Femoral Osteohistology in American Alligators (Alligator mississippiensis) Reveals High Variation in Growth and Facilitates Interpretation of an Early Pliocene Alligator

Histological analysis of long bone thin sections is commonly used to infer growth rates and ecology of extinct vertebrates, particularly within Archosauria. However, most comparative neontological studies have used small samples of captive individuals, limiting the scope of variation. To fill this gap, 44 femoral thin sections of wild Alligator mississippiensis were prepared and analyzed. Comparison of slides revealed that larger individuals from cooler climates tend to show more LAGs compared to southerly A. mississippiensis of similar size, however, there is considerable variation. This pronounced variation in wild specimens emphasizes the need to use caution when interpreting paleohistological data with little modern comparative samples. Finally, thin sections of early Pliocene Alligator sp. fossils from the Gray Fossil Site (GFS), Washington Co., Tennessee were prepared. The GFS Alligator grew more slowly than A. mississippiensis examined and may have reached reproductive maturity at smaller sizes

Investigation of the DYRK1A Regulation by LZTS2-SIPA1L1 Complex

A region on chromosome 21, the Down Syndrome critical region (DSCR), is associated with major defects found in Down Syndrome, such as craniofacial malformations. DYRK1A is a gene found on chromosome 21 within the DSCR that encodes an enzyme, dual specificity tyrosine-phosphorylation-regulated kinase 1A. DYRK1A is known to phosphorylate many substrate proteins and is thought to be involved in tumor suppression, neurological development, cell cycle regulation, and aging. Recently, the Litovchick lab and others reported that DYRK1A also plays a role in the double-strand break repair of DNA, which could lead to mutations and tumorigenesis, if deregulated. The Litovchick lab is currently investigating novel interactions of DYRK1A, and their implications for cancer. One of these proteins, DCAF7, is already a well-known DYRK1A interacting partner. Another less characterized protein is LZTS2, also known as LAPSER1 or leucine-zipper tumor suppressor 2. LZTS2 is found to be deleted in many human tumors and is known to bind a signaling intermediate SIPA1L1.2 Our preliminary data show that LZTS2 may promote DYRK1A phosphorylation, thereby regulating DYRK1A kinase activity. We suspect that SIPA1L1 may be involved in this interaction and, as this complex is known to be involved in the WNT pathway that plays a role in both cancer and orofacial formation, To test this hypothesis, we started characterization of the DYRK1A-LZTS2 interaction using ectopic expressions of the full-length LZTS2 and DYRK1A as well as their fragments expressed in human T98G cells. We will further perform experiments investigating the physical binding and functional interactions between DCAF7, SIPA1L1, and the DYRK1A-LZTS2 complex.https://scholarscompass.vcu.edu/uresposters/1442/thumbnail.jp

The Experience of First-Generation College Students from the Appalachian Region at Walters State Community College.

First-generation college students from the Appalachian region may be at risk in terms of their successful transition from home to college and in their persistence to graduation. I investigated possible influences on the college experiences of a purposeful sample of 10 Walters State Community College students. Participants were of diverse ethnicity, included both genders, and ranged in age from 18 to 45 years. In-depth interviews were conducted to aid in a narrative study that explored their experiences and the obstacles they faced in the college environment. Many of the findings of this study concur with the review of the literature in that socioeconomic and generational status play a role in Appalachian students\u27 college experience. This study, unlike the review of literature, found that the families of many first-generation students not only recognize the value of a college education, but also fully support the academic endeavors of their college students

Testing paleohistological assumptions using a large-scale study of Alligator mississippiensis with application to a fossil alligator from the southern Appalachians

Histological analysis of long bone thin sections has in recent decades been broadly applied to infer growth rates and ecology in extinct vertebrates, particularly within non-analogous clades. Meaningful interpretation of bone histology and extrapolation to an extinct organism’s life history requires a robust understanding of the factors influencing bone growth and histological presentation. Archosaurs are commonly the subject of osteohistological studies and, as such, much of our knowledge of their paleohistology is derived from the two extant lineages: avian dinosaurs and crocodilians. The American alligator (A. mississippiensis) is widely available for study in the United States and several osteohistological analyses have been published. These studies focused on intraskeletal variation, histovariability, and skeletochronology in one or a few specimens, and in one study a larger sample of pen-raised captive born specimens. However, no published studies test paleohistological assumptions using large-scale geographic and climatic variation in bone histology among extant wild crocodilians. To fill this gap in our knowledge of archosaurian osteohistology, we prepared a collection of humeral and femoral thin sections of 45 Alligator from North Carolina, Arkansas, Georgia, and South Carolina. Previously prepared thin sections from pen-raised Louisiana Alligator were also included. For this study we began by comparing growth rates inferred from counts and measurements of arrested growth (LAGs), which represent annual cycles, and femoral dimensions which correlate strongly to body length. Comparison of these data revealed that, on average, Alligator specimens subject to shorter growing seasons (i.e., those in cooler climates) tend to show more LAGs when compared to more southerly Alligator specimens of similar size. Bone tissue also varies between specimens, suggesting a variable tempo of bone growth in response to differing climatic and environmental regimes. Finally, histological thin sections of early Pliocene Alligator fossils from the Gray Fossil Site (GFS), Washington Co., Tennessee were prepared to explore the paleobiology of this biogeographically unique Appalachian alligator. Assessing variation in this fossil taxon’s closest living relative (A. mississippiensis) provides insight into the paleoecology and growth rates of the GFS Alligator, as well as the climate of the southern Appalachians during the past. Results suggest that the fossil species may have grown more slowly than extant relatives along the southeastern United States coastal plain, and that some parts of the skeleton reached asymptotic growth at a smaller size

A new genus of desmognathan salamander (Plethodontidae) from the early Pliocene Gray Fossil Site of Northeast Tennessee

Many organisms are known to reach high levels of endemism and biodiversity in the temperate forests of Southern Appalachia, especially in the dense forests and rugged terrain of the Blue Ridge physiographic province. Many plants and fungi reach their highest levels of biodiversity in these mountains, as does one group of vertebrates: the lungless salamanders, Plethodontidae. This family of salamanders hosts the most species of any other group of salamanders on earth and has adapted to a wide range of habitats. Only two of the approximately twenty-seven known genera are not found in North or South America, and while we know much about the modern-day biology of this family, few fossils older than ~15,000 years have been recovered, complicating our understanding of the historical distribution of this group and the timing of key evolutionary events within the family. Recently discovered salamander fossils from the Gray Fossil Site provide the foundation of this project. We describe these exceptionally large plethodontid remains to a new genus that belongs to the group containing dusky salamanders, or desmognathans. The morphology of the fossil material resembles Phaeognathus hubrichti, an extant burrowing species from southern Alabama with a suite of primitive characteristics. Comparison of the fossil material to modern desmognathans using geometric statistical methods has revealed that the extinct form was likely similar in lifestyle to P. hubrichti, but considerably larger. It was unparalleled in the southern Appalachians in terms of size and ecology, and reveals a more complex evolutionary history for desmognathan salamanders

Nonlinear analysis of framed structures with a plasticity minded beam element

SCOPUS: ar.jinfo:eu-repo/semantics/publishe