Biomedical subjects

E Ingham

Publications and source records attributed to E Ingham.

At least 19 recordsLinked to original sources

PubMed2001

Quantitative characterization of polyethylene debris isolated from periprosthetic tissue in early failure knee implants and early and late failure Charnley hip implants.

This study isolated and characterized UHMWPE particles from 3 explant groups: early Charnley hip failures (ECE; < 10 years), late Charnley hip failures (LCE; > 10 years) and early knee failures (EKE; < 10 years). Debris isolated from the 3 groups had percentage particle number and percentage volumetric concentration distributions that were not significantly different. The greatest number of particles were found in the 0.1-0.5 microm size range and 19-20.6% of the volumetric concentration was below 1 microm in size in all groups. However, there were significant differences in the total volumetric concentration of debris isolated per g of tissue. LCE had significantly higher volumes of debris than ECE and EKE, there was no significant difference in the volume of debris from the EKE and ECE. The mean aspect ratio and mean irregularity ratio of the LCE group were also significantly higher than the ECE and EKE, suggesting that different wear mechanisms were occurring in the late Charnley group compared to the early Charnley and knee groups. These results also suggest that early knees, with normal surface wear, may have similar wear mechanisms to early Charnley hips and indicate that similar volumes of biologically active micrometer and sub-micrometer UHMWPE particles were produced. This may have important implications in the longer-term outcome of total knee arthroplasties, because it indicates a similar potential for osteolysis induced by wear debris.

Aged↗

PubMed2001

Invasion of human type II pneumocytes by Burkholderia cepacia.

Burkholderia cepacia is known to invade and survive within respiratory epithelial cells. Previous studies have employed transformed cell lines and it is not known whether the bacterium is capable of manifesting the same phenomena in primary cell culture. Two strains of B. cepacia of environmental (NCTC 10661) and clinical origin (C1359) were examined for their ability to invade and survive (over a 24 h period) within type II pneumocytes in primary culture using a gentamicin-ceftazidime antibiotic protection assay. Both strains of B. cepacia were capable of invasion of type II pneumocytes in primary culture. Strain C1359 was capable of multiplying intracellularly as indicated by a seven-fold increase in the numbers of bacteria from 4-24 h, whereas strain 10661, although unable to replicate intracellularly, was found to survive in the pneumocytes for at least 24 h. Future studies on the invasiveness of B. cepacia can employ A549 cells as a valid surrogate for primary cell culture assays which are time-consuming, labour-intensive and expensive to perform.

Adult↗

PubMed2001

A novel low wearing differential hardness, ceramic-on-metal hip joint prosthesis.

Osteolysis and loosening of artificial joints caused by polyethylene wear debris has prompted renewed interest in alternative bearing materials for hip prosthesis designs. Lower wearing metal-on-metal (MOM) and ceramic-on-ceramic prostheses are being used more extensively, and there is considerable interest in further improving on their performance. This study investigated the wear properties and debris morphology of a novel differential hardness ceramic-on-metal (COM) prosthesis, in comparison with MOM articulations in a physiological anatomical hip joint simulator. The COM pairings were found to have wear rates approximately 100-fold lower than the MOM pairings. The MOM pairings showed a higher "bedding in" wear rate (3.09+/-0.46mm(3)/10(6) cycles) in the first million cycles, which then reduced to a steady state wear rate of 1.23+/-0.5mm(3)/10(6) cycles. The wear rate of the COM pairings over the duration of the test was approximately 0.01mm(3)/10(6) cycles with very little wear detected on the surface of the prosthesis components. The wear particles from both articulations were oval to round in shape and in the nanometer size range. After one million cycles the mean maximum diameter of the MOM and COM wear particles were 30+/-2.25 and 17.57+/-1.37nm, respectively. After five million cycles the wear particles were statistically significantly smaller than at one million cycles, 13.9+/-0.72nm for the MOM pairings and 6.11+/-0.40nm for the COM pairings. The wear rates of the MOM prostheses were representative of clinical values. The use of differential hardness COM pairings dramatically reduced the wear rate compared to MOM hip prostheses. The wear particles from the MOM articulation were similar to particles found in retrieved tissues from around MOM prostheses. The extremely low wearing differential hardness COM bearings presented in this study produced far smaller volumetric particle loads compared to MOM prostheses currently used clinically.

Biocompatible Materials↗

PubMed2001

An evaluation of the capacity of differently prepared demineralised bone matrices (DBM) and toxic residuals of ethylene oxide (EtOx) to provoke an inflammatory response in vitro.

Demineralised bone matrix (DBM) is a form of allogeneic tissue graft widely used in oral and maxillofacial procedures. There is a long history of controversy relating to the suitability of ethylene oxide gas (EtOx) as a terminal sterilisation agent for this graft, relating to its effects on the clinical performance of the grafts. Furthermore, the generation of a toxic residual chemical (ethylene chlorohydrin, ECl) during the ethylene oxide sterilisation of patellar tendon allografts has been implicated in the failure of these grafts owing to the induction of a localised inflammatory response. In this study we have investigated the capacity of a range of different DBM preparations, and ECl dilutions, to induce the production of three pro-inflammatory cytokines, interleukin-6 (IL-6), interleukin-1beta (IL-1beta), and tumour necrosis factor alpha (TNF-alpha) from human peripheral blood mononuclear cells (PBMNCs). The levels of EtOx and ECl in EtOx terminally sterilised DBM and mineralised bone grafts were measured by gas chromatography. It was found that the only factor capable of rendering DBM pro-inflammatory was the presence of small (<20 micrometre diameter) DBM particles. No other processing or sterilisation technique resulted in the DBM becoming pro-inflammatory. Although it was also found that DBM, when EtOx-sterilised, retained more ECI than mineralised bone grafts following a standard EtOx sterilisation protocol, ECl did not provoke an inflammatory response in vitro at levels up to and including those which are cytotoxic to PBMNCs.

Bone Demineralization Technique↗

PubMed2001

Wear of HIPed and non-HIPed alumina-alumina hip joints under standard and severe simulator testing conditions.

Wear and the biological response to wear debris of artificial joints remain major concerns in total hip arthroplasty (THA). The long-term effects of UHMWPE wear debris are well documented and these have led to interest in alternate bearing materials for THA. Alumina ceramic-ceramic hip joints have been successfully used for more than 30 years with low wear and little incidence of osteolysis. The most common wear pattern observed on retrieved components is an elliptical wear 'stripe' on the heads and a corresponding worn area on the cup with an approximated wear rate of 1-5 mm3 pa. More severe wear has also occasionally occurred, usually in association with an abnormal clinical history. Modern alumina-alumina THAs use an improved HIPed (hot isostatically pressed) alumina ceramic-bearing material which may be more resistant to severe wear. Previous in vitro simulator studies have not replicated in vivo wear rates or mechanisms. The aim of this study was to compare previous generation non-HIPed alumina and modern HIPed alumina in a hip joint simulator under 'normal' and 'harsh' testing conditions. HIPed alumina was found to have a lower wear rate than non-HIPed alumina, although the difference was not statistically significant at the 95% confidence level. Testing in Gelofusine and water lubricants did not elevate the wear rates of either material. Elevated swing phase load testing also had no significant effect on the wear rates of either material. Testing in the absence of any lubricant produced very severe wear of the non-HIPed material in one specimen only.

Aluminum Oxide↗

PubMed2001

Cell-mediated immunity to the mycelial phase of Malassezia spp. in patients with pityriasis versicolor and controls.

BACKGROUND: Malassezia is the aetiological agent of pityriasis versicolor. The mycelial phase of the organism predominates in lesions of pityriasis versicolor. OBJECTIVES: To evaluate the cell-mediated immune (CMI) response to the mycelial phase of Malassezia in patients with this disease, which has not previously been studied. METHODS: The CMI status of 12 patients with pityriasis versicolor and 12 age- and sex-matched controls to mycelial antigen(s) of the organism was examined. The responses to the mycelial form of three strains of the organism were assessed using lymphocyte transformation and leucocyte migration inhibition assays. RESULTS: The transformation responses of the lymphocytes from both patients and controls gave transformation indices < or = 3, although the responses of lymphocytes from patients with pityriasis versicolor to the mycelial form of Malassezia strains were generally higher than those of the controls. In the leucocyte migration inhibition assay, leucocytes from patients with pityriasis versicolor and controls responded to the mycelial antigens of three different Malassezia strains; however, there was no significant difference in leucocyte response between patients with pityriasis versicolor and controls. CONCLUSIONS: Patients with pityriasis versicolor do not therefore have a CMI deficiency to Malassezia mycelial antigens but fail to generate a protective CMI response to mycelial antigens over and above that of control individuals during active disease.

Adult↗

PubMed2001

Production of the mycelial phase of Malassezia in vitro.

To study the pathogenicity of Malassezia, the agent of pityriasis versicolor, it is necessary to obtain the mycelial form in vitro. A range of different components and conditions were tested to induce yeast cells of the organism to produce mycelia in vitro using different culture media. A mycelial culture medium was developed that consisted of bacteriological peptone, glucose, yeast extract, ox bile, glycerol, glycerol monostearate, Tween 80, squalene, glycine, potassium nitrate, sodium chloride, ferrous sulphate and magnesium sulphate with or without agar. The liquid and solid medium had a pH of 5.6 and the temperature of incubation was 30 degrees C. Cultures were incubated in air. This medium was able to induce some strains of Malassezia to produce up to 40% mycelium in vitro. In total, 33 different strains of Malassezia obtained from the skin of the healthy individuals and patients with pityriasis versicolor were tested for mycelium production. The strains of Malassezia capable of producing mycelium in vitro all possessed the serovar A antigen.

Culture Media↗

PubMed2001

PerR controls oxidative stress resistance and iron storage proteins and is required for virulence in Staphylococcus aureus.

The Staphylococcus aureus genome encodes three ferric uptake regulator (Fur) homologues: Fur, PerR, and Zur. To determine the exact role of PerR, we inactivated the gene by allelic replacement using a kanamycin cassette, creating strain MJH001 (perR). PerR was found to control transcription of the genes encoding the oxidative stress resistance proteins catalase (KatA), alkyl hydroperoxide reductase (AhpCF), bacterioferritin comigratory protein (Bcp), and thioredoxin reductase (TrxB). Furthermore, PerR regulates transcription of the genes encoding the iron storage proteins ferritin (Ftn) and the ferritin-like Dps homologue, MrgA. Transcription of perR was autoregulated, and PerR repressed transcription of the iron homeostasis regulator Fur, which is a positive regulator of catalase expression. PerR functions as a manganese-dependent, transcriptional repressor of the identified regulon. Elevated iron concentrations produced induction of the PerR regulon. PerR may act as a peroxide sensor, since addition of external hydrogen peroxide to 8325-4 (wild type) resulted in increased transcription of most of the PerR regulon, except for fur and perR itself. The PerR-regulated katA gene encodes the sole catalase of S. aureus, which is an important starvation survival determinant but is surprisingly not required for pathogenicity in a murine skin abscess model of infection. In contrast, PerR is not necessary for starvation survival but is required for full virulence (P < 0.005) in this model of infection. PerR of S. aureus may act as a redox sentinel protein during infection, analogous to the in vitro activities of OxyR and PerR of Escherichia coli and Bacillus subtilis, respectively. However, it differs in its response to the metal balance within the cell and has the added capability of regulating iron uptake and storage.

Amino Acid Sequence↗

PubMed2001

In Staphylococcus aureus, fur is an interactive regulator with PerR, contributes to virulence, and Is necessary for oxidative stress resistance through positive regulation of catalase and iron homeostasis.

The Staphylococcus aureus genome encodes three ferric uptake repressor (Fur) homologues: Fur, PerR, and Zur. To determine the exact role of Fur in S. aureus, we inactivated the fur gene by allelic replacement using a tetracycline resistance cassette, creating strain MJH010 (fur). The mutant had a growth defect in rich medium, and this defect was exacerbated in metal-depleted CL medium. This growth defect was partially suppressed by manganous ion, a metal ion with known antioxidant properties. This suggests that the fur mutation leads to an oxidative stress condition. Indeed, MJH010 (fur) has reduced levels of catalase activity resulting from decreased katA transcription. Using a katA-lacZ fusion we have determined that Fur functions, either directly or indirectly, as an iron-dependent positive regulator of katA expression. Transcription of katA is coregulated by Fur and PerR, since in MJH010 (fur) transcription was still repressed by manganese while transcription in MJH201 (fur perR) was unresponsive to the presence of iron or manganese. Siderophore biosynthesis was repressed by iron in 8325-4 (wild-type) but in MJH010 (fur) was constitutive. A number of putative Fur-regulated genes were identified in the incomplete genome databases using known S. aureus Fur box sequences. Of those tested, the sstABCD and sirABC operons and the fhuD2 and orf4 genes were found to have Fur-regulated expression. MJH010 (fur) was attenuated (P<0.04) in a murine skin abscess model of infection, as was double-mutant MJH201 (fur perR) (P<0.03). This demonstrates the importance in vivo of iron homeostasis and oxidative stress resistance regulation in S. aureus.

Animals↗

PubMed2001

Influence of simulator kinematics on the wear of metal-on-metal hip prostheses.

There is now considerable interest in metal-on-metal bearings for hip prostheses. Extremely low wear rates (0.1 mm3/10(6) cycles) have been reported in some simulator studies, while in vivo studies, although still very low, have shown wear rates of the order of 1 mm3/10(6) cycles. The aim of this study was to compare wear rates of metal-on-metal bearings in two hip simulators with different kinematic inputs. In the simulator with three independent input motions which produced an open elliptical wear path with a low level of eccentricity, the wear rates were very low as recorded previously in other simulators. In the simulator with two input motions which produced an open elliptical wear path with greater eccentricity the wear rate was at least ten times higher and closer to clinical values. The motion and kinematic conditions in the contact are critical determinants of wear in metal-on-metal bearings.

Biomechanical Phenomena↗

PubMed2001

A novel method for the prediction of functional biological activity of polyethylene wear debris.

The comparative performance of artificial hip joints has been extensively investigated in vitro through measurements of wear volumes. In vivo a major cause of long-term failure is wear-debris-induced osteolysis. These adverse biological reactions are not simply dependent on wear volume, but are also controlled by the size and volumetric concentration of the debris. A novel model is presented which predicts functional biological activity; this is determined by integrating the product of the biological activity function and the volumetric concentration function with the wear volume over the whole particle size range. This model combines conventional wear volume measurements with particle analysis and the output from in vitro cell culture studies to provide a new indicator of osteolytic potential. The application of the model is demonstrated through comparison of the functional biological activity of wear debris from polyethylene acetabular cups articulating under three different conditions in a hip joint simulator.

Biocompatible Materials↗

PubMed2001

The influence of phospholipid concentration in protein-containing lubricants on the wear of ultra-high molecular weight polyethylene in artificial hip joints.

There is considerable interest in the wear of polyethylene and the resulting wear-debris-induced osteolysis in artificial hip joints. Proteins play an important role as boundary lubricants in vivo in the pseudosynovial fluid, and these are reproduced in in vitro tests through the use of bovine serum. Little is known, however, about the effect of phospholipid concentrations within proteinaceous solutions on the wear of ultra-high molecular weight polyethylene (UHMWPE). The effects of protein-containing lubricants with 0.05, 0.5 and 5 per cent (w/v) phosphatidyl choline concentrations on the wear of ultra-high molecular weight polyethylene (UHMWPE) were compared with 25 per cent (v/v) bovine serum which had 0.01 per cent (w/v) lipid; the effects were compared in a hip joint simulator with smooth (n = 4) and scratched (n = 3) femoral heads. The control bovine serum lubricant produced UHWMPE wear of 55 and 115 mm3/10(6) cycles on the smooth and rough heads respectively. The increased phospholipid concentration significantly reduced the wear rate. At the higher concentration (5% w/v phosphatidyl choline) the average wear was reduced to less than 2 mm3/10(6) cycles. Even with the relatively low concentrations of 0.05% w/v phosphatidyl choline the wear was reduced by at least threefold compared with the bovine serum tests for both the smooth and rough femoral heads. There may be considerable differences in the phospholipid concentrations in patients' synovial fluid and this is highly likely to produce considerable variation in wear rates. In vitro, differences in the phospholipid concentration of lubricants may also cause variation in wear rates between different simulator tests.

Hip Prosthesis↗

PubMed2001

A novel three-dimensional tissue equivalent model to study the combined effects of cyclic mechanical strain and wear particles on the osteolytic potential of primary human macrophages in vitro.

The effects of cyclic mechanical strain and challenge with physiologically relevant doses of submicrometre-size polyethylene (PE) particles on the osteolytic potential of primary human mononuclear phagocytes were investigated. Cells were seeded into a three-dimensional tissue matrix and co-cultured with particles (mean size 0.21 microm) at particle volume to cell number ratios of 7.5, 15, 30 and 100 microm3/cell. Matrices were then either cultured statically or subjected to 20 per cent cyclic compressional strain in the 'ComCell' for 16 h prior to the assessment of cell viability and quantification of the pro-inflammatory cytokine tumour necrosis factor alpha (TNFalpha). The MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazdium bromide) assay was shown to be too insensitive to detect changes in cell viability. However, when quantified by the adenosine triphosphate (ATP) assay, cell viability was demonstrated to be reduced following exposure to cyclic strain. Macrophages cultured in the static three-dimensional tissue equivalent model produced very high levels of TNFalpha in response to submicrometre PE particles at a ratio of 100 microm3/cell. Cyclic strain in the absence of particles gave only a small increase in TNFa production. However, the combined effects of strain and particle stimulation at a ratio of 30 microm3/cell resulted in the secretion of significantly more TNFalpha than was produced by macrophages subjected to strain alone, or the cells-only control. This synergy between cyclic strain and PE particle stimulation was only evident when the volume of particles was reduced below the volume that maximally stimulated cells. These results suggest that while cyclic strain may not be the primary factor responsible for macrophage activation and periprosthetic osteolysis, at low particle load, it may contribute significantly to the osteolytic potential of macrophages in vitro or in vivo.

Coculture Techniques↗

PubMed2001

A retrieval study of capital hip prostheses with titanium alloy femoral stems.

We have examined 26 retrieved, failed titanium-alloy femoral stems. The clinical details, radiological appearances and the histology of the surrounding soft tissues in each patient were also investigated. The stems were predominantly of the flanged design and had a characteristic pattern of wear. A review of the radiographs showed a series of changes, progressive with time. The first was lateral debonding with subsidence of the stem. This was followed by calcar resorption and fragmentation or fracture of the cement. Finally, osteolysis was seen, starting with a radiolucency at the cement-bone interface and progressing to endosteal cavitation. Three histological appearances were noted: granulomatous, necrobiotic and necrotic. We suggest that an unknown factor, possibly related to the design of the stem, caused it to move early. After this, micromovement at the cement-stem interface led to the generation of particulate debris and fracture of the cement. A soft-tissue reaction to the debris resulted in osteolysis and failure of fixation of the prostheses.

Aged↗

PubMed2001

Comparative wear and wear debris under three different counterface conditions of crosslinked and non-crosslinked ultra high molecular weight polyethylene.

The wear debris generated from ultra high molecular weight polyethylene (UHMWPE) have been recognised as one of the major causes of failure in total hip replacements (THR). It is essential to reduce the wear debris generated from UHMWPE acetabular cups in order to minimise this problem. Debris in the submicron size range is believed to have greater osteolytic potential. It is now known that crosslinked UHMWPE acetabular cups have reduced volumetric wear rates but little is known about the influence of crosslinking on the size and morphology of the wear debris. In this study, the wear of grade GUR 1020 crosslinked (vacuum gamma irradiated), GUR 1120 crosslinked (acetylene enhanced irradiated) and non cross linked (ethylene oxide sterilised) GUR 1020 UHMWPE was compared in multidirectional pin-on-plate wear tests under three different counterface conditions (smooth, isotropically rough and scratched counterfaces). Multidirectional motion was chosen because this motion was closer to the relative motion in the natural hip. From this study, better wear resistance of crosslinked UHMWPE compared with non-crosslinked UHMWPE was demonstrated for the smooth counterface conditions. However, in the rough and scratched counterface conditions, the vacuum gamma irradiated crosslinked material produced significantly higher wear rates than the non-crosslinked material. The analysis of the wear debris showed that the majority of the volume of the acetylene enhanced crosslinked UHMWPE wear debris was in the most biologically active size range (0.1 to 0.5 microm). In contrast, the non-crosslinked material and the vacuum gamma irradiated crosslinked material had a greater proportion of the volume of the debris in the larger size ranges which are less biologically active. This has important implications for its osteolytic potential.

Acetylene↗

PubMed2001

Quantitative analysis of wear and wear debris from metal-on-metal hip prostheses tested in a physiological hip joint simulator.

Osteolysis and loosening of artificial joints caused by UHMWPE wear debris has prompted renewed interest in metal-on-metal (MOM) hip prostheses. This study investigated the wear and wear debris morphology generated by MOM prostheses in a physiological anatomical hip simulator for different carbon content cobalt chrome alloys. The low carbon pairings demonstrated significantly higher "bedding in" and steady state wear rates than the mixed and high carbon pairings. The in vitro wear rates reported here were up to one or two orders of magnitude lower than the clinical wear rates for first-generation MOM hip prostheses. Two methods for characterising the metal wear debris were developed, involving digestion, scanning electron microscopy and transmission electron microscopy. The metal wear particles characterised by the two methods were similar in size, 25-36 nm, and comparable to particles isolated from periprosthetic tissues from first and second-generation MOM hip prostheses. Due to the small size of the metal particles, the number of particles generated per year for MOM prostheses in vitro was estimated to be up to 100 times higher than the number of polyethylene particles generated per year in vivo. The volumetric wear rates were affected by the carbon content of the cobalt chrome alloy and the material combinations used. However, particle size and morphology was not affected by method of particle characterisation, the carbon content of the alloy or material combination.

Biomechanical Phenomena↗

PubMed2001

Comparative analysis of two different types of alumina-alumina hip prosthesis retrieved for aseptic loosening.

We compared and quantified the modes of failure and patterns of wear of 11 Mittelmeier and 11 Ceraver-Ostal retrieved alumina-alumina hip prostheses with reference to the corresponding clinical and radiological histories. Macroscopic wear was assessed using a three-dimensional co-ordinate measuring machine. Talysurf contacting profilometry was used to measure surface roughness on a microscopic scale and SEM to determine mechanisms of wear at the submicron level. The components were classified into one of three categories of wear: low (no visible/measurable wear), stripe (elliptical wear stripe on the heads and larger worn areas on the cups) and severe (macroscopic wear, large volumes of material lost). Overall, the volumetric wear of the alumina-alumina prostheses was substantially less than the widely used metal and ceramic-on-polyethylene combinations. By identifying and eliminating the factors which accelerate wear, it is expected that the lifetime of these devices can be further increased.

Adolescent↗

PubMed2000

Heat shock proteins and inflammatory acne vulgaris: molecular cloning, overexpression and purification of a propionibacterium acnes GroEL and DnaK homologue.

Propionibacterium acnes is associated with inflammatory acne. The genes encoding two putative mediators of inflammation, the heat shock proteins GroEL and DnaK, were cloned from this organism and sequenced. groEL and dnaK encode proteins of 56.8 and 66.4 kDa, respectively, which show a high degree of homology (>75% similarity) to the GroEL and DnaK proteins of mycobacteria and streptomycetes. The promoter regions of both genes contain inverted repeat sequences believed to be involved in the transcriptional regulation of heat shock genes. Recombinant P. acnes GroEL and DnaK were overexpressed in Escherichia coli with C-terminal histidine tags. The recombinant proteins were purified from E. coli by metal affinity chromatography. These proteins will now be used in immunological investigations to determine their role in inflammatory acne.

Acne Vulgaris↗