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Biomedical subjects

R Miller

Publications and source records attributed to R Miller.

At least 37 records · Page 2Linked to original sources
PubMed2005

Plaster cast immobilisation during air travel-analysis of current practice and aircraft-simulated experimental study.

BACKGROUND: There is an increase in aircraft transportation of patients with lower limb fractures. Current practice is variable. Our aim was to study current practice and to analyse the situation in an experimental simulated aircraft flight. METHODS: Current advice supplied by commercial airline offices in the UK was noted. Postal questionnaires were sent to Orthopaedic Consultants in the UK to obtain their current practice. Experimental aircraft travel was simulated in a decompression chamber with five medically fit volunteers with no fracture, immobilised in an above knee plaster cast. Compartment pressure and venous return was documented and the results analysed in two different positions with the leg elevated and dependant. RESULTS: Airlines do not have any formal guidelines. Orthopaedic consultants in the UK note variable advise in this situation. Experimental study in the aircraft simulation showed that two volunteers developed significant increase in compartmental pressure with the leg elevated to 90 degrees , which settled after the plaster cast was split. There was no increase in compartment pressure noted with leg dependant on the floor with 45 degrees of flexion at hip. CONCLUSION: The literature on this issue is limited. With our analysis we feel that patients can be transported with the plaster cast split with limb dependant on the floor i.e. hip flexion less than 45 degrees . Our volunteers had no fractures so direct comparison with pathological changes in acute fracture is problematical. Further studies into this problem are recommended.

Adult↗
PubMed2005

Fluorometric assay for detection and quantitation of polyamidoamine dendrimers.

Polyamidoamine dendrimers are protein-like nanomaterials that have many potential biological applications. Research studies using dendrimers often require their detection and quantitation. This article describes a simple, inexpensive, and rapid fluorometric assay based on the ability of dendrimers to bind the fluorescent probe, 8-anilino-1-naphthalene-sulfonic acid. This interaction leads to an enhanced fluorescence intensity of the dye that shows a linear relationship with dendrimer concentration. The procedure is applicable to dendrimers that have various surface functional groups and internal cores. Amine- and hydroxyl-terminated dendrimers gave the best calibration curves under alkaline conditions (pH 7.4). Carboxyl-terminated dendrimers required acidic conditions for their measurement. The assay for dendrimers with an amine surface and an ethylene diamine core was accurate between 0 and 100 microM and produced a within-run coefficient of less than 5%. Under the assay conditions used, the fluorescence signal strength was dependent on type of surface group and core length of the dendrimer.

Anilino Naphthalenesulfonates↗
PubMed2005

Surface viscoelastic properties of floating polyelectrolyte multilayers films: a capillary wave study.

A capillary wave technique was used to study the viscoelastic properties of floating polyelectrolyte multilayers of (PSS/PAH)(n) at the air-water interface. Oppositely charged polyelectrolyte layers were adsorbed onto two different Langmuir monolayers, either the lipid dimethyldioctadecylammonium bromide (DODAB) or the block copolymer poly(styrene-b-sodium acrylate) (PS-b-PAA). The results allow to propose a schematic representation of the multilayers in three zones: Zone I as a precursor, representing the adhesion between the Langmuir monolayer and the bulk polyelectrolyte multilayer. Zone II forms a bulk or core zone of the multilayer. Zone III as an outer zone in direct contact with the aqueous phase. The results show an increase of the elasticity after the formation of four polyelectrolyte layers accompanied by an apparent negative viscosity. This behaviour was interpreted as a translation of elasticity dominance from zone I to zone II. The Young modulus of seven layers was in the same order of magnitude as observed for planar polyelectrolyte multilayer films.

Journal Article↗
PubMed2005

Surface dilational rheology of mixed beta-lactoglobulin/surfactant layers at the air/water interface.

The general theoretical model by Garrett and Joos proposed in 1976 for the estimation of the dilational elasticity of mixed surfactant solutions, and also the theoretical model proposed by Joos for the limiting elasticity of such mixtures, demonstrate quite satisfactory agreement with experimental results obtained from the oscillating bubble shape method for mixtures of a nonionic surfactant and a protein, that is, beta-lactoglobuline and decyl dimethyl phosphine oxide, C10DMPO.

Air↗
PubMed2005

Photon blockade in an optical cavity with one trapped atom.

At low temperatures, sufficiently small metallic and semiconductor devices exhibit the 'Coulomb blockade' effect, in which charge transport through the device occurs on an electron-by-electron basis. For example, a single electron on a metallic island can block the flow of another electron if the charging energy of the island greatly exceeds the thermal energy. The analogous effect of 'photon blockade' has been proposed for the transport of light through an optical system; this involves photon-photon interactions in a nonlinear optical cavity. Here we report observations of photon blockade for the light transmitted by an optical cavity containing one trapped atom, in the regime of strong atom-cavity coupling. Excitation of the atom-cavity system by a first photon blocks the transmission of a second photon, thereby converting an incident poissonian stream of photons into a sub-poissonian, anti-bunched stream. This is confirmed by measurements of the photon statistics of the transmitted field. Our observations of photon blockade represent an advance over traditional nonlinear optics and laser physics, into a regime with dynamical processes involving atoms and photons taken one-by-one.

Journal Article↗
PubMed2005

Kinetics of the desorption of surfactants and proteins from adsorption layers at the solution/air interface.

It is shown by experiments that the DeSNa desorption kinetics is governed by a pure diffusion mechanism, while the desorption of more surface active surfactants such as C13DMPO and Triton X-100 obeys a mixed mechanism. The BLG desorption kinetics, as shown by experiments, is determined by a barrier mechanism. From the analysis of the temperature dependence of the BLG desorption kinetics it is possible to calculate the activation energy of this process, which is quite close to the free energy of BLG adsorption. The theoretical model of desorption kinetics predicts that these two energetic parameters are approximately equal to each other if the adsorption activation energy is low. This can explain the fact that the higher the adsorption activity of a substance is, the lower is its desorption rate.

Adsorption↗
PubMed2005

Dilational rheology of adsorbed surfactant layers--role of the intrinsic two-dimensional compressibility.

The frequency and concentration dependencies of the dilational elasticity and viscosity of adsorbed surfactant layers is yet not quantitatively understood. Especially at a surface coverage above 50% the measured high frequency limits of the elasticity pass typically a maximum or reach a plateau while classical models expect an exponential increase to very high values. The consideration of an intrinsic two-dimensional compressibility allows a much better description of experimental data. There are various surfactant systems discussed in literature following this new model. Although the impact of these interfacial characteristics on the dilational rheology is significant, the adsorption isotherm and equation of state change only slightly.

Adsorption↗
PubMed2005

Adsorption behavior and dilational rheology of the cationic alkyl trimethylammonium bromides at the water/air interface.

The dynamic and equilibrium surface tensions of C(n)TAB solutions for n = 12, 14, and 16 are studied using ring and bubble pressure tensiometry. Together with respective literature values, including neutron reflectivity and dilational surface rheology measurements, the experimental data are analyzed on the basis of two theoretical models, the Frumkin model and a modified reorientation model that takes into account an intrinsic compressibility of adsorbed surfactant molecules. It turns out that this new reorientation model, earlier applied to nonionic surfactant adsorption layers, is also applicable to ionic surfactants and superior to the Frumkin isotherm. All adsorption properties of one particular surfactant can be described by a single set of model parameters.

Adsorption↗
PubMed2005

Ellipsometric study of nonionic polymer solutions.

The thickness and refractive index of adsorption films of poly(vinylpyrrolidone) (PVP) and poly(ethylene glycol) (PEG) were determined by null-ellipsometry at the air-aqueous solution interface. Both parameters, in the same way as the earlier studied dynamic surface elasticity and surface tension, exhibit rather abrupt changes when the concentration approaches the range of semidilute solutions. This behavior can be explained by the worsening of the solvent quality with increasing PEG concentration and by the PVP displacement from the surface by a contamination of high surface activity.

Journal Article↗
PubMed2005

Motexafin gadolinium induces mitochondrially-mediated caspase-dependent apoptosis.

Motexafin gadolinium (MGd, Xcytrin) is a tumor-localizing redox mediator that catalyzes the oxidation of intracellular reducing molecules including NADPH, ascorbate, protein and non-protein thiols, generating reactive oxygen species (ROS). MGd localizes to tumors and cooperates with radiation and chemotherapy to kill tumor cells in tissue culture and animal models. In this report, we demonstrate that MGd triggers the mitochondrial apoptotic pathway in the HF-1 lymphoma cell line as determined by loss of mitochondrial membrane potential, release of cytochrome c from mitochondria, activation of caspase-9 prior to caspase-8, cleavage of PARP and annexin V binding. There was minimal effect on MGd-induced apoptosis by the caspase inhibitor z-VAD-fmk, even though caspase-3 activity (as measured by DEVD-cleavage) was completely inhibited. However, MGd-induced apoptosis was reduced to baseline levels by the more potent caspase inhibitor Q-VD-OPh, demonstrating that MGd-induced apoptosis is indeed caspase-dependent. Apoptosis induced by dexamethasone, doxorubicin and etoposide (mediated through the mitochondrial pathway) was also more sensitive to inhibition by Q-VD-OPh than z-VAD-fmk. Our results demonstrating differential sensitivity of drug-induced apoptosis to caspase inhibitors suggest that the term "caspase-independent apoptosis" cannot be solely defined as apoptosis that is not inhibited by z-VAD-fmk as has been utilized in some published studies.

Amino Acid Chloromethyl Ketones↗
PubMed2005

Effects of botulinum toxin B on refractory detrusor overactivity: a randomized, double-blind, placebo controlled, crossover trial.

PURPOSE: Open, observational studies of intradetrusor injections of botulinum toxin for detrusor overactivity have reported beneficial effects. We tested the efficacy and safety of botulinum toxin B for the treatment of the overactive bladder in a randomized, double-blind, placebo controlled crossover trial. MATERIALS AND METHODS: A total of 20 patients 18 to 80 years old with detrusor overactivity unresponsive to oral antimuscarinic agents participated in the study. They were injected with either placebo (20 ml normal saline) or botulinum toxin B (5,000 IU diluted up to 20 ml) intravesically in a day case setting. After 6 weeks the treatments were crossed over without washout in line with previous findings. The primary outcome was the paired difference in change in average voided volumes. Frequency, incontinence episodes and paired differences in quality of life measured by the King's Health Questionnaire were the secondary outcome measures. RESULTS: The Wilcoxon signed ranks test was used to test the paired difference in change between treatment phases. Little carryover was noted in the second arm placebo and the placebo data from both arms were included in analysis. There were clinically statistically significant paired differences in the change in average voided volume, urinary frequency and episodes of incontinence between active treatment and placebo (average voided volume: 95% CI difference 16, 122; Z2.5; p = 0.012/weekly frequency: 95% CI -21, -1; Z2.1, p=0.033/weekly incontinence: 95% CI -26, -7; Z3.3; p = 0.001). There were similarly significant paired differences in the change in quality of life affecting 5 domains of the King's Health Questionnaire. CONCLUSIONS: This double-blind, placebo controlled, crossover study provides evidence of the efficacy of botulinum toxin B in the treatment of overactive bladder. Autonomic side effects were observed in 4 patients. The short duration of action will presumably limit the use to patients who have experienced tachyphylaxis with botulinum toxin A.

Administration, Intravesical↗
PubMed2005

An approach to haemorrhoids.

OBJECTIVE: Many patients with haemorrhoids are investigated because of the fear of missing colorectal cancer (CRC). The aim of this study was to determine whether a primarily clinical approach regarding the need for investigation was safe and did not miss patients with CRC. PATIENTS AND METHODS: Data was collected prospectively on 589 consecutive patients with the principle diagnosis of haemorrhoids at first clinic visit. All had clinical assessment including rigid sigmoidoscopy and were treated by phenol injection or banding. They were categorized for (1) no review unless symptoms persisted -'One Stop SOS' (2) outpatient review or (3) investigation. To check for the development of CRC they were contacted by postal questionnaire or telephone interview with a minimum of one year from diagnosis and treatment. All 589 patients were cross-referenced with the Pathology database and the Hospital Information Services System. RESULTS: Four hundred and sixty-nine (80%) answered the questionnaire; 352 patients (60% of the total group) fell in the 'one stop SOS' outpatient category; 95 (16%) patients were followed up to review response to treatment for large haemorrhoids; 105 (18%) were investigated with barium enema (12%), flexible sigmoidoscopy (4%), colonoscopy (1%) and miscellaneous (1%); 37 (6%) patients were either given a haemorrhoidectomy date or referred on with a different diagnosis. No patients selected for 'one-stop' treatment developed CRC. Five (0.8%) patients were diagnosed with CRC after appropriate investigation was instituted for suspicious symptoms. One patient with distal transverse colon cancer had a delayed diagnosis as she was investigated initially by flexible sigmoidoscopy. CONCLUSION: Most patients with the primary diagnosis of symptomatic haemorrhoids do not need investigation.

Adolescent↗
PubMed2005

How has the 'two-week wait' rule affected the presentation of colorectal cancer?

OBJECTIVE: To assess the impact of the 'two-week wait' rule on the presentation of colorectal cancer. METHODS: A retrospective study of all patients referred to a fast-track clinic in a colorectal cancer centre over an 18-month period, documenting outcome, especially colorectal cancer diagnosis. Comparison was made with patients diagnosed with colorectal cancer presenting via other routes in the same time period. RESULTS: Over an 18-month period, 462 patients were seen in the fast-track clinic and 64 (13.8%) were diagnosed with colorectal cancer. A further 131 patients with colorectal cancer presented to the department in the same time period through other means; 66 via standard out-patient letters, 26 from other departments and 39 (20%) as emergency admissions. Median (range) time to first clinic was 12 (2-28) days for fast-track and 24 (1-118) days for standard referrals (P < 0.0001); median time to first treatment was a further 36 (9-134) and 36.5 (1-226) days, respectively. The fast-track cohort had more advanced staging than those referred by standard letter. There were 19 Dukes' B, 22 Dukes' C and 14 Dukes' D cancers in the fast-track group compared with 28 Dukes' B, 25 Dukes' C and 6 Dukes' D in the standard referral group. After patient interview, only 337 (73%) of 462 fast-track patients appeared to fulfil the referral criteria but of the 64 diagnosed with cancer, 59 (92%) satisfied the criteria. Of the 66 patients with cancer referred by standard letter, 61 (92%) fulfilled the criteria. CONCLUSION: Patients referred to the fast-track clinic were seen quicker than those referred by standard letter, but they tended to have more advanced disease. The fast-track referral criteria were fulfilled by most patients with cancer (whether or not they were referred to the fast track clinic), confirming their validity. After detailed interview in the clinic, a quarter of fast-track referrals were found not to satisfy referral criteria, suggesting that prioritization in primary care could be improved.

Chi-Square Distribution↗
PubMed2005

Is ritonavir boosting associated with gout?

Asymptomatic hyperuricaemia is associated with ritonavir therapy, but gout has rarely been reported. We present a retrospective cohort study of 1825 HIV-positive patients seen at one inner London HIV clinic over a two-year period. In all, 18 patients had gout, of whom 15 were receiving antiretroviral therapy. Seven had predisposing risk factors for gout (e.g. pyrazinamide therapy, haematological malignancy). Of the remaining 11 patients, two were on no medication and eight (73%) were receiving ritonavir as a boosted protease inhibitor (PI). By comparison, 11% of HIV-positive patients without gout were receiving ritonavir (odds ratio = 22; confidence interval = 5-104). Seven of the 18 patients had documented features of lipodystrophy and dyslipidaemia. Gout was seen in patients with known risk factors for gout or who were receiving ritonavir as a boosted PI and who also had lipodystrophy.

Gout↗
PubMed2004

Rheological surface properties of C12DMPO solution as obtained from amplitude- and phase-frequency characteristics of an oscillating bubble system.

The experimental data on the surface rheological characteristics of dodecyl dimethyl phosphine oxide solutions obtained in a fully automatic oscillating bubble device under microgravity conditions in the frequency range 0.01-100 Hz are presented. The complex surface elasticity modulus is obtained form the amplitude- and phase-frequency characteristics of established pressure oscillations in a closed cell without calibration experiments by direct calculation of the necessary coefficients. The characteristics of the adsorption layers obtained from the elasticity modulus are in good agreement with adsorption isotherms and equations of state accounting for the intrinsic (2D) monolayer compressibility.

Journal Article↗
PubMed2004

Observation of the vacuum Rabi spectrum for one trapped atom.

The transmission spectrum for one atom strongly coupled to the field of a high finesse optical resonator is observed to exhibit a clearly resolved vacuum Rabi splitting characteristic of the normal modes in the eigenvalue spectrum of the atom-cavity system. A new Raman scheme for cooling atomic motion along the cavity axis enables a complete spectrum to be recorded for an individual atom trapped within the cavity mode, in contrast to all previous measurements in cavity QED that have required averaging over 10(3)-10(5) atoms.

Journal Article↗