Biomedical subjects

F J Baumgartner

Publications and source records attributed to F J Baumgartner.

40 records · Page 3Linked to original sources

PubMed1983

Synthesis and myocardial kinetics of N-13 and C-11 labeled branched-chain L-amino acids.

Glutamate dehydrogenase (GDH), immobilized on CNBr-activated Sepharose supports, was used with N-13 ammonia to aminate alpha-ketoisocaproic acid (KIC), and alpha-ketoisovaleric acid (KIV) to produce N-13-labeled branched-chain L-amino acids with radiochemical yields ranging from 29% to 35%. From kinetic and practical considerations, pH 7.5-8.0 was established to be optimal for the synthesis of N-13-labeled branched-chain-L-amino acids. Myocardial time-activity curves in dogs at control, during low-flow ischemia, reperfusion, and after transaminase inhibition following intracoronary bolus injection of the N-13-labeled amino acids were biexponential. Higher retention of N-13 activity was observed in ischemic segments both during low-flow ischemia (29.2%) and reperfusion (23.2%) when compared with controls (20.0%), (n = 4). On the other hand, transaminase inhibition decreased residue fractions from 21.0% at control to 13.9% (n = 4). The residual activity with L-[1-11C]leucine allows for the calculation of protein synthesis rates.

Amino Acids, Branched-Chain↗

PubMed1982

L-[4-11C]aspartic acid: enzymatic synthesis, myocardial uptake, and metabolism.

Sterile, pyrogen-free L-[4-11C]aspartic acid was prepared from 11CO2 using phosphoenolpyruvate carboxylase and glutamic/oxaloacetic acid transaminase immobilized on Sepharose supports to determine if it is a useful indicator for in vivo, noninvasive determination of myocardial metabolism. An intracoronary bolus injection of L-[4-11C]aspartic acid into dog myocardium showed a triexponential clearance curve with maximal production of 11CO2 100 s after injection. Inactivation of myocardial transaminase activity modified the tracer clearance and inhibited the production of 11CO2. Positron-computed tomography imaging showed that the 11C activities retained in rhesus monkey myocardium are higher than those observed in dog heart after intravenous injection of L-[4-11C]aspartic acid. These findings demonstrated the rapid incorporation of the carbon skeleton of L-aspartic acid into the tricarboxylic acid cycle after enzymatic transamination in myocardium and suggested that L-[4-11C]aspartic acid could be of value for in vivo, noninvasive assessment of local myocardial metabolism.

Animals↗

PubMed1981

13N-labeled L-amino acids for in vivo assessment of local myocardial metabolism.

The hot cell synthesis of sterile, pyrogen-free 13N-labeled L-amino acids was accomplished by employing the appropriate immobilized enzymes on a CNBr-activated Sepharose support and using remote, semiautomated systems. The syntheses were completed 6-12 min after cyclotron production of [13N]ammonia. Myocardial time-activity curves after intracoronary injection of 13N-labeled L-amino acids in dogs were triexponential in both normal and ischemic myocardium. Higher retention of 13N activity was observed in ischemic segments. Positron computed tomography imaging also showed increased uptake of 13N-labeled L-glutamate and L-alanine in ischemic segments compared with normal myocardium when blood flow corrections were made. Myocardial transaminases are primarily responsible for the observed retention fractions. It suggests the participation of the carbon skeletons of these amino acids in the Krebs cycle.

Amino Acids↗

PubMedDate not supplied

Ultrasonic debridement of mitral calcification.

Dense annular calcification to the valve attachment is particularly hazardous during mitral valve replacement because of the difficulty of placing sutures and the risk of atrioventricular rupture. We report 11 patients who underwent decalcification of the mitral anulus with the Cavitron Ultrasound Surgical Aspirator (CUSA) during mitral valve replacement. This resulted in a greatly simplified suture placement and prosthetic valve seating as well as enlargement of the annular orifice. Four other patients underwent CUSA debridement of the anterior leaflet of the mitral valve during concomitant aortic valve replacement and CUSA debridement of the aortic anulus. There were no operative deaths or major complications. Ultrasonic debridement is a useful adjunct in the surgical management of the heavily calcified mitral valve.

Adult↗