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ET-1 is found to be significantly elevated in the CSF of stroke patients during the 18 hours after stroke. No elevation was demonstrated in plasma at this time period. ET-1 may be used as an additional indicator of ischemic vascular events in the early diagnosis of stroke. The dissimilarity between the CSF and plasma ET-1 concentrations may lead also to an hypothesis that there is a vasoconstrictive effect on the cerebral vessels or a neuronal effect caused by ET-1 in the mechanism of the progression of brain ischemia.

Brain-machine interfaces (BMI) were born to control “actions from thoughts” in order to recover motor capability of patients with impaired functional connectivity between the central and peripheral nervous system. The final goal of our studies is the development of a new proof-of-concept BMI—a neuromorphic chip for brain repair—to reproduce the functional organization of a damaged part of the central nervous system. To reach this ambitious goal, we implemented a multidisciplinary “bottom-up” approach in which in vitro networks are the paradigm for the development of an in silico model to be incorporated into a neuromorphic device. In this paper we present the overall strategy and focus on the different building blocks of our studies: (i) the experimental characterization and modeling of “finite size networks” which represent the smallest and most general self-organized circuits capable of generating spontaneous collective dynamics; (ii) the induction of lesions in neuronal networks and the whole brain preparation with special attention on the impact on the functional organization of the circuits; (iii) the first production of a neuromorphic chip able to implement a real-time model of neuronal networks. A dynamical characterization of the finite size circuits with single cell resolution is provided. A neural network model based on Izhikevich neurons was able to replicate the experimental observations. Changes in the dynamics of the neuronal circuits induced by optical and ischemic lesions are presented respectively for in vitro neuronal networks and for a whole brain preparation. Finally the implementation of a neuromorphic chip reproducing the network dynamics in quasi-real time (10 ns precision) is presented.

Incubation of endothelins (ETs) with bovine kidney neutral endopeptidase (NEP) resulted in a selective two-step degradation with loss of biochemical activity. The Km of the enzyme indicated high-affinity binding, and hydrolysis was completely inhibited by phosphoramidon. The first step was nicking of the Ser5-Leu' bond, followed by cleavage at the amino side of ile". The nicked peptide exhibited biochemical activities comparable to those of the intact peptide-i.e., binding to the ET receptor, induction of inositol phospholipid hydrolysis, and toxicity. The twice-cleaved product was inactive. The sarafotoxins (SRTXs) were more resistant than the ETs to NEP: for example, the half-time for ET-1 was 41 hr, while it was =4 hr for SRTX-b and even higher for SRTX-c. These in vitro rmdings may indicate a regulatory role of NEP (or similar enzymes) in the physiological inactivation of ETs. They might also help to explain why under certain physiological conditions ETs may be less toxic than SRTXs.The endothelins (ETs) and the sarafotoxins (SRTXs) are two classes of a recently discovered family of peptides containing 21 amino acids (reviewed in refs. 1 and 2). The ETs (isolated from mammalian systems) and the SRTXs (from snake venom) are among the most potent vasoconstrictor agents known (refs. 1 and 2 and references therein) and are highly lethal (3). The two classes of peptides show a considerable sequence homology: they each possess four cysteinyl residues, and "'60%o of the 21 amino acid residues are common to both. Since ET-1 was described, three other ETs have been detected and are designated ET-2, ET-3 (4), and (Vic) (5) (Fig. 1). Also, four SRTXs-SRTX-a, SRTX-b, SRTX-c, and SRTX-d (6)-have been characterized so far (Fig. 1). The four cysteinyl residues in the ETs and in the SRTXs are interconnected by disulfide bridges between positions 1 and 15 and 3 and 11, forming an intramolecular loop structure (see diagram in Fig. 1 (19). The substrates cleaved by NEP appear to be restricted to peptides of molecular mass ==3 kDa (18,19). These considerations prompted us to examine whether the ETs and/or the SRTXs might be good substrates for NEP. The effect of the enzyme can be evaluated by measuring enzyme-associated changes in the biochemical activities of the peptides, such as binding to the receptor, induction of inositol phospholipid hydrolysis, immunogenicity (20, 21), and lethality. As shown in this in vitro study, NEP inactivates ETs as a result of nicking the bond at Ser5-Leu6 followed by rapid cleavage at the amino side of Ile"9. Under identical experimental conditions, NEP also inactivated SRTXs, but at a much slower rate. MATERIALS AND METHODSET-1, ET-2, ET-3, and ET-4 (Vic) were purchased from American Peptide (Santa Clara, CA). SRTX-b and SRTX-c were those used in a previous study (20). 125I-labeled ET-1 (125I-ET-1) was prepared by iodination with Enzymobeads (Bio-Rad) and was purified as described (8). Bovine kidney NEP (0.4 mg/ml) was purified by Triton X-100 extraction followed by DEAE-Sepharose Fast...

We suggest for the first time, a dual role for γ-secretase in Alzheimer's disease. One role is the cleavage of the amyloid precursor protein for pathologic β-amyloid production and the other is to regulate microglia activity that is important for clearing neurotoxic β-amyloid deposits. Further studies of γ-secretase-mediated cellular pathways in microglia may provide useful insights into the development of Alzheimer's disease and other neurodegenerative diseases, providing future avenues for therapeutic intervention.

Evidence suggests that astrocytes play key roles in structural and functional organization of neuronal circuits. To understand how astrocytes influence the physiopathology of cerebellar circuits, we cultured cells from cerebella of mice that lack the gene. Mutations in are causative of the human cerebellar degenerative disease ataxia-telangiectasia. Cerebellar cultures grown from mice had disrupted network synchronization, atrophied astrocytic arborizations, reduced autophagy levels, and higher numbers of synapses per neuron than wild-type cultures. Chimeric circuitries composed of wild-type astrocytes and neurons were indistinguishable from wild-type cultures. Adult cerebellar characterizations confirmed disrupted astrocyte morphology, increased GABAergic synaptic markers, and reduced autophagy in compared with wild-type mice. These results indicate that astrocytes can impact neuronal circuits at levels ranging from synaptic expression to global dynamics.

Ataxia-telangiectasia (A-T) and

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