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Objective To study stress relaxation behaviors of cartilage scaffolds under different degradation cycles by using finite element analysis combined with theoretical models. Methods Based on the established degradation theoretical model, the elastic modulus of the scaffold was calculated under different degradation cycles. The finite element model of cartilage scaffolds was established and stress relaxation simulation was performed to analyze the variation of scaffold relaxation stress with time. The stress relaxation constitutive model was established to predict mechanical properties of the scaffold. Results The elastic modulus of cartilage scaffolds at 14 th, 28th, 42nd, 56th day after degradation was 32. 35, 31. 12, 29. 91, 28. 74 kPa, respectively. The upper layer for cartilage scaffolds was the largest. The overall relaxation stress of the scaffold decreased rapidly with time and then tended to be stable. At 8th week after degradation, the stress which the scaffold couldwithstand was still within the physiological load range of the cartilage. The predicted results of the stress relaxation constitutive model were in good agreement with the finite element simulation results. Conclusions The elastic modulus of the scaffold gradually decreases with the increase of degradation time. The longer the degradation period is, the less stress the scaffold can withstand. At the same degradation period, the larger the applied compressive strain, the larger the stress on the scaffold. Both the finite element simulation and stress relaxation constitutive model can effectively predict stress variations of cartilage scaffolds under degradation
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Objective:To compare the effect of extracorporeal membrane oxygenation(ECMO)on pulmonary transplantation(LTx)in patients with idiopathic pulmonary fibrosis(IPF)complicated with pulmonary hypertension(PH).Methods:From January 2017 to December 2020, clinical data were retrospectively reviewed for 112 IPF patients complicated with PH undergoing LTx assisted by venous ECMO(VV-ECMO group, n=68)or venous arterial ECMO(VA-ECMO group, n=44). Gender, age, mechanical ventilation time, oxygenation index, cold ischemic time, preoperative gender, age, smoking history, PO 2, PCO 2, PH degree, NYHA cardiac function grade, right cardiac function, ejection fraction(EF)and complications(hypertension & diabetes)of two groups were compared. Intraoperative approach, operative duration, ECMO transfer time, blood loss, blood transfusion, urine volume, postoperative blood transfusion, mechanical ventilation time, ICU stay time, re-thoracotomy, pulmonary infection, primary graft dysfunction(PGD)and renal insufficiency were recorded. And the effects of two different diversion modes on early postoperative complications and short-term outcomes of LTx were further analyzed by multiple factors. Cox proportional risk model was employed for comparing VV-ECMO and VA-ECMO flow patterns with factors related to recipient survival after transplantation. Results:The preoperative PO 2 of 58.3(51.3, 72.0)mmHg was significantly lower in VV-ECMO bypass group than that of 73.2(63.3, 96.8)mmHg in VA-ECMO group and the difference was statistically significant( P<0.006). Compared with VV-ECMO group, 24(54.5%), 15(34.1%)and 22(50.0%)had NYHA class Ⅲ, severe PH and preoperative right heart enlargement in VA-ECMO group respectively and the differences were statistically significant compared with 17(25.0%), 6(8.8%)and 16(23.5%)in VV-ECMO group( P<0.05 for all). No significant inter-group differences existed in postoperative PGD, postoperative mechanical ventilation time(≥3 d), pulmonary infection, postoperative thoracotomy ratio, postoperative renal insufficiency, ICU stay, hospital stay and other aspects( P>0.05). And 6-month postoperative survival rates of VV-ECMO and VA-ECMO groups were 80.9% and 61.4%, respectively and no significant inter-group difference existed in short-term survival rate(6 months)after adjustment by multivariate Cox regression model( P>0.05). Multivariate statistics indicated that the risk of delayed postoperative withdrawal was 14.452-fold higher in VV-ECMO group than in VA-ECMO group and the inter-group difference was statistically significant(95% CI: 2.448-85.323, P=0.03). Conclusions:No differences exist in postoperative complications or short-term survival rate between IPF recipients with mild PH on VV-ECMO mode and IPF recipients with severe PH on VA-ECMO mode. VV-ECMO flow reversal can delay the transplant back-off time.
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The relationship between the expression of resistin in polycystic ovary syndrome (PCOS) and insulin resistance was investigated. The plasma resistin concentrations in 35 patients with PCOS and 40 controls were measured by ELISA. Luteinizing hormone (LH), follicle-stimulating hormone (FSH), and fasting insulin (FIN) were tested by radioimmunoassay. Insulin resistance index (HOMA-IR) was calculated. Fasting plasma glucose (FPG) was determined by oxidase test. Western blot and reverse transcriptase PCR (RT-PCR) methods were used to detect the expression of resistin in adipose tissues. The levels of plasma resistin, LH, LH/FSH and FIN and HOMA-IR in patients with PCOS were significantly higher than those in control group (all P<0.05). Plasma resistin was correlated positively with FPG, FIN, HOMA-IR, LH and LH/FSH (r=0.56, 0.60, 0.65, 0.48, and 0.42 respectively). Resistin protein and mRNA expression levels in patients with PCOS were significantly higher than those in normal tissues (all P<0.01). It was concluded that resistin might be involved in the pathogenesis of insulin resistance of PCOS.