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At least 235 records · Page 13Linked to original sources
PubMed1999

Practical Synthesis of BILA 2157 BS, a Potent and Orally Active Renin Inhibitor: Use of an Enzyme-Catalyzed Hydrolysis for the Preparation of Homochiral Succinic Acid Derivatives.

We have developed a highly convergent and stereoselective synthesis of BILA 2157 BS, a potent and orally active renin inhibitor. The synthesis proceeds in 15 distinct chemical steps (with several integrated, multistep operations) from aminodiol 4. The key step in the synthesis involves the use of an enantiospecific, enzyme-catalyzed hydrolysis of a substituted succinate diester to provide a homochiral succinic acid derivative in 98% enantiomeric excess (>/=2.5 kg scale). Recycling of the unwanted enantiomer is accomplished through base-catalyzed racemization, leading to an efficient deracemization of the starting racemic diester. The entire sequence proceeds without chromatographic purifications and delivers the product with >97% homogeneity. In addition, compared to the previously reported syntheses of BILA 2157 BS, this approach avoids the use of expensive chiral auxiliaries and cryogenics and, thus, should be amenable to the preparation of large quantities of this peptidomimetic inhibitor.

Journal Article↗
PubMed1998

99mTechnetium-dimercapto-succinic acid renal scan in the evaluation of potential long-term renal parenchymal damage associated with extracorporeal shock wave lithotripsy in children.

PURPOSE: Extracorporeal shock wave lithotripsy (ESWL) has been reported as efficient and safe in children. Because of reports of renal parenchymal damage in adults, this study was designed to assess the effects of ESWL in pediatric kidneys evaluated before and after treatment with (99m)technetium dimercapto-succinic acid (DMSA) renal scan. MATERIALS AND METHODS: A total of 15 children, 9 months to 15 years old (mean age 6.5 years), underwent ESWL treatment for urolithiasis. Evaluation imaging included plain abdominal radiography, excretory urogram and/or renal sonography. DMSA renal scan was performed 24 hours before ESWL and at least 6 months after treatment. RESULTS: ESWL was performed in 1 session for 8 patients, 2 sessions for 6 and 3 sessions for 1, delivering a range of 600 to 3,000 shock waves per session. Treatment was successful in achieving stone-free status in 87% of the cases. Long-term followup (1 to 5 years) showed no blood pressure changes. On DMSA renal scan no acquired parenchymal scar was identified at least 6 months after ESWL treatment. CONCLUSIONS: The efficacy of ESWL in treating pediatric urolithiasis is confirmed. Renal parenchymal trauma associated with ESWL does not appear to cause long-term lesions identifiable by DMSA renal scan.

Adolescent↗
PubMed2003

Incidence of new renal parenchymal inflammatory changes following breakthrough urinary tract infection in patients with vesicoureteral reflux treated with antibiotic prophylaxis: evaluation by 99MTechnetium dimercapto-succinic acid renal scan.

PURPOSE: Breakthrough urinary tract infections (UTI) are considered an indication for surgical intervention in children with vesicoureteral reflux (VUR) with the goal of preventing new or progressive renal scarring. We assessed the incidence of new renal parenchymal inflammatory changes following breakthrough UTI in patients on antibiotic prophylaxis for VUR. MATERIALS AND METHODS: We prospectively analyzed 38 patients (62 refluxing renal units) with VUR. All patients experienced a culture documented breakthrough UTI (greater than 100,000 cfu/ml) while taking antibiotic prophylaxis. Dimercapto-succinic acid (DMSA) scans were obtained 4 to 6 weeks after UTI to detect new renal inflammatory changes and all scans were reviewed by the same pediatric nuclear medicine specialist (MM). To avoid misinterpretation of preexistent renal scarring for acute inflammation, new pyelonephritis was confirmed by comparison to prior DMSA scan. RESULTS: Of 38 patients 14 (38%) had preexistent renal scarring but only 1 (7%) manifested new changes on DMSA scan. Of the remaining 24 patients with normal baseline studies 3 (12.5%) had changes after UTI. Overall, only 4 patients (10.5%) manifested new changes on DMSA scan. Three additional patients who did not have a baseline scan for comparison demonstrated unequivocal changes of acute pyelonephritis on DMSA scan, increasing the incidence to 17% (7 of 41). Of the patients 7 (17%) underwent surgical correction of reflux and 34 (83%) were maintained on antibiotic prophylaxis. CONCLUSIONS: Of patients with VUR who experienced a single breakthrough UTI while on antibiotic prophylaxis, at most only 17% had renal inflammatory changes on acute DMSA scan. Our findings endorse the usefulness of DMSA scan in tailoring management of VUR and breakthrough UTI cases, and lend support to continued nonoperative management for the majority.

Antibiotic Prophylaxis↗
PubMed1978

Depolarization of the Electrogenic Transmembrane Electropotential of Zea mays L. by Bipolaris (Helminthosporium) maydis Race T Toxin, Azide, Cyanide, Dodecyl Succinic Acid, or Cold Temperature.

The transmembrane electrical potential of root cells of Zea mays L. cv. W64A in a modified 1x Higinbotham solution was partially depolarized by semipurified toxin obtained from Bipolaris (Helminthosporium) maydis race T. At a given toxin concentration depolarization of Texas cytoplasm cells was much greater than for normal cytoplasm cells. This observation correlated directly to the differential host susceptibility to the fungus. The time course and magnitude of depolarization were dependent on toxin concentration; at high concentration the electropotential difference change was rapid. Cortex cells depolarized more slowly than epidermal cells indicating that the toxin slowly permeated intercellular regions. Toxin concentrations which affected electropotential difference were of the same magnitude as those required to inhibit root growth, ion uptake, and mitochondrial processes.Azide, cyanide, and cold temperature (5 C) gave the same partial depolarization as did the toxin. Dodecyl succinic acid caused complete depolarization. These and other data indicate that one of the primary actions of the toxin is to inhibit electrogenic ion pumps in the plasmalemma.

Journal Article↗
PubMed1989

Effect of esters of succinic acid and other citric acid cycle intermediates on insulin release and inositol phosphate formation by pancreatic islets.

Esters of carboxylic acids are permeable to cells and once inside the cell are hydrolyzed to carboxylic acids. Methyl and ethyl esters of succinate and other citric acid cycle intermediates were tested to find out whether they are insulin secretagogues. Monomethyl succinate stimulated insulin release from pancreatic islets in a concentration-dependent manner with maximal release attained at a concentration of 10 mM. Dimethyl succinate (10 mM) was as effective as monomethyl succinate, but pyruvate methyl ester, monoethyl succinate, and dimethyl fumarate were ineffective as primary secretagogues. However, dimethyl fumarate potentiated both leucine- and leucine-plus-glutamine-induced insulin release. Glucose, leucine, leucine plus glutamine, and monomethyl succinate increased inositol tris-, bis- and monophosphate formation in pancreatic islets and antimycin A inhibited this formation. Since mitochondrial metabolism is probably essential for glucose-induced insulin release and the metabolism of succinate and leucine (without or with glutamine) involves mitochondrial respiration exclusively, these results might indicate that mitochondrial metabolism generates conditions or factors that are transmitted to the cytosol to increase inositol trisphosphate formation and thus calcium mobilization and insulin release. Since succinate is believed to enter metabolism at site II of the mitochondrial respiratory chain, it is interesting that rotenone, an inhibitor of NADH dehydrogenase and site I of the respiratory chain, was a potent inhibitor of monomethyl succinate-induced insulin released. Rotenone also inhibited leucine (plus or minus glutamine)-induced insulin release. These results indicate that beta cell metabolism of monomethyl succinate and leucine, like glucose, influences dehydrogenases that produce NADH.

Animals↗
PubMed1963

Succinic acid turnover and propionate production in the bovine rumen.

High velocity constants for conversion of added succinate to propionate, together with estimations of pool size, showed that extracellular succinate is the major precursor of the propionate formed in the rumen. Some bacteria give off succinate as a final fermentation product which is decarboxylated by others to propionate.

Animals↗