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771.
WS Kubal 《Canadian Metallurgical Quarterly》1997,18(6):423-436
Categorizing globe lesions based on clinical presentation can suggest a short list of diagnostic possibilities. Imaging of the globe with ultrasound, CT and MRI is presented with a focus on key differential points. The radiologist can then efficiently tailor the examination in order to differentiate among the diagnostic possibilities. 相似文献
772.
IR spectra directly probe specific vibrators in bovine heart cytochrome c oxidase, yielding quantitative as well as qualitative information on structures and reactions at these vibrators. C-O IR spectra reveal that CO binds to Fe2+ a3 as two conformers each in isolated immobile environments sensitive to Fea and/or CuA oxidation state but remarkably insensitive to pH, medium, anesthetics, and other factors that affect activity. C-N IR spectra reveal that the one CN- that binds to fully and partially oxidized enzyme can be in three different structures. These structures vary in relative amounts with redox level, thereby reflecting dynamic electron exchange among Fea, CuA, and CuB with associated changes in protein conformation of likely significance in O2 reduction and H(+)-pumping. Azide IR spectra also reflect redox-dependent long-range effects. The amide I IR bands, due to C-O vibrators of peptide linkages and composed of multiple bands derived from different secondary structures, reveal high levels of alpha-helix (approximately 60%) and subtle changes with redox level and exposure to anesthetics. N2O IR spectra reveal that these anesthetic molecules at clinically relevant levels occupy three sites of different polarity within the enzyme as the enzyme is reversibly, but only partially, inhibited. 相似文献
773.
Aldose reductase and aldehyde reductase were purified to homogeneity from multiple samples of human kidney cortex and medulla. A single form of aldose reductase is expressed in kidney that is kinetically and immunochemically indistinguishable from aldose reductase expressed in other human tissues. The results support the conclusion that there is a single human aldose reductase, and that aldose reductase is expressed in a reduced form, characterized by high sensitivity to aldose reductase inhibitors and ability to catalyze the reduction of glucose. Aldose reductase is easily oxidized to a form that is insensitive to aldose reductase inhibitors and unable to catalyze the reduction of glucose. This form does not appear to exist in vivo, even in kidney from diabetics. There is wide variation in the level of expression of aldose reductase in kidney, especially in cortex. The immunochemically separate but similar aldehyde reductase is also expressed in kidney as a single enzyme indistinguishable from aldehyde reductase from other human tissues. Aldehyde reductase levels exceed those of aldose reductase, both in cortex and medulla. 相似文献
774.
WS Ewart 《Canadian Metallurgical Quarterly》1997,16(2):57-61; quiz 86-7
775.
In contrast to the F1-ATPases from bovine mitochondria and the thermophilic Bacillus PS3, which are reversibly inhibited by dequalinium in the absence of irradiation, the Mg2+-ATPase activity of heat- or dithiothreitol-activated chloroplast F1 (CF1) from spinach chloroplasts is slightly stimulated by dequalinium. Conversely, dequalinium is a partial inhibitor (maximal inhibition is 85-90%) of the Ca2+-ATPase of CF1 activated by heat, dithiothreitol, or octylglucoside. The Mg2+- and Ca2+-ATPase activities of CF1 respond differently in the presence of lauryl dimethylamine oxide (LDAO) in the assay medium. Whereas the Mg2+-ATPase activity of heat- or dithiothreitol-activated CF1 is stimulated up to 14-fold by increasing concentrations of LDAO, the Ca2+-ATPase is inhibited in a biphasic manner by increasing concentrations of LDAO. In the presence of LDAO, dequalinium does not stimulate the heat-activated Mg2+-ATPase over that promoted by LDAO alone. That dequalinium slightly stimulates Mg2+-ATPase activity although it inhibits Ca2+-ATPase activity can be reconciled by assuming that dequalinium binds to two sites in CF1, a stimulatory site that also binds LDAO and an inhibitory site. By acting as a partial inhibitor of the Mg2+-ATPase activity that it activates, the combined effect of dequalinium is modest stimulation. Irradiation of heat- or dithiothreitol-activated CF1 or the alpha3beta3gamma subcomplex of CF1 in the presence of 12 microM dequalinium led to rapid photoinactivation. ATP and ADP, separately or in combination with Mg2+, protect against photoinactivation. After photoinactivating the alpha3beta3gamma subcomplex of CF1 with [14C]dequalinium, tryptic and peptic digests of the isolated, derivatized beta subunit were fractionated by high performance liquid chromatography. Sequencing of the isolated, radioactive tryptic and peptic peptides revealed that Metbeta183, which is at or near the catalytic site, is derivatized in a single beta subunit when CF1 is photoinactivated with [14C]dequalinium. 相似文献
776.
Antibiotic-associated diarrhea (AAD) is a common complication of antibiotics and recent findings on the epidemiology, etiologies and treatment strategies are reviewed. Rates of AAD vary from 5 to 39% depending upon the specific type of antibiotic. The severity of AAD may include uncomplicated diarrhea, colitis or pseudomembranous colitis. The pathogenesis of AAD may be mediated through the disruption of the normal flora and overgrowth of pathogens or through metabolic imbalances. The impact of AAD is reflected by increased hospital stays, higher medical costs and increased rates of comorbidity. The key to decreasing these consequences is prompt diagnosis followed by effective treatment and institution of control measures. 相似文献
777.
RD Lloyd GN Taylor SC Miller FW Bruenger WS Jee 《Canadian Metallurgical Quarterly》1997,73(4):684-689
Statistical analyses have indicated that there was a significant difference between dogs injected with bone volume-seeking 226Ra as compared to those given bone surface-seeking 239Pu with respect to location within the skeleton of 334 radiation-induced primary bone malignancies. Corresponding differences also were evident when dogs given bone volume-seeking 90Sr or bone surface-seeking 241Am, 228Th, (249,252)Cf, or 224Ra (which decays mostly on bone surfaces because of its short, 3.6 d half time) were included along with the 226Ra or 239Pu, respectively (562 total tumors). Further analysis suggested that higher values of percent red marrow (M) and bone turnover rate (R) are correlated with increased probability of tumor appearance at a particular location within the skeleton for the surface seekers. Proportionately higher values of M and R are associated with skeletal sites containing mostly trabecular bone as compared to those with mostly compact (cortical) bone. Coefficients of determination (r2) for the relationship between percent of total tumors vs the combination of percent red marrow and turnover rate (= MR) was about 0.7 for the surface seekers but only about 0.1 for the volume seekers. This indicates that the neoplastic effects of surface seekers, but not volume seekers, are associated with the presence of trabecular bone at the various sites of radionuclide deposition within the skeleton. 相似文献
778.
How do feelings influence the effort of entrepreneurs? To obtain data on this issue, the authors implemented experience sampling methodology in which 46 entrepreneurs used cell phones to provide reports on their affect, future temporal focus, and venture effort twice daily for 24 days. Drawing on the affect-as-information theory, the study found that entrepreneurs’ negative affect directly predicts entrepreneurs’ effort toward tasks that are required immediately. Results were consistent for within-day and next-day time lags. Extending the theory, the study found that positive affect predicts venture effort beyond what is immediately required and that this relationship is mediated by future temporal focus. The mediating effects were significant only for next-day outcomes. Implications of findings on the nature of the affect–effort relationship for different time lags are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
779.
AM Settles A Yonetani A Baron DR Bush K Cline R Martienssen 《Canadian Metallurgical Quarterly》1997,278(5342):1467-1470
The bacterial Sec and signal recognition particle (ffh-dependent) protein translocation mechanisms are conserved between prokaryotes and higher plant chloroplasts. A third translocation mechanism in chloroplasts [the proton concentration difference (DeltapH) pathway] was previously thought to be unique. The hcf106 mutation of maize disrupts the localization of proteins transported through this DeltapH pathway in isolated chloroplasts. The Hcf106 gene encodes a receptor-like thylakoid membrane protein, which shows homology to open reading frames from all completely sequenced bacterial genomes, which suggests that the DeltapH pathway has been conserved since the endosymbiotic origin of chloroplasts. Thus, the third protein translocation pathway, of which HCF106 is a component, is found in both bacteria and plants. 相似文献
780.
Dirk E. De Vos Joeri Denayer Frederik van Laar Gino V. Baron Pierre A. Jacobs 《Topics in Catalysis》2003,23(1-4):191-198
The hydrophobic or hydrophilic properties of solid catalysts often have a crucial influence on their properties in liquid-phase catalytic reactions. Several methods to measure liquid-phase adsorption on catalytic solids are compared, and special attention is given to the liquid chromatographic method. The experimental setup and the determination of adsorption constants are discussed. Finally, adsorption data measured via the chromatographic method are used to gain insight into liquid-phase catalytic reactions, particularly oxidations with Ti zeolites. 相似文献