The Habit of Seeking: Liberal Education and the Library at Berea College

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Ecological and Evolutionary Dynamics of Complex Host-Parasite Communities

Parasites are ubiquitous in nature, and embedded in complex communities of hosts and parasites. Most parasite species infect multiple host species, and most host species are infected by multiple parasite species. However, it’s very challenging to study the complex web of host- parasite interactions in natural settings, and controlled lab experiments are often limited to small numbers of host or parasite species. Additionally, parasites can evolve rapidly, so host-parasite interactions change over time. In my dissertation, I used field surveys, network analyses, and lab experiments to understand how different host species influence parasite infections in another host species, how parasites differ in their ability to infect multiple host species, how hosts respond to the threat of multiple parasites, and how parasites evolve over the course of an epidemic. My general aims were to untangle the web of interactions in host-parasite communities and to understand the evolutionary consequences of those interactions. In Chapter 2, I estimated potential cross-species transmission of different parasite species and built networks of hosts and parasites connected by these interactions. In Chapter 3, I investigated the consequences of multiple parasites on host behavior, namely sexual reproduction. Lastly, in Chapter 4, I looked to see if parasites were evolving in response to ecological dynamics such as the growth phase of an epidemic. Overall, I found that particular host and parasite species may disproportionately contribute to cross-species transmission, hosts alter their reproductive behavior in response to biotic factors, and parasite virulence can evolve rapidly over the course of a natural epidemic.PHDEcology and Evolutionary BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163257/1/cgowler_1.pd

Investigating the role of neurotrophins in the development of pain responses in animal models of joint pain

Background: The chronic joint disease osteoarthritis (OA) represents a significant global problem, not only at the present time, but also for the future. Characterised by articular cartilage degeneration, inflammation of the synovium, and subchondral bone changes, it is the chronic pain associated with OA which presents the most serious consequences. There is a clear need to understand the mechanisms under lying chronic joint pain, and to identify novel therapeutic targets. Two targets which may have therapeutic potential are BDNF and cordycepin. Objectives: The objectives of this thesis are two-fold; firstly to establish a slow progressing murine model of OA that is representative of post-traumatic OA, and secondly to investigate peripheral targets which may modulate chronic OA pain. Methods: Surgical destabilisation of the medial meniscus (DMM) was carried out in adult C57BL/6 mice. Weight bearing asymmetry and hindpaw withdrawal threshold were measured up to 16 weeks post-surgery. Joint pathology was then assessed post-mortem at 16 weeks post-surgery. Another cohort of adult C57BL/6 mice underwent a modified surgical destabilization of the medial meniscus. Pain behaviour and joint pathology outcomes were measured 16 weeks and 20 weeks post-surgery. Osteoarthritis was induced in adult male Sprague Dawley rats via intra-articular injection of monosodium iodoacetate (MIA) or vehicle (50ul 0.9 % saline. A second cohort of male Sprague Dawley rats underwent either meniscal transection (MNX) or sham surgery. Rats then received intra-articular injections of either trkB-fc or human IgG. Pain behaviour was tested up to 3 hours post injection. Adult C57BL/6 mice underwent DMM or sham surgery. Pain behaviour was measured up to 16 weeks post-surgery. From 14 weeks post-surgery mice were orally dosed with either cordycepin or vehicle every two days for two weeks. Joint pathology was then assessed post-mortem at 16 weeks post-surgery. Results:There was a significant increase in weight bearing asymmetry from 13 weeks post DMM surgery in C57BL/6 mice, but no changes in hindpaw withdrawal thresholds. There were also significant increases in chondropathy and synovitis at 16 weeks post-surgery. When the surgical induction of the DMM model was modified there were still significant changes in joint pathology, but no significant changes in pain behaviour. Intra-articular injection of TrkB/fc chimera in rats with established MIA induced joint pain was found to acutely reduce weight bearing asymmetry and increase ipsilateral hindpaw withdrawal thresholds. There was also a significant reduction in pain behaviour in rats with MNX established joint pain when TrkB/fc chimera was injected into the knee joint. Following systemic administration of cordycepin in mice with DMM induced joint pain there was a significant reduction in weightbearing asymmetry when compared to vehicle treated mice. There was also a significant reduction in DMM induced chondropathy, subchondral bone thickening, and osteophytosis in mice treated with cordycepin compared to vehicle treated mice. Conclusions: The changes in pain behaviour outcomes between the traditional and modified DMM, despite similar joint pathology outcomes, suggests a role for meniscal damage as a peripheral driver of OA pain. Localised injection of TrkB/fc chimera into the knee joint of rats with both MIA and MNX induced joint pain was found to acutely reverse joint pain. This implies that peripheral BDNF may be involved in mediating OA joint pain. Oral administration of cordycepin was found to reduce both pain behaviour and joint pathology changes in the DMM model in mice. These results suggest a role for local protein translation underlying both OA chronic pain and joint damage

Systematic review of interventions to improve patient uptake and completion of pulmonary rehabilitation in COPD

ABSTRACT Pulmonary rehabilitation is considered a key management strategy for chronic obstructive pulmonary disease (COPD), but its effectiveness is undermined by poor patient uptake and completion. The aim of this review was to identify, select and synthesise the available evidence on interventions for improving uptake and completion of pulmonary rehabilitation in COPD. Electronic databases and trial registers were searched for randomised trials evaluating the effect of an intervention compared with a concurrent control group on patient uptake and completion. The primary outcomes were the number of participants who attended a baseline assessment and at least one session of pulmonary rehabilitation (uptake), and the number of participants who received a discharge assessment (completion). Only one quasi-randomised study (n=115) (of 2468 records identified) met the review inclusion criteria and was assessed as having a high risk of bias. The point estimate of effect did, however, indicate greater programme completion and attendance rates in participants allocated to pulmonary rehabilitation plus a tablet computer (enabled with support for exercise training) compared with controls ( pulmonary rehabilitation only). There is insufficient evidence to guide clinical practice on interventions for improving patient uptake and completion of pulmonary rehabilitation in COPD. Despite increasing awareness of patient barriers to pulmonary rehabilitation, our review highlights the existing under-appreciation of interventional trials in this area. This knowledge gap should be viewed as an area of research priority due to its likely impact in undermining wider implementation of pulmonary rehabilitation and restricting patient access to a treatment considered the cornerstone of COPD

Lipidomic identification of plasma lipids associated with pain behaviour and pathology in a mouse model of osteoarthritis

© 2020, The Author(s). Introduction: Osteoarthritis (OA) is the most common form of joint disease, causing pain and disability. Previous studies have demonstrated the role of lipid mediators in OA pathogenesis. Objectives: To explore potential alterations in the plasma lipidomic profile in an established mouse model of OA, with a view to identification of potential biomarkers of pain and/or pathology. Methods: Pain behaviour was assessed following destabilisation of the medial meniscus (DMM) model of OA (n = 8 mice) and compared to sham controls (n = 7). Plasma and knee joints were collected at 16weeks post-surgery. Plasma samples were analysed using ultra-high performance liquid chromatography accurate mass high resolution mass spectrometry (UHPLC-HR-MS) to identify potential differences in the lipidome, using multivariate and univariate statistical analyses. Correlations between pain behaviour, joint pathology and levels of lipids were investigated. Results: 24 lipids, predominantly from the lipid classes of cholesterol esters (CE), fatty acids (FA), phosphatidylcholines (PC), N-acylethanolamines (NAE) and sphingomyelins (SM), were differentially expressed in DMM plasma compared to sham plasma. Six of these lipids which were increased in the DMM model were identified as CE(18:2), CE(20:4), CE(22:6), PC(18:0/18:2), PC(38:7) and SM(d34:1). CEs were positively correlated with pain behaviour and all six lipid species were positively correlated with cartilage damage. Pathways shown to be involved in altered lipid homeostasis in OA were steroid biosynthesis and sphingolipid metabolism. Conclusion: We identify plasma lipid species associated with pain and/or pathology in a DMM model of OA

Peripheral brain-derived neurotrophic factor contributes to chronic osteoarthritis joint pain

Brain-derived neurotrophic factor (BDNF) and the high-affinity receptor tropomyosin receptor kinase B (TrkB) have important roles in neuronal survival and in spinal sensitization mechanisms associated with chronic pain. Recent clinical evidence also supports a peripheral role of BDNF in osteoarthritis (OA), with synovial expression of TrkB associated with higher OA pain. The aim of this study was to use clinical samples and animal models to explore the potential contribution of knee joint BDNF/TrkB signalling to chronic OA pain. Brain-derived neurotrophic factor and TrkB mRNA and protein were present in knee synovia from OA patients (16 women, 14 men, median age 67 years [interquartile range: 61-73]). There was a significant positive correlation between mRNA expression of NTRK2 (TrkB) and the proinflammatory chemokine fractalkine in the OA synovia. Using the surgical medial meniscal transection (MNX) model and the chemical monosodium iodoacetate (MIA) model of OA pain in male rats, the effects of peripheral BDNF injection, vs sequestering endogenous BDNF with TrkB-Fc chimera, on established pain behaviour were determined. Intra-articular injection of BDNF augmented established OA pain behaviour in MIA rats, but had no effect in controls. Intra-articular injection of the TrkB-Fc chimera acutely reversed pain behaviour to a similar extent in both models of OA pain (weight-bearing asymmetry MIA: -11 ± 4%, MNX: -12 ± 4%), compared to vehicle treatment. Our data suggesting a contribution of peripheral knee joint BDNF/TrkB signalling in the maintenance of chronic OA joint pain support further investigation of the therapeutic potential of this target

An interactive patient transfer network and model visualization tool for multidrug-resistant organism prevention strategies

Background: The CDC’s new Public Health Strategies to Prevent the Spread of Novel and Targeted Multidrug-Resistant Organisms (MDROs) were informed by mathematical models that assessed the impact of implementing preventive strategies directed at a subset of healthcare facilities characterized as influential or highly connected based on their predicted role in the regional spread of MDROs. We developed an interactive tool to communicate mathematical modeling results and visualize the regional patient transfer network for public health departments and healthcare facilities to assist in planning and implementing prevention strategies. Methods: An interactive RShiny application is currently hosted in the CDC network and is accessible to external partners through the Secure Access Management Services (SAMS). Patient transfer volumes (direct and indirect, that is, with up to 30 days in the community between admissions) were estimated from the CMS fee-for-service claims data from 2019. The spread of a carbapenem-resistant Enterobacterales (CRE)–like MDROs within a US state was simulated using a deterministic model with susceptible and infectious compartments in the community and healthcare facilities interconnected through patient transfers. Individuals determined to be infectious through admission screening, point-prevalence surveys (PPSs), or notified from interfacility communication were assigned lower transmissibility if enhanced infection prevention and control practices were in place at a facility. Results: The application consists of 4 interactive tabs. Users can visualize the statewide patient-sharing network for any US state and select territories in the first tab (Fig. 1). A feature allows users to highlight a facility of interest and display downstream or upstream facilities that received or sent transfers from the facility of interest, respectively. A second tab lists influential facilities to aid in prioritizing screening and prevention activities. A third tab lists all facilities in the state in descending order of their dispersal rate (ie, the rate at which patients are shared downstream to other facilities), which can help identify highly connected facilities. In the fourth tab, an interactive graph displays the predicted reduction of MDRO prevalence given a range of intervention scenarios (Fig. 2). Conclusions: Our RShiny application, which can be accessed by public health partners, can assist healthcare facilities and public health departments in planning and tailoring MDRO prevention activity bundles

Cell type–specific super-resolution imaging reveals an increase in calcium-permeable AMPA receptors at spinal peptidergic terminals as an anatomical correlate of inflammatory pain

Spinal hyperexcitability is a key event in the development of persistent pain, and arises partly from alterations in the number and localization of α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-type glutamate receptors. However, determining precisely where these changes occur is challenging due to the requirement for multiplex labelling and nanoscale resolution. The recent development of super-resolution light microscopy provides new tools to address these challenges. Here, we apply combined confocal/direct STochastic Optical Reconstruction Microscopy (dSTORM) to reveal changes in calcium-permeable subunits of AMPA-type glutamate receptors (GluA1) at identified spinal cord dorsal horn (SCDH) peptidergic axon terminals in a model of inflammatory pain. L4/5 lumbar spinal cord was collected from adult male C57BL/6J mice 24 hours after unilateral hind paw injection of saline or 1% carrageenan (n = 6/group). Tissue was immunolabelled for markers of peptidergic axon terminals (substance P; SP), presynaptic active zones (Bassoon), and GluA1. Direct stochastic optical reconstruction microscopy revealed a 59% increase in total GluA1 immunolabelling in the SCDH in the carrageenan group, which was not detected by confocal microscopy. Cell type–specific analyses identified a 10-fold increase in GluA1 localized to SP+ structures, and identified GluA1 nanodomains that scaled with behavioural hypersensitivity, and were associated with synaptic release sites. These findings demonstrate that dSTORM has the sensitivity and power to detect nanoscale anatomical changes in the SCDH, and provides new evidence for synaptic insertion of GluA1+-AMPA-Rs at spinal peptidergic nociceptive terminals in a model of inflammatory pain

Anxiety enhances pain in a model of osteoarthritis and is associated with altered endogenous opioid function and reduced opioid analgesia

Introduction: Negative affect, including anxiety and depression, is prevalent in chronic pain states such as osteoarthritis (OA) and associated with greater use of opioid analgesics, potentially contributing to present and future opioid crises.Objectives: We tested the hypothesis that the interaction between anxiety, chronic pain, and opioid use results from altered endogenous opioid function.Methods: A genetic model of negative affect, the Wistar–Kyoto (WKY) rat, was combined with intra-articular injection of monosodium iodoacetate (MIA; 1 mg) to mimic clinical presentation. Effects of systemic morphine (0.5–3.5 mg·kg−1) on pain behaviour and spinal nociceptive neuronal activity were compared in WKY and normo-anxiety Wistar rats 3 weeks after MIA injection. Endogenous opioid function was probed by the blockade of opioid receptors (0.1–1 mg·kg−1 systemic naloxone), quantification of plasma β-endorphin, and expression and phosphorylation of spinal mu-opioid receptor (MOR).Results: Monosodium iodoacetate–treated WKY rats had enhanced OA-like pain, blunted morphine-induced analgesia, and greater mechanical hypersensitivity following systemic naloxone, compared with Wistar rats, and elevated plasma β-endorphin levels compared with saline-treated WKY controls. Increased MOR phosphorylation at the master site (serine residue 375) in the spinal cord dorsal horn of WKY rats with OA-like pain (P = 0.0312) indicated greater MOR desensitization.Conclusions: Reduced clinical analgesic efficacy of morphine was recapitulated in a model of high anxiety and OA-like pain, in which endogenous opioid tone was altered, and MOR function attenuated, in the absence of previous exogenous opioid ligand exposure. These findings shed new light on the mechanisms underlying the increased opioid analgesic use in high anxiety patients with chronic pain