Biology Commons^™

The Role Of Semaphorins In Response To Injury In C. Elegans Neurons, Maria Belen Harreguy Alfonso

Dissertations

When neural tissue is injured by trauma, delicate neuronal processes such as axons and dendrites are prone to lesion damage and often disconnect. The molecular, cellular, and circuit mechanisms that underlie the regrowth and reconnection of these processes and the recovery of behavior are major challenges in the fields of neuroscience, regeneration, and resilience. At the molecular and cellular levels, signaling pathways that mediate neuronal growth cone guidance during development can play a role in neuronal regeneration and recovery from injury. One family of signaling proteins involved in this process comprises the highly conserved semaphorins and their receptors, the plexins. …

Repeated Low-Level Blast Induces Chronic Neuroinflammation And Neurobehavioral Changes In Rat Models, Arun Reddy Ravula

Dissertations

Blast-induced neurotrauma (bTBI) is a signature medical concern for military personnel when they are exposed to explosions in active combat zones. However, soldiers as well as law enforcement personnel are also repeatedly exposed to low-level blasts during training sessions with heavy weaponries as part of combat readiness. Service personnel who sustain brain injuries from repeated low-level blasts (rLLBs) do not display overt pathological symptoms immediately but rather develop cognitive impairments, attention deficits, anxiety, and sleep disturbances over time. An improved rat model of rLLB was developed in this thesis by applying controlled low-level blast pressures (10 psi) repeated five times …

The Roles Of Inhibition In C. Elegans Locomotion, Lan Deng

Dissertations

Inhibition plays important roles in modulating neural activities at different levels from small synapses to brain regions, and different systems from sensory to motor. To achieve translocation, locomotor systems produce alternation of antagonist muscles, including axial posture and limb movement and alternation. In the nematode C. elegans, a cross-inhibition circuit, involving excitatory cholinergic and inhibitory GABAergic motoneurons, is believed to generate the dorsoventral alternation of body-wall muscles that supports backward undulatory locomotion. This dissertation challenges this prevalent hypothesis, delves into studying different roles of inhibition, and depicts the expression pattern and functional role of ionotropic GABAA receptor, UNC-49, in motoneurons …

Evolution Of Caffeine Biosynthetic Enzymes And Pathways In Flowering Plants, Ruiqi Huang

Dissertations

Convergent evolution generally refers to the independent evolution of similar biological function more than once in unrelated species. Caffeine is thought to have evolved by convergence, and is naturally produced through secondary metabolism in plants to defend against pathogen attack and insect feeding or to attract pollinators. The same caffeine biosynthetic pathway has been elucidated in Camellia (tea) and Coffea (coffee), in which xanthosine is sequentially methylated to caffeine via 7-methylxanthine and theobromine. However, although the same catalysis pathway is used, different (paralogous) enzymes in the SAMT/BAMT/theobromine synthase (SABATH) multigene family are used in the two species. In my dissertation, …

Regulation Of Glial Cell Line-Derived Neurotrophic Factor (Gdnf) Production In Voluntary And Involuntary Muscle, John-Mary Vianney

Dissertations

Glia cell line-derived neurotrophic factor (GDNF) is a survival factor for subpopulations of neurons, including somatic and autonomic motor neurons. These neurons depend, in part, on GDNF that is synthesized and secreted by their target tissues. It has been shown that a number of tissues in the periphery express GDNF and these target tissues differ in their composition, function, and in the case of different muscle cell types, their contractile characteristics. Whether the processes regulating GDNF production in these different tissues is similar or different is poorly understood. The broad goal of this study is to examine factors that normally …

Exposure Of Nervous System Cells To Polychlorinated Biphenyls (Pcbs), Results In Alterations Of Neurotrophic Factor Expression, Gordon H. Gurley

Dissertations

Toxic insult by PCBs results in learning and memory deficits in humans. Alterations in expression of neurotrophic factors (NF) and/or their receptors have been linked to changes in learning and memory. How PCBs affect cognition is not known. We suggest that PCBs affect cognition by altering NF expression.

We exposed cultured C6 rat glioblastoma cells (an astrocyte cell-line) to medium containing PCB (Aroclor 1254 (10ppm)). Control cells were treated with dimethyl sulfoxide (DMSO) or regular medium. Enzyme-linked immunosorbent assays (ELISA) were used to determine glial cell-line derived neurotrophic factor(GDNF) and nerve growth factor (NGF) concentrations in all samples. We also …