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Steller's sea cow, an extinct sirenian and one of the largest Quaternary mammals, was described by Georg Steller in 1741 and eradicated by humans within 27 years. Here, we complement Steller's descriptions with paleogenomic data from 12 individuals. We identified convergent evolution between Steller's sea cow and cetaceans but not extant sirenians, suggesting a role of several genes in adaptation to cold aquatic (or marine) environments. Among these are inactivations of lipoxygenase genes, which in humans and mouse models cause ichthyosis, a skin disease characterized by a thick, hyperkeratotic epidermis that recapitulates Steller's sea cows' reportedly bark-like skin. We also found that Steller's sea cows' abundance was continuously declining for tens of thousands of years before their description, implying that environmental changes also contributed to their extinction.

Steller's sea cow, an extinct sirenian and one of the largest Quaternary mammals, was described by Georg Steller in 1741 and eradicated by humans within 27 years. Here, we complement Steller's descriptions with paleogenomic data from 12 individuals. We identified convergent evolution between Steller's sea cow and cetaceans but not extant sirenians, suggesting a role of several genes in adaptation to cold aquatic (or marine) environments. Among these are inactivations of lipoxygenase genes, which in humans and mouse models cause ichthyosis, a skin disease characterized by a thick, hyperkeratotic epidermis that recapitulates Steller's sea cows' reportedly bark-like skin. We also found that Steller's sea cows' abundance was continuously declining for tens of thousands of years before their description, implying that environmental changes also contributed to their extinction.

The mobile conjugate reinforcement (MCR) paradigm, made famous by Carolyn Rovee-Collier and her colleagues (Rovee & Rovee, 1969), has long been used to study infant learning and memory. In MCR studies, the infant's foot is tethered to a mobile hanging overhead, and the mobile responds directly to the infant's kicking. Infant kicking rate triples within a few minutes of interacting with the mobile. This result was classically interpreted as evidence of reinforcement learning. Kelso and Fuchs (2016) reinterpreted it as evidence that a coordinative structure, or functional synergy, forms between infant and mobile, triggering a positive feedback loop between the two. Positive feedback is proposed to give rise to an `Aha!' moment as the (prelinguistic) infant suddenly realizes it is an agent in control of the mobile's motion. While some have theorized the realization of self as causal agent emerges from organism-environment interactions, Kelso and Fuchs (2016) developed a mathematical model of the coordination dynamics between the infant and mobile, providing mechanistic explanations for the formation of agency. The current study was the first to measure movement of the mobile and analyze how dynamics of coordination between infant and mobile relate to possible transitions from spontaneous to intentional action. Novel measures of infant and mobile dynamics were used to test model predictions. Infant activity dropped drastically in response to non-contingent mobile movement and remained suppressed at the start of infant~mobile contingency, suggesting that mobile movement triggers a qualitatively different context for infants. This finding challenges the widely held assumption that mobile movement rewards and stimulates infant movement and calls into question the sufficiency of standard contingency detection cut-offs and explanations of conjugate reinforcement learning. Assessing coordination dynamics on a fine time scale using new analytical techniques made it possible to, 2022, Includes bibliography., Degree granted: Dissertation (Ph.D.)--Florida Atlantic University, 2022., Collection: FAU Electronic Theses and Dissertations Collection

Background Elucidation of lipid metabolism and accumulation mechanisms is of paramount importance to understanding obesity and unveiling therapeutic targets. In vitro cell models have been extensively used for these purposes, yet, they do not entirely reflect the in vivo setup. Conventional lipomas, characterized by the presence of mature adipocytes and increased adipogenesis, could overcome the drawbacks of cell cultures. Also, they have the unique advantage of easily accessible matched controls in the form of subcutaneous adipose tissue (SAT) from the same individual. We aimed to determine whether lipomas are a good model to understand lipid accumulation. Methods We histologically compared lipomas and control SAT, followed by assessment of the lipidome using high-resolution 1H NMR spectroscopy and ESI-IT mass spectrometry. RNA-sequencing was used to obtain the transcriptome of lipomas and the matched SAT. Results We found a significant increase of small-size (maximal axis < 70 µm) and very big (maximal axis > 150 µm) adipocytes within lipomas. This suggests both enhanced adipocyte proliferation and increased lipid accumulation. We further show that there is no significant change in the lipid composition compared to matched SAT. To better delineate the pathophysiology of lipid accumulation, we considered two groups with different genetic backgrounds: (1) lipomas with HMGA2 fusions and (2) without gene fusions. To reduce the search space for genes that are relevant for lipid pathophysiology, we focused on the overlapping differentially expressed (DE) genes between the two groups. Gene Ontology analysis revealed that DE genes are enriched in pathways related to lipid accumulation. Conclusions We show that the common shared lipid accumulation mechanism in lipoma is a reduction in lipolysis, with most gene dysregulations leading to a reduced cAMP in the adipocyte. Superficial lipomas could thus be used as a model for lipid accumulation through altered lip