白念珠菌生物被膜耐药株麦角甾醇检测的方法学研究

目的：分别采用高效液相色谱法和气相色谱质谱联用法测定白念珠菌麦角甾醇含量,并对这两种方法进行比较。方法：采用浓度梯度递增法诱导白念珠菌耐药株,采用KONT真菌显色MIC药敏系统鉴定耐药性。构建6、12、24h生物被膜,采用高效液相色谱法和气相色谱质谱联用法测定麦角甾醇含量。结果：高效液相色谱法检测出麦角甾醇含量,最低检出浓度为0.05mg/L,而气相色谱质谱联用法未检测出麦角甾醇含量。结论：高效液相色谱法能准确测定白念珠菌麦角甾醇含量。与气相色谱质谱联用法比较,高效液相色谱法简单、高效和可靠。     

The Science behind Topical Negative Pressure Therapy

Topical negative pressure therapy (TNP) is an established part of modern wound healing. With an increasing choice in TNP providers, understanding the differing modes of action, the biochemical and biophysical effects on the wound at a microscopic and macroscopic level, plus the role of the interface dressings, will aid the clinician in planning a clear goal of therapy. This article reviews the scientific evidence for TNP to date and explores each mechanism of action and the implications for wound healing and patient outcomes.     

Bone Remodeling and in Vivo Strain Analysis of Intact and Implanted Greyhound Proximal Femora

Pre- and poststudy motion and gait analyses of eight size-matched male greyhounds confirmed uniform loading of their femora. Subminiature strain gages implanted on the intact inferior and anterior aspects of the femoral neck in six greyhounds indicated in vivo strain variations among test animals. Motion and gait analyses confirmed uniform loading of femora following unilateral hemiarthroplasty with cobalt-chromium hip implants. In vivo strain measurements adjacent to the implants indicated large variations among test animals. A consistent direction of strain change relative to the intact femur was noted, even though strain changes varied in magnitude. Image analysis of microradiographs indicated insignificant differences in the cortical areas of implanted and intact femora. Extensive new trabecular bone formation was noted along the implant in the endosteal cavity and correlated with a combination of implant placement and exercise level. Most of the bone was formed with centrally placed implants in exercised dogs, and the least with stems on the medial neck surface in rested dogs. Iliac crest biopsies indicated that bone formation rates slowed in rested animals and remained constant throughout the study in exercised animals. All implanted femora had a thin (<1 mm thick) aligned fibrous tissue layer separating the implant from bone. It varied in thickness as a function of the aspect of the implant. Exercised dogs had a larger proportion of fibrous tissue on the anterior and posterior aspects, while rested dogs had a larger proportion of fibrous tissue on the medial and lateral aspects.     

Congenital Coxa Vara and Perthes' Disease

Mechanical properties of fractured and intact femora have been studied in young and adult, male rats. A standardized, closed, mid-diaphyseal fracture was produced in the left femur, the right femur serving as control. The fracture was left to heal without immobilization. At various intervals, both fractured and intact femora were loaded in torsion until failure.

The fractured femora regained the mechanical properties of the contralateral, intact bones after about 4 weeks in young and after about 12 weeks in adult rats. For intact bones, both the ultimate torsional moment (strength) and the torsional stiffness increased with age of the animals, whereas the ultimate torsional angle remained unchanged. For bone as a material, however, the ultimate torsional stress (strength) and the modulus of rigidity (stiffness) increased with age only in young rats, being almost constant in the adult animals.

The various biomechanical parameters of the healing fractures did not reach those of the contralateral, intact bones simultaneously. The torsional moment required to twist a healing femoral fracture 20 degrees (0.35 radians), a deformation close to what an intact femur can resist, proved to be a functional and simple measure of the degree of fracture repair in rats.     

The effect of cyclic mechanical strain on the expression of adhesion-related genes by periodontal ligament cells in two-dimensional culture

Saminathan A, Vinoth KJ, Wescott DC, Pinkerton MN, Milne TJ, Cao T, Meikle MC. The effect of cyclic mechanical strain on the expression of adhesion‐related genes by periodontal ligament cells in two‐dimensional culture. J Periodont Res 2012; 47: 212–221. © 2011 John Wiley & Sons A/S Background and Objective: Cell adhesion plays important roles in maintaining the structural integrity of connective tissues and sensing changes in the biomechanical environment of cells. The objective of the present investigation was to extend our understanding of the effect of cyclic mechanical strain on the expression of adhesion‐related genes by human periodontal ligament cells. Material and Methods: Cultured periodontal ligament cells were subjected to a cyclic in‐plane tensile deformation of 12% for 5 s (0.2 Hz) every 90 s for 6–24 h in a Flexercell FX‐4000 Strain Unit. The following parameters were measured: (i) cell viability by the MTT assay; (ii) caspase‐3 and ‐7 activity; and (iii) the expression of 84 genes encoding adhesion‐related molecules using real‐time RT‐PCR microarrays. Results: Mechanical stress reduced the metabolic activity of deformed cells at 6 h, and caspase‐3 and ‐7 activity at 6 and 12 h. Seventy‐three genes were detected at critical threshold values < 35. Fifteen showed a significant change in relative expression: five cell adhesion molecules (ICAM1, ITGA3, ITGA6, ITGA8 and NCAM1), three collagen α‐chains (COL6A1, COL8A1 and COL11A1), four MMPs (ADAMTS1, MMP8, MMP11 and MMP15), plus CTGF, SPP1 and VTN. Four genes were upregulated (ADAMTS1, CTGF, ICAM1 and SPP1) and 11 downregulated, with the range extending from a 1.76‐fold induction of SPP1 at 12 h to a 2.49‐fold downregulation of COL11A1 at 24 h. Conclusion: The study has identified several mechanoresponsive adhesion‐related genes, and shown that onset of mechanical stress was followed by a transient reduction in overall cellular activity, including the expression of two apoptosis ‘executioner’ caspases.     

Relative motion between the flexor digitorum superficialis tendon and paratenon in zone V increases with wrist flexion angle

Carpal tunnel syndrome is characterized by non‐inflammatory fibrosis of the subsynovial connective tissue (SSCT), a paratenon‐like structure inside the carpal tunnel. This pathology suggests repetitive and/or excessive shear forces are involved in injury development. We assessed relative motion between the flexor digitorum superficialis (FDS) tendon and adjacent paratenon in Zone V using colour Doppler imaging as 16 healthy participants completed three long finger movements (metacarpophalangeal joint flexion, proximal and distal interphalangeal joint flexion, full finger flexion) in three wrist postures (30° extension, 0°, 30° flexion). While the type of finger movement did not affect tendon‐paratenon relative motion, we found a significant main effect of wrist posture (p < 0.001). Relative displacement between the FDS tendon and paratenon (as a percentage of tendon displacement) increased from 27.2% (95%CI = 24.8–29.5%) in 30° wrist extension to 39.9% (95%CI = 37.3–42.4%) in 30° wrist flexion. Optical motion capture confirmed that wrist posture did not affect metacarpophalangeal joint range of motion (p = 0.265) or proximal interphalangeal joint range of motion (p = 0.582). These results indicate that relative motion increased due to paratenon strain when the wrist was flexed. While our findings agree with previous cadaveric research in wrist flexion, we found that relative displacement decreased in 30° wrist extension (compared to 0°). These results differ from cadaveric research, possibly due to challenges maintaining anatomic fidelity of the viscoelastic paratenon tissue in vitro. Overall, our study suggests a greater susceptibility to shear injury during repetitive finger movements, particularly when the wrist is flexed. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1248–1255, 2016.     

Assessing mechanical function of the zygomatic region in macaques: validation and sensitivity testing of finite element models

Crucial to the interpretation of the results of any finite element analysis of a skeletal system is a test of the validity of the results and an assessment of the sensitivity of the model parameters. We have therefore developed finite element models of two crania of Macaca fascicularis and investigated their sensitivity to variations in bone material properties, the zygomatico-temporal suture and the loading regimen applied to the zygomatic arch. Maximum principal strains were validated against data derived from ex vivo strain gauge experiments using non-physiological loads applied to the macaque zygomatic arch. Elastic properties of the zygomatic arch bone and the zygomatico-temporal suture obtained by nanoindentation resulted in a high degree of congruence between experimental and simulated strains. The findings also indicated that the presence of a zygomatico-temporal suture in the model produced strains more similar to experimental values than a completely separated or fused arch. Strains were distinctly higher when the load was applied through the modelled superficial masseter compared with loading an array of nodes on the arch. This study demonstrates the importance of the accurate selection of the material properties involved in predicting strains in a finite element model. Furthermore, our findings strongly highlight the influence of the presence of craniofacial sutures on strains experienced in the face. This has implications when investigating craniofacial growth and masticatory function but should generally be taken into account in functional analyses of the craniofacial system of both extant and extinct species.     

A Recruitment Model of Quasi-Linear Power-Law Stress Adaptation in Lung Tissue

When lung tissue is subjected to a step in strain, it exhibits a stress adaptation profile that is a power function of time. Furthermore, this power function is independent of the strain, even though the quasi-static stress–strain relationship of the tissue is highly nonlinear. Such behavior is known as quasi-linear viscoelasticity, but its mechanistic basis is unknown. We describe a model of soft tissue rheology based on the sequential recruitment of Maxwell bodies. The model is homogeneous in its elemental constitutive properties, yet predicts both power-law stress relaxation and quasi-linear viscoelasticity even when the stress–strain behavior of the model is nonlinear. The model suggests that stress relaxation in lung tissue could occur via a sequence of micro-rips that cause stresses to be passed from one local stress bearing region to another.