Survey of South Polar skuas (Catharacta maccormicki) for blood parasites in the Vestfold Hills region of Antarctica

Thin blood smears prepared from 125 South Polar skuas (Catharacta maccormicki) at breeding islands and feeding sites in the Vestfold Hills region of Antarctica between December 1999 and January 2000 did not contain hematozoa. These findings confirm results of previous smaller studies, and provide baseline data for this species.     

Hierarchical genetic algorithm for near optimal feedforward neural network design

In this paper, we propose a genetic algorithm based design procedure for a multi layer feed forward neural network. A hierarchical genetic algorithm is used to evolve both the neural networks topology and weighting parameters. Compared with traditional genetic algorithm based designs for neural networks, the hierarchical approach addresses several deficiencies, including a feasibility check highlighted in literature. A multi objective cost function is used herein to optimize the performance and topology of the evolved neural network simultaneously. In the prediction of Mackey Glass chaotic time series, the networks designed by the proposed approach prove to be competitive, or even superior, to traditional learning algorithms for the multi layer Perceptron networks and radial basis function networks. Based upon the chosen cost function, a linear weight combination decision making approach has been applied to derive an approximated Pareto optimal solution set. Therefore, designing a set of neural networks can be considered as solving a two objective optimization problem.     

Microbial biohydrogenation of oleic acid to trans isomers in vitro

Ruminant products are significant sources of dietary trans fatty acids. Trans fatty acids, including various conjugated linoleic acid isomers, have been shown to act as metabolic modifiers of lipid metabolism. Trans fatty acids originate from biohydrogenation of dietary unsaturated fatty acids by gut microbes; however, the exact synthetic pathways are unclear. It was our goal to examine the biohydrogenation pathway for oleic acid, where oleic acid is hydrogenated directly to stearic acid. Our objective in this study was to trace the time course of appearance of 13C in labeled oleic acid to determine if trans monoenes are formed from the 13C-labeled oleic acid or if the 13C appears only in stearic acid as described in reviews of earlier work. Enrichments were calculated from the mass abundance of 13C in major fatty acid fragments and expressed as a percentage of total carbon isotopomers. Significant 13C enrichment was found in stearic acid, oleic acid, trans-6, trans-7, and in all trans C18:1 in positions 9-16. We concluded that the biohydrogenation of oleic acid by mixed ruminal microbes involves the formation of several positional isomers of trans monoenes rather than only direct biohydrogenation to form stearic acid as previously described.     

Signaling mechanisms that regulate actin-based motility processes in the nervous system

Actin-based motility is critical for nervous system development. Both the migration of neurons and the extension of neurites require organized actin polymerization to push the cell membrane forward. Numerous extracellular stimulants of motility and axon guidance cues regulate actin-based motility through the rho GTPases (rho, rac, and cdc42). The rho GTPases reorganize the actin cytoskeleton, leading to stress fiber, filopodium, or lamellipodium formation. The activity of the rho GTPases is regulated by a variety of proteins that either stimulate GTP uptake (activation) or hydrolysis (inactivation). These proteins potentially link extracellular signals to the activation state of rho GTPases. Effectors downstream of the rho GTPases that directly influence actin polymerization have been identified and are involved in neurite development. The Arp2/3 complex nucleates the formation of new actin branches that extend the membrane forward. Ena/VASP proteins can cause the formation of longer actin filaments, characteristic of growth cone actin morphology, by preventing the capping of barbed ends. Actin-depolymerizing factor (ADF)/cofilin depolymerizes and severs actin branches in older parts of the actin meshwork, freeing monomers to be re-incorporated into actively growing filaments. The signaling mechanisms by which extracellular cues that guide axons to their targets lead to direct effects on actin filament dynamics are becoming better understood.     

Interactive gene expression pattern in prostate cancer cells exposed to phenolic antioxidants

Dietary phenolic compounds are known to elicite vital cellular responses such as cell cycle arrest, apoptosis and differentiation by activating a cascade of molecular events. As there is an increasing interest to improve the efficacy of these compounds for use as potential chemopreventive agents, we wanted to understand the impact of phenolic compounds on target genes in prostate cancer. In this study we used human cDNA microarrays with 2400 clones consisting of 17 prosite motifs to characterize alterations in gene expression pattern in response to the phenolic antioxidants ellagic acid (EA) and resveratrol (RE). Over a 48-hr exposure of androgen - sensitive LNCaP cells to EA and RE, a total of 593 and 555 genes respectively, showed more than a two fold difference in expression. A distinct set of genes in both EA-and RE-treated cells may represent the signature profile of phenolic antioxidant-induced gene expression in LNCaP cells. Although extensive similarity was found between effects of EA - and RE - responsive genes in prostate cancer cells, out of 246 genes with overlapping responses, 25 genes showed an opposite effect. Quantitative RT-PCR was used to verify and validate the differential expression of selected genes identified from cDNA microarrays. In-depth analysis of the data from this study provided insight into the alterations in the p53 - responsive genes, p300, Apaf-1, NF-kBp50 and p65 and PPAR families of genes, suggesting the activation of multiple signaling pathways that leads to growth inhibition of LNCaP cells. This is a first study to look for changes in a large number of human genes in response to dietary compounds.     

Metabolic profile of NO-flurbiprofen (HCT1026) in rat brain and plasma: a LC-MS study

Male rats were given the nitrooxybutyl ester of flurbiprofen HCT1026 (15 mg/Kg) by oral administration and plasma and brain levels of the parent drug and its potential metabolites (HCT1027 and flurbiprofen) were determined at different times post-administration by a validated HPLC method (UV-DAD detection; LOQ: 0.13 nmoles/ml and 0.3 nmoles/g respectively in plasma and brain tissue). Structural confirmation of the analytes was achieved by MS monitoring of their de-protonated (negative ion mode) or cationized/protonated (positive ion mode) molecular ions and of the relative fragment ions obtained by collision-induced dissociation (CID) experiments. The results indicate that flurbiprofen is the only metabolite found at measurable levels in both plasma and brain, while HCT1026 or its de-nitrated metabolite HCT1027 were always below the limit of detection at all the observation times. The same was observed after administration of the higher dose of HCT1026 (100 mg/Kg, i.p.). In orally-treated animals the time-course of flurbiprofen formation strictly parallels that of NOx (nitrite/nitrate) in plasma but not in brain, where the levels were always in the range of the controls. These data indicate that the NO molecule is not released from the parent drug within the brain.     

Chemokine receptor inhibition by AMD3100 is strictly confined to CXCR4

This study was undertaken to demonstrate the unique specificity of the chemokine receptor CXCR4 antagonist AMD3100. Calcium flux assays with selected chemokine/cell combinations, affording distinct chemokine receptor specificities, revealed no interaction of AMD3100 with any of the chemokine receptors CXCR1 through CXCR3, or CCR1 through CCR9. In contrast, AMD3100 potently inhibited CXCR4-mediated calcium signaling and chemotaxis in a concentration-dependent manner in different cell types. Also, AMD3100 inhibited stromal cell-derived factor (SDF)-1-induced endocytosis of CXCR4, but did not affect phorbol ester-induced receptor internalization. Importantly, AMD3100 by itself was unable to elicit intracellular calcium fluxes, to induce chemotaxis, or to trigger CXCR4 internalization, indicating that the compound does not act as a CXCR4 agonist. Specific small-molecule CXCR4 antagonists such as AMD3100 may play an important role in the treatment of human immunodeficiency virus infections and many other pathological processes that are dependent on SDF-1/CXCR4 interactions (e.g. rheumatoid arthritis, atherosclerosis, asthma and breast cancer metastasis).     

Allosteric effects potentiating the release of the second fibrinopeptide A from fibrinogen by thrombin

Fibrin formation depends on the release of the two N-terminal fibrinopeptides A (FPA) from fibrinogen, and its formation is accompanied by an intermediate, alpha-profibrin, which lacks only one of the FPA. In this study, we confirm that the maximal levels of alpha-profibrin found over the course of thrombin reactions with human fibrinogen are only half of what would be expected if the first and second FPA were being released independently with equal rate constants. The rapidity of release of the fibrinopeptides by thrombin had been shown to depend on an allosteric transformation that is induced when Na(+) binds to a site defined by the 215-227 residues of thrombin, a transformation that results in the exposure of its fibrinogen-binding exosites transforming the thrombin from a slow to a fast acting form toward fibrinogen. When choline was substituted for sodium to transform thrombin to its slow form, the maximal levels of alpha-profibrin rose to those expected for independent release of the two FPA. Thus, it is only the fast thrombin that releases the second FPA fast, and that fast release only occurs when both FPA are present because of a partial coupling of its release with that of the first FPA. The release of the FPA from purified alpha-profibrin with the first FPA already missing is no faster than the release of any FPA. Surprisingly, we also found that slow thrombin became increasingly transformed to a fast form in the absence of sodium when the fibrinogen was elevated to high concentrations. This potentiation by concentrated fibrinogen also occurs with the recombinant mutant thrombin (Y225P), which is otherwise slow in both the presence and absence of Na(+). The potentiation of thrombin by fibrinogen must be short-lived so that the thrombin reverts to its slow acting form in the interim among encounters with other fibrinogen molecules in dilute fibrinogen solutions lacking Na(+), whereas at high fibrinogen concentrations the thrombin encounters other molecules before it reverts back to the slow form.     

Phosphatidylinositol 3-kinase activity negatively regulates stability of cyclooxygenase 2 mRNA

Human alveolar macrophages have both lipopolysaccharide (LPS)-induced and constitutive phosphatidylinositol 3-kinase (PI3K) activity. We observed that blocking PI3K activity increased release of prostaglandin E2 after LPS exposure, and increasing PI3K activity (interleukin-13) decreased release of prostaglandin E2 after LPS exposure. This was not because of an effect of PI3K on phospholipase 2 activity. PI3K inhibition resulted in an increase in cyclooxygenase 2 (COX2) protein, mRNA, and mRNA stability. PI3K negatively regulated activation of the p38 pathway (p38, MKK3/6, and MAPKAP2), and an active p38 was necessary for COX2 production. The data suggest that PI3K inhibition of p38 modulates COX2 expression via destabilization of LPS-induced COX2 mRNA.