Biosynthetic production of 13C-labeled amino acids with site-specific enrichment.

We have developed two Escherichia coli strains for the production of specifically labeled amino acids suitable for high resolution nuclear magnetic resonance experiments. The 13C atoms from the enriched carbon sources, [1-13C]lactate, [1,4-13C2]succinate, and [1-13C]-acetate, are incorporated into the amino acids producing multilabeled molecules with relatively few instances of adjacent enriched carbons. This greatly simplifies the resultant spectra as compared to the extensively spin-coupled spectra of uniformly enriched samples.

Adenylate kinase of Escherichia coli: evidence for a functional interaction in phospholipid synthesis.

Previous genetic and biochemical experiments have suggested that the adenylate kinase of Escherichia coli may be directly involved in phospholipid synthesis through formation of a complex with sn-glycerol-3-phosphate acyltransferase, the membrane-bound enzyme that catalyzes the first step in phospholipid synthesis. In this paper we report direct experiments to test this hypothesis. A mutation within the adenylate kinase structural gene is described that results in a temperature-sensitive phospholipid synthesis (assayed in vivo) and a temperature-sensitive acyltransferase.

Renal cysts: curios and caveats.

Interesting, unusual, and confusing renal cysts from a group of 200 cysts punctured percutaneously during the past decade are presented. Some cases illustrate pressure phenomena in cysts adjacent to each other or causing calyceal obstruction. Also reported are cyst wall findings, unusual cyst configurations, infection in pre-existing cysts, examples of cysts simulating renal cell carcinoma, and renal cell carcinoma presenting as cysts.

Ultrasonic inaccuracies in diagnosing renal obstruction.

Renal ultrasound is an excellent screening examination for suspected urinary tract obstruction. Its usefulness is based on the ability to detect hydronephrosis. However, it must be recognized that a significant number of conditions exist which can mimic or produce dilatation of the collecting system without urinary tract obstruction.

Filling defects in small bowel urinary conduits.

Radiographic evaluation of patients with urinary diversion by small bowel conduit includes excretory urography, loopography, and, if necessary, percutaneous pyelography. Five patients with discrete filling defects in their conduits are discussed. These defects represented stones (two cases), antirefluxing ureteral nipples, metastatic bladder carcinoma, and a "turn-in" loop construction defect.

Chemical synthesis of acyl thioesters of acyl carrier protein with native structure.

The acyl carrier protein (ACP) of Escherichia coli was converted to acyl-ACP by imidazole-catalyzed S-acylation with N-acylimidazole. The acylation was specific to the sulfhydryl group; no acylation of tyrosine or amino groups of the protein occurred. The acyl-ACP substrates synthesized had a native structure as determined by gel electrophoresis, hydrophobic chromatography, and enzymatic activity.

A mutant of Escherichia coli conditionally defective in the synthesis of holo-[acyl carrier protein].

Supplementation of Escherichia coli pantothenate auxotrophs with varying concentrations of pantothenate results in a concomitant variation of the intracellular level of CoA but has no effect on the level of holo-[acyl carrier protein] (holo-[ACP]) (Alberts, A., and Vagelos, P. R.

Molecular properties of acyl carrier protein derivatives.

Acyl carrier protein (ACPSH) functions as the acyl carrier in fatty acid biosynthesis. The acyl moieties are bound to the sole sulfhydryl of the protein located on the 4'-phosphopantetheine prosthetic group. Disulfide-linked dimers of ACPSH were formed by the reaction of ACPSH with acyl-ACP or the mixed disulfide of ACPSH and thionitrobenzoate.

Phospholipid synthesis in Escherichia coli. Characteristics of fatty acid transfer from acyl-acyl carrier protein to sn-glycerol 3-phosphate.

Two kinetically distinguishable sn-glycerol 3-phosphate (glycerol-P) acryltransferase activities were detected in Escherichia coli inner membranes using acyl-acyl carrier protein (ACP) substrates. The first system was characterized as having a Michaelis constant (Km) for glycerol-P of 90 microM and utilized palmitoyl-ACP to form primarily 1-acylglycerol-P. Palmitoyl-CoA and cis-vaccenoyl-ACP were also utilized by this system but, with these substrates, significantly more phosphatidic acid was formed as compared to palmitoyl-ACP.

Structural, enzymatic, and genetic studies of beta-ketoacyl-acyl carrier protein synthases I and II of Escherichia coli.

Beta-Ketoacyl-acyl carrier protein synthases I and II of Escherichia coli were purified and characterized. Synthase I was shown to have a molecular weight of 80,000 +/- 5,000 and to be composed of two similarly sized subunits. Synthase II had a molecular weight of 85,000 +/- 5,000 and also was apparently homodimeric.

Ultrasound in experimental and clinical renal vein thrombosis.

Static ultrasound was used to study five dogs with surgically produced unilateral renal vein thrombosis and eight patients with unilaterally occluded renal veins. In both clinical and experimental situations, renal vein thrombosis acutely led to decreased cortical echogenicity and nephromegaly. Between 10 days and three weeks, there was an increase in cortical echogenicity with preservation of corticomedullary definition; the late changes were decreased renal size, increased cortical echogenicity, and loss of corticomedullary definition.

The positional distribution of fatty acids in Escherichia coli phospholipids is not regulated by sn-glycerol 3-phosphate levels.

Large changes in the intracellular concentration of sn-glycerol 3-phosphate had no effect on the acyl chain distribution of the phospholipids of Escherichia coli. This result directly contradicts the prediction by other workers based on in vitro experiments.

Acetaldehyde coenzyme A dehydrogenase of Escherichia coli.

Mutants of Escherichia coli (adh) in which alcohol dehydrogenase is derepressed under aerobic conditions were also found to overproduce acetaldehyde coenzyme a dehydrogenase. However, acetaldehyde coenzyme A dehydrogenase was induced by ethanol or acetaldehyde and subject to strong catabolite repression, whereas alcohol dehydrogenase was little affected by these conditions. Mutants no longer able to use ethanol as carbon source were isolated from an adh strain.