It has recently been suggested that a substitution of glutamlne for arginlne at residue 3500 of apolipoprotein (apo) B-100 causes familial defective apo B-100 (FDB), an autosomal, dominantly Inherited disorder, which leads to Increased serum cholesterol levels. From a sample of 243 patients from Munich with type Ma hyperllpoprotelnemia (HL), we have Identified eight individuals with the apo B-100 arglnlne ( j 600) -»glutamine mutation. In a group of 57 subjects with defective low density llpoproteln receptor (LOLR), no mutant apo B alleles were detected. The frequency of FDB In patients with type Ha HL was estimated to be 3%. In the kindreds of three of the probands, 10 additional carriers of the apo B mutation were Identified. Clinical and biochemical data reveal a striking similarity between patients with FDB and those with a defect in the LDLR gene. Our data support previous findings that FDB Is a serious disorder causing premature atherosclerosis.
Nine healthy men and a patient with myoadenylate deaminase deficiency were exercised on a bicycle ergometer (30 minutes, 125 Watts) with and without oral ribose administration at a dose of 2 g every 5 minutes of exercise. Plasma or serum levels of glucose, free fatty acids, lactate, ammonia and hypoxanthine and the urinary hypoxanthine excretion were determined. After 30 minutes of exercise without ribose intake the healthy subjects showed significant increases in plasma lactate (p less than 0.05), ammonia (p less than 0.01) and hypoxanthine (p less than 0.05) concentrations and a decrease in serum glucose concentration (p less than 0.05). When ribose was administered, the plasma lactate concentration increased significantly higher (p less than 0.05) and the increase in plasma hypoxanthine concentration was no longer significant. The patient showed the same pattern of changes in serum or plasma concentrations with exercise with the exception of hypoxanthine in plasma which increased higher when ribose was administered.
Leber's hereditary optic neuropathy (LHON) is characterized by acute or subacute bilateral (usually permanent) loss of central vision, caused by neuroretinal degeneration. The maternal inheritance is explained by the mitochondrial origin of the disease. Recently, a single mitochondrial DNA (mtDNA) mutation, a G to A substitution at position 11778 that converts a highly conserved arginine to histidine, has been associated with LHON. The mutation eliminates an SfaNI restriction enzyme recognition site and thus provides a method for detection of the mutation by amplification, enzyme digestion and agarose gel electropheresis of polymerase chain reaction (PCR) products. Leukocyte mtDNA from 7 German families with LHON, diagnosed by clinical criteria, was tested for the presence of the G to A mutation at bp 11778. The mtDNa mutation, detected as a loss of the SfaNI site, was seen in one family. The G to A mtDNA mutation is the only known gene alteration associated with LHON so far. It has been identified in patients of different ethnic origin and recent reports strongly support the hypothesis that it represents the most frequent cause of LHON. Identification of the mtDNA replacement mutation using PCR and restriction enzyme digestion requires only a small amount of blood and can be performed rapidly. This method is thus a useful tool in the diagnosis of LHON.
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