Molecular and Cellular Neuroscience Commons^™

Different Cohort, Disparate Results: Selection Bias Is A Key Factor In Autopsy Cohorts, Kathryn Gauthreaux, Walter A. Kukull, Karin B. Nelson, Charles Mock, Yen-Chi Chen, Kwun C. G. Chan, David W. Fardo, Yuriko Katsumata, Erin L. Abner, Peter T. Nelson

Neurology Faculty Publications

INTRODUCTION: Research-oriented autopsy cohorts provide critical insights into dementia pathobiology. However, different studies sometimes report disparate findings, partially because each study has its own recruitment biases. We hypothesized that a straightforward metric, related to the percentage of research volunteers cognitively normal at recruitment, would predict other inter-cohort differences.

METHODS: The National Alzheimer’s Coordinating Center (NACC) provided data on N = 7178 autopsied participants from 28 individual research centers. Research cohorts were grouped based on the proportion of participants with normal cognition at initial clinical visit.

RESULTS: Cohorts with more participants who were cognitively normal at recruitment contained more individuals who …

Re-Programming Transcription Factor Function For Neuroscience Research Of Addiction: Investigating The Role Of Zinc Finger Proteins In Driving Cocaine Reinforcement In Mice, Joseph A. Picone

Theses and Dissertations

Administration of addictive drugs like cocaine or morphine initiates aberrant gene transcription within brain reward circuitry neurons, which contributes to the lasting behavioral maladaptations that define addiction. The drug-induced expression and function of key brain transcription factors (TFs) is one major mechanism through which these drugs are able to regulate transcription, and as a consequence, lasting damaging drug-related behaviors including compulsive drug use. The goal of this dissertation is to more fully understand the molecular mechanistic drug-specific actions of TFs within the rodent nucleus accumbens (NAc). The findings from these studies could serve as the basis to identify novel candidate …

Examining The Effects Of Artemisia Annua On Neuro2a Cells, Wesley Lim

Honors Undergraduate Theses

Artemisia annua L. is a well-known medicinal herb used in Traditional Chinese Medicine for many centuries and contains artemisinin, which exhibits antimalarial properties [1] and is a potential treatment for SARS-CoV-2 [2]. However, the neurological effect of A. annua and its compounds are poorly understood. We hypothesize that A. annua extracts and artemisinin will provide protection against oxidative stress in mouse neuronal Neuro2A cells. Superoxide dismutase 1 (SOD1) is an anti-oxidant enzyme that protects against oxidative damage [3]. Growth Arrest and DNA Damage-inducible 45 alpha (Gadd45a) is involved in DNA repair and is a common biomarker for DNA damage[4]. SOD1 …

A Tool To Automate Neuropathological Assessment In Huntington Disease Mouse Models, Samuel A. Moldenhauer

Honors Undergraduate Theses

As our life expectancy continues to rise, so does the prevalence of neurodegenerative diseases, such as Huntington disease (HD). Neurodegeneration leads to progressive regional brain atrophy, typically initiating prior to symptom onset. With the advancements of medical treatments designed to target neurodegeneration, researchers measure their impact on atrophy in animal models to assess their effectiveness. This is important because treatments designed to combat neuropathology are more likely to modify the disease itself, per contra to treatments designed to mask or treat symptoms. One method of brain region size quantification is magnetic resonance imaging (MRI), which while accurate, is prohibitively expensive. …

Cognitive Decline, Aβ Pathology, And Blood–Brain Barrier Function In Aged 5xfad Mice, Geetika Nehra, Sasivimon Promsan, Ruedeemars Yubolphan, Wijitra Chumboatong, Pornpun Vivithanaporn, Bryan J. Maloney, Anusorn Lungkaphin, Bjoern Bauer, Anika M. S. Hartz

Markey Cancer Center Faculty Publications

Background

Patients with Alzheimer’s disease (AD) develop blood–brain barrier dysfunction to varying degrees. How aging impacts Aβ pathology, blood–brain barrier function, and cognitive decline in AD remains largely unknown. In this study, we used 5xFAD mice to investigate changes in Aβ levels, barrier function, and cognitive decline over time.

Methods

5xFAD and wild-type (WT) mice were aged between 9.5 and 15.5 months and tested for spatial learning and reference memory with the Morris Water Maze (MWM). After behavior testing, mice were implanted with acute cranial windows and intravenously injected with fluorescent-labeled dextrans to assess their in vivo distribution in the …

Oxidative Stress Alters Mitochondrial Homeostasis In Isolated Brain Capillaries, Gopal V. Velmurugan, Hemendra J. Vekaria, Anika M. S. Hartz, Björn Bauer, William Brad Hubbard

Markey Cancer Center Faculty Publications

Background

Neurovascular deficits and blood-brain barrier (BBB) dysfunction are major hallmarks of brain trauma and neurodegenerative diseases. Oxidative stress is a prominent contributor to neurovascular unit (NVU) dysfunction and can propagate BBB disruption. Oxidative damage results in an imbalance of mitochondrial homeostasis, which can further drive functional impairment of brain capillaries. To this end, we developed a method to track mitochondrial-related changes after oxidative stress in the context of neurovascular pathophysiology as a critical endophenotype of neurodegenerative diseases.

Methods

To study brain capillary-specific mitochondrial function and dynamics in response to oxidative stress, we developed an ex vivo model in which …

Impacts Of Xylazine On Fentanyl Demand, Body Weight, And Acute Withdrawal In Rats: A Comparison To Lofexidine, Safiyah M. Sadek, Shailesh N. Khatri, Zachary A. Kipp, Kelly E. Dunn, Joshua S. Beckmann, William W. Stoops, Terry D. Hinds, Jr., Cassandra D. Gipson

Markey Cancer Center Faculty Publications

The opioid use landscape has recently shifted to include xylazine, a veterinary anesthetic, as an adulterant in the fentanyl supply. The health impacts of xylazine as an emerging fentanyl adulterant has raised alarm regarding xylazine as a public health threat, warranting research on the impacts of xylazine on fentanyl’s behavioral effects. No prior studies have evaluated the effects of xylazine on fentanyl consumption at various unit doses, fentanyl demand, or withdrawal as compared to the Food and Drug Administration-approved opioid withdrawal medication, lofexidine (Lucemyra®). This is important because lofexidine and xylazine are both adrenergic α2a (A2aR) agonists, however, lofexidine is …

Oxycodone Withdrawal Is Associated With Increased Cocaine Self-Administration And Aberrant Accumbens Glutamate Plasticity In Rats, Shailesh N. Khatri, Hanaa Ulangkaya, Erin E. Maher, Safiyah M. Sadek, Mei Hong, Andrea M. Woodcox, William W. Stoops, Cassandra D. Gipson

Markey Cancer Center Faculty Publications

Individuals with opioid use disorder (OUD) frequently use other substances, including cocaine. Opioid with- drawal is associated with increased likelihood of cocaine use, which may represent an attempt to ameliorate opioid withdrawal effects. Clinically, 30% of co-using individuals take opioids and cocaine exclusively in a sequential manner. Preclinical studies evaluating mechanisms of drug use typically study drugs in isolation. However, polysubstance use is a highly prevalent clinical issue and thus, we established a novel preclinical model of sequential oxycodone and cocaine self-administration (SA) whereby rats acquired oxycodone and cocaine SA in an A-B-A-B design. Somatic signs of withdrawal were evaluated …

Investigating The Roles Of Dapk, P53/Cep-1, And Mitochondrial Damage In Necrotic Neurodegeneration In C. Elegans, Anil Singh

Dissertations and Theses

Stroke is one of the leading causes of death in the U.S., with minority groups, suffering higher fatality rates. Stroke is caused by ischemia, where occlusion of blood supply to the brain results in neurodegeneration. Most of the damage is attributed to excitotoxicity, where an accumulation of the neurotransmitter glutamate in the synapse overstimulates postsynaptic neurons and ultimately leads to cell death (largely by necrosis). Stroke treatments are often ineffective, due to the delay between the onset of stroke and the delivery of effective treatment. To address this, we focus our study on putative later-acting mediators of excitotoxicity such as …

Traumatic Brain Injury Induces Cerebrovascular Dysfunction: Consequences For Ischemia And Cerebral Hypoperfusion, Bailey J. Whitehead

Graduate Theses, Dissertations, and Problem Reports (ETD)

Traumatic brain injury (TBI) is a significant health concern across the United States as well as the broader globe, affecting millions of individuals on an annual basis. While most recover from their TBI and resume their lives normally, some subsets of TBI survivors continue to experience impairments and increased risk for future diseases like cardiovascular disease, stroke, and aging related disease like Alzheimer’s Disease or VCID.

TBI remains a fundamentally difficult neurological injury to pin down mechanistically, due to the variability in severity, timing, and age of patient, among other factors. One significant factor in the pathology has consistently been …

Cell-Type-Specific Effects Of Synaptic Zinc In Mouse Auditory Cortex, Mason Mccollum

Graduate Theses, Dissertations, and Problem Reports (ETD)

Synaptic zinc signaling modulates synaptic activity and is present in specific populations of cortical neurons, suggesting that synaptic zinc contributes to the diversity of intracortical synaptic microcircuits and their auditory tuning properties. Stimulus-specific adaptation is a hallmark of sensory processing in which a repeated stimulus results in diminished successive neuronal responses, but a deviant stimulus will still elicit robust responses from the same neurons. Recent work has established that synaptically released zinc is an endogenous mechanism that shapes neuronal responses to sounds in the auditory cortex. Here, to understand the role of zinc signaling in the auditory cortex and the …

Gaba Transporter Loss-Of-Function Mutations In Pediatric Epilepsy: Neural Mechanisms And A Novel Fatty Acid Based Therapeutic Approach, Alessandra G. Jester

Graduate Student Theses, Dissertations, & Professional Papers

An increasing number of spontaneous mutations in the GABA transporter gene SLC6A1 (GAT-1) have been associated with pediatric epilepsy and neurodevelopmental disorders. The molecular mechanisms and impact of mutations on GABA homeostasis and neuronal circuit function are poorly understood. Furthermore, there are currently no validated therapeutic approaches to treat patients. A de novo mutation (S295L) in the GABA transporter gene SLC6A1 that was identified in a pediatric patient was introduced into a human cDNA construct, and mutant and wild-type transporters were expressed and studied in Xenopus oocytes by voltage clamp and radiolabeled GABA flux measurement. In addition, the effect of …

Structural And Functional Consequences Of Pde6 Prenylation In Rod And Cone Photoreceptors, Faezeh Moakedi

Graduate Theses, Dissertations, and Problem Reports (ETD)

Phosphodiesterase-6 (PDE6) serves as a pivotal component in the phototransduction pathways of both cone and rod photoreceptors. In cones, PDE6 consists of tetrameric subunits: inhibitory (γ') and catalytic (α'). The catalytic subunit, PDE6α', contains a C-terminal prenylation motif. Deletion of this motif is associated with achromatopsia (ACHM), a form of color blindness. The mechanisms underlying the disease and the roles of PDE6 lipidation in vision remain elusive. Meanwhile, rod PDE6 is composed of α and β catalytic subunits and γ inhibitory subunits, with alterations in the C-terminal "prenylation motif" of PDE6β linked to retinitis pigmentosa (RP) pathology. In this comprehensive …

An Inhibitory Recurrent Network In The Olfactory System, Farzaan Salman

Graduate Theses, Dissertations, and Problem Reports (ETD)

Neuromodulatory circuits are a necessary component of neural flexibility as they are able to act differentially depending on the receptors expressed by their downstream targets. Identifying the synaptic partners of modulatory neurons and determining the neurotransmitter and receptor content of these partners is necessary to identify the rules governing neuromodulatory circuits. In this study, I characterized the circuit of the contralaterally projecting, serotonin-immunoreactive deutocerebral neurons (CSDns), the sole synaptic source of the neuromodulator serotonin in the olfactory circuit of Drosophila melanogaster, by identifying the strongest synaptic partners of the CSDns, and the expression of genes encoding neurotransmitters and receptors of …

Androgen Regulation Of The Hpa Axis And Stress-Related Behaviors In Mice: The Role Of Crf And Crf Receptor 1, Krystyna Ann Rybka

Electronic Theses & Dissertations (2024 - present)

Mood disorders such as anxiety and depression are nearly twice as prevalent in women when compared to men, with potential contributing factors involving sex-dependent exposure to gonadal hormones and dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Androgen actions through androgen receptors (AR) or actions at estrogen receptors such as ERα, following the conversion of androgens to estradiol, have been shown to regulate stress-related behaviors as well as HPA axis responsiveness. Where androgen actions at AR appear to decrease the stress response and subsequent stress-related behaviors, actions at ERα seem to do the opposite and increase HPA axis reactivity. When the HPA …

Measuring Spontaneous Neurotransmission Using Genetically Encoded Fluorescent Indicators, Amelia Jane Ralowicz

Dartmouth College Ph.D Dissertations

Synaptic connections throughout the nervous system exhibit two forms of neurotransmitter release caused by synaptic vesicle fusion, evoked and spontaneous release. Despite being discovered 70 years ago, the mechanisms governing spontaneous release have remained elusive. Our understanding of spontaneous release lacks mechanistic details including discrepancies in the sources of synaptic vesicles supporting it, the source(s) of calcium supporting it, and most importantly an unclear relationship (cooperative or antagonistic) with evoked release. These gaps exist due to a lack of experimental methods specific to the study of spontaneous release at individual synapses.

This thesis addresses these gaps in two ways. Firstly, …

Biogenesis And Function Of Microglial Extracellular Vesicles In Neuroinflammation And Parkinson’S Disease, Karl E. Biggs

Dartmouth College Ph.D Dissertations

Microglia are subject to chronic proteinaceous and environmental stress during the progression of prevalent neurodegenerative diseases such as Parkinson’s Disease (PD). Chronic stress can activate the NLR family pyrin domain containing 3 (NLRP3) pattern recognition receptor resulting in the formation of the NLRP3 inflammasome, proinflammatory signaling, and pyroptotic cell death. A distinct subset of extracellular vesicles (EVs) are released from cells upon NLRP3 activation. We studied WT and Nlrp3^-/- primary microglia exposed to bacterial stimulating agents and alpha synuclein preformed fibrils (αsyn PFFs), which model Parkinson’s disease and associated synucleinopathies. We identified the NLRP3-dependent release of the endosome fate …

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. …

Role Of The Anti-Viral Immune Response In Neural Cell Modulation And Neurological Sequelae Of Childhood Viral Infections, Yashika Kamte

Electronic Theses and Dissertations

Viral infections of the central nervous system (CNS) often result in neurological sequelae and are considered a risk factor for the development of neurological disease. Moreover, the outcomes of a viral infection are largely dependent on the age of the host, with younger hosts developing more profound neuropathology. Perhaps the developing brain coupled with an immature immune system contributes to worse outcomes in the very young. Children suffering from brain infections are more prone to develop enduring neurological impairments even after recovery from the infection. Although majority of the brain growth occurs in utero, neurodevelopment continues throughout the juvenile …

Cardiac Vagal Dysfunction And Ventricular Arrhythmogenesis In Type 2 Diabetes Mellitus After Myocardial Infarction, Dongze Zhang

Theses & Dissertations

Diabetes is the eighth leading cause of death in the United States. Every eight seconds a person dies from diabetes around the world. Among various types of diabetes, type 2 diabetes mellitus (T2DM) is the most common form, representing 90% to 95% of all diabetes populations. The leading cause of mortality and morbidity in T2DM patients is cardiovascular disease, among which acute myocardial infarction (MI)-induced ventricular arrhythmia is the major cause of death in T2DM. Patients with T2DM are two to four times more likely to die from MI than non-diabetic patients. Although well-known therapies including better glycemic control have …