754 research outputs found
Expression of ECM proteins fibulin-1 and -2 in acute and chronic liver disease and in cultured rat liver cells
Fibulin-2 has previously been considered as a marker to distinguish rat liver myofibroblasts from hepatic stellate cells. The function of other fibulins in acute or chronic liver damage has not yet been investigated. The aim of this study has been to evaluate the expression of fibulin-1 and -2 in models of rat liver injury and in human liver cirrhosis. Their cellular sources have also been investigated. In normal rat liver, fibulin-1 and -2 were both mainly present in the portal field. Fibulin-1-coding transcripts were detected in total RNA of normal rat liver, whereas fibulin-2 mRNA was only detected by sensitive, real-time quantitative polymerase chain reaction. In acute liver injury, the expression of fibulin-1 was significantly increased (17.23-fold after 48 h), whereas that of fibulin-2 was not modified. The expression of both fibulin-1 and -2 was increased in experimental rat liver cirrhosis (19.16- and 26.47-fold, respectively). At the cellular level, fibulin-1 was detectable in hepatocytes, “activated” hepatic stellate cells, and liver myofibroblasts (2.71-, 122.65-, and 469.48-fold over the expression in normal rat liver), whereas fibulin-2 was restricted to liver myofibroblasts and was regulated by transforming growth factor beta-1 (TGF-β1) in 2-day-old hepatocyte cultures and in liver myofibroblasts. Thus, fibulin-1 and -2 respond differentially to single and repeated damaging noxae, and their expression is differently present in liver cells. Expression of the fibulin-2 gene is regulated by TGF-β1 in liver myofibroblasts
A conserved enhancer of the human and murine Hoxa-7 gene specifies the anterior boundary of expression during embryonal development
Subsurface microbial methanotrophic mats in the Black Sea
A nodule-shaped microbial mat was found subsurface in sediments of a gas seep in the anoxic Black Sea. This mat was dominated by ANME-1 archaea and consumed methane and sulfate simultaneously. We propose that such subsurface mats represent the initial stage of previously investigated microbial reefs
Sagnac Interferometer Enhanced Particle Tracking in Optical Tweezers
A setup is proposed to enhance tracking of very small particles, by using
optical tweezers embedded within a Sagnac interferometer. The achievable
signal-to-noise ratio is shown to be enhanced over that for a standard optical
tweezers setup. The enhancement factor increases asymptotically as the
interferometer visibility approaches 100%, but is capped at a maximum given by
the ratio of the trapping field intensity to the detector saturation threshold.
For an achievable visibility of 99%, the signal-to-noise ratio is enhanced by a
factor of 200, and the minimum trackable particle size is 2.4 times smaller
than without the interferometer
Thiomicrospira arctica sp nov and Thiomicrospira psychrophila sp nov., psychrophilic, obligately chemolithoautotrophic, sulfur-oxidizing bacteria isolated from marine Arctic sediments
Two psychrophilic, chemolithoautotrophic, sulfur-oxidizing bacteria were isolated from marine Arctic sediments sampled off the coast of Svalbard with thiosulfate as the electron donor and CO(2) as carbon source. Comparative analysis of 16S rRNA gene sequences suggested that the novel strains, designated SVAL-D(T) and SVAL-E(T), represent members of the genus Thiomicrospira. Further genotypic (DNA-DNA relatedness, DNA G+C content) and phenotypic characterization revealed that the strains represent members of two novel species. Both organisms are obligately autotrophic and strictly aerobic. Nitrate was not used as an electron acceptor. Chemolithoautotrophic growth was observed with thiosulfate, tetrathionate and sulfur. The temperature limits for growth of both strains were between -2 degrees C and 20.8 degrees C, with optima of 11.5-13.2 degrees C (SVAL-E(T)) and 14.6-15.4 degrees C (SVAL-D(T)), which is about 13-15 degrees C lower than the optima of all other recognized Thiomicrospira species. The maximum growth rate on thiosulfate at 14 degrees C was 0.14 h(-1) for strain SVAL-E(T) and 0.2 h(-1) for strain SVAL-D(T). Major fatty acids of SVAL-D(T) are C(16 : 1), C(18 : 0) and C(16 : 0), and those of SVAL-E(T) are C(16 : 1), C(18 : 1), C(16 : 0) and C(14 : 1). Cells of SVAL-D(T) and SVAL-E(T) are rods, like those of their closest relatives. To our knowledge the novel strains are the first psychrophilic, chemolithoautotrophic, sulfur-oxidizing bacteria so far described. The names Thiomicrospira arctica sp. nov. and Thiomicrospira psychrophila sp. nov. are proposed for SVAL-E(T) (=ATCC 700955(T)=DSM 13458(T)) and SVAL-D(T) (=ATCC 700954(T)=DSM 13453(T)), respectively
Fundamental constraints on particle tracking with optical tweezers
A general quantum limit to the sensitivity of particle position measurements
is derived following the simple principle of the Heisenberg microscope. The
value of this limit is calculated for particles in the Rayleigh and Mie
scattering regimes, and with parameters which are relevant to optical tweezers
experiments. The minimum power required to observe the zero-point motion of a
levitating bead is also calculated, with the optimal particle diameter always
smaller than the wavelength. We show that recent optical tweezers experiments
are within two orders of magnitude of quantum limited sensitivity, suggesting
that quantum optical resources may soon play an important role in high
sensitivity tracking applications
Diverse syntrophic partnerships from deep-sea methane vents revealed by direct cell capture and metagenomics
Microorganisms play a fundamental role in the cycling of nutrients and energy on our planet. A common strategy for many microorganisms mediating biogeochemical cycles in anoxic environments is syntrophy, frequently necessitating close spatial proximity between microbial partners. We are only now beginning to fully appreciate the diversity and pervasiveness of microbial partnerships in nature, the majority of which cannot be replicated in the laboratory. One notable example of such cooperation is the interspecies association between anaerobic methane oxidizing archaea (ANME) and sulfate-reducing bacteria. These consortia are globally distributed in the environment and provide a significant sink for methane by substantially reducing the export of this potent greenhouse gas into the atmosphere. The interdependence of these currently uncultured microbes renders them difficult to study, and our knowledge of their physiological capabilities in nature is limited. Here, we have developed a method to capture select microorganisms directly from the environment, using combined fluorescence in situ hybridization and immunomagnetic cell capture. We used this method to purify syntrophic anaerobic methane oxidizing ANME-2c archaea and physically associated microorganisms directly from deep-sea marine sediment. Metagenomics, PCR, and microscopy of these purified consortia revealed unexpected diversity of associated bacteria, including Betaproteobacteria and a second sulfate-reducing Deltaproteobacterial partner. The detection of nitrogenase genes within the metagenome and subsequent demonstration of 15N2 incorporation in the biomass of these methane-oxidizing consortia suggest a possible role in new nitrogen inputs by these syntrophic assemblages
Manufacture of silicide coatings for the protection of niobium alloys against high temperature oxidation
At the moment, silicide coatings provide the best protection against high temperature oxidation for niobium alloys. These are envisaged for replacing nickel base alloys currently used in the hot section of turbo-engines. Silicides confer higher protectiveness to Nb base system when compared to the environmental resistance presented by Nb alloys coated with aluminides. One major advantage of silicides is probably the great number of possibilities for modifying their composition as well as their crystallographic structure. Thus, many elemental substitutions were performed over the past 20 years in order to optimize their performances in terms of oxidation resistance. The works performed at the University of Nancy focused currently on the M3M\u273CrSi6 phase which has Nb3Fe3CrSi6 as prototype [i]. Initially, the coatings were developed for the protection of niobium alloys, strengthened by solid solution and in which the niobium content was rather high, in the range of 95 weight %. The first stage of the works was devoted to thermodynamic studies leading to the determination of phase equilibria in the Nb-Fe-Cr-Si system. Then, the obtained results were used to determine the compositions of masteralloys and the conditions of the pack-cementation processs (temperature, gas atmosphere and time) for depositing the Nb3Fe3CrSi6 phase as superficial layer, in avoiding the growth of brittle silicides as well as silicide sensitive to pest phenomeno
Biological measurement beyond the quantum limit
Quantum noise places a fundamental limit on the per photon sensitivity
attainable in optical measurements. This limit is of particular importance in
biological measurements, where the optical power must be constrained to avoid
damage to the specimen. By using non-classically correlated light, we
demonstrated that the quantum limit can be surpassed in biological
measurements. Quantum enhanced microrheology was performed within yeast cells
by tracking naturally occurring lipid granules with sensitivity 2.4 dB beyond
the quantum noise limit. The viscoelastic properties of the cytoplasm could
thereby be determined with a 64% improved measurement rate. This demonstration
paves the way to apply quantum resources broadly in a biological context
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