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1.
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. 相似文献
2.
OL Lopez RP Brenner JT Becker RF Ulrich F Boller ST DeKosky 《Canadian Metallurgical Quarterly》1997,48(6):1521-1525
We examined whether either psychotic features (e.g., delusions and hallucinations) or EEG abnormalities are associated with more rapid progression of Alzheimer's disease (AD). AD patients with psychosis have exhibited more EEG abnormalities than those without psychosis, and both abnormal EEG and psychosis have been noted to be predictors of functional and cognitive decline in AD. Ninety-five probable AD patients participating in a longitudinal study of dementia had an EEG and a semistructured psychiatric interview at baseline. Using EEG spectral analysis, we classified records as normal/abnormal based on the parasagittal mean frequency. Patients with abnormal EEGs were more functionally (e.g., Blessed Rating Scale for activities of daily living) and cognitively (e.g., Mini-Mental State) impaired than patients with normal EEG. AD patients with psychosis were only more functionally impaired than patients without psychosis. A two-factor analysis showed no interaction between abnormal EEG and psychosis. In addition, using a Cox proportional hazard model adjusted for age and education, the presence of an abnormal EEG or psychotic symptom at study entry was associated with higher risk of reaching severe cognitive and functional impairment during follow-up. Neither abnormal EEG nor the presence of psychosis predicted death. These results indicate that both abnormal EEG and psychosis are independent predictors of disease progression but not of physical survival. 相似文献
3.
A transformational approach for proving termination of parallel logic programs such as GHC programs is proposed. A transformation
from GHC programs to term rewriting systems is developed; it exploits the fact that unifications in GHC-resolution correspond
to matchings. The termination of a GHC program for a class of queries is implied by the termination of the resulting rewrite
system. This approach facilitates the applicability of a wide range of termination techniques developed for rewrite systems
in proving termination of GHC programs. The method consists of three steps: (a) deriving moding information from a given GHC
program, (b) transforming the GHC program into a term rewriting system using the moding information, and finally (c) proving
termination of the resulting rewrite system. Using this method, the termination of many benchmark GHC programs such as quick-sort,
merge-sort, merge, split, fair-split and append, etc., can be proved.
This is a revised and extended version of Ref. 12). The work was partially supported by the NSF Indo-US grant INT-9416687
Kapur was partially supported by NSF Grant nos. CCR-8906678 and INT-9014074.
M. R. K. Krishna Rao, Ph.D.: He currently works as a senior research fellow at Griffith University, Brisbane, Australia. His current interests are in
the areas of logic programming, modular aspects and noncopying implementations of term rewriting, learning logic programs
from examples and conuterexamples and dynamics of mental states in rational agent architectures. He received his Ph.D in computer
science from Tata Institute of Fundamental Research (TIFR), Bombay in 1993 and worked at TIFR and Max Planck Institut für
Informatik, Saarbrücken until January 1997.
Deepak Kapur, Ph.D.: He currently works as a professor at the State University of New York at Albany. His research interests are in the areas
of automated reasoning, term rewriting, constraint solving, algebraic and geometric reasoning and its applications in computer
vision, symbolic computation, formal methods, specification and verification. He obtained his Ph.D. in Computer Science from
MIT in 1980. He worked at General Electric Corporate Research and Development until 1987. Prof. Kapur is the editor-in-chief
of the Journal of Automated Reasoning. He also serves on the editorial boards of Journal of Logic Programming, Journal on
Constraints, and Journal of Applicable Algebra in Engineering, Communication and Computer Science.
R. K. Shyamasundar, Ph.D.: He currently works as a professor at Tata Institute of Fundamental Research (TIFR), Bombay. His current intersts are in
the areas of logic programming, reactive and real time programming, constraint solving, formal methods, specification and
verification. He received his Ph.D in computer science from Indian Institute of Science, Bangalore in 1975 and has been a
faculty member at Tata Institute of Fundamental Research since then. He has been a visiting/regular faculty member at Technological
University of Eindhoven, University of Utrecht, IBM TJ Watson Research Centre, Pennsylvania State University, University of
Illinois at Urbana-Champaign, INRIA and ENSMP, France. He has served on (and chaired) Program Committees of many International
Conferences and has been on the Editorial Committees. 相似文献
4.
A strong motivation for insertion of optical interconnects in short-distance applications such as chip-to-chip or back-plane communication, apart from high bit rates, is their potential to achieve these bit rates at low power compared to the currently prevalent copper based interconnects. Thus, it is imperative to construct design methodologies which minimize the total optical link power dissipation. We present one such methodology, where we optimize the quantum-well modulators to minimize the power dissipation in modulator-based optical interconnects. In the first part of the paper, the focus is on obtaining the optimal modulator metrics [contrast ration (CR) and insertion loss], which yield the lowest total power (receiver and the modulator). The trends are studied as a function of the input laser power and bit rate. Having obtained the desirable modulator metrics and the corresponding power dissipation, in the second part, the focus is on the feasibility of these metrics in the light of voltage swing constraints. The biggest concern with the modulator based optical link is the low CR, especially at low voltage swing. While studying these concerns, we also provide insight into the physical design of the modulator including, its intrinsic region thickness, pre-bias voltage, and the size and the number of quantum-wells. Specifically, we outline the method to obtain the design parameters, which allows minimum power dissipation with the least laser power. This ultimately yields higher aggregate I/O bandwidth for chip to chip communication in power limited chips. 相似文献
5.
6.
OBJECTIVE: To evaluate the effect of preoperative localization studies on the surgical management of patients with primary hyperparathyroid disease (PHPT). SUMMARY BACKGROUND DATA: Reported cure rates of initial surgical exploration for PHPT are close to 95%. Preoperative localization studies are frequently obtained to improve surgical success and decrease operative time. METHODS: Initial cervical exploration was performed in 113 patients with PHPT from 1981 to 1993. Twenty-four patients (21%) had surgery without preoperative localization studies. The remaining 89 patients (79%) had 132 noninvasive preoperative localization studies. Success of the localization studies in tumor localization, pathologic findings, postoperative serum calcium levels, and operative times were compared. Patient costs of the studies were calculated. RESULTS: Disease was identified during operation in 23 of 24 patients (96%) having cervical exploration without preoperative localization studies, and they had normal calcium levels after surgery. Eighty-seven of 89 patients (98%) having preoperative localization studies were surgically cured. The highest sensitivity rate (60%) and highest positive predictive value (79%) of the localization studies were found with thallium-technetium scintiscanning. Average cost of the localization studies was $901 per patient. Combination studies were obtained in 32 patients at an average cost of $1,314 per patient without improving sensitivity. Mean operating time did not differ for localized and nonlocalized patients. CONCLUSIONS: Preoperative localization studies did not improve parathyroid localization or cure rate and did not substantially shorten operating time in initial cervical exploration for PHPT. The economic burden of routine preoperative localization studies in these patients is not justified. 相似文献
7.
LJ Jones RH Upson RP Haugland N Panchuk-Voloshina M Zhou RP Haugland 《Canadian Metallurgical Quarterly》1997,251(2):144-152
We have prepared casein conjugates of two BODIPY dyes for use as fluorogenic protease substrates in homogeneous assays. Both conjugates are labeled to such an extent that the dyes are efficiently quenched in the protein, yielding virtually nonfluorescent substrate molecules. These fluorogenic substrates release highly fluorescent BODIPY dye-labeled peptides upon protease digestion, with fluorescence increases proportional to enzyme activity. These quenched substrates are suitable for the continuous assay of enzymatic activity using standard fluorometers, filter fluorometers, or fluorescence microplate readers using either fluorescein excitation and emission wavelengths to measure BODIPY FL casein hydrolysis or Texas Red wavelengths to detect proteolysis of BODIPY TR-X casein. Most current techniques for detecting protease activity, such as the fluorescein thiocarbamoyl casein (FTC-casein) protease assay, require extensive manipulation, including separation steps, and are therefore labor intensive and error-prone. In comparison, we found the BODIPY dye-labeled casein protease assays to be simple and precise and to have greater sensitivity and a broader dynamic range of detection than the FTC-casein assay. We were able to sensitively detect the activities of a wide variety of enzymes with these new substrates, including serine, acid, sulfhydryl, and metalloproteases. We also found the assay suitable for quantitating protease inhibitor concentrations and for real-time analysis of proteolysis. 相似文献
8.
9.
RJ Linnola RP Happonen OH Andersson E Vedel AU Yli-Urpo U Krause L Laatikainen 《Canadian Metallurgical Quarterly》1996,63(4):471-478
The current problem with keratoprosthesis is the ingrowth of corneal or conjunctival epithelium into the anterior chamber. This may lead to infections and extrusion of the prosthesis as well as to the development of retroprosthetic membrane and secondary glaucoma. Glass-ceramic coated and uncoated titanium has been tested as material for the keratoprosthesis to prevent epithelial ingrowth. Twenty-two Supra-Descemet's membrane keratoprostheses were inserted in the eyes of 22 rabbits for 1, 2, 4, 8, or 12 months. The prosthesis had an optic part made of polymethylmetacrylate (PMMA). The support for the optic part and the flange of the prosthesis were made of titanium. Eleven of the prostheses were coated with glass-ceramic. The histological sections of the enucleated eyes were prepared through the central part of the cornea and the prosthesis using a cutting-grinding method. The histological analysis was made on both halves of the implants separately giving two analysis areas in each eye. All 11 titanium prostheses were retained for the time period planned. Two glass-ceramic coated prostheses were lost at 2 and 4 weeks, respectively. This was caused by difficulties at surgery due to a thick coating. These eyes were excluded from the histological analysis. No significant ingrowth of epithelium was seen in 15/18 (83%) and in 16/22 (73%) of the analysed areas of the glass-ceramic coated and titanium prostheses, respectively. Titanium appears to be a suitable material for the keratoprosthesis. The ingrowth of the epithelium may be hindered further by coating the titanium with bioactive glass-ceramic. 相似文献
10.