[Comparison of different biomaterials for vaginal surgery using an in vivo model of meshes infection in rats]. / Comparaison de différents biomatériaux destinés à la chirurgie vaginale dans un modèle in vivo d'infection de prothèse chez le rat.

OBJECTIVES: The purpose of this study was to develop an animal model of prosthetic infection and compare in vivo bacterial infectiosity of different biomaterials used in vaginal surgery. MATERIALS AND METHODS: We implanted 36 prostheses of poly(lactic acid) with 94% L forms (PLA94), in a model of incisional abdominal hernia in Wistar rats. Bacterial inoculation was done just after implantation with three strains of Escherichia coli of variable virulence, two different concentrations and two different times of inoculation (during surgery or 48 hours after). All meshes were explanted and animals sacrificed on day 30 after intervention. Bacteriology and histology were then performed. In the same way, three materials used in vaginal surgery (knitted light-weight polypropylene [PP], thermoformed PP [Uratape] and polyurethane coated poly[ethylene terephtalate] [PTFE]) were tested and compared to the PLA94 using the same protocol. RESULTS: All inoculated prostheses were still infected at day 30 after implantation with the same E. coli strain. There was a significant difference in bacterial infectiosity linked to virulence of the inoculated strain (p=.005) and the amount injected (P<0.001). Infectiosity was significantly lower for PLA94 when compared to the three other prostheses (P=0.008). The most important infectiosity was seen with PTFE and thermoformed PP. For histologists, PLA94 also gave the weakest inflammatory reaction. DISCUSSION AND CONCLUSION: An original animal model of prosthetic infection allowed us to compare in vivo bacterial infectiosity of different biomaterials used in vaginal surgery and to demonstrate that the PLA94 mesh induces a milder risk of infection than polypropylene.

Evaluation of cardiac troponin I and T levels as markers of myocardial damage in doxorubicin-induced cardiomyopathy rats, and their relationship with echocardiographic and histological findings.

BACKGROUND: Cardiac troponins I (cTnI) and T (cTnT) have been shown to be highly sensitive and specific markers of myocardial cell injury. We investigated the diagnostic value of cTnI and cTnT for the diagnosis of myocardial damage in a rat model of doxorubicin (DOX)-induced cardiomyopathy, and we examined the relationship between serial cTnI and cTnT with the development of cardiac disorders monitored by echocardiography and histological examinations in this model. METHODS: Thirty-five Wistar rats were given 1.5 mg/kg DOX, i.v., weekly for up to 8 weeks for a total cumulative dose of 12 mg/kg BW. Ten rats received saline as a control group. cTnI was measured with Access(R) (ng/ml) and a research immunoassay (pg/ml), and compared with cTnT, CK-MB mass and CK. By using transthoracic echocardiography, anterior and posterior wall thickness, LV diameters and LV fractional shortening (FS) were measured in all rats before DOX or saline, and at weeks 6 and 9 after treatment in all surviving rats. Histology was performed in DOX-rats at 6 and 9 weeks after the last DOX dose and in all controls. RESULTS: Eighteen of the DOX rats died prematurely of general toxicity during the 9-week period. End-diastolic (ED) and end-systolic (ES) LV diameters/BW significantly increased, whereas LV FS was decreased after 9 weeks in the DOX group (p<0.001). These parameters remained unchanged in controls. Histological evaluation of hearts from all rats given DOX revealed significant slight degrees of perivascular and interstitial fibrosis. In 7 of the 18 rats, degeneration and myocyte vacuolisation were found. Only five of the controls exhibited evidence of very slight perivascular fibrosis. A significant rise in cTnT was found in DOX rats after cumulative doses of 7.5 and 12 mg/kg in comparison with baseline (p<0.05). cTnT found in rats after 12 mg/kg were significantly greater than that found after 7.5 mg/kg DOX. Maximal cTnI (pg/ml) and cTnT levels were significantly increased in DOX rats compared with controls (p=0.006, 0.007). cTnI (ng/ml), CK-MB mass and CK remained unchanged in DOX rats compared with controls. All markers remained stable in controls. Analysis of data revealed a significant correlation between maximal cTnT and ED and ES LV diameters/BW (r=0.81 and 0.65; p<0.0001). A significant relationship was observed between maximal cTnT and the extent of myocardial morphological changes, and between LV diameters/BW and histological findings. CONCLUSIONS: Among markers of ischemic injury after DOX in rats, cTnT showed the greatest ability to detect myocardial damage assessed by echocardiographic detection and histological changes. Although there was a discrepancy between the amount of cTnI and cTnT after DOX, probably due to heterogeneity in cross-reactivities of mAbs to various cTnI and cTnT forms, it is likely that cTnT in rats after DOX indicates cell damage determined by the magnitude of injury induced and that cTnT should be a useful marker for the prediction of experimentally induced cardiotoxicity and possibly for cardioprotective experiments.

Changes in wall mechanics after endovascular stenting in the rabbit aorta: comparison of three stent designs.

OBJECTIVE: The aim of this study was to evaluate changes in the wall mechanics of small-diameter arteries after endovascular placement of three different stents. SUBJECTS AND METHODS: Five self-expandable stents (Wallstent), five balloon-expandable noncovered Palmaz stents, and three balloon-expandable covered stents (Jostent) were placed in the infrarenal aorta of 13 New Zealand white rabbits. Systolic blood pressure changes, blood-flow velocity, systolic diameter, and diameter changes were measured and used to calculate the diameter compliance, the distensibility coefficient, and the pulsatility index. RESULTS: Compliance (10(-3) mm kPa(-1)) was 75.3 +/- 20.1 before stenting and reached 94.7 +/- 42.2 upstream, 38.8 +/- 14.2 at the stent level (p < 0.05), and 70.8 +/- 23.2 downstream from the stent. Distensibility (10(-3) kPa(-1)) was 24.3 +/- 6.3 before stenting and reached 27.8 +/- 10.3 upstream, 10.5 +/- 4.4 at the stent level (p < 0.001), and 21.9 +/- 8.6 downstream from the stent. Compliance and distensibility were significantly lower at the stent level than upstream and downstream (p < 0.05). Aortic diameter increased significantly at the stent level from 3.11 +/- 0.40 mm before to 3.76 +/- 0.42 mm after stenting. No significant difference was found among the three stent designs for all the studied data. CONCLUSION: Regardless of the three tested stent designs, endovascular stenting produces a significant decrease in arterial wall compliance of the rabbit aorta.

Acute changes in aortic wall mechanical properties after stent placement in rabbits.

PURPOSE: To evaluate mechanical property changes after endovascular stent placement in small-diameter arteries. MATERIALS AND METHODS: Self-expanding stents (Wallstent) were placed in the infrarenal aorta of five New Zealand White rabbits via a surgical right femoral approach. Blood pressure changes (deltaP) were monitored in the aorta. Blood flow velocity was measured with a 20-MHz, pulsed Doppler probe (n = 4) to calculate the pulsatility index. Aortic diameter (dA) and diameter changes (delta(d)) were measured with a 20-MHz probe in echo-tracking mode. Diameter compliance (Cd) and distensibility coefficient (DC) were calculated as Cd = 2(delta)d/(delta)P and DC = 2delta(d)/delta(P)/dA. RESULTS: Aortic diameter increased from 3.360 +/- 0.4033 mm to 4.020 +/- 0.3033 mm after stent placement at the stent level only. Compliance decreased from 77.644 +/- 24.306 mm kPa(-1) to 31.150 +/-8.245 x 10(-3) mm kPa(-1) at the stent level, and was then significantly lower than upstream (98.500 +/- 53.196 mm kPa(-1)) and down-stream (59.047 +/- 13.833 mm kPa(-1)). There was no significant change in pulsatility index. CONCLUSIONS: Endovascular stent placement produces a significant decrease in arterial wall compliance of the rabbit abdominal aorta.