Structural and serological characterisation of the O-antigenic polysaccharide of the lipopolysaccharide from Acinetobacter baumannii strain 24

Extraction of dry bacteria of Acinetobacter baumannii strain 24 by phenol-water yielded a lipopolysaccharide (LPS) that was studied by serological methods and fatty acid analysis. After immunisation of BALB/c mice with this strain, monoclonal antibody S48-3-13 (IgG(3) isotype) was obtained, which reacted with the LPS in western blot and characterized it as S-form LPS. Degradation of the LPS in aqueous 1% acetic acid followed by GPC gave the O-antigenic polysaccharide, whose structure was determined by compositional analyses and NMR spectroscopy of the polysaccharide and O-deacylated polysaccharide as [carbohydrate structure: see text] where QuiN4N is 2,4-diamino-2,4,6-trideoxyglucose and GalNAcA 2-acetamido-2-deoxygalacturonic acid. The amino group at C-4 of the QuipN4N residues is acetylated in about 2/3 of LPS molecules and (S)-3-hydroxybutyrylated in the rest.     

Interleukin-8 stimulates human immunodeficiency virus type 1 replication and is a potential new target for antiretroviral therapy

Production of the C-X-C chemokines interleukin-8 (IL-8) and growth-regulated oncogene alpha (GRO-alpha) in macrophages is stimulated by exposure to human immunodeficiency virus type 1 (HIV-1). We have demonstrated previously that GRO-alpha then stimulates HIV-1 replication in both T lymphocytes and macrophages. Here we demonstrate that IL-8 also stimulates HIV-1 replication in macrophages and T lymphocytes. We further show that increased levels of IL-8 are present in the lymphoid tissue of patients with AIDS. In addition, we demonstrate that compounds which inhibit the actions of IL-8 and GRO-alpha via their receptors, CXCR1 and CXCR2, also inhibit HIV-1 replication in both T lymphocytes and macrophages, indicating potential therapeutic uses for these compounds in HIV-1 infection and AIDS.     

Functional interaction in establishment of ribosomal integrity between small subunit protein rpS6 and translational regulator rpL10/Grc5p

Functional ribosomes synthesize proteins in all living cells and are composed of two labile associated subunits, which are made of rRNA and ribosomal proteins. The rRNA of the small 40S subunit (SSU) of the functional eukaryotic 80S ribosome decodes the mRNA molecule and the large 60S subunit (LSU) rRNA catalyzes protein synthesis. Recent fine structure determinations of the ribosome renewed interest in the role of ribosomal proteins in modulation of the core ribosomal functions. RpL10/Grc5p is a component of the LSU and is a multifunctional translational regulator, operating in 60S subunit biogenesis, 60S subunit export and 60S subunit joining with the 40S subunit. Here, we report that rpL10/Grc5p functionally interacts with the nuclear export factor Nmd3p in modulation of the cellular polysome complement and with the small subunit protein rpS6 in subunit joining and differential protein expression.     

Can light-saturated photosynthesis in lowland tropical forests be estimated by one light level?

Leaf-level net photosynthesis (A_n) estimates and associated photosynthetic parameters are crucial for accurately parameterizing photosynthesis models. For tropical forests, such data are poorly available and collected at variable light conditions. To avoid over- or underestimation of modeled photosynthesis, it is critical to know at which photosynthetic photon flux density (PPFD) photosynthesis becomes light-saturated. We studied the dependence of A_n on PPFD in two tropical forests in French Guiana. We estimated the light saturation range, including the lowest PPFD level at which A_sat (A_n at light saturation) is reached, as well as the PPFD range at which A_sat remained unaltered. The light saturation range was derived from photosynthetic light-response curves, and within-canopy and interspecific differences were studied. We observed wide light saturation ranges of A_n. Light saturation ranges differed among canopy heights, but a PPFD level of 1,000 µmol m⁻² s⁻¹ was common across all heights, except for pioneer trees species that did not reach light saturation below 2,000 µmol m⁻² s⁻¹. A light intensity of 1,000 µmol m⁻² s⁻¹ sufficed for measuring A_sat of climax species at our study sites, independent of the species or the canopy height. Because of the wide light saturation ranges, results from studies measuring A_sat at higher PPFD levels (for upper canopy leaves up to 1,600 µmol m⁻² s⁻¹) are comparable with studies measuring at 1,000 µmol m⁻² s⁻¹.     

A comprehensive and comparative phenotypic analysis of the collaborative founder strains identifies new and known phenotypes

Mammalian Genome - The collaborative cross (CC) is a large panel of mouse-inbred lines derived from eight founder strains (NOD/ShiLtJ, NZO/HILtJ, A/J, C57BL/6J, 129S1/SvImJ, CAST/EiJ, PWK/PhJ, and...     

Expression of Caenorhabditis elegans PCS in the AtPCS1‐deficient Arabidopsis thaliana cad1‐3 mutant separates the metal tolerance and non‐host resistance functions of phytochelatin synthases

Phytochelatin synthases (PCS) play key roles in plant metal tolerance. They synthesize small metal‐binding peptides, phytochelatins, under conditions of metal excess. Respective mutants are strongly cadmium and arsenic hypersensitive. However, their ubiquitous presence and constitutive expression had long suggested a more general function of PCS besides metal detoxification. Indeed, phytochelatin synthase1 from Arabidopsis thaliana (AtPCS1) was later implicated in non‐host resistance. The two different physiological functions may be attributable to the two distinct catalytic activities demonstrated for AtPCS1, that is the dipeptidyl transfer onto an acceptor molecule in phytochelatin synthesis, and the proteolytic deglycylation of glutathione conjugates. In order to test this hypothesis and to possibly separate the two biological roles, we expressed a phylogenetically distant PCS from Caenorhabditis elegans in an AtPCS1 mutant. We confirmed the involvement of AtPCS1 in non‐host resistance by showing that plants lacking the functional gene develop a strong cell death phenotype when inoculated with the potato pathogen Phytophthora infestans. Furthermore, we found that the C. elegans gene rescues phytochelatin synthesis and cadmium tolerance, but not the defect in non‐host resistance. This strongly suggests that the second enzymatic function of AtPCS1, which remains to be defined in detail, is underlying the plant immunity function.     

Mitochondrial Dysfunction and Decrease in Body Weight of a Transgenic Knock-in Mouse Model for TDP-43

The majority of amyotrophic lateral sclerosis (ALS) cases as well as many patients suffering from frontotemporal lobar dementia (FTLD) with ubiquitinated inclusion bodies show TDP-43 pathology, the protein encoded by the TAR DNA-binding protein (Tardbp) gene. We used recombinase-mediated cassette exchange to introduce an ALS patient cDNA into the mouse Tdp-43 locus. Expression levels of human A315T TDP-43 protein were 300% elevated in heterozygotes, whereas the endogenous mouse Tdp-43 was decreased to 20% of wild type levels as a result of disturbed feedback regulation. Heterozygous TDP-43^A315TKi mutants lost 10% of their body weight and developed insoluble TDP-43 protein starting as early as 3 months after birth, a pathology that was exacerbated with age. We analyzed the splicing patterns of known Tdp-43 target genes as well as genome-wide gene expression levels in different tissues that indicated mitochondrial dysfunction. In heterozygous mutant animals, we observed a relative decrease in expression of Parkin (Park2) and the fatty acid transporter CD36 along with an increase in fatty acids, HDL cholesterol, and glucose in the blood. As seen in transmission electron microscopy, neuronal cells in motor cortices of TDP-43^A315TKi animals had abnormal neuronal mitochondrial cristae formation. Motor neurons were reduced to 90%, but only slight motoric impairment was detected. The observed phenotype was interpreted as a predisease model, which might be valuable for the identification of further environmental or genetic triggers of neurodegeneration.