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Mg–xSi (x=0, 1.5, 3.3) alloys were fabricated and subjected to cyclic closed-die forging (CCDF), a new severe plastic deformation process, at 450 °C for 1, 3, and 5 passes. With applying CCDF, tensile strength, elongation and hardness increase, while coarse Mg2Si particles break into smaller pieces and exhibit more uniform distribution. Mg–1.5%Si alloy exhibits a combination of improved strength and elongation after 5 passes of CCDF processing. The tensile strength is about 142 MPa and elongation is about 8%. The improvement in mechanical properties was further characterized by dry sliding wear testing. The results show that wear resistance improves with silicon content and CCDF process passes, particularly the first pass. The wear resistance increases by about 38% for Mg–3.3%Si after 5 passes of CCDF compared with pure Mg. The improvement of wear is related to microstructure refinement and homogenization based on the Archard equation and friction effect.

Purpose: The bacterial resistance of refrigerated and cryopreserved aortic allografts in a highly virulent infection in a dog model was studied. Methods: The infrarenal aorta of 12 dogs was replaced with either a cryopreserved aortic allograft (group I, n = 6) or a refrigerated aortic allograft (group II, n = 6) in infected sites. Allografts were harvested from dogs and stored for 1 week, either by cryopreservation (-140^oC) or refrigerated method (4^oC), in a preservation medium. At the time of implantation, induction of infection was achieved with an infected piece of knitted Dacron placed just beneath the allograft. The Dacron was contaminated in vitro by soaking it in a solution with Staphylococcus aureus PR209. All 12 dogs received no adjunct antibiotic or antithrombotic therapy. Four weeks after implantation, the animals were killed to recover the grafts for bacteriological and histological analyses. Bacterial results were expressed as colony-forming units (CFU)/cm^2 of graft material. Results: In group I, only one allograft grew bacteria at 2.16 x 10^6 CFU/cm^2, with a blood culture positive for S aureus. In group II, one dog died at 3 weeks from a false septic aneurysm rupture, all the allografts were infected (P < .05) with a mean bacterial count of 9.41 +/- 6.8 x 10^4 CFU/cm^2, and three blood cultures were positive for S aureus. The patency of the grafts was analyzed at the time of recovery. Three laminar thrombi without occlusion were present in group I; none were present in group II. A better preserved endothelium in group I was revealed by means of histologic analysis staining with factor VIII antibody before implantation. After 4 weeks of implantation in the infected site, infected allografts presented polynuclear infiltrates in the media with a high degree of inflammatory reaction, and endothelial recovery was more significant in group I, with numerous young plump cells. Conclusion: This study demonstrates that cryopreserved allografts implanted in infected sites in a dog model can produce greater bacterial resistance. (J Vasc Surg 1999;29:1090-6.)

A gas chromatographic/mass spectrometric method for the specific determination of oxprenolol and 2H6-labelled oxprenolol when both are present in the same sample is described. After addition of 13C3-labelled oxprenolol as internal standard, plasma is alkalized and extracted by a mixture of dicholoromethane and diethyl ether. The residue following evaporation of the organic phase is derivatized with heptafluorobutyric anhydride. Negative ion detection with N2O as reagent gas is used for the measurements at m/z488, 491 and 494 for oxprenolol, the 13C3-labelled internal standard and 2H6-labelled oxprenolol, respectively. The precision and accuracy of the analytical method were investigated using samples containing both unlabelled and 2H6-labelled oxprenolol. The overall mean recovery (%±SD, n= 70) in the concentration range 20–1500 nmol l-1(around 6–450 ng ml-1of the hydrochloride salts) was 100.6±3.3 and 101.0±3.5 for oxprenolol and 2H6-labelled oxprenolol, respectively. The limit of quantification was around 20 nmol l-1for both compounds.

Animal experimentation with total parenteral nutrition (TPN) has revealed the occurrence of atrophy of the intestinal mucosa and decreased enzyme activities of the brush border, notably the disaccharidases. These findings have heretofore not been confirmed in human investigation. We performed endoscopic biopsies in the third part of the duodenum in 7 adults before TPN, after 21 days of TPN, and after a progressive oral refeeding. We noted a clear-cut decrease of major enzyme activities during TPN (sucrase, maltase, lactase, glucoamylase, acid aminopeptidase, dipeptidyl peptidase) without any morphologic modifications as observed with standard histology. Electron microscopy showed a slight but significant decrease in the height of microvilli. The decreased enzyme activities were rapidly restored after oral refeeding. Thus, the functional consequences of the modifications observed during medium-term TPN in adults are probably limited.

A case of juvenile gastrointestinal polyposis in an infant is described and the literature is reviewed. Major clinical problems are related to the extent of the juvenile polyposis. The disease has a poor prognosis. The endoscopic techniques used when polyposis is limited allow histologic evaluation of the polyps and conservative treatment.

A case of juvenile gastrointestinal polyposis in an infant is described and the literature is reviewed. Major clinical problems are related to the extent of the juvenile polyposis. The disease has a poor prognosis. The endoscopic techniques used when polyposis is limited allow histologic evaluation of the polyps and conservative treatment.

Les lésions bronchiques de bas grade (dysplasie modérée ou inférieur) évoluent en cancer invasif dans 3 %des cas. Leur surveillance n’est pas consensuelle. L’objectif de cette étude est de comparer une surveillance endoscopique semestrielle à une surveillance standard chez des patients présentant uniquement des lésions précancéreuses bronchiques de grade inférieur ou égal à une dysplasie modérée.