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101.
Gabrielle Thiébaut Guillaume Tixier François Guérold Serge Muller 《Hydrobiologia》2006,570(1):159-164
The aim of our study was to assess the water quality of the upper Moselle river by using biological indices. Simultaneous
physico-chemical surveys were also undertaken from May 1999 to April 2000. Twelve sampling sites were selected in order to
provide a wide range of potential pollution. Chemical analysis did not reveal any major problem of pollution. However a lower
water quality resulting from domestic pollution was established for some sampling sites. A biological monitoring combining
both macroinvertebrates and macrophytes was performed. Biological indices based on plant community structure and macrophyte
composition were not pertinent tools, whereas simple indices based on taxonomic richness of particular groups of macroinvertebrates
were strongly correlated with several chemical parameters, showing that such simple biological variables should represent
powerful indicators of ecosystem degradation. 相似文献
102.
Ghislain Vieilledent Benoît Courbaud Georges Kunstler Jean-François Dhôte James S. Clark 《Oecologia》2010,163(3):759-773
Tree species differences in crown size and shape are often highlighted as key characteristics determining light interception strategies and successional dynamics. The phenotypic plasticity of species in response to light and space availability suggests that intraspecific variability can have potential consequences on light interception and community dynamics. Species crown size varies depending on site characteristics and other factors at the individual level which differ from competition for light and space. These factors, such as individual genetic characteristics, past disturbances or environmental micro-site effects, combine with competition-related phenotypic plasticity to determine the individual variability in crown size. Site and individual variability are typically ignored when considering crown size and light interception by trees, and residual variability is relegated to a residual error term, which is then ignored when studying ecological processes. In the present study, we structured and quantified variability at the species, site, and individual levels for three frequently used tree allometric relations using fixed and random effects in a hierarchical Bayesian framework. We focused on two species: Abies alba (silver fir) and Picea abies (Norway spruce) in nine forest stands of the western Alps. We demonstrated that species had different allometric relations from site to site and that individual variability accounted for a large part of the variation in allometric relations. Using a spatially explicit radiation transmission model on real stands, we showed that individual variability in tree allometry had a substantial impact on light resource allocation in the forest. Individual variability in tree allometry modulates species’ light-intercepting ability. It generates heterogeneous light conditions under the canopy, with high light micro-habitats that may promote the regeneration of light-demanding species and slow down successional dynamics. 相似文献
103.
Sudano MJ Paschoal DM Rascado Tda S Magalhães LC Crocomo LF de Lima-Neto JF Landim-Alvarenga Fda C 《Theriogenology》2011,75(7):1211-1220
The objective was to evaluate supplementation of fetal calf serum (FCS) and phenazine ethosulfate (PES), a metabolic regulator that inhibits fatty acid synthesis, in culture media during in vitro production (IVP) of bovine embryos. Taking oocyte fertilization (n = 4,320) as Day 0, four concentrations of FCS (0, 2.5, 5, and 10%) and three periods of exposure to PES (without addition—Control; after 60 h—PES Day 2.5 of embryo culture; and after 96 h—PES Day 4) were evaluated. Increasing FCS concentration in the culture media enhanced lipid accumulation (P < 0.05), increased apoptosis in fresh (2.5%: 19.1 ± 1.8 vs 10%: 28.4 ± 2.3, P < 0.05; mean ± SEM) and vitrified (2.5%: 42.8 ± 2.7 vs 10%: 69.2 ± 3.4, P < 0.05) blastocysts, and reduced blastocoele re-expansion after vitrification (2.5%: 81.6 ± 2.5 vs 10%: 67.3 ± 3.5, P < 0.05). The addition of PES in culture media, either from Days 2.5 or 4, reduced lipid accumulation (P < 0.05) and increased blastocoele re-expansion after vitrification (Control: 72.0 ± 3.0 vs PES Day 2.5: 79.9 ± 2.8 or PES Day 4: 86.2 ± 2.4, P < 0.05). However, just the use of PES from D4 reduced apoptosis in vitrified blastocysts (Control: 52.0 ± 3.0 vs PES Day 4: 39.2 ± 2.4, P < 0.05). Independent of FCS withdrawal or PES addition to culture media, the in vivo control group had lesser lipid accumulation, a lower apoptosis rate, and greater cryotolerance (P < 0.05). The increased lipid content was moderately correlated with apoptosis in vitrified blastocysts (r = 0.64, P = 0.01). In contrast, the increased apoptosis in fresh blastocysts was strongly correlated with apoptosis in vitrified blastocysts (r = 0.94, P < 0.0001). Therefore, using only 2.5% FCS and the addition of PES from Day 4, increased the survival of IVP embryos after vitrification. Moreover, embryo quality, represented by the fresh apoptosis rate, was better than lipid content for predicting embryo survival after vitrification. 相似文献
104.
Shibin Gao Carlos Martinez Debra J. Skinner Alan F. Krivanek Jonathan H. Crouch Yunbi Xu 《Molecular breeding : new strategies in plant improvement》2008,22(3):477-494
Leaf collection from the field, labeling and tracking back to the source plants after genotyping are rate limiting steps in
leaf DNA-based genotyping. In this study, an optimized genotyping method using endosperm DNA sampled from single maize seeds
was developed, which can be used to replace leaf DNA-based genotyping for both genetic studies and breeding applications.
A similar approach is likely to be suitable for all plants with relatively large seeds. Part of the endosperm was excised
from imbibed maize seeds and DNA extracted in 96-tube plates using individuals from eight F2 populations and seven inbreds. The quality of the resultant DNA was functionally comparable to DNA extracted from leaf tissue.
Extraction from 30 mg of endosperm yields 3–10 μg DNA, which is sufficient for analysis of 200–400 agarose-gel PCR-based markers,
with the potential for several million chip-based SNP marker analyses. By comparing endosperm DNA and leaf DNA for individuals
from an F2 population, genotyping errors caused by pericarp contamination and hetero-fertilization were found to average 3.8 and 0.6%,
respectively. Endosperm sampling did not affect germination rates under controlled conditions, although under normal field
conditions the germination rate, seedling establishment, and growth vigor were significantly lower than that of non-sampled
controls for some genotypes. However, careful field management can compensate for these effects. Seed DNA-based genotyping
lowered costs by 24.6% compared to leaf DNA-based genotyping due to reduced field plantings and labor costs. A substantial
advantage of this approach is that it can be used to select desirable genotypes before planting. As such it provides an opportunity
for dramatic improvements in the efficiency and selective gain of breeding systems based on optimum combinations of marker-assisted
selection and phenotypic selection within and between generations. 相似文献
105.
Jean-Baptiste Boulé Emmett Johnson François Rougeon Catherine Papanicolaou 《Molecular biotechnology》1998,10(3):199-208
Terminal deoxynucleotidyl transferase (TdT) is a highly conserved vertebrate enzyme that possesses the unique ability to catalyze
the random addition of deoxynucleoside 5′-triphosphates onto the 3′-hydroxyl group of a single-stranded DNA. It plays an important
role in the generation of immunoglobin and T-cell receptor diversity. TdT is usually obtained from animal thymus gland or
produced in a baculovirus system, but both procedures are rather tedious, and proteolysis occurs during purification. Attempts
to overexpress TdT in bacteria have been unsuccessful or have yielded an enzyme with a lower specific activity. A dearth of
TdT has thus hampered detailed structural and functional studies. In the present study, we report that by lowering growth
temperature and overexpressing a rare arginyl tRNA, it is possible to boost the production inEscherichia coli of murine TdT with minimal proteolysis and high specific activity. 相似文献
106.
Gloria Alvarez-Sola Iker Uriarte Maria U. Latasa Maddalen Jimenez Marina Barcena-Varela Eva Santamaría Raquel Urtasun Carlos Rodriguez-Ortigosa Jesús Prieto Pedro Berraondo Maite G. Fernandez-Barrena Carmen Berasain Matías A. Avila 《生物化学与生物物理学报:疾病的分子基础》2018,1864(4):1326-1334
The liver has an extraordinary regenerative capacity rapidly triggered upon injury or resection. This response is intrinsically adjusted in its initiation and termination, a property termed the “hepatostat”. Several molecules have been involved in liver regeneration, and among them bile acids may play a central role. Intrahepatic levels of bile acids rapidly increase after resection. Through the activation of farnesoid X receptor (FXR), bile acids regulate their hepatic metabolism and also promote hepatocellular proliferation. FXR is also expressed in enterocytes, where bile acids stimulate the expression of fibroblast growth factor 15/19 (FGF15/19), which is released to the portal blood. Through the activation of FGFR4 on hepatocytes FGF15/19 regulates bile acids synthesis and finely tunes liver regeneration as part of the “hepatostat”. Here we review the experimental evidences supporting the relevance of the FXR-FGF15/19-FGFR4 axis in liver regeneration and discuss potential therapeutic applications of FGF15/19 in the prevention of liver failure. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen. 相似文献
107.
Little information exists on mixed-species groups between primates and other mammals in Neotropical forests. In this paper, we describe three such associations observed during an extensive large-vertebrate survey in central Amazonia, Brazil. Mixed-species groups between a primate species and another mammal were observed on seven occasions between squirrel monkeys (Saimiri cf. ustus) and either South American coatis (Nasua nasua) or tayras (Eira barbara) and between brown capuchins (Cebus apella) and coatis. All associations were restricted to floodplain forest during its dry stage. We suggest that the associations involving the coatis are connected to foraging and vigilance but may be induced by a common alternative food resource at a time of food shortage. 相似文献
108.
Lentiviral vectors have been used for gene transfer into the liver but their ability to efficiently transduce quiescent hepatocytes
remains controversial. Lentivirus-mediated gene transfer is more efficient in cycling cells. We determine the effect of H-IL6
in the lentiviral transduction. The lentiviral vector was used to transduce HepG2 cells and mice liver cells, previously treated
with H-IL6. The highest transduction level was observed in HepG2 cells treated with 30 ng/mL H-IL6 and in the mice that received
4 μg H-IL6. Our results suggest that H-IL6 is an inducer of lentiviral gene transfer into the liver cells without any toxicity. 相似文献
109.
110.
Carolina C. Lisboa Richard T. Conant Michelle L. Haddix Carlos Eduardo P. Cerri Carlos C. Cerri 《Ecosystems》2009,12(7):1212-1221
The effect of conversion from forest-to-pasture upon soil carbon stocks has been intensively discussed, but few studies focus
on how this land-use change affects carbon (C) distribution across soil fractions in the Amazon basin. We investigated this
in the 20 cm depth along a chronosequence of sites from native forest to three successively older pastures. We performed a
physicochemical fractionation of bulk soil samples to better understand the mechanisms by which soil C is stabilized and evaluate
the contribution of each C fraction to total soil C. Additionally, we used a two-pool model to estimate the mean residence
time (MRT) for the slow and active pool C in each fraction. Soil C increased with conversion from forest-to-pasture in the
particulate organic matter (>250 μm), microaggregate (53–250 μm), and d-clay (<2 μm) fractions. The microaggregate comprised
the highest soil C content after the conversion from forest-to-pasture. The C content of the d-silt fraction decreased with
time since conversion to pasture. Forest-derived C remained in all fractions with the highest concentration in the finest
fractions, with the largest proportion of forest-derived soil C associated with clay minerals. Results from this work indicate
that microaggregate formation is sensitive to changes in management and might serve as an indicator for management-induced
soil carbon changes, and the soil C changes in the fractions are dependent on soil texture. 相似文献