Magnetometric evaluation for the effects of silicon carbide whiskers on alveolar macrophages. (65/3384)

Alveolar macrophages are thought to play an important role in fibrogenesis in the lungs caused by various types of exposure to dust. In this experiment, we evaluated the effect of silicon carbide whiskers (SiC) on alveolar macrophages mainly by unique magnetometry and also by established methods such as lactate dehydrogenase (LDH) activity, apoptosis measurement and morphological observations. Alveolar macrophages obtained from Syrian golden hamsters by bronchoalveolar lavages were exposed in vitro to Fe3O4 for 18 hours as an indicator for magnetometry and SiC for experiments. A rapid decrease of the remanent magnetic field, so called "relaxation", was observed after cessation of an external magnetic field in macrophages phagocytizing Fe3O4 alone, while relaxation was delayed in those concurrently exposed to SiC. Release of LDH from SiC-exposed macrophages into the medium was not significantly higher than the controls, but it increased dose-dependently. Apoptosis was recognized in macrophages exposed to 60 micrograms/ml of SiC by the DNA ladder detection method and morphological observations. Electron microscopic examination revealed irregular forms of nuclei and organellas in macrophages exposed to SiC. Magnetometry, LDH release and electron microscopic observation indicated mild cytotoxicity of SiC to alveolar macrophages.  (+info)

Shear stress-induced apoptosis of adherent neutrophils: a mechanism for persistence of cardiovascular device infections. (66/3384)

The mechanisms underlying problematic cardiovascular device-associated infections are not understood. Because the outcome of the acute response to infection is largely dependent on the function of neutrophils, the persistence of these infections suggests that neutrophil function may be compromised because of cellular responses to shear stress. A rotating disk system was used to generate physiologically relevant shear stress levels (0-18 dynes/cm(2); 1 dyne = 10 microN) at the surface of a polyetherurethane urea film. We demonstrate that shear stress diminishes phagocytic ability in neutrophils adherent to a cardiovascular device material, and causes morphological and biochemical alterations that are consistent with those described for apoptosis. Complete neutrophil apoptosis occurred at shear stress levels above 6 dynes/cm(2) after only 1 h. Morphologically, these cells displayed irreversible cytoplasmic and nuclear condensation while maintaining intact membranes. Analysis of neutrophil area and filamentous actin content demonstrated concomitant decreases in both cell area and actin content with increasing levels of shear stress. Neutrophil phagocytosis of adherent bacteria decreased with increasing shear stress. Biochemical alterations included membrane phosphatidylserine exposure and DNA fragmentation, as evaluated by in situ annexin V and terminal deoxynucleotidyltransferase-mediated dUTP end labeling (TUNEL) assays, respectively. The potency of the shear-stress effect was emphasized by comparative inductive studies with adherent neutrophils under static conditions. The combination of tumor necrosis factor-alpha and cycloheximide was ineffective in inducing >21% apoptosis after 3 h. These findings suggest a mechanism through which shear stress plays an important role in the development of bacterial infections at the sites of cardiovascular device implantation.  (+info)

Above-knee prosthetic femoropopliteal bypass for intermittent claudication. Results of the initial and secondary procedures. (67/3384)

OBJECTIVES: [corrected] to report the results of primary and secondary prosthetic above-knee femoropopliteal bypass for intermittent claudication. DESIGN: a retrospective study in a University hospital. PATIENTS: one hundred and twelve operations performed in 103 patients (26 women) between January 1990 and June 1997. METHODS: a comparison of primary assisted patency was made between Dacron and PTFE, between men and women and between operations performed early and late in the study period. Patency of secondary procedures was also studied. RESULTS: there were no operative deaths. The 5-year survival rate was 81% and equal to that of a demographically matched population. The primary assisted graft patency was 58% after two years. Women had a significantly better graft patency than men (79% vs. 49%). The type of graft and the date of the operation did not influence the outcome. Forty of the 55 occluded grafts were subjected to a redo procedure with a 1-year patency of 29%. CONCLUSIONS: the results after prosthetic above-knee femoropopliteal bypass procedures are disappointing, and a controversy persists as to whether this operation should be performed for intermittent claudication. The results of secondary procedures are even worse, and perhaps should only be considered in patients suffering critical ischaemia.  (+info)

Endoluminal femoropopliteal bypass for intermittent claudication. (68/3384)

OBJECTIVES: (i) to describe our initial clinical experience with endoluminal femoropopliteal bypass using a technique developed in a cadaveric model; (ii) to identify areas requiring technical modification to improve patency and complication rates. DESIGN: prospective, experimental pilot study. MATERIALS AND METHODS: fourteen consecutive patients with disabling intermittent claudication and superficial femoral artery occlusion underwent endarterectomy through a groin incision and endoluminal placement of a polytetrafluoroethylene graft. Follow-up was by duplex ultrasound and arteriography. RESULTS: two endovascular technical failures required conversion to open surgery. The cumulative primary (1 degrees), 1 degrees-assisted and secondary (2 degrees) patency rates at 1 year were 35.7%, 42.8% and 71.4% respectively; at 2 years the patency rates were 14.3%, 31.2% and 57.1%. Twenty-three endovascular interventions were required to maintain graft patency in 10 patients. Five patients subsequently required conventional bypass, of whom two proceeded to major amputation because of graft infection. Seven endovascular grafts remain patent at a mean follow-up of 50 months. CONCLUSIONS: this minimally invasive surgical technique is feasible, with acceptable patency rates. However, considerable investment of time and resources is required to maintain graft patency. With increasing experience and improved technical design, this procedure may offer a real alternative to conventional surgery in patients disabled by short-distance claudication.  (+info)

Endovascular treatment of penetrating thoracic outlet arterial injuries. (69/3384)

OBJECTIVES: to establish the feasibility of stent-graft treatment of penetrating thoracic outlet arterial injuries. DESIGN: prospective study. MATERIALS AND METHODS: forty-one patients with penetrating injuries to the carotid, subclavian and proximal axillary arteries admitted between August 1998 and May 1999 were studied. Patients requiring urgent surgical exploration for active bleeding (n=26) were excluded. Remaining patients underwent arteriography to assess suitability for stent-graft placement. After successful stent-graft treatment clinical and sonographic follow-up were done at 1 month and thereafter 3-monthly. RESULTS: of the 15 patients considered, 10 patients qualified for stent-graft treatment (seven male, three female, mean age 27 years). The vessels involved were subclavian artery (seven), carotid artery (two) and axillary artery (one). Seven had arteriovenous fistulae and three, pseudoaneurysms. Stent-graft treatment was successful in all 10 patients with no procedure-related complications. On mean follow-up of 7 months no complications were encountered. CONCLUSION: endovascular treatment shows promise as a treatment modality for thoracic outlet arterial injuries. Long-term follow-up is required for comparison to the results of standard surgical repair.  (+info)

Increased risk of restenosis after placement of gold-coated stents: results of a randomized trial comparing gold-coated with uncoated steel stents in patients with coronary artery disease. (70/3384)

BACKGROUND: Gold is a highly biocompatible material. Experimental evidence suggests that coating the stent with a gold layer may have a beneficial influence. In this randomized trial, we assessed whether gold-coated stents were associated with a better clinical and angiographic outcome after coronary placement. METHODS AND RESULTS: Patients with symptomatic coronary artery disease were randomly assigned to receive either a gold-coated Inflow stent (n = 367) or an uncoated Inflow stainless steel stent (n = 364) of identical design. Follow-up angiography was routinely performed at 6 months. The primary end point of the study was the occurrence of any adverse clinical event (death, myocardial infarction, or target-vessel revascularization) during the first year after stenting. At 30 days, there was no significant difference in the combined incidence of adverse events, with 7.9% in the gold-stent group versus 5.8% in the steel-stent group (P = 0.25). The incidence of angiographic restenosis (> or =50% diameter stenosis) was 49.7% in the gold-stent group and 38.1% in the steel-stent group (P = 0.003). One-year survival free of myocardial infarction was 88.6% in the gold-stent group and 91.8% in the steel-stent group (P = 0.14). One-year event-free survival was significantly less favorable in the gold-stent group (62.9% versus 73.9% in the steel-stent group; P = 0.001). CONCLUSIONS: Coating steel stents with gold had no significant influence on the thrombotic events observed during the first 30 days after the intervention. However, gold-coated stents were associated with a considerable increase in the risk of restenosis over the first year after stenting.  (+info)

Effects of five different barrier materials on postsurgical adhesion formation in the rat. (71/3384)

Postsurgical adhesion formation is a significant clinical problem within every surgical specialism. Due to the problems that adhesions cause, a wide variety of adjunctive treatments to prevent the formation and reformation of adhesions have been proposed. One of the modalities that has been studied extensively and that has been showing the most promising results is the so-called barrier method. The purpose of the present study was to compare the efficacy of five of these barrier materials in the prevention of postsurgical adhesion formation in a standardized rat adhesion model. It was concluded that no beneficial effect of Ringer's lactate on adhesion formation was seen. Significant reductions (P < 0.0001) in adhesion percentages compared to control animals were seen with Polyactive((TM)), PRECLUDE Peritoneal Membrane((TM)), Seprafilm((TM)) and Tissucol((TM)), but only PRECLUDE Peritoneal Membrane and Seprafilm significantly reduced adhesions (P < 0.01) when the barrier-treated peritoneal defects were compared with contralateral control-side peritoneal defects. The results of our study suggest that Seprafilm and PRECLUDE Peritoneal Membrane are superior to Tissucol and Polyactive in preventing adhesion formation. When Polyactive was still attached to the site of application during the second laparotomy, similar results to Seprafilm and PRECLUDE Peritoneal Membrane were seen. Future studies on the efficacy of a material to decrease adhesion formation should always include a comparison of several control materials in the same model. Our study indicates that Seprafilm or PRECLUDE Peritoneal Membrane might be used as standards of control.  (+info)

Ges, A human GTPase of the Rad/Gem/Kir family, promotes endothelial cell sprouting and cytoskeleton reorganization. (72/3384)

Rad, Gem/Kir, and mRem (RGK) represent a unique GTPase family with largely unknown functions (Reynet, C., and C.R. Kahn. 1993. Science. 262:1441-1444; Cohen, L., R. Mohr, Y. Chen, M. Huang, R. Kato, D. Dorin, F. Tamanoi, A. Goga, D. Afar, N. Rosenberg, and O. Witte. Proc. Natl. Acad. Sci. USA. 1994. 91:12448-12452; Maguire, J., T. Santoro, P. Jensen, U. Siebenlist, J. Yewdell, and K. Kelly. 1994. Science. 265:241-244; Finlin, B.S., and D.A. Andres. 1997. J. Biol. Chem. 272:21982-21988). We report that Ges (GTPase regulating endothelial cell sprouting), a human RGK protein expressed in the endothelium, functions as a potent morphogenic switch in endothelial cells (ECs). Ges function is sufficient to substitute for angiogenic growth factor/extracellular matrix (ECM) signals in promoting EC sprouting, since overexpression of Ges in ECs cultured on glass leads to the development of long cytoplasmic extensions and reorganization of the actin cytoskeleton. Ges function is also necessary for Matrigel-induced EC sprouting, since this event is blocked by its dominant negative mutant, Ges(T94N), predicted to prevent the activation of endogenous Ges through sequestration of its guanine nucleotide exchange factor. Thus, Ges appears to be a key transducer linking extracellular signals to cytoskeleton/morphology changes in ECs.  (+info)