It's not all biochemistry in the body: scientists are discovering that mechanical forces can have important effects at the cellular level: "Atherosclerotic narrowing and hardening of coronary arteries typically appear first at vessel branches, and a [study] reports that the type of mechanical stretching found at those branches activates a cellular protein known to damage cells. The report is the first to link mechanical forces with structural and biochemical changes in blood vessel cells that could explain why atherosclerotic lesions form preferentially at branches of coronary arteries. ... The cellular protein in question is called JNK, which is short for c-jun N-terminal kinase. The protein is a key barometer of outside stresses on a variety of cell types. Researchers are examining the role of JNK in many diseases because it regulates the expression of genes involved in programmed cell death, tumor genesis, and other stress responses."