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111.
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EcoRII methyltransferase (M.EcoRII) is a cytosine-C5 DNA methylating
enzyme. A model of its three-dimensional structure is proposed on the basis
of homology modeling. Crystal structures of two members of the same family
of enzymes, HaeIII and HhaI methyltransferases (M.HaeIII and M.HhaI
respectively), were used as template molecules. Molecular dynamics was used
to ensure sampling of conformationally stable structures. The final model
has good geometry. The DNA and cofactor binding residues are in expected
positions and form proper interactions. M.EcoRII is 147 amino acids longer
than the template molecules, and hence the model contains several loops
that are significantly longer than those in M.HaeIII and M.HhaI. The model
provides a framework for interpretation and designing site-directed mutants
that have a potential to improve crystallization experiments of this
enzyme, and possibly other similar enzymes.
相似文献
114.
JL Grem N McAtee RF Murphy FM Balis E Cullen AP Chen JM Hamilton SM Steinberg M Quinn JM Sorensen SG Arbuck D Lawrence J Pang CJ Allegra 《Canadian Metallurgical Quarterly》1997,3(7):1125-1134
The combination of IFN-alpha-2a (IFN-alpha) and IFN-gamma-1b (IFN-gamma) has been found to produce more than additive cytotoxicity with fluorouracil (5-FU) in HT 29 colon cancer cells due to enhanced DNA-directed effects. We therefore studied the combination of IFN-gamma with IFN-alpha, 5-FU, and leucovorin (LV) in a clinical trial. Fifty-three patients received an initial cycle of 5 million units (MU)/m2 IFN-alpha s.c. on days 1-7 with 500 mg/m2 LV and 370 mg/m2 5-FU i.v. on days 2-6. IFN-gamma was then added once tolerable doses of 5-FU and IFN-alpha were established for each patient. IFN-gamma was administered at one of six dose levels between 0.3-4.8 MU/m2 s.c. on days 1-7. This design permitted comparison of the clinical toxicity and pharmacokinetics of 5-FU in two consecutive cycles in an individual treated with the same doses of 5-FU/LV/IFN-alpha in the absence and presence of IFN-gamma. In 43 matched patient cycles, the addition of IFN-gamma did not seem to worsen gastrointestinal toxicity, and skin toxicity tended to be milder. 5-FU clearance was higher in 14 cycles with IFN-gamma compared to the patient's prior cycle with the same doses of 5-FU/LV/IFN-alpha: 798 +/- 309 versus 601 +/- 250 ml/min/m2 (mean +/- SD; P = 0.04). In these 28 cycles, the median 5-FU clearance was significantly lower in 11 cycles that were complicated by more severe diarrhea: 524 versus 798 ml/min/m2 (grade 2 versus 0-1; P = 0. 0032). Overall, 38% and 26% of patients had grade 3-4 diarrhea and mucositis. Dose reductions of IFN-gamma for chronic fatigue, malaise, or anorexia were ultimately required more frequently with >/=2.4 MU/m2 (P = 0.018), and the maximum tolerated dose of IFN-gamma was considered to be 1.2 MU/m2/ day. Objective responses were seen in 41% of 29 measurable colorectal cancer patients. Compared to our previous experience with 5-FU/LV/IFN-alpha, IFN-gamma and IFN-alpha appeared to have opposite effects on 5-FU clearance. These results suggest that any potential benefit of adding IFN-alpha to 5-FU/LV on this schedule may not depend solely on alterations in 5-FU clearance. 相似文献
115.
JE Manning DN Batson TW Gansman CA Murphy SG Perretta EA Norfleet 《Canadian Metallurgical Quarterly》1997,4(9):883-890
With the aim of developing foetal gene therapy for cystic fibrosis, we have investigated the possibility of gene targeting to the mouse foetus with two different viral vector systems and at different times of gestation. We report here that recombinant retrovirus producing cells administered into the intra-amniotic cavity of mid- to late-gestation mouse MF1 foetuses survive in the amniotic fluid and are able to engraft to a certain extent in foetal tissues. By production of infectious virus they mediate transduction and beta-galactosidase transgene expression in neighbouring foetal tissues 24 to 72 h following injection. Retrovirus producer cells could, therefore, become a means to overcome the limitations of low retroviral titre, for in vivo foetal gene transfer. To investigate the developmental stage at which transduction of the airways and enteral systems can be obtained we also administered a highly infective first generation adenoviral vector (AdRSV beta gal) into the amniotic cavity of foetal mice between 13 to 16 days post coitus, beta-galactosidase activity was detected between 24 to 120 h after injection. The highest levels of transgene expression were generally observed between 48 to 72 h following injection of the adenoviral vector. We demonstrate that infection of the pulmonary airways is dependent on the developmental stage of the foetus and can be achieved on the 15th day of gestation. 相似文献
116.
DL Nahrwold SG Pereira J Dupuis 《Canadian Metallurgical Quarterly》1995,222(3):263-6; discussion 266-9
OBJECTIVE: The authors hypothesized that less research performed in the United States was reported in the five major general surgical journals in 1993 than in 1983. SUMMARY BACKGROUND DATA: Academic surgeons believe they have less time and fewer funds for research than previously. METHODS: Five journals were analyzed for the number of pages and articles devoted to basic and clinical research in 1983 and 1993 and for the country in which the research was performed. RESULTS: The number of U.S. research pages and articles decreased over the past decade, and the number of non-U.S. pages and articles increased. CONCLUSIONS: The reason(s) for the decrease in U.S. research reported in the general surgical journals should be studied, identified, and, if possible, rectified. 相似文献
117.
RV Parry K Reif G Smith DM Sansom BA Hemmings SG Ward 《Canadian Metallurgical Quarterly》1997,27(10):2495-2501
The intracellular signaling pathways activated upon ligation of the co-stimulatory receptor CD28 remain relatively ill-defined, although CD28 ligation does result in the strong association with, and activation of, phosphatidylinositol (PI) 3-kinase. The downstream effector targets of the CD28-activated PI 3-kinase-dependent signaling pathway remain poorly defined, but recent evidence from other systems has shown that Akt/protein kinase B (PKB) is a major target of PI 3-kinase and have indicated that a major function of PKB is the regulation of cell survival events. Given the strong coupling of CD28 to PI 3-kinase and the known protective effects of both CD28 and PI 3-kinase against apoptosis in different cell models, we investigated the effects of CD28 on PKB activation. We demonstrate that ligation of CD28 by either anti-CD28 monoclonal antibodies or the natural ligand B7.1, results in the marked activation of PKB in both the leukemic T cell line Jurkat and freshly isolated human peripheral blood-derived normal T lymphocytes. Our data suggest therefore, that PKB may be an important intracellular signal involved in CD28 signal transduction and demonstrate CD28 coupling to downstream elements of a signaling cascade known to promote cell survival. 相似文献
118.
119.
1. Contracting for Safety (CFS) has become an integral part of nursing practice but never has been subjected to scientific scrutiny. 2. Clinical reasons for avoiding the use of contracting with some patient populations exist, including that some patients may construe CFS as a failure of empathy by the caregiver. 3. CFS can, in some instances, be helpful in establishing a therapeutic relationship or aiding in assessment, but never should be the sole basis for determining a patient's lethality. 相似文献
120.