Aiming at the problem of the influence of preloading force on its mechanical response in soft tissue compression experiments, an elimination method of preloading force based on linear loading region is proposed. Unconfined compression experiments under a variety of different preloading forces are performed. The influence of the preloading force on the parameters of constitutive model is analyzed. In the preload phase, the mechanical response of the soft tissue is taken as a linear model. The preloading force is eliminated by taking the preloading phase into account throughout the response process. According to five different preloading forces of the unconfined compression experiments, the elimination method is validated with two different constitutive models of soft tissue, and the error between the models obtained by the preloading force elimination method and the traditional method with the experimental results is compared. The results show that the error obtained by preloading force elimination method is significantly smaller than the traditional method. The preloading force elimination method can eliminate the influence of preloading force on mechanical response to a certain extent, and constitutive model parameters which are closer to the true properties of soft tissue can be obtained.
A geometrical model of L4-L5 lumbar segment was constructed using a three-dimensional graphics software. Four conditions of the degenerated discs, i.e. light degeneration, moderate degeneration, severe degeneration and complete excision degeneration, were simulated with loading situations using finite element method under the condition of appropriate computational accuracy. By applying a vertical load of 378.93 N on L4 vertebral plate, stress nephograms on joint isthmus under four different working conditions were obtained. The results showed that the contacted area of facet joint was influenced by the degree of intervertebral disc degeneration level, which influenced the mises stress on joint isthmus. It was proved that joint isthmus was the important pressure-proof structure of the back of lumbar vertebra, and the stress values and distribution were related to structural stiffness of the back of lumbar vertebra as well as the contact area of facet joint. The conclusion could be the theoretical reference for the analysis of spinal biomechanics and artificial disc replacement as well.
Objective To study the effect of vancomycin-loaded polymethylmethacrylate (VCMPMMA) in the treatment of an experimental hemiprosthetic hip infectionof rabbits. Methods The infected hemiprosthetic hip joints of the rabbits underwent debridement and one-stage revision arthroplasty. Requested by the “fixed” method, 24 rabbits were equally divided into 2 groups: the control group and theexperimental group. The prostheses were fixed with PMMA in the control group, but with VCM-PMMA in the experimental group. X-ray films were taken immediately after operation, and then 4, 8, and 12 weeks after operation. The C reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) were measured before operation, then measured 1, 3, and 7 days after operation, and then 2, 4, 8, and 12 weeks after operation, i.e., they were measured at the above 8 time points. All the rabbits were sacrificed 12 weeks later. The cure rate of the infection was determined by the blood culture for the corresponding bacteria and the Rhodamine-labeled anti-Staphylococcus epidermidisimmune serum staining. Results The X-ray films revealed that6 hemiprosthetic hip joints were dislocated in the control group, but 3 in the experimental group; 58.3% and 16.7% of the hemiprosthetic hip joints were reinfected in the control group and the experimental group, respectively. At 8 weeks in the control group, the serum CRP level decreased to a greater extent than that measured at the time of debridement, but in the experimental group just at 2 weeks （Plt;0.01）. ESR remained elevated in the control group, but at 4 weeks ESR were significantly lowered compared with that measured at the time of debridement（Plt;0.01）. The test results for the pathogenic organisms revealed that the re-infection incidences were respectively 58.3% (7/12) and 16.7% (2/12) in the control group and the experimental group, with the successful revision rates of 41.7% and 83.3% respectively in the above 2 groups. The light microscopy revealed that therewas a heavy infiltration by the inflammatory cells in the reinfected tissues, but there was a proliferation of the fibrocytes in the tissues of the cured patients. Conclusion Onestage revision arthroplasty can significantly promote the control of the hemiprosthetic hip joint infection in rabbits by the use of VCM-PMMA.
OBJECTIVETo study the repairing method of facial nerve defect using nerve elongation, and the biomechanical properties of peripheral nerves. METHODS A novel device for peripheral nerve elongation was designed and manufactured. With the device, facial nerves of rabbits were expanded acutely and chronically by string-type loading. The facial nerves were studied with histological and electrophysiological examinations before and after elongation. RESULTS There were no considerable necrosis, degeneration, and infection in the facial nerves after elongation. The experimental animals took food normally and their body temperature were stable. Histological examinations showed dispersing Sunderland degree III injury and occasionally broken capillary blood vessels in the acute group, thicker nerve and fibroblasts hyperplasia between nerve bundles in the chronic group. The electromyogram(EMG) of buccal muscle and nerve conductive velocity(NCV) showed the maximal range was (18.7 +/- 2.4)% in the acute group, and (30.8 +/- 2.4)% in the chronic group. CONCLUSION It suggests that the novel nerve elongation method is feasible, and it can be used to study the nerve elongation basically and clinically.
Vascular calcification is an active, adjustable and complex biological process. It is an independent hazard factor for cardiovascular events and there is a lack of effective treatment. As a newly discovered regulated cell death, ferroptosis is closely related to iron metabolism, lipid metabolism, glutathione metabolism and so on. In recent years, studies have shown that ferroptosis may be implicated in the occurrence and progression of vascular calcification. Based on the introduction of ferroptosis, this review will discuss the close relationship between ferroptosis and vascular calcification from intimal calcification, medial calcification and heart valve calcification, in order to provide new ideas for the prevention and treatment of vascular calcification.
Objective To evaluate the influence of tidal volume on the accuracy of stroke volume variation ( SVV) to predict volume state of pigs with ventilation.Methods Thirty-six healthy pigs were anesthetized after tracheal intubation and ventilated. With the envelope method, they were randomized into a normovolemia group, a hemaerrhagic shock group, and a hypervolemia group, with 12 pigs in each group. The pigs in the hemaerrhagic shock group were removed 20 percent of blood, and the pigs in the hypervolemia group received additional infusion of 20 percent 6% hydroxyethyl starch. In each group, ventilator settings were changed in a randomized order by changing VT [ VT = 5 mL/kg ( VT5 ) , VT =10 mL/kg ( VT10 ) , and VT =15 mL/kg ( VT15 ) ] . Hemodynamic measurements [ heart rate ( HR) , mean arterial boold pressure ( MAP) , systemic vascular resistance index ( SVRI) , cardiac index ( CI) , stroke volume index ( SVI) , intrathoracic blood volume index( ITBVI) , and SVV] were obtained after 10 minutes of stabilization. Results SVV was increased in the hemaerrhagic shock group comparing with the normovolemia group for VT10 [ ( 21 ±5) % vs. ( 11 ±2) % , P lt;0. 05] , but SVV was decreased in the hypervolemia group comparing with the normovolemia group [ ( 7 ±2) % vs. ( 11 ±2) % , P lt; 0. 05] . The variation tendency for VT15 was the same with VT10 , moreover SVV were all above 12% for the hemaerrhagic shock group, the normovolemia group, and the hypervolemia group [ ( 30 ±7) % , ( 19 ±3) % , and ( 15 ±4) % ] . There were no significant diffrences among the hemaerrhagic shock group, hypervolemia group and normovolemia group [ ( 8 ±6) % ,( 7 ±5) % , and ( 7 ±4) % , P gt; 0. 05] for VT5 . Conclusions SVV was a precise indicator of cardiac preload, but SVV was less sensitive to the changes of volume during low tidal volume ( 5 mL/kg) ventilation. The threshold of SVV for predicting fluid responsiveness maybe above 12% with a high tidal volume ( 15 mL/kg) ventilation.
In order to check the neck response and injury during motor vehicle accidents, we developed a detailed finite element model for human cervical spine C4-C6. This model consisted of cortical bone, cancellous bone, annulus, nucleus, ligaments and articular facet, and it also set up contact in the contacting parts for simulating the movement perfectly under frontal impact. This model could be used for stress and strain distribution after the frontal impact load was applied on this model. During the process of frontal impact, the most displacement simulated data were in the interval range of experimental data. The experimental results showed that this model for the human cervical spine C4-C6 simulated the movement under the frontal impact with fidelity, and reflected the impact dynamics response on the whole.
This study aimed to explore the role of miR-130a-3p in cardiomyocyte hypertrophy and its underlying mechanisms. Pressure-overload induced myocardial hypertrophy mice model was constructed by thoracic aortic constriction (TAC). In vitro, norepinephrine (NE) was used to stimulate neonatal rat cardiomyocytes (NRCMs) and H9c2 rat cardiomyocytes to induce hypertrophic phenotypes. The expression of miR-130a-3p was detected in mice hypertrophic myocardium, hypertrophic NRCMs and H9c2 cells. The mimics and inhibitors of miR-130a-3p were transfected into H9c2 cells to observe the role of miR-130a-3p on the hypertrophic phenotype change of cardiomyocytes separately. Furthermore, whether miR-130a-3p regulated hypertrophic related signaling pathways was explored. The results showed that the expression of miR-130a-3p was significantly decreased in hypertrophic myocardium, hypertrophic NRCMs and H9c2 cells. After transfection of miR-130a-3p mimics, the expression of hypertrophic marker genes, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and β-myosin heavy chain (β-MHC), and the cell surface area were notably down-regulated compared with the control group (mimics N.C. + NE group). But after transfection of miR-130a-3p inhibitor, the expression of ANP, BNP and β-MHC in H9c2 cells increased significantly, and the cell area increased further. By Western blot, it was found that the protein phosphorylation level of Akt and mTOR were down-regulated after over-expression of miR-130a-3p. These results suggest that miR-130a-3p mimics may alleviate the degree of cardiomyocyte hypertrophy, meanwhile its inhibitor can further aggravate cardiomyocyte hypertrophy. Over-expression of miR-130a-3p may attenuate cardiomyocytes hypertrophy by affecting the Akt pathway.
Objective To explore the effect of rolling compression loading bioreactor on chondrogenesis of rabbit bone marrow mesenchymal stem cells (BMSCs) with different loading parameters. Methods BMSCs were isolated from New Zealand rabbits, aged 2.5 months. BMSCs at passage 3 were used to prepare BMSCs-agarose gels (4 mm in diameter and height, respectively). Samples were divided into 8 groups: 10% (group A1), 20% (group A2), and 30% (group A3) compression groups (0.4 Hz, 3 h/ d) and 20 minutes (group B1), 3 hours (group B2), and 12 hours (group B3) rolling time groups and static culture (control groups). The living cell rate, the collagen type II and Aggrecan gene expressions, and glycosaminoglycan (GAG) content were determined, and histological staining was done at 24 hours, 7 days, 14 days, and 21 days after culture. Results At 14 and 21 days, the living cell rates of groups A1 and A2 were significantly higher than that of group A3 (P lt; 0.05), groups B1 and B2 were significantly higher than group B3 (P lt; 0.05). Collagen type II and Aggrecan gene expressions of the experimental groups at each time point were significantly higher than those of the control groups (P lt; 0.05); at 14 and 21 days, collagen type II and Aggrecan gene expressions of groups A1 and A2 were significantly higher than those of group A3, and groups B1 and B2 were also significantly higher than group B3 (P lt; 0.05). At 14 and 21 days, the GAG contents of groups A1 and A2 were significantly higher than those of group A3 (P lt; 0.05); groups B1 and B2 were also significantly higher than group B3 (P lt; 0.05). At 21 days, toluidine blue staining showed that obvious blue-staining and even cartilage lacunae were seen in groups A2 and B2, but light and quite rare blue-staining in groups A1, A3, B1, and B3. Conclusion The rolling compression loading bioreactor has great promotion effect on chondrogenesis of rabbit BMSCs with rolling parameters of 0.4 Hz, 3 hours, and 20% compression.
To evaluate the efficacy and the surgical procedures of submandibular sialoadenectomy by a modified retroauricular approach. Methods Between October 2008 and April 2009, 8 patients with benign submandibular gland disorders underwent removal of benign submandibular gland lesions using a retroauricular approach. There were 4 males and 4 females with an average age of 38.5 years (range, 32-54 years), including 3 pleomorphic adenoma and 5 chronic sialadenitis with sialol ithiasis. The disease duration was from 2 months to 5 years. The anterior facial vein and the facial artery were reserved only by the l igation of branching vessels in the submandibular gland. Results Submandibular sialoadenectomy were successfully performed in 8 cases. The operative time was 45-75 minutes (mean, 60 minutes). All incisions obtained heal ing by first intention. No nerve paralysis occurred, including marginal mandibular branch of the facial nerve, the l ingual nerve, and hypoglossal nerve. One patient had poor blood circulation of flap due to excessive traction during operation, but it returned normal after 24 hours without special treatment. Other flaps had good blood circulation. All patients were followed up 1-6 months (mean, 3 months). The incision scars were hidden with satisfactory appearance. Conclusion The modified retroauricular approach has some advantages such as simple operation, better cosmetic outcome, and no compl ication.