A pathological hallmark of Alzheimer’s disease (AD) is an accumulation of insoluble plaque containing the amyloid-β peptide (Aβ) of 40–42 aa residues1. Prefibrillar, soluble oligomers of Aβ have been recognized to be early and key intermediates in AD-related synaptic dysfunction2–9. At nanomolar concentrations, soluble Aβ-oligomers block hippocampal long-term potentiation7, cause dendritic spine retraction from pyramidal cells5,8 and impair rodent spatial memory2. Soluble Aβ-oligomers have been prepared from chemical syntheses, from transfected cell culture supernatants, from transgenic mouse brain and from human AD brain2,4,7,9. Together, these data imply a high affinity cell surface receptor for soluble Aβ-oligomers on neurons, one that is central to the pathophysiological process in AD. Here, we identify the cellular Prion Protein (PrPC) as an Aβ-oligomer receptor by expression cloning. Aβ-oligomers bind with nanomolar affinity to PrPC, but the interaction does not require the infectious PrPSc conformation. Synaptic responsiveness in hippocampal slices from young adult PrP null mice is normal, but the Aβ-oligomer blockade of long-term potentiation is absent. Anti-PrP antibodies prevent Aβ-oligomer binding to PrPC and rescue synaptic plasticity in hippocampal slices from oligomeric β. Thus, PrPC is a mediator of Aβoligomer induced synaptic dysfunction, and PrPC-specific pharmaceuticals may have therapeutic potential for Alzheimer’s disease.

Synapsin III is a neuron-specific phosphoprotein that plays an important role in synaptic transmission and neural development. While synapsin III is abundant in embryonic brain, expression of the protein in adults is reduced and limited primarily to the hippocampus, olfactory bulb and cerebral cortex. Given the specificity of synapsin III to these brain areas and because it plays a role in neurogenesis in the dentate gyrus, we investigated whether it may affect learning and memory processes in mice. To address this point, synapsin III knockout mice were examined in a general behavioral screen, several tests to assess learning and memory function, and conditioned fear. Mutant animals displayed no anomalies in sensory and motor function or in anxiety-and depressive-like behaviors. Although mutants showed minor alterations in the Morris water maze, they were deficient in object recognition 24 h and 10 days after training and in social transmission of food preference at 20 min and 24 h. In addition, mutants displayed abnormal responses in contextual and cued fear conditioning when tested 1 or 24 h after conditioning. The synapsin III knockout mice also showed aberrant responses in fear-potentiated startle. As synapsin III protein is decreased in schizophrenic brain and because the mutant mice do not harbor obvious anatomical deficits or neurological disorders, these mutants may represent a unique neurodevelopmental model for dissecting the molecular pathways that are related to certain aspects of schizophrenia and related disorders.

The use of CT/MRI for evaluation of atraumatic headache increased dramatically in EDs in the USA between 1998 and 2008. The prevalence of ICP among patients who received CT/MRI declined concurrently, suggesting a role for clinical decision support to guide more judicious use of imaging.

Proton magnetic resonance imaging (MRI) of the processes of freezing and thawing in the wood frog Rana sylvatica provided noninvasive and real-time analysis of the mode of ice propagation through the body of a freeze-tolerant vertebrate. MRI revealed a directional movement of ice from the exterior inward that required several hours to reach completion. Freezing in core organs such as liver, which produces and exports cryoprotectant, and heart, which circulates it, was delayed and occurred well after the organs were surrounded by extraorgan ice. Natural thawing was a very different process; thawing began uniformly throughout the body, but core organs melted more rapidly than peripheral ones, an adaptation that may be key to the early restoration of heartbeat and breathing. The images presented demonstrate the sensitivity and power of MRI and its potential to become a critical monitoring technology in the development of cryopreservation techniques for mammalian organ explants.

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