Snapshots of Life: Mending Broken Hearts

Green strings over blue ovals and red dots

Caption: Micrograph of laboratory-grown rat heart muscle cells. Fluorescent labeling shows mitochondria (red), cytoskeleton (green), and nuclei (blue).
Credit: Credit: Douglas B. Cowan and James D. McCully, Harvard Medical School, Boston

This may not look like your average Valentine’s Day card, but it’s an image sure to warm the hearts of many doctors and patients. Why? This micrograph, a winner in the Federation of American Societies for Experimental Biology’s 2013 BioArt Competition, shows cells that have been specially engineered to repair the damage done by heart attacks—which strike more than 700,000 Americans every year.

Working with rat heart muscle cells grown in a lab dish, NIH-supported bioengineers at Harvard Medical School used transplant techniques to boost the number of tiny powerhouses, called mitochondria, within the cells. If you look closely at the image above, you’ll see the heart muscle cells are tagged in green, their nuclei in blue, and their mitochondria in red.

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Brown Fat, White Fat, Good Fat, Bad Fat

Photo of adipocytes in white adipose

Caption: Brown fat cells (stained brown with antibodies against the brown fat-specific protein Ucp1) nestled in amongst white fat cells.
Credit: Patrick Seale, University of Pennsylvania School of Medicine

Fat has been villainized; but all fat was not created equal. Our two main types of fat—brown and white—play different roles. Now, two teams of NIH-funded researchers have enriched our understanding of adipose tissue. The first team discovered the genetic switch that triggers the development of brown fat [1], and the second figured out how the body can recruit white fat and transform it into brown [2].

Why would we want to change white fat into brown? White fat stores energy as large fat droplets, while brown fat has much smaller droplets and is specialized to burn them, yielding heat. Brown fat cells are packed with energy generating powerhouses called mitochondria that contain iron—which gives them their brown color. Infants are born with rich stores of brown fat (about 5% of total body mass) on the upper spine and shoulders to keep them warm. It used to be thought that brown fat disappeared by adulthood—but it turns out we harbor small reserves in our shoulders and neck. Continue reading

Protein Machines at Work

This video shows a molecular view of the reactions that take place inside the pyruvate dehydrogenase complex, a protein machine found in the cell’s powerhouse, the mitochondria. 3D imaging of this machine by high-resolution electron microscopy reveals how the different components essential for the reaction are organized. Watch the flexible arms move inside the protein machine as pyruvate (an essential compound made from glucose) gets converted into acetyl-CoA (a precursor to the cell’s energy supply).

Credit: Jacqueline Milne and Sriram Subramaniam, Laboratory of Cell Biology, National Cancer Institute; Donald Bliss, National Library of Medicine; NIH

References:

Molecular architecture and mechanism of an icosahedral pyruvate dehydrogenase complex: a multifunctional catalytic machine. Milne JL, Shi D, Rosenthal PB, Sunshine JS, Domingo GJ, Wu X, Brooks BR, Perham RN, Henderson R, Subramaniam S. EMBO J. 2002 Nov 1;21(21):5587-98.

Molecular structure of a 9-MDa icosahedral pyruvate dehydrogenase subcomplex containing the E2 and E3 enzymes using cryoelectron microscopy. Milne JL, Wu X, Borgnia MJ, Lengyel JS, Brooks BR, Shi D, Perham RN, Subramaniam S. J Biol Chem. 2006 Feb 17;281(7):4364-70.

Extended polypeptide linkers establish the spatial architecture of a pyruvate dehydrogenase multienzyme complex. Lengyel JS, Stott KM, Wu X, Brooks BR, Balbo A, Schuck P, Perham RN, Subramaniam S, Milne JL. Structure. 2008 Jan;16(1):93-103

 

Science Becomes Art

Illustration of a human bone cancer cell

Credit: Dylan T. Burnette, NICHD, NIH

This stunning picture of a human bone cancer cell won artistic accolades: 3rd place in the Nikon Small World Competition. DNA, the blueprint of life, is actually blue in this photo. The yellow squiggles are little powerhouses called mitochondria that generate ATP ‘fuel’ for the cell. The purple wisps are filaments of actin, which help the cell move, keep its shape, and traffic chemicals from one part of the cell to another.

Happy New Year everyone.