يوليو 2012: من هذا الشهر في [جوف]

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 – 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.