Mutations in NADH:ubiquinone oxidoreductase of Escherichia coli affect growth on mixed amino acids.

We isolated and characterized mutants defective in nuo, encoding NADH dehydrogenase I, the multisubunit complex homologous to eucaryotic mitochondrial complex I. By Southern hybridization and/or sequence analysis, we characterized three distinct mutations: a polar insertion designated nuoG::Tn10-1, a nonpolar insertion designated nuoF::Km-1, and a large deletion designated delta(nuoFGHIJKL)-1. Cells carrying any of these three mutations exhibited identical phenotypes. Each mutant exhibited reduced NADH oxidase activity, grew poorly on minimal salts medium containing acetate as the sole carbon source, and failed to produce the inner, L-aspartate chemotactic band on tryptone swarm plates. During exponential growth in tryptone broth, nuo mutants grew as rapidly as wild-type cells and excreted similar amounts of acetate into the medium. As they began the transition to stationary phase, in contrast to wild-type cells, the mutant cells abruptly slowed their growth and continued to excrete acetate. The growth defect was entirely suppressed by L-serine or D-pyruvate, partially suppressed by alpha-ketoglutarate or acetate, and not suppressed by L-aspartate or L-glutamate. We extended these studies, analyzing the sequential consumption of amino acids by both wild-type and nuo mutant cells growing in tryptone broth. During the lag and exponential phases, both wild-type and mutant cells consumed, in order, L-serine and L-aspartate. As they began the transition to stationary phase, both cell types consumed L-tryptophan. Whereas wild-type cells then consumed L-glutamate, glycine, L-threonine, and L-alanine, mutant cells utilized these amino acids poorly. We propose that cells defective for NADH dehydrogenase I exhibit all these phenotypes, because large NADH/NAD+ ratios inhibit certain tricarboxylic acid cycle enzymes, e.g., citrate synthase and malate dehydrogenase.

Novel mutations in the pheA gene of Escherichia coli K-12 which result in highly feedback inhibition-resistant variants of chorismate mutase/prephenate dehydratase.

The bifunctional enzyme chorismate mutase/prephenate dehydratase (EC 5.4.99.5/4.2.1.51), which is encoded by the pheA gene of Escherichia coli K-12, is subject to strong feedback inhibition by L-phenylalanine. Inhibition of the prephenate dehydratase activity is almost complete at concentrations of L-phenylalanine greater than 1 mM. The pheA gene was cloned, and the promoter region was modified to enable constitutive expression of the gene on plasmid pJN302. As a preliminary to sequence analysis, a small DNA insertion at codon 338 of the pheA gene unexpectedly resulted in a partial loss of prephenate dehydratase feedback inhibition. Four other mutations in the pheA gene were identified following nitrous acid treatment of pJN302 and selection of E. coli transformants that were resistant to the toxic phenylalanine analog beta-2-thienylalanine. Each of the four mutations was located within codons 304 to 310 of the pheA gene and generated either a substitution or an in-frame deletion. The mutations led to activation of both enzymatic activities at low phenylalanine concentrations, and three of the resulting enzyme variants displayed almost complete resistance to feedback inhibition of prephenate dehydratase by phenylalanine concentrations up to 200 mM. In all four cases the mutations mapped in a region of the enzyme that has not been implicated previously in feedback inhibition sensitivity of the enzyme.

Cardiac surgery at the San Pablo Heart Institute: an update of statistics on surgical mortality and morbidity.

We performed 1,739 cardiac surgery procedures between August 1988 and July 1991 at the San Pablo Heart Institute. The statistics for mortality and morbidity are among the best in the nation and they showed an overall mortality for the entire period of 1.8%, a mortality for coronary artery bypass graft of 1.5% no patient has died as a result of mitral valve replacement, and a mortality of 1.1% for aortic valve replacement. We have demonstrated that our cardiac surgery team is capable of performing a high volume of these procedures with good results.

Surgery for acquired valvular heart disease: the San Pablo Heart Institute experience.

Ninety-nine patients underwent surgery for acquired diseases of the mitral and aortic valves between August 22, 1988 and August 21, 1990, of these, 64 procedures were done on the aortic valve and 35 procedures on the mitral valve. The early mortality for mitral valve surgery was 5.8% and late death occurred at a rate of 8.8%. As for the aortic valve surgery the operative mortality was zero and late death occurred at a rate of 3.4%. Thromboembolism occurred at a rate of 3.3% per patient year for patient undergoing mitral valve surgery and 6.3% per patient year for those undergoing aortic valve surgery. Valve thrombosis occurred at a rate of 6.6% per patient year for patients undergoing mitral valve surgery and zero for patients undergoing aortic valve surgery. Anticoagulation related bleeding occurred at a rate of 49% per patient year for patients undergoing mitral valve surgery and fatal bleeding at a rate of 3.3% per patient year. For those patients undergoing aortic valve surgery bleeding occurred at a rate of 25% per patient year and fatal bleeding occurred at a rate of 3.1%. This rate of bleeding appears high; and is due to poorly monitored anticoagulation.

Cardiac surgery at San Pablo Heart Institute: a preliminary report of the first year experience.

A series of 341 patients undergoing cardiac surgery, of which 276 underwent coronary artery bypass grafting (CABG) and 37 underwent valve replacement, is presented herein. Results of mortality and morbidity are shown, discussed and compared to that of other institutions, and found favorable. These patients represent our first year of experience at the San Pablo Heart Institute.

The prevention of invasive cancer of the rectum.

The results of the 25+ year Cancer Detection Center study, including 20,000 participants and 100,000+ patient-years experience, demonstrate the obviation of appearance of most lower bowel cancers associated with a program of proctosigmoidoscopy and adenomatous polyp removal. Once on a schedule of periodic examinations, study participants developed only a fraction of the anticipated number of rectal cancers; most of the cancers which did develop were detected while at an early stage and with involvement of only the mucosa. Not a single death from lower bowel cancer has occurred among active study participants or for 7+ years following the most recent examination at the Center.