Developmental expression of pIgR gene in sheep mammary gland and hormonal regulation

Secretory IgA found in external secretions are constituted by polymeric IgA (pIgA) bound to the extra-cellular part of the polymeric immunoglobulin receptor (pIgR). The receptor mediates transcytosis of pIgA across epithelial cells. The aim of the present study was to analyse the evolution of pIgR expression in the sheep mammary gland during the development of the mammary gland and to analyse its hormonal regulation. Gene expression of the pIgR was analysed in sheep mammary gland during pregnancy and lactation. By Northern Blot analysis, we observed that low levels of pIgR mRNA are expressed until day 70 of pregnancy. Accumulation of pIgR mRNA started during the third part of pregnancy and intensified 3 d after parturition to reach highest levels during established lactation (day 70). In situ hybridization analysis was used to confirm the increase in pIgR gene expression per mammary epithelial cell. In order to examine the hormonal regulation of the pIgR expression, virgin ewes were hormonally treated. Treatment with oestradiol and progesterone increased pIgR mRNA levels slightly. Subsequent addition of gluocotricoids induced a significant accumulation of pIgR mRNA in the mammary gland of the treated animals. Immunohistochemical analysis was performed to verify that the increase of pIgR mRNA level was associated with enhancement of the pIgR protein in mammary cells. No increase of pIgR mRNA levels were observed if PRL secretion was blocked by bromocryptine injections throughout the hormonal procedure. In conclusion, the present experiments suggest that the enhancement of pIgR levels during lactation result from combined effects of both prolactin and glucocorticoids.     

Nanostructured macro-mesoporous zirconia impregnated by noble metal for catalytic total oxidation of toluene

Hierarchical bimodal macro-mesoporous zirconia oxide has been synthesized by a simple method in the presence of CTMABr surfactant. The synthesized zirconia having uniform macropores of 300–600 nm in diameter with wormhole-like mesoporous walls and high surface area was calcined at 400 and 600 °C and impregnated with 0.5 wt.% of palladium and compared with classical 0.5 wt.% Pd/ZrO₂ catalyst for toluene oxidation. The highest activity of 0.5 wt.%/macro-mesoporous zirconia calcined at 600 °C was mainly explained by a rather high Pd dispersion and by H₂-TPR measurements showing a higher quantity of PdO species easily reducible at 0 °C.     

CO2 reforming of methane over NixMg6−xAl2 catalysts: Effect of lanthanum doping on catalytic activity and stability

Ni_xMg_6?xAl₂ and Ni_xMg_6?xAl_1.8La_0.2 (x = 2, 4 or 6) catalysts were prepared via a co-precipitation method and calcined under an air flow at 800 °C. X-ray diffraction (XRD) results showed that the Ni_xMg_6?xAl_1.8La_0.2 catalysts contained different lanthanum oxide species after calcination. Fourier Transform Infrared Spectroscopy (FTIR) spectra demonstrated that the lanthanum doped catalysts adsorbed more CO₂ compared to the lanthanum free solids. This improved basicity was verified in the CO₂-TPD profiles. Temperature programmed reduction (TPR) analyses proved that the addition of lanthanum affected nickel species distribution in the catalysts and strengthened NiO-MgO interactions inside the solid matrix. The CO₂ reforming of methane reaction (Ar/CO₂/CH₄:60/20/20; GHSV 60000 mL g^?1 h^?1) was carried out over the different catalysts in the temperature range of 600 °C–800 °C. Lanthanum addition improved the catalytic activity particularly by favoring the methane dry reforming reaction over all the other secondary reactions in addition to the creation of more basic sites that enhanced CO₂ adsorption and contributed to the removal of carbon deposits. The most active lanthanum containing catalyst kept a constant catalytic performance for 14 h on stream despite the formation of carbon deposits. These carbon deposits can be removed under an oxidative atmosphere at moderate temperature due to the presence of lanthanum oxide species in the catalyst.