Biomedical subjects

S Benard

Publications and source records attributed to S Benard.

6 recordsLinked to original sources

PubMed2001

Detection of individual phospholipids in lipid mixtures by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: phosphatidylcholine prevents the detection of further species.

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry is an established tool for the analysis of proteins, whereas it gained by far less interest in the field of lipid analysis. This method works well with phospholipids as well as organic cell extracts and provides high sensitivity and reproducibility. The aim of the present paper is to extend our previous studies to the analysis of lysophospholipids and phospholipid mixtures. To study the suitability of MALDI-TOF mass spectrometry for the analysis of lysophospholipids, different phospholipids like phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidic acid, and phosphatidylinositol as well as their mixtures were digested with phospholipase A(2). Positive and negative ion mass spectra of all phospholipids before and after digestion were recorded. In all these cases, the molecular ions of the expected digestion products could be detected and only a very small extent of further fragmentation was observed. On the other hand, spectra of phospholipid mixtures containing phosphatidylcholine were strongly dominated by phosphatidylcholine and lysophosphatidylcholine signals, which prevented the detection of further phospholipids even if those lipids were present in comparable amounts. This is of paramount interest for the analysis of tissue and cell extracts.

Animals↗

PubMed2000

Cartilage degradation by stimulated human neutrophils: reactive oxygen species decrease markedly the activity of proteolytic enzymes.

BACKGROUND: Although neutrophilic granulocytes clearly contribute to cartilage degradation in rheumatic diseases, it is unclear if reactive oxygen species (ROS) or proteolytic enzymes are the most important components in cartilage degradation and how they interact. RESULTS: Neutrophils were stimulated by chemicals conferring a different degree of ROS formation and enzyme release. Supernatants of neutrophils were incubated with thin slices of pig articular cartilage. Supernatants of cartilage were assayed by NMR spectroscopy, MALDI-TOF mass spectrometry and relevant biochemical methods. Stimulation conditions of neutrophils correlated well with the extent of cartilage degradation. Due to the release of different enzymes, cartilage degradation could be best monitored by NMR since mainly low-mass degradation products were formed. Astonishingly, the suppression of the formation of ROS resulted in decreased cartilage degradation. CONCLUSION: ROS formed by neutrophils are not directly involved in cartilage degradation but influence the activity of proteolytic enzymes, which are the main effectors of cartilage degradation.

Animals↗

PubMed1999

Cartilage degradation by hyaluronate lyase and chondroitin ABC lyase: a MALDI-TOF mass spectrometric study.

Matrix-assisted laser desorption ionization and time-of-flight mass spectrometry (MALDI-TOF MS) has been used to investigate degradation products of two selected polysaccharides of cartilage (chondroitin sulfate and hyaluronic acid). Testicular hyaluronate lyase and chondroitin ABC lyase were used for enzymic digestion of both polysaccharides as well as of cartilage specimens. Polysaccharide solutions and cartilage supernatants were assayed by positive and negative MALDI-TOF MS. Especially chondroitin ABC lyase produced high amounts of digestion products (unsaturated di- and tetrasaccharides) from polysaccharides as well as from cartilage, clearly monitored by MALDI-TOF MS. It is concluded that MALDI-TOF MS provides a precise and fast tool for the determination of oligosaccharides since no previous derivatization is required.

Animals↗

PubMed1999

Lipid analysis by matrix-assisted laser desorption and ionization mass spectrometry: A methodological approach.

Whereas matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has gained high importance in the field of protein analysis, surprisingly few studies were published about the use of MALDI for lipid analysis. Lipids, however, are well-suited for MALDI since all experiments can be performed in a sole organic phase and, thus, extremely homogeneous matrix/analyte mixtures are formed. We report here for the first time the application of MALDI-TOF-MS for the analysis of diacylglycerols, phosphatidylcholines, and (poly)phosphoinositides. It is shown that in a matrix of 2,5-dihydroxybenzoic acid the molecular ions (M + 1) of phosphatidylcholines as well as the corresponding adducts of different phosphoinositides are easily detected even in complex mixtures, and thus, detailed data on the fatty acid composition are provided. In contrast, diacylglycerols are mainly detected as the corresponding sodium or potassium adducts, but not as the protonated forms. Fragmentation reactions of fatty acids on the double bonds and on the polar lipid head group are observed to a minor extent in the spectra of all investigated lipids. Generally, choline derivatives are most sensitive toward further fragmentation reactions. Due to its very high sensitivity (up to picomolar concentrations) MALDI-TOF-MS can be used for the direct investigation of biologically relevant lipid mixtures occurring, e.g. , in cell membranes. The analysis of the lipid composition of neutrophilic granulocytes is given as a representative example for future applications.

Diglycerides↗

PubMed1997

Expression of p53 in oesophageal squamous epithelium from surgical specimens resected for squamous cell carcinoma of the oesophagus, with special reference to uninvolved mucosa.

Accumulation of p53 protein has been considered an intermediate biomarker in multistage oesophageal carcinogenesis. The aim of the present study was to investigate p53 expression by immunohistochemistry in 13 thoroughly sampled oesophagectomy specimens from a geographical area with a high oesophageal cancer incidence (Basse Normandie, France). Expression of p53 was looked for in tissue samples of cancer, intraepithelial neoplasia, and uninvolved mucosa. The streptavidin biotin peroxidase complex method was used for p53 immunostaining. p53 expression was found in invasive squamous cell carcinoma in 8 out of 11 cases and in intraepithelial neoplasia in 10 out of 11 cases. In all 13 cases, in uninvolved oesophageal mucosa, expression of p53 was focally present in areas of chronic oesophagitis. Chronic oesophagitis has been regarded by epidemiologists as a precursor lesion for squamous cell carcinoma of the oesophagus. Since oesophageal carcinogenesis is a multistage process, the study of precursor lesions could provide information on the timing of p53 gene abnormalities during oesophageal carcinogenesis. These preliminary data require to be confirmed by molecular analysis of the p53 gene.

Carcinoma in Situ↗

PubMedDate not supplied

Modulation of luminol chemiluminescence of fMet-Leu-Phe-stimulated neutrophils by affecting dephosphorylation and the metabolism of phosphatidic acid.

This paper is addressed to study how PKC-mediated effects and phosphatidic acid interact together in activation of NADPH-oxidase in formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe) stimulated neutrophils as detected by luminol chemiluminescence. The early luminescence response in fMet-Leu-Phe-stimulated cells (up to 5 min after stimulation) depends mainly on reactive oxygen species generated extracellularly, whereas all later events are caused by oxidation of luminol inside the cells. The two protein phosphatase inhibitors, okadaic acid and calyculin A, dramatically increased the late luminescence of cells. This enhancement was totally inhibited by the phospholipase D modulator butanol, while the protein kinase C (PKC) inhibitor bisindolylmaleimide I was insensitive. The early luminescence response of the cells was slightly inhibited by both protein phosphatase inhibitors and depended on protein kinase C as well as on phospholipase D activities. Propranolol, an inhibitor of phosphatidate phosphohydrolase, enhanced all parts of luminescence response of fMet-Leu-Phe-stimulated neutrophils at concentrations up to 2.5 x 10(-5) mol/L. While the late luminescence response of propranolol-treated cells was not inhibited by the PKC inhibitor bisindolylmaleimide I, the first response depended on protein kinase C. The inhibitor of diacylglycerol kinase R59949 enhanced the luminescence signal only during the first 4 min in fMet-Leu-Phe-stimulated cells. Only diacylglycerols derived from phospholipase C, such as 1-stearoyl-2-arachidonoyl-sn-glycerol, were able to initiate an oxidative burst in cells. Saturated diacylglycerols (e.g. 1,2-dipalmitoyl-sn-glycerol or 1,2-distearoyl-sn-glycerol) did not yield any luminol chemiluminescence, although they were incorporated into the plasma membrane, as evidenced by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Our results demonstrate that phosphatidic acid produced by phospholipase D is responsible for NADPH-oxidase activity in fMet-Leu-Phe-stimulated neutrophils over the entire measuring time, whereas PKC-mediated processes are only involved during the first 5 min.

Diglycerides↗