Biomedical subjects

Paolo Bonifazi

Publications and source records attributed to Paolo Bonifazi.

4 recordsLinked to original sources

PubMed2007

Sensitive and selective determination of glutathione in probiotic bacteria by capillary electrophoresis-laser induced fluorescence.

Glutathione (GSH) is a thiol with an important function in protecting tissue against the oxidative stress which has been related to carcinogenesis in the colon. For this reason the development of probiotic species producing glutathione could be of great interest. To determine the glutathione content of some probiotic bacteria of the Bifidobacterium and Lactococcus genera, a very sensitive and selective analytical method based on capillary electrophoresis coupled to laser-induced fluorescence detection has been developed. Pretreatment of cell-lysate samples is very simple--precipitation of protein with acetonitrile in 1:2 volume ratio. The fluorophore 5-iodoacetamidofluorescein (5-IAF) was chosen for glutathione derivatisation; it reacts with thiols at pH 12.5, forming a fluorescent adduct which is excited by a laser at 488 nm for detection. The reaction conditions optimised were temperature, time, and 5-IAF/GSH molar ratio. Electrophoresis was performed with a carbonate buffer (25 mmol L(-1), pH 9.8) as background electrolyte and a voltage of 30 kV; an electrophoretic run was complete in less than 7 min. There was a good linear relationship between concentration and response in the range 2.5-500 ng mL(-1) and the LOD was 0.5 ng mL(-1). The glutathione content of probiotic cells was determined by using the standard additions method to reduce matrix effects. The method was fully validated and shown to be of suitable sensitivity and selectivity for determination of GSH in probiotic cell lysates.

Acetonitriles↗

PubMed2006

Embryonic stem cell-derived neurons form functional networks in vitro.

Embryonic stem (ES) cells provide a flexible and unlimited source for a variety of neuronal types. Because mature neurons establish neuronal networks very easily, we tested whether ES-derived neurons are capable of generating functional networks and whether these networks, generated in vitro, are capable of processing information. Single-cell electrophysiology with pharmacological antagonists demonstrated the presence of both excitatory and inhibitory synaptic connections. Extracellular recording with planar multielectrode arrays showed that spontaneous bursts of electrical activity are present in ES-derived networks with properties remarkably similar to those of hippocampal neurons. When stimulated with extracellular electrodes, ES-derived neurons fired action potentials, and the evoked electrical activity spread throughout the culture. A statistical analysis indicated that ES-derived networks discriminated between stimuli of different intensity at a single trial level, a key feature for an efficient information processing. Thus, ES-derived neurons provide a novel in vitro strategy to create functional networks with defined computational properties.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed2005

Toward the neurocomputer: image processing and pattern recognition with neuronal cultures.

Information processing in the nervous system is based on parallel computation, adaptation and learning. These features cannot be easily implemented on conventional silicon devices. In order to obtain a better insight of how neurons process information, we have explored the possibility of using biological neurons as parallel and adaptable computing elements for image processing and pattern recognition. Commercially available multielectrode arrays (MEAs) were used to record and stimulate the electrical activity from neuronal cultures. By mapping digital images, i.e., arrays of pixels, into the stimulation of neuronal cultures, a low and bandpass filtering of images could be quickly and easily obtained. Responses to specific spatial patterns of stimulation were potentiated by an appropriate training (tetanization). Learning allowed pattern recognition and extraction of spatial features in processed images. Therefore, neurocomputers, (i.e., hybrid devices containing man-made elements and natural neurons) seem feasible and may become a new generation of computing devices, to be developed by a synergy of Neuroscience and Material Science.

Animals↗

PubMed2005

Statistical properties of information processing in neuronal networks.

Information processing and coding were analysed in dissociated hippocampal cultures, grown on multielectrode arrays. Multisite stimulation was used to activate different neurons and pathways of the network. The neural activity was binned into firing rates and the variability of the firing of individual neurons and of the whole population was analysed. In individual neurons, the timing of the first action potential (AP) was rather precise from trial to trial, whereas the timing of later APs was much more variable. Pooling APs in an ensemble of neurons reduced the variability of the response and allowed stimuli varying in intensity to be distinguished reliably in a single trial. A similar decrease of variability was observed pooling the first evoked APs in an ensemble of neurons. The size of the neuronal pool (approximately 50-100 neurons) and the time bin (approximately 20 ms) necessary to provide reproducible responses are remarkably similar to those obtained in in vivo preparations and in small nervous systems. Blockage of excitatory synaptic pathways mediated by NMDA receptors improved the mutual information between the evoked response and stimulus properties. When inhibitory GABAergic pathways were blocked by bicuculline the opposite effect was obtained. These results show how ensemble averages and an appropriate balance between inhibition and excitation allow neuronal networks to process information in a fast and reliable way.

Action Potentials↗