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- All Subjects: Biology
- Creators: Department of Psychology
The bull shark, Carcharhinus leucas, is a large species that it is commonly distributed worldwide in tropical and subtropical waters. Despite the bull sharks global distribution, little is known about its life history. In particular, the limited reproductive information suggests the bull shark is placental viviparous, assumed to have a biennial cycle, and that newborn pup nurseries are near the coast. In order to conserve and protect any species, an understanding of the habitats where reproductive events occur is needed. In order to better understand the habitat use in Biscayne bay, Fla, and whether certain areas are critical during the reproductive cycle of bull sharks, I will evaluate circulating levels of the hormones progesterone, estradiol, and testosterone using radioimmunoassay. These samples were collected by the University of Miami opportunistically between 2012-2020 shipped to Arizona State University, where they were analyzed. For my study a total of 73 mature samples, 27 females and 46 males, were collected over the sampling period. The results indicated that Biscayne bay is an important gestation area for bull sharks. The hormonal trends for males and females demonstrated an interesting reproductive cycle, which were further supported through other placental viviparous reproductive patterns. Females had a low level of estradiol throughout most of the year, besides in the summer where there were no sharks in the bay due to movement to estuaries. During their return to the bay, there was a peak in progesterone indicating early pregnancy. Male testosterone levels indicated that there was a production in sperm right before females speculated peak in estradiol.
receptor (RAR) and vitamin D receptor (VDR). The RXR/RAR dimer is activated by ligand all
trans retinoic acid (ATRA), which culminates in gut-specific effector T cell migration. Similarly,
the VDR/RXR dimer binds 1,25(OH)2D3 to cause skin-specific effector T cell migration.
Targeted migration is a potent addition to current vaccines, as it would induce activated T cell
trafficking to appropriate areas of the immune system and ensure optimal stimulation (40).
ATRA, while in use clinically, is limited by toxicity and chemical instability. Rexinoids
are stable, synthetically developed ligands specific for the RXR. We have previously shown that
select rexinoids can enhance upregulation of gut tropic CCR9 receptors on effector T cells.
However, it is important to establish whether these cells can actually migrate, to show the
potential of rexinoids as vaccine adjuvants that can cause gut specific T cell migration.
Additionally, since the RXR is a major contributor to VDR-mediated transcription and
epidermotropism (15), it is worth investigating whether these compounds can also function as
adjuvants that promote migration by increasing expression of skin tropic CCR10 receptors on T
cells.
Prior experiments have demonstrated that select rexinoids can induce gut tropic migration
of CD8+ T cells in an in vitro assay and are comparable in effectiveness to ATRA (7). The effect
of rexinoids on CD4+ T cells is unknown however, so the aim of this project was to determine if
rexinoids can cause gut tropic migration in CD4+ T cells to a similar extent. A secondary aim
was to investigate whether varying concentrations in 1,25-Dihydroxyvitamin D3 can be linked to
increasing CCR10 upregulation on Jurkat CD4+ T cells, with the future aim to combine 1,25
Dihydroxyvitamin D3 with rexinoids.
These hypotheses were tested using murine splenocytes for the migration experiment, and
human Jurkat CD4+ T cells for the vitamin D experiment. Migration was assessed using a
Transwell chemotaxis assay. Our findings support the potential of rexinoids as compounds
capable of causing gut-tropic migration in murine CD4+ T cells in vitro, like ATRA. We did not
observe conclusive evidence that vitamin D3 causes upregulated CCR10 expression, but this
experiment must be repeated with a human primary T cell line.
Differences between basic and applied research were explored through a wet-lab case study. Vaccinia virus (VACV) infections are a prime model of the competition between a virus and its host. VACV contains a gene that is highly evasive of the host immune system, gene E3L. The protein encoded by E3L is E3, which contains two highly conserved regions, a C-terminus, and a N-terminus. While the C-terminus is well-understood, the mechanism by which the N-terminus grants IFN resistance was previously unknown. This project demonstrated that the N-terminus prevents the initiation of programmed necrosis through host-encoded cellular proteins RIP3 and DAI. These findings provide insight into the function of the N-terminus of E3, as well as the unique functions of induced programmed necrosis.
This project was an example of “basic” research. However, it highlights the interconnectivity of basic and applied research and the danger in isolating both projects and perspectives. It points to the difficult decisions that must be made in science, and the need for a better research classification system that considers what makes science “good” outside of antiquated social class ideologies that have shaped science since ancient Greece. While there are no easy answers to determine what makes research “good,” thinking critically about the types of research projects that will be pursued, and the effects that research has on both science and society, will raise awareness, initiate new conversations, and encourage more dialogue about science in the 21st century.