1,721,073 research outputs found
Milk Fat Globule Membrane Proteomics: A 'Snapshot' of Mammary Epithelial Cell Biology
No full textLipids are released in milk as fat globules, which are droplets of apolar lipids sur-rounded by a complex membrane deriving from the mammary epithelial cell (MEC) and called the milk fat globule membrane (MFGM). The structure of the MFGM is highly com-plex and closely related to the mechanisms of milk fat globule secretion in the mammary epithelial cell. Indeed, MFGM is composed of two biological membranes, a phospholipid monolayer, deriving from the endoplasmic reticulum, and a phospholipid bilayer, which originates from the apical plasma membrane of the MEC, with variable amounts of cyto-plasm trapped between. Biochemical techniques (i.e. sodium dodecyl sulphate-polyacryl-amide gel electrophoresis followed by different staining procedures) have been employed historically to characterize major MFGM proteins, namely MUC-1, fatty acid synthase, xan-thine oxidase, butyrophilin, lactadherin, and adipophilin. However, recent advances in the field of proteomics (mostly development of one-dimensional gel electrophoresis approach coupled with tandem mass spectrometry) have led to the identification of hundreds of proteins associated with the MFGM. Surprisingly, newly identified MFGM proteins were not only involved in lipid metabolic or exocytosis-related biological processes, but also in cell signalling, translation, or host defense-related mechanisms. Therefore, the milk fat globule should no longer be viewed as an inert structure only devoted to the delivery of lipids to the newborn, but rather as a dynamic and informative compartment which can contribute to the improvement of our comprehension of the mammary gland biology
Major proteins of the goat milk fat globule membrane
No full textFat is present in milk as droplets of triglycerides surrounded by a complex membrane derived from the mammary epithelial cell called milk fat globule membrane (MFGM). Although numerous studies have been published on human or bovine MFGM proteins, to date few studies exist on MFGM proteins from goat milk. The objective of this study was thus to investigate the protein composition of the goat MFGM. Milk fat globule membrane proteins from goat milk were separated by 6% and 10% sodium dodecyl sulfate-PAGE and were Coomassie or periodic acid–Schiff stained. Most of MFGM proteins [mucin-1, fatty acid synthase, xanthine oxidase, butyrophilin, lactadherin (MFG EGF-8, MFG-E8), and adipophilin] already described in cow milk were identified in goat milk using peptide mass fingerprinting. In addition, lectin staining provided a preliminary characterization of carbohydrate structures occurring on MFGM proteins from goat milk depending on αS1-casein genotype and lactation stage. We provide here first evidence of the presence of O-glycans on fatty acid synthase and xanthine oxidase from goat milk. A prominent difference between the cow and the goat species was demonstrated for lactadherin. Indeed, whereas 2 polypeptide chains were easily identified by peptide mass fingerprinting matrix-assisted laser desorption/ionization–time of flight analysis within bovine MFGM proteins, lactadherin from goat milk consisted of a single polypeptide chain. Another striking observation was the presence of caseins associated with MFGM preparations from goat milk, whereas virtually no caseins were found in MFGM extracts from bovine milk. Taken together, these observations strongly support the existence of a singular secretion mode previously hypothesized in the goat
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Le Programme LIPOMEC (Apis-Gene, 2018-2020) Lipolyse et qualité du lait : vers une meilleure compréhension des mécanismes moléculaires contrôlant la dégradation de la matière grasse laitière
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Biosynthèse des lipides du lait et mécanismes de régulation par des facteurs génétiques ou environnementaux
No full textLipids are released in milk as fat globules, which are droplets of apolar lipids surrounded by a complex membrane deriving from the mammary epithelial cell (MEC) and called the Milk Fat Globule Membrane (MFGM). The structure of the MFGM is highly complex and closely related to the mechanisms of milk fat globule secretion in the MEC. Indeed, MFGM is composed of two biological membranes, a phospholipid monolayer deriving from the endoplasmic reticulum and a phospholipid bilayer which originates from the apical plasma membrane of the MEC, with variable amounts of cytoplasm trapped between. We have characterized this complex membrane in several species, including the goat species or camelids. Newly identified MFGM proteins were not only involved in lipid metabolic or exocytosis-related biological processes, but also in cell signaling, translation, or host-defense related mechanisms. Therefore, the milk fat globule should no longer be viewed as an inert structure only devoted to the delivery of lipids to the newborn, but rather as a dynamic and informative compartment which can contribute to improve our comprehension on the mammary gland biologyLa cellule épithéliale mammaire (CEM) produit les lipides du lait par un mécanisme original en biologie. La synthèse des triglycérides du lait est initiée au niveau du réticulum endoplasmique de la CEM. Les gouttelettes lipidiques néoformées vont ensuite fusionner et migrer vers le pôle apical de la cellule pour être libérées sous la forme de globules gras, éléments figurant la matière grasse du lait. Après avoir caractérisé la composition fine de la membrane du globule gras dans différentes espèces (chèvre, jument, dromadaire), je m’attache désormais à mieux comprendre les mécanismes de biosynthèse des gouttelettes lipidiques, précurseurs des globules gras, dans la CEM et les effets de la génétique ou de l’environnement sur ces mécanismes de biosynthèse
Biosynthèse des lipides du lait et mécanismes de régulation par des facteurs génétiques ou environnementaux
No full textLipids are released in milk as fat globules, which are droplets of apolar lipids surrounded by a complex membrane deriving from the mammary epithelial cell (MEC) and called the Milk Fat Globule Membrane (MFGM). The structure of the MFGM is highly complex and closely related to the mechanisms of milk fat globule secretion in the MEC. Indeed, MFGM is composed of two biological membranes, a phospholipid monolayer deriving from the endoplasmic reticulum and a phospholipid bilayer which originates from the apical plasma membrane of the MEC, with variable amounts of cytoplasm trapped between. We have characterized this complex membrane in several species, including the goat species or camelids. Newly identified MFGM proteins were not only involved in lipid metabolic or exocytosis-related biological processes, but also in cell signaling, translation, or host-defense related mechanisms. Therefore, the milk fat globule should no longer be viewed as an inert structure only devoted to the delivery of lipids to the newborn, but rather as a dynamic and informative compartment which can contribute to improve our comprehension on the mammary gland biologyLa cellule épithéliale mammaire (CEM) produit les lipides du lait par un mécanisme original en biologie. La synthèse des triglycérides du lait est initiée au niveau du réticulum endoplasmique de la CEM. Les gouttelettes lipidiques néoformées vont ensuite fusionner et migrer vers le pôle apical de la cellule pour être libérées sous la forme de globules gras, éléments figurant la matière grasse du lait. Après avoir caractérisé la composition fine de la membrane du globule gras dans différentes espèces (chèvre, jument, dromadaire), je m’attache désormais à mieux comprendre les mécanismes de biosynthèse des gouttelettes lipidiques, précurseurs des globules gras, dans la CEM et les effets de la génétique ou de l’environnement sur ces mécanismes de biosynthèse
Composition fine du lait: Vers une meilleure compréhension de la biologie de la lactation
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