Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0020473 (hyperlipidemia)
 15,891 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Animal cholesterol synthesis shows a marked diurnal variation, a phenomenon, at the moment, not known to occur in man. Since cholesterol precursors in serum reflect overall cholesterol synthesis in many conditions, a 24-hr profile of squalene and methyl sterols was studied in plasma lipoproteins in order to demonstrate whether these cholesterol precursors could exhibit a diurnal cycling in healthy human subjects. During the 24-hr period, lipoproteins of density < 1.006 g/ml transported 30-50% of the plasma squalene. Free methyl sterols were found mainly in low density lipoproteins (LDL) and esterified methyl sterols in LDL and high density lipoproteins (HDL). Postprandial hyperlipidemia at noon was associated with an inconsistent increase of the squalene and free methyl sterol concentrations in the lipoproteins of density < 1.006 g/ml. In terms of micro g per mg of cholesterol, the precursor contents were, however, low in each lipoprotein during the daytime. During the night and early morning, the values were several times higher. Thus the peak plasma squalene and methyl sterol contents occurred at midnight and 4 am. The highest variation was found for squalene in the density class < 1.006 g/ml and for lanosterol and diunsaturated dimethyl sterol in LDL and HDL. For different methyl sterols, the mean diurnal variation was 3.5- to 6.9-fold in LDL, 2.0- to 4.5-fold in HDL, and 2.6- to 3.6-fold in the density class < 1.006 g/ml. The respective values for squalene were 2.2, 1.4, and 2.9. Esterified methyl sterols varied slightly in the density class < 1.006 g/ml only, and the percentage esterification exhibited a diurnal fluctuation that was the reciprocal of that of free methyl sterol levels. The rapid and marked diurnal fluctuation of squalene and free methyl sterols in plasma lipoproteins suggests that these precursors are metabolized on and off lipoproteins. The variation is most likely caused by changes in cholesterol synthesis, inferring that circadian rhythm also regulates human cholesterol production.-Miettinen, T. A. Diurnal variation of cholesterol precursors squalene and methyl sterols in human plasma lipoproteins.
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PMID:Diurnal variation of cholesterol precursors squalene and methyl sterols in human plasma lipoproteins. 720 May 4

The immunoassays methods need avoiding interferences that can influence result interpretation. Main sources of interference arise from either patient status, preparation and physiology or laboratory process and procedures. The aim of this non-systematic critical review is to highlight the preanalytical interferences on laboratory immunoassays. Blood hormone profile changes according with age and depending on sex: these are important variables, mainly in newborn, during both sexual maturation and childbearing. Gonadotropins FSH and LH show a sharp increase with age in females, whereas in males LH appears rather stable. With age both males and females show progressive decay of the hormone profile. Stress causes variations, as it influences GH, prolactin, Cortisol and the total/free ratio of thyroid hormone. Diurnal variations, day of cycle, influence by estrogens on thyroid hormone are relevant for result variability. Paraproteins and autoantibodies can interfere in some assays particularly drug, vitamin D and thyroid hormone. As regards the variables due to sample matrix, and to evacuated tubes components, some additives and anticoagulants have been reported to influence specific assays, e.g. thyroid hormone. Hemolysis, lipemia and bilirubin cause interferences on specific techniques/tests, e.g. ferritin, TSH, Vitamin B12, progesterone and folic acid. Nicotine and cocaine addictions interfere with some hormones. Thus, laboratory professionals should be aware of preanalytical problems particularly important when dealing with the immunoassays, by taking appropriate actions to avoid any relevant interferences.
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PMID:Causes of Preanalytical Interferences on Laboratory Immunoassays - A Critical Review. 3225 91