Integrating mechanical sensor readouts into organ-on-a-chip platforms

Organs-on-a-chip have emerged as next-generation tissue engineered models to accurately capture realistic human tissue behaviour, thereby addressing many of the challenges associated with using animal models in research. Mechanical features of the culture environment have emerged as being critically important in designing organs-on-a-chip, as they play important roles in both stimulating realistic tissue formation and function, as well as capturing integrative elements of homeostasis, tissue function, and tissue degeneration in response to external insult and injury. Despite the demonstrated impact of incorporating mechanical cues in these models, strategies to measure these mechanical tissue features in microfluidically-compatible formats directly on-chip are relatively limited. In this review, we first describe general microfluidically-compatible Organs-on-a-chip sensing strategies, and categorize these advances based on the specific advantages of incorporating them on-chip. We then consider foundational and recent advances in mechanical analysis techniques spanning cellular to tissue length scales; and discuss their integration into Organs-on-a-chips for more effective drug screening, disease modeling, and characterization of biological dynamics

Micro- and nanofluidic technologies for epigenetic profiling

This short review provides an overview of the impact micro- and nanotechnologies can make in studying epigenetic structures. The importance of mapping histone modifications on chromatin prompts us to highlight the complexities and challenges associated with histone mapping, as compared to DNA sequencing. First, the histone code comprised over 30 variations, compared to 4 nucleotides for DNA. Second, whereas DNA can be amplified using polymerase chain reaction, chromatin cannot be amplified, creating challenges in obtaining sufficient material for analysis. Third, while every person has only a single genome, there exist multiple epigenomes in cells of different types and origins. Finally, we summarize existing technologies for performing these types of analyses. Although there are still relatively few examples of micro- and nanofluidic technologies for chromatin analysis, the unique advantages of using such technologies to address inherent challenges in epigenetic studies, such as limited sample material, complex readouts, and the need for high-content screens, make this an area of significant growth and opportunityopen4

Structural Capacity Analysis of Corroded Steel Girder Bridges

More than 9% of the bridges in the United States were labeled structurally deficient according to the 2017 American Society of Civil Engineers’ infrastructure report card. The main causes of bridge deterioration are repeated vehicular loads and adverse environmental exposure. The most dominant deterioration form for steel bridges is corrosion, which is characterized by the loss of metal area resulting in reduction of structural capacity. Corrosion in steel multi-girder bridges is common in cold regions because of the frequent use of deicing chemicals during the winter season as well as leakage caused by bridge joint damage. At times, the rust is serious enough to disconnect the web from the flanges of the girder. This poses significant concerns for load capacity especially at girder ends. The consequences of bridge failure can be disastrous. This research investigates the structural capacity of these corroded steel girders. The mechanical behaviors of deteriorated girders are studied by 3-D finite element models built in ABAQUS and by lab testing. Our analysis is focused on web area loss and web thinning due to corrosion, and their consequences for load capacity reduction. The effects of location, size, and shape of area loss on shear and web buckling resistance will be studied. Lab tests on steel girder models will be conducted to verify the results from finite element modeling. Based on our analysis and findings, a simple and dependable rating method to evaluate deteriorated steel girder bridges will be developed

Media additives to promote spheroid circularity and compactness in hanging drop platform

Three-dimensional spheroid cultures have become increasingly popular as drug screening platforms, especially with the advent of different high throughput spheroid forming technologies. However, comparing drug efficacy across different cell types in spheroid culture can be difficult due to variations in spheroid morphologies and transport characteristics. Improving the reproducibility of compact, circular spheroids contributes to standardizing and increasing the fidelity of the desired gradient profiles in these drug screening three-dimensional tissue cultures. In this study we discuss the role that circularity and compaction has on spheroids, and demonstrate the impact methylcellulose (MethoCel) and collagen additives in the culture media can contribute to more compact and circular spheroid morphology. We demonstrate that improved spheroid formation is not a simple function of increased viscosity of the different macromolecule additives, suggesting that other macromolecular characteristics contribute to improved spheroid formation. Of the various macromolecular additives tested for hanging drop culture, MethoCel provided the most desirable spheroid formation. Additionally, the higher viscosity of MethoCel-containing media improved the ease of imaging of cellular spheroids within hanging drop cultures by reducing motion-induced image blur.open2

Soil-borne fungi alter the apoplastic purinergic signaling in plants by deregulating the homeostasis of extracellular ATP and its metabolite adenosine

Purinergic signaling activated by extracellular nucleotides and their derivative nucleosides trigger sophisticated signaling networks. The outcome of these pathways determine the capacity of the organism to survive under challenging conditions. Both extracellular ATP (eATP) and Adenosine (eAdo) act as primary messengers in mammals, essential for immunosuppressive responses. Despite the clear role of eATP as a plant damage-associated molecular pattern, the function of its nucleoside, eAdo, and of the eAdo/eATP balance in plant stress response remain to be fully elucidated. This is particularly relevant in the context of plant-microbe interaction, where the intruder manipulates the extracellular matrix. Here, we identify Ado as a main molecule secreted by the vascular fungus Fusarium oxysporum. We show that eAdo modulates the plant's susceptibility to fungal colonization by altering the eATP-mediated apoplastic pH homeostasis, an essential physiological player during the infection of this pathogen. Our work indicates that plant pathogens actively imbalance the apoplastic eAdo/eATP levels as a virulence mechanism

Risk Factors for Optic Disc Hemorrhage in the Low-Pressure Glaucoma Treatment Study

PurposeTo investigate risk factors for disc hemorrhage detection in the Low-Pressure Glaucoma Treatment Study.DesignCohort of a randomized, double-masked, multicenter clinical trial.MethodsLow-Pressure Glaucoma Treatment Study patients with at least 16 months of follow-up were included. Exclusion criteria included untreated intraocular pressure (IOP) of more than 21 mm Hg, visual field mean deviation worse than −16 dB, or contraindications to study medications. Patients were randomized to topical treatment with timolol 0.5% or brimonidine 0.2%. Stereophotographs were reviewed independently by 2 masked graders searching for disc hemorrhages. The main outcomes investigated were the detection of disc hemorrhage at any time during follow-up and their recurrence. Ocular and systemic risk factors for disc hemorrhage detection were analyzed using the Cox proportional hazards model and were tested further for independence in a multivariate model.ResultsTwo hundred fifty-three eyes of 127 subjects (mean age, 64.7 ± 10.9 years; women, 58%; European ancestry, 71%) followed up for an average ± standard deviation of 40.6 ± 12 months were included. In the multivariate analysis, history of migraine (hazard ratio [HR], 5.737; P = .012), narrower neuroretinal rim width at baseline (HR, 2.91; P = .048), use of systemic β-blockers (HR, 5.585; P = .036), low mean systolic blood pressure (HR, 1.06; P = .02), and low mean arterial ocular perfusion pressure during follow-up (HR, 1.172; P = .007) were significant and independent risk factors for disc hemorrhage detection. Treatment randomization was not associated with either the occurrence or recurrence of disc hemorrhages.ConclusionsIn this cohort of Low-Pressure Glaucoma Treatment Study patients, migraine, baseline narrower neuroretinal rim width, low systolic blood pressure and mean arterial ocular perfusion pressure, and use of systemic β-blockers were risk factors for disc hemorrhage detection. Randomization assignment did not influence the frequency of disc hemorrhage detection

Evolution of a key enzyme of aerobic metabolism reveals Proterozoic functional subunit duplication events and an ancient origin of animals

The biological toolkits for aerobic respiration were critical for the rise and diversification of early animals. Aerobic life forms generate ATP through the oxidation of organic molecules in a process known as Krebs’ Cycle, where the enzyme isocitrate dehydrogenase (IDH) regulates the cycle's turnover rate. Evolutionary reconstructions and molecular dating of proteins related to oxidative metabolism, such as IDH, can therefore provide an estimate of when the diversification of major taxa occurred, and their coevolution with the oxidative state of oceans and atmosphere. To establish the evolutionary history and divergence time of NAD-dependent IDH, we examined transcriptomic data from 195 eukaryotes (mostly animals). We demonstrate that two duplication events occurred in the evolutionary history of NAD-IDH, one in the ancestor of eukaryotes approximately at 1967 Ma, and another at 1629 Ma, both in the Paleoproterozoic Era. Moreover, NAD-IDH regulatory subunits β and γ are exclusive to metazoans, arising in the Mesoproterozoic. Our results therefore support the concept of an ‘‘earlier-than-Tonian’’ diversification of eukaryotes and the pre-Cryogenian emergence of a metazoan IDH enzyme

Species‐specific transpiration responses to intermediate disturbance in a northern hardwood forest

Intermediate disturbances shape forest structure and composition, which may in turn alter carbon, nitrogen, and water cycling. We used a large‐scale experiment in a forest in northern lower Michigan where we prescribed an intermediate disturbance by stem girdling all canopy‐dominant early successional trees to simulate an accelerated age‐related senescence associated with natural succession. Using 3 years of eddy covariance and sap flux measurements in the disturbed area and an adjacent control plot, we analyzed disturbance‐induced changes to plot level and species‐specific transpiration and stomatal conductance. We found transpiration to be ~15% lower in disturbed plots than in unmanipulated control plots. However, species‐specific responses to changes in microclimate varied. While red oak and white pine showed increases in stomatal conductance during postdisturbance (62.5 and 132.2%, respectively), red maple reduced stomatal conductance by 36.8%. We used the hysteresis between sap flux and vapor pressure deficit to quantify diurnal hydraulic stress incurred by each species in both plots. Red oak, a ring porous anisohydric species, demonstrated the largest mean relative hysteresis, while red maple, bigtooth aspen, and paper birch, all diffuse porous species, had the lowest relative hysteresis. We employed the Penman‐Monteith model for LE to demonstrate that these species‐specific responses to disturbance are not well captured using current modeling strategies and that accounting for changes to leaf area index and plot microclimate are insufficient to fully describe the effects of disturbance on transpiration.Key PointsPlot level scaling of evaporation from sap flux evaluated with eddy fluxDisturbance changes intradaily transpiration dynamicsHydraulic strategy causes species‐specific transpiration differencesPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110637/1/jgrg20315.pd

Single Cell Deposition and Patterning with a Robotic System

Integrating single-cell manipulation techniques in traditional and emerging biological culture systems is challenging. Microfabricated devices for single cell studies in particular often require cells to be spatially positioned at specific culture sites on the device surface. This paper presents a robotic micromanipulation system for pick-and-place positioning of single cells. By integrating computer vision and motion control algorithms, the system visually tracks a cell in real time and controls multiple positioning devices simultaneously to accurately pick up a single cell, transfer it to a desired substrate, and deposit it at a specified location. A traditional glass micropipette is used, and whole- and partial-cell aspiration techniques are investigated to manipulate single cells. Partially aspirating cells resulted in an operation speed of 15 seconds per cell and a 95% success rate. In contrast, the whole-cell aspiration method required 30 seconds per cell and achieved a success rate of 80%. The broad applicability of this robotic manipulation technique is demonstrated using multiple cell types on traditional substrates and on open-top microfabricated devices, without requiring modifications to device designs. Furthermore, we used this serial deposition process in conjunction with an established parallel cell manipulation technique to improve the efficiency of single cell capture from ∼80% to 100%. Using a robotic micromanipulation system to position single cells on a substrate is demonstrated as an effective stand-alone or bolstering technology for single-cell studies, eliminating some of the drawbacks associated with standard single-cell handling and manipulation techniques