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OBJECTIVE: Fine touch sensing relies on peripheral-to-central neurotransmission of somesthetic percepts, as well as on active motion policies shaping tactile exploration. This paper presents a novel neuroengineering framework for robotic applications based on the multistage processing of fine tactile information in the closed action-perception loop. APPROACH: The integrated system modules focus on (i) neural coding principles of spatiotemporal spiking patterns at the periphery of the somatosensory pathway, (ii) probabilistic decoding mechanisms mediating cortical-like tactile recognition and (iii) decision-making and low-level motor adaptation underlying active touch sensing. We probed the resulting neural architecture through a Braille reading task. MAIN RESULTS: Our results on the peripheral encoding of primary contact features are consistent with experimental data on human slow-adapting type I mechanoreceptors. They also suggest second-order processing by cuneate neurons may resolve perceptual ambiguities, contributing to a fast and highly performing online discrimination of Braille inputs by a downstream probabilistic decoder. The implemented multilevel adaptive control provides robustness to motion inaccuracy, while making the number of finger accelerations covariate with Braille character complexity. The resulting modulation of fingertip kinematics is coherent with that observed in human Braille readers. SIGNIFICANCE: This work provides a basis for the design and implementation of modular neuromimetic systems for fine touch discrimination in robotics.

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The intact brain is continuously targeted by a wealth of stimuli with distinct spatio-temporal patterns which modify, since the very beginning of development, the activity and the connectivity of neuronal networks. In this paper, we used dissociated neuronal cultures coupled to microelectrode arrays (MEAs) to study the response of cortical neuron assemblies to low-frequency stimuli constantly delivered over weeks in vitro. We monitored the spontaneous activity of the cultures before and after the stimulation sessions, as well as their evoked response to the stimulus. During in vitro development, the vast majority of the cultures responded to the stimulation by significantly increasing the bursting activity and a widespread stabilization of electrical activity was observed after the third week of age. A similar trend was present between the spontaneous activity of the networks observed over 30 min after the stimulus and the responses evoked by the stimulus itself, although no significant differences in spontaneous activity were detected between stimulated and non-stimulated cultures belonging to the same preparations. The data indicate that the stimulation had a delayed effect modulating responsiveness capability of the network without directly affecting its intrinsic in vitro development.

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Dissociated cortical neurons from rat embryos cultured onto micro-electrode arrays exhibit characteristic patterns of electrophysiological activity, ranging from isolated spikes in the first days of development to highly synchronized bursts after 3-4 weeks in vitro. In this work we analyzed these features by considering the approach proposed by the self-organized criticality theory: we found that networks of dissociated cortical neurons also generate spontaneous events of spreading activity, previously observed in cortical slices, in the form of neuronal avalanches. Choosing an appropriate time scale of observation to detect such neuronal avalanches, we studied the dynamics by considering the spontaneous activity during acute recordings in mature cultures and following the development of the network. We observed different behaviors, i.e. sub-critical, critical or super-critical distributions of avalanche sizes and durations, depending on both the age and the development of cultures. In order to clarify this variability, neuronal avalanches were correlated with other statistical parameters describing the global activity of the network. Criticality was found in correspondence to medium synchronization among bursts and high ratio between bursting and spiking activity. Then, the action of specific drugs affecting global bursting dynamics (i.e. acetylcholine and bicuculline) was investigated to confirm the correlation between criticality and regulated balance between synchronization and variability in the bursting activity. Finally, a computational model of neuronal network was developed in order to interpret the experimental results and understand which parameters (e.g. connectivity, excitability) influence the distribution of avalanches. In summary, cortical neurons preserve their capability to self-organize in an effective network even when dissociated and cultured in vitro. The distribution of avalanche features seems to be critical in those cultures displaying medium synchronization among bursts and poor random spiking activity, as confirmed by chemical manipulation experiments and modeling studies.

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The quaternary structure of Molluscan hemocyanins is not still defined, in particular the spatial distribution and the structural subunits. It is important to establish the number and the nature of interations between functional units. Here we present two non-proteolytic methods for the depolymerization of hemocyanins. The results suggest that the carbohydrate moieties apparently play a basic role in the organization of the structural subunits.

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The gluthathione S-transferase gene of the atrazine-degrading bacterium Ochrobactrum anthropi (OaGST) encodes a single-subunit polypeptide of 201 amino acid residues (Favaloro et al. 1998, Biochem. J. 335, 573-579). RNA blot analysis showed that the gene is transcribed into an mRNA of about 800 nucleotides, indicating a monocistronic transcription of the OaGST gene. The modulation of OaGST in this bacterium, in the presence of different stimulants, was investigated. The level of expression of OaGST was detected both by measuring the mRNA level and by immunoblotting experiments. OaGST is a constitutive enzyme which is also inducible by several stimulants. In fact, atrazine caused an increase in the expression of OaGST even at concentrations which had no effect on growth rates of the bacteria. Moreover, the presence of other aromatic substrates of this bacterium, such as phenol and chlorophenols, leads to a marked enhancement in OaGST expression. In this case, the expression of OaGST was related to growth inhibition and membrane damage caused by these hydrophobic compounds, and to the adaptive responses of the cell membranes. On the other hand, toluene and xylene, two aromatic compounds not degradable by this bacterium, did not induce the OaGST expression. The same was observed for other stress conditions such as low pH, heat shock, hydrogen peroxide, osmotic stress, starvation, the presence of aliphatic alcohols or heavy metals. These results suggest a co-regulation of the OaGST gene by the catabolic pathways of phenols and chlorophenols in this bacterium. Therefore, OaGST could function as a detoxifying agent within the catabolism of these xenobiotics.

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Oral vaccination of 19 human adult volunteers with a killed trivalent E. coli vaccine induced an antibody response detectable either in sera and feces. Production of specific IgA immunoglobulins in the intestine was also observed. Antibody titres reached the highest levels 5-10 days after vaccination and were still detectable in the majority of volunteers about 2 months later.

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