It has been hypothesized that effective treatment of neurodegenerative diseases, such as Huntington’s Disease and Alzheimer’s, may be possible through the manipulation of neural stem cells to divide and replenish afflicted neuronal cell populations. A crucial component of this treatment would be the creation of a vehicle for the efficient delivery of stimulating genetic material into target cells. Prospective virus-based vectors accomplish this by making use of a recombinant virus and its natural ability for gene transfer. These viral vectors, while inherently effective, have significant safety issues with the possibility of eliciting harmful immune responses. Peptide-based copolymers are a promising non-viral alternative for delivery systems. While safer, these synthetic vectors have thus far proven less efficient. One problem is lack of consistent cell membrane penetration, preventing the therapeutics from reaching areas within the cell where they would come into effect. Our laboratory has recently incorporating the membrane-lytic peptide melittin (a molecule derived from bee venom) into our base DNA-binding peptide-based polymers. The melittin-functionalized materials were shown to increase gene delivery efficiency by at least 10-fold compared to control materials both in vitro and by injection into mouse brain. This current study seeks to develop a multifunctional delivery system by incorporating the neuronal-targeting peptide “Tet1,” for specialized treatment of neurodegenerative diseases. Previous work showed that conjugation of Tet1 to control polymers results in increased transfer specificity to neuronal cells in vivo. Potentially, Tet1 and melittin can synergize to further improve gene delivery to the central nervous system.

One of the most vital roles of mitochondria is to provide the cell with energy through oxidative phosphorylation (OXPHOS). Mutations within the mitochondrial DNA (mtDNA) can affect gene products that function in OXPHOS. While maternally inherited mtDNA mutations often affect the nervous system and musculature, and somatic mtDNA mutations are associated with aging and age related diseases, the cellular mechanisms that influence the frequency of mtDNA mutations are poorly understood. We are using the fruit fly Drosophila to address this matter because our recent work indicates that the mtDNA mutational patterns in flies share many features with vertebrates, including a similar somatic mtDNA mutation frequency, a prevalence of transition mutations, and an accumulation of mutations with age. A high prevalence of mtDNA mutations can lead to dysfunctional mitochondria, and previous work in Drosophila has shown that a mitochondrial quality control mechanism exists to degrade dysfunctional mitochondria. Although it is clear that this mitochondrial quality control mechanism can detect and degrade damaged mitochondria, whether it can influence the mtDNA mutation frequency by detecting and degrading mitochondria with a mtDNA mutation is unknown. To address this matter we will use a high-fidelity Duplex Sequencing approach to detect rare mtDNA variants. Genetic manipulations in mitochondrial quality control factors will be used to probe their effect on mtDNA mutation frequency. We predict that loss of these quality control factors will cause an increase in mtDNA mutations and that overexpression of these factors will cause a decrease in mtDNA mutations. The results from these studies will lead to improved understanding about factors that influence mtDNA mutation frequency and also diseases caused by mtDNA mutations.

Perineuronal nets (PNNs) are a matrix of proteins that surround nerve cells and reinforce the most often used synaptic connections between neurons, essentially hard-wiring neural connections made as a child into permanent pathways that respond to specific stimuli. By dissolving these PNNs, we recreate the plasticity characteristic of a young developing brain, granting us the ability to rewire the brain with respect to any stimulus. In this study, we are looking at PNNs within the vestibular system – the sensory system that, under natural conditions, is primarily responsible for maintaining images on the fovea during movement. Hair cells within the semicircular canals of the vestibular system register head accelerations and then send reflex signals through vestibular afferent nerve endings to extra-ocular eye muscles that drive eye movements. This vestibular ocular reflex aids the maintenance of stability of images on the retina. As a therapy for vestibular loss, our lab has developed a vestibular prosthesis that electrically stimulates the afferent nerve endings of the vestibular system, thereby simulating natural vestibular response to movement. This electrical stimulation, however, spreads to untargeted as well as targeted vestibular afferents and cause inaccurate eye movements as a result. By dissolving the PNNs in the vestibular nuclei and then allowing them to regrow during a period of adaptation, we hope to suppress inappropriate eye movements in response to our prosthesis’ electrical stimulation. If our lab can prove that electrically elicited eye-movements become more accurate after the dissolving and guided re-growing of PNNs, we can show that it is possible to restore plasticity to the brain and shape its neural connections through controlled electrical stimulation to the target system. By extension, such results will ascertain if it is possible to use this method to re-wire a physiological system to accept prosthetic stimulation in place of a non-functioning system.

The vestibular system is responsible for maintaining stable vision and posture by interpreting accelerations of the head in various planes. Impaired function of this system can cause debilitating vertigo, as seen in Meniere ’s disease. Our lab has developed a prosthesis that aims to counteract these deleterious pathologies through electrical stimulation, and our research is directed towards improving the effectiveness of this device. In order to stabilize gaze, the vestibular system must incorporate demands from several neural inputs, many of which are dependent on direction of the line of sight. Additionally, the effectiveness of electrical stimulation may be altered by the background activity of the activated neural pathways, which vary with orbital eye positions. Therefore, in this study, I am focusing on the dependency of stimulation-evoked eye velocities on initial position of the eye. I have collected data from two Rhesus Macaques by stimulating the right lateral, posterior, and superior semicircular canals at different eye positions. My data shows linearly graded velocities depending on stimulus amplitude, so it is clear that eye position must be taken into account when evaluating eye velocities. Speculation into the cause of this phenomenon will help to better customize our implant’s effectiveness according to the physiology of the patient in consideration.

Identifying effective antimicrobial interventions to reduce foodborne pathogen risk are important for the fresh apple packing industry. Apple packing antimicrobial interventions are commonly applied for short application times using spray bars and longer application times in flumes. The objective of this study was to investigate the potential for using lactic acid for spray bar applications and peroxyacetic acid (PAA) for flume applications based on reduction of generic and pathogenic Escherichia coli (E. coli) on fresh apples. For each replication, fresh apples (n=220) were randomly assigned to treatments. Uninoculated controls (5 apples) were examined for background microbial levels (total coliforms, generic E. coli and aerobic plate counts) and the remainder were inoculated with pathogenic (E. coli O157:H7) or generic E. coli. Lactic acid (1% and 2%) and water treatments were examined at application times of 5, 15 and 30 seconds to mimic spray bar applications. PAA (60 and 80 ppm) and water treatments were examined at application times of 2, 3.5 and 5 minutes to mimic flume applications. Lactic acid (1 and 2%) treatments with short application times do not appear to reduce microbial levels sufficiently for consideration as a spray-bar application for fresh apple packing. PAA treatments of 80 ppm for 2-5 minutes and 60 ppm for 3.5-5 minutes reduced microbial levels sufficiently for consideration as a flume application for fresh apple packing.

Barrett’s Esophagus (BE) is an inflammation of the lower esophagus. This inflammation can progress to cancer through a stage called High Grade Dysplasia (HGD). One approach to early detection of HGD is the use of light emitting “beacons “consisting of fluorescently labeled peptides targeted to HGD tissue biomarkers. Our laser based Scanning Fiber Endoscope (SFE) possesses the ability to capture live images of the esophagus during examinations and also excite and locate fluorescently tagged targets. Refining SFE fluorescence imaging for clinical use requires mathematical algorithms such as image stitching and distance compensation. Image stitching combines a series of partial views of a 3-D surface into a composite view of the entire surface. Distance compensation addresses the issue of fluorescence signal reduction as the distance between the light emitting beacon and endoscope increases. Phantoms are synthetic mimics of disease conditions used to refine and calibrate new medical devices. This research was directed toward the development of a low-cost, flexible, and durable esophagus phantom with color matching to provide a realistic model of BE. The color of inflamed BE tissue and healthy tissue were matched using quantitative combinations of commercial acrylic paints to create recipes for both tissue types. The resulting paint mixtures were applied to the interior of a latex cast cylinder mimicking the dimensions of an adult esophagus. The painted latex models were shown to a panel of gastroenterologists for approval. The end result was the development of a color realistic phantom onto which fluorescent targets could be affixed. The phantom was imaged using the SFE and demonstrates 2D stitching with distance compensation. (C. Yang, V. Hou, L. Nelson, E. Seibel. J. Biomed. Optics, Feb 2013) Future work extends similar techniques to develop brain tissue phantoms for the calibration of the SFE after integration onto the RAVEN surgical robot.

One of the functions of the vestibular system is to engage neural reflexes, which ensures the stabilization of a visual image during head movements. This is accomplished through the stimulation of vestibular hair cells, which respond to accelerations, and then produce compensatory eye movements opposing head motion. This called the vestibulo-ocular reflex (VOR). Hair cell loss results in vestibular deficits, and for these individuals, this loss of function is debilitating and results in vertigo and decreased visual acuity. To address these deficits, the Phillips lab has developed a vestibular prosthesis, which aims to use electrical stimulation to restore function by artificially activating individual branches of the vestibular nerve. However, it is not known precisely how the system changes after hair cell loss; this may have implications for the effectiveness of the prosthesis in treating vestibular loss. To explore this, we examined the interaction between the electrical activity and residual vestibular activity after vestibular loss. We first introduced a vestibular deficit in a rhesus macaque through successive gentamicin injections into the middle ear to destroy vestibular hair cells, and measured VOR responses to verify the progressive vestibular loss. Next, we recorded eye velocities in response to electrical stimulation to characterize changes in the efficacy of stimulation, thus providing insight into the prosthetic mechanism. Finally, modulated electrical stimulation was provided during rotation of the rhesus macaque to test the efficacy of the prosthesis in restoring VOR in conjunction with residual vestibular activity. Characterizing prosthetic function during increasing vestibular deficit is important in determining the mechanism of stimulation, the physiological responses succeeding hair cell loss, and ultimately a model for the prosthetic efficacy for human patients.