A Look Inside a Beating Heart Cell

Caption: Microtubules (blue) in a beating heart muscle cell, or cardiomyocyte. Credit: Lab of Ben Prosser, Ph.D., Perelman School of Medicine, University of Pennsylvania

You might expect that scientists already know everything there is to know about how a healthy heart beats. But researchers have only recently had the tools to observe some of the dynamic inner workings of heart cells as they beat. Now an NIH-funded team has captured video to show that a component of a heart muscle cell called microtubules—long thought to be very rigid—serve an unexpected role as molecular shock absorbers.

As described for the first time recently in the journal Science, the microtubules buckle under the force of each contraction of the muscle cell before springing back to their original length and form. The team also details a biochemical process that allows a cell to fine-tune the level of resistance that the microtubules provide. The findings have important implications for understanding not only the mechanics of a healthy beating heart, but how the abnormal stiffening of heart cells might play a role in various forms of cardiac disease.

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Snapshots of Life: Green Eggs and Heart Valves

three-day old chicken embryo

Credit: Jessica Ryvlin, Stephanie Lindsey, and Jonathan Butcher, Cornell University, Ithaca, NY

What might appear in this picture to be an exotic, green glow worm served up on a collard leaf actually comes from something we all know well: an egg. It’s a 3-day-old chicken embryo that’s been carefully removed from its shell, placed in a special nutrient-rich bath to keep it alive, and then photographed through a customized stereo microscope. In the middle of the image, just above the blood vessels branching upward, you can see the outline of a transparent, developing eye. Directly to the left is the embryonic heart, which at this early stage is just a looped tube not yet with valves or pumping chambers.

Developing chicks are one of the most user-friendly models for studying normal and abnormal heart development. Human and chick hearts have a lot in common structurally, with four chambers and four valves pumping two circulations of blood in parallel. Unlike mammalian embryos tucked away in the womb, researchers have free range to study the chick heart in or out of the egg as it develops from a simple looped tube to a four-chambered organ.

Jonathan Butcher and his NIH-supported research group at Cornell University, Ithaca, NY, snapped this photo, a winner in the Federation of American Societies for Experimental Biology’s 2015 BioArt competition, to monitor differences in blood flow through the developing chick heart. You can get a sense of these differences by the varying intensities of green fluorescence in the blood vessels. The Butcher lab is interested in understanding how the force of the blood flow triggers the switching on and off of genes responsible for making functional heart valves. Although the four valves aren’t yet visible in this image, they will soon elongate into flap-like structures that open and close to begin regulating the normal flow of blood through the heart.

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Cool Videos: Better Computation, Better Hope for Movement Disorders

Video for OpenSimAvatar. Pick your Sim. The entertainment world has done an amazing job developing software that generates animated characters with strikingly realistic movement. But scientists have taken this one step further to create models that can help kids with cerebral palsy walk better, delay the onset of osteoarthritis, and even answer a question in the minds of children of all ages: How exactly did T. rex run?

That’s what the researchers behind this video—an entrant in the NIH Common Fund’s recent video competition—have done. They’ve developed OpenSim: a free software tool that combines state-of-the-art musculoskeletal modeling and dynamic computer simulations to produce highly accurate representations of the underlying biomechanics of motion. OpenSim was designed at the NIH-supported center for physics-based Simulation of Biological Structures (Simbios) at Stanford University, Palo Alto, CA. And now, researchers around the world are using OpenSim to find more effective interventions for a variety of movement disorders.

Links:

NIH Common Fund Video Competition

OpenSim (Stanford University, Palo Alto, CA)

NIH Support: Common Fund; Eunice Kennedy Shriver National Institute of Child Health and Human Development; National Institute for General Medical Sciences