Sterol regulatory element-binding proteins (SREBPs) belong to a family of nuclear transcription factors. The question of which is the most important positive regulator in milk fat synthesis in dairy cow mammary epithelial cells (DCMECs) between SREBPs or other nuclear transcription factors, such as peroxisome proliferator-activated receptor γ (PPARγ), remains a controversial one. Recent studies have found that mTORC1 (the mammalian target of rapamycin C1) regulates SREBP1 to promote fat synthesis. Thus far, however, the interaction between the SREBP1 and mTOR (the mammalian target of rapamycin) pathways in the regulation of milk fat synthesis remains poorly understood. This study aimed to identify the function of SREBP1 in milk fat synthesis and to characterize the relationship between SREBP1 and mTOR in DCMECs. The effects of SREBP1 overexpression and gene silencing on milk fat synthesis and the effects of stearic acid and serum on SREBP1 expression in the upregulation of milk fat synthesis were investigated in DCMECs using immunostaining, Western blotting, real-time quantitative PCR, lipid droplet staining, and detection kits for triglyceride content. SREBP1 was found to be a positive regulator of milk fat synthesis and was shown to be regulated by stearic acid and serum. These findings indicate that SREBP1 is the key positive regulator in milk fat synthesis.

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The efficient treatment of oil–water emulsions under acidic condition remains a widespread concern. Poly­(amidoamine) (PAMAM) dendrimer with hyperbranched structures and a large amount of primary and tertiary amino groups has exhibited advantages to solve this issue. Here, a novel poly­(vinylidene fluoride)-graft-(SiO2 nanoparticles and PAMAM dendrimers) (PVDF-g-SiO2 NPs/PAMAM) membrane was fabricated using a surface-grafting strategy. SiO2 NPs were immobilized on PVDF-g-poly­(acrylic acid) (PAA) membranes for improving the surface roughness, and PAMAM dendrimers were further immobilized on the membrane surface by interfacial polymerization (IP) for improving the surface energy. The obtained membrane demonstrated a water contact angle and a stable underwater–oil contact angle of 0° and >150°, respectively. These characteristics endowed the membrane with excellent water permeability [>3100 L/(m2·h) at 0.9 bar] and separation efficiency (>99%) during oil–water separation. Furthermore, the PAMAM chain will extend from a collapsed state into a fully extension state because of the protonation of amine groups under acidic condition, thus achieving a low underwater oil-adhesion property, fouling resistance, desirable stability, and recyclability (over 12 cycles) during usage. This work shows a promising prospect for the treatment of corrosive emulsions under acidic condition.

Membrane surface design is significant for the development and application of synthetic polymer hemodialysis membranes. In this study, the influence of zwitterionic cysteine on poly(vinylidene fluoride) (PVDF) hollow fiber membrane was investigated. The polydopamine layer was formed through dopamine self-polymerization on PVDF membrane surface, and then cysteine was covalent grafted onto the layer to improve the anti-biofouling property and hemocompatibility. The elementary composition of membrane surfaces was characterized by X-ray photoelectron spectroscopy. The influence of polydopamine and cysteine on modified membrane surface morphologies was studied by field emission scanning electron microscopy. The modified PVDF membranes were confirmed to have excellent hydrophilicity, stable mechanical properties and good hemocompatibility (dynamic and static anti-protein adsorption, hemolysis ratio, plasma coagulation). And these properties were increased with the incorporation of polydopamine and cysteine. The optimized modified membranes exhibited high pure water flux (∼ 195.5 L/m h at 0.1 MPa) and selectivity (clearance ratio of urea and lysozyme was 75.1 and 55.4%, and rejection rate of bovine serum albumin was 98.8%). This work provides a surface modification method of PVDF hollow fiber membranes and suggests a potential application of PVDF membranes in hemodialysis field. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2869-2877, 2018.