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Biomedical subjects

T Fearn

Publications and source records attributed to T Fearn.

12 recordsLinked to original sources
PubMed2001

A new test for 'sufficient homogeneity'.

Certified reference materials and materials distributed in proficiency testing need to be 'sufficiently homogeneous', that is, the variance in the mean composition of the distributed portions of the material must be negligibly small in relation to the variance of the analytical result produced when the material is in normal use. The requirement for sufficient homogeneity suggests the use of a formal test. Such tests as have been formulated rely on the duplicated analysis of the material from a number of portions, followed by analysis of variance. However, the outcome is not straightforward. If the analytical method used is very precise, then an undue proportion of the materials will be found to be significantly heterogeneous. If it is too imprecise, the test may be unable to detect heterogeneity. Moreover, the Harmonised Protocol Procedure (M. Thompson and R. Wood, Pure Appl. Chem., 1993, 65, 2123) seems to be unduly prone to the rejection of material that is in fact satisfactory. We present a simple new statistical approach that overcomes some of these problems.

Journal Article↗
PubMed1999

Near-infrared spectroscopy for dairy management: measurement of unhomogenized milk composition.

The potential of near-infrared spectroscopy to measure fat, total protein, and lactose contents of unhomogenized milk was studied for use in dairy management, as a new tool for on-line milk analysis in the process of milking. Influence of the spectral region, sample thickness, and spectral data treatment on the accuracy of determination was investigated. Transmittance spectra of 258 milk samples, collected at different stages of the milking process, were obtained with a spectrophotometer (NIRSystems 6500; FOSS-NIRSystems, Silver Spring, MD) in the wavelength range from 400 to 2500 nm with sample thicknesses of 1 mm, 4 mm, and 10 mm. The spectral region and sample thickness were found to be significant factors for milk fat and total protein determination but not the lactose determination. The best accuracy was obtained with the 1100 to 2400 nm region, 1-mm sample thickness, and the first derivative data transformation. For the spectral region from 700 to 1100 nm, close accuracy was obtained for fat with a 10-mm sample and for total protein with a 1-mm sample thickness. The sample thickness did not change significantly the accuracy of lactose determination. Different treatments of spectral data did not improve the calibrations for fat and protein. For the region from 700 to 1100 nm, where inexpensive on-line sensors could be used, the highest positive coefficients for fat were at 930, 968, 990, 1026, 1076, and 1092 nm; for lactose were at 734, 750, 786, 812, 908, 974, 982, and 1064 nm; and for total protein were at 776, 880, 902, 952, and 1034 nm.

Animals↗
PubMed1998

Risk of lung cancer associated with residential radon exposure in south-west England: a case-control study.

Studies of underground miners occupationally exposed to radon have consistently demonstrated an increased risk of lung cancer in both smokers and non-smokers. Radon exposure also occurs elsewhere, especially in houses, and estimates based on the findings for miners suggest that residential radon is responsible for about one in 20 lung cancers in the UK, most being caused in combination with smoking. These calculations depend, however, on several assumptions and more direct evidence on the magnitude of the risk is needed. To obtain such evidence, a case-control study was carried out in south-west England in which 982 subjects with lung cancer and 3185 control subjects were interviewed. In addition, radon concentrations were measured at the addresses at which subjects had lived during the 30-year period ending 5 years before the interview. Lung cancer risk was examined in relation to residential radon concentration after taking into account the length of time that subjects had lived at each address and adjusting for age, sex, smoking status, county of residence and social class. The relative risk of lung cancer increased by 0.08 (95% CI -0.03, 0.20) per 100 Bq m(-3) increase in the observed time-weighted residential radon concentration. When the analysis was restricted to the 484 subjects with lung cancer and the 1637 control subjects with radon measurements available for the entire 30-year period of interest, the corresponding increase was somewhat higher at 0.14 per 100 Bq m(-3) (95% CI 0.01, 0.29), although the difference between this group and the remaining subjects was not statistically significant. When the analysis was repeated taking into account uncertainties in the assessment of radon exposure, the estimated increases in relative risk per 100 Bq m(-3) were larger, at 0.12 (95% CI -0.05, 0.33) when all subjects were included and 0.24 (95% CI -0.01, 0.56) when limited to subjects with radon measurements available for all 30 years. These results are consistent with those from studies of residential radon carried out in other countries in which data on individual subjects have been collected. The combined evidence suggests that the risk of lung cancer associated with residential radon exposure is about the size that has been postulated on the basis of the studies of miners exposed to radon.

Aged↗
PubMed1995

Leukemia mortality after X-ray treatment for ankylosing spondylitis.

Leukemia mortality has been studied in 14,767 adult ankylosing spondylitis patients diagnosed between 1935 and 1957 in the United Kingdom, of whom 13,914 patients received X-ray treatment. By 1 January 1992, there were 60 leukemia deaths among the irradiated patients, almost treble that expected from national rates. Leukemia mortality was not increased among unirradiated patients. Among those irradiated, the ratio of observed to expected deaths for leukemia other than chronic lymphocytic leukemia was greatest in the period 1-5 years after the first treatment (ratio = 11.01, 95% confidence interval 5.26-20.98) and decreased to 1.87 (95% confidence interval 0.94-3.36) in the 25+ year period. There was no significant variation in this ratio with sex or age at first treatment. The ratio for chronic lymphocytic leukemia was slightly but not significantly raised (ratio = 1.44, 95% confidence interval 0.62-2.79). Most irradiated patients received all their exposure within a year. Based on a 1 in 15 random sample, the mean total marrow dose was 4.38 Gy. Doses were nonuniform, with heaviest doses to the lower spine. The risk for nonchronic lymphocytic leukemia was adequately described by a linear-exponential model that allowed for cell sterilization in heavily exposed parts of the marrow and time since exposure. Ten years after first exposure, the linear component of excess relative risk was 12.37 per Gy (95% confidence interval 2.25-52.07), and it was estimated that cell sterilization reduced the excess relative risk by 47% at 1 Gy (95% confidence interval 17%-79%). The average predicted relative risk in the period 1-25 years after exposure to a uniform dose of 1 Gy was 7.00.

Adult↗
PubMed1994

Comparison of cervical magnetic stimulation and bilateral percutaneous electrical stimulation of the phrenic nerves in normal subjects.

Cervical magnetic stimulation is a new technique for stimulating the phrenic nerves, and may offer an alternative to percutaneous electrical stimulation for assessing diaphragmatic strength in normal subjects and patients in whom electrical stimulation is technically difficult or poorly tolerated. We compared cervical magnetic stimulation with conventional supramaximal bilateral percutaneous electrical stimulation in nine normal subjects. We measured oesophageal pressure (Poes), gastric pressure (Pgas) and transdiaphragmatic pressure (Pdi). The maximal relaxation rate (MRR) was also measured. The mean magnetic twitch Pdi was 36.5 cmH2O (range 27-48 cmH2O), significantly larger than electrical twitch Pdi, mean 29.7 cmH2O (range 22-40 cmH2O). The difference in twitch Pdi was explained entirely by twitch Poes, and it is possible that the magnetic technique stimulates some of the nerves to the upper chest wall muscles as well as the phrenic nerves. We compared bilateral, rectified, integrated, diaphragm surface electromyographic (EMG) responses in three subjects and found results within 10% in each subject, indicating similar diaphragmatic activation. The within occasion coefficient of variation, i.e. same subject/same session, was 6.7% both for magnetic and electrical twitch Pdi. The between occasion coefficient of variation, i.e. same subject/different days, was 6.6% for magnetic stimulation and 8.8% for electrical. There was no difference between relaxation rates measured with either technique. We conclude that magnetic stimulation is a reproducible and acceptable technique for stimulating the phrenic nerves, and that it provides a potentially useful alternative to conventional electrical stimulation as a nonvolitional test of diaphragm strength.

Action Potentials↗
PubMed1994

Patterns of lung cancer mortality among uranium miners in West Bohemia with varying rates of exposure to radon and its progeny.

Lung cancer mortality in a cohort of 4320 miners first employed during 1948-1959 at the Jáchymov and Horní Slavkov uranium mines in West Bohemia and followed until 1 January 1991 has been studied to gain a greater understanding of the consequences of exposure to radon and its progeny. Among men whose exposure rates never exceeded 10 working levels, excess relative risks per unit exposure were greater in younger men, and exposures received in the periods 15-24, 25-34 and 35+ years previously were found to have 47, 24 and 0% of the effect of exposures 5-14 years previously. Within this low-exposure-rate group excess relative risk increased linearly with time-weighted cumulative exposure and did not depend on exposure rate or duration of exposure. For men who spent less than 20% of their employment at the Jáchymov mine the excess relative risk per working level month was 1.36% (95% confidence interval 0.52-3.54) in the baseline category (age group 55+ and exposure received 5-14 years previously). For men who spent more than 20% of their employment at Jáchymov, the corresponding excess relative risk per working level month was higher by a factor of 1.80 (95% confidence interval 1.27-2.97). The difference may be due to the fact that men who spent more than 20% of their employment at Jáchymov were exposed to the much higher levels of arsenic in the dust at the Jáchymov mine than at other mines. When men with exposure rates above 10 working levels were included in the analysis, patterns of risk were complex and depended on both exposure rate and duration of exposure in addition to the factors mentioned above. If these findings are confirmed elsewhere, calculation of risk estimates for extrapolation to modern occupational or environmental exposures should be based on miners with exposure rates below about 10 working levels. Further investigation is desirable of the influence of dusts containing arsenic on lung cancer risk in miners exposed to radon.

Adult↗
PubMed1989

A low-cost system for computerized rodent weight logging with statistical analysis.

A system comprising a suite of 4 computer programs has been developed for on-line rodent weight data collection and statistical analysis using an IBM personal computer. Data can be collected from up to 3 separate trials simultaneously, and can be stored for later statistical analysis. Mettler balances were used for the animal weighing. A Mettler current loop adapter and a multiplexer were used to interface the balances with the computer.

Animals↗
PubMed1985

Cereal dietary fiber consumption and diverticular disease: a lifespan study in rats.

The relationship between consumption of dietary fiber (DF) from white bread, wholemeal bread, or bran and the development of diverticular disease of the colon has been investigated in a lifespan study using 1800 Wistar rats in nine diet groups. Use of the rat as a model for the human condition was validated by demonstration of significant relationships between fiber intake and fecal output and transit time, and the observation of true acquired diverticula, both single and multiple. Significant inverse relationships (mostly with p less than 0.001) were observed between the incidence of diverticula (and prediverticula) and the concentrations of fiber in the diets, measured by the neutral detergent fiber and Southgate methods. The study offers strong support to the Painter-Burkitt view of human diverticular disease as being due to fiber deficiency, if the extrapolation from rat to man is valid. On the same assumption, the amount of additional fiber required to be consumed in order to achieve a substantial reduction in incidence of the disease is very large. Effects of fiber on body weight, food intake, mineral levels, blood composition and properties, mortality, organ weights, and incidence of tumors and lesions are reported. Significantly fewer mammary tumors were found in rats fed the very high fiber stock diet than in those fed the purified diets.

Animals↗
PubMed1979

The Chatham Blood Pressure Study. An application of Bayesian growth curve models to a longitudinal study of blood pressure in children.

Recent developments in statistics have produced powerful methods that facilitate the analysis of longitudinal studies. These methods are illustrated by an analysis of a longitudinal study of blood pressure in children. The results of the study show a clear tendency for blood pressure to increase with age, and Asian children tend to have lower blood pressures than their Caucasian counterparts of the same age. There is evidence to support the hypothesis that blood pressures track.

Age Factors↗
PubMedDate not supplied

Impact of process conditions on the centrifugal recovery of a disabled herpes simplex virus.

Despite continuous improvements in culturing and recovery techniques, high-titer stocks of purified disabled herpes simplex virus type-1 (HSV-1 DIS) vector for drug discovery and use in preclinical and clinical trials are currently difficult to achieve. Efforts to improve their centrifugal recovery have been addressed in this paper. The operation of a swing-out centrifuge rotor was assessed, and its operational conditions were defined for the recovery of viable HSV-1 DIS. 80% virus recovery was achieved after 90 min at 26000g. The 20% loss of virus was attributed to damage to the viral envelope by overcompaction of the pellet and impaction with the base of the centrifuge tube. Virus recovery was increased by a further 10% by using a fixed-angle centrifuge rotor operating at 26000g. Plaque assays of recovered HSV-1 DIS gave values on the order of 10(6) pfu/mL, compared to values typically above 10(9) pfu/mL obtained for the replication-competent HSV-1 viron.

Animals↗