Soluble enzymes from sage (Salvia officinalis) and tansy (Tanacetum vulgare), which catalyze the cyclization of geranyl pyrophosphate and the presumptive intermediate linalyl pyrophosphate to the (+) and (-) enantiomers, respectively, of 2-bornyl pyrophosphate, were employed to evaluate mechanistic alternatives for the pyrophosphate migration in monoterpene cyclization reactions. Separate incubation of [1-3H2,alpha-32P]- and [1-3H2,beta- 32P]geranyl and (+/-)-linalyl pyrophosphates with partially purified preparations of each enantiomer-generating cyclase gave [3H, 32P]bornyl pyrophosphates, which were selectively hydrolyzed to the corresponding bornyl phosphates. Measurement of 3H:32P ratios of these monophosphate esters established that two ends of the pyrophosphate moiety retained their identifies in the cyclization of both precursors to both products and also indicated that there was no appreciable exchange with exogenous inorganic pyrophosphate in the reaction. Subsequent incubations of each cyclase with [8,9-14C,1-18O]geranyl pyrophosphate and with (1E)-(+/-)-[1-3H,3-18O]linalyl pyrophosphate gave the appropriate (+)- or (-)-bornyl pyrophosphates, which were hydrolyzed in situ to the corresponding borneols. Analysis of the derived benzoates by mass spectrometry demonstrated each of the product borneols to possess an 18O enrichment essentially identical with that of the respective acyclic precursor. The absence of P alpha-P beta interchange and the complete lack of positional 18O isotope exchange of the pyrophosphate moiety are compatible with tight ion pairing of intermediates in the coupled isomerization-cyclization of geranyl pyrophosphate and establish a remarkably tight restriction on the motion of the transiently generated pyrophosphate anion with respect to its cationic terpenyl reaction partner.

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An experimental animal model of hibernating myocardium is presented. Sixteen animals were initially prepared of which seven were selected for final review. Hearts were instrumented in two separate surgical procedures such that maximum phasic flow velocity in the left anterior descending (LAD) coronary artery was reduced by 50% and followed over 1 wk. Regional shortening declined at 1 wk to 62% of aerobic values (P less than 0.048) and did not improve over 2 h reperfusion. Metabolic determinations, obtained after 1 wk of coronary stenosis and immediately sampled before and after release of the LAD flow constrictor, showed no evidence of acidosis, hypercarbia, or an inability to extract oxygen at the tissue level. Thereafter, during the 2-h reperfusion period, hearts were able to respond to dobutamine (10 micrograms/kg infusion over 1 min) challenge with an appropriate shift in an end-systolic length estimate of contractility. Mitochondrial respiration at the conclusion of the studies in the reperfused bed demonstrated near normal recovery compared with aerobic values. None of the seven hearts showed gross evidence of infarction and only one heart was noted to have a few microfocal changes of healing infarction. Thus a new model of coronary stenosis is presented, which affected substantial reductions in mechanical function consistent with the concepts of hibernating myocardium. These mechanical events were not associated with marked metabolic abnormalities, reflecting advanced ischemia or mitochondrial dysfunction and could be transiently improved with inotropic stimuli. This model may prove beneficial as a tool in understanding mechanistic events underlying the hibernating heart.

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Studies were conducted in extracorporeally perfused, intact, working pig hearts to determine whether, in heart muscle, trace-labeled deoxyglucose serves as an accurate marker of glycolytic flux in reperfusion after exposures to mild to moderate regional ischemia. In the main study, two groups of hearts were compared, as distinguished by levels of glucose in the whole-blood perfusate (euglycemic hearts [