Unusual “Politics as Usual”: The 2017 Ballot Proposition Calling for a Constitutional Convention in New York

The first task of constitutional reformers is to make the people of the state aware that they live under a constitution that, for better or worse, affects their everyday lives whether they live on in remotes sections of the Adirondacks routes in villages or a teeming megalopolis. Until this is done, the people are not likely to demand or even accept the more thoroughgoing revision so badly needed in New York

Simultaneous Application of Interstitial Flow and Cyclic Mechanical Strain to a Three-Dimensional Cell-Seeded Hydrogel

The present study describes the design and validation of a simple apparatus to apply simultaneous mechanical and fluidic stress to three-dimensional (3D) cell-seeded collagen hydrogels. Constructs were formed in wells in a silicone substrate that could be stretched cyclically, and were also fitted with inlet ports to apply fluid flow. Acid etching was used to retain adhesion of the gels to the walls of the well, and an acellular layer of collagen hydrogel was used to distribute flow evenly. Finite element modeling showed that 5% uniaxial strain applied to the entire silicone substrate resulted in -6.5% strain in each of the gel constructs. Permeability testing and flow observation showed that acellular hydrogels were fourfold more permeable than cardiac fibroblast-seeded gels, and that the fluid distributed evenly in the acellular layer before entering the cell-seeded gel. Viability testing and imaging demonstrated that cells remained viable with expected fibroblast morphology for the 120-h duration of the experiments. These results demonstrate that this simple bioreactor can be used to study the effects of mechanical strain and interstitial flow in 3D protein hydrogels. Such 3D tissue models have utility in studying cell and tissue responses to their mechanical environment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90463/1/ten-2Etec-2E2010-2E0547.pd

Peristaltic flow in the glymphatic system.

The flow inside the perivascular space (PVS) is modeled using a first-principles approach in order to investigate how the cerebrospinal fluid (CSF) enters the brain through a permeable layer of glial cells. Lubrication theory is employed to deal with the flow in the thin annular gap of the perivascular space between an impermeable artery and the brain tissue. The artery has an imposed peristaltic deformation and the deformable brain tissue is modeled by means of an elastic Hooke\u27s law. The perivascular flow model is solved numerically, discovering that the peristaltic wave induces a steady streaming to/from the brain which strongly depends on the rigidity and the permeability of the brain tissue. A detailed quantification of the through flow across the glial boundary is obtained for a large parameter space of physiologically relevant conditions. The parameters include the elasticity and permeability of the brain, the curvature of the artery, its length and the amplitude of the peristaltic wave. A steady streaming component of the through flow due to the peristaltic wave is characterized by an in-depth physical analysis and the velocity across the glial layer is found to flow from and to the PVS, depending on the elasticity and permeability of the brain. The through CSF flow velocity is quantified to be of the order of micrometers per seconds

Cellular Mechanotransduction in the Pathogenesis and Treatment of Cardiac Fibrosis

Cardiac fibrosis occurs after myocardial infarction, and contributes to both systolic and diastolic heart failure. Activation of cardiac fibroblasts to a myofibroblast phenotype is essential for fibrotic scar development. The present dissertation focuses on this phenotypic transition, specifically on the effects of mechanical stress and interactions with mesenchymal stem cells (MSC). The experimental platform used was a flexible 3D culture well that allowed simultaneous application of fluid flow and cyclic strain to collagen type I hydrogels seeded with primary rat neonatal cardiac fibroblasts. The results indicated that fibroblasts transitioned to myofibroblasts in static culture in the absence of exogenous biochemical or mechanical stimulation. Interstitial fluid flow significantly stimulated the myofibroblast transition, while cyclic strain had an opposing effect. Using chemical antagonists and lentivirally-delivered shRNA, it was found that the acute response to flow was mediated by angiotensin II receptor type I (AT1R) and transforming growth factor β (TGF-β). Cyclic strain also influenced the TGF-β pathway by attenuating the phosphorylation of smad2, a downstream effector of this signaling pathway. The experimental results were augmented with a poroelastic model of flow and gel displacement within the collagen hydrogels, which indicated that cyclic strain produced substantial interstitial fluid flow in the absence of applied cross flow. The results of the analytical model, combined with the experimental findings, suggested that cyclic strain decreased fibroblast activation even in the presence of interstitial flow. Finally, GFP-labeled MSC were injected into the cell-seeded collagen hydrogels to examine their effect on the cardiac fibroblast response. The presence of MSC significantly attenuated cardiac fibroblast activation under both static conditions and during biochemical and mechanical stimulation. Hypoxia, not mechanical stress, induced the highest levels of MSC migration, as well as the highest release of the paracrine factor, VEGF. The data suggest that AT1R can be targeted to prevent the myofibroblast transition, due to its role in fluid shear-induced fibroblast activation. Additionally, the observed beneficial effects of cyclic strain may have implications for therapies that unload the myocardium, including the use of ventricular assist devices (VADs). Finally, the effects of MSC on fibroblast activation may illuminate the mechanisms of MSC-based therapies.Ph.D.Biomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/89758/1/pgalie_1.pd

Transcriptomic analysis of a 3D blood-brain barrier model exposed to disturbed fluid flow.

Cerebral aneurysms are more likely to form at bifurcations in the vasculature, where disturbed fluid is prevalent due to flow separation at sufficiently high Reynolds numbers. While previous studies have demonstrated that altered shear stress exerted by disturbed flow disrupts endothelial tight junctions, less is known about how these flow regimes alter gene expression in endothelial cells lining the blood-brain barrier. Specifically, the effect of disturbed flow on expression of genes associated with cell-cell and cell-matrix interaction, which likely mediate aneurysm formation, remains unclear. RNA sequencing of immortalized cerebral endothelial cells isolated from the lumen of a 3D blood-brain barrier model reveals distinct transcriptional changes in vessels exposed to fully developed and disturbed flow profiles applied by both steady and physiological waveforms. Differential gene expression, validated by qRT-PCR and western blotting, reveals that lumican, a small leucine-rich proteoglycan, is the most significantly downregulated gene in endothelial cells exposed to steady, disturbed flow. Knocking down lumican expression reduces barrier function in the presence of steady, fully developed flow. Moreover, adding purified lumican into the hydrogel of the 3D blood-brain barrier model recovers barrier function in the region exposed to fully developed flow. Overall, these findings emphasize the importance of flow regimes exhibiting spatial and temporal heterogeneous shear stress profiles on cell-matrix interaction in endothelial cells lining the blood-brain barrier, while also identifying lumican as a contributor to the formation and maintenance of an intact barrier