Pathology Associated with AAV Mediated Expression of Beta Amyloid or C100 in Adult Mouse Hippocampus and Cerebellum

Accumulation of beta amyloid (Aβ) in the brain is a primary feature of Alzheimer’s disease (AD) but the exact molecular mechanisms by which Aβ exerts its toxic actions are not yet entirely clear. We documented pathological changes 3 and 6 months after localised injection of recombinant, bi-cistronic adeno-associated viral vectors (rAAV2) expressing human Aβ40-GFP, Aβ42-GFP, C100-GFP or C100^V717F-GFP into the hippocampus and cerebellum of 8 week old male mice. Injection of all rAAV2 vectors resulted in wide-spread transduction within the hippocampus and cerebellum, as shown by expression of transgene mRNA and GFP protein. Despite the lack of accumulation of Aβ protein after injection with AAV vectors, injection of rAAV2-Aβ42-GFP and rAAV2- C100^V717F-GFP into the hippocampus resulted in significantly increased microgliosis and altered permeability of the blood brain barrier, the latter revealed by high levels of immunoglobulin G (IgG) around the injection site and the presence of IgG positive cells. In comparison, injection of rAAV2-Aβ40-GFP and rAAV2-C100-GFP into the hippocampus resulted in substantially less neuropathology. Injection of rAAV2 vectors into the cerebellum resulted in similar types of pathological changes, but to a lesser degree. The use of viral vectors to express different types of Aβ and C100 is a powerful technique with which to examine the direct in vivo consequences of Aβ expression in different regions of the mature nervous system and will allow experimentation and analysis of pathological AD-like changes in a broader range of species other than mouse.     

Trophic Ecology of Atlantic Bluefin Tuna (Thunnusthynnus) Larvae from the Gulf of Mexico and NW Mediterranean Spawning Grounds: A Comparative Stable Isotope Study

The present study uses stable isotopes of nitrogen and carbon (δ¹⁵Nandδ¹³C) as trophic indicators for Atlantic bluefin tuna larvae (BFT) (6–10 mm standard length) in the highly contrasting environmental conditions of the Gulf of Mexico (GOM) and the Balearic Sea (MED). These regions are differentiated by their temperature regime and relative productivity, with the GOM being significantly warmer and more productive. MED BFT larvae showed the highest δ¹⁵N signatures, implying an elevated trophic position above the underlying microzooplankton baseline. Ontogenetic dietary shifts were observed in the BFT larvae from the GOM and MED which indicates early life trophodynamics differences between these spawning habitats. Significant trophic differences between the GOM and MED larvae were observed in relation to δ¹⁵N signatures in favour of the MED larvae, which may have important implications in their growth during their early life stages.These low δ¹⁵N levels in the zooplankton from the GOM may be an indication of a shifting isotopic baseline in pelagic food webs due to diatrophic inputs by cyanobacteria. Lack of enrichment for δ¹⁵N in BFT larvae compared to zooplankton implies an alternative grazing pathway from the traditional food chain of phytoplankton—zooplankton—larval fish. Results provide insight for a comparative characterization of the trophic pathways variability of the two main spawning grounds for BFT larvae.     

Seasonal variation in horizontal and vertical structure of larval fish assemblages off south-western Australia, with implications for larval transport

The coastal ocean off south-western Australia is characterisedby the southward-flowing Leeuwin Current, which suppresses theupwelling typically associated with other eastern boundary currentsin the southern hemisphere. This results in a unique environmentfor the transport and survival of planktonic fish larvae. Thehorizontal and vertical structure of larval fish assemblagesoff south-western Australia was investigated during winter (August2003) and summer (January 2004), and related to these unusualregional oceanographic and biological processes. Larval fishwere sampled along a four station transect running from theinner continental shelf to offshore waters, using depth-integratedbongo net tows and depth-stratified EZ net tows. The distributionof taxa across the shelf and offshore was strongly influencedby the current regime at the time of sampling. Larval fish assemblagestructure reflected the distinctive oceanographic conditionsfound during each season, and vertical depth distributions oflarvae affected their horizontal location. Continental shelfsamples were dominated by larvae of pelagic fishes, such asclupeiform species (e.g. Sardinops sagax), whereas offshoreassemblages were characterised by larvae of oceanic families,such as Myctophidae and Phosichthyidae. The winter cruise (August2003) was completed during a time of strong, southerly LeeuwinCurrent flow, whereas the northward-flowing Capes Current, incombination with surface offshore Ekman transport, predominatedduring summer. The vertical depth preferences of larvae wereparticularly influential in affecting their horizontal position;especially so for surface-dwelling larval fishes found duringsummer. This study represents the first documentation of thevertical structure of ichthyoplankton assemblages in the oligotrophicwaters off south-western Australia.     

Reproduction and larval biology in tunas,and the importance of restricted area spawning grounds

Tunas show a wide variety of life history strategies, spatial distributions and migratory behaviors, yet they share a common trait of spawning only in tropical and sub-tropical regions. The warm-water tuna species generally show significant overlap between spawning and feeding grounds, and longer spawning seasons of several months to near year-round. In contrast, the cool-water bluefin tunas migrate long distances between feeding and spawning grounds, and may spawn over periods as short as 2 months. Here, we examine the spatial distributions of tuna larvae in the world’s oceans, and examine interspecific differences in the light of adult behaviors and larval ecology. We discuss the links between larval tuna and their oceanographic environments and relate these to current knowledge of larval growth, feeding and trophodynamics, with a focus on the better-studied bluefin tunas. We show that larval tunas have moderate to fast growth rates and selective feeding habits, and thus appear to be adapted for survival in warm, oligotrophic seas. We also examine the challenges of sustainably managing species which migrate across multiple management boundaries to reach spatio-temporally restricted spawning grounds and discuss the previous and future anthropogenic impacts on tuna spawning areas.     

Evidence of climate‐driven ecosystem reorganization in the Gulf of Mexico

The Gulf of Mexico is one of the most ecologically and economically valuable marine ecosystems in the world and is affected by a variety of natural and anthropogenic phenomena including climate, hurricanes, coastal development, agricultural runoff, oil spills, and fishing. These complex and interacting stressors, together with the highly dynamic nature of this ecosystem, present challenges for the effective management of its resources. We analyze a compilation of over 100 indicators representing physical, biological, and economic aspects of the Gulf of Mexico and find that an ecosystem‐wide reorganization occurred in the mid‐1990s. Further analysis of fishery landings composition data indicates a major shift in the late 1970s coincident with the advent of US national fisheries management policy, as well as significant shifts in the mid‐1960s and the mid‐1990s. These latter shifts are aligned temporally with changes in a major climate mode in the Atlantic Ocean: the Atlantic Multidecadal Oscillation (AMO). We provide an explanation for how the AMO may drive physical changes in the Gulf of Mexico, thus altering higher‐level ecosystem dynamics. The hypotheses presented here should provide focus for further targeted studies, particularly in regard to whether and how management should adjust to different climate regimes or states of nature. Our study highlights the challenges in understanding the effects of climatic drivers against a background of multiple anthropogenic pressures, particularly in a system where these forces interact in complex and nonlinear ways.