Retinoic Acid Restores Adult Hippocampal Neurogenesis and Reverses Spatial Memory Deficit in Vitamin A Deprived Rats

A dysfunction of retinoid hippocampal signaling pathway has been involved in the appearance of affective and cognitive disorders. However, the underlying neurobiological mechanisms remain unknown. Hippocampal granule neurons are generated throughout life and are involved in emotion and memory. Here, we investigated the effects of vitamin A deficiency (VAD) on neurogenesis and memory and the ability of retinoic acid (RA) treatment to prevent VAD-induced impairments. Adult retinoid-deficient rats were generated by a vitamin A-free diet from weaning in order to allow a normal development. The effects of VAD and/or RA administration were examined on hippocampal neurogenesis, retinoid target genes such as neurotrophin receptors and spatial reference memory measured in the water maze. Long-term VAD decreased neurogenesis and led to memory deficits. More importantly, these effects were reversed by 4 weeks of RA treatment. These beneficial effects may be in part related to an up-regulation of retinoid-mediated molecular events, such as the expression of the neurotrophin receptor TrkA. We have demonstrated for the first time that the effect of vitamin A deficient diet on the level of hippoccampal neurogenesis is reversible and that RA treatment is important for the maintenance of the hippocampal plasticity and function

AB type polyaddition route to thermoplastic polyurethanes from fatty acid derivatives

Naturally occurring oleic acid and undecylenic acid derivatives were successfully utilized to synthesize a series of new semi-crystalline polyurethanes via the AB-type polycondensation approach. A set of four novel AB-type monomers was prepared via the use of environmentally benign thiol-ene chemistry. These AB-type monomers were self-polycondensed (with or without catalyst) in two ways: (a) the hydroxyl-acyl azide approach and (b) the melt transurethane method in order to obtain reasonably high molar mass polyurethanes. The resulting polymers were thoroughly characterized by NMR, SEC, DSC, TGA and MALDI-TOF mass spectroscopy. The MALDI-TOF analysis confirmed the formation of linear polyurethanes with a trace amount of macrocycles. All the polyurethanes exhibited fair thermal stability with no significant weight loss below 200 degrees C. The polyurethanes based on undecylenic acid as a monomer displayed a thermoplastic behavior with well-identified melting transitions. Further, DSC analysis revealed that polyurethanes prepared from undecylenic acid by different methods showed different glass and melting transitions. Two glass transition temperatures due to soft and hard segments were observed for polyurethanes synthesized from oleic acid derivatives, indicating a phase-separated morphology

Novel fatty acid based di-isocyanates towards the synthesis of thermoplastic polyurethanes

Fatty acid derivatives have been successfully transformed into diisocyanates via a non-phosgene and green method. The structure of these novel diisocyanates was confirmed through FTIR and H-1 NMR spectroscopies. These diisocyanates were reacted with commercially available and fatty acid based diols to obtain partially and fully bio-based polyurethanes respectively. The selected diols were of various structural features: with linear methylene spacers from 3 to 12 units, with sulfur-containing unit, ester linkages or cyclo-aliphatic units. The polyurethanes obtained were thoroughly characterized by FTIR, H-1 NMR spectroscopy, SEC studies, DSC and TGA experiments. Most of the polyurethanes were semi-crystalline in nature with well-identified melting transitions. However, due to plasticization and/or conformational issues, insertion of methylene dangling chains or cyclic moieties imparted amorphous feature to the polyurethanes. The polyurethanes displayed fair thermal stability with no significant weight loss below 235 degrees C

Aliphatic polycarbonates and poly(ester carbonate)s from fatty acid derived monomers

Fatty acid derivatives were efficiently used as starting materials for the synthesis of polycarbonates and poly(ester carbonate)s. A novel AB-type self-condensable monomer, ethyl(9-hydroxy-10-methoxyoctadecyl)carbonate (EHMOC) and a dicarbonate monomer, 4-[(ethoxycarbonyl)oxy]butyl-12-[(ethoxycarbonyl)oxy]octadec-9-enoate (EOBEOE) were prepared from oleyl alcohol and ricinoleic acid, respectively. Of these, EHMOC was polymerized by the alcohol-carbonate exchange self-polycondensation approach, while EOBEOE was polycondensed with various biobased diols to give polycarbonates and poly(ester carbonate) s, respectively. The monomers and polymers were well characterized by FTIR and H-1-NMR spectroscopy. The C-13-NMR spectroscopy revealed the formation of randomly distributed sequences in the poly(ester carbonate) s due to the carbonate interchange reaction. An unexpected formation of polyricinoleate was observed and confirmed by NMR and MALDI-TOF spectroscopy. Most of the polymers displayed good thermal stability with the temperature at 10% weight loss in the range 273-325 degrees C. Due to the presence of aliphatic segments, these materials exhibit very low glass transition temperature

Novel green fatty acid-based bis-cyclic carbonates for the synthesis of isocyanate-free poly(hydroxyurethane amide)s

Fatty acid-based bis-cyclic 5-membered carbonates containing amide linkages were prepared from methyl 10-undecenoate. The reaction in bulk of these bio-based carbonates with a series of di-amines led to poly(hydroxyurethane amide)s with molar masses up to 31 000 g mol(-1). As expected, the so-formed bio-based thermoplastic poly(hydroxyurethane)s exhibit amorphous to semi-crystalline features with respect to the chemical structure of the monomers used

Glycolipids as a source of polyols for the design of original linear and cross-linked polyurethanes

Two novel sugar-based fatty ester polyols were synthesized by selective transesterification of epoxidized methyl or ethyl oleate with unprotected methyl alpha-D-glucopyranoside and sucrose respectively, followed by hydrolysis of the epoxide moiety. The so-formed polyols were then used as polyurethane (PU) precursors in the polyaddition with isophorone diisocyanate (IPDI) in the presence of dibutyl tin dilaurate (DBTDL) as a catalyst. Interestingly, the reactivity of the hydroxyl functions attached to the sugar and to the fatty ester chain moieties respectively could be discriminated with respect to the solvent used, enabling the synthesis of either linear or cross-linked PUs. The linear PUs were studied by means of FTIR, H-1 NMR spectroscopy and size exclusion chromatography, SEC. The thermo-mechanical properties of these original PUs bearing pendant or intramolecular sugar units were also analyzed by differential scanning calorimetry, DSC