Re-dispersible dry emulsions stabilised with protein polysaccharide conjugates

Recently the need for more functional food products has opened new fields of research on the subject. Dry emulsions present an opportunity not only for the production of functional ingredients but also for the reduction of industrial costs. However drying emulsions comes with limitations fixed by both the composition of the emulsified product and the drying process used. In the case of reconstitution by rehydration it is important that the emulsified product keep the same textural properties to be a viable commercial product. The work presented in this thesis investigates the use of promising emulsifiers for the drying and rehydration of emulsions. Maillard conjugates also called glycoconjugates have been used for the production of oil-in-water emulsions. Because of the thicker membrane they form at the oil/water interface, Maillard conjugates are potential candidates for the stabilisation of emulsions destined to be dried. The key challenge when drying complex structures rests in their preservation. The strength and the nature of the interface are two of the parameters that need to be taken into account when attempting to dry an emulsion. Due to the constant relationship between product formulation and drying process this study proposes a combination of formulation development and process engineering. To carry out this project conjugates were produced, analysed and tested in model emulsions. Conjugate stabilised oil-in-water emulsions with identical formulation (20% w/w sunflower oil, 80% w/w water) were produced and analysed in different scenarii. Subsequently their ability to be dried and rehydrated was assessed using freeze-drying and spray-drying. The results showed that the conjugates particle size was highly dependent on the pH of the conjugation reaction. Smaller particle size could be produced without affecting the yield of reaction. The enhanced stability of the systems to external stresses was confirmed. However experiments using a charged polysaccharide showed that at pH close to pKa the stability of the system was challenged. All emulsions showed good stability to drying at different emulsifier concentrations. The textural components (viscosity and friction coefficient) were well preserved. The adjustment of the formulation by addition of additives significantly improved the stability of the systems to freeze-drying and spray drying. Overall this study filled some gap of knowledge in the use of Maillard conjugates in oil in-water emulsions. The study of the stability to external stresses such as salt addition or pH modification contributed to the understanding of the functional properties of these conjugates. Drying and rehydration experiments provided a better understanding of dry emulsions behaviour

Role of transglutaminase 2 in PAC1 receptor mediated protection against hypoxia-induced cell death and neurite outgrowth in differentiating N2a neuroblastoma cells

The PAC1 receptor and tissue transglutaminase (TG2) play important roles in neurite outgrowth and modulation of neuronal cell survival. In this study, we investigated the regulation of TG2 activity by the PAC1 receptor in retinoic acid-induced differentiating N2a neuroblastoma cells. TG2 transamidase activity was determined using an amine incorporation and a peptide cross linking assay. In situ TG2 activity was assessed by visualising the incorporation of biotin-X-cadaverine using confocal microscopy. TG2 phosphorylation was monitored via immunoprecipitation and Western blotting. The role of TG2 in PAC1 receptor-induced cytoprotection and neurite outgrowth was investigated by monitoring hypoxia-induced cell death and appearance of axonal-like processes, respectively. The amine incorporation and protein crosslinking activity of TG2 increased in a time and concentration-dependent manner following stimulation with pituitary adenylate cyclase-activating polypeptide-27 (PACAP-27). PACAP-27 mediated increases in TG2 activity were abolished by the TG2 inhibitors Z-DON and R283 and by pharmacological inhibition of protein kinase A (KT 5720 and Rp-cAMPs), protein kinase C (Ro 31-8220), MEK1/2 (PD 98059), and removal of extracellular Ca2+. Fluorescence microscopy demonstrated PACAP-27 induced in situ TG2 activity. TG2 inhibition blocked PACAP-27 induced attenuation of hypoxia-induced cell death and outgrowth of axon-like processes. TG2 activation and cytoprotection were also observed in human SH-SY5Y cells. Together, these results demonstrate that TG2 activity was stimulated downstream of the PAC1 receptor via a multi protein kinase dependent pathway. Furthermore, PAC1 receptor-induced cytoprotection and neurite outgrowth are dependent upon TG2. These results highlight the importance of TG2 in the cellular functions of the PAC1 receptor

Etude des gènes régulés par le PACAP au cours de la différenciation des cellules de phéochromocytome : rôle du nuclear factor kappa B, du tumor necrosis factor alpha et de la sélénoprotéine T

ROUEN-BU Sciences (764512102) / SudocROUEN-BU Sciences Madrillet (765752101) / SudocSudocFranceF

Experimental investigation of Euler’s elastica: in-situ SEM nanowire post-buckling

An in-situ nanoindenter with a flat tip was employed to conduct buckling tests of a single nanowire with simultaneous SEM imaging. A series of SEM images allowed us to calculate deflection. The deflection was confronted with the mathematical model of elastica. The post-buckling behaviour of nanowires is conducted in the framework of the nonlinear elasticity theory. Results show the significant effect of geometrical parameters on the stability of buckled nanowires

The Neuroprotective Role of Protein Quality Control in Halting the Development of Alpha-Synuclein Pathology

Synucleinopathies are a family of neurodegenerative disorders that comprises Parkinson’s disease, dementia with Lewy bodies, and multiple system atrophy. Each of these disorders is characterized by devastating motor, cognitive, and autonomic consequences. Current treatments for synucleinopathies are not curative and are limited to improvement of quality of life for affected individuals. Although the underlying causes of these diseases are unknown, a shared pathological hallmark is the presence of proteinaceous inclusions containing the α-synuclein (α-syn) protein in brain tissue. In the past few years, it has been proposed that these inclusions arise from the self-templated, prion-like spreading of misfolded and aggregated forms of α-syn throughout the brain, leading to neuronal dysfunction and death. In this review, we describe how impaired protein homeostasis is a prominent factor in the α-syn aggregation cascade, with alterations in protein quality control (PQC) pathways observed in the brains of patients. We discuss how PQC modulates α-syn accumulation, misfolding and aggregation primarily through chaperoning activity, proteasomal degradation, and lysosome-mediated degradation. Finally, we provide an overview of experimental data indicating that targeting PQC pathways is a promising avenue to explore in the design of novel neuroprotective approaches that could impede the spreading of α-syn pathology and thus provide a curative treatment for synucleinopathies

Pituitary Adenylate Cyclase-activating Polypeptide (PACAP) Promotes Both Survival and Neuritogenesis in PC12 Cells through Activation of Nuclear Factor κB (NF-κB) Pathway

International audienceThe pituitary adenylate cyclase-activating polypeptide (PACAP) is a trophic factor that promotes neuronal survival and neurite outgrowth. However, the signaling pathways and the transcriptional mechanisms involved are not completely elucidated. Our previous studies aimed at characterizing the transcriptome of PACAP-differentiated PC12 cells revealed an increase in the expression of nuclear factor κB2 (NF-κB2) gene coding for p100/p52 subunit of NF-κB transcription factor. Here, we examined the role of the NF-κB pathway in neuronal differentiation promoted by PACAP. We first showed that PACAP-driven survival and neuritic extension in PC12 cells are inhibited following NF-κB pathway blockade. PACAP stimulated both c-Rel and p52 NF-κB subunit gene expression and nuclear translocation, whereas c-Rel down-regulation inhibited cell survival and neuritogenesis elicited by the neuropeptide. PACAP-induced c-Rel nuclear translocation was inhibited by ERK1/2 and Ca2+ blockers. Furthermore, the neuropeptide stimulated NF-κB p100 subunit processing into p52, indicative of activation of the NF-κB alternative pathway. Taken together, our data show that PACAP promotes both survival and neuritogenesis in PC12 cells by activating NF-κB pathway, most likely via classical and alternative signaling cascades involving ERK1/2 kinases, Ca2+, and c-Rel/p52 dimers

AMPK Activation of PGC-1α/NRF-1-Dependent SELENOT Gene Transcription Promotes PACAP-Induced Neuroendocrine Cell Differentiation Through Tolerance to Oxidative Stress

International audienc

AMPK Activation of PGC-1α/NRF-1-Dependent SELENOT Gene Transcription Promotes PACAP-Induced Neuroendocrine Cell Differentiation Through Tolerance to Oxidative Stress

International audienc

Expression of trophic amidated peptides and their receptors in benign and malignant pheochromocytomas: high expression of adrenomedullin RDC1 receptor and implication in tumoral cell survival

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