Enzymic synthesis,chemical characterisation and Sda activity of GalNAcß1-4[NeuAcα2-3]Galß1-4GlcNAc and GalNAcß1-4[NeuAcα2-3]Galß1-4Glc

The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and¹H-500 MHz NMR spectroscopy. In Sd^a serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity.     

Approaches to breeding for salinity tolerance - a case study on Porteresia coarctata

Cereals are the world's major source of food for human nutrition. Among these, rice (Oryza sativa) is the most prominent and represents the staple diet for more than two-fifths (2.4 billion) of the world's population, making it the most important food crop of the developing world (Anon., 2000a). Rice production in vast stretches of coastal areas is hampered due to high soil salinity. This is because rice is a glycophyte and it does not grow well under saline conditions. In order to increase rice production in these areas there is a need to develop rice varieties suited to saline environments. Research has shown that Porteresia coarctata, a highly salt tolerant wild relative of rice growing in estuarine soils, is an important material for transferring salt tolerant characteristics to rice. It is quite possible that Porteresia may be used as a parent for evolving better and truly salt resistant varieties. The inadequate results and the difficulties associated with conventional breeding techniques necessitate the use of the tools of crop biotechnology in unravelling some of the characteristics of Porteresia that have been highlighted in this report. In view of the limited resources available for increasing salinity tolerance to the breeders to wild rice germplasm, Porteresia is undoubtedly one of the key source species for elevating salinity tolerance in cultivated rice.     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Ecdysteroid glycosides from Sida rhombifolia L

Seven ecdysteroids, including the three new compounds 1-3, were isolated from Sida rhombifolia L. Their structures and configurations were determined by extensive spectroscopic techniques in combination with chemical derivatization. The four known compounds--ecdysone (4), 20-hydroxyecdysone (5), 2-deoxy-20-hydroxyecdysone-3-O-beta-D-glucopyranoside (6), and 20-hydroxyecdysone-3-O-beta-D-glucopyranoside (7)--are reported for the first time from this plant.     

Maintenance of NF-kappaB activation in T-lymphocytes and a naive T-cell population in autoimmune-prone (NZB/NZW)F(1) mice by feeding a food-restricted diet enriched with n-3 fatty acids

We have previously shown that feeding a fish oil (FO) supplemented diet in combination with 40% food restriction (FO/FR) has a greater impact on extending life span in lupus-prone (NZB x NZW)F1 mice than either FO ad libitum (FO/AL) or corn oil food restricted (CO/FR) alone. Lupus disease is associated with increased Th-2 (i.e., IL-6 and IL-10) cytokine production and reduced IL-2 production and NF-kappaB activation. We hypothesized that the mechanism of action by which FO/FR increases life span may involve alterations in T-lymphocyte signaling and subsequent cytokine production. To test this hypothesis, we isolated and then stimulated splenic T-lymphocytes ex vivo with anti-CD3 and -CD28 monoclonal antibodies. We report here that CO/FR and FO/FR and to a lesser extent FO/AL offset disease-associated losses in Th-1 cytokine production, CD69 expression, and NF-kappaB activation in splenic T-lymphocytes activated ex vivo. Similarly, CO/FR and FO/FR prevented the disease-dependent rise in Th-2 cytokine production ex vivo and CD69 expression in vivo. In essence, the T-lymphocyte phenotype in the old CO/FR and FO/FR groups was identical to that in the young disease-free mice. Taken together, the data suggest that both CO/FR and FO/FR increase life span, in part, by maintaining a youthful immune phenotype in autoimmune-prone mice. However, FO/FR appears to represent a more potent dietary strategy in delaying disease-associated immune dysregulation than CO/FR.     

Modulation of lipid peroxidation and antioxidant enzymes in murine salivary gland by dietary fatty acid ethyl esters

The present study was undertaken to investigate the effect of n-9, n-6, and n-3 dietary fatty acid ethyl esters on basal (uninduced) and Fe2+/ascorbate (induced) lipid peroxidation (LPO) in salivary gland (SG) of mice. Feeding n-3 ethyl ester polyunsaturated fatty acids (PUFA) increased the uninduced and induced LPO in SG homogenates. In contrast, feeding olive oil ethyl esters (n-9) significantly lowered the induced and uninduced LPO in SG tissue. Salivary gland susceptibility to LPO increased in the order of: olive oil < corn oil < safflower oil < n-3 ethyl esters. Olive oil esters in the diet increased primarily the 18:1 levels in SG tissue. Whereas feeding n-3 PUFA notably increased the superoxide dismutase (SOD) and catalase activities in SG homogenates, no significant changes were seen between n-9 and n-6 PUFA-fed mice. Lower levels of Vitamin E (Vit E) in the tissues of n-3 PUFA-fed mice indicate that the higher the dietary lipid unsaturation, the higher the requirement for Vit E in the diet. Our results indicate that, similar to other organs, salivary gland susceptibility to uninduced or induced oxidation depends on the source of dietary PUFA. In conclusion, feeding olive oil increases the resistance of SGs to induced and uninduced LPO.     

Phosphorylation of Saccharomyces cerevisiae choline kinase on Ser30 and Ser85 by protein kinase A regulates phosphatidylcholine synthesis by the CDP-choline pathway

The Saccharomyces cerevisiae CKI-encoded choline kinase is phosphorylated on a serine residue and stimulated by protein kinase A. We examined the hypothesis that amino acids Ser(30) and Ser(85) contained in a protein kinase A sequence motif in choline kinase are target sites for protein kinase A. The synthetic peptides SQRRHSLTRQ (V(max)/K(m) = 10.8 microm(-1) nmol min(-1) mg(-1)) and GPRRASATDV (V(max)/K(m) = 0.15 microm(-1) nmol min(-1) mg(-1)) containing the protein kinase A motif for Ser(30) and Ser(85), respectively, within the choline kinase protein were substrates for protein kinase A. Choline kinase with Ser(30) to Ala (S30A) and Ser(85) to Ala (S85A) mutations were constructed alone and in combination by site-directed mutagenesis and expressed in a cki1Delta eki1Delta double mutant that lacks choline kinase activity. The mutant enzymes were expressed normally, but the specific activity of choline kinase in cells expressing the S30A, S85A, and S30A,S85A mutant enzymes was reduced by 44, 8, and 60%, respectively, when compared with the control. In vivo labeling experiments showed that the extent of phosphorylation of the S30A, S85A, and S30A,S85A mutant enzymes was reduced by 70, 17, and 83%, respectively. Phosphorylation of the S30A, S85A, and S30A,S85A mutant enzymes by protein kinase A in vitro was reduced by 60, 7, and 96%, respectively, and peptide mapping analysis of the mutant enzymes confirmed the phosphorylation sites in the enzyme. The incorporation of (3)H-labeled choline into phosphocholine and phosphatidylcholine in cells bearing the S30A, S85A, and S30A,S85A mutant enzymes was reduced by 56, 27, and 81%, respectively, and by 58, 33, and 84%, respectively, when compared with control cells. These data supported the conclusion that phosphorylation of choline kinase on Ser(30) and Ser(85) by protein kinase A regulates PC synthesis by the CDP-choline pathway.     

Identification and Characterization of Rvs162/Rvs167-3, a Novel N-BAR Heterodimer in the Human Fungal Pathogen Candida albicans

Membrane reshaping resides at the core of many important cellular processes, and among its mediators are the BAR (Bin, Amphiphysin, Rvs) domain-containing proteins. We have explored the diversity and function of the Rvs BAR proteins in Candida albicans and identified a novel family member, Rvs167-3 (orf19.1861). We show that Rvs167-3 specifically interacts with Rvs162 to form a stable BAR heterodimer able to bind liposomes in vitro. A second, distinct heterodimer is formed by the canonical BAR proteins Rvs161 and Rvs167. Purified Rvs161/Rvs167 complex also binds liposomes, indicating that C. albicans expresses two functional BAR heterodimers. We used live-cell imaging to localize green fluorescent protein (GFP)-tagged Rvs167-3 and Rvs167 and show that both proteins concentrate in small cortical spots. However, while Rvs167 strictly colocalizes with the endocytic marker protein Abp1, we do not observe any colocalization of Rvs167-3 with sites of endocytosis marked by Abp1. Furthermore, the rvs167-3Δ/Δ mutant is not defective in endocytosis and strains lacking Rvs167-3 or its partner Rvs162 do not display increased sensitivity to high salt concentrations or decreased cell wall integrity, phenotypes which have been observed for rvs167Δ/Δ and rvs161Δ/Δ strains and which are linked to endocytosis defects. Taken together, our results indicate different roles for the two BAR heterodimers in C. albicans: the canonical Rvs161/Rvs167 heterodimer functions in endocytosis, whereas the novel Rvs162/Rvs167-3 heterodimer seems not to be involved in this process. Nevertheless, despite their different roles, our phenotypic analysis revealed a genetic interaction between the two BAR heterodimers, suggesting that they may have related but distinct membrane-associated functions.