Biomedical subjects

J E Williams

Publications and source records attributed to J E Williams.

At least 19 recordsLinked to original sources

PubMed2006

A simplified approach to analysing bio-electrical impedance data in epidemiological surveys.

BACKGROUND: Bio-electrical impedance analysis (BIA) is widely used to estimate body composition. It is simple, quick and cheap, but less accurate than other methods. It has potential epidemiological value, but has conventionally required validation before application. AIMS: To develop a simple method of expressing weight, height and impedance data that avoids the need for population-specific validation equations in order to facilitate epidemiological application. METHODS: Body composition was measured using the four-component model in young adults (43 males, 90 females). Impedance (R) was measured hand-foot and foot-foot. Lean mass and fat mass were adjusted for height to give lean mass index (LMI) and fat mass index (FMI). Based on theoretical principles, we generated the index 1/R, which provides an index of body water adjusted for height. Sex-specific regression models were used to investigate the relationships between (a) 1/R and LMI, and (b) body mass index (BMI) adjusted for 1/R and FMI. The success of this approach was evaluated in relation to the conventional BIA approach, using correlation analysis. RESULTS: 1/R was a highly significant predictor of LMI. BMI adjusted for 1/R was a significant predictor of FMI. Our approach performed as well as the conventional approach for LMI, but not for FMI. DISCUSSION: Direct use of BIA data, rather than their combination with population-specific equations for the prediction of total body water, proved successful at ranking individuals of both sexes in terms of LMI and FMI. The index 1/R may prove particularly valuable in epidemiological studies where ranking of LMI is required.

Adipose Tissue↗

PubMed2006

Body composition in normal weight, overweight and obese children: matched case-control analyses of total and regional tissue masses, and body composition trends in relation to relative weight.

BACKGROUND: Childhood obesity is defined on the basis of weight and height, using body mass index (BMI). There is little detailed information on the body composition characteristic of overweight and obesity. OBJECTIVE: To evaluate total and regional body composition in overweight, obese and control children aged 7-14 years. DESIGN: Body composition was measured by the four-component model and dual X-ray absorptiometry in 38 age- and sex-matched pairs of obese and control children. Body composition trends were also evaluated by quintile of BMI standard deviation score (SDS) in these and 31 other children (n=107; BMI SDS range -1.0 to 4.3). RESULTS: Obese children were taller than controls (Delta=0.6 SDS; P=0.01) and had greater hydration of fat-free mass (FFM) (Delta=1.8 %, P<0.0001). After adjusting for these variables, obese children had greater FFM, fat mass (FM) and mineral (P<0.0001). Regional analyses showed that these differences were apparent in the arm, leg and trunk, but the three tissues had different proportional distributions of the excess. Fat was primarily in the trunk, but mineral in the leg. FM, FFM, hydration and mineral mass all increased across BMI SDS quintiles (P<0.0001), but the trend for FM was much the steepest. DISCUSSION: The greater weight of obese children is due to excess FFM including mineral as well as excess fatness. Increasing weight has a strong continuous relationship with increasing FM across the whole spectrum of weight.

Absorptiometry, Photon↗

PubMed2006

The effect of L-alanine therapy in a patient with adult onset glycogen storage disease type II.

Adult-onset glycogen storage disease type II (GSD II) (McKusick 232300) is a progressive disabling myopathy. At present there is no treatment of proven clinical efficacy. Enzyme replacement therapy may in the future provide benefit but it will be costly and is not yet freely available. L-Alanine, a simple and relatively cheap therapy, has been shown to reduce protein degradation in GSD II patients but has not previously been assessed for clinical benefit in a controlled study. In this study L-alanine was assessed in a double blind, placebo-controlled, crossover n = 1 study. Assessments consisted of spirometry, cardiopulmonary exercise testing, quality of life measurements, biochemical markers and assessment by the criterion 4-component model of body composition. Alanine therapy was associated with a 15% gain in total body protein. However, the patient showed no functional improvement and reported feeling worse after treatment. Further controlled studies in a small group may be warranted, but not widespread use of this therapy.

Aged↗

PubMed2005

Composition of the fat-free mass in obese and nonobese children: matched case-control analyses.

OBJECTIVE: Most body composition techniques assume constant properties of the fat-free mass (FFM), such as hydration, density and mineralisation. Previous studies suggested that FFM composition may change in childhood obesity; however, this issue has not been investigated in detail. AIM: To compare FFM composition in obese and nonobese children. DESIGN: Observational matched case-control analyses. SUBJECTS: A total of 28 obese children (13 boys, 15 girls) and 22 nonobese children (10 boys, 12 girls) aged 7-14 y. Obesity was defined as body mass index centile >95. METHODS: Measurements were made of weight, height, total body water, and body volume. Bone mineral content was estimated in a subsample. Body composition was calculated using three- and four-component models. RESULTS: According to the three-component model (n=22 matched pairs), obese children had greater hydration (P<0.05), and reduced density (P=0.057) of FFM. According to the four component model (n=11 pairs), obese children had greater hydration (P<0.01) and reduced density (P<0.002) of FFM. The mineralisation of FFM was increased, but not significantly so. CONCLUSION: The greater hydration and reduced density of FFM of obese children should be taken into account if body composition is to be measured with optimum accuracy during treatment programmes. These differences may be addressed by using multicomponent rather than two-component models of body composition. Although the greater mineralisation of FFM in obese children was not significant in the present study, the four-component model is best able to address the combined differences in hydration and mineralisation that occur in childhood obesity.

Absorptiometry, Photon↗

PubMed2005

Assessing the acceptability and feasibility of the MEND Programme in a small group of obese 7-11-year-old children.

BACKGROUND AND AIMS: An uncontrolled, pilot study to evaluate feasibility and acceptability of a new community based childhood obesity treatment programme. METHODS: The mind, exercise, nutrition and diet (MEND) programme was held at a sports centre, twice-weekly, for 3 months. The programme consists of behaviour modification, physical activity and nutrition education. The primary outcome measure was waist circumference. Secondary outcomes were body mass index (BMI), cardiovascular fitness (heart rate, blood pressure and number of steps in 2 min), self-esteem and body composition. BMI of parents was also measured. See http://www.mendprogramme.org. RESULTS: Eleven obese children (7-11 years) and their families were recruited. Mean attendance was 78% (range 63-88%) with one drop out. Waist circumference, cardiovascular fitness and self-esteem were all significantly improved at 3 months and continued to improve at 6 months. BMI was significantly improved at 3 months but lost significance by 6 months. Deuterium studies showed a beneficial trend but were not significant. Of the 17 parents measured, seven were obese (BMI >/= 30) and eight overweight (BMI >/= 25). CONCLUSIONS: Although limited by the small number of participants and no control group, the MEND programme was acceptable to families and produced significant improvements in a range of risk factors associated with obesity that persisted over 3 months.

Body Mass Index↗

PubMed2005

Prediction of total body water in infants and children.

BACKGROUND: In paediatric clinical practice treatment is often adjusted in relation to body size, for example the calculation of pharmacological and dialysis dosages. In addition to use of body weight, for some purposes total body water (TBW) and surface area are estimated from anthropometry using equations developed several decades previously. Whether such equations remain valid in contemporary populations is not known. METHODS: Total body water was measured using deuterium dilution in 672 subjects (265 infants aged <1 year; 407 children and adolescents aged 1-19 years) during the period 1990-2003. TBW was predicted (a) using published equations, and (b) directly from data on age, sex, weight, and height. RESULTS: Previously published equations, based on data obtained before 1970, significantly overestimated TBW, with average biases ranging from 4% to 11%. For all equations, the overestimation of TBW was greatest in infancy. New equations were generated. The best equation, incorporating log weight, log height, age, and sex, had a standard error of the estimate of 7.8%. CONCLUSIONS: Secular trends in the nutritional status of infants and children are altering the relation between age or weight and TBW. Equations developed in previous decades significantly overestimate TBW in all age groups, especially infancy; however, the relation between TBW and weight may continue to change. This scenario is predicted to apply more generally to many aspects of paediatric clinical practice in which dosages are calculated on the basis of anthropometric data collected in previous decades.

Adolescent↗

PubMed2004

Within- and between-laboratory precision in the measurement of body volume using air displacement plethysmography and its effect on body composition assessment.

OBJECTIVE: To determine and compare the extent of within- and between-laboratory precision in body volume (BV) measurements using air displacement plethysmography (ADP), the BOD POD body composition system, and to interpret any such variability in terms of body composition estimates. DESIGN: Repeated test procedures of BV assessment using the BOD POD ADP were reproduced at two laboratories for the estimation of precision, both within and between laboratories. SUBJECTS: In total, 30 healthy adult volunteers, 14 men (age, 19-48 y; body mass index (BMI), 19.7-30.3 kg/m2) and 16 women (age, 19-40 y; BMI, 16.3-35.7 kg/m2), were each subjected to two test procedures at both laboratories. Two additional volunteers were independently subjected to 10 repeated test procedures at both laboratories. MEASUREMENTS: Repeated measurements of BV, uncorrected for the effects of isothermal air in the lungs and the surface area artifact, were obtained using the BOD POD ADP, with the identical protocol being faithfully applied at both laboratories. Uncorrected BV measurements were adjusted to give estimates of actual BV that were used to calculate body density (body weight (BWt)/actual BV) from which estimates of body composition were derived. The differences between repeated BV measurements or body composition estimates were used to assess within-laboratory precision (repeatability), as standard deviation (SD) and coefficient of variation; the differences between measurements reproduced at each laboratory were used to determine between-laboratory precision (reproducibility), as bias and 95% limits of agreement (from SD of the differences between laboratories). RESULTS: The extent of within-laboratory methodological precision for BV (uncorrected and actual) was variable according to subject, sample group and laboratory conditions (range of SD, 0.04-0.13 l), and was mostly due to within-individual biological variability (typically 78-99%) rather than to technical imprecision. There was a significant (P<0.05) bias between laboratories for the 10 repeats on the two independent subjects (up to 0.29 l). Although no significant bias (P=0.077) was evident for the sample group of 30 volunteers (-0.05 l), the 95% limits of agreement were considerable (-0.68 to 0.58 l). The effects of this variability in BV on body composition were relatively greater: for example, within-laboratory precision (SD) for body fat as % BWt was between 0.56 and 1.34% depending on the subject and laboratory; the bias (-0.59%) was not significant between laboratories, but there were large 95% limits of agreement (-3.67 to 2.50%). CONCLUSION: Within-laboratory precision for each BOD POD instrument was reasonably good, but was variable according to the prevailing conditions. Although the bias between the two instruments was not significant for the BV measurements, implying that they can be used interchangeably for groups of similar subjects, the relatively large 95% limits of agreement indicate that greater consideration may be needed for assessing individuals with different ADP instruments. Therefore, use of a single ADP instrument is apparently preferable when assessing individuals on a longitudinal basis.

Adult↗

PubMed2004

Evaluating the performance of the Framingham risk equations in a population with diabetes.

AIMS: The Framingham risk equations are widely used to estimate risk of coronary heart disease (CHD). The purpose of this study was to evaluate the reliability of these equations in predicting CHD risk in people with diabetes and the reliability of using imputed mean HDL-cholesterol values. METHODS: Data describing the baseline characteristics of recognized CHD risk factors for 938 people aged 30-74 years were extracted from the Cardiff Diabetes Database. Data describing CHD events were available for up to 4 years following the baseline year (1996). Several mathematical techniques were used to assess the reliability of predictions provided by the Framingham equations in this population. RESULTS: Thirty-four percent of males and 25% of females who experienced CHD events had a predicted 10-year CHD risk >/= 30%. Seventy-five percent of males and 58% of females had a predicted 10-year CHD risk >/= 20%. Using imputed HDL-cholesterol values, 26% of males and 6% of females who later developed CHD events had a 10-year CHD risk >/= 30%. Using imputed HDL-cholesterol values, the CHD risk predicted by the Framingham equations consistently underestimated the actual risk of CHD events. However, refitting the Framingham risk equations to the Cardiff data resulted in only marginal improvements in discriminatory capabilities. CONCLUSIONS: The Framingham risk equations can be unreliable when applied to the diabetic population, tending to underestimate an individual's probability of progressing to CHD; the equations perform marginally better in women than in men. The use of imputed mean HDL-cholesterol values improved the reliability of the estimates of risk.

Adult↗

PubMed2004

Nested PCR on blood and milk for the detection of Mycobacterium avium subsp paratuberculosis DNA in clinical and subclinical bovine paratuberculosis.

OBJECTIVE: To determine the potential of PCR on blood and milk to detect cattle infected with Mycobacterium avium subsp paratuberculosis. PROCEDURE: A nested PCR method probing for IS900 was developed and compared to ELISA serology in 11 clinically infected and 46 subclinically infected, lactating Holstein cows from a herd with confirmed paratuberculosis (Johne's disease). RESULTS: When compared to serum ELISA the nested blood- and milk PCRs were equal in identifying DNA from clinically infected animals. The PCR procedures also gave positive DNA results with some subclinically infected animals when these only gave suspicious or negative results in the ELISA test. Most clinically and subclinically infected animals were detected with milk PCR. CONCLUSION: Since there may well be a haematological phase in paratuberculosis, nested PCR testing of blood and milk samples shows potential to detect animals subclinically infected with M a paratuberculosis. More subclinically infected animals need to be tested and confirmed infected before estimates of sensitivity and specificity can be made.

Animals↗

PubMed2002

Spatial resolution of spin waves in an ultracold gas.

We present the first spatially resolved images of spin waves in a gas. The complete longitudinal and transverse spin field as a function of time and space is reconstructed. Frequencies and damping rates for a standing-wave mode are extracted and compared with theory.

Journal Article↗

PubMed2002

Longitudinal spin waves in a dilute bose gas.

We present a kinetic theory for a dilute noncondensed Bose gas of two-level atoms that predicts the transient spin segregation observed in a recent experiment. The underlying mechanism driving spin currents in the gas is due to a mean-field effect arising from the quantum interference between the direct and exchange scattering of atoms in different spin states. We numerically solve the spin Boltzmann equation, using a one-dimensional model, and find excellent agreement with experimental data.

Journal Article↗

PubMed2002

Dynamical instability of a condensate induced by a rotating thermal gas.

We study surface modes of the condensate in the presence of a rotating thermal cloud in an axisymmetric trap. By considering collisions that transfer atoms between the condensate and the noncondensate, we find that m>0 modes, which rotate in the same sense as the thermal cloud, damp less strongly than m<0 modes, where m is the polarity of the excitation. We show that above a critical angular rotation frequency, equivalent to the Landau stability criterion, m>0 modes become dynamically unstable, leading to the possibility of vortex nucleation. We also generalize our stability analysis to treat the case where the stationary state of the condensate already possesses a single vortex.

Journal Article↗

PubMed2002

Trends in radiological anatomy teaching in the U.K. and Ireland.

AIM: To determine the prevalence of radiological anatomy teaching in modern medical curricula. MATERIALS AND METHODS: The present paper details a survey carried out amongst 21 medical schools in the U.K. and Ireland to determine the variability of the inclusion of radiological anatomy in their different curricula. RESULTS: In all the institutions surveyed teaching of anatomy as revealed by radiological techniques was delivered by anatomy departments. There was considerable variation, however, in the way in which it was delivered, by whom and in the range of radiological material available. Most anatomy departments had links with radiology departments, though the precise arrangements of these also varied. CONCLUSION: This study highlights the need for standardization between anatomy departments with regard to the content and level of radiological anatomy taught to ensure that an appropriate basis for clinical undergraduate training is provided.

Anatomy↗

PubMed2002

Performance of steers grazing rhizomatous and nonrhizomatous birdsfoot trefoil in pure stands and in tall fescue mixtures.

This study investigated the performance of steers grazing rhizomatous birdsfoot trefoil (Lotus corniculatus L.) (RBFT) compared to nonrhizomatous birdsfoot trefoil (BFT) in pure stands or when interseeded with endophyte-free tall fescue (Festuca arundinacea Schreb.; TF). Five forage treatments of RBFT, BFT, TF, RBFT+TF, and BFT+TF (four replicate paddocks per treatment) were continuously stocked in spring and fall of 1998 and spring of 1999. Grazing for individual treatments was terminated when pasture mass fell below 900 kg/ha. Average daily gain was greatest (P < 0.10) in pure stands of BFT and RBFT, but total forage production, and thus grazing days, for these treatments was low. Average daily gain for steers grazing BFT+TF and RBFT+TF treatments was not different from (spring and fall 1998) or greater (P < 0.10) (spring 1999) than that for TF. Total forage production of BFT+TF and RBFT+TF was greater (P < 0.10) than that of TF in spring 1998. In fall 1998, BFT+TF produced more (P < 0.10) total forage than either RBFT+TF or TF, and in spring 1999, RBFT+TF had less (P < 0.10) total forage than TF or BFT+TF. Total steer days on mixed pastures were greater (P < 0.10) than that for TF in spring and fall 1998 but not different from those for TF in spring 1999. In all three trials total weight gain/hectare was greater (P < 0.10) for RBFT+TF and BFT+TF than for TF. The RBFT+TF and BFT +TF had greater (P < 0.05) CP than TF in spring and fall 1998 and less (P < 0.05) NDF and ADF in fall 1998. We concluded that either RBFT or BFT could be interseeded with tall fescue to enhance ADG and total steer days.

Animal Feed↗

PubMed2001

Effects of an angry temperament on coronary heart disease risk : The Atherosclerosis Risk in Communities Study.

The objective of the study was to determine which component of an anger-prone personality more strongly predicts coronary heart disease (CHD) risk. Proneness to anger, as assessed by the Spielberger Trait Anger Scale, is composed of two distinct subcomponents-anger-temperament and anger-reaction. Participants were 12,990 middle-aged Black men and women and White men and women from the Atherosclerosis Risk in Communities Study who were followed for the occurrence of acute myocardial infarction (MI)/fatal CHD, silent MI, or cardiac revascularization procedures (average = 53 months; maximum = 72 months) through December 31, 1995. Among normotensive persons, a strong, angry temperament (tendency toward quick, minimally provoked, or unprovoked anger) was associated with combined CHD (acute MI/fatal CHD, silent MI, or cardiac revascularization procedures) (multivariate-adjusted hazard ratio = 2.10, 95% confidence interval: 1.34, 3.29) and with 'hard" events (acute MI/fatal CHD) (multivariate adjusted hazard ratio = 2.28, 95% confidence interval: 1.29, 4.02). CHD event-free survival among normotensives who had a strong, angry temperament was not significantly different from that of hypertensives at either level of anger. These data suggest that a strong, angry temperament rather than anger in reaction to criticism, frustration, or unfair treatment places normotensive, middle-aged persons at increased risk for cardiac events and may confer a CHD risk similar to that of hypertension.

Anger↗

PubMed2001

Sensitivity and specificity of serum copper determination for detection of copper deficiency in feeder calves.

OBJECTIVE: To determine the relationship between serum and liver copper concentrations and evaluate serum copper determination for diagnosis of copper deficiency in juvenile beef calves. DESIGN: Cross-sectional study. ANIMALS: 105 juvenile beef calves. PROCEDURE: Copper concentrations were measured in paired liver and serum samples from 6- to 9-month-old beef calves. Regression models that predicted liver copper concentration as a function of serum copper concentration were developed. Sensitivity and specificity of serum copper concentration for detection of low liver copper concentration were determined, using a range of serum copper concentrations as test endpoints. Positive and negative predictive values were calculated. RESULTS: The association between serum and liver copper concentrations was significant; however, regression models accounted for only a small portion of the variation in liver copper concentrations. For a serum copper concentration endpoint of 0.45 microg/g, sensitivity and specificity for detection of low liver copper concentration were 0.53 and 0.89, respectively. Positive and negative predictive values of serum copper concentration for detection of low liver copper concentration ranged from 0.37 to 0.85 and 0.63 to 0.94, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Regression models are inappropriate for predicting copper status as a function of serum copper concentration. Serum copper concentration is fairly specific for detection of low liver copper concentration but only marginally sensitive when serum copper concentration of 0.45 microg/g is used as a test endpoint. The value of serum copper concentration as a diagnostic indicator depends on prevalence of copper deficiency.

Animals↗

PubMed2001

Establishing a cancer pain clinic in a developing country: effect of a collaborative link project with a UK cancer pain center.

This paper describes a project for the establishment of a cancer pain clinic in a developing country. The project was conducted according to guidelines from the World Health Organization and utilized a link with an existing cancer pain clinic in the UK. The principal methods used for establishing the new pain clinic included: an assessment of barriers to effective cancer pain control, teaching programs for nurses and trainee doctors, educational links with a UK cancer pain clinic, and analgesic guidelines and introduction of a pain assessment tool. As a result of these interventions, a new cancer pain clinic was founded. The methods used serve as one possible model for establishing cancer pain treatment facilities in developing countries.

Cooperative Behavior↗

PubMed2001

Development of a self-reported Chronic Respiratory Questionnaire (CRQ-SR).

BACKGROUND: The Chronic Respiratory Questionnaire (CRQ) is an established measure of health status for chronic obstructive pulmonary disease (COPD). It has been found to be reproducible and sensitive to change, but as an interviewer led questionnaire is very time consuming to administer. A study was undertaken to develop a self-reported version of the CRQ (CRQ-SR) and to compare the results of this questionnaire with the conventional interviewer led CRQ (CRQ-IL). METHODS: Fifty two patients with moderate to severe COPD participated in the study. Subjects completed the CRQ-SR 1 week after completing the CRQ-IL, and a further CRQ-SR was administered 1 week later. For patients in group A (n=27) the dyspnoea provoking activities that they had previously selected were transcribed onto the second CRQ-SR, while patients in group B (n=25) were not informed of their previous dyspnoea provoking activities when they completed the second CRQ-SR. To assess the short term reproducibility and reliability of the CRQ-SR it was then administered twice at an interval of 7-10 days to a further group of 21 patients. The CRQ-IL was not administered. Longer term reproducibility was examined in 39 stable patients who completed the CRQ-SR at initial assessment and then again 7 weeks later. RESULTS: Mean scores per dimension, mean differences, and limits of agreement are given for each dimension in the comparison of the two questionnaires. There were no statistically significant differences between the CRQ-IL and CRQ-SR in the mastery and fatigue dimensions (p>0.05). A statistically significant difference between the two scores was found in the dyspnoea dimension (p=0.006) and the emotional function dimension (p=0.04), but these differences were well within the minimum clinically important threshold. No statistically significant difference in the mean dyspnoea score was seen between groups A and B. The CRQ-SR was found to be reproducible both in the short term and after the longer period of 7 weeks, with no statistically or clinically significant differences in any dimension. Test-retest reliability was found to be high in each dimension, both in the short and longer term. CONCLUSIONS: The CRQ-SR is a reproducible, reliable, and stable measure of health status. It compares well with the CRQ-IL but cannot be used interchangeably. The main advantage of the CRQ-SR over the CRQ-IL is that is quick to administer, reducing assessment time and hence cost.

Aged↗