56 research outputs found
Dust and gas in luminous infrared galaxies - results from SCUBA observations
We present new data taken at 850 m with SCUBA at the JCMT for a sample
of 19 luminous infrared galaxies. Fourteen galaxies were detected. We have used
these data, together with fluxes at 25, 60 and 100 m from IRAS, to model
the dust emission. We find that the emission from most galaxies can be
described by an optically thin, single temperature dust model with an exponent
of the dust extinction coefficient () of
. A lower is required to model the dust
emission from two of the galaxies, Arp 220 and NGC 4418. We discuss various
possibilities for this difference and conclude that the most likely is a high
dust opacity. In addition, we compare the molecular gas mass derived from the
dust emission, , with the molecular gas mass derived from the CO
emission, , and find that is on average a factor 3 higher than
.Comment: 10 pages, 6 figures, latex, with MN-macros, accepted by MNRAS -
revised version (changed flux values for some galaxies
Anomalous Features of EMT during Keratinocyte Transformation
During the evolution of epithelial cancers, cells often lose their characteristic features and acquire a mesenchymal phenotype, in a process known as epithelial-mesenchymal transition (EMT). In the present study we followed early stages of keratinocyte transformation by HPV16, and observed diverse cellular changes, associated with EMT. We compared primary keratinocytes with early and late passages of HF1 cells, a cell line of HPV16-transformed keratinocytes. We have previously shown that during the progression from the normal cells to early HF1 cells, immortalization is acquired, while in the progression to late HF1, cells become anchorage independent. We show here that during the transition from the normal state to late HF1 cells, there is a progressive reduction in cytokeratin expression, desmosome formation, adherens junctions and focal adhesions, ultimately leading to poorly adhesive phenotype, which is associated with anchorage-independence. Surprisingly, unlike “conventional EMT”, these changes are associated with reduced Rac1-dependent cell migration. We monitored reduced Rac1-dependent migration also in the cervical cancer cell line SiHa. Therefore we can conclude that up to the stage of tumor formation migratory activity is eliminated
The Submillimeter Array 1.3 mm line survey of Arp 220
We present the first aperture synthesis unbiased spectral line survey toward
an extragalactic object. The survey covered the 40 GHz frequency range between
202 and 242 GHz of the 1.3 mm atmospheric window. We find that 80% of the
observed band shows molecular emission, with 73 features identified from 15
molecular species and 6 isotopologues. The 13C isotopic substitutions of HC3N
and transitions from H2(18)O, 29SiO, and CH2CO are detected for the first time
outside the Galaxy. Within the broad observed band, we estimate that 28% of the
total measured flux is due to the molecular line contribution, with CO only
contributing 9% to the overall flux. We present maps of the CO emission at a
resolution of 2.9"x1.9" which, though not enough to resolve the two nuclei,
recover all the single-dish flux. The 40 GHz spectral scan has been modelled
assuming LTE conditions and abundances are derived for all identified species.
The chemical composition of Arp 220 shows no clear evidence of an AGN impact on
the molecular emission but seems indicative of a purely starburst-heated ISM.
The overabundance of H2S and the low isotopic ratios observed suggest a
chemically enriched environment by consecutive bursts of star formation, with
an ongoing burst at an early evolutionary stage. The large abundance of water
(~10^-5), derived from the isotopologue H2(18)O, as well as the vibrationally
excited emission from HC3N and CH3CN are claimed to be evidence of massive star
forming regions within Arp 220. Moreover, the observations put strong
constraints on the compactness of the starburst event in Arp 220. We estimate
that such emission would require ~2-8x10^6 hot cores, similar to those found in
the Sgr B2 region in the Galactic center, concentrated within the central 700
pc of Arp 220.Comment: Accepted for publication in A&
The evolution of prey‐wrapping behaviour in spiders
We traced the evolution of silk use by spiders in attacks on prey by combining previous publications with new observations of 31 species in 16 families. Two new prey‐wrapping techniques are described. One, in which the spider holds a tense line (often covered with viscid silk) with both legs IV and applies it to the prey with a simultaneous movement of both legs, may be a synapomorphy linking Theridiidae, Nesticidae, and Synotaxidae. The other, in which the spider stands over the prey and turns in place, is apparently very ancient; it occurs in Theraphosidae, Tengellidae, and Agelenidae. The use of legs IV to wrap prey is described for the first time in Filistatidae and Scytodidae. Using a recent phylogeny of spiders, we propose that prey wrapping with legs IV has evolved convergently at least four times. We propose that prey wrapping originally evolved from egg‐sac construction behaviour.Instituto Smithsoniano de Investigaciones Tropicales (STRI)Universidad de Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí
Estereotipia e plasticidade na seqüência predatória de Theridion evexum keyserling 1884 (Araneae: Theridiidae)
Lista das espécies de aranhas (Arachnida, Araneae) do estado do Rio Grande do Sul, Brasil
A phylogenetic analysis of the nursery-web spider family Pisauridae, with emphasis on the genera Architis and Staberius (Araneae: Lycosoidea)
TSC1 Promotes B Cell Maturation but Is Dispensable for Germinal Center Formation.
Accumulating evidence indicates that the tuberous sclerosis complex 1 (TSC1), a tumor suppressor that acts by inhibiting mTOR signaling, plays an important role in the immune system. We report here that TSC1 differentially regulates mTOR complex 1 (mTORC1) and mTORC2/Akt signaling in B cells. TSC1 deficiency results in the accumulation of transitional-1 (T1) B cells and progressive losses of B cells as they mature beyond the T1 stage. Moreover, TSC1KO mice exhibit a mild defect in the serum antibody responses or rate of Ig class-switch recombination after immunization with a T-cell-dependent antigen. In contrast to a previous report, we demonstrate that both constitutive Peyer's patch germinal centers (GCs) and immunization-induced splenic GCs are unimpaired in TSC1-deficient (TSC1KO) mice and that the ratio of GC B cells to total B cells is comparable in WT and TSC1KO mice. Together, our data demonstrate that TSC1 plays important roles for B cell development, but it is dispensable for GC formation and serum antibody responses
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