Cytosolic phospholipase A2-driven PGE2 synthesis within unsaturated fatty acids-induced lipid bodies of epithelial cells

Cytoplasmic lipid bodies (also known as lipid droplets) are intracellular deposits of arachidonic acid (AA), which can be metabolized for eicosanoid generation. PGE₂ is a major AA metabolite produced by epithelial cells and can modulate restoration of epithelium homeostasis after injury. We studied lipid body biogenesis and their role in AA metabolic pathway in an epithelial cell line derived from normal rat intestinal epithelium, IEC-6 cells. Lipid bodies were virtually absent in confluent IEC-6 cells. Stimulation of confluent IEC-6 cells with unsaturated fatty acids, including AA or oleic acid (OA), induced rapid lipid body assembly that was independent on its metabolism to PGE₂, but dependent on G-coupled receptor-driven signaling through p38, PKC, and PI3K. Newly formed lipid bodies compartmentalized cytosolic phospholipase (cPL)A₂-α, while facilitated AA mobilization and synthesis of PGE₂ within epithelial cells. Thus, both lipid body-related events, including highly regulated biogenesis and functional assembly of cPLA₂-α-driven enhanced AA mobilization and PGE₂ production, may have key roles in epithelial cell-driven inflammatory functions, and may represent relevant therapeutic targets of epithelial pathologies.     

Toward the active conformations of rhodopsin and the beta2-adrenergic receptor

Using sets of experimental distance restraints, which characterize active or inactive receptor conformations, and the X-ray crystal structure of the inactive form of bovine rhodopsin as a starting point, we have constructed models of both the active and inactive forms of rhodopsin and the beta2-adrenergic G-protein coupled receptors (GPCRs). The distance restraints were obtained from published data for site-directed crosslinking, engineered zinc binding, site-directed spin-labeling, IR spectroscopy, and cysteine accessibility studies conducted on class A GPCRs. Molecular dynamics simulations in the presence of either "active" or "inactive" restraints were used to generate two distinguishable receptor models. The process for generating the inactive and active models was validated by the hit rates, yields, and enrichment factors determined for the selection of antagonists in the inactive model and for the selection of agonists in the active model from a set of nonadrenergic GPCR drug-like ligands in a virtual screen using ligand docking software. The simulation results provide new insights into the relationships observed between selected biochemical data, the crystal structure of rhodopsin, and the structural rearrangements that occur during activation.     

"Live high-train low" using normobaric hypoxia: a double-blinded, placebo-controlled study

The combination of living at altitude and training near sea level [live high-train low (LHTL)] may improve performance of endurance athletes. However, to date, no study can rule out a potential placebo effect as at least part of the explanation, especially for performance measures. With the use of a placebo-controlled, double-blinded design, we tested the hypothesis that LHTL-related improvements in endurance performance are mediated through physiological mechanisms and not through a placebo effect. Sixteen endurance cyclists trained for 8 wk at low altitude (<1,200 m). After a 2-wk lead-in period, athletes spent 16 h/day for the following 4 wk in rooms flushed with either normal air (placebo group, n = 6) or normobaric hypoxia, corresponding to an altitude of 3,000 m (LHTL group, n = 10). Physiological investigations were performed twice during the lead-in period, after 3 and 4 wk during the LHTL intervention, and again, 1 and 2 wk after the LHTL intervention. Questionnaires revealed that subjects were unaware of group classification. Weekly training effort was similar between groups. Hb mass, maximal oxygen uptake (VO(2)) in normoxia, and at a simulated altitude of 2,500 m and mean power output in a simulated, 26.15-km time trial remained unchanged in both groups throughout the study. Exercise economy (i.e., VO(2) measured at 200 W) did not change during the LHTL intervention and was never significantly different between groups. In conclusion, 4 wk of LHTL, using 16 h/day of normobaric hypoxia, did not improve endurance performance or any of the measured, associated physiological variables.     

Crystal proteins from Bacillus thuringiensis serovar. medellin

Colombian strains 163-131 and 24-726 of the Bacillus thuringiensis serovar. medellin (Btmed), serotype H-30, are very toxic to mosquito larvae. Strain 24-726 was serologically and biochemically characterized. It is almost identical to the reference-strain 163-131. The parasporal inclusion of Btmed strain 163-131 was analysed by electron microscopy. The crystal protein matrix was very similar to that observed in B. thuringiensis serovar. israelensis (Bti). Aedes aegypti, Anopheles albimanus and Culex quinquefasciatus larvae were exposed to 500× the half-lethal concentration (LC₅₀) of Btmed strains, Bti strain 1884 and B. thuringiensis serovar. morrisoni (Btm) strain PG-14. Mortality of Aedes aegypti occurred within approx. 60 min with the four strains, whereas C. quinquefasciatus mortality was three times slower with Btmed than with strains 1884 and PG14. The onset mortality of Anopheles albimanus starts when other species are already dead. The thermolabilities of the mosquitocidal activities of the crystal proteins were tested by incubation of cultures of 20 min at various temperatures. Btmed lost all mosquitocidal activity at 73°C, and 1884 and PG-14 at 79°C. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis of the crystals purified from strain 163-131 shows polypeptides at 100 kDa, multiple bands at 80, 75, 70, 67, and 65 kDa, and two doubles at 40–41 and 28–30 kDa. Immunodetection with antibodies raised against Bti toxins shows cross-reaction between the 30-kDa and to a lesser extent the 28-kDa polypeptides of Btmed crystals and Cyt A of Bti. A slight response is observed with the 65-kDa Btmed to serum raised against Cry IV D of Bti. Correspondence to: I. Thiéry     

Morphological and biological notes on Encarsia meritoria Gahan (Hymenoptera,Aphelinidae), a parasitoid of Trialeurodes vaporariorum (Westwood) (Homoptera,Aleyrodidae) new in Europe

Encarsia meritoria Gahan, a Neartic species recorded only in the USA, was found naturally occurring in Catalonia (north‐east Spain) in 1987. The morphology of immature stages, the rate of development in the range 12°C‐34°C, the longevity and fecundity at 24°C and some observations on its searching and host feeding behaviour are presented in this paper. Mean development times from egg laying to adult emergence ranged from 75 days at 12° C to 11 days at 28°C. The Lower Developmental Threshold computed from linear regression equations was 9°C. Females laid an average of 198 eggs (range 89–330) in an average of 34 days (longevity range 19–54 days). The intrinsic rate of increase at 24° C was 0.1717, slightly greater than the r_m of T. vaporariorum and smaller than the values reported for E. tricolor and E. formosa, which is not very promising for biological control. However, this may not be a definitive conclusion, because factors other than those considered in our experiments may play an important role infield conditions.     

MLL2: A new mammalian member of the trx/MLL family of genes.

We have identified a gene at chromosome band 19q13.1, which is closely related to MLL. MLL is located in a region of chromosome 11q23 that has partial synteny with chromosome 19q. We have named this gene at 19q13.1, MLL2. MLL2 encodes a protein that exhibits a high level of similarity to MLL over several important protein domains. MLL2 is also ubiquitously expressed among adult human tissues, as is MLL. MLL is a homologue of the Drosophila gene trithorax (trx), which encodes a regulator of homeotic gene expression. MLL is involved in chromosome rearrangements associated with leukemia in mammals. However, no MLL2 rearrangements associated with leukemia have been recorded.     

Chaperone-mediated autophagy prevents collapse of the neuronal metastable proteome

1. Download : Download high-res image (170KB)
2. Download : Download full-size image

     

Genomic microarrays in the spotlight

Microarray-based comparative genomic hybridization (array-CGH) has emerged as a revolutionary platform, enabling the high-resolution detection of DNA copy number aberrations. In this article we outline the use and limitations of genomic clones, cDNA clones and PCR products as targets for genomic microarray construction. Furthermore, the applications and future aspects of these arrays for DNA copy number analysis in research and diagnostics, epigenetic profiling and gene annotation are discussed. These recent developments of genomic microarrays mark only the beginning of a new generation of high-resolution and high-throughput tools for genetic analysis.