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21.
L. Balaguer E. Manrique A. de los Rios C. Ascaso K. Palmqvist M. Fordham J. D. Barnes 《Oecologia》1999,119(2):166-174
Acclimation to elevated CO2 was investigated in Parmelia caperata originating from the vicinity of a natural CO2 spring, where the average daytime CO2 concentration was 729 ± 39 μmol mol−1 dry air. Thalli showed no evidence of a down-regulation in photosynthetic capacity following long-term exposure to CO2 enrichment in the field; carboxylation efficiency, total Ribulose bisphosphate carboxylase/oxygenase (Rubisco) content, apparent
quantum yield of CO2 assimilation, and the light-saturated rate of CO2 assimilation (measured under ambient and saturating CO2 concentrations) were similar in thalli from the naturally CO2 enriched site and an adjacent control site where the average long-term CO2 concentration was about 355 μmol mol−1. Thalli from both CO2 environments exhibited low CO2 compensation points and early saturation of CO2 uptake kinetics in response to increasing external CO2 concentrations, suggesting the presence of an active carbon-concentrating mechanism. Consistent with the lack of significant
effects on photosynthetic metabolism, no changes were found in the nitrogen content of thalli following prolonged exposure
to elevated CO2. Detailed intrathalline analysis revealed a decreased investment of nitrogen in Rubisco in the pyrenoid of algae located
in the elongation zone of thalli originating from elevated CO2, an effect associated with a reduction in the percentage of the cell volume occupied by lipid bodies and starch grains. Although
these differences did not affect the photosynthetic capacity of thalli, there was evidence of enhanced limitations to CO2 assimilation in lichens originating from the CO2-enriched site. The light-saturated rate of CO2 assimilation measured at the average growth CO2 concentration was found to be significantly lower in thalli originating from a CO2-enriched atmosphere compared with that of thalli originating and measured at ambient CO2. At lower photosynthetic photon flux densities, the light compensation point of net CO2 assimilation was significantly higher in thalli originating from elevated CO2, and this effect was associated with higher usnic acid content.
Received: 8 May 1998 / Accepted: 22 January 1999 相似文献
22.
JF Yuan SJ Zhang O Jafer RA Furlong OE Chausiaux CA Sargent GH Zhang NA Affara 《BMC microbiology》2009,9(1):246
Background
Pseudorabies virus (PRV) is an alphaherpesviruses whose native host is pig. PRV infection mainly causes signs of central nervous system disorder in young pigs, and respiratory system diseases in the adult. 相似文献23.
Background
Most studies examining the commensal human oral microbiome are focused on disease or are limited in methodology. In order to diagnose and treat diseases at an early and reversible stage an in-depth definition of health is indispensible. The aim of this study therefore was to define the healthy oral microbiome using recent advances in sequencing technology (454 pyrosequencing). 相似文献24.
Background
The past several years have seen a flurry of papers seeking to clarify the utility and limits of DNA barcoding, particularly in areas such as species discovery and paralogy due to nuclear pseudogenes. Heteroplasmy, the coexistence of multiple mitochondrial haplotypes in a single organism, has been cited as a potentially serious problem for DNA barcoding but its effect on identification accuracy has not been tested. In addition, few studies of barcoding have tested a large group of closely-related species with a well-established morphological taxonomy. In this study we examine both of these issues, by densely sampling the Hawaiian Hylaeus bee radiation. 相似文献25.
alpha-Tocopherol and protein kinase C inhibition enhance platelet-derived nitric oxide release. 总被引:7,自引:0,他引:7
Platelet activation is tightly regulated by products of the endothelium and platelets including nitric oxide (NO). Excess vascular oxidative stress has been associated with impaired NO release, and antioxidant status has been shown to alter endothelium-derived NO bioactivity. Although physiological levels of a-tocopherol are known to inhibit platelet function, the effect of a-tocopherol on platelet NO release is unknown. Loading platelets with physiologic levels of a-tocopherol increased platelet NO production approximately 1.5-fold (Pa-tocopherol, platelet NO release increased 50% (Pa-Tocopherol-loaded platelets also produced 74% less superoxide as compared with control (Pa-tocopherol inhibited PKC-dependent eNOS phosphorylation as determined by immunoprecipitation. Lastly, platelets isolated from NOS3-deficient mice released 80% less superoxide as compared with control animals (P=0.011), and incubation of NOS III-deficient platelets with 500 mM a-tocopherol only caused a modest additional decrease in platelet superoxide release (NS). Thus, a-tocopherol appears to enhance platelet NO release both in vitro and in vivo through antioxidant- and PKC-dependent mechanisms. 相似文献
26.
27.
The sequences of the 5' long-terminal repeat (LTR) and adjacent leader
regions of 27 full-length copia elements isolated from natural populations
of Drosophila melanogaster, D. simulans, and D. mauritiana are presented.
Phylogenetic analyses indicate that although D. melanogaster copia elements
are distinct from those of D. simulans and D. mauritiana, the elements of
these latter two species are not distinguishable from one another. LTRs and
adjacent 5' leader regions of elements isolated from D. simulans and D.
mauritiana are structurally similar to one another and carry substantial
deletional variation mapping to regions previously identified as being of
potential importance for copia expression.
相似文献
28.
Comparisons of the molecular evolutionary process at rbcL and ndhF in the grass family (Poaceae) 总被引:2,自引:1,他引:1
We examine rate heterogeneity among evolutionary lineages of the grass
family at two plasmid loci, ndhF and rbcL, and we introduce a method to
determine whether patterns of rate heterogeneity are correlated between
loci. We show both that rates of synonymous evolution are heterogeneous
among grass lineages and that are heterogeneity is correlated between loci
at synonymous sites. At nonsynonymous sites, the pattern of rate
heterogeneity is not correlated between loci, primarily due to an aberrant
pattern of rate heterogeneity at nonsynonymous sites of rbcL. We compare
patterns of synonymous rate heterogeneity to predictors based on the
generation time effect and the speciation rate hypotheses. Although there
is some evidence for generation time effects, neither generation time
effects nor speciation rates appear to be sufficient to explain patterns of
rate heterogeneity in the grass plastid sequences.
相似文献
29.
Background
Host parasitism by Trichomonas vaginalis is complex. Adherence to vaginal epithelial cells (VECs) is mediated by surface proteins. We showed before that antisense down-regulation of expression of adhesin AP65 decreased amounts of protein, which lowered levels of T. vaginalis adherence to VECs. We now perform antisense down-regulation of expression of the ap33 gene to evaluate and confirm a role for AP33 in adherence by T. vaginalis. We also used an established transfection system for heterologous expression of AP33 in T. foetus as an additional confirmatory approach. 相似文献30.
Avivar A García-Macias MC Ascaso E Herrera G O'Connor JE de Mora JF 《FEBS letters》2006,580(22):5222-5226
Here we report a new model of pre-clinical breast cancer which has been generated by overexpressing the steroid receptor coactivator AIB1 at moderate levels in breast epithelium. Transgenic female mice display mammary hyperplasia at the onset of puberty, consistent with enhanced proliferation of primary mammary epithelial cultures and augmented levels of cyclin D1 and E-cadherin. Studies of BrdU incorporation revealed that AIB1 localizes to the nucleus during or after S phase, implicating a new role for AIB1 in cell-cycle progression subsequent to G1. Our findings suggest that moderate overexpression of AIB1 may represent one of the pre-neoplastic changes in breast tissue. 相似文献