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11.
Susana Pascoal Joana Esteves de Lima Jonathan D. Leslie Simon M. Hughes Leonor Saúde 《PloS one》2013,8(6)
Background
Accurate regulation of Notch signalling is central for developmental processes in a variety of tissues, but its function in pectoral fin development in zebrafish is still unknown.Methodology/Principal Findings
Here we show that core elements necessary for a functional Notch pathway are expressed in developing pectoral fins in or near prospective muscle territories. Blocking Notch signalling at different levels of the pathway consistently leads to the formation of thin, wavy, fragmented and mechanically weak muscles fibres and loss of stress fibres in endoskeletal disc cells in pectoral fins. Although the structural muscle genes encoding Desmin and Vinculin are normally transcribed in Notch-disrupted pectoral fins, their proteins levels are severely reduced, suggesting that weak mechanical forces produced by the muscle fibres are unable to stabilize/localize these proteins. Moreover, in Notch signalling disrupted pectoral fins there is a decrease in the number of Pax7-positive cells indicative of a defect in myogenesis.Conclusions/Significance
We propose that by controlling the differentiation of myogenic progenitor cells, Notch signalling might secure the formation of structurally stable muscle fibres in the zebrafish pectoral fin. 相似文献12.
13.
Brewery's spent grain was treated with water in a process oriented towards the production of xylo-oligosaccharides (XOS). A wide range of temperatures and reaction times were tested and the effects of these operational variables on hemicellulose solubilization and reaction products were investigated. The maximal XOS yield (61% of the feedstock xylan) was obtained at 190 degrees C after 5 min of reaction. Several oligosaccharide mixtures with different molecular weight distributions were obtained depending on temperature and reaction time. Longer reaction times led to decreased oligosaccharide production and enhanced concentrations of monosaccharides, sugar decomposition products and acetic acid. With reaction times leading to the maximal yields of XOS, little decomposition into organic acids and aldehydes was found at all the temperatures assayed. From the composition of processed solids, it was calculated that 63-77% of the initial xylan was selectively solubilized in autohydrolysis treatments. 相似文献
14.
Among domesticated mammals, rabbit (Oryctolagus cuniculus) is the only species possessing not more than one subclass of immunoglobulin (IgG) antibodies. The rabbit IGHGCH2 or e locus presents two serologically defined alleles, the e14 and e15 allotypes, which are correlated with amino acid variation at the IgG CH2-CH3 interface. Genetic studies, while revealing the adaptive value of this polymorphism, have relied so far entirely upon allo-antisera. Here we show how these alleles can be distinguished by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods. The proposed PCR-RFLP approach allows the monitoring of IGHG locus diversity in rabbit. 相似文献
15.
Clear water associated with biomass and nutrient variation during the growth of a Charophyte stand after a drawdown,in a tropical coastal lagoon 总被引:1,自引:1,他引:0
The community of Charophytes in the Imboassica coastal lagoon in Brazil (22° 24 S and 42° 42 W) sometimes occupies almost the entire benthic region, and presents a large variation in C:N:P ratio. The effect of drawdown on the regeneration and buildup of biomass and on the nutrient concentration of these macroalgae was studied at three different sampling sites. Drawdown results in a high level of mortality in the macroalgae stands and after the water level later rises, the process of oospore germination begins. The drawdowns occurred in November 96 and January 97, and after March 97 we took samples in order to determine biomass values and the concentration of carbon, nitrogen and phosphorus. The results indicate that the fast growth of Charophytes may absorb a great amount of the nutrients entering the lagoon. The biomass reached maximum values of between 400 and 600 g DW m–2, and the C:N:P ratio varied from 51:7:1 to 1603:87:1, indicating that this macroalgae may grow in a wide range of nutrient concentration. The presence of this community in the Imboassica lagoon may act as one of the limiting factors controlling phytoplanktonic primary production, decreasing nutrient availability in the water column (`bottom-up' control) and keeping the water clear after drawdowns. Probably through the habitat structure produced by the great biomass reached, they provide substrate and shelter for the structuring of a community with grazing zooplankton, which acts as a `top-down' controlling mechanism on the phytoplankton. 相似文献
16.
Influence of photoperiod on the uptake of nitrogen and phosphorus in the water by Eichhornia crassipes and Salvinia auriculata 总被引:1,自引:0,他引:1
The main goal of this research was to quantify the concentrations of total and ammonium N, nitrate, total and soluble P in the water in the presence of Eichhornia crassipes and Salvinia auriculata, which were submitted to two different photoperiods in a 24 hours incubation period in the laboratory. The macrophytes were incubated in plastic vials of approximately 1.5 litters, with a previously prepared solution with NH4NO3, NH4Cl, and KH2PO4. Eichhornia crassipes showed the highest average rate of reduction of all the nutrients analysed in relation to Salvinia auriculata. The largest photoperiod reflected in a higher average rate of reduction of nutrients, in both plants. Therefore, we may expect that in some periods of the year (e.g. summer), the aquatic macrophytes would show higher growth rates and higher rates of nitrogen and phosphorus absorption. These results are important for the implementation and management of wastewater treatment systems in tropical areas using aquatic macrophytes. 相似文献
17.
The rates of denitrification and biological nitrogen fixation of the periphyton communities associated with the culms and
adventitious root of Oryza glumaepatula in Lake Batata, State of Pará, Brazilian Amazonia, were investigated over the course
of 24 h. N2O was not detected during the period, demonstrating that denitrification was not occurring. The low concentration of nitrate
in the water column was indicated as the main factor limiting the denitrification process. The rates of biological nitrogen
fixation (BNF) in culms were lowest at night and early morning, while the highest values were measured at 1200 h. BNF rates
in periphyton associated with adventitious roots were lowest during the morning, while highest values were measured at 1600
h. The difference in the daily patterns of BNF rates in the periphyton of culms and roots of O. glumaepatula in the euphotic
zone was attributed to defferences in the availability of organic carbon which supports this process. In the periphyton of
the culms, the BNF process was carried out by heterocystous cyanobacteria, which was photoautotrophs. In the periphyton of
the adventitious roots, BNF was carried out by periphytic bacteria, and is heterotrophically mediated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
19.
Kristina Nystr?m Joana Abrantes Ana Margarida Lopes Béatrice Le Moullac-Vaidye Stéphane Marchandeau Jézabel Rocher Nathalie Ruvo?n-Clouet Pedro J. Esteves Jacques Le Pendu 《PLoS pathogens》2015,11(4)
RHDV (rabbit hemorrhagic disease virus), a virulent calicivirus, causes high mortalities in European rabbit populations (Oryctolagus cuniculus). It uses α1,2fucosylated glycans, histo-blood group antigens (HBGAs), as attachment factors, with their absence or low expression generating resistance to the disease. Synthesis of these glycans requires an α1,2fucosyltransferase. In mammals, there are three closely located α1,2fucosyltransferase genes rSec1, rFut2 and rFut1 that arose through two rounds of duplications. In most mammalian species, Sec1 has clearly become a pseudogene. Yet, in leporids, it does not suffer gross alterations, although we previously observed that rabbit Sec1 variants present either low or no activity. Still, a low activity rSec1 allele correlated with survival to an RHDV outbreak. We now confirm the association between the α1,2fucosyltransferase loci and survival. In addition, we show that rabbits express homogenous rFut1 and rFut2 levels in the small intestine. Comparison of rFut1 and rFut2 activity showed that type 2 A, B and H antigens recognized by RHDV strains were mainly synthesized by rFut1, and all rFut1 variants detected in wild animals were equally active. Interestingly, rSec1 RNA levels were highly variable between individuals and high expression was associated with low binding of RHDV strains to the mucosa. Co-transfection of rFut1 and rSec1 caused a decrease in rFut1-generated RHDV binding sites, indicating that in rabbits, the catalytically inactive rSec1 protein acts as a dominant-negative of rFut1. Consistent with neofunctionalization of Sec1 in leporids, gene conversion analysis showed extensive homogenization between Sec1 and Fut2 in leporids, at variance with its limited degree in other mammals. Gene conversion additionally involving Fut1 was also observed at the C-terminus. Thus, in leporids, unlike in most other mammals where it became extinct, Sec1 evolved a new function with a dominant-negative effect on rFut1, contributing to fucosylated glycan diversity, and allowing herd protection from pathogens such as RHDV. 相似文献
20.
Emanuele Luciani Patrick L. S. van Dun Jorge Eduardo Esteves Christian Lunghi Marco Petracca Liria Papa Olivier Merdy Anne J?kel Francesco Cerritelli 《PloS one》2015,10(6)