Cellular and Molecular Physiology Commons^™

Expanding The Role Of Muscle Stem Cell Fusion In Muscle Under Hypertrophic Stimulus, Jensen Goh Zhong Sheng

Theses and Dissertations--Physiology

Muscle stem cells (MuSCs) are a unique stem cell population that can activate in response to both injury and growth stimuli. Studies on muscle regeneration have shown MuSC activation follows a uniform progression through proliferation, differentiation, and fusion. Therefore, to determine whether MuSC replication is a prerequisite for differentiation under hypertrophic stimulus, I used a lineage-tracking mouse model (Pax7^rtTA; TRE-H2B-GFP) to label MuSC nuclei and simultaneously tracked DNA synthesis via EdU incorporation. This dual-labeling approach allowed us to not only distinguish MuSC-derived nuclei but also demarcate which MuSC had proliferated prior to fusion. I then employed a mechanical …

A Tale Of Two Serpins: Pathologic And Protective Roles Of Agt And Pai-1 In Metabolic And Cardiovascular Disease, Alex C. Pettey

Theses and Dissertations--Physiology

Metabolic and cardiovascular diseases are leading causes of morbidity and mortality worldwide. Conditions such as metabolic dysfunction-associated steatotic liver disease (MASLD), aortic aneurysm, and cardiac fibrosis have limited pharmacological therapies, underscoring the need for deeper mechanistic investigations. Serine protease inhibitors (serpins) have been implicated in these pathologies and represent potential therapeutic targets. Despite structural homology, serpins regulate diverse physiological processes through both protease inhibition and non-inhibitory mechanisms. This dissertation examines the roles of two serpins, angiotensinogen (AGT) and plasminogen activator inhibitor-1 (PAI-1), in preclinical models of metabolic and cardiovascular disease to identify novel mechanisms that may inform future therapeutic strategies. …

Rad Reduction Reveals Therapeutic Potential Of Targeting Cardiomyocyte L-Type Calcium Channel Regulation For Heart Failure, Garrett Elmore

Theses and Dissertations--Physiology

Heart failure (HF) is prevalent and is predicted to increase with the aging population. Dilated cardiomyopathy (DCM) is a common cause of systolic HF. Current therapies fail to address principal issues: compromised systolic function and dysfunctional Ca²⁺ handling. No therapeutic approach exists for direct, positive modulation of cardiomyocyte L-type calcium channels (LTCC). RAD (Ras associated with diabetes) is a key regulator of the cardiac LTCC. RAD is a downstream phosphorylated target of the ß-adrenergic receptor (ß-AR)/cAMP/protein kinase A pathway; phosphorylation augments LTCC activity, contributing to chronotropy, inotropy, and lusitropy. RAD overexpression results in LTCC inhibition, whereas knockout positively modulates …

Disorganization Of Actin Within The Shafts Of Stereocilia Is A Key Difference Between Temporary And Permanent Noise-Induced Hearing Loss (Nihl), Shadan Hadi

Theses and Dissertations--Physiology

During sound stimulation, mechanosensory stereocilia of the auditory hair cell pivot around their bases, where their actin cores become denser and form rootlets protruding into the cuticular plate. It is believed that actin-based cuticular plate provides a stable mechanical support for stereocilia, while rootles are responsible for their pivotal flexibility and life-long resilience to mechanical stimuli. Not surprisingly, damage to the stereocilia bundles is known as a hallmark of permanent noise-induced hearing loss (NIHL). Yet, despite decades of NIHL studies, it is still unknown which ultrastructural changes in the stereocilia bundles are evoked directly by mechanical overstimulation.

Here, we explored …

Novel Mammalian Models For Understanding And Treating Spinal Cord Injury, Michael B. Orr

Theses and Dissertations--Physiology

Spinal cord injury (SCI) is devastating and often leaves the injured individual with persistent dysfunction. The injury persists because humans have poor wound repair and there are no pharmacologic treatments to induce wound repair after SCI. The continued efforts to discover therapeutic targets and develop treatments heavily relies on animal models. The purpose of this project is to develop and study novel mammalian models of SCI to provide insights for the development and effective implementation of SCI therapies.

Lab mice (Mus musculus) are a powerful tool for recapitulating the progression and persistent damage evident in human SCI, but …

Myelin, Cpla2, And Azithromycin: Modulation Of Macrophage Activation In Spinal Cord Injury Inflammation, Timothy J. Kopper

Theses and Dissertations--Physiology

Spinal cord injury (SCI) produces a chronic inflammatory state primarily mediated by macrophages consisting of resident microglia and infiltrating monocytes. These chronically activated SCI macrophages adopt a pro-inflammatory, pathological state that continues to cause additional damage after the initial injury and inhibits recovery. While the roles of macrophages in SCI pathophysiology are well documented, the factors contributing to this maladaptive response are poorly understood. Here, we identify the detrimental effects of myelin debris on macrophage physiology and demonstrate a novel, activation state-dependent role for cytosolic phospholipase-A2 (cPLA₂) in myelin- mediated potentiation of pro-inflammatory macrophage activation. Macrophage- mediated inflammatory …

Remodeling In The Actin Core Of The Auditory Hair Cell Stereocilia As A Novel Component Of Temporary Noise-Induced Hearing Loss, Jonathan Michael Grossheim

Theses and Dissertations--Physiology

The rigid, paracrystalline actin core of auditory hair cell stereocilia is extremely stable and after initial formation must persist for the life of the cell to preserve hearing in mammals. In healthy hair cells, turnover of actin molecules occurs only in a small region near the tips of stereocilia, while the actin filaments of the shaft are stable. For decades damage to the actin core of stereocilia from acoustic trauma has only been attributed to cases of permanent noise-induced hearing loss. Here, we show that repairable actin core damage occurs in temporary noise-induced hearing loss from moderate acoustic trauma.

We …

Β-Catenin Regulation Of Adult Skeletal Muscle Plasticity, Yuan Wen

Theses and Dissertations--Physiology

Adult skeletal muscle is highly plastic and responds readily to environmental stimuli. One of the most commonly utilized methods to study skeletal muscle adaptations is immunofluorescence microscopy. By analyzing images of adult muscle cells, also known as myofibers, one can quantify changes in skeletal muscle structure and function (e.g. hypertrophy and fiber type). Skeletal muscle samples are typically cut in transverse or cross sections, and antibodies against sarcolemmal or basal lamina proteins are used to label the myofiber boundaries.

The quantification of hundreds to thousands of myofibers per sample is accomplished either manually or semi-automatically using generalized pathology software, and …

Alterations In Gabaergic Nts Neuron Function In Association With Tle And Sudep, Isabel Diane Derera

Theses and Dissertations--Physiology

Epilepsy is a neurological disorder that is characterized by aberrant electrical activity in the brain resulting in at least two unprovoked seizures over a period longer than 24 hours. Approximately 60% of individuals with epilepsy are diagnosed with temporal lobe epilepsy (TLE) and about one third of those individuals do not respond well to anti-seizure medications. This places those individuals at high risk for sudden unexpected death in epilepsy (SUDEP). SUDEP is defined as when an individual with epilepsy, who is otherwise healthy, dies suddenly and unexpectedly for unknown reasons. SUDEP is one of the leading causes of death in …

The Mechanical Properties Of Non-Failing And Failing Human Myocardium, Cheavar A. Blair

Theses and Dissertations--Physiology

Heart failure is a clinical syndrome that manifests when there are structural and functional impairments to the heart that reduces the ability of the ventricles to fill or eject blood. The syndrome affects ~6 million Americans and is responsible for nearly 300,000 deaths annually. At the core of the syndrome are dysfunctional sarcomeres, the machinery that drives cardiac contraction and relaxation. By assessing the mechanical properties of human cardiac tissue, the information provided in this dissertation will provide data that demonstrates how sarcomeric dysfunction contributes to heart failure in the left and right ventricles. Additionally, these data will supply information …

Ppap2b Expression Limits Lesion Formation In Murine Models Of Atherosclerosis, Paul A. Mueller

Theses and Dissertations--Physiology

Coronary artery disease (CAD) is the leading cause of death in both men and women worldwide and is defined as a narrowing of the coronary arteries due to accumulation of atherosclerotic plaques. Genome-wide association studies have identified risk loci within the gene PPAP2B that confers increased risk of developing CAD. Evidence suggests these aforementioned SNPs are regulating PPAP2B expression in a cis-manner through the interruption of transcription factor binding sites. PPAP2B encodes the lipid phosphate phosphatase 3 enzyme that plays a key role in degrading bioactive lysophosphatidic acid (LPA). LPA has a plethora of effects on vascular tissue and is …

Trpa1 Channels In Cochlear Supporting Cells Regulate Hearing Sensitivity After Noise Exposure, Alejandra C. Velez-Ortega

Theses and Dissertations--Physiology

TRPA1 channels are sensors for noxious stimuli in a subset of nociceptive neurons. TRPA1 channels are also expressed in cells of the mammalian inner ear, but their function in this tissue remains unknown given that Trpa1^–/– mice exhibit normal hearing, balance and sensory mechanotransduction. Here we show that non-sensory (supporting) cells of the hearing organ in the cochlea detect tissue damage via the activation of TRPA1 channels and subsequently modulate cochlear amplification through active cellshape changes.

We found that cochlear supporting cells of wild type but not Trpa1^–/– mice generate inward currents and robust long-lasting Ca²⁺ responses …

Transmural Heterogeneity Of Cellular Level Cardiac Contractile Properties In Aging And Heart Failure, Premi Haynes

Theses and Dissertations--Physiology

The left ventricle of the heart relaxes when it fills with blood and contracts to eject blood into circulation to meet the body’s metabolic demands. Dysfunction in either relaxation or contraction of the left ventricle can lead to heart failure. Transmural heterogeneity is thought to contribute to normal ventricular wall motion but it is not well understood how transmural modifications affect the failing left ventricle. The overall hypothesis of this dissertation is that normal left ventricles exhibit transmural heterogeneity in cellular level contractile properties and with aging and heart failure there are region-specific changes in cellular level contractile mechanisms.

Age …

The Cardiac L-Type Calcium Channel Distal Carboxyl- Terminus Auto-Inhibition Is Regulated By Calcium, Shawn M. Crump

Theses and Dissertations--Physiology

The L-type calcium channel (LTCC) provides trigger Ca²⁺ for sarcoplasmic reticulum Ca²⁺-release and LTCC function is influenced by interacting proteins including the LTCC Distal Carboxyl-terminus (DCT) and calmodulin. DCT is proteolytically cleaved, and re-associates with the LTCC complex to regulate calcium channel function. DCT reduces LTCC barium current (IBa,L) in reconstituted channel complexes, yet the contribution of DCT to ICa,L in cardiomyocyte systems is unexplored. This study tests the hypothesis that DCT attenuates cardiomyocyte ICa,L. We measured LTCC current and Ca²⁺ transients with DCT co-expressed in murine cardiomyocytes. We also heterologously co-expressed DCT and CaV1.2 constructs …