Studies on the control of cell division in a green alga, Ankistrodesmus gracilis (Chlorococcales) III. Induction synchrony with controlled division patterns

When stagnant cells of Ankistrodesmus gracilis obtained froma standard culture were inoculated into the basal medium atcell densities lower than 1.0 ? 10⁷ cells/ml, cell proliferationoccurred stepwise at time intervals of about 30 hr. At a densityof 5.5 ? 10⁴cells/ml, the increase in cell number per step wasabout 2.7-fold. When inoculated into a glutamine medium thetime interval was 24 hr, and the average increase of cell numberwas about 4-fold. When cells were preincubated at about 5.0? 10⁵ cells per ml in the basal medium for 30 hr, then transferredinto a glutamine or arginine medium at about 7.0 ? 10⁶ cells/ml,synchronous division occurred about 18 hr later with binaryfission or about 33 hr later with multiple fission, respectively. (Received May 16, 1979; )     

Isolation of norbergenin from Saxifraga stolonifera

Norbergenin, a C-glucoside, was isolated from Saxifraga stolonifera and its structure assigned as 2β-d-glucopyranosylgallic acid °-lactone.     

Somatostatin is involved in anorexia in mice fed a valine-deficient diet

The ingestion of a valine (Val)-deficient diet results in a significant reduction of food intake and body weight within 24 h, and this phenomenon continues throughout the period over which such a diet is supplied. Both microarray and real-time PCR analyses revealed that the expression of somatostatin mRNA was increased in the hypothalamus in anorectic mice that received a Val-deficient diet. On the other hand, when somatostatin was administered intracerebroventricularly to intact animals that were fed a control diet, their 24-h food intake decreased significantly. In addition, Val-deficient but not pair-fed mice or those fasted for 24 h showed a less than 0.5-fold decrease in the hypothalamic mRNA expression levels of Crym, Foxg1, Itpka and two unknown EST clone genes and a more than twofold increase in those of Slc6a3, Bdh1, Ptgr2 and one unknown EST clone gene. These results suggest that hypothalamic somatostatin and genes responsive to Val deficiency may be involved in the central mechanism of anorexia induced by a Val-deficient diet.     

N-glycans of SREC-I (scavenger receptor expressed by endothelial cells): essential role for ligand binding, trafficking and stability

Scavenger receptor expressed by endothelial cells (SREC-I) mediates the endocytosis of chemically modified lipoproteins such as acetylated low-density lipoprotein (Ac-LDL) and oxidized LDL and is implicated in atherogenesis. We produced recombinant SREC-I in Chinese hamster ovary-K1 cells and identified three potential glycosylation sites, Asn(289), Asn(382) and Asn(393), which were all glycosylated. To determine the function of N-glycans in SREC-I, we characterized SREC-I mutant proteins by intracellular distribution and the cellular incorporation rate of Ac-LDL. N382Q/N393Q and N289Q/N382Q/N393Q were sequestered in the endoplasmic reticulum, resulting in a severe reduction in the cellular incorporation of Ac-LDL. N382Q showed a normal cell surface residency and an enhanced affinity for Ac-LDL, resulting in an elevated Ac-LDL cellular incorporation. These results indicate that the N-glycan of Asn(393) regulates the intracellular sorting of SREC-I and that the N-glycan of Asn(382) controls ligand-binding affinity. Furthermore, we detected an enhanced trypsin sensitivity of the N289Q. Glycan structure analyses revealed that the core-fucosylated bi-antennary is the common major structure at all glycosylation sites. In addition, tri- and tetra-antennary were detected as minor constituents at Asn(289). A bisecting GlcNAc was also detected at Asn(382) and Asn(393). Structural analyses and homology modeling of SREC-I suggest that the N-glycan bearing a β1-6GlcNAc branch at Asn(289) protects from proteinase attack and thus confers a higher stability on SREC-I. These data indicate that Asn(289)-, Asn(382)- and Asn(393)-linked N-glycans of SREC-I have distinct functions in regulating proteolytic resistance, ligand-binding affinity and subcellular localization, all of which might be involved in the development of atherogenesis.     

Serine-Type Carboxypeptidase KexA of Aspergillus oryzae Has Broader Substrate Specificity than Saccharomyces cerevisiae Kex1 and Is Required for Normal Hyphal Growth and Conidiation

Aspergillus oryzae has an ortholog of Saccharomyces cerevisiae KEX1, termed kexA. A truncated form of KexA protein showed serine-type carboxypeptidase activity and somewhat broader substrate specificity than Kex1 protease. Furthermore, our results indicated that KexA is required for normal growth of A. oryzae and that it might be involved in hyphal branching.