Germ Cell Nuclear Factor: An Orphan Receptor in Search of a Function

Germ Cell Nuclear Factor (GCNF) is an orphan member of the nuclearreceptor gene superfamily. Much has been understood about thefunctioning of GCNF which represents a candidate receptor fora novel hormonal signalling pathway. GCNF is not closely relatedto other members of the nuclear receptor superfamily and formsits own branch within the superfamily tree. It has a uniqueexpression pattern that spans both embryonic and adult stagesof development. In the adult, it is expressed in the germ cells:oocytes and spermatogenic cells as well as specific neuronalcells within the brain. In the embryo, GCNF expression is turnedon after gastrulation in all germ layers the ectoderm, mesodermand endoderm. An antero-posterior gradient of GCNF is establishedin the neuroectoderm of the embryo, suggesting a role in regulationof neuronal and germ cell development. Regulation of physiologicalprocesses by a nuclear receptor is achieved through regulationof gene expression. GCNF is the only nuclear receptor to specifcallybind to DR0 hormone response elements to regulate gene expression.In the absense of a ligand, GCNF represses gene expression.GCNF is capable of regulating the expression of the protaminegenes in a response element-dependent manner. At present theligand for GCNF is unknown, but it is hypothesized that GCNFis a receptor for a novel hormonal signalling pathway that effectsits biological response by regulating the expression of a subsetof genes containing DR0 response elements.     

Evaluating habitat effects on population status: influence of habitat restoration on spring-run Chinook salmon

1. A key element of conservation planning is the extremely challenging task of estimating the likely effect of restoration actions on population status. To compare the relative benefits of typical habitat restoration actions on Pacific salmon (Oncorhynchus spp.), we modelled the response of an endangered Columbia River Chinook salmon (O. tshawytscha) population to changes in habitat characteristics either targeted for restoration or with the potential to be degraded. 2. We applied a spatially explicit, multiple life stage, Beverton‐Holt model to evaluate how a set of habitat variables with an empirical influence on spring‐run Chinook salmon survivorship influenced fish population abundance, productivity, spatial structure and diversity. Using habitat condition scenarios – historical conditions and future conditions with restoration, no restoration, and degradation – we asked the following questions: (i) how is population status affected by alternative scenarios of habitat change, (ii) which individual habitat characteristics have the potential to substantially influence population status and (iii) which life stages have the largest impact on population status? 3. The difference in population abundance and productivities resulting from changes in modelled habitat variables from the ‘historical’ to ‘current’ scenarios suggests that there is substantial potential for improving population status. Planned restoration actions directed toward modelled variables, however, produced only modest improvements. 4. The model predicted that population status could be improved by additional restoration efforts directed toward further reductions in the percentage of fine sediments in the streambed, a factor that has a large influence on egg survival. Actions reducing fines were predicted to be especially effective outside the national forest that covers most of the basin. Scenarios that increased capacity by opening access to habitat in good condition also had a positive but smaller effect on spawner numbers. 5. Degradation in habitat quality, particularly in percent fine sediments, within stream reaches located in the national forest had great potential to further reduce this population’s viability. This finding supports current forest planning efforts to minimise road density and clear‐cut harvests and to return forest stand structure in dry regions to the historical condition that promoted frequent low‐intensity fires rather than catastrophic stand‐replacing fires, as these landscape factors have been shown to influence percent fine sediment in streams. 6. Together, these results suggest that planning focusing on protecting currently good habitat, reducing fine sediments to promote egg survival and increasing spawner capacity will be beneficial to endangered spring‐run Chinook population status.     

Linking landscape-level change to habitat quality: an evaluation of restoration actions on the freshwater habitat of spring-run Chinook salmon

1. Conservation planning is often hampered by the lack of causal quantitative links between landscape characteristics, restoration actions and habitat conditions that impact the status of imperilled species. Here we present a first step toward linking actions on the landscape to the population status of endangered stream‐type Chinook salmon (Oncorhynchus tshawytscha). 2. We developed relationships between land use, landscape characteristics and freshwater habitat of spring Chinook salmon in the Wenatchee River basin. Available data allowed us to find relationships that described water temperatures at several life stages (prespawning, egg incubation and summer rearing) and substratum characteristics, including fine sediments, cobble and embeddedness. Predictors included altitude, gradient, mean annual precipitation, total and riparian forest cover, road density, impervious surface and alluvium. We used a model averaging approach to account for parameter and model selection uncertainty. Key predictors were total forest cover and impervious surface area for prespawning and summer rearing temperatures; precipitation and stream gradients were important predictors of the percent of fine sediments in stream substrata. 3. We estimated habitat conditions using these relationships in three alternative landscape scenarios: historical, no restoration and one that included a set of restoration actions from local conservation planning. We found that prespawning and summer temperatures were estimated to be slightly higher historically relative to current conditions in dry sparsely forested areas, but lower in some important Chinook salmon spawning and rearing areas and lower in those locations under the restoration scenario. Fine sediments were lower in the historical scenario and were reduced as a consequence of restoration actions in two areas currently unoccupied by Chinook salmon that contain reaches with some potential for high quality spawning and rearing. Cobble and embeddedness in general were predicted to be higher historically and changed little as a result of restoration actions relative to current conditions. 4. This modelling framework converts suites of restoration actions into changes in habitat condition, thereby enabling restoration planners to evaluate alternative combinations of proposed actions. It also provides inputs to models linking habitat conditions to population status. This approach represents a first step in estimating impacts of restoration strategies, and can provide key information for conservation managers and planners.     

Effects of Poorly Metabolized Hydrocarbons on Substrate Oxidation by Cladosporium resinae

Twelve hydrocarbons which singly support no growth or little growth of Cladosporium resinae were examined for their effects on utilization of four substrates which do support growth of the fungus. Of the 48 combinations of an oxidizable substrate with a potential hydrocarbon substrate, 8 combinations supported increased oxygen consumption above the level obtained with the oxidizable substrate alone. There was no evidence of co-oxidation of the potential co-substrates toluene or p -xylene; their effects on increasing O₂-uptake appear to be due to permeability changes. With hexadecane alone, the ratio hexadecane oxidized to CO₂: hexadecane taken up by cells was 97:3. Addition of p -xylene or toluene decreased that ratio slightly to 96:4 and 89:11, respectively. These high ratios of hydrocarbon oxidized to hydrocarbon taken up may be advantageous during degradation of petroleum in the natural environment, since petroleum components could be degraded without formation of a large biomass.