Removal of 10-hydroxycarbazepine by plasmapheresis.

Removal of the oxcarbazepine metabolite 10-hydroxycarbazepine (MHD) by plasmapheresis was evaluated during a series of six plasmaphereses of a 13-year-old boy with Rasmussen encephalitis. Plasmapheresis was performed after steady-state concentrations of MHD had been achieved with a dose of 2550 mg oxcarbazepine daily. The mean amount of MHD removed per plasmapheresis was 78.9 mg (SD: 6.0 mg), representing 3% to 4% of the daily oxcarbazepine dose and approximately 5% to 6% of body stores of MHD. The mean steady-state trough MHD concentration was 33.3 mg/L (SD: 1.8 mg/L), and this was remarkably stable during the entire plasmapheresis period. The serum concentration of MHD was only mildly reduced by the procedure. The areas under the concentration curve of MHD on the first and sixth day of plasmapheresis were 99% and 94%, respectively, of the pre-plasmapheresis values. The results are in agreement with studies on other anticonvulsant medications (carbamazepine, valproic acid, phenobarbital, and phenytoin), indicating that minor fractions (2% to 10%) of body stores of these drugs are depleted during plasmapheresis. The authors conclude that it is unnecessary to adjust the oxcarbazepine dosage when performing single-volume plasma exchanges or even multiple exchanges during an extended period. It is further proposed that plasmapheresis is unlikely to be of therapeutic benefit in the treatment of an oxcarbazepine overdose.

DNA deletions in the low density lipoprotein (LDL) receptor gene in Danish families with familial hypercholesterolemia.

DNA samples from 25 unrelated Danish patients with familial hypercholesterolemia (FH) were screened by Southern blot hybridization to detect gross alterations in the low density lipoprotein (LDL) receptor gene. Three FH-patients were found to have a deletion. Two of these delete part of the cysteine rich domain, which comprises the ligand binding region of the LDL-receptor. The third deletion encompasses coding regions for the cytoplasmic part of the receptor. As two of these deletions could be equivalent to previously described LDL-receptor gene alterations, these data seem to support a notion of recombination hot spots which involve Alu-sequences.

Detection of point mutations in amplified single copy genes by biotin-labelled oligonucleotides: diagnosis of variants of alpha-1-antitrypsin.

Specific analysis for point mutations in genomic DNA has until recently been a difficult and time-consuming task, using large amounts of unstable, hazardous and expensive 32P. By enzymatically amplifying the mutation-bearing sequence of the DNA the sensitivity of the analysis is increased several 100-fold, making the detection possible with stable, non-radioactive and inexpensive biotinylated oligonucleotides. We have applied this method (polymerase chain reaction (PCR] to the detection of the Z-mutation in the alpha-1-antitrypsin gene. After amplification, dot-blots of amplified DNA were subjected to hybridization with allele specific biotinylated oligonucleotide probes and washed at temperatures giving allele specificity. The bound biotin was visualized with avidin conjugated alkaline phosphatase using 5-bromo-4-chloro-3-indolylphosphate and nitro blue tetrazolium as colour reagents. The detection can be performed on less than 1 microgram genomic DNA, and is therefore applicable on small amounts of blood, fibroblasts and chorionic villus biopsies.

Enzymatic assay for methotrexate in erythrocytes.

Methotrexate (MTX) accumulates in erythrocytes in MTX-treated patients. We present a modified enzymatic assay measuring MTX concentrations between 10 and 60 nmol/l in erythrocytes, adapted for a centrifugal analyser (Cobas Bio). About 40 patient's samples could be analysed within 1 h. The detection limit was 3 nmol/l. Within run and between-run precision was 7.4% and 13.5% for control 10 nmol/l and 1.2% and 3.2% for control 50 nmol/l. Recovery was 85-115% of MTX added to haemolysed erythrocytes. We found the method useful for pharmacokinetic studies of MTX in erythrocytes in MTX-treated patients.

Creatine kinase in the serum of patients with acute infections of the central nervous system.

Serum creatine kinase was assessed in 94 consecutive patients without convulsions admitted to hospital due to suspicion of infection of the central nervous system. No reliable discrimination between patients with aseptic and those with bacterial meningitis was obtained. Patients with bacterial meningitis and brain oedema, as well as patients with encephalitis, had significantly higher values (P less than 0.01) than patients with meningism, aseptic meningitis and bacterial meningitis without cerebral oedema. Very high values, above 2500 U/1, were encountered in only the most severe cases of bacterial meningitis. The highest serum CK value found in patients with encephalitis was 725 U/l. Reference values for control patients with meningism were 16-269 U/1. In a subset of 9 patients creatine kinase isoenzyme analysis was performed. In all cases only muscle type (MM) isoenzyme was found.

Creatine kinase and creatine kinase subunit-B in coronary sinus blood in pacing-induced angina pectoris.

In nine out of 10 patients with angiographic documented coronary artery disease, pacing-induced angina pectoris provoked myocardial production of lactate, whereas no significant release of either creatine kinase or creatine kinase subunit-B to coronary sinus and peripheral venous blood could be detected.