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1.
Gilbert Held 《International Journal of Network Management》2003,13(2):163-169
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Gilbert Held 《International Journal of Network Management》2006,16(5):375-379
One of the software programs we take for granted is antivirus software. Perhaps part of the reason for not being excited about protecting our computers resides in the fact that most PCs marketed over the past few years are bundled with an antivirus solution. When you initialize the computer you also start your virus protection program, which will often provide you with only a short period of protection before pop‐up messages appear reminding you to renew your antivirus program license to ensure your protection is up to date. What is more than likely never mentioned to consumers is the fact that the antivirus software bundled with your computer was positioned there due to the software vendor paying the computer manufacturer a fee. While most third‐party software placed on new computers must pass a certain level of quality assurance, the computer manufacturer is more interested in the placement fee than whether the software is the best for the purchaser of the computer. Thus, one of the things we should do when our antivirus software license expires, if not sooner, is to look at other possible solutions beyond the software bundled with the computer. One such antivirus product that warrants our attention and which is the focus of this column is ESET's NOD32 for Windows antivirus solution, which was originally developed in Slovakia. 相似文献
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Dyspnea may be easily appreciated during exercise with dyspneic scales, but methodological standardisation still needs to be specified. Authors review the basic physiological mechanism relating dyspnea to indices obtained during a stress test. They propose to use the dyspnea/VE relationship. With the concept of dyspneic threshold (close to the ventilatory threshold) and the ramp that both could be modified (for instance by rehabilitation programmes including exercise training). Interpretation of dyspnea during an exercise test obviously needs to be integrated with other parameters studied during exercise. 相似文献
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LM Sayre RT Naismith MA Bada WS Li ME Klein MD Tennant 《Canadian Metallurgical Quarterly》1996,1296(2):250-256
Horseradish peroxidase (HRP) is well known for mediating the electron-transfer oxidation of electron-rich aromatic 'donors' such as phenols and anilines, but has not been described to oxidize aliphatic amines. We here confirm the inability of HRP to oxidize typical aliphatic amines, even those which would exist significantly as free bases at the operative pH. In contrast, trans-2-phenylcyclopropylamine (2-PCPA) is both a substrate (turnover product is cinnamaldehyde) and a time-dependent inactivator of HRP. These activities of 2-PCPA are consistent with either a concerted or rapid sequential one-electron-oxidation/ring-opening to give an intermediate capable of covalent binding to the enzyme. 2-PCPA is the first known example of a simple aliphatic amine which serves as a substrate for HRP under turnover conditions. 相似文献
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Enzymic catalysts of thiol:disulfide oxidoreduction contain two cysteine residues in their active sites. Another common residue is an aspartate (or glutamate), the role of which has been unclear. Escherichia coli thioredoxin (Trx) is the best characterized thiol:disulfide oxidoreductase, and in Trx these three active-site residues are Cys32, Cys35, and Asp26. Structural analyses had indicated that the carboxylate of Asp26 is positioned properly for the deprotonation of the thiol of Cys35, which would facilitate its attack on Cys32 in enzyme-substrate mixed disulfides. Here, Asp26 of Trx was replaced with isologous asparagine and leucine residues. D26N Trx and D26L Trx are reduced and oxidized more slowly than is wild-type Trx during catalysis by E.coli thioredoxin reductase. Stopped-flow spectroscopy demonstrated that the cleavage of the mixed disulfide between Trx and a substrate is slower in the D26N and D26L enzymes. Buffers increase the rate of mixed disulfide cleavage in these variants but not in wild-type Trx. These results indicate that Asp26 serves as an acid/base in the oxidation/reduction reactions catalyzed by Trx. Specifically, Asp26 protonates (during substrate oxidation) or deprotonates (during substrate reduction) the thiol of Cys35. A similar role is likely filled by the analogous aspartate (or glutamate) residue in protein disulfide isomerase, DsbA, and other thiol:disulfide oxidoreductases. Moreover, these results provide the first evidence for general acid/base catalysis in a thiol:disulfide interchange reaction. 相似文献
9.
C Held P Hjemdahl N Rehnqvist NH Wallén I Bj?rkander SV Eriksson L Forslund B Wiman 《Canadian Metallurgical Quarterly》1997,95(10):2380-2386
BACKGROUND: Disturbed fibrinolytic function may influence the progression of coronary atherosclerosis and contribute to thrombotic cardiovascular (CV) events. METHODS AND RESULTS: In the Angina Prognosis Study in Stockholm (APSIS), patients with stable angina pectoris were studied prospectively during double-blind treatment with metoprolol or verapamil. Various measures of fibrinolytic function were studied in 631 (of 809) patients. During a median follow-up time of 3.2 years (2132 patient-years), 32 patients suffered a CV death, 21 had a nonfatal myocardial infarction (MI), and 77 underwent revascularization. Plasma levels of tissue plasminogen activator (TPA) activity and antigen (ag), plasminogen activator inhibitor (PAI-1) activity at test, and TPA responses to exercise were determined at baseline and after 1 month's treatment and were related to subsequent fatal and nonfatal CV events. Univariate Cox regression analysis revealed that elevated levels of TPA-ag at rest (P < .05), high PAI-1 activity (P < .05), and low TPA-ag responses to exercise (P < .05) were associated with increased risk of subsequent CV death. After adjustment for baseline risk factors, TPA-ag independently predicted CV death or MI. In addition, PAI-1 activity independently predicted CV death or MI in male patients. Verapamil treatment was associated with a 10% decrease of TPA-ag levels and metoprolol treatment with a 2% increase (P < .001 for treatment difference). CONCLUSIONS: Plasma TPA-ag levels at rest, and among male patients PAI-1 activity as well, independently predict subsequent CV death or MI in patients with stable angina pectoris. 相似文献
10.
The p53 tumor suppressor gene encodes a phosphoprotein which when overexpressed can induce growth arrest at the G1 and G2/M phases of the cell cycle, promote differentiation and apoptosis. This paper demonstrates that p53 can associate with trk tyrosine kinase. Expression of a murine temperature-sensitive (ts) p53 mutant in PC12 cells overexpressing trk (a model system to analyse cellular differentiation and signal transduction induced by NGF) induces morphological changes in the absence of NGF stimulation at 32 degrees C but not at 37 degrees C. In cells differentiated by p53, trk, but not EGFr, was hyperphosphorylated on tyrosine. Furthermore trk was not phosphorylated when expressed in Saos-2 cells (human osteosarcoma cells that lack expression of both endogenous trk and p53) at either temperature. However, transfection of ts p53 into these cells induces trk phosphorylation at 32 degrees C in the absence of NGF stimulation. Association of trk and p53 can be detected in NIH3T3 and PC12 cells co-expressing trk and the ts p53 mutant, in NIH3T3 and PC12 cells transfected with trk alone, and in untransfected PC12 cells, showing that overexpressed and/or endogenous trk associates with endogenous, low levels of p53. These data suggest a novel function for p53 which involves the stimulation of signal transduction pathways (mediating morphological properties of cells), possibly through association with and hyperphosphorylation of trk. 相似文献