The impact of cardiopulmonary bypass on selenium status, thyroid function, and oxidative defense in children

Selenium has important functions for oxidative defense and thyroid hormone metabolism. Selenium-dependent enzymes include 5'-iodothyronine deiodinase and glutathione peroxidase (GPX). The objective of this study was to investigate the relationship between plasma selenium, GPX activity, and thyroid hormone status in pediatric cardiac surgical patients. Plasma concentrations of selenium, free triiodothyronine (fT3), free thyroxin (fT4), and c-reactive protein as well as plasma activity of GPX were prospectively evaluated at anesthetic induction and 48 hours postoperatively in 59 children requiring cardiopulmonary bypass (CPB). GPX was measured at additional time points at 6, 12, and 24 hours postoperatively. There was a significant reduction in the plasma selenium concentration after cardiopulmonary bypass with obtained median measurements of 0.61 micromol/L (induction) and 0.51 micromol/L (48 hours postoperatively). The fT3/fT4 ratio decreased significantly from 0.28 at anesthetic induction to 0.22 at 48 hours postoperatively. There were no significant changes of GPX activity. 48 hours fT3 concentration, fT3/fT4 ratio, and selenium concentration were significantly negatively correlated with the time spent in intensive care. The concentration of plasma selenium in children undergoing cardiopulmonary bypass significantly decreases, resulting in diminished deiodinase activity, and a subsequent reduction in the conversion of T4 to T3.

Refined mapping of the epilepsy susceptibility locus EJM1 on chromosome 6

Juvenile myoclonic epilepsy (JME) is a genetically determined common subtype of idiopathic generalized epilepsy. Linkage to the HLA complex on chromosome 6p21.3 and an allelic association with HLA-DR13 and -DQB1 alleles suggest that a susceptibility locus for JME, designated as "EJM1," is located within or near the HLA region. However, further studies revealed controversial results, and genetic heterogeneity has been suspected. The present study was designed to evaluate the validity of the association and linkage findings and to refine the map position of EJM1. Our association analysis showed no significant difference of the frequency of HLA-DR13 carriers in 62 German JME patients compared with that in 77 German controls (X2 = 0.98, df = 1, p = 0.161, one-tailed). Multipoint linkage analysis with use of microsatellite markers from the chromosomal region 6p25-q13 in 29 German families of JME patients provided significant evidence that an epilepsy locus (EJM1) close to the HLA locus confers susceptibility to "idiopathic" generalized seizures (Zmax = 3.27 at theta max = 0.033 centromeric to the HLA-DQ locus), assuming an autosomal dominant mode of inheritance with 70% penetrance. Haplotype analyses revealed key recombinations in five families, which locate EJM1 to the centromeric side of the HLA-DQ locus. This study confirms a causative role of EJM1 in the pathogenesis of idiopathic generalized seizures in the majority of German families of JME patients and refines a candidate region of 10.1 cM in the chromosomal region 6p21 between the flanking loci HLA-DQ and D6S1019. A possible explanation for the current controversial results in families of different populations might be ethnic variation of interfering polygenic effects that could be permissive for heterogeneous susceptibility alleles.