Physiology

Cardiac ischemia, stroke and some neurodegenerative disorders are all characterized by cell damage and death due to low oxygen levels. Comparative studies show that anoxia tolerant model systems present a unique opportunity to study "survival" instead of death in the complete absence of oxygen. The freshwater turtle (Trachemys scripta elegans) is unique in its ability to survive total oxygen deprivation for hours to days, as well as reoxygenation insult after anoxia. The broad objective of this study is to understand the modulation of key molecular mechanisms involving stress proteins and VEGF that offer neuroprotection and enhance cell survival in the freshwater turtle through anoxia and reoxygenation. In vivo analyses have shown that anoxia induced stress proteins (Hsp72, Hsp60, Grp94, Hsp60, Hsp27, HO-1); modest changes in the Bcl2/Bax ratio and no change in cleaved caspase-3 expression suggesting resistance to neuronal damage. These results were corroborated with immunohistochemical evidence indicating no damage in turtle brain when subjected to the stress of anoxia and A/R. To understand the functional role of Hsp72, siRNA against Hsp72 was utilized to knockdown Hsp72 in vitro (neuronally enriched primary cell cultures established from the turtle). Knockdown cultures were characterized by increased cell death associated with elevated ROS levels. Silencing of Hsp72 knocks down the expression of Bcl2 and increases the expression of Bax, thereby decreasing the Bcl2/Bax ratio. However, there was no increase in cytosolic Cytochrome c or the expression levels of cleaved Caspase-3. Significant increase in AIF was observed in the knockdown cultures that increase through anoxia and reoxygenation, suggesting a caspase independent pathway of cell death.

The thymus provides a unique microenvironment that facilitates T lymphocytes differentiation and maturation. However, the thymus atrophies after puberty which leads to an overall expression of metabolism gene pathways and low gene expression of certain peroxide scavenger enzymes such as catalase in thymic stromal compartments. From this data, we postulate that thymic stromal cells are highly susceptible to oxidative damage. We utilized a transgenic mice model overexpressing human catalase targeted to the mitochondria (mCat) to test our hypothesis that gerater oxidative protection should lower the degree of thymus atrophy. Our experiment focused on a direct comparison of organ weights (thymus, kidney, lymph nodes, spleen and heart), cellularity and histology between transgenic and wildtype mice. We found that mCat had selective increases in thymus size.

Talin is a ubiquitous, high-molecular-weight, flexible protein that plays a critical role in focal adhesions by activating, as well as connecting, integrins to the actin cytoskeleton. Talin's inactive auto-inhibitory state is speculated to be one of its modes of regulation inside the cell and is achieved through its head-tail interactions. In order to decipher the stability of this interaction, the head domain (residues 206-405) was cloned into a modified pET28m vector while the tail domains (residues 1654-2344 and 2225-2344) were cloned into the pET32a vector to obtain octa-histidine tagged and un-tagged peptide, respectively. Neither co-expression nor pull-down using the His-tagged head domain was successful in purifying a stable head-tail complex. Our results indicate rather weak interactions between the talin head and rod domains and hence, under our experimental conditions, do not lead to a stable auto-inhibitory complex that can be purified for further studies.

The effects of the recently introduced species, the curlytail lizard, on the Florida ecosystems are relatively unknown. Previous research conducted in the Bahamas showed that brown anole lizards, once introduced to curlytail lizards, became arboreal to evade the threat of the curlytail lizards. To attempt to see if such a niche shift in the brown anole population is occurring in Florida, data were collected using two areas located on the Harriet L. Wilkes Honors College of FAU. One area was inhabited by only brown anoles whereas the other area was inhabited by brown anoles and curlytail lizards, the latter which newly invaded this site in 2006. Observations were made by walking through the selected area, and counting and recording all lizards that were visible. Data were collected at specific times during the day, four times a day. After comparing the two locations, it was found that the brown anoles have become arboreal when sharing an environment with curlytail lizards.

Extensive blooms of the marine cyanobacterium Lyngbya majuscula occurred during 2006 in Halodule wrightii seagrass beds. We examined the effects of L. majuscula blooms on seagrass by removal treatments and assessed if this was primarily an effect of shading by conducting artificial shade treatments. We tested the effects of L. majuscula removal and artificial shading on fifty individual 0.25 m2 experimental seagrass plots infested with L. majuscula in a fully crossed, two-way experiment. Measurements included blade elongation, biomass, and stem density. Blade lengths of H. wrightii were significantly increased by the presence of artificial shading and L. majuscula. L. majuscula removal resulted in increased below ground biomass in shaded plots, suggesting an increase in stores, when possible, for accelerated recovery following a shading event. Adverse L. majuscula effects occurred after declines in bloom biomass indicating that L. majuscula can have a prolonged negative effect on H. wrightii production.

Harvestmen are known to secrete a wide range of defensive chemicals in order to protect themselves from predators. An earlier study examined the phylogenetic pattern of defensive secretions produced by 22 species of harvestmen. This research, however, assumed that there is a genetic link between the defensive secretions. I wished to determine whether harvestmen defensive secretions may be diet-based by introducing several irritants into their food and then testing their secretions in the same manner. I performed a GC-MS analysis on 13 samples from the Vonones sp. But I found no initial GC-MS readings that showed this species of harvestmen to contain any irritants in their secretions. The absence of irritants does not allow any evaluation of whether harvestmen secretions are genetically or dietarily based.