Word: role
(lookup in dictionary)
(lookup stats)
Dates: during 1980-1989
Sort By: most recent first
(reverse)
...LDLs are called "bad" cholesterol because an excess of cholesterol carried by them can lead to the buildup of harmful deposits in the arteries. The other cholesterol carriers, known as HDLs (for high-density lipoproteins), are considered "good" because, far from being killers, they may actually play a vital role in preventing heart disease. They seem to act like biological vacuum cleaners, sucking up excess cholesterol in the bloodstream. It is because the 50-odd Cincinnati families possess unusually high levels of HDL that they are believed to have such a resilient blood chemistry -- and such long lives...
...good and bad labels, however, can be simplistic and misleading. Pure cholesterol is a life-sustaining substance that plays an essential role in building cell membranes and sex hormones as well as aiding digestion. Problems begin when the body is saddled with an excess of LDL, which normally carries some 60% to 80% of the blood's total cholesterol. This excess can trigger the formation of plaque on the interior walls of the coronary arteries, a condition called atherosclerosis. In time, this hardened, sludge-filled growth narrows the artery and allows a clot to form, severely blocking the blood flow...
Clinical studies suggest that cholesterol's role in this lethal process is much more complicated than previously imagined. Some scientists now believe that in certain cases of atherosclerosis, too little HDL may be as important a factor as too much LDL. On the other hand, the higher the level of HDL, the more it may aid in counteracting the effects of the bad cholesterol. This is the view of Dr. William Castelli, medical director of the Framingham Heart Study, a major research project that for the past 40 years has been following the cardiac history of residents of Framingham, Mass...
Just how HDL plays its apparently vital role in ridding the body of excess cholesterol is not entirely clear. The substance is, after all, only one element in an alphabet soup of particles that make up the so-called lipid transport system, which moves cholesterol through the bloodstream. Though individual cells can make their own cholesterol, much of their supply comes from the bloodstream, arriving from the liver aboard macromolecular ferryboats, known as very-low-density lipoproteins, or VLDLs. These carrier particles are loaded in the liver with cholesterol and dietary fats known as triglycerides, which are used by cells...
...bloodstream; the VLDL then metamorphoses into an LDL, which is picked up by an LDL receptor in the liver. Others think HDL may in fact be a passive player -- a sort of biological signal light that indicates how efficiently excess cholesterol is being removed, without necessarily taking any direct role...