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The kinetic properties of a continuous enzyme reactor containing rabbit muscle lactate dehydrogenasc, horse liver alcohol dehydrogenase and poly(ethylene glycol)abound NAD (PEG-NAD) were investigated experimentally and theoretically. The enzymes and PEG-NA!) were retained in the reactor with an ultrafiltration membrane, and the substrates (pyruvate and ethanol) were fed continuously. The reactions of the dehydrogenases were coupled by the recycling of the cofactor. The steady-state concentration of L-lactate, one of the products, was measured under different experimental conditions and compared with the corresponding theoretical value. The theoretical value was calculated based on a simplified ordered bi-bi mechanism for the individual enzyme reactions, of which kinetic constants were determined by independent kinetic studies. Differences were found between the kinetic constants of the enzymes for NAID(H) and PEG-NAD(H). The steady-state values obtained by continuous operation were lower than those calculated, possibly due to the simplification made for the kinetic model; but there was general agreement between them in the dependence on the experimental conditions. The steady-state behavior of the enzyme reactor was explained semi-quantitatively by the simple kinetic model. [ABSTRACT FROM AUTHOR]

Preanesthetic evaluation is essential for the perioperative period. We report 2 preoperative patients with benign disease, whose preoperative chest radiography revealed intrathoracic malignant tumors. Case 1: A woman in her eighties with vascular necrosis of the femoral head was scheduled for bipolar hip arthroplasty under general anesthesia. On preanesthetic evaluation, widened mediastinum was detected on preoperative chest radiography. Instead of the scheduled operation, she underwent thoracoscopic surgery under general and epidural anesthesia. She was diagnosed with malignant thymoma. Case 2: A woman in her thirties with bilateral oviduct obstruction was scheduled for laparoscopic surgery. On preanesthetic evaluation, right middle lung lesion was detected. She underwent thoracoscopic biopsy under general and epidural anesthesia, and was diagnosed with malignant lymphoma. The result of preanesthetic chest radiography is reported to change the perioperative treatment only in 0.1%; our cases indicate the importance of preanesthetic evaluation of chest radiography in detecting possible underlying disease in the preoperative patient.