Biomedical subjects

Dirk Heimbach

Publications and source records attributed to Dirk Heimbach.

4 recordsLinked to original sources

PubMed2006

Selective indole-based ECE inhibitors: synthesis and pharmacological evaluation.

Inhibition of the metalloprotease ECE-1 may be beneficial for the treatment of coronary heart disease, cancer, renal failure, and urological disorders. A novel class of indole-based ECE inhibitors was identified by high throughput screening. Optimization of the original screening lead structure 6 led to highly potent inhibitors such as 11, which bears a bisaryl amide moiety linked to the indole C2 position through an amide group. Docking of 11 into a model structure of ECE revealed a unique binding mode in which the Zn center of the enzyme is not directly addressed by the inhibitor, but key interactions are suggested for the central amide group. Testing of the lead compound 6 in hypertensive Dahl S rats resulted in a decrease in blood pressure after an initial period in which the blood pressure remained unchanged, most probably the result of ET-1 already present. Indole derivative 6 also displays a cardio-protective effect in a mouse model of acute myocardial infarction after oral administration. The more potent chloropyridine derivative 9 antagonizes big-ET-1-induced increase in blood pressure in rats at intravenous administration of 3 mg kg-1. All ECE inhibitors of the indole class showed high selectivity for ECE over related metalloproteases such as NEP and ACE. Therefore, these compounds might have further potential as drugs for the treatment of coronary heart diseases.

Aspartic Acid Endopeptidases↗

PubMed2005

Novel, selective indole-based ECE inhibitors: lead optimization via solid-phase and classical synthesis.

A novel class of indole-based endothelin-converting enzyme (ECE) inhibitors was identified by high throughput screening. We report systematic optimization of this compound class by means of classical and solid-phase chemistry. Optimized compounds with a bisarylamide side chain at the 2-position of the indole skeleton exhibit low-nanomolar activity on ECE.

Aspartic Acid Endopeptidases↗

PubMed2003

Evaluation of synchronous twin pulse technique for shock wave lithotripsy: determination of optimal parameters for in vitro stone fragmentation.

PURPOSE: The Twinheads extracorporeal shock wave lithotriptor (THSWL) is composed of 2 identical shock wave generators and reflectors. One reflector is under the table and the other is over the table with a variable angle between the axes of the 2 reflectors. The 2 reflectors share a common second focal point, making it possible to deliver an almost synchronous twin pulse to the targeted stone. We studied the optimal parameters for in vitro stone fragmentation. MATERIALS AND METHODS: Two types of 1 cm artificial stones were used, namely Bon(n)-stones of 3 compositions (75% calcium oxalate monohydrate [COM] plus 25% uric acid, struvite and cystine) and plaster of Paris. The parameters tested were shock wave number (100, 500 and 1,000), shock wave power (8, 11 and 14 kV) and angle between the reflector axes (67, 90 and 105 degrees). After the optimal parameters were determined we studied the disintegrative efficacy of THSWL for 3 types of human urinary calculi, including COM, calcium hydrogen phosphate (brushite) and cystine. Each stone received 1,000 twin shock waves at 14 kV with an angle of 90 degrees between the reflectors. All experiments were done using a rate of 60 twin shock waves per minute. Following lithotripsy stone fragments were processed and sized. The ratio of the weight of fragments greater than 2 mm-to-total weight of all fragments was calculated. RESULTS: Optimal stone fragmentation results for THSWL were obtained with the maximum number of shock waves (1,000) and full power (14 kV). There was no significant statistical difference in fragment size or the ratio of fragments greater than 2 mm with the use of different angles except for cystine and plaster of Paris calculi, for which the right angle was most effective. At application of the optimal parameters to human stones THSWL produced small fragment size for COM and cystine stones, while brushite stones were not fragmented to the same extent. CONCLUSIONS: The efficacy of synchronous twin pulse technology improves as the number of shock waves and power increase. A 90-degree angle between the shock wave reflectors is advantageous for certain stones (that is cystine and plaster of Paris) but it is not a factor for other stone compositions. THSWL has satisfactory disintegrative efficacy for human stones, especially COM and cysteine calculi.

Calcium Oxalate↗

PubMed2002

Comparison of blood group versus HLA-dependent transplantation and its influence on donor kidney survival.

BACKGROUND: The advantages of organ allocation based on human leukocyte antigen (HLA) typing are controversial. This evaluation compares the results of HLA-dependent and non-HLA-dependent allocation in the transplantation of donor kidneys. METHODS: Seventy-seven donor kidney pairs explanted locally between 1984 and 1994 were examined. One half of each pair was transplanted locally in Bonn on the basis of criteria including blood group, waiting time and currently negative cross-match. The other half of these pairs was allocated in accordance with the Eurotransplant (ET) criteria. RESULTS: Cold ischaemia time was an average of 14.02 h in Bonn vs. 24.18 h in the ET group (P<0.0001). The number of HLA mismatches was calculated and, for example, for locus A it was 1.13 in Bonn vs. 0.73 in the ET group (P=0.0003). One-year graft survival for the locally transplanted kidneys was 92.2% and, for the ET kidneys, 90.9%. Five-year survival was 79.5% vs. 81.7%, respectively. Patient survival after 1 year was 100% vs. 97.4%, and after 5 years, 93.4% vs. 93.1%. CONCLUSION: The results show that it is possible to provide patients with a locally allocated kidney graft that enables good function after a short waiting period. This procedure avoids long cold ischaemia time and long waiting periods.

Adult↗