Expression of long-term depression underlies visual recognition memory

The modifications occurring in the brain during learning and memory are still poorly understood but may involve long-lasting changes in synaptic transmission (synaptic plasticity). In perirhinal cortex, a lasting decrement in neuronal responsiveness is associated with visual familiarity discrimination, leading to the hypothesis that long-term depression (LTD)-like synaptic plasticity may underlie recognition memory. LTD relies on internalization of AMPA receptors (AMPARs) through interaction between their GluR2 subunits and AP2, the clathrin adaptor protein required for endocytosis. We demonstrate that a peptide that blocks interactions between GluR2 and AP2 blocks LTD in perirhinal cortex in vitro. Viral transduction of this peptide in perirhinal cortex produced striking deficits in visual recognition memory. Furthermore, there was a deficit of LTD in perirhinal cortex slices from virally transduced, recognition memory-deficient animals. These results suggest that internalization of AMPA receptors, a process critical for the expression of LTD in perirhinal cortex, underlies visual recognition memory.     

Peptides from Liza aurata: Natural Source Attenuate Paracetamol Induced Nephrotoxicity by Modulation of the Inflammatory Response and DNA Damage

International Journal of Peptide Research and Therapeutics - The present study investigates the nephroprotective and the molecular mechanisms effects of Liza aurata protein hydrolysates (LAPHs)...     

2,4-D induction of somaclonal variations in in vitro grown date palm (Phoenix dactylifera L. cv Barhee)

Plant Cell, Tissue and Organ Culture (PCTOC) - The present study is a part of a program designed at improving the date palm, Phoenix dactylifera L. cv. Barhee, through induced somaclonal variation....     

Divergence in symbiotic interactions between same genotypic PCR–RFLP Frankia strains and different Casuarinaceae species under natural conditions

The symbiotic interactions between Frankia strains and their associated plants from the Casuarinaceae under controlled conditions are well documented but little is known about these interactions under natural conditions. We explored the symbiotic interactions between eight genotypically characterized Frankia strains and five Casuarinaceae species in long-term field trials. Characterization of strains was performed using the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) for the nifD – nifK intergenic transcribed spacer (ITS) and 16S–23S ITS. Assessments of the symbiotic interactions were based on nodulation patterns using nodule dry weight and viability, and on actual N₂ fixation using the δ¹⁵N method. The PCR–RFLP patterns showed that the analyzed strains belonged to the same genotypic group (CeD group), regardless of the host species and environment of origin. The nodule viability index is introduced as a new tool to measure the viability of perennial nodules and to predict their effectiveness. The host Casuarinaceae species was a key factor influencing both the actual N₂-fixing activity of the associated Frankia strain and the viability of nodules within a location. This is the first study providing information on the symbiotic interactions between genotypically characterized Frankia strains and actinorhizal plants under natural conditions. The results revealed a way to improve a long-term management of the Casuarinaceae symbiosis.     

Differential tolerance to iron deficiency of chickpea varieties and Fe resupply effects

The consequences of direct iron deficiency and iron resupply were evaluated during development stages of two Tunisian chickpea varieties (INRAT88 and Chetoui) cultivated in continuously aerated solution with or without 20 muM Fe. The chlorosis score was estimated during culture. Growth parameters, chlorophyll concentration, acidification capacity and Fe concentration were measured every three days during the 21-day treatment. After three weeks of treatment, the chlorosis index was 3-fold higher in Chetoui than in INRAT88, and a considerable decrease of chlorophyll concentration was observed in Chetoui plants since the 6th day of -Fe deprivation. Iron deficiency significantly inhibited whole-plant biomass deposition in both varieties. However, the growth reduction appeared earlier, and was more pronounced in Chetoui than in INRAT88. The whole-plant Fe content decreased dramatically under deficient conditions, and we note an Fe enrichment in shoots at the expense of roots. The sensitivity of Chetoui as compared to INRAT88 was confirmed by the behaviour of resupplied (-Fe/+Fe) plants. In fact, the addition of iron to deficient plants had no significant effect in Chetoui, whereas it led to a total recovery in INRAT88. The capacity of INRAT88 to maintain plant growth and to preserve adequate chlorophyll synthesis under limited iron conditions is related to its better Fe-use efficiency, in addition to its capacity to rapidly recover from this stress.     

Stability of Secondary and Tertiary Structures of Virus-Like Particles Representing Noroviruses: Effects of pH,Ionic Strength,and Temperature and Implications for Adhesion to Surfaces

Loss of ordered molecular structure in proteins is known to increase their adhesion to surfaces. The aim of this work was to study the stability of norovirus secondary and tertiary structures and its implications for viral adhesion to fresh foods and agrifood surfaces. The pH, ionic strength, and temperature conditions studied correspond to those prevalent in the principal vehicles of viral transmission (vomit and feces) and in the food processing and handling environment (pasteurization and refrigeration). The structures of virus-like particles representing GI.1, GII.4, and feline calicivirus (FCV) were studied using circular dichroism and intrinsic UV fluorescence. The particles were remarkably stable under most of the conditions. However, heating to 65°C caused losses of β-strand structure, notably in GI.1 and FCV, while at 75°C the α-helix content of GII.4 and FCV decreased and tertiary structures unfolded in all three cases. Combining temperature with pH or ionic strength caused variable losses of structure depending on the particle type. Regardless of pH, heating to pasteurization temperatures or higher would be required to increase GII.4 and FCV adhesion, while either low or high temperatures would favor GI.1 adhesion. Regardless of temperature, increased ionic strength would increase GII.4 adhesion but would decrease GI.1 adhesion. FCV adsorption would be greater at refrigeration, pasteurization, or high temperature combined with a low salt concentration or at a higher NaCl concentration regardless of temperature. Norovirus adhesion mediated by hydrophobic interaction may depend on hydrophobic residues normally exposed on the capsid surface at pH 3, pH 8, physiological ionic strength, and low temperature, while at pasteurization temperatures it may rely more on buried hydrophobic residues exposed upon structural rearrangement.