PCR Analysis of expR Gene Regulating Biosynthesis of Exopolysaccharides in Sinorhizobium meliloti

Exopolysaccharide (EPS) production by the rhizobacterium Sinorhizobium meliloti is essential for root nodule formation on its legume host (alfalfa), and for establishment of a nitrogen-fixing symbiosis between the two partners. Production of EPS II (galactoglucan) by certain S. meliloti strains results in a mucoid colony phenotype. Other strains that are unable to produce EPS II display a dry phenotype, due to the presence of an insertion element in the gene expR, a key regulator involved in many important cellular processes, including production of low-molecular-weight EPS II. We describe a series of three programmed undergraduate biochemistry laboratory classes teaching PCR and electrophoresis procedures to detect non-functional expR loci in S. meliloti.Fil: Sorroche, Fernando Guido. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Giordano, Walter Fabian. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentin

Evaluation of in vitro neurotoxicity of methyl mercury, PCB153 and PCB126

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On optimal three-impulse Earth–Moon transfers in a four-body model

Within the emerging age of lunar exploration, optimizing transfer trajectories is a fundamental measure toward achieving more economical and efficient lunar missions. This study addresses the possibility of reducing the fuel cost of two-impulse Earth–Moon transfers in a four-body model with the Earth, the Moon, and the Sun as primaries. Lawden’s primer vector theory is applied within this framework to derive a set of necessary conditions for a fuel-optimal trajectory. These conditions are used to identify which trajectories from an existing database could benefit from the insertion of an additional intermediate impulse. More than 10,000 three-impulse transfers are computed with a direct numerical optimization method. These solutions contribute to enriching the database of impulsive trajectories, useful to perform trade-off analyses. While the majority of trajectories exhibit only marginal improvements, a significant breakthrough emerges for transfers featuring an initial gravity assist at the Moon. Implementing a corrective maneuver after the lunar encounter yields substantial reductions in fuel costs

Submarine Volcanism of the Cabo de Gata Magmatic Arc in the Betic-Rif Orogen, SE Spain: Processes and Products

Volcanic eruptions in subaqueous settings have been traditionally characterized by the study of ancient deposits and, more recently, by indirect observation of the sea floor with different geophysical means. Subaqueous volcanism is largely governed by the physical properties of water and the way water interacts with magma. Among the characteristic products of subaqueous volcanism are hyaloclastite breccias of dense clasts and of pumiceous clasts produced by the quench fragmentation of hot magma in effusive eruptions. Pumice breccias driven by fragmentation of magma in explosive eruptions are not infrequent. The Miocene volcanic zone of Cabo de Gata in southeastern Spain provides excellent exposures where to test the current understanding on subaqueous volcanism. In particular, submarine lavas with a coherent core and an outer carapace of vesicular hyaloclastite together with pumice breccias and crystal tuffs of the El Barronal Formation provide clues to understand transient conditions during explosive and effusive eruptions. Debris avalanches deposits are rather common in Cabo de Gata, such as those of the Los Frailes Formation and the Cerro Estorvillas Formation, and help to understand the instability processes of submarine volcanic edifices and the resultant mass flows. Interbedding of volcanic rocks with shallow water sedimentary rocks allows inferring water depth conditions for volcanism and the subsidence history of the volcano-sedimentary basin

Molecular adaptations in Antarctic fish and bacteria

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Nitric oxide involvement in the acrosome reaction triggered by leptin in pig sperm

<p>Abstract</p> <p>Background</p> <p>Nitric oxide (NO) is a signaling molecule produced by intracellular nitric oxide synthase (NOS) enzymes. This free radical appears to affect sperm capacitation, a maturation step preceding acrosome reaction. Recent studies have reported leptin ability to promote capacitation and acrosome reaction in pig male gametes.</p> <p>Methods</p> <p>This study has investigated nitric oxide production in leptin-treated pig spermatozoa by fluorescence-activated cell sorting, while the intracellular NOS isoforms were assessed by Western blot analysis. In addition, acrosome status of treated-spermatozoa was evaluated by FITC-PNA staining.</p> <p>Results</p> <p>Significant increases of nitric oxide levels and acrosome reaction extent were detected in leptin-treated spermatozoa, but both the effects were reversed in presence of <it>L</it>-NAME. Furthermore, the immunoblots of sperm extracts have evidenced three bands of ~160 Kd(bNOS), ~130 Kd (iNOS) and ~135 Kd (eNOS).</p> <p>Conclusions</p> <p>The identification of the three intracellular NOS isoforms suggests that pig spermatozoa could produce NO, while the augmented nitric oxide levels in leptin-treated male gametes indicates the capacity of the hormone to induce nitric oxide production. Furthermore, the inhibitory effect of <it>L</it>-NAME and of Ab-ObR on the promotion of acrosome reaction triggered by leptin suggests a possible involvement of NO in the hormone action.</p