Mechanistic studies of the tyrosinase-catalyzed oxidative cyclocondensation of 2-aminophenol to 2-aminophenoxazin-3-one.

Tyrosinase (EC 1.14.18.1) catalyzes the monophenolase and diphenolase reaction associated with vertebrate pigmentation and fruit/vegetable browning. Tyrosinase is an oxygen-dependent, dicopper enzyme that has three states: Emet, Eoxy, and Edeoxy. The diphenolase activity can be carried out by both the met and the oxy states of the enzyme while neither mono- nor diphenolase activity results from the deoxy state. In this study, the oxidative cyclocondensation of 2-aminophenol (OAP) to the corresponding 2-aminophenoxazin-3-one (APX) by mushroom tyrosinase was investigated. Using a combination of various steady- and pre-steady state methodologies, we have investigated the kinetic and chemical mechanism of this reaction. The kcat for OAP is 75 ± 2s(-1), K(OAP)M = 1.8 ± 0.2mM, K(O2)M =25 ± 4 µM with substrates binding in a steady-state preferred fashion. Stopped flow and global analysis support a model where OAP preferentially binds to the oxy form over the met (k7 ≫ k1). For the met form, His269 and His61 are the proposed bases, while the oxy form uses the copper-peroxide and His61 for the sequential deprotonation of anilinic and phenolic hydrogens. Solvent KIEs show proton transfer to be increasingly rate limiting for kcat/K(OAP)M as [O2] → 0 µM (1.38 ± 0.06) decreasing to 0.83 ± 0.03 as [O2] → ∞ reflecting a partially rate limiting µ-OH bond cleavage (E met) and formation (E oxy) following protonation in the transition state. The coupling and cyclization reactions of o-quinone imine and OAP pass through a phenyliminocyclohexadione intermediate to APX, forming at a rate of 6.91 ± 0.03 µM(-1)s(-1) and 2.59E-2 ± 5.31E-4s(-1). Differences in reactivity attributed to the anilinic moiety of OAP with o-diphenols are discussed.

Dermatologic adverse events in pediatric patients receiving targeted anticancer therapies: a pooled analysis.

BACKGROUND: The dermatologic adverse events (AEs) of various molecularly targeted therapies are well-described in adult cancer patients. Little has been reported on the incidence and clinical presentation of such AEs in pediatric patients with cancer. To address this gap, we analyzed the dermatologic AEs reported across clinical trials of targeted anticancer therapies in pediatric patients. PROCEDURES: We conducted an electronic literature search (PubMed, American Society of Clinical Oncology annual meetings' abstracts, ClinicalTrials.gov, NCI's Pediatric Oncology Branch webpage) to identify clinical trials involving targeted anticancer therapies that reported dermatologic AEs in their safety data. Studies were limited to the pediatric population, monotherapy trials (oncology), and English language publications. RESULTS: Pooled data from 19 clinical studies investigating 11 targeted anticancer agents (alemtuzumab, rituximab, imatinib, dasatinib, erlotinib, vandetanib, sorafenib, cabozantinib, pazopanib, everolimus, and temsirolimus) were analyzed. The most frequently encountered dermatologic AEs were rash (127/660; 19%), xerosis (18/100; 18%), mucositis (68/402; 17%), and pruritus (12/169; 7%). Other AEs included pigmentary abnormalities of the skin/hair (13%), hair disorders (trichomegaly, hypertrichosis, alopecia, and madarosis; 14%), urticaria (7%), palmoplantar erythrodysesthesia (7%), erythema, acne, purpura, skin fissures, other 'unknown skin changes', exanthem, infection, flushing, telangiectasia, and photosensitivity. CONCLUSION: This study describes the dermatologic manifestations of targeted anticancer therapy-related AEs in the pediatric population. Since these AEs are often associated with significant morbidity, it is imperative that pediatric oncologists be familiar with their recognition and management, to avoid unnecessary dose modifications and/or termination, and to prevent impairments in patients' quality of life.

Role of simulation in preparation for the care of conjoined twins-prenatal preparation to separation.

The rarity and complexity of conjoined twins creates a challenge for prenatal planning, delivery resuscitation, and postnatal management. The modality of simulation offers a safe practice environment for a multidisciplinary group consisting of neonatal providers, nurses, respiratory therapists, and surgeons in which to identify and address clinical decision making, procedural, and behavioral plans related to routine and emergency care of these patients. Simulation-based clinical rehearsals (SbCR) provide a unique opportunity to prepare for rare, complex, and patient specific clinical procedures and scenarios. This primer serves as a revisable tool that promotes the development of proper timing, technique, and confidence to allow for an optimal setting for delivery of safe care to conjoined twins. We describe the development and implementation of a simulation approach to all stages of care from the antenatal life, NICU care, to preparation for postnatal separation of conjoined twins.

Efforts to improve subsequent treatment of cardiovascular risk factors in older patients with diabetes hospitalized for a cardiac event.

OBJECTIVE: To improve the treatment of risk factors of cardiovascular disease (CVD) for older patients with diabetes after a cardiac event by using a low-literacy reminder card describing these risk factors in community settings. STUDY DESIGN: A multicenter, randomized, interventional study. METHODS: Patients aged 55 years or older with diabetes hospitalized with an acute myocardial infarction, congestive heart failure exacerbation, or unstable angina were eligible to enter the study. Control and experimental patients were recruited from 4 sites and were enrolled in the study before discharge from the hospital. Experimental subjects received education and a reminder card describing risk factors of CVD. They were instructed to discuss the risk factors described on the reminder card with their primary care physician on their first appointment after discharge. Control subjects did not receive any intervention but were given consent to be able to review their charts. RESULTS: One hundred sixty patients completed the study, 82 in the control group and 78 in the experimental group. At the end of the study there was no difference in blood pressure control, lipid levels, and glycosylated hemoglobin levels between the control and experimental patients. Aspirin use and ACE inhibitor use were found to be significantly higher in the control group (P = .001 and .03, respectively). CONCLUSIONS: Reminder cards given to patients to discuss with their primary care providers in community settings did not improve process measures of CVD risk in patients with documented CVD and diabetes. Other approaches will be needed to improve the treatment of risk factors in these high-risk patients.

The impact of using a low-literacy patient education tool on process measures of diabetes care in a minority population.

This study evaluated the current level of diabetes care in three county clinics serving an underserved minority population and determined if a low-literacy, diabetes reminder card would enhance certain diabetes process care measures. Patients from two intervention sites were given the low-literacy, diabetes reminder card. Two-hundred-nineteen patients (87%) showed the card to their provider, and 209 charts were reviewed. American Diabetes Association guidelines had been met 37%, 71%, and 41% for foot exam, and urine and lipid tests, respectively, at the time the card was given to the patients. Of the patients who needed a foot exam, urine test, and lipid panel that day (based on ADA guidelines), 48%, 67%, and 35% received them, respectively (card effect). In the third (nonintervention) site, charts of 218 patients were reviewed. Guidelines met were 95%, 89%, and 45% for foot exam, urine and lipid tests, respectively. Interestingly, standardized progress notes containing the first two (but not the third) process measures were used at this site. We conclude that although low-literacy reminder cards did improve the ordering of process measures somewhat, they were not as effective as the utilization of progress forms with specific diabetes-related measures.