Chemical and antigenic structure of the O-polysaccharide of the lipopolysaccharides from two Acinetobacter haemolyticus strains differing only in the anomeric configuration of one glycosyl residue in their O-antigens.

In a previous study [Pantophlet, R., Brade, L., Dijkshoorn, L., and Brade, H. (1998) J. Clin. Microbiol. 36, 1245-1250] the O-polysaccharide of the lipopolysaccharides (LPS) from Acinetobacter haemolyticus strains 57 and 61 exhibited indistinguishable banding-patterns following Western blot and immunostaining with homologous or heterologous rabbit antiserum. In this report, the molecular basis for the observed cross-reactivity was elucidated, by determining the chemical structure of the polysaccharides by compositional analysis and NMR spectroscopy. The structures are: [sequence: see text] for strain 61 [GulpNAcA, 2-acetamido-2-deoxy-gulopyranosyluronic acid; ManpNAcA, 2-acetamido-2-deoxy-mannopyranosyluronic acid; QuipN4N, 2,4-diamino-2,4,6-trideoxy-glucopyranose; acyl (S)-3-hydroxybutyryl], thus, differing only in the anomeric configuration of the QuipN4N residue. The antigenic structures were determined by generating murine monoclonal antibodies, which were characterized by Western blot using LPS as antigen, by ELISA using LPS and de-O-acylated LPS as solid-phase antigens, and by ELISA inhibition studies using LPS, polysaccharide, and de-O-acylated LPS as inhibitors. Of the four antibodies selected, two were specific for the respective LPS moieties and two were cross-reactive. All antibodies were found to require the presence of the O-acetyl group for reactivity.     

Structural analysis of the lipopolysaccharide from Chlamydia trachomatis serotype L2.

The lipopolysaccharide (LPS) of Chlamydia trachomatis L2 was isolated from tissue culture-grown elementary bodies using a modified phenol/water procedure followed by extraction with phenol/chloroform/light petroleum. From a total of 5 x 10(4) cm2 of infected monolayers, 22.3 mg of LPS were obtained. Compositional analysis indicated the presence of 3-deoxy-D-manno-oct-2-ulopyranosonic acid (Kdo), GlcN, phosphorus, and fatty acids in a molar ratio of 2.8:2:2.1:4.5. Matrix-assisted laser-desorption ionization mass spectrometry performed on the de-O-acylated LPS gave a major molecular ion peak at m/z 1781.1 corresponding to a molecule of 3 Kdo, 2 GlcN, 2 phosphates, and two 3-hydroxyeicosanoic acid residues. The structure of deacylated LPS obtained after successive treatment with hydrazine and potassium hydroxide was determined by 600 MHz NMR spectroscopy as Kdoalpha2-->8Kdoalpha2-->4Kdoalpha2-->6D-GlcpNbeta1 -->6D-GlcpNalpha 1,4'-bisphosphate. These data, together with those published recently on the acylation pattern of chlamydial lipid A (Qureshi, N., Kaltashov, I., Walker, K., Doroshenko, V., Cotter, R. J., Takayama, K, Sievert, T. R., Rice, P. A., Lin, J.-S. L., and Golenbock, D. T. (1997) J. Biol. Chem. 272, 10594-10600) allow us to present for the first time the complete structure of a major molecular species of a chlamydial LPS.     

Glucagon-like peptide-1, glucose homeostasis and diabetes

Incretins, enhancers of insulin secretion, are essential for glucose tolerance, and a reduction in their function might contribute to poor beta-cell function in patients with type-2 diabetes mellitus. However, at supraphysiological doses, the incretin glucagon-like peptide-1 (GLP-1) protects pancreatic beta cells, and inhibits glucagon secretion, gastric emptying and food intake, leading to weight loss. GLP-1 mimetics, which are stable-peptide-based activators of the GLP-1 receptor, and incretin enhancers, which inhibit the incretin-degrading enzyme dipeptidyl peptidase-4, have emerged as therapies for type-2 diabetes and have recently reached the market. The pathophysiological basis the clinical use of these therapeutics is reviewed here.     

Latent manganese deficiency increases transpiration in barley (Hordeum vulgare)

To investigate if latent manganese (Mn) deficiency leads to increased transpiration, barley plants were grown for 10 weeks in hydroponics with daily additions of Mn in the low n M range. The Mn-starved plants did not exhibit visual leaf symptoms of Mn deficiency, but Chl a fluorescence measurements revealed that the quantum yield efficiency of PSII (F_v/F_m) was reduced from 0.83 in Mn-sufficient control plants to below 0.5 in Mn-starved plants. Leaf Mn concentrations declined from 30 to 7 μg Mn g⁻¹ dry weight in control and Mn-starved plants, respectively. Mn-starved plants had up to four-fold higher transpiration than control plants. Stomatal closure and opening upon light/dark transitions took place at the same rate in both Mn treatments, but the nocturnal leaf conductance for water vapour was still twice as high in Mn-starved plants compared with the control. The observed increase in transpiration was substantiated by ¹³C-isotope discrimination analysis and gravimetric measurement of the water consumption, showing significantly lower water use efficiency in Mn-starved plants. The extractable wax content of leaves of Mn-starved plants was approximately 40% lower than that in control plants, and it is concluded that the increased leaf conductance and higher transpirational water loss are correlated with a reduction in the epicuticular wax layer under Mn deficiency.     

The Validation and Assessment of Machine Learning: A Game of Prediction from High-Dimensional Data

In applied statistics, tools from machine learning are popular for analyzing complex and high-dimensional data. However, few theoretical results are available that could guide to the appropriate machine learning tool in a new application. Initial development of an overall strategy thus often implies that multiple methods are tested and compared on the same set of data. This is particularly difficult in situations that are prone to over-fitting where the number of subjects is low compared to the number of potential predictors. The article presents a game which provides some grounds for conducting a fair model comparison. Each player selects a modeling strategy for predicting individual response from potential predictors. A strictly proper scoring rule, bootstrap cross-validation, and a set of rules are used to make the results obtained with different strategies comparable. To illustrate the ideas, the game is applied to data from the Nugenob Study where the aim is to predict the fat oxidation capacity based on conventional factors and high-dimensional metabolomics data. Three players have chosen to use support vector machines, LASSO, and random forests, respectively.     

Chemical structure of wall teichoic acid isolated from Enterococcus faecium strain U0317

Wall teichoic acid (WTA) was isolated from Enterococcus faecium strain U0317 and structurally characterized using ¹H, ¹³C, and ³¹P NMR spectroscopy, including two-dimensional COSY, TOCSY, ROESY, HMQC, and HMBC experiments. Further compositional determination was undertaken using classical chemical methods and HF treatment followed by GLC and GLC–MS analyses. The repeating unit of WTA consisted of two residues of 2-acetamido-2-deoxy-d-galactose, glycerol (Gro), and phosphate, and has the structure shown below:→6)-α-d-GalpNAc-(1→3)-β-d-GalpNAc-(1→2)-Gro-(3→P→     

Structural characterization of the O-specific polysaccharide from the lipopolysaccharide of the fish pathogen Aeromonas bestiarum strain P1S

The O-specific polysaccharide obtained by mild-acid degradation of lipopolysaccharide of Aeromonas bestiarum P1S was studied by sugar and methylation analyses along with ¹H and ¹³C NMR spectroscopy. The sequence of the sugar residues was determined using ¹H,¹H NOESY and ¹H,¹³C HMBC experiments. The O-specific polysaccharide was found to be a high-molecular-mass polysaccharide composed of tetrasaccharide repeating units of the structureSince small amounts of a terminal Quip3N residue were identified in methylation analysis, it was assumed that the elucidated structure also represented the biological repeating unit of the O-specific polysaccharide.     

Quallen an Nord‐ und Ostseeküste

Jellyfishes in the North and the Baltic Sea Jellyfish masses are not only a nuisance for bathers but have significant negative effects on marine ecosystems and economy. The causes of worldwide increasing jellyfish mass occurrences are not fully understood until today. Anthropogenic influences as submarine constructions, overfishing, eutrophication and climate warming are assumed as possible causes. Jellyfish and their relatives have fascinating capabilities and features, including their amazing regeneration potential, a high adaptability on changing environments and especially their weapons, the stinging capsules. Despite the simplicity of their nervous system jellyfish have astonishing perception senses.     

Enhanced cytokinin degradation in leaf primordia of transgenic Arabidopsis plants reduces leaf size and shoot organ primordia formation

The plant hormone cytokinin is a key morphogenic factor controlling cell division and differentiation, and thus the formation and growth rate of organs during a plant's life cycle. In order to explore the relevance of cytokinin during the initial phase of leaf primordia formation and its impact on subsequent leaf development, we increased cytokinin degradation in young shoot organ primordia of Arabidopsis thaliana by expressing a cytokinin oxidase/dehydrogenase (CKX) gene under control of the AINTEGUMENTA (ANT) promoter. The final leaf size in ANT:CKX3 plants was reduced to ∼27% of the wild-type size and the number of epidermal cells was reduced to ∼12% of the wild type. Kinematic analysis revealed that cell proliferation ceased earlier and cell expansion was accelerated in ANT:CKX3 leaves, demonstrating that cytokinin controls the duration of the proliferation phase by delaying the onset of cell differentiation. The reduction of the cell number was partially compensated by an increased cell expansion. Interestingly, ANT:CKX3 leaf cells became about 60% larger than those of 35S:CKX3 leaves, indicating that cytokinin has an important function during cell expansion as well. Furthermore, ANT:CKX3 expression significantly reduced the capacity of both the vegetative as well as the generative shoot apical meristem to initiate the formation of new leaves and flowers, respectively. We therefore hypothesize that the cytokinin content in organ primordia is important for regulating the activity of the shoot meristem in a non-autonomous fashion.