Phytanic acid and docosahexaenoic acid increase the metabolism of all-trans-retinoic acid and CYP26 gene expression in intestinal cells.

Retinoids are essential for growth and cell differentiation of epithelial tissues. The effects of the food compounds phytol, the phytol metabolite phytanic acid, and the fatty acid docosahexaenoic acid (DHA) on the retinoid signaling pathway in intestinal cells were studied. Phytol inhibited the formation of all-trans-retinoic acid (RA) from dietary retinol in intestinal cells. Phytanic acid, a known retinoic X receptor (RXRalpha) and peroxisome proliferator activating receptor (PPARalpha) activator, also activated PPARdelta, and to a lesser degree PPARgamma, in a transactivation assay. Phytanic acid had no effect on intestinal RA hydroxylase CYP26 (also named P450RAI) gene expression and metabolism of all-trans-RA in intestinal Caco-2 cells. However, in combination with retinoic acid receptor (RAR)-ligands (all-trans-RA or synthetic Am580) phytanic acid enhanced the induction of CYP26 and RA-metabolism in comparison to treatments with all-trans-RA or Am580 alone. Also treatment with DHA did not affect CYP26 gene expression and RA-metabolism but cotreatment of the cells with DHA and all-trans-RA or Am580 enhanced the induction of CYP26, in comparison to the induction caused by all-trans-RA or Am580 alone. This study indicates that food compounds such as phytanic acid and DHA that are RXR-agonists and have an impact on intestinal CYP26 gene expression and metabolism of all-trans-RA in intestinal cells.     

Inhibition of photosynthesis by Colletotrichum lindemuthianum in bean leaves determined by chlorophyll fluorescence imaging

Infection of bean leaves by Colletotrichum lundemuthianum causes vein necrosis and subsequent localized wilting of the blade. The effect of infection on photosynthesis was investigated by imaging leaf chlorophyll fluorescence as a means of mapping stomatal and metabolic inhibition of photosynthesis. During infection, CO₂ assimilation (An), stomatal conductance to water vapour, and photosynthetic electron transport rate (J_t) decreased, whereas dark respiration increased. An decreased more than was expected from the reduction in green leaf area, showing that photosynthesis was inhibited in apparently healthy areas. Under subsaturating irradiance, images of J_t in air showed that photosynthesis decreased gradually, with this effect shifting from green to necrotic areas. Sudden increase in CO₂ concentration to 0·74% in the atmosphere around the leaf only partially reversed this inhibition, showing that both stomatal and metabolic inhibition occurred. Under limiting irradiance, decreases in J_t and in maximal J_t during high CO₂ exposure as leaf damage severity increased suggested that metabolic inhibition was mediated through an inhibition of Ribulose 1·5‐bisphosphate (RuBP) regeneration. Finally, the importance of our data in terms of assessing the loss of photosynthetic yield from visible symptoms – as is currently performed in epidemiology – is discussed.     

The cell polarity protein ASIP/PAR-3 directly associates with junctional adhesion molecule (JAM).

The establishment and maintenance of cellular polarity are critical for the development of multicellular organisms. PAR (partitioning-defective) proteins were identified in Caenorhabditis elegans as determinants of asymmetric cell division and polarized cell growth. Recently, vertebrate orthologues of two of these proteins, ASIP/PAR-3 and PAR-6, were found to form a signalling complex with the small GTPases Cdc42/Rac1 and with atypical protein kinase C (PKC). Here we show that ASIP/PAR-3 associates with the tight-junction-associated protein junctional adhesion molecule (JAM) in vitro and in vivo. No binding was observed with claudin-1, -4 or -5. In fibroblasts and CHO cells overexpressing JAM, endogenous ASIP is recruited to JAM at sites of cell-cell contact. Over expression of truncated JAM lacking the extracellular part disrupts ASIP/PAR-3 localization at intercellular junctions and delays ASIP/PAR-3 recruitment to newly formed cell junctions. During junction formation, JAM appears early in primordial forms of junctions. Our data suggest that the ASIP/PAR-3-aPKC complex is tethered to tight junctions via its association with JAM, indicating a potential role for JAM in the generation of cell polarity in epithelial cells.     

Study of pyoverdine type and production by Pseudomonas aeruginosa isolated from cystic fibrosis patients: prevalence of type II pyoverdine isolates and accumulation of pyoverdine-negative mutations

The lungs of cystic fibrosis patients are frequently colonized by Pseudomonas aeruginosa, which produces high-affinity fluorescent peptidic siderophores, pyoverdines. Three pyoverdines which differ in their peptide chain and are easily differentiated by isoelectric focusing exist, only one being produced by a given strain. P. aeruginosa isolates from cystic fibrosis patients of a German hospital were analyzed by sequential, pulse-field gel electrophoresis (PFGE) and for pyoverdine production and type. Only producers of type I and type II pyoverdine were found. There was a perfect correlation between the type of pyoverdine produced and the clonality determined by PFGE. PFGE clone C, the most prevalent among cystic fibrosis patients, and found in an aquatic environment, produced type II pyoverdine. Pyoverdine-negative mutants seemed to increase as a function of the lung colonization time, but retained the capacity to take up pyoverdines. Most isolates that took up type II pyoverdine were also able to utilize type I pyoverdine as judged by growth stimulation experiments. No correlation was observed between the loss of pyoverdine production and mucoidy.     

Microsatellites in the genus Xiphophorus,developed in Xiphophorus montezumae

Species of the genus Xiphophorus (swordtails and platies) are of great interest for the study of evolution of sexually selected traits like the sword, which is an elongation of ventral fin rays of the male caudal fin, that has evolved in several species within this genus. The detection of 10 microsatellites within the genus Xiphophorus will enable studies about the correlation of this trait with sexual reproductive success of males possessing swords of different lengths. These microsatellites will also be useful in determining population structure and enable paternity analysis in these species, where sperm storage is widespread.     

Microsatellite markers for Bromus tectorum (cheatgrass)

Bromus tectorum (cheatgrass) is a flourishing invasive weed in the western United States. The objective of our study is to characterize its genetic diversity. We made a B. tectorum genomic library in lambda phage and screened approximately 4000 clones for poly CA and poly CT dinucleotide repeats. Of 38 sequences with dinucleotide repeats isolated from the library, we designed primer sets for 18 loci. A preliminary screen of 40 individuals from four populations indicated that seven loci were polymorphic. These loci will be valuable for elucidation of cheatgrass genetic diversity and population structure.     

Adipose Depletion and Apoptosis Induced by Trans-10, Cis-12 Conjugated Linoleic Acid in Mice*

Objective: To compare the effectiveness of a conjugated linoleic acid (CLA) isomer mixture (mCLA) with each main isomer [trans-10,cis-12 CLA (CLA10,12) and cis-9,trans-11 CLA (CLA9,11)] in causing body lipid loss and adipose tissue apoptosis. Research Methods and Procedures: Mice selected over 16 generations for high (MH) or low (ML) energy expenditure and a control group (MC) were fed diets containing either soy oil or soy oil plus mCLA, CLA10,12, or CLA9,11 for 5 days in one study and 14 days in a second study. Results: Mice fed mCLA or CLA10,12 had less body lipid (p < 0.05), smaller retroperitoneal fat pads (p < 0.05), and ate less (p < 0.01) than mice fed no CLA or CLA9,11 for 5 days. Mice consuming 1% mCLA or 0.5% CLA10,12 gained less weight (p < 0.01) and had less body lipid (p < 0.05) and smaller epididymal (p < 0.05) and retroperitoneal fat pads (p < 0.01) than mice consuming either control or 0.5% CLA9,11-containing diets for 14 days. Only mCLA and CLA10,12 increased apoptosis in retroperitoneal fat pads (p < 0.01). The effects of mCLA and CLA10,12 were independent of genetic line except for the effect on adipocyte apoptosis. Mice of the MH line were slightly less sensitive than MC or ML mice to CLA-induced adipose tissue apoptosis. Discussion: CLA10,12, but not CLA9,11, can induce both body fat loss and adipose apoptosis. Although mice of a genotype with less body fat and greater metabolic rate and feed intake appear less sensitive, these CLA effects are robust for mice of varying metabolic background.     

Expression and localization of P-glycoprotein in human heart: effects of cardiomyopathy.

ABC-type transport proteins, such as P-glycoprotein (P-gp), modify intracellular concentrations of many substrate compounds. They serve as functional barriers against entry of xenobiotics (e.g., in the gut or the blood-brain barrier) or contribute to drug excretion. Expression of transport proteins in the heart could be an important factor modifying cardiac concentrations of drugs known to be transported by P-gp (e.g., beta-blockers, cardiac glycosides, doxorubicin). We therefore investigated the expression and localization of P-gp in human heart. Samples from 15 human hearts (left ventricle; five non-failing, five dilated cardiomyopathy, and five ischemic cardiomyopathy) were analyzed for expression of P-gp using real-time RT-PCR, immunohistochemistry, and in situ hybridization. Immunohistochemistry revealed expression of P-gp in endothelium of both arterioles and capillaries of all heart samples. Although P-gp mRNA was detected in all samples, its expression level was significantly reduced in patients with dilated cardiomyopathy. We describe variable expression of P-gp in human heart and its localization in the endothelial wall. Thus, intracardiac concentrations of various compounds may be modified, depending on the individual P-gp level.