PubMed Health⌕ Search

Biomedical subjects

R Fletcher

Publications and source records attributed to R Fletcher.

At least 19 recordsLinked to original sources
PubMed2003

Diffusion thermopower of a two-dimensional hole gas in SiGe in a quantum Hall insulating state.

Both the temperature dependence of resistivity and thermopower of a two-dimensional hole gas in SiGe show a reentrant metal-insulator transition at filling factor nu=1.5, but with strikingly different behavior of the two coefficients. As the temperature is decreased in the insulating state, the resistivity diverges exponentially while the thermopower decreases rapidly, suggesting that the insulating state is due to the presence of a mobility edge rather than a gap at the Fermi energy.

Journal Article↗
PubMed2003

Gyrus bipolar electrovaporization vs transurethral resection of the prostate: a randomized prospective single-blind trial with 1 y follow-up.

The Gyrus system uses bipolar electrocautery with saline irrigation to vaporize prostatic tissue and is compared to transurethral resection of the prostate (TURP) in a randomized prospective study with 1 y follow-up. Outcomes measured were fluid absorption, blood loss, period of catheterization, hospital stay, symptom scores, quality of life, flow rates, and post-void residual volumes at 3, 6, and 12 months. All measured parameters were similar, although re-catheterization rates were higher (30% vs 5%) in the Gyrus group. Clot evacuation rates were higher in the TURP group (19% vs 0%). The Gyrus device is safe and produces results that are similar to TURP at 1 y.

Aged↗
PubMed2003

Preliminary evaluation of a scale to assess cognitive function in adults with Down's syndrome: the Prudhoe Cognitive Function Test.

BACKGROUND: In the clinical diagnosis of dementia in Down's syndrome (DS), it may be difficult to distinguish between cognitive deterioration and the various degrees of pre-existing intellectual disability (ID). Serial measurements of both cognitive function and behaviour are required. The aim of the present study was to evaluate the performance of non-demented adults with DS on a subject-directed instrument, the Prudhoe Cognitive Function Test (PCFT), preliminary to its serial use in a prospective study. METHODS: From 1985 to 1986, 85 non-demented hospitalized adults with DS were interviewed using the PCFT. The Adaptive Behavior Scale (ABS) was administered to the carers. The subjects' levels of ID (graded from mild through moderate, severe and profound to untestable) were based on their scores on the Stanford-Binet Intelligence Scale, as reported in the medical records, and the relationship between level of disability and performance on the PCFT and ABS, and their respective domains, was examined. RESULTS: Both scales produced a wide range of scores and the correlation between them was highly significant. Both scales correlated highly significantly with the degree of ID, but more subjects with high levels (i.e. profound to untestable) of disability obtained very low or zero scores on the PCFT and its domains than on the ABS. CONCLUSIONS: The PCFT provides a reliable quantitative measure of cognitive function in subjects with DS, and could be a useful adjunct to the diagnosis of dementia in prospective studies. However, the almost uniformly low scores obtained by those with high levels of ID suggests that its power to detect cognitive decline will be limited to those who are less disabled, while the ABS may be more useful than the PCFT in detecting deterioration in people with profound ID.

Adult↗
PubMed2001

Phosphorylation and local presynaptic protein synthesis in calcium- and calcineurin-dependent induction of crayfish long-term facilitation.

Long-term facilitation at the crayfish opener muscle is elicited by prolonged high frequency stimulation, and arises from an increase in functional active zones, resulting in increased transmitter release. LTF induction depends critically upon presynaptic calcium accumulation and calcineurin (PP2B) activity. The protein synthesis dependence of this synaptic strengthening was investigated. LTF occurred without transcription, but the translation inhibitors cycloheximide and anisomycin, or local presynaptic injection of mRNA cap analog m7GpppG, impaired LTF expression. Both MAP kinase and phosphatidylinositol 3-OH kinase (PI3K) activation are implicated in this rapamycin-sensitive synaptic potentiation. This study defines an important role for protein synthesis in the expression of activity-dependent plasticity, and provides mechanistic insight for the induction of this process at presynaptic sites.

Animals↗
PubMed2001

Maintenance of intact sediment box cores as laboratory mesocosms.

Mesocosms consisting of physically and biologically intact segments of natural communities are an ideal compromise between single species tests and ecosystem experiments in the assessment of sediment contamination. Therefore, large intact sediment cores, as mesocosms with naturally co-adapted communities, would allow sediment contamination to be assessed using the replicability and statistical power of laboratory techniques, while retaining much of the ecological realism of field studies. This study investigates the collection and maintenance of such cores, collected from an unimpacted site in Lake Erie. It demonstrates that box cores containing relatively undisturbed freshwater sediments can be brought back to the laboratory and maintained for up to 8 weeks with little change in the resident benthic fauna. Feeding the systems is not required, nor is it deleterious to the indigenous fauna.

Animals↗
PubMed2001

The use of benthic mesocosms for the assessment of sediment contamination.

The diagnostic capability of changes in the benthic macroinvertebrate community composition to determine the cause in contaminated sediments were addressed using box core mesocosms subjected to cadmium, atrazine and nutrient enrichment. Intact cores of lake sediment were collected from Lake Erie at four occasions during 1996 and were returned to laboratory where they were maintained and manipulated. The benthic community composition of the artificially polluted mesocosms was compared with field data, collected at the same time as the intact cores, and to untreated control boxes. Community composition was related to the measured environmental variables using multi-dimensional scaling (MDS) and principle axis correlation (PCC). Community responses to different treatments were both different and consistent, suggesting that the community structure of these mesocosms could be used to identify the primary source of impact.

Animals↗
PubMed2001

Pressure-controlled inverse ratio ventilation after cardiac surgery.

BACKGROUND AND OBJECTIVE: Pressure-controlled inverse ratio ventilation was compared with controlled mechanical ventilation in patients after cardiac surgery. METHODS: Ten patients were ventilated after sternal closure using a Siemens Servo 900C ventilator to a target end-tidal PCO2 of 4.0 kPa. They were randomized to receive controlled mechanical ventilation or pressure-controlled inverse ratio ventilation. CO2-based data were recorded on a laptop personal computer, which together with arterial PCO2 permitted measurement of the respiratory dead space. Once measurements were complete the ventilator was switched to the other mode and new measurements taken. RESULTS: PaCO2 and VCO2 were virtually the same in both modes. Peak airway pressure (17.2 +/- 2.7 vs. 20.8 +/- 2.5 cmH2O, P < 0.01) and minute ventilation (4.9 +/- 1.1 vs. 5.3 +/- 1.1 cmH2O, P < 0.01) were less during pressure-controlled inverse ratio ventilation. Physiological dead space fraction (0.39 +/- 0.06 vs. 0.51 +/- 0.05, P < 0.001), airway dead space (56 +/- 15 vs. 81 +/- 15 mL, P < 0.001) and alveolar dead space fraction (0.25 +/- 0.07 vs. 0.31 +/- 0.09, P < 0.01) were all less during pressure-controlled inverse ratio ventilation. There were no differences in heart rate or mean arterial pressure. CONCLUSIONS: The prolonged inspiratory period and pressure-controlled flow pattern of pressure-controlled inverse ratio ventilation reduce the alveolar and airway dead spaces, and give lower peak airway pressures, compared with conventional ventilation, in cardiac surgical patients.

Adult↗
PubMed2001

Arterial to end-tidal carbon dioxide tension difference in children with congenital heart disease.

In children with congenital cyanotic heart disease, right-to-left intracardiac shunting causes an obligatory difference between arterial and end-tidal carbon dioxide tension (PaCO2-PE'CO2) as venous blood, rich in carbon dioxide, is added to the arterial circulation. This obligatory PaCO2-PE'CO2 difference, which can be predicted from knowledge of oxygen saturation, haemoglobin concentration and PaCO2, increases as oxygen saturation decreases, most markedly when the haemoglobin concentration is high. A second possible cause of the PaCO2-PE'CO2 difference is the effect of pulmonary hypoperfusion caused by the shunt. We studied 60 children undergoing cardiac surgery and compared the predicted the PaCO2-PE'CO2 difference with measured values to investigate the extent to which additional factors influence the clinically observed PaCO2-PE'CO2. In many children, observed values were much greater than predicted, which is compatible with some degree of pulmonary hypoperfusion. However, this was not felt to represent the complete picture in all patients. Another cause of ventilation-perfusion mismatch was suspected in those children who showed a considerable improvement in oxygen saturation during ventilation with an increased FIO2. We believe that pulmonary congestion caused by large left-to-right shunts may further increase the PaCO2-PE'CO2 difference.

Anesthesia, General↗
PubMed2000

Comparison of human telomerase reverse transcriptase messenger RNA and telomerase activity as urine markers for diagnosis of bladder carcinoma.

BACKGROUND: Human telomerase reverse transcriptase (hTERT) has been identified as the catalytic subunit of telomerase ribonucleoprotein complex known to be required for cellular immortality and oncogenesis. Although human telomerase activity (hTA) is considered as a general marker for malignancy based on its presence in most malignant tumors including bladder cancer, its detection in urine is affected by many factors. The objective of this study was to compare the clinical utility of detecting urine hTERT messenger RNA (mRNA) by multiplex hTERT/GAPDH RT-PCR and urine hTA by telomerase repeat amplification protocol (TRAP) in the diagnosis of bladder cancer. METHODS AND RESULTS: Cystoscopy urine samples or bladder washes prospectively collected from 35 patients with confirmed (35) or clinically suspected (5) transitional cell carcinoma (TCC) of the bladder were examined by TRAP, hTERT/GAPDH RT-PCR, and urine cytology. The control group comprised 21 healthy volunteers and 3 patients without TCC. The hTERT/GAPDH RT-PCR test showed significantly higher diagnostic sensitivity than TRAP assay (94.3% vs 48.6%, P <.001) and urine cytology (95.2% vs 61.9%, P =.008) for confirmed TCCs. In particular, for superficial TCCs low grade (I-II), the hTERT/GAPDH RT-PCR test outperformed TRAP (90% vs 25%, P <.001) and urine cytology (91.7% vs 58.3%, P =.46). The overall specificity of the hTERT/GAPDH RT-PCR, TRAP and urine cytology was 92% (22/24), 100% (24/24), and 100% (3/3), respectively. A positive hTERT mRNA expression was also detected in urologic specimens from 3 patients with previous history of TCC, 3 to 6 months before cystoscopic evidence of cancer. CONCLUSION: In this pilot study, the hTERT mRNA expression in urine sediments is a more sensitive marker for diagnosis of TCC of the bladder than hTA and cytology. However, there is a higher false-positive rate.

Adult↗
PubMed2000

National crisis, supranational opportunity: the Irish construction of abortion as a European service.

In the late 1980s, the anti-abortion movement successfully sought injunctions against pregnancy counselling centres and students' unions in Ireland, preventing them from distributing information on how to obtain an abortion abroad. One of the defensive arguments that the students' unions employed was to claim that the distribution of abortion information was protected as an aspect of the free movement of services under European Community law. This paper addresses the implications of categorising abortion as a supranational economic service for feminist legal strategy. The advantages of categorising abortion as a service to which women have access as consumers are that it legitimates abortion and it provides a new strategy for making abortion claims. The disadvantages are that a woman's legal interest in abortion is based on her capacity to buy the service, fetal life is rendered devoid of value, and the service supplier has as much say about the abortion transaction as the woman consumer. If feminist legal strategy is to successfully use the legal construction of abortion as an economic service, it must work to minimise such negative implications.

Abortion, Legal↗
PubMed2000

Can we improve the estimate of arterial PCO2 from end-tidal PCO2?

To use end-tidal PCO2 as a non-invasive estimate of arterial PCO2, one adds a nominal value, representing the arterial-end-tidal PCO2 difference. How much does one add? We hypothesized that, halving the ventilator rate and simultaneously doubling tidal volume, the immediate change in end-tidal PCO2 would be proportional to the original arterial-end-tidal PCO2 difference. We ventilated 31 patients at 20 breaths per minute (bpm), sampled arterial blood, and changed the rate to 10 bpm. The change in end-tidal PCO2 was, as hypothesized, positively correlated to the original arterial-end-tidal difference at 20 bpm (r=0.64). End-tidal PCO2 increased in 23 patients. Thus, in theory, this method could offer some improvement in the estimate of arterial PCO2 from end-tidal. However, because of the considerable spread of values, a separate study is needed for verification.

Adult↗
PubMed2000

Patient participation in research in the managed care environment: key perceptions of members in an HMO.

This study's objective was to elicit the views of research among enrollees in an HMO. A questionnaire was mailed to 207 adult enrollees, 55% had been exposed to research and 45% had not. Ninety-four percent of respondents supported research within the HMO, and 87% thought using information from medical records for research was acceptable. Sixty-three percent thought participation in research increased patient understanding of health care. Significantly more prior research participants thought that participation in research improves care. More patients would participate if written information were provided (67%), if feedback of results was provided (72%), and if their clinician invited them (67%). Only a modest percentage (20%) of patients would participate in a randomized trial.

Adult↗
PubMed2000

Positive end-expiratory pressure has little effect on carbon dioxide elimination after cardiac surgery.

UNLABELLED: We investigated the effects of positive end-expiratory pressure (PEEP) on carbon dioxide (CO2) elimination in a cross-over study of 14 patients whose lungs were ventilated after cardiac surgery. They initially received either 7.5 cm H2O PEEP or zero end-expiratory pressure and were then changed over to the other mode. We measured CO2 minute elimination (Vco2) and "efficiency," a quantification of the shape of CO2 single-breath test (SBT-CO2), the plot of expired CO2 against expired volume. Vco2 and efficiency (and therefore the shape of SBT-CO2) were not significantly affected by PEEP. These results agree with findings in patients with acute lung injury, but are in contrast with those in an open-chest dog model, in which 7.5 cm H2O PEEP caused a 19% decrease in Vco2 and significant changes in SBT-CO2. IMPLICATIONS: During artificial ventilation, applying a positive pressure in expiration expands the lung and improves the uptake of oxygen, but there is a theoretical risk of reduced carbon dioxide elimination. We applied positive end-expiratory pressure to patients immediately after heart surgery and found that it has no effect on carbon dioxide elimination.

Aged↗