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81.
Jon Chorover Peter M. Vitousek Daniel A. Everson Anne M. Esperanza Douglas Turner 《Biogeochemistry》1994,26(2):115-144
Solution chemistry profiles of mixed-conifer forests in granitic catchments of the Sierra Nevada were measured for three years before (1987–1990) and three years after (1990–1993) prescribed fire. Wet deposition, throughfall and soil solution samplers were installed in both white-fir and giant-sequoia dominated forest stands underlain by poorly developed inceptisols. Stream water chemistry was monitored as part of an ongoing study of catchment outputs. Calcium, NO
3
–
and Cl– were the major ions in precipitation. Canopy leaching increased mean concentrations of all major ions, especially K+ and Ca2+. Water flux through the soil occurred largely during spring snowmelt. Forest floor leachate represented the most concentrated solutions of major ions. Interaction with the mineral soil decreased mean concentrations of most species and the average composition of soil solutions closely resembled stream water at baseflow. Bicarbonate alkalinity, Ca2+, Mg2+, and Na+ were enriched in stream water relative to precipitation whereas inputs of H+, NH
4
+
, NO
3
–
and SO
4
2–
were retained within the catchments.Burning of the forest understory and litter layer increased solute concentrations in soil solution and stream water. Mean soil solution Ca2+, Mg2+ and K+ concentrations increased more than 10 fold, but the relative predominance of these cations was not affected by burning. Sulfate concentration, which was very low in soil solutions of undisturbed stands (<25 mmolc m–3), increased more than 100 times following fire. Ammonium concentration exhibited a rapid, short-term increase and then a decrease below pre-burn levels. Changes in soil solution chemistry were reflected in catchment outputs.Corresponding author. 相似文献
82.
M. Isabel González Siso Manuel Becerra Mónica Lamas Maceiras ángel Vizoso Vázquez M. Esperanza Cerdán 《Biotechnology letters》2012,34(12):2161-2173
Recent advances in the knowledge of molecular mechanisms that control the adaptation to low oxygen levels in yeast and their biotechnological applications, including bioproduct synthesis, such as ethanol, glutathione or recombinant proteins, as well as pathogenic virulence, are reviewed. Possible pathways and target genes, which might be of particular interest for the improvement of biotechnological applications, are evaluated. 相似文献
83.
Jesús Vaquero Mercedes Zurita Miguel A. Rico Concepcion Aguayo Cecilia Fernandez Gregorio Rodriguez-Boto Esperanza Marin Noemi Tapiador Marta Sevilla Joaquin Carballido David Vazquez Damian Garcia-Olmo Hector Guadalajara Miguel Leon Ignacio Valverde 《Cytotherapy》2018,20(6):796-805
Background aims
Recently, clinical studies show that cell therapy with mesenchymal stromal cells (MSCs) improves the sequelae chronically established in paraplegic patients, being necessary to know which of them can obtain better benefit.Methods
We present here a phase 2 clinical trial that includes six paraplegic patients with post-traumatic syringomyelia who received 300 million MSCs inside the syrinx and who were followed up for 6 months. Clinical scales, urodynamic, neurophysiological, magnetic resonance (MR) and studies of ano-rectal manometry were performed to assess possible improvements.Results
In all the cases, MR at the end of the study showed a clear reduction of the syrinx, and, at this time, signs of improvement in the urodynamic studies were found. Moreover, four patients improved in ano-rectal manometry. Four patients improved in neurophysiological studies, with signs of improvement in evoked potentials in three patients. In the American Spinal Injury Association (ASIA) assessment, only two patients improved in sensitivity, but clinical improvement in neurogenic bowel dysfunction was observed in four patients and three patients described improvement in bladder dysfunction. Spasms reduced in two of the five patients who had them previous to cell therapy, and spasticity was improved in the other two patients. Three patients had neuropathic pain before treatment, and it was reduced or disappeared completely during the study. Only two adverse events ocurred, without relation to the cell therapy.Conclusions
Cell therapy can be considered as a new alternative to the treatment of post-traumatic syringomyelia, achieving reduction of syrinx and clinical improvements in individual patients. 相似文献84.
Yulin Ren Gerardo D. Anaya-Eugenio Austin A. Czarnecki Tran Ngoc Ninh Chunhua Yuan Hee-Byung Chai Djaja D. Soejarto Joanna E. Burdette Esperanza J. Carcache de Blanco A. Douglas Kinghorn 《Bioorganic & medicinal chemistry》2018,26(15):4452-4460
Syzygium is a large genus of flowering plants, with several species, including the clove tree, used as important resources in the food and pharmaceutical industries. In our continuing search for anticancer agents from higher plants, a chloroform extract of the leaves and twigs of Syzygium corticosum collected in Vietnam was found to be active toward the HT-29 human colon cancer cell line. Separation of this extract guided by HT-29 cells and nuclear factor-kappa B (NF-κB) inhibition yielded 19 known natural products, including seven triterpenoids, three ellagic acid derivatives, two methylated flavonoids, a cyclohexanone, four megastigmanes, a small lactone, and an aromatic aldehyde. The full stereochemistry of (+)-fouquierol (2) was defined for the first time. Biological investigations showed that (+)-ursolic acid (1) is the major cytotoxic component of S. corticosum, which exhibited also potent activities in the NF-κB and mitochondrial transmembrane potential (MTP) inhibition assays conducted, with IC50 values of 31?nM and 3.5?µM, respectively. Several analogues of (+)-ursolic acid (1) were synthesized, and a preliminary structure-activity relationship (SAR) study indicated that the C-3 hydroxy and C-28 carboxylic acid groups and 19,20-dimethyl substitution are all essential in the mediation of the bioactivities observed for this triterpenoid. 相似文献
85.
The Leguminosae is one of the largest families of plants. It has a broad geographical distribution. The principal legume species have defined sites of origin and these coincide with the diversification centers for their “specific” symbiotic bacteria. These nitrogen-fixing bacteria, which form nodules in the roots or stems of the plants, belong to different bacterial lineages (Rhizobium, Bradyrhizobium, and Azorhizobium) related to other nonsymbiotic bacteria. A remarkable characteristic of these bacteria is their large genetic diversity. The genetic relationships among the different bacterial groups are being defined based mainly on the analysis of the sequences of the ribosomal genes. Recent results point out the need to have a broader genomic scope. Gene maps, genome sizes, and sequence of metabolic genes would serve to validate the present Rhizobium and Bradyrhizobium phylogenies. More realistic phylogenies should perhaps consider lateral transfer between clusters of bacteria.
A compilation of records of bacterial genetic diversity, including enterobacteria and pathogens, is presented and compared with Rhizobium diversity. It is proposed that human activities are having important effects on microbe diversity. 相似文献
86.
87.
Severo Vázquez-Prieto Esperanza Paniagua Florencio M. Ubeira Humberto González-Díaz 《International journal of peptide research and therapeutics》2016,22(4):445-450
In the present study, three different physicochemical molecular properties for peptides were calculated using the program MARCH-INSIDE: atomic polarizability, partition coefficient, and polarity. These measures were used as input parameters of a linear discriminant analysis (LDA) in order to develop three different quantitative structure–property relationship (QSPR)-perturbation models for the prediction of B-epitopes reported in the immune epitope database (IEDB) given perturbations in peptide sequence, in vivo process, experimental techniques, and source or host organisms. The accuracy, sensitivity and specificity of the models were >90 % for both training and cross-validation series. The statistical parameters of the models were compared to the results achieved with the electronegativity QSPR-perturbation model previously reported by González-Díaz et al. (J Immunol Res. doi: 10.1155/2014/768515, 2014). The results indicate that this type of approach may constitute a potentially valuable route for predicting “in silico” new optimal peptide sequences and/or boundary conditions for vaccine development. 相似文献
88.
Independent origins of resistance or susceptibility of parasitic wasps to a defensive symbiont
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Mariana Mateos Lauryn Winter Caitlyn Winter Victor M. Higareda‐Alvear Esperanza Martinez‐Romero Jialei Xie 《Ecology and evolution》2016,6(9):2679-2687
Insect microbe associations are diverse, widespread, and influential. Among the fitness effects of microbes on their hosts, defense against natural enemies is increasingly recognized as ubiquitous, particularly among those associations involving heritable, yet facultative, bacteria. Protective mutualisms generate complex ecological and coevolutionary dynamics that are only beginning to be elucidated. These depend in part on the degree to which symbiont‐mediated protection exhibits specificity to one or more members of the natural enemy community. Recent findings in a well‐studied defensive mutualism system (i.e., aphids, bacteria, parasitoid wasps) reveal repeated instances of evolution of susceptibility or resistance to defensive bacteria by parasitoids. This study searched for similar patterns in an emerging model system for defensive mutualisms: the interaction of Drosophila, bacteria in the genus Spiroplasma, and wasps that parasitize larval stages of Drosophila. Previous work indicated that three divergent species of parasitic wasps are strongly inhibited by the presence of Spiroplasma in three divergent species of Drosophila, including D. melanogaster. The results of this study uncovered two additional wasp species that are susceptible to Spiroplasma and two that are unaffected by Spiroplasma, implying at least two instances of loss or gain of susceptibility to Spiroplasma among larval parasitoids of Drosophila. 相似文献
89.
The strength of the association between heterozygosity and probability of interannual local recruitment increases with environmental harshness in blue tits
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Esperanza S. Ferrer Vicente García‐Navas Juan José Sanz Joaquín Ortego 《Ecology and evolution》2016,6(24):8857-8869
The extent of inbreeding depression and the magnitude of heterozygosity–fitness correlations (HFC) have been suggested to depend on the environmental context in which they are assayed, but little evidence is available for wild populations. We combine extensive molecular and capture–mark–recapture data from a blue tit (Cyanistes caeruleus) population to (1) analyze the relationship between heterozygosity and probability of interannual adult local recruitment and (2) test whether environmental stress imposed by physiologically suboptimal temperatures and rainfall influence the magnitude of HFC. To address these questions, we used two different arrays of microsatellite markers: 14 loci classified as neutral and 12 loci classified as putatively functional. We found significant relationships between heterozygosity and probability of interannual local recruitment that were most likely explained by variation in genomewide heterozygosity. The strength of the association between heterozygosity and probability of interannual local recruitment was positively associated with annual accumulated precipitation. Annual mean heterozygosity increased over time, which may have resulted from an overall positive selection on heterozygosity over the course of the study period. Finally, neutral and putatively functional loci showed similar trends, but the former had stronger effect sizes and seemed to better reflect genomewide heterozygosity. Overall, our results show that HFC can be context dependent, emphasizing the need to consider the role of environmental heterogeneity as a key factor when exploring the consequences of individual genetic diversity on fitness in natural populations. 相似文献
90.
Sulfhydryl Groups Modulate the Allosteric Interaction Between Glycine Binding Sites at the Inhibitory Glycine Receptor 总被引:2,自引:0,他引:2
Ana Ruiz-Gómez Clara Fernández-Shaw Esperanza Morato Juan Carlos G. Marvizón Jesús Vázquez Fernando Valdivieso Federico Mayor Jr. 《Journal of neurochemistry》1991,56(5):1690-1697
We have investigated the effect of chemical reagents that modify sulfhydryl groups on the ligand binding properties of the glycine receptor (GlyR). The Hill coefficient (nH) for the displacement of [3H]strychnine binding by glycine was increased from approximately 0.8 to values significantly above 1 (approximately 1.2-1.4) in membranes pretreated with the disulfide-reducing agent dithiothreitol or glutathione. However, the affinity of strychnine or glycine for the GlyR was not affected by these treatments. This indicates that several glycine binding sites interact cooperatively for displacing bound strychnine under such experimental circumstances. A similar increase in the nH for glycine has been observed when the temperature of the binding assay was increased to 37 degrees C. Combination of dithiothreitol pretreatment and increased binding temperature led to nH variations similar to those observed with either of these treatments alone, a finding suggesting that their mechanisms of action are not independent. Conversely, modification of rat spinal cord membranes or of purified and reconstituted GlyR preparations with the sulfhydryl-alkylating agent N-ethylmaleimide or fluorescein-maleimide decreased nH values to approximately 0.5, without affecting glycine or strychnine affinities. This effect may be caused by an increased heterogeneity of GlyR populations. It is interesting that occupancy of the receptor by glycine or beta-alanine (but not by antagonists) specifically protects from the effects of the different sulfhydryl reagents. Moreover, the presence of some of the Eccles' anions, i.e., anions that permeate through the channels associated with GlyRs and gamma-aminobutyric acidA receptors, seems to be required for the action of both dithiothreitol and N-ethylmaleimide.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献