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Biomedical subjects

E Ingham

Publications and source records attributed to E Ingham.

At least 91 records · Page 5Linked to original sources
PubMed1998

The Staphylococcus aureus alternative sigma factor sigmaB controls the environmental stress response but not starvation survival or pathogenicity in a mouse abscess model.

The role of sigmaB, an alternative sigma factor of Staphylococcus aureus, has been characterized in response to environmental stress, starvation-survival and recovery, and pathogenicity. sigmaB was mainly expressed during the stationary phase of growth and was repressed by 1 M sodium chloride. A sigB insertionally inactivated mutant was created. In stress resistance studies, sigmaB was shown to be involved in recovery from heat shock at 54 degreesC and in acid and hydrogen peroxide resistance but not in resistance to ethanol or osmotic shock. Interestingly, S. aureus acquired increased acid resistance when preincubated at a sublethal pH 4 prior to exposure to a lethal pH 2. This acid-adaptive response resulting in tolerance was mediated via sigB. However, sigmaB was not vital for the starvation-survival or recovery mechanisms. sigmaB does not have a major role in the expression of the global regulator of virulence determinant biosynthesis, staphylococcal accessory regulator (sarA), the production of a number of representative virulence factors, and pathogenicity in a mouse subcutaneous abscess model. However, SarA upregulates sigB expression in a growth-phase-dependent manner. Thus, sigmaB expression is linked to the processes controlling virulence determinant production. The role of sigmaB as a major regulator of the stress response, but not of starvation-survival, is discussed.

Abscess↗
PubMed1998

Contraction duration affects metabolic energy cost and fatigue in skeletal muscle.

It has been suggested that during a skeletal muscle contraction the metabolic energy cost at the onset may be greater than the energy cost related to holding steady-state force. The purpose of the present study was to investigate the effect of contraction duration on the metabolic energy cost and fatigue process in fully perfused contracting muscle in situ. Canine gastrocnemius muscle (n = 6) was isolated, and two contractile periods (3 min of isometric, tetanic contractions with 45-min rest between) were conducted by each muscle in a balanced order design. The two contractile periods had stimulation patterns that resulted in a 1:3 contraction-to-rest ratio, with the difference in the two contractile periods being in the duration of each contraction: short duration 0.25-s stimulation/0.75-s rest vs. long duration 1-s stimulation/3-s rest. These stimulation patterns resulted in the same total time of stimulation, number of stimulation pulses, and total time in contraction for each 3-min period. Muscle O2 uptake, the fall in developed force (fatigue), the O2 cost of developed force, and the estimated total energy cost (ATP utilization) of developed force were significantly greater (P < 0.05) with contractions of short duration. Lactate efflux from the working muscle and muscle lactate concentration were significantly greater with contractions of short duration, such that the calculated energy derived from glycolysis was three times greater in this condition. These results demonstrate that contraction duration can significantly affect both the aerobic and anaerobic metabolic energy cost and fatigue in contracting muscle. In addition, it is likely that the greater rate of fatigue with more rapid contractions was a result of elevated glycolytic production of lactic acid.

Adenosine Triphosphate↗
PubMed1998

Investigation into the effect of proteoglycan molecules on the tribological properties of cartilage joint tissues.

The aim of this research was to investigate the role of the hydrophilic properties of the proteoglycan molecules within the cartilage matrix, on the tribological properties of joint tissues in the mixed and boundary lubricating regime. Bovine articular cartilage, bovine meniscus and bovine cartilage that had been degraded to remove the chondroitin sulphate from its proteoglycans were studied in order to investigate differences in their friction and compression responses. The tissues were tested 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 compression tests showed the cartilage and meniscus deforming at the same rates, but the degraded cartilage deformed more quickly to reach its equilibrium position in a shorter period of time. The friction tests carried out at a constant load revealed the friction of the meniscus rising more rapidly with loading time than the cartilage. The degraded cartilage followed an almost identical curve as the untreated cartilage. Although the reduced proteoglycan content of the degraded cartilage substantially altered the biphasic compression response, it did not have an effect on the frictional properties of the tissue.

Animals↗
PubMed1998

Quantitative comparison of wear debris from UHMWPE that has and has not been sterilised by gamma irradiation.

Ultra-high-molecular-weight polyethylene (UHMWPE) components for total joint replacement generate wear particles which cause adverse biological tissue reactions leading to osteolysis and loosening. Sterilisation of UHMWPE components by gamma irradiation in air causes chain scissions which initiate a long-term oxidative process that degrades the chemical and mechanical properties of the polyethylene. Using a tri-pin-on-disc tribometer we studied the effect of ageing for ten years after gamma irradiation in air on the volumetric wear, particle size distribution and the number of particles produced by UHMWPE when sliding against a stainless-steel counterface. The aged and irradiated material produced six times more volumetric wear and 34 times more wear particles per unit load per unit sliding distance than non-sterilised UHMWPE. Our findings indicate that oxidative degradation of polyethylene after gamma irradiation in air with ageing produces more wear.

Air↗
PubMed1998

Quantification of third-body damage and its effect on UHMWPE wear with different types of femoral head.

We examined stainless-steel, cobalt-chrome, titanium and alumina and zirconia ceramic femoral heads retrieved at revision surgery. All the heads had articulated against ultra-high-molecular-weight-polyethylene (UHMWPE) acetabular cups. We studied the simulation of third-body damage and the wear of UHMWPE against the various materials used for the heads. The surfaces of the retrieved heads were analysed using a two-dimensional contacting profilometer. Third-body damage was characterised by the mean height of the scratches above the mean line (Rpm). The alumina ceramic and zirconia ceramic retrieved heads were found to have significantly less damage. In laboratory studies the ceramics were also more resistant to simulated third-body damage than the metal alloys. We studied the wear of UHMWPE against the damaged counterfaces in simple configuration tests. The damaged ceramics produced less polyethylene wear than the damaged metal counterfaces. The wear factor of UHMWPE against the damaged materials was dependent on the amount of damage to the counterface (Rp). Our study has shown the benefit of using the harder and more damage-resistant ceramic materials for femoral heads.

Aluminum Oxide↗
PubMed1998

The effects of Malassezia on pro-inflammatory cytokine production by human peripheral blood mononuclear cells in vitro.

Malassezia spp., the causative agents of pityriasis versicolor, are members of the normal human cutaneous microflora. Utilizing a combination of both enzyme-linked immunosorbent assay (ELISA) and bioassay, we have investigated the ability of both formalin-preserved and viable Malassezia (serovars A, B and C) to modulate pro-inflammatory cytokine (IL-6, IL-1beta and TNF-alpha) release by human peripheral blood mononuclear cells (PBMNC) in vitro, over a 48-h co-incubation period. The results demonstrated that formalin-preserved Malassezia (serovars A, B and C) at mid-exponential phase were generally able to induce a pro-inflammatory cytokine response at a yeast cell to PBMNC ratio of 1:1. In addition, the results consistently demonstrated that at a yeast cell to PBMNC ratio of 20:1, formalin-preserved Malassezia, irrespective of serovar, growth phase or PBMNC donor, were capable of significantly (P<0.05) decreasing the release of both immunochemical IL-6 and IL-1beta plus bioactive IL-1beta and TNF-alpha below that of unstimulated culture medium control values. This was apparent following 24- and 48-h co-incubation times, where maximal cytokine production was detected after 24 h. Similar results were obtained for the effect of viable Malassezia on pro-inflammatory cytokine release by PBMNC. Our results suggest that a possible inhibitory component, present perhaps within the cell wall of Malassezia, was responsible for this depressive effect on pro-inflammatory cytokine production.

Biological Assay↗
PubMed1997

An investigation into the potential of extracellular matrix factors for attachment and proliferation of human keratinocytes on skin substitutes.

The purpose of this investigation was to assess the potential of commercially available extracellular matrix proteins, as enhancers of human keratinocyte attachment and proliferation, with a view to their incorporation into a skin equivalent. The following substrates were studied: type I and type IV collagen, fibronectin, gelatin and laminin. Human keratinocytes were cultured in low-calcium, serum-free medium. The number of cells attached to each substrate, observed under phase-contrast inverted microscopy in randomly selected fields of view, were counted 2 h afterseeding. Measurements of growth rate and colony-forming efficiency were made at 24-h intervals. None of the substrates tested were found to have an effect significant enough to warrant further investigation or inclusion into skin equivalent.

Analysis of Variance↗
PubMed1997

Effect of burn patient serum on fibroblast and keratinocyte cell morphology.

The effect of burn patient serum on fibroblast and keratinocyte cell morphology in culture was investigated using the scanning electron microscope. Serum was taken from five patients with burn injuries ranging from 8 to 65 per cent TBSA (10-65 per cent full-thickness). One patient had superficial burns. Pooled serum from 23 volunteers was used as the control serum. The cells were seeded onto collagen-coated glass coverslips and incubated for 5 days with culture medium containing 10 per cent (v/v) control serum or patient serum taken during the early postburn period. Scanning electron micrographs demonstrated a reduction in fibroblast cell density with serum from patients with full-thickness burns. Furthermore, the spindle shape of the fibroblast cell was greatly exaggerated compared with control cultures. The integrity of the keratinocyte sheet was destroyed when keratinocyte cells were incubated with serum fron patients with full-thickness burns. Globular-like structures or membrane protrusions were present in concentrated areas on keratinocyte cells which were not present in control cultures. This study demonstrated the vulnerability of cutaneous cells to systemic factors present in the early postburn serum. The extent of the effect appears to be related to the presence of full-thickness injury. This effect may further explain the frequent aberrant wound healing response to burn injury.

Adult↗
PubMed1997

Production and characterization of monoclonal antibodies to human interleukin-12.

Interleukin-12 is a cytokine that plays a central role in mediating cell mediated immunity via enhancement of a TH1 cell response. IL-12, unusually for a cytokine, has a heterodimeric structure made up of 35 kDa and 40 kDa subunits. The aim of this study was to produce and characterize monoclonal antibodies to recombinant human IL-12. Twenty-two monoclonal antibodies to IL-12 were successfully produced and subunit specificity determined using recombinant human IL-12 and chimeric murine/human IL-12. All antibodies were shown to react with the p40 subunit by ELISA and immunoblotting with three of the MAbs being found to cross-react with murine IL-12. Using two individual bioassays for IL-12, seven of the MAbs were shown to neutralize biological activity of IL-12. Ten of the antibodies were found to be of use in immunocytochemistry, reacting with LPS-stimulated peripheral blood monocytes. The approaches and difficulties encountered in characterizing antibodies to a heterodimeric cytokine are discussed together with possible reasons for the failure to generate antibodies to the p35 subunit.

Animals↗
PubMed1997

The development of an evaluation tool for grading clinical competence.

A perceived difficulty in grading clinical practice has meant that over the past two decades, educators in nursing have focused on non-graded results for clinical practicum. However, students expect rewards for achievement. Hospitals and universities require a means of differentiating levels of performance for employment and further study. This exploratory study uses quantitative and qualitative methods to evaluate a tool for grading clinical competence. The aims of the study were to determine the distribution of clinical grades, compare the clinical grades with the cumulative theoretical grades and compare the clinicians' and students' perceptions of competence. Study findings show that students and clinicians rated clinical performance well above the expected level. These grades for clinical performance exceeded comparative results in theoretical work for the practicum topic. In addition, content analysis of the qualitative data indicates that clinicians may have difficulty in using the ANCI Competencies to rate a student's performance for registration as a nurse.

Clinical Competence↗
PubMed1997

A study of the combined effects of shelf ageing following irradiation in air and counterface roughness on the wear of UHMWPE.

Damage to polished femoral heads in vivo can cause increased wear of acetabular cups. Oxidation and ageing after sterilisation by gamma irradiation in air, can also change the mechanical properties and wear resistance of ultra high molecular weight polyethylene (UHMWPE). This study investigated the combined effect of these changes in material properties on the wear of UHMWPE for different counterface roughnesses, representative of new femoral heads and those damaged in vivo. Wear rates were studied on a tri-pin-on-disc tribometer in a protein-containing solution. A comparison was made of the wear, using three different counterface roughnesses, of specimens that were manufactured from polyethylene acetabular cups of different shelf ages (3-120 months) after gamma irradiation in air but never implanted. These were compared to the wear of control specimens that were manufactured from cups that had not been sterilised. The wear surfaces were tested 1 mm below the initial articulating surface of the cup, the position of high degradation. The wear rate of UHMWPE which had been sterilised by gamma irradiation in air was shown to increase significantly with ageing time on the shelf for all counterface conditions. The wear rate of all materials increased markedly as the counterface roughness increased, but to different extents depending on the age of the material. The combined effect of ageing and increase in counterface roughness had a dramatic effect (as high as 2000 fold increase) on the wear rate. Both ageing of the polymer and damage to the femoral head have been cited as causing increased wear in vivo. The results of this study demonstrate that these variables can act synergistically to markedly effect UHMWPE wear rate.

Air↗
PubMed1997

IgG subclasses specific to Staphylococcus epidermidis and Propionibacterium acnes in patients with acne vulgaris.

IgG subclasses specific to Staphylococcus epidermidis and Propionibacterium acnes were determined in sera from patients with mild, moderate or severe acne and from a control group. Titres specific to S. epidermidis were all within the same range and did not differ between groups. The titres of IgG subclasses to specific to P. acnes did vary between groups. IgG1 and IgG3 were significantly higher in severe acne patients compared with moderate acne patients, while IgG2 was significantly higher in moderate and severe patients compared with controls. Titres of IgG4 did not differ between groups. The pattern of titres observed suggests that, while the antibody response to S. epidermidis is relatively harmless, antibodies to P. acnes may be involved in the pathogenesis of acne vulgaris.

Acne Vulgaris↗
PubMed1997

Donor valves as substitutes for heart valve replacement.

The main problems of heart valve replacement in Sri Lanka are the cost of prosthetic valves and anticoagulant related complications. The use of human donor heart valves (homografts; allogeneic heart valves [AHV]) will alleviate these shortcomings. Recipients of AHV do not require anticoagulant therapy. Moreover, cryopreservation of AHV offers the opportunity for the storage of valves for an extended length of time with the preservation of valve integrity which is essential for their function after implantation. A donor valve bank can potentially provide diameter matched valves for recipients. Current research suggests that the adverse immunological reactions initiated by AHV cause tissue degeneration in a proportion of these implants. However, the grafts may be improved before implantation during the disinfection and storage of the valves. In this essay an overview on the advantages of using AHV, current concepts of valve banking, recent advances in the understanding of AHV immunogenicity, emerging techniques for immunomodulation of AHV and the possibility of setting up a donor heart valve bank in Sri Lanka are discussed.

Heart Valves↗
PubMed1996

The effect of cryopreservation on the immunogenicity of allogeneic cardiac valves.

A proportion of implanted cryopreserved allogeneic cardiac valves (ACV) fail due to tissue degeneration initiated by immunological reactions. This study was carried out in a rat model system [Brown Norway (BN; RT1(n)) to Lewis (RT1(l))] to determine the possibility of cryoimmunomodulation of ACV. The immunogenicity of fresh and cryopreserved (1 degrees, 5 degrees, 10 degrees, 30 degrees, and >100 degrees C/min) BN aortic valve conduits (AVC) was assessed using a mixed AVC cell/responder lymphocyte reaction. No significant differences (p > 0.05) in immunogenicity between fresh and cryopreserved (1 degrees C/min and 5 degrees C/min) AVC were observed between 120 and 168 h of co-culture. A significant reduction in immunogenicity was observed with AVC cryopreserved using cooling rates of 10 degrees, 30 degrees, and >100 degrees C/min. The viability of fresh and cryopreserved AVC was determined by a [3H]proline uptake assay. A decrease in viability was observed at cooling rates of more than 1 degrees C/min. The feasibility of cryoimmunomodulation of ACV with the maintenance of viability of a proportion of cells was demonstrated.

Animals↗
PubMed1996

Human keratinocyte isolation and cell culture: a survey of current practices in the UK.

A survey was conducted to establish current techniques for isolation and culture of human keratinocytes. A questionnaire was sent to all units thought to be involved in keratinocyte culture, a total of 34 individuals; 62 per cent of those surveyed responded to the questionnaires. The proportion of individuals using high-calcium medium to culture keratinocytes was 53 per cent, while 47 per cent used low-calcium serum-free medium. The majority of replies followed trends dependent on the culture method employed. Details of anatomical donor skin site, keratinocyte isolation and culture were compared. In particular, the problems associated with the use of commercially prepared low-calcium, serum-free medium were reported. The basic principles of keratinocyte culture reported in the literature were seen amongst all the replies received. It is interesting to note the variations in methods adopted as techniques are passed on and continuously modified to suit the requirements of the individual worker. This survey also highlights the difficulties that can occur when using mass-produced complex media.

Adolescent↗