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Cities can be incubators for innovation and key drivers of sustainable development. The conditionality for urban landscapes to be inclusive, will depend on the creativity for new orders and new str...

Although fat content affects the texture and flavor of meat and meat products, the fat discrimination thresholds are unknown. This study aimed to elucidate the discrimination threshold of fat in meat products using broth from chicken thigh meat as a meat taste model. In Experiment 1, triangle tests were conducted between 1%, 0.2%, 0.04%, and 0.008% (w/v) chicken oil-supplemented broth and broth without chicken oil. The results indicated the discrimination threshold to be between 0.04% and 0.008% (w/v). In Experiment 2, similar triangle tests were conducted using oil supplementation at 0.1%, 0.0333%, 0.0111%, and 0.0037% to refine the discrimination threshold. Logistic regression analysis revealed that the discrimination threshold of emulsified chicken oil in chicken broth was 0.0387% (w/v). We demonstrated that chicken oil made a sensory difference in chicken broth at a low concentration and indicates that the chicken oil strongly affects the sensory characteristics of chicken broth.

Xersotomia is associated with food avoidance and low nutritional assessment. This review seeks to document whether products called "saliva substitutes" or "artificial saliva" can really replace saliva in food oral processing. Pubmed and Science Direct were searched for articles using the keywords "saliva substitutes" and "artificial saliva." An advanced search was applied using the terms "xerostomia" and/or "food oral processing" and/or "eating" and/or "mastication" and/or "chewing" and/or "swallowing." The analysis methods and the inclusion criteria were documented in a protocol published in the International prospective register of systematic reviews (PROSPERO with the registration number CRD42019124585). The search included 43 articles, published between 1979 and 2017. Among the included studies, 17 were observational studies, 5 were pilot studies, 21 were crossover studies, and 14 of these studies were blinded. The Strobe score for the included articles varied from 7.5 to 20. The possible effects of the use of saliva substitutes on the ingestion function were poorly investigated. No evidence was based on physiological studies. It is unknown whether using a saliva substitute has an effect on the composition and rheological properties of the food bolus, on the lubrication of the oral and laryngeal mucosa or on both phenomena. Moreover, saliva substitutes were not formulated to improve food oral processing and most of them are flavored. New saliva substitutes and artificial saliva should be designed and formulated to improve food oral processing.

International audience; The gelatin used for the hard capsules manufacturing must meet strict dissolution specification to ensure the delivery of drugs at right time in the digestive tract. However, the environment of production and storage time affect the quality of gelatin dissolution. This study aimed to identify the mechanisms underlying the geographical environment of production and aging impact on the gelatin dissolution rate. Gelatins from 3 different origins of production (A, B & C), whose dissolution rate had been previously characterized, were analyzed by Raman microspectroscopy before and after aging. The principal component analysis (PCA) clearly separated the aged gelatins from non-aged ones. The spectra interpretation suggested the denaturation of gelatin triple-helices. In addition, the formation of cross-links such as dityrosine, glucosyl-galactosylhydroxylysinonorleucine and proteoglycan-like sugar adducts was strongly suspected. Whatever the gelatin aging state, PCA systematically separated the B-gelatins from A and C-gelatins. Pentosidine cross-link was likely to vary depending on the production origin. Finally, the quality of dissolution was discriminated for aged gelatins of A-origin: the non-compliant gelatins exhibited higher lipid content than the compliant ones.

International audience; People with poor oral status and/or neuromuscular deficiencies avoid eating meat because of chewing and swallowing difficulties. Consequently, they expose themselves to the risk of malnutrition and sarcopenia or nutrient deficiencies. To develop a new process for meat preparation, it is necessary to understand how meat is broken down during food oral processing to become a swallowable bolus. However, it is unknown whether the initial texture of meat impacts the meat bolus granulometry. As meat particles are fibrous, making the granulometry analysis with sieving methods is difficult. As the approach of meat bolus granulometry is necessary, it is of importance to control the methodological parameters that affect the measures. This study describes a procedure that allows granulometry analysis of shredded meat before and after in vitro mastication. Meat particles were dispersed in glycerol before image analysis. Granulometry curves were then drawn using generalized linear models, particle by particle, or after applying virtual sieves. Artificial meat bolus granulometry was also analyzed by manual sieving and the different methods were compared through several characteristics, including D50. Image analysis in glycerol preserves meat particles and allows particle distribution characterization and shape descriptors analysis. This method is well adapted to shredded meat and could be performed to evaluate the mastication of meat preparations adapted for deficient mastication.

International audience; Gelatin is a biopolymer produced worldwide through its dissolution rate is variable. During the manufacturing process, gelatin is exposed to high temperatures known to be responsible for cross-link formation. Moreover, bleaching agents such as hydrogen peroxide are added to lighten the gelatin, leading to oxidation reactions that form cross-links. Cross-links have been reported in the literature to be formed between amino acids and related to decreased gelatin dissolution. The variability of gelatin dissolution is important since gelatin is used in the pharmaceutical industry to make hard capsules which have to satisfy strict dissolution specifications. The objective of this study was to determine how the oxidative potential of gelatin may explain the variability of its dissolution. Amino acid composition was assessed by HPLC and gelatin chemical composition was studied with HRMAS-NMR. Iron and aldehyde contents were also measured. Cross-links involving aldehyde functions were strongly suspected to be formed with aging, as were desmosine-like and dityrosine cross-links. All these cross-links were formed during oxidation reactions that are also strongly suspected to occur during aging. In addition, the origin of production affects the oxidative potential of gelatins when considering their iron content. The amount of aldehyde functions, which reflects the oxidation state of gelatins, differed as a function of their origin of production. The dissolution rate of gelatins could be linked to their oxidative potential (iron content) and the aldehydic products of lipid oxidation. Interestingly, the causes for differences in dissolution varied as a function of their origin of production.

Gelatin is used to make hard capsules and has to meet strict dissolution specifications to guarantee homogeneous drug delivery. The aging of gelatin induces a decrease of its dissolution rate due to the formation of intra- and intermolecular cross-links. Cross-link formation has shown to be dependent on the environmental conditions of production, such as temperature and humidity, and therefore on the geographic origin of production. Gelatin structure consists of an amorphous phase (coil structure) and a crystal phase (triple-helixes) and is very sensitive to environmental changes. The present work aims at understanding the role and effects of structural changes during aging on gelatin dissolution, taking into account the origin of production. The molecular structure of pig skin gelatins from three different production sites of the same company were studied by differential scanning calorimetry, synchrotron circular dichroism and 1H nuclear magnetic resonance. It turned out that aging induced the melting of triple-helixes, an increase of random coils and, probably, β-turn conformations. The gelatin structure varied with the origin of production and thus affected the dissolution rate. Gelatins with non-compliant dissolution rates exhibited a higher amount of amorphous phase after aging than compliant gelatins. Although it was not possible to formulate any certain interpretation of the synchrotron circular dichroism results regarding gelatin dissolution, this technique is able to differentiate compliant dissolutions from non-compliant ones, even before gelatin aging.

International audience; The pharmaceutical industry requires narrow variability in the dissolution rate of hard gelatin capsules. To test this property, gelatin is aged in high temperature and humidity conditions to mimic gelatin shelf-life. These conditions induce cross-link formation in gelatin chains and change the properties of the capsule. Gelatin is produced worldwide in various environmental conditions. This study set out to evaluate the impact of geographic production origin on gelatin composition, before and after aging treatment, and on its dissolution properties. Non-aged and aged pig skin gelatins from three different production plants (A, B and C) were analyzed in raw granules and in powder by near infrared and fluorescence spectroscopy to identify the mechanisms of cross-link formation during aging. Gelatin composition (lipids, dityrosine, 3,4 dihydroxyphenylalanine (DOPA)) and oxidation level, before and after aging, varied according to production origin. The gelatin from C showed no variability in dissolution rate, while gelatins from A and B dissolved more slowly after aging. Near infrared spectroscopy results suggest that water was more strongly bound to the gelatin chains in the gelatins that yielded non-compliant dissolution test results. Non-compliant gelatin exhibited more CH2, usually assigned to lipids, and more aldehydes. Even before aging we found that non-compliant gelatins tended to fluoresce more at 344 nm under 280 nm excitation. These results open new perspectives for designing tools to predict the dissolution quality of freshly produced gelatins.

Early detection of liver metastases may improve the prognosis for successful treatment in dogs with primary tumors. Hepatobiliary-specific contrast agents have been shown to allow an increase in magnetic resonance imaging (MRI) detection of liver metastases in humans. The purpose of this prospective study was to test the feasibility for using one of these agents, gadobenate dimeglumine, to detect liver metastases in dogs. Ten consecutive dogs known to have a primary tumor were recruited for inclusion in the study. All dogs were scanned using the same protocol that included a T2-weighted respiratory-triggered sequence, T1 VIBE, diffusion-weighted imaging, and 3D-FLASH before and after dynamic injection of gadobenate dimeglumine contrast medium. Delayed imaging was performed less than 30 min after injection and up to 60 min in two cases. Histological analysis of liver lesions identified in delayed phases was performed for each case and confirmed metastatic origin. In all cases, lesion number detected in hepatobiliary contrast-enhanced sequences was statistically higher than in other sequences. Optimal lesion detection occurred with a 3D-FLASH sequence acquired in the transverse plane and less than 30 min after injection. Findings indicated that gabobenate dimeglumine enhanced MRI is a feasible technique for detecting liver metastases in dogs.

The magnetic resonance imaging features of a cauda equina paraganglioma in a 5-year-old dog are described. Imaging revealed a well-defined, strongly contrast-enhancing mass invading the adjacent vertebral body and infiltrating the intervertebral foramen bilaterally. Flow void, compatible with increased drainage veins around the mass, and macroscopically visible neovessels in contrast-enhanced magnetic resonance angiography, as reported in numerous human studies, were not visible in this single case. The tumor recurred despite aggressive surgery and radiotherapy. This neoplasm should be considered in the differential diagnosis of cauda equina abnormalities in dogs.

An abdominal mass was incidentally detected in a 12-year-old, neutered female, crossed breed dog. Abdominal ultrasonographic examination showed a well-delineated, irregular, heterogeneous mass that did not generate any distal acoustic shadowing. Transcutaneous US-guided biopsy of the mass were nonconclusive but raised the possibility of neoplasia. Surgery discovered a mass embedded in the omentum and a large quantity of surgical sponges were identified in cut section. To the authors' knowledge, this represents the first published case of gossypiboma casting no characteristic distal acoustic shadowing.

The gelatin is an animal protein that comes from collagen skin or bone. It is used in pharmaceutical industry to make hard capsules. The variations of environmental conditions of production applied to the collagen and therefore gelatin may have an impact on its chemical composition and, as a consequence, on the capsules properties (1). Indeed, previous studies revealed that the gelatin tends to form cross-links between its amino acids in high temperature and humidity conditions or in the presence of chemical compounds as aldehydes (sugars, lipids, oxidations) (2). To understand the impact of the processing on the chemical composition of the gelatin, pig skins gelatin produced under different environmental conditions were analyzed in High-Resolution Magic Angle Spinning NMR (HRMAS). 1D proton NMR spectra were acquired and analyzed using PCA (Principal Components Analysis). The environmental conditions of production were discriminated and the spectral zones contributing to separate them showed differences on the amino acids composition and their structural arrangement. However, the abundance of amino acids masked the possible presence of other molecules. In our conditions, the HRMAS, alone, did not allow identifying all the molecules as the cross-links, sugars or lipids, but suggested the formation of Desmosine-type cross-link under one environmental condition of production.

Pig skins gelatin results of the collagen solubilization. Gelatin is used, amongst other applications, in the pharmaceutical industry to make hard capsules. Raw gelatin, on delivery, contains about 8-12% of water [1] and is a partially-crystalline polymer being composed of an amorphous phase (coil structure with primary chains) and a crystal phase [2]. The latter consists of partially reformed triple-helices of collagen. The shelf life of hard capsules is evaluated through gelatin USP dissolution test after aging under high temperature and high humidity conditions. After aging, the dissolution rate of gelatin is variable: either unchanged or reduced. The decrease of gelatin dissolution rate is partially due to intra- and intermolecular crosslinks formation in the amorphous phase which stabilize that structure [3]. Water in gelatin plays a role of plasticizer in the amorphous phase and is either free or bound to the polymer chains. The state of water in gelatin has been studied but no relation with aging or dissolution rate has been established. The aim of the present study was to understand how aging affects the gelatin structure and its water mobility, and in addition, to identify structural differences according to gelatin dissolution rate. Thus, sixty pig skin gelatins with correct and non-correct dissolution rate were analyzed using Differential Scanning Calorimetry (DSC). Proton Nuclear Magnetic Resonance (1H-NMR) spectroscopy was used on a subgroup of twelve gelatin films to measure the spin-spin relaxation time (T2). For both methods, samples were taken before and after aging. Aging decreased the amount and the stability to heating of crystals phase and increased the amorphous phase. The water mobility was increased which can be explained by the denaturation of crystals releasing the trapped water from the triple-helices [4]. After aging, the gelatins which failed the dissolution test showed a higher amount of amorphous phase but the water mobility was not modified. These results showed that the structure plays a major role in the gelatin dissolution rate. In order to support this major role of structural characteristics of gelatin, the conformation of the single chains and multiple helices will be assessed using circular dichroism.

National audience; Deuxième prix du jury : Antoine VERNAY, qui effectue sa thèse intitulée « Rôle des interactions azote - eau du sol dans les rapports de compétition entre plantes suite à une éclaircie - Application à la régénération de jeunes plants de Chêne en compétition avec la Molinie »

Gelatin, extracted from the collagen of animal’s skins or bone, is used, amongst other applications, in the pharmaceutical industry to make hard capsules. Dried gelatin contains about 10-12 % water and is a partiallycrystalline polymer being composed of an amorphous phase (coil structure with primary chains) and a crystal phase. The latter consists of triple-helical fragments that are remnants of the triple-helices naturally found in collagen. Dried gelatin, placed under high temperature and high humidity conditions, a step called aging in industry, tends to loose water solubility in time. This is due to intra- and intermolecular crosslinks formation which modify and stabilize the structure. Aging is always applied to gelatin to test the shelf life of hard capsules. A wide range of variable environmental conditions (pH and time, temperature, humidity …) are observed in the production process and the storage of gelatin. Our goal was to understand how aging and the production sites affect the dried gelatin’s internal structure and if structural differences were involved in the dissolution variability. For that purpose, sixty pig skin gelatins from different origins of production with different dissolution characteristics (pass or fail the USP dissolution test) were analysed using Differential Scanning Calorimetry (DSC) as a function of aging. Significant differences in glass transition temperatures, melting temperatures and the enthalpies of melting were observed according to the origin of production of the samples (different factories). The results showed that the amount of crystals and their stability to heating decreased with aging while the amorphous phase increased. Gelatins from different production sites display different amounts of crystals and a differential stability of both amorphous and crystalline phases. After aging, the gelatins which failed the dissolution test showed a higher amount of amorphous phase. On the basis of these results, schemes of the gelatin structure were proposed.

Session 7 : Processing Meat and Meat Product Quality; National audience; The gelatin is an animal protein that comes from collagen skin or bone. It is used in pharmaceutical industry to make hard capsules. The variations of environmental conditions of production applied to the collagen and therefore gelatin may have an impact on its chemical composition and, as a consequence, on the capsules properties. Indeed, previous studies revealed that the gelatin tends to form cross-links between its amino acids in high temperature and humidity conditions or in the presence of chemical compounds as aldehydes (sugars, lipids, oxidations). To understand the impact of the processing on the chemical composition of the gelatin, pig skins gelatin produced under different environmental conditions were analyzed in High-Resolution Magic Angle Spinning NMR (HRMAS). 1D proton NMR spectra were acquired and analyzed using PCA (Principal Components Analysis). The environmental conditions of production were discriminated and the spectral zones contributing to separate them showed differences on the amino acids composition and their structural arrangement. However, the abundance of amino acids masked the possible presence of other molecules. In our conditions, the HRMAS, alone, did not allow identifying all the molecules as the cross-links, sugars or lipids, but suggested the formation of Desmosine-type cross-link under one environmental condition of production.

International audience; Gelatin obtained from pig skin constitutes about 50% of world production and is mainly composed of collagen extracted from skin by acidic baths and thermal treatments. The gelatin is used to make various products, notably hard gelatin capsules (HGC) which of varying solubility in water. This issue has been known for many years and has been, and remains, a subject of study and debate. The main reason for low gelatin dissolution rates is its tendency to form cross-links in the denatured collagen chains under specific conditions which stabilize the gel network and prevent dissolution. As it is extracted from animal tissues, gelatin may contain molecules other than collagen (sugars, lipids and other proteins) which may react with collagen chains to form covalent bonds. Although this biopolymer has been the subject of numerous publications, its structure and composition is not well defined. Indeed, there are many differences from an article to another. Consequently, the causes of HGC dissolution are not well identified and controlled.

Early detection of liver metastases may improve the prognosis for successful treatment in dogs with primary tumors. Hepatobiliary-specific contrast agents have been shown to allow an increase in magnetic resonance imaging (MRI) detection of liver metastases in humans. The purpose of this prospective study was to test the feasibility for using one of these agents, gadobenate dimeglumine, to detect liver metastases in dogs. Ten consecutive dogs known to have a primary tumor were recruited for inclusion in the study. All dogs were scanned using the same protocol that included a T2-weighted respiratory-triggered sequence, T1 VIBE, diffusion-weighted imaging, and 3D-FLASH before and after dynamic injection of gadobenate dimeglumine contrast medium. Delayed imaging was performed less than 30 min after injection and up to 60 min in two cases. Histological analysis of liver lesions identified in delayed phases was performed for each case and confirmed metastatic origin. In all cases, lesion number detected in hepatobiliary contrast-enhanced sequences was statistically higher than in other sequences. Optimal lesion detection occurred with a 3D-FLASH sequence acquired in the transverse plane and less than 30 min after injection. Findings indicated that gabobenate dimeglumine enhanced MRI is a feasible technique for detecting liver metastases in dogs.

Gadolinium-enhanced three-dimensional magnetic resonance angiography is a relatively new technique in the veterinary field. A mature dog with suspected patent ductus arteriosus underwent contrast-enhanced magnetic resonance angiography at 1.0 T with a three-dimensional fast low-angle shot (FLASH) gradient-echo technique. Qualitatively, three-dimensional images of the ductus were particularly clear with surface reconstructions, and ductus diameters were easy to assess in native images. Contrast-enhanced magnetic resonance angiography is a fast, relatively non-invasive procedure that could be particularly useful when non-surgical interventional procedures are anticipated for ductus occlusion.

Using two-dimensional electrophoresis, we have recently identified in human bronchoalveolar lavage fluid a novel protein, termed B166, with a molecular mass of 17 kDa. Here, we report the cloning of human and rat cDNAs encoding B166, which has been renamed AOEB166 for antioxidant enzyme B166. Indeed, the deduced amino acid sequence reveals that AOEB166 represents a new mammalian subfamily of AhpC/TSA peroxiredoxin antioxidant enzymes. Human AOEB166 shares 63% similarity with Escherichia coli AhpC22 alkyl hydroperoxide reductase and 66% similarity with a recently identified Saccharomyces cerevisiae alkyl hydroperoxide reductase/thioredoxin peroxidase. Moreover, recombinant AOEB166 expressed in E. coli exhibits a peroxidase activity, and an antioxidant activity comparable with that of catalase was demonstrated with the glutamine synthetase protection assay against dithiothreitol/Fe3+/O(2) oxidation. The analysis of AOEB166 mRNA distribution in 30 different human tissues and in 10 cell lines shows that the gene is widely expressed in the body. Of interest, the analysis of N- and C-terminal domains of both human and rat AOEB166 reveals amino acid sequences presenting features of mitochondrial and peroxisomal targeting sequences. Furthermore, human AOEB166 expressed as a fusion protein with GFP in HepG2 cell line is sorted to these organelles. Finally, acute inflammation induced in rat lung by lipopolysaccharide is associated with an increase of AOEB166 mRNA levels in lung, suggesting a protective role for AOEB166 in oxidative and inflammatory processes.

The magnetic resonance imaging features of a cauda equina paraganglioma in a 5-year-old dog are described. Imaging revealed a well-defined, strongly contrast-enhancing mass invading the adjacent vertebral body and infiltrating the intervertebral foramen bilaterally. Flow void, compatible with increased drainage veins around the mass, and macroscopically visible neovessels in contrast-enhanced magnetic resonance angiography, as reported in numerous human studies, were not visible in this single case. The tumor recurred despite aggressive surgery and radiotherapy. This neoplasm should be considered in the differential diagnosis of cauda equina abnormalities in dogs.

Co-direction de ce numéro spécial de la revue Livraison; Le numéro 14 de la revue d'art contemporain Livraison est dédié à une résidence qui s'est tenue à Belleville (Paris) en 2009-2010, réunissant quelque trente plasticiens, performeurs et écrivains issus de et/ou travaillant dans de nombreux pays du " Sud ". Il s'agit de la cinquième résidence d'artistes co-organisée par le collectif SCu2, dans le cadre de son projet Scénographies Urbaines (Douala, Alexandrie, Kinshasa, Johannesburg, Paris / 2000-2010). La particularité du projet réside dans ce que SCu2 nomme un principe d'inversion " Sud - Nord " des regards. Contrairement à ce qui s'est précédemment passé au sein des Scénographies Urbaines, ce sont ici des artistes de pays dits du " Sud " qui portent un regard sur un environnement urbain d'une ville du " Nord ". La condition postcoloniale aidant, ce genre de regard est commun dans la vie des villes à l'aube du 21ème siècle, mais (la condition postcoloniale aidant encore), lorsqu'il est affirmé, il tend à gêner, car il déplace des habitudes qui se veulent dominantes. En tant que tel, il est un facteur potentiel de polémique et c'est cela qui intéresse les éditeurs du numéro spécial de Livraison. Articuler un espace autour de regards comme ceux dont il est question ici revient à prendre (ou du moins à tenter de prendre) une position éthique et politique. Celle-ci peut se lire à plusieurs niveaux, comme un positionnement par rapport au contexte actuel qui prévaut en Europe et, simultanément, comme une manière de se positionner par rapport à ce que SCu2 souhaite être les échanges avec les artistes qui sont ses collaborateurs au sein des Scénographies Urbaines.

Retrocaval ureter and transposition of the caudal vena cava are each, rare developmental anomalies. We describe the usefulness of static fluid magnetic resonance urography and dynamic contrast-enhanced magnetic resonance urography in the diagnosis of these anomalies. Basic techniques, benefits, and drawbacks of magnetic resonance urography are presented.

Peroxiredoxin 5 (PRDX5) is a mammalian thioredoxin peroxidase ubiquitously expressed in tissues. Its role as antioxidant enzyme has been previously supported in different pathological situations. In this study, we determined the complete human PRDX5 genomic organization and isolated the 5'-flanking region of the gene. Human PRDX5 gene is composed of six exons and five introns similarly to other chordate PRDX5 genes. Several single nucleotide polymorphisms were identified. Six out of them have amino acid substitutions in protein-coding region. Analysis of the 5'-flanking region of human PRDX5 revealed the presence of a TATA-less promoter containing a canonical CpG island and several putative response elements for transcription factors. To analyze the regulatory mechanisms controlling human PRDX5 expression, we characterized the 5'-flanking region by cloning various segments of this region in front of a luciferase reporter sequence. Transfection in HepG2 cells indicate that the 5'-flanking region contains regulatory elements for constitutive expression of human PRDX5. Multiple transcription start sites were also identified by 5'-RACE-PCR in human liver. Moreover, although no corresponding proteins were reported, we present new alternative splicing variants encoded specifically by human PRDX5 gene. The characterization of human PRDX5 gene revealed the complexity of its regulation and a high variability of sequences that might be associated with pathological situations.

Fimbria-fornix lesions abolish the hippocampal electrophysiological activity time-locked to the theta rhythm and alter some functional characteristics of place cells. The present experiment investigated whether homotopic grafts of fetal septal cells can alleviate some of these alter-ations when combined with a polymeric hydrogel bridging a fimbria-fornix lesion-cavity. Eleven months after grafting surgery, unit recordings were obtained from hippocampal neurons of seven rats [two sham-operated (S), two lesion-only (L) and three grafted (G)] while they explored a radial maze. The lesions induced dramatic loss of hippocampal acetylcholinesterase(AChE)-positive reaction products. Surviving grafts were found in the three grafted rats and several AChE-positive processes could be observed in the polymeric hydrogel, as well as in the most dorsal portion of the hippocampal parenchyma. Of 168 recorded units, 132 were hippocampal interneurons (i.e., fired rapidly everywhere in the maze), and 36 were pyramidal place cells (i.e., fired only when the rat was in a specific location in the maze, the place field). The overall firing characteristics of either cell type were similar in S, L and G rats. However, while none of the interneurons recorded from L rats was found to fire rhythmically, a significant proportion of interneurons recorded from S and G rats had an activity pattern time-locked to the theta rhythm [S: 16/19 (84 %); G : 22/70 (31 %)]. In addition, the increase in firing activity observed in interneurons recorded from S rats when they were moving was disrupted in cells from L rats, but partially restored in cells from G rats. Concerning place cells, most (93 %) place fields in S rats were stable relative to extra-maze cues when the radial maze was rotated, while they followed the maze rotation in both L and G rats. Because of the low number of rats used, the present results should be considered with caution. Nevertheless, they indicate graft-induced recovery of some properties of hippocampal function following fimbria-fornix damage, and suggest that homotopic transplants of projection neurons may foster some func-tional recovery when provided with a biomaterial allowing the host or grafted neurons to cross the lesion cavity.

To examine the regeneration capacity of dorsal septohippocampal neurons in the presence of an artificial growth-promoting substrate, biocompatible polymeric hydrogels were implanted between the septum and the hippocampus in a fimbria-fornix lesion cavity. Unmodified (control) or aminosugar-containing (glucosamines or N-acetyl-glucosamines) hydrogels were implanted immediately or ten days after the lesions. Six months later, brain sections were processed for cresyl-violet, acetylcholinesterase, and immunocytochemical (glial fibrillary acidic protein, protein S100, neurofilaments, laminin, fibronectin) staining. All hydrogels were well integrated in the brain, constituting a stable bridge between the septum and the hippocampus. Weak gliosis occasionally surrounded the hydrogel in rats from the immediate-implantation group, whereas a more pronounced gliosis was observed in those from the delayed-implantation group. The hydrogels contained blood vessels and were invaded by host cells including astrocytes. Astrocytes formed a loose tissue network filling the porous structure of the hydrogels. Within the hydrogels, laminin-, fibronectin- or neurofilaments-immunopositive networks were also observed. Moreover, numerous acetylcholinesterase-positive fibers penetrated into the hydrogels from the septal, cortical and striatal areas. Fibre penetration was most important in the N-acetylglucosamines-containing hydrogels. Despite these features, the hippocampus failed to show any increase of acetylcholinesterase-staining as compared to that seen in lesion-only rats. These results confirm the regeneration capacity of severed septohippocampal neurons into polymeric substrates used as a bridge inserted in a fimbria-fornix lesion cavity. As such, biomaterials might be of clinical interest not only in the case of spinal cord sections, but also in cases of brain trauma.

International audience