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Biomedical subjects

J N S Matthews

Publications and source records attributed to J N S Matthews.

9 recordsLinked to original sources
PubMed2006

Removal of acetabular bone in resurfacing arthroplasty of the hip: a comparison with hybrid total hip arthroplasty.

Resurfacing arthroplasty of the hip is being performed more frequently in the United Kingdom. The majority of these patients are younger than 55 years of age, and in this group the key benefits include conservation of femoral bone stock and the potential reduction in the rate of dislocation afforded by the larger resurfacing head. Early aseptic loosening is well recognised in patients younger than 55 years of age, and proponents of resurfacing believe that the improved wear characteristics of the metal-on-metal bearing may improve the long-term survival of this implant. There has been some concern, however, that resurfacing may not be conservative of acetabular bone. We compared a series of 33 consecutive patients who had a hybrid total hip arthroplasty with an uncemented acetabular component and a cemented femoral implant, with 35 patients undergoing a Birmingham hip resurfacing arthroplasty. We compared the diameter of the implanted acetabulum in both groups and, because they were not directly comparable, we corrected for patient size by measuring the diameter of the contralateral femoral head. The data were analysed using unpaired t-tests and analysis of covariance. There was a significantly larger acetabulum in the Birmingham arthroplasty group (mean diameter 56.6 mm vs 52.0 mm; p < 0.001). However, this group had a significantly larger femoral head diameter on the contralateral side (p = 0.03). Analysis of covariance revealed a significant difference between the mean size of the acetabular component implanted in the two operations. The greatest difference in the size of acetabulum was in those patients with a larger diameter of the femoral head. This study shows that more bone is removed from the acetabulum in hip resurfacing than during hybrid total hip arthroplasty, a difference which is most marked in larger patients.

Acetabulum↗
PubMed2005

A stable isotope titration method to determine the contribution of acetate disproportionation and carbon dioxide reduction to methanogenesis.

A novel stable isotope titration approach was developed to determine the contributions to total methane production made by CO(2) reduction and the disproportionation of acetate in anoxic environments. (13)CH(4), (12)CH(4), (13)CO(2) and (12)CO(2) production rates were measured in the head space of replicate anaerobic microcosms titrated with increasing amounts of (13)C-labelled substrates. The contribution of CO(2) reduction was calculated from the linear relationship between ratios of labelled and total CH(4) production and ratios of labelled and total CO(2) after the addition of (13)C-bicarbonate. In the case of acetoclastic methanogenesis rates of (13)CH(4) and (12)CH(4) production were fitted to a model based on an assumption that the relationship between the concentration of (13)C-labelled acetate and the rates of labelled and unlabelled methane production followed Michaelis-Menten kinetics. A comparison of the raw data with the model supported the assumption and provided both an estimate of the contribution of acetate to methane production and an estimate of the size of the indigenous acetate pool without the need to measure acetate directly. The method was applied to a freshwater sediment in the English Lake District where it was found that 66.3% (se 4.9) of methane production was due to acetate disproportionation and 28.9% (se 1.9) of methane production resulted from CO(2) reduction. This is in agreement with theoretical predictions and other empirical measurements of methanogenesis.

Acetates↗
PubMed2005

Does antenatal pelvic dilation predict renal scarring?

Moderate antenatal renal pelvic dilation (5-15 mm) may suggest vesicoureteric reflux, but it is not known to predict renal scarring. Dimercaptosuccinic acid scans on such children aged over 4 years showed a scarring rate (0/133 boys, 1/56 girls) similar to our local population. Investigation and treatment of moderate dilation may not be required.

Adolescent↗
PubMed2004

A case control study to examine the pharmacological factors underlying ventricular septal defects in the North of England.

BACKGROUND: Amphetamine exposure is associated with congenital cardiac abnormalities in animals. We previously reported an association between recreational use of 2,4-methylenedioxymethamphetamine (ecstasy, MDMA) and ventricular septal defect in babies born to users. We have carried out a case control study to investigate risks in the occurrence of ventricular septal defect in a cohort of babies born in the North East of England. METHODS: Cases were identified from paediatric cardiology units in Newcastle upon Tyne and Leeds, and controls were recruited from the mothers of babies born in the same hospital as the index case. Research nurses carried out interviews using a structured questionnaire. RESULTS: A total of 296 case control pairs were studied. There was insufficient exposure to ecstasy to test the primary hypothesis. Increased risk of ventricular septal defect was found to be associated with consumption of cough and cold remedies [pre-conception OR 2.2, 95% CI 1.41, 3.51; pregnancy OR 5.1, 95% CI 2.56, 11.27; exposure in either OR 2.83, 95% CI 1.85, 4.45; P<0.005] and in the case of non-steroidals for exposures in pregnancy (OR 4.2, 95% CI 1.54, 14.26; P<0.005). CONCLUSIONS: These findings suggest that ventricular septal defect is associated with consuming the medications identified. They are also compatible with the hypothesis that sympathomimetics (pseudoephedrine, phenylephrine and phenylpropanolamine) present in cough mixtures cause the increased risk, and with our original hypothesis that sympathomimetics and amphetamines are potentially cardiotoxic in utero.

Adolescent↗
PubMed2004

Optimal designs for Michaelis-Menten kinetic studies.

Many reactions in enzymology are governed by the Michaelis-Menten equation. Characterising these reactions requires the estimation of the parameters K(M) and V(max) which determine the Michaelis-Menten equation and this is done by observing rates of reactions at a set of substrate concentrations. The choice of substrate concentrations is investigated by determining Bayesian D-optimal designs for a model in which residuals have a normal distribution with constant variance. Designs which focus on alternative quantities, such as K(M) or the ratio V(max)/K(M) are also considered. The effect on the optimal designs of alternative error distributions is also considered.

Bayes Theorem↗
PubMed2004

Changes over 20 years in macronutrient intake and body mass index in 11- to 12-year-old adolescents living in Northumberland.

Monitoring adolescent diets over time enables the assessment of the effectiveness of public health messages which are particularly important in vulnerable groups such as adolescents. In 2000, 424 children aged 11-12 years old completed two 3 d estimated dietary records. On the fourth day one nutritionist interviewed each child to clarify the information in the diary and foods were quantified with the aid of food models. Nutrient intake was calculated using computerised food tables. These children attended the same seven schools in the same Northumberland area as the 11- to 12-year-old children who recorded their diet using the same method in 1980 (n 405) and 1990 (n 379), respectively. Height and weight, and parental occupation were recorded in all three surveys for each child. Height and weight were used to calculate BMI, weight was used to estimate BMR and parental occupation was used to determine social class. Comparing the macronutrient intakes in 2000 with 1980 and 1990, energy intakes (EI) fell in boys (to 8.45 MJ) and girls (to 7.60 MJ). This fall may, at least in part, be due to an increase in low energy reporting. For 1980, 1990 and 2000 the percentage of boys with EI:BMR below 1.1 was 6, 15 and 23 %, respectively; for girls, 3, 14 and 18 %, respectively. Percentage energy from fat was unchanged between 1980 and 1990 but fell to 35 % (about 76 g/d) in 2000, alongside a 3 % increase in percentage energy from starch (30 %). Percentage energy from non-milk extrinsic sugars remained above recommendations (16 %; about 82 g/d). The number of overweight and obese children increased from 11 % to 30 % between 1980 and 2000. Positive changes have occurred in the Northumbrian adolescent diet but social inequalities, reported in previous surveys, remain.

Body Mass Index↗
PubMed2004

The effect of otitis media with effusions on balance in children.

There is increasing interest in the effect, otitis media with effusions (OME) has on the balance in children. The aim of our investigation was to determine whether a universal effect on balance could be demonstrated in children with OME by using sway posturography. Assessment was made in 20 children with proven OME before and after the insertion of bilateral ventilation tubes. Sway posturography was performed on each occasion in each of the four recording conditions in the presence and absence of both reduced optic fixation and reduced proprioception. The pathlength traversed during the recording interval was measured and analysed by a split-unit anova. The results demonstrate an overall improvement in mean pathlength of 20% following treatment of the effusions (P < 0.001) (95% CI 14-25%). The effect of reduced optic fixation and of reduced proprioception were similar when increasing the mean pathlength by 22% (P < 0.001). These results demonstrate that OME has a universal effect on balance in all recording conditions.

Acoustic Impedance Tests↗
PubMed2002

Methods for the analysis and design of limiting dilution assays.

Limiting dilution assays are a useful device for extracting quantitative information when the underlying analytical tool can only provide information on presence or absence. Analysis by maximum likelihood is advocated and some alternative methods are discussed. Several interval estimators, including one based directly on the log-likelihood are presented. Methods for determining designs which permit efficient estimation are considered and some of their weaknesses are mentioned. Opportunities for further methodological development are outlined.

Bayes Theorem↗