ABSTRACT
Cholesterol is required for chondrocyte differentiation and bone formation. Apolipoprotein A1 (apoA-1) plays a major role in lipoprotein clearance and cholesterol redistribution. We report here that apoA-1 is expressed during chondrocyte differentiation in vitro and in vivo. In differentiating chondrocytes, the expression of the liver X receptor (LXR) is modulated and its expression correlates to the expression of apoA-1. The expression of other LXR target genes related to cholesterol homeostasis such as ABCA1 cholesterol transporter and sterol regulatory element-binding protein 1 (SREBP1) is similarly regulated. Small molecule ligands activating either LXR or retinoid X receptor (RXR) lead to a dramatic increase in apoA-1 mRNA and protein expression in cultured chondrocytes. These ligands strongly induce ABCA1 cholesterol transporter expression and effectively mediate cholesterol efflux from hypertrophic chondrocytes. In addition, we report that, in the same cells, the ligands down modulate Serum Amyloid A expression induced by bacterial lipopolysaccharide. Our studies provide evidence that LXR/RXR mediate a fine regulation of cholesterol homeostasis in differentiating chondrocytes.
Subject(s)
Apolipoprotein A-I/chemistry , Cholesterol/metabolism , Chondrocytes/metabolism , Gene Expression Regulation , Retinoid X Receptors/physiology , Transcription Factors/physiology , Animals , Blotting, Western , CCAAT-Enhancer-Binding Proteins/metabolism , Cartilage/metabolism , Cell Adhesion , Cell Culture Techniques , Cell Differentiation , Chick Embryo , Chondrocytes/cytology , Collagen Type X/metabolism , Culture Media, Serum-Free/pharmacology , DNA-Binding Proteins/metabolism , Dimerization , Electrophoresis, Polyacrylamide Gel , Homeostasis , Immunoprecipitation , Ligands , Lipopolysaccharides/metabolism , Lipoproteins/chemistry , Liver X Receptors , Orphan Nuclear Receptors , Polymerase Chain Reaction , RNA/metabolism , RNA, Messenger/metabolism , Receptors, Cytoplasmic and Nuclear , Retinoid X Receptors/chemistry , Reverse Transcriptase Polymerase Chain Reaction , Serum Amyloid A Protein/biosynthesis , Sterol Regulatory Element Binding Protein 1 , Temperature , Time Factors , Transcription Factors/chemistry , Transcription Factors/metabolismABSTRACT
Altering the analytical channel for the determination of uric acid on a SMAC analyzer affords greater analytical specificity and sensitivity. The proposed alterations do not require any change of the analyzer soft-ware.
Subject(s)
Uric Acid/analysis , Autoanalysis/instrumentation , Autoanalysis/methods , Regression AnalysisABSTRACT
The precision and practicability of the Merckognost-Urea Test Strips was tested in plasma, haemolysate, capillary and venous blood. The diacetylmonoxim method using an AutoAnalyzer II was taken as the reference method. The possibility of varying haematocrit values influencing the whole blood findings was taken into consideration in the investigations.
Subject(s)
Urea/blood , Autoanalysis , Hematocrit , Humans , Reagent Strips , Spectrophotometry/methodsABSTRACT
A new AutoAnalyzer method is described for the determination of glucose in 20 mul of haemolysate, urine, or cerebrospinal fluid, using glucose dehydrogenase. Without loss of precision, accuracy, sensitivity, or linearity, 900 samples may be analyzed, using the same volume of reagents normally required for the manual analysis of 75 samples. A comparison with the hexokinase method yields a correlation of 0.9978. A haemolysing solution compatible with the reagents used is described.
Subject(s)
Glucose/analysis , Alcohol Oxidoreductases , Autoanalysis/methods , Hexokinase , Humans , Indicators and Reagents , Microchemistry , SolutionsABSTRACT
A continuous flow method is described for the determination of glucose in haemolysates and other materials with hexokinase/glucose-6-phosphate dehydrogenase as reagents. It is a micro-method (20 microliter) which can be used with the 2. generation auto-analyzer. The new method was compared with a hexokinase manual method.
