Biomedical subjects

R Miller

Publications and source records attributed to R Miller.

At least 19 recordsLinked to original sources

PubMed2007

[Experience with laryngotracheal reconstruction in subglottic stenosis in a 30 years time period].

BACKGROUND: Severe subglottic stenosis is a difficult condition to manage. It can be treated by laryngotracheal reconstruction or cricotracheal resection. PATIENTS AND METHODS: In this retrospective study the experiences for treatment of isolated subglottic stenosis in 37 patients (age: 3-78 years; stenosis grading: 20 x grade II, 13 x grade III, and 4 x grade IV) by laryngotracheal reconstruction in a 30-years experience are presented. RESULTS: In 33 out of 37 patients (89.2 %) a sufficient subglottic patency (postoperative endoscopic finding: stenosis less than 30 %) was achieved by laryngotracheal reconstruction. However, 5 patients of this series had required revision of laryngotracheal recontruction and in 22 patients endoscopic removal of granulation tissue had been performed. Sufficient widening of the subglottic space had been possible in all grade II stenosis (20/20), in 11 out of 13 patients with grade III stenosis, and in 3 out of 4 patients with grade IV stenosis. In one child an accidental decannulation occurred and due to asphyxia an apallic syndrome developed. CONCLUSIONS: Even through laryngotracheal reconstruction is a demanding surgical technique requiring great experience it is an effective option for treatment of subglottic stenosis less than 90 %. For severe subglottic stenosis (> 90 %) treatment by laryngotracheal reconstruction is possible and should be considered if mobilisation of the trachea by scar tissue is suited to be worse or to extended cricotracheal stenosis is present, both being not good candidates for cricotracheal resection.

Adolescent↗

PubMed2006

Composite interfacial layers containing micro-size and nano-size particles.

Surface layers of micro- and nanoparticles at fluid/liquid interfaces in absence and presence of surfactants are of large importance in the process of re-discovering Pickering systems, i.e. emulsions and foams stabilized by particles. The surface pressure/area isotherms of such layers can provide information about the properties of the used particles (dimensions, interfacial contact angles), the structure of interfacial layers, the interactions between the particles as well as about relaxation processes within the layers. For a correct description of Pi-A isotherms of composite surface layers containing particles the significant difference in size of these particles to that of solvent and surfactant molecules should be taken into account. Corresponding equations can be derived on the basis of the two-dimensional solution theory. The gained equations provide satisfactory agreement with experimental data and predict realistic values for the area of particles at the interface. Also equations of state and of the dilational elasticity for composite surface layers containing particles can be obtained in the framework of the presented methodology.

Adsorption↗

PubMed2006

Intravesical explosions during transurethral endoscopic procedures.

Every Urologist, during the course of fulguration treatment of bladder tumours, has at some time or another experienced small intravesical explosions usually manifesting as a "pop". Major intravesical explosions are rare but potentially devastating complications of transurethral endoscopic resections. The damage to the bladder can range from small mucosal tears to bladder rupture, which can either be intraperitoneal (requiring laparotomy and open bladder repair) or extraperitoneal. We review the literature on intravesical explosions to determine the aetiology of these explosions and suggest strategies to prevent these. A comprehensive literature search was performed using Medline and Ovid to obtain information using search terms: intravesical explosions, transurethral procedures, endoscopic procedures, diathermyIntravesical explosions occur due to the production of explosive gases during use of diathermy on human tissues. The most dangerous combination is hydrogen and oxygen. Hydrogen alone is not explosive and it only becomes explosive when admixed with oxygen. Oxygen is not produced in sufficient quantity during diathermy to cause explosions but can enter into the bladder from the atmosphere during endoscopic procedures. Careful operative technique (correct use of the Ellick evacuator bulb and reducing the frequency of manual irrigations of the bladder) with minimisation of the operative time and using the coagulation current at moderate power as well as judicious coagulation of tissues can reduce the risk of this dangerous complication arising.

Humans↗

PubMed2006

Cooling to the ground state of axial motion for one atom strongly coupled to an optical cavity.

Localization to the ground state of axial motion is demonstrated for a single, trapped atom strongly coupled to the field of a high finesse optical resonator. The axial atomic motion is cooled by way of coherent Raman transitions on the red vibrational sideband. An efficient state detection scheme enabled by strong coupling in cavity QED is used to record the Raman spectrum, from which the state of atomic motion is inferred. We find that the lowest vibrational level of the axial potential with zero-point energy variant Planck's over 2 h omega a/2kB = 13 microK is occupied with probability P0 approximately 0.95.

Journal Article↗

PubMed2006

Application of the maximum bubble pressure technique for dynamic surface tension studies of surfactant solutions using the Sugden two-capillary method.

Exact knowledge of the dead time as part of the bubble lifetime in the maximum bubble pressure method is an important prerequisite for accurate dynamic surface tension measurements. The duration of the dead time depends essentially on the capillary geometry and affects significantly the measured surface tensions of concentrated surfactant solutions. Increase of the dead time leads to a significant surface tension decrease of a freshly formed bubble surface due to the significantly higher residual adsorption of the surfactant molecules. It is shown that correct dynamic surface tensions are obtained with the experimental procedure of Sugden's method only when in addition to the fixed frequency of bubble formation, also the dead time values for the two capillaries are kept constant.

Adsorption↗

PubMed2006

Widespread neonatal brain damage following calcium channel blockade.

An abundance of evidence exists that shows calcium channel blockade promotes injury in cultured neurons. However, few studies have addressed the in vivo toxicity of such agents. We now show that the L-type calcium channel antagonist nimodipine promotes widespread and robust injury throughout the neonatal rat brain, in an age-dependent manner. Using both isolated neuronal as well as brain slice approaches, we address mechanisms behind such injury. These expanded studies show a consistent pattern of injury using a variety of agents that lower intracellular calcium. Collectively, these observations indicate that postnatal brain development represents a transitional period for still developing neurons, from being highly sensitive to reductions in intracellular calcium to being less vulnerable to such changes. These observations directly relate to current therapeutic strategies targeting neonatal brain injury.

Animals↗

PubMed2006

Surface dilational rheology of mixed adsorption layers at liquid interfaces.

The dilational rheology for mixed solutions of surface active compounds is easy to measure with existing methods, however, there are very few attempts only to analyse the resulting data on the basis of a theoretical model. Models by Jiang et al., Joos, and by Lucassen and van den Tempel (for single compounds) are compared here and applied to experimental data. The mentioned models converge to each other after some small modifications and represent a very good scientific background for studies of the mechanical behaviour of mixed adsorption layers. As example, the experimental results for mixed solutions containing a globular protein (beta-lactoglobulin) and a non-ionic surfactant (alkyl dimethyl phosphine oxide) are analysed by the obtained dependencies, using some new proposed numerical procedures.

Adsorption↗

PubMed2006

Reversibility and irreversibility of adsorption of surfactants and proteins at liquid interfaces.

It is shown experimentally that the desorption of sodium decyl sulphate from the liquid/air interface is purely diffusion controlled, while the desorption of higher surface active surfactants such as the non-ionic surfactants Triton X-100 and tridecyl dimethyl phosphine oxide obeys a mixed mechanism. The desorption kinetics of beta-lactoglobulin (BLG) and beta-casein is, however, determined by a barrier mechanism. From the analysis of the BLG and beta-casein desorption kinetics at different temperatures the activation energy of desorption is calculated. The values obtained are rather close to the free energy of adsorption. The theoretical model of desorption kinetics predicts that these two energetic parameters are similar if the adsorption activation energy is low. This explains why substances with a higher adsorption activity have a lower desorption rate. Adsorption kinetics studies for beta-casein with and without forced convection show the same equilibrium surface tension values. This leads to the conclusion that the protein adsorption at liquid interfaces is thermodynamically reversible, although the slow desorption kinetics would allow to assume it to be an irreversible process.

Adsorption↗

PubMed2006

Dynamic surface tension of micellar solutions in the millisecond and submillisecond time range.

The analysis of the available bubble life times and dead times for the bubble pressure tensiometer BPA-1S shows that dynamic surface tensions can be measured also for surfactant solutions at concentrations many times higher than the corresponding CMC. For the three nonionic surfactants Triton X-100, Triton X-45, and C14EO8 experiments are performed for solutions with a concentration of up to 200 times the CMC (C14EO8). Comparison of the experimental data with micelle kinetics models yields rate constants for the fast micelle dissolution process, which are in a good agreement with values obtained by other experimental methodologies.

Adsorption↗

PubMed2006

MK801-induced caspase-3 in the postnatal brain: inverse relationship with calcium binding proteins.

Age-dependent, neuronal apoptosis following N-methyl-D-aspartate receptor blockade has been linked to loss of calcium. To further explore this relationship, we examined expression of activated caspase-3, as well as the calcium binding proteins, calbindin-D 28K, calretinin and parvalbumin, following injection of vehicle or the N-methyl-D-aspartate receptor blocker, MK801, in postnatal day 7 or 21 rats. At postnatal day 7, MK801-induced activated caspase-3 expression was most frequently found in mutually exclusive cell populations to those expressing any of the three calcium binding proteins. For example, in the somatosensory cortex, most immunoreactivity for activated caspase-3 was found in layers IV/V, layered between areas of high calbindin or calretinin expression. Further, in the caudate putamen, activated caspase-3 rarely invaded zones of intense calbindin immunoreactivity. Suggesting expression patterns of these proteins were inversely related, these same brain regions no longer displayed MK801-induced activated caspase-3 at postnatal day 21, but instead robustly expressed calcium binding proteins. This later surge in expression was especially true for parvalbumin in regions such as the somatosensory and retrosplenial cortex, as well as the subicular complex. Calbindin-D 28K was also found to increase in the same regions though not as impressively as parvalbumin. Thus, developmental regulation of calcium binding protein expression may be a critical factor in age-dependent sensitivity to agents that disrupt calcium homeostasis in maturing neurons, providing a possible mechanistic explanation for age-dependent MK801 toxicity.

Age Factors↗

PubMed2006

Dynamic surface elasticity of polyelectrolyte/surfactant adsorption films at the air/water interface: dodecyltrimethylammonium bromide and copolymer of sodium 2-acrylamido-2-methyl-1-propansulfonate with N-isopropylacrylamide.

The complex dynamic surface elasticity of the solutions of copolymer of sodium 2-acrylamido-2-methyl-1-propansulfonate with N-isopropylacrylamide and dodecyltrimethylammonium bromide was measured as a function of the surfactant concentration and the surface age by the oscillating bubble and drop methods. The kinetic dependencies of the surface elasticity proved to be non-monotonic at low concentrations and the main features of the surface viscoelasticity differed from the results for other polyelectrolyte/surfactant solutions films studied so far. The observed peculiarities were connected with the properties of the copolymer chain.

Journal Article↗

PubMed2006

Quantum chemical analysis of the thermodynamics of 2D cluster formation of n-carboxylic acids at the air/water interface.

Within the framework of PM3 molecular orbital approximation the thermodynamic function characteristics for the formation and geometrical structure of monomers, dimers, trimers, and tetramers of nondissociated n-carboxylic acids C(n)H(2n+1)COOH with n = 5-15 are calculated. It is shown that spontaneous aggregation of homologous fatty acids for the homologues with carbon atoms numbers n > or = 13 at the air/water interface can take place, leading to the formation of infinite plane rectangular clusters, whereas for the homologues with n < 11 spontaneous decomposition of large aggregates is energetically preferable. At the same time, the formation of trimers is more probable for the lower homologues (8 < n < 13). These results agree well both with the experimental data reported by various authors and with thermodynamic models developed earlier for soluble and insoluble monolayers. The slopes of the regressions calculated for the dependencies of the thermodynamic parameters on the alkyl chain length for all the clusters considered are all equal to each other. This fact indicates that the contributions of the CH2 groups to the thermodynamic characteristics of alcohols and acids are the same, and the differences in the formation of clusters by these substances should be attributed only to the differences in the structure and interactions of relevant functional groups. Therefore, it enables one to describe both acids and alcohols within the framework of the developed method, and it makes it possible to extend the proposed approach onto other classes of amphiphilic compounds.

Air↗

PubMed2006

Dilational viscoelasticity of PEO-PPO-PEO triblock copolymer films at the air-water interface in the range of high surface pressures.

The dynamic dilational elasticity of adsorbed and spread films of PEO-PPO-PEO triblock copolymers at the air-water interface was measured as a function of surface pressure, surface age, and frequency. At low surface pressures (<10 mN/m), the surface viscoelasticity is identical to that of PEO homopolymer films. The results at higher surface pressures can be explained by the desorption of PPO segments from the interface and then mixing with PEO segments in water. Unlike some recent results, the spread and adsorbed films are not identical. Spread films exhibit a maximum real part of the dynamic surface elasticity of about 20 mN/m and probably begin to dissolve in water at surface pressures above 19 mN/m. However, the surface elasticity of the adsorbed films decreases beyond the maximum, indicating the formation of a loose surface structure.

Journal Article↗

PubMed2006

Surface-pressure isotherms of monolayers formed by microsize and nanosize particles.

The thermodynamic model of a 2D solution developed earlier for protein monolayers at liquid interfaces is generalized for monolayers composed of micro- and nanoparticles. Surface pressure isotherms of particle monolayers published in the literature for a wide range of particles sizes (between 75 microm and 7.5 nm) are described by the theoretical model with one modification. The calculations of surface pressure pi on area A provide satisfactory agreement with the experimental data. The theory also yields reasonable cross-sectional area values of the solvent molecule water in the range between 0.12 and 0.18 nm2, which is almost independent of particle size. Also, the area per particle in a closely packed monolayer obtained from the theory is quite realistic.

Membranes, Artificial↗

PubMed2006

Autonomic side effects of Botulinum toxin Type B intravesical injections: report of 4 cases and review of the literature.

Recently, intravesical injections of Botulinum toxin type B (BT-B) have been trialled in an attempt to treat detrusor overactivity. Use of Botulinum toxin A (BT.-A), for the same in the past, has been quite successful without many reported side effects. Soon after commencing the clinical use of BT-B, a side effect profile was noticed not reported with BT-A. A total of 20 patients with refractory detrusor overactivity were included in this randomized, double blind, placebo controlled, cross over trial. As per protocol, 5000 MU (1 ml) BT-B diluted to a volume of 20 mls with normal saline were injected in 10 different sites into the detrusor, sparing the trigone. We report four cases of autonomic side effects after these injections which strongly suggest clinically relevant systemic spread of the toxin.

Administration, Intravesical↗

PubMed2006

A cyclosporine-based immunosuppressive regimen may be better than tacrolimus for long-term liver allograft survival in recipients transplanted for hepatitis C.

UNLABELLED: Rapid recurrence of severe hepatitis C (HCV) after liver transplantation is a major barrier to survival of the transplanted liver. While cyclosporine (CsA) in vitro has been shown to suppress HCV replication, an effect is not seen with tacrolimus (Tac). Evidence is inconsistent whether or how this translates to clinical practice. To expand the evidence on this issue, we analyzed graft survival and histological outcomes after liver transplantation for HCV hepatitis. METHODS: Using our longitudinal database (1991 onward) graft outcomes for all liver transplant recipients with HCV were evaluated (105 grafts in 97 patients). Severe activity, severe fibrosis, and graft survival were analyzed. All liver biopsies were scored (blinded) according to the Ludwig scale. Immunosuppression was based on prednisone and a calcineurin inhibitor (Tac n = 89, 85%; CsA n = 15, 14%). Comparisons of outcomes using CsA versus Tac therapy were done using survival analysis via the log-rank test. RESULTS: Graft survival was significantly better in the CsA group. Although there was no apparent difference in severe activity (grade 2), there was a statistically significant difference in graft survival without fibrosing cholestatic hepatitis (P = .01) and a trend toward a difference in fibrosis-free survival (P = 0.1). The rate of sustained response to antiviral therapy was twice as high in the CsA group, 50% versus 22% (P = 0.16; NS). CONCLUSIONS: Graft survival in liver transplant recipients with HCV may be greater with CsA-based immunosuppression. There may also be a lower rate of fibrosing cholestatic hepatitis in this group.

Biopsy↗

PubMed2006

Case series data to encourage randomized trials of bladder retraining compared to antimuscarinic agents.

PURPOSE: This study was designed to test the power potential of a number of different clinical trial designs that could be deployed to test the efficacy of an antimuscarinic drug against bladder retraining. MATERIALS AND METHODS: This was an observational cohort study. Data were collected prospectively from patients treated for an overactive bladder by antimuscarinic agents with bladder retraining, or by bladder retraining alone. At initiation and at followup data on frequency, incontinence, urgency and urge incontinence were collected. Data from visits up to 16 weeks of treatment were analyzed using the parametric methods.708 patients were studied, 44 males and 664 females, and their mean age was 54 (sd 22). 52 patients used pure bladder retraining and 656 used bladder retraining and an antimuscarinic agent. The drug was oxybutynin, tolterodine or imipramine combined with oxybutynin or tolterodine as combination therapy. RESULTS: A between groups analysis demonstrated that bladder retraining was associated with a greater improvement in urinary frequency compared to antimuscarinic therapy (Z = -4.6, 95% CI of difference -3.3, -1.4, p <0.001) whereas antimuscarinic therapy was associated with a greater improvement in incontinence compared to bladder retraining (Z = -2.6, 95% CI of difference -0.93, -0.27, p = 0.024). The within group change in incontinence episodes in the bladder retraining group did not appear to show an effect (95% CI of change -0.19, 0.43). A subgroup showing greatest DeltaInc was sought. Boxplots of DeltaInc against age group, sex and the grading of symptoms were examined for maximum effect. Female sex, age group of 50 or greater and patients describing urge incontinence demonstrated the greatest DeltaInc. Their mean daily frequency was 11.45 (sd 6.1) and incontinence 1.6 (sd 2.1). A sample with such characteristics would be most sensitive to treatment effect. The bladder retraining group had a higher daily frequency (Z = -3.2, p = 0.001, 95% CI for bladder retraining 10 to 11, 95% CI for antimuscarinic group 10 to 12) and a lower daily incontinence compared to the antimuscarinic group (Z = -3.4, p <0.001, 95% CI of median for bladder retraining 0.75, 0.85, 95% CI of median for antimuscarinic group 0.75, 1.75). CONCLUSIONS: Change in frequency is a poor outcome measure, DeltaInc is significantly superior. An antimuscarinic tested against bladder retraining, using DeltaInc for outcome, would probably compare favorably.

Biofeedback, Psychology↗

PubMed2006

Effect of tracheal mucus and tracheal cytology on racing performance in Thoroughbred racehorses.

REASON FOR PERFORMING STUDY: Accumulations of mucus within the trachea are often found during endoscopic examinations of the airways of poorly performing racehorses, but the clinical importance of this finding is unknown. OBJECTIVES: To determine the effect of tracheal mucus, pharyngeal lymphoid hyperplasia (PLH) and cytological indices of tracheal aspirate on racing performance in Thoroughbred horses assessed by race place and whether the horse was raced. METHODS: Endoscopic examination of the nasopharynx, larynx and trachea was performed, and a tracheal aspirate obtained monthly at Thistledown racetrack from April to December, 2002 and 2003. Horses received a score of 0-4 for the degree of PLH and 0-4 for the amount of mucus visible in the trachea. The tracheal aspirate was assessed for turbidity, and total and differential cell counts. Generalised estimating equations models were used as repeated measures models for each risk factor and the level of association assessed through the risk factor's P value in the model. RESULTS: Moderate to severe tracheal mucus (2-4) was a risk factor for poor racing performance. There was no association between degree of PLH, cell counts or turbidity of tracheal wash fluid and racing performance. However, horses that raced had higher total neutrophil counts in tracheal wash aspirates than horses that did not race. CONCLUSIONS: Grades 2-4 tracheal mucus should be considered a potential cause of poor racing performance in Thoroughbred horses. CLINICAL RELEVANCE: Because moderate to severe tracheal mucus accumulation, and not increased tracheal neutrophils, was a risk factor for poor racing performance, functionally significant airway inflammation may best be confirmed by the presence of mucus rather than increased number of neutrophils in the trachea.

Age Factors↗