Magnetic navigation in percutaneous coronary and non-coronary interventions

There is no question that Percutaneous Coronary Intervention has revolutionized the way we manage coronary artery disease. Over the past two decades we have witnessed maturity in several techniques and equipment enabling the interventional cardiologist to manage lesions that have previously been entirely in the domain of the cardiac surgeon. Despite these remarkable achievements there still remain lesions that are complex enough to create a challenge in the most experienced hands.The inherent tortuosity in complex vascular anatomies, branching segments and chronically occluded vessel have been all associated with lower procedural success and higher complication rates when compared to the “straight forward vessels”. The Magnetic Navigation System (MNS) is a novel and versatile technology that allows the re-orientation of a wire within the patient’s body. This unique ability means that the “trial and error” method of externally re-shaping the tip of the wire and re-engaging the vessel can be effectively eliminated. As such previously “unreachable areas” in the heart or within the vascul

Nutrient Addition Effects on Phytoplankton Communities in the Amazon River Plume

The types and abundance of phytoplankton is largely controlled by availability of sunlight and bioavailable nutrients. Phytoplankton require essential nutrients including nitrate, phosphate, and silicate to grow, so understanding the role of these macronutrients in limiting the growth phytoplankton communitiesand the way this may differ depending on community compositionis key to understanding the controls on phytoplankton biomass and community structure. We aimed to explore how the availability of these nutrients affects the health and composition of phytoplankton communities by conducting a series of nutrient amendment experiments (NAEs) with samples from the Western Tropical North Atlantic, which is heavily influenced by the nutrient-rich, low salinity waters of the Amazon River Plume. These experiments, conducted at five locations in and around the plume, provide greater resolution and further our understanding about the ways nutrients affect communities in dynamic coastal regions

Depression in diabetic patients presenting to the emergency department in Trinidad and Tobago – a hidden epidemic

The likelihood of depression in diabetics presenting to the Emergency Department in developing countries is unknown. The aim of this study was to determine the prevalence of undiagnosed depression among diabetic patients presenting to the Emergency Department in Trinidad and Tobago, and to determine the risk factors associated with depression in these patients. The prevalence of depression was 46.2%, of which 76.1% had mild depression, 20.6% moderate depression and 3.3% severe depression. Depressed patients were more likely to be Indo Trinidadian (69.7%), married (61.8%) and working in the public sector (42.3%). Factors independently associated with depression included lower education level (p=0.003), and a history of co-existing heart disease (p=0.048), myocardial infarction (p=0.04) or other co-morbidities (p=0.010). Depressed patients had higher HbA1c% values (p<0.0001), and were less likely to adhere to meal plans (p=0.015) and exercise regimes (p=0.028). Depression is an unrecognised epidemic among diabetics in the Trinidad and Tobago. This study suggests that screening for depression among diabetics in the Emergency Department may be a useful method of identifying these patients. Additionally, the association between poor diabetic control and depression in these patients suggests the need for more research into this phenomenon

Factors affecting mortality in major trauma patients in Trinidad and Tobago – a view from the developing world

Background: There is little data on major trauma in the developing world. This study investigated the characteristics and outcomes of seriously injured patients in Trinidad and Tobago, using TRISS methodology. Conclusion: Multiple factors influence mortality in major trauma patients in Trinidad and Tobago, including age, co-morbidities and injury mechanism. TRISS methodology accurately predicted survival in this population. A multi-centre trial is required to validate these findings

Polypharmacy and potential drug-drug interactions in emergency department patients in the Caribbean

Background Potential Drug–Drug Interactions (DDI) account for many emergency department visits. Polypharmacy, as well as herbal, over-the-counter (OTC) and combination medication may compound this, but these problems are not well researched in low-and-middle-income countries. Objective To compare the incidence of drug–drug interactions and polypharmacy in older and younger patients attending the Emergency Department (ED). Setting The adult ED of a tertiary teaching hospital in Trinidad. Methods A 4 month cross sectional study was conducted, comparing potential DDI in older and younger patients discharged from the ED, as defined using Micromedex 2.0. Main outcome measure The incidence and severity of DDI and polypharmacy (defined as the use of ≥5 drugs simultaneously) in older and younger patients attending the ED. Results 649 patients were included; 275 (42.3%) were ≥65 years and 381 (58.7%) were female. There were 814 DDIs, of which 6 (.7%) were contraindications and 148 (18.2%) were severe. Polypharmacy was identified in 244 (37.6%) patients. Older patients were more likely to have potential DDI (67.5 vs 48.9%) and polypharmacy (56 vs 24.1%). Herbal products, OTC and combination drugs were present in 8, 36.7 and 22.2% of patients, respectively. On multivariate analysis, polypharmacy and the presence of hypertension and ischaemic heart disease were associated with an increased risk of potential DDI. Conclusion Polypharmacy and potential drug–drug interactions are common in ED patients in the Caribbean. Older patients are particularly at risk, especially as they are more likely to be on multiple medications. The association between herbal medication and polypharmacy needs further investigation. This study indicates the need for a more robust system of drug reconciliation in the Caribbean

Synaptic Plasticity Can Produce and Enhance Direction Selectivity

The discrimination of the direction of movement of sensory images is critical to the control of many animal behaviors. We propose a parsimonious model of motion processing that generates direction selective responses using short-term synaptic depression and can reproduce salient features of direction selectivity found in a population of neurons in the midbrain of the weakly electric fish Eigenmannia virescens. The model achieves direction selectivity with an elementary Reichardt motion detector: information from spatially separated receptive fields converges onto a neuron via dynamically different pathways. In the model, these differences arise from convergence of information through distinct synapses that either exhibit or do not exhibit short-term synaptic depression—short-term depression produces phase-advances relative to nondepressing synapses. Short-term depression is modeled using two state-variables, a fast process with a time constant on the order of tens to hundreds of milliseconds, and a slow process with a time constant on the order of seconds to tens of seconds. These processes correspond to naturally occurring time constants observed at synapses that exhibit short-term depression. Inclusion of the fast process is sufficient for the generation of temporal disparities that are necessary for direction selectivity in the elementary Reichardt circuit. The addition of the slow process can enhance direction selectivity over time for stimuli that are sustained for periods of seconds or more. Transient (i.e., short-duration) stimuli do not evoke the slow process and therefore do not elicit enhanced direction selectivity. The addition of a sustained global, synchronous oscillation in the gamma frequency range can, however, drive the slow process and enhance direction selectivity to transient stimuli. This enhancement effect does not, however, occur for all combinations of model parameters. The ratio of depressing and nondepressing synapses determines the effects of the addition of the global synchronous oscillation on direction selectivity. These ingredients, short-term depression, spatial convergence, and gamma-band oscillations, are ubiquitous in sensory systems and may be used in Reichardt-style circuits for the generation and enhancement of a variety of biologically relevant spatiotemporal computations

Bursts and Isolated Spikes Code for Opposite Movement Directions in Midbrain Electrosensory Neurons

Directional selectivity, in which neurons respond strongly to an object moving in a given direction but weakly or not at all to the same object moving in the opposite direction, is a crucial computation that is thought to provide a neural correlate of motion perception. However, directional selectivity has been traditionally quantified by using the full spike train, which does not take into account particular action potential patterns. We investigated how different action potential patterns, namely bursts (i.e. packets of action potentials followed by quiescence) and isolated spikes, contribute to movement direction coding in a mathematical model of midbrain electrosensory neurons. We found that bursts and isolated spikes could be selectively elicited when the same object moved in opposite directions. In particular, it was possible to find parameter values for which our model neuron did not display directional selectivity when the full spike train was considered but displayed strong directional selectivity when bursts or isolated spikes were instead considered. Further analysis of our model revealed that an intrinsic burst mechanism based on subthreshold T-type calcium channels was not required to observe parameter regimes for which bursts and isolated spikes code for opposite movement directions. However, this burst mechanism enhanced the range of parameter values for which such regimes were observed. Experimental recordings from midbrain neurons confirmed our modeling prediction that bursts and isolated spikes can indeed code for opposite movement directions. Finally, we quantified the performance of a plausible neural circuit and found that it could respond more or less selectively to isolated spikes for a wide range of parameter values when compared with an interspike interval threshold. Our results thus show for the first time that different action potential patterns can differentially encode movement and that traditional measures of directional selectivity need to be revised in such cases