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51.
RNA tertiary structure mediation by adenosine platforms   总被引:4,自引:0,他引:4  
The crystal structure of a group I intron domain reveals an unexpected motif that mediates both intra- and intermolecular interactions. At three separate locations in the 160-nucleotide domain, adjacent adenosines in the sequence lie side-by-side and form a pseudo-base pair within a helix. This adenosine platform opens the minor groove for base stacking or base pairing with nucleotides from a noncontiguous RNA strand. The platform motif has a distinctive chemical modification signature that may enable its detection in other structured RNAs. The ability of this motif to facilitate higher order folding provides one explanation for the abundance of adenosine residues in internal loops of many RNAs.  相似文献   
52.
Glycosaminoglycans synthesized by human skin fibroblasts were simultaneously radiolabelled with D-[1-(3H)]glucosamine and Na2(35)SO4. Considering 3H incorporation, we found that IFNgamma increased the production of glycosaminoglycan synthesis, including hyaluronic acid, heparan and chondroitin/dermatan sulfate. In contrast, the production of heparan and chondroitin/dermatan sulfate was slightly decreased on the basis of the 35S signal. Furthermore, when heparan sulfate was treated with nitrous acid, the release of free 35S was greater in control than in treated cells, although the 3H patterns of depolymerization with this agent were similar. These data demonstrate that IFNgamma inhibits the incorporation of sulfate from extracellular medium into heparan sulfate.  相似文献   
53.
54.
A prospectively studied group of 55 uncemented Press Fit Condylar total knee arthroplasties was compared retrospectively with a matched group of 51 cemented Press Fit Condylar total knee arthroplasties at a mean of 10 years after operation. For the cemented group, the pain and function scores improved from 32 and 45 preoperatively to 95 and 77, respectively. For the uncemented group the scores improved from 33 and 50 preoperatively to 93 and 60, respectively. There were 10 revisions in the uncemented group for femoral or tibial aseptic loosening or osteolysis compared with two revisions in the cemented group. Exclusive of problems related to patellar metal backing, survival to revision for aseptic failure or radiographic loosening was 72% in the uncemented group and 94% in the cemented group at 10 years. A significantly higher revision rate was found in the uncemented compared with cemented total knee arthroplasty of the Press Fit Condylar design.  相似文献   
55.
56.
PURPOSE: A bladder injury model was developed using protamine sulfate (PS) and endotoxin lipopolysaccharide (LPS) administered intravesically to female Sprague-Dawley rats. MATERIALS AND METHODS: Experimental and control animals were catheterized and intravesically exposed to PS-LPS, PS, LPS, or phosphate buffered saline. After 4, 24 or 72 hours, rats were sacrificed. Urines and bladder tissues were then obtained. Bladder mucosal permeability was evaluated by measuring 14C-urea uptake 24 hours after injury. Repeated instillations of PS/LPS were also made in another group of rats over a period of 5 weeks to attempt to establish a more serious mucosal injury, possibly reflected by altered staining of the collagen IV component of the urinary basement membrane (UBM). RESULTS: Histological examination of the tissues indicated a maximal inflammatory response in the mucosa 4 hours after instillation of PS/LPS. Neutrophils and macrophages in close proximity to the UBM and intraepithelially could be demonstrated. Bladder permeability was significantly altered (26.9% 14C-urea uptake) in rats assayed 24 hours after the PS/LPS treatment, but not after exposure to PS or LPS alone (11.9 and 17.5%, respectively). Protease activity detected in urines from experimental, but not control, animals coincided with the appearance of inflammatory cells in the lamina propria. Inflammatory injury did not appear to alter the collagen IV staining of the UBM. CONCLUSIONS: This rat bladder injury model is useful for examining controversial issues regarding bladder wall structure-function alterations induced by inflammation and possibly important in the pathobiological mechanisms involved in some patients with interstitial cystitis.  相似文献   
57.
The surB gene was identified as a gene product required for Escherichia coli cells to exit stationary phase at 37 degrees C under aerobic conditions. surB was shown to be the same as cydC, whose product is required for the proper assembly and activity of cytochrome d oxidase. Cytochrome d oxidase, encoded by the cydAB operon, is one of two alternate terminal cytochrome oxidases that function during aerobic electron transport in E. coli. Mutations inactivating the cydAB operon also cause a temperature-sensitive defect in exiting stationary phase, but the phenotype is not as severe as it is for surB mutants. In this study, we examined the phenotypes of surB1 delta(cydAB) double mutants and the ability of overexpression of cytochrome o oxidase to suppress the temperature-sensitive stationary-phase-exit defect of surB1 and delta(cydAB) mutants and analyzed spontaneous suppressors of surB1. Our results indicate that the severe temperature-sensitive defect in exiting stationary phase of surB1 mutants is due both to the absence of terminal cytochrome oxidase activity and to the presence of a defective cytochrome d oxidase. Membrane vesicles prepared from wild-type, surB1, and delta(cydAB) strains produced superoxide radicals at the same rate in vitro. Therefore, the aerobic growth defects of the surB1 and delta(cydAB) strains are not due to enhanced superoxide production resulting from the block in aerobic electron transport.  相似文献   
58.
The multiple genetic hit model of cancer predicts that normal individuals should have stable populations of cancer-prone, but noncancerous, mutant cells awaiting further genetic hits. We report that whole-mount preparations of human skin contain clonal patches of p53-mutated keratinocytes, arising from the dermal-epidermal junction and from hair follicles. These clones, 60-3000 cells in size, are present at frequencies exceeding 40 cells per cm2 and together involve as much as 4% of the epidermis. In sun-exposed skin, clones are both more frequent and larger than in sun-shielded skin. We conclude that, in addition to being a tumorigenic mutagen, sunlight acts as a tumor promoter by favoring the clonal expansion of p53-mutated cells. These combined actions of sunlight result in normal individuals carrying a substantial burden of keratinocytes predisposed to cancer.  相似文献   
59.
Plasma levels of fibrinogen, factor VIIc and prothrombin fragment F1 + 2, a marker of thrombin generation in vivo, were studied in 68 subjects with serum total cholesterol (TC) levels between 135 and 349 mg/dl but without clinical evidence of cardiovascular disease and other atherosclerotic risk factors. F1 + 2 plasma levels were directly correlated with TC (p < 0.0004), low-density lipoprotein cholesterol (LDL-C; p < 0.0018) and factor VIIc (p < 0.024). Thirty-five subjects with TC greater than 249 mg/dl (median value of the whole group) showed higher levels of F1 + 2 (p < 0.0001) and fibrinogen (p < 0.0015) than those with TC lower than 249 mg/dl. In subjects with TC > 249 mg/dl and F1 + 2 > 1.2 nM (median value of the whole group), a cholesterol-lowering drug (simvastatin) was able to reduce F1 + 2 (p < 0.009) as well as TC and LDL-C. This study shows a relationship between serum cholesterol and the rate of thrombin generation supporting the hypothesis that a hypercoagulable state may occur in hypercholesterolemic subjects before the onset of clinical evidence of atherosclerotic cardiovascular disease.  相似文献   
60.
The shortage of suitable liver donors for children has motivated the use of ABO-incompatible (ABO-I) grafts for transplantation in urgent situations. However, survival after ABO-I liver grafts has been reported at about 30% as compared with 80% in cases of ABO-identical or -compatible liver grafts. This difference has been attributed to antibody-mediated, hyperacute or chronic liver rejection, due to preformed ABO antibodies (alloantibodies). In this study, we report our results with ABO-I livers in children without alloantibodies at the time of transplantation. From January 1988 to June 1993, 143 OLT were performed in 122 children. Eight children received 8 ABO-I liver grafts. Of these, 7 patients were included in the study. All 7 were alloantibody free before OLT. Five children were spontaneously alloantibody free, while in 2 children, the plasma alloantibodies were eliminated before and after transplantation using intravenous infusion of specific blood group antigens of the donor blood group (soluble antigens). Immunosuppression consisted of a triple-drug treatment combining CsA, AZA, and steroids. The follow-up period was between 10 and 48 months. One child died from a surgical complication. Six children survived, but 1 died 10 months later from intestinal obstruction. There were no graft losses and no episodes of hyperacute or chronic rejection. The graft and patient survival rate was 71%. There was a 28% incidence of rejection, but all were mild (requiring steroid boluses only). Our results suggest that the absence of ABO alloantibodies at the time of and after transplantation can protect ABO-I liver grafts against antibody-mediated rejection, whether hyperacute or chronic, and that soluble antigens are effective in eliminating alloantibodies in children.  相似文献   
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