Biology

Permanent URI for this collectionhttps://hdl.handle.net/10315/27613

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Access status: Open Access ,
Declining Ice Duration and Changing Ice Quality Drive Key Under-Ice Ecological Changes in Wisconsin Lakes
(2025-11-11) Sandrock, Phoenix Kieran; Sharma, Sapna
Lakes are rapidly losing ice cover. We expect that ice loss will have widespread ecological consequences, but these consequences are poorly understood, particularly over long temporal scales. Here, we ask: how do changing ice duration and ice quality influence under-ice photic depth, water temperatures, dissolved oxygen concentrations, and chlorophyll a concentrations? We analyzed winter data from 11 lakes across Wisconsin, USA, with time-series extending from 1982 to 2023. Shorter ice durations and less snow were associated with deeper photic depths, colder under-ice water temperatures, and higher dissolved oxygen saturations. Snow and ice conditions were significantly related to chlorophyll a concentrations; however, the relationship was mediated by nutrient concentrations. We suggest that the drivers of under-ice ecology are as complex as those of the open water season and advocate for the use of integrative models to understand the future of ice-covered lakes.
Access status: Open Access ,
Reclaiming Autumn in Limnology: Evidence of Shifting Autumn Phenology and Impacts on Winter Conditions and Cross-Seasonal Lake Dynamics
(2025-11-11) Ferrato, Faith Renee; Sharma, Sapna
Autumn remains understudied in limnology, despite its recognized ecological importance in other disciplines. In this thesis, we addressed the need for greater integration of autumn into limnological research (Chapter 1) and demonstrated how climate-driven shifts in autumn phenology affect ice formation and winter thermal conditions (Chapter 2). Using 37–50 years of data from 47 Finnish lakes, we found that autumn surface waters have warmed significantly, resulting in widespread delays in ice formation. Delayed ice formation was associated with colder bottom under-ice temperatures. Stronger autumn winds and larger lake size were also associated with colder under-ice conditions through their influence on pre-freeze mixing and heat loss. Furthermore, higher maximum summer surface water temperatures were observed in years with later ice-on dates. As climate change continues to disrupt seasonal patterns, a greater focus on autumn will be critical to effectively predict the impacts of warming on ecosystem functioning of northern lakes.
Access status: Open Access ,
Examining Sex Differences of Adipose Endothelial Cells and the Effects of Foxo1 Deletion
(2025-11-11) Pislaru, Alexandra; Haas, Tara
During obesity, adipose tissue undergoes significant remodeling to store excess energy. Adequate vascular growth is required for adipose expansion, which ensures proper oxygen and nutrient supply and prevents insulin resistance and metabolic disease. Thus, coordinated angiogenesis is critical for metabolic health during obesity. Transcriptomic analysis of adipose endothelial cells (ECs) from high-fat fed mice revealed that female ECs displayed a proliferative and chromatin-remodeled profile, while male ECs were enriched in inflammatory and senescence-associated signatures. Similar sex differences were observed in aging ECs. To assess the influence of sex hormones, a gonadectomy model was used. Surprisingly, the loss of gonadal hormones increased capillary density despite reduced levels of VEGFA in the adipose microenvironment. However, gonadectomy had no long-term effect on EC metabolism in culture, though direct estradiol stimulation did increase mitochondrial ATP production. One candidate contributor of sex differences is the endothelial quiescence-inducing transcription factor forkhead box O1 (FoxO1), which is more highly expressed in female ECs despite higher angiogenic activity. FoxO1 knockdown or inhibition in females led to a dysfunctional EC phenotype which was marked by inflammation, oxidative stress, impaired mitochondrial function, and DNA damage. These endothelial disturbances caused by FoxO1 loss were accompanied by lower capillary content in the females, a response not mirrored in males. Overall, these studies demonstrate that female ECs exhibit a healthier phenotype under obesogenic conditions, a trait that appears to be largely independent of sex hormones. Instead, FoxO1 emerges as a major contributor to this protective and resilient female endothelial profile.
Access status: Open Access ,
Structural and RNA-Binding Characteristics of Three Yeast LA Motif Domains
(2025-11-11) Pacheco, Evan Moniz; Donaldson, Logan
La-related proteins (LARP) are a conserved class of RNA-binding proteins that function in RNA metabolism, including mRNA stabilization, translation regulation, and non-coding RNA processing. In humans, La-related protein 1 (LARP1) regulates translation and stability of 5′ terminal oligopyrimidine (TOP) tract-containing mRNAs linked to cell growth and proliferation. Although its role as a downstream effector of the mTORC1 pathway is established, the molecular interactions of LARP1 and yeast homologs remain poorly defined. This thesis examines the structure–function relationship of the La motif domain (LaM) in yeast proteins Slr1p, Slf1p, and Sro9p using isothermal titration calorimetry (ITC), circular dichroism (CD), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC). Findings show these proteins share conserved features and bind RNA and ligands with high affinity (low micromolar Kd). NMR line broadening observed for Slf1p–RNA interactions suggests conformational sampling. Collectively, these results advance understanding of conserved mechanisms underlying LARP1-mediated translational regulation.
Access status: Open Access ,
The Vestibular System's Influence on the Perceived Duration of Lights, Sounds, and Touches
(2025-11-11) Ghasemi, Fatemeh; Harris, Laurence
Time perception is essential to human experience, but factors like microgravity can alter it (Navarro Morales et al., 2023). To explore the role of gravity, I compared time perception in standing and supine postures. Participants (n=124) judged whether stimuli (light, sound, tactile vibration) lasted longer or shorter than 1 second. In Experiment 1, participants judged light duration; in Experiment 2, sound; in Experiment 3, tactile vibration; and in Experiment 4, visual duration with and without disruptive galvanic vestibular stimulation (dGVS). Results revealed that light and tactile stimuli were perceived as longer than auditory stimuli, but the perception of auditory and tactile durations was unaffected by posture. However, visual duration was perceived as significantly longer when supine (45ms) or with dGVS (66ms). These findings suggest that the vestibular system influences visual time perception, with disruptions slowing the perception of time.
Access status: Open Access ,
ALY688 Protects Against Ferroptosis Via Nrf2 Activation in Skeletal Muscle
(2025-11-11) Haetanurak, Photsathorn; Sweeney, Gary
Ferroptosis is a regulated form of cell death that is characterized by excessive lipid peroxidation. Arachidonic acid (AA), a polyunsaturated fatty acid (PUFA), can be incorporated into cell membrane phospholipids, thereby increasing their susceptibility to oxidative damage and ultimately ferroptosis. In this study, AA was found to enhance susceptibility to ferroptosis in both rat L6 cells and human iPSC-derived skeletal muscle cells. In the presence of AA, cells responded to iron overload (IO) with elevated oxidative stress, total cellular lipid peroxidation and mitochondrial lipid peroxidation, culminating in more ferroptotic cell death. These effects were significantly attenuated by ALY688, an adiponectin receptor agonist. We observed that ALY688 activated Nrf2 signaling in both L6 and iPSC-derived skeletal muscle cells and that the cytoprotective effect of ALY688 was abolished by ML385, an Nrf2 inhibitor. Together, these findings identified that AA increased skeletal muscle cell susceptibility to detrimental effects of iron and established that ALY688 mitigated the combined effects of AA and IO via an Nrf2-dependent mechanism.
Access status: Open Access ,
Spatio-Temporal Variation in Ringed Seal (Pusa Hispida) Density and Habitat Use in the Last Ice Area
(2025-11-11) MacLean, Roxanne Dawn; Thiemann, Gregory W.
The Arctic is experiencing warming at a rate approximately four times faster than the global average, contributing to precipitous declines in the extent, thickness, age, and seasonal duration of sea ice. The full effects of these rapid changes in sea ice habitat on the Arctic marine ecosystem remain unknown, especially in the High Arctic where ecological research has been limited due to its remoteness. Ringed seals (Pusa hispida) are an abundant ice-associated pinniped species with a habitat range spanning the circumpolar region, making them an ideal study species for exploring ecological changes under changing environmental conditions. Using observations from aerial surveys, this thesis provides the first study on spatio-temporal variation in ringed seal density and habitat use in their northern most range in the Canadian High Arctic, highlighting the importance of bathymetry and marine terminating glaciers to the summer habitat use of ringed seals in the Last Ice Area.
Access status: Open Access ,
Investigating the Anti-Inflammatory Mechanism of the Adiponectin Receptor Agonist, ALY688, in Iron Overload-Induced Macrophage Activation
(2025-11-11) Zhang, Bojun; Sweeney, Gary
Chronic inflammation, driven by fa tors such as iron overload, contributes to metabolic, cardiovascular, and degenerative diseases. Excess iron promotes pro-inflammatory cytokines release and increased production of reactive oxygen species (ROS) in macrophages via transcription factors, such as IRF and NF-κB. This study investigated whether ALY688, an adiponectin receptor agonist, mitigate iron-induced inflammation. Using ferrous sulfate (FeSO₄) treated RAW 264.7 macrophages, I found that ALY688 markedly reduced the activation of both NF-κB and IRF pathways, suppressed ROS levels, and reversed the expression of inflammatory and antioxidant genes. Iron overload significantly upregulated pro-inflammatory cytokines (IL-1β, TNF-α, IL-6) and oxidative stress-related genes (NOX2), while downregulating anti-inflammatory mediators such as IL-10. Together, these findings support a regulatory role of ALY688 in attenuating iron-induced oxidative stress and inflammation in macrophages, suggesting that ALY688 may serve as a promising therapeutic candidate for iron overload-associated inflammatory disorders.
Access status: Open Access ,
Beyond the Croak: Decoding the Silent Communication of Frogs
(2025-11-11) Ortega Paez, Jhael Alejandra; Schott, Ryan K.
Frogs rely on vocal signals for social interactions, which depend on a functional auditory system. Yet multiple lineages have independently lost critical auditory structures, raising questions about how communication is maintained. We hypothesized that visual adaptations could compensate for reduced auditory capacity. To test this, we measured eye and corneal size across 264 anuran species and assessed associations with ecological traits and auditory condition. We also sequenced the genome of Pristimantis brevicrus, an earless species, to examine the molecular evolution of visual opsins. Species with auditory reductions had smaller eyes, but non-fossorial taxa exhibited enlarged corneas, enhancing light sensitivity at lower metabolic cost. Analyses of RH1, SWS1, SWS2, and LWS revealed predominant purifying selection, while species with auditory loss showed relaxed constraint and positive selection, particularly in SWS1 and LWS. These findings suggest that visual adaptations compensate for auditory loss, highlighting sensory trade-offs as drivers of anuran communication and evolution.
Access status: Open Access ,
Activity-Dependent Suppression of Synaptic Strength in the Mouse Hippocampus
(2025-11-11) Karimi Tari, Parisa; Connor, Steven; Zoidl, Georg R.
This thesis focuses on understanding how synapses are weakened, which represents the cellular basis for information erasure within the brain. In Project 1, age-dependent changes in mechanisms supporting “depotentiation,” an activity-dependent weakening of recently strengthened synapses, was assessed in aged mice. Ageing is associated with exaggerated forgetting, which may be due to impaired memory consolidation or rapid degradation of recently generated memories. Memory consolidation is regulated by neuromodulators, neurochemicals that modify the ability of synapses to undergo activity-dependent changes. Noradrenaline is a neuromodulator secreted during arousal and novelty detection which boosts long-term potentiation (LTP). Accordingly, I sought to determine if 1) depotentiation is altered in aged hippocampus synapses and 2) if noradrenaline provides immunity against depotentiation during ageing. I found that aging increases the temporal window for depotentiating synapses which was reversed by treating aged brain slices with noradrenaline. Mechanistically, noradrenaline prevented depotentiation through activation of beta-adrenergic receptors and recruitment of protein synthesis, suggesting that activating beta-adrenergic receptors reverses aged-related synaptic deficits through boosting translation. In Project 2, I further explored how synapses are weakened through characterizing an alternative form of synaptic depression: the phenomenon of LTP decay. LTP is a leading cellular model for the synaptic changes that encode memories. However, not all forms of LTP last, and there is growing evidence that intrinsic neuronal mechanisms actively oppose synaptic potentiation. In this study, I probed how gains in synaptic strength during potentiation are actively reversed. My approach was to block select cellular signals after inducing LTP, when synaptic strength “decays” or returns back to baseline. Using this strategy, I discovered that LTP decays in an activity-dependent manner, which requires extrasynaptic GluN2B-containing NMDA receptors and downstream recruitment of Rac1. Interestingly, inhibition of Rac1 facilitated the recruitment of ERK and converted decaying LTP into an enduring, translation-dependent form. These findings suggest that intrinsic mechanisms within the hippocampus may actively promote forgetting by recruiting Rac1-mediated signaling pathways that suppress parallel molecular pathways that normally promote memory consolidation. Taken together, this thesis revealed novel cellular processes that actively reduce synapse potentiation, providing new insights into the neural basis for forgetting.
Access status: Open Access ,
Investigating EV as a Mechanism Mediating the Cellular Effects of Adiponectin
(2025-11-11) Chung, Wing Yan; Sweeney, Gary
Adiponectin provides systemic protection in cardiometabolic health, yet the mechanisms underlying its tissue-specific effects remain poorly understood due to its functional complexity. Therapeutic development is further hindered by difficulties in generating stable, bioactive forms with sustained and targeted activity. Emerging evidence highlights extracellular vesicles (EV) as mediators of inter-organ communication and promising vehicles for the development of new therapeutics. This thesis investigates the cardioprotective role of plasma or adipocyte-derived EV isolated from mice that were treated with or without the adiponectin-mimetic peptide ALY688. EV isolated from adipocytes after mice were treated with ALY688, versus control, enhanced autophagic flux plus reduced reactive oxygen species, caspase-3/7 activation, and cell death in H9c2 cardiomyoblasts under hypoxia ± reoxygenation. EV were also isolated from HEK cells genetically modified to overexpress adiponectin and compared to wild-type cells. These EV improved insulin sensitivity in L6 skeletal muscle cells. This study identifies a previously uncharacterized role of adiponectin in modulating EV biogenesis and cargo to elicit cardioprotective and beneficial metabolic effects. This demonstrates the potential of EV-based adiponectin therapeutics as a new strategy for treating cardiometabolic diseases.
Access status: Open Access ,
Impact of Nitrite on the Molecular Physiology of the Guppy (Poecilia Reticulata Peters, 1859) Gill Epithelium Tight Junction Complex
(2025-11-11) Canale, Alexandra Marie; Kelly, Scott Philip
Nitrite (NO2-) levels in natural freshwater (FW) are typically low, but anthropogenic activity can elevate them, impairing osmoregulatory mechanisms in FW teleost gills. While transcellular disruption by NO2- is documented, its impact on paracellular osmoregulation via the gill tight junction (TJ) complex remains unexplored. This study examined how sublethal waterborne NO2- exposure (7 days) affects osmoregulation in FW guppies (Poecilia reticulata), focusing on the molecular physiology of the gill TJ complex. Gills were analyzed for TJ protein gene transcript abundance, Na+,K+-ATPase activity, and ultrastructural changes. Elevated NO2- reduced carcass Na+ and Cl- levels and gill Na+,K+-ATPase activity, indicating osmoregulatory imbalance. TJ gene transcript abundance was unaffected except claudin-10e, which decreased with NO2-, suggesting reduced mitochondria-rich cells (MRCs). Ultrastructural changes in MRCs revealed transcellular dysfunction (e.g., fewer mitochondria, tubular vacuolization) and compromised paracellular integrity (e.g., shallow junctions). Findings concur that NO2- primarily disrupts osmoregulation through transcellular pathways, with limited paracellular effects.
Access status: Open Access ,
Understanding the Effects of Osmoregulatory Stress on Ion and Water Transport in Select Terrestrial and Aquatic Arthropods
(2025-11-11) Picinic, Britney Nicole; Donini, Andrew; Paluzzi, Jean-Paul
Arthropods including insects and crustaceans inhabit a wide range of environmental habitats and thus require fine-tuned mechanisms for ion and water balance (osmoregulation). Terrestrial insects face dehydration while freshwater insects face dilution of body fluids; both scenarios present challenges to osmoregulatory homeostasis. Adult female mosquitoes must deal with a salt and water load when blood feeding, while aquatic larval midges face a salt load from salinization of freshwater habitats. This research examined how transmembrane water channels known as aquaporins (AQPs) are involved in osmoregulation when arthropods face these challenges. The thesis focused on (1) AQP protein localization and abundance in adult mosquitoes (Aedes aegypti); (2) the effect of neurohormones on a specific AQP (AaAQP1) in mosquitoes; (3) cloning and characterization of a novel AQP from midge (Chironomus riparius) larvae; and (4) effects of road de-icers on osmoregulation in two freshwater arthropods, a crustacean (Hyalella azteca) and C. riparius larvae. In mosquitoes, AaAQP1 was localized to the apical membrane of the Malpighian tubules (MTs) while blood feeding had no effect on AaAQP1 localization or abundance. However, AaAQP1 proved to be vital for diuretic action of MTs. Starvation reduced AaAQP1 and AaAQP4 (another Ae. aegypti AQP) protein abundance in the male MTs, relative to sugar-fed males. In midge larvae, CrAQP2 expression was abundant in the MTs relative to other osmoregulatory organs and was salinity responsive in anal papillae and midgut. Knockdown of CrAQP2 expression resulted in dehydration of larval midges and survival decreased following 72-96hr de-icer exposure. Commercial de-icer containing beet juice caused profound changes in osmoregulatory parameters of H. azteca, including decreased activity of major enzymatic ion-transporters proving to be as harmful to freshwater amphipods as traditional de-icers. Overall, this thesis presents two significant advances in the field. Firstly, the characterization of AaAQP1 in the disease vector Ae. aegypti revealing a previously unknown role for an AQP in the diuretic and anti-diuretic hormone control of primary urine production. Secondly, this research uncovered the deleterious impact of a beet-juice based de-icer on the osmoregulatory physiology of representatives from two important aquatic arthropods, the larval insect C. riparius and the amphipod H. azteca.
Access status: Open Access ,
Selective Prevention of MDGA-Neuroligin-2 Interactions Increases Inhibitory Synaptic Transmission, Fear Memory, and Anxiety
(2025-11-11) Jiang, Jie; Connor, Steven; Xie, Yicheng
Within the CNS, synapse organizer proteins serve as potent modulators of synapse development and function. Among the known synapse organizers, neuroligins (NLs) have well-established roles in promoting synapse development. In contrast, MAM domain containing glycosylphosphatidylinositol anchor (MDGA) proteins repress synapse formation. Human gene linkage analysis has implicated NLs and MDGAs in brain dysfunction. For example, mutations in NL2 or MDGAs contribute to major neurodevelopmental disorders, including autism. However, how NL2/MDGA interactions specifically regulate synapse properties and behavioral outputs remains unclear. NL2 is an inhibitory synapse-specific synapse organizer, whereas MDGAs suppress synapses through blocking the interaction of NL2 and presynaptic NRXNs. To examine the roles of NL2-MDGA interactions in regulating excitatory (glutamatergic) and inhibitory (GABAergic) balance (E/I balance) in synaptic connectivity, we designed a novel and specific NL2ΔSite II transgenic mouse model with the NL2 site II mutated which selectively disrupts NL2/MDGA binding, without affecting other protein interactions. Using a combination of immunohistochemistry, diverse behavior paradigms, and electrophysiology techniques, we sought to determine how synapse development, neural transmission and behaviors are altered in male NL2ΔSite II transgenic mice. We found that NL2ΔSite II mice showed increased anxiety, elevated fear memory and impaired social memory. These mice also exhibited increased expression of inhibitory synapse proteins and upregulated GABAergic transmission whereas excitatory synapse proteins and synaptic transmission appeared normal. Overall, our results suggest that NL2ΔSite II specifically modulates inhibitory synapses and leads to behavioral abnormalities, which could have clinical implications for treatment of neurodevelopmental disorders including autism, schizophrenia and bipolar disorders. A second major project focused on addressing the critical question of how loss of both MDGAs (Mdga1/2 double knockout; DKO) in adult mice affects synapse development in vivo. Preliminary results revealed that MDGA1/2 DKO in hippocampal CA1 pyramidal neurons elevates intrinsic excitability of CA1 pyramidal neurons, increases excitatory synaptic transmission but decreases inhibitory synaptic transmission. These findings suggest dual loss of MDGAs elevates the excitation/inhibition ratio if favor of glutamatergic transmission which may have implications for understanding increased susceptibility to neurodevelopmental disorders following MDGA loss of function.
Access status: Open Access ,
Myogenic Protein Interactions in Rhabdomyosarcoma
(2025-11-11) Shithi, Shezote Talukder; McDermott, John Charles
Rhabdomyosarcoma (RMS), a pediatric soft tissue sarcoma, is characterized by impaired myogenic differentiation and uncontrolled proliferation, often driven by dysregulated transcriptional and signaling networks. In this thesis, we unveil the first comprehensive protein interactomes of MEF2A and β-catenin—two pivotal regulators of skeletal myogenesis and oncogenesis—within RMS subtypes using nanobody-mediated affinity purification coupled with high-resolution mass spectrometry. Strikingly, despite reduced MEF2A expression in RMS cells, RD cells paradoxically exhibited elevated transcriptional activity, implicating compensatory post- translational modifications or unique cofactor interactions. In contrast, β-catenin activity was nearly abolished in the aggressive RH30 subtype, suggesting Wnt pathway evasion and reliance on alternative oncogenic circuits. Interactome mapping revealed subtype-specific regulatory landscapes: RD-derived MEF2A associated with splicing and transcriptional machinery, while RH30 networks were dominated by chromatin remodelers and epigenetic regulators. β-catenin’s interaction profile likewise diverged, linking to tumor-suppressive pathways in RD cells but shifting toward mitotic and nuclear export regulators in RH30. Enrichment analyses identified novel protein hubs—such as TRIM32, HDAC1, XPO1, and RACK1—that modulate gene expression, RNA metabolism, and cell cycle control, and may represent uncharted therapeutic nodes.
Access status: Open Access ,
Proteomic Study Of The Ubiquitin E3 Ligase HUWE1 Interaction With Ubiquitin And ADP-Ribose Modified Proteins
(2025-07-23) Nader, Nour; Sheng, Yi
Ubiquitination and ADP-ribosylation are important post-translational modifications (PTMs), especially in cellular response to DNA damage. HECT, UBA, and WWE domain containing E3 ubiquitin protein ligase 1 (HUWE1) is an important ubiquitin E3 ligase involved in many cellular processes. HUWE1 contains regions involved in substrate interaction and domains for PTM recognition. Specifically, HUWE1 WWE and tandem ubiquitin-binding motif (tUBM) domains interact with ADPr/iso-ADPr and ubiquitin, respectively. However, the interaction between these domains and cellular ADP-ribose and ubiquitin and potentially substrate interactions are not well investigated. Thus, this project aimed to investigate the interactome of HUWE1 WWE and tUBM domain, focusing on their ability to bind proteins modified by mono-ADP-ribose (MAR)/poly-ADP-ribose (PAR) and ubiquitin using GST pulldown assay. First, using Western blot and confocal microscopy, distinct dynamics of ubiquitination and ADP-ribosylation were observed in response to different DNA damage treatments. Second, the study demonstrated that the WWE-tUBM domain interacts with both cellular ADP-ribose and ubiquitin. Moreover, through a proteomic approach using affinity mass spectrometry, this study identified novel proteins that interact with the WWE and tUBM domains following Ultraviolet (UV) induced DNA damage. Together, the findings of this project contribute to a better understanding of how HUWE1 engages with its substrates and highlight the role of WWE and tUBM domains and their ability to recognize PTMs in mediating these interactions.
Access status: Open Access ,
Genome Wide Analysis Of Admixture In Apis Mellifera Intermissa
(2025-07-23) Ritchie, Caroline Rose; Zayed, Amro
Unraveling the evolutionary history of Apis mellifera reveals how populations have adapted to diverse environments, resisted disease, and responded to human influence. An admixed population of A. m. intermissa in Morocco has sparked debate over the dispersal routes of A. mellifera and the origin of the European (M) lineage. Yet, despite its identification, the genomic consequences of this admixture remain largely unexplored. We analyzed global and local ancestry, estimated admixture timing, and assessed genetic diversity in this A. m. intermissa population. Our findings reveal recent admixture, occurring ~14 generations ago, with genome-wide diversity reflecting an intermediate value between progenitor lineages. Notable regions on chromosomes 7 and 11 showed high enrichment for M lineage ancestry. Functional enrichment and prior studies suggest these regions influence detoxification, immunity, development, and hormonal regulation. Four QTLs with 18 loci further support M lineage contributions to Varroa destructor resilience. These findings reveal the functional role of M lineage ancestry in North African Apis mellifera populations and offer a framework for further exploring the genomic outcomes of admixture.
Access status: Open Access ,
Probing the Activity of Fmta, A Novel Esterase in Staphylococcus Aureus, in Vitro and in Vivo Through Mutagenesis.
(2025-07-23) Sengupta, Saptarshi; Golemi-Kotra, Dasantila
The versatile bacterium Staphylococcus aureus (S. aureus) resides within the human microbiota, manifesting commensal and pathogenic characteristics. The emergence of methicillin-resistant S. aureus (MRSA) underscores the global challenge of antibiotic resistance. FmtA, a protein exhibiting structural similarities and distinct features relative to Penicillin-binding proteins (PBPs) within the Penicillin penicillin-recognizing proteins (PRPs) umbrella, significantly contributes to the S. aureus antibiotic resistance mechanism. FmtA acts on Wall Teichoic Acid (WTA), an abundant poly-ribitol polymer in S. aureus peptidoglycan, where FmtA removes D-Alanine (D-Ala) from WTA, which is esterified post-synthesis where the D-alanylation level in WTA is an important contributor in S. aureus antibiotic resistance and physiology. Previous research addressed the structural intricacies of FmtA and based on the positioning of key amino acid residues, it was proposed that the enzyme's active site has evolved to specifically bind WTA. It was further hypothesized that FmtA has adapted to carry out D-amino esterase activity against WTA, highlighting its specialized functional evolution. In this study, I investigate the role of specific amino acid residues present in the active site of FmtA, focusing on their interactions with WTA using both in vitro and in vivo approaches. Given the overall negative charge of WTA, derived from its phosphodiester backbone, it is a target for cationic polymers like Branched Polyethyleneimine (BPEI). Previous research has shown that BPEI binding to WTA creates a steric hindrance, disrupting the function of penicillin-binding proteins (PBPs) such as PBP4 in Staphylococcus aureus and PBP2a in Staphylococcus epidermidis. This disruption impacts key bacterial physiological processes, including cell division, virulence, and peptidoglycan biosynthesis. My findings reveal that BPEI can compete with FmtA for WTA binding, though less effectively, leading to partial inhibition of FmtA's enzymatic activity. Additionally, BPEI binding affects the physiological activities of S. aureus, including biofilm formation, which is typically mediated by FmtA. These results suggest that while BPEI hinders FmtA's interaction with WTA and its subsequent enzymatic function, it does not completely block FmtA activity.
Access status: Open Access ,
Does Motion Parallax Improve Communication Efficiency in Video Chats?
(2025-07-23) Funkhouser, Ashley Jayne; Troje, Nikolaus
As video communication has become more prevalent in our day-to-day lives, it becomes evident that face-to-face communication vastly outclasses video chat in terms of peer communication. Motion parallax is a perceptual effect that arises when an observer moves relative to their surroundings, or their surroundings move relative to them, causing nearby objects in their visual field to appear to move more quickly than distant objects. This relative motion provides a depth cue that the brain can use to estimate the relative distances and orientations of the objects. Directionality is a mutual understanding of the distance and orientation of people in 3D space (Troje, 2023). Previous studies have found that motion parallax is important in determining the direction of objects (Wang & Troje, 2023). Motion parallax can help provide directionality in day-to-day life, including aiding with nonverbal cues such as pointing or turning one’s head. This study examines whether adding motion parallax to video chat with avatars can enhance communication efficiency, as indicated by performance on an instruction task. Many nonverbal cues like mutual gaze, pointing, and eye contact rely on directionality to function accurately. Video chat can create misleading cues due to the lack of motion parallax, causing misunderstandings (Troje, 2023). This study found that the use of motion parallax while video chatting did not enhance performance on a shared task between two subjects, relative to the control. Further research is required to clarify the relationship between motion parallax and communication efficiency in video chat with avatars.
Access status: Open Access ,
Exploring the Effects of Shared Home Ranges on Human-Wildlife Interactions, Parasite Overlap, and Stress Responses in Vervet Monkeys (Chlorocebus Pygerythrus) in East Africa
(2025-07-23) Upadhayay, Pooja; Schoof, Valerie
As human populations expand and encroach upon natural habitats, boundaries between human settlements and wildlife become increasingly blurred. These shared spaces influence human-wildlife interactions and elevate the risk of zoonotic disease transmission. This dissertation investigates the consequences of overlapping home ranges for human-wildlife conflict, parasite community structure, and physiological and behavioral stress responses in vervet monkeys (Chlorocebus pygerythrus). Chapter 2 compares human-wildlife conflicts (HWCs) at sites in Uganda and Kenya, analyzing how socioeconomic factors shape local responses. Respondents reported both positive and negative effects of living near a research station or conservancy, with significant variation in conflict severity and frequency. Chapter 3 examines gastrointestinal parasite communities in sympatric hosts—humans, dogs, livestock, and vervets—around Lake Nabugabo, Uganda. Findings revealed overlapping parasite taxa across species, suggesting shared transmission pathways. Chapter 4 uses a parasite removal experiment (deworming and natural reinfection) to assess how gastrointestinal parasites affect vervet monkey fecal glucocorticoid metabolites (fGC) and behaviors. Reinfection elevated fGC levels and altered behaviors, though not always in predicted ways. This interdisciplinary research integrates ecological, parasitological, and ethological approaches to understand how habitat sharing influences disease ecology and stress in wildlife. The findings underscore the complexity of human-wildlife coexistence and highlight the importance of incorporating both ecological and social dimensions into conservation and public health strategies.

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