The effect of osmotic and ion-osmotic stresses on the blood and urine composition and urine flow of rainbow trout (Salmo gairdneri)

1. 1. Changes in urine and plasma concentrations (sodium, potassium, magnesium, calcium and total osmotic) and urine production were determined in fish exposed to various concentrations of an ionically active substance, sodium chloride, and a non-electrolyte, mannitol, as well as freshwater.2. 2. Responses occurred for the most part over a short crisis period preceeding establishment of new stable conditions.3. 3. It was shown that plasma homeostasis was not maintained in response to changing ion-osmotic and osmotic gradients.4. 4. Urinary osmotic and ionic concentrations were unaffected and urine production was shown to be inversely related to the external concentration.5. 5. It is suggested that ionic shifts between body compartments are an important aspect of ion-osmotic adaptation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24991/1/0000418.pd

Visualizing Interactions along the Escherichia coli Twin-Arginine Translocation Pathway Using Protein Fragment Complementation

The twin-arginine translocation (Tat) pathway is well known for its ability to export fully folded substrate proteins out of the cytoplasm of Gram-negative and Gram-positive bacteria. Studies of this mechanism in Escherichia coli have identified numerous transient protein-protein interactions that guide export-competent proteins through the Tat pathway. To visualize these interactions, we have adapted bimolecular fluorescence complementation (BiFC) to detect protein-protein interactions along the Tat pathway of living cells. Fragments of the yellow fluorescent protein (YFP) were fused to soluble and transmembrane factors that participate in the translocation process including Tat substrates, Tat-specific proofreading chaperones and the integral membrane proteins TatABC that form the translocase. Fluorescence analysis of these YFP chimeras revealed a wide range of interactions such as the one between the Tat substrate dimethyl sulfoxide reductase (DmsA) and its dedicated proofreading chaperone DmsD. In addition, BiFC analysis illuminated homo- and hetero-oligomeric complexes of the TatA, TatB and TatC integral membrane proteins that were consistent with the current model of translocase assembly. In the case of TatBC assemblies, we provide the first evidence that these complexes are co-localized at the cell poles. Finally, we used this BiFC approach to capture interactions between the putative Tat receptor complex formed by TatBC and the DmsA substrate or its dedicated chaperone DmsD. Our results demonstrate that BiFC is a powerful approach for studying cytoplasmic and inner membrane interactions underlying bacterial secretory pathways

Energy expenditure for osmoregulation in rainbow trout, Salmo gairdneri

Master of ScienceResource EcologyUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/113960/1/39015003265850.pd