STRATEGIES TO IMPROVE ELECTROCHEMICAL DETECTION OF NITRIC OXIDE IN BIOLOGICAL ENVIRONMENTS

Nitric oxide (NO) is a gaseous molecule of vast biological significance whose activity is likely to be concentration-dependent. As our understanding of this molecule becomes more nuanced and precise, so too must detection strategies evolve to detect NO with greater precision and accuracy. Spectroscopic techniques are able to measure NO with high specificity, but the only technique unhindered by complex instrumentation and the requirement for additional reagents, and able to measure NO directly in situ, is electrochemistry. However, bare electrodes are unable measure NO with sufficient selectivity and sensitivity, particularly in biological environments, necessitating the use of transducer surface modifiers to improve performance. Herein, systematic evaluations and comparisons of electrochemical NO sensor modifications were carried out. Electropolymerized films (EPFs) represent a class of selectivity-enhancing membranes favorable for their reproducible and self-terminating depositions. Six different monomers were evaluated for their permselectivity characteristics for NO against a panel of electroactive biological interferents. After tailored optimizations of their deposition parameters, polymers were also evaluated for their anti-fouling properties in simulated wound fluid. In addition to EPFs, another common strategy to improve NO sensor performance is the incorporation of metallophthalocyanine (MPc) electrocatalysts. Four MPc macrocycles (M = iron, cobalt, nickel, and zinc) previously determined to have the highest electrocatalytic activity towards NO oxidation were evaluated for their selectivity characteristics. The ability to specifically coordinate with NO at the metal center (as opposed to weak physisorption on the aromatic periphery) proved an adequate predictor of selectivity findings. Based on these evaluations of different modifiers, a solid-state electrochemical NO sensor was designed for long-term use in proteinaceous media. With extensive characterizations of sensocompatibility, the final NO sensor was capable of high sensitivity and selectivity retention with continuous operation in culture media. The sensor was then used to successfully interrogate the temporal (> 24 h) and spatial concentration profiles of macrophage NO release under neutral and pro-inflammatory stimulated conditions. Lastly, hydrogen sulfide (H2S) is another gasotransmitter responsible for mediating many of the same biological processes as NO, and may either upregulate or inhibit NO production in a manner likely to be concentration-dependent. An EPF-modified, solid-state electrode was therefore developed for selective detection of H2S for subsequent incorporation into a NO/H2S dual-sensor.Doctor of Philosoph

SB50-12/13: Recognition

SB50-12/13: Recognition. This resolution passed during the February 6, 2013 meeting of the Associated Students of the University of Montana (ASUM)

SB14-12/13: Recognition

SB14-12/13: Recognition. This resolution passed with unanimous consent during the September 12, 2012 meeting of the Associated Students of the University of Montana (ASUM)

Analysis of Knee Motion to Prevent and Treat the Increasing Incidence of Premature Knee OA

Purpose/Background: Osteoarthritis (OA) is a costly, debilitating musculoskeletal disease. A disparity in OA incidence in young individuals who don body borne load while physically active, such as service members, reportedly exists. Incidence of premature OA in service members is greater than twice the general population and steadily increasing at the knee. Moreover, there is disparity in knee OA incidence for female and African-American service members, who are 15%-25% more likely to develop the disease. A service member’s physical activity directly contributes to premature knee OA development. Specific knee locomotion biomechanics indicative of joint instability, including large and/or abrupt knee adduction motions, may increase their likelihood of OA development. Yet, no objective measure of knee instability currently exists; nor is it understood how body borne load leads to altered, and potentially hazardous knee locomotion biomechanics that increase incidence of premature knee OA among service members. This study sought to determine whether knee motions posited to be indicative of joint instability progressively increase with body-borne load and duration of load carriage. Materials & Methods: To date, six recreationally active adults had knee biomechanics quantified while walking 1.3 m/s for 60 minutes with a different, randomly ordered body borne load: (unloaded: 0 kg, 15 kg and 30 kg). During the load carriage task, dominant limb knee biomechanics were quantified from three walk trials (1.3 m/s ± 5%) recorded at minute 0, and every 15 minutes thereafter (i.e., 5, 15, 30, etc.). For each trial, the peak, range, and jerk cost of knee adduction angle was quantified using data from the video-based motion capture system and accelerometer-based IMU sensors. To determine whether body-borne load or the duration of load carriage increases knee joint instability, each dependent knee adduction measure was submitted to a RM ANOVA to test the main effect and interaction between time (minutes 0, 15, 30…60) and load (0,15 and 30 kg). To compare the video-based and accelerometer-based data, each dependent knee adduction measure was submitted to equivalence testing, or two one-sided t-tests of the difference between these measures, in the same participant. Alpha was p \u3c 0.05. Results: Preliminary analysis found neither body borne load, nor time had a significant effect on peak, range, or jerk cost of knee adduction (p\u3e0.05) (Table 1 and Figure 1). No significant difference was evident between the video-based and accelerometer-based derived knee adduction measures (p\u3e0.05). Discussion/Conclusion: Walking with body borne load may increase knee OA risk for service members. During locomotion, current participants exhibited a non-significant increased in range and jerk cost of knee adduction, and OA risk with each addition of body borne load. Specifically, participants exhibited a 11% and 22% increase in range and jerk cost of knee adduction with the 30 kg load. In contradiction to our hypothesis, participants did not further increase knee adduction throughout the duration of locomotion, despite the 33% increase in jerk cost after 45 minutes of load carriage. With additional testing, we expect a statistically significant increase range and jerk cost of knee adduction with body borne load, but only an increase in jerk cost throughout the duration of load carriage

Investigation of Receptors for the Modulation of Neuronal Growth by Chondroitin Sulfate

A major obstacle to neural regeneration after injury in the central nervous system (CNS) is the environment encountered by injured axons. This environment is inhibitory due to proteins expressed by the CNS myelin as well as molecules present in the glial scar. Experimental results have implicated chondroitin sulfate proteoglycans (CSPGs) as major inhibitors of axonal regeneration after CNS injury, but until recently, the mechanisms of this inhibition were not well understood. Furthermore, the complex nature of the chondroitin sulfate (CS) chains made it difficult to study their contribution to CSPG function. This thesis describes a specific carbohydrate epitope, CS-E, that is primarily responsible for the inhibition of CNS axonal regrowth in the presence of CSPGs. We show that removal or blocking of the CS-E motif via genetic elimination of the enzyme responsible for generating CS-E or a monoclonal antibody that binds specifically to the CS-E motif significantly reduces the inhibitory activity of CSPGs on axon growth. Furthermore, we show that CS-E functions as a protein recognition element to engage receptors, including the transmembrane protein tyrosine phosphatase PTPσ, which had been previously established to be a receptor for CSPGs. Finally, we show that the protein tyrosine kinase receptor EphA4 is a novel receptor for the CS-E motif, and as with PTPσ, neurons deficient in EphA4 exhibit reduced inhibition by CS-E. Our results demonstrate that a specific sugar epitope within chondroitin sulfate polysaccharides directs important physiological processes, and establish the importance of the chemical structure of CS chains in modulating the activity of CSPGs in vivo. The identification of receptors that mediate the inhibitory effect of CS-E advances our understanding of the mechanisms of axon regeneration following injury to the CNS when CS-E expression is upregulated. These findings provide us with the opportunity to develop therapies for the recovery of axonal outgrowth after damage to the nervous system, which in conjunction with blocking approaches targeting the CS motif, can provide a powerful strategy for allowing recovery after injury to the CNS

Rapid Recovery

A poster presented by Abby Smith, Adnan Shaik, Alex Reliford, Ella Abney, Ethan Lawhorn and Micah Brown for the class Business, Accounting, and Entrepreneurship.https://scholarworks.moreheadstate.edu/gsp_projects_2019/1013/thumbnail.jp

Fortnightly tides and subtidal motions in a choked inlet

This paper is not subject to U.S. copyright. The definitive version was published in Estuarine, Coastal and Shelf Science 150, Pt.B (2014): 325-331, doi:10.1016/j.ecss.2014.03.025.Amplitudes of semi-diurnal tidal fluctuations measured at an ocean inlet system decay nearly linearly by 87% between the ocean edge of the offshore ebb-tidal delta and the backbay. A monochromatic, dynamical model for a tidally choked inlet separately reproduces the evolution of the amplitudes and phases of the semi-diurnal and diurnal tidal constituents observed between the ocean and inland locations. However, the monochromatic model over-predicts the amplitude and under-predicts the lag of the lower-frequency subtidal and fortnightly motions observed in the backbay. A dimensional model that considers all tidal constituents simultaneously, balances the along-channel pressure gradient with quadratic bottom friction, and that includes a time-varying channel water depth, is used to show that that these model-data differences are associated with nonlinear interactions between the tidal constituents that are not included in non-dimensional, monochromatic models. In particular, numerical simulations suggest that the nonlinear interactions induced by quadratic bottom friction modify the amplitude and phase of the subtidal and fortnightly backbay response. This nonlinear effect on the low-frequency (subtidal and fortnightly) motions increases with increasing high-frequency (semi-diurnal) amplitude. The subtidal and fortnightly motions influence water exchange processes, and thus backbay temperature and salinity.We thank the Office of Naval Research (N0001411WX20962; N0001412WX20498) for funding

Emergence of Clinical Clostridioides Difficile Isolates With Decreased Susceptibility to Vancomycin

BACKGROUND: Clostridioides difficile infection (CDI) is a leading cause of hospital-associated antibiotic-related diarrhea and deaths worldwide. Vancomycin is one of the few antibiotics recommended for both nonsevere and severe CDI cases. We sought to determine whether vancomycin nonsusceptible C. difficile strains are circulating in the patient population. METHODS: Stool samples from patients with CDI were collected from 438 and 98 patients at a large university hospital in Houston, Texas, and Nairobi, Kenya, respectively. The stools were examined for the presence of vancomycin and metronidazole nonsusceptible C. difficile using broth dilution culture, Etest (BioMérieux, France), polymerase chain reaction (PCR), whole-genome sequencing, and in vivo testing in a CDI mouse model. RESULTS: Of the Houston stool samples, 114/438 (26%) had vancomycin nonsusceptible C. difficile isolates and 128/438 (29%) were metronidazole nonsusceptible. Similarly, 66 out of 98 (67%) and 83/98 (85%) of the Nairobi patients harbored vancomycin and metronidazole nonsusceptible isolates, respectively. Vancomycin treatment of a CDI mouse model infected with a vancomycin nonsusceptible isolate failed to eradicate the infection. Whole-genome sequencing analyses did not identify vanA genes, suggesting a different mechanism of resistance. CONCLUSIONS: C. difficile strains exhibiting reduced susceptibility to vancomycin are currently circulating in patient populations. The spread of strains resistance to vancomycin, a first-line antibiotic for CDI, poses a serious therapeutic challenge. Routine susceptibility testing may be necessary