Objective To explore the influence of hook deflection angle and inclination angle on mechanical properties of the soft tissue suture passer hook. Methods Taking the end face far away from the tip of the needle (end face 1) as the study object, a mathematical model was established with the moment as dependent variable and the hook deflection angle and inclination angle as the independent variable. The moment was solved by the mathematical model with the deflection angle and inclination angle of 0°, 10°, 20° and 30°. Based on the finite element analysis method, 16 three-dimensional geometric hook models with deflection angle and inclination angle of 0°, 10°, 20° and 30° were established by SolidWorks. The stress analysis was carried out by ANSYS Workbench. Under the same puncture force, the maximum von Mises stress of each hook and the reaction moment of end face far away from the tip of the needle were calculated. Results The results from theoretical analysis and numerical simulation showed that the reaction moment of end face 1 increased with the increase of deflection angle, and increased with the decrease of inclination angle. The hook with deflection angle of 0° and inclination angle of 30° had the minimum reaction moment. The finite element analysis results showed that with the deflection angle of 0°, the maximum von Mises stress of the hook was the smallest and did not change with the inclination angle of the hook changing. Conclusions The established mathematical model can accurately explain the relationship between the moment at the end face of the hook and the deflection angle and inclination angle of the hook. This study provides the theoretical basis for designing hook geometry of the soft tissue suture passer, and improves the safety of the soft tissue suture passer in operation process.

BACKGROUNDMuch research has been focused on ischemia/reperfusion injury (IRI) to the transplanted organs. As a free radical, nitric oxide (NO) plays an important role in IRI. In this study, the production of NO and its functions during IRI were monitored in rat models after allotransplantation of kidney grafts.

METHODSOf 75 male LEW rats, 30 served as donors, and the remaining 45 rats were divided into three groups (15 rats in each group): controls (group 1), kidney allotransplantation followed by bilateral nephrectomy during reperfusion (group 2), 2 hours before operation, donors and recipients were treated with N(G)-nitro L-arginine methyl ester (L-NAME), a NO synthase inhibitor, at a dose of 30 mg/kg (group 3). Bilateral nephrectomies were performed while kidney grafts were reperfused. The kidney grafts were hypothemically stored for 24 hours. The production of NO before and after reperfusion was measured by electron paramagnetic resonance (EPR). The creatinine level, the glomerular filtration rate (GFR) and the protein carbonyl content in tissue samples were recorded on the first and the fifth day after operation. The data were evaluated by one-way analysis of variance. Differences were considered to be statistically significant when a P value was less than 0.05.

RESULTSAfter reperfusion for 15 minutes, the production of NO increased remarkably and kept increasing till 120 minutes, after which the level returned to normal. In group 3, which was pretreated with L-NAME, creatinine levels were higher than those in group 2 at the 24th hour (4.10 +/- 0.50 mg/dl vs. 3.77 +/- 0.42 mg/dl, P < 0.05) and the 120th hour (3.19 +/- 0.79 mg/dl vs. 2.22 +/- 0.53 mg/dl, P < 0.05). GFR levels in group 3 were lower than those in group 2 at the 24th hour (0.50 +/- 0.12 ml/min vs. 0.71 +/- 0.19 ml/min, P < 0.05) and the 120th hour (0.59 +/- 0.38 ml/min vs. 1.27 +/- 0.23 ml/min, P < 0.01). The content of protein carbonyl in tissue samples of group 3 was lower than that in group 2 at the 24th hour (29.01 +/- 7.02 nmol/mg protein vs. 49.39 +/- 13.13 nmol/mg protein, P < 0.05), but was higher than that at the 120th hour (75.71 +/- 16.74 nmol/mg protein vs. 57.93 +/- 15.32 nmol/mg protein, P < 0.05).

CONCLUSIONSAfter transplantation of hypothemically stored kidney grafts, the increased NO production in the early stage has protective effects on the transplanted kidney. Application of L-NAME to inhibit NO production is harmful to the recovery of the renal functions of kidney grafts.

Animals ; Creatinine ; blood ; Electron Spin Resonance Spectroscopy ; Glomerular Filtration Rate ; Kidney Transplantation ; Male ; Nitric Oxide ; biosynthesis ; Oxidation-Reduction ; Proteins ; metabolism ; Rats ; Rats, Inbred Lew ; Reperfusion Injury ; metabolism