87,172 research outputs found
Changes in eeg power spectral density and cortical connectivity in healthy and tetraplegic patients during a motor imagery task
Get PDFKnowledge of brain connectivity is an important aspect of modern neuroscience, to understand how the brain realizes its functions. In this work, neural mass models including four groups of excitatory and inhibitory neurons are used to estimate the connectivity among three cortical regions of interests (ROIs) during a foot-movement task. Real data were obtained via high-resolution scalp EEGs on two populations: healthy volunteers and tetraplegic patients. A 3-shell Boundary Element Model of the head was used to estimate the cortical current density and to derive cortical EEGs in the three ROIs. The model assumes that each ROI can generate an intrinsic rhythm in the beta range, and receives rhythms in the alpha and gamma ranges from other two regions. Connectivity strengths among the ROIs were estimated by means of an original genetic algorithm that tries to minimize several cost functions of the difference between real and model power spectral densities. Results show that the stronger connections are those from the cingulate cortex to the primary and supplementary motor areas, thus emphasizing the pivotal role played by the CMAL during the task. Tetraplegic patients exhibit higher connectivity strength on average, with significant statistical differences in some connections. The results are commented and virtues and limitations of the proposed method discussed. Copyright © 2009 Filippo Cona et al
Molecular basis for the binding of competitive inhibitors of maize polyamine oxidase
No full textMaize polyamine oxidase (MPAO), the only member of the polyamine oxidase (PAO) family
whose three-dimensional structure is known, is characterized by a 30 Å long U-shaped catalytic tunnel
located between the substrate binding domain and the FAD. To shed light on the MPAO ligand binding
mode, we studied the inhibition properties of linear diamines, agmatine, prenylagmatine (G3), G3 analogues,
and guazatine, and analyzed the structural determinants of their biological activity. Linear diamines
competitively inhibited MPAO, with the inhibitory activity increasing as a function of the number of
methylene groups. With regard to the guanidino competitive inhibitors, including agmatine, G3, and G3
analogues, the presence of a hydrophobic substituent constitutes the principal factor influencing MPAO
inhibition, as the addition of a hydrophobic substituent to the guanidino group of both G3 and G3 analogues
greatly increases the inhibitory activity. Moreover, results obtained by a molecular modeling procedure
indicated that in their preferred orientation, G3 analogues point the ammonium group toward the narrow
entrance of the tunnel, while the terminal hydrophobic group is located within the large entrance. The
high binding affinity for MPAO exhibited by G3 and G3 analogues bearing a prenyl group as a substituent
on the guanidino moiety is in agreement with the observation that the prenyl group binds in a welldefined
hydrophobic pocket, mainly formed by aromatic residues. Finally, docking simulations performed
with the charged and uncharged forms of MPAO inhibitors indicate that the stereoelectronic properties of
the MPAO active site are consistent with the binding of inhibitors in the protonated form
I boschi del Parco Nazionale del Vesuvio
No full textIl Parco nazionale del Vesuvio è caratterizzato da un basso grado di naturalità, e da comunità nel complesso giovani, con dinamiche che nel complesso si sono sviluppate per un arco di 2 millenni. Diverse specie arboree sono state introdotte e coltivate dall'uomo sin dall'antichità, mentre altre sono relativamente recenti. Pinete e castagneti possono essere considerati i due paesaggi forestali principali
A neural mass model to simulate different rhythms in a cortical region
Get PDFAn original neural mass model of a cortical region has been used to investigate the origin of EEG rhythms. The model consists of four interconnected neural populations: pyramidal cells, excitatory interneurons and inhibitory interneurons with slow and fast synaptic kinetics, GABA A,slow and GABA A,fast respectively. A new aspect, not present in previous versions, consists in the inclusion of a self-loop among GABA A,fast interneurons. The connectivity parameters among neural populations have been changed in order to reproduce different EEG rhythms. Moreover, two cortical regions have been connected by using different typologies of long range connections. Results show that the model of a single cortical region is able to simulate the occurrence of multiple power spectral density (PSD) peaks; in particular the new inhibitory loop seems to have a critical role in the activation in gamma (γ) band, in agreement with experimental studies. Moreover the effect of different kinds of connections between two regions has been investigated, suggesting that long range connections toward GABA A,fast interneurons have a major impact than connections toward pyramidal cells. The model can be of value to gain a deeper insight into mechanisms involved in the generation of rhythms and to provide better understanding of cortical EEG spectra
<i>PKC-θ<sup>−/−</sup></i> mice are resistant to ConA-induced hepatitis.
No full text<p><i>PKC-θ<sup>−/−</sup></i> mice and age and sex matched WT mice were challenged with a lethal dosage of ConA (25 mg/kg). Survival was monitored every 3 h. N = 7, from 2 independent experiments. A) Survival curve of mice challenged with ConA. B) Serum ALT and AST levels 6 h after ConA challenge. C) Levels of the indicated cytokines in serum 1 h after ConA challenge. D) Levels of the indicated cytokines in serum 2 h after ConA challenge. E) Levels of the indicated cytokines in serum 6 h after ConA challenge. F) Levels of serum OPN different times after ConA challenge. (*, P<0.05; **, P<0.01; ***, P<0.001).</p
Cortical rhythms induced by TMS stimulation: analysis with a neural mass model
No full textKnowledge of cortical rhythms represents an important aspect of modern neuroscience, to understand how the brain realizes its functions. Recent data suggest that different regions in the brain may exhibit distinct rhythms when perturbed by Transcranial Magnetic Stimulation (TMS) (Rosanova et al., 2009) and that these rhythms can change due to the connectivity among regions. In this context, neural mass models can be very useful to simulate specific aspects of electrical brain activity and, above all, to analyze and identify the overall frequency content of EEG in a cortical region of interest (ROI). In this work we implemented a model of connectivity among cortical regions (Ursino, Cona and Zavaglia, 2010) to fit the impulse responses in three ROIs during an experiment of TMS stimulation. In particular we investigated Brodmann Area (BA) 19 (occipital lobe), BA 7 (parietal lobe) and BA 6 (frontal lobe). Results show that the model can reproduce the natural rhythms of the three regions quite well, acting on a few internal parameters. Moreover, model can explain most rhythm changes induced by stimulation of another region, by using just a few long-range connectivity parameters among ROIs.
A barley polyamine oxidase isoform with distinct structural features and subcellular localization
No full textTwo cDNAs encoding polyamine oxidase (PAO) isoforms
(BPAO1 and BPAO2) and the corresponding gene copies
were isolated from barley cultivar Aura. Gene organization
is not conserved between these two nonallelic coding
sequences. Both precursor proteins include a cleavable
N-terminal leader of 25 amino acids. N-terminal sequencing
of PAO purified from barley seedlings reveals a unique
amino-acid sequence corresponding to the BPAO2
N-terminus as predicted from the corresponding cDNA.
BPAO2 has been purified, characterized and compared to
maize PAO (MPAO), the best characterized member of this
enzyme class. The two proteins show different pH optima
for catalytic activity, Km and Vmax values with spermidine
and spermine as substrates. Molecular modelling of BPAO2
reveals the same global fold as in MPAO. However,
substitution of the active site residue Phe403 by a tyrosine,
provides a rationale for the different catalytic properties of
the two enzymes. In barley leaves PAO-specific activity is
higher in isolated mesophyll protoplasts than in the
extracellular fluids, whereas in maize the reverse is true.
The C-terminus of BPAO2 shows homology with the
endoplasmic reticulum retention signal that might be
responsible for the subcellular localization observed. We
conclude that BPAO2 is a symplastic PAO in barley
mesophyll cells. Production of BPAO2 mRNA and the
corresponding protein is induced by light, and has a
different pattern of accumulation in leaves and coleoptile
Influence of ozone and ultraviolet (UV-C) radiation on in vivo and in vitro tobacco culture
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