Antioxidant activity of isocoumarins isolated from Paepalanthus bromelioides on mitochondria

The isocoumarins (1-50 microM) paepalantine (9,10-dihydroxy-5,7-dimethoxy-1H-naptho(2,3c)pyran-1-one), 8,8'-paepalantine dimer, and vioxanthin isolated from Paepalanthus bromelioides, were assessed for antioxidant activity using isolated rat liver mitochondria and non-mitochondrial systems, and compared with the flavonoid quercetin. The paepalantine and paepalantine dimers, but not vioxanthin, were effective at scavenging both 1,1-diphenyl-2-picrylhydrazyl (DPPH(*)) and superoxide (O(2)(-)) radicals in non-mitochondrial systems, and protected mitochondria from tert-butylhydroperoxide-induced H(2)O(2) accumulation and Fe(2+)-citrate-mediated mitochondrial membrane lipid peroxidation, with almost the same potency as quercetin. These results point towards paepalantine, followed by paepalantine dimer, as being a powerful agent affording protection, apparently via O(2)(-) scavenging, from oxidative stress conditions imposed on mitochondria, the main intracellular source and target of those reactive oxygen species. This strong antioxidant action of paepalantine was reproduced in HepG2 cells exposed to oxidative stress condition induced by H(2)O(2).     

Influence of sea turtle nesting on hunting behavior and movements of jaguars in the dry forest of northwest Costa Rica

Jaguars (Panthera onca) are opportunistic predators that prey on large profitable prey items, such as sea turtles at nesting beaches. Here, we use jaguar and sea turtle track-count surveys, combined with satellite telemetry of one jaguar, to evaluate whether jaguar hunting behavior and movements are influenced by seasonal sea turtle nesting in the Sector Santa Rosa of Área de Conservación Guanacaste in northwest Costa Rica. We used generalized linear models to evaluate the effect of moon phase and sea surface temperature on olive ridley (Lepidochelis olivacea) and green turtle (Chelonia mydas) nesting abundance, as well as the combination of these predictors on the frequency of jaguar predation activity (proximity to nesting beaches) and movements. For home-range size and location analyses, we calculated kernel density estimates for each season at three different temporal scales. Sea turtle nesting season influenced jaguar activity patterns, as well as sea turtle abundance was related to jaguar locations and predation events, but jaguar home-range size (88.8 km² overall) did not differ between nesting seasons or among temporal scales. Environmental conditions influenced sea turtle nesting and, as a consequence, also influenced jaguar movements and foraging activity. Our study defined the home range of a female jaguar in the tropical dry forest and its relationship to seasonally abundant turtles. Additional information related to the effect of tourism on jaguar–sea turtle interactions would improve conservation of these species at unique nesting beaches in the area.     

Pharmacological screening and transcriptomic functional analyses identify a synergistic interaction between dasatinib and olaparib in triple-negative breast cancer

Identification of druggable vulnerabilities is a main objective in triple-negative breast cancer (TNBC), where no curative therapies exist. Gene set enrichment analyses (GSEA) and a pharmacological evaluation using a library of compounds were used to select potential druggable combinations. MTT and studies with semi-solid media were performed to explore the activity of the combinations. TNBC cell lines (MDAMB-231, BT549, HS-578T and HCC3153) and an additional panel of 16 cell lines were used to assess the activity of the two compounds. Flow cytometry experiments and biochemical studies were also performed to explore the mechanism of action. GSEA were performed using several data sets (GSE21422, GSE26910, GSE3744, GSE65194 and GSE42568), and more than 35 compounds against the identified functions were evaluated to discover druggable opportunities. Analyses done with the Chou and Talalay algorithm confirmed the synergy of dasatinib and olaparib. The combination of both agents significantly induced apoptosis in a caspase-dependent manner and revealed a pleotropic effect on cell cycle: Dasatinib arrested cells in G0/G1 and olaparib in G2/M. Dasatinib inhibited pChk1 and induced DNA damage measured by pH2AX, and olaparib increased pH3. Finally, the effect of the combination was also evaluated in a panel of 18 cell lines representative of the most frequent solid tumours, observing a particularly synergism in ovarian cancer. Breast cancer, triple negative, dasatinib, olaparib, screening.     

Na<Superscript>+</Superscript>,K<Superscript>+</Superscript>-ATPase Activity in the Posterior Gills of the Blue Crab, <Emphasis Type="Italic">Callinectes ornatus</Emphasis> (Decapoda,Brachyura): Modulation of ATP Hydrolysis by the Biogenic Amines Spermidine and Spermine

We investigated the effect of the exogenous polyamines spermine, spermidine and putrescine on modulation by ATP, K⁺, Na⁺, NH₄ ⁺ and Mg²⁺ and on inhibition by ouabain of posterior gill microsomal Na⁺,K⁺-ATPase activity in the blue crab, Callinectes ornatus, acclimated to a dilute medium (21‰ salinity). This is the first kinetic demonstration of competition between spermine and spermidine for the cation sites of a crustacean Na⁺,K⁺-ATPase. Polyamine inhibition is enhanced at low cation concentrations: spermidine almost completely inhibited total ATPase activity, while spermine inhibition attained 58%; putrescine had a negligible effect on Na⁺,K⁺-ATPase activity. Spermine and spermidine affected both V and K for ATP hydrolysis but did not affect ouabain-insensitive ATPase activity. ATP hydrolysis in the absence of spermine and spermidine obeyed Michaelis–Menten behavior, in contrast to the cooperative kinetics seen for both polyamines. Modulation of V and K by K⁺, Na⁺, NH₄ ⁺ and Mg²⁺ varied considerably in the presence of spermine and spermidine. These findings suggest that polyamine inhibition of Na⁺,K⁺-ATPase activity may be of physiological relevance to crustaceans that occupy habitats of variable salinity.     

Experimental Test of Connector Rotation during DNA Packaging into Bacteriophage ϕ29 Capsids

The bacteriophage ϕ29 generates large forces to compact its double-stranded DNA genome into a protein capsid by means of a portal motor complex. Several mechanical models for the generation of these high forces by the motor complex predict coupling of DNA translocation to rotation of the head-tail connector dodecamer. Putative connector rotation is investigated here by combining the methods of single-molecule force spectroscopy with polarization-sensitive single-molecule fluorescence. In our experiment, we observe motor function in several packaging complexes in parallel using video microscopy of bead position in a magnetic trap. At the same time, we follow the orientation of single fluorophores attached to the portal motor connector. From our data, we can exclude connector rotation with greater than 99% probability and therefore answer a long-standing mechanistic question.     

Community structure and physiological characterization of microbial mats in Byers Peninsula, Livingston Island (South Shetland Islands, Antarctica)

The community structure and physiological characteristics of three microbial mat communities in Byers Peninsula (Livingston Island, South Shetland Islands, Antarctica) were compared. One of the mats was located at the edge of a stream and was dominated by diatoms (with a thin basal layer of oscillatorian cyanobacteria), whereas the other two mats, located over moist soil and the bottom of a pond, respectively, were dominated by cyanobacteria throughout their vertical profiles. The predominant xanthophyll was fucoxanthin in the stream mat and myxoxanthophyll in the cyanobacteria-dominated mats. The sheath pigment scytonemin was absent in the stream mat but present in the soil and pond mats. The stream mat showed significantly lower delta13C and higher delta15N values than the other two mats. Consistent with the delta15N values, N2 fixation was negligible in the stream mat. The soil mat was the physiologically most active community. It showed rates of photosynthesis three times higher than in the other mats, and had the highest rates of ammonium uptake, nitrate uptake and N2 fixation. These observations underscore the taxonomic and physiological diversity of microbial mat communities in the maritime Antarctic region.     

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.     

Method for the characterization of size-exclusion chromatography media for preparative purification of DNA restriction fragments

A protocol has been developed to characterize the potential of size exclusion chromatography media for the separation of DNA fragments at a preparative scale. A standard DNA mixture composed of -DNA cut with the restriction enzymes, AluI and HaeIII, was chromatographed on a column packed with the gel of interest. Fractions were collected and examined by PAGE. A digitized image of the gel was analyzed with the aid of a computer software program to determine the DNA fractionation range and selectivity curve for each chromatography gel. Four gels were characterized using this protocol. The effect of the elution buffer ionic strength on the fractionation of DNA was also investigated.The US Government right to retain a non-exclusive royalty-freelicense in and to any copyright is acknowledged.     

Study of Liquid Dimethyl Sulfoxide by Computer Simulation

The paper reports Monte Carlo and molecular dynamicsresults for pure liquid dimethyl sulfoxide (DMSO) at298 K and 1 atm. The classical 6–12 Lennard–Jones plusCoulomb pairwise potential was used to calculateintermolecular interaction energy. Potentialparameters for the liquid were optimized in this work.Some thermodynamic and dynamical properties obtained,such as heat of vaporization, density and diffusioncoefficient, are in good agreement with theexperimental values. The present model is comparedwith other models for DMSO reported previously. It isshown to be an improvement over earlier potentials.The structure factors and the radial distributionfunctions (rdf), are compared with experimentalresults for the liquid. The analysis shows that thestructure of DMSO is not completely understood yet anddeserves deeper investigation. The geometry of thedimer that corresponds to the rdf plots obtained, isreported. The results suggest that the dipole momentof this dimer plays an important role in the structureof the liquid.     

Relationships between tree component structure,topography and soils of a riverside forest,Rio Botucaraí, Southern Brazil

The relationships among floristic, structural and physiognomic variables of the tree component, flooding regime variations and soil fertility were investigated in a riparian forest fragment (ca. 43 ha) in the Rio Botucaraí watershed near the confluence with the Rio Jacuí, southern Brazil. All the trees with a dbh ≥ 15 cm were surveyed in 100 contiguous 10 × 10 m plots and soil chemical and textural variables were obtained from the analyses of 15 topsoil samples (0–20 cm depth) collected at different locations. The sample sites encompass all the topographic variation of the area. We used canonical correspondence analysis (CCA) to seek correlations between environmental variables and tree component distribution. The 1,547 surveyed individuals belonged to 30 species and 16 botanical families. The Shannon diversity index (H′) and the Pielou equability (J′) were 1.995 and 0.586 nats ind.⁻¹, respectively. Sebastiania commersoniana, Casearia sylvestris, Eugenia uniflora and Eugenia hyemalis presented the highest importance values. Species’ densities chiefly correlated with site elevation, flooding regime and soil chemical fertility. The analyses of ecological categories (EC) revealed that most species are heliophylous and typical of early successional stages. Richness and diversity (P < 0.001) variations from different topographic positions reflect that at the local scale, flooding was a limiting factor for the establishment of certain species suggesting that local processes control species richness and diversity.