Dan Med Bull
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Normal function of the hepatic low-density lipoprotein (LDL) receptor is obligate for normal levels of plasma LDL cholesterol. The LDL receptor regulates the concentration of plasma LDL cholesterol by internalizing apolipoprotein B-100- and apolipoprotein E-containing lipoproteins by receptor-mediated endocytosis. Mutations in the gene encoding the LDL receptor protein give rise to one of the most common classical autosomal dominant inherited disorders in man, familial hypercholesterolemia (FH). ⋯ Familial defective apolipoprotein B (FDB) caused by the R3500Q apolipoprotein B gene mutation may mimic FH but the clinical course, however, is often milder than that seen in patients with LDL receptor gene mutations. A newly discovered third major locus at chromosome 1 may also be of future diagnostic importance although the exact gene remains to be identified. The overall molecular genetic knowledge obtained about FH in Denmark forms the basis for the implementation and use of molecular genetic diagnostics of FH in daily clinical practice.
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Iron is essential for virtually all types of cells and organisms. The significance of the iron for brain function is reflected by the presence of receptors for transferrin on brain capillary endothelial cells. The transport of iron into the brain from the circulation is regulated so that the extraction of iron by brain capillary endothelial cells is low in iron-replete conditions and the reverse when the iron need of the brain is high as in conditions with iron deficiency and during development of the brain. ⋯ After about 20 days of age, iron transport into the brain decreased rapidly, and transferrin receptors appeared on neurons. Iron and transferrin injected into the ventricular system of the developing brain were much more widely distributed in the brain parenchyma than in the adult brain. This high accumulation of substances injected into the ventricles in young animals is probably due to the lower rate of production and turnover of CSF, which will increase the time available for diffusion of proteins into the brain parenchyma, thus giving neurons of the developing brain the opportunity to take up transferrin originating from the CSF.