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PubMed2002

Acoustics of friction.

This article presents an overview of the acoustics of friction by covering friction sounds, friction-induced vibrations and waves in solids, and descriptions of other frictional phenomena related to acoustics. Friction, resulting from the sliding contact of solids, often gives rise to diverse forms of waves and oscillations within solids which frequently lead to radiation of sound to the surrounding media. Among the many everyday examples of friction sounds, violin music and brake noise in automobiles represent the two extremes in terms of the sounds they produce and the mechanisms by which they are generated. Of the multiple examples of friction sounds in nature, insect sounds are prominent. Friction also provides a means by which energy dissipation takes place at the interface of solids. Friction damping that develops between surfaces, such as joints and connections, in some cases requires only microscopic motion to dissipate energy. Modeling of friction-induced vibrations and friction damping in mechanical systems requires an accurate description of friction for which only approximations exist. While many of the components that contribute to friction can be modeled, computational requirements become prohibitive for their contemporaneous calculation. Furthermore, quantification of friction at the atomic scale still remains elusive. At the atomic scale, friction becomes a mechanism that converts the kinetic energy associated with the relative motion of surfaces to thermal energy. However, the description of the conversion to thermal energy represented by a disordered state of oscillations of atoms in a solid is still not well understood. At the macroscopic level, friction interacts with the vibrations and waves that it causes. Such interaction sets up a feedback between the friction force and waves at the surfaces, thereby making friction and surface motion interdependent. Such interdependence forms the basis for friction-induced motion as in the case of ultrasonic motors and other examples. Last, when considered phenomenologically, friction and boundary layer turbulence exhibit analogous properties and, when compared, each may provide clues to a better understanding of the other.

Journal Article↗

PubMed1991

Acute anterior uveitis, arthritides and enteric antigens.

One hundred and fourteen patients with acute anterior uveitis were studied for the presence of the HLA-B27 tissue type, the prevalence of spondylitis and arthritis and the occurrence of gastro-intestinal and urogenital infections or diarrhoeal illness in the history. Eighty-seven (76%) were B27+ and 27 (24%) B27-. Forty-two (48%) of the B27+ group had ankylosing spondylitis (AS); 13 (30%) of them were females. Sacroilitis (SI) with no spinal involvement was present in 21 patients (24%), 13 (61%) males and 8 (38%) females. Peripheral arthritis occurred in 6 patients. Thus, 68 (78%) of the HLA-B27+ positive patients had inflammatory spinal and/or joint disease, compared with 1 (4%) of the HLA-B27- group (p less than 0.001). The AS diagnosis was unknown previous to our examination in 31% of the males and 54% of the females, and SI was undiscovered in 61% of the males and 62% of the females. The occurrence of acute enteric infections was significantly increased in the B27+ AAU group, compared with the B27- patients and the patients reported exacerbation of AAU in connection with episodes of diarrhoea. An increased occurrence of urogenital infections was shown only in co-comparison with the males of the B-27+ AAU group. Thirty-three out of 47 AAU patients assayed by enzyme immuno-assay (EIA) for the quantification of IgM, IgA and IgG antibodies against Klebsiella pneumoniae, E coli, and Proteus mirabilis had significantly raised antibody titres against one or more of the antibodies studied, as compared to 62 healthy controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗

PubMed2005

In vitro, ex vivo, and in vivo methodological approaches for studying therapeutic targets of osteoporosis and degenerative joint diseases: how biomarkers can assist?

Although our approach to the clinical management of osteoporosis (OP) and degenerative joint diseases (DJD)-major causes of disability and morbidity in the elderly-has greatly advanced in the past decades, curative treatments that could bring ultimate solutions have yet to be found or developed. Effective and timely development of candidate drugs is a critical function of the availability of sensitive and accurate methodological arsenal enabling the recognition and quantification of pharmacodynamic effects. The established concept that both OP and DJD arise from an imbalance in processes of tissue formation and degradation draws attention to need of establishing in vitro, ex vivo, and in vivo experimental settings, which allow obtaining insights into the mechanisms driving increased bone and cartilage degradation at cellular, organ, and organism levels. When addressing changes in bone or cartilage turnover at the organ or organism level, monitoring tools adequately reflecting the outcome of tissue homeostasis become particularly critical. In this context, bioassays targeting the quantification of various degradation and formation products of bone and cartilage matrix elements represent a useful approach. In this review, a comprehensive overview of widely used and recently established in vitro, ex vivo, and in vivo set-ups is provided, which in many cases effectively take advantage of the potentials of biomarkers. In addition to describing and discussing the advantages and limitations of each assay and their methods of evaluation, we added experimental and clinical data illustrating the utility of biomarkers for these methodological approaches.

Animals↗

PubMed2002

[Cross sectional study of the relationship between physical fitness and life style, health-status in healthy aged males].

PURPOSE: The purpose of this study was to investigate the relationships between physical fitness and life style, as well as health-status in aged males living in a community. METHOD: A total of 304 males aged 60 to 89 years volunteered as subjects for this study. Eleven performance-test items were selected from four physical fitness domains of muscle, joint, neuromuscular and lung functions, with consideration given to the safety, reliability, and feasibility of the tests. To assess life style and health-status, a questionnaire consisting of 40 items was constructed. Principal component analysis was applled to the correlation matrix consisting of 11 physical fitness variables. Statistical techniques for Creamer's association coefficient and theory of quantification I were used to examine the relationships between life style, medical condition and fundamental physical fitness (FPF). RESULTS: Cramer's association coefficient was only significant for the variable of quantity consumed at dinner. Multiple correlation coefficient between FPF and age-grade, life style, and health-status were significant (P < 0.01). Partial correlation coefficients were high for the variables of aged-grade, sleeping hours, and receiving medical treatment. CONCLUSION: Fundamental physical fitness showed a decreasing trend with age. It was inferred that acquisltion of adequate sleeping hours and not taking medical treatment for injury of illness might be related to the decline of FPF level with aging in aged males.

Aged↗

PubMed1993

Behavioral and immunohistochemical changes in an experimental arthritis model in rats.

An experimental arthritis induced by injection of kaolin and carrageenan into the knee joint resulted in a temporal relationship between glutamate dorsal horn content and paw withdrawal latency (PWL) which was positively correlated. Limping, guarding, increased response to heat stimuli (hyperalgesia) and altered staining patterns for glutamate (GLU), substance P (SP), and calcitonin gene-related peptide (CGRP) were monitored in the awake behaving arthritic rat over a 1 week time course. A decrease in PWL occurred on the side ipsilateral to the inflamed knee as early as 4 h after the induction of arthritis indicating the animals are hyperalgesic. The PWL remained decreased through the first 24 h. Computer-assisted quantification of the density of immunohistochemical staining indicated the content of GLU, SP and CGRP was altered differentially throughout the time course of the arthritis. The changes observed for all three substances occurred across the entire superficial dorsal horn. There was an initial depletion of SP followed by an increase in both SP and CGRP content which was maintained through 1 week. The GLU content was increased during the hyperalgesic period. The GLU changes followed the same time course and were positively correlated with the changes in PWL. In a small group of animals injected with kaolin and carrageenan, hyperalgesia did not develop. In this group of animals, no change in dorsal horn GLU or SP content occurred. Rather, there was an increase in CGRP content in the middle portion of the superficial dorsal horn which is the termination site of knee joint afferents. These data indicate that the development of heat hyperalgesia is dependent on GLU and possibly SP. Since inflammation of the knee joint does not involve the foot pad, the heat hyperalgesia observed during the first 24 h following induction of arthritis represents a central neuronal sensitization.

Animals↗

PubMed1998

Proteoglycan expression in the rat temporomandibular joint in response to unilateral bite raise.

The vertebrate articular tissue consists of collagen fibers embedded in a ground substance. Collagen resists tensile forces, while proteoglycans in the ground substance provide resilience and resistance to compression. It was hypothesized that unilateral bite raise would induce increasing expression of proteoglycans in TMJ articular tissues. As a test of this hypothesis, six- and nine-week-old Sprague-Dawley rats received unilateral bite-raising appliances bonded to their right upper molars for 4 wks. A group of nine-week-old rats was housed for an additional 4 wks after removal of the appliances they had worn for 4 wks. Proteoglycans that carry abundant chondroitin sulfate and keratan sulfate side-chains, most likely aggrecans, were detected by safranin O in the fibrocartilaginous zone of the condyle in parasagittal sections. A monoclonal antibody against a large chondroitin sulfate proteoglycan related to versican reacted strongly in the surface fibrous layer of the mandibular condyle and moderately in the discs of the treated specimens. Computer quantification for safranin O and anti-versican antibody staining revealed that the average intensities of the treated specimens were significantly higher than those of their corresponding sham-operated controls, and the average intensities of the treatment-reversal specimens had no significant differences from their corresponding sham-operated controls. Thus, unilateral bite raise appeared to have induced an increase in the expression of aggrecan in the condylar cartilage and a proteoglycan related to versican in the TMJ disc and the articular surface of the condyle. The elevated proteoglycan expression is interpreted to suggest that unilateral bite raise leads to an increase in the magnitude of compressive forces in the rat temporomandibular joint.

Aggrecans↗

PubMed2004

[Repairing porcine knee joint osteochondral defects at non-weight bearing area by autologous BMSC].

OBJECTIVE: To test the possibility of using bone marrow stromal cells (BMSC) and biodegradable polymers to repair articular osteochondral defects at non-weight bearing area of porcine knee joints. METHODS: Bone marrows were harvested from 18 hybrid pigs. BMSC were cultured and in vitro expanded and induced with dexamethasone (group A) or with dexamethasone and transforming growth factor-beta1 (TGF-beta1) (group B) respectively. Immunohistochemistry and RT-PCR were used to evaluate chondrogenic differentiation of induced cells. Part of BMSC of 2 animals were retrovirally-labeled with green fluorescent protein (GFP). After induction and label, cells were seeded on a construct of polyglycolic acid (PGA) and polylactic acid (PLA) and co-cultured for 1 week before implantation. Total 4 osteochondral defects (8 mm in diameter, 5 mm in depth) in each animal were created at the non-weight bearing areas of knee joints on both sides. The defects were repaired with dexamethasone induced BMSC-PGA/PLA construct in group A, with dexamethasone and TGF-beta1 induced BMSC-PGA/PLA construct in group B, with PGA/PLA construct alone (group C) or left untreated (group D) as controls. Animals were sacrificed at 3 months (n = 6) or 6 months (n = 10) post-repair. Gross observation, histology, glycosaminoglycan (GAG) quantification and biomechanical test were applied to analyze the results. The two animals with GFP-labeled cells were sacrificed at 7 months post-repair to observe with confocal microscope the distribution of GFP-labeled cells in repaired tissue. RESULTS: Stronger expression of type II collagen and aggrecan were observed in BMSCs induced with both dexamethasone and TGF-beta1. At both time points, Gross observation and histology showed that the defects in most of group A were repaired by engineered fibrocartilage and cancellous bone with an irregular surface, minority defects were repaired by engineered hyaline cartilage and cancellous bone. However, in most of group B, the defects were completely repaired by engineered hyaline cartilage and cancellous bone. No repair or only fibrous tissue were observed in groups C and D. Besides, the compressive moduli of repaired cartilage in groups A and B reached 30.37% and 43.82% of normal amount at 3 months and 62.69% and 80.27% at 6 months respectively, which was further supported by the high levels of GAG contents in engineered cartilage of group A (78.03% of normal contents) and group B (no statistical difference from normal contents). More importantly, confocal microscope revealed the presence of GFP-labeled cells in engineered cartilage lacuna and repaired underlying cancellous bone. CONCLUSION: The results demonstrated that implanted BMSC can differentiate into either chondrocytes or osteoblasts at different local environments and repair a complex articular defect with both engineered cartilage and bone. TGF-beta1 and dexamethasone in vitro induction can promote chondrogenic differentiation of BMSC and thus improve the results of repairing articular defects.

Animals↗

PubMed1998

Assessment of disease activity in rheumatoid arthritis using magnetic resonance imaging: quantification of pannus volume in the hands.

We attempted to assess whether pannus volume measured by magnetic resonance imaging (MRI) can be used as an indicator of disease activity in rheumatoid arthritis (RA). Eleven women (mean age 46 yr) with uncontrolled RA were studied for 1 yr. Pannus formation in both hands was quantified using MRI at the start of the study, and at 6 and 12 months thereafter. The volume of enhancing pannus (VEP) was compared with changes in the radiological scores, grip strength, joint tenderness counts, joint swelling counts, erythrocyte sedimentation rate (ESR), and serum C-reactive protein (CRP). Patients were classified into three groups based on VEP changes between 0 and 12 months: unchanged (n = 2), decreased (n = 6) and increased (n = 3). VEP at 6 months and at 12 months differed significantly between the three groups. No statistically significant differences were found between the groups in radiographic scores, physical parameters or laboratory parameters despite the fact that some of these parameters changed in the direction indicated by the changes in VEP. VEP can be used as a new indicator to assess disease activity in individual RA patients and, using this parameter, treatment outcome can be assessed in fewer subjects than with traditional measures.

Adult↗

PubMed2006

Short-term outcome after anti-tumor necrosis factor-alpha therapy in rheumatoid arthritis: do we need to revise our assessment criteria?

OBJECTIVE: To evaluate the Disease Activity Score (DAS) using various aggregated dimensions to quantify treatment outcome in patients with rheumatoid arthritis (RA), in order to determine the best instrument to be used as an endpoint that indicates good response in terms of EULAR response criteria and DAS28 remission criteria, and which satisfies the demands of clinical rheumatology. METHODS: Using raw data for each patient subjected to anti-tumor necrosis factor-a therapy (81 patients), before and 6 months after treatment, DAS28 was calculated 4 times using the standard equation, as follows: (1) DAS 1 (the standard DAS28): tender joint count (TJC), swollen joint count (SJC), patient global assessment (PGA), erythrocyte sedimentation rate (ESR); (2) DAS 2: TJC, SJC, PGA, C-reactive protein (CRP); (3) DAS 3: TJC, SJC, physician global assessment (PhGA), ESR; and (4) DAS 4: TJC, SJC, PhGA, CRP. Disease activity was identified if DAS score exceeded 5.1. A clinically significant response was recorded if there had been improvement of > 1.2 of the DAS score. RESULTS: DAS 2, DAS3, and DAS4 were superior to the current DAS score used for assessment of RA activity (effect size differences were -0.35, -0.13, and -0.48, respectively). Assessment of disease activity using TJC, SJC, PhGA, and CRP was the best tool to assess response to therapy. ESR was marginally superior to CRP in its sensitivity to monitor disease activity changes (effect sizes 1.08 and 1.03, respectively). CONCLUSION: These results suggest that self-report indices on their own, such as PGA and pain score, are inadequate indicators of disease activity. The DAS might profitably be amended by one or 2 continuous measures for better quantification of the degree of improvement of patients on a given therapeutic modality. Using PhGA and CRP instead of PGA and ESR, respectively, in the DAS equation discriminated better between different patients' responses than the traditional DAS score.

Adult↗

PubMed1980

Identification and quantification of asbestos fibres in human tissues.

The examination of three dust preparations by two independent laboratories using analytical transmission microscopic techniques has shown that comparable results can be produced. Further interlaboratory collaboration is required, however, to clarify and improve the results that can be obtained. Those areas that require further investigation are data interpretation from energy-dispersive X-ray analysis equipment and counting procedures. The results that have been obtained so far by interlaboratory collaboration are very encouraging, and it is hoped that such joint efforts will be expanded in the future.

Asbestos↗

PubMed1991

Estimation of impurity profiles of drugs and related materials. Part VIII: Combined application of high-performance liquid chromatography and NMR spectroscopy in the impurity profiling of drugs.

The usefulness of the joint application of HPLC and NMR spectroscopy in drug impurity profiling is demonstrated by the following examples: (1) identification of Z and E isomers of 17 alpha-ethynyl-4-oestrene-3 beta, 17-diol-3-acetate-17-(3'-acetoxy-2'-butenoate) in ethynodiol diacetate; (2) identification of the p-tolyl analogue as the impurity of enalapril maleate; (3) identification and quantification of 2'-dehydro-pipecuronium bromide in pipecuronium bromide. The possibilities of utilizing NMR spectroscopy for the identification and quantification of the impurities with and without their isolation are discussed.

Androstane-3,17-diol↗

PubMed2000

[11C]Hyaluronan uptake with positron emission tomography in liver disease.

BACKGROUND: A hyaluronan-loading test has been developed for assessment of hyaluronan kinetics and applied in patients with liver and joint diseases. This test describes the metabolic process of hyaluronan but cannot define the specific contribution of different organs. A method for labelling of hyaluronan with the short-lived positron-emitting radionuclide 11C has been published and in this study applied in healthy subjects and liver diseases. MATERIALS AND METHODS: Positron emission tomography (PET) was used for the regional assessment and quantification of [11C]hyaluronan uptake in three healthy subjects, four patients with alcoholic liver cirrhosis, one with alcoholic hepatitis and one with liver steatosis. After intravenous administration of 60 MBq of 11C-labelled hyaluronan, a 55-min PET scan was performed over the liver and plasma radioactivity was analysed. Rate constants describing the transport of the [11C]hyaluronan tracer from plasma to the liver were calculated. RESULTS: High uptake was observed in the liver combined with a rapid elimination of tracer from plasma. The liver uptake rate (k1) was significantly lower in patients (0.018 min-1) than in healthy subjects (0.043 min-1, P = 0.002). The rate constants seem to be related to the severity of the disease as defined by the Child-Pugh score. CONCLUSIONS: The study suggests that PET with [11C]hyaluronan could be an accurate method by which to assess liver dysfunction, in conditions where endothelial cell function is impaired. The possibility of quantification over extended portions of the body also opens up possibilities to explore regional differences in liver function and to assess other elimination routes of hyaluronan.

Adult↗

PubMed2001

Quantification of the UPDRS Rigidity Scale.

In the clinical setting, parkinsonian rigidity is assessed using subjective rating scales such as that of the Unified Parkinson's Disease Rating System (UPDRS). However, such scales are susceptible to problems of sensitivity and reliability. Here, we evaluate the reliability and validity of a device designed to quantify parkinsonian rigidity at the elbow and the wrist. The method essentially quantifies the clinical examination and employs small sensors to monitor forces and angular displacements imposed by the clinician onto the limb segment distal to the joint being evaluated. Force and displacement data are used to calculate elastic and viscous stiffnesses and their vectorial sum, mechanical impedance. Interexaminer agreement of measures of mechanical impedance in subjects with Parkinson's disease was comparable to that of clinical UPDRS scores. Examiners tended to overrate rigidity on the UPDRS scale during reinforcement manoeuvres. Mechanical impedance was nonlinearly related to UPDRS ratings of rigidity at the elbow and wrist; characterization of such relationships allows interpretation of impedance measurements in terms of the clinical rating scales.

Biomechanical Phenomena↗

PubMed1996

Articular cartilage volume in the knee: semiautomated determination from three-dimensional reformations of MR images.

PURPOSE: To determine the accuracy of semiautomated quantification of articular cartilage volume from three-dimensional (3D) reformations of magnetic resonance (MR) images. MATERIALS AND METHODS: Sagittal, fat-suppressed, 3D, spoiled gradient-recalled-echo MR imaging of two bovine and two human cadaver knees was performed. Articular cartilage volume was calculated from 3D reformations of the MR images by using a semiautomated program written at the authors' institution. Calculated volumes were compared with directly measured volumes of the surgically removed articular cartilage. RESULTS: The percentage of error of the MR imaging-determined volumes was 6.53% +/- 4.75 (mean +/- standard deviation). A strong correlation between the two sets of observations was shown (r=.997). Linear regression showed the calculated volumes to be highly accurate (slope=1.002, P>.25). Repeated reformations yielded volumes that were reproducible (mean absolute error, 0.013 mL +/- 0.019) and not significantly different from the measured volume (P>.10). CONCLUSION: Semiautomated quantification of knee articular cartilage from MR images yields highly accurate cartilage volumes.

Animals↗

PubMed1991

[Static and dynamic loading measurements of the post-traumatic foot].

There are several possibilities to assess loading of the foot after trauma. This paper gives an overview of the quantitative techniques presently applied for the measurement of kinetic (ground reaction forces, pressure distribution) and kinematic parameters (joint angles) during movement analysis; emphasis is placed on simple and reliable techniques (e.g., time variables of the roll-over process, pressure distribution), which are explained with examples of their clinical use. In addition, several mathematical foot models are introduced. None of the techniques mentioned has found a permanent place in the clinical environment for support of the diagnosis of trauma, the quantification of trauma, or the therapeutical decision. In other areas (e.g. biomechanics) these techniques are already established. Therefore, the experience to date in these areas should be taken into consideration by the clinicians and used for their purposes.

Biomechanical Phenomena↗

PubMed2005

In vitro testing of gentamicin-vancomycin loaded bone cement to prevent prosthetic joint infection.

Sepsis is a greatly feared complication of total joint arthroplasty. One key question is how to prevent perioperative bacterial adherence, and therefore the potential for infectious complications. The objective of our study was to appraise the emerging capacity of staphylococcal survival on prosthetic materials and to analyze the in vitro effects of gentamicin and vancomycin loaded polymethylmethacrylate (PMMA) cement on bacterial adherence and growth. Hospital acquired staphylococcal strains were systematically inoculated on four orthopedic materials (ultrahigh molecular weight polyethylene, PMMA without antibiotic, commercially produced PMMA loaded with gentamicin, and manually mixed PMMA loaded with gentamicin and vancomycin). Staphylococci were identified using culture and biochemical tests. The inoculated material was allowed to incubate in a liquid broth growth media and subsequently prepared for scanning electron microscopy and bacterial growth quantification. Materials without antibiotics showed evidence of staphylococcal growth. PMMA loaded with only gentamicin grew methicillin-resistant Staphylococcus aureus. Gentamicin-vancomycin loaded PMMA completely inhibited any bacterial growth. Low-dose gentamicin-vancomycin loaded PMMA prevents staphylococcal colonization better than commercially manufactured PMMA loaded with gentamicin. We recommend this combination in high-risk procedures and revision surgeries requiring bone cement.

Anti-Bacterial Agents↗

PubMed1999

Variation in movement traces of the kinematic center of the temporomandibular joint.

AIM: The purpose of this study was to compare the variation in movement traces of the kinematic center of the temporomandibular joint with that of 4 nearby condylar reference points. METHODS: Jaw movement recordings were made with an optoelectronic jaw movement recording system. Four asymptomatic participants performed 14 to 18 open-close mandibular movements. The movements were performed with deliberate alterations of the rotation/translation ratio during opening. The kinematic center of the condyle and 4 nearby condylar points (the corner points of a square placed in the condylar sagittal plane, centered around the kinematic center, and with an edge length of 10 mm) were used as reference points. The standard deviations in the downward displacements at the halfway point in the mandibular opening of these reference points were calculated as a quantification of the variation in the movement tracings of these points. RESULTS: The movement traces of the kinematic center showed the smallest variation in comparison to the traces of the 4 nearby reference points (2-way analysis of variance and subsequent contrast analysis; P = 0.0026). CONCLUSION: In comparison to 4 nearby condylar reference points, the movement traces of the kinematic center show the lowest sensitivity to variations in the way mandibular movements are performed.

Adult↗

PubMed1996

Knee extension dynamometer: a new device for dynamic isokinetic magnetic resonance spectroscopy experiments.

In the present study we introduce a new device for exercise magnetic resonance spectroscopy (MRS). It operates in a standard whole-body scanner. Mechanical exertion unit allows maximal 10 degrees to 15 degrees short-arc knee extensions. The device operates hydraulically and is based on isokinetic movement. The force and work conducted are automatically controlled by the electronic control and computer unit. A small surface coil placed on the vastus medialis muscle allows the collection of spectra without interfering spectra from nearby resting muscles. The force used for the extensions can be followed simultaneously as a curve on the screen in the operator's room and the data is transferred to a personal computer for later analysis. Total work and fatigue percentage are also calculated by the device. It also allows the use of different isokinetic exercise protocols. The measurements of force proved reliable in repeat measurements using an isokinetic test device as a control. This device has been used clinically for over a year, is easy to operate, and offers reliable measurements. It is well suited to trials where muscle energy states versus time are followed since it allows noninvasive simultaneous quantification of muscle performance and collecting MRS spectra at rest, during exercise, and in the recovery phase.

Ergometry↗