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Biomedical subjects

J G Steele

Publications and source records attributed to J G Steele.

At least 55 records · Page 3Linked to original sources
PubMed2000

Effect of porosity and surface hydrophilicity on migration of epithelial tissue over synthetic polymer.

The relative effects of porosity and surface chemistry on the migration of epithelial tissue over the surface of a polymer were determined in vitro. These studies compared nonporous polymers with those having 0.1-microm diameter track-etched pores and were conducted on polycarbonate and polyester. Epithelial tissue migration over the polymer surface was stimulated by the presence of these pores. The surface chemistries of the polymers were modified by deposition of various polymer films using radio frequency gas deposition, giving a range of surfaces that varied in air:water sessile contact angle (SCA) of between 26 and 100 degrees. Tissue migration on the nonporous surfaces was affected by the surface chemistry, being generally linear as a function of the SCA and higher on hydrophilic than on hydrophobic surfaces but reduced if the hydrophilic surface had a mobile chemistry. The effects of the 0.1-microm diameter pores and the surface hydrophilicity were additive with the maximal level of epithelial tissue migration occurring on a porous, hydrophilic polymer surface.

Animals↗
PubMed2000

Protein adsorption and cell attachment to patterned surfaces.

To better understand the events involved in the generation of defined tissue architectures on biomaterials, we have examined the mechanism of attachment of human bone-derived cells (HBDC) to surfaces with patterned surface chemistry in vitro. Photolithography was used to generate alternating domains of N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (EDS) and dimethyldichlorosilane (DMS). At 90 min after seeding, HBDC were localized preferentially to the EDS regions of the pattern. Using sera specifically depleted of adhesive glycoproteins, this spatial organization was found to be mediated by adsorption of vitronectin (Vn) from serum onto the EDS domains. In contrast, fibronectin (Fn) was unable to adsorb in the face of competition from other serum components. These results were confirmed by immunostaining, which also revealed that both Vn and Fn were able to adsorb to EDS and DMS regions when coated from pure solution, i.e., in the absence of competition. In this situation, each protein was able to mediate cell adhesion across a range of surface densities. Cell spreading was constrained on the EDS domains, as indicated by cell morphology and the lack of integrin receptor clustering and focal adhesion formation. This spatial constraint may have implications for the subsequent expression of differentiated function.

Animals↗
PubMed2000

Using partial recording to assess tooth wear in older adults.

OBJECTIVES: To establish whether partial recording can be used for the measurement and reporting of tooth wear data in samples of adult populations, whilst maintaining the usefulness of the index. METHODS: Using whole mouth coronal tooth wear data from a large random population sample of 1200 dentate older adults in England, several different partial recording systems were investigated to establish which teeth would maintain a high level of sensitivity for the most economic use of codes and index teeth. Tooth wear data were recorded on a surface-by-surface basis on all teeth in the sample using the tooth wear index. RESULTS: Five different partial mouth recording systems were assessed, including half-mouth scoring, assessment of just upper or just lower anterior teeth, assessment of all anterior teeth and use of six index teeth. The 12 anterior teeth were the ones most often affected by moderate or severe wear, and when all 12 teeth were used as the index teeth few wear cases were missed, and all the most extensive and severe cases of coronal wear were classified as having some wear. A limited index of only six anterior teeth (three uppers and three lowers) was almost as sensitive, but allowed less flexibility when reporting the extent of coronal wear. Other systems for partial recording were less sensitive. CONCLUSIONS: Partial recording using six or 12 anterior teeth is appropriate for measuring and reporting tooth wear data in large population surveys.

Age Distribution↗
PubMed2000

Impact of treatment provision on the epidemiological recording of root caries.

The estimation of root caries prevalence and the identification of risk factors for decay depend upon the successful identification of carious lesions in epidemiological studies. Root surface restorations can either be placed to manage decay or cervical wear/sensitivity. The handling of data for restorations during epidemiological surveys is critical to the accurate assessment of caries prevalence. The objective of this study was to determine the relative frequency of dentists' placing root surface restorations according to their reason for placement. Data for 696 restorations were recorded from 35 dentists. Forty-five % of restorations were placed because of decay compared with 55% for cervical wear/sensitivity. There were no significant differences in proportion of placement of restoration with age of the patient or between regular and irregular attenders of different ages. Using these data a correction factor was developed for inclusion in the Root Caries Index (RCI) to make allowance for the proportion of restorations placed because of wear/sensitivity. When this correction factor was introduced into an existing data-set for root caries, the RCI was reduced for all groups. This reduction was greatest in regular attenders. When these data were analysed without making allowance for treatment effects, there was a significant difference in RCI between regular and irregular attenders. When the correction factor was applied to these data, this difference was eliminated.

Adult↗
PubMed2000

Use of rubber dam and irrigant selection in UK general dental practice.

AIM: To evaluate factors which influence rubber dam use and irrigant selection in UK National Health Service (NHS) endodontics. METHODOLOGY: A postal survey was conducted amongst two age cohorts of dentists, representing all of the 1970-73 (older) and 1990-93 (younger) graduates of two northern English dental schools (n = 643). Key and supplementary questions were posed on levels of rubber dam use, irrigant selection, and factors influencing practice in NHS endodontics. After manual checking, validated (dual) entry of responses was made to a flat ASCII data file before analysis with SPSS software. The threshold for statistical significance was set at the 95% probability level. RESULTS: Eighty-five per cent of the valid sample responded to the questionnaire. Regardless of age and qualifying school, less than one-fifth of dentists always or frequently used rubber dam, whilst 60% never used it. Qualifying school had a significant influence on rubber dam use, whilst age had a variable influence. Major disincentives to the use of rubber dam included the perception that patients do not like it, that the NHS fee was inadequate to justify its use, that it took too long to apply, and that dentists had received inadequate training. Frequent users of rubber dam were significantly less likely to cite these disincentives than nonusers. Overall, local anaesthetic solution was the most common endodontic irrigant. Irrigant choice was strongly linked to rubber dam use, and to graduation cohort. Seventy-one per cent of rubber dam users irrigated with sodium hypochlorite, compared with only 38% of nonusers. This pattern was reversed for local anaesthetic irrigation. Younger graduates were significantly more likely to irrigate with local anaesthetic solution than their older counterparts, and the younger graduates of one school showed a highly significant increase in the use of chlorhexidine. CONCLUSIONS: 1) The majority of UK Health Service dentists never use rubber dam isolation in endodontic treatment. 2) Qualifying school has a significant impact on rubber dam use, and irrigant selection. 3) Use of rubber dam has a significant association with irrigant choice in endodontics.

Age Factors↗
PubMed2000

Oral health and nutrition in older people.

The theoretical link between foods choice and masticatory efficiency has long been established. Recent evidence has confirmed this association, demonstrating a progressive alteration in food choice with decreasing numbers of teeth, with the greatest effect being among those who are edentulous. This altered food selection results in significant differences in the hematological status for some key nutrients in the one study in which this association was investigated. This paper summarizes some of the literature relevant to diet as a risk factor for systemic disease and identifies areas where altered food choice as a consequence of reduced masticatory efficiency might be placing individuals at increased risk of life-threatening conditions, such as atherosclerosis and cancer.

Aged↗
PubMed2000

Vitronectin or fibronectin is required for corneal fibroblast-seeded collagen gel contraction.

PURPOSE: The wound healing process in the corneal stroma involves the activation of corneal keratocytes and the expression of associated phenotypes (fibroblasts and myofibroblasts). One of these phenotypes, the myofibroblasts, synthesizes alpha-smooth muscle actin in order to affect wound closure by contracting the surrounding matrix. Excessive contraction results in the formation of unresolvable scars that are undesirable in the corneal stroma. The authors tested the effect of vitronectin and fibronectin on the contraction process associated with corneal wound healing. METHODS: Collagen gels were prepared and were exposed to different treatments of fetal calf serum (FCS). The FCS used was either depleted of fibronectin and vitronectin or contained a known concentration of fibronectin, vitronectin, or both at 50 microg/ml. Contraction was measured using image analysis and cross sections of contracted gels were examined for alpha-smooth muscle actin expression using laser confocal microscopy. RESULTS: Fibroblasts seeded in collagen gels paralleled the morphologic characteristics and cell distribution of keratocytes in unwounded cornea. Matrix contraction was dependent on the presence of fibronectin and/or vitronectin where myofibroblasts were present. The cell-mediated contraction process was maximal at 0.5 x 10(5) fibroblasts/ml. CONCLUSIONS: These studies showed that vitronectin or fibronectin is required for the myofibroblast-associated contraction to occur in this in vitro model of stromal wound healing. This model system shows a distinct potential for further studies relating to the corneal wound healing process.

Actins↗
PubMed2000

Epithelialization of a synthetic polymer in the feline cornea: a preliminary study.

PURPOSE: This study examined the potential of a synthetic polymer to support stable epithelial growth when implanted in the feline cornea. METHODS: A perfluoropolyether-based polymer was cast into lenticules that were coated with collagen I and implanted in four feline corneas. Epithelial growth onto the lenticules was monitored clinically for 6 weeks, after which time the animals were killed, and three corneas were evaluated histologically. Immunohistochemistry was used to identify proteins associated with the formation of a basement membrane (laminin) and adhesion complexes (bullous pemphigoid antigen and collagen VII). Electron microscopy was used to examine the tissue-polymer interface for evidence of the assembly of these adhesive structures. RESULTS: Postoperative epithelial growth began on days 2 to 3, and lenticules were fully epithelialized by days 5 to 9. Lenticules were clinically well tolerated and histology showed epithelium consisting of multiple layers adherent to the lenticule's surface. Laminin, bullous pemphigoid antigen and collagen VII were identified at the tissue-polymer interface using immunohistochemistry. Ultrastructural examination showed evidence of assembly of these proteins into a recognizable basement membrane and hemidesmosomal plaques. CONCLUSIONS: A perfluoropolyether-based polymer coated with collagen I was implanted in the feline cornea and supported epithelial growth that showed signs of persistent adhesion, both clinically and histologically. This polymer shows potential for ophthalmic applications that require sustained epithelialization.

Animals↗
PubMed1999

Measuring oral health: does your treatment really make a difference.

An understanding of a broader concept of health is increasingly important for all health professionals, including dentists, and has recently been incorporated as a key principle in the Government White Paper, The New NHS. This aims to deliver a dependable, high quality, egalitarian health service. In the past, performance measurements in the UK have often relied simply on those areas which are most easily quantified. For example, within the hospital service, performance was measured in terms of the cost and the number of finished consultant episodes, from which the 'purchaser efficiency index' was calculated. This tended to produce a driving force rewarding those doing more rather than those doing more better. It is analogous to the system which has been the backbone of NHS dental practice for many years, 'fee per item of service', where throughout is rewarded rather than outcome. However, the White Paper has signalled a move away from simply counting activity. From April 1999 within the hospital service the purchaser efficiency index has been replaced with more rounded measures, reflecting the changing concepts of health, in a new broader performance framework to determine what really counts for patients. It will focus on measuring health improvement, fairer access, better quality and outcome, including the views of patients.

Dental Care↗
PubMed1999

Persistent adhesion of epithelial tissue is sensitive to polymer topography.

The persistent adhesion of corneal epithelial tissue to the surface of a porous polymer is of interest in the development of a corneal onlay. Using an in vitro model system, this study examined the effect of polymer surface topography on the assembly of basement membrane and hemidesmosomes. Corneal epithelial tissue was grown on polycarbonate surfaces with a range of pore sizes (0.1-3.0 micron, pore diameter) and an equivalent nonporous surface. The ultrastructure of the tissue-polymer interface was evaluated using electron microscopy. On the porous surfaces, the tissue responded to a balance between the size of the discontinuity (pores) and the amount of polymer surface between the pores. Continuous basement membrane and a regular pattern of hemidesmosomal plaque occurred only on the 0.1 micron surface, where both the pores and the total surface area covered by pores were relatively small. The assembly of adhesive structures on surfaces with pore diameters between 0.4-2.0 microns was restricted to regions of polymer between pores. No adhesive structures assembled on the nonporous or on the 3.0-micron surface. These results demonstrate that, in addition to porosity, surface topography is a significant factor in the formation of structures involved in the persistent adhesion of stratified epithelial tissue on a polymer.

Animals↗
PubMed1999

Modulation of corneal epithelial stratification by polymer surface topography.

The topography and porosity of a polymer may affect the epithelialization of a corneal implant. We used an in vitro model to examine the effect of polymer surface topography on corneal epithelial tissue stratification and the deposition of proteins associated with epithelial adhesion. A range of topographies was provided by polycarbonate membranes with nominal pore diameters of 0.1, 0.4, 0.8, 1.0, 2.0, or 3.0 microm and a nonporous surface. Stratification of epithelial tissue outgrowth on these surfaces was evaluated using light and electron microscopy. Deposition of proteins associated with basement membrane and adhesion complex formation at the tissue-polymer interface was assessed using immunohistochemistry. Surfaces with pores in the 0.1-0.8-microm-diameter range supported superior stratification and protein deposition compared with those containing pores of > or = 1.0 microm. Cytoplasmic processes penetrated single pores 2.0 and 3.0 microm in diameter and fused pores 1.0 microm in diameter. Tissue on the nonporous surface had a lower level of stratification compared with surfaces with pores 0.1-0.8 microm in diameter. These results point to the significance of surface topography in biomaterial applications that require persistent epithelialization.

Animals↗
PubMed1999

Attachment of cultured human bone cells to novel polymers.

The initial attachment of human bone-derived cells (HBDC) to several polymer systems has been studied in vitro. A novel polymer system based on poly(ethyl methacrylate) polymer and tetrahydrofurfuryl methacrylate monomer (PEMA/THFMA) was compared with a variant in which THFMA was replaced by 2-hydroxyethyl methacrylate (PEMA/HEMA). Tissue culture polystyrene (TCPS) and polystyrene (PS) were used as reference materials. The ability of the substrates to adsorb the attachment glycoproteins fibronectin (Fn) and vitronectin (Vn) from serum and the subsequent effect on radiolabeled HBDC attachment were examined. Initial cell attachment from the medium containing 10% (v/v) serum was highest on TCPS; on PEMA/THFMA and PEMA/HEMA substrates it was about 25% of this level, and on PS it was only 10% of that on TCPS. Attachment of HBDC to all substrates was dependent on the presence of Vn, which, unlike Fn, was able to adsorb in the face of competition from other serum components. Both Vn and Fn were able to support cell attachment when precoated onto all substrates. In comparison to TCPS, PEMA/THFMA did not show enhanced adsorption of either Fn or Vn from serum, and this was reflected in the level of cell attachment. Interestingly, the potency of preadsorbed Fn for cell attachment was much higher on this substrate than on any other: 45 ng/cm2 Fn when adsorbed to PEMA/THFMA gave a level of cell attachment 1.6-fold higher than the same density of Fn on PS or TCPS. The maximum Fn surface density achieved on HEMA/PEMA was 16 ng/cm2. Cells on PEMA/THFMA showed typical clustering of the alpha5 beta1 Fn receptor, but this was not evident in cells attached to PEMA/HEMA even when precoated with Fn. This study indicates that the initial attachment of HBDC to all substrates was Vn dependent. It also indicates that on PEMA/THFMA the favorable presentation of subsequently adsorbed Fn may assist matrix assembly.

Biocompatible Materials↗
PubMed1999

A thin glycoprotein coating of a synthetic lenticule does not cause nutritional deficiency of the anterior cornea.

PURPOSE: This study investigated whether a glycoprotein coating that will be used to enhance corneal epithelialization affects in situ nutritional passage through a permeable membrane. METHODS: Sixteen adult cats were equally divided into two groups. Polycarbonate membranes with pore size of 0.1 microm and total pore area (porosity) of 3.1% were used as implant materials. The membranes for Group 1 were coated with a thin layer of Collagen I, while the membranes for Group 2 were uncoated. Each membrane with 8-mm diameter was implanted into an interlamellar pocket of the cornea. The eyes were observed for approximately 35 days to monitor clinical signs of nutritional deficiency of the cornea, and then 7 membranes were removed from the eyes. The permeability of the explanted membranes to glucose, inulin and albumin was used to predict the in situ difference between the coated and uncoated groups in regard to nutritional passage through the membranes. To investigate the long-term effect of the surface coating on corneal health, two animals from Group 1 were followed for up to two years and then both eyes of each animal underwent histological examination. RESULTS: Clinically, no post-surgical complications associated with nutritional deficiency were observed in any of the eyes. Nutritional permeability tests showed no significant differences between the coated and uncoated membranes. Histologically, the long-term animals showed no abnormal morphology associated with nutritional deficiency in the cornea anterior or posterior to the membranes. CONCLUSIONS: A thin glycoprotein coating on a permeable membrane does not appear to affect the nutritional supply of the anterior cornea and therefore can be used to enhance epithelialization of synthetic corneal onlays in vivo.

Animals↗
PubMed1999

The impact of oral health on stated ability to eat certain foods; findings from the National Diet and Nutrition Survey of Older People in Great Britain.

OBJECTIVES: To assess how the dental status of older people's mouths affected their stated ability to eat common foods. DESIGN: Cross sectional study. SUBJECTS: Survey was part of the oral health component of the nationwide British National Diet and Nutrition Survey: people aged 65 years and older. Two separate representative samples aged 65 and over: a free-living and an institutional sample. 881 free-living and 275 institution subjects had a dental exam and were interviewed about ability to eat key foods. RESULTS: Significant percentages of free-living people had difficulty or could not eat at least 4 of 16 foods, and about 1 in 5 dentate stated they had difficulty eating or could not eat raw carrots, apples, well-done steak or nuts. More of the edentate subjects stated that they had difficulty eating than the dentate. Perceived chewing ability increased with increasing numbers of natural teeth and pairs of opposing posterior teeth. Subjects reporting a sociodental impact were more likely to consider that they were unable to eat foods that required more chewing. Associations remained valid after correction for the effects of age, sex, social class and denture wearing status and region. Perceived dryness did not affect significantly the stated ease of eating most foods. There were more dietary restrictions reported by the institution sample. Some foods, such as nuts, apples and raw carrots could not be eaten easily by over half of edentate people in the institution sample. CONCLUSIONS: The stated selection of foods are substantially affected by numbers of teeth and occluding pairs of posterior teeth and presence of full dentures in significant percentages of older people.

Aged↗
PubMed1999

Cell interactions with perfluoropolyether-based network copolymers.

We have investigated the potential of several polymers based on perfluoropolyether (PFPE) macromonomers for use in biomaterial applications. Polymer networks were synthesised from the PFPE macromonomers of increasing chain length and the adhesion and proliferation of corneal, vascular and bone cells was evaluated on these polymers. The polymer surfaces were quite hydrophobic, having sessile air-water contact angles ranging between 96 and 125 degrees. However, these polymers supported the attachment and growth of bovine corneal epithelial and endothelial cells and fibroblasts at 60-100% of the rate of cell growth on the culture substratum, TCPS. Furthermore, the PFPE polymers supported the attachment and growth of vascular endothelial cells (from human umbilical artery) and human bone-derived cells over a 7 day period at an equal level to TCPS. The relationship between the macromonomer chain length (n = 1 to 4) and the ability of the resulting PFPE homopolymer to support the overgrowth of corneal epithelial tissue was also evaluated. The PFPE-containing polymers supported corneal epithelial tissue overgrowth, with the most effective having a performance equivalent to that of TCPS. In addition to these homopolymers, copolymers comprising of PFPE and N,N-dimethylaminoethyl methacrylate (DMAEMA) were also synthesised. Surprisingly, the addition of DMAEMA to the PFPE polymer network lead to a reduction in the growth and attachment of corneal epithelial cells and fibroblasts. These results indicate that PFPE-based materials show a potential for use in the development of biomaterials in the ocular, vascular and orthopaedic areas.

Animals↗
PubMed1999

Prevalence of gingival overgrowth induced by calcium channel blockers: a community-based study.

BACKGROUND: The prevalence of gingival overgrowth induced by chronic medication with calcium channel blockers is uncertain. Although there have been several studies examining this question, the results are conflicting, with previous estimates ranging from 20% to 83%. There have been only 2 studies examining the prevalence of overgrowth induced by diltiazem and amlodipine, with estimates of 74% and 3.3%, respectively. METHODS: The current study aimed to address the problems associated with these studies by examining a sample of patients taking one of 3 calcium channel blockers, who were drawn from a community-based population in northeastern England. Nine hundred eleven (911) subjects were recruited from general medical practices in the area. Of these, 442 were taking nifedipine, 181 amlodipine, and 186 diltiazem. In addition, 102 control subjects were examined. Drug and demographic data for each subject were recorded. The periodontal condition of all subjects was assessed including plaque index, papillary bleeding index, and a photograph of the anterior gingivae for subsequent analysis of overgrowth severity. RESULTS: More than six percent (6.3%) of subjects taking nifedipine were seen to have significant overgrowth. This overgrowth was statistically greater than the amount of overgrowth seen in either of the other 2 drug groups or the control population. The prevalence of gingival overgrowth induced by amlodipine or diltiazem was not statistically significant when compared to the control group. The severity of overgrowth within the nifedipine group was found to be related to the amount of gingival inflammation and also to the gender of the subject, with males being 3 times as likely to develop overgrowth than females. CONCLUSIONS: The prevalence of clinically significant overgrowth related to chronic medication with calcium channel blockers is low, i.e., 6.3% for nifedipine. Males are 3 times as likely as females to develop clinically significant overgrowth. The presence of gingival inflammation is an important cofactor for the expression of this effect.

Adult↗
PubMed1998

Polymer surface chemistry and a novel attachment mechanism in corneal epithelial cells.

The initial attachment reaction of most cultured cell types to polymers is based on a linkage of integrin receptors to serum-derived fibronectin and vitronectin that adsorb onto the polymer surface. Recently isolated corneal epithelial cells have an additional attachment mechanism, known to operate on tissue culture polystyrene, which involves endogenous protein synthesis and an intact system of microtubules. Here, we determine if this novel attachment mechanism is operative on polymers of different surface chemistries. The attachment, growth, and deposition of basement membrane proteins by corneal epithelial cells was compared on two hydrophilic surfaces (tissue culture polystyrene and Primaria) and one relatively hydrophobic surface (unmodified polystyrene). Superior levels of cell attachment were found on the hydrophilic polymers, but cells also attached effectively to the hydrophobic surface. Growth rates showed that the cells were able to overcome the differential effects of polymer surface chemistry during a 7-day time period. Polymer surface chemistry had subtle effects on the temporal pattern of biosynthesis of extracellular matrix proteins likely to be involved in cell adhesion. These results show that effective attachment and growth can occur on a hydrophobic polymer when corneal epithelial cells use the endogenous attachment mechanism.

Animals↗