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131.
David S. Auld Ikuo Atsuya Carmen Campino Pablo Valenzuela 《Biochemical and biophysical research communications》1976,69(2):548-554
Microwave excitation spectrometry and metal binding inhibition studies show that zinc is a catlytically essential component of the highly purified RNA polymerase I from yeast, the first eukaryotic RNA polymerase I available in quantities sufficient for such studies. It contains 2.4 g-atom of zinc based on a molecular weight of 6.5 × 105 (8). Copper, iron, manganese and magnesium are absent, i.e., below the limits of detection, 10?13 to 10?14 g-atoms. A number of derivatives of 1,10-phenanthroline reversibly inhibit the polymerase catalyzed reaction, apparently by forming a ternary polymerase·Zn·OP complex while the nonchelating isomer, 1,7-phenanthroline, is ineffective. 相似文献
132.
Vanessa Robitzch Pablo Saenz‐Agudelo Michael L. Berumen 《Ecology and evolution》2020,10(15):8265-8278
Coral reef fish larvae are tiny, exceedingly numerous, and hard to track. They are also highly capable, equipped with swimming and sensory abilities that may influence their dispersal trajectories. Despite the importance of larval input to the dynamics of a population, we remain reliant on indirect insights to the processes influencing larval behavior and transport. Here, we used genetic data (300 independent single nucleotide polymorphisms) derived from a light trap sample of a single recruitment event of Dascyllus abudafur in the Red Sea (N = 168 settlers). We analyzed the genetic composition of the larvae and assessed whether kinship among these was significantly different from random as evidence for cohesive dispersal during the larval phase. We used Monte Carlo simulations of similar‐sized recruitment cohorts to compare the expected kinship composition relative to our empirical data. The high number of siblings within the empirical cohort strongly suggests cohesive dispersal among larvae. This work highlights the utility of kinship analysis as a means of inferring dynamics during the pelagic larval phase. 相似文献
133.
Ricardo Pablo Garay 《生物化学与生物物理学报:生物膜》1982,688(3):786-792
Human erythrocytes are able to incorporate cyclic AMP (cAMP) in amounts larger than those required to saturate cAMP-dependent protein kinase. In contrast to previous observations in avian red blood cells in which cAMP stimulates the Na+/K+ cotransport system, we demonstrate that cAMP inhibits this system in human erythrocytes. The cotransport inhibition is enhanced by addition of phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine to the incubation medium. The cAMP concentration giving half-maximal cotransport inhibition showed a wide variation among different individuals (from 0.1 to 5 mM external cAMP concentration). In contrast to cAMP, cyclic GMP showed little effect on the cotransport system. Ca2+ introduced into the cell interior was an inhibitor of the Na+/K+ cotransport system. These results suggest that in human cells in which endogeneous levels of cAMP and Ca2+ are modulated by hormones, the Na+/K+ cotransport system may be under hormonal regulation. 相似文献
134.
Ecophysiology of six selected shrub species in different plant communities at the periphery of the Atlantic Forest of SE-Brazil 总被引:1,自引:1,他引:1
Heitor Monteiro Duarte Arthur Geßler Fabio Rubio Scarano Augusto Csar Franco Eduardo Arcoverde de Mattos M. Nahm Heinz Rennenberg Pablo Jos Francisco Pena Rodrigues Henrique Leo Teixeira Zaluar Ulrich Lüttge 《Flora》2005,200(5):456-476
The Atlantic rain forest of Brazil is one of the 25 biodiversity hotspots of the world. It is surrounded by distinct marginal plant communities which are floristically related to the rain forest. We performed an in situ ecophysiological study of six shrub and tree species which are abundant in one or more of these marginal ecosystems. They formed three pairs of taxonomically related species, which, however, differed in geographic distribution and/or habitat preference. We aimed to answer the following questions: (1) Do habitat generalists and specialists differ in ecophysiological behaviour? (2) Are there general trends responsive to site characteristics, irrespective of taxonomic affiliation? (3) In which variables between-site intraspecific variation is more often detected? Plants chosen were the Clusiaceae Calophyllum brasiliense Cambess (swamp forest specialist) and Rheedia brasiliensis (Mart.) Planch &; Triana (a generalist plant, occurring in swamp forests and dry, sandy coastal vegetation); the Myrsinaceae Myrsine parvifolia A.DC. (widespread in sandy plains) and Myrsine gardneriana A.DC. (widespread in high-altitude habitats); and the Euphorbiaceae Styllingia dichotoma Muell. Arg. (a coastal inselberg specialist) and Croton compressus Lam. (a generalist found in coastal inselbergs and dry forests). We compared measurements of photosynthesis (chlorophyll fluorescence parameters), stable isotope (δ13C, δ15N) and metabolic carbon and nitrogen compounds. Generalists and specialists did not always differ in ecophysiological behaviour: for instance, while widespread generalists such as M. parvifolia and C. compressus were ecophysiologically versatile, R. brasiliense appeared to perform below optimum in all sampled habitats. Light and water were abiotic factors which apparently explained most of the variation found. Overall, ecophysiological responses were often more clearly related to individual species rather than to taxonomic affinities in higher hierarchies (family, genus) or habitat. These results are discussed as a further indication of high biodiversity even in habitats marginal to the rain forest hotspot. 相似文献
135.
The purpose of this paper was to analyze the diversity patterns of Cactaceae at a global scale, to identify those countries
where conservation actions should be performed. In order to do this, the species richness and the number of endemic species
for 34 American countries were determined. With these data, the relationship between the total number of species or the number
of endemic species and the area of the countries were analyzed. In addition, a complementarity analysis was conducted to determine
the most important countries for cactus conservation. Results showed that Mexico had the highest number of total and endemic
species followed by Argentina, Bolivia, Brazil, and Peru, among others. There was a significant positive relationship between
both, the total and endemic species, and the area of the countries. Despite this fact, the cactus diversity in Mexico, Argentina,
Peru, Bolivia, Chile, and Costa Rica was higher than expected according to their area. Further, these countries also presented
the highest proportions of endemic species. The complementarity analysis indicated that 24 countries are necessary to preserve
all cactus species. However, 94% of all species could be preserved with only 10 countries. Considering the diversity patterns
and the complementarity analysis, three important groups for cactus conservation were identified: (1) Mexico, Argentina, Peru,
Bolivia, Chile, and Costa Rica, (2) Paraguay and Cuba, and (3) Brazil and USA. Conservation efforts should be focused on these
countries in order to preserve cactus diversity. 相似文献
136.
Autonomic Adaption to Clinical Simulation in Psychology Students: Teaching Applications 总被引:1,自引:0,他引:1
Vicente Javier Clemente-Suárez Ana Isabel Beltrán-Velasco Alberto Bellido-Esteban Pablo Ruisoto-Palomera 《Applied psychophysiology and biofeedback》2018,43(3):239-245
Simulation is used to facilitate new learning in a variety of situations. One application of simulation could be to help therapists gain therapeutic skills prior to seeing clients. This particular study was interested in measuring changes in stress response by looking at subjective and objective measures of distress (as measured by SUDS, HR, and HRV) over three sessions of simulated therapy. 16 second year psychology students participated in three sessions, and had their HR and HRV measured by Polar watches. Over the three sessions, there was a decrease in perceived distress, as measured by SUDS ratings. During and between sessions, there was inconclusive change in physiological parameters. 相似文献
137.
138.
139.
A comprehensive examination of the network position hypothesis across multiple river metacommunities
Renato Henriques‐Silva Maxime Logez Nathalie Reynaud Pablo A. Tedesco Sebastien Brosse Stephanie R. Januchowski‐Hartley Thierry Oberdorff Christine Argillier 《Ecography》2019,42(2):284-294
The hierarchical branching nature of river networks can have a strong influence on the assembly of freshwater communities. This unique structure has spurred the development of the network position hypothesis (NPH), which states that the strength of different assembly processes depends on the community position in the river network. Specifically, it predicts that 1) headwater communities should be exclusively controlled by the local environment given that they are more isolated and environmentally heterogeneous relative to downstream reaches. In contrast, 2) downstream communities should be regulated by both environmental and dispersal processes due to increased connectivity given their central position in the riverscape. Although intuitive, the NPH has only been evaluated on a few catchments and it is not yet clear whether its predictions are generalizable. To fill this gap, we tested the NPH on river dwelling fishes using an extensive dataset from 28 French catchments. Stream and climatic variables were assembled to characterize environmental conditions and graph theory was applied on river networks to create spatial variables. We tested both predictions using variation partitioning analyses separately for headwater and downstream sites in each catchment. Only 10 catchments supported both predictions, 11 failed to support at least one of them, while in 7 the NPH was partially supported given that spatial variables were also significant for headwater communities. We then assembled a dataset at the catchment scale (e.g. topography, environmental heterogeneity, network connectivity) and applied a classification tree analysis (CTA) to determine which regional property could explain these results. The CTA showed that the NPH was not supported in catchments with high heterogeneity in connectivity among sites. In more homogeneously connected catchments, the NPH was only supported when headwaters were more environmentally heterogeneous than downstream sites. We conclude that the NPH is context dependent even for taxa dispersing exclusively within streams. 相似文献
140.
T cells are crucial for the anti-metastatic effect of anti-epidermal growth factor receptor antibodies 总被引:2,自引:0,他引:2
Garrido G Lorenzano P Sánchez B Beausoleil I Alonso DF Pérez R Fernández LE 《Cancer immunology, immunotherapy : CII》2007,56(11):1701-1710
Experimental evidences supporting the epidermal growth factor receptor (EGFR) as an important molecule for tumor metastasis
had been accumulated. Currently, anti-EGFR monoclonal antibodies (mAbs) constitute a promising approach for the treatment
of patients with metastatic tumors. However, the mechanisms associated with the potent anti-metastatic effect of these mAbs
have not been completely elucidated due to the lack of appropriate syngeneic preclinical models. In this paper, we have investigated
the effects of 7A7, an antibody specific to murine EGFR, on the metastatic properties of D122 murine lung carcinoma. 7A7 mAb
significantly impaired metastatic spread of D122 cells in C57BL/6 mice by direct anti-proliferative and pro-apoptotic effects
on tumor metastasis. 7A7 mAb capacity to inhibit EGFR activation on D122 cells could contribute to its anti-metastatic effect.
In addition, 7A7 mAb was able to induce in vitro antibody-dependent cell-mediated cytotoxicity on D122 cells. Interestingly,
7A7 mAb treatment increased the number of natural killer cells, T lymphocytes and dendritic cells infiltrating the metastatic
sites. More strikingly, depletion of CD8+ and CD4+ T cells in vivo completely abrogated the 7A7 mAb anti-metastatic activity whereas function of natural killer cells was irrelevant.
This study supports an in vivo role for T cell response in the mechanism of action of anti-EGFR mAbs, suggesting the induction
of an adjuvant effect.
This work was supported by the Cuban Government. 相似文献