Studies on Sphingolipids, I. Gas-liquid Chromatographic Analyses of Sphingosine Bases.

Three different methods ; permanganate-periodate oxidation, periodate oxidation and trimethylsilylation, for gas-liquid chromatography of sphingosine bases were compared to one another, using authentic dihydrosphingosine as well as bases of cerebroside isolated from pig brain and sphingolipids from yeast powder, with the data on the occurrences of shorter chain homologs of sphingosine bases. The trimethylsilylation method was most suitable for the qualitative determination and identification of individual sphingosine base. This method was also available for the quantitative determination of sphingosine base composition. The periodate method was most suitable for the quantitative determination of sphingosine base composition, except that some uncertainties such as C-15 saturated aldehyde could be derived from either C17-dihydrosphingosine or C18-phytosphingosine, remain to be solved by other methods such as Trimethylsilylation method or thin-layer chromatography etc. The permanganate-periodate method was less suitable for the determination of sphingosine base composition for higher appearance of some oxidation products as well as uncertainties due to same acids could be derived from different parent bases by this method than by periodate method. But it is still useful for the exact determination of the double bond position and helps the identification of the bases with other methods. C16-sphingosine, C16-dihydrosphingosine and probably C17-sphingosine occured at low level in pig brain cerebroside. C18-dihydrosphingosine was predominant base in yeast sphingolipids but the occurrences of C18-phytosphingosine and C20-dihydrosphingosine were also confirmed.departmental bulletin pape

Studies on Sphingolipids, II. Sphingolipid Bases in Rat Brain, Liver and Kindney.

The sphingolipids, such as cerebroside, sphingomyelin and mucolipid were isolated from rat brain, liver and kidney. The isolation of sphingosine bases from each sphingolipid was performed according to the method of Gayer and Sweely. The analysis of sphingosine bases was carried out according to the procedure of Sweely and Moscatelli, that is, by gas-liquid chromatography of long chain aldehydes obtained from sphingosine bases by periodate oxidation, and the results are summarized as follows. 1. Sphingosine bases are mainly consisted of C18-sphingosine (70-93%) and C18- dihydrosphingosine (4-15%) in all sphingolipids of rat tissues examined. But some quantitative differences in sphingosine base composition were observed between different sphingolipids and in lesser degree between a sort of sphingolipids in different tissues. 2. Brain mucolipid contained a substantial amount (23%) of C20-sphingosine and brain sphingomyelin also contained a small amount (3%), but no C20-sphingosine was detected in the sphingosine bases of brain cerebroside, brain sulfatide and all sphingolipids from other tissues. 3. There was a distinct tendency for more C18-dihydrosphingosine to occur in cerebroside than in sphingomyelin, which was seen not only in brain but also in other tissues. 4. Liver cerebroside contained 7.5% of phytosphingosine in addition to C,8-sphingosine and C18-dihydrosphingosine. Lesser amount of phytosphingosine was found in kidney cerebroside. The occurrence of phytosphingosine was further confirmed by thinlayer chromatography

A star formation study of the ATLAS3D early-type galaxies with the AKARI all-sky survey

The star formation properties of early-type galaxies (ETGs) are currently the subject of considerable interest, particularly whether they differ from those of gas-rich spirals. We perform a systematic study of star formation in a large sample of local ETGs using polycyclic aromatic hydrocarbon (PAH) and dust emission, focusing on the galaxies' star formation rates (SFRs) and star formation efficiencies (SFEs). Our sample is composed of the 260 ETGs from the ATLAS3D survey, from which we use the cold gas measurements (HI and CO). The SFRs are estimated from stellar, PAH and dust fits to spectral energy distributions created from new AKARI measurements and literature data from WISE and 2MASS. The mid-infrared luminosities of non-CO-detected galaxies are well correlated with their stellar luminosities, showing that they trace (circum)stellar dust emission. CO-detected galaxies show an excess above these correlations, uncorrelated with their stellar luminosities, indicating that they likely contain PAHs and dust of interstellar origin. PAH and dust luminosities of CO-detected galaxies show tight correlations with their molecular gas masses, and the derived current SFRs are typically 0.01-1 Msun/yr. These SFRs systematically decrease with stellar age at fixed stellar mass, while they correlate nearly linearly with stellar mass at fixed age. The majority of local ETGs follow the same star-formation law as local star-forming galaxies, and their current SFEs do not depend on either stellar mass or age. Our results clearly indicate that molecular gas is fueling current star formation in local ETGs, that appear to acquire this gas via mechanisms regulated primarily by stellar mass. The current SFEs of local ETGs are similar to those of local star-forming galaxies, indicating that their low SFRs are likely due to smaller cold gas fractions rather than a suppression of star formation.Comment: 30 pages, 12 figures, 4 tables, accepted for publication in A&

A novel type of binding specificity to phospholipids for rat mannose-binding proteins isolated from serum and liver

AbstractMannose-binding protein (MBP) belongs to the collectin subgroup of C-type lectins with specificity for mannose and N-acetylglucosamine sugars. We investigated whether rat MBPs isolated from serum (S-MBP) and liver (L-MBP) interact with phospholipids using antibody against each MBP. Both S- and L-MBPs bound to phosphatidylinositol coated onto microtiter wells in a concentration- and a Ca2+-dependent manner. L-MBP also bound to phosphatidylglycerol and weakly to phosphatidylserine. MBPs interacted with liposomes composed of these lipids. S- and L-MBPs bound to phosphatidylinositol 4-monophosphate. L-MBP also bound to cardiolipin. These results provide evidence for a novel type of ligand binding specificity for MBPs, and raise the possibility that phospholipids are ligands for collectins

Binding of GTP to transducin is not inhibited by arrestin and phosphorylated rhodopsin

AbstractIn the presence of a photobleaching intermediate of unphosphorylated or phosphorylated rhodopsin (Rh∗), the binding of GppNHp to transducin was measured with or without arrestin for elucidation of the shut-off mechanism of the visual transduction process in bovine rod outer segments. The ability of Rh∗ to catalyze the formation of the transducin-GppNHp complex in the absence of arrestin was independent of the degree of phosphorylation of Rh∗. Furthermore, the catalyzing ability of the phosphorylated Rh∗ was not reduced by the addition of arrestin. These observations indicate that the interaction between phosphorylated Rh∗ and transducin was not inhibited by arrestin. Thus, the hypothesis was not supported that the PDE shut-off process is a simple competition between transducin and arrestin for binding to phosphorylated Rh∗