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A Petrie

Publications and source records attributed to A Petrie.

At least 37 records · Page 2Linked to original sources
PubMed2002

Further statistics in dentistry. Part 2: Research designs 2.

To facilitate statistical discussion, it is essential to have an understanding of factors, effects, interactions, confounding, bias, estimation and hypothesis testing, to name but a few terms commonly used in statistical investigations in dentistry. These terms were explained in the previous paper in this series. This second paper is concerned with describing and differentiating between the various research designs that may be adopted.

Dental Research↗
PubMed2002

Further statistics in dentistry: Part 1: Research designs 1.

This new series of articles is designed to supplement, rather than replace, the material contained in the earlier series on statistics in dentistry published in the British Dental Journal and subsequently made available in book form.(1) With the increasing availability of calculators, personal computers and computer statistical software packages, the need for details of the 'nuts and bolts' of statistical theory has diminished, but the need for an understanding of how and when such theory should be applied, and how studies should be designed to make best use of it, has probably increased. It is with these thoughts in mind that this new series is being offered.

Dental Research↗
PubMed2002

The association between iliocostal distance and the number of vertebral and non-vertebral fractures in women and men registered in the Canadian Database For Osteoporosis and Osteopenia (CANDOO).

BACKGROUND: The identification of new methods of evaluating patients with osteoporotic fracture should focus on their usefulness in clinical situations such that they are easily measured and applicable to all patients. Thus, the purpose of this study was to examine the association between iliocostal distance and vertebral and non-vertebral fractures in patients seen in a clinical setting. METHODS: Patient data were obtained from the Canadian Database of Osteoporosis and Osteopenia (CANDOO). A total of 549 patients including 508 women and 41 men participated in this cross-sectional study. There were 142 women and 18 men with prevalent vertebral fractures, and 185 women and 21 men with prevalent non-vertebral fractures. RESULTS: In women multivariable regression analysis showed that iliocostal distance was negatively associated with the number of vertebral fractures (-0.18, CI: -0.27, -0.09; adjusted for bone mineral density at the Ward's triangle, epilepsy, cerebrovascular disease, inflammatory bowel disease, etidronate use, and calcium supplement use) and for the number of non-vertebral fractures (-0.09, CI: -0.15, -0.03; adjusted for bone mineral density at the trochanter, cerebrovascular disease, inflammatory bowel disease, and etidronate use). However, in men, multivariable regression analysis did not demonstrate a significant association between iliocostal distance and the number of vertebral and non-vertebral fractures. CONCLUSIONS: The examination of iliocostal distance may be a useful clinical tool for assessment of the possibility of vertebral fractures. The identification of high-risk patients is important to effectively use the growing number of available osteoporosis therapies.

Journal Article↗
PubMed2002

Origins and consequences of mitochondrial decline in nucleated erythrocytes.

Cellular aging in nucleated erythrocytes from lower vertebrates is accompanied by losses in mitochondria but it remains unclear (i) how these losses accrue (ii) if these changes alter energetics and (iii) whether such changes increase the propensity for apoptosis. We addressed these questions using trout erythrocytes that were separated into age classes using inherent differences in buoyant density. The oldest cells showed a profound decline in mtDNA transcripts, due to reductions in both transcription (90% decline in total RNA) and mtDNA copy number (35%). No alterations in the ratio of 16S rRNA to COX I mRNA were detected, nor was there an accumulation of unprocessed mtDNA transcripts. While older cells had reduced basal respiration, there were no changes in mitochondrial enzymes stoichiometries, tissue ATP levels or dinitrophenol-induced (maximal) respiration rates. Apoptosis could not be induced in either whole blood, young or old erythrocytes by pro-oxidants, mitochondrial inhibitors or staurosporine. In contrast, cyclosporin A (CsA) caused caspase 3 activation, DNA laddering and LDH leakage, but only in young cells. Both CsA and a combination of azide, oligomycin and dinitrophenol cause mitochondrial depolarization and caspase 9 activation, but only CsA induced caspase 3 and apoptosis. Caspase inhibitor studies support the conclusion that mitochondrial changes may accompany CsA-induced cell death, but are not essential in its progression. While pifithrin failed to induce cell death, it enhanced the effects of CsA, implicating a role for p53. Collectively, these studies suggest that the mitochondrial changes with aging do not compromise cellular function, although trout erythrocytes can initiate apoptosis by non-mitochondrial pathways.

Animals↗
PubMed2000

Introduction to Bayesian modelling in dental research.

OBJECTIVE: To explain the concepts and application of Bayesian modelling and how it can be applied to the analysis of dental research data. BASIC DESIGN: Methodological in nature, this article introduces Bayesian modelling through hypothetical dental examples. SETTING: The synthesis of RCT results with previous evidence, including expert opinion, is used to illustrate full Bayesian modelling. Meta-analysis, in the form of empirical Bayesian modelling, is introduced. An example of full Bayesian modelling is described for the synthesis of evidence from several studies that investigate the success of root canal treatment. Hierarchical (Bayesian) modelling is demonstrated for a survey of childhood caries, where surface data is nested within subjects. RESULTS: Bayesian methods enhance interpretation of research evidence through the synthesis of information from multiple sources. CONCLUSIONS: Bayesian modelling is now readily accessible to clinical researchers and is able to augment the application of clinical decision making in the development of guidelines and clinical practice.

Bayes Theorem↗
PubMed2000

Introduction to multilevel modelling in dental research.

OBJECTIVE: To explain the concepts and application of multilevel modelling (MLM) and how it can be applied to the analysis of dental research data. BASIC DESIGN: Methodological in nature, this article introduces MLM through actual and hypothetical dental examples. SETTING: Examples of MLM in periodontal research illustrate cross-sectional and longitudinal analyses of hierarchical dental data. Multilevel multivariate modelling is illustrated by an example in orthodontic research. The potential implications of study design in the context MLM is extensively discussed, including study sample size and accounting for examiner variability. RESULTS: The fine detail and greater insight provided by MLM enables dental researchers to review and revise old hypotheses and to generate new ones that could not be addressed by single-level methods. CONCLUSIONS: MLM has the potential to increase our understanding of oral disease and health and offers the opportunity to rethink some aspects of dental research procedure.

Analysis of Variance↗
PubMed1999

Alkaline phosphatase activity is upregulated in regenerating human periodontal cells.

The activity of alkaline phosphatase (ALP) is considered to indicate the presence of osteoblast cells and the formation of new bone. In the present study this enzyme was investigated in cells obtained from retrieved polytetrafluoroethylene membranes (M cells) of periodontal disease patients treated by guided tissue regeneration (GTR) and from the regenerated tissue underlying the membrane (RT cells). Normal periodontal ligament (PL) and gingival cells were also grown from the corresponding healthy tissues of human subjects. ALP activity was measured colourimetrically, using paranitrophenyl phosphate as the substrate, after 4 and 7 d of culture in the absence and presence of dexamethasone (DEX), a synthetic glucocorticoid which induces osteoblast differentiation. The results showed that basal levels of ALP activity were expressed by all the cells and that DEX upregulated ALP levels in the M, RT and PL cells but not in the gingival cells. Moreover, both the basal and DEX-induced ALP activities were statistically significantly higher in the RT cells than in any of the other cells. Our results suggest that both the GTR-associated and normal PL cells express osteoblast-like characteristics and, furthermore, that the RT cultures in particular contain a high proportion of osteoprogenitor cells.

Adolescent↗
PubMed1999

36 month intermittent cyclical etidronate treatment in patients with established corticosteroid induced osteoporosis.

OBJECTIVE: To determine the longterm safety and efficacy of etidronate therapy in patients in whom corticosteroid induced bone loss has already occurred. METHODS: We performed a 36 month observational cohort study in which all data were obtained from Canadian Database of Osteoporosis and Osteopenia (CANDOO) patients. The etidronate group consisted of 24 patients who received 400 mg of etidronate disodium for 14 days, followed by 76 days of calcium carbonate (500 mg of elemental calcium), repeated every 3 mo; the control group included 37 patients who received calcium carbonate 500 to 1000 mg daily. Outcome measurements included changes within groups from baseline and differences between groups in the bone mineral density (BMD) of the lumbar spine, femoral neck, and trochanter at 12, 24, and 36 months. The incidence of vertebral fractures was also determined. RESULTS: Etidronate therapy resulted in a meaningful percentage increase from baseline in lumbar spine BMD, primarily during the first 24 months of treatment, and this increase was sustained for the remainder of the 36 month study period (5.2%; p = 0.016). Analysis of covariance revealed a significant percentage difference (SD) between groups in lumbar spine BMD at 12 [5.5 (13.5) percent; p = 0.003] and 24 months [6.0 (17.4) percent; p = 0.011] in favor of the etidronate group. After 3 years of therapy, one patient (4%) experienced one vertebral fracture in the etidronate group, whereas 3 patients (8%) experienced 5 vertebral fractures in the control group. CONCLUSION: Etidronate treatment administered for 36 months reversed lumbar spine bone loss, and appeared to be safe in patients with established corticosteroid induced osteoporosis.

Adrenal Cortex Hormones↗
PubMed1998

Evaluation of osteocalcin and pyridinium crosslinks of bone collagen as markers of bone turnover in gingival crevicular fluid during different stages of orthodontic treatment.

Osteocalcin (Oc) and the collagen cross-links pyridinoline (Pyr) and deoxypyridinoline (dPyr) are used as markers of bone turnover in metabolic bone diseases. The aims of this study were: 1) to establish if Oc, Pyr and dPyr can be detected in GCF and 2) using the orthodontic tooth movement model of alveolar bone resorption to evaluate GCF levels of osteocalcin and these collagen cross-links as markers of bone breakdown. Plaque, colour and bleeding indices, probing measurements and GCF samples were collected at two sites in each of 20 adolescents, during 4 stages of fixed appliance therapy: (1) prior to appliance fit, (2) post appliance fit, (3) during active retraction of the maxillary canines, (4) during retention. GCF was collected onto filter paper strips and the volume determined by weighing. An ELISA kit was used for the detection of osteocalcin, whereas Pyr and dPyr were assayed using high performance liquid chromotography (HPLC). Wilcoxon signed ranks test and Bonferroni correction revealed statistically significant increases in plaque (p= 0.012), GCF volume (p=0.024) and osteocalcin concentration (p=0.012), between stages 1 and 2. There were no statistically significant differences between the other variables at this stage or between any of the variables at stages 2 and 3, or between stages 3 and 4. All but 3 of the GCF samples yielded detectable osteocalcin, with large site and subject variation. The median values of osteocalcin and osteocalcin concentration of all the samples were 87.5 pg and 66 pg/microl, with a range of 0-1,248 pg, 0-1,572 pg/microl. The detection of osteocalcin in GCF during every stage, the wide variation between subjects, and the lack of a consistent pattern related to stages of orthodontic treatment, suggests that osteocalcin may merely be a constituent of GCF associated with the developing dentition, which would reduce its potential as a marker of bone turnover in this group. None of the 16 GCF samples analysed for Pyr and dPyr gave a positive result. This study confirms that fitting an orthodontic appliance results in plaque accumulation and increased gingival inflammation, and that GCF volume is the most sensitive indicator of that inflammation. Osteocalcin was detected in GCF collected from adolescents, whereas Pyr and dPyr could not be detected. Further work is required to establish whether GCF osteocalcin levels can be used as a marker of bone turnover, and whether improvements in the sensitivity of detecting Pyr & dPyr make further study of these promising bone markers worthwhile.

Adolescent↗
PubMed1997

In vitro accuracy and reproducibility of automated and conventional periodontal probes.

The aim of this study was to investigate the accuracy and reproducibility of experienced and inexperienced examiners using 3 automated periodontal probes (Florida Pocket Probe, Florida Disk Probe, Peri Probe) in comparison with 3 conventional periodontal probes (Marquis, Williams and EN-15 probes). Test blocks of aluminium had 30 holes of diameter 1.10 mm and depths ranging from 2.75 to 10.0 mm. machined with a tolerance of +/- 0.01 mm. 8 experienced examiners and 8 inexperienced examiners were selected to perform duplicate measurements on the blocks over 6 visits using each of the 6 probes. 1 automated and 1 conventional probe were used at each examination. The % accuracy and reproducibility for each of the duplicate measurements was calculated and analysed using Friedman 2-way analysis of variance and the Wilcoxon matched pairs test. On average, all probes showed high reproducibility, with the Florida Disk Probe, the Florida Pocket Probe and the Williams probe ranked best and the other 3 probes were less reproducible. On average, all probes showed a high degree of accuracy, automated probes were ranked best and were significantly better than conventional probes. Experience had little effect on reproducibility, with only the Peri Probe showing significant differences at the 5% level between the groups. Experience appeared to be more important for accuracy, as experienced examiners were more accurate than inexperienced examiners, with significant differences at the 5% level for the EN-15, Florida Disk Probe and Peri Probe. However, inexperienced examiners were significantly more accurate using the Williams probe. This in vitro study has shown that automated probes offer increased accuracy over conventional probes and the Florida Pocket and disk probes compare well with conventional probes for reproducibility.

Adult↗
PubMed1992

Protein A-calmodulin fusions: a novel approach for investigating calmodulin function in yeast.

A novel gene fusion approach which may be of more general use has been developed for investigating the function of calmodulin in the budding yeast Saccharomyces cerevisiae. By fusing a portion of the Staphylococcus aureus spa gene (encoding protein A) to CMD1, the S. cerevisiae gene encoding calmodulin, we have generated a yeast calmodulin with an affinity tag able to bind immunoglobulins. The chimaeric protein A-calmodulin (ProtA-CaM) polypeptide functions in vivo and shows Ca(2+)-dependent binding to calmodulin target proteins. The spa-CMD1 fusion has been used (i) to prepare (by affinity chromatography) a fraction of yeast proteins which interact with calmodulin, (ii) to isolate genes encoding calmodulin target proteins by direct screening of an expression library, and (iii) to visualize calmodulin-binding proteins in crude extracts by Western blot analysis.

Amino Acid Sequence↗
PubMed1991

Promotion of visual development of severely visually impaired babies: evaluation of a developmentally based programme.

A developmentally based programme (PVD) to promote the visual development of babies with severe visual impairment was evaluated in 58 infants aged between one month and 13 months of age. Progress in nine aspects of visual development was significantly greater for babies receiving the programme. This benefit extended to those with severe learning disability, or with minimal or apparently no vision at entry. The PVD favourably influenced visual outcome when introduced at any time during the first 13 months of life, although earlier introduction enabled greater benefit to be derived from the improved vision. Therefore, it is recommended that infants are referred to a developmental centre as soon as severe visual impairment is suspected.

Attention↗
PubMed1984

Optimum weights for commercial divers.

Obesity is one of the factors which increase the risk of decompression sickness. It has been suggested that any diver whose weight is more than 20% in excess of that derived from currently accepted tables should therefore be stopped from diving until he has lost enough weight. Published tables of average and standard weights for men, however, are unsuitable for application to men recruited for commercial diving, as the populations on which the tables were based differ in important respects from divers. Furthermore, the tables may assume that men are weighed and measured clothed and in shoes, whereas in most medical examinations the measurements are made on men without shoes and partially clad . Analysis of weight measurements of 1520 divers whose records are in the Decompression Sickness Central Registry in Newcastle upon Tyne suggests that divers as a group are substantially heavier than other populations on whom height-weight tables have been based. A table derived from American data of 1935-53 is often used as a guide. If this table is used the percentage of divers rejected as overweight may be as high as 13.6%. More recent and more appropriate data on heights and weights are required for use as reference standards for divers, or perhaps another measurement indicating obesity should be used.

Adult↗
PubMed1983

Lung cancer associated with chloromethyl methyl ether manufacture: an investigation at two factories in the United Kingdom.

The prevalence of deaths from lung cancer, other cancer, and all other causes was studied in workers and former workers at two factories (A and B) in the United Kingdom at which chloromethyl methyl ether has been manufactured, at one since about 1948 and at the other since 1956. At factory A in South Wales 571 men were traced and at factory B in the north east of England 1196. A statistically significant excess of observed deaths from lung cancer but not other cancer compared with the number expected was found in factory A when the death rates for the population of Glamorgan were applied. The deaths from lung cancer at factory A were related to risk in terms of total exposure time, and average exposure rate and dosage. The degree of exposure was more important than the duration of exposure. There has so far been no demonstrable excess of deaths from lung cancer in employees working at factory A since the process was changed in 1972. In factory B the risk was low over the whole period, and there was no excess of lung or other cancers compared with the rates for the Tyneside conurbation. Despite improvements in the process in both factories continued surveillance of the workers is needed for some years yet.

Adolescent↗
PubMed1982

Serum levels of C-reactive protein in Crohn's disease and ulcerative colitis.

Prospective measurements were made of serum C-reactive protein levels and erythrocyte sedimentation rate in sixty-four patients with Crohn's disease and fifty with ulcerative colitis. The results were related to clinical assessment of disease activity. C-reactive protein levels were raised in both groups but were significantly higher in Crohn's disease than ulcerative colitis for all categories of disease severity: with mild disease the median and range of C-reactive protein concentration were 4, 0-65 mg/l in Crohn's disease v. 0, 0-15 mg/l in ulcerative colitis, P less than 0.01; in moderate disease the values were 15, 1-100 mg/l v. 3, 0-29 mg/l respectively, P less than 0.05 and in cases of severe disease, 85, 15-183 mg/l v. 12, 2-33 mg/l respectively, P less than 0.001. Erythrocyte sedimentation rate was also higher in Crohn's disease but did not closely reflect disease activity in individual patients. C-reactive protein levels corresponded closely with clinical and pathological indices of relapse, remission and response to therapy in patients with Crohn's disease. The precise assay of serum C-reactive protein provides an objective criterion of inflammatory activity, which may be useful in the assessment, management and study of Crohn's disease.

Adolescent↗
PubMed1982

Exploratory electromyography in the study of vibration-induced white finger in rock drillers.

Electrophysiological observations made in the hands of a group of 16 rock-drillers were compared with 15 controls. Motor and sensory conduction velocities in the median and ulnar nerves together with the latency, duration, and amplitude of the evoked action potentials were measured. The differences between the groups were statistically significant mainly in latency, duration, and amplitude, especially of the sensory action potentials. Measurement of the conduction velocities, in general, proved to be less sensitive, and the only significant change observed was in the sensory conduction velocity in the median nerve when the first digit in the right hand was stimulated. The most interesting result was evidence of an increased prevalence of possible carpal tunnel syndrome in the exposed (44% compared with 7% in the control group). A similar set of data, but exclusively sensory and not standardised for age and sex, was obtained from 25 university students for comparison with the assigned groups. The results showed that apart from sensory duration the control group had values that were closest to the students while the vibration group had values furthest away.

Adult↗