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fluorescence microscopy

Fibers from cultured muscle stem cells

Credit: Kevin Murach, Charlotte Peterson, and John McCarthy, University of Kentucky, Lexington

As many of us know from hard experience, tearing a muscle while exercising can be a real pain. The good news is that injured muscle will usually heal quickly for many of us with the help of satellite cells. Never heard of them? They are the adult stem cells in our skeletal muscles long recognized for their capacity to make new muscle fibers called myotubes.

This striking image shows what happens when satellite cells from mice are cultured in a lab dish. With small adjustments to the lab dish’s growth media, those cells fuse to form myotubes. Here, you see the striated myotubes (red) with multiple cell nuclei (blue) characteristic of mature muscle fibers. The researchers also used a virus to genetically engineer some of the muscle to express a fluorescent protein (green).

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Let’s kick off the Fourth of July weekend with some biological fireworks! While we’ve added a few pyrotechnic sound effects just for fun, what you see in this video is the product of some serious research. Using a specialized microscope equipped with a time-lapse camera to image fluorescence-tagged proteins in real-time, an NIH-funded team has captured a critical step in the process of cell division, or mitosis: how filaments called microtubules (red) form new branches (green) and fan out to form mitotic spindles.

In this particular experimental system, the team led by Sabine Petry at Princeton University, Princeton, NJ, studies the dynamics of microtubules in a cell-free extract of cytoplasm taken from the egg of an African clawed frog (Xenopus laevis). Petry’s ultimate goal is to learn how to build mitotic spindles, molecule by molecule, in the lab. Such an achievement would mark a major step forward in understanding the complicated mechanics of cell division, which, when disrupted, can cause cancer and many other health problems.

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Keratinocyte

Credit: Torsten Wittmann, University of California, San Francisco

Cells are constantly on the move. They shift, grow, and migrate to new locations—for example, to heal a wound or to intercept an infectious agent as part of an immune response. But how do cells actually move?

In this image, Torsten Wittmann, an NIH-funded cell biologist at the University of California, San Francisco, reveals the usually-invisible cytoskeleton of a normal human skin cell that lends the cell its mobility. The cytoskeleton is made from protein structures called microtubules—the wispy threads surrounding the purple DNA-containing nucleus—and filaments of a protein called actin, seen here as the fine blue meshwork in the cell periphery. Both actin and microtubules are critical for growth and movement.

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Credit: Xueting Luo and Kevin Park, University of Miami

Fasten your seat belts! We’re going to fly through the brain of a mouse. Our tour guide is Kevin Park, an NIH-funded neuroscientist at the University of Miami, who has developed a unique method to visualize neurons in an intact brain. He’s going to give us a rare close-up of the retinal ganglion cells that carry information from the eye to the brain, where the light signals are decoded and translated.

To make this movie, Park has injected a fluorescent dye into the mouse eye; it is taken up by the retinal cells and traces out the nerve pathways from the optic nerve into the brain.

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Image of black spirals

Caption: Snapshot of changes that occur (black) when surfactant molecules are stressed by carbon nanoparticles. For the less spectacular “before” image, click the “Continue reading” link.
Source: Prajnaparamita Dhar, Department of Chemical Engineering, University of Kansas, Lawrence

These eye-catching spirals may resemble a trendy print from Diane von Furstenberg’s Spring Collection, but they’re actually a close-up of lung surfactant—a lipid-protein film that coats the inside of the air sacs in the lungs, making it easier to breathe. Made using fluorescence microscopy techniques, this image shows what happens to the surfactant (black) when it interacts with carbon nanoparticles.

Scientists found that carbon nanoparticles rearrange the surfactant molecules from kidney bean shaped clusters into solid spirals. Since carbon nanoparticles may be effective drug delivery vehicles, it’s important to know how these molecules alter the surfactant—and whether these changes are harmful.

The verdict is still out on whether disrupting the surfactant triggers breathing problems, but we can still be mesmerized by the image. (more…)

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