A prospective randomized evaluation of a pharmacogenomic approach to antiplatelet therapy among patients with ST-elevation myocardial infarction: the RAPID STEMI study.

Treatment of carriers of the CYP2C19*2 allele and ABCB1 TT genotype with clopidogrel is associated with increased ischemic complications after percutaneous coronary intervention (PCI). We sought to evaluate a pharmacogenomic strategy among patients undergoing PCI for ST-elevation myocardial infarction (STEMI), by performing a randomized trial, enrolling 102 patients. Point-of-care genetic testing for CYP2C19*2, ABCB1 TT and CYP2C19*17 was performed with carriers of either the CYP2C19*2 allele or ABCB1 TT genotype randomly assigned to a strategy of prasugrel 10 mg daily or an augmented dosing strategy of clopidogrel (150 mg daily for 6 days then 75 mg daily). The primary end point was the proportion of at-risk carriers exhibiting high on-treatment platelet reactivity (HPR), a marker associated with increased adverse cardiovascular events, after 1 month. Fifty-nine subjects (57.8%) were identified as carriers of at least one at-risk variant. Treatment with prasugrel significantly reduced HPR compared with clopidogrel by P2Y12 reaction unit (PRU) thresholds of >234 (0 vs 24.1%, P=0.0046) and PRU>208 (3.3 vs 34.5%, P=0.0025). The sensitivity of point-of-care testing was 100% (95% CI 88.0-100), 100% (86.3-100) and 96.9% (82.0-99.8) and specificity was 97.0% (88.5-99.5), 97.1% (89.0-99.5) and 98.5% (90.9-99.9) for identifying CYP2C19*2, ABCB1 TT and CYP2C19*17, respectively. Logistic regression confirmed carriers as a strong predictor of HPR (OR=6.58, 95% CI 1.24-34.92; P=0.03). We confirmed that concurrent identification of three separate genetic variants in patients with STEMI receiving PCI is feasible at the bedside. Among carriers of at-risk genotypes, treatment with prasugrel was superior to an augmented dosing strategy of clopidogrel in reducing HPR.

Inversion-recovery-prepared SSFP for cardiac-phase-resolved delayed-enhancement MRI.

Delayed-enhancement magnetic resonance imaging (DE-MRI) can be used to visualize myocardial infarction (MI). DE-MRI is conventionally acquired with an inversion-recovery gradient-echo (IR-GRE) pulse sequence that yields a single bright-blood image. IR-GRE imaging requires an accurate estimate of the inversion time (TI) to null the signal from the myocardium, and a separate cine acquisition is required to visualize myocardial wall motion. Simulations were performed to examine the effects of a steady-state free precession (SSFP) readout after an inversion pulse in the setting of DE-MRI. Using these simulations, a segmented IR-SSFP sequence was optimized for infarct visualization. This sequence yields both viability and wall motion images over the cardiac cycle in a single breath-hold. Viability images at multiple effective TIs are produced, providing a range of image contrasts. In a study of 11 patients, IR-SSFP yielded infarct sizes and left ventricular ejection fractions (LVEFs) similar to those obtained by IR-GRE and standard SSFP, respectively. IR-SSFP images yielded improved visualization of the infarct-blood border because of the simultaneous nulling of healthy myocardium and blood. T(1) (*) recovery curves were extracted from IR-SSFP images and showed excellent qualitative agreement with theoretical simulations.

MRI relaxation fluctuations in acute reperfused hemorrhagic infarction.

MRI evaluations of intramyocardial hemorrhage in acute infarction have relied on T(2) and T(2)(*) shortening only. We propose a more comprehensive evaluation of hemorrhagic infarction based on the concept that fluctuations in T(2) and T(1) relaxation in acute reperfused infarction will reflect transient edema and hemoglobin oxidative denaturation to uncompartmentalized methemoglobin. Anteroapical infarction was created via percutaneous balloon in young swine (22-25 kg, N = 12). T(2), T(1), diastolic wall thickness (DWT), and the Gd-DTPA partition coefficient (lambda) were measured on days 0, 2, and 7. DWT was elevated at 1 hr postreperfusion (128% +/- 53%, P = 0.0001), and alleviated on days 2 and 7 (48% +/- 10%, P = 0.008; 53% +/- 24%, P = 0.003). T(2) and T(1) elevations were coincident with early edema (DeltaT(2) = 55% +/- 24%, P < 0.0001; DeltaT(1) = 27% +/- 18%, P < 0.04). T(2) and T(1) were nearly normal on day 2 (DeltaT(2) = 8% +/- 8%, P = 0.27; DeltaT(1) = 0% +/- 1%, P = 0.65). On day 7, T(2) increased while T(1) decreased (DeltaT(2) = 27% +/- 16%, P = 0.005; DeltaT(1) = -14% +/- 10%, P = 0.02). Lambda was elevated by >150% at all time points (P < or = 0.002). Histology verified hemorrhagic injury. T(1) and T(2) fluctuations are consistent with transient edema, as well as hemoglobin oxidative denaturation to decompartmentalized methemoglobin. This methodological development may broaden our understanding of hemorrhagic microvascular injury and improve its detection in clinical populations.

T2 fluctuations in ischemic and post-ischemic viable porcine myocardium in vivo.

T2 relaxation can augment delayed-enhancement viability imaging because it is sensitive to tissue edema and microcirculatory oxygen state. We demonstrate the T2 'signatures' of sub-lethal ischemia and stunning in porcine myocardium perfused by the distal left anterior descending artery, by imaging during percutaneous balloon occlusion for 25 minutes and subsequent reperfusion (n = 9). Muscle displayed ischemic dysfunction and partial post-ischemic functional recovery (p < or = 0.0004), concommitant with an elevated post-ischemic T2 (deltaT2 = 27 +/- 18%, p = 0.005). TTC staining verified muscle viability. The T2 fluctuations may reflect hyperemia and tissue cellular edema in accord with the known pathophysiology of ischemic and post-ischemic yet viable muscle.

Acyloxymethyl acidic drug derivatives: in vitro hydrolytic reactivity.

A series of acyloxymethyl drug derivatives of the NH-acidic drugs, phenytoin and theophylline and of the carboxylic acid drugs, thioctic acid and indomethacin, were prepared in order to determine the effect of varying the nature of the drug on the in vitro rate of hydrolysis catalyzed by porcine liver esterase and human plasma. The acyl portion was comprised of either valeric acid (val) or gamma-linolenic acid (GLA). With the exception of some GLA prodrugs, the derivatives displayed first-order kinetics in both enzyme systems. The NH-acidic drug derivatives were hydrolyzed faster than the carboxylic drug derivatives by porcine liver esterase and human plasma. It was found that the short chain valeric acid derivatives were hydrolyzed faster than the GLA derivatives. The rates of hydrolysis for the relatively smaller prodrugs of theophylline and thioctic acid were greater than the rates of hydrolysis for the bulkier phenytoin and indomethacin prodrugs indicating steric hindrance was important. The lipophilicity index, log K, of the valeric acid drug derivatives was plotted against the logarithm of the hydrolysis rate constant, k, and it was observed that log k decreased with an increase in log K. A comparison of these results with those of previous studies where the alkyl and acyl moieties were varied of acyloxyalkyl theophylline derivatives has provided a rationale, based on lipophilicity, for the structure of a prodrug to be designed based on an in vitro desired rate of hydrolysis.

Cell Wall Metabolism in Ripening Fruit: IV. Characterization of the Pectic Polysaccharides Solubilized during Softening of ;Bartlett' Pear Fruit.

Fractionation of pectic polysaccharides from the juice of ripening ;Bartlett' pears (Pyrus communis) gave two general types of polyuronides. The major type was a homogalacturonan (HGA) whose molecular weight decreased upon ripening. The other type comprised heteropolymers composed of various amounts of arabinose, rhamnose, and galactose. Treatment of the major arabinose-containing heteropolymeric fraction of high molecular weight (400,000) with a pear exo-polygalacturonase to degrade contaminating HGA gave a polyuronide which was inert to tomato endopolygalacturonase. Glycosyl-linkage analysis of this arabinosyl-polyuronide gave results expected from a rhamnogalacturonan I-like polysaccharide with large, highly branched araban side chains (RG-I). A linkage between HGA and RG-I was not found. RG-I, in ripening pears, appeared to be degraded with the initial loss of much of its arabinose.

Aminopeptidase I activities in several microorganisms.

Aminopeptidase I activity which was found to be localized in the same subcellular fraction and to be similarly heat stable was partially purified by a common procedure from Escherichia coli B, Escherichia coli K12, Enterobacter aerogenes, Salmonella typhimurium, Serratia marcescens Pseudomonas aeruginosa, and Proteus vulgaris. The enzyme preparations were shown to contain a single animopeptidase active toward both leucylleucine and methionylalanylserine by mixed-substrate initial-velocity kinetic analysis. The Km value for leucylleucine was virtually identical for the aminopeptidases of all of the organisms, as was the Km value for methionylalanylserine.