Lovastatin inhibits the extracellular-signal-regulated kinase pathway in immortalized rat brain neuroblasts

Arachidonic acid is a potential paracrine agent released by the uterine endometrial epithelium to induce PTGS2 [PG (prostaglandin)-endoperoxide synthase 2] in the stroma. In the present study, bovine endometrial stromal cells were used to determine whether PTGS2 is induced by arachidonic acid in stromal cells, and to investigate the potential role of PPARs (peroxisome-proliferator-activated receptors) in this effect. Arachidonic acid increased PTGS2 levels up to 7.5-fold within 6 h. The cells expressed PPARalpha and PPARdelta (also known as PPARbeta) (but not PPARgamma). PTGS2 protein level was increased by PPAR agonists, including polyunsaturated fatty acids, synthetic PPAR ligands, PGA1 and NSAIDs (non-steroidal anti-inflammatory drugs) with a time course resembling that of arachidonic acid. Use of agonists and antagonists indicated PPARalpha (but not PPARdelta or PPARgamma) was responsible for PTGS2 induction. PTGS2 induction by arachidonic acid did not require PG synthesis. PTGS2 levels were increased by the PKC (protein kinase C) activators 4beta-PMA and PGF(2alpha), and the effects of arachidonic acid, NSAIDs, synthetic PPAR ligands and 4beta-PMA were blocked by PKC inhibitors. This is consistent with PPAR phosphorylation by PKC. Induction of PTGS2 protein by 4beta-PMA in the absence of a PPAR ligand was decreased by the NF-kappaB (nuclear factor kappaB) inhibitors MG132 and parthenolide, suggesting that PKC acted through NF-kappaB in addition to PPAR phosphorylation. Use of NF-kappaB inhibitors allowed the action of arachidonic acid as a PPAR agonist to be dissociated from an effect through PKC. The results are consistent with the hypothesis that arachidonic acid acts via PPARalpha to increase PTGS2 levels in bovine endometrial stromal cells.     

Resistance to glyphosate in the cyanobacterium <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> as result of pre-selective mutations

Adaptation of Microcystis aeruginosa (Cyanobacteria) to resist the herbicide glyphosate was analysed by using an experimental model. Growth of wild-type, glyphosate-sensitive (G^s) cells was inhibited when they were cultured with 120 ppm glyphosate, but after further incubation for several weeks, occasionally the growth of rare cells resistant (G^r) to the herbicide was found. A fluctuation analysis was carried out to distinguish between resistant cells arising from rare spontaneous mutations and resistant cells arising from other mechanisms of adaptation. Resistant cells arose by rare spontaneous mutations prior to the addition of glyphosate, with a rate ranging from 3.1 × 10⁻⁷ to 3.6 × 10⁻⁷ mutants per cell per generation in two strains of M. aeruginosa; the frequency of the G^r allele ranged from 6.14 × 10⁻⁴ to 6.54 × 10⁻⁴. The G^r mutants are slightly elliptical in outline, whereas the G^s cells are spherical. Since G^r mutants have a diminished growth rate, they may be maintained in uncontaminated waters as the result of a balance between new resistants arising from spontaneous mutation and resistants eliminated by natural selection. Thus, rare spontaneous pre-selective mutations may allow the survival of M. aeruginosa in glyphosate-polluted waters via G^r clone selection.     

Phenotypical characteristics of Shiga-like toxin Escherichia coli isolated from sheep dairy products

AIMS: To analyse phenotypical characteristics of Shiga toxin-producing Escherichia coli (STEC) strains from ovine origin. METHODS AND RESULTS: A total of 13 STEC strains (eight O157 and five non-O157) isolated from sheep dairy products were used in this study. Biochemical traits, motility, haemolytic activity, resistance to tellurite-cefixime, maximum growth temperature and antibiotic resistance were determined. The STEC strains were grouped into nine biochemical and physiological biotypes (five for the O157 and four for the non-O157 strains). All STEC strains showed resistance to bacitracin, cloxacilin, penicillin and tylosin. CONCLUSIONS: Different biotypes and antibiotic resistance patterns of STEC isolated from sheep dairy products were observed. SIGNIFICANCE AND IMPACT OF THE STUDY: This work will be a contribution to the better characterization of STEC isolated from sheep dairy products, which have, to date, been scarcely studied, and to the better understanding of the risks associated with its consumption.     

The nuclear RhoA exchange factor Net1 interacts with proteins of the Dlg family, affects their localization, and influences their tumor suppressor activity

Net1 is a RhoA-specific guanine nucleotide exchange factor which localizes to the nucleus at steady state. A deletion in its N terminus redistributes the protein to the cytosol, where it activates RhoA and can promote transformation. Net1 contains a PDZ-binding motif at the C terminus which is essential for its transformation properties. Here, we found that Net1 interacts through its PDZ-binding motif with tumor suppressor proteins of the Dlg family, including Dlg1/SAP97, SAP102, and PSD95. The interaction between Net1 and its PDZ partners promotes the translocation of the PDZ proteins to nuclear subdomains associated with PML bodies. Interestingly, the oncogenic mutant of Net1 is unable to shuttle the PDZ proteins to the nucleus, although these proteins still associate as clusters in the cytosol. Our results suggest that the ability of oncogenic Net1 to transform cells may be in part related to its ability to sequester tumor suppressor proteins like Dlg1 in the cytosol, thereby interfering with their normal cellular function. In agreement with this, the transformation potential of oncogenic Net1 is reduced when it is coexpressed with Dlg1 or SAP102. Together, our results suggest that the interaction between Net1 and Dlg1 may contribute to the mechanism of Net1-mediated transformation.     

Conformational changes in human integrin alphaIIbbeta3 after platelet activation, monitored by FRET

Integrin alpha(IIb)beta(3), an abundant heterodimeric receptor at the surface of blood platelets, binds adhesive proteins after platelet activation and plays a primary role in haemostasis. In solution, it has been observed mainly in two conformations: the bent and the extended forms. Based on X-ray crystallography, electron microscopy and immunochemical observations of full-length integrin ectodomains and intact integrins, it has been agreed that unactivated integrins are in the bent conformation, both isolated in solution and in living cells. However, consensus is yet to emerge on the bent or extended conformation of activated integrins and on their mechanism of activation (the switchblade, the deadbolt and the S-S reduction models), which require further experimental tests at the cell level to become established facts. Here, we tested the proposed structural rearrangements undergone by integrin alpha(IIb)beta(3) after cell activation, by using F?rster-type fluorescence resonance energy transfer (FRET) and attached fluorescent labels to Fab fragments of monoclonal antibodies directed to the betaA domain of the beta(3) subunit (donor, Alexa488-P97 Fab) and to the Calf-2 domain of the alpha(IIb) subunit (acceptor, Cy3-M3 Fab or Cy3-M10 Fab). The FRET efficiencies observed after ADP or TRAP platelet activation changed less than 20% from the resting values, showing that the distance between the labeled Fab fragments changes only modestly after platelet activation by physiological agonists. This observation is consistent with a conformational model of the activated integrin in the cell less extended than in the switchblade model.     

Biodiversity of Fusarium species in Mexico associated with ear rot in maize, and their identification using a phylogenetic approach

Fusarium proliferatum, F. subglutinans, and F. verticillioides are known causes of ear and kernel rot in maize worldwide. In Mexico, only F. verticillioides and F. subglutinans, have been reported previously as causal agents of this disease. However, Fusarium isolates with different morphological characteristics to the species that are known to cause this disease were obtained in the Highland-Valley region of this country from symptomatic and symptomless ears of native and commercial maize genotypes. Moreover, while the morphological studies were not sufficient to identify the correct taxonomic position at the species level, analyses based in the Internal Transcribed Spacer region and the Nuclear Large Subunit Ribosomal partial sequences allowed for the identification of F. subglutinans, F. solani, and F. verticillioides, as well as four species (F. chlamydosporum, F. napiforme, F. poae, and F. pseudonygamai) that had not previously been reported to be associated with ear rot. In addition, F. napiforme and F. solani were absent from symptomless kernels. Phylogenetic analysis showed genetic changes in F. napiforme, and F. pseudonygamai isolates because they were not true clones, and probably constitute separate sibling species. The results of this study suggest that the biodiversity of Fusarium species involved in ear rot in Mexico is greater than that reported previously in other places in the world. This new knowledge will permit a better understanding of the relationship between all the species involved in ear rot disease and their relationship with maize.     

A P system and a constructive membrane-inspired DNA algorithm for solving the Maximum Clique Problem

We present a P system with replicated rewriting to solve the Maximum Clique Problem for a graph. Strings representing cliques are built gradually. This involves the use of inhibitors that control the space of all generated solutions to the problem. Calculating the maximum clique for a graph is a highly relevant issue not only on purely computational grounds, but also because of its relationship to fundamental problems in genomics. We propose to implement the designed P system by means of a DNA algorithm. This algorithm is then compared with two standard papers that addressed the same problem and its DNA implementation in the past. This comparison is carried out on the basis of a series of computational and physical parameters. Our solution features a significantly lower cost in terms of time, the number and size of strands, as well as the simplicity of the biological implementation.     

Which are fatty acids of the green alga Chlorella?

Fatty acid composition of three species of Chlorella were studied under conditions of photoautotrophic and heterotrophic cultivation, nitrogen starvation, and outdoor in a photobioreactor. The composition 14:0, 16:0, 16:1, 16:2, 16:3, 18:0, 18:1, 18:2, α-18:3 is confirmed for Chlorella. Fatty acids with 20 carbon atoms and four or five double bonds are considered not originating from Chlorella. Other exceptions of this composition are interpreted as mixed algal culture, bacterial contamination or impurities.     

Field patterns of leaf plasticity in adults of the long-lived evergreen Quercus coccifera

BACKGROUND AND AIMS: Quercus coccifera, as a long-lived sprouter, responds plastically to environmental variation. In this study, the role of foliar plasticity as a mechanism of habitat selection and modification within the canopy and across contrasted habitats was characterized. An examination was made of the differential contribution of inner and outer canopy layers to the crown plasticity expressed in the field by adult individuals and its dependence on environmental and genetic factors. METHODS: Within-crown variation in eight foliar traits was examined in nine populations dominated by Q. coccifera. The difference between mean trait values at the inner and outer canopy layers was used as a proxy for crown plasticity to light. Correlations between geographic distances, environmental differences (climatic and edaphic) and phenotypic divergence (means and plasticities) were assessed by partial Mantel tests. A subset of field measurements was compared with data from a previous common garden experiment. KEY RESULTS: Phenotypic adjustment of sun leaves contributed significantly to the field variation in crown plasticity. Plasticity in leaf angle, lobation, xanthophyll cycle pigments and beta-carotene content was expressed in sun and shade leaves concurrently and in opposite directions. Phenotypic plasticity was more strongly correlated with environmental variation than mean trait values. Populations of taller plants with larger, thinner (higher specific leaf area) and less spiny leaves exhibited greater plasticity. In these populations, the midday light environment was more uniform at the inner than at the outer canopy layers. Field and common garden data ranked populations in the same order of plasticity. CONCLUSIONS: The expression of leaf plasticity resulted in a phenotypic differentiation that suggests a mechanism of habitat selection through division of labour across canopy layers. Signs of plasticity-mediated habitat modification were found only in the most plastic populations. Intracanopy plasticity was sensitive to environmental variation but also exhibited a strong genetic component.