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Biomedical subjects

R Turner

Publications and source records attributed to R Turner.

At least 19 recordsLinked to original sources
PubMed2006

Removing the effects of CSF partial voluming on fitted CBF and arterial transit times using FAIR, a pulsed arterial spin labelling technique.

FAIR, an arterial spin labelling technique, provides non-invasive, quantitative CBF values and arterial transit times deltat. This paper focuses on the negative impact of CSF partial voluming on FAIR results. To understand and solve this problem, we performed a theoretical analysis and a range of simulations. We then acquired FAIR data from a volunteer to illustrate our findings. We found that the determinant effect of CSF is a delayed zero-crossing during inversion recovery. The subtraction of magnitude inversion recovery data in FAIR generates erroneous negative data and distorted fit results: we simulated that for CSF percentages of 0-40%, CBF and deltat will be progressively overestimated by up to 50%. For higher CSF percentages the errors were found to increase steeply. We explored a straightforward solution: taking the magnitude of the FAIR data before fitting. This provided a remarkably strong antidote against the effects of CSF partial voluming: for CSF percentages of 0-40%, simulations now gave CBF values accurate within 1%, and deltat within 5%. The fit remained robust for high CSF fractions. Our analysis and simulations demonstrate that using magnitude FAIR data minimises the detrimental effects of CSF partial voluming. Data from a healthy volunteer illustrate these results.

Artifacts↗
PubMed2006

Language control in the bilingual brain.

How does the bilingual brain distinguish and control which language is in use? Previous functional imaging experiments have not been able to answer this question because proficient bilinguals activate the same brain regions irrespective of the language being tested. Here, we reveal that neuronal responses within the left caudate are sensitive to changes in the language or the meaning of words. By demonstrating this effect in populations of German-English and Japanese-English bilinguals, we suggest that the left caudate plays a universal role in monitoring and controlling the language in use.

Adult↗
PubMed2006

Relations among questionnaire and laboratory measures of rhinovirus infection.

Due to high incidence and quality-of-life impact, upper respiratory infection substantially impacts on population health. To test or compare treatment effectiveness, a well-designed and validated illness-specific quality-of-life instrument is needed. Data reported in the current study were obtained from a trial testing echinacea for induced rhinovirus infection. Laboratory-assessed biomarkers included interleukin (IL)-8, nasal neutrophil count (polymorphonuclear neutrophils (PMN)), mucus weight, viral titre and seroconversion. The questionnaires used included the general health short form (SF)-8 (24-h recall version), the eight-item Jackson cold scale, and the 44-item Wisconsin Upper Respiratory Symptom Survey (WURSS). In total, 399 participants were inoculated with rhinovirus and monitored over 2,088 person-days. Statistically significant associations were found among nearly all variables. Between-questionnaire correlations were: WURSS-Jackson = 0.81; WURSS-SF-8 = 0.62; and Jackson-SF-8 = 0.60. Correlations with laboratory values were as follows: WURSS-mucus weight = 0.53; Jackson-mucus weight = 0.55; WURSS-viral titre = 0.37; Jackson-viral titre = 0.46; WURSS-IL-8 = 0.31; Jackson-IL-8 = 0.36; WURSS-PMN = 0.31; and Jackson-PMN = 0.28. Neither WURSS nor Jackson yielded satisfactory cut-off scores for diagnosis of infection. Symptomatic and biological outcomes of upper respiratory infection are highly variable, with only modest associations. While Wisconsin Upper Respiratory Symptom Survey and Jackson questionnaires both correlate with biomarkers, neither is a good predictor of induced infection. The inclusion of functional and quality-of-life items in the Wisconsin Upper Respiratory Symptom Survey does not significantly decrease the strength of association with laboratory-assessed biomarkers.

Adult↗
PubMed2006

Germ cell development in equine testis tissue xenografted into mice.

Grafting of testis tissue from immature animals to immunodeficient mice results in complete spermatogenesis, albeit with varying efficiency in different species. The objectives of this study were to investigate if grafting of horse testis tissue would result in spermatogenesis, and to assess the effect of exogenous gonadotropins on xenograft development. Small fragments of testis tissue from 7 colts (2 week to 4 years of age) were grafted under the back skin of castrated male immunodeficient mice. For 2 donor animals, half of the mice were treated with gonadotropins. Xenografts were analyzed at 4 and 8 months post-transplantation. Spermatogenic differentiation following grafting ranged from no differentiation to progression through meiosis with appearance of haploid cells. Administration of exogenous gonadotropins appeared to support post-meiotic differentiation. For more mature donor testis samples where spermatogenesis had progressed into or through meiosis, after grafting an initial loss of differentiated germ cells was observed followed by a resurgence of spermatogenesis. However, if haploid cells had been present prior to grafting, spermatogenesis did not progress beyond meiotic division. In all host mice with spermatogenic differentiation in grafts, increased weight of the seminal vesicles compared to castrated mice showed that xenografts were releasing testosterone. These results indicate that horse spermatogenesis occurs in a mouse host albeit with low efficiency. In most cases, spermatogenesis arrested at meiosis. The underlying mechanisms of this spermatogenic arrest require further investigation.

Animals↗
PubMed2005

Identification of respiratory isolates of Stenotrophomonas maltophilia by commercial biochemical systems and species-specific PCR.

One hundred strains of Stenotrophomonas maltophilia isolates from respiratory specimens were biochemically identified using the API 20NE strip and the VITEK2 ID-GNB card. The identification was confirmed by a species-specific PCR using two primers specific for the 23S rRNA gene. The API 20NE showed only 1 strain with "low discrimination" whereas the VITEK2 gave 12. In any case, the two biochemical systems showed good reliability compared to SS-PCR.

Bacteriological Techniques↗
PubMed2005

Hyperbaric oxygen therapy for promoting fracture healing and treating fracture non-union.

BACKGROUND: Hyperbaric oxygen therapy (HBOT) consists of intermittently administering 100% oxygen at pressures greater than one atmosphere absolute (ATA) in a pressure vessel. This technology has been used to treat a variety of diseases and has been described as helping patients who have delayed healing or established non-union of bony fractures. OBJECTIVES: The aim of this review was to assess the evidence for the benefit of hyperbaric oxygen treatment (HBOT) for the treatment of delayed bony healing and established non-union of bony fractures. SEARCH STRATEGY: We searched the Cochrane Musculoskeletal Injuries Group trials register (to January week 3, 2004), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 4, 2003), MEDLINE (OVID 1966 to January week 3, 2004), CINAHL (OVID 1982 to January week 3, 2004), EMBASE (OVID 1980 to February 2004), the locally developed Database of Randomised Controlled Trials in Hyperbaric Medicine (available at www.hboevidence.com) from inception to March 2004, and reference lists of articles. SELECTION CRITERIA: We aimed to include all randomised controlled trials that compared the effect of HBOT with no HBOT (no treatment or sham). DATA COLLECTION AND ANALYSIS: Two authors using standardised forms attempted to extract data independently. MAIN RESULTS: No trials met the inclusion criteria. We excluded one trial that compared HBOT with no treatment because no clinical outcomes were reported. AUTHORS' CONCLUSIONS: This systematic review failed to locate any relevant clinical evidence to support or refute the effectiveness of HBOT for the management of delayed union or established non-union of bony fractures. Good quality clinical trials are needed to define the role, if any, of HBOT in the treatment of these injuries.

Fracture Healing↗
PubMed2005

Exhaled breath condensate pH assays are not influenced by oral ammonia.

BACKGROUND: Measurement of pH in exhaled breath condensate (EBC) is robust and simple. Acidic source fluid (airway lining fluid) traps bases while volatilising acids, leading to EBC acidification in many lung diseases. Lower airway ammonia is one determinant of airway lining fluid pH, raising the concern that addition of the base ammonia by contamination from the mouth might confound EBC pH assays. METHODS: Three discrete methods were used to limit oral ammonia contamination of EBC collections: endotracheal intubation, oral rinsing, and -40 degrees C condenser temperatures. Separately, ammonia was removed from collected EBC samples by lyophilisation and resuspension. Intraweek and intraday variability of ammonia concentration was determined in 76 subjects, and ammonia and pH from a further 235 samples were graphically compared. Ammonia was assayed spectrophotometrically and pH was assessed after deaeration. RESULTS: Data from 1091 samples are presented. Ammonia was reduced in EBC by all methods. Endotracheal intubation decreased EBC ammonia from a mean (SD) of 619 (124) microM to 80 (24) microM (p<0.001, n=32). Oral rinsing before collection also led to a decline in EBC ammonia from 573 (307) microM to 224 (80) microM (p=0.016, n=7). The colder the condensation temperature used, the less ammonia was trapped in the EBC. Lyophilisation removed 99.4 (1.9)% of ammonia. Most importantly, the pH of EBC never decreased after removal of ammonia by any of these methods. Intraweek and intraday coefficients of variation for ammonia were 64 (27)% and 60 (32)%, which is substantially more variable than EBC pH assays. CONCLUSIONS: Although ammonia and pH appear to correlate in EBC, the oral ammonia concentration is not an important determinant of EBC pH. No precautions need to be taken to exclude oral ammonia when EBC pH is of interest. The low pH and low ammonia found in EBC from patients with lung diseases appear to be independent effects of volatile compounds arising from the airway.

Adult↗
PubMed2005

Physical and biological properties of a novel siloxane adhesive for soft tissue applications.

The aim of this study was to investigate the adhesive properties of an in-house aminopropyltrimethoxysilane-methylenebisacrylamide (APTMS-MBA) siloxane system and compare them with a commercially available adhesive, n-butyl cyanoacrylate (nBCA). The ability of the material to perform as a soft tissue adhesive was established by measuring the physical (bond strength, curing time) and biological (cytotoxicity) properties of the adhesives on cartilage. Complementary physical techniques, X-ray photoelectron spectroscopy, Raman and infrared imaging, enabled the mode of action of the adhesive to the cartilage surface to be determined. Adhesion strength to cartilage was measured using a simple butt joint test after storage in phosphate-buffered saline solution at 37 degrees C for periods up to 1 month. The adhesives were also characterised using two in vitro biological techniques. A live/dead stain assay enabled a measure of the viability of chondrocytes attached to the two adhesives to be made. A water-soluble tetrazolium assay was carried out using two different cell types, human dermal fibroblasts and ovine meniscal chondrocytes, in order to measure material cytotoxicity as a function of both supernatant concentration and time. IR imaging of the surface of cartilage treated with APTMS-MBA siloxane adhesive indicated that the adhesive penetrated the tissue surface marginally compared to nBCA which showed a greater depth of penetration. The curing time and adhesion strength values for APTMS-MBA siloxane and nBCA adhesives were measured to be 60 s/0.23 MPa and 38 min/0.62 MPa, respectively. These materials were found to be significantly stronger than either commercially available fibrin (0.02 MPa) or gelatin resorcinol formaldehyde (GRF) adhesives (0.1 MPa) (P < 0.01). Cell culture experiments revealed that APTMS-MBA siloxane adhesive induced 2% cell death compared to 95% for the nBCA adhesive, which extended to a depth of approximately 100-150 microm into the cartilage surface. The WST-1 assay demonstrated that APTMS-MBA siloxane was significantly less cytotoxic than nBCA adhesive as an undiluted conditioned supernatant (P < 0.001). These results suggest that the APTMS-MBA siloxane may be a useful adhesive for medical applications.

Acrylamides↗
PubMed2005

Xanthoma disseminatum: a case report and literature review.

This case report describes the neuro-opthalmologic and respiratory manifestations of xanthoma disseminatum, a rare histiocytosis syndrome characterized by disseminated lesions in a young male adult. Multimodality management of this disease, including the role of local radiotherapy, is discussed accompanied by a review of the literature.

Adolescent↗
PubMed2004

The personal dental service as a setting for an undergraduate clinical programme.

OBJECTIVE: To investigate the feasibility and benefits of placing dental undergraduates into a general dental practice setting for part of their clinical programme. SETTING: Two six-surgery general dental practices in the North West of England operating within the personal dental service of the NHS. METHOD: Six volunteer final year students worked within the practices for one-day-per week for 11 weeks. Evaluation included patients', practitioners' and students' views obtained from questionnaires and/or interviews and an analysis of students' clinical records. RESULTS: The students saw a large positive impact from: working alongside a dental nurse; developing their clinical skills; working in a busy practice environment; and developing interpersonal skills. Patients were very positive with 98% (44/45) being complimentary about the treatment they received, and commenting that they would be willing to participate in future student training programmes. The practice principals would also welcome continuation of the programme. CONCLUSION: The programme was both feasible and educationally beneficial. The financial implications need further research.

Attitude of Health Personnel↗
PubMed2004

Optimisation of the 3D MDEFT sequence for anatomical brain imaging: technical implications at 1.5 and 3 T.

An algorithm for the optimisation of 3D Modified Driven Equilibrium Fourier Transform (MDEFT) sequences for T1-weighted anatomical brain imaging is presented. Imaging parameters are optimised for a clinical whole body scanner and a clinical head scanner operating at 1.5 and 3 T, respectively. In vivo studies show that the resulting sequences allow for the whole brain acquisition of anatomical scans with an isotropic resolution of 1 mm and high contrast-to-noise ratio (CNR) in an acceptable scan time of 12 min. Typical problems related to the scanner-specific hardware configurations are discussed in detail, especially the occurrence of flow artefacts in images acquired with head transmit coils and the enhancement of scalp intensities in images acquired with phased array receive coils. It is shown both theoretically and experimentally that these problems can be avoided by using spin tagging and fat saturation.

Adult↗
PubMed2004

Overview of the Martian radiation environment experiment.

Space radiation presents a hazard to astronauts, particularly those journeying outside the protective influence of the geomagnetosphere. Crews on future missions to Mars will be exposed to the harsh radiation environment of deep space during the transit between Earth and Mars. Once on Mars, they will encounter radiation that is only slightly reduced, compared to free space, by the thin Martian atmosphere. NASA is obliged to minimize, where possible, the radiation exposures received by astronauts. Thus, as a precursor to eventual human exploration, it is necessary to measure the Martian radiation environment in detail. The MARIE experiment, aboard the 2001 Mars Odyssey spacecraft, is returning the first data that bear directly on this problem. Here we provide an overview of the experiment, including introductory material on space radiation and radiation dosimetry, a description of the detector, model predictions of the radiation environment at Mars, and preliminary dose-rate data obtained at Mars.

Astronauts↗
PubMed2004

Report of the use of hyperbaric oxygen therapy (HBO2) in an unusual case of secondary infertility.

We report the use of hyperbaric oxygen therapy (HBO2) in the treatment of an unusual case of secondary infertility. The patient had failed to conceive after a 1-year period of in-vitro fertilization, during which oral sildenafil had also been administered. However she became pregnant after an IVF cycle and the use of adjunctive HBO2 and sildenafil, which was administered intravaginally on this occasion. There is currently very little evidence to support the use of HBO2 in this context. The possible mechanisms of action of HBO2 in this case are discussed.

Adult↗
PubMed2003

Use of simulated clients in training veterinary undergraduates in communication skills.

A course in communication skills has been developed specifically for veterinary students, based on those delivered at many medical schools, and making extensive use of professional actors as simulated clients. Its aim is to raise awareness of the importance of communication among veterinary undergraduates at all stages of the curriculum, and it allows them to role-play in acted-out scenarios. Facilitated small groups provide an environment in which students can receive feedback on their own performance and also give feedback to their colleagues. An independent evaluation suggests that the opportunity to role-play increased the students' confidence in communicating with others. They were able to identify their personal strengths as communicators and gain insights into the aspects of communication they could improve. Feedback and subsequent discussions were highly valued, with the actors playing a crucial role in providing feedback from the client's perspective. Students were able to use the knowledge they acquired when consulting with real clients. Most of the students suggested that the course should continue in its current format, but with more time provided for it in the curriculum.

Communication↗
PubMed2003

Optimized EPI for fMRI studies of the orbitofrontal cortex.

A common problem in gradient-echo echo planar imaging (EPI) is the occurrence of image distortions and signal losses caused by susceptibility gradients near air/tissue interfaces. Since EPI is frequently used for functional magnetic resonance imaging experiments based on the blood oxygenation level-dependent effect, functional studies of certain brain regions affected by susceptibility gradients, such as the temporal lobes and the orbitofrontal cortex, may be compromised. In this work a method for signal recovery in certain regions of the orbitofrontal cortex is presented. The influence of in-plane susceptibility gradients is reduced by optimization of the imaging slice orientation. Through-plane susceptibility gradients are partly compensated by means of a moderate preparation gradient pulse similar to z-shimming. In contrast to several other techniques proposed in the literature for reducing susceptibility effects, this method does not compromise the temporal resolution and is therefore applicable to event-related studies.

Algorithms↗
PubMed2003

Antioxidant and free radical scavenging activity of isoflavone metabolites.

1. Soy isoflavones have been extensively studied because of their possible health-promoting effects. Genistein and daidzein, the major isoflavone aglycones, have received most attention; however, they undergo extensive metabolism in the gut and liver, which might affect their biological properties. 2. The antioxidant activity, free radical-scavenging properties and selected cellular effects of the isoflavone metabolites equol, 8-hydroxydaidzein, O-desmethylangiolensin, and 1,3,5 trihydroxybenzene were investigated in comparison with their parent aglycones, genistein and daidzein. 3. Electron spin resonance spectroscopy indicated that 8-hydroxydaidzein was the most potent scavenger of hydroxyl and superoxide anion radicals. Isoflavone metabolites also exhibited higher antioxidant activity than parent compounds in standard antioxidant (FRAP and TEAC) assays. However, for the suppression of nitric oxide production by activated macrophages, genistein showed the highest potency, followed by equol and daidzein. 4. The metabolism of isoflavones affects their free radical scavenging and antioxidant properties, and their cellular activity, but the effects are complex.

Animals↗