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991.
In this paper we investigate the relation between electrical stability and oxide deposition conditions in sputtered oxide. We found that lower sputtering pressure and lower discharge voltage with the addition of oxygen in sputtering gas mixture give better resistance to interface states generation during constant current stress. Also sputtered oxide applied in TFTs showed a remarkable stability under moderate stress fields. 相似文献
992.
Pseudomonas carboxyl proteinase (PCP), isolated from Pseudomonas sp. 101, and Xanthomonas carboxyl proteinase (XCP), isolated from Xanthomonas sp. T-22, are the first and second examples of unique carboxyl proteinases [EC 3.4.23.33] which are insensitive to aspartic proteinase inhibitors, such as pepstatin, diazoacetyl-DL-norleucine methylester, and 1,2-epoxy-3(p-nitrophenoxy)propane. The substrate specificities of PCP and XCP were studied using a series of synthetic chromogenic peptide substrates with the general structure, P5-P4-P3-P2-Phe-Nph-P2'-P3' (P5, P4, P3, P2, P2', P3': a variety of amino acids, Nph is p-nitro-L-phenylalanine, and the Phe-Nph bond is cleaved). PCP and XCP were shown to hydrolyze a synthetic substrate, Lys-Pro-Ala-Leu-Phe-Nph-Arg-Leu, most effectively among 28 substrates. The kinetic parameters of this peptide for PCP were Km = 6.3 microM, Kcat = 51.4 s-1, and kcat/Km = 8.16 microM-1.s-1. The kinetic parameters for XCP were Km = 3.6 microM, kcat = 52.2 s-1, and kcat/Km = 14.5 microM-1.s-1. PCP showed a stricter substrate specificity than XCP. That is, the specificity constant (kcat/Km) of each substrate for PCP was in general < 0.5 microM-1.s-1, but was drastically improved by the replacement of Lys by Leu at the P2 position. On the other hand, XCP showed a less stringent substrate specificity, with most of the peptides exhibiting reasonable kcat/Km values (> 1.0 microM-1.s-1). Thus it was found that the substrate specificities of PCP and XCP differ considerably, in spite of the high similarity in their primary structures. In addition, tyrostatin was found to be a competitive inhibitor for XCP, with a Ki value of 2.1 nM, as well as for PCP (Ki = 2.6 nM). 相似文献
993.
BM Johnston 《Canadian Metallurgical Quarterly》1995,7(3):639-645
Epidemiological studies have linked low birth weight and increased placental weight with increased risk of hypertension in adult life. It has been proposed that the cardiovascular changes which lead to hypertension are initiated in utero by processes associated with intrauterine growth retardation. The alternative possibility, that hypertension may result from genetic influences which also determine fetal and placental size, has had less support because birth weight is not determined genetically in humans. However, in the spontaneously hypertensive rat (SHR) essential hypertension is known to be transmitted genetically. Fetal and placental weights were, therefore, measured at Day 20 gestation in SHRs and compared with those in the normotensive Wistar Kyoto (WKY) control strain. Fetal weight (1.93 +/- 0.04 g) was significantly (P < 0.001) reduced in SHRs compared with WKY fetuses (2.23 +/- 0.01 g) but placental weight was heavier (P < 0.001) in SHRs (0.347 +/- 0.005 g) than in WKY rats (0.300 +/- 0.006 g) although litter size was not different. As expected, maternal blood pressure recorded under 1% halothane anaesthesia was higher (126 +/- 2.7 mm Hg) in SHR than WKY rats (100 +/- 2.1 mm Hg; 1 mm Hg = 133 Pa). In addition the concentration of maternal blood glucose in SHR was significantly (P < 0.001) higher (4.8 +/- 0.32 mM v. 3.7 +/- 0.11 mM) and the concentration of plasma insulin was significantly (P < 0.05) lower in SHRs (18.8 +/- 3.0 ng mL-1) than in WKY dams (29.4 +/- 3.1 ng mL-1). Thus, the data support human population studies which show an association between adult hypertension and a reduced fetal:placental weight ratio at birth. However, because hypertension in the SHR is genetically determined, these data suggest that fetal growth retardation and increased placental weight may also be determined genetically. 相似文献
994.
NMR study of G.A and A.A pairing in (dGCGAATAAGCG)2 总被引:2,自引:0,他引:2
One- and two-dimensional NMR, UV absorption experiments, and molecular mechanics calculations were conducted on an oligonucleotide duplex (dGCGAATAAGCG)2 which will be referred to as the T-11-mer. This oligonucleotide forms a duplex that is primarily B-form and contains two adjacent G.A and A.A base pairs and two 3' unpaired guanosines. The adjacent mismatch base pairs have an unusual structure which includes overwinding the helix and stacking with the base from the complementary strand (A4 with A8 and G3 with A7) instead of stacking with the base which is sequential on the strand. The exchangeable and nonexchangeable proton NMR spectra of the duplex have been characterized in H2O and D2O solution at neutral and acidic pH. The duplex is stabilized upon protonation; however, no additional hydrogen bonds are formed. We have observed the amino protons of adenosines A4 and A8 and guanosine G3 as a function of temperature and pH. These amino protons are involved in hydrogen bonds with the purine N3 or N7 acting as acceptors. Through the observation of a variety of NOE signals, the structure of the G.A and A.A mismatch base pairs has been defined. 相似文献
995.
B Agrawal MJ Krantz MA Reddish BM Longenecker 《Canadian Metallurgical Quarterly》1998,10(12):1907-1916
Antigen-specific MHC class II- and class I-restricted helper and cytotoxic T cell responses are important anti-cancer immune responses. MUC1 mucin is a potentially important target for immunotherapy because of its high expression on most human adenocarcinomas. MUC1 peptide-specific type 1 T cell responses were generated in vitro using human peripheral blood lymphocytes (PBL), incubated with liposomes containing synthetic MUC1 lipopeptide antigen. Only two weekly stimulations with the liposomal MUC1 formulation led to the generation of potent anti-MUC1-specific T cell proliferation as well as class I-restricted cytotoxic responses. Thus the use of PBL pulsed with liposome-encapsulated antigen provides an effective approach of rapidly generating effective antigen-presenting cell (APC) function as well as antigen specific T cells in vitro. It may be feasible to use this technology for the rapid and effective generation of APC and/or T cells as cellular vaccines for adenocarcinomas. 相似文献
996.
997.
OBJECTIVES: To study the benefits of a clinical pharmacokinetic service in optimising phenytoin use in the Western Cape. DESIGN: Assessment of the response to treatment was based on the number of seizures during the 3 months before entering the study (first baseline period), 3 months after entering the study (second baseline period) and 3 months before the termination of the study (test period). Patients kept a seizure diary throughout the study. The Michaelis-Menten model was used to calculate doses and predict steady-state serum concentrations. SETTING: Nine epilepsy clinics. SUBJECTS: One hundred and ninety-five (113 black and 82 coloured) compliant people with epilepsy receiving generic phenytoin monotherapy. OUTCOME MEASURES: Reduction in seizure frequency and adverse effects. RESULTS: A reduction in seizure frequency (64.8% compared with pre-optimisation) was experienced by 64.9% of patients. Mean seizure frequency was reduced from 3.39 to 1.18 per month. Reductions in seizure frequency of 100% and more than 50% were reported by 39.2% and 58.7% of patients, respectively. Adverse effects of phenytoin were reduced from 20.5% at the first visit to 3.2% at the last visit. CONCLUSION: The clinical pharmacokinetic dosing service for phenytoin applied in this study contributed significantly to the success of epilepsy management. 相似文献
998.
999.
P Franchetti L Cappellacci GA Sheikha HN Jayaram VV Gurudutt T Sint BP Schneider WD Jones BM Goldstein G Perra A De Montis AG Loi P La Colla M Grifantini 《Canadian Metallurgical Quarterly》1997,40(11):1731-1737
The synthesis and biological activity of selenophenfurin (5-beta-D-ribofuranosylselenophene-3-carboxamide, 1), the selenophene analogue of selenazofurin, are described. Glycosylation of ethyl selenophene-3-carboxylate (6) under stannic chloride-catalyzed conditions gave 2- and 5-glycosylated regioisomers, as a mixture of alpha- and beta-anomers, and the beta-2,5-diglycosylated derivative. Deprotected ethyl 5-beta-D-ribofuranosylselenophene-3-carboxylate (12 beta) was converted into selenophenfurin by ammonolysis. The structure of 12 beta was determined by 1H- and 13C-NMR, crystallographic, and computational studies. Selenophenfurin proved to be antiproliferative against a number of leukemia, lymphoma, and solid tumor cell lines at concentrations similar to those of selenazofurin but was more potent than the thiophene and thiazole analogues thiophenfurin and tiazofurin. Incubation of K562 cells with selenophenfurin resulted in inhibition of IMP dehydrogenase (IMPDH) (76%) and an increase in IMP pools (14.5-fold) with a concurrent decrease in GTP levels (58%). The results obtained confirm the hypothesis that the presence of heteroatoms such as S or Se in the heterocycle in position 2 with respect to the glycosidic bond is essential for both cytotoxicity and IMP dehydrogenase inhibitory activity in this type of C-nucleosides. 相似文献
1000.
One hundred and twenty-nine Charnley acetabular components were acquired at the time of revision surgery and a tribological investigation undertaken. The relative occurrence of pitting in the unworn and worn regions of the sockets suggest that most of the cement ingress occurs during the early part of the service life. The penetration depth of the explanted sockets was determined using the shadowgraph technique. Observation of the profiles in the wear planes suggest that, in general, the creep component was not a significant proportion of the overall change in the inner bore of the socket. Using weighted ordinary least squares regression, in which the intercept was not assumed to be zero, mean penetration and wear volume rates of 0.02 (SE = 0.02) mm/year and 55 (SE = 5) mm3/year, respectively, were recorded and are in agreement with other retrieval studies. In neither case was the intercept found to be significantly different from zero. A mean clinical wear factor, Kclinical, equal to 2.1 (SE = 0.2) x 10(-6) mm3/N m was calculated which is considerably larger than that found in laboratory experiments which purport to reflect in vivo conditions. In this analysis, a significant positive intercept was observed [96 (SE = 36) mm3] and may be evidence of the small initial penetration due to creep reported in simulator experiments. A strong positive association between kclinical and the arithmetical mean roughness, Ra, of the femoral head was also demonstrated although the rate of change was not as great as that cited for laboratory experiments. 相似文献