They then show us how purified protein is spun into fibers and demonstrate methods for collecting these fibers, as well as assessing their strength. Spider silk is of great interest to biomaterial scientists, because of its biocompatibility and mechanical properties, which make it stronger than tensile steel. The Vierra lab has shown us laboratory-scale production of spider silk that can potentially be extended to a large scale manufacturing process. 
This brief summary synopsizes four of the fifty articles that JoVE will release this July. Other noteworthy publications include demonstrations of ex ovo electroporation in late stage chicken embryos, production of secreted proteins from human cells, and the ex vivo culturing of fruit fly brains.

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

July 2012: This Month in JoVE

Historically, JoVE, The Journal of Visualized Experiments, has focused primarily on biomedical research and has developed subsections for Bioengineering, Clinical and Translational Medicine, Immunology and Infection, and Neuroscience. This July, JoVE launches its Applied Physics section, which includes a range of content from Plasma Physics to Materials Science. We begin the new section with a notable article from Purdue University, where researchers in the Center for Laser-Based Manufacturing are studying.

Historically, JoVE, The Journal of Visualized Experiments, has focused primarily on biomedical research and has developed subsections for Bioengineering, ...

Research

JoVE Journal

Biology

19.1K Views.  JoVE Content Production. Historically, JoVE, The Journal of Visualized Experiments, has focused primarily on biomedical research and has developed subsections for Bioengineering, Clinical and Translational Medicine, Immunology and Infection, and Neuroscience. This July, JoVE launches its Applied Physics section, which includes a range of content from Plasma Physics to Materials Science. We begin the new section with a notable article from Purdue University, where researchers in the Center for ...

Video: July 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 ...

February 2012: This Month in JoVE

The February issue of the Journal of Visualized Experiments (JoVE) takes a clinical theme with the release of two articles, which demonstrate implantations of medical devices used to treat cardiac arrhythmia. More specifically, both articles focus on treating atrial fibrillation - a devastating condition that can ultimately lead to stroke.
The first procedure, led by Professor Dietmar Baensch from the University Hospital Rostock, involves the surgical implantation of an implantable cardioverter-defibrillator, or ICD. ICDs are devices widely used for the termination of ventricular arrhythmias. However, if the site of abnormal pacemaking is supraventricular in origin, such as in the left atrium, these devices can deliver inappropriate and painful shocks. To overcome this issue with potential misdiagnosis, as well as higher complication rates observed with dual chamber elecectrodes, Biotronik has developed a single ICD lead, which is capable of both atrial and ventricular sensing. Guided by X-ray fluoroscopy and electrophysiology, Dr. Baensch and his team demonstrate the surgical procedure for inserting, testing, and anchoring the single chamber electrode. Following electrode positioning, the Lumax defibrillator is joined to the electrode and inserted into the patient. To assess device function ventricular fibrillation is induced via a T-wave shock, and the ability of the defibrillator to sense arrhythmia and administer a corrective shock to is assessed.
While the Lumax ICD system can attenuate cardiac arrhythmia by correcting cardiac pacemaking, the WATCHMAN left atrial appendage (LAA) occlusion device from Boston Scientific is designed to address a severe complication with atrial fibrillation - thromboembolic stroke. In patients with atrial fibrillation, the left atrial appendage, a muscular pouch in the left atrium, can act as a reservoir for clotting blood, which if dislodged, can form emboli that can cause stroke. When implanted, the WATCHMAN device can trap clots within the LAA before they exit. Following assessment of LAA morphology, our authors, led by Dr. Sven M&ouml;bius-Winkler from the University of Leipzig, demonstrate methods for inserting a guidewire through the femoral artery into the heart, advancing the device into the left atrium, and deployment of the device in the left atrial appendage. Studies have shown that patients receiving WATCHMAN intervention have a reduced probability of adverse cardiac events when compared to patients given the anticoagulant medication warfarin.
While both the Lumax ICD system and the WATCHMAN occlusion device show promise for treating cardiac arrhythmia and its complications, neither device is approved for use in the US. Through video-publication in JoVE, our authors have provided a resource for US physicians to view these sensitive device implantation procedures before they become available across the Atlantic.
One consequence of thromboembolism is hypoxia, and JoVE travels to the University of Rochester to document a method for 2-photon imaging of microregional hypoxia in the cerebral cortex. Our authors illustrate a detailed open cranial window preparation followed by 2-photon imaging of endogenous nicotinamide adenine dinucleotide, or NADH, fluorescence. NADH is well known for its ability to transport electrons during cellular respiration, and it just so happens that NADH fluorescence exhibits a nonlinear relationship with the partial pressure of oxygen in tissues. In the cortex, NADH fluorescence increases as hypoxia is induced, allowing these investigators to determine which cortical areas are most vulnerable to hypoxia, as well as the geometrical pattern of oxygen diffusion from vessels.
For Bioengineering, JoVE heads to Wayne State University to capture a procedure for visualizing the breast cancer tumor microenvironment, in vitro. Our authors demonstrate a procedure for the assembly of a breast cancer co-culture system, which they refer to as Mammary Architecture and Microenvironment Engineering, or MAME. Briefly, these culture models consist of a layer of human breast fibroblasts in collagen 1 matrix, below a layer of reconstituted basement membrane matrix, upon which ductal carcinoma cells from the breast are added before the entire model is submerged in medium. When imaged in 4D, or in 3 dimensions over time, the proliferation of carcinoma cells can be tracked. In addition, degradation of the basement membrane can be assessed as well, thanks to the incorporation of a type of collagen that fluoresces when hydrolyzed. This innovative culture system can provide insight for breast cancer researchers into the proteolytic pathways that promote invasive phenotypes in breast cancer cells and can be used to screen for new small molecule inhibitors that may hinder tumor proliferation.
In Immunology and Infection, JoVE shifts its focus to vector borne disease, where investigators from the Center for Disease control in Fort Collins, Colorado, present three fundamentally important procedures for understanding how infectious pathogens migrate through the tick. The first procedure involves removing one of the legs from the tick, which enables the collection of hemolymph - the fluid carries oxygen to the tick's organs. The bacteria that cause Lyme Disease, Borrelia burgdorferi, will move to the hemolymph of the tick once a bloodmeal has been absorbed by the midgut. The second dissection protocol illustrates steps for accessing the hemocoel and removing the salivary glands, which is where Borrrelia reside before transmission to a host. The final protocol begins with application of the muscarinic agonist, pilocarpine, to the dorsal surface of an engorged tick, in order to induce salivation. Saliva is collected from a mouthpart referred to as the hypostome and manual techniques for promoting tick salivation via gentle massage, are demonstrated.
From vector borne disease to medical device implantation, February is brimming with content submitted from authors dedicated to understanding and treating human disease. Other notable articles for the month of February include methods for assessing the metastatic potential of ovarian cancer, spatial analysis of neuropeptides in a rodent model of Parkinson's, and measurements of ventricular pressure in neonatal and embryonic mice. From bench to bedside, no other journal provides a window into biomedical research quite like JoVE. Stay tuned for February's content!

Here are some highlights from the February 2012 Issue of Journal of Visualized Experiments (JoVE).

The February issue of the Journal of Visualized Experiments (JoVE) takes a clinical theme with the release of two articles, which demonstrate ...

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 ...