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Welcome to the Christensen Lab Homepage!
Our research interests are currently focused on two biological questions:
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How do some fish maintain an internal ion homeostasis when the environmental salinity changes?
Fish in freshwater or seawater face different physiological challenges.
In freshwater, diffusive ion loss and water gain must be counteracted by active ion uptake and retention, and dilute urine production.
Conversely, in seawater, diffusive ion gain and water loss must be countered by active ion extrusion and increased water consumption.
For fishes that remain in freshwater or seawater, the mechanisms that maintain ion homeostasis may be relatively static.
On the other hand, fish which can adapt to freshwater and seawater, termed euryhaline, must do so by regulating the expression of proteins important for ion-transport and trans-epithelial resistance in tissues that are critical for maintaining ion-homeostasis, such as the gill.
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Ionocytes (see top panels, white/orange cells) are a class of highly specialized cells found in the gill and larval integument. These cells are a major site of ion transport between a fish and the aqueous environment. The morphology, arrangement (see left, freshwater-FW vs. seawater-SW) and expression profiles of these cells are dependent on environmental salinity. We are interested in developing a clearer understanding of how environmental factors, such as salinity, impact the origin and fate of these cells, as well the expression profiles of proteins important for ion-homeostasis, such as the Na+/K+-ATPase and Cystic Fibrosis Transmembrane Conductance Regulator (CFTR).
The more we understand about how cells, and in turn, animals maintain ion-homeostasis, the better equipped we will be to determine how these processes may be impaired by environmental contaminants and changing environmental conditions. |
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How are environmental contaminants of emerging concern impacting early developmental processes, such as retinal patterning, in local aquatic species?
The vertebrate retina arises from a layer of pseudostratified multipotent cells, wherein mitosis is limited to the apical surface, and postmitotic cells migrate basally to differentiate based on temporal and spatial cues.
The mature retina is a highly organized tissue composed of Müller glial cells and six neuronal cell classes that are organized into three functional layers which receive, process and transmit visual information from the environment.
We are interested in determining the impacts of specific anthropogenic compounds, such as those detected in sewage effluent entering a local estuary (Jamaica Bay), on early developmental processes like retinal patterning.
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