Low-density Lipoprotein: From 2 Different Sources
One of a group of proteins that are combined with lipids in the plasma. Low density lipoproteins (LDLs) are involved in the transport of
cholesterol in the bloodstream. An excess of LDLs (see hyperlipidaemias) is associated with atherosclerosis. (See also high density lipoprotein.)
(LDL) a *lipoprotein that is the principal form in which *cholesterol is transported in the bloodstream: it accounts for approximately 70% of the circulating cholesterol in an individual. LDL is derived from *very low-density lipoprotein and is eventually cleared from the circulation by the liver. LDL may be deposited within the lining of arteries, thus causing *atheroma; the higher the circulating concentration of LDL, the higher the likelihood of atheroma developing (see also hypercholesterolaemia). *Statins are effective in lowering circulating LDL levels.
One of a group of proteins that transport lipids in the blood. High levels of high density lipoprotein can help protect against atherosclerosis. (See also fats and oils; low density lipoprotein.)... high density lipoprotein
The ratio of the number of new cases of the disease and the amount of population-time of follow-up (e.g. person-year) of the disease-free population.... average incidence density
Compounds containing lipids and proteins (see LIPID; PROTEIN). Most lipids in blood PLASMA are present in this form and are characterised according to their densities: very low (VLDL), intermediate (IDL), low (LD), high (HDL) and very high (VHDL). Concentrations of lipoproteins are key factors in assessing the risk of cardiovascular disease (see HEART, DISEASES OF).... lipoproteins
The number of malaria parasites in a specified volume of blood.... parasite density
The number of a given vector species present. It may be expressed in relative terms (e.g., the biting density in relation to the human host) or in absolute numbers (e.g., the number present in a room, cattle-shed or artificial shelter).... vector density
The compactness of bone tissue in relation to its volume. A decrease in bone density is a normal part of aging. However, in some people, excessive loss of density (see osteoporosis) can lead to fractures. Less commonly, an increase in bone density (see osteosclerosis) occurs in certain disorders (see osteopetrosis; Paget’s disease). Bone density can be measured by a technique known as densitometry, which uses low-dose X-rays.... bone density
The “compactness” of a substance, defined as its mass per unit volume. In radiology, the term relates to the amount of radiation absorbed by the structure being X-rayed. Bone, which absorbs radiation well, appears white on X-ray film. A lung, which contains mostly air, absorbs little radiation and is dark on film. The same holds true in CT scanning and MRI. (See also specific gravity.)... density
an enzyme that catalyses the hydrolysis of triglycerides in *chylomicrons and *very low-density lipoproteins to free fatty acids, which are absorbed from the capillaries into local tissues. Deficiency of this enzyme results in severe *hypertriglyceridaemia.... lipoprotein lipase
see specific gravity.... relative density
(VLDL) a *lipoprotein that is the precursor of *low-density lipoprotein (LDL). Containing triglycerides and cholesterol, it is produced in the liver and circulates in the bloodstream, where its triglycerides are hydrolysed to free fatty acids by *lipoprotein lipase. The remaining lipoprotein becomes progressively denser and richer in cholesterol to form LDL.... very low-density lipoprotein
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