A comparison of consecutive off-pump versus conventional coronary artery bypass.

BACKGROUND: Coronary revascularization on the beating heart is an attractive alternative to conventional coronary artery bypass grafts (CCABG), but remains controversial. Our study compares the outcomes of consecutive patients undergoing off-pump CABG (OPCABG) with a group of similar patients undergoing consecutive CCABG. METHODS: A retrospective analysis of 268 patients who underwent elective CABG between July 1998 and July 1999 at St. Michael's Medical Center yielded 134 consecutive patients who underwent OPCABG and 134 consecutive patients who had CCABG. Patients' medical charts were reviewed for age, preoperative risk factors, operative findings, postoperative complications, and length of stay (LOS). RESULTS: The two cohorts were well matched, with similar ages (66.4 +/- 11.2 for OPCABG vs. 65.8 +/- 10 for CCABG, p = 0.66) and preoperative ejection fractions (EF) (44 +/- 13 vs. 44 +/- 12, p = 0.85). There were no hospital mortalities, and there were five conversions to cardiopulmonary bypass. The OPCABG group had a significantly shorter ICU and postoperative LOS. CONCLUSIONS: Our data suggests that a fair number of patients are potential candidates for OPCABG, the only contraindications being technical limitations or the surgeon's comfort level. Six- to twelve-month follow-up indicates that OPCABG can be performed safely with a decrease in LOS, and should be part of the surgeon's armamentarium.

Transaortic repair of mitral regurgitation.

BACKGROUND: In the operative management of mitral regurgitation (MR) associated with aortic valve disease, a transaortic approach combining the bowtie mitral valve repair with replacement of the aortic valve appears to offer a less invasive and technically simple, expeditious alternative to conventional left atriotomy and Carpentier style repair. METHODS: Between February 1997 and December 1999, four patients underwent a bowtie repair of the mitral valve via the aortic root with concomitant aortic valve replacement. The diagnosis of MR was established and followed postoperatively by echocardiogram. The operative technique involved a transaortic annular approach to the mitral valve with a single edge-to-edge suture approximating the prolapsing posterior mitral leaflet to a normal segment of the anterior leaflet. RESULTS: There were no operative mortalities. Mean cross-clamp time for both valve procedures was 104 +/- 24 min and cardiopulmonary bypass was 155 +/- 31. Mean postoperative cardiac output was 5 +/- 1 L/min. Semiquantitative estimation of mitral regurgitation by doppler improved from a mean of 3.2 +/- 0.5 preoperatively to a mean of 0.25 +/- 0.5 (p = 0.0052) postoperatively, while ejection fraction (EF) remained stable (48 +/- 9% preoperatively and 49 +/- 9% prior to discharge). One patient with rheumatic mitral pathology had a mild increased mitral gradient which did not resolve with takedown of the bowtie repair. Mitral stenosis was not evident in any of the other patients. CONCLUSIONS: Our initial experience with the combined transaortic bowtie repair and aortic valve replacement has demonstrated that this approach is very quick, feasible, effective, and technically simple with gratifying midterm results.

Role of hydrophobic interactions in binding S-(N-aryl/alkyl-N-hydroxycarbamoyl)glutathiones to the active site of the antitumor target enzyme glyoxalase I.

Hydrophobic interactions play an important role in binding S-(N-aryl/alkyl-N-hydroxycarbamoyl)glutathiones to the active sites of human, yeast, and Pseudomonas putida glyoxalase I, as the log K(i) values for these mechanism-based competitive inhibitors decrease linearly with increasing values of the hydrophobicity constants (pi) of the N-aryl/alkyl substituents. Hydrophobic interactions also help to optimize polar interactions between the enzyme and the glutathione derivatives, given that the K(i) value for S-(N-hydroxycarbamoyl)glutathione (pi = 0) with the human enzyme is 35-fold larger than the interpolated value for this compound obtained from the log K(i) versus pi plot. Computational studies, in combination with published X-ray crystallographic measurements, indicate that human glyoxalase I binds the syn-conformer of S-(N-aryl-N-hydroxycarbamoyl)glutathiones in which the N-aryl substituents are in their lowest-energy conformations. These studies provide both an experimental and a conceptual framework for developing better inhibitors of this antitumor target enzyme.

Pharmacokinetics and antitumor properties in tumor-bearing mice of an enediol analogue inhibitor of glyoxalase I.

PURPOSE: The enediol analogue S-(N-p-chlorophenyl-N-hydroxycarbamoyl)glutathione (CHG) is a powerful, mechanism-based, competitive inhibitor of the methylglyoxal-detoxifying enzyme glyoxalase I. The [glycyl,glutamyl]diethyl ester prodrug form of this compound (CHG(Et)2) inhibits the growth of different tumor cell lines in vitro, apparently by inducing elevated levels of intracellular methylglyoxal. The purpose of this study was to evaluate the pharmacokinetic properties of CHG(Et)2 in plasma esterase-deficient C57BL/6 (Es-1e) mice after intravenous (i.v.) or intraperitoneal (i.p.) administration of bolus doses of CHG(Et)2. In addition, the in vivo antitumor properties of CHG(Et)2 were evaluated against murine B16 melanoma in these mice, and against androgen-independent human prostate PC3 tumor and human colon HT-29 adenocarcinoma in plasma esterase-deficient nude mice. METHODS: Pharmacokinetics were evaluated after either i.v. or i.p. administration of CHG(Et)2 at the maximally tolerated dose of 120 mg/kg to both tumor-free male and female mice and male and female mice bearing subcutaneous B16 tumors. Tissue concentrations of CHG(Et)2, CHG and the [glycyl]monoethyl ester CHG(Et) were measured as a function of time by reverse-phase C18 high-performance liquid chromatography of deproteinized tissue samples. The efficacy of CHG(Et)2 in tumor-bearing mice was evaluated after i.v. bolus administration of CHG(Et)2 at 80 or 120 mg/kg for 5 days each week for 2 weeks, or after 14 days continuous infusion of CHG(Et)2 using Alzet mini-osmotic pumps. Hydroxypropyl-beta-cyclodextrin was used as a vehicle in the efficacy studies. RESULTS: Intravenous administration of CHG(Et)2 resulted in the rapid appearance of CHG(Et)2 in the plasma of tumor-bearing mice with a peak value of 40-60 microM, followed by a first-order decrease with a half-life of about 10 min. There was a corresponding increase in the concentration of inhibitory CHG in the B16 tumors, with a maximum concentration in the range 30-60 microM occurring at 15 min, followed by a decrease to a plateau value of about 6 microM after 120 min. Neither CHG(Et)2 nor its hydrolysis products were detectable in plasma, after i.p. administration of CHG(Et)2 to tumor-free female mice. From the efficacy studies, dosing schedules were identified that resulted in antitumor effects comparable to those observed with the standard antitumor agents Adriamycin (with B16 tumors), cisplatin (with PC3 tumors), and vincristine (with HT-29 tumors). CONCLUSION: This is the first demonstration that a mechanism-based competitive inhibitor of glyoxalase I effectively inhibits the growth of solid tumors in mice when delivered as the diethyl ester prodrug.

Reaction mechanism of glyoxalase I explored by an X-ray crystallographic analysis of the human enzyme in complex with a transition state analogue.

The structures of human glyoxalase I in complexes with S-(N-hydroxy-N-p-iodophenylcarbamoyl)glutathione (HIPC-GSH) and S-p-nitrobenzyloxycarbonylglutathione (NBC-GSH) have been determined at 2.0 and 1.72 A resolution, respectively. HIPC-GSH is a transition state analogue mimicking the enediolate intermediate that forms along the reaction pathway of glyoxalase I. In the structure, the hydroxycarbamoyl function is directly coordinated to the active site zinc ion. In contrast, the equivalent group in the NBC-GSH complex is approximately 6 A from the metal in a conformation that may resemble the product complex with S-D-lactoylglutathione. In this complex, two water molecules occupy the liganding positions at the zinc ion occupied by the hydroxycarbamoyl function in the enediolate analogue complex. Coordination of the transition state analogue to the metal enables a loop to close down over the active site, relative to its position in the product-like structure, allowing the glycine residue of the glutathione moiety to hydrogen bond with the protein. The structure of the complex with the enediolate analogue supports an "inner sphere mechanism" in which the GSH-methylglyoxal thiohemiacetal substrate is converted to product via a cis-enediolate intermediate. The zinc ion is envisioned to play an electrophilic role in catalysis by directly coordinating this intermediate. In addition, the carboxyl of Glu 172 is proposed to be displaced from the inner coordination sphere of the metal ion during substrate binding, thus allowing this group to facilitate proton transfer between the adjacent carbon atoms of the substrate. This proposal is supported by the observation that in the complex with the enediolate analogue the carboxyl group of Glu 172 is 3.3 A from the metal and is in an ideal position for reprotonation of the transition state intermediate. In contrast, Glu 172 is directly coordinated to the zinc ion in the complexes with S-benzylglutathione and with NBC-GSH.

A new method for rapidly generating inhibitors of glyoxalase I inside tumor cells using S-(N-aryl-N-hydroxycarbamoyl)ethylsulfoxides.

The enediol analogue S-(N-p-chlorophenyl-N-hydroxycarbamoyl)glutathione is a powerful mechanism-based competitive inhibitor of the anticancer target enzyme glyoxalase I. Nevertheless, this compound exhibits limited toxicity toward tumor cells in vitro because it does not readily diffuse across cell membranes. We describe an efficient method for indirectly delivering the enzyme inhibitor into murine leukemia L1210 cells via acyl interchange between intracellular glutathione and the cell-permeable prodrug S-(N-p-chlorophenyl-N-hydroxycarbamoyl)ethylsulfoxide. The second-order rate constant for the acyl-interchange reaction in a cell-free system is 1.84 mM-1 min-1 (100 mM potassium phosphate buffer, 5% ethanol, pH 7.5, 25 degrees C). Incubation of L1210 cells with the sulfoxide in vitro results in a rapid increase in the intracellular concentration of the glyoxalase I inhibitor (kapp = 1. 41 +/- 0.03 min-1 (37 degrees C)) and inhibition of cell growth (GI50 = 0.5 +/- 0.1 microM). This represents an improvement in both efficiency and potency over the dialkyl ester prodrug strategy in which the inhibitor is indirectly delivered into tumor cells as the [glycyl,glutamyl] diethyl or dicyclopentyl esters. The fact that pi-glutathione transferase catalyzes the acyl-interchange reaction between GSH and the sulfoxide suggests that the sulfoxide, or related compounds, might exhibit greater selective toxicity toward tumor cells that overexpress the transferase.

The surgical intensive care unit as a cost-efficient substitute for an operating room at a Level I trauma center.

Critically ill patients in the surgical intensive care unit (SICU) continue to require operative procedures. Traditionally, this has meant the transport of these critically ill patients out of the safe, monitored confines of the SICU to the operating room (OR). This can be hazardous to the patient, as well as expensive. Performing the procedures in the OR can avoid both the dangers of transport and the expense of the OR. Herein is a descriptive study of 80 procedures performed on 36 patients in the SICU. We believe that these data show that the SICU can be a cost-effective alternative to the OR in a trauma center in critically ill patients. Significant cost savings may be realized without increasing the iatrogenic or infectious complications.

Mechanism-based competitive inhibitors of glyoxalase I: intracellular delivery, in vitro antitumor activities, and stabilities in human serum and mouse serum.

S-(N-Aryl-N-hydroxycarbamoyl)glutathione derivatives (GSC(O)N(OH)C6H4X, where GS = glutathionyl and X = H (1), Cl (2), Br (3)) have been proposed as possible anticancer agents, because of their ability to strongly inhibit the methylglyoxal-detoxifying enzyme glyoxalase I. In order to test this hypothesis, the in vitro antitumor activities of these compounds and their [glycyl,glutamyl] diethyl ester prodrug forms (1(Et)2-3(Et)2) have been examined. All three diethyl esters inhibit the growth of L1210 murine leukemia and B16 melanotic melanoma in culture, with GI50 values in the micromolar concentration range. Cell permeability studies with L1210 cells indicate that growth inhibition is associated with rapid diffusion of the diethyl esters into the cells, followed by enzymatic hydrolysis of the ethyl ester functions to give the inhibitory diacids. In contrast, the corresponding diacids neither readily diffuse into nor significantly inhibit the growth of these cells. Consistent with the hypothesis that cell growth inhibition is due to competitive inhibition of glyoxalase I, preincubation of L1210 cells with 2(Et)2 increases the sensitivity of these cells to the inhibitory effects of exogenous methylglyoxal. Compound 2(Et)2 is much less toxic to nonproliferating murine splenic lymphocytes, possibly reflecting reduced sensitivity to methylglyoxal and/or reduced chemical stability of the diacid inside these cells. Finally, a plasma esterase-deficient murine model has been identified that should allow in vivo testing of the diethyl esters.

S-(N-aryl-N-hydroxycarbamoyl)glutathione derivatives are tight-binding inhibitors of glyoxalase I and slow substrates for glyoxalase II.

S-(N-Aryl-N-hydroxycarbamoyl)glutathione derivatives are powerful competitive inhibitors of the anticancer target enzyme glyoxalase I. Indeed, the N-p-bromophenyl derivative is the strongest inhibitor of the enzyme from human erythrocytes yet reported (Ki = 1.4 x 10(-8) M). Structure-activity correlations indicate that the high affinities of the derivatives for both human and yeast glyoxalase I are due to the fact that the derivatives are hydrophobic analogs of the enediol(ate) intermediate associated with the glyoxalase I reaction. The derivatives also proved to be slow substrates for the thioester hydrolase glyoxalase II (bovine liver). Compounds of this type are of interest as potential tumor-selective anticancer agents, based on the abnormally low levels of glyoxalase II activity in some types of cancer cells.