transcriptional regulation of nuclear genes controlling plastid differentiation in tomato

ABSTRACTSeveral mechanisms which control transcription of genes encoding plastidial proteins in tomato are overviewed: light, the circadian clock, photooxidative stress and tissue-specific factors. Protein factors binding promoters of genes responding to such stimuli are described, as well as their abundance during the various phases of the light-dark cycle. Finally, the structure and regulation of a novel class of genes encoding plastidial enzymes, controlling carotenoid biosynthesis, are describe

Determinants of synaptic integration and heterogeneity in rebound firing explored with data-driven models of deep cerebellar nucleus cells

Significant inroads have been made to understand cerebellar cortical processing but neural coding at the output stage of the cerebellum in the deep cerebellar nuclei (DCN) remains poorly understood. The DCN are unlikely to just present a relay nucleus because Purkinje cell inhibition has to be turned into an excitatory output signal, and DCN neurons exhibit complex intrinsic properties. In particular, DCN neurons exhibit a range of rebound spiking properties following hyperpolarizing current injection, raising the question how this could contribute to signal processing in behaving animals. Computer modeling presents an ideal tool to investigate how intrinsic voltage-gated conductances in DCN neurons could generate the heterogeneous firing behavior observed, and what input conditions could result in rebound responses. To enable such an investigation we built a compartmental DCN neuron model with a full dendritic morphology and appropriate active conductances. We generated a good match of our simulations with DCN current clamp data we recorded in acute slices, including the heterogeneity in the rebound responses. We then examined how inhibitory and excitatory synaptic input interacted with these intrinsic conductances to control DCN firing. We found that the output spiking of the model reflected the ongoing balance of excitatory and inhibitory input rates and that changing the level of inhibition performed an additive operation. Rebound firing following strong Purkinje cell input bursts was also possible, but only if the chloride reversal potential was more negative than −70 mV to allow de-inactivation of rebound currents. Fast rebound bursts due to T-type calcium current and slow rebounds due to persistent sodium current could be differentially regulated by synaptic input, and the pattern of these rebounds was further influenced by HCN current. Our findings suggest that active properties of DCN neurons could play a crucial role for signal processing in the cerebellum

In vitro behaviour of hybrid lipid/chitosan nanoparticles for the oral delivery of heparin

Enhanced oral bioavailability of poorly aqueous soluble drugs encapsulated in a number of lipid-based formulations, including emulsions, micellar systems, self-emulsifying drug delivery systems, liposomes and solid lipid nanoparticles (SLN) via lymphatic delivery has been documented (Ali Khan et al. 2013). In the present work, SLN were designed for the oral delivery of heparin in order to take advantage from the lymphatic intestinal transport pathway. In order to improve the incorporation of a high hydrophilic compound in a lipid matrix, heparin was “insolubilized” by the coupling with chitosan. In this aim we have developed chitosan/heparin Polyelectrolyte complexes (PEC). Such as systems are able to complex stably heparin (up to pH < 6.8) (Paliwal R. et al. 2012) and after pelletization by centrifugation were embedded in SLN obtaining a hybrid system lipid/chitosan nanoparticles (PEC-SLN). Since no in-vitro lymphoid tissue is currently available, CaCo-2 cell monolayer could be considered an alternative in vitro model to be used as a screening tool before animal studies are undertaken (Ali Khan et al. 2013). In this work naked PEC, hybrid PEC-SLN as well as heparin-loaded SLN (Hep-SLN) were characterized as regard as the size, Z-potential, morphology, drug loading and in vitro drug release. Moreover, FITC labeled PEC along with Red Nile labeled PEC-SLN and empty SLN were evaluated on CaCo-2 cell line in order to study their cytotoxicity by MTT test and their cell internalization ability by cytometric and confocal analysis. Finally, transepithelial electrical resistance (TEER) was measured on NCM460 cells in order to evaluate the integrity of the tight junctions