La depresión submarina de Guaracayal, estado Sucre, Venezuela: Una barrera para la propagación de la ruptura cosísmica a lo largo de la falla de el pilar

La depresión de Guaracayal, en el golfo de Cariaco, estado Sucre, Venezuela, fue inicialmente reconocida a partir de un levantamiento batimétrico realizado en la década de los ochenta. Un levantamiento de sísmica somera de alta resolución adquirido en el golfo de Cariaco a bordo del B/O Guaiquerí II en enero 2006 reveló que esta depresión resulta ser una cuenca en tracción activa (“active pull-apart basin”) sobre la traza activa submarina de la falla dextral de El Pilar, por su geometría y lo fresco y prominente de los escarpes de fallas que la limitan. Esta cuenca, con una profundidad de aguas de ~15m mayor que el fondo plano ubicado a unos -80m, mide aproximadamente 8km de longitud en dirección este-oeste y unos 2km transversalmente. La cuenca se forma en un relevo dextro, es decir transtensivo, de la traza submarina de la falla de El Pilar, que secciona en dos porciones lo propuesto anteriormente como un único segmento de falla con extensión entre Cumaná y Casanay-Guarapiche. Esta separación entre ambas trazas de 2km parece ser suficiente barrera para la propagación lateral de la ruptura sísmica, tal como lo evidencia la sismicidad contemporánea e histórica. El tramo de falla Cumaná-Casanay, de unos 80km de longitud, ha requerido en dos ocasiones de la conjunción de dos sismos contiguos en dirección oeste-este (1797-1684 y 1929-1997) para romperse en su totalidad. No obstante, no se excluye la posibilidad de un evento que rompa toda la extensión del segmento, a pesar de este comportamiento sísmico reiterado

Nitrogen effects on plant species richness in herbaceous communities are more widespread and stronger than those of phosphorus

Both nitrogen (N) and phosphorus (P) enrichment are known to impact plant diversity globally. Recent studies suggest that P enrichment may be as important, or even more important, as a driver of terrestrial plant species loss as N enrichment. However, the generality and relative contribution of these critical nutrients to species losses remains unclear. Here, we quantitatively compared effects of N, P and combined NP enrichment on species richness of natural and semi-natural herbaceous ecosystems across the world in a meta-analysis of 189 long-term nutrient addition experiments in the field. Our experiment-based approach shows that, across terrestrial and wetland ecosystems, N and NP enrichment had widespread and strong negative effects on plant species richness. N reduced plant species richness across experiments by on average 16% (p < 0.001), while P did not (on average 3%, NS). Combined NP enrichment also reduced species richness, by on average 16% (p = 0.009), with the dominant effect statistically attributed to N. N enrichment effects were greater in China than in Europe and America, which may be explained by background atmospheric N deposition rates and earlier species losses in Europe and America. P enrichment reduced species numbers only in the most species-rich communities and even increased species numbers at high latitudes. All nutrient enrichment combinations (N, P, NP) stimulated aboveground biomass production, and biomass-mediated mechanisms are likely to have contributed to reported species losses. Our findings demonstrate that for the protection of the world's herbaceous plant diversity, it is of the highest priority that N loads be drastically reduced

Molecular mechanism of violacein-mediated human leukemia cell death

Violacein, a pigment isolated from Chromobacterium violaceum in the Amazon River, presents diverse biologic properties and attracts interest as a consequence of its antileukemic activity. Elucidation of the molecular mechanism mediating this activity will provide further relevant information for understanding its effects on the cellular physiology of untransformed cells and for considering its possible clinical application. Here, we show that violacein causes apoptosis in HL60 leukemic cells but is ineffective in this respect in other types of leukemia cells or in normal human lymphocytes and monocytes. Violacein cytotoxicity in HL60 cells was preceded by activation of caspase 8, transcription of nuclear factor kappaB (NF-kappaB) target genes, and p38 mitogen-activated protein (MAP) kinase activation. Thus, violacein effects resemble tumor necrosis factor alpha (TNF-alpha) signal transduction in these cells. Accordingly, infliximab, an antibody that antagonizes TNF-alpha-induced signaling abolished the biologic activity of violacein. Moreover, violacein directly activated TNF receptor 1 signaling, because a violacein-dependent association of TNF receptor-associated factor 2 (TRAF2) to this TNF receptor was observed in coimmunoprecipitation experiments. Hence, violacein represents the first member of a novel class of cytotoxic drugs mediating apoptosis of HL60 cells by way of the specific activation of TNF receptor

Microarthropod communities and their ecosystem services restore when permanent grassland with mowing or low-intensity grazing is installed

The current focus on intensification and maximizing productivity in agriculture can endanger soil biota and the ecosystem services they provide in such a way that it acts counterproductive and increases the dependence on external inputs. In this study, we aimed to identify the factors that are most limiting for the restoration of soil biota and their ecosystem services on sandy soils. To this end, we assessed microarthropod communities, their relationship with the aboveground food web and their effect on organic matter decomposition, in two land-use types: grasslands with agricultural land use and grasslands with nature land use. The latter are grasslands converted from agricultural land use, for the development of the Dutch National Ecological Network. For these land-use types, we took into account two main factors of disturbance: the number of years since the last tillage (i.e., plowing event), and the current grassland management (mowing or grazing). We found that the diversity of microarthropods was higher in nature grasslands than in agricultural grasslands. The abundance of microarthropods increased with time since last tillage for grasslands that were mown, but not for grasslands that were grazed. An agricultural grassland without tillage since 39 years had a microarthropod abundance similar to reference natural grasslands reported in previous research. The number of predatory beetles increased with a higher microarthropod abundance in mown grasslands, but not so in grazed grasslands. The number of fungivorous and herbofungivorous grazer microarthropods positively influenced the decomposition of soil organic matter as measured with the Tea Bag Index. Furthermore, we found a negative effect of Difenyl and total fungicide concentrations in the soil on (herbo)fungivorous grazers. Contrary to our expectations, we found more pesticide residues in nature grasslands than in agricultural grasslands. In conclusion, to restore the soil microarthropods and the ecosystem services they contribute to, the best practice is to strive for permanent grassland (without tillage) with mowing or low-intensity grazing (without compaction of the topsoil)

Tetrahydroxyquinone Induces Apoptosis Of Leukemia Cells Through Diminished Survival Signaling.

Tetrahydroxyquinone is a molecule best known as a primitive anticataract drug but is also a highly redox active molecule that can take part in a redox cycle with semiquinone radicals, leading to the formation of reactive oxygen species (ROS). Its potential as an anticancer drug has not been investigated. The effects of tetrahydroxyquinone on HL60 leukemia cells are investigated using fluorescein-activated cell sorting-dependent detection of phosphatidylserine exposure combined with 7-amino-actinomycin D exclusion, via Western blotting using phosphospecific antibodies, and by transfection of constitutively active protein kinase B. We observe that in HL60 leukemia cells tetrahydroxyquinone causes ROS production followed by apoptosis through the mitochondrial pathway, whereas cellular physiology of normal human blood leukocytes was not affected by tetrahydroxyquinone. The antileukemic effect of tetrahydroxyquinone is accompanied by reduced activity of various antiapoptotic survival molecules including the protein kinase B pathway. Importantly, transfection of protein kinase B into HL60 cells and thus artificially increasing protein kinase B activity inhibits tetrahydroxyquinone-dependent cytotoxicity. Tetrahydroxyquinone provokes cytotoxic effects on leukemia cells by reduced protein kinase B-dependent survival signaling followed by apoptosis through the mitochondrial pathway. Thus, tetrahydroxyquinone may be representative of a novel class of chemotherapeutic drugs, inducing apoptosis in cancer cells through diminished survival signaling possibly as a consequence of ROS generation.34188-9

The Immunoconjugate “Icon” Targets Aberrantly Expressed Endothelial Tissue Factor Causing Regression of Endometriosis

Endometriosis is a major cause of chronic pain, infertility, medical and surgical interventions, and health care expenditures. Tissue factor (TF), the primary initiator of coagulation and a modulator of angiogenesis, is not normally expressed by the endothelium; however, prior studies have demonstrated that both blood vessels in solid tumors and choroidal tissue in macular degeneration express endothelial TF. The present study describes the anomalous expression of TF by endothelial cells in endometriotic lesions. The immunoconjugate molecule (Icon), which binds with high affinity and specificity to this aberrant endothelial TF, has been shown to induce a cytolytic immune response that eradicates tumor and choroidal blood vessels. Using an athymic mouse model of endometriosis, we now report that Icon largely destroys endometriotic implants by vascular disruption without apparent toxicity, reduced fertility, or subsequent teratogenic effects. Unlike antiangiogenic treatments that can only target developing angiogenesis, Icon eliminates pre-existing pathological vessels. Thus, Icon could serve as a novel, nontoxic, fertility-preserving, and effective treatment for endometriosis