An Arenic Paleustults savannah was cropped with adapted species and fertilized with unique doses of 1,0 and 0,3 Mg ha-1 of phosphoric rock and NPK, respectively. Random sampling of the treated soils at three depths 0-3,0; 3,1-6,0 and 6,1-10,0 cm allowed the determination of: soil organic carbon (SOC), light fraction of the soil organic matter (LF SOM), total nitrogen (N) and phosphorus (P), exchangeable cations, texture, soil bulk density, water-pH and KCl-pH, and available-P in samples from natural (NS) and cultivated savannas (CS). Statistical analysis of the data included: a two way ANOVA, PCA and path analysis for the establishment of multicausal statistical models. The CS showed significant changes in the fertility associated with higher carbon sequestration in the order of 2,970 kg ha-1 and a 50% increase in the electronegativity of the net coloidal charge density which is related with the LF SOM, COS and soil bulk density in comparion to the NS where variation factors were related to inorganic nature.

Un Arenic Paleustults de sabana fue cultivado con especies adaptadas y fertilizado con dosis únicas de 1,0 y 0,3 Mg ha-1 de roca fosfórica (RF) y NPK, respectivamente. Un muestreo aleatorio de suelo, en los tratamientos, sabana natural (SN) y sabana cultivada (SC), a las profundidades de 0-3,0; 3,1-6,0 y 6,1-10,0 cm, permitió las determinaciones de textura, COS, fracción ligera de la materia orgánica del suelo (FL MOS), pHagua, pHKCl, densidad aparente (Da), contenidos totales de nitrógeno (N) y fósforo (P), P-disponible y bases intercambiables. Los análisis estadísticos incluyeron: ANOVA, ACP y un análisis de ruta, que generó modelos estadísticos multicausales. La SC mostró cambios significativos al acumular 2.970 kg ha-1 de COS y presentar una densidad de carga neta coloidal (DCNC) 50% más electronegativa, que se relacionó con la FL MOS, el COS y la Da, en contraste con la SN, cuyos factores de variación fueron de naturaleza inorgánicas.

Over the last years, the aquifer of La Paz, BCS has been seriously affected by over-exploitation generated by population growth, that has resulted in its pollution by salt water intrusion. It may thus be seen that the management of the resource has been inadequate, as more water than that provided by natural recharges from rainfall has been extracted. In order to estimate the volumes of some of the main components of the hydrologic system of the La Paz basin, the hydrologic equilibrium general equation applied to a geographical information system (GIS) was used, and digital models were produced for rainfall, temperature, evapotranspiration, runoff and recharge, with climate data for 25 years (1980 to 2004). Estimated data were a rainfall of 410 Mm³ year−1, 330 Mm³ year−1 of evapotranspiration, 15 Mm³ year−1 of surface runoff, and a potential rainfall recharge of 65 Mm³ year−1. Rainfall recharge mainly takes place in the mountain heights located to the east and southeast of the basin (Las Cruces and El Novillo mountain ranges) and is equivalent to 15.9% of the rainfall. The sub-basin of El Novillo covers the larger surface and receives more than 50% of the total rainfall.

Durante los últimos años, el acuífero de La Paz, BCS se ha visto seriamente afectado por la sobreexplotación debida a un mayor abastecimiento requerido por el crecimiento de la población, lo que ha provocado su contaminación por intrusión de agua de mar, de lo que se deduce que el manejo del recurso es inadecuado ya que se ha extraído más agua que la que proporciona la recarga natural por lluvias. Con el objetivo de estimar los volúmenes que manejan algunas de las componentes principales del sistema hidrológico de la cuenca de La Paz, se utilizó la ecuación general de balance hidrológico aplicada en un sistema de información geográfica (SIG) con lo que se generaron modelos digitales de precipitación, temperatura, evapotranspiración, escurrimiento y recarga, a partir de datos climatológicos de 25 años (1980 a 2004). Se estimó una precipitación de 410 Mm³ año−1, evapotranspiración de 330 Mm³ año−1, escurrimiento superficial de 15 Mm³ año−1, y una recarga potencial por lluvias de 65 Mm³ año−1. La recarga por lluvias ocurre principalmente en las elevaciones montañosas ubicadas al este y sureste de la cuenca (sierra Las Cruces y El Novillo) y es equivalente al 15.9% de la precipitación. La subcuenca de El Novillo es la que cubre una mayor superficie y capta más del 50% del total de las lluvias.

Based on gravity data, the depth to crystalline basement in the valley of La Paz, Baja California Sur was estimated. Geometry of the tectonic depression that underlies the valley was interpreted with support of the aeromagnetic anomaly. For regional-residual separation of gravity data, regional effect was considered as a horizontal plane. In order to estimate depth to basement, the formula for the calculation of gravity in a point over a horizontal layer of infinite extension was used. A density contrast of 0.66 g/cm³ was used, based on the general characteristics of basement and sedimentary infill. Estimated depths were normalized to a depth to basement obtained in a magnetic profile from another study. Two sections were modeled to evaluate the procedure. The depth to basement in the valley of La Paz ranges from 100 to 500 m on the east and the center-south, to more than 1500 m to the NNE, NW and west. A graben delimited by two main lineaments is evident, one lineament extends on the east with a N-S direction, and the other on the west with a SSE-NNW orientation, which are respectively attributed to the La Paz and El Carrizal faults. The graben is tilted towards the WNW.

Con base en datos gravimétricos se estimó la profundidad al basamento cristalino en el valle de La Paz, Baja California Sur, y con apoyo de la anomalía aeromagnética se interpretó la geometría de la fosa tectónica que subyace al valle. En la separación regional-residual de los datos de gravedad, se consideró el efecto regional como un plano horizontal. Para estimar la profundidad al basamento se utilizó la fórmula para el cálculo de la gravedad en un punto sobre una capa horizontal de extensión infinita, con un contraste de densidad de 0.66 g/cm³ de acuerdo a las características generales del basamento y del relleno sedimentario. Con la profundidad al basamento obtenida a partir de un perfil magnético de otro estudio se normalizaron las profundidades estimadas. Se modelaron dos secciones para evaluar el procedimiento. La profundidad al basamento en el valle de La Paz varía desde 100 a 500 m en el este y centro-sur, a más de 1500 m al NNE, NW y oeste. Es evidente la existencia de un graben delimitado por dos lineamientos principales, uno al este con orientación casi N-S y el otro al oeste con rumbo SSE-NNW, los cuales se atribuyen a las fallas La Paz y El Carrizal respectivamente. El graben presenta un basculamiento en dirección WNW.

The protein-containing extracts prepared from the venom ducts of Conus austini, Conus spurius and Polystira albida caused a concentration-dependent inhibition of spontaneous contractions in guinea pig ileum. The most potent extract was obtained from P. albida venom ducts (IC50 = 0.11 ± 0.02 µg protein/mL). The three extracts produced a moderate inhibition of contractions elicited by acetylcholine (ACh 1 µM), suggesting the presence of anticholinergic compounds. The contractile response elicited by nicotine (10 µM) was significantly reduced by the extracts prepared from the ducts of C. austini and P. albida, which indicates that the venom produced by these species contains toxins that target neuronal nicotinic receptors. All three extracts significantly inhibited contractions evoked by histamine (0.5 µM), particularly those from C. spurius and P. albida. These findings reveal the presence of antihistaminergic compounds not previously described in any conoidean venom. Finally, we found that only the extract prepared from C. spurius ducts decreased KCl (60 mM)-induced contractions, indicating that the venom of this snail contains compounds that block voltage-dependent Ca2+ or Na+ channels.