51 results on '"Dan L. Bader"'
Search Results
2. Investigating the release of inflammatory cytokines in a human model of incontinence-associated dermatitis
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David Voegeli, Dan L. Bader, and Sofoklis Koudounas
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Microdialysis ,Urinary system ,medicine.medical_treatment ,Physiology ,Inflammation ,Dermatology ,Absorption (skin) ,Dermatitis, Contact ,Pathology and Forensic Medicine ,Proinflammatory cytokine ,030207 dermatology & venereal diseases ,03 medical and health sciences ,0302 clinical medicine ,Interleukin-1alpha ,medicine ,Humans ,030504 nursing ,Tumor Necrosis Factor-alpha ,business.industry ,Interleukin 1 Receptor Antagonist Protein ,Urinary Incontinence ,Cytokine ,Cytokines ,Tumor necrosis factor alpha ,medicine.symptom ,0305 other medical science ,Complication ,business ,Fecal Incontinence - Abstract
Incontinence-associated dermatitis (IAD) is a painful complication in elderly patients, leading to reduced quality of life. Despite recent attention, its underlying inflammatory mechanisms remain poorly understood. This study was designed to quantify the release of inflammatory cytokines in a human model of IAD. The left volar forearm of ten healthy volunteers was exposed to synthetic urine and synthetic faeces for 2 h, simulating the effects of urinary and faecal incontinence, respectively, and the subsequent cytokine response compared to that of an untreated control site. Inflammatory cytokines were collected using both the Sebutape® absorption method and dermal microdialysis and quantified using immunoassays. Results from the former demonstrated an upregulation in IL-1α, IL-1RA and TNF-α. Synthetic urine caused a higher median increase in IL-1α from baseline compared to synthetic faeces, whereas synthetic faeces were associated with significantly higher median TNF-α levels compared to synthetic urine (p = 0.01). An increase in IL-1α/IL-1RA ratio was also observed with significant differences evident following exposure to synthetic urine (p = 0.047). Additionally, microdialysis revealed a time-dependent increase in IL-1β and IL-8 following exposure of up to 120 min to synthetic urine and synthetic faeces, respectively. This study demonstrated the suitability of both sampling approaches to recover quantifiable cytokine levels in biofluids for the assessment of skin status following exposure to synthetic fluids associated with incontinence. Findings suggest some differences in the inflammatory mechanisms of IAD, depending on moisture source, and the potential of the cytokines, IL-1α and TNF-α, as responsive markers of early skin damage caused by incontinence.
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- 2021
3. A combined experimental and computational approach to evaluate microclimate control at the support surface interface
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Cees W. J. Oomens, Peter Worsley, M.-T. Fung, Dan L. Bader, and J.G.M.V. Van Asten
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Airflow ,Microclimate ,Dermatology ,Pathology and Forensic Medicine ,030207 dermatology & venereal diseases ,03 medical and health sciences ,0302 clinical medicine ,Skin Physiological Phenomena ,Humans ,Medicine ,Computer Simulation ,Boundary value problem ,Program Development ,Pressure Ulcer ,030504 nursing ,Moisture ,business.industry ,Temperature ,Humidity ,Models, Theoretical ,Finite element method ,Control system ,Support surface ,0305 other medical science ,business ,Biological system - Abstract
Temperature and humidity conditions at the interface between a support surface and the skin, termed microclimate, has been implicated in the development of pressure ulcers. Support surface technologies have been developed to control microclimate conditions, although only a few standard test methods exist to evaluate their performance. This study describes a combined experimental-computational approach to analyzing microclimate control systems. The study used a modified physical model protocol to evaluate two specific support surface systems involving a spacer fabric cover with i) no air flow and ii) an active fan. The physical model deposited moisture at a controlled rate for 25 min, and the microclimate conditions under the model and the surrounding area were monitored for 24 h. Using the experimental data as boundary conditions, a finite element model was developed using mass transport principles, which was calibrated using experimental results. Model inputs included mass density and mass diffusivity, resulting in an estimated absolute humidity change over time. The physical model tests revealed distinct differences between the support surfaces with and without active airflow, with the former having little effect on local humidity levels (RH>75% for 24hr). By contrast, there was a spatial and temporal change in microclimate with the active fan, with sensors positioned towards the source of airflow reaching ambient conditions within 24hr. The computational model was refined to produce comparable results with respect to both the spatial distribution of microclimate and the change in values over time. The combined experimental and computation approach was able to distinguish distinct difference in microclimate change between two support surface designs. The approach could enable the efficient evaluation of different mattress design principles to aid decision making for personalized support surface solutions, for the prevention of pressure ulcers.
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- 2021
4. Bioengineering considerations in the prevention of medical device-related pressure ulcers
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Peter Worsley, Amit Gefen, and Dan L. Bader
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medicine.medical_specialty ,Medical device ,Polymers ,Interface (computing) ,Biophysics ,Early detection ,Bioengineering ,Prosthesis Design ,Body weight ,03 medical and health sciences ,0302 clinical medicine ,Pressure ,Humans ,Medicine ,Computer Simulation ,Orthopedics and Sports Medicine ,Intensive care medicine ,Skin ,Pressure Ulcer ,Community based ,business.industry ,Body Weight ,Soft tissue ,030229 sport sciences ,Respiration, Artificial ,business ,Healthcare providers ,030217 neurology & neurosurgery - Abstract
BackgroundIn recent years, it has become increasingly apparent that medical device-related pressure ulcers represent a significant burden to both patients and healthcare providers. Medical devices can cause damage in a variety of patients from neonates to community based adults. To date, devices have typically incorporated generic designs with stiff polymer materials, which impinge on vulnerable soft tissues. As a result, medical devices that interact with the skin and underlying soft tissues can cause significant deformations due to high interface pressures caused by strapping or body weight.MethodsThis review provides a detailed analysis of the latest bioengineering tools to assess device related skin and soft tissue damage and future perspectives on the prevention of these chronic wounds. This includes measurement at the device-skin interface, imaging deformed tissues, and the early detection of damage through biochemical and biophysical marker detection. In addition, we assess the potential of computational modelling to provide a means for device design optimisation and material selection.InterpretationFuture collaboration between academics, industrialists and clinicians should provide the basis to improve medical device design and prevent the formation of these potentially life altering wounds. Ensuring clinicians report devices that cause pressure ulcers to regulatory agencies will provide the opportunity to identify and improve devices, which are not fit for purpose.
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- 2019
5. Investigating the influence of intermittent and continuous mechanical loading on skin through non-invasive sampling of IL-1α
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Cees W. J. Oomens, Peter Worsley, J.F.J. Soetens, Dan L. Bader, and Soft Tissue Biomech. & Tissue Eng.
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Adult ,Male ,Pressure Ulcer/etiology ,Dermatology ,Stress ,Pathology and Forensic Medicine ,030207 dermatology & venereal diseases ,03 medical and health sciences ,0302 clinical medicine ,Refractory ,Interleukin-1alpha ,Healthy volunteers ,Individual data ,Tissue damage ,Humans ,Medicine ,Non invasive sampling ,Skin ,Aged ,Pressure Ulcer ,030504 nursing ,business.industry ,Skin response ,Skin/injuries ,Middle Aged ,Mechanical ,Regimen ,Anesthesia ,Female ,Stress, Mechanical ,Interleukin-1alpha/analysis ,0305 other medical science ,business ,Healthcare system - Abstract
Pressure ulcers (PUs) are a major burden to both patients, carers and the healthcare system. It is therefore important to identify patients at risk and detect pressure ulcers at an early stage of their development. The pro-inflammatory cytokine IL-1α is a promising indicator of tissue damage. The aim of this study was to compare the temporal skin response, by means of IL-1α expression, to different loading regimens and to investigate the presence of individual variability. The sacrum of eleven healthy volunteers was subjected to two different loading protocols. After a baseline measurement, the left and right side of the sacrum were subjected to continuous and intermittent loading regimen, respectively, at a pressure of 100 mmHg. Data was collected every 20 min, allowing for a total experimental time of 140 min. Sebum, collected at ambient conditions using Sebutape, was analyzed for the pro-inflammatory cytokine IL-1α. Most robust results were obtained using a baseline normalization approach on individual data. The IL-1α level significantly changed upon load application and removal ( p 0.05 ) for both loading regimens. Highest IL-1α ratio increase, 3.7-fold, was observed for 1 h continuous loading. During the refractory periods for both loading regimen the IL-1α levels were still found to be up-regulated compared to baseline ( p 0.05 ). The IL-1α level increased significantly for the two initial loading periods ( p 0.05 ), but stabilized during the final loading period for both loading regimens. Large individual variability in IL-1α ratio was observed in the responses, with median values of 1.91 (range 1.49–3.08), and 2.52 (range 1.96–4.29), for intermittent and continuous loading, respectively, although the differences were not statistically significant. Cluster analysis revealed the presence of two distinct sub-populations, with either a low or high response to the applied loading regimen. The measurement after the first loading period proved to be representative for the subsequent measurements on each site. This study revealed that trends in normalized IL-1α provided an early indicator for tissue status following periods of mechanical loading and refractory unloaded conditions. Additionally, the observed individual variability in the response potentially identifies patients at risk of developing PUs.
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- 2019
6. A combined kinematic and kinetic analysis at the residuum/socket interface of a knee-disarticulation amputee
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Piotr Laszczak, David Moser, Jinghua Tang, Nicholas Hale, Saeed Zahedi, Dan L. Bader, Michael McGrath, and Liudi Jiang
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Adult ,Male ,030506 rehabilitation ,Interface (computing) ,0206 medical engineering ,Biomedical Engineering ,Biophysics ,Pilot Projects ,02 engineering and technology ,Kinematics ,Motion capture ,03 medical and health sciences ,Residuum ,Gait (human) ,Amputees ,Disarticulation ,Humans ,Knee ,Gait ,Mechanical Phenomena ,Coupling ,business.industry ,Biomechanics ,Mechanics ,Structural engineering ,020601 biomedical engineering ,Biomechanical Phenomena ,Shear (sheet metal) ,Kinetics ,0305 other medical science ,business ,Geology - Abstract
BackgroundThe bespoke interface between a lower limb residuum and a prosthetic socket is critical for an amputee’s comfort and overall rehabilitation outcomes. Analysis of interface kinematics and kinetics is important to gain full understanding of the interface biomechanics, which could aid clinical socket fit, rehabilitation and amputee care. This pilot study aims to investigate the dynamic correlation between kinematic movement and kinetic stresses at the interface during walking tests on different terrains.MethodsOne male, knee disarticulation amputee participated in the study. He was asked to walk on both a level surface and a 5° ramped surface. The movement between the residuum and the socket was evaluated by the angular and axial couplings, based on the outputs from a 3D motion capture system. The corresponding kinetic stresses at anterior-proximal (AP), posterior-proximal (PP) and anterior-distal (AD) locations of the residuum were measured, using individual stress sensors.FindingsApproximately 8° of angular coupling and up to 32mm of axial coupling were measured when walking on different terrains. The direction of the angular coupling shows strong correlation with the pressure difference between the PP and AP sensors. Higher pressure was obtained at the PP location than the AP location during stance phase, associated with the direction of the angular coupling. A strong correlation between axial coupling length, L, and longitudinal shear was also evident at the PP and AD locations i.e. the shortening of L corresponds to the increase of shear in the proximal direction. Although different terrains did not affect these correlations in principle, interface kinematic and kinetic values suggested that gait changes can induce modifications to the interface biomechanics.Clinical relevance It is envisaged that the reported techniques could be potentially used to provide combined kinematics and kinetics for the understanding of biomechanics at the residuum/socket interface, which may play an important role in the clinical assessment of prosthetic component settings, including socket fit quality.
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- 2017
7. Does leg predomination affect measuring vasti muscle onsets during single leg squatting? A reliability study
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Javid Mostamand, Dan L. Bader, and Zoe Hudson
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Adult ,Male ,Complementary and Manual Therapy ,medicine.medical_specialty ,Knee Joint ,Intraclass correlation ,Paired difference test ,Physical Therapy, Sports Therapy and Rehabilitation ,Affect (psychology) ,Functional Laterality ,Quadriceps Muscle ,Young Adult ,03 medical and health sciences ,0302 clinical medicine ,Physical medicine and rehabilitation ,Reliability study ,medicine ,Humans ,Observer Variation ,030222 orthopedics ,Electromyography ,business.industry ,Rehabilitation ,Significant difference ,Reproducibility of Results ,030229 sport sciences ,Repeatability ,medicine.disease ,body regions ,Complementary and alternative medicine ,Patellofemoral Pain Syndrome ,Physical therapy ,Squatting position ,Female ,business ,Patellofemoral pain syndrome - Abstract
Introduction Although measuring vasti muscle onset may reveal whether pain relief is associated with altering this parameter during activities in subjects with patellofemoral pain syndrome (PFPS), it may be necessary to determine whether the inherent properties of the dominant leg influences the reliability of measuring VMO-VL muscle onset. The aim of the present study was to examine the effect of leg predomination on reliability testing of the VMO-VL muscle onset measurement during single leg squatting in healthy subjects. Methods The onset of VMO and VL muscles of ten healthy subjects with a right dominant leg was assessed during single leg squatting. Data was collected from the muscle bellies of the VMO and VL. This procedure was performed on the both legs, during three separate single leg squats from a neutral position to a depth of approximately 30° of knee flexion. Subjects were then asked to repeat the test procedure after a minimum of a week's interval. The full wave rectified onsets of VMO and VL were then calculated. Results There was no significant difference between the VMO-VL onset mean values of paired test of right and left knees. The ICC (intra class correlation coefficient) values during within and between sessions tests showed the poor reliability of these measurements on both knees. Conclusion The low intratester reliability of within and between sessions measurement of VMO-VL onset on the both dominant and non-dominant legs revealed that repeatability of these measurements have little accepted reliability, however similar values of these measurements indicated that leg predomination does not affect the measurements during single leg squatting.
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- 2017
8. Reflections on pressure ulcers
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Dan L. Bader
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Pressure Ulcer ,medicine.medical_specialty ,business.industry ,MEDLINE ,Dermatology ,History, 21st Century ,Pathology and Forensic Medicine ,Text mining ,Risk Factors ,Terminology as Topic ,medicine ,Humans ,Intensive care medicine ,business - Published
- 2021
9. Identifying barriers and facilitators to participation in pressure ulcer prevention in allied healthcare professionals: a mixed methods evaluation
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Peter Worsley, Paul Clarkson, Dan L. Bader, and Lisette Schoonhoven
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Adult ,Male ,Health Knowledge, Attitudes, Practice ,Inservice Training ,National Health Programs ,Constant comparison ,Attitude of Health Personnel ,Personnel Staffing and Scheduling ,Staffing ,Physical Therapy, Sports Therapy and Rehabilitation ,Cohort Studies ,Hospitals, University ,03 medical and health sciences ,Professional Role ,0302 clinical medicine ,Occupational Therapists ,Nursing ,Professional boundaries ,Humans ,Medicine ,030212 general & internal medicine ,Pressure Ulcer ,030504 nursing ,Health professionals ,business.industry ,Focus Groups ,Middle Aged ,University hospital ,Focus group ,Physical Therapists ,Pressure Ulcer Prevention ,Female ,0305 other medical science ,business ,Cohort study - Abstract
ObjectivesTo evaluate the barriers and facilitators for allied health professional's participation in pressure ulcer prevention.DesignMixed method cohort study.SettingSingle centre study in an acute university hospital trust.ParticipantsFive physiotherapists and four occupational therapists were recruited from the hospital trust. Therapists had been working in the National Health Service (NHS) for a minimum of one year.Main outcome measuresTherapist views and experiences were collated using an audio recorded focus group. This recording was analysed using constant comparison analysis. Secondary outcomes included assessment of attitudes and knowledge of pressure ulcer prevention using questionnaires.ResultsKey themes surrounding barriers to participation in pressure ulcer prevention included resources (staffing and equipment), education and professional boundaries. Fewer facilitators were described, with new training opportunities and communication being highlighted. Results from the questionnaires showed the therapists had a positive attitude towards pressure ulcer prevention with a median score of 81% (range 50 to 83%). However, there were gaps in knowledge with a median score of 69% (range 50 to 77%).ConclusionsThe therapist reported several barriers to pressure ulcer prevention and few facilitators. The primary barriers were resources, equipment and education. Attitudes and knowledge in AHPs were comparable to data previously reported from experienced nursing staff.
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- 2017
10. COVID19: Challenging tissue viability in both patients and clinicians
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Fran Spratt, Peter Worsley, and Dan L. Bader
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Tissue Survival ,2019-20 coronavirus outbreak ,Coronavirus disease 2019 (COVID-19) ,business.industry ,Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ,COVID-19 ,Dermatology ,Virology ,Article ,Pathology and Forensic Medicine ,Humans ,Medicine ,business ,Tissue viability - Published
- 2020
11. An evaluation of fluid immersion therapy for the prevention of pressure ulcers
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B. Parsons, Peter Worsley, and Dan L. Bader
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Adult ,Male ,Sacrum ,medicine.medical_specialty ,Supine position ,Posture ,0206 medical engineering ,Biophysics ,Beds ,02 engineering and technology ,Increased carbon dioxide ,Young Adult ,030207 dermatology & venereal diseases ,03 medical and health sciences ,0302 clinical medicine ,Pressure ,Immersion (virtual reality) ,medicine ,Humans ,Orthopedics and Sports Medicine ,Aged ,Tissue viability ,Aged, 80 and over ,Pressure Ulcer ,Cross-Over Studies ,business.industry ,Temperature ,Carbon Dioxide ,Middle Aged ,020601 biomedical engineering ,Physiological responses ,Impaired mobility ,Oxygen ,Physical therapy ,Female ,Transcutaneous oxygen ,business ,Blood Gas Monitoring, Transcutaneous ,High-sitting - Abstract
Background: Individuals with impaired mobility can spend prolonged periods on support surfaces, increasing their risk of developing pressure ulcers. Manufacturers have developed mattresses to maximise contact area. The present study evaluated both the biomechanical and physiological responses to lying postures on a Fluid Immersion Simulation mattress.Methods: Seventeen healthy participants were recruited to evaluate the mattress during three prescribed settings of immersion (high, medium and low). Parameters reflecting biomechanical and physiological responses, and the microclimate were monitored during three postures (supine, lateral and high-sitting) over a 90 minute test session. Transcutaneous oxygen and carbon dioxide gas responses were categorised according to three criteria and data were compared between each condition.Findings: Results indicated that interface pressures remained consistent, with peak sacral values ranging from 21 to 27 mm Hg across all immersion settings and postures. The majority of participants (82%) exhibited minimal changes in gas tensions at the sacrum during all test conditions. By contrast, three participants exhibited decreased oxygen with increased carbon dioxide tensions for all three immersion settings. Supine and high sitting sacral microclimate values ranged between 30.1–30.6 °C and 42.3–44.5% for temperature and relative humidity respectively. During lateral tilt there was a reduction of 1.7–2.5 °C and 3.3–5.3% in these values. The majority of participants reported high comfort scores, although a few experienced bottoming out during the high-sitting posture at the high immersion setting.Interpretation: Fluid Immersion Simulation provides an intelligent approach to increase the support area. Further research is required to provide evidence based guidance on the use of personalised support surfaces.
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- 2016
12. 3D models of chondrocytes within biomimetic scaffolds: Effects of cell deformation from loading regimens
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Julia C. Shelton, Dan L. Bader, and Erica Di Federico
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Scaffold ,Materials science ,Biophysics ,Chondrocyte ,Weight-Bearing ,Extracellular matrix ,03 medical and health sciences ,Chondrocytes ,0302 clinical medicine ,Biomimetics ,Stress relaxation ,medicine ,Animals ,Orthopedics and Sports Medicine ,Mechanotransduction ,Tissue Engineering ,Tissue Scaffolds ,Cartilage ,Hydrogels ,030229 sport sciences ,Extracellular Matrix ,medicine.anatomical_structure ,Shear (geology) ,Dynamic loading ,Proteoglycans ,Collagen ,030217 neurology & neurosurgery ,Biomedical engineering - Abstract
BackgroundMechanical conditioning has been widely used to attempt to enhance chondrocyte metabolism for the evolution of functionally competent cartilage. However, although upregulation of proteoglycans have been reported through the application of uniaxial compression, minimal collagen has been produced. The study is designed to examine whether alternative loading regimens, equivalent to physiological conditions, involving shear in addition to compression can enhance collagen production.MethodsFinite element models were developed to determine how the local chondrocyte environments within agarose constructs were influenced by a range of static and dynamic loading regimens. 3-D poro-viscoelastic models were validated against experimental data. In particular, these models were used to characterise chondrocyte deformation in compression with and without shear superimposed, with special reference to the formation of pericellular matrix around the cells.FindingsThe models of the hydrogel constructs under stress relaxation and dynamic cyclic compression conditions were highly correlated with the experimental data. The cell deformation (y/z) in the constructs was greatest in the centre of the constructs, increasing with magnitude of compression up to 25%. The superposition of shear however did not produce significant additional changes in deformation, with the presence of PCM reducing the chondrocyte deformation.InterpretationThe use of FE models can prove important in the definition of appropriate, optimised mechanical conditioning regimens for the synthesis and organisation of mature extra cellular matrix by chondrocyte-seeded constructs. They will also provide insight into the mechanisms relating cell deformation to mechanotransduction pathways, thereby progressing the development of functionally competent tissue engineered cartilage.
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- 2020
13. Design and validation of an in vitro loading system for the combined application of cyclic compression and shear to 3D chondrocytes-seeded agarose constructs
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Julia C. Shelton, Dan L. Bader, and Erica Di Federico
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Materials science ,Tissue Engineering ,Cell Survival ,Sepharose ,Cartilage ,Finite Element Analysis ,Biomedical Engineering ,Biophysics ,Reproducibility of Results ,Equipment Design ,Compression (physics) ,Finite element method ,Shear (sheet metal) ,Mechanical system ,chemistry.chemical_compound ,Chondrocytes ,medicine.anatomical_structure ,chemistry ,Shear stress ,medicine ,Agarose ,Stress, Mechanical ,Deformation (engineering) ,Cells, Cultured ,Biomedical engineering - Abstract
Physiological loading is essential for the maintenance of articular cartilage by regulating tissue remodelling, in the form of both catabolic and anabolic processes. To promote the development of tissue engineered cartilage which closely matches the long term functionality of native tissue, bioreactors have been developed to provide a combination of loading modalities, which reflect the nature of normal physiological loads. This study describes the design and validation of an in vitro mechanical system for the controlled application of bi-axial loading regimes to chondrocyte-seeded agarose constructs. The computer-controlled system incorporates a robust gripping system, which ensures the delivery of precise values of cyclic compressive and shear strain to 3D cell-seeded constructs. Sample prototypes were designed, optimised using finite element analysis and validated performing compressive and shear fatigue mechanical tests. The horizontal and vertical displacements within the bioreactor are precisely controlled by a dedicated programme that can be easily implemented. The synchronisation of the orthogonal displacements was shown to be accurate and reproducible. Constructs were successfully loaded with a combined compressive and shear loading regimen at 1 Hz for up to 48 h with no appreciable loss of cell viability or mechanical integrity. These features along with the demonstrated high consistency make the system ideally suitable for a systematic investigation of the response of chondrocytes to a complex physiologically relevant deformation profile.
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- 2014
14. Cell Mechanics, Structure, and Function Are Regulated by the Stiffness of the Three-Dimensional Microenvironment
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Priyanka Pravincumar, Jerome Irianto, Sheetal R. Inamdar, Jinju Chen, David A. Lee, Martin M. Knight, and Dan L. Bader
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Finite Element Analysis ,Biophysics ,Extracellular matrix ,Prophase ,Chondrocytes ,medicine ,Actin ,Mechanical Phenomena ,Cell Nucleus ,Chemistry ,Linear elasticity ,Stiffness ,Cortical actin cytoskeleton ,Chromatin ,Elasticity ,Biomechanical Phenomena ,Extracellular Matrix ,Crystallography ,Actin Cytoskeleton ,medicine.anatomical_structure ,Cellular Microenvironment ,Cell Biophysics ,Self-healing hydrogels ,medicine.symptom ,Nucleus - Abstract
This study adopts a combined computational and experimental approach to determine the mechanical, structural, and metabolic properties of isolated chondrocytes cultured within three-dimensional hydrogels. A series of linear elastic and hyperelastic finite-element models demonstrated that chondrocytes cultured for 24 h in gels for which the relaxation modulus is
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- 2012
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15. Anisotropic time-dependant behaviour of the aortic valve
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Hazel R. C. Screen, Dan L. Bader, and Afshin Anssari-Benam
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Time Factors ,Materials science ,Swine ,Mechanical Phenomena ,Biomedical Engineering ,Microstructure ,Viscoelasticity ,Biomechanical Phenomena ,Biomaterials ,Stress (mechanics) ,Creep ,Mechanics of Materials ,Aortic Valve ,Materials Testing ,Stress relaxation ,Animals ,Anisotropy ,Stress, Mechanical ,Composite material - Abstract
The complex tri-layered structure of the aortic valve (AV) results in anisotropic quasi-static mechanical behaviour. However, its influence on AV viscoelasticity remains poorly understood. Viscoelasticity may strongly influence AV dynamic mechanical behaviour, making it essential to characterise the time-dependent response for designing successful substitutes. This study attempts to characterise the time-dependent behaviour of the AV at different strain and load increments, and to gain insight into the contribution of the microstructure to this behaviour. Uniaxial incremental stress-relaxation and creep experiments were undertaken, and the experimental data analysed with a generalised Maxwell model, to determine the characteristic time-dependent parameters. Results showed that the time dependent response of the tissue differed with the loading direction, and also with the level of applied load or strain, in both stress-relaxation and creep phenomena. Both phenomena were consistently more pronounced in the radial loading direction. Fitting of the Maxwell model highlighted that the time dependent modes required to model the data also varied in different increments, and additionally with the loading direction. These results suggest that different micro-structural mechanisms may be activated in stress-relaxation and creep, determined by the microstructural organisation of the valve matrix in each loading direction, at each strain or load increment.
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- 2011
16. A multidisciplinary approach to pressure ulcer prevention: exploring healthcare professionals’ knowledge and attitudes to pressure ulcer prevention in the community
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Peter Worsley, Lisette Schoonhoven, Paul Clarkson, and Dan L. Bader
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030207 dermatology & venereal diseases ,03 medical and health sciences ,0302 clinical medicine ,Nursing ,Health professionals ,Multidisciplinary approach ,business.industry ,Pressure Ulcer Prevention ,Medicine ,Physical Therapy, Sports Therapy and Rehabilitation ,030212 general & internal medicine ,business - Published
- 2016
17. Response to Letter from Abraham and colleagues, regarding 'Monitoring the biomechanical and physiological effects of postural changes during leisure chair sitting'
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Peter Worsley and Dan L. Bader
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Sitting Position ,medicine.medical_specialty ,business.industry ,Posture ,0206 medical engineering ,MEDLINE ,02 engineering and technology ,Dermatology ,Sitting ,020601 biomedical engineering ,Biomechanical Phenomena ,Pathology and Forensic Medicine ,03 medical and health sciences ,Leisure Activities ,0302 clinical medicine ,Physical medicine and rehabilitation ,Medicine ,business ,030217 neurology & neurosurgery - Published
- 2018
18. The importance of internal strain as opposed to interface pressure in the prevention of pressure related deep tissue injury
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Cwj Cees Oomens, S Sandra Loerakker, Dan L. Bader, and Soft Tissue Biomech. & Tissue Eng.
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Pressure Ulcer ,medicine.medical_specialty ,business.industry ,Strain (injury) ,Dermatology ,Structural engineering ,medicine.disease ,Models, Biological ,Risk Assessment ,Biomechanical Phenomena ,Rats ,Pathology and Forensic Medicine ,Surgery ,Deep tissue ,Tissue damage ,Interface pressure ,Skeletal Muscle Tissue ,medicine ,Animals ,Humans ,Pressure Ulcer Prevention ,Computer Simulation ,Muscle, Skeletal ,business - Abstract
For pressure ulcer prevention an ambitious goal would be the establishment of a mechanical threshold for tissue damage. In the past, several researchers have sought to establish such a threshold often involving the loading time. However, they have not resulted in a unique reliable value that could be used in practice. This limitation is probably due to the focus on interface pressure. The objective of this paper is to clarify to an audience with no conventional background in mechanics, why interface pressure is not the appropriate parameter to define a damage threshold, whereas internal local deformations (strains) may prove more suitable. The paper reveals that it may be possible to identify a damage threshold for healthy skeletal muscle tissue based on local internal deformations.
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- 2010
19. Diffusion of water in skeletal muscle tissue is not influenced by compression in a rat model of deep tissue injury
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Klaas Nicolay, Bastiaan J. van Nierop, Cees W. J. Oomens, A Anke Stekelenburg, Dan L. Bader, S Sandra Loerakker, Gustav J. Strijkers, Soft Tissue Biomech. & Tissue Eng., and Other departments
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Compressive Strength ,Biomedical Engineering ,Biophysics ,Deformation (meteorology) ,Models, Biological ,Diffusion ,Gastrocnemius muscle ,Body Water ,medicine ,Animals ,Humans ,Effective diffusion coefficient ,Computer Simulation ,Orthopedics and Sports Medicine ,Diffusion (business) ,Muscle, Skeletal ,Pressure Ulcer ,medicine.diagnostic_test ,Chemistry ,Rehabilitation ,Biomechanics ,Skeletal muscle ,Magnetic resonance imaging ,Anatomy ,Compression (physics) ,Rats ,Disease Models, Animal ,medicine.anatomical_structure - Abstract
Sustained mechanical loading of skeletal muscle may result in the development of a severe type of pressure ulcer, referred to as deep tissue injury. Recently it was shown that the diffusion of large molecules (10-150 kDa) is impaired during deformation of tissue-engineered skeletal muscle, suggesting a role for impaired diffusion in the aetiology of deep tissue injury. However, the influence of deformation on diffusion of smaller molecules on its aetiology is less clear. This motivated the present study designed to investigate the influence of deformation of skeletal muscle on the diffusion of water, which can be measured with diffusion tensor magnetic resonance imaging (MRI). It could be predicted that this approach will provide valuable information on the diffusion of small molecules. Additionally the relationship between muscle temperature and diffusion was investigated. During deformation of the tibialis anterior a decrease of the apparent diffusion coefficient (ADC) was observed (7.2±3.9%). The use of a finite element model showed that no correlation existed between the maximum shear strain and the decrease of the ADC. The ADC in the uncompressed gastrocnemius muscle decreased with 5.9±3.7%. In an additional experiment a clear correlation was obtained between the decrease of the ADC and the relative temperature change of skeletal muscle tissue as measured by MRI. Taken together, it was concluded that (1) the decreased diffusion of water was not a direct effect of tissue deformation and (2) that it is likely that the observed decreased ADC during deformation was a result of a decreased muscle temperature. The present study therefore provides evidence that diffusion of small molecules, particularly oxygen and carbon dioxide, is not impaired during deformation of skeletal muscle tissue. © 2009 Elsevier Ltd. All rights reserved.
- Published
- 2010
20. Laboratory measurement of the interface pressures applied by active therapy support surfaces: A consensus document
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Cees W. J. Oomens, Michael Clark, Makamoto Takahashi, Shyam V.S. Rithalia, Margareta Lindgren, Per Ask, Richard H. M. Goossens, Dan L. Bader, and Carol Dealey
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Pressure Ulcer ,medicine.medical_specialty ,Consensus ,business.industry ,Interface (computing) ,Advisory Committees ,Mechanical engineering ,Guidelines as Topic ,Beds ,Equipment Design ,Dermatology ,Manikins ,Skin Care ,Pathology and Forensic Medicine ,Surgery ,Europe ,Patient support ,Human Experimentation ,Materials Testing ,medicine ,Humans ,Pressure Ulcer Prevention ,business - Abstract
A key element in pressure ulcer prevention and management is the selection of appropriate pressure redistributing (PR) patient support surfaces for use while seated and in bed. However little explicit guidance exists allowing standardised quantitative comparison of different PR surfaces based upon their ability to redistribute pressure from anatomical landmarks such as the heels and sacrum. In 2008 a working group was established in Europe through the US National Pressure Ulcer Advisory Panel (NPUAP) support surface standardisation initiative (S3I) and under the aegis of the European Pressure Ulcer Advisory Panel with the specific remit of developing test methods for the evaluation of active therapy support surfaces (alternating pressure air mattresses). This report describes a consensus development process to agree test methods appropriate to compare active therapy surfaces based upon their ability to redistribute pressure from the sacrum and the heels.
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- 2010
21. The free diffusion of macromolecules in tissue-engineered skeletal muscle subjected to large compression strains
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LH Lisette Cornelissen, Debby Gawlitta, Amit Gefen, Dan L. Bader, Cwj Cees Oomens, and Soft Tissue Biomech. & Tissue Eng.
- Subjects
Muscle tissue ,Pathology ,medicine.medical_specialty ,Compressive Strength ,Diffusion ,Biomedical Engineering ,Biophysics ,Strain (injury) ,Cell Line ,Mice ,Tissue engineering ,In vivo ,medicine ,Animals ,Orthopedics and Sports Medicine ,Muscle, Skeletal ,Pressure Ulcer ,Microscopy, Confocal ,Tissue Engineering ,Chemistry ,Rehabilitation ,Fluorescence recovery after photobleaching ,Skeletal muscle ,Dextrans ,medicine.disease ,Compression (physics) ,medicine.anatomical_structure ,Sprains and Strains ,Fluorescence Recovery After Photobleaching ,Biomedical engineering - Abstract
Pressure-related deep tissue injury (DTI) represents a severe pressure ulcer, which initiates in compressed muscle tissue overlying a bony prominence and progresses to more superficial tissues until penetrating the skin. Individual subjects with impaired motor and/or sensory capacities are at high risk of developing DTI. Impaired diffusion of critical metabolites in compressed muscle tissue may contribute to DTI, and impaired diffusion of tissue damage biomarkers may further impose a problem in developing early detection blood tests. We hypothesize that compression of muscle tissue between a bony prominence and a supporting surface locally influences the diffusion capacity of muscle. The objective of this study was therefore, to determine the effects of large compression strains on free diffusion in a tissue-engineered skeletal muscle model. Diffusion was measured with a range of fluorescently labeled dextran molecules (10, 20, 150kDa) whose sizes were representative of both hormones and damage biomarkers. We used fluorescence recovery after photobleaching (FRAP) to compare diffusion coefficients (D) of the different dextrans between the uncompressed and compressed (48-60% strain) states. In a separate experiment, we simulated the effects of local partial muscle ischemia in vivo, by reducing the temperature of compressed specimens from 37 to 34 degrees C. Compared to the D in the uncompressed model system, values in the compressed state were significantly reduced by 47+/-22% (p0.02). A 3 degrees C temperature decrease further reduced D in the compressed specimens by 10+/-6% (p0.05). In vivo, the effects of large strains and ischemia are likely to be summative, and hence, the present findings suggest an important role of impaired diffusion in the etiology of DTI, and should also be considered when developing biochemical screening methods for early detection of DTI.
- Published
- 2008
22. Integrin-mediated mechanotransduction processes in TGFβ-stimulated monolayer-expanded chondrocytes
- Author
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David A. Lee, Donald Salter, Dan L. Bader, and Tina T. Chowdhury
- Subjects
Adult ,Integrins ,Adolescent ,medicine.medical_treatment ,Integrin ,Cell Culture Techniques ,Biophysics ,Sulfuric Acid Esters ,Sulfur Radioisotopes ,Tritium ,Mechanotransduction, Cellular ,Biochemistry ,chemistry.chemical_compound ,Chondrocytes ,Tissue engineering ,Transforming Growth Factor beta ,medicine ,Humans ,Mechanotransduction ,Molecular Biology ,Cells, Cultured ,Nitrites ,biology ,Chemistry ,Growth factor ,Cell Biology ,Transforming growth factor beta ,Middle Aged ,Culture Media ,Cell biology ,Cartilage ,Cell culture ,biology.protein ,Stress, Mechanical ,Thymidine ,Transforming growth factor - Abstract
Previous studies have demonstrated that passage in monolayer detrimentally affects the response of articular chondrocytes to the application of dynamic compression. Transforming growth factor β (TGFβ) is known to regulate metabolic processes in articular cartilage and can enhance the re-expression of a chondrocytic phenotype following monolayer expansion. The current study tests the hypothesis that TGFβ also modulates the response of monolayer-expanded human chondrocytes to the application of dynamic compression, via an integrin-mediated mechanotransduction process. The data presented demonstrate that TGFβ 3 enhanced 35 SO 4 and [ 3 H]thymidine incorporation and inhibited nitrite release after 48 h of culture when compared to unsupplemented constructs. Dynamic compression also enhanced 35 SO 4 and [ 3 H]thymidine incorporation and inhibited nitrite release in the presence of TGFβ 3 . By contrast, dynamic compression did not alter these parameters in the absence of the growth factor. The addition of the peptide, GRGDSP, which acts as a competitive ligand for the α5β1 integrin, reversed the compression-induced stimulation of 35 SO 4 incorporation, [ 3 H]thymidine incorporation, and suppression of nitrite release. No effect was observed when the control peptide, GRADSP, was used. The current data clearly demonstrate that the dynamic compression-induced changes observed in cell metabolism for human monolayer-expanded chondrocytes were dependent on the presence of TGFβ 3 and are integrin-mediated.
- Published
- 2004
23. Increased presence of cells with multiple elongated processes in osteoarthritic femoral head cartilage
- Author
-
Martin M. Knight, Michael V. Kayser, I. Holloway, G. Bentley, David A. Lee, and Dan L. Bader
- Subjects
Cartilage, Articular ,Pathology ,medicine.medical_specialty ,Population ,Biomedical Engineering ,Osteoarthritis ,Matrix (biology) ,Chondrocyte ,Osteoarthritis, Hip ,Extracellular matrix ,Femoral head ,Chondrocytes ,Rheumatology ,medicine ,Humans ,Vimentin ,Orthopedics and Sports Medicine ,Mechanotransduction ,education ,Cytoskeleton ,education.field_of_study ,Microscopy, Confocal ,Chemistry ,Cartilage ,Femur Head ,Anatomy ,medicine.disease ,Extracellular Matrix ,medicine.anatomical_structure ,Microscopy, Fluorescence ,Confocal - Abstract
Objective: This study examined the morphology of chondrocytes in articular cartilage from osteoarthritic (OA) and non-OA human femoral heads and in particular the appearance of a sub-population of cells with multiple elongated processes radiating up to 30μm into the extracellular matrix. Methods: Cartilage explants were removed from 8 anatomical sites over the surface of OA ( n =6) and non-OA ( n =5) femoral heads. Cells were labeled for vimentin intermediate filaments and visualized using epi-fluorescence and confocal microscopy. The percentage of cells with elongated processes was correlated with macroscopic and histological indicators of osteoarthritis. Results: Cells with processes accounted for less than 10% of the total cell population in non-OA cartilage. By contrast, in the peripheral regions of the OA femoral head these cells accounted for 20–45% of the total cell population, the differences being statistically significant. These peripheral areas are habitually non-load bearing and were also the most likely to show gross fibrillation and pannus formation. A statistically significant correlation was demonstrated between the percentage of cells with processes and the histological extent of the OA degradation, quantified in terms of the Mankin score. Conclusions: The extension of cell processes, which may be associated with localized breakdown of the pericellular matrix, will undoubtedly alter numerous aspects of cell function including phenotypic expression and mechanotransduction. Hence these significant changes in chondrocyte morphology are likely to have important implications for the aetiology of osteoarthritis and the development of potential treatment strategies.
- Published
- 2004
- Full Text
- View/download PDF
24. Cell and nucleus deformation in compressed chondrocyte–alginate constructs: temporal changes and calculation of cell modulus
- Author
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David A. Lee, J. van de Breevaart Bravenboer, G.J.V.M. van Osch, Harrie Weinans, Martin M. Knight, Dan L. Bader, Orthopedics and Sports Medicine, and Otorhinolaryngology and Head and Neck Surgery
- Subjects
Time Factors ,Compressive Strength ,Alginates ,Cell ,Biophysics ,Deformation (meteorology) ,Biochemistry ,Chondrocyte ,Viscoelasticity ,Chondrocytes ,Tissue engineering ,Pressure ,medicine ,Animals ,Mechanotransduction ,Molecular Biology ,Cell Size ,Cell Nucleus ,Microscopy, Confocal ,Tissue Engineering ,Anatomy ,Compression (physics) ,medicine.anatomical_structure ,Cattle ,Gels ,Nucleus ,Mathematics - Abstract
Mechanical loading is essential for the homeostasis of articular cartilage and may be necessary for achieving functional tissue engineered cartilage repair using isolated cells seeded in scaffolds such as alginate. Chondrocyte mechanotransduction is poorly understood, but may involve cell deformation and associated distortion of intracellular organelles. The present study used confocal microscopy to examine cell and nucleus morphology in isolated chondrocytes compressed in alginate constructs. Compression of 2% alginate resulted in cell deformation from a spherical to an oblate ellipsoid morphology with conservation of cell volume. Cell deformation was associated with deformation, to a lesser degree, of the nucleus. Despite constant cell deformation over a 25 min period of static compression, the nucleus deformation reduced significantly, particularly in the axis perpendicular to the applied compression. Constructs made of a lower alginate concentration exhibited a reduced compressive modulus with an altered cellular response to compression. In 1.2% alginate, compression resulted in cell deformation which was initially of a similar magnitude to that in 2% alginate but subsequently reduced over a 60 min period reflecting the viscoelastic behaviour of the gel. This phenomenon enabled the calculation of a stress-strain relationship for the cell with an estimated Young's modulus value of approx. 3 kPa.
- Published
- 2002
25. Dynamic Compression Inhibits the Synthesis of Nitric Oxide and PGE2 by IL-1β-Stimulated Chondrocytes Cultured in Agarose Constructs
- Author
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David A. Lee, Dan L. Bader, and Tina T. Chowdhury
- Subjects
Cartilage, Articular ,Cell Culture Techniques ,Biophysics ,Stimulation ,Nitric Oxide ,Tritium ,Models, Biological ,Biochemistry ,Dinoprostone ,Chondrocyte ,Nitric oxide ,Weight-Bearing ,chemistry.chemical_compound ,Chondrocytes ,medicine ,Proteoglycan synthesis ,Animals ,Mechanotransduction ,Molecular Biology ,Cells, Cultured ,Nitrites ,Sulfates ,Cell growth ,Chemistry ,Sepharose ,Cartilage ,Cell Biology ,Anatomy ,Cell biology ,medicine.anatomical_structure ,Agarose ,Cattle ,Stress, Mechanical ,Interleukin-1 ,Thymidine - Abstract
Both mechanical loading and interleukin-1beta (IL-1beta) are known to regulate metabolic processes in articular cartilage through pathways mediated by nitric oxide ((*)NO) and PGE(2). This study uses a well-characterized model system involving isolated chondrocytes cultured in agarose constructs to test the hypothesis that dynamic compression alters the synthesis of (*)NO and PGE(2) by IL-1beta-stimulated articular chondrocytes. The data presented demonstrate for the first time that dynamic compression counteracts the effects of IL-1beta on articular chondrocytes by suppressing both (*)NO and PGE(2) synthesis. Inhibitor experiments indicated that the dynamic compression-induced inhibition of PGE(2) synthesis and stimulation of proteoglycan synthesis were (*)NO mediated, while compression-induced stimulation of cell proliferation was (*)NO independent. The inhibition of (*)NO and PGE(2) by dynamic compression is a finding of major significance that could contribute to the development of novel strategies for the treatment of cartilage-degenerative disorders.
- Published
- 2001
26. Chondrocyte deformation within mechanically and enzymatically extracted chondrons compressed in agarose
- Author
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A. F. Sherwin, Martin M. Knight, C.A. Poole, David A. Lee, J.M. Ross, and Dan L. Bader
- Subjects
Cartilage, Articular ,In situ ,Morphology (linguistics) ,Cell ,Biophysics ,Cell Separation ,Matrix (biology) ,Biochemistry ,Chondrocyte ,chemistry.chemical_compound ,Chondrocytes ,Dogs ,medicine ,Animals ,Molecular Biology ,Cell Size ,Microscopy, Confocal ,Chemistry ,Sepharose ,Cartilage ,Anatomy ,Immunohistochemistry ,Extracellular Matrix ,medicine.anatomical_structure ,Keratan Sulfate ,Agarose ,Collagen ,Deformation (engineering) - Abstract
Within articular cartilage, the chondron microenvironment will influence chondrocyte behaviour and response to loading. Chondrons were extracted from intact cartilage using either mechanical homogenisation (MC) or enzymatic digestion (EC) and cell and matrix morphology in unstrained and compressed agarose constructs was examined. Isolated chondrocytes (IC) were used for comparison. Immunolocalisation of type VI collagen and keratan sulphate revealed differences in the structure of the pericellular microenvironment such that MC most closely resembled chondrons in situ. The unstrained cell diameters of IC and EC were larger than MC at day 1 and increased significantly over a 7 day culture period. In contrast, cell diameters for MC remained constant. Compression of constructs at day 1 resulted in cell deformation for IC and EC but not MC. The two chondron extraction methods yielded chondrons of differing matrix morphology and associated differences in cell size and cellular response to load. The results indicate that the pericellular microenvironment of MC initially possessed a greater mechanical integrity than that of EC. Although these differences may be reduced with time in culture, characterisation of mechanically isolated chondrons suggests that the stiffness of the chondrons in situ may be greater than previous estimates.
- Published
- 2001
27. A system for monitoring the response of uniaxial strain on cell seeded collagen gels
- Author
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David A. Lee, Dan L. Bader, Julia C. Shelton, C Cacou, and Douglas K. Palmer
- Subjects
Mechanical load ,Materials science ,Strain (chemistry) ,Tension (physics) ,Cell ,Biomedical Engineering ,Biophysics ,Stiffness ,Fibroblasts ,Biomechanical Phenomena ,Culture Media ,medicine.anatomical_structure ,Tissue engineering ,Cell culture ,medicine ,Humans ,Seeding ,Collagen ,medicine.symptom ,Cells, Cultured ,Biomedical engineering - Abstract
The success of cell seeded constructs for the repair of collagenous tissues may be improved by the use of mechanical stimulation in vitro. A mechanical loading apparatus, termed the cell straining system, was developed according to a set of design criteria, to enable cell seeded constructs to be cyclically loaded in tension. A suitable cell seeded collagen gel model system was used to characterise the apparatus. These gels were subjected to a cyclic strain of 10% superimposed on two separate tare loads of 2 and 10 mN, while being maintained in cell culture conditions. The computer controlled apparatus was shown to be capable of monitoring the individual loads on six specimens simultaneously, to an accuracy of 0.02 mN. Results indicated a wide variability between individual specimens. Following cyclic loading, the cell seeded collagen gels exhibited an increase in structural stiffness compared with the unloaded controls. This novel and versatile apparatus will provide a means of enhancing structural and mechanical integrity of tissue engineered repair systems.
- Published
- 2000
28. Determination of molecular changes in soft tissues under strain using laser Raman microscopy
- Author
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Dan L. Bader, Costas Galiotis, and Y.-N. Wang
- Subjects
Materials science ,Strain (chemistry) ,Tension (physics) ,Lasers ,Rehabilitation ,Biomedical Engineering ,Biophysics ,Soft tissue ,Spectrum Analysis, Raman ,Compression (physics) ,Rats ,symbols.namesake ,Nuclear magnetic resonance ,Microscopy ,symbols ,Animals ,Wavenumber ,Female ,Orthopedics and Sports Medicine ,Collagen ,Stress, Mechanical ,Rats, Wistar ,Deformation (engineering) ,Raman spectroscopy - Abstract
The paper presents a non-contact technique to examine the molecular changes in a collagen fibre subjected to in vitro axial tension. Laser Raman microscopy was employed to monitor the vibrational changes in specific assignments of the Raman spectrum of collagen. Results were presented in the form of Raman wavenumber shift as a function of applied tensile strain. Two distinct reponses were observed depending on whether the vibrations were axial to, or normal to, the collagen backbone. The former response produced a decrease in wavenumber values, indicating tension, whereas the latter produced an increase, indicating compression. The rate of wavenumber shift with applied strain was non-linear in form, with a marked increase at higher levels of applied strain, for example, a strain 4% in the case of axial vibrations. This technique can prove to be a powerful tool for examining deformation at the molecular level in collagenous tissues.
- Published
- 2000
29. The influence of elaborated pericellular matrix on the deformation of isolated articular chondrocytes cultured in agarose
- Author
-
David A. Lee, Martin M. Knight, and Dan L. Bader
- Subjects
Cartilage, Articular ,Hyaluronoglucosaminidase ,Matrix (biology) ,Deformation (meteorology) ,Chondrocyte ,Compressive strain ,Glycosaminoglycan ,Sepharose ,Extracellular matrix ,chemistry.chemical_compound ,Cell deformation ,Chondrocytes ,medicine ,Animals ,Mechanotransduction ,Molecular Biology ,Cells, Cultured ,Glycosaminoglycans ,Chemistry ,Anatomy ,Cell mechanics ,Cell Biology ,Biomechanical Phenomena ,Confocal microscopy ,Hydroxyproline ,medicine.anatomical_structure ,Biophysics ,Agarose ,Cattle ,Stress, Mechanical - Abstract
This study investigates the mechanical influence of pericellular matrix on the deformation of isolated articular chondrocytes compressed within 3% agarose specimens. After 1 day in culture, the cells were associated with minimal amounts of sulphated glycosaminoglycan (GAG) and hydroxyproline and exhibited substantial deformation from a spherical to an oblate ellipsoid morphology when subjected to 20% gross compressive strain. However, over the 6 day culture period, there was a reduction in cell deformation associated with an increase in matrix content. Treatment with testicular hyaluronidase at days 3 and 6 reduced sulphated GAG content to levels observed in untreated specimens at day 1. At day 3, the resulting cell deformation during 20% compression was equivalent to that in specimens compressed at day 1. However, at day 6 cell deformation was only partially restored, suggesting the presence of additional structural matrix components, other than sulphated GAG, which were not present at day 3. Dual scanning confocal microscopy indicated that the elaborated matrix formed a pericellular shell which did not deform during compression and was therefore stiffer than the 3% agarose substrate. Therefore, the elaboration of a mechanically functional pericellular matrix within 6 days, effectively limits the potential involvement of cell deformation in mechanotransduction within cell seeded systems such as those employed for cartilage repair.
- Published
- 1998
- Full Text
- View/download PDF
30. Dynamic Mechanical Compression Influences Nitric Oxide Production by Articular Chondrocytes Seeded in Agarose
- Author
-
Peter Lees, David A. Lee, Stephen P. Frean, and Dan L. Bader
- Subjects
Cartilage, Articular ,Lipopolysaccharides ,Male ,Lipopolysaccharide ,medicine.medical_treatment ,Biophysics ,Stimulation ,Nitric Oxide ,Biochemistry ,Dexamethasone ,Nitric oxide ,chemistry.chemical_compound ,medicine ,Animals ,Nitrite ,Mechanotransduction ,Molecular Biology ,Cells, Cultured ,Nitrites ,Cell growth ,Sepharose ,Cell Biology ,Cell biology ,Enzyme Activation ,Kinetics ,NG-Nitroarginine Methyl Ester ,Cytokine ,chemistry ,Agarose ,Cattle ,Stress, Mechanical ,Nitric Oxide Synthase ,Cell Division ,Thymidine - Abstract
Nitric oxide (NO) has been implicated in the inhibition of cell proliferation in cytokine and lipopolysaccharide (LPS)-stimulated chondrocytes and is known to be influenced by physical forces in several tissues. In this study, a well-characterized model system utilizing bovine chondrocytes embedded in 3% agarose constructs has been used to investigate the effect of dynamic strain at 0.3, 1, or 3 Hz on NO production. LPS induced a significant increase in nitrite levels, which was reversed by both l -NAME and dexamethasone. Dynamic compressive strain produced a significant reduction in nitrite production. The effect was partially blocked by l -NAME but unaffected by dexamethasone. l -NAME also reversed dynamic compression-induced stimulation of [3H]-thymidine incorporation. NO appears to be a constituent of mechanotransduction pathways which influence proliferation of bovine chondrocytes seeded within agarose constructs. The inhibitor experiments also infer that alterations in cNOS activity primarily determine the response.
- Published
- 1998
31. Variability of forces applied by experienced therapists during spinal mobilization
- Author
-
Dan L. Bader and M.C. Harms
- Subjects
medicine.medical_specialty ,Mobilization ,business.industry ,Biophysics ,Repeatability ,Low back pain ,Trunk ,Clinical Practice ,Physical medicine and rehabilitation ,Spinal mobilization ,Physical therapy ,Medicine ,Orthopedics and Sports Medicine ,Lumbar spine ,medicine.symptom ,business - Abstract
OBJECTIVE: To determine the variation in forces used by different therapists during mobilization of the lumbar spine and the repeatability and reproducibility of individual therapists. DESIGN: An instrumented mobilization couch was developed to measure the forces applied to the trunk during spinal mobilization. BACKGROUND: Due to limitations in equipment design and data analysis, previous related studies demonstrate equivocal results. METHODS: The system was used to collect data from a sample of 30 experienced therapists to evaluate variation, repeatability and reproducibility during the application of five mobilization procedures. RESULTS: The variation in forces used by different therapists when performing the same technique was substantial, ranging between 63 and 347 N for one technique. During this procedure, 30% of the therapists were found to be relatively consistent, repeating the magnitude of the force applied at the first session within 5%. Others demonstrated considerable variation, exhibiting a difference as great as 34%. CONCLUSIONS: The inconsistency between experienced therapists has considerable implications for clinical practice. Changes in the magnitude and rate of loading are likely to have different effects due to the inherent viscoelastic behaviour of soft tissues. RELEVANCE: Spinal mobilization and manipulation techniques are frequently used by manual therapists in the treatment of musculoskeletal disorders. Despite the reliance on these techniques in clinical practice, there is little scientific evidence to substantiate their use. Before progress in this area can be made, it is necessary to characterize the forces used during typical mobilization procedures. The results can be used to develop teaching strategies and as a basis for comparative research on the efficacy of these techniques.
- Published
- 1997
32. Reliability testing of the patellofemoral joint reaction force (PFJRF) measurement during double-legged squatting in healthy subjects: a pilot study
- Author
-
Javid Mostamand, Zoe Hudson, and Dan L. Bader
- Subjects
Adult ,Male ,Complementary and Manual Therapy ,musculoskeletal diseases ,medicine.medical_specialty ,Intraclass correlation ,Pilot Projects ,Physical Therapy, Sports Therapy and Rehabilitation ,Patellofemoral joint ,Motor Activity ,Models, Biological ,Patellofemoral Joint ,Young Adult ,Reference Values ,Image Processing, Computer-Assisted ,medicine ,Humans ,Orthodontics ,Reproducibility ,business.industry ,Rehabilitation ,Biomechanics ,Healthy subjects ,Reproducibility of Results ,Repeatability ,medicine.disease ,Arthralgia ,Biomechanical Phenomena ,body regions ,Complementary and alternative medicine ,Reaction ,Physical therapy ,Squatting position ,Female ,business ,Patellofemoral pain syndrome - Abstract
Summary Introduction Anterior knee pain or patellofemoral pain syndrome (PFPS) is supposed to be related to patellofemoral joint reaction forces (PFJRF). Measuring these forces may therefore provide reliable evidence for conservative treatments to correct probable malalignment in subjects with PFPS. The aim of the present study was to examine the reliability of PFJRF measurements during double-legged squatting in healthy subjects. Methods Using a motion analysis system and one forceplate, PFJRF of 10 healthy subjects were assessed during double-legged squatting. Data were collected from superficial markers taped to selected landmarks. This procedure was performed on the right knees, at three different knee flexion angles of 30, 45 and 60° during three separate double-legged squats. Subjects were then requested to repeat this test procedure on two separate test sessions at different occasions. The PFJRF was calculated using a biomechanical model of the patellofemoral joint. Results The data reveal an increase in PFJRF values (from mean, SD of 425.2, 35.5N to 1075.4, 70.1N)with an increase in the tibiofemoral joint angle during double-legged squatting. The CV (coefficient of variation) values during within and between session tests, revealed the high repeatability and reproducibility of PFJRF measurements, while the ICC (intra class correlation coefficient) values showed the low reliability of these measurements. Conclusion The low reliability of PFJRF measurements suggests that the PFJRF measurement during double-legged squatting should be performed with caution with improving the method of kinetic measurement of the patellofemoral joint in healthy subjects.
- Published
- 2015
33. Editorial
- Author
-
Dan L. Bader
- Subjects
Pathology ,medicine.medical_specialty ,business.industry ,medicine ,MEDLINE ,Dermatology ,Tissue survival ,business ,Pathology and Forensic Medicine ,Tissue viability - Published
- 2013
34. Quantification of Sulfated Glycosaminoglycans in Chondrocyte/Alginate Cultures, by Use of 1,9-Dimethylmethylene Blue
- Author
-
David A. Lee, Brian O. Enobakhare, and Dan L. Bader
- Subjects
Bacteriological Techniques ,Alginates ,Chemistry ,Hexuronic Acids ,Chondroitin Sulfates ,Biophysics ,Dimethylmethylene blue ,Cell Biology ,Hydrogen-Ion Concentration ,Biochemistry ,Chondrocyte ,Methylene Blue ,Glycosaminoglycan ,Cartilage ,medicine.anatomical_structure ,Sulfation ,Glucuronic Acid ,medicine ,Animals ,Cattle ,Molecular Biology ,Glycosaminoglycans - Published
- 1996
35. Raising the bar
- Author
-
Dan L. Bader
- Subjects
Tissue Survival ,business.industry ,Bar (music) ,Medicine ,Dermatology ,Periodicals as Topic ,Composite material ,business ,Pathology and Forensic Medicine - Published
- 2012
36. On the specimen length dependency of tensile mechanical properties in soft tissues: Gripping effects and the characteristic decay length
- Author
-
Afshin Anssari-Benam, Hazel R. C. Screen, Kirsten Legerlotz, and Dan L. Bader
- Subjects
Tail ,Materials science ,Rehabilitation ,Biomedical Engineering ,Biophysics ,Uniaxial tension ,Modulus ,Soft tissue ,Models, Biological ,Rats ,Tendons ,Decay length ,Ultimate tensile strength ,Ultimate stress ,Animals ,Orthopedics and Sports Medicine ,Specimen length ,Material properties ,Biomedical engineering - Abstract
Uniaxial tensile tests to failure have regularly been employed to characterise the material properties of various biological tissues, ranging from heart valves (Anssari-Benam et al., 2011) and arteries (Teng et al., 2009; Lillie et al., 2010) to tendons (Legerlotz et al., 2010), intervertebral discs (Nerurkar et al., 2010) and liver (Brunon et al., 2010), providing valuable quantitative data on important mechanical properties such as ultimate stress, strain and modulus. These properties, by definition, are intrinsic material properties and thus should not depend on the geometry of the specimen
- Published
- 2012
37. Reflections on a challenging year
- Author
-
Dan L. Bader
- Subjects
Medical education ,business.industry ,Medicine ,Dermatology ,business ,Pathology and Forensic Medicine - Published
- 2012
38. It’s all change for the new editor – Not another bioengineer
- Author
-
Dan L. Bader
- Subjects
Tissue Survival ,World Wide Web ,business.industry ,Medicine ,Bioengineering ,Dermatology ,Periodicals as Topic ,business ,Pathology and Forensic Medicine - Published
- 2011
39. The conference season
- Author
-
Dan L. Bader
- Subjects
Societies, Scientific ,Tissue Survival ,business.industry ,Medicine ,Dermatology ,Congresses as Topic ,business ,Socioeconomics ,United Kingdom ,Pathology and Forensic Medicine - Published
- 2014
40. α5β1 integrin mediates compression-induced inhibition of catabolic effects induced by fibronectin fragments in an oxygen-dependent manner
- Author
-
B. Pinguaan-Murphy, Dan L. Bader, E. Parker, Sandrine Vessillier, Tina T. Chowdhury, and Wan Abu Bakar Wan Abas
- Subjects
biology ,Dependent manner ,Catabolism ,Biomedical Engineering ,chemistry.chemical_element ,Oxygen ,α5β1 integrin ,Cell biology ,Fibronectin ,Rheumatology ,chemistry ,Compression (functional analysis) ,biology.protein ,Orthopedics and Sports Medicine ,Integrin, beta 6 - Published
- 2014
41. T-20 Multichannel EMG of the Hamstring and Calf Muscles – What New Information Can It Tell Us?
- Author
-
R. Foster, Dan L. Bader, S. Sakthibalan, Yang Hao, R. C. Woledge, Richard Twycross-Lewis, Dylan Morrissey, and J. Douglas
- Subjects
medicine.medical_specialty ,Physical medicine and rehabilitation ,business.industry ,Rehabilitation ,Biomedical Engineering ,Biophysics ,medicine ,Orthopedics and Sports Medicine ,business ,Hamstring ,Calf muscles - Published
- 2010
42. The quantitative assessment of flexor tendon scarring – Novel models to evaluate new therapies
- Author
-
Adriaan O. Grobbelaar, Dan L. Bader, Olivier A. Branford, and D. Lee
- Subjects
medicine.medical_specialty ,Flexor tendon ,business.industry ,Quantitative assessment ,Medicine ,Surgery ,business - Published
- 2006
43. Response to letter to the editor: 'End effects in mechanical testing of biomaterials'
- Author
-
Hazel R. C. Screen, Dan L. Bader, Afshin Anssari-Benam, and Kirsten Legerlotz
- Subjects
Tail ,Cognitive science ,End effect ,Engineering ,Letter to the editor ,business.industry ,Rehabilitation ,Biomedical Engineering ,Biophysics ,Context (language use) ,Models, Biological ,Tendons ,Decay length ,Animals ,Orthopedics and Sports Medicine ,business ,Biomedical engineering - Abstract
We appreciate the detailed response from Professor Horgan, discussing our letter to the editor concerned with end effects when mechanical testing soft tissues (Anssari-Benam et al., 2012a), and providing further insightful analysis. The concepts of end effects and characteristic decay length have indeed been well established for a long time in the context of solid mechanics, with substantial contributions from Professor Horgan, towards establishing theoretical and analytical criteria for their characterisation, as referenced in our previous publication (Anssari-Benam et al., 2012b; from Horgan (1972), Choi and Horgan (1977).
- Published
- 2013
44. PRESSURE RATE SENSITIVE VISCOELASTIC CELL DEFORMATION INVOLVES ACTIN REMODELLING
- Author
-
Dan L. Bader, Martin M. Knight, and Priyanka Pravincumar
- Subjects
Materials science ,Rehabilitation ,Biomedical Engineering ,Biophysics ,Pressure Rate ,Orthopedics and Sports Medicine ,Actin ,Viscoelasticity ,Cell deformation - Published
- 2012
45. Mechanical signals modulate the C-type natriuretic peptide receptors via cGMP and PKG dependent pathways
- Author
-
Donald Salter, Manoj Ramachandran, P. Achan, Nicholas Peake, Dan L. Bader, and Tina T. Chowdhury
- Subjects
Cartilage homeostasis ,Chemistry ,Cartilage ,Biomedical Engineering ,Stimulation ,Metabolism ,NPR2 ,Cell biology ,Pathogenesis ,C-type natriuretic peptide receptors ,medicine.anatomical_structure ,Rheumatology ,medicine ,Orthopedics and Sports Medicine ,Tissue homeostasis - Abstract
compression) (Figure). Supernatant GAG content, marker of matrix remodeling, appeared unaffected by the treatment. Conclusions: Mechanical stimulation plays a central role in the maintenance of cartilage homeostasis, but is also involved in the pathogenesis of OA. Our data seem to indicate that physiological compression of OA human cartilage tissue could counteract the effect of the inflammatory milieu by modulating cartilage matrix component metabolism. These data stimulate further studies to better elucidate the role of mechantransduction on cartilage behaviour both in normal and pathologic conditions. It is of particular interest the use of healthy human cartilage, where the absence of an altered tissue homeostasis could better highlight the effect of loading.
- Published
- 2012
46. Low intensity pulsed ultrasound does not stimulate cartilage matrix synthesis in 3d agarose constructs
- Author
-
Dan L. Bader, Martin M. Knight, and N. Vaughan
- Subjects
chemistry.chemical_compound ,Materials science ,chemistry ,Rehabilitation ,Biomedical Engineering ,Biophysics ,Agarose ,Orthopedics and Sports Medicine ,Bone matrix ,Low-intensity pulsed ultrasound ,Biomedical engineering - Published
- 2006
47. Tendon micromechanics and its implications in mechanotransduction
- Author
-
H.C.R. Screen, J.C. Shelton, M. Tamiwa, and Dan L. Bader
- Subjects
medicine.anatomical_structure ,Materials science ,Rehabilitation ,Biomedical Engineering ,Biophysics ,medicine ,Micromechanics ,Orthopedics and Sports Medicine ,Mechanotransduction ,Tendon ,Biomedical engineering - Published
- 2006
48. Probing mechanical heterogeneity in chondrocytes using passive microtheology
- Author
-
Martin M. Knight, Ze’ev Bomzon, Eitan Kimmel, and Dan L. Bader
- Subjects
Rehabilitation ,Biomedical Engineering ,Biophysics ,Orthopedics and Sports Medicine - Published
- 2006
49. Gene Therapy and Tissue Engineering in Orthopaedic and Sports Medicine (2000)
- Author
-
David A. Lee and Dan L. Bader
- Subjects
medicine.medical_specialty ,Sports medicine ,Tissue engineering ,business.industry ,Biomedical Engineering ,Biophysics ,medicine ,Medical physics ,business - Published
- 2001
50. Soft tissue response to repetitive loading
- Author
-
Dan L. Bader
- Subjects
Materials science ,Rehabilitation ,Biomedical Engineering ,Biophysics ,Orthopedics and Sports Medicine ,Soft Tissue Response ,Biomedical engineering - Published
- 1990
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