Lipid domain formation and membrane shaping by C24-ceramide.

Ceramides are an important group of sphingolipids that modulate several cellular events. The mechanisms underlying biological actions of ceramides are not fully known, but evidence suggests that ceramides can act through regulation of the biophysical properties of the membrane. However, ceramide-induced changes on membrane properties are complex and depend on several factors. To gain further insight into this subject, we characterized the biophysical impact of very-long acyl chain C24-ceramide in a fluid model membrane under thermodynamic equilibrium and non-equilibrium conditions. Our results show that C24-ceramide readily forms two types of gel domains with distinct properties, likely corresponding to different interdigitated metastable gel phases. Upon reaching thermodynamic equilibrium, only partially interdigitated gel phase coexists with the fluid phase. In addition, C24-ceramide promotes strong changes in the shape of the vesicles, including domains with sharp edges and tubule-like structures. The results suggest that the formation of very long acyl chain ceramides in response to stress stimuli will initially induce a multitude of changes in the organization and fluidity of biological membranes that might be responsible for the activation of different cellular processes.

Solar photo-Fenton process on the abatement of antibiotics at a pilot scale: Degradation kinetics, ecotoxicity and phytotoxicity assessment and removal of antibiotic resistant enterococci.

This work investigated the application of a solar driven advanced oxidation process (solar photo-Fenton), for the degradation of antibiotics at low concentration level (µg L(-1)) in secondary treated domestic effluents at a pilot-scale. The examined antibiotics were ofloxacin (OFX) and trimethoprim (TMP). A compound parabolic collector (CPC) pilot plant was used for the photocatalytic experiments. The process was mainly evaluated by a fast and reliable analytical method based on a UPLC-MS/MS system. Solar photo-Fenton process using low iron and hydrogen peroxide doses ([Fe(2+)](0) = 5 mg L(-1); [H(2)O(2)](0) = 75 mg L(-1)) was proved to be an efficient method for the elimination of these compounds with relatively high degradation rates. The photocatalytic degradation of OFX and TMP with the solar photo-Fenton process followed apparent first-order kinetics. A modification of the first-order kinetic expression was proposed and has been successfully used to explain the degradation kinetics of the compounds during the solar photo-Fenton treatment. The results demonstrated the capacity of the applied advanced process to reduce the initial wastewater toxicity against the examined plant species (Sorghum saccharatum, Lepidium sativum, Sinapis alba) and the water flea Daphnia magna. The phytotoxicity of the treated samples, expressed as root growth inhibition, was higher compared to that observed on the inhibition of seed germination. Enterococci, including those resistant to OFX and TMP, were completely eliminated at the end of the treatment. The total cost of the full scale unit for the treatment of 150 m(3) day(-1) of secondary wastewater effluent was found to be 0.85 € m(-3).

Follicle-stimulating hormone increases cell proliferation in the ovary and the testis of the chick embryo.

Previous studies have demonstrated that FSH stimulates cell proliferation in the ovary and the testis of the chick embryo. This study analyzed the presence of FSH receptor and the cell subpopulations that proliferate in response to FSH in chick embryo gonads. FSH receptor mRNA was detected by reverse transcription-polymerase chain reaction (RT-PCR) in the male and female gonads of the 6 to 14-day-old chick embryo. Somatic cells of the ovary expressed the FSH receptor in the 14-day-old chick embryo. Ovarian surface epithelium of the 14-day-old chick embryo increased the mitotic index 15-18 h after FSH treatment. Similarly, the mitotic index in oogonia was increased 24 h after receiving a pulse of FSH; this result was confirmed by an increase in the number of germ cells that incorporated bromodeoxyuridine (BrdU). Somatic cells of the medullary cords in the ovary displayed an increase in the mitotic index 15-21 h after the FSH injection. In the chick embryo testis, at the same stage of development, the treatment with FSH increased the mitotic index in cells of the seminiferous tubules and to a lesser extent in cells at a peritubular and interstitial location. Present results demonstrate that in the chick embryo, FSH stimulates the proliferation of ovarian surface epithelium, oogonia in the cortex, and somatic cells of the medullary cords of the chick embryo ovary. In the chick embryo testis, FSH stimulates cell proliferation in seminiferous tubules and peritubular cells.