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Stress generates multiple physiological effects through activation of neuroendocrine signaling. An increase in the hormone cortisol (or the analog corticosterone in some species), causes a significant decrease in circulating B-lymphocytes (the immune cells that produce antibodies), making the antibody immunoglobulin A (IgA) a good stress marker. The objective of these experiments was to examine IgA secretion after psychological and physical stressor treatments were applied. IgA was extracted from the salivary samples of college students who did or did not have a scheduled exam to test impacts of purely psychological stress, and from fecal samples of mice treated with human handling (psychological stress), forced exercise (physical stress), or a combination of the two. An enzyme-linked immunosorbent assay was used to measure IgA level in each sample. In humans, exam-taking was significantly associated with low salivary IgA levels (p < 0.05), suggesting that the psychological stressor negatively impacted the immune response. In mice, the handling group did not exhibit any significant change in fecal IgA level (p > 0.05), which may or may not have been a result of habituation to handling. However, both the physical stress group and combined physical and psychological stress group exhibited significantly reduced fecal IgA levels (p < 0.05) in comparison to the control. This study supports other findings that different stressors have different effects on physiological markers of stress, such as IgA level, and demonstrates those differences in humans and a controlled model of psychological and physical stressors in mice.
The process of oocyte maturation involves both nuclear and cytoplasmic events that are essential for the production of viable eggs and subsequent fertilization in sexually reproducing animals. In zebrafish, oocyte nuclear maturation (meiotic resumption) is marked by a transition from opaque to translucent ovarian follicles. This transition is called clearing and results from germinal vesicle breakdown (GVBD) and the transformation of vitellogenin into yolk proteins. Oocyte maturation can be perturbed by endocrine-disrupting chemicals (EDCs). These EDCs have been broadly shown to interfere with reproductive development. Many herbicides and pesticides used agriculturally act as EDCs. These chemicals can enter aquatic ecosystems via runoff and erosion. To evaluate the effects of EDCs on zebrafish oocyte maturation, zebrafish ovarian follicles were cultured and exposed to various concentrations of either atrazine, 2,4-D, or diazinon. Follicles were evaluated at 2, 3, and 4 hours for size and viability, but clearing was assessed only at 4 hours post-exposure. Atrazine and diazinon significantly reduced follicle clearing at the tested concentrations. No effect was observed with 2,4-D exposure. At low enough concentrations, none of the chemicals produced endocrine-disrupting effects. The results suggest that at or above environmentally relevant concentrations, some EDCs impair oocyte maturation in exposed zebrafish follicles. The results support the need to monitor EDC exposure to prevent harmful effects not only on aquatic organisms, but also on humans and wildlife that are also exposed to these contaminants.
Bluff prairies are extreme habitats centered on southwestern facing bluffs along major rivers in the driftless area of the upper Midwest. Characterized by steep slopes, thin soils, and intense exposure to sun and wind, bluff prairies harbor a much warmer, drier microclimate than is found elsewhere in the region. Such harsh conditions help preserve bluff prairie habitat for unique communities of plants and animals. However, like many prairie habitats, bluff prairies are shrinking in size and experiencing fragmentation, resulting in smaller prairie remnants rather than larger, intact prairies. This shrinking and fragmentation is likely a consequence of non-prairie and/or non-native plants encroaching from the edges. One prominent introduced invasive species, leafy spurge (Euphorbia esula), has the ability to spread quickly and displace native plants. During the summer of 2012, the native flowering plant communities (excluding grasses, rushes, and sedges), prairie remnant sizes, and invasive leafy spurge presence and cover were surveyed in 10 bluff prairies in southeastern Minnesota. It was found that native flowering plant species richness is positively correlated with prairie remnant area and negatively correlated with percent leafy spurge cover. The current study provides insight into the current habitat quality of southeastern Minnesota bluff prairies and enables future studies to monitor changes in prairie size and community composition over time.
In today's society, numerous people suffer from anxiety and depression, so it is important to develop effective treatments for these disorders. However, there is limited knowledge of the mechanisms underlying them. Previous studies show that increased acetylcholine (ACh) levels in the hippocampus positively correlate with increased depression. Acetylcholinesterase (AChE) is the principle degradative enzyme of ACh in the brain and limits the concentrations of ACh in the neuronal synapse. Furthermore, chronic administration of the antidepressant fluoxetine resulted in reduced anxiety- and depression-like behavior in mice. Therefore, we hypothesized that mice receiving chronic administration of fluoxetine would show reduced anxiety- and depression-like behaviors, which would negatively correlate with higher levels of AChE in the hippocampus. These hypotheses were tested using behavioral and molecular assays. Adult male Swiss-Webster mice received daily i.p. injections of either 20 mg/kg fluoxetine or vehicle. After two weeks of treatment, relative levels of anxiety- and depression-like behavior were determined. The novelty-induced hypophagia (NIH) and open field tests determined anxiolytic-like efficacy of fluoxetine, and the tail suspension and forced swim tasks evaluated depression-like behavior. Upon completion of behavioral testing, the brains were extracted, core samples were taken from the striatum, dorsal hippocampus, and basolateral amygdala, and the AChE levels were measured. Fluoxetine-treated mice showed significantly reduced latencies to ingest a palatable solution in a novel environment, suggestive of reduced anxiety-like behavior (p < 0.05). Significant positive correlations were observed between AChE levels in the striatum and time spent in center in the open field test (p < 0.05), suggesting decreased cholinergic tone correlates to reduced anxiety, but the correlations were not consistent across behavioral assays.
Peatlands are among the most important ecosystems in the global carbon cycle. These wetlands store roughly one-third of the terrestrial soil organic matter (SOM) and are important sources of the potent greenhouse gas methane (CH4) to the atmosphere. Understanding carbon cycling, and in particular CH4 dynamics, within peatland soils has important implications for understanding biosphere-climate feedbacks. There is mounting evidence that under anaerobic conditions microbes can reduce organic terminal electron acceptors in place of oxygen in peatland soils. This microbial respiration of SOM can dominate anaerobic decomposition and competitively suppress CH4 production, but the controls of this process are not well understood. We explored SOM reduction in a peatland soil using laboratory microcosms that allowed for water-table level manipulations. Measurements of electron shuttling demonstrate that SOM was progressively reduced following flooding and was quickly re-oxidized following water-table draw down, with impacts on CH4 production in this peat soil. These results highlight that successive reduction and oxidization of SOM from changes in water-table level may be an important control on anaerobic carbon cycling in peatlands.
Agonistic interactions in most animals reflect individual social experience and nutritional status. Crustaceans establish social hierarchies in which dominant individuals tend to be largest, most aggressive, and have the greatest access to resources such as mates, shelter, and food. Subordinates, on the other hand, are smaller and lack access to resources. However, to become dominant, individuals must grow, a process that requires nutrients. Crustacean grow through a process known as molting, where animals shed their external skeleton and rebuild a larger carapace. During molt, animals are very vulnerable to predators and potential competitors. Thus, an animal must balance the potential benefit of growth with the risk of injury resulting from agonistic interactions during molting. In this study we asked how being in a social group influences molting behavior. The crayfish Orconectes obscurus were isolated for 7 days and then placed into either an individual tank or into a tank with 2 same-sex crayfish. Interactions in group tanks were recorded and analyzed to determine social status of each individual. Animals were observed daily for 30 days to note movement patterns and molts. Although dominant individuals typically have greater access to limited resources required for molting and would theoretically molt sooner and more frequently than subordinates, when food was equally available to all individuals, subordinates actually molted sooner and more frequently than dominant individuals. Additionally, there was a seasonal effect in which the molt rate and frequency was greatest in the summer. These findings suggest that sociality and seasonality strongly influence molting behavior in crustaceans.
The following chapters have sent in officer slates for 2016-2017. Officers are listed in the order of President, Vice President, Secretary, Treasurer, Historian, and Faculty Advisor unless otherwise noted. The chapters are listed alphabetically by Greek name. Please submit new slates, changes and corrections to Lori.Kelman@montgomerycollege.edu.