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P Barber

Publications and source records attributed to P Barber.

At least 19 recordsLinked to original sources
PubMed2006

Technique for measurement of fluorescence lifetime by use of stroboscopic excitation and continuous-wave detection.

A study of the practicality a simple technique for obtaining time-domain information that uses continuous wave detection of fluorescence is presented. We show that this technique has potential for use in assays for which a change in the lifetime of an indicator occurs in reaction to an analyte, in fluorescence resonance energy transfer, for example, and could be particularly important when one is carrying out such measurements in the scaled-down environment of a lab on a chip (biochip). A rate-equation model is presented that allows an objective analysis to be made of the relative importance of the key measurement parameters: optical saturation of the fluorophore and period of the excitation pulse. An experimental demonstration of the technique that uses a cuvette-based analysis of a carbocyanine dye and for which the excitation source is a 650 nm wavelength, self-pulsing AlGaInP laser diode is compared with the model.

Algorithms↗
PubMed2004

Root canal obturation by ultrasonic condensation of gutta-percha. Part II: an in vitro investigation of the quality of obturation.

AIM: To compare the quality of root canal obturation using ultrasonic or cold condensation of gutta-percha and to determine the effect of power setting and activation time on the quality of obturation using the former technique. METHODOLOGY: An extracted human maxillary canine was used in an in vitro split tooth model to allow repeated obturation of the same root canal system using an ultrasonic device to thermocompact gutta-percha without sealer. After each obturation, the root filling was removed from the tooth to allow evaluation of its quality and for the tooth to be re-obturated. The influence of combinations (n = 10 per combination) of power setting (1, 3, 5) and activation times (4, 10, 15 s) was tested on the quality of root filling, assessed by measuring the voids within the body of the root filling as well as at the surface. Image analysis was used to quantify the voids within the body of the root filling. Cold lateral condensation of gutta-percha served as a control. RESULTS: Both surface and cross-sectional analyses revealed that different power setting and activation time combinations produced significantly fewer voids than cold lateral condensation (P < 0.05) at the apical, mid-root and coronal levels. CONCLUSIONS: Taking surface and cross-sectional analysis together only power setting 5 and activation times of 10 and 15 s consistently produced ultrasonically thermocompacted root canal fillings with fewer voids than cold lateral condensation without sealer.

Cold Temperature↗
PubMed2002

Differential gene expression in rats following subacute exposure to the anticonvulsant sodium valproate.

Sodium valproate (VPA) is clinically employed as an anticonvulsant and, to a lesser extent, as a mood stabilizer. While the incidence of toxicity associated with the clinical use of valproate is low, serious hepatotoxicity makes up a significant percentage of these rare adverse effects, with fatalities occurring mainly in children receiving polypharmacy. Previous studies have highlighted the different pharmacological effects of acute valproate exposure, a combination of which are likely to underpin its observed broad-spectrum anticonvulsant efficacy. However, limited studies have been undertaken to investigate the subacute effects of this compound and how genomic effects may underlie the observed hepatotoxic effects. Investigation into the mild hepatoxicity observed in rats exposed to high doses of VPA may provide important information on the human situation. Male Sprague-Dawley rats were dosed with 500 mg/kg/day sodium valproate: after necropsy, mRNA was subjected to suppression PCR subtractive hybridization, identifying 8 up-regulated and 14 down-regulated mRNA species. The down-regulation of several mRNA species coding for enzymes involved in cellular energetics (e.g., succinate dehydrogenase, aldolase B) was of particular interest, as mitochondrial dysfunction is a key feature of valproate hepatotoxicity. In vitro studies were then undertaken to examine the dose and time dependence of these changes and also their effect on the overall energy levels within the cell. We demonstrate that, both in vivo and in vitro, valproate exposure in rats results in a significant decrease in pathways involved in cellular energy homeostasis. These changes may provide insight into the rare human hepatoxicity associated with this compound.

Animals↗
PubMed2002

Smoking in young adolescents: an approach with multilevel discrete choice models.

STUDY OBJECTIVE: To understand the context for tobacco smoking in young adolescents, estimating the effects of individual, family, social, and school related factors. DESIGN: Cross sectional analysis performed by multilevel logistic regression with pupils at the first level and schools at the second level. The data came from a stratified sample of students surveyed on their own, their families' and their friends' smoking habits, their schools, and their awareness of cigarette prices and advertising. SETTING: The study was performed in the Island of Gran Canaria, Spain. PARTICIPANTS: 1877 students from 30 secondary schools in spring of 2000 (model's effective sample sizes 1697 and 1738). MAIN RESULTS: 14.2% of the young teenagers surveyed use tobacco, almost half of them (6.3% of the total surveyed) on a daily basis. According to the ordered logistic regression model, to have a smoker as the best friend increases significantly the probability of smoking (odds ratio: 6.96, 95% confidence intervals (CI) (4.93 to 9.84), and the same stands for one smoker living at home compared with a smoking free home (odds ratio: 2.03, 95% CI 1.22 to 3.36). Girls smoke more (odds ratio: 1.85, 95% CI 1.33 to 2.59). Experience with alcohol, and lack of interest in studies are also significant factors affecting smoking. Multilevel models of logistic regression showed that factors related to the school affect the smoking behaviour of young teenagers. More specifically, whether a school complies with antismoking rules or not is the main factor to predict smoking prevalence in schools. The remainder of the differences can be attributed to individual and family characteristics, tobacco consumption by parents or other close relatives, and peer group. CONCLUSIONS: A great deal of the individual differences in smoking are explained by factors at the school level, therefore the context is very relevant in this case. The most relevant predictors for smoking in young adolescents include some factors related to the schools they attend. One variable stood out in accounting for the school to school differences: how well they enforced the no smoking rule. Therefore we can prevent or delay tobacco smoking in adolescents not only by publicising health risks, but also by better enforcing no smoking rules in schools.

Adolescent↗
PubMed2000

Clinical and quality of life outcomes in the first United Kingdom randomized trial of endobronchial brachytherapy (intraluminal radiotherapy) vs. external beam radiotherapy in the palliative treatment of inoperable non-small cell lung cancer.

BACKGROUND AND PURPOSE: A randomized controlled trial was designed to evaluate the clinical and quality of life (QL) outcomes of patients receiving endobronchial brachytherapy (EBT) or external beam radiotherapy (XRT) as a primary palliative treatment in advanced lung cancer. MATERIALS AND METHODS: Ninety-nine patients presenting de novo with lung cancer were randomized to receive EBT or XRT. Eleven key symptoms or clinical signs were assessed by clinicians and patient ratings using self-assessment questionnaires were obtained at the same time. The primary endpoints were a comparison of EBT and XRT for symptom relief and acute and late side-effects (palliation) and their effect on patients' functional status and patient-rated QL outcomes. A secondary objective was a comparison of clinician assessments with patient self-reported symptoms. RESULTS: Both treatments produced good levels of symptom relief. They were better for XRT at the expense of more acute morbidity. Late side-effects were similar. The functional status of patients was well maintained and changed similarly with time in both groups. XRT gave a better duration of palliation. Twenty-eight percent of XRT patients required EBT (at a median time of 304 days) whereas 51% of EBT patients subsequently had XRT (at a median of 125 days). There was a significant modest gain in median survival with initial XRT (287 vs. 250 days). When clinician and patient assessments were compared, doctors were found to underestimate the severity of breathlessness, anorexia, tiredness and nausea. CONCLUSIONS: Fractionated XRT is preferred to EBT as an initial treatment in better performance patients because it provides better overall and more sustained palliation with fewer retreatments and a modest gain in survival time. QL assessment is required in the evaluation of palliative treatments because clinicians frequently underestimate the incidence and severity of key symptoms.

Adult↗
PubMed2000

Spinal teratoma: is there a place for adjuvant treatment? Two cases and a review of the literature.

Spinal teratomas are rare intradural spinal tumours, commonly of benign histological profile. The main treatment remains surgical excision which often is incomplete as the tumour is frequently intimately related to surrounding nerve roots and adjacent spinal cord. The value of adjuvant treatment in the form of radiotherapy has not been clearly identified. We report two patients with spinal teratomas in the lower thoracic and conus region, who were treated with surgical excision and did not receive radiotherapy. One of the tumours recurred at 38 months following surgical excision and required a second operation. We review in addition another 20 patients reported in the literature with such tumours. With a mean follow-up of 25 months a local recurrence rate of 10% was observed, the same in both total and subtotal excision groups. No deaths were reported. Analysis of cumulative survival from surgery to treatment failure demonstrated that recurrence occurs late, verifying a slow biological progression of this tumour type. Although no reliable information of the effect of radiotherapy can be obtained, it is difficult to see how radiotherapy could have an impact on such a slow growing tumour. Initial treatment of choice remains surgical excision. If the teratoma shows any malignant histological features or germ cell elements radiotherapy should be employed after surgical excision, even if apparently totally excised. In the presence of benign histology it would seem appropriate to avoid radiotherapy after initial surgery. In case of tumour recurrence or progression to explore the possibility of further surgery first, before considering radiotherapy which even then may have doubtful efficacy.

Female↗
PubMed1999

Transport and temperature effects on measurement of serum and plasma potassium.

Transport of blood samples from general practice to a central laboratory can result in spuriously high or low potassium concentrations. The importance of this phenomenon was studied in a general practice serving a population of 15,000 patients, 27 km from the pathology laboratory that routinely measured serum potassium. The design involved comparison of potassium levels between control serum (plain gel-separation serum tubes centrifuged in the surgery), routine serum (plain gel-separation tubes centrifuged in the laboratory) and routine plasma samples (lithium-heparin tubes centrifuged in the laboratory). Complete triple sets of data were obtained for 371 samples. Altman and Bland plots for the control serum vs routine serum samples showed a mean difference of +0.1 mmol/L with limits of agreement (+/- 2SD) +0.6 mmol/L, -0.4 mmol/L and for control serum vs routine plasma a mean difference of +0.2 mmol/L with limits of agreement +0.8 mmol/L, -0.4 mmol/L. There was a negative association between mean weekly routine plasma potassium levels with mean weekly temperatures achieved. Regression analysis indicated that both maximum temperature achieved and time to centrifugation significantly contributed to differences observed in the routine plasma samples, but not with the routine serum samples. For plasma samples exposed to high temperatures a clinically significant lowering of potassium concentrations can arise. These results confirm that spurious lowering of potassium concentrations occurs in plasma samples collected in a primary care setting. The preferred method is to centrifuge samples soon after venepuncture. Where this is not possible, collection into plain gel-separation tubes (serum) ensures less variation due to temperature and time to centrifugation than does collection into lithium-heparin tubes (plasma).

Blood Preservation↗
PubMed1998

Central neurocytoma: a correlative clinicopathologic and radiologic analysis.

BACKGROUND: Central neurocytoma was described as a well differentiated tumor of neuronal origin, distinct from ganglion cell tumors and neuroblastoma. An initially perceived benign biologic behavior has been questioned by subsequent reports of anaplastic and recurrent tumors. We report six cases of central neurocytoma, with variable clinical and pathologic features that stimulate discussion on the management of these tumors. METHODS: Of the 95 oligodendrogliomas treated in our institution in the last 40 years, three tumors were reclassified as central neurocytomas on histologic reappraisal. Three additional cases prospectively diagnosed as central neurocytomas are reported. The clinical, pathologic, and radiologic features are reviewed. RESULTS: Early recurrence, not related to malignant histologic features, was noted in two patients who had not received postoperative radiotherapy. Anaplastic histologic changes were not accompanied by malignant biologic behavior in another patient. Neither patient with recurrent tumor was controlled by radiotherapy alone. Chemotherapy with carboplatin reduced tumor size temporarily in one of these patients. CONCLUSION: An entirely benign nature for this tumor is questioned and it appears that there may be malignant variants. Surgery should aim for maximum possible excision, as the location of the tumor allows. The role of postoperative radiotherapy remains controversial and may be considered in cases of subtotal excision of tumors with anaplastic histologic features. Chemotherapy may be of benefit in cases recurring despite surgery and radiotherapy.

Adolescent↗
PubMed1998

The self-reported well-being of employees facing organizational change: effects of an intervention.

The objective of this study was to investigate the self-reported well-being of employees facing organizational change, and the effect of an intervention. It was a controlled intervention study. Subjects were allocated to study and control groups, and brief individual counselling was offered to the subjects in the study groups. Questionnaire measures were administered before and after counselling (a 3-month interval), and non-counselled subjects also completed questionnaires at the same times. The setting was 15 estate offices in an urban local authority Housing Department. Subjects comprised the total workforce of the Housing Management division: 193 employees, male and female, aged 22-62 years, facing compulsory competitive tendering between 1994-97. Main outcome measures were baseline and comparative measures of psychological morbidity, including the General Health Questionnaire (GHQ) and the Occupational Stress Indicator (OSI). Questionnaire response rates were 72% and 47% on first and second occasions respectively. The uptake of counselling was 37%. In comparison with (1) the UK norms for the OSI and (2) the norms for a similar occupational group, this group of workers were under more work-related pressure and their self-reported health was markedly poorer. They were not however at a disadvantage in terms of coping strategies. Those accepting the offer of counselling were subject to greater levels of work stress, had poorer self-reported health and markedly lower levels of job satisfaction than those who did not. Questionnaire scores were not significantly different before and after counselling, giving no evidence of treatment effects on symptomatology. However, almost all subjects rated counselling as having been extremely helpful. This study suggests that adverse effects on staff facing organizational change may be ameliorated by improved management practice.

Adult↗
PubMed1997

A review of 105 negligence claims against accident and emergency departments.

OBJECTIVE: To examine 105 successive negligence claims against NHS accident and emergency (A&E) departments in the United Kingdom and to highlight risk management points. METHODS: A systematic review of sociodemographic, clinical, and legal issues was conducted on each claim. RESULTS: 54 claims involved the missed diagnosis of a fracture because of failure to x ray or to interpret the films correctly; 27 claims alleged a missed or delayed diagnosis other than fracture and were mainly due to incomplete clinical examination or failure to x ray or to interpret the films correctly; 24 claims alleged clinical mismanagement in the A&E department; in 82 claims (78%) an SHO was allegedly responsible for the mistake. By the end of August 1996, 92 claims (87.6%) had been closed, of which 38 had been settled out of Court and 54 had not been pursued by the patient after disclosure of the records and--where appropriate--a repudiation of liability. Of the 13 claims remaining open, seven are considered to be defensible and six will have to be settled. CONCLUSIONS: SHOs employed in A&E departments need careful training and supervision, with ready access to senior medical advice, both clinical and radiological. Most errors leading to claims appear in retrospect to have been simple failures of history taking, physical examination, interpretation of radiographs, and communication. Poor quality notes imply substandard care. About half the claims were found to be indefensible.

Adolescent↗
PubMed1997

Validation of current practice and a near patient testing method for oral-anticoagulant control in general practice.

When oral anticoagulant control is monitored in general practice, venous blood samples are usually transported to a central laboratory for determination of international normalized ratio (INR). An alternative is near patient testing by a commercial method. In a rural general practice 27 km from a central haematology laboratory, whole blood samples were drawn from patients receiving oral anticoagulants and analysed by three methods: after centrifugation, plasma separated and frozen in liquid nitrogen, transported to the laboratory, thawed and immediately analysed (control); courier transport of citrated sample to the laboratory for analysis (routine); near patient testing of whole blood sample (NPT). Maximum temperature achieved and time to analysis for routine samples were recorded. 306 complete sets of data were obtained. Comparison between the routine method and the control method revealed acceptable agreement. On multiple regression analysis, maximum temperature achieved did not contribute to differences observed but time to analysis of over 5 hours did make a significant contribution. Comparison between the NPT method and control method showed acceptable agreement, with persistent under-recording by the NPT method. The routine method for INR determination was validated as robust and reproducible with the proviso that needle-to-analysis time should be kept below 5 hours. The NPT method was valid under conditions of normal general practice. Strict quality control of NPT methods is essential if performance is to be comparable with that of established methods.

Anticoagulants↗
PubMed1996

Paediatric meningeal tumours.

We review our experience of meningeal tumours in patients under 16 years who were treated between 1957 and 1993. These were 16 with meningiomas (median age 12 years) and 5 with poorly differentiated malignant meningeal tumours (median age 3 years). The incidence of meningeal tumours in this period was 1.62% of all CNS tumours. There were 19 supratentorial tumours (5 intraventricular), 1 tentorial and 1 cervical. Surgical excision was complete in 12 patients and incomplete in 6; in 2 patients a biopsy only was undertaken. The remaining patient had radiological diagnosis only. All 5 patients in the group with malignant poorly differentiated tumours died (median survival 5 months), confirming the aggressive nature of these lesions. Of the 16 patients with meningiomas, 4 died during followup but 11 of the 12 meningioma patients remaining alive had complete resections. There is a strong tendency for paediatric meningeal tumours to have a supratentorial origin and intraventricular location. The female preponderance found in adults is not evident in children. Incomplete surgical excision or focal neurological deficit at presentation was associated with poor outcome.

Adolescent↗