Reaction of cytochrome P450 with cumene hydroperoxide: ESR spin-trapping evidence for the homolytic scission of the peroxide O-O bond by ferric cytochrome P450 1A2

ESR spin trapping was used to investigate the reaction of rabbit cytochrome P450 (P450) 1A2 with cumene hydroperoxide. Cumene hydroperoxide-derived peroxyl, alkoxyl, and carbon-centered radicals were formed and trapped during the reaction. The relative contributions of each radical adduct to the composite ESR spectrum were influenced by the concentration of the spin trap. Computer simulation of the experimental data obtained at various 5,5-dimethyl-1-pyrroline N-oxide (DMPO) concentrations was used to quantitate the contributions of each radical adduct to the composite ESR spectrum. The alkoxyl radical was the initial radical produced during the reaction. Experiments with 2-methyl-2-nitrosopropane identified the carbon-centered adducts as those of the methyl radical, hydroxymethyl radical, and a secondary carbon-centered radical. The reaction did not require NADPH-cytochrome P450 reductase or NADPH. It is concluded that the reaction involves the initial homolytic scission of the peroxide O-O bond to produce the cumoxyl radical. Methyl radicals were produced from the beta-scission of the cumoxyl radical. The peroxyl adduct was not observed in the absence of molecular oxygen. We conclude that the DMPO peroxyl radical adduct detected in the presence of oxygen was due to the methylperoxyl radical formed by the reaction of the methyl radical with oxygen. At a higher P450 concentration, a protein-derived radical adduct was also detected.     

One or two incisions for nephroureterectomy in transitional cell renal pelvis tumours

A retrospective study comprising 18 patients with transitional cell renal pelvis tumours (TCPT) was carried out to evaluate the results after two different surgical procedures for nephroureterectomy. The kidney was removed by a flank incision and the lower part of the ureter by either an incision in the lower part of the abdomen or intussusception of the ureter followed by transurethral resection of the ureteral orifice. Eight patients were subjected to nephroureterectomy by means of two incisions and another eight patients underwent a simple nephrectomy followed by ureteral intus-susception and transurethral resection. Two patients received other treatments. After nephroureterectomy with a separate incision for ureterectomy, the average hospital stay was 12 days, compared with 7.5 days in patients operated upon with only one abdominal incision. Recurrence of tumour or survival was not significantly different in the two groups.     

Applications of a super element model for non-linear analysis of stiffened box structures

Numerical investigations are carried out to verify the new super element model developed in Reference 1 for non-linear analysis of stiffened box structures. The results presented here are obtained from a variety of examples which are chosen to illustrate the accuracy and convergence of the model in various applications. Good agreement is obtained for most of the problems considered and the present formulation is found to be accurate and economical for preliminary engineering design.     

Kinetics of hydantoin formation

The reaction of lignite in a slagging gasifier produces reactants which in turn form 5,5-dimethylhydantoin (DMH) as a major constituent in the condensate water. Variations in plant operating conditions made it impossible to accurately study the kinetics of formation of DMH in the actual gasifier water, and thus a model system was chosen. The reaction of acetone cyanohydrin in the presence of excess ammonium carbonate at concentrations approaching those obtained in the condensate water were studied at 50,70, and 90 °C. Secondorder kinetics were obeyed, and the pseudo second-order rate constants at the respective temperatures were 1.86, 3.6, and 4.62 dm³ mol^{? 1} h^{? 1}. Independent variation of the concentration of either acetone, cyanide, ammonia or carbonate gave results consistent with the interpretation that the formation of DMH is first order in all reactants: rate of formation of DMH = k[acetone][HCN][NH₃][CO₂]. The pseudo second-order rate constant is a complex rate constant including several rapid equilibria. A mechanism consistent with the kinetic data is presented.     

The transjugular stent implantation for the treatment of malignant portal and hepatic vein obstruction in cancer patients

BACKGROUND: The increase in portal vascular resistance is a significant complication of metastatic disease to the liver or locally advanced cancer, e.g., biliary cancer. PATIENTS AND METHODS: This paper describes the successful palliative treatment of two cancer patients with portal hypertension presenting with the symptoms of tense ascites, mesenteric congestion, and severe variceal bleeding. By creating a stenttract between a hepatic vein and a main branch of the portal vein and/or by placing an extendable stent into the portal vein, the transjugular intrahepatic portosystemic stent-shunt (TIPS) technique was used to decompress the portovascular system. RESULTS: The TIPS-technique offers a new, safe and effective palliation for malignant portal hypertension. In both patients, the symptoms of the portal hypertension disappeared after the procedure. This was accompanied by a significant improvement of the patients performance status allowing an early ambulation. CONCLUSION: Our findings demonstrate the feasibility and effectiveness of the TIPS procedure as a minimal invasive treatment for portal vein decompression in selected tumor patients.     

Stereotactic radiosurgery of malignant and benign intracranial lesions utilizing a patient rotator

The objective of this survey was to demonstrate whether a primary care track internal medicine residency program emphasizing community-based health care of the urban sick poor trains physicians who will continue to practice in general internal medicine or similar fields. Thirty-five primary care residents (100% of graduates) who trained from 1976 through 1993 in the Adult Primary Care Track of the Internal Medicine Residency Program at St. Vincent's Hospital, New York were used as participants.