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Biomedical subjects

K Webb

Publications and source records attributed to K Webb.

At least 37 records · Page 2Linked to original sources
PubMed2000

Fibronectin immobilized by a novel surface treatment regulates fibroblast attachment and spreading.

In order to understand the influence of cell-adhesive molecules on anchorage-dependent cell behavior on biomaterial surfaces, a model system is required where these molecules can be applied to surfaces with controlled surface ligand density and resistance to the adsorption of additional proteins present in the medium. This study asked whether fibronectin could be immobilized in a controlled manner to a hydrophobic surface with a chemically modified triblock surfactant. ELISA studies indicated that variation of the soluble fibronectin concentration used for immobilization could be used to control the amount of fibronectin immobilized to the surface. Furthermore, fibroblasts seeded on these surfaces in 10% serum-containing medium attached and spread as a function of the amount of immobilized fibronectin. Surfaces treated with unmodified surfactant did not support cell attachment, suggesting that cell attachment and spreading were primarily regulated by the immobilized fibronectin with minimal interference from adsorption of serum proteins. Together, these results suggest that covalent immobilization to Pluronic F108 provides a method for studying cellular responses to cell adhesive proteins with little interference from competing adsorbates, even in the presence of complex biological fluids such as serum. This technique may be applicable to a variety of existing hydrophobic biomedical polymers as a basic science tool as well as for influencing cell behavior at implant interfaces.

Animals↗
PubMed1999

Analysis of some folate monoglutamates by high-performance liquid chromatography-mass spectrometry. I.

The use of high-performance liquid chromatography for the determination of folates is well documented. The methods used are based on reversed-phase chromatography with UV and/or fluorescence detection. In many instances it is difficult to reach the required detection limits and many of the methods lack specificity. High-performance liquid chromatography-mass spectrometry (LC-MS) has become a well established analytical tool in modern laboratories. It can offer superior specificity and often lower detection limits than conventional LC detection methods and thus is ideally suited to the analysis of folates. A system capable of separating the four main folates [folic acid (pteroylglutamic acid, PGA)], 5-methyltetrahydrofolic acid, terahydrofolic acid and 5- and/or 10-formyltetrahydrofolic acid [folinic acid (CHOTHF)] using LC-MS with negative ion electrospray has been developed. After optimisation, a system using a 12.5 cm x 3 mm, 3 microm Hypersil ODS column and a mobile phase of 2.5 mM acetic acid-acetonitrile (88:12, v/v) was developed which was capable of separating the four folates in under 10 min without the use of a gradient system. Extraction of the folates is by heat treatment and sample clean-up is by solid-phase extraction (C18). On column limits of confirmation are 0.6 ng for PGA and CHOTHF.

Acetic Acid↗
PubMed1999

Dietary antioxidants and age-related maculopathy: the Blue Mountains Eye Study.

OBJECTIVE: To assess associations between the stages of age-related maculopathy (ARM) and dietary intake of carotene, vitamin C, retinol, and zinc. DESIGN: Cross-sectional, population-based study. PARTICIPANTS: A total of 3654 subjects 49 years of age and older from a defined area, west of Sydney, Australia, participated. A total of 2900 participants (79.4%) completed accurate food records. INTERVENTION: Masked grading of stereoscopic macular photographs, detailed interviewer-administered questionnaire, and 145-item self-administered food frequency questionnaire. MAIN OUTCOME MEASURES: Late ARM and early ARM were diagnosed from photographic grading. RESULTS: The authors found no statistically significant associations between ARM and dietary intake of either carotene, zinc, or vitamins A or C, either from diet or supplements or from the combined intake from diet and supplements. Multivariate-adjusted odds ratios (95% confidence interval) were calculated comparing highest to lowest dietary intake quintiles. For late ARM, the odds ratios were carotene, 0.7 (range, 0.3-2.0); vitamin A, 1.2 (range, 0.5-3.3); vitamin C, 1.3 (range, 0.5-3.4); and zinc, 1.0 (range, 0.4-2.8). For early ARM, the odds ratios were carotene, 0.7 (range, 0.4-1.1); vitamin A, 1.2 (range, 0.7-2.0); vitamin C, 0.9 (range, 0.5-1.4); and zinc, 0.8 (range, 0.5-1.3). No significant trends were apparent. Adjustment for energy intake also showed no associations between these antioxidants and ARM. Further, no associations were found between increasing intake of foods high in antioxidant vitamins and decreasing prevalence of either late or early ARM. CONCLUSIONS: The authors found no associations between ARM and dietary antioxidants, either from diet alone or including supplements, or from selected foods, in the Blue Mountains Eye Study population.

Aged↗
PubMed1998

Relative importance of surface wettability and charged functional groups on NIH 3T3 fibroblast attachment, spreading, and cytoskeletal organization.

Understanding the relationships between material surface properties, adsorbed proteins, and cellular responses is essential to designing optimal material surfaces for implantation and tissue engineering. In this study, we have prepared model surfaces with different functional groups to provide a range of surface wettability and charge. The cellular responses of attachment, spreading, and cytoskeletal organization have been studied following preadsorption of these surfaces with dilute serum, specific serum proteins, and individual components of the extracellular matrix. When preadsorbed with dilute serum, cell attachment, spreading, and cytoskeletal organization were significantly greater on hydrophilic surfaces relative to hydrophobic surfaces. Among the hydrophilic surfaces, differences in charge and wettability influenced cell attachment but not cell area, shape, or cytoskeletal organization. Moderately hydrophilic surfaces (20-40 degree water contact angle) promoted the highest levels of cell attachment. Preadsorption of the model surfaces with bovine serum albumin (BSA) resulted in a pattern of cell attachment very similar to that observed following preadsorption with dilute serum, suggesting an important role for BSA in regulating cell attachment to biomaterials exposed to complex biological media.

3T3 Cells↗
PubMed1998

Clinical outcome in relation to care in centres specialising in cystic fibrosis: cross sectional study.

OBJECTIVES: To assess the effect on clinical outcome of managing paediatric and adult patients with cystic fibrosis at specialised cystic fibrosis centres. DESIGN: Cross sectional study. SETTING: Two adult cystic fibrosis centres in the United Kingdom. SUBJECTS: Patients from an adult cystic fibrosis centre in Manchester were subdivided into those who had received continuous care from paediatric and adult cystic fibrosis centres (group A), and those who had received paediatric care in a centre not specialising in cystic fibrosis followed by adult care in a cystic fibrosis centre (group B). Group C were referrals to the new adult cystic fibrosis centre in Cambridge who had received neither paediatric nor adult centre care for their cystic fibrosis. MAIN OUTCOME MEASURES: Body mass index (weight (kg)/height (m2)), lung function (forced expiratory volume in one second (FEV1 percentage of predicted)), the Northern chest x ray film score, and age at colonisation with Pseudomonas aeruginosa. RESULTS: A prominent stepwise increase in body mass index was associated with increasing amounts of care at a cystic fibrosis centre; 18.3, 20.2, and 21.3 for groups C, B, and A respectively (P<0.001). Improved nutritional status was correlated with a higher FEV1 and better (lower) chest x ray film scores; r=0. 52 and -0.45 respectively (P<0.001 for both). CONCLUSION: These findings provide the first direct evidence that management of cystic fibrosis in paediatric and adult cystic fibrosis centres results in a better clinical outcome, and strongly supports the provision of these specialist services.

Adult↗
PubMed1998

Validity and reproducibility of a self-administered food frequency questionnaire in older people.

This study assesses the validity and reproducibility of a 145-item self-administered food frequency questionnaire (FFQ) in a representative older population aged 63 to 80. Semi-quantitative FFQs were completed by 89% of 3,654 residents attending a community-based eye study in Sydney, Australia. The FFQ's validity was assessed against three, four-day weighed food records (WFRs) completed four months apart by 79 people. A further 152 subjects completed a repeat FFQ about a year after the baseline FFQ, of whom 131 completed a second repeat FFQ about six weeks later. Both short and long-term reproducibility of the FFQ were assessed using data from these subjects. Comparison of the FFQ with the average of the three, four-day weighed food records resulted in energy-adjusted Spearman correlations above 0.5 for most of the nutrients. The proportion of subjects correctly classified to within one quintile category for each nutrient intake ranged from 57% for zinc to 82% for vitamin C. with most nutrients correctly classified within one quintile for about 70% of subjects. Quadratic weighted kappas were reasonable, between 0.3 and 0.5 for most nutrients. The FFQ was highly reproducible in the short term, with correlations for most nutrients about 0.70 to 0.80 and acceptably reproducible in the longer term, with correlations mostly 0.60 to 0.70. The results verify that it is possible to use relatively simple, but comprehensive, self-administered FFQs to study nutrient exposures in large-scale epidemiological studies of the elderly and to expect reasonably high FFQ response rates.

Aged↗
PubMed1996

A decision-making aid for long-term care waiting list policies: modelling first-come, first-served vs. needs-based criteria.

A chronic care hospital in London, Ontario, was faced with the question of whether to continue to admit applicants on a first-come, first-served basis, or to implement a needs-based admission criterion To provide information relevant to this decision, a simple computer modelling technique was used to model the waiting list under both policies. Analysis of the results indicated substantial variability in the need for care demonstrated by waiting list applicants, and individual placement priority under the two schemes. Descriptions of individuals affected by the proposed change in policy provided additional information. The information provided by the waiting list analysis contributed to the decision-making process about waiting list policy. The method used is applicable to waiting list management decisions in other institutions.

Computer Simulation↗
PubMed1996

Body mass index in screening for adiposity in children and adolescents: systematic evaluation using receiver operating characteristic curves.

Body mass index (BMI) has been recommended for use in adolescent screening programs to select subjects with excess body fat for appropriate interventions. No systematic evaluation of MBI in screening for high degrees of adiposity was available when these recommendations were formulated. The purpose of this paper was to evaluated the screening performance of BMI using appropriate epidemiologic methods. Percentage body fat (TBF%) was measured by dual-energy X-ray absorptiometry DXA) in a convenience sample of 230 (119 males, 111 females) health Australian volunteers aged 4-20 y inclusive. Receiver operating characteristic (ROC) curves were prepared for detecting TBF% at or beyond the 85th percentile, using BMI as the screening test. Screening performance was slightly better for girls than for boys, but the differences were not significant. Reasonable true-positive (0.71, 95% CI: 0.53, 0.85) and low false-positive (0.05, 95% CI: 0.02, 0.09) rates were observed at the 85th percentile cutpoint for BMI. At the 95th percentile cutpoint for BMI, both true-positive (0.29, 95% CI: 0.15, 0.47) and false-positive (0.01, 95% CI: 0.00, 0.03) rates were lower. Screening for excess adiposity by using an appropriate percentile cutoff for BMI gives acceptable performance. ROC curves facilitate design of screening programs by allowing an explicit tradeoff between true-positive and false-positive rates. Although large sample sizes are required for precise estimates, the cutoff points that have been recommended appear to offer a reasonable compromise between true-and false-positive rates.

Absorptiometry, Photon↗
PubMed1996

Adiposity and body mass indices in children: Benn's index and other weight for height indices as measures of relative adiposity.

OBJECTIVES: Several forms of weight for height or body mass index (BMI) are in widespread epidemiological and clinical use as measures of relative adiposity. The form derived by Benn for adults has been advocated for use in children and practical aspects of this proposition are considered. METHODS: Height and weight data from 8492 Australian schoolchildren aged 7 to 15 were studied. A subsample of 2753 children aged 9, 12 and 15 years had skinfold thicknesses measured. The sum of four skinfolds and percentage body fat predicted from skinfolds were used as measures of adiposity. RESULTS: Of the various forms of power type BMI examined, weight/(height)2 was most closely associated with adiposity in this sample. Benn's assumption of low correlation between height and adiposity (which holds in adults) was not satisfied in children. CONCLUSIONS: Benn's index is not recommended for general use as a body mass index in children. However, Benn's relative weight has advantages as an indirect measure of adiposity which may be of value in epidemiological studies among children.

Adipose Tissue↗
PubMed1995

Recommended body mass index cutoff values for overweight screening programmes in Australian children and adolescents: comparisons with North American values.

OBJECTIVE: Guidelines for screening children and adolescents for overweight have recently been published by a North American Expert Committee. As Australian clinicians might uncritically adopt these recommendations, we explore the consequences of applying North American body mass index (BMI) cutoff values to an Australian population. METHODOLOGY: The Australian BMI cutoffs were calculated using the methods recommended from height and weight data for 8492 schoolchildren aged 7-15 years old. RESULTS: Smoothed Australian BMI cutoffs were similar to those derived from the first United States National Health and Nutrition Examination Survey (NHANES-I) values for whites. However, the NHANES-I cutoffs would result in systematic misclassification. Among 7 year olds, the NHANES-I 85th percentile cutoff would wrongly classify 4.6% of normal males and 9.1% of normal females as 'at risk of overweight'. At age 14 years, the NHANES-I 95th percentile cutoff would misclassify 3.5% of children as 'overweight' instead of 'at risk of overweight'. CONCLUSION: Australian screening programmes should use BMI cutoffs appropriately derived from local measurements, and these are given for Australian children.

Adolescent↗
PubMed1995

Long-term outcome of saliva-control surgery.

Thirty-nine patients who had undergone transposition of the submandibular ducts and unilateral ligation of a parotid duct for saliva control were followed up six years after surgery. Overall improvement was documented according to a drooling quotient, drooling severity and drooling frequency measures. Despite this superficially favourable outcome, a significant proportion of patients (39 per cent) or their caregivers had not found the surgery helpful. Complications included ranula formation, complaints of dry mouth, difficulty with swallowing, and changes in the consistency of oral secretions. More knowledge is needed of the likely outcomes of this procedure in individual patients, so that appropriate advice can be given and complications minimised.

Adolescent↗
PubMed1995

Defining potential targets for immunotherapy in Burkholderia cepacia infection.

Burkholderia cepacia has become a serious source of infection in patients with cystic fibrosis. Antibiotic therapy is difficult as the bacteria are intrinsically resistant to most antibiotics. The present study compared the antibody response by immunoblot of 50 negative control sera, 22 patients with cystic fibrosis and no evidence of B. cepacia, 9 clinically well patients with cystic fibrosis colonised by B. cepacia and 5 patients with cystic fibrosis and deteriorating or fatal B. cepacia infection. Nineteen antigenic bands varying in apparent molecular weights from 19 to 170 kDa were identified. Two bands at 19 and 21 kDa were only present when the organism was grown in an iron-deficient medium. The band at 30 kDa was identified as a porin and the possession of IgG antibody carried a statistically significant (P = 0.00003) better prognosis. This antigen was thus a potential target for immunotherapy.

Antibodies, Bacterial↗
PubMed1992

A cost description of an adult cystic fibrosis unit and cost analyses of different categories of patients.

BACKGROUND: There is little information on the costs of running an adult cystic fibrosis centre. The aim of this study was to provide detailed costs to assist funding and planning for these patients. METHODS: The cost of a regional adult cystic fibrosis centre serving 119 cystic fibrosis patients, categorised according to four treatment regimens, was determined. District health authority, family health service authority, and voluntary resources used from April 1989 to March 1990 were determined, with appropriate bases for allocation of costs and patient based costs from local information. RESULTS: The total annual cost of treating the 119 patients was 980,646 pounds, with an average cost 8241 pounds per patient. An outpatient reviewed at three monthly intervals cost 2792 pounds a year; an outpatient receiving intravenous antibiotics cost 8606 pounds; an inpatient receiving intravenous antibiotics cost 13,501 pounds; and a patient needing a high level of care cost 19,955 pounds. Medication accounted for 57% (561,395 pounds) of the total cost. CONCLUSIONS: This analysis has helped us to secure funding for patients with cystic fibrosis and it facilitates the prediction of future requirements. The study also indicates the limitations of using average patient costs and difficulties as a result of the poorly structured British National Health Service accounting and information systems.

Adolescent↗