Browsing by Author "Becker, C. M."

Single nucleotide polymorphisms (SNPs) may contribute to the malignant process and may show clinicopathological importance as prognostic markers. The multidrug resistance gene MDR1 encodes a membrane transporter which confers cytostatic drug resistance in tumors and protects normal tissues from xenobiotics. We analyzed the C3435T SNP in the MDR1 gene which is associated with altered cellular drug uptake in matched tumor and normal tissues of 45 patients suffering from colorectal carcinoma. We have developed a highly sensitive matrix-assisted laser desorption ionization time-of-flight mass spectrometty (MALDI-TOF-MS) method to survey the C3435T polymorphism in PCR-amplified fragments of the MDR1 gene. Thirteen patients were homozygous for C/C (29 %), 15 were heterozygous (33%) and 17 were homozygous for TIT (38%). None of the tumor samples showed an altered SNP compared to their matched normal tissue samples. As analyzed by the Kruskall-Wallis test, none of the clinicopathological parameters was significantly associated with homo- or heterozygosity. The combination of PCR, allele-specific primer extension reactions and MALDI-TOF-MS offers a promising alternative method for genotyping the MDR1 gene especially for heterozygous situations. The inherent advantages of MALDI-TOF-MS based genotyping include its high molecular resolution, high signal-to-noise-ratios and reproducibility, combined with an excellent sensitivity. As none of the tumor samples showed state compared to their matched normal tissue samples, the genotypic frequency of this polymorphism seems not to be altered during colorectal tumorigenesis.

Since glycinergic inhibition is important for respiratory rhythm generation in mature mammals, we tested the hypothesis that the loss of glycine receptors during postnatal development (P17-P23) of homozygous mutant oscillator mice (spd(ot)/spd(ot)) may result in serious impairment of respiratory rhythm. We measured breathing in a plethysmographic recording chamber on conscious oscillator mice and used an in situ perfused brainstem preparation to record phrenic nerve activity, as well as membrane properties of respiratory neurones. The deletion of glycinergic inhibition did not result in failure of respiratory rhythm: homozygous mutant oscillator mice continue to generate a disturbed respiratory rhythm until death. Postsynaptic activity and membrane potential trajectories of respiratory neurones revealed a persistence of GABAergic inhibition and changes in respiratory rhythm and pattern generation. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.