Structure et dynamique de la liaison hydrogène dans l'eau confinée ou aux interfaces

International audienceLorsque de l'eau est confinée dans une cavité nanométrique, ses propriétés structurales et dynamiques sont modifiées par rapport à celles de l'eau dans le volume. Les propriétés de l'eau confinée dans des oxydes présentent un intérêt à la fois fondamental et pratique, mais l'état du réseau percolatif dans ces cavités rigides est mal connu. Jusqu'à présent, la majorité des résultats a été obtenue sur de l'eau confinée dans de la matière molle. Nous présenterons ici des résultats obtenus sur la structure et la dynamique de l'eau confinée dans des systèmes rigides comme les oxydes. Pour cela, la spectroscopie infrarouge est une technique de choix, que ce soit par la grande gamme spectrale qu'elle offre (de l'infrarouge lointain, qui permet d'étudier des modes collectifs, au moyen infrarouge avec l'étude de la bande d'élongation O-H), mais aussi par la possibilité de faire des études de spectroscopie d'absorption transitoire femtoseconde qui donnent accès à la durée de vie du vibrateur O-H et à la rotation des molécules d'eau. Ces études ont été réalisées sur l'eau de surface (eau sur une surface d'alumine 1 ou à la surface d'un verre de silice 2 ,3) et l'eau confinée dans des géométries particulières, que ce soit un confinement tridimensionnel comme dans les pores de silice nanométrique 2 ou bidimensionnel comme dans les argiles 4. Les différences de comportement dynamique et de structure du réseau de liaisons hydrogène de l'eau confinée dans des systèmes « durs}) comme les oxydes ou « mous}) comme dans les échantillons biologiques (myoglobine concentrées ...) seront également discutées

The Oxysterol Synthesising Enzyme CH25H Contributes to the Development of Intestinal Fibrosis

Intestinal fibrosis and stenosis are common complications of Crohn's disease [CD], frequently requiring surgery. Anti-inflammatory strategies can only partially prevent fibrosis; hence, anti-fibrotic therapies remain an unmet clinical need. Oxysterols are oxidised cholesterol derivatives with important roles in various biological processes. The enzyme cholesterol 25-hydroxylase [CH25H] converts cholesterol to 25-hydroxycholesterol [25-HC], which modulates immune responses and oxidative stress. In human intestinal samples from CD patients, we found a strong correlation of CH25H mRNA expression with the expression of fibrosis markers. We demonstrate reduced intestinal fibrosis in mice deficient for the CH25H enzyme, using the sodium dextran sulphate [DSS]-induced chronic colitis model. Additionally, using a heterotopic transplantation model of intestinal fibrosis, we demonstrate reduced collagen deposition and lower concentrations of hydroxyproline in CH25H knockouts. In the heterotopic transplant model, CH25H was expressed in fibroblasts. Taken together, our findings indicate an involvement of oxysterol synthesis in the pathogenesis of intestinal fibrosis

Columnar cell lesions of the canine mammary gland: pathological features and immunophenotypic analysis

<p>Abstract</p> <p>Background</p> <p>It has been suggested that columnar cell lesions indicate an alteration of the human mammary gland involved in the development of breast cancer. They have not previously been described in canine mammary gland. The aim of this paper is describe the morphologic spectrum of columnar cell lesions in canine mammary gland specimens and their association with other breast lesions.</p> <p>Methods</p> <p>A total of 126 lesions were subjected to a comprehensive morphological review based upon the human breast classification system for columnar cell lesions. The presence of preinvasive (epithelial hyperplasia and in situ carcinoma) and invasive lesions was determined and immunophenotypic analysis (estrogen receptor (ER), progesterone receptor (PgR), high molecular weight cytokeratin (34βE-12), E-cadherin, Ki-67, HER-2 and P53) was perfomed.</p> <p>Results</p> <p>Columnar cell lesions were identified in 67 (53.1%) of the 126 canine mammary glands with intraepithelial alterations. They were observed in the terminal duct lobular units and characterized at dilated acini may be lined by several layers of columnar epithelial cells with elongated nuclei. Of the columnar cell lesions identified, 41 (61.2%) were without and 26 (38.8%) with atypia. Association with ductal hyperplasia was observed in 45/67 (67.1%). Sixty (89.5%) of the columnar cell lesions coexisted with neoplastic lesions (20 in situ carcinomas, 19 invasive carcinomas and 21 benign tumors). The columnar cells were ER, PgR and E-cadherin positive but negative for cytokeratin 34βE-12, HER-2 and P53. The proliferation rate as measured by Ki-67 appeared higher in the lesions analyzed than in normal TDLUs.</p> <p>Conclusions</p> <p>Columnar cell lesions in canine mammary gland are pathologically and immunophenotypically similar to those in human breast. This may suggest that dogs are a suitable model for the comparative study of noninvasive breast lesions.</p

Metaplastic breast carcinomas exhibit EGFR, but not HER2, gene amplification and overexpression: immunohistochemical and chromogenic in situ hybridization analysis

INTRODUCTION: Metaplastic breast carcinomas constitute a heterogeneous group of neoplasms, accounting for less than 1% of all invasive mammary carcinomas. Approximately 70–80% of metaplastic breast carcinomas overexpress the epidermal growth factor receptor (EGFR). Human epidermal growth factor receptor (HER)2 and EGFR have attracted much attention in the medical literature over the past few years owing to the fact that humanized monoclonal antibodies against HER2 and therapies directed against the extracellular ligand-binding domain or the intracellular tyrosine kinase domain of EGFR have proven successful in treating certain types of human cancer. We investigated whether HER2 and EGFR overexpression was present and evaluated gene amplification in a series of metaplastic breast carcinomas. METHOD: Twenty-five metaplastic breast carcinomas were immunohistochemically analyzed using a monoclonal antibody (31G7) for EGFR and two antibodies for HER2 (Herceptest and CB11) and scored using the Herceptest scoring system. Gene amplification was evaluated by chromogenic in situ hybridization using Zymed Spot-Light EGFR and HER2 amplification probe. The results were evaluated by bright field microscopy under 40× and 63× objective lenses. RESULTS: Nineteen (76%) metaplastic breast carcinomas exhibited EGFR ovexpression, and among these EGFR amplification (defined either by large gene clusters or >5 signals/nucleus in >50% of neoplastic cells) was detected in seven cases (37%): three carcinomas with squamous differentiation and four spindle cell carcinomas. One case exhibited HER2 overexpression of grade 2+ (>10% of cells with weak to moderate complete membrane staining), but HER2 gene amplification was not detected. CONCLUSION: Metaplastic breast carcinomas frequently overexpressed EGFR, which was associated with EGFR gene amplification in one-third of cases. Our findings suggest that some patients with metaplastic breast carcinomas might benefit from novel therapies targeting EGFR. Because most metaplastic breast carcinomas overexpress EGFR without gene amplification, further studies to evaluate EGFR activating mutations are warranted

One Step Nucleic Acid Amplification (OSNA) - a new method for lymph node staging in colorectal carcinomas

<p>Abstract</p> <p>Background</p> <p>Accurate histopathological evaluation of resected lymph nodes (LN) is essential for the reliable staging of colorectal carcinomas (CRC). With conventional sectioning and staining techniques usually only parts of the LN are examined which might lead to incorrect tumor staging. A molecular method called OSNA (One Step Nucleic Acid Amplification) may be suitable to determine the metastatic status of the complete LN and therefore improve staging.</p> <p>Methods</p> <p>OSNA is based on a short homogenisation step and subsequent automated amplification of cytokeratin 19 (CK19) mRNA directly from the sample lysate, with result available in 30-40 minutes. In this study 184 frozen LN from 184 patients with CRC were investigated by both OSNA and histology (Haematoxylin & Eosin staining and CK19 immunohistochemistry), with half of the LN used for each method. Samples with discordant results were further analysed by RT-PCR for CK19 and carcinoembryonic antigen (CEA).</p> <p>Results</p> <p>The concordance rate between histology and OSNA was 95.7%. Three LN were histology+/OSNA- and 5 LN histology-/OSNA+. RT-PCR supported the OSNA result in 3 discordant cases, suggesting that metastases were exclusively located in either the tissue analysed by OSNA or the tissue used for histology. If these samples were excluded the concordance was 97.2%, the sensitivity 94.9%, and the specificity 97.9%. Three patients (3%) staged as UICC I or II by routine histopathology were upstaged as LN positive by OSNA. One of these patients developed distant metastases (DMS) during follow up.</p> <p>Conclusion</p> <p>OSNA is a new and reliable method for molecular staging of lymphatic metastases in CRC and enables the examination of whole LN. It can be applied as a rapid diagnostic tool to estimate tumour involvement in LN during the staging of CRC.</p

Excitation energy transfer in native and unstacked thylakoid membranes studied by low temperature and ultrafast fluorescence spectroscopy

In this work, the transfer of excitation energy was studied in native and cation-depletion induced, unstacked thylakoid membranes of spinach by steady-state and time-resolved fluorescence spectroscopy. Fluorescence emission spectra at 5 K show an increase in photosystem I (PSI) emission upon unstacking, which suggests an increase of its antenna size. Fluorescence excitation measurements at 77 K indicate that the increase of PSI emission upon unstacking is caused both by a direct spillover from the photosystem II (PSII) core antenna and by a functional association of light-harvesting complex II (LHCII) to PSI, which is most likely caused by the formation of LHCII-LHCI-PSI supercomplexes. Time-resolved fluorescence measurements, both at room temperature and at 77 K, reveal differences in the fluorescence decay kinetics of stacked and unstacked membranes. Energy transfer between LHCII and PSI is observed to take place within 25 ps at room temperature and within 38 ps at 77 K, consistent with the formation of LHCII-LHCI-PSI supercomplexes. At the 150-160 ps timescale, both energy transfer from LHCII to PSI as well as spillover from the core antenna of PSII to PSI is shown to occur at 77 K. At room temperature the spillover and energy transfer to PSI is less clear at the 150 ps timescale, because these processes compete with charge separation in the PSII reaction center, which also takes place at a timescale of about 150 ps. © 2007 Springer Science+Business Media B.V

Investigation of ubiquinol formation in isolated photosynthetic reaction centers by rapid-scan Fourier transform IR spectroscopy

Light-induced formation of ubiquinol-10 in Rhodobacter sphaeroides reaction centers was followed by rapid-scan Fourier transform IR difference spectroscopy, a technique that allows the course of the reaction to be monitored, providing simultaneously information on the redox states of cofactors and on protein response. The spectrum recorded between 4 and 29 ms after the second flash showed bands at 1,470 and 1,707 cm–1, possibly due to a QH– intermediate state. Spectra recorded at longer delay times showed a different shape, with bands at 1,388 (+) and 1,433 (+) cm–1 characteristic of ubiquinol [Mezzetti et al. FEBS Lett. 537:161–165 (2003)]. These spectra reflect the location of the ubiquinol molecule outside the QB binding site. This was confirmed by Fourier transform IR difference spectra recorded during and after continuous illumination in the presence of an excess of exogenous ubiquinone molecules, which revealed the process of ubiquinol formation, of ubiquinone/ubiquinol exchange at the QB site and between detergent micelles, and of QB– and QH2 reoxidation by external redox mediators. Kinetics analysis of the IR bands allowed us to estimate the ubiquinone/ubiquinol exchange rate between detergent micelles to approximately 1 s. The reoxidation rate of QB– by external donors was found to be much lower than that of QH2, most probably reflecting a stabilizing/protecting effect of the protein for the semiquinone form. A transient band at 1,707 cm–1 observed in the first scan (4–29 ms) after both the first and the second flash possibly reflects transient protonation of the side chain of a carboxylic amino acid involved in proton transfer from the cytoplasm towards the QB site

Functional Pattern of Photosystem I in Oxygen Evolving Organisms in. Primary Processes of Photosynthesis : Basic Principles and Apparatus

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