Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 35
Filter
1.
Acta Paediatr ; 113(1): 91-97, 2024 Jan.
Article in English | MEDLINE | ID: mdl-37548086

ABSTRACT

AIM: Specific questionnaires about food allergy and health-related quality of life (HRQoL) have been developed and validated in several languages, but not Finnish. We aimed to validate the Finnish Food Allergy Quality of Life Questionnaire-Parent Form (FAQLQ-PF) for children under age 13 years. METHODS: The original FAQLQ-PF and Food Allergy Independent Measure (FAIM) were translated into Finnish per World Health Organisation guidelines and tested by 72 parents of children under age 13 years with suspected severe peanut or tree nut allergy who were recruited at Allergy Centre in Tampere University Hospital in Tampere, Finland. We calculated the construct validity of the questionnaire by calculating the coefficients between the two measures and used Cronbach's alpha to establish the internal consistency. RESULTS: The FAQLQ-PF showed strong correlations with domain structure and internal consistency, based on Spearman's correlations (rho) for the HRQoL questions, FAIM questions and FAIM mean values. The total questionnaire score correlated significantly with the mean FAIM (rho = 0.95, p < 0.001) and individual FAIM questions. The FAQLQ-PF and domains had good or excellent internal consistency (Cronbach's alpha >0.70). CONCLUSION: The Finnish FAQLQ-PF demonstrated good construct validity and excellent internal consistency for measuring food allergy HRQoL in children under age 13 years.


Subject(s)
Food Hypersensitivity , Quality of Life , Child , Humans , Adolescent , Finland , Food Hypersensitivity/diagnosis , Food Hypersensitivity/epidemiology , Surveys and Questionnaires , Parents , Reproducibility of Results
2.
Science ; 377(6614): 1513-1519, 2022 09 30.
Article in English | MEDLINE | ID: mdl-36007094

ABSTRACT

The geological units on the floor of Jezero crater, Mars, are part of a wider regional stratigraphy of olivine-rich rocks, which extends well beyond the crater. We investigated the petrology of olivine and carbonate-bearing rocks of the Séítah formation in the floor of Jezero. Using multispectral images and x-ray fluorescence data, acquired by the Perseverance rover, we performed a petrographic analysis of the Bastide and Brac outcrops within this unit. We found that these outcrops are composed of igneous rock, moderately altered by aqueous fluid. The igneous rocks are mainly made of coarse-grained olivine, similar to some martian meteorites. We interpret them as an olivine cumulate, formed by settling and enrichment of olivine through multistage cooling of a thick magma body.

3.
J Parasitol ; 107(5): 794-798, 2021 09 01.
Article in English | MEDLINE | ID: mdl-34643697

ABSTRACT

Hummingbirds are vital members of terrestrial ecosystems, and because of their high metabolic requirements, they serve as indicators of ecosystem health. Monitoring the parasitic infections of hummingbirds is thus especially important. Haemosporidians, a widespread group of avian blood parasites, are known to infect hummingbirds, but little is known about the prevalence and diversity of these parasites in hummingbirds. The prevalence of haemosporidians in several hummingbird species was examined and we compared 4 different tissue types in detecting parasites by polymerase chain reaction (PCR). Blood samples from 339 individuals of 3 different hummingbird species were tested, and 4 individuals were found positive for haemosporidian infection, a prevalence of 1.2%. Hummingbird carcasses (n = 70) from 5 different hummingbird species were also sampled to assess differences in detection success of haemosporidians in heart, kidney, liver, and pectoral muscle tissue samples. Detection success was similar among tissue types, with haemosporidian prevalence of 9.96% in heart tissue, 9.52% in kidney tissue, 10.76% in liver tissue, and 11.76% in pectoral muscle tissue. All tissue samples positive for haemosporidian infection were from the Black-chinned Hummingbird (Archilochus alexandri). Possible reasons for low prevalence of these blood parasites could include low susceptibility to insect vectors or parasite incompatibility in these hummingbirds.


Subject(s)
Bird Diseases/epidemiology , Bird Diseases/parasitology , Haemosporida/isolation & purification , Protozoan Infections, Animal/epidemiology , Animals , Arizona/epidemiology , Bird Diseases/blood , Birds , California/epidemiology , Female , Male , Prevalence , Protozoan Infections, Animal/blood , Protozoan Infections, Animal/parasitology
4.
Sol Phys ; 294(3)2019 Mar.
Article in English | MEDLINE | ID: mdl-31057186

ABSTRACT

We have conducted a survey of 575 slow-to-fast stream interaction regions (SIRs) using Solar Terrestrial Relations Observatory (STEREO) A and B data, analyzing their properties while extending a Level-3 data product through 2016. Among 518 pristine SIRs, 54% are associated with heliospheric current sheet (HCS) crossings, and 34% are without any HCS crossing. The other 12% of the SIRs often occur in association with magnetic sectors shorter than three days. The SIRs with HCS crossings have slightly slower speeds but higher maximum number densities, magnetic-field strengths, dynamic pressures, and total pressures than the SIRs without an HCS. The iron charge state is higher throughout the SIRs with an HCS than the SIRs without an HCS, by about 1/3 charge unit. In contrast with the comparable phases of Solar Cycle 23, slightly more SIRs and higher recurrence rates are observed in the years 2009 - 2016 of Cycle 24, with a lower HCS association rate, possibly attributed to persistent equatorial coronal holes and more pseudo-streamers in this recent cycle. The solar-wind speed, peak magnetic field, and peak pressures of SIRs are all lower in this cycle, but the weakening is less than for the comparable background solar-wind parameters. Before STEREO-B lost contact in October 2014, 151 SIR pairs were observed by the twin spacecraft. Of the dual observations, the maximum speed is the best correlated of the plasma parameters. We have obtained a sample of plasma-parameter differences analogous to those that would be observed by a mission at Lagrange points 4 or 5. By studying several cases with large discrepancies between the dual observations, we investigate the effects of HCS relative location, tilt of stream interface, and small transients on the SIR properties. To resolve the physical reasons for the variability of SIR structures, mesoscale multi-point observations and time-dependent solar-wind modeling are ultimately required.

5.
Allergy ; 73(3): 560-568, 2018 03.
Article in English | MEDLINE | ID: mdl-29052245

ABSTRACT

BACKGROUND: We previously reported that probiotic and peanut oral immunotherapy (PPOIT) was effective at inducing sustained unresponsiveness compared with placebo in a double-blind, placebo-controlled randomized trial. This study evaluated the impact of PPOIT on health-related quality of life (HRQL). METHOD: Fifty-one participants (PPOIT 24; placebo 27) from the PPOIT trial completed Food Allergy Quality of Life Questionnaire (FAQLQ-PF) and Food Allergy Independent Measure (FAIM) at pre-treatment, end-of-treatment and 3 months after end-of-treatment. A total of 42 participants (20 PPOIT; 22 placebo) completed measures at 12 months post-treatment. Changes over time in PPOIT and placebo groups were examined by repeated-measures analysis of variance and paired t tests. RESULTS: Probiotic and peanut oral immunotherapy was associated with significant improvement in FAQLQ-PF (F = 3.63, P = .02), with mean difference 0.8 at 3 months post-treatment (P = .05) and 1.3 at 12 months post-treatment (P = .005), exceeding the 0.5 minimal clinically important difference for FAQLQ-PF. For FAIM, mean difference was 0.5 (P = .03) at 3 months and 0.4 (P = .04) at 12 months post-treatment. In placebo group, post-treatment FAQLQ and FAIM remained unchanged from pretreatment. Improvement in FAQLQ-PF and FAIM scores related specifically to acquisition of sustained unresponsiveness rather than to receiving PPOIT treatment or participation in the trial. CONCLUSIONS: Probiotic and peanut oral immunotherapy has a sustained beneficial effect on psychosocial impact of food allergy at 3 and 12 months after end-of-treatment. Treatment was not associated with reduced HRQL relative to baseline in either PPOIT or placebo groups, indicating that PPOIT was well tolerated and psychological well-being was not negatively impacted. Improved HRQL was specifically associated with acquisition of sustained unresponsiveness.


Subject(s)
Desensitization, Immunologic/methods , Peanut Hypersensitivity/prevention & control , Peanut Hypersensitivity/psychology , Probiotics/therapeutic use , Quality of Life , Child , Child, Preschool , Double-Blind Method , Female , Humans , Infant , Longitudinal Studies , Male , Surveys and Questionnaires
6.
Article in English | MEDLINE | ID: mdl-27329076

ABSTRACT

In food allergy, since the likelihood of a fatal reaction is low but fear, uncertainty, and lifestyle restrictions high, health-related quality of life (HRQL) may be a more meaningful measure of outcome in research and practice. HRQL is influenced by physiological, psychological, and environmental variables and can be best understood by considering the interactions of factors that cut across multiple levels. In this article we review both quantitative and qualitative research findings to provide an in-depth picture of the impact of food allergy on the concerns and the everyday lives of children, teens, adults, and parents. Research on factors that are related to, and impact on, HRQL is also discussed. We conclude by exploring some methodological and design issues in relation to the measurement of HRQL in food allergy and offer some recommendations for research and practice.


Subject(s)
Activities of Daily Living/psychology , Food Hypersensitivity/epidemiology , Food Hypersensitivity/psychology , Quality of Life/psychology , Stress, Psychological/epidemiology , Stress, Psychological/psychology , Adolescent , Adult , Age Distribution , Aged , Aged, 80 and over , Child , Child, Preschool , Comorbidity , Cost of Illness , Female , Health Impact Assessment , Humans , Infant , Infant, Newborn , Male , Middle Aged , Prevalence , Prognosis , Risk Factors , Sex Distribution , Young Adult
7.
Eur Ann Allergy Clin Immunol ; 48(3): 82-7, 2016 May.
Article in English | MEDLINE | ID: mdl-27152603

ABSTRACT

Food allergy is a health problem with significant negative impact in Quality of Life (QoL). We aimed to translate into Portuguese and culturally adapt to our population the Food Allergy Quality of Life Questionnaire - Parent Form (FAQLQ-PF). Cross-cultural translation was performed according to guidelines. Linguistic validation consisted in 3 steps: forward translation, backward translation and comprehensibility testing. A consensual version was obtained and tested in parents of food allergic children by cognitive debriefing. Twelve questionnaires were fulfilled, all completed in ≤ 15 min. No comments, doubts or suggestions were posed, except for 2 parents regarding a question about the number of food their children had to avoid. Two gave special positive feedback about the utility of FAQLQ-PF. Changes have been included after this pre-test in accordance to doubts and suggestions of participants, and the Portuguese version is now able to be used in clinics and research.


Subject(s)
Food Hypersensitivity , Humans , Parents , Quality of Life , Surveys and Questionnaires
8.
Waste Manag ; 46: 278-86, 2015 Dec.
Article in English | MEDLINE | ID: mdl-26257054

ABSTRACT

Twenty samples of recycled aggregates from construction and demolition waste (CDW) with different compositions collected at six recycling plants in the Andalusia region (south of Spain) were characterised according to the Landfill Directive criteria. Chromium and sulphate were identified as the most critical compounds in the leachates. To detect the sources of these two pollutant constituents in recycled aggregate, environmental assessments were performed on eight construction materials (five unused ceramic materials, two old crushed concretes and one new mortar manufactured in the laboratory). The results confirmed that leached sulphate and Cr were mainly released by the ceramic materials (bricks and tiles). To predict the toxicological consequences, the oxidation states of Cr (III) and Cr (VI) were measured in the leachates of recycled aggregates and ceramic materials classified as non-hazardous. The bricks and tiles mainly released total Cr as Cr (III). However, the recycled aggregates classified as non-hazardous according to the Landfill Directive criteria mainly released Cr (VI), which is highly leachable and extremely toxic. The obtained results highlight the need for legislation that distinguishes the oxidative state in which chromium is released into the environment. Leaching level regulations must not be based solely on total Cr, which can lead to inaccurate predictions.


Subject(s)
Chromium/analysis , Construction Materials/analysis , Industrial Waste/analysis , Recycling , Sulfates/analysis , Waste Management , Spain
9.
Waste Manag ; 34(9): 1693-704, 2014 Sep.
Article in English | MEDLINE | ID: mdl-24889792

ABSTRACT

Each year, millions of tonnes of waste are generated worldwide, partially through the construction and demolition of buildings. Recycling the resulting waste could reduce the amount of materials that need to be manufactured. Accordingly, the present work has analysed the potential reuse of construction waste in concrete manufacturing by replacing the natural aggregate with recycled concrete coarse aggregate. However, incorporating alternative materials in concrete manufacturing may increase the pollutant potential of the product, presenting an environmental risk via ground water contamination. The present work has tested two types of concrete batches that were manufactured with different replacement percentages. The experimental procedure analyses not only the effect of the portion of recycled aggregate on the physical properties of concrete but also on the leaching behaviour as indicative of the contamination degree. Thus, parameters such as slump, density, porosity and absorption of hardened concrete, were studied. Leaching behaviour was evaluated based on the availability test performed to three aggregates (raw materials of the concrete batches) and on the diffusion test performed to all concrete. From an environmental point of view, the question of whether the cumulative amount of heavy metals that are released by diffusion reaches the availability threshold was answered. The analysis of concentration levels allowed the establishment of different groups of metals according to the observed behaviour, the analysis of the role of pH and the identification of the main release mechanisms. Finally, through a statistical analysis, physical parameters and diffusion data were interrelated. It allowed estimating the relevance of porosity, density and absorption of hardened concrete on diffusion release of the metals in study.


Subject(s)
Construction Materials/analysis , Water Pollutants, Chemical/analysis , Materials Testing , Metals, Heavy/analysis , Porosity , Recycling
10.
Insights Imaging ; 5(1): 113-22, 2014 Feb.
Article in English | MEDLINE | ID: mdl-24399610

ABSTRACT

UNLABELLED: Meningiomas are the most common non-glial tumour of the central nervous system (CNS). There are a number of characteristic imaging features of meningiomas on magnetic resonance imaging (MRI) that allow an accurate diagnosis, however there are a number of atypical features that may be diagnostically challenging. Furthermore, a number of other neoplastic and non-neoplastic conditions may mimic meningiomas. This pictorial review discusses the typical and atypical MRI features of meningiomas and their mimics. TEACHING POINTS: There are several characteristic features of meningiomas on MRI that allow an accurate diagnosis Some meningiomas may display atypical imaging characteristics that may be diagnostically challenging Routine MRI sequences do not reliably distinguish between benign and malignant meningiomas Spectroscopy and diffusion tensor imaging may be useful in the diagnosis of malignant meningiomas A number of conditions may mimic meningiomas; however, they may have additional differentiating features.

11.
Allergy ; 68(11): 1353-61, 2013 Nov.
Article in English | MEDLINE | ID: mdl-24117770

ABSTRACT

BACKGROUND: Anaphylaxis is an acute, potentially fatal, multi-organ system, allergic reaction caused by the release of chemical mediators from mast cells and basophils. Uncertainty exists around epidemiological measures of incidence and prevalence, risk factors, risk of recurrence, and death due to anaphylaxis. This systematic review aimed to (1) understand and describe the epidemiology of anaphylaxis and (2) describe how these characteristics vary by person, place, and time. METHODS: Using a highly sensitive search strategy, we identified systematic reviews of epidemiological studies, descriptive and analytical epidemiological investigations, and studies involving analysis of routine data. RESULTS: Our searches identified a total of 5,843 potentially eligible studies, of which 49 satisfied our inclusion criteria. Of these, three were suitable for pooled estimates of prevalence. The incidence rates for all-cause anaphylaxis ranged from 1.5 to 7.9 per 100,000 person-years. These data indicated that an estimated 0.3% (95% CI 0.1-0.5) of the population experience anaphylaxis at some point in their lives. Food, drugs, stinging insects, and latex were the most commonly identified triggers. CONCLUSIONS: Anaphylaxis is a common problem, affecting an estimated 1 in 300 of the European population at some time in their lives. Future research needs to focus on better understanding of the trends across Europe and identifying those most likely to experience fatal reactions.


Subject(s)
Anaphylaxis/epidemiology , Anaphylaxis/diagnosis , Anaphylaxis/immunology , Animals , Europe/epidemiology , Humans , Incidence , Prevalence , Risk Factors , Syndrome , Time Factors
12.
Proc Inst Mech Eng H ; 225(1): 16-24, 2011 Jan.
Article in English | MEDLINE | ID: mdl-21381484

ABSTRACT

Artificial joints employing ultra-high molecular weight polyethylene (UHMWPE) are widely used to treat joint diseases and trauma. Wear of the polymer bearing surface largely limits the use of these joints in younger and more active patients. Previous studies have shown the wear factor used in Archard's law for the conventional polyethylene to be highly dependent on contact pressure and this has produced variability in experimental data and has constrained the reliability and applicability of previous computational predictions. A new wear law is proposed, based on wear volume being dependent on, and proportional to, the product of the sliding distance and contact area. The dimensionless proportional constant, wear coefficient, which was independent of contact pressure, was determined from a multi-directional pin on plate study. This was used in computational predictions of the wear of the conventional UHMWPE hip joints. The wear of the polyethylene cup was independently experimentally determined in physiological full hip joint simulator studies. The predicted wear rate from the new computational model was generally increased, with an improved agreement with the experimental measurement compared with the previous computational model. It was shown that wear in the UHMWPE hip joints increased as head size and contact area increased. This resulted in a much larger increase in the wear rate as the head size increased, compared with the previous computational model, and is consistent with clinical observations. This new understanding of the wear mechanism in artificial joints using the UHMWPE bearing surfaces, and the improved ability to predict wear independently and to address previously described discrepancies offer new opportunities to optimize design parameters.


Subject(s)
Hip Prosthesis , Polyethylenes , Prosthesis Failure , Biocompatible Materials , Biomedical Engineering , Computer Simulation , Equipment Failure Analysis/statistics & numerical data , Finite Element Analysis , Humans , In Vitro Techniques , Materials Testing
13.
Proc Inst Mech Eng H ; 224(10): 1175-83, 2010 Oct.
Article in English | MEDLINE | ID: mdl-21138235

ABSTRACT

The wear and creep characteristics of highly crosslinked ultrahigh-molecular-weight polyethylene (UHMWPE) articulating against large-diameter (36mm) ceramic and cobalt chrome femoral heads have been investigated in a physiological anatomical hip joint simulator for 10 million cycles. The crosslinked UHMWPE/ceramic combination showed higher volume deformation due to creep plus wear during the first 2 million cycles, and a steady-state wear rate 40 per cent lower than that of the crosslinked UHMWPE/cobalt chrome combination. Wear particles were isolated and characterized from the hip simulator lubricants. The wear particles were similar in size and morphology for both head materials. The particle isolation methodology used could not detect a statistically significant difference between the particles produced by the cobalt chrome and alumina ceramic femoral heads.


Subject(s)
Biocompatible Materials/chemistry , Ceramics/chemistry , Chromium Alloys/chemistry , Hip Prosthesis , Polyethylene/chemistry , Arthroplasty, Replacement, Hip , Biomechanical Phenomena , Cobalt/chemistry , Humans
14.
Proc Inst Mech Eng H ; 222(7): 1049-64, 2008 Oct.
Article in English | MEDLINE | ID: mdl-19024153

ABSTRACT

The effect of multi-directional cross-shear (CS) motion and contact pressure on ultra-high molecular weight polyethylene (UHMWPE) wear was investigated in this study, based on an integrated experimental and computational approach. The wear factor as a function of CS was determined experimentally from a multi-directional pin-on-plate wear tester under a nominal contact pressure of 1 MPa. A computational wear model was developed which included the effects of CS as well as the load and sliding distance imposed on the hip joint employing a UHMWPE cup against a metallic femoral head under both gait and Leeds ProSim hip joint simulator conditions. The CS ratios were quantified over the articular surface of the UHMWPE cup and the CS-dependent wear factors derived from multi-directional pin-on-plate studies were applied in the computational wear model. Outputs from the computational wear model were validated independently against an experimental hip simulator study. Comparisons of linear and volumetric wear were made between the computational wear model and the hip simulator testing for a nominal conventional (0 MRad) UHMWPE cup of 28mm diameter and a highly cross-linked (10 MRad) UHMWPE cup. The difference between the computed and experimental volumetric wear was approximately 30 per cent for the 0 MRad UHMWPE, although the worn areas between the prediction and the measurement were similar. For the 10 MRad UHMWPE, the discrepancy was reduced to 16 per cent. In both cases, the computational model predicted a lower wear rate than the experimental simulator testing. The effect of using alternative wear factors under a different nominal contact pressure of 3MPa was also considered. The input wear factor to the computational model, derived from a constant loaded pin-on-plate test configuration, may underestimate the dynamic effect due to the variation in the load in the hip joint simulator.


Subject(s)
Equipment Failure Analysis/instrumentation , Equipment Failure Analysis/methods , Hip Joint/physiopathology , Hip Prosthesis , Models, Biological , Polyethylenes/chemistry , Equipment Failure , Humans , Pressure , Shear Strength , Weight-Bearing
15.
Proc Inst Mech Eng H ; 222(7): 1073-80, 2008 Oct.
Article in English | MEDLINE | ID: mdl-19024155

ABSTRACT

Alumina ceramic heads have been previously shown to reduce polyethylene wear in comparison to cobalt chrome (CoCr) heads in artificial hip joints. However, there are concerns about the brittle nature of ceramics. It is therefore of interest to investigate ceramic-like coatings on metallic heads. The aim of this study was to compare the friction and wear of ultra-high molecular weight polyethylene (UHMWPE) against alumina ceramic, CoCr, and surface-engineered ceramic-like coatings in a friction simulator and a hip joint simulator. All femoral heads tested were 28 mm diameter and included: Biolox Forte alumina, CoCr, arc evaporative physical vapour deposition (AEPVD) chromium nitride (CrN) coated CoCr, plasma-assisted chemical vapour deposition (PACVD) amorphous diamond-like carbon (aDLC) coated CoCr, sputter CrN coated CoCr, reactive gas controlled arc (RGCA) AEPVD titanium nitride (TiN) coated CoCr, and Graphit-iC coated CoCr. These were articulated against UHMWPE acetabular cups in a friction simulator and a hip joint simulator. Alumina and CoCr gave the lowest wear volumes whereas the sputter coated CrN gave the highest. Alumina also had the lowest friction factor. There was an association between surface parameters and wear. This study indicates that surface topography of surface-engineered femoral heads is more important than friction and wettability in controlling UHMWPE wear.


Subject(s)
Acetabulum , Equipment Failure Analysis , Femur Head , Hip Prosthesis , Polyethylenes/chemistry , Prosthesis Failure , Humans , Materials Testing , Surface Properties
16.
Proc Inst Mech Eng H ; 222(8): 1289-93, 2008 Nov.
Article in English | MEDLINE | ID: mdl-19143421

ABSTRACT

Debris-induced osteolysis due to surface wear is a potential long-term problem in total knee replacements (TKRs). Wear between the tibial tray and ultra-high molecular weight polyethylene insert is thought to contribute to the wear. This study investigated the influence of tibial tray design on the wear of fixed-bearing TKRs. Specifically, this study investigated the influence of the material's surface finish and design characteristics of the locking mechanism of the tibial tray on the wear in fixed-bearing knees for both cruciate-retaining (CR) and posterior-stabilized designs. A new fixed-bearing tibial tray design using Co-Cr and with an improved locking mechanism significantly reduced polyethylene wear from 22.8 +/- 6.0 mm3 per 10(6) cycles to 15.9 +/- 2.9 mm3 per 10(6) cycles compared with a previous titanium alloy tray with a CR design. The wear rates were similar to those of a fixed-bearing insert clamped into a tibial tray, suggesting that the decrease in wear was due to a reduction in backside wear. There was no significant difference between the wear rates of a cruciate-retaining design and a posterior-stabilized design under the two kinematic conditions tested.


Subject(s)
Equipment Failure Analysis , Knee Prosthesis , Prosthesis Design , Vitallium/chemistry , Friction , Stress, Mechanical
17.
Proc Inst Mech Eng H ; 221(1): 1-10, 2007 Jan.
Article in English | MEDLINE | ID: mdl-17315763

ABSTRACT

Crosslinked ultra-high molecular weight polyethylene (UHMWPE) has been developed and introduced into clinical practice in order to reduce wear in the hip. Zero wear of highly crosslinked UHMWPE in vitro has been reported by some groups using lubricants with high concentrations of serum proteins in hip simulators. In contrast, some clinical studies have reported finite wear rates. The aim of this study was to compare the wear rates, wear surfaces, and wear debris produced by UHMWPE with different levels of crosslinking in a hip joint simulator, with lower, more physiologically relevant concentrations of protein in the lubricant. The UHMWPEs were tested in the Leeds ProSim hip joint simulator against cobalt-chromium (CoCr) femoral heads. The wear particles were isolated and imaged using a field emission gun scanning electron microscope (FEGSEM) at high resolution. The highly crosslinked UHMWPEs had significantly lower wear volumes than the non-crosslinked UHMWPEs. No significant difference was found in the percentage number and percentage volume of the particles in different size ranges from any of the materials. They had similar values of specific biological activity. The functional biological activity (FBA), which takes into account the wear volume and specific biological activity, showed that the highly crosslinked UHMWPEs had lower FBAs due to their lower wear volume.


Subject(s)
Biocompatible Materials/chemistry , Blood Proteins/chemistry , Hip Joint/chemistry , Hip Prosthesis , Nanoparticles/chemistry , Nanoparticles/ultrastructure , Polyethylenes/chemistry , Equipment Failure Analysis , Hip Joint/surgery , Lubrication , Materials Testing , Particle Size
18.
J Biomed Mater Res A ; 78(3): 473-80, 2006 Sep 01.
Article in English | MEDLINE | ID: mdl-16721797

ABSTRACT

There is currently considerable interest in the wear debris and osteolytic potential of different types of bearings used in total joint replacements. The biological activity of the wear debris is dependent on the size and volume of the particles produced. Wear volume also plays an important role in the functional biological activity of a joint replacement. In vitro studies have shown that crosslinking of ultra high molecular weight polyethylene (UHMWPE) acetabular cups and tibial trays produces a reduction in wear volume, and crosslinking has now been introduced clinically for both types of prostheses. Previous studies have identified both micron and submicron-sized polyethylene wear particles. The aim of this study was to characterize the wear and wear particles generated from moderately crosslinked GUR 1,020 GVF UHMWPE acetabular cups and tibial trays in hip and knee joint wear simulators down to 10 nanometers in size. The wear rates of the two prosthesis types were very similar at 25.6 +/- 5.3 mm(3) per million cycles for the hip prostheses and 22.75 +/- 5.95 mm(3) per million cycles for the knee prostheses. Nanometer-sized wear particles were isolated and characterized from both hip and knee simulator lubricants for the first time. Significantly higher numbers (p < 0.05) of particles in the nanometer (<0.1 microm) size range were produced by the hip prostheses compared to the knee prostheses. The knee prostheses produced larger particles, with the mode of particle size in the 0.1-1.0 microm size range, compared to <0.1 microm size range for the hip prostheses. In addition, the knee prostheses produced a greater volumetric concentration of wear particles in the 1.0-10 microm size range, and consequently lower specific biological activity and functional biological activity indices. These results indicated that the knee prostheses had a lower osteolytic potential compared to the hip prostheses.


Subject(s)
Hip Prosthesis , Knee Prosthesis , Nanostructures/chemistry , Polyethylenes/chemistry , Polyethylenes/isolation & purification , Biocompatible Materials/chemistry , Biocompatible Materials/isolation & purification , Particle Size
19.
Proc Inst Mech Eng H ; 220(1): 33-46, 2006 Jan.
Article in English | MEDLINE | ID: mdl-16459444

ABSTRACT

A fully coupled contact and wear model was developed in the present study for hip implants employing an ultra-high molecular weight polyethylene (UHMWPE) cup in combination with a metallic or ceramic femoral head. A simple elasticity equation based on the concept of constrained column model was employed to solve the contact mechanics between the acetabular cup and the femoral head under the three-dimensional physiological loading condition. The wear model was based on the classical Archard-Lancaster equation in common with all other studies reported in the literature. The fully coupled contact and wear model was applied to both conventional and cross-linked UHMWPE cups under a wide range of design parameters such as the clearance and the femoral head radius. The predicted linear and volumetric wear as well as their rates for conventional UHMWPE cups were found to be in good agreement with those obtained from a similar analysis by Maxian but using the finite element method for the contact mechanics analysis. The predicted maximum contact pressure was found to decrease rapidly within the first 10(6) cycles, and below the limit to cause plastic deformation within the UHMWPE cup with a nominal radial clearance of 0.2 mm. The effect of the clearance between the head and the cup on the predicted wear was found to be negligible. For the cross-linked UHMWPE cup with relatively large diameters up to 48 mm and a fixed outside diameter of 50 mm, the predicted wear, which was found to increase with increasing femoral head radius, remained small owing to the small wear factor associated with these materials. Furthermore, if the head diameter increases beyond 42 mm, a rapid increase in the contact pressure was predicted, owing to the decrease in the wall thickness of the cross-linked UHMWPE cup.


Subject(s)
Equipment Failure Analysis/methods , Hip Joint/physiopathology , Hip Prosthesis , Materials Testing/methods , Models, Biological , Models, Chemical , Polyethylenes/chemistry , Animals , Biocompatible Materials/analysis , Biocompatible Materials/chemistry , Computer Simulation , Elasticity , Friction , Hip Joint/surgery , Humans , Polyethylenes/analysis , Pressure , Stress, Mechanical , Surface Properties , Systems Integration , Weight-Bearing
20.
Gut ; 45(4): 593-8, 1999 Oct.
Article in English | MEDLINE | ID: mdl-10486371

ABSTRACT

BACKGROUND: The anti-idiotypic monoclonal antibody 105AD7 mimics the tumour associated antigen 791Tgp72, expressed on 70-80% of colorectal cancers. Phase I studies have shown that the vaccine is non-toxic, and a number of patients have been immunised prior to resection of their primary tumours. AIMS: To assess lymphocyte activation at the tumour site by measuring expression of the alpha subunit of the interleukin 2 receptor (CD25). METHODS: Nineteen patients with primary colorectal cancer were immunised with varying doses of 105AD7 prior to resection of their primary tumours. Samples of normal bowel and tumour edge/centre from 16 patients were available for immunohistochemical staining with a monoclonal antibody against CD25. Samples from a matched control group were also stained. Fresh tumours from 14 immunised patients and 31 unimmunised control patients were disaggregated, and the lymphocytes obtained labelled for CD25. Samples were analysed blindly by flow cytometry. RESULTS: Median infiltration of lymphocytes expressing CD25, measured immunohistochemically, was higher in trial patients, as was the ratio of tumour to normal bowel infiltration. Flow cytometric analysis of fresh tumour from immunised patients showed a significantly higher percentage of lymphocytes expressing CD25 tumour infiltrating lymphocytes than their matched and unmatched controls. DISCUSSION: The alpha subunit of the interleukin 2 receptor is increased on tumour infiltrating lymphocytes, in patients immunised with the colorectal cancer vaccine 105AD7. This suggests a population of activated lymphocytes capable of targeting 791Tgp72 expressing tumour cells, such as circulating micrometastases. 105AD7 may have a role as adjuvant therapy in early stage disease.


Subject(s)
Cancer Vaccines/immunology , Colorectal Neoplasms/immunology , Lymphocyte Activation , Lymphocytes, Tumor-Infiltrating/immunology , Aged , Aged, 80 and over , Antibodies, Anti-Idiotypic/immunology , Antibodies, Monoclonal/immunology , Antibodies, Neoplasm/immunology , CD4-Positive T-Lymphocytes/immunology , Female , Humans , Image Processing, Computer-Assisted , Immunization , Male , Middle Aged , Receptors, Interleukin-2/metabolism
SELECTION OF CITATIONS
SEARCH DETAIL
...