Biomedical subjects

E Ingham

Publications and source records attributed to E Ingham.

At least 73 records · Page 4Linked to original sources

PubMed2000

The effects of lipid extraction on the immunomodulatory activity of Malassezia species in vitro.

Malassezia spp. are believed to be the causative agents of pityriasis versicolor and are strongly implicated in seborrhoeic dermatitis. The yeast also forms part of the normal human cutaneous microflora. We have previously shown that when Malassezia yeast cells are incubated with human peripheral blood mononuclear cells (PBMCs), they are capable of reducing the levels of pro-inflammatory cytokines produced. In order to test the hypothesis that this immunoevasive phenomenon may be related to the unusually high level of lipid in the Malassezia yeast cell wall, we have compared the immunomodulatory capacity of normal and lipid-depleted yeast cells. Stationary phase yeast cells of Malassezia sympodialis, M. globosa and M. restricta were treated with chloroform/methanol to extract the surface lipids. The lipid-depleted and non-depleted yeast cells were then co-cultured with human PBMCs from three different human donors at a ratio of 20 yeasts per leukocyte for 24 h. The levels of interleukin (IL)-1beta, IL-6 and tumour necrosis factor (TNF)-alpha were then determined by enzyme-linked immunosorbent assay (ELISA). The results demonstrated that extraction of lipid reversed the yeast cell capacity to reduce the levels of pro-inflammatory cytokines. The levels of IL-1beta, IL-6 and TNF-alpha produced in response to lipid-extracted Malassezia of all three species were either no different from or significantly greater (P < 0.05; ANOVA) than the constitutive control levels. These results suggest that the lipid microfibrillar layer of Malassezia may prevent the yeast cells from inducing inflammation and provide an explanation for the normal commensal status of the organism on human skin. The hypothesis that the lipid layer is absent or altered in seborrhoeic dermatitis may provide an explanation for the inflammatory nature of this dermatosis.

Cells, Cultured↗

PubMed2000

Biological reactions to wear debris in total joint replacement.

The vast majority of total hip prostheses currently implanted consist of a hard metal or ceramic femoral head articulating against an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup. Over the last 10 years, evidence has accumulated to show that these prostheses are prone to failure due to late aseptic loosening and few survive beyond 25 years. With an increasing need to implant hip prostheses in the younger, more active patient the need to understand the mechanisms of failure and to develop artificial hip joints using alternative materials have become major issues in the orthopaedic community. This review focuses initially on our current understanding of the biological reactions to UHMWPE prosthetic wear debris in vivo and in vitro since this is believed to be the main cause of late aseptic loosening. While the precise mechanisms of osteolysis induced by UHMWPE wear debris have not been elucidated, the major message to emerge is that it is not the wear volume that determines the biological response to the debris, but the concentration of the wear volume that is within the critical size range (0.2-0.8 micron) for macrophage activation. The review then considers whether the problem of wear-debris-induced osteolysis may be overcome with the use of new generation metal-on-metal or ceramic-on-ceramic prostheses. For metal-on-metal prostheses, the prospects for increasing the osteolysis free life of the implant are good but additional biological problems associated with the nanometre size and reactivity of the wear particles in vivo may emerge. For the ceramic-on-ceramic prostheses, although initial prospects are encouraging, more data are needed on the characteristics of the wear particles generated in vivo before predictions can be made. It is concluded that the pre-clinical testing of any new materials for joint replacement must include an analysis of the wear particle characteristics and their biological reactivity in addition to the usual assessment of wear.

Biocompatible Materials↗

PubMed2000

Investigation into the tribological condition of acetabular tissue after bipolar joint replacement hip surgery.

The aim of this research was to investigate the tribological condition of acetabular tissue before and after bipolar hip surgery. Articular cartilage was taken from the femoral head of patients undergoing primary joint replacement as a control. Tissue was also taken from the acetabular cups of patients undergoing revision hip surgery after primary bipolar surgery and compared with the control cartilage. The biomechanical characteristics of the two tissue types were tested using friction and compression tests. The friction tests were carried out on a sliding friction rig under nominal contact stresses of 0.5 and 4 MPa. The compression tests were carried out under a 0.8 MPa contact stress. The majority of the bipolar patients produced friction coefficients that were significantly higher than those produced by the control group, and the compression tests highlighted that the tissue from the bipolar patients produced a much greater rate of increase in displacement compared with the control cartilage. Histology showed major differences between the control cartilage and the bipolar tissue. The control cartilage showed a healthy collagen structure with a good distribution of proteoglycan whereas the majority of the bipolar tissue had lost tissue architecture and had a sparse fibrous structure. The high friction coefficients with the bipolar tissue imply that the frictional torque at the outer head of the bipolar prosthesis would be large compared with the inner bearing frictional torque. It was therefore predicted that the motion of the bipolar prosthesis should occur at the inner bearing.

Acetabulum↗

PubMed2000

Influence of gelatin and bovine serum lubricants on ultra-high molecular weight polyethylene wear debris generated in in vitro simulations.

Ultra-high molecular weight polyethylene (UHMWPE) wear debris induced osteolysis has a major role in the late aseptic loosening and ultimate failure of total hip replacements (THR). Clinically relevant in vitro simulations of wear are essential to predict the osteolytic potential of bearing surfaces in artificial hip joints. Newborn calf or bovine serum has been accepted as a boundary lubricant for such in vitro tests, but its biological stability has been questioned. This study compared the wear factors, number of wear particles and levels of microbial contamination produced in bovine serum and a gelatin-based lubricant. The wear factors produced by the two lubricants were not significantly different, however the wear debris morphology produced was substantially different. The bovine serum became contaminated with micro-organisms within 28 h, whereas the protein-based lubricant remained uncontaminated. The results showed that bovine serum was not a stable boundary lubricant. They also showed that although the wear factors for the two solutions were not significantly different, the protein-based lubricant was not a suitable alternative to bovine serum because the wear debris produced was not clinically relevant.

Animals↗

PubMed2000

Frictional behaviour of bovine articular cartilage.

The experimentally measured indentation displacement and friction of normal and degraded (treated with chondroitinase AC) bovine articular cartilage plugs against a smooth steel plate were compared with the predictions based on the biphasic theory using the finite element method. It was found that the measured indentation displacement of both cartilage specimens could be predicted from the biphasic theory and the permeability for the degraded cartilage specimen was increased approximately three times. However, the measured friction coefficient was much lower for short period of loading, and the difference in the finite element prediction of friction coefficient between the normal and degraded cartilage specimens was not observed in the experiment. Therefore, it was concluded that both biphasic and other mechanisms were important in controlling the frictional and lubricating characteristics of articular cartilage in mixed and boundary lubrication regimes.

Animals↗

PubMed2000

Cardiac valve replacement: a bioengineering approach.

The second most common major heart operation in the western world is valve replacement. Any one of the four heart valves may become either so stenotic or regurgitant that it needs to be replaced in order to restore normal heart function. Although replacement surgery of dysfunctional heart valves has a very high success rate, it can provide the surgeon with a difficult decision regarding the choice of a suitable prosthesis for the individual patient. Over the years many different types of artificial heart valves have been devised. Surgeons typically deal with a heart valve replacement by installing a mechanical prosthesis or by using a bioprosthetic valve, hand-crafted from animal tissue. Least commonly, valves can be taken from human organ donors. Mechanical valve substitutes have a long fatigue life but the central flow occluders often induce blood cell trauma. Tissue substitutes have an unimpeded central orifice when open, cause minimal cell damage but have a relatively short fatigue life, especially in children where calcification may be a major problem. More recently alternative materials, such as polyurethane, have been used in artificial heart valve design while the new concept of tissue-engineering has enhanced the prospects towards an ideal cardiac valve replacement. Today's artificial valves are designed with a better understanding of the cardiovascular system with the aid of computers. Advances in computer software have allowed simulations of fluid flows through valve substitutes, both in cardiac flow simulators and the heart itself.

Animals↗

PubMed2000

Comparison of the response of primary murine peritoneal macrophages and the U937 human histiocytic cell line to challenge with in vitro generated clinically relevant UHMWPE particles.

The response of primary murine macrophages and the U937 human histiocytic cell line to challenge with clinically relevant UHMWPE wear debris of known particle size and dose was evaluated. Particles with mean sizes of 0.24, 0.45, 1.71, 7.62 and 88 microm were co-cultured with cells for 24 hours prior to assessment of cell viability and production of the osteolytic mediators IL-1beta, IL-6, TNFalpha and, in supernatants from murine phagocytes, PGE2 and GM-CSF. All particle fractions were evaluated at particle volume (microm3) to cell number ratios of 10 : 1 and 100 : 1 (and, additionally, 0.1 : 1 and 1 : 1 for U937 cells). These ratios had previously been identified as the most stimulatory and clinically relevant. Although the results for the cell line were highly variable, stimulation with phagocytosable particles (range 0.1 to 15 microm) resulted in enhanced levels of cytokine secretion by both murine macrophages and U937 histiocytes. The most biologically active particles were sub-micrometre in size. However, U937 cells responded to wear debris at much lower particle volume to cell number ratios (>0.1 microm3 per cell) than the murine cells (> 10 microm3 per cell). No GM-CSF was produced by particle or LPS stimulated murine macrophages. Similarly, U937 histiocytes failed to secrete any IL-1beta. Neither macrophage population responded to stimulation with the largest (88 microm) particles. These results confirm earlier findings and suggest that the size of UHMWPE wear particles is a critical factor in macrophage activation. Moreover, primary murine macrophages have been demonstrated to be a suitable model for studying cell-particle interactions in vitro.

Animals↗

PubMed1999

Analysis of retrieved alumina ceramic components from Mittelmeier total hip prostheses.

This study analyses explanted prostheses from a single surgeon's 16-yr series of Mittelmeier cementless total hip replacements. The patient group was young (patients aged 15-60, average 40) and active. Revision was related to various factors. All components were measured using a Kemco 3D coordinate measurement machine. Wear surfaces and linear wear penetrations of 11 retrieved Mittelmeier Autophor ceramic hip components (average implantation time 8.6 yr, range 1-13 yr) were analysed and the different types of wear identified. Surface analysis was then performed using Talysurf contacting profilometry and scanning electron microscopy. Three types of wear were identified: low wear (1 case), stripe wear (6 cases) and severe wear (4 cases). Stripe wear was characterised as a stripe of worn area on the head up to 150 microns deep whilst the rest of the head showed very low wear. The cups in the stripe wear cases were worn over about 40-50% of the surface. Severe wear cases had very large areas of heavy wear and visible volume loss on both heads and cups. The four cases of severe wear were associated with abnormal clinical histories.

Adolescent↗

PubMed1999

Quantitative analysis of the wear and wear debris from low and high carbon content cobalt chrome alloys used in metal on metal total hip replacements.

The biological reactions to polyethylene wear debris have been shown to result in osteolysis and loosening of total hip arthroplasties. This has led to renewed interest in the use of metal on metal bearings in hip prostheses. This study employed uniaxial and biaxial multistation pin on plate reciprocators to assess how the carbon content of the cobalt chrome alloy and the types of motion affected the wear performance of the bearing surfaces and the morphology of the wear debris generated. The low carbon specimens demonstrated higher wear factors than both the mixed carbon pairings and the high carbon pairings. The biaxial motion decreased the wear rates of all specimens. Plate wear was significantly reduced by the biaxial motion, compared to pin wear. The metal wear particles isolated were an order of magnitude smaller than polyethylene particles, at 60-90 nm, and consequently, 100-fold more particles were produced per unit volume of wear compared to polyethylene. The low carbon specimens produced significantly larger particles than the other material combinations, although it is thought unlikely that the difference would be biologically significant in vivo. The volumetric wear rates were affected by the carbon content of the cobalt chrome alloy, the material combination used and type of motion applied. However, particle morphology was not affected by the carbon content of the alloy or the type of motion applied.

Journal Article↗

PubMed1999

The immunology of Propionibacterium acnes and acne.

The majority of recent publications on the immunology of Propionibacterium acnes relate to the potential use of the bacterium as an adjuvant or its use in rodent models of human inflammatory disease. These studies have increased the understanding of the potential effects of Propionibacterium acnes on cells of the mononuclear phagocyte system. Research into the immunology of acne and the role that Propionibacterium acnes plays in inflammatory acne has been limited, with efforts being focussed on the problems of Propionibacterium acnes resistance to antibiotics. Recent studies have indicated that inflammatory acne is a T cell-mediated disease, but whether Propionibacterium acnes is the initial stimulus for either the specific or non-specific recruitment of T cells in acne lesions is still a matter for conjecture.

Journal Article↗

PubMed1999

The influence of lubricant on the morphology of ultra-high molecular weight polyethylene wear debris generated in laboratory tests.

Since the implication of polyethylene wear debris as a major cause of osteolysis in total joint replacements, there has been much interest in polyethylene wear studies and in cell culture studies using ultra-high molecular weight polyethylene (UHMWPE) wear debris. Studies have shown that particles in the 0.1-10 microns size range are particularly important in causing adverse cellular reactions resulting in osteolysis. The morphology, the mass and size distributions, and the number of wear particles produced at the joint surfaces are influenced by the tribological conditions at the joint. Laboratory wear tests are used to investigate the wear properties of prosthetic joint materials and different research groups have used different lubricants in these tests. This paper shows that the volumetric wear and morphology of UHMWPE particles generated in vitro are influenced by the type of lubricant used. This study compared, quantitatively, UHMWPE wear debris generated in deionized water to debris that was generated in a system lubricated by bovine serum which was diluted to 25 per cent. The wear factors of UHMWPE in water and serum lubricants were significantly different (p < 0.05). UHMWPE wore 14 times more in water than in serum. Quantitative analysis of the wear particles showed that the debris that was generated in serum was morphologically different from debris that was produced in a water-lubricated system. Furthermore, the particles produced in serum showed a closer similarity to those found in retrieved acetabular tissues.

Blood↗

PubMed1999

Analysis of debris from brushing the femoral canal with a plastic brush--a potential cause of loosening in total hip replacement.

The generation of submicrometre sized polyethylene particles has been shown to be one of the major causes of osteolysis, loosening and failure of total replacement joints. It has been reported that intramedullary brushing of the femoral canal with polymer brushes prior to total hip arthroplasty results in the release of polymer particles into the femoral canal. The aim of this study was to isolate and characterize these particles on the basis of morphology and size and to determine whether these particles may play a role in osteolysis and loosening of the total hip prostheses. It was found that the majority of the particles shed by the polymer brushes were submicrometre in size and were similar in morphology to UHMWPE wear particles isolated from periprosthetic tissues. In addition, the majority of the particles released by the brushes were in the biologically active size range (0.1-10 microns), and may contribute to osteolysis and loosening of hip prostheses.

Arthroplasty, Replacement, Hip↗

PubMed1999

A comparison of the wear and debris generation of GUR 1120 (compression moulded) and GUR 4150HP (ram extruded) ultra high molecular weight polyethylene.

The wear debris generated from UHMWPE (ultra high molecular weight polyethylene) has been recognised as one of the major causes of failure in THR (total hip replacement). GUR 1120 (compression moulded) and GUR 4150HP (ram extruded) which are currently the most frequently used materials in THR were studied in pin-on-plate wear test. The wear particles generated from this test were observed by scanning electron micrograph and analysed by image analysis. The results from this study showed that GUR 4150HP had superior wear resistance than GUR 1120 under relatively high wear factor conditions. These results also highlighted the importance of multidirectional motion and its effect on the wear rates of UHMWPE. The multidirectional motion tended to show a higher wear factor than previous studies using unidirectional motion conducted under otherwise similar conditions. The wear debris analysis conducted with the wear particles collected from unidirectional (relatively rough) pin-on-plate wear tests (GUR 1120 and GUR 4150HP) showed that the greatest number of particles had a size range of 0.1-0.5 micron followed by 0.5-1.0 micron, 1.0-5.0 microns and 5.0-10.0 microns, in both GUR 1120 and GUR 4150HP. However, comparing the masses of the wear particles, the bigger size range of greater than 10 microns, had the highest percent mass followed by 1.0-5.0 microns, 0.5-1.0 micron, 0.1-0.5 micron and 5.0-10.0 microns.

Biocompatible Materials↗

PubMed1998

Polyethylene particles of a 'critical size' are necessary for the induction of cytokines by macrophages in vitro.

Particulate wear debris from total hip prosthetic components can stimulate macrophages to produce mediators of osteolysis which may cause aseptic implant loosening. This study evaluated the in vitro response of murine peritoneal macrophages to polyethylene particles of definitive size distributions at varying volume doses. Ceridust 3615 polyethylene particles with a mean size of 0.21, 0.49, 4.3 and 7.2 microm and GUR 120 polyethylene resin with a mean size of 88 microm were co-cultured with C3H murine peritoneal macrophages at volume (microm)3 to cell number ratios of 100:1, 10:1, 1:1 and 0.1: 1. The secretion of IL-6, IL-1beta and TNF-alpha was determined by ELISA. Significantly elevated levels of TNF-alpha and IL-1beta were determined at 100:1 ratios when the macrophages were challenged with particles with a mean size of 0.49, 4.3 and 7.2 microm, and at 10:1 ratios for particles with a mean size of 0.49 and 4.3 microm. IL-6 production was significantly elevated at 100:1 ratios for mean particle sizes of 0.49 and 4.3 microm. Particles outside this range produced considerably less cytokine suggesting that both the size and volume (or number) of polyethylene particles are critical factors in macrophage activation. Therefore particles in the phagocytosable size range of 0.3-10 microm appear to be the most biologically active.

Animals↗

PubMed1998

Investigation into the effects of proteins and lipids on the frictional properties of articular cartilage.

The aim of this study was to investigate the effects of the proteins and the lipids on the frictional properties of articular cartilage in the mixed and boundary lubricating regimes. Bovine articular cartilage that had been treated to remove the lipids, and cartilage that had been treated to remove the proteins, from the surface layer were studied in order to investigate differences in their lubricating abilities. Tests were carried out on a sliding friction rig under contact pressures of 0.5 and 4 MPa. The results of the friction tests carried out under the 4 MPa contact pressure showed a slight increase in friction coefficient for both the lipid and the protein deficient cartilage when compared with the control cartilage. These differences were more apparent at the shorter loading times but none of the differences were found to be statistically significant. The tests at the lower contact pressure of 0.5 MPa showed that removing the lipids by washing the surface with detergent increased the friction coefficient at the shorter loading times but had no effect at the longer loading times. Digesting the cartilage with trypsin to remove the proteins from the surface layer had no effect on the friction coefficient at the shorter loading times but reduced the friction coefficient at the longer loading times. Both these results were confirmed with specimens that had both the lipids and the proteins removed from the surface layer.

Animals↗

PubMed1998

Challenges in understanding RLK function.

Plants use receptor-like kinases (RLKs) to transduce extracellular signals into the cell. Recent advancements in RLK research include the cloning of the BRASSINOSTEROID INSENSITIVE 1 and CLAVATA 1 genes, revealing RLK roles in development. Our understanding of RLK function has also been broadened by transgenic approaches in the study of the RLKs pollen receptor kinase 1, and wall associated kinase 1. These results extend the observations that RLKs function in developmental processes and plant defense responses. Additionally, expression based studies suggest roles for other newly reported RLKs in development and light responses. Taken together, the studies confirm the importance of RLKs in diverse plant processes, yet major challenges remain. These include identifying ligands that activate RLKs and characterizing downstream pathways. These challenges can be conquered by coordinated efforts from investigators using molecular, genetic, and biochemical approaches.

Amino Acid Sequence↗

PubMed1998

Release of the angiogenic cytokine vascular endothelial growth factor (VEGF) from platelets: significance for VEGF measurements and cancer biology.

Vascular endothelial growth factor (VEGF) is a potent angiogenic factor with a key role in several pathological processes, including tumour vascularization. Our preliminary observations indicated higher VEGF concentrations in serum samples than in matched plasma samples. We have now demonstrated that this difference is due to the presence of VEGF within platelets and its release upon their activation during coagulation. In eight healthy volunteers, serum VEGF concentrations ranged from 76 to 854 pg ml(-1) and were significantly higher (P < 0.01) than the matched citrated plasma VEGF concentrations, which ranged from < 9 to 42 pg ml(-1). Using platelet-rich plasma, mean (s.d.) platelet VEGF contents of 0.56 (0.36) pg of VEGF 10(-6) platelets were found. Immunocytochemistry demonstrated the cytoplasmic presence of VEGF within megakaryocytes and other cell types within the bone marrow. From examination of the effects of blood sample processing on circulating VEGF concentrations, it is apparent that for accurate measurements, citrated plasma processed within 1 h of venepuncture should be used. Serum is completely unsuitable. The presence of VEGF within platelets has implications for processes involving platelet and endothelial cell interactions. e.g. wound healing, and in tumour metastasis, when platelets adhering to circulating tumour cells may release VEGF at points of adhesion to endothelium, leading to hyperpermeability and extravasation of cells.

Adult↗

PubMed1998

Immunohistochemical investigation of evolving inflammation in lesions of acne vulgaris.

The mechanisms involved in the development of inflammation in acne vulgaris have yet to be elucidated. Previous studies have shown that the initial cellular infiltrate in early inflammatory lesions is mononuclear, predominantly CD4 positive T cells. The aims of this study were to investigate the pattern of expression of adhesion molecules and HLA-DR in evolving acne lesions. Forty-nine patients with moderate to severe acne were biopsied following lesion mapping. Lesions were classified according to their duration of inflammation as up to 6 h, from 6 to 24 h, from 24 to 48 h and from 48 to 72 h. The cellular infiltrate was determined using monoclonal antibodies to CDI, CD3, CD4 and CD8. The expression of ICAM-1, E-selectin. VCAM-1 and HLA-DR was determined. Early (6 h) lesions had perivascular CD3 positive T-cell infiltrates which were predominantly CD4 positive. This was associated with vascular expression of ICAM-1, E-selectin, VCAM-1 and HLA-DR. Periductal infiltrates were present in 70% of the early lesions (up to 6 h). The cells were predominantly CD4 positive and associated with a high level of HLA-DR and ICAM-1 expression. Periductal infiltration increased with time and persisted to 72 h. ICAM-1 and HLA-DR were expressed epidermally in early and late lesions. CD1 positive cells were a minor, but consistent element in the perivascular and periductal infiltrates of early and late lesions. There was no statistically significant difference in the levels of expression of E-selectin, VCAM-1, ICAM-1 or HLA-DR for lesions of different duration. The pattern of HLA-DR and adhesion molecule expression plus the nature of the cellular infiltrate supports the hypothesis that inflammation in acne is mediated by CD4 positive T cells.

Acne Vulgaris↗