Biomedical subjects

Dieter Muller

Publications and source records attributed to Dieter Muller.

3 recordsLinked to original sources

PubMed2006

Adult-to-adult right lobe living donor liver transplantation: comparison of endoscopic retrograde cholangiography with standard T2-weighted magnetic resonance cholangiography for evaluation of donor biliary anatomy.

AIM: To compare the value of endoscopic retrograde cholangiography (ERC) and standard T2-weighted magnetic resonance cholangiography (MRC) in the evaluation process as adult-to-adult right lobe living donor liver transplantation (LDLTx) demands a successful outcome, and exact knowledge of the biliary tree is implicated to avoid biliary complications, postoperatively. METHODS: After starting the LDLTx program, 18 liver transplant candidates were selected for LDLTx by a stepwise evaluation process. ERC and standard T2-weighted MRC were performed to evaluate the biliary system of the donor liver. The anatomical findings of ERC and MRC mapping were compared using the Ohkubo classification. RESULTS: ERC allowed mapping of the whole biliary system in 15/15 (100%) cases, including 14/15 (93.3%) with biliary variants while routine MRC was only accurate in 2/13 (15.4%) cases. MRC was limited in depicting the biliary system proximal of the hepatic bifurcation. Postoperative biliary complications occurred in 2 donors and 8 recipients. Biliary complications were associated with Ohkubo type C, E or G in 6/8 recipients, and 2/3 recipients with biliary leak received a graft with multiple (>=2) bile ducts. CONCLUSION: Pretransplant ERC is safe and superior over standard MRC for detection of biliary variations that occur with a high frequency. However, precise knowledge of biliary variants did not reduce the incidence of postoperative biliary complications.

Adult↗

PubMed2005

Retinal perfusion response to a slow multifocal M-sequence flicker stimulation.

PURPOSE: To assess, if a slow multifocal stimulus (mfS) can provoke a perfusion response that can be measured with the Retinal Vessel Analyzer (RVA). METHODS: Seventeen eyes were examined. Pupils were dilated. A 120-second baseline recording was obtained with the RVA. The subject then turned to view an mfS for 56 s. The mfS consisted of 103 hexagons flickering according to an m-sequence with a stimulus base interval of 53.3 ms (L(max) = 100 cd/m(2), L(min) < 1 cd/m(2)). Immediately thereafter, the subject turned to the RVA, where measurements were resumed as soon as the same retinal vessel was targeted and continued for 104 s. Stimulation and recording was repeated twice. The diameter of a retinal vein and artery was measured for a length of at least 1 mm. The maximum vessel response was obtained by linear interpolation of the measured response within the 20 s following mfS. RESULTS: On average, veins dilated by 6.8% and arteries by 7% following mfS (p > 0.005). Such a dilatation could be observed in 9 veins and 7 arteries. Three venous and 2 arterial measurements did not show a dilatation following mfS. However, 13 of 34 measurements could not be analyzed due to signal problems or because the time from the end of mfS and the uptake of measurement exceeded 20 s. CONCLUSION: This slow multifocal ERG stimulus results in a dilatation of arteries and veins that can be measured with the RVA. Coupling an mfS to the RVA has the potential to topographically map changes in retinal perfusion in relation to the respective retinal area stimulated. When implementing the mfS into the RVA setup in order not to lose time due to the refixation in the RVA following mfS, one is required to take the transient nature of this perfusion change into consideration.

Adult↗

PubMed2003

Gene expression in two hepatic cell lines, cultured primary hepatocytes, and liver slices compared to the in vivo liver gene expression in rats: possible implications for toxicogenomics use of in vitro systems.

Microarray technology allows the simultaneous analysis of mRNA expression levels of thousands of genes. In the field of toxicogenomics, this technology could help to identify potentially unsafe compounds based on the changes in mRNA expression patterns they induce. Rodent in vivo and in vitro systems are currently the experimental models of choice for predictive toxicology, especially in early phases of development. This study characterizes several hepatic in vitro systems based on mRNA expression profiles, comparing them to gene expression in liver tissue. The in vitro systems investigated comprise two rat liver cell lines (BRL3A and NRL clone 9), primary hepatocytes in conventional monolayer or in sandwich culture, and liver slices. The results demonstrate that liver slices exhibit the strongest similarity to liver tissue regarding mRNA expression, whereas the two cell lines are quite different from the whole liver. We were able to identify genes with strong changes in expression levels in all or at least one of the in vitro systems relative to whole liver. In particular, for some cytochrome P450s the differences observed on the mRNA expression level were paralleled by protein expression and enzymatic activity. In addition, the effect of time in culture was assessed. We were able to show a profound effect of the duration of culture. Expression patterns change most rapidly soon after cell isolation and culture initiation and stabilize with time in culture. The findings are discussed with respect to the usefulness of the various hepatic in vitro systems for microarray-based toxicological testing of compounds.

Animals↗