Median effective dose of 0.5% ropivacaine for ultrasound-guided femoral nerve block: dose per unit femoral nerve cross-sectional area / 中华麻醉学杂志

Objective:To determine the median effective dose (ED 50) of 0.5% ropivacaine based on femoral nerve cross-sectional area for ultrasound-guided femoral nerve block. Methods:Patients of both sexes, aged 18-64 yr, of American Society of Anesthesiologists physical status I or Ⅱ, with body mass index of 20-30 kg/m 2, scheduled for elective open reduction and internal fixation for patella fracture or removal of patella fracture by internal fixation, were enrolled in this study.Ultrasonic localization of femoral nerve was performed for measurement of the femoral nerve cross-sectional area, and 0.5% ropivacaine was injected based on the area.ED 50 was determined by Dixon′s up-and-down sequential method.The initial dose was 0.22 ml/mm 2, and the difference between the two successive doses was 0.02 ml/mm 2.The effective block was defined as complete loss of pain sensation in the areas of anterior skin of knee joint, skin on the inner side of the calf and dorsal medial skin of the foot and the degree of motor block was in stages 1-3 assessed using Brunnstrom motor function within 30 min after nerve block.Nerve block was considered ineffective if pain occurred in any nerve distribution area mentioned above.The study was terminated if 7 effective and ineffective alternating waves occurred.ED 50 and 95% confidence interval (CI) were calculated using Probit analysis. Results:Twenty-seven patients were enrolled in the study with the femoral nerve cross-sectional area (75±5) mm 2.ED 50 (95%CI) of 0.5% ropivacaine for ultrasound-guided femoral nerve block was 0.106 (0.069-0.125) ml/mm 2. Conclusion:ED 50 of 0.5% ropivacaine based on femoral nerve cross-sectional area for ultrasound-guided femoral nerve block is 0.106 ml/mm 2.

Effect of the disruption of three cytoskeleton components on chondrocyte metabolism in rabbit knee cartilage / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Chondrocytes' phenotype and biosynthesis of matrix are dependent on having an intact cytoskeletal structure. Microfilaments, microtubules, and intermediate filaments are three important components of the cytoskeletal structure of chondrocytes. The aims of this study were to determine and compare the effects of the disruption of these three cytoskeletal elements on the apoptosis and matrix synthesis by rabbit knee chondrocytes in vitro.</p><p><b>METHODS</b>Chondrocytes were isolated from full-thickness knee cartilage of two-month-old rabbits using enzymatic methods (n = 24). The isolated cells were stabilized for three days and then exposed to low, medium, and high doses of chemical agents that disrupt the three principal cytoskeletal elements of interest: colchicine for microtubules, acrylamide for intermediate filaments, and cytochalasin D for actin microfilaments. A group of control cells were treated with carrier. Early apoptosis was assessed using the Annexin-FITC binding assay by flow cytometry on days 1 and 2 after exposure to the disrupting chemical agents. The components and distribution of the cytoskeleton within the cells were analyzed by laser scanning confocal microscopy (LSCM) with immunofluorescence staining on day 3. The mRNA levels of aggrecan (AGG) and type II collagen (Col-2) and their levels in culture medium were analyzed using real-time PCR and enzyme-linked immunosorbent serologic assay (ELISA) on days 3, 6, and 9.</p><p><b>RESULTS</b>In the initial drug-dose-response study, there was no significant difference in the vitality of cells treated with 0.1 µmol/L colchicine, 2.5 mmol/L acrylamide, and 10 µg/L cytochalasin D for two days when compared with the control group of cells. The concentrations of colchicine and acrylamide treatment selected above significantly decreased the number of viable cells over the nine-day culture and disrupted significantly more cell nuclei. Real-time PCR and ELISA results showed that the mRNA levels and medium concentrations of AGG and Col-2 were significantly decreased for cultures treated with colchicine and acrylamide when compared with untreated cells at three, six, and nine days, and this inhibition was correlated with higher matrix metalloprotease-13 expression in these cells. Cellular proliferation, monolayer morphology, and matrix metabolism were unaffected in cytochalasin D-treated cells when compared with control cells over the nine-day culture period.</p><p><b>CONCLUSIONS</b>The disruption of the microtubulin and intermediate filaments induced chondrocyte apoptosis, increased matrix metalloprotease expression, and decreased AGG and Col-2 expression in rabbit knee chondrocyte cultures. Our findings suggest that microtubulin and intermediate filaments play a critical role in the synthesis of cartilage matrix by rabbit knee chondrocytes.</p>

Differentiation of bone marrow mesenchymal stem cells into chondrocyte-like cells under the conditions of transforming growth factor beta and cyclical tensile strain / 中国组织工程研究

BACKGROUND:Transforming growth factor-βhas been shown to exert an obvious induction effect on the differentiation of bone marrow mesenchymal stem cells into chondrocytes. Cyclical tensile strain simulates mechanical environment of chondrocytes in the body, and plays an important regulatory role in cellproliferation and differentiation. OBJECTIVE:To discuss the synergy of transforming growth factor-βand cyclical tensile strain in inducing the differentiation of bone marrow mesenchymal stem cells into chondrocyte-like cells. METHODS:A total of 10 2-month-old New Zealand rabbits were selected. Bone needle was used to penetrate the medul ary cavity of bone. 3.0-4.0 mL of bone marrow was extracted for isolation and culture of bone marrow mesenchymal stem cells. Passage 3 cells were randomly assigned to four groups:blank, transforming growth factor-β, cyclical tensile strain and cyclical tensile strain+transforming growth factor-βgroups. After 1, 3 and 6 days, cells were obtained. General morphology was observed using safranin O staining. Glycosaminoglycan levels were detected by alcian blue staining. Matrix metal oproteinase-13 and tissue inhibitor of metal oproteinase-1 levels in supernatant were measured using ELISA. Type II col agen, matrix metal oproteinase-13 and tissue inhibitor of metal oproteinase-1 mRNA relative expression was detected using RT-PCR. RESULTS AND CONCLUSION:Safranin O staining showed fusiform or irregular triangular cells. cellnumber and matrix secretion increased in each experimental group than in blank group. Glycosaminoglycan levels in the supernatant were greater in the transforming growth factor-βand cyclical tensile strain+transforming growth factor-βgroups than in the blank group (P<0.05). Type II col agen mRNA relative expression was higher in the cyclical tensile strain+transforming growth factor-βgroup than in the blank group (P<0.05). Results indicated that transforming growth factor-βand cyclical tensile strain could induce the differentiation of bone marrow mesenchymal stem cells into chondrocytes, showing an apparent cooperative action.