Maleylacetone cis-trans-isomerase: affinity chromatography on glutathione-bound sepharose. Two-substrate-binding sequence from inhibition patterns

Maleylacetone cis-trans-isomerase isolated from Vibrio 01 binds glutathione strongly; Km = 1.4 X 10(-4) M. Oxidized glutathione and S-methylglutathione are competitive inhibitors, KI = 9.4 X 10(-4) and 1.2 X 10(-3) M, respectively. Based on these interactions, three different glutathione-bound agarose affinity adsorbents were synthesized and tested. Affinity chromatography of the isomerase with one of these affords 70- to 100-fold purifications. In separate syntheses, portions of the affinity arm were prepared and examined as to their inhibitory properties in the enzyme-catalyzed reaction. The fragment, containing glutathione bound through its sulfur to the carbon chain, is a powerful competitive inhibitor for glutathione (KI = 6 X 10(-5) M). The results described suggest that the isomerase binds glutathione through the backbone of the tripeptide and that the thiol group is required for activity. The initial velocity patterns of the enzyme-catalyzed reaction resulting from simultaneous variation of glutathione and maleylacetone concentrations were examined in the absence and presence of inhibitors resembling glutathione. The observed kinetic patterns suggest an ordered sequence of binding maleylacetone first followed by glutathione.     

Laser ablation ICP-MS analysis of the radial distribution of lead in the femur of Alligator mississippiensis

A laser ablation ICP-MS technique has been used to examine the radial distribution of lead in transverse sections of alligator femur. Annual bone growth in the femur results in the deposition of incremental layers of calcified tissue at the periphery of existing bone. Patterns of lead concentration within these layers provide a record of time-dependent accumulation from which exposure history can potentially be deduced. Femur specimens obtained from captive-reared alligators exhibited levels of lead accumulation that were entirely consistent with previously documented clinical signs of lead intoxication. In contrast, femurs obtained from wild alligators contained only minor amounts of lead that were likely accumulated as a result of incidental exposure.     

Multiscale modeling of composite materials: a roadmap towards virtual testing

A bottom-up, multiscale modeling approach is presented to carry out high-fidelity virtual mechanical tests of composite materials and structures. The strategy begins with the in situ measurement of the matrix and interface mechanical properties at the nanometer-micrometer range to build up a ladder of the numerical simulations, which take into account the relevant deformation and failure mechanisms at different length scales relevant to individual plies, laminates and components. The main features of each simulation step and the information transferred between length scales are described in detail as well as the current limitations and the areas for further development. Finally, the roadmap for the extension of the current strategy to include functional properties and processing into the simulation scheme is delineated.     

Negative predictive value of imaging-guided abdominal biopsy results: cytologic classification and implications for patient management

OBJECTIVE: Our purpose was to assess the negative predictive value of imaging-guided abdominal biopsy results and correlate it with cytology classification, lesion size, needle gauge, and cancer history. MATERIALS AND METHODS: A retrospective study was performed of 100 patients with proven diagnoses who had undergone imaging-guided abdominal biopsies showing no cells that were malignant or suspicious for malignancy. Specimens were classified as normal or benign, nondiagnostic, or atypical. Negative predictive value was calculated for each cytologic category, lesion size, needle gauge, and cancer history. Logistic regression analysis was performed to allow us to identify predictors of false-negative results. RESULTS: Overall negative predictive value was 67%. Other negative predictive values were normal or benign result, 78%; nondiagnostic result, 66%; and atypical result, 29%. Negative predictive value was greater when the lesion was large (> or =3 cm) (p = .031). Logistic regression analysis allowed us to predict a 9.3% chance of a false-negative result for a specimen of normal or benign cytology that was taken from a large lesion in a patient with no cancer history but an 87% chance of a false-negative when a specimen of atypical cytology was taken from a small (<3 cm) lesion in a patient with a cancer history. CONCLUSION: Imaging-guided abdominal biopsy specimens containing atypical cells should be viewed with caution. In patients without cancer, if a lesion is large and the specimen contains normal target organ or benign cells, the likelihood of a false-negative result may be low enough that imaging surveillance at appropriate intervals may be sufficient.     

AIDS, homosexuality, public opinion, and changing correlates over time

Comparing data from national Los Angeles Times surveys allows for an examination of changes in attitudes toward AIDS in 1985, when the crisis was first coming to public attention, and in 1987, when public opinion had a greater opportunity to stabilize. The primary predictors of public opinion did not change from 1985 to 1987, but there were somewhat less irrational attitudes among most segments of the population by 1987. However, among those who were conservative on the issue of homosexuality, personal concern for AIDS fell and support for repression grew.