Biology

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

Browse

Now showing 1 - 20 of 388

Access status: Open Access ,
Investigating the Drivers and Consequences of Individual Dietary Specialization in an Arctic Marine Top Predator
(2026-03-10) Finkbeiner, Griffin; Thiemann, Gregory W.
Due to climate warming, reduced sea-ice extent and concentration in the Arctic has altered prey availability and limited foraging opportunities for polar bears (Ursus maritimus). My thesis examined individual foraging patterns across the Foxe Basin and Davis Strait subpopulations to identify drivers and consequences of dietary specialization. Using quantitative fatty acid signature analysis and proportional similarity (PSi) scores, I assessed how dietary specialization varies across intrinsic and extrinsic factors, and its relationship to body condition. Results revealed distinct diets and differing levels of specialization influenced by intrinsic and extrinsic variables. Sea-ice metrics were linked to variations in prey choice and individual specialization, suggesting altered access to preferred prey. Differences in individual specialization corresponded to variations in body condition, suggesting demographic groups experience energetic costs differently. These findings emphasize the role of individual-level variation in a warming Arctic, and underscore the importance of continued monitoring for polar bear conservation and management.
Access status: Open Access ,
Spatiotemporal Variation in the Foraging Ecology, Habitat Use, and Distribution of Arctic Marine Mammals in Relation to Sea Ice
(2026-03-10) Roberts, Jessica Michelle; Thiemann, Gregory W.
The Arctic is shifting under climate change, with loss of sea ice altering marine ecosystem structure. This thesis examined two Arctic marine mammals: Bowhead whales (Balaena mysticetus) and ringed seals (Pusa hispida), both being at risk of the effects of sea ice loss. Using biomarker analysis for bowhead whales (δ13C, δ15N, fatty acids) and observations from aerial surveys for ringed seals, this study investigated spatiotemporal variability in (1) foraging of bowheads from 1993-2023 in the eastern Canadian Arctic and (2) density and distribution of ringed seals from 1994 to 2024 in Western Hudson Bay, Canada. The biomarker results indicated spatiotemporal shifts in bowhead whale diet, including a nonlinear relationship between δ13C and sea ice concentration, declining δ15N values, narrowing of isotopic niche widths, and shifts in fatty acid profiles- especially in Hudson Bay. Ringed seal density declined from 1994-2024, with sea ice and distance to shore as key predictors.
Access status: Open Access ,
The Effects of Modulated Global Levels of Sumoylation on Gene Expression
(2026-03-10) Moallem, Marjan; Rosanina, Emanuel
Hundreds of proteins are modified by SUMO (small ubiquitin-like modifier) peptides, the majority of which are nuclear and involved in gene expression. Through SUMO chromatin immunoprecipitation sequencing (ChIP-seq), sumoylated proteins can be readily detected at numerous distinct chromatin sites. This includes promoters of protein-coding genes thus linking sumoylation with transcription regulation. Cells can coordinately modulate levels of sumoylation globally. For example, there is a surge in SUMO conjugation in response to heat shock, an effect that we attribute here to the degradation of the major SUMO protease, Ulp1, in budding yeast. Whereas the effects of sumoylation have been examined for many individual target proteins, not much is known about how coordinated global changes to sumoylation levels impact transcription. To address this, we investigated whether changing cellular sumoylation levels in yeast impacts (1) cell growth in normal and stress conditions, and (2) global transcription and gene expression patterns. Primarily, this was accomplished using strains that express mutant forms of Ubc9, the sole E2 conjugating enzyme, or Ulp1, which harbour constitutively reduced or elevated sumoylation levels, respectively. We find that cells with dramatically reduced levels of sumoylation grow near-normally in optimal, non-stress conditions. While they tolerate multiple stress conditions very well, they show strong sensitivity to heat shock specifically. Both reduced and elevated sumoylation levels lead to widespread changes to transcription, but intriguingly, both result in a gene expression pattern that resembles that of stressed cells. Therefore, heat-shock genes have high levels of expression, even in non-stress conditions. This indicates that both sumoylation and desumoylation are important for suppressing stress response gene expression in non-stress conditions, and paradoxically, our results correlate constitutive expression of stress response genes with temperature sensitivity. Finally, our data implicate activation of the key stress response factors, Msn2 and Hog1, in driving the inappropriate induction of heat-shock genes in Ubc9 and Ulp1 mutants even in the absence of stress.
Access status: Open Access ,
Interplay of Iron and Hydrogen Sulfide in Pathophysiology of Vascular Damage
(2026-03-10) Arif, Hassan Mustafa; Wang, Rui
Hydrogen sulfide (H₂S) and iron are fundamental regulators of redox biology, exerting opposing influences on oxidative stress and vascular homeostasis, yet their mechanistic interplay remains unresolved. This dissertation addresses this gap through a series of studies spanning molecular, mitochondrial, cellular, and whole-animal levels. The molecular basis of H₂S–iron interactions in vascular smooth muscle cells was defined, demonstrating that endogenous H₂S upregulates ferritin expression, balances apoptosis–autophagy signaling, and protects against iron overload–induced cellular dysfunction. These findings were then extended to mitochondrial physiology, showing that CSE-derived H₂S safeguards mitochondrial respiration, spare respiratory capacity, and membrane potential under iron stress, thereby enhancing cellular resilience. To enable accurate translational assessment, a high-performance liquid chromatography method using a methylene blue/methylene green (MBMG) system was developed, establishing a robust, sensitive, and stable platform for plasma H₂S quantification with broad research applicability. Applying this method in murine models of acute iron overload demonstrated that CSE deficiency led to impaired ferritin upregulation, increased vascular iron deposition, elastin degradation, inflammatory remodeling, and severe vasomotor dysfunction—effects that were mitigated in wild-type mice via compensatory CSE/H₂S induction. Collectively, these studies establish a continuum of evidence linking H₂S to iron metabolism and vascular adaptation, from cellular and mitochondrial mechanisms to systemic physiology. By integrating conceptual review, mechanistic cell studies, methodological innovation, and translational animal models, this thesis identifies endogenous H₂S as both a biomarker and a therapeutic target for iron-related vascular disease.
Access status: Open Access ,
Assessing the Role of Maternal Social Network Inheritance in the Social Integration of Immature Vervet Monkeys (Chlorocebus Pygerythrus)
(2026-03-10) Dupuis, Margaux Cyrielle Eleonore; Schoof, Valerie A.
Specific mechanisms of social network integration in juvenile animals are still largely obscure. However, much research indicates that mothers have a wide range of effects on their offspring, including on their sociality. Using a Bayesian framework, I investigated factors of social integration, such as maternal proximity, network influences (i.e., inheritance), age, dominance rank, and offspring traits from May-July 2025 in wild vervet monkeys (Chlorocebus pygerythrus) at Lake Nabugabo, Uganda. My results suggest that maternal influences exist mainly in proximity but less in grooming networks. Older offspring were more distant from their mothers and less central in proximity networks than younger offspring. Notably, offspring sex was a strong predictor of social ontogeny in vervet monkeys, with daughters being more integrated in grooming networks than sons. Overall, these results provide insight into the importance of mothers in social ontogeny, while also highlighting the pivotal role of offspring sex on their social integration.
Access status: Open Access ,
Modelling Bone Marrow Extracellular Matrix Interactions Reveal CD36-Dependant Vulnerabilities in Acute Myeloid Leukemia
(2026-03-10) Cifligu, Zhaklina; Sachlos, Terry
Understanding how the bone marrow microenvironment influences metabolic dependencies is crucial for improving therapeutic strategies in acute myeloid leukemia (AML). CD36, a fatty acid transporter associated with lipid uptake and chemoresistance in AML, may be functionally influenced by interactions with the extracellular matrix (ECM). This thesis investigated whether ECM engagement alters CD36-dependent responses in AML. OCI-AML2 cells were cultured on either standard polystyrene (PS) or an ECM-based scaffold and assessed following CD36 inhibition using flow cytometry. Scaffold-cultured cells exhibited reduced viability, fatty acid uptake, and clonogenic capacity under CD36 inhibition compared to PS culture. Primary AML samples were then evaluated to assess patient-specific responses. ECM scaffold culture revealed phenotypic adaptations following CD36 inhibition, including reduced fatty acid uptake and increased CD11b expression for two patient samples, suggestive of enhanced ECM interaction and myeloid differentiation. Overall, these findings demonstrate that ECM interactions modulate CD36-dependent vulnerabilities in AML not evident under standard PS culture conditions.
Access status: Open Access ,
Unlocking Phytoalexin Biosynthesis Using Multigene Engineering
(2026-03-10) Ly, Melissa Thanh; Kovinich, Nikola
Plants have evolved sophisticated defense mechanisms to balance growth and immunity, with phytoalexins and lignin playing central roles in pathogen resistance. In Arabidopsis thaliana, the jasmonate repressor JAZ1 and transcription factor ANAC042 act as opposing regulators of this process. The regulation of phytoalexin biosynthesis is highly complex, and manipulating individual transcription factors has generally proven insufficient to fully activate the pathway. To address this limitation, this study investigates whether the knockout of JAZ1 in combination with the overexpression of ANAC042 can more effectively unlock phytoalexin biosynthesis. While JAZ1 knockout promoted systemic lignification under prolonged stress, while ANAC042 overexpression alone did not strongly induce phytoalexins. However, their combination enhanced accumulation of hydroxyindole-3-carbonyl nitrile and monolignols. Transcriptional analysis revealed altered regulation of WRKY33 and MYB15, suggesting that JAZ1 and ANAC042 are a part of a broader defense regulatory network. Growth-defense trade-offs showed growth penalties in all tested genotypes under Flg22 elicitation, except in ANAC042 overexpression lines, where growth was unaffected by the elicitor, highlighting the metabolic costs associated with sustained immunity. Extending these findings to soybean, a dual-gene plasmid (pGEMINI-B) was constructed to co-overexpress two positive regulators of glyceollin biosynthesis, while silencing GmJAZ1 genes. Collectively, these findings demonstrate that manipulating antagonistic regulatory factors simultaneously can unlock levels of phytoalexin accumulation that are unattainable through single-gene modifications. The underlying shifts in gene expression and metabolism driving this effect are unconventional and warrant deeper investigation, as elevated phytoalexin biosynthetic gene expression does not directly account for the observed increases in phytoalexin levels.
Access status: Open Access ,
Effects of MDGA2 Reduction on Synaptic Long-Term Depression and Development in Male Mice
(2026-03-10) Andrec, Katherine Emily; Connor, Steven
MDGA2, an autism-linked synapse organizer, restricts excitatory synaptogenesis by inhibiting neurexin-neuroligin adhesion complexes and BDNF/TrkB signaling. Mdga2+/- mice, modeling autism-associated mutations, show increased excitatory synapse density and hyperexcitation in adulthood, resulting in altered hippocampus-dependent cognition and plasticity. Despite the critical role of synapse organizers in development, the effects of Mdga2 reduction on synaptogenesis, synaptic pruning, and long-term depression (LTD) remain unclear. To address this gap, this study investigated synaptic weakening via LTD induction, spine development across postnatal stages via Golgi-Cox staining, and proteomic alterations in the hippocampus of Mdga2+/- mice. Results reveal that Mdga2 reduction induces premature synapse maturation and enhanced synaptogenesis in the dorsal hippocampus, alongside deficits in NMDAR-dependent LTD. Proteomic analyses uncovered dysregulation of signaling, ion homeostasis, ubiquitination, translation, oxidative stress, and neuroinflammation pathways. These findings suggest that Mdga2 loss disrupts early synaptic development and circuit refinement, contributing to autism-like phenotypes and persistent alterations in synaptic signaling.
Access status: Open Access ,
The Potential Role of Nodal in Zebrafish Testis
(2026-03-10) Jani, Riddhi; Peng, Chun
The TGF-β superfamily regulates a range of physiological processes, including development, cell differentiation, and reproduction. While several TGF-β members are well characterized in adult gonadal function, the role of Nodal, a key regulator of early embryogenesis, remains poorly understood in reproduction. This project investigated the potential involvement of Nodal in zebrafish testis physiology. Analysis of offspring from heterozygous ndr1 mutant crosses revealed no significant changes in sex ratio compared to wild-type fish. Gene expression profiling indicated that ndr1 is highly expressed in 9-month-old testis. Ex vivo testis culture with recombinant human Nodal induced time-dependent upregulation of the Nodal inhibitor lft1. RNA-seq analysis of Nodal-treated testis identified modest but coordinated changes in pathways associated with reproductive processes, sperm–egg interactions, cellular organization, and immune response. These findings provide new insight into Nodal pathway activity in the zebrafish testis and lay groundwork for future studies on its role in vertebrate reproductive biology.
Access status: Open Access ,
Investigating the Behavioral, Neural, and Computational Mechanisms of Object Recognition and Memorability Under Temporal Constraints
(2026-03-10) Ziaee, Soroush; Kar, Kohitij
The primate inferior temporal (IT) cortex transforms retinal inputs into object-centered representations supporting visual recognition. Recent work suggests IT also predicts image memorability, yet IT activity disappears within hundreds of milliseconds after stimulus offset, raising questions about how information is maintained during delays. This thesis investigates IT's contributions to recognition and memory. In Aim 1, we combined human behavior, macaque neurophysiology, and neural network modeling to test whether optimizing networks for recognition and memorability improves correspondence with IT. Jointly trained models explained more neural variance and better predicted both behavioral measures. In Aim 2, we examined these representations in a delayed match-to-sample task. Behavioral accuracy declined with increasing delay despite IT activity vanishing, suggesting that maintaining object-selective representations requires transformation of transient IT codes into persistent states in downstream circuits. These findings show IT encodes representations optimized for multiple functions, while maintenance across time depends on recurrent processing beyond IT.
Access status: Open Access ,
Regulation Of TAZ (WWTR1) By Protein-Protein Interactions In Striated Muscle
(2026-03-10) Sansone, Stephanie; McDermott, John Charles
Tissue growth depends on cellular proliferation, survival, and differentiation. Hippo signaling controls these processes by regulating transcriptional co-activators Yap/Taz. Taz function is context-dependent, including repression of myogenic differentiation. Taz does not bind DNA; its activity is determined by interacting partners. To discover functional regulators of Taz, nuclear FLAG-affinity purification and LC-MS/MS were performed in HEK293T, identifying 57 interactors (33 unique; 24 ³3-fold enriched). Among these, transcription factor Yin-Yang1 (YY1) was prioritized. Biochemical analyses revealed YY1 binds Taz at/near its Tead-binding domain, with Tead1 enhancing this interaction. YY1 repressed Taz-mediated transcription on a Tead-responsive reporter. In proliferating myoblasts, YY1 increased phospho-Taz (Ser89), its Hippo-inactivated form. Taz formed LLPS-driven nuclear condensates, during which YY1 was excluded from the nucleus. During differentiation, YY1-mediated stabilization of phospho-Taz (Ser89) was not observed, and Taz and YY1 co-operatively repressed myogenic gene expression. Collectively, these findings identify YY1 as a regulator of Taz function in striated muscle.
Access status: Open Access ,
Unravelling the Ecological and Evolutionary Mysteries of the Rough Fescue Grasses F. Hallii and F. Campestris.
(2026-03-10) LeBlanc, Jenna Marie; McFarlane, S. Eryn
The rough fescue grasslands of western North America are diverse, unique ecosystems that provide essential ecological and agricultural services, yet have been significantly fragmented by land conversion, urbanization, and energy infrastructure. Only around 5% of their historic 137,000km^2 extent remains unmodified, and remaining prairie fragments face ongoing threat from unsustainable grazing practices, invasive crop species, and disruption of their natural disturbance regimes. Conserving and restoring rough fescue grasslands remains challenging due to the sensitivity of their defining species, the rough fescue grasses Festuca hallii and F. campestris, and a limited understanding of how rough fescue ecology and life history affects their fitness and persistence in disturbed environments. This dissertation addresses three components of rough fescue autecology that have direct applications for conservation and restoration; Chapter 2 investigates the role of dormancy and cold exposure on rough fescue seed germination using a comparative germination assay between F. hallii and F. campestris. It finds that the temperature and duration of seed storage has significant impacts on rough fescue germination, and can greatly enhance or stifle germination in seeds of the same age and provenance. Chapter 3 examines the prevalence of Epichloë fungal endophytes in wild rough fescue populations across a mosaic of disturbance conditions at Glenbow Ranch Provincial Park near Cochrane, Alberta. Here, I found high (µ >80%) levels of endophyte infection across all sites, and confirmed, for the first time, the presence of an Epichloë symbiosis in F. hallii. My final chapter explores the taxonomic and genetic relationship between F. hallii and F. campestris through a province-wide genomic survey of both allopatric and sympatric rough fescue populations. I discovered the occurrence of extensive and ongoing hybridization between the two species in their ranges of overlap, and additionally, found evidence of F. campestris introgression into allopatric populations of F. hallii. Collectively, these findings provide actionable ecological insights into the early life stages, mutualistic interactions, and genetic structure of rough fescue grasses, offering a foundation for more targeted and effective restoration practices in this imperiled grassland ecosystem.
Access status: Open Access ,
Identifying Novel Interaction Between SENP1 and the Deubiquitinating Enzyme Ubiquitin-Specific Protease 7 (USP7)
(2026-03-10) Dhindsa, Kanwarpartap; Saridakis, Vivian
Ubiquitin Specific Protease 7 (USP7) is a well-characterized deubiquitinating enzyme involved in numerous cellular pathways. Despite extensive studies, many USP7-regulated proteins and pathways remain unidentified. One emerging area of interest is the SUMOylation and deSUMOylation pathways, dynamic post-translational modifications increasingly recognized for their importance in protein regulation and disease progression. Through bioinformatics analysis, we identified SENP1, a deSUMOylating enzyme that contains a P/A/ExxS consensus motif, characteristic of known USP7 substrates. We hypothesized that USP7 interacts with and regulates SENP1, thereby modulating its stability and activity. Using various methods, including co-immunoprecipitation, silencing and overexpression in HCT116 cells, our findings demonstrate that USP7 interacts with and deubiquitinates SENP1, thus regulating its stability. Given SENP1’s involvement in various diseases, including cancer progression, and hypoxia signalling, our findings provide a novel insight into USP7-mediated regulation of deSUMOylation and highlights its potential as a therapeutic target.
Access status: Open Access ,
Identifying Novel Interaction Between the E3 Ubiquitin Ligase Ring Finger Protein 20 (RNF20) and the Deubiquitinating Enzyme Ubiquitin Specific Protease 7 (USP7)
(2026-03-10) Gill, Jatin; Saridakis, Vivian
USP7, which is a ubiquitin-specific protease, is an essential deubiquitinating enzyme involved in a plethora of cellular processes such as epigenetic regulation, DNA damage response and oncogenic processes. In this study, RNF20, which is an E3 ligase, has been identified as a novel substrate for USP7. Through various biochemical and functional assays, including endogenous co-immunoprecipitation, comparing parental and USP7 knockout HCT116 cells, reconstitution assay, overexpression with USP7 or the catalytic mutant USP7, cycloheximide chase and a deubiquitination assay, we show that RNF20 stability is dependent upon USP7 removing ubiquitin chains that would mark RNF20 for proteasomal degradation. This interaction was seen within multiple cell lines, with the catalytic activity of USP7 being crucial to the stability of RNF20. These findings provide the foundation for future studies on how the regulation of RNF20 through USP7 can contribute to epigenetic regulation, DNA damage response, and oncogenic processes.
Access status: Open Access ,
Evaluation of the Role of Iron on Physiological Performance and Functional Characterization of Major Iron Transporter in Zebrafish (Danio Rerio)
(2026-03-10) Chandrapalan, Theanuga; Kwong, Raymond W. M.
Iron is essential for a multitude of biological processes, and its acquisition and regulation are critical for survival. In fishes, iron is obtained from the water via the gills and the diet through the gastrointestinal tract. While the diet is the predominant source of iron absorption, the physiological consequences of dietary iron availability and its underlying mechanisms of uptake and metabolism remain poorly understood compared to waterborne studies. In this thesis, I investigated the effects of dietary iron levels (~11, 420, and 2300 mg Fe/kg) and exposure duration (20 and 40 days) in zebrafish (Danio rerio). Short-term iron supplementation enhanced aerobic scope, maximum metabolic rate, and critical swimming speed, as well as reproductive output and offspring survival. In contrast, prolonged high-iron exposure led to iron loading in the brain and intestine, highlighting a narrow window between nutritional benefits and overload. Offspring of high-iron-fed parents exhibited greater swimming and metabolic performance than those of the low-iron group, revealing potential intergenerational consequences of parental iron status. To help elucidate the molecular mechanisms underlying iron homeostasis, a CRISPR-Cas9 knockout of the iron transporter, divalent metal transporter 1 (DMT1; slc11a2), was generated. The systemic consequences of DMT1 loss in developing and adult zebrafish were characterized using trace metal analysis, gene expression, and RNA sequencing. During early development, DMT1 loss caused anemia and disrupted iron, zinc, cobalt, and manganese homeostasis. Despite these disruptions, mutants displayed remarkable physiological plasticity and partial recovery through compensatory regulation of alternate transporters, including heme carrier protein 1 (hcp1). Broad transcriptional reprogramming was also evident in the gill and intestine of adult dmt1-/- fish, which included induction of iron transport, storage, and erythropoietic genes, alongside suppression of hepcidin/BMP-Smad signalling. Tissue-specific responses identified two candidates for DMT1-compensation, including zrt- and irt-like protein 4 (zip4) in the intestine and epithelial calcium channel (ecac) in the gills. Broad reprogramming of ion regulation, immunity, and redox pathways was also present. Collectively, this thesis advances our understanding of iron metabolism from cellular transport to whole-animal physiology, providing a framework with implications for environmental toxicology, aquaculture nutrition, and a vertebrate model for studying iron-related disorders.
Access status: Open Access ,
Investigating Chamber-Dependent Cardiac Remodelling in a Murine Model of Heart Failure with Preserved Ejection Fraction
(2026-03-10) Barakat, Christian Paul; Backx, Peter
Heart failure with preserved ejection fraction (HFpEF) is strongly associated with atrial fibrillation (AF), yet chamber-specific mechanisms remain poorly defined. This thesis characterizes a HFpEF model using high-fat diet, sucrose, and L-NAME (HFDLS), a combination that has not been explored in the CD1 mouse strain. Relative to normal-diet controls, HFDLS mice showed greater percent body-weight gain (45.9 to 70.8%), reduced exercise tolerance (408 to 276 m), and elevated mean arterial pressure (84.7 to 107.6 mmHg). Invasive hemodynamics demonstrated increased LV end-diastolic pressure (6.7 to 11.8 mmHg), consistent with impaired diastolic filling. Echocardiography confirmed preserved ejection fraction with concentric remodeling. Histological analysis revealed increased fibrosis in the left atrium (5.96 to 12.15%) and left ventricle (1.71 to 3.76%). Intracardiac electrophysiology showed significantly prolonged atrial arrhythmia duration (2.6 to 23.6 s), with unchanged ventricular refractoriness. F4/80⁺ immunostaining demonstrated increased macrophage density in both chambers. Overall, the model produced a modest HFpEF phenotype that will require further refinement to strengthen disease severity, but it nevertheless revealed clear atrial-dominant structural and electrical remodeling, establishing a platform to investigate TNFαmediated mechanisms linking HFpEF and AF. Keywords: Heart Failure with Preserved Ejection Fraction, Atrial Fibrillation, CD1 mouse strain, High-Fat diet+L-NAME+Sucrose
Access status: Open Access ,
Factors Affecting Nest Site Selection and Daily Nest Survival of Killdeer (Charadrius Vociferus) in a Highly Urbanized Environment
(2026-03-10) Koekebakker Low, Kazuo Abraham; McKinnon, Laura
Killdeer (Charadrius vociferus) are a commonly found ground nesting shorebird within urbanized environments in North America. Killdeer population numbers have been decreasing and this study aimed to investigate their nest site selection preferences and Daily Survival Rate (DSR) in Downsview Park, located in Toronto, Ontario, Canada. Nest survival checks were performed on Killdeer nests during the nesting period in 2023 and 2024. I also performed habitat analyses and placed motion-triggered cameras around the park to measure predator and anthropogenic disturbance rates. I found no significant difference in habitat between real nest sites and randomly selected sites, indicating no strong nest site selection preferences. DSR for nests was within range at 0.949 (27% nest success) and decreased as Canine activity rates increased. Human activity rates had no effect on DSR. There was no evidence of an ecological trap.
Access status: Open Access ,
Exploring Eastern Musk Turtle (Sternotherus odoratus) Population Dynamics and Phenotypic Plasticity in Comal Springs, Texas
(2026-03-10) Owen, Ethan Cromwell; Macdonald, Suzanne E.
Freshwater turtles are vital to aquatic ecosystems but are increasingly affected by anthropogenic change. The eastern musk turtle (Sternotherus odoratus) is a small, omnivorous species inhabiting spring systems in Central Texas, where invasive gastropods have become abundant. This study investigates whether dietary shifts toward these gastropods are associated with variations in head and body morphology. Seventy-one individuals were captured in June and July 2024. Morphometric data and fecal samples were collected to assess diet composition and morphological variations. Dietary analyses identified Tarebia granifera as the dominant prey item. Males exhibited stronger allometric relationships between head width and body size. Head width did not significantly differ between sexes. A comparison with museum specimens revealed significant increases in carapace length and head width. These findings suggest that invasive prey may be driving morphological changes through phenotypic plasticity and highlight the capacity for freshwater turtles to adapt to novel ecological pressures.
Access status: Open Access ,
Elucidating Leukemic Stem Cell Interactions with the Tumor Extra Cellular Matrix Niche
(2026-03-10) Hajari, Sara; Sachlos, Eleftherios
Stem cells in niches rely on the extracellular matrix (ECM) for structural support and behavioral regulation. ECM composition is critical for tissue health; alterations can lead to diseases like acute myeloid leukemia (AML). Studies show myeloid malignancies alter hematopoietic niches to support leukemic growth, underscoring the importance of cell-ECM interactions. Our study aimed to identify effective ECM combinations for culturing primary AML samples. We tested patient-derived mononuclear cells on 18 ECM-enriched matrices, including collagen, elastin, and hydroxyapatite. Post a 72-hour incubation, we evaluated cell viability and progenitor potential using colony-forming unit assays, finding conditions that enhance cell life and maintain stem cell potential. Additionally, we identified key ECM genes overexpressed in leukemic versus normal cells and conducted in silico screening of a 1280 compound drug library, targeting αM/β2 integrin. These insights enable future ex vivo AML studies and shed light on niche mechanisms in health and disease.
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.

Browse

Recent Submissions