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Biomedical subjects

R Miller

Publications and source records attributed to R Miller.

At least 91 records · Page 5Linked to original sources
PubMed2002

Dynamic Surface Properties of Poly(vinylpyrrolidone) Solutions.

The dynamic surface tension and the complex dynamic surface elasticity of poly(vinylpyrrolidone) (PVP) solutions were measured in the concentration range 10(-5) wt% up to about 1 wt%. The surface tension changed slowly with time at low (<10(-4) wt%) and high concentrations (>0.1 wt%). At low concentrations this is a consequence of the slow transport by diffusion of PVP molecules from the depth of the bulk phase to the surface. At high concentrations the time effect is unexpected and probably the result of PVP contamination of high surface activity. The dynamic surface elasticity of PVP solutions gradually decreases with increasing concentration up to the range of high concentrations (>0.1 wt%) where an abrupt increase in the elasticity caused by the adsorbed impurity is observed. At low and medium concentrations the viscoelastic behavior of PVP adsorbed films is similar to that of the previously investigated poly(ethylene oxide) and poly(ethylene glycol) films and is determined by the number of loops and tails protruding into the bulk phase.

Models, Theoretical↗
PubMed2002

The effects of chronic ethanol consumption on neurotrophins and their receptors in the rat hippocampus and basal forebrain.

Damage to the basal forebrain frequently results in deficits in learning and memory. Mnenonic dysfunction also occurs following prolonged ethanol consumption in humans and in animal models of chronic ethanol intake, accompanied by specific abnormalities in synaptic transmission between the basal forebrain and hippocampus. The integrity of at least some of the reciprocal neuronal connections between these brain regions is influenced by target-derived neurotrophic factors. We used a semiquantitative reverse transcription polymerase chain reaction technique to measure the messenger RNA for neurotrophins BDNF and NGF, and for their receptors trkB, trkA, and the low affinity receptor, p75(NTR) in the hippocampus and basal forebrain of rats after 28 weeks of alcohol consumption without malnutrition. This chronic ethanol treatment (CET) resulted in a marked and selective reduction in basal forebrain trkA mRNA. Western blotting revealed a similar reduction of basal forebrain trkA protein. CET effects on basal forebrain trkA may reflect impaired NGF signaling that could compromise septohippocampal synaptic connections, cholinergic differentiation, and emergent functional abilities dependent on these properties.

Alcohol Drinking↗
PubMed2002

Beta-casein bilayer adsorption at the solution/air interface: experimental evidences and theoretical description.

Ellipsometric and surface pressure studies of beta-casein adsorption layers at the water/air interface support the idea of a model that assumes the formation of a second layer adjacent to the primary adsorption layer. A thermodynamic model describes the concentration behavior of the surface pressure and the adsorbed amount with one and the same set of model parameters over the entire concentration range studied.

Adsorption↗
PubMed2002

Frequency characteristics of amplitude and phase of oscillating bubble systems in a closed measuring cell.

The amplitude- and phase-frequency characteristics of oscillating bubble systems with a closed measuring cell are analyzed. The shape of the frequency characteristics is qualitatively different for bubbles smaller or larger than a hemisphere, respectively, and also for diluted and concentrated surfactant solutions. Moreover, the presence of a surfactant in the solution strongly influences the characteristic frequencies of the system. The experiments performed under ground and microgravity conditions show a good qualitative agreement with theoretically predicted amplitude- and phase-frequency characteristics and confirm the adequacy of the proposed theory. The comparison of high-frequency limits of the surface dilatational elasticity with the theoretical Gibbs elasticities calculated according to the respective adsorption isotherm shows good agreement for small surfactant concentrations. At higher concentrations large discrepancies are observed which can possibly be explained by the violation of the linearity condition for the surface layer.

Elasticity↗
PubMed2002

Adsorption behavior of oxyethylated surfactants at the air/water interface.

Literature data for homologous series of nonionic and ionic surfactants, such as C(n)OH, C(n)EO(m), Tritons, C(n)SO4Na, and C(n)EO(m)SO4Na, were analyzed on the basis of the Frumkin and reorientation models. The thermodynamic quantities obtained from the reorientation model agree best with the experimental data. They yield the standard free energy of adsorption which can be split into contributions from the alkyl chain, and the polar head group. An additional contribution to the increment of the polar group deltaG0(P) from m EO groups deltaG0(EO(m)) is extracted which can be accounted for by deltaG0(EO(m)) = -2.35 square root(m) kJ/mol. The standard free energy of adsorption is well understood by the increment method used.

Adsorption↗
PubMed2002

Dynamic properties of poly(styrene)-poly(ethylene oxide) diblock copolymer films at the air-water interface.

The complex dynamic elasticity of monolayers of the diblock copolymer poly(styrene)-poly(ethylene oxide) at the air-water interface in the pancake, quasi-brush, and brush regimes has been studied by means of three experimental techniques--the surface transverse and longitudinal waves and the oscillating barrier method. In the pancake regime the surface viscoelastic properties in the frequency range under investigation (0.01-520 Hz) prove to be indistinguishable from the surface properties of the homopolymer PEO. Transition to the quasi-brush regime is accompanied by rather abrupt changes in both components of the surface viscoelasticity. The surface viscosity in the brush regime exceeds significantly the results calculated from the theory of D. M. A. Buzza et al. (J. Chem. Phys.109, 5008 (1998)), which takes into account the dissipation arising from the flow of solvent through the brush phase. Possible reasons of this discrepancy are discussed.

Journal Article↗
PubMed2002

Simple model for prediction of surface tension of mixed surfactant solutions.

A rigorous theoretical model is presented which describes the equilibrium behaviour of a surfactant mixtures at liquid/fluid interfaces. The theory describes mixtures of surfactants with different molar areas and accounts for the non-ideality of the surface layer. The theoretical results are in good agreement with experimental data and support the idea of additivity of the interaction parameters in the surface layer. The rigorous equation of state is transformed into simple relationships for the description of the adsorption behaviour of mixed surfactant systems. The model requires surface tensions of the single surfactant systems or the adsorption isotherms to construct the isotherm of the mixture while no extra interaction parameters between the different compounds are assumed. The model is tested with a number of literature data, such as mixed sodium alkyl sulfates, mixtures of betaine homologues BHB12 with BHB16, non-ionic surfactant mixtures, and anionic-nonionic mixtures (1-butanol with BHB12, and oxethylated decanol (C10EO5) with sodium dodecyl sulfate). The agreement between experimental data and the theoretical calculations is excellent. This approach can be especially important for practical applications of surfactant mixtures for which experimental data are scarce.

Adsorption↗
PubMed2002

Psychostimulants for hypersomnia (excessive daytime sleepiness) in myotonic dystrophy.

BACKGROUND: Excessive daytime sleepiness is a common symptom of myotonic dystrophy. Psychostimulants are drugs increasingly used to treat hypersomnia in myotonic dystrophy. OBJECTIVES: To search systematically for, and combine all evidence from, randomised trials relating to the effects of psychostimulants in myotonic dystrophy patients with hypersomnia. SEARCH STRATEGY: We searched the Cochrane Neuromuscular Disease Trial Register (searched May 2001) for randomised trials concerning psychostimulants in myotonic dystrophy, we searched of the bibliographies of identified papers and we contacted the authors of the papers. SELECTION CRITERIA: We considered all randomised or quasi randomised trials that have evaluated any type of psychostimulants (versus a placebo or no treatment) in children or adults with proven myotonic dystrophy and hypersomnia. DATA COLLECTION AND ANALYSIS: Potentially relevant papers were scrutinised by two reviewers and the selection of eligible studies was agreed by them and a third reviewer. Data were extracted by one reviewer and checked by a second reviewer. MAIN RESULTS: Primary outcome We found no trial that assessed the effect of a psychostimulant on the results of the maintenance of wakefulness tests. Secondary outcomes Only one eligible trial was found. In this crossover double blind study of 10 patients with myotonic dystrophy, the efficacy of selegiline was evaluated against a placebo on the multiple sleep latency test. There was no difference between the selegiline and placebo periods in mean improvement in the multiple sleep latency test scale. REVIEWER'S CONCLUSIONS: There is no evidence to support the use of a psychostimulant to treat hypersomnia in myotonic dystrophy. Randomised trials are needed to evaluate the efficacy and safety of psychostimulants.

Disorders of Excessive Somnolence↗
PubMed2002

Development of a nanofiltration process to improve the stability of a novel anti-MRSA carbapenem drug candidate.

The benzenesulfonate salt of an anti-methicillin-resistant Staphylococcus aureus carbapenem antibiotic studied is a crystalline, nonhygroscopic powder which is stable at room temperature, making it an ideal compound for long-term storage. However, the limited aqueous solubility of this salt prohibits parenteral administration. Conversely, the chloride salt of this carbapenem demonstrates opposing characteristics; it is quantitatively soluble in water, however is amorphous and subject to significant hydrolytic degradation in the solid state. Given two such extreme alternatives for pharmaceutical salt selection, a common approach taken is to develop the bioavailable salt and devise manufacturing and storage conditions that minimize degradation. This report describes a different approach to this manufacturing dilemma via the application of a simple and efficient nanofiltration process to convert the benzenesulfonate salt (storage entity) to the chloride salt (formulated drug product). Such an approach combines the positive attributes of these two salt forms into a single scalable process that reduces processing cycle times via elimination of redundant unit operations, increases the flexibility in manufacturing schedule, and improves overall product quality.

Benzenesulfonates↗
PubMed2002

Comparative study of 137Cs partitioning between solid and liquid phases in Lakes Constance, Lugano and Vorsee.

The methodology for estimating radiocaesium distribution between solid and liquid phases in lakes is applied for three prealpine lakes: Lake Constance (Germany), Lake Lugano (Switzerland) and Lake Vorsee (Germany). It is based on use of the exchangeable distribution coefficient and application of the exchangeable radiocaesium interception potential (RIPex). The methodology was tested against experimental data. Good agreement was found between estimated and measured 137Cs concentrations in Lake Constance and Lake Lugano, whereas for Lake Vorsee a discrepancy was found. Bottom sediments in Lake Vorsee are composed mainly of organic material and probably cannot be described in terms of the specific sorption characteristics attributed to illitic clay minerals.

Absorption↗
PubMed2002

Firing modes of midbrain dopamine cells in the freely moving rat.

There is a large body of data on the firing properties of dopamine cells in anaesthetised rats or rat brain slices. However, the extent to which these data relate to more natural conditions is uncertain, as there is little quantitative information available on the firing properties of these cells in freely moving rats. We examined this by recording from the midbrain dopamine cell fields using chronically implanted microwire electrodes. (1) In most cases, slowly firing cells with broad action potentials were profoundly inhibited by the dopamine agonist apomorphine, consistent with previously accepted criteria. However, a small group of cells was found that were difficult to classify because of ambiguous combinations of properties. (2) Presumed dopamine cells could be divided into low and high bursting (>40% of their spikes in bursts) groups, with the majority having low bursting rates. The distribution of burst incidence was similar to that previously reported with chloral hydrate anaesthesia, but the average intraburst frequency was higher in the conscious animal at rest and was higher again in bursts triggered by salient stimuli. (3) There was no evidence for spike frequency adaptation within bursts on average, consistent with the hypothesis that afterhyperpolarisation currents may be disabled during behaviourally induced bursting. (4) Presumed dopamine cells responded to reward-related stimuli with increased bursting rates and significantly higher intraburst frequencies compared to bursts emitted outside task context, indicating that modulation of afferent activity might not only trigger bursting, but may also regulate burst intensity. (5) In addition to the irregular single spike and bursting modes we found that extremely regular (clock-like) firing, previously only described for dopamine cells in reduced preparations, can also be expressed in the freely moving animal. (6) Cross-correlation analysis of activity recorded from simultaneously recorded neurones revealed coordinated activity in a quarter of dopamine cell pairs consistent with at least "functional" connectivity. On the other hand, most dopamine cell pairs showed no correlation, leaving open the possibility of functional sub-groupings within the dopamine cell fields. Taken together, the data suggest that the basic firing modes described for dopamine cells in reduced or anaesthetised preparations do reflect natural patterns of activity for these neurones, but also that the details of this activity are dependent upon modulation of afferent inputs by behavioural stimuli.

Action Potentials↗
PubMed2002

Is 'watchful waiting' a real choice for men with prostate cancer? A qualitative study.

OBJECTIVE: To understand what leads men to choose 'watchful waiting' rather than active treatment for cancer of the prostate. PATIENTS AND METHODS: Fifty men with confirmed prostate cancer in England, Wales and Scotland were interviewed about all aspects of their illness, for a Database of Individual Patients' Experience of illness. The sample included men at different stages of diagnosis and with experience of a wide range of treatments. We report here only what men said about their choice of treatment and the decision-making process. RESULTS: Watchful waiting would have been clinically inappropriate for almost half of the men (those with serious urinary symptoms and those with metastatic disease). However, few of the men who might have chosen watchful-waiting remembered this being presented as a serious option. Most in this group chose radical prostatectomy, radiotherapy, brachytherapy or cryosurgery. The few who chose watchful waiting had found doctors who supported their decision, had assessed the evidence from Internet sites, and were concerned about the side-effects and uncertain outcome of treatment. Men who chose watchful waiting, as well as those who opted for treatment, described considerable pressure from family members, doctors or support groups, to seek active treatment. CONCLUSION: This study helps to explain why some men will not contemplate watchful waiting, and why others may find it difficult to pursue that option. Understanding men's concerns may help clinicians to support men's treatment decisions. Treatment for prostate cancer is highly controversial because no randomized, controlled trials have shown whether or not active intervention increases survival. If trials are not completed it cannot be determined whether active treatments are the best course of action for men with prostate cancer.

Aged↗
PubMed2002

No correlation between aggregates of Cu/Zn superoxide dismutase and cell death in familial amyotrophic lateral sclerosis.

Aggregates of Cu/Zn superoxide dismutase (SOD) have been demonstrated in familial amyotrophic lateral sclerosis (FALS) and other neurodegenerative diseases; however, their role in disease pathogenesis is unclear. In this study, we investigated the presence of SOD aggregates in nerve growth factor (NGF)-differentiated PC12 cells and cell viability following: (i) transduction with replication-deficient recombinant adenoviruses (AdVs) expressing wild-type SOD (SODWT) or mutant SOD (SODMT, V148G or A4V); (ii) transfection of yellow fluorescent protein-tagged SODWT (SODWT-YFP) or SODMT (SODA4V-YFP, SODV148G-YFP). SOD aggregates were more prominent in cells following transduction of AdSODMT than AdSODWT and following treatment with H2O2, suggesting that mutant SOD leads to oxidation of cellular components. In addition, cells expressing SODMT-YFP yielded SOD aggregates that were significantly larger and more frequent than SOD aggregates in cells expressing SODWT-YFP. Proteasome inhibitors, but not cathepsin B inhibitors, increased aggregate formation but did not increase cell death. In addition, treatments that increased cell viability did not significantly decrease SOD aggregates. Taken together, our data demonstrate that there is no association between SOD aggregates and cell death in FALS.

Amino Acid Substitution↗
PubMed2002

Caecal carcinomas in the elderly: useful signs in minimal preparation CT.

OBJECTIVE: Frail, elderly and immobile patients frequently have difficulty in tolerating formal colonic investigations. Caecal tumours may account for up to 35% of colonic tumours. Barium enema and colonoscopy have limitations in assessing this region. The aims of this study were to evaluate the accuracy of a minimal preparation CT technique (merely with prolonged oral contrast medium) in identifying caecal carcinomas and to determine helpful radiological signs. MATERIALS AND METHODS: The CT technique involved helical acquisition following 2 days of preparation with oral contrast medium. The outcome of 4 years' experience (1995-1998) was reviewed. The gold-standards were pathological and cancer registration records, together with colonoscopy and barium enema where available, with a minimum of 15 months' follow-up. RESULTS: CT correctly identified 27 of 30 caecal carcinomas, and missed three, in a total of 1077 CT studies in 1031 patients (median age 80 years). There were also 21 false-positive cases in which CT incorrectly raised the possibility of a caecal tumour. The sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) were 90%, 98%, 99% and 56%, respectively. Serosal margin blurring, tumour length, presence of abnormal peri-colic fat and terminal ileal wall thickening were identified as useful radiological signs. CONCLUSIONS: Minimal preparation CT is able to identify caecal carcinomas with fair accuracy. Such evaluation may become important given the increasing population age and evidence of a 'proximal shift' in the site of colonic tumours in the elderly.

Aged↗
PubMed2002

Lactic acidosis and abnormal liver function in advanced HIV disease.

A 48 year old man receiving HAART presented with late stage HIV disease, non-specific symptoms, a normal sized liver, ascites, and lactic acidosis. Following a failed liver biopsy worsening acidosis developed, requiring ICU support. Progressive liver failure occurred. Endoscopy showed oesophageal varices and a transjugular liver biopsy showed non-cirrhotic cholestasis; findings that were ascribed to HAART.

Acidosis, Lactic↗
PubMed2002

News from the frontline: sexually transmitted infections in teenagers attending a genitourinary clinic in south east London.

OBJECTIVES: To define the incidence and characterise the clinical presentation of sexually transmitted infections (STI) in people aged <or=16 years old attending a genitourinary clinic in south east London. METHODS: Cross sectional analysis of clients aged <or=16 years attending one genitourinary clinic. A subgroup was identified for priority treatment. Data collected included age, reason for presentation, diagnosis, contraceptive use, and adherence to therapy. Diagnoses were compared to the KC60 codes for female attendances of all ages. RESULTS: 144 females and 18 males with a mean age of 15.4 years attended, of whom 49% were symptomatic. Compared to other attenders, clients aged <or=16 years were significantly more likely to have an STI (64% versus 22%, p <0.00000001); 27 were pregnant (of whom 96% requested a termination of pregnancy); 47% did not return for follow up; and 12% did not adhere to treatment plan. Those diagnosed with an STI were significantly less likely to reattend (p<0.001). CONCLUSIONS: There is a high rate of STIs in 16 year olds compared to national figures and to general clinic attenders. Poor contraception is often overlooked within the genitourinary medicine clinic. Young attenders frequently fail to reattend for follow up. Priority treatment did not affect outcome. Further strategies are needed to identify ways to improve young people's access to genitourinary medicine clinics.

Adolescent↗
PubMed2002

Histopathological correlates of abnormal pericolic fat on CT in the assessment of colorectal carcinoma.

The aim of this study was to assess the pathological significance of abnormal pericolic fat shown by CT in the context of colorectal carcinoma. CT and histopathological findings of 63 resected colorectal carcinomas were retrospectively reviewed. CT examinations were assessed by two observers for the presence or absence of abnormal pericolic fat (typically linear or nodular opacities) at tumour sites. Specimens were reviewed histopathologically for depth of tumour invasion, extramuscular tissue reaction, and number and largest size of tumour-involved and tumour-free lymph nodes. The sensitivity, specificity, positive predictive value and negative predictive value of pericolic fat in identifying extension of tumour infiltration beyond the muscle coat were 79% (42/53), 33% (2/6), 91% (42/46) and 15% (2/13), respectively. Despite these indicators of efficacy, the association between the presence of pericolic fat abnormality on CT and extramuscular extension of tumour (infiltration and/or nodal disease) or tissue reaction alone or in combination did not reach statistical significance (p>0.3 in all cases). Abnormal ("misty" or "mucky") pericolic fat in the assessment of colorectal cancer on CT is not a precise indicator of extramuscular extension of tumour, as it cannot clearly distinguish between tumour infiltration and tissue reaction beyond the muscle coat, or pericolic nodal involvement. However, it is a very helpful CT sign that may draw attention to the presence and site of a potential colonic abnormality.

Adipose Tissue↗