Oxidized Amino Acids in Lens Protein with Age: Measurement of o-Tyrosine and Dityrosine in the Aging Human Lens

The concentrations of ortho-tyrosine (o-Tyr) and dityrosine (DT) were measured in noncataractous human lenses in order to assess the role of proteinoxidation reactions in the aging of lens proteins. The measurements were conducted by selected ion monitoring-gas chromatography/mass spectrometry using deuterium-labeled internal standards, which provided both high sensitivity and specificity for the quantitation of o-Tyr and DT. Between ages 1 and 78 years, the o-Tyr concentration in lens proteins varied from 0.3 to 0.9 mmol of o-Tyr/mol of Phe (n = 19), while DT ranged from 1 to 3 mumol of DT/mol of Tyr (n = 30). There were no significant changes in levels of o-Tyr with lens age. There was a statistically significant, but only slight, increase in DT in lens proteins with age (approximately 33% increases between ages 1 and 78, r = 0.5, p \u3c 0.01). At the same time, totalprotein fluorescence, measured at DT wavelengths (Ex = 317 nm, Em = 407 nm), increased 11-fold between ages 1 and 78 and correlated strongly with age (r = 0.82, p \u3c 0.0001). Although the fluorescence maxima of lens proteins were similar to those of DT, DT accounted for less than 1% of the DT-like fluorescence in lens protein at all ages. These observations indicate that oxidation of Phe and Tyr plays a limited role in the normal aging of lens proteins in vivo

Are faculty predictions or item taxonomies useful for estimating the outcome of multiple-choice examinations?

The purpose of this study was to evaluate whether multiple-choice item difficulty could be predicted either by a subjective judgment by the question author or by applying a learning taxonomy to the items. Eight physiology faculty members teaching an upper-level undergraduate human physiology course consented to participate in the study. The faculty members annotated questions before exams with the descriptors easy, mod- erate, or hard and classified them according to whether they tested knowledge, comprehension, or application. Overall analysis showed a statistically significant, but relatively low, correlation between the intended item difficulty and actual student scores (ρ =-0.19, P\u3c 0.01), indicating that, as intended item difficulty increased, the result- ing student scores on items tended to decrease. Although this expected inverse relationship was detected, faculty members were correct only 48% of the time when estimating difficulty. There was also significant individual variation among faculty members in the ability to predict item difficulty (χ2= 16.84, P = 0.02). With regard to the cognitive level of items, no significant correlation was found between the item cognitive level and either actual student scores (ρ=0.09, P = 0.14) or item discrimination (ρ=0.05, P = 0.42). Despite the inability of faculty members to accurately predict item difficulty, the examina- tions were of high quality, as evidenced by reliability coefficients (Cronbach\u27s α) of 0.70-0.92, the rejection of only 4 of 300 items in the postexamination review, and a mean item discrimination (point biserial) of 0.37. In conclusion, the effort of assigning annotations describing intended difficulty and cognitive levels to multiple-choice items is of doubtful value in terms of controlling examination difficulty. However, we also report that the process of annotating questions may enhance examination validity and can reveal aspects of the hidden curriculum. © 2011 The American Physiological Society

Outcomes of Limb-Sparing Surgery Using Two Generations of Metal Endoprosthesis in 45 Dogs With Distal Radial Osteosarcoma. A Veterinary Society of Surgical Oncology Retrospective Study

OBJECTIVE: To report outcomes in dogs with distal radial osteosarcoma (OSA) treated with metal endoprosthesis limb-sparing surgery and compare outcomes between 2 generations of endoprosthesis. STUDY DESIGN: Multi-institutional retrospective case series. ANIMALS: Forty-five dogs with distal radial OSA treated with endoprosthesis and chemotherapy. METHODS: Data of dogs treated with either first-generation endoprosthesis (GEN1) or second-generation endoprosthesis (GEN2) were sourced from medical records and radiographs. Surgical outcomes included postoperative lameness assessment and the presence, severity, and time to onset of complications. Oncologic outcomes included presence of local recurrence or metastasis, time to onset of local recurrence, metastasis-free interval (MFI), and survival time. Results for surgical and oncologic outcomes were compared between GEN1 and GEN2. RESULTS: Twenty-eight dogs received GEN1 and 17 dogs received GEN2. There were 39 complications (96%, 14 minor, 29 major) including infection (78%), implant-related complication (36%), and local recurrence (24%). Metastatic frequency was 67% and median MFI was 188 days (95% confidence interval [CI]: 126-250 days). Survival time ranged from 34 days to 6.1 years with a median of 289 days (95% CI: 207-371 days). There was no significant difference in complication severity, frequency, time to complication, MFI, or survival time between dogs receiving GEN1 and GEN2. CONCLUSION: There was no significant difference in outcomes between dogs receiving GEN1 and GEN2 for limb-sparing surgery of the radius. Metastatic frequency and survival time for metal endoprosthesis were similar to that of amputation with curative intent chemotherapy