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Snapshots of Life

The Science of Saliva

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Artificial salivary glands

Credit: Swati Pradhan-Bhatt, Christiana Care Health System, Newark, DE

Whether it’s salmon sizzling on the grill or pizza fresh from the oven, you probably have a favorite food that makes your mouth water. But what if your mouth couldn’t water—couldn’t make enough saliva? When salivary glands stop working and the mouth becomes dry, either from disease or as a side effect of medical treatment, the once-routine act of eating can become a major challenge.

To help such people, researchers are now trying to engineer replacement salivary glands. While the research is still in the early stages, this image captures a crucial first step in the process: generating 3D structures of saliva-secreting cells (yellow). When grown on a scaffold of biocompatible polymers infused with factors to encourage development, these cells cluster into spherical structures similar to those seen in salivary glands. And they don’t just look like salivary cells, they act like them, producing the distinctive enzyme in saliva, alpha amylase (blue).

Cool Videos: Another Kind of Art Colony

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BioArt-Berkmen and PenilAs long as researchers have been growing bacteria on Petri dishes using a jelly-like growth medium called agar, they have been struck by the interesting colors and growth patterns that microbes can produce from one experiment to the next. In the 1920s, Sir Alexander Fleming, the Scottish biologist who discovered penicillin, was so taken by this phenomenon that he developed his own palette of bacterial “paints” that he used in his spare time to create colorful pictures of houses, ballerinas, and other figures on the agar [1].

Fleming’s enthusiasm for agar art lives on among the current generation of microbiologists. In this short video, the agar (yellow) is seeded with bacterial colonies and, through the magic of time-lapse photography, you can see the growth of the colonies into what appears to be a lovely bouquet of delicate flowers. This piece of living art, developing naturally by bacterial colony expansion over the course of a week or two, features members of three bacterial genera: Serratia (red), Bacillus (white), and Nesterenkonia (light yellow).

Snapshots of Life: Host vs. Pathogen

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Cryptoccocus neoformans

Caption: This scanning electron microscopy image shows mouse macrophages (green) interacting with a fungal cell (blue).
Credit: Sabriya Stukes and Hillary Guzik, Albert Einstein College of Medicine

Macrophages are white blood cells that generally destroy foreign invaders by engulfing them. It’s a tried-and-true strategy, but it doesn’t always work. Cryptoccocus neoformans, a deadly fungal pathogen commonly found in the feces of pigeons, can foil even the best macrophages. No one has captured this grand escape—but researchers are getting a whole lot closer to doing so.

Sabriya Stukes, an NIH-funded microbiologist at New York’s Albert Einstein College of Medicine, studies the interactions between C. neoformans and macrophages to determine how the former causes the lung infection cryptococcosis, which can be deadly for people with compromised immune systems. Stukes believes what makes C. neoformans so dangerous is that it can survive the acid death chamber inside macrophages—a situation that spells doom for most other pathogens. A big reason behind this fungus’s power of survival is its thick coat of polysaccharides, which serves as woolly-looking armor. Once a macrophage engulfs the fungus, this coat can give the white blood cell “indigestion,” prompting it to spit the fungus back into the lungs where it can cause disease. 

Snapshots of Life: The Hard Working Hepatocyte

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Human hepatocyte

Caption: Magnified image of a hepatocyte: nuclei in blue; actin fibers in red, yellow, orange, and green.
Credit: Donna Beer Stolz, University of Pittsburgh

The humble hepatocyte handles a lot of the body’s maintenance and clean up work. It detoxifies the blood, metabolizing medications and alcohol. It secretes important proteins that regulate carbohydrates and fats—including both the good and bad kinds of cholesterol. It’s also the most common cell in one of the few human organs that regenerate: the liver. When this organ is damaged, hepatocytes begin dividing to repair the tissue.

Its regenerative ability is just one reason that Donna Beer Stolz, a microscopist and cell biologist at the University of Pittsburgh, in Pennsylvania, has been studying the hepatocyte for more than 20 years. She captured this image while conducting one of her experiments. As she was carefully scanning a dish of cells, one particular hepatocyte caught her eye. It was perfectly round. Struck by its symmetry and beauty, Stolz snapped pictures of the cell at different layers and then used software to reconstruct and color the image.

Snapshots of Life: Sore Throat as Art

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Scanning electron micrograph of Strep A bacteria

Credit: Vincent A. Fischetti, The Rockefeller University

Most parents and kids wouldn’t consider strep throat the subject of high art. But the judges of the Federation of American Societies for Experimental Biology’s 2013 BioArt competition think it is. In this silver-toned scanning electron micrograph, you can see hundreds of tiny spheres—bacteria called Group A streptococci—attached to a human pharyngeal (throat) cells grown in a lab dish. These bacteria are responsible for a very nasty type of pharyngeal inflammation commonly known as strep throat. Strep infections are usually treated with antibiotics; left untreated, they can lead to rheumatic fever, rheumatic heart disease, and even kidney disease.