Showing 1361 - 1370 of 2705 Items
Mitochondrial adaptation in the green crab hybrid zone of the Gulf of Maine
Date: 2024-01-01
Creator: Jared Lynch
Access: Open access
- The mitochondrial genome has historically been relegated to a neutral genetic marker, but new evidence suggests mitochondrial DNA to be a target for adaptation to environmental stress. The invasive European green crab (Carcinus maenas) exemplifies this in the Gulf of Maine’s hybrid zone, where interbreeding populations exhibit thermal tolerances influenced by mitochondrial genotype. To better understand the mechanism behind this phenomenon, the effect of mitochondrial genotype on mitochondrial activity was tested by measuring mtDNA copy number (mtCN) and the activity of complex I, II, and IV of the electron transport system via high-resolution respirometry. Mitochondria isolated from frozen heart tissue were measured at three temperature points—5°C, 25°C, and 37°C—to represent thermal stresses and a control. It was predicted that cold-adapted haplogroups would exhibit both higher mtCN and increased activity for each complex, either across all temperatures or exclusively at 5°C compared to a warm-adapted haplogroup. Initial comparisons of mitochondria from fresh and frozen tissue at 25°C found lower activity for complex II and IV in frozen extracts, but they continued to be used for convenience. No differences were observed across haplogroups for mtCN or high-resolution respirometry, suggesting that mitochondrial activity does not underlie differences in thermal tolerance. However, temperature greatly influenced activity measurements with complex II and IV exhibiting the highest rates at 37°C while complex I exhibited optimal activity at 25°C. This study represents the first of its kind for C. maenas, providing a foundation for future experiments to continue exploring mitochondria in the context of adaptive evolution.
Characterizing the Roles of Toll7 in the Gryllus Bimaculatus Peripheral Nervous System Development
Date: 2023-01-01
Creator: Rowland Luo
Access: Open access
- The study of neuronal development could provide foundational information on neurogenesis and neuroplasticity. The small size and relatively simple nervous system of Orthoptera make them ideal models for neurodevelopmental studies. The peripheral nervous system development is an intricate and precise process that each sensory neurons are able to reach their central nervous system partners in a relatively short amount of time. Although the peripheral nervous system in limb buds and their genetic regulations are well understood in grasshopper embryos, few studies have explored the developing nervous system in a cricket model. Therefore, the first goal of the current experiment is to characterize the normal peripheral nervous system development in cricket embryos. Previous studies in Drosophila have suggested Toll6 and Toll7 receptors could serve as important targets for the neurotrophic-like factors Spaetzle2 and 5. Malfunctioning neurotrophic pathways could lead to abnormal nervous system development. Therefore, the second goal of the current study is to explore the roles of Toll7 in the development of the cricket peripheral nervous system. Immunohistochemical staining using anti-horseradish peroxidase (Anti-HRP) was used to illustrate crickets' embryonic developing peripheral nervous system in the limb buds from developmental stage 7.0 to 11.0. Cricket eggs were injected with Toll7 double stranded RNA (dsRNA) and rhodamine dye to suppress the Toll7 mRNA level. The control eggs were injected with GFP dsRNA and rhodamine dye. The peripheral nervous system development in cricket embryos is largely homologous to that observed in grasshopper embryos. All later-emerged sensory neurons followed the pathway established by the first pioneer neuron Ti1. Ti1 made stereotypical turns following the steering signals on epithelial and guidepost cell surfaces and eventually fasciculate with lateral motor axons from the central nervous system. When examining the peripheral nervous system development with Toll7 knockdown, a decrease in limb bud volume was observed at stage 7.7 and stage 8.0, suggesting Toll7’s potential roles in aiding cell-cell intercalation processes in Orthoptera embryos. Furthermore, a delay in Ti1 pioneer neuron development was observed with Toll7 knockdown at early developmental stages, providing evidence for Toll-Spaetzle pathway’s neurotrophic-like functions. The results of the current experiment provide the first description of the peripheral nervous system development in the cricket limb buds and further evidence of Toll-Spaetzle pathway’s neurotrophic properties.
Virtual Reality Accessibility with Predictive Trails
Date: 2020-01-01
Creator: Dani Paul Hove
Access: Open access
- Comfortable locomotion in VR is an evolving problem. Given the high probability of vestibular-visual disconnect, and subsequent simulator sickness, new users face an uphill battle in adjusting to the technology. While natural locomotion offers the least chance of simulator sickness, the space, economic and accessibility barriers to it limit its effectiveness for a wider audience. Software-enabled locomotion circumvents much of these barriers, but has the greatest need for simulator sickness mitigation. This is especially true for standing VR experiences, where sex-biased differences in mitigation effectiveness are amplified (postural instability due to vection disproportionately affects women). Predictive trails were developed as a shareable Unity module in order to combat some of the gaps in current mitigation methods. Predictive trails use navigation meshes and path finding to plot the user’s available path according to their direction of vection. Some of the more prominent software methods each face distinct problems. Vignetting, while largely effective, restricts user field-of-vision (FoV), which in prolonged scenarios, has been shown to disproportionately lower women’s navigational ability. Virtual noses, while effective without introducing FoV restrictions, requires commercial licensing for use. Early testing of predictive trails proved effective on the principal investigator, but a wider user study - while approved - was unable to be carried out due to circumstances of the global health crisis. While the user study was planned around a seated experience, further study is required into the respective sex-biased effect on a standing VR experience. Additional investigation into performance is also required.
The Architecture of Bowdoin College
Date: 1988-01-01
Creator: Patricia McGraw Anderson
Access: Open access
- The Architecture of Bowdoin College (1988), by Patricia McGraw Anderson, is the best single resource for the architectural history of Bowdoin’s campus buildings, gates, and memorials.
Catalogue of the Marbles, Gems, Bronzes, and Coins of the Warren Collection of Greek and Roman Antiquities
Date: 1934-01-01
Access: Open access
- Descriptive catalogue of the Warren Classical Collection of Bowdoin College.
Robert Birmelin: Recent Paintings, Maine and New York
Date: 1980-01-01
Access: Open access
- Catalogue of an exhibition held at Bowdoin College Museum of Art, Mar. 14 to May 25, 1980.
Recent Acquisitions, 1961-1968
Date: 1968-01-01
Access: Open access
- "One thousand copies of this catalogue were set in Linotype Janson and printed by the Anthoensen Press, Portland, Maine. Design by Thomas Cornell"--P. [28]
Thomas Cornell: Drawings & Prints
Date: 1971-01-01
Access: Open access
- Catalogue of an exhibition held at Bowdoin College Museum of Art, Nov. 5-Dec. 19, 1971 and the Art Museum, Princeton University, Jan. 14-Feb. 13, 1972.
Descriptive Catalogue of the Paintings, Sculpture and Drawings and of the Walker Collection
Date: 1930-01-01
Access: Open access
- "A considerably modified reprint of the preceding edition. [Descriptive catalogue of the art collections of Bowdoin college] compiled by the late Professor Henry Johnson along with a verbatim reprint of his descriptive catalogue of the Bowdoin collection of old masters' drawings."--Prefatory note