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Biomedical subjects

P D Bridge

Publications and source records attributed to P D Bridge.

At least 19 recordsLinked to original sources
PubMed2003

Repeatability of airway resistance measurements made using the interrupter technique.

BACKGROUND: To be able to interpret any measurement, its repeatability should be known. This study reports the repeatability of airway resistance measurements using the interrupter technique (Rint) in children with and without respiratory symptoms. METHODS: Children aged 2-10 years who were healthy, had persistent isolated cough, or who had previous wheeze were studied. On the same occasion, three Rint measurements were made 15 minutes apart, before and after placebo and salbutamol given in random order. Results from those given placebo first were analysed for within-occasion repeatability. Between-occasion repeatability measurements were made 2-20 weeks apart (median 3 weeks). RESULTS: For 85 pairs of measurements before and after placebo the limits of agreement were 20% expected resistance and were unaffected by age or health status. The change in resistance following bronchodilator in one of 18 healthy children, 12 of 28 with cough, and 22 of 39 with wheeze exceeded this threshold. For between-occasion measurements the limits of agreement were 32% in 72 healthy subjects, 49% in 57 with cough, and 53% in 95 with previous wheeze. CONCLUSION: The measurement of airways resistance by the interrupter technique is clinically meaningful when change following an intervention such as the administration of bronchodilator is greater than its within-occasion repeatability. Between-occasion repeatability is too poor to judge change confidently.

Airway Resistance↗
PubMed2002

Phenotypic degeneration occurs during sector formation in Metarhizium anisopliae.

AIMS: The formation of sectors was observed during subculturing of an isolate of the entomopathogenic fungus Metarhizium anisopliae, a fungus used for biological control of insect pests. The aim of the investigation was to establish whether sector formation was accompanied by changes in physiological characters. METHODS AND RESULTS: Four degenerative morphological states, with reduced sporulation capacity, were characterized. Subcultures were taken from each sector and four new culture lines established. The new lines were further subcultured every 21 d. A physiological assessment of each line was undertaken after 42 d using TLC of secondary metabolites and fluorogenic enzyme tests. Full sporulation capacity was not regained on subculture, although some cultures recovered partially. Changes in secondary metabolite profiles and the loss in detection of activity of specific enzymes were observed. CONCLUSIONS: Sector formation was frequently accompanied by changes in the ability to produce secondary metabolites and enzymes. SIGNIFICANCE AND IMPACT OF THE STUDY: The results illustrate the importance of maintaining the stability of important cultures during routine subculture. The consequences could have significant implications if degenerate cultures are used as inocula for liquid fermentation cultures or industrial scale production.

Enzymes↗
PubMed2002

Airway resistance measured by the interrupter technique: normative data for 2-10 year olds of three ethnicities.

BACKGROUND AND AIMS: The measurement of airway resistance using the interrupter technique (R(int)) is feasible in preschool children and other subjects unable to undertake spirometry. This makes it potentially useful for the measurement of lung function in these groups. Commercial devices use different algorithms to measure pressure and flow from which R(int) is derived. This study provides normative values for British children using devices from a single manufacturer. METHODS: R(int) was measured in 236 healthy children of three ethnic groups (Afro-Caribbean and black African, Bangladeshi, and white British) aged 2-10 years using Micro Medical devices. Software in the devices calculated R(int) from pressure measured by the two point, back extrapolation method from the pressure transient during valve closure, with flow measured just before valve closure. RESULTS: R(int) is related to both age and height, but when age is allowed for there is not a significant relation with height. Neither gender nor any of the ethnicities studied was significantly related to R(int). DISCUSSION: These measurements in healthy children using this technique may be used as reference data for similar populations.

Aging↗
PubMed2001

Bronchodilator responsiveness and atopy in 5-10-yr-old coughers.

Cough-variant asthma is considered by some to be an asthma phenotype. Bronchodilator responsiveness (BDR) is an undisputed feature of asthma. Of school-aged wheezers, 90% are atopic. Are school-aged coughers who demonstrate BDR also atopic? If so, then it would be reasonable to reserve the diagnosis cough-variant asthma for this particular group. Airway resistance was measured by the interrupter technique (Rint) before and after salbutamol in controls (n=73), coughers (n=63) and previous wheezers (n=63) aged 5-10 yrs. Immunoglobulin (Ig)-E was measured in coughers and wheezers. BDR was expressed as the ratio baseline:post-salbutamol Rint. Groups were of similar age (mean 6.7, range 5-9.9 yrs). Geometric mean baseline Rint was similar in controls and coughers (0.66 and 0.68 kPa x L(-1) x s), but the baseline Rint for wheezers (0.73 kPa x L(-1) s) was greater than that for controls (p=0.05) but not significantly different from coughers (p=0.17). Geometric mean BDR in coughers was 1.22, controls 1.13 and wheezers 1.30 (p=0.01 for coughers and controls; p=0.08 for coughers and wheezers; p<0.001 for controls and wheezers). IgE was lower in coughers than wheezers (geometric means 36 and 364 International Units (IU) x L(-1), p<0.001) and was unrelated to BDR in both groups. In summary, atopy, and not bronchodilator responsiveness, distinguishes groups of coughers from groups of wheezers. A diagnosis of cough-variant asthma cannot be reserved for even those school-aged coughers, who demonstrate bronchodilator responsiveness.

Airway Resistance↗
PubMed2001

Airway resistance measured by the interrupter technique: expiration or inspiration, mean or median?

The measurement of airway resistance by the interrupter technique (Rint) needs standardization. Should measurements be made be during the expiratory or inspiratory phase of tidal breathing? In reported studies, the measurement of Rint has been calculated as the median or mean of a small number of values, is there an important difference? Subjects were 2.5-5.0 yrs (median 4.0 yrs) who had previous respiratory symptoms. The Rint in expiration (RintE) and inspiration (RintI) pre and postsalbutamol, the coefficient of variation (CV) of values contributing to measurements, and bronchodilator responsiveness(BDR) in both phases were compared. Measurements using median and mean were compared. RintE was higher than RintI by 4% (p < 0.01). The CV of values making up RintE and RintI, and BDR measured in expiration and inspiration were similar. The median difference between means and medians of values making up measurements was 0.6% (range -6-11%). RintE has been shown to be consistently greater then RintI but the difference in this study is small. It is suggested that one or the other is chosen as the standard. In the present data the mean of a set of values contributing to a measurement was not significantly different from the median. However, the use of the median has been recommended since it is less affected by possible outlying values such as might be included by fully automated equipment.

Airway Resistance↗
PubMed2000

Airway resistance and atopy in preschool children with wheeze and cough.

The extent to which the measurement of airways resistance by the interrupter technique (Rint) distinguishes preschool children with previous wheeze from those with no respiratory symptoms and helps to classify subjects with persistent cough, was investigated. Rint was measured before and after salbutamol treatment in 82 children with recurrent wheeze, 58 with isolated cough and 48 with no symptoms (control subjects). Their mean age (range) was 3.7 yrs (2-<5 yrs). Median baseline Rint was higher (p<0.0001) in wheezers than in either coughers or control subjects (1.16, 0.94 and 0.88 kPa x L(-1) x s(-1) respectively); coughers did not differ significantly from control subjects (p=0.14). The median ratios of baseline to post-salbutamol measurements (bronchodilator response (BDR)) in the groups differed significantly (1.40, 1.27 and 1.07, p< or =0.01 for all), suggesting that coughers occupy an intermediate position. A BDR ratio of >1.22 had a specificity and sensitivity for wheeze of 80% and 76% respectively. Twenty-eight coughers had a BDR ratio >1.22. Wheezers' immunoglobulin E was inversely related to baseline Rint. It is concluded that measurements of airway resistance by the interrupter technique are useful for classifying preschool children with respiratory symptoms and could be used to monitor the effect of interventions. The relation between atopy and airways resistance suggests that they have separate roles in preschool wheezing. Coughers with a high bronchodilator response could represent "cough-variant" asthma in children who have baseline airway resistance by the interrupter technique measurements similar to control subjects. Whether these children develop classical asthma will only be known at follow-up later in childhood.

Airway Resistance↗
PubMed2000

Using evaluation methods to guide the development of a tobacco-use prevention curriculum for youth: a case study.

BACKGROUND: Fundamental to the development of educational programs and curricula is the evaluation of processes and outcomes. Unfortunately, many otherwise well-designed programs do not incorporate stringent evaluation methods and are limited in measuring program development and effectiveness. Using an advertising lesson in a school-based tobacco-use prevention curriculum as a case study, the authors examine the role of evaluation in the development, implementation, and enhancement of the curricular lesson. METHODS: A four-phase formative and summative evaluation design was developed to divide the program-evaluation continuum into a structured process that would aid in the management of the evaluation, as well as assess curricular components. RESULTS AND CONCLUSIONS: Formative and summative evaluation can provide important guidance in the development, implementation, and enhancement of educational curricula. Evaluation strategies identified unexpected barriers and allowed the project team to make necessary "time-relevant" curricular adjustments during each stage of the process.

Adolescent↗
PubMed2000

Terminal-sequence conservation identifies spliceosomal introns in ascomycete 18S RNA genes.

Twenty-four new insertions were obtained from seven different locations in the nuclear 18S rDNA for seven species of the lichen-forming fungal genus PHYSCONIA: They were analyzed allowing for terminal sequence conservation by adopting a flexible approach to exact insertion site position, and they were compared with 12 previously reported small insertion sequences from the 18S ribosomal RNA gene. Such insertions have previously been proposed to be degenerate self-splicing group I introns; however, the methodology used here identified consensus terminal sequences characteristic of spliceosomal introns. This finding is the first suggestion that multiple spliceosomal introns occur in ribosomal genes.

Ascomycota↗
PubMed1999

Increasing physicians' awareness of the impact of statistics on research outcomes: comparative power of the t-test and and Wilcoxon Rank-Sum test in small samples applied research.

To effectively evaluate medical literature, practicing physicians and medical researchers must understand the impact of statistical tests on research outcomes. Applying inefficient statistics not only increases the need for resources, but more importantly increases the probability of committing a Type I or Type II error. The t-test is one of the most prevalent tests used in the medical field and is the uniformally most powerful unbiased test (UMPU) under normal curve theory. But does it maintain its UMPU properties when assumptions of normality are violated? A Monte Carlo investigation evaluates the comparative power of the independent samples t-test and its nonparametric counterpart, the Wilcoxon Rank-Sum (WRS) test, to violations from population normality, using three commonly occurring distributions and small sample sizes. The t-test was more powerful under relatively symmetric distributions, although the magnitude of the differences was moderate. Under distributions with extreme skews, the WRS held large power advantages. When distributions consist of heavier tails or extreme skews, the WRS should be the test of choice. In turn, when population characteristics are unknown, the WRS is recommended, based on the magnitude of these power differences in extreme skews, and the modest variation in symmetric distributions.

Epidemiologic Studies↗
PubMed1999

Measurement of airway resistance using the interrupter technique in preschool children in the ambulatory setting.

This study describes the feasibility, repeatability, and interrater reliability of the measurement of airway resistance by the interrupter technique (Rint) in children 2-5 yrs of age, and examines whether reversibility to bronchodilator can be demonstrated in wheezy children. The mean of six Rint values was taken as a measurement. If subjects could complete one measurement and then a second 15 min after bronchodilator, baseline testing and reversibility testing were considered feasible. To measure repeatability, two measurements 30 s apart and measurements before and 15 min after placebo bronchodilator were compared. Measurements by two testers were compared for interrater reliability. Change in Rint in wheezy children was measured after bronchodilator. Fifty-six per cent of 2-3-yr-olds (n=79), 81% of 3-4-yr-olds (n=104) and 95% of 4-5-yr-olds (n=88) completed baseline testing, and 53%, 71% and 91% completed reversibility testing. Baseline measurements were 0.47-2.56 kPa x L(-1) x s. Repeatabilities (2 SD of the mean differences between measurements) at 30 s in the three age bands were 0.21, 0.17 and 0.15 kPa x L(-1) x s and 0.19 kPa x L(-1) x s after placebo. Using 0.21 kPa x L(-1) x s as the threshold for reversibility, reversibility was demonstrated in most wheezy children. Interrater reliability was 0.15 kPa x L(-1) x s. Preschool children can undertake measurements of airway resistance by the interrupter technique in ambulatory settings and reversibility to bronchodilator in wheezy children can be demonstrated. This technique promises to be a useful clinical and research tool.

Airway Resistance↗
PubMed1999

Presence of a 20 bp insertion/deletion in the ITS1 region of Verticillium lecanii.

Polymerase chain reaction (PCR) amplification of the complete ribosomal RNA internally transcribed spacer (ITS) region of 36 isolates of Verticillium lecanii and related species gave a single 620 bp product in 31 isolates. Five isolates received as V. lecanii, however, gave a single product of 600 bp. Restriction fragment analysis of the PCR products from all isolates gave consistent patterns for the 31 isolates with a 620 bp product. The five isolates with the 600 bp product showed only minor discrepancies to these, generally related to the size of only one restriction fragment. The total ITS region was sequenced from 10 typical 620 bp isolates and one 600 bp isolate. Sequence variation between the isolates varied from 0 to 14.5%, and the 20 bp size discrepancy was found to relate to an insertion or deletion in the centre of the ITS1 region.

Base Sequence↗
PubMed1997

Physiological and biochemical characterization of Trichoderma harzianum, a biological control agent against soilborne fungal plant pathogens.

Monoconidial cultures of 15 isolates of Trichoderma harzianum were characterized on the basis of 82 morphological, physiological, and biochemical features and 99 isoenzyme bands from seven enzyme systems. The results were subjected to numerical analysis which revealed four distinct groups. Representative sequences of the internal transcribed spacer 1 (ITS 1)-ITS 2 region in the ribosomal DNA gene cluster were compared between groups confirming this distribution. The utility of the groupings generated from the morphological, physiological, and biochemical data was assessed by including an additional environmental isolate in the electrophoretic analysis. The in vitro antibiotic activity of the T. harzianum isolates was assayed against 10 isolates of five different soilborne fungal plant pathogens: Aphanomyces cochlioides, Rhizoctonia solani, Phoma betae, Acremonium cucurbitacearum, and Fusarium oxysporum f. sp. radicis lycopersici. Similarities between levels and specificities of biological activity and the numerical characterization groupings are both discussed in relation to antagonist-specific populations in known and potential biocontrol species.

Antibiosis↗
PubMed1996

A portable device based on the interrupter technique to measure bronchodilator response in schoolchildren.

A new device for measuring airway resistance following brief airflow interruption (Microlab 4000; Micromedical Ltd, UK) was evaluated in 25 asthmatic school children in comparison with well-established methods. Airway resistance was measured during brief airflow interruption (Rint), before and after administration of salbutamol 200 micrograms by metered-dose inhaler, and in the spirometric parameters, forced expiratory volume in one second (FEV1) and peak expiratory flow (PEF), and total respiratory system resistance at 6 Hz (Rrs,6) measured by the forced oscillation technique (FOT). The sensitivity index (SI) (mean change/baseline standard deviation) was calculated for each subject. At baseline, interrupter conductance, the reciprocal of Rint, correlated well with FEV1 (r = 0.837; p < 0.001) and PEF (r = 0.773; p < 0.001), and Rint correlated highly with Rrs,6 (r = 0.942; p < 0.001). The median intrasubject coefficient of variation of the interrupter method was higher than the FOT or either spirometric parameter; Rint 11%, Rrs,6 9%, FEV1 5% and PEF 5%. However, the sensitivity to detect change after bronchodilator, expressed as the median SI, did not differ significantly between measurements: Rint 3.5, Rrs,6 3.6, FEV1 2.4 and PEF 3.0. A significant response (SI > 2) was shown by the interrupter in 22 of the subjects compared with 16 by FEV1. The interrupter technique is useful for assessing changes in airway calibre in asthmatic school children, with a sensitivity at least as good as standard methods. Such a device could be of particular value in those too young to perform spirometry.

Airway Resistance↗
PubMed1995

Rapid mitochondrial probes for analysis of polymorphisms in Fusarium oxysporum special forms.

A method is described for the production of simple mitochondrial DNA probes from filamentous fungi for the partial characterization of mitochondrial DNA without the need for cloning, gradient centrifugation or PCR amplification. A probe (P449) consisting of a 3.38 kb mitochondrial fragment from an isolate of Fusarium oxysporum special form cubense was used to determine RFLPs in restriction digests of total DNA from 28 isolates of F. oxysporum from a variety of hosts and locations. The probe showed mtDNA polymorphisms within and between different special forms.

Blotting, Southern↗