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W Rees

Publications and source records attributed to W Rees.

6 recordsLinked to original sources
PubMed1992

Circular DNA molecules imaged in air by scanning force microscopy.

Routine and reproducible imaging of DNA molecules in air with the scanning force microscope (SFM) has been accomplished. Circular molecules of plasmid DNA were deposited onto red mica and imaged under various relative humidities. In related experiments, the first images of the Escherichia coli RNA polymerase-DNA complex have also been obtained. This has been possible by (1) the use of specially modified SFM tips with a consistent radius of curvature of 10 nm or less, to minimize the amount of image distortion introduced by the finite dimensions of commercially available tips, (2) the optimization of a method to deposit and bind DNA molecules to the mica surface in a stable fashion, and (3) careful control of the sample humidity, to prevent solvation of the molecules and detachment from the surface by the scanning tip or stylus. Contact forces in the range of a few nanonewtons are routinely possible in air and in the presence of residual humidity. The spatial resolution of the images appears determined by the radius of curvature of the modified styli, which can be estimated directly from the apparent widths of the DNA molecules in the images.

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PubMed1979

Hypnosis.

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Child↗
PubMed1979

Pathogenesis of aortoduodenal fistula: experimental and clinical correlates.

An aortoduodenal fistula (ADF) is believed to stem from erosion of a rigid prosthesis into the fixed retroperitoneal duodenum. Experimental and clinical data do not support a mechanical etiology, but indicate that the pathogenesis is an unrecognized graft infection with pseudoaneurysm formation. A 5 cm segment of Dacron was interposed in the infrarenal aortas of 24 dogs that were divided into four groups of six animals each. In group 1 (control) the duodenum was fixed by sutures to the proximal anastomosis of the Dacron graft. At 6 weeks' follow-up, no ADFs or deaths had occurred among this group. In group 2 the duodenum was fixed to the aortoprosthetic anastomosis and the dogs received an intravenous infusion of 10(8) S. aureus; two of these dogs developed ADF (P less than 0.01). In group 3 the duodenum was incorporated as a patch on the anterior aspect of the aortoprosthetic suture line, creating a false aneurysm; three of these animals died as a result of ADF. A false aneurysm was created in group 4 dogs, as in group 3, but in addition, 10(8) S. aureus was administered intravenously; here five to six animals developed ADF. Clinical and bacteriological evidence of graft infection was present in seven of 11 patients with ADF who were seen over an 18 year period. Five had pseudoaneurysm formation at the proximal anastomosis. Operation was performed in eight patients; three had closure of the aortic leak and repair of the duodenum with omentum interposition. All resulted in recurrent fistula and delayed hemorrhage. Simple graft excision in two patients without reconstitution of peripheral circulation resulted in lower extremity gangrene. The three survivors had graft excision and axillofemoral bypass. These data suggest that the etiology of ADF is primary low-grade infection. Successful operation necessitates excision of the graft, duodenal closure, and an extraanatomical axillofemoral bypass graft.

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