Injectable hydrogels based on alginates grafted with LCST side-chains of different chemistry

A homologous series of thermoassociating copolymers was prepared by grafting onto alginates different amounts of three different temperature responsive polymers: poly(N-isopropylacrylamide), poly(di(ethylene glycol)methacrylate) and poly(ethylene oxide-co-propylene oxide). From a large set of analytical techniques combining rheology, calorimetry, NMR and SAXS, the relevant parameters controlling the sol/gel transition and the gel properties, mainly the degree of entanglement of macromolecules and the fraction of responsive stickers, were highlighted and interpreted objectively by considering the particularities of the phase diagrams of LCST polymers. Complementary analyses were implemented to investigate adhesiveness, injectabilty, gel swelling and molecular release in physiological environment of thermogelling formulations. In particular, it is shown that steady shear experiments allow to predict the injection forces by taking into account the characteristics of the system (syringe and needle), and that the rapid gelation of the formulations when they are heated at 37 °C delays the release of small molecules into the environment. The overall set of data is discussed in the framework of scaling relations in order to draw quantitative guidelines for the design of injectable thermoresponsive hydrogels.

Food Insecurity and Hearing Loss Are Interrelated: A Cross-Sectional Population-Based Study

OBJECTIVES

We aimed to assess whether objectively measured hearing loss and self-perceived hearing handicap in adults are independently associated with food insecurity, and vice versa.

DESIGN

Cross-sectional population-based study.

POPULATION

2,500 participants aged 50+ years from the Blue Mountains Hearing Study, with both complete pure-tone audiometry data and information on food security status.

MEASUREMENTS

The pure-tone average of frequencies 0.5, 1.0, 2.0 and 4.0 kHz (PTA0.5-4KHz) >25 dB HL in the better ear, established the presence of hearing loss. Self-perceived hearing handicap was assessed by administering the Hearing Handicap Inventory for Elderly Screening (HHIE-S total scores of ≥8 indicates hearing handicap). A 12-item food security survey was administered, comprising statements related to individual and household food situations.

RESULTS

Food insecurity was reported by 12.8% of study participants. After adjusting for all potential confounders, any self-perceived hearing handicap significantly increased the likelihood of participants reporting food insecurity by 94% (p<0.0001). Participants reporting any, mild or severe self-perceived hearing handicap had around 2-fold greater odds of experiencing food insecurity. Objectively measured hearing loss did not significantly influence the food security status of study participants. Conversely, food insecurity was significantly associated with both objectively measured hearing loss and self-perceived hearing handicap: multivariate-adjusted OR 1.37 (95% CI 1.01-1.88) and OR 1.83 (95% CI 1.40-2.39), respectively.

CONCLUSIONS

Food insecurity was an important social determinant of hearing health among community-dwelling adults. Conversely, participants with a significant self-perceived hearing handicap were more likely to experience food insecurity. These findings add to our understanding of the substantial public health impact of both food insecurity and hearing loss and may highlight areas for future intervention.

An optimized Factor H-Fc fusion protein against multidrug-resistant Neisseria gonorrhoeae

Novel therapeutics against the global threat of multidrug-resistant Neisseria gonorrhoeae are urgently needed. Gonococci evade killing by complement by binding factor H (FH), a key inhibitor of the alternative pathway. FH comprises 20 short consensus repeat (SCR) domains organized as a single chain. Gonococci bind FH through domains 6 and 7, and C-terminal domains 18 through 20. Previously, we showed that a chimeric protein comprising (from the N- to C-terminus) FH domains 18-20 (containing a point mutation in domain 19 to prevent lysis of host cells) fused to human IgG1 Fc (called FH*/Fc1) killed gonococci in a complement-dependent manner and reduced the duration and bacterial burden in the mouse vaginal colonization model of gonorrhea. Considering the N. gonorrhoeae-binding FH domains 18-20 are C-terminal in native FH, we reasoned that positioning Fc N-terminal to FH* (Fc1/FH*) would improve binding and bactericidal activity. Although both molecules bound gonococci similarly, Fc1/FH* displayed a 5-fold lower IC50 (the concentration required for 50% killing in complement-dependent bactericidal assays) than FH*/Fc1. To further increase complement activation, we replaced human IgG1 Fc in Fc1/FH* with Fc from human IgG3, the most potent complement-activating IgG subclass, to obtain Fc3/FH*. Bactericidal activity was further increased ~2.3-fold in Fc3/FH* compared to Fc1/FH*. Fc3/FH* killed (defined by <50% survival) 45/45 (100%) diverse PorB1B-expessing gonococci, but only 2/15 PorB1A-expressing isolates, in a complement-dependent manner. Decreased Fc3/FH* binding accounted for the limited activity against PorB1A strains. Fc3/FH* was efficacious against all four tested PorB1B gonococcal strains in the mouse vaginal colonization model when administered at a dose of 5 µg intravaginally, daily. Furthermore, Fc3/FH* retained bactericidal activity when reconstituted following lyophilization or spray-drying, suggesting feasibility for formulation into intravaginal rings. In conclusion, Fc3/FH* represents a promising prophylactic immunotherapeutic against multidrug-resistant gonococci.

CD97 is associated with mitogenic pathway activation, metabolic reprogramming, and immune microenvironment changes in glioblastoma

Glioblastoma (GBM) is the most common primary brain tumor with a median survival under two years. Using in silico and in vitro techniques, we demonstrate heterogeneous expression of CD97, a leukocyte adhesion marker, in human GBM. Beyond its previous demonstrated role in tumor invasion, we show that CD97 is also associated with upregulation of the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/Erk) and phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathways in GBM. While CD97 knockout decreased Akt activation, CD97 targeting did not alter MAPK/Erk activation, did not slow GBM cell proliferation in culture, and increased levels of glycolytic and oxidative phosphorylation metabolites. Treatment with a soluble CD97 inhibitor did not alter activation of the MAPK/Erk and PI3K/Akt pathways. Tumors with high CD97 expression were associated with immune microenvironment changes including increased naïve macrophages, regulatory T cells, and resting natural killer (NK) cells. These data suggest that, while CD97 expression is associated with conflicting effects on tumor cell proliferative and metabolic pathways that overall do not affect tumor cell proliferation, CD97 exerts pro-tumoral effects on the tumor immune microenvironment, which along with the pro-invasive effects of CD97 we previously demonstrated, provides impetus to continue exploring CD97 as a therapeutic target in GBM.

Effects of seeking compensation on the psychological health and recovery of injured patients: the role of stress vulnerability and injury-related disability

BACKGROUND

Seeking compensation has been shown to have an adverse effect on the psychological health and recovery of injured patients, however, this effect requires clarification.

METHODS

A total of 2019 adults sustaining a traffic injury were recruited. Of these, 709 (35.1%) lodged a compensation claim. Interviews occurred at 1-, 6- and 12-month post-injury. Outcomes were psychological distress (posttraumatic stress (PTS) and depressive symptoms) and health-related functioning (HrF) (quality of life measured by EQ-5D-3L and disability by WHODAS) over 12-months post-injury. Covariates included individual stress vulnerability (preinjury, injury-related factors).

RESULTS

Compared with non-compensation participants, compensation groups had higher stress vulnerability (more severe injuries and negative reactions) and poorer baseline outcomes (psychological health and HrF). After adjustment, we found an effect of compensation on HrF [β-0.09 (-0.11 to -0.07), p < 0.001] and PTS [β = 0.36 (0.16 to 0.56), p = 0.0003], but not on depression [β = -0.07 (-0.42 to 0.28), p = 0.7]. Both groups improved over time. Vulnerable individuals (β = 1.23, p < 0.001) and those with poorer baseline outcomes (PTS: β = 0.06, p = 0.002; HrF: β = -1.07, p < 0.001) were more likely to lodge a claim. In turn, higher stress vulnerability, poor baseline outcomes and claiming compensation were associated with long-term psychological distress and HrF. Nevertheless, concurrent HrF in the model fully accounted for the compensation effect on psychological distress (β = -0.14, p = 0.27), but not vice versa.

CONCLUSIONS

This study provides convincing evidence that seeking compensation is not necessarily harmful to psychological health. The person's stress vulnerability and injury-related disability emerge as major risk factors of long-term psychological distress, requiring a whole-systems approach to address the problem.

Development of Complement Factor H-Based Immunotherapeutic Molecules in Tobacco Plants Against Multidrug-Resistant Neisseria gonorrhoeae

Novel therapeutics against the global threat of multidrug-resistant Neisseria gonorrhoeae are urgently needed. Gonococci possess several mechanisms to evade killing by human complement, including binding of factor H (FH), a key inhibitor of the alternative pathway. FH comprises 20 short consensus repeat (SCR) domains organized in a head-to-tail manner as a single chain. N. gonorrhoeae binds two regions in FH; domains 6 and 7 and domains 18 through 20. We designed a novel anti-infective immunotherapeutic molecule that fuses domains 18-20 of FH containing a D-to-G mutation in domain 19 at position 1119 (called FH*) with human IgG1 Fc. FH*/Fc retained binding to gonococci but did not lyse human erythrocytes. Expression of FH*/Fc in tobacco plants was undertaken as an alternative, economical production platform. FH*/Fc was expressed in high yields in tobacco plants (300-600 mg/kg biomass). The activities of plant- and CHO-cell produced FH*/Fc against gonococci were similar in vitro and in the mouse vaginal colonization model of gonorrhea. The addition of flexible linkers [e.g., (GGGGS)2 or (GGGGS)3] between FH* and Fc improved the bactericidal efficacy of FH*/Fc 2.7-fold. The linkers also improved PMN-mediated opsonophagocytosis about 11-fold. FH*/Fc with linker also effectively reduced the duration and burden of colonization of two gonococcal strains tested in mice. FH*/Fc lost efficacy: i) in C6-/- mice (no terminal complement) and ii) when Fc was mutated to abrogate complement activation, suggesting that an intact complement was necessary for FH*/Fc function in vivo. In summary, plant-produced FH*/Fc represent promising prophylactic or adjunctive immunotherapeutics against multidrug-resistant gonococci.

Outcomes after traffic injury: mental health comorbidity and relationship with pain interference

BACKGROUND

Mental health symptoms, like depressive mood (DM) and post-traumatic stress (PTS), and pain interference (PI) with daily functioning often co-occur following traffic injury and their comorbidity can complicate recovery. This study aimed to map the course and overlapping trajectories of mental health symptoms, and associations with PI in a traffic injury population.

METHODS

In total, 2019 adults sustaining minor-to-moderate traffic injury were recruited within 28 days post-injury and assessed using phone interviews at 1, 6 and 12-months post-injury. Trajectories of DM, PTS and PI were established and relationships between DM, PTS and PI trajectories were explored using dual trajectory modelling. Bio-psychosocial predictors (e.g. pre-injury health, catastrophizing, acute distress, quality of life, social support) of mental health trajectories were investigated.

RESULTS

Up to five typical post-trauma trajectories were identified for DM, PTS and PI. Most people were in a resilient mental health trajectory (over 60%, DM or PTS), or in a chronic PI trajectory (almost 60%) 12 months post-injury. While recovery/resilient mental health trajectories were strongly interrelated (73.4% joint probability and > 94% conditional probabilities), DM/PTS comorbidity in chronic trajectories was not straightforward, suggesting a possibly asymmetric relationship. That is, persistent DM was more likely associated with persistent PTS (90.4%), than vice versa (31.9%), with a 22.5% probability that persistent PTS was associated with none or milder depression (i.e. following a recovery/resilient DM trajectory). An asymmetrical relationship was also found between mental health and PI. The majority of those with persistent PI were likely to be in a recovery/resilient DM/PTS trajectory (almost 70%), but those in a non-resilient DM/PTS trajectory showed a high risk of persistent PI. Predictors of non-resilient mental health trajectories included poorer pre-injury health and social support, and shared factors like acute psychological distress and pain catastrophizing.

CONCLUSIONS

Strong interrelations were confirmed between mental health symptoms and PI following traffic injury. However, persistent DM was more strongly linked to persistent PTS, than vice versa. Persistent PI was only linked with persistent DM/PTS in vulnerable subgroups. Early psychiatric/psychological interventions should target elevated psychological distress and negative appraisals in vulnerable individuals, to reduce long-term mental health morbidity/comorbidity and PI.

TRIAL REGISTRATION

ACTRN12613000889752.

Hydrogel Matrix-Grafted Impedimetric Aptasensors for the Detection of Diclofenac

Driven by the growing concern about the release of untreated emerging pollutants and the need for determining small amounts of these pollutants present in the environment, novel biosensors dedicated to molecular recognition are developed. We have designed biosensors using a novel class of grafted polymers, surface-attached hydrogel thin films, on conductive transducers as a biocompatible matrix for biomolecule immobilization. We showed that they can be dedicated to the molecular recognition of diclofenac (DCL). The immobilization of the aptamer onto surface-attached hydrogel thin films by covalent attachment provides a biodegradable shelter, providing the aptamer with excellent environments to preserve its active and functional structure while allowing the detection of DCL. The grafting of the aptamer is obtained using the formation of amide bonds via the activation of carboxylic acid groups of the poly(acrylic acid) hydrogel thin film. For improved sensitivity and higher stability of the sensor, a high density of the immobilized aptamer is enabled. The aptamer-modified electrode was then incubated with DCL solutions at different concentrations. The performances of the aptasensor were investigated by electrochemical impedance spectroscopy. The change in charge-transfer resistance was found to be linear with DCL concentration in the 30 pM to 1 μM range. The detection limit was calculated to be 0.02 nM. The improvement of the limit of detection can be mainly attributed to the three-dimensional environment of the hydrogel matrix which improves the grafting density of the aptamer and the affinity of the aptamer to DCL.

Daytime sleepiness and its relationships to fatigue and autonomic dysfunction in adults with spinal cord injury

OBJECTIVE

To determine the extent of daytime sleepiness in adults with spinal cord injury (SCI) and investigate the contribution of fatigue and autonomic function to sleepiness status.

METHODS

Participants included 45 adults with SCI attending outpatient services or living in the community and 44 able-bodied controls. The Oxford Sleep Resistance Test (OSLER) was used to assess daytime sleepiness, while eye blink rate duration (electrooculography) and the Iowa Fatigue Scale assessed fatigue. Heart rate variability (HRV) was used to assess autonomic function. Survival analysis (Kaplan Meier) was used to estimate the rate of loss in participation in the OSLER task, as a measure of daytime sleepiness. Repeated measures ANOVA was used to determine HRV differences between groups. Regression analysis was used to establish factors that contributed to daytime sleepiness.

RESULTS

Participants with high lesions ("T3 and above") had significantly increased daytime sleepiness. OSLER results revealed only 33% of those with high lesions remained awake during the task. Those with high lesions also had significantly reduced sympathetic activity while no differences in parasympathetic activity were found between groups. Lesion completeness had no effect. Standardized variation in heart rate, slow eye blinks, low frequency HRV and self-reported fatigue contributed to daytime sleepiness.

CONCLUSION

Neurological lesions at "T3 or above" have an increased risk of daytime sleepiness, impacting on independence in daily functional tasks and work performance. Autonomic imbalance alters cardiovascular control, affecting health and wellbeing. The interaction of these factors requires further investigation.

Post mortem tryptase cut-off level for anaphylactic death

Serum mast cell tryptase is used to support the diagnosis of anaphylaxis. The recommended clinical cut-off for total tryptase (<11.4μg/L) appears unsuitable in the post mortem setting due to largely unknown processes which result in significantly elevated levels in these samples. Consequently there is no widely accepted tryptase cut-off level for diagnosing an anaphylactic death. This 5-year retrospective study compared total tryptase levels in post mortem femoral blood in anaphylactic deaths and control. Univariate and multivariate analysis was used to assess the relative contribution of other factors (age, gender, post mortem interval, and presence of resuscitation) on post mortem tryptase levels. Nine anaphylactic deaths and 45 controls were identified. Receiver-operating characteristic (ROC) curve analysis identified an optimal cut-off of 53.8μg/L, with sensitivity of 89%, and specificity of 93%, for total post mortem tryptase in femoral blood to diagnosis anaphylaxis. No other factors showed any statistical significant contribution to post mortem tryptase elevation. Femoral total post mortem tryptase level of 53.8μg/L and above is a useful ancillary test in diagnosing an anaphylactic death.

Poroelastic indentation of mechanically confined hydrogel layers

We report on the poroelastic indentation response of hydrogel thin films geometrically confined within contacts with rigid spherical probes of radii in the millimeter range. Poly(PEGMA) (poly(ethylene glycol) methyl ether methacrylate), poly(DMA) (dimethylacrylamide) and poly(NIPAM) (N-isopropylacrylamide) gel films with thickness less than 15 μm were grafted onto glass substrates using a thiol-ene click chemistry route. Changes in the indentation depth under constant applied load were monitored over time as a function of the film thickness and the radius of curvature of the probe using an interferometric method. In addition, shear properties of the indented films were measured using a lateral contact method. In the case of poly(PEGMA) films, we show that poroelastic indentation behavior is adequately described within the framework of an approximate contact model derived within the limits of confined contact geometries. This model provides simple scaling laws for the characteristic poroelastic time and the equilibrium indentation depth. Conversely, deviations from this model are evidenced for poly(DMA) and poly(NIPAM) films. From lateral contact experiments, these deviations are found to result from strong changes in the shear properties as a result of glass transition (poly(DMA)) or phase separation (poly(NIPAM)) phenomena induced by the drainage of the confined films squeezed between the rigid substrates.

Submicrometric Films of Surface-Attached Polymer Network with Temperature-Responsive Properties

Temperature-responsive properties of surface-attached poly(N-isopropylacrylamide) (PNIPAM) network films with well-controlled chemistry are investigated. The synthesis consists of cross-linking and grafting preformed ene-reactive polymer chains through thiol-ene click chemistry. The formation of surface-attached and cross-linked polymer films has the advantage of being well-controlled without any caution of no-oxygen atmosphere or addition of initiators. PNIPAM hydrogel films with same cross-link density are synthesized on a wide range of thickness, from nanometers to micrometers. The swelling-collapse transition with temperature is studied by using ellipsometry, neutron reflectivity, and atomic force microscopy as complementary surface-probing techniques. Sharp and high amplitude temperature-induced phase transition is observed for all submicrometric PNIPAM hydrogel films. For temperature above LCST, surface-attached PNIPAM hydrogels collapse similarly but without complete expulsion of water. For temperature below LCST, the swelling of PNIPAM hydrogels depends on the film thickness. It is shown that the swelling is strongly affected by the surface attachment for ultrathin films below ∼150 nm. For thicker films above 150 nm (to micrometers), surface-attached polymer networks with the same cross-link density swell equally. The density profile of the hydrogel films in the direction normal to the substrate is confronted with in-plane topography of the free surface. It results that the free interface width is much larger than the roughness of the hydrogel film, suggesting pendant chains at the free surface.

Anti-infective immunoadhesins from plants

Immunoadhesins are recombinant proteins that combine the ligand-binding region of a receptor or adhesion molecule with immunoglobulin constant domains. All FDA-approved immunoadhesins are designed to modulate the interaction of a human receptor with its normal ligand, such as Etanercept (Enbrel(®) ), which interferes with the binding of tumour necrosis factor (TNF) to the TNF-alpha receptor and is used to treat inflammatory diseases such as rheumatoid arthritis. Like antibodies, immunoadhesins have long circulating half-lives, are readily purified by affinity-based methods and have the avidity advantages conferred by bivalency. Immunoadhesins that incorporate normal cellular receptors for viruses or bacterial toxins hold great, but as yet unrealized, potential for treating infectious disease. As decoy receptors, immunoadhesins have potential advantages over pathogen-targeted monoclonal antibodies. Planet Biotechnology has specialized in developing anti-infective immunoadhesins using plant expression systems. An immunoadhesin incorporating the cellular receptor for anthrax toxin, CMG2, potently blocks toxin activity in vitro and protects animals against inhalational anthrax. An immunoadhesin based on the receptor for human rhinovirus, ICAM-1, potently blocks infection of human cells by one of the major causes of the common cold. An immunoadhesin targeting the MERS coronavirus is in an early stage of development. We describe here the unique challenges involved in designing and developing immunoadhesins targeting infectious diseases in the hope of inspiring further research into this promising class of drugs.

Abnormal patterns of theta frequency oscillations during the temporal evolution of freezing of gait in Parkinson's disease

OBJECTIVE

We sought to characterize the electrophysiological signature of Freezing of gait in Parkinson's disease.

METHODS

We examined 24 patients with idiopathic Parkinson's disease and significant freezing of gait as they performed a series of timed up-and-go tasks in their 'off' state while electroencephalographic data was collected from four scalp leads. Fast Fourier Transformation was utilized to explore the power spectral density between periods of normal walking and periods of freezing, as well as during the transition between the two states. In addition, Cross Spectrum and Cross Frequency analyses were used to explore the role of impaired temporal and spatial connectivity.

RESULTS

When compared to walking, episodes of freezing were associated with a significant increase in theta band power within the central and frontal leads. The transition from normal walking to freezing of gait was also associated with increased theta frequency coupling between the central and frontal leads, along with an increase in cross-frequency coupling in the central lead.

CONCLUSIONS

Episodes of freezing of gait in Parkinson's disease are associated with abnormal oscillatory activity in the brain.

SIGNIFICANCE

These results provide novel insights into the pattern of spatiotemporal dynamics underlying freezing of gait and may provide a potential means for therapeutic prediction and alleviation of freezing episodes in susceptible patients.

Effects of mental fatigue on 8-13Hz brain activity in people with spinal cord injury

Brain computer interfaces (BCIs) can be implemented into assistive technologies to provide 'hands-free' control for the severely disabled. BCIs utilise voluntary changes in one's brain activity as a control mechanism to control devices in the person's immediate environment. Performance of BCIs could be adversely affected by negative physiological conditions such as fatigue and altered electrophysiology commonly seen in spinal cord injury (SCI). This study examined the effects of mental fatigue from an increase in cognitive demand on the brain activity of those with SCI. Results show a trend of increased alpha (8-13Hz) activity in able-bodied controls after completing a set of cognitive tasks. Conversely, the SCI group showed a decrease in alpha activity due to mental fatigue. Results suggest that the brain activity of SCI persons are altered in its mechanism to adjust to mental fatigue. These altered brain conditions need to be addressed when using BCIs in clinical populations such as SCI. The findings have implications for the improvement of BCI technology.

Electrochemical and spectroscopic investigation of counterions exchange in polyelectrolyte brushes

Scanning electrochemical microscopy (SECM) is employed to characterize the transport of redox-active probe ions through quenched polyelectrolyte brushes. The counterion exchange through polyelectrolyte brushes is also investigated by infrared spectroscopy in attenuated total reflection (FTIR-ATR), X-ray photolectron spectroscopy (XPS), and cyclic voltammetry (CV). The synthesis of poly(methacryloyloxy)ethyl trimethylammonium chloride (PMETAC) brushes is performed using surface-initiated atom transfer radical polymerization followed by in situ quaternization reaction. The chloride (Cl(-)) counterions of the positively charged polymer brush are exchanged by ferrocyanide (Fe(CN)(6)(4-)) and ferricyanide (Fe(CN)(6)(3-)) ions that are both detectable by spectroscopy and electrochemically active. A good agreement is found when comparing the results obtained by spectroscopic (FTIR-ATR and XPS) and electrochemical (SECM and CV) methods. The counterions exchange is completely reversible and reproducible. We show that (Fe(CN)(6)(4-)) and (Fe(CN)(6)(3-)) species form stable ion pairs with the quaternary ammonium groups of the polymer brush. The transport of iodide (I(-)) redox-active ions is also investigated. In all cases (ferrocyanide, ferricyanide, or iodide), we find that chloride counterions are partially replaced by electroactive ions. This partial exchange may be attributed to an osmotic effect, since the external salt concentration for the exchange is much lower than the counterion concentration inside the brush.

Increase in regularity and decrease in variability seen in electroencephalography (EEG) signals from alert to fatigue during a driving simulated task

Driver fatigue is a prevalent problem and a major risk for road safety accounting for approximately 20-40% of all motor vehicle accidents. One strategy to prevent fatigue related accidents is through the use of countermeasure devices. Research on countermeasure devices has focused on methods that detect physiological changes from fatigue, with the fast temporal resolution from brain signals, using the electroencephalogram (EEG) held as a promising technique. This paper presents the results of nonlinear analysis using sample entropy and second-order difference plots quantified by central tendency measure (CTM) on alert and fatigue EEG signals from a driving simulated task. Results show that both sample entropy and second-order difference plots significantly increases the regularity and decreases the variability of EEG signals from an alert to a fatigue state.

Electroencephalographic slowing and reduced reactivity in neuropathic pain following spinal cord injury

STUDY DESIGN

Brain wave activity in people with paraplegia, with and without neuropathic pain, was compared to brain wave activity in matched able-bodied controls.

OBJECTIVES

To investigate whether spinal cord injury with neuropathic pain is associated with a slowing of brain wave activity.

SETTING

Australia.

METHODS

Electroencephalographic (EEG) data were collected in the eyes open (EO) and eyes closed (EC) states from 16 participants with paraplegia (eight with neuropathic pain and eight without pain) and matched able-bodied controls. Common EEG artefacts were removed using independent component analysis (ICA). Peak frequency in the theta-alpha band and EEG power in the delta, theta, alpha and beta frequency bands were compared between groups.

RESULTS

The results show significant slowing of the EEG in people with neuropathic pain, consistent with the presence of thalamocortical dysrhythmia (TCD). Furthermore, people with neuropathic spinal cord injury (SCI) pain had significantly reduced EEG spectral reactivity in response to increased or decreased sensory input flowing into the thalamocortical network, as modulated by the eyes open and eyes closed states.

CONCLUSION

The results provide further evidence for alterations in brain electric activity that may underlie the development of neuropathic pain following SCI.

Synthesis and swelling behavior of pH-responsive polybase brushes

We synthesize polybase brushes and investigate their swelling behavior. Poly(2-(dimethylamino)ethyl methacrylate)) (PDMAEMA) brushes are prepared by the "grafting from" method using surface-initiated Atom Transfer Radical Polymerization to obtain dense brushes with relatively monodisperse chains (PDI = 1.35). In situ quaternization reaction can be performed to obtain poly(2-(trimethylamino)ethyl methacrylate)) (PTMAEMA) brushes. We determine the swollen thickness of the brushes using ellipsometry and neutron reflectivity techniques. Brushes are submitted to different solvent conditions to be investigated as neutral brushes and weak and strong polyelectrolyte brushes. The swelling of the brushes is systematically compared to scaling models. It should be pointed out that the scaling analysis of different types of brushes (neutral polymer and weak and strong polyelectrolyte brushes) is performed with identical samples. The scaling behavior of the PDMAEMA brush in methanol and the PTMAEMA brush in water is in good agreement with the predicted scaling laws for a neutral polymer brush in a good solvent and a polyelectrolyte brush in the osmotic regime. The salt-induced contraction of the quaternized brush is observed for high salt concentration, in agreement with the predicted transition between the regimes of the osmotic brush and the salted brush. From the crossover concentration, we calculate the effective charge ratio of the brush following the Manning counterion condensation. We also use PDMAEMA brushes as pH-responsive polybase brushes. The swelling behavior of the polybase brush is intermediate with respect to the behavior of the neutral polymer brush in a good solvent and the behavior of the quenched polyelectrolyte brush, as expected. The effective charge ratio of the PDMAEMA brush is determined as a function of pH using the scaling law of the polyelectrolyte brush in the osmotic regime.

Adsorption of randomly annealed polyampholytes at the silica-water interface

We have investigated the adsorption of randomly annealed polyampholytes containing [2-(dimethylamino)ethyl methacrylate)] (DMAEMA), methacrylic acid (MAA), and [3-(2-methylpropionamido)propyl] trimethylammonium chloride (MAPTAC) with various molar compositions. The adsorption was performed from dilute aqueous solutions onto silicon substrates. The adsorbed layers were characterized by reflectivity techniques such as reflectometry, ellipsometry, and neutron specular reflection. As expected for annealed polyampholytes, the adsorption was found to depend strongly on the pH, with a maximum within the isoelectric domain of the polyampholyte. The monomer volume fraction profiles of the adsorbed layers were determined from neutron specular reflection measurements. In the isoelectric domain, the polyampholyte chains adopt a compact conformation, with a layer thickness of about 60 A. The polyampholyte layer is as dense as the adsorbed layer of fully charged polyelectrolyte but much thicker. Finally, we found that changing the ratio of neutral units along the polyampholyte chain in the isoelectric domain had no significant effect on the concentration profile of the adsorbed layer.

Using independent component analysis to remove artifact from electroencephalographic measured during stuttered speech

The electro-encephalographic (EEG) activity of people who stutter could provide invaluable information about the association of neural processing and stuttering. However, the EEG has never been adequately studied during speech in which stuttering naturally occurs. This is owing, in part, to the masking of the EEG signal by artifact from sources such as the speech musculature and from ocular activity. The aim of this paper was to demonstrate the ability of independent component analysis (ICA) to remove artifact from the EEG of stuttering children recorded while they are speaking and stuttering. The EEG of 16 male children who stuttered and 16 who did not stutter was recorded during a reading task. The recorded EEG that contained artifact was then subjected to ICA. The results demonstrated that the EEG assessed during stuttered speech had substantially more noise than the EEG of speech that did not contain stuttering (p < 0.01). Furthermore, it was shown that ICA could effectively remove this artifact in all 16 children (p < 0.01). The results from one child highlight the findings that ICA can be used to remove dominant artifact that has prevented the study of EEG activity during stuttered speech in children.

Levels of brain wave activity (8-13 Hz) in persons with spinal cord injury

STUDY DESIGN

Brain wave activity in people with spinal cord injury (SCI) was compared to brain wave activity in able-bodied controls.

OBJECTIVES

To investigate whether a spinal injury results in changes in levels of brain wave activity in the 8-13 Hz spectrum of the electroencephalography (EEG).

SETTING

Sydney, Australia.

METHODS

Monopolar, multichannel EEG assessment was completed for 20 persons with SCI and 20 able-bodied, sex- and age-matched controls. A total of 14 channels of EEG were measured across the entire scalp for all participants. Comparisons between the able-bodied and SCI participants were made across the frontal, central, parietal, occipital and temporal regions. Comparisons were also made for impairment level, that is, between participants with tetraplegia and paraplegia.

RESULTS

Compared to the able-bodied controls, consistently reduced brain wave activity (measured by magnitude and peak amplitude) in the 8-13 Hz component of the EEG occurred in persons with SCI across all regions and sites, and differences were larger in the central, parietal and occipital sites. The SCI group also had consistently lower frequencies than the able-bodied controls. Furthermore, the subgroup of SCI participants with tetraplegia generally had significantly reduced brain activity (magnitude and peak amplitude) compared with the paraplegic subgroup and able-bodied controls.

CONCLUSIONS

The findings of this research enhance our understanding of changes in brain wave activity that could be associated with deafferentation that occurs following SCI, as well as provide essential data on the potential of SCI persons to use a 'hands free' environmental control system that is based upon 8-13 Hz brain activity.

Effect of luminance level on electro-encephalogram alpha-wave synchronisation

A control system for the remote activation of electronic devices, based on alpha-wave synchronisation, must be robust over a wide range of lighting conditions. This study investigates the effect that low light levels have on the increase in amplitude of the occipital alpha-wave component of the human electro-encephalogram spectrum in response to eye closure. Measurements of the time required for the amplitude of the occipital alpha wave to increase above a predetermined threshold, upon eye closure, were taken from 21 subjects and at four illuminances, ranging from 2 x 10(-1) lx to 2 x 10(-5) lx. The light source used to provide these illuminances was a featureless, uniformly illuminated white paper that subtended 30 degrees of the visual field. Statistical analysis showed that the time to exceed threshold (TTET) upon eye closure was not independent (p< 0.001) of illuminance, and that the main source of this lack of independence occurred at the lowest illuminance, 2 x 10(-5) lx. At this luminance, the median TTET value was 15.0s. However, at 2 x 10(-4) lx, the median value of the TTET was 4.2s. This is a sufficiently short time for device activation, and therefore a control system based on alpha-wave synchronisation is functional at very low light levels.

Synthesis of poly(styrene sulfonate) brushes

Dense poly(styrene sulfonate sodium salt) brushes were prepared on silicone wafers using a two-step procedure: polystyrene (PS) chains, terminated by a reactive trichlorosilane group, were first covalently grafted, and then the PS brush was converted to a poly(styrene sulfonate) brush by a soft sulfonation reaction. Ellipsometry and infrared spectroscopy in ATR were used to characterize the samples and to optimize the procedure: in particular, the sulfonation was shown to be homogeneous along the chain backbone and the neutralization complete. In some cases, the polymer layer revealed to be quite fragile: the chains were pulled out of the brush. A consolidation treatment which consisted in grafting oligomers inbetween the long PS chains significantly increased the robustness of the layer. This might be relevant for industrial applications.

The effectiveness of activating electrical devices using alpha wave synchronisation contingent with eye closure

Increases in alpha wave amplitude occur with eye closure (EC) and decreases occur when the eyes are opened (EO). The research reports in this paper emphasise effectiveness of people using these alpha wave changes to activate electrical devices. Effectiveness was measured in terms of time taken and errors made when selecting the correct device. Ten non-disabled subjects significantly decreased the time taken and errors made to activate correctly a device using a six-option environmental control system (ECS) in the laboratory. In addition, a severely disabled person was shown to use the ECS successfully to control her television in her home environment. This research demonstrates that alpha wave manipulation contingent with EC and EO can be the basis for a reliable and quick switching system for controlling electrical devices. Applications to disability are discussed.

Polyelectrolyte brushes: counterion distribution and complexation properties

The structure of dense grafted polyelectrolyte layers has been studied with a combination of neutron reflectivity and infrared spectroscopy techniques. The polyelectrolyte brushes were made of poly(styrene sulfonate) neutralized by different counterions. Small counterions are distributed throughout the brush in order to ensure a highly local electroneutrality. In addition, they can be readily exchanged with other small ions. On the other hand, macromolecular counterions (as well as some proteins) are irreversibly trapped by the brush, but are located outside the grafted layer and cannot reach the surface.

Novel regions of allelic deletion on chromosome 18p in tumors of the lung, brain and breast

Lung cancer is now the number one cause of cancer death for both men and women. An age-adjusted analysis over the past 25 years shows that in women specifically, lung cancer incidence is on the rise. It is estimated that 10-20 genetic events including the alteration of oncogenes and tumor suppressor genes will have occurred by the time a lung tumor becomes clinically evident. In an effort to identify regions containing novel cancer genes, chromosome 18p11, a band not previously implicated in disease, was examined for loss of heterozygosity (LOH). In this study, 50 matched normal and NSCLC tumor samples were examined using six 18p11 and one 18q12.3 PCR-based polymorphic markers. In addition, LOH was examined in 29 glioblastoma pairs and 14 paired breast carcinomas. This analysis has revealed potentially two regions of LOH in 18p11 in up to 38% of the tumor samples examined. The regions of LOH identified included a 2 cm area between markers D18S59 and D18S476, and a more proximal, 25 cm region of intermediate frequency between D18S452 and D18S453. These results provide evidence for the presence of one or more potential tumor suppressor genes on the short arm of chromosome 18 which may be involved in NSCLC, brain tumors and possibly breast carcinomas as well.