The GetReal Trial Tool: design, assess and discuss clinical drug trials in light of Real World Evidence generation.

Methodologies incorporating Real World Elements into clinical trial design (also called pragmatic trials) offer an attractive opportunity to assess the effect of a treatment strategy in routine care and as such guide decision making in practice. Uptake of these methods is slow for several reasons, including uncertainty about acceptability of trial results, lack of experience with the methodology and operational challenges. We developed the "GetReal Trial Tool," an easy-to-use online interface, which allows users to assess the impact of design choices on generalizability to routine clinical practice, while taking into account risk of bias, precision, acceptability and operational feasibility. The tool is grounded in the scientific literature combined with knowledge of experts from academia, pharmaceutical companies, HTA bodies, patient organizations, and regulators. The aim is to help researchers optimize trial design and facilitate translation of evidence from pragmatic trials to clinical practice. In this paper we describe the development, structure and application of the GetReal Trial Tool.

INTREPID: single- versus multiple-inhaler triple therapy for COPD in usual clinical practice.

INTRODUCTION: Real-world trial data comparing single- with multiple-inhaler triple therapy (MITT) in COPD patients are currently lacking. The effectiveness of once-daily single-inhaler fluticasone furoate (FF)/umeclidinium (UMEC)/vilanterol (VI) and MITT were compared in usual clinical care. METHODS: INTREPID was a multicentre, randomised, open-label, phase IV effectiveness study comparing FF/UMEC/VI 100/62.5/25 µg via the ELLIPTA inhaler with a clinician's choice of any approved non-ELLIPTA MITT in usual COPD clinical practice in five European countries. Primary end-point was proportion of COPD Assessment Test (CAT) responders (≥2-unit decrease in CAT score from baseline) at week 24. Secondary end-points in a subpopulation included change from baseline in forced expiratory volume in 1 s (FEV1) and percentage of patients making at least one critical error in inhalation technique at week 24. Safety was also assessed. RESULTS: 3092 patients were included (FF/UMEC/VI n=1545; MITT n=1547). The proportion of CAT responders at week 24 was significantly greater with FF/UMEC/VI versus non-ELLIPTA MITT (OR 1.31, 95% CI 1.13-1.51; p<0.001) and mean change from baseline in FEV1 was significantly greater with FF/UMEC/VI (77 mL versus 28 mL; treatment difference 50 mL, 95% CI 26-73 mL; p<0.001). The percentage of patients with at least one critical error in inhalation technique was low in both groups (FF/UMEC/VI 6%; non-ELLIPTA MITT 3%). Safety profiles, including incidence of pneumonia serious adverse events, were similar between treatments. CONCLUSIONS: In a usual clinical care setting, treatment with once-daily single-inhaler FF/UMEC/VI resulted in significantly more patients gaining health status improvement and greater lung function improvement versus non-ELLIPTA MITT.

Patient and healthcare professional experiences of the Salford Lung Studies: qualitative insights for future effectiveness trials.

BACKGROUND: Randomized controlled trials (RCTs) conducted in the routine care setting provide the opportunity to better understand the effectiveness of new medicines but can present recruitment difficulties. An improved understanding of the challenges/opportunities for patient and healthcare professional (HCP) engagement in clinical research is needed to enhance participation and trial experience. In this study, we explored patient and HCP drivers for, and experiences of, participation in the Salford Lung Studies (SLS), and their views on future trial participation and the overall value of such trials. METHODS: This was a qualitative study set in Salford, UK, comprising patient telephone interviews (N = 10) and HCP advisory boards (one with general practitioners [GPs], one with practice managers [PMs]); all individuals had participated in the SLS. Semi-structured telephone interviews were recorded, transcribed and analysed thematically. Advisory board meetings were analysed based on transcriptions of audio recordings and field notes. RESULTS: For patients, key positive aspects of the SLS were the ease/convenience of study assessments and excellent relationships with study nurses. GPs and PMs considered the SLS to be well-organized and highlighted the value of research nurse support; they also described minor challenges relating to trial systems, initial financial strain on practices and staff turnover. All participants indicated that they were very likely to participate in future trials, citing a design closely aligned with routine care practice as essential. Several strategies to encourage trial participation were suggested, such as clearly communicating benefits to patients and ensuring flexible study assessments. CONCLUSIONS: Patients and HCPs had positive experiences of the SLS. The study design, closely aligned with routine care, was considered important to their high likelihood of participating in future trials. The experiences of patients and HCPs in the SLS provide valuable insights that will help inform future best practice in the design and conduct of future real-world effectiveness RCTs in primary care. The detailed first-hand experiences of HCPs will be of significant value to others considering engaging in clinical research and participating in effectiveness RCTs.

Late changes in blood-brain barrier permeability in a rat tMCAO model of stroke detected by gadolinium-enhanced MRI.

OBJECTIVES: After cerebral ischaemia the blood-brain barrier (BBB) may be compromised and this has been observed in both clinical and preclinical studies. The timing of BBB disruption after ischaemia has long been considered to be biphasic, however some groups contest this view. Therefore, the purpose of this study was to characterize the BBB permeability timecourse in a rat model at both acute and chronic time points. METHODS: Unilateral transient middle cerebral artery occlusion (tMCAO) was performed in 15 male Sprague Dawley rats. Change in T1-weighted MR signal before and after an injection of gadolinium-based contrast agent was calculated voxelwise to derive a BBB permeability index (BBBPI) at both early (6 h, 12 h, and 24 h) and late (7 and 14 days) time points. RESULTS: As expected, BBBPI in the non-lesioned ROI was not significantly different from pre-occlusion baseline at any time point. However, BBBPI in the ipsilateral (lesioned) ROI was statistically different to baseline at day 7 (p < 0.001) and day 14 (p < 0.01) post-tMCAO. There was a small, but not-significant increase in BBBPI in the earlier phase (at 6 hours). DISCUSSION: Our results indicate a significant late opening of the BBB. This is important as the majority of previous studies have only characterised an early acute BBB permeability in ischemia. However, the later period of increased permeability may indicate an optimal time for drug delivery across the BBB, when it is especially suited to drugs targeting delayed processes.

Clinical effectiveness of once-daily fluticasone furoate/umeclidinium/vilanterol in usual practice: the COPD INTREPID study design.

Effectiveness studies complement conventional randomised controlled trials by providing a holistic view of treatments in the setting of usual clinical practice. We present the protocol for the ongoing INTREPID (INvestigation of TRelegy Effectiveness: usual PractIce Design; ClinicalTrials.gov identifier: NCT03467425) study, a randomised, open-label, 24-week effectiveness study of once-daily fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI; Trelegy) delivered by the ELLIPTA inhaler versus non-ELLIPTA multiple-inhaler triple therapy in patients with chronic obstructive pulmonary disease (COPD) in usual practice settings. INTREPID was designed to provide evidence of FF/UMEC/VI effectiveness in patients with COPD managed in routine healthcare systems across multiple European countries. Between study initiation and end-of-study visits, patients will receive their medication and care as they would ordinarily receive it, from their usual healthcare provider at their usual healthcare centre. Study-specific intervention will be minimal. The primary end-point will be the proportion of COPD assessment test (CAT) responders, defined as a clinically meaningful improvement from baseline of ≥2 units, at week 24. The CAT was chosen as it provides health status information relevant to patients, physicians, health technology agencies and payers. Lung function (forced expiratory volume in 1 s) and critical inhaler errors will also be assessed in a subgroup of patients. The strengths and weaknesses of the protocol and some of the challenges associated with conducting this multicountry study, such as differences in healthcare systems and treatment practices across sites, will also be discussed.

Series: Pragmatic trials and real world evidence: Paper 3. Patient selection challenges and consequences.

This paper addresses challenges of identifying, enrolling, and retaining participants in a trial conducted within a routine care setting. All patients who are potential candidates for the treatments in routine clinical practice should be considered eligible for a pragmatic trial. To ensure generalizability, the recruited sample should have a similar distribution of the treatment effect modifiers as the target population. In practice, this can be best achieved by including-within the selected sites-all patients without further selection. If relevant heterogeneity between subgroups is expected, increasing the relative proportion of the subgroup of patients in the heterogeneous trial could be considered (oversampling) or a separate trial in this subgroup can be planned. Selection will nevertheless occur. Low enrollment and loss to follow-up can introduce selection and can jeopardize validity as well as generalizability. Pragmatic trials are conducted in clinical practice rather than in a dedicated research setting, which could reduce recruitment rates. However, if a trial poses a minimal burden to the physician and the patient and routine clinical practice is maximally adhered to, the participation rate may be high and loss to follow-up will not be a specific problem for pragmatic trials.

Series: Pragmatic trials and real world evidence: Paper 2. Setting, sites, and investigator selection.

This second article in the series on pragmatic trials describes the challenges in selection of sites for pragmatic clinical trials and the impact on validity, precision, and generalizability of the results. The selection of sites is an important factor for the successful execution of a pragmatic trial and impacts the extent to which the results are applicable to future patients in clinical practice. The first step is to define usual care and understand the heterogeneity of sites, patient demographics, disease prevalence and country choice. Next, specific site characteristics are important to consider such as interest in the objectives of the trial, the level of research experience, availability of resources, and the expected number of eligible patients. It can be advisable to support the sites with implementing the trial-related activities and minimize the additional burden that the research imposes on routine clinical practice. Health care providers should be involved in an early phase of protocol development to generate engagement and ensure an appropriate selection of sites with patients who are representative of the future drug users.

Series: Pragmatic trials and real world evidence: Paper 7. Safety, quality and monitoring.

OBJECTIVE: Pragmatic trials offer the opportunity to obtain real-life data on the relative effectiveness and safety of a treatment before or after market authorization. This is the penultimate paper in a series of eight, describing the impact of design choices on the practical implementation of pragmatic trials. STUDY DESIGN AND SETTING: This paper focuses on the practical challenges of collecting and reporting safety data and of monitoring trial conduct while maintaining routine clinical care practice. CONCLUSION: Current ICH guidance recommends that all serious adverse events and all drug-related events must be reported in an interventional trial. In line with current guidance, we propose a risk-based approach to the collection of non-drug-related non-serious adverse events and even serious events not related to treatment based on the risk profile of the medicine/class in the patient population of interest. Different options available to support the collection and reporting of safety data while minimizing study-related follow-up visits are discussed. A risk-based approach to monitoring trial conduct is also discussed, highlighting the difference in the balance of risks likely to occur in a pragmatic trial compared to traditional clinical trials and the careful consideration that must be given to the mitigation and management of these risks to maintain routine care.

Series: Pragmatic trials and real world evidence: Paper 1. Introduction.

This is the introductory paper in a series of eight papers. In this series, we integrate the theoretical design options with the practice of conducting pragmatic trials. For most new market-approved treatments, the clinical evidence is insufficient to fully guide physicians and policy makers in choosing the optimal treatment for their patients. Pragmatic trials can fill this gap, by providing evidence on the relative effectiveness of a treatment strategy in routine clinical practice, already in an early phase of development, while maintaining the strength of randomized controlled trials. Selecting the setting, study population, mode of intervention, comparator, and outcome are crucial in designing pragmatic trials. In combination with monitoring and data collection that does not change routine care, this will enable appropriate generalization to the target patient group in clinical practice. To benefit from the full potential of pragmatic trials, there is a need for guidance and tools in designing these studies while ensuring operational feasibility. This paper introduces the concept of pragmatic trial design. The complex interplay between pragmatic design options, feasibility, stakeholder acceptability, validity, precision, and generalizability will be clarified. In this way, balanced design choices can be made in pragmatic trials with an optimal chance of success in practice.

GSK249320, A Monoclonal Antibody Against the Axon Outgrowth Inhibition Molecule Myelin-Associated Glycoprotein, Improves Outcome of Rodents with Experimental Stroke.

Myelin-associated glycoprotein (MAG) is an inhibitor of axon growth. MAG levels increase after stroke. GSK249320 is a monoclonal antibody that neutralizes MAG-mediated inhibition and so may promote axon outgrowth and improve post-stroke outcomes. The current study tested the hypothesis that GSK249320 initiated 24 hours or 7 days after experimental stroke improves behavioural outcomes. Rats with right middle cerebral artery occlusion for 90 minutes were randomized to receive 6 weeks of intravenous (a) GSK249320 starting 24 hours post-stroke, (b) GSK249320 starting 7 days post-stroke, or (c) vehicle. Behavioral testing was performed over 7 weeks. Serial MRI demonstrated no differences in infarct volume across groups. Animals treated with GSK249320 24 hours post-stroke showed larger increases in Neuroscore (time X group, p = 0.0008) and staircase test (main effect of group, p = 0.0214) as compared to controls, but animals treated 7 days post-stroke showed no significant behavioral benefit. No significant results were found for the sticky tape or cylinder tests. A separate set of animals with experimental stroke received a single intravenous dose of GSK249320 or vehicle at 1 hour, 24 hours, 48 hours or 1 week post-stroke, and immunohistochemistry methods were used to measure GSK249320 distribution; GSK249320 was found in the ipsilesional hemisphere only, the extent of which increased with later times of injection. These data suggest that intravenous GSK249320 penetrates the lesion site and is associated with a small effect on functional outcomes when initiated 24 hours post-stroke and so support the translational potential of this monoclonal antibody as a restorative therapy for patients with stroke.

Pragmatic trial design elements showed a different impact on trial interpretation and feasibility than explanatory elements.

OBJECTIVES: To illustrate how pragmatic trial design elements or inserting explanatory trial elements in pragmatic trials affect validity, generalizability, precision, and operational feasibility. STUDY DESIGN AND SETTING: From illustrative examples identified through the IMI Get Real Consortium, we selected randomized drug trials with a pragmatic design feature. We searched all publications on these trials for information on how pragmatic trial design features affect validity, generalizability, precision, or feasibility. RESULTS: We present examples from the Salford lung study, International Suicide Prevention Trial, Sequenced Treatment Alternatives to Relieve Depression, and Cluster Randomized Usual care vs. Caduet Investigation Assessing Long-term-risk trial. These examples show that incorporating pragmatic trial design elements in trials may affect generalizability, precision and validity and may lead to operational challenges different from traditional explanatory trials. Inserting explanatory trial elements into pragmatic trials may also affect validity, generalizability, and operational feasibility, especially when these trial elements are incorporated in one arm of the trial only. Design choices that positively affect one of these domains (e.g., generalizability) may negatively affect others (e.g., feasibility). CONCLUSION: Consequences of incorporating pragmatic or explanatory trial design elements in pragmatic trials should be explicitly considered and balanced for all relevant domains, including validity, generalizability, precision, and operational feasibility. Tools are needed to make these consequences more transparent.

Rosiglitazone enhances learning, place cell activity, and synaptic plasticity in middle-aged rats.

As an antidiabetic agent, rosiglitazone (ROSI) binds and activates peroxisome proliferator-activator receptor gamma (PPARγ), altering the expression of genes involved in glucose uptake and disposal, ultimately affecting glucose regulation. ROSI might therefore be a potential treatment to ameliorate age-related decline in cognitive function, particularly on an insulin-resistant background, where improvements in peripheral insulin sensitivity and central nervous system (CNS) glucose utilization may facilitate recovery of cognitive function. We therefore examined the amelioration potential of ROSI for neurocognitive deficits resulting from aging in an animal model. Behaviorally, acute and chronic ROSI treatments enhanced acquisition of learning in the water plus maze, a modified version of the Morris water maze task. In parallel, restoration of synaptic plasticity in the dentate gyrus of ROSI-treated middle-aged rats was evident after a single dose intake. Additionally, the spatial receptive fields of hippocampal CA1 place cells were significantly improved by chronic ROSI administration. ROSI treatment reversed basal plasma insulin abnormalities and increased hippocampal glucose transporter (GLUT)-3 expression in middle-aged rats. Taken together, these results suggest that ROSI modulates hippocampal circuitry effectively to promote an improvement in cognitive function, possibly via a glucose transporter-3 mechanism.

Disease tracking markers for Alzheimer's disease at the prodromal (MCI) stage.

Older persons with Mild Cognitive Impairment (MCI) feature neurobiological Alzheimer's Disease (AD) in 50% to 70% of the cases and develop dementia within the next 5 to 7 years. Current evidence suggests that biochemical, neuroimaging, electrophysiological, and neuropsychological markers can track the disease over time since the MCI stage (also called prodromal AD). The amount of evidence supporting their validity is of variable strength. We have reviewed the current literature and categorized evidence of validity into three classes: Class A, availability of multiple serial studies; Class B a single serial study or multiple cross sectional studies of patients with increasing disease severity from MCI to probable AD; and class C, multiple cross sectional studies of patients in the dementia stage, not including the MCI stage. Several Class A studies suggest that episodic memory and semantic fluency are the most reliable neuropsychological markers of progression. Hippocampal atrophy, ventricular volume and whole brain atrophy are structural MRI markers with class A evidence. Resting-state fMRI and connectivity, and diffusion MR markers in the medial temporal white matter (parahippocampus and posterior cingulum) and hippocampus are promising but require further validation. Change in amyloid load in MCI patients warrant further investigations, e.g. over longer period of time, to assess its value as marker of disease progression. Several spectral markers of resting state EEG rhythms that might reflect neurodegenerative processes in the prodromal stage of AD (EEG power density, functional coupling, spectral coherence, and synchronization) suffer from lack of appropriately designed studies. Although serial studies on late event-related potentials (ERPs) in healthy elders or MCI patients are inconclusive, others tracking disease progression and effects of cholinesterase inhibiting drugs in AD, and cross-sectional including MCI or predicting development of AD offer preliminary evidence of validity as a marker of disease progression from the MCI stage. CSF Markers, such as Aß 1-42, t-tau and p-tau are valuable markers which support the clinical diagnosis of Alzheimer's disease. However, these markers are not sensitive to disease progression and cannot be used to monitor the severity of Alzheimer's disease. For Isoprostane F2 some evidence exists that its increase correlates with the progression and the severity of AD.

Protection against Aß-mediated rapid disruption of synaptic plasticity and memory by memantine.

Soluble amyloid-ß protein (Aß) may cause cognitive impairment in Alzheimer's disease in the absence of significant neurodegeneration. Here, the ability of the NMDA receptor (NMDAR) antagonist memantine to prevent synthetic Aß-mediated rapid functional deficits in learned behavior and synaptic plasticity was assessed in the rat. In vitro, pretreatment with a clinically relevant, NMDAR blocking concentration of memantine partially inhibited the induction of long-term potentiation (LTP) in the dentate gyrus and prevented further inhibition caused by exposure to Aß(1-42). Whereas systemic injection with memantine alone inhibited LTP in the CA1 area in vivo, a subthreshold dose partially abrogated the inhibition of LTP by intracerebroventricular soluble Aß(1-42). Similarly, systemic treatment with memantine alone impaired performance of an operant learning task and a subthreshold dose prevented the Aß(1-42)-mediated increase in perseveration errors. The acute protection afforded by memantine, albeit in a narrow dose range, against the rapid disruptive effects of soluble Aß(1-42) on synaptic plasticity and learned behavior strongly implicate NMDAR-dependent reversible dysfunction of synaptic mechanisms in Aß-mediated cognitive impairment.

Cadmium toxicity and uptake by mats of the freshwater diatom: Navicula pelliculosa (Bréb) Hilse.

Contaminant uptake by algae, and its subsequent toxicity, has important ramifications for aquatic biomonitoring and environmental risk assessment. To study the effects of cadmium on diatom mats, a series of experiments was undertaken. These investigated the sensitivity of Navicula pelliculosa mats to cadmium, uptake of cadmium across a range of exposure concentrations, influence of mat biomass and thickness on uptake, and cadmium uptake by mats over time. Diatom mat formation proved to be sensitive to cadmium exposure, with a 96-h EC(50) of 31 microg/L. The rapid uptake of cadmium over 15 min was a linear function of exposure concentration and was not significantly affected by mat thickness. Cadmium uptake over time was also a linear function of exposure concentration for time periods up to 5 h. Linear uptake was likely due to the availability of algal binding sites as cadmium ions diffused through the diatom mats. Internal high-pH microenvironments may also have influenced uptake, through cadmium precipitation or enhanced adsorption within the mats. The lack of a significant relationship between mat biomass and uptake could be explained by the static water exposure conditions. Other studies have shown that cadmium uptake by algal mats was only significantly affected by biomass under flowing water conditions. Flowing water appeared to facilitate the diffusion of cadmium ions through the algal mats. Our research demonstrates the propensity of diatom mats to adsorb cadmium to achieve concentrations that could inhibit macroinvertebrate grazing. Overall, these findings contribute to a greater understanding of cadmium bioavailability in aquatic ecosystems and to the further development of benthic algae as an effective biomonitoring tool.

The identification of potent, selective and CNS penetrant furan-based inhibitors of B-Raf kinase.

Modification of the potent imidazole-based B-Raf inhibitor SB-590885 resulted in the identification of a series of furan-based derivatives with enhanced CNS penetration. One such compound, SB-699393 (17), was examined in vivo to challenge the hypothesis that selective B-Raf inhibitors may be of value in the treatment of stroke.

SB 234551 selective ET(A) receptor antagonism: perfusion/diffusion MRI used to define treatable stroke model, time to treatment and mechanism of protection.

Mismatches between tissue perfusion-weighted imaging (PWI; an index of blood flow deficit) and cellular diffusion-weighted imaging (DWI; an index of tissue injury) provide information on potentially salvageable penumbra tissue in focal stroke and can identify "treatable" stroke patients. The present pre-clinical studies were conducted to: a.) Determine PWI (using perfusion delay) and DWI measurements in two experimental stroke models, b.) Utilize these measurements to characterize selective ET(A) receptor antagonism (i.e., determine efficacy, time-to-treatment and susceptibility to treatment in the different stroke models), and c.) Determine if increasing the reduced blood flow following a stroke is a mechanism of protection. Permanent middle cerebral artery occlusion (MCAO) or sham surgeries were produced in Sprague Dawley rats (SD; proximal MCAO; hypothesized to be a model of slowly evolving brain injury with a significant penumbra) and in spontaneously hypertensive rats (SHR; distal MCAO; hypothesized to be a model of rapidly evolving brain injury with little penumbra). Infusions of vehicle or SB 234551 (3, 10, or 30 microg/kg/min) were initiated at 0, 75, and/or 180 min post-surgery and maintained for the remainder of 24 h post-surgery. Hyper-intense areas of perfusion delay (PWI) in the forebrain were measured using Gadolinium (Gd) bolus contrast. DWI hyper-intense areas were also measured, and the degree of forebrain DWI-PWI mismatch was determined. Region specific analyses (ROI) were also conducted in the core ischemic and low perfusion/penumbra areas to provide indices of perfusion and changes in the degree of tissue perfusion due to SB 234551 treatment. At 24 h post-surgery, final infarct volume was measured by DWI and by staining forebrain slices. Following SD proximal MCAO, there was a significant mismatch in the ischemic forebrain PWI compared to DWI (PWI>DWI) at 60 min which was maintained up to 150 min (all p<0.05). By 24 h post-stroke, infarct volume was identical to the area of early perfusion deficit/PWI, suggesting a slow progression of infarct development that expanded into the significant, earlier cortical penumbra (i.e., model with salvageable tissue with potential for intervention). When SB 234551 was administered within the period of peak mismatch (i.e., at 75 min post-stroke), SB 234551 provided significant dose-related reductions in cortical (penumbral) progression to infarction (p<0.05). Cortical protection was related to an increased/normalization of the stroke-induced decrease in tissue perfusion in cortical penumbra areas (p<0.05). No SB 234551-induced changes in reduced tissue perfusion were observed in the striatum core ischemic area. Also, when SB-234551 was administered beyond the time of mismatch, no effect on cortical penumbra progression to infarct was observed. In comparison and strikingly different, following SHR distal MCAO there was no mismatch between PWI and DWI (PWI=DWI) as early as 60 min post-stroke, with this early change in SHR DWI being identical to the final infarct volume at 24 h, suggesting a rapidly occurring brain injury with little cortical penumbra (i.e., model with little salvageable tissue or potential for intervention). In distal MCAO, SB 234551 administered immediately at the time of stroke did not have any effect on infarct volume in SHR. These data demonstrate that selective blockade of ET(A) receptors is protective following proximal MCAO in SD (i.e. a model similar to "treatable" clinical patients). The protective mechanism appears to be due to enhanced collateral blood flow and salvage of penumbra. Therefore, the use of PWI-DWI mismatch signatures can identify treatable stroke models characterized by a salvageable penumbra and can define appropriate time to treatment protocols. In addition, tissue perfusion information obtained under these conditions might clarify mechanism of protection in the evaluation of protective compounds for focal stroke.

Effects of arsenic speciation and low dissolved oxygen condition on the toxicity of arsenic to a lotic mayfly.

The influence of site-specific conditions on contaminant bioavailability and toxicity to benthic invertebrates is a key consideration in the environmental risk assessment process. This is particularly relevant for contaminants with complex speciation chemistries, such as arsenic. The present study addressed uncertainties regarding arsenic toxicity to a mayfly (Baetis tricaudatus) under low dissolved oxygen (DO) conditions characteristic of many contaminated sites. Arsenic toxicity (arsenite, As(III); arsenate, As(V)) to mayfly nymphs was assessed under two DO scenarios (68 and 84% saturation). Arsenic speciation ratios were determined during testing to confirm the nature of arsenic exposure. The present study found that As(III) was more lethal and bioaccumulated to a greater degree in B. tricaudatus compared to As(V), but the sublethal toxicities of the two arsenic species were similar. Nymph growth and development were significantly inhibited after 12 d of exposure to both 1 mg/L of As(III) and As(V). Exposure to arsenic under low DO conditions (6.5 mg/L, 68% saturation) did not significantly affect As(III) or As(V) toxicity and bioaccumulation over 12 d. The DO level of 6.5 mg/L, however, appeared to be marginally lethal to B. tricaudatus. Results indicate that the Canadian arsenic criterion for the protection of aquatic life (5 microg/L) is protective of B. tricaudatus and is low enough to accommodate differences in arsenic toxicity because of the interconversions between As(III) and As(V). These findings provide insight regarding the toxicity and speciation of arsenic under DO conditions considered to be low for this lotic mayfly species and representative of existing conditions at mine sites in northern Canada.

Peri-infarct depolarizations lead to loss of perfusion in ischaemic gyrencephalic cerebral cortex.

In the light of accumulating evidence for the occurrence of spontaneous cortical spreading depression and peri-infarct depolarizations in the human brain injured by trauma or aneurysmal subarachnoid haemorrhage, we used DC electrode recording and laser speckle imaging to study the relationship between depolarization events and perfusion in the ischaemic, gyrencephalic brain. In 14 adult male cats anaesthetized with chloralose, one cerebral hemisphere was exposed and the middle cerebral artery occluded. Surface cortical perfusion in core and penumbral territories was imaged semiquantitatively at intervals of 13 s for 4 h. Cortical surface DC potential was recorded. Time interval between changes in DC potential and in perfusion was examined, and this comparison was repeated using microelectrodes for DC potential in five similar experiments in a second laboratory. Mean pre-occlusion perfusion was 11707 +/- 4581 units (equivalent to CBF (cerebral blood flow) approximately 40.5 +/- SD 14.4 ml/100 g/min), and fell on occlusion to 5318 +/- 2916 (CBF approximately 17.1 +/- 8.3), 5291 +/- 3407 (CBF approximately 17.0 +/- 10.1), and 6711 +/- 3271 (CBF approximately 22.2 +/- 9.6), quickly recovering to 8704 +/- 4581 (CBF approximately 29.5 +/- 14.4), 9741 +/- 4499 (CBF approximately 33.3 +/- 14.1) and 10 314 +/- 3762 (CBF approximately 35.4 +/- 11.4) on the core, intermediate and outer penumbral gyri, respectively. Mean perfusion later fell secondarily on core and intermediate gyri but, overall, was preserved on the outer (upper level of perfusion) gyrus during the period of observation. Pattern and severity of transient changes in perfusion associated with depolarization events varied with gyral location; falls in perfusion were sometimes profound and irreversible, and followed rather than preceded depolarization. In this model of occlusive stroke, reductions in perfusion linked to peri-infarct depolarization events contribute to secondary deterioration in penumbral areas. The findings suggest that such events play a central rather than a subsidiary role in cerebral infarction in the gyrencephalic brain.

Symptomatic treatment of Alzheimer's disease: identification of biomarkers to aid translation from bench to bedside.

In the absence of robust pharmacodynamic markers, the potential success of novel therapeutic agents for the symptomatic relief of Alzheimer's disease is largely unknown until the drugs enter relatively large studies, assessing clinical outcome over a 6-month period. In order to increase the efficiency of future clinical development there is, therefore, a need to identify pharmacodynamic markers of drug response, pharmacodynamic models that allow early prediction of efficacy and markers to aid the stratification of the patient population. Using literature available from cholinesterase inhibitors, memantine and Ginkgo biloba, this review focuses on the identification of potential pharmacodynamic markers/models and highlights the utility of these end points throughout the drug discovery process, from preclinical to clinical development.