On The Mobile Behavior of Solid 4^4He at High Temperatures

We report studies of solid helium contained inside a torsional oscillator, at temperatures between 1.07K and 1.87K. We grew single crystals inside the oscillator using commercially pure $^4$He and $^3$He-$^4$He mixtures containing 100 ppm $^3$He. Crystals were grown at constant temperature and pressure on the melting curve. At the end of the growth, the crystals were disordered, following which they partially decoupled from the oscillator. The fraction of the decoupled He mass was temperature and velocity dependent. Around 1K, the decoupled mass fraction for crystals grown from the mixture reached a limiting value of around 35%. In the case of crystals grown using commercially pure $^4$He at temperatures below 1.3K, this fraction was much smaller. This difference could possibly be associated with the roughening transition at the solid-liquid interface.Comment: 15 pages, 6 figure

Systematic documentation and analysis of human genetic variation in hemoglobinopathies using the microattribution approach

We developed a series of interrelated locus-specific databases to store all published and unpublished genetic variation related to hemoglobinopathies and thalassemia and implemented microattribution to encourage submission of unpublished observations of genetic variation to these public repositories. A total of 1,941 unique genetic variants in 37 genes, encoding globins and other erythroid proteins, are currently documented in these databases, with reciprocal attribution of microcitations to data contributors. Our project provides the first example of implementing microattribution to incentivise submission of all known genetic variation in a defined system. It has demonstrably increased the reporting of human variants, leading to a comprehensive online resource for systematically describing human genetic variation in the globin genes and other genes contributing to hemoglobinopathies and thalassemias. The principles established here will serve as a model for other systems and for the analysis of other common and/or complex human genetic diseases

Multi-Membership and the Effectiveness of Regional Trade Agreements in Western and Southern Africa: A Comparative Study of ECOWAS and SADC

Using a gravity model for 35 countries and the years 1995-2006 we estimate the impact of regional trade agreements in Africa (in particular ECOWAS and SADC) and compare this to the a benchmark of North South trade integration (Europe’s preferential trade agreement). We find that • ECOWAS and SADC membership significantly increases bilateral trade flows (and by more than for example preferential trade agreements with the EU do), • SADC membership has a stronger impact compared to ECOWAS and • that the impact of multi-membership critically depends on the characteristics of the overlapping RTA. We find a positive impact if an additional membership complements the integration process of the original RTA: overlapping memberships had a significant positive effect on bilateral trade within the ECOWAS bloc but it is insignificant for SADC

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Beta Chemokine expression in an in vitro model of the human blood-brain barrier

It is now well established that the interactions between endothelium and circulating white blood cells are of critical importance in the evolution of an inflammatory response. Chemokines are small chemoattractant cytokines with the unique ability to stimulate and guide the movement of specific classes of inflammatory cells to sites of inflammation. The role of chemokines in CNS inflammation has not been fully elucidated. Over the last decade, various studies have suggested that CCL2(MCP-1) and CCL3 (MIP-1α) are major players in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalitis (EAE). The aim of the present study is to investigate the expression and cytokine upregulation of CCL2 and CCL3 by human brain microvessel endothelial cells (HBMEC), an in vitro model of the human bloodbrain barrier. Primary cultures of HBMEC grown to confluence were stimulated with TNFα, IFNγ, IL-1β or LPS for 24-72 h. RNA expression was confirmed by RT-PCR and intracellular protein expression was detected with immunogold silver staining (IGSS). Protein release was quantitated with ELISA. CCL2 RNA levels were similar in both unstimulated and cytokine-treated cells. CCL3 RNA was upregulated upon cytokine stimulation. IGSS confirmed chemokine expression in both unstimulated and cytokinetreated cells. The basal release of CCL2 by resting HBMEC was significantly upregulated after cytokine treatment in a concentration and time-dependent manner. ELISA of the supernatants showed CCL3 release only after stimulation. Immunoelectron microscopy studies show chemokine binding to the apical and basal surfaces of HBMEC. These studies suggest that the cerebral endothelium may play an active role in the initiation, selective recruitment and activation of circulating lymphocytes and monocytes during CNS inflammation.Medicine, Faculty ofPathology and Laboratory Medicine, Department ofGraduat

Bioelectronic Intervention in Cardiovascular Control

The autonomic nervous system (ANS) has a profound influence on cardiac function. Alterations in ANS balance has tremendous impact on the initiation and progression of cardiac pathology. Current standards of care (pharmacology, surgery, devices) have proven efficacy, but well-known limitations as well. Bioelectronic therapy has the potential to provide a reversible, on demand, scalable approach to cardiac control. The hypothesis of this thesis is that imbalances in information processing between different levels of the cardiac neuraxis is a primary determinant in mediating electrical instability of the heart and progression into heart failure. As a corollary, mitigating imposed neural imbalances within the hierarchy for cardiac control is cardioprotective. To investigate bioelectronic modulation of the parasympathetic control of cardiac pathology, vagal nerve stimulation (VNS) was employed in a guinea pig pressure overload (PO) model of heart failure with preserved ejection fraction (HFpEF). Guinea pigs were subjected to aortic constriction, in the presence or absence of VNS. The effects on disease were assessed in the whole animal (echocardiography) and at the neural (intracellular current clamp recordings of intrinsic cardiac (IC) neurons) and myocyte (protein expression) levels. To investigate bioelectronic modulation of sympathetic drive to the heart, proof of concept studies involving kilohertz frequency alternating current (KHFAC) and charge-balanced direct current carousel (CBDCC) were employed in an anesthetized porcine model. CBDCC was also used to determine impact on arrhythmia potential in a porcine myocardial infarction (MI) model. With VNS therapy, PO-induced hemodynamic responses (increased cardiac output, systolic/diastolic left ventricular volumes) were prevented. Enhancements in synaptic efficacy muscarinic sensitivity were also mitigated. Myocyte hypertrophy was prevented using right-sided VNS. PO-induced hypertrophic myocardium also abnormal energetics, which was modulated with VNS application. For sympathetic control, KHFAC and CBDCC demonstrated reversible, current-dependent impact on cardiac indices (activation recovery intervals (ARI), heart rate, and contractility). In the MI model, extrasystolic (S1-S2) stimulations induced ventricular arrhythmias in all animals (n=7), whereas right-sided CBDCC application reduced inducibility by 83%. The ventricular effective refractory period (VERP) was prolonged with CBDCC (323�26 ms) compared to baseline (271�32 ms).In conclusion, the data within this thesis provides validation for a mechanism-based approach to cardiac therapy that combines the potential of bioelectronic therapy with a detailed knowledge of cardiac neuraxis structure/function, addressing a significant unmet need in managing both arrhythmia burden and the progression of heart failure

Regulation of CCL2 and CCL3 expression in human brain endothelial cells by cytokines and lipopolysaccharide

Background. Chemokines are emerging as important mediators of CNS inflammation capable of activating leukocyte integrins and directing the migration of leukocyte subsets to sites of antigenic challenge. In this study we investigated the expression, release and binding of CCL2 (MCP-1) and CCL3 (MIP-1α) in an in vitro model of the human blood-brain barrier. Methods The kinetics of expression and cytokine upregulation and release of the β-chemokines CCL2 and CCL3 were studied by immunocytochemistry and enzyme-linked immunosorbent assay in primary cultures of human brain microvessel endothelial cells (HBMEC). In addition, the differential binding of these chemokines to the basal and apical endothelial cell surfaces was assessed by immunoelectron microscopy. Results Untreated HBMEC synthesize and release low levels of CCL2. CCL3 is minimally expressed, but not released by resting HBMEC. Treatment with TNF-α, IL-1β, LPS and a combination of TNF-α and IFN-γ, but not IFN-γ alone, significantly upregulated the expression and release of both chemokines in a time-dependent manner. The released CCL2 and CCL3 bound to the apical and basal endothelial surfaces, respectively. This distribution was reversed in cytokine-activated HBMEC resulting in a predominantly basal localization of CCL2 and apical distribution of CCL3. Conclusions Since cerebral endothelial cells are the first resident CNS cells to contact circulating leukocytes, expression, release and presentation of CCL2 and CCL3 on cerebral endothelium suggests an important role for these chemokines in regulating the trafficking of inflammatory cells across the BBB in CNS inflammation.Medicine, Faculty ofPathology and Laboratory Medicine, Department ofNon UBCReviewedFacult

Bioelectronic neuromodulation of the paravertebral cardiac efferent sympathetic outflow and its effect on ventricular electrical indices

BackgroundNeuromodulation of the paravertebral ganglia by using symmetric voltage controlled kilohertz frequency alternating current (KHFAC) has the potential to be a reversible alternative to surgical intervention in patients with refractory ventricular arrhythmias. KHFAC creates scalable focal inhibition of action potential conduction.ObjectiveThe purpose of this article was to evaluate the efficacy of KHFAC when applied to the T1-T2 paravertebral chain to mitigate sympathetic outflow to the heart.MethodsIn anesthetized, vagotomized, porcine subjects, the heart was exposed via a midline sternotomy along with paravertebral chain ganglia. The T3 paravertebral ganglion was electrically stimulated, and activation recovery intervals (ARIs) were obtained from a 56-electrode sock placed over both ventricles. A bipolar Ag electrode was wrapped around the paravertebral chain between T1 and T2 and connected to a symmetric voltage controlled KHFAC generator. A comparison of cardiac indices during T3 stimulation conditions, with and without KHFAC, provided a measure of block efficacy.ResultsRight-sided T3 stimulation (at 4 Hz) was titrated to produce reproducible ARI changes from baseline (52 ± 30 ms). KHFAC resulted in a 67% mitigation of T3 electrical stimulation effects on ARI (18.5 ± 22 ms; P < .005). T3 stimulation repeated after KHFAC produced equivalent ARI changes as control. KHFAC evoked a transient functional sympathoexcitation at onset that was inversely related to frequency and directly related to intensity. The optimum block threshold was 15 kHz and 15 V.ConclusionKHFAC applied to nexus (convergence) points of the cardiac nervous system produces a graded and reversible block of underlying axons. As such, KHFAC has the therapeutic potential for on-demand and reversible mitigation of sympathoexcitation