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Science over Sleep

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Michaela. biomedical science. chemistry. statistics. research. no sleep. my life.
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Muscle Power

Muscles are the powerhouses of the human body. To take just a single step, around 200 of your muscles will be put to work. The disease FSHD targets these powerhouses, weakening them to the point that a fifth of patients end up wheelchair bound. The disease is caused by the inappropriate presence of the protein DUX4. Researchers investigated what DUX4 is up to in developing muscle cells from humans (pictured) and mice. Normally these cells turn into mature muscle cells bearing the muscle proteins myogenin (green), desmin (red) and myosin heavy chain (grey). Increasing the amount of DUX4 in these developing cells increased the levels of an enzyme called Ret. Ret stopped the cells developing into mature muscle. Adding a drug to block the activity of Ret allowed these cells to mature normally. This drug may therefore someday be useful in treating FSHD.

Written by Lux Fatimathas

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Ink drops atop a layer of glycerol spread in a beautiful fan of blue and white. The ink’s motion is the result of two processes: molecular diffusion and the Marangoni effect. Molecular diffusion is the mixing that occurs due to the random background motion of molecules. Since glycerol is a very viscous liquid, the ink is quite slow to spread in this manner. 

The second factor, the Marangoni effect, is driven by differences in surface tension. The ink and glycerol have different surface tensions, and the exact values depend on concentration. Notice how the ink drops spread fastest from areas where the ink is densely concentrated. This tells us that the ink’s surface tension is lower than the glycerol’s. As a result, the glycerol’s higher surface tension tends to pull ink toward it. As the ink spreads and its concentration decreases relative to the glycerol, the ink-glycerol mixture’s surface tension increases. Since the difference between the surface tension of the mixture and the pure glycerol is not as large, the Marangoni force is reduced and the spreading slows. (Image credit: C. Kalelkar, source)

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