Desmin forms toxic, seeding-competent amyloid aggregates that persist in muscle fibers

Desmin-associated myofibrillar myopathy (MFM) has pathologic similarities to neurodegeneration-associated protein aggregate diseases. Desmin is an abundant muscle-specific intermediate filament, and disease mutations lead to its aggregation in cells, animals, and patients. We reasoned that similar to neurodegeneration-associated proteins, desmin itself may form amyloid. Desmin peptides corresponding to putative amyloidogenic regions formed seeding-competent amyloid fibrils. Amyloid formation was increased when disease-associated mutations were made within the peptide, and this conversion was inhibited by the anti-amyloid compound epigallocatechin-gallate. Moreover, a purified desmin fragment (aa 117 to 348) containing both amyloidogenic regions formed amyloid fibrils under physiologic conditions. Desmin fragment-derived amyloid coaggregated with full-length desmin and was able to template its conversion into fibrils in vitro. Desmin amyloids were cytotoxic to myotubes and disrupted their myofibril organization compared with desmin monomer or other nondesmin amyloids. Finally, desmin fragment amyloid persisted when introduced into mouse skeletal muscle. These data suggest that desmin forms seeding-competent amyloid that is toxic to myofibers. Moreover, small molecules known to interfere with amyloid formation and propagation may have therapeutic potential in MFM

In vitro models to evaluate ingestible devices:present status and current trends

Orally ingestible medical devices offer significant opportunity in the diagnosis and treatment of gastrointestinal conditions. Their development necessitates the use of models that simulate the gastrointestinal environment on both a macro and micro scale. An evolution in scientific technology has enabled a wide range of in vitro, ex vivo and in vivo models to be developed that replicate the gastrointestinal tract. This review describes the landscape of the existing range of in vitro tools that are available to characterize ingestible devices. Models are presented with details on their benefits and limitations with regards to the evaluation of ingestible devices and examples of their use in the evaluation of such devices is presented where available. The multitude of models available provides a suite of tools that can be used in the evaluation of ingestible devices that should be selected on the functionality of the device and the mechanism of its function

Dissolution profile of theophylline modified release tablets, using a biorelevant Dynamic Colon Model (DCM)

AbstractThe human proximal colon has been considered a favourable site to deliver drugs for local and systemic treatments. However, modified dosage forms face a complex and dynamically changing colonic environment. Therefore, it has been realized that in addition to the use of biorelevant media, the hydrodynamics also need to be reproduced to create a powerful in vitro dissolution model to enable in vivo performance of the dosage forms to be predicted.A novel biorelevant Dynamic Colon Model (DCM) has been developed which provides a realistic environment in terms of the architecture of the smooth muscle, the physical pressures and the motility patterns occurring in the proximal human colon. Measurements of pressure inside the DCM tube confirmed a direct association between the magnitude of the pressure signal with the occlusion rate of the membrane and the viscosity of the fluid.The dissolution profile and the distribution of the highly soluble drug, theophylline, were assessed by collecting samples at different locations along the DCM tube. Differences in the release rates of the drug were observed which were affected by the sampling point location, the viscosity of the fluid and the mixing within the DCM tube. Images of the overall convective motion of the fluid inside the DCM tube obtained using Positron Emission Tomography enabled relation of the distribution of the tracer to likely areas of high and low concentrations of the theophylline drug.This information provides improved understanding of how extensive phenomena such as supersaturation and precipitation of the drug may be during the passage of the dosage form through the proximal colon

Use of PLIF to assess the mixing performance of small volume USP 2 apparatus in shear thinning media

AbstractPlanar Laser Induced Fluorescence (PLIF) was used to assess mixing in small volume USP 2 dissolution apparatus for a range of viscous fluids which mimic gastrointestinal media, especially in the fed state. The release into the media from a specially prepared tablet containing Rhodamine 6G dye was tracked in time and the areal distribution method developed by Alberini et al. (2014a) was implemented to characterise the mixing performance. The distributions of the individual striations for selected mixing levels were also presented. These findings illustrate the poor mixing performance of the apparatus resulting in high variance of the dissolution data when working with viscous media. Analysis of data using CoV gives misleading results for the mixing performance of the small volume USP 2 dissolution apparatus. The results showed that the best mixing was mainly located above the blade and close to the wall, i.e. in the region where intensive motion takes place. This work presents important guidelines and precautions for choosing the proper sampling point for a wide range of liquid viscosities to minimize the variability of the dissolution data

Sustainable Energy Transitions: Changing the ‘Business as usual’ trajectory in sub-Saharan African urban areas

This paper describes a novel approach to helping municipal authorities address the sustainable energy challenges associated with rapidly growing urban populations in Sub-Saharan Africa. Population in Africa is expected to double between 2010 and 2040, and substantial urban growth is expected in small and medium-sized cities where local government capacity constraints are most serious. A long-term partnership between municipal authorities, NGOs, and academics can build capacity, and a prescribed strategy can lead to progress on the ground. In order to contribute to future action, the paper argues for a greater role of local government in sustainable energy transitions, and presents some of the lessons learned from work in municipality-based energy work undertaken in South Africa over a 17-year period. It provides evidence of change, but more importantly, considers the process by which that change occurred and the intentional strategy of policy influence. Several South African cities engaged in this process with the assistance of the non-profit organization Sustainable Energy Africa have been able to move to greater renewable energy and energy efficiency implementation, and have strengthened their energy capacity and governance frameworks. The paper reviews the changing energy characteristics of South African cities, and describes the key processes that create a policy environment conducive to moving away from business as usual and responding to sustainable energy imperatives around clean energy and energy poverty. The use of energy modeling to support municipal energy strategy development is also described as an important informant for decision-makers regarding the consequences of decisions taken, or not taken, today. As such, it provides the groundwork for transferring the methodological process to other countries, wjile the latter part of the paper draws on recent experiences in Uganda and Ghana in replicating the work

Resolving singular forces in cavity flow: Multiscale modeling from atoms to millimeters

A multiscale approach for fluid flow is developed that retains an atomistic description in key regions. The method is applied to a classic problem where all scales contribute: The force on a moving wall bounding a fluid-filled cavity. Continuum equations predict an infinite force due to stress singularities. Following the stress over more than six decades in length in systems with characteristic scales of millimeters and milliseconds allows us to resolve the singularities and determine the force for the first time. The speedup over pure atomistic calculations is more than fourteen orders of magnitude. We find a universal dependence on the macroscopic Reynolds number, and large atomistic effects that depend on wall velocity and interactions.Comment: 4 pages,3 figure

Turbulent boundary layers and channels at moderate Reynolds numbers

The behaviour of the velocity and pressure fluctuations in the outer layers of wall-bounded turbulent flows is analysed by comparing a new simulation of the zero-pressure-gradient boundary layer with older simulations of channels. The 99 % boundary-layer thickness is used as a reasonable analogue of the channel half-width, but the two flows are found to be too different for the analogy to be complete. In agreement with previous results, it is found that the fluctuations of the transverse velocities and of the pressure are stronger in the boundary layer, and this is traced to the pressure fluctuations induced in the outer intermittent layer by the differences between the potential and rotational flow regions. The same effect is also shown to be responsible for the stronger wake component of the mean velocity profile in external flows, whose increased energy production is the ultimate reason for the stronger fluctuations. Contrary to some previous results by our group, and by others, the streamwise velocity fluctuations are also found to be higher in boundary layers, although the effect is weaker. Within the limitations of the non-parallel nature of the boundary layer, the wall-parallel scales of all the fluctuations are similar in both the flows, suggesting that the scale-selection mechanism resides just below the intermittent region, y/¿=0.3¿0.5. This is also the location of the largest differences in the intensities, although the limited Reynolds number of the boundary-layer simulation (Re¿ ¿ 2000) prevents firm conclusions on the scaling of this location. The statistics of the new boundary layer are available from http://torroja.dmt.upm.es/ftp/blayers/

The effect of biorelevant hydrodynamic conditions on drug dissolution from extended-release tablets in the dynamic colon model

The in vitro release of theophylline from an extended-release dosage form was studied under different hydrodynamic conditions in a United States Pharmacopoeial (USP) dissolution system II and a bespoke in vitro tubular model of the human colon, the Dynamic Colon Model (DCM). Five biorelevant motility patterns extracted from in vivo data were applied to the DCM, mimicking the human proximal colon under baseline conditions and following stimulation using polyethylene glycol or maltose; these represent the lower and upper bounds of motility normally expected in vivo. In the USPII, tablet dissolution was affected by changing hydrodynamic conditions at different agitation speeds of 25, 50 and 100 rpm. Applying different motility patterns in the DCM affected the dissolution profiles produced, with theophylline release at 24 h ranging from 56.74 ± 2.00% (baseline) to 96.74 ± 9.63% (maltose-stimulated). The concentration profiles of theophylline were markedly localized when measured at different segments of the DCM tube, highlighting the importance of a segmented lumen in intestine models and in generating spatial information to support simple temporal dissolution profiles. The results suggested that the shear stresses invoked by the unstimulated, healthy adult human colon may be lower than those in the USPII at 25 rpm and thus insufficient to achieve total release of a therapeutic compound from a hydroxyethyl cellulose matrix. When operated under stimulated conditions, drug release in the DCM was between that achieved at 25 and 50 rpm in the USPII

Loss of residues 119 – 136, including the first β-strand of human prion protein, generates an aggregation-competent partially “open” form

In prion replication, the cellular form of prion protein (PrPC) must undergo a full conformational transition to its disease-associated fibrillar form. Transmembrane forms of PrP have been implicated in this structural conversion. The cooperative unfolding of a structural core in PrPC presents a substantial energy barrier to prion formation, with membrane insertion and detachment of parts of PrP presenting a plausible route to its reduction. Here, we examined the removal of residues 119 - 136 of PrP, a region which includes the first β-strand and a substantial portion of the conserved hydrophobic region of PrP, a region which associates with the ER membrane, on the structure, stability and self-association of the folded domain of PrPC. We see an "open" native-like conformer with increased solvent exposure which fibrilises more readily than the native state. These data suggest a stepwise folding transition, which is initiated by the conformational switch to this "open" form of PrPC