Biomedical subjects

J G Steele

Publications and source records attributed to J G Steele.

At least 73 records · Page 4Linked to original sources

PubMed1998

Is there a link between periodontal disease and coronary heart disease?

OBJECTIVE: To provide a critical review of the studies completed to date that have investigated a link between coronary heart disease and dental health. DESIGN: Retrospective analysis. SETTING: Mainly hospital-based patients or subjects involved in longitudinal health care studies. MAIN OUTCOME MEASURES: The incidence of coronary heart disease and its relationship to dental health and other recognised risk factors. RESULTS: Evidence suggests that dental health, in particular periodontal disease, may be a significant risk factor for coronary heart disease and further coronary events. Possible biological mechanisms that link the two diseases are appraised. CONCLUSIONS: There does appear to be increasing evidence that a relationship exists between dental health and coronary heart disease, especially in males aged 40-50 years. The presence of a hyperinflammatory monocyte phenotype may provide a common biological mechanism that links the two diseases.

Adult↗

PubMed1998

Surface topography can interfere with epithelial tissue migration.

Corneal epithelial tissue migration over the surface of a synthetic polymer can be inhibited by pores in the substrate. The effects of this substrate topography upon epithelial tissue migration were studied in vitro. Membranes of different porosities and structures were used to provide two series of surfaces having a graded increase in discontinuities: cellulose nitrate/acetate membranes with a tortuous network of pores, and track-etched polycarbonate membranes with columnar pores. Corneal epithelial tissue outgrowth was inhibited by increased pore size, and for both series of membranes, outgrowth was completely halted on membranes with mean diameter of the pores 0.9 microm at the pore densities measured. On the track-etched membranes with pores of <0.9 microm diameter, tissue outgrowth could be partially "rescued" by coating with fibronectin or collagen, but above this size, the inhibition predominated. The effect of porosity of the track-etched membranes upon the migration of dissociated epithelial cells was also examined. Although migration of these cells was reduced on membranes having pore sizes larger than 0.9 microm, it was not completely inhibited even on membranes of 2.3-microm pore diameter. Therefore, tissue movement of adult stratified epithelium may be inhibited by specific surface topographies, and in this assay system, epithelial tissue outgrowth was more affected than was the migration of dissociated epithelial cells.

Animals↗

PubMed1998

Persistent adhesion of corneal epithelial tissue on synthetic lenticules in vivo.

PURPOSE: In intact cornea, firm anchorage of the epithelium to its underlying stroma is provided by a system of adhesive structures, which include the epithelial basement membrane, adhesion complexes and associated alpha6beta4 integrin receptors. In the present study we sought to determine whether the sustained epithelialization of synthetic lenticules observed in vivo involved the formation of adhesive structures at the epithelial-lenticule interface similar to those present in intact tissue. METHODS: Collagen I-coated microporous polycarbonate membranes were implanted in the anterior stroma of adult cats. Successfully epithelialized lenticules were maintained on eye for 9-12 weeks, after which time the epithelial-lenticule interface was examined for evidence of adhesive structures using immunohistochemistry and electron microscopy. RESULTS: Immunohistochemistry identified laminin, hemidesmosomal plaque, collagen VII and alpha6 integrin at the tissue lenticule interface. Ultrastructural examination showed evidence of assembly of these components into a basement membrane and adhesion complexes. CONCLUSIONS: The formation of these adhesive structures is likely to have contributed to the sustained epithelialization observed clinically on the collagen-coated synthetic lenticules.

Animals↗

PubMed1998

Effects of surface topography on corneal epithelialization in vivo: a preliminary study.

PURPOSE: In this study we investigated the relationship between surface topography and initial epithelialization of synthetic lenticules in vivo. METHODS: Millipore ultrafiltration membranes of three different pore sizes were used as model lenticule materials. The nominal membrane pore sizes were 0.1 microm, 0.45 microm, and 3 microm; the surface roughness increased in the same order The membranes were coated with a thin layer of collagen I and implanted in a circular pocket of the anterior cornea of adult cats, and were clinically evaluated for the extent of epithelialization and the persistence of epithelial attachment. RESULTS/CONCLUSIONS: It was demonstrated that a smooth surface appears more attractive for initial epithelialization than a rough surface in vivo.

Animals↗

PubMed1998

Considerations when planning occlusal rehabilitation: a review of the literature.

As one of the most demanding tasks facing the restorative dentist, planning and executing an occlusal rehabilitation should not be undertaken lightly. The stakes are high and failure is costly. Treatment planning decisions should be undertaken on the basis of scientific evidence, where this is available, or on the basis of documented experience where it is not. This review article identifies the major biological and clinical considerations used when planning an occlusal rehabilitation. These include the indications for reorganising the occlusion, the choice of condylar position and occlusal scheme, the implications of and indications for increasing the vertical dimension, replacing missing teeth and the choice of materials. Finally, the literature surrounding the controversial issue of occlusal rehabilitation as a means to treat temporo-mandibular disorders is also reviewed.

Decision Making↗

PubMed1998

Polymer surface chemistry and bone cell migration.

Implant devices for orthopaedic applications may be improved if the surface of the biomaterial provides for osteointegration. To understand the effect of hydrophilicity on colonisation by human bone derived (HBD) cells, we compared untreated polystyrene (PS) and a sulfuric acid-treated PS surface for mechanisms of cell migration. The chemical composition of the acid-treated PS surface was analysed by monochromatic X-ray photoelectron spectroscopy and found to contain various oxidatively produced groups and a minor amount of sulfonate groups. It was found that migration of HBD cells on both PS and acid-treated PS surface was dependent on the presence of vitronectin (Vn) and was higher on the hydrophilic acid-treated surface. Minimal migration of HBD cells occurred on either surface in the absence of Vn, even when fibronectin was present in the culture medium. Using radiolabelled protein, it was shown that Vn adsorption onto the acid-treated surface was two to three fold greater than that on the hydrophobic PS. When HBD cells were seeded onto a patterned surface in a medium containing Vn, the cells preferentially colonised the hydrophilic region and few, if any, cells traversed the haptotactic boundary from the hydrophilic to the hydrophobic side. Thus the enhanced HBD cell migration seen on the acid-treated PS compared with the untreated PS surface and the haptotactic boundary phenomenon, relate to Vn adsorption.

Adolescent↗

PubMed1998

Albumin-binding surfaces: synthesis and characterization.

The nature of the proteinaceous film deposited on a biomaterial surface following implantation is a key determinant of the subsequent biological response. To achieve selectivity in the formation of this film, monoclonal antibodies have been coupled to a range of solid substrates using avidin-biotin technology. Antibody clones varied in their antigen-binding activity following insertion of biotin groups into lysine residues. Biotinylated antibodies coupled to solid substrates via an immobilized avidin bridge retained their biological activity. During immobilization of avidin a significant proportion of the protein molecules were passively adsorbed rather than covalently attached to the surface. This loosely bound material could be removed by stringent elution procedures which resulted in a surface density of 5.4 pmol avidin cm(-2). Although these conditions would be harsh enough to denature monoclonal antibodies, they did not destroy the biotin-binding activity of the residual surface-coupled avidin, enabling the subsequent immobilization of biotinylated antibodies. The two-step immobilization technique allowed the use of gentle protein modification procedures, reduced the risk of surface-induced denaturation and removed loosely bound material from the surface. The versatility of the technique encourages its application to a wide range of immobilization systems where retention of biological activity is a key requirement.

Adsorption↗

PubMed1998

Albumin-binding surfaces: in vitro activity.

Immobilized monoclonal antibodies (Mabs) have been used to attract specific molecules to a solid surface from complex mixtures such as blood, plasma or serum, thereby directing the response to the modified substrate, a key goal in rational biomaterial design. The nature of the Mab dictated the nature of the response: anti-albumin antibodies were used to prevent cell and platelet adhesion in vitro, whilst anti-fibronectin Mabs promoted attachment. Patterned surfaces could be formed, bearing Mabs that generated adhesive and non-adhesive regions. Fibrinogen adsorption from plasma showed a Vroman peak on unmodified control polymer, which was reduced by 64% in the presence of surface-bound anti-albumin Mab. Immobilization of a control Mab reduced fibrinogen adsorption only slightly, implying an albumin-mediated effect. In static tests, platelet adhesion from human platelet rich plasma was significantly reduced by the immobilization of anti-HSA Mab when compared to the untreated FEP surface (p < 0.0001). This effect was also seen with citrated blood flowing through Mab-treated polyurethane tubing at a shear rate of 132 s(-1) (p=0.034). Since platelets and proteins (as blood, plasma or serum) were introduced to the surface simultaneously, the generation of a defined protein film must have been sufficiently rapid as to shape the platelet or cell response.

Antibodies, Monoclonal↗

PubMed1998

Nutritional requirements of the corneal epithelium and anterior stroma: clinical findings.

PURPOSE: To monitor the health of the epithelium and the anterior stroma when porous membranes are implanted into the feline cornea and to determine membrane diffusivity characteristics needed to maintain corneal integrity. METHODS: Filtration membranes in a range of effective pore sizes of less than 15 nm (groups 1 and 2, n = 11), 25 nm (group 3, n = 8), 50 nm (group 4, n = 16), and 100 nm (group 5, n = 15) were implanted into an interlamellar corneal pocket of the stroma. The implanted membranes ranged in thickness from 6 nm to 15 nm and were between 8 mm and 12 mm in diameter. Animals were monitored for clinical signs of intolerance to the implants. RESULTS: At 1 month, thinning and ulceration had occurred in the epithelium and the anterior stroma of all animals in groups 1 and 2; epithelial changes, anterior stromal thinning, and ulceration had developed in 75% of animals of group 3; 50% of animals showed vascularization and only 7% showed epithelial degeneration in group 4; and local anterior stromal thinning was observed in 7% of animals in group 5, indicating clinical acceptance of the implanted membrane. In the long term (greater than 50 days), 30% and 73% of the group 4 and 5 corneas, respectively, were clinically quiet. Analysis of the failure times indicated an inverse relation between failure rate and pore size: less than 15 nm > 25 nm > 50 nm > 100 nm. The difference between the 100-nm and 50-nm membranes was significant (P = 0.03). CONCLUSIONS: A corneal implant must have a porosity greater than that provided by 50-nm membranes. The 100-nm membranes used in this study establish the porosity needed to satisfy the nutritional requirements of the cornea.

Animals↗

PubMed1997

Multiple attachment mechanisms of corneal epithelial cells to a polymer--cells can attach in the absence of exogenous adhesion proteins through a mechanism that requires microtubules.

The initial adhesion of epithelial cells is recognized as a critical determinant in the epithelialization of a polymer. Previously, the attachment of a variety of cell types to a polymer has been shown to be mediated by fibronectin and/or vitronectin that adsorb onto the polymer surface from the serum used to supplement the culture medium. Such an attachment reaction, dependent upon exogenous cell-adhesive proteins, is likely to involve the actin cytoskeleton and integrin receptors on the cell surface. In the current study, we have examined the attachment of recently isolated corneal epithelial cells to tissue culture polystyrene in the absence of such exogenous cell-adhesive proteins. Under these circumstances, there is an alternative mechanism of attachment operative between corneal epithelial cells and the polymer surface which is essentially independent of the adsorption of serum-derived fibronectin and vitronectin. This is an unusual phenomenon not previously observed with other normal cell types. The presence of cycloheximide inhibited this alternative attachment mechanism in corneal epithelial cells, indicating the role of newly synthesized proteins in this reaction. Additionally, we found that cell attachment to the polymer surface in the absence of cell-adhesive proteins was substantially inhibited by the presence of demecolcine, but not by cytochalasin B, thereby demonstrating the involvement of microtubules rather than actin microfilaments in this reaction. In the presence of serum-derived fibronectin and vitronectin, the attachment of corneal epithelial cells to a polymer may involve dual attachment mechanisms.

Actins↗

PubMed1997

The role of vitronectin in the attachment and spatial distribution of bone-derived cells on materials with patterned surface chemistry.

In recent years a central objective of tissue engineering has been understanding the interaction of cells with biomaterial surfaces. In this study we examined the protein adsorption events necessary to control the attachment and the subsequent spatial distribution of bone-derived cells exposed to chemically modified surfaces. Silane chemistry and photolithography techniques were used to create substrates with alternating regions of an aminosilane, N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (EDS), along side an alkylsilane, dimethyldichlorosilane (DMS), on quartz surfaces. Sera depleted of fibronectin (Fn), vitronectin (Vn), or both were used to determine if these proteins were necessary for the initial attachment and spatial distribution of bone-derived cells exposed to modified surfaces in vitro. The kinetics and mechanisms of the spatial distribution of cells were examined using light microscopy and digital image acquisition and subsequently were analyzed. Compared to complete serum, the use of serum depleted of fibronectin with vitronectin included had minimal effect on the cell attachment, spreading, and spatial distribution on the EDS regions of the surface. However, the use of serum depleted of vitronectin with or without fibronectin included resulted in greatly reduced cell attachment and spreading. Thus the presence of vitronectin was required for the attachment, spreading, and spatial distribution of bone-derived cells exposed to EDS/DMS-patterned surfaces.

Adsorption↗

PubMed1997

Mechanism of initial attachment of corneal epithelial cells to polymeric surfaces.

The initial attachment of cultured bovine corneal epithelial cells and stromal fibroblasts to two oxygen-containing synthetic polymers was studied. Cultured epithelial cells and stromal fibroblasts were seeded onto two oxygen-containing surfaces: 'tissue culture' polystyrene (TCPS) and a polymer film deposited by RF plasma deposition using a methylmethacrylate monomer (MMA/FEP). To establish the mechanism of cell attachment, the effect of the selective removal of the vitronectin and fibronectin from the serum used in the culture medium was tested. The attachment of cultured epithelial cells during the first 90 min of culture was reduced by 40% (TCPS)-80% (MMA/FEP) as a result of removing vitronectin from the medium. Attachment of these cells to TCPS was reduced by 85-95% when the serum was depleted of both fibronectin and vitronectin. However, depletion of fibronectin reduced cell attachment to TCPS by 20%, whilst on MMA/FEP cell attachment was equivalent, or higher, than that for intact serum. The attachment of cultured corneal stromal fibroblasts was similarly dependent on vitronectin but less dependent on fibronectin. Therefore, for the attachment of both cultured epithelial cells and fibroblasts to oxygen-containing surfaces in the presence of serum, there is a high requirement for serum vitronectin but a lesser requirement for fibronectin. The effects of the establishment of corneal epithelial cells in culture and the site of origin of the cells, were determined. Primary isolates of epithelial cells isolated from the limbal, central or peripheral regions of the cornea were less dependent on vitronectin for initial attachment to TCPS than were these cells after several passages in culture. Furthermore, the primary isolates were dramatically less responsive to vitronectin than the cultured cells. These results indicate that the mechanism of attachment of corneal epithelial cells to TCPS varies with the culture experience of the cells. Cells that are culture neophytes can employe endogenous mechanisms for the initial attachment to TCPS, whereas cells established in culture are dependent on exogenous vitronectin in order to attach.

Animals↗

PubMed1997

Effects of biologically modified surfaces of synthetic lenticules on corneal epithelialization in vivo.

PURPOSE: The present study investigated the association of extracellular matrix (ECM) glycoprotein coatings with initial epithelialization of artificial lenticules in vivo. METHODS: Collagen I, collagen IV, ECM and fibronectin were individually coated onto the surface of polycarbonate membranes. The membranes were then implanted in the anterior stroma of adult cats and were clinically assessed for rapidity and extent of epithelialization and the persistence of epithelial attachment. RESULTS/CONCLUSIONS: It was demonstrated that membrane surfaces modified by collagen I, collagen IV and ECM consistently supported initial migration and attachment of corneal epithelial cells and that the surface modified with collagen I performed best.

Animals↗

PubMed1997

Clinical factors related to reported satisfaction with oral function amongst dentate older adults in England.

This paper aims to identify the features of a natural dentition, specifically the number and distribution of teeth, which are important for oral satisfaction and freedom from eating problems in the elderly. Data were gathered on the dental condition, satisfaction and function of 1211 dentate adults aged 60 years or over, randomly sampled from three areas in England. Multiple logistic regression was used to identify the clinical factors which contribute to satisfaction with aesthetics and the ability to bite and chew. Satisfaction with biting and chewing was influenced by specific reported eating problems, dry month and increasing age. The presence of these eating problems was related to a complex series of factors describing the number and distribution of teeth and dentures, and some variables describing symptoms and disease. Having 21 or more natural teeth and no removable partial dentures (odds ratio 3.2), 2 or more posterior contacting pairs of teeth (odds ratio 1.7), and few anterior spaces were important factors related to the absence of eating problems. Unfilled anterior spaces (odds ratio 3.9), and widespread caries and periodontal disease were associated with aesthetic dissatisfaction. Many of the principles of shortened dental arch are consistent with good function and satisfaction in the elderly.

Aged↗

PubMed1997

Partial dentures as an independent indicator of root caries risk in a group of older adults.

OBJECTIVES: To estimate the independent association between the wearing of removable partial dentures (RPD) and the presence of root caries in a population of older adults. DESIGN: Multivariate logistic regression modeling of root caries prevalence using different measures of root caries as dependent variables. The model included measures of disease history as indicators of historical risk. SETTING: Data collected in the field from three areas of England. SUBJECTS: Random sample of adults aged 60 years and over, drawn from lists of patients registered with general medical practitioners. INTERVENTION: Field measurements of a range of oral health variables including oral disease, disease history, oral status and various social and demographic measures. MAIN OUTCOME MEASURES: The presence of root caries, unsound and sound root restorations. RESULTS: Of the five different models of root caries prevalence which were used, RPDs featured as an independent risk indicator for root surface caries in the three which were related to the presence of untreated disease. The odds ratios for the contribution made by RPDs were all over 1.6, and when considered alone was in excess of 2 in one model. These models were generally well fitting. RPDs did not feature as a risk indicator in the two models which related only to the presence of root surface restorations. CONCLUSIONS: In this study, where RPDs were present, the odds of untreated disease being present increased substantially.

Age Factors↗

PubMed1997

Strategies to improve the quality of oral health care for frail and dependent older people.

The dental profile of the population of most industrialised countries is changing. For the first time in at least a century most elderly people in the United Kingdom will soon have some of their own natural teeth. This could be beneficial for the frail and dependent elderly, as natural teeth are associated with greater dietary freedom of choice and good nutrition. There may also be problems including high levels of dental disease associated with poor hygiene and diet. New data from a national oral health survey in Great Britain is presented. The few dentate elderly people in institutions at the moment have poor hygiene and high levels of dental decay. If these problems persist as dentate younger generations get older, the burden of care will be substantial. Many dental problems in elderly people are preventable or would benefit from early intervention. Strategies to approach these problems are presented.

Aged↗

PubMed1996

Dental attitudes and behaviour among a sample of dentate older adults from three English communities.

Improvements in oral health have resulted in impressive reductions in edentulousness in the middle aged and elderly. As part of a large, three-centred survey of adults aged 60 or over, 1211 dentate subjects were interviewed about their dental attendance pattern, their reasons for non-attendance, attitudes to edentulousness, treatment preferences and oral hygiene practices. The three areas sampled allowed north-south and urban-rural comparisons to be assessed. 19-28% of all subjects were dental non-attenders, but the prevalence was highest in the north. A perception that there was no need to seek dental care was the commonest reason given for non-attendance. Subjects from the northern samples were less likely to be upset at the prospect of edentulousness and less likely to opt for restorative treatment than their southern counterparts. Gender differences were pronounced in the north, with men being less concerned about edentulousness, less likely to opt for restoration and less likely to visit the dentist than women. In the south this difference was less evident. Generally, expectations were high and attitudes were based on the preservation of natural teeth. This is a positive development, but caution must be exercised to ensure that expectations are realistic.

Aged↗

PubMed1996

Migraine: the effect of acrylic appliance design on clinical response.

This study aimed to evaluate the relationship between the nocturnal wearing of an acrylic appliance of 2 mm thickness covering all occlusal surfaces of the teeth and the frequency of attacks of migraine. Nineteen patients were studied and all fulfilled accepted criteria for migraine with or without aura. Two appliance designs were employed, one covering the maxillary occlusal surfaces of the dentition and another which contacted the palatal mucosa only and was free of the occlusion. Treatment outcome was expressed as the number of attacks of migraine per week per patient. The occlusal cover appliance reduced the number of attacks on average to about 40% of that normally experienced. The improvement was most marked in those who had frequent attacks of migraine ie two attacks per week on a regular basis. In summary, acrylic appliance therapy is of value in migraineurs who have attacks on waking but the appliance design has to involve covering of the occlusal surfaces of all of the teeth.

Acrylic Resins↗