Mangala Iyengar, Student

Robert Grossfeld, Faculty Mentor

Effects of ATP and Glutamate on Sciatic Nerve Glia 

Adenosine triphosphate (ATP) and glutamate are considered to be major neurotransmitters by which neurons and glia, the two main cell types, communicate with each other in the central and peripheral nervous systems. The current consensus is that glutamate acts on glial cells by stimulating the release of ATP, which then binds to the relevant receptors to create its effect. We, therefore, would expect that the neural responses to ATP and glutamate should be similar and that both should be blocked by antagonists of ATP receptors. Most glial cells do not generate the types of electrical responses that characterize neurons but they do respond to stimulation with changes in cytoplasmic calcium. We used optical imaging of calcium responses to study and quantify the responses of glia to ATP and glutamate in the developing rat sciatic nerve, a model peripheral nerve. ATP produced a consistent and robust response, but application of glutamate produced little or no response. In rat optic nerve, a model central nerve studied in our laboratory, ATP and glutamate also produced different responses. These results suggest the need to reevaluate the means by which these substances may mediate intercellular chemical communication between neurons and glia in intact nerves.

Courtney H. Fox, Student

Tony Cass, Faculty Mentor

Biosensors for the Detection of Glucose in Human Interstitial Fluid

Biosensors are devices comprising of a selective interface in close proximity or integrated with a transducer, which relays an interaction between the surface and analyte. Additionally, electrochemical biosensors are capable of operating in turbid media, much like the interstitial fluid of the human body. Enzyme-based biosensors are highly effective tools for detecting the presence of a biological molecule in vivo that can be utilized in medical devices and diagnostics. This research project focused on the development of a robust glucose biosensor system that can detect glucose in subcutaneous human interstitial fluid. Large biological molecules, like enzymes or antibodies, can be immobilized to the surface of microelectrodes by forming a stable acyl amino ester on the electrode surface. The co-addition of N’-(3-dimethyaminopropyl)-N’-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS) forms a stable amino ester. Large biological molecules can be easily intercalated into this network, and will be immobilized in the immediate proximity of the electrode. Glucose oxidase (GOx) was densely substituted into this network by replacing the active NHS esters with the primary amines of the enzyme. When tested and calibrated in a solution designed to mimic the composition of human interstitial fluid, the glucose biosensors accurately measured the concentration glucose over an eight-hour operational period, particularly at glucose concentrations within the hyperglycemic regime.

Deborah C. White, Student

Russell E. Gorga, Faculty Mentor

Fabrication and characterization of polycarporlactone nanofibers doped with tri-calcium phosphate

Polycaprolactone nanofibers were created using the electrospinning process. The polymer was dissolved in chloroform and methanol and the resulting solution spun through a variety of conditions in order to determine optimum parameters for fiber size and uniformity. Once these conditions were established, a range of concentrations of tri-calcium phosphate particles were electrospun to examine loading, dispersion, and fiber size. Samples were examined using a scanning electron microscope and a transmission electron microscope. The average fiber size was near 700 nanometers. The particles showed a tendency to aggregate within the fibers causing inconsistencies in the fiber structure. Future work would include increasing the dispersion of the particles and using the resulting nanofiber mats as scaffolds for cell growth.

Jennifer L. Puetzer, Student

Elizabeth G. Loboa, Faculty Mentor

The Effects of Cyclic Hydrostatic Pressure on Chondrogenesis and Viability of Human Adipose and Bone Marrow Derived Adult Stem Cells

Treatments for cartilage defects due to trauma, genetic predisposition, or metabolic conditions are often invasive and only serve to temporarily reduce pain. Adult stem cells have been shown to differentiate into multiple musculoskeletal tissue lineages making them a favorable means of treatment. However, the retrieval of bone marrow to isolate mesenchymal stem cells is still quite invasive for patients already suffering from cartilage injury. For this reason, the use of human adipose-derived adult stem cells (hASCs) has gained increasing interest since they are less invasive to retrieve and also have multipotential differentiation capabilities. The purpose of this study was to determine if, in the absence of chondrogenic media, hASCs would initiate chondrogenic differentiation in response to cyclic hydrostatic pressure (CHP). We hypothesized that CHP alone would be enough to induce chondrogenesis of hASCs as evidenced by upregulation of mRNA expression of Sox9, aggrecan, collagen II, and/or cartilage oligomeric matrix protein (COMP). To further investigate viability of hASCs as compared to bone marrow derived human mesenchymal stem cells (hMSCs) in response to CHP, the experiment was repeated. The purpose of this component of the study was to determine if, in the absence of chondrogenic media, hASCs and/or hMSCs demonstrated a lack of viability at any time during, or after, 21 days of exposure to CHP in 3-D agarose constructs. This study found indications of CHP induced chondrogenesis in hASCs along with a lack of cell viability by day 21 in loaded and unloaded samples of hMSCs and hASCs.

Thomas C. Pope, Student

John M. Blondin, Faculty Mentor

Black Hole Growth Excites Spin

Looking up at the night sky with an x-ray telescope reveals hundreds of thousands of x-ray sources invisible to your eyes. These objects are powered by accretion, the process by which the gravity of a compact star like a black hole will attract and capture material. The theory of hydrodynamic accretion was first described 70 years ago by Hoyle and Lyttleton (1939), and has become a fundamental building block for understanding compact x-ray sources. Modern research on gravitational accretion has focused on the use of numerical simulations to study the stability of accretion and the possibility of accretion of angular momentum, which does not exist in the steady- state theory of Hoyle and Lyttleton. After 20 years and dozens of published papers there is still no consensus on the stability of such. We have attempted to address this confusion by using high- fidelity numerical simulations run on the NSF’s ‘Ranger’ supercomputer. By starting from an initially steady-state axisymmetric solution we are able to show – for the first time – that Hoyle-Lyttleton accretion is unstable to small perturbations. We use these simulations to quantify the growth rate and oscillation period of the unstable accretion shock as a function of Mach number and size of the accreting star. Provided the star is sufficiently small, the secular evolution is described by sudden jumps between states with counter rotating semi-Keplerian accretion disks feeding the star with a specific angular momentum comparable to a Keplerian orbit at the surface of the star.

Justin J. Hicks, Student

Peter Mente, Faculty Mentor

In vitro biomechanical comparison of internal spinal fixation techniques on the canine lumbosacral vertebrae

Spinal fixation is commonly used in small animal surgery for traumatic injuries to the canine lumbar vertebrae. In patients with unstable spinal injuries surgical intervention is often promptly needed to prevent further neurologic damage by reestablishing anatomical alignment, addressing spinal cord compression, providing rigid stabilization of affected vertebrae and relieving or moderating pain. Several surgical techniques have been described, among those, internal and external fixation. An optimal configuration or system of fixation has yet to be determined. The two fixation techniques that are mostly used and clinically accepted utilizes: 1) positive profile threaded pins and polymethylmethacrylate (PMMA) to form an internal fixator bridging the unstable lumbosacral spine segments or 2) bilateral transarticular screws. A recently developed SOP™ Locking Plate System offers many advantages and unique abilities when compared to the conventional approach in spinal fixation. The SOP system is intended to allow locking screw technology using standard orthopedic screws but since the plate can be contoured to any shape, the locking screws can be positioned in a variety of orientations. The SOP™ system was designed to be significantly stiffer and provide more stable fixation of fractured fragments with compromised bone quality than comparable compression or locking plates. The system has a smaller footprint than standard orthopedic plates and pins/PMMA internal fixation. The purpose of this canine cadaver study is to evaluate the biomechanical characteristics of the canine lumbosacral spine in flexion and extension via four-point bending test using three different types of internal fixation techniques. 1) Basic 6-pin system; positive profile threaded pins and polymethylmethacrylate; 2) bilateral transarticular screws and 3) SOP™ Locking Plate System.

Nathan Bihlmeyer, Student

Robert G. Franks, Faculty Mentor

Characterization of Physical Interactions within a Multimeric Transcriptional Corepressor Complex in Arabidopsis

In Arabidopsis thaliana, proper AGAMOUS (AG) gene expression is required for cell differentiation of floral meristem into the four different flower organs. Previous studies have implicated several proteins as being in a complex to regulate AG; however, only SEUSS (SEU) and LEUNIG (LUG), transcriptional corepressors, have been shown to physically interact to repress AG expression. In addition, SEUSS-LIKE (SLK) proteins have been found that show functional redundancy with SEU, but it has not been established if they physically interact with LUG or SEU. We hypothesize the proteins SEU, SLK1, SLK2, LUG, and the DNA binding transcriptional regulator AINTEGUMENTA (ANT) are part of a multimeric complex that represses the gene AG. This complex may also regulate the development of other important structures like the ovules/seeds. I am performing protein-protein in vitro interaction assays to determine which of these five proteins physically interact; including whether or not each protein interacts with itself. Once it is known which proteins interact with which other proteins, a new theoretical model of the multimeric complex that represses the gene AG can be formed.  

Steven G. Somers, Student

Bill F. Hunt Jr., Faculty Mentor

Can Blood Lead Levels in Children Be Reduced?

Lead exposure, whether acute or chronic, is a serious public concern due to the associated health hazards. Chronic lead poisoning, defined as a small amount of lead intake over a long time period, is more common among children and can have severe adverse effects on their cognitive development. Even low levels of lead intake have been shown to cause damaging effects after prolonged exposure. Our objective is to investigate Elevated Blood Lead Level (EBLL) rates per 1000 children. We have compared the 2003 California EBLL data to another EBLL data set they submitted in 2006 and found the 2003 data to be incorrect. We have contacted other state officials to validate the integrity of all the data and have also contacted states that didn’t submit data to the CDC in hopes of gaining access to their data. We are hoping to predict EBLL as a function of environmental factors and believe different regions of the country will have different significant factors. We have also produced a map that depicts the concentration of EBLL rates, highlighting the rustbelt as the main area of concern for our nation. Using exploratory statistical methods, we hope to better inform the USEPA of areas with high EBLL. Our final objective is to provide a more accurate data base than the one currently available for the CDC and attempt to determine the next major contributor to the current high EBLL in children. Co-Authors: Ashley Myers & Erika Burger.