Patency of internal mammary-coronary grafts

Patency of internal mammary artery (IMA) coronary grafts was evaluated in 150 patients having an early (20 days) and late (13 months) postoperative angiogram. Early and late failure for 76 right IMA grafts was 3 and 5 respectively and for 139 left IMA grafts 7 and 7 an overall IMA patency of 95% and 90%. The IMA and coronary internal diameter did not relate to graft closure. Right IMA free flow did not correlate with graft closure. Free flow for thrombosed left IMA grafts (91 ml/min) was significantly (P less than 0.05) lower than for patent grafts (118 ml/min). Right IMA anastomotic flow of 55 ml/min was significantly (P less than 0.001) higher than occluded graft flow of 26 ml/min as was true for patent left IMA grafts (55 ml/min) and occluded grafts (43 ml/min) (P less than 0.025). Five of 215 IMA grafts had diffuse stenosis (greater than 50%). Saphenous vein coronary bypass was performed in 88 instances with an early patency of 89% (79/88) and a late patency of 88% (78/88). Only one of 38 vein grafts to the right coronary artery failed whereas eight of 44 grafts to the circumflex artery occluded. Experience was associated with increased late IMA patency from 81% (57/70), to 89% (;8/76), to 99% (68/69) in each successive group of 50 patients. Currently, the left IMA is routinely used for the left anterior descending artery and the right IMA is rarely used.

Drug-biomolecule interactions: drug toxicity and vitamin coenzyme depletion

Thirteen pyridine compounds, phenylbutazone, and three salicylates were studied for their effects upon the turnover of 7-14C-nicotinamide dinucleotides in the mouse. The compounds were administered at equitoxic doses (LD25) to 7-14C-nicotinic acid- (niacin) pretreated mice, and the induced excretion of urinary-14C was analyzed in terms of total 14C and percentage of total 14C as known metabolites of nicotinic acid. Of the 17 compounds, 12 afforded significant alterations in the total 14C excreted and five of these caused alterations in the disposition of the 7-14C-nicotinamide endogenously liberated from the 7-14C-nicotinamide adenine dinucleotide pool. Comparative depletions of 14C from brain, lungs, liver, and kidneys were studied with 10 of the pyridine compounds. Several tissues were found to be the sources of the urinary-14C, with the lungs being the most accessible source. Some compounds had effects at doses less than the LD25's, as shown by increased hexobarbital sleeping time in acute experiments with rats. These pyridine compounds were initially considered to act at the level of the nicotinamide dinucleotides in the normal biosynthetic pathway (nicotinic acid site) and/or at the level of glycohydrolase (nicotinamide site). In view of the inclusion of nicotinic acid, nicotinamide, salicylic acid, and phenylbutazone in this correlation between toxicity and 7-14C-nicotinamide mobilization, it is not necessary that the formation of compounds analogous to the nicotinamide dinucleotides plays a significant role in the toxic manifestations of the nicotinamide analogs. The displacement of 7-14C-nicotinamide dinucleotides from their corresponding apoenzymes with subsequent metabolism of the dinucleotides could explain the noted increased 7-14C-nicotinamide dinucleotide turnover and depletion which led to the toxic effects.

Soluble cytochrome P-450 from housefly microsomes. Partial purification and characterization of two hemoprotein forms

Housefly microsomes contain two spectrally different forms of cytochrome P-450 which we have termed P-450 and P-450I. Methods have been developed for the fractionation and chromatographic purification of these two hemoprotein forms. Microsomes are solubilized first with Triton X-100 in the presence of glycerol, dithiothreitol, ethylenediaminetetra-acetic acid, and phenobarbital. Cytochrome P-450 is recovered in a floating pellet after the addition of 25% ammonium sulfate followed by centrifugation, whereas cytochrome P-450I remains in the 25% ammonium sulfate supernatant fluid. Cytochrome P-450 is purified further by Sephadez G-200 and DEAE-Sephadex A-50 column chromatography, which also allows the isolation of cytochrome b5 and NADPH-dependent cytochrome P-450 reductase in good yields and with little cross-contamination. Cytochrome P-450 apparently is free of cytochromes b5 and P-420 as well as of reductase and is obtained in a final yield of approximately 16% with a 6.9-fold purification. Its maximum absorbance is at 45 mn in the CO-difference spectrum and its average extinction coefficient is 103 cm-1 nm-1. Cytochrome P-450I is purified by Sephadex G-25 column chromatography but still contains some cytochromes b5 and P-420 as well as reductase. Its maximum absorbance is at 448.5 nm in the CO-difference spectrum and its extinction coefficient is 83 to 86 cm-1 mM-1. Both cytochromes hydroxylate type I substrates such as aminopyrine. Sufficient amounts of reductase are present in the cytochrome P-450I preparation to sustain activity, but the reductase has to be added to cytochrome P-450 in a reconstituted system for activity. Cytochrome P-450 is fairly stable, whereas cytochrome P-450I can be isolated only when protected by a substrate (phenobarbital). Detergent-solubilized housefly cytochromes P-450 and P-450I seem to correspond to either aggregates or oligomeric proteins. Cytochrome P-450 appears to correspond to a tetramer, each subunit having a molecular weight of 45,000, whereas cytochrome P-450I may correspond to an aggregate of at least 10 subunits. The cytochrome P-450 aggregate is dissociated by 6 M urea, but cytochrome P-450I remains as such.

Bacterial metabolism of 3-hydroxy-3-methylglutaric acid

An organism belonging to Pseudomonadaceae and capable of utilizing 3-hydroxy-3-methylglutarate as sole carbon source has been isolated from soil. Whole-cell preparations catalyze the oxidation of acetoacetate, acetate, glyoxylate, and citric acid cycle intermediates. Cell-free extracts of 3-hydroxy-3-methylglutarate-grown cells show an adenosine triphosphate, coenzyme A (CoA), and Mg(2+)-dependent conversion of 3-hydroxy-3-methylglutarate to 3-hydroxy-3-methylglutaryl-CoA. Succinyl-CoA-generating system has no effect on the activation and catabolism of 3-hydroxy-3-methylglutarate.