17 research outputs found
RNA-Seq identifies SPGs as a ventral skeletal patterning cue in sea urchins
The sea urchin larval skeleton offers a simple model for formation of developmental patterns. The calcium carbonate skeleton is secreted by primary mesenchyme cells (PMCs) in response to largely unknown patterning cues expressed by the ectoderm. To discover novel ectodermal cues, we performed an unbiased RNA-Seq-based screen and functionally tested candidates; we thereby identified several novel skeletal patterning cues. Among these, we show that SLC26a2/7 is a ventrally expressed sulfate transporter that promotes a ventral accumulation of sulfated proteoglycans, which is required for ventral PMC positioning and skeletal patterning. We show that the effects of SLC perturbation are mimicked by manipulation of either external sulfate levels or proteoglycan sulfation. These results identify novel skeletal patterning genes and demonstrate that ventral proteoglycan sulfation serves as a positional cue for sea urchin skeletal patterning
Observation of Extended VHE Emission from the Supernova Remnant IC 443 with VERITAS
We present evidence that the very-high-energy (VHE, E > 100 GeV) gamma-ray
emission coincident with the supernova remnant IC 443 is extended. IC 443
contains one of the best-studied sites of supernova remnant/molecular cloud
interaction and the pulsar wind nebula CXOU J061705.3+222127, both of which are
important targets for VHE observations. VERITAS observed IC 443 for 37.9 hours
during 2007 and detected emission above 300 GeV with an excess of 247 events,
resulting in a significance of 8.3 standard deviations (sigma) before trials
and 7.5 sigma after trials in a point-source search. The emission is centered
at 06 16 51 +22 30 11 (J2000) +- 0.03_stat +- 0.08_sys degrees, with an
intrinsic extension of 0.16 +- 0.03_stat +- 0.04_sys degrees. The VHE spectrum
is well fit by a power law (dN/dE = N_0 * (E/TeV)^-Gamma) with a photon index
of 2.99 +- 0.38_stat +- 0.3_sys and an integral flux above 300 GeV of (4.63 +-
0.90_stat +- 0.93_sys) * 10^-12 cm^-2 s^-1. These results are discussed in the
context of existing models for gamma-ray production in IC 443.Comment: 7 pages, accepted by ApJ
Regulatory interactions among autologous T cell clones. Human bifunctional T cell clones regulate the activity of an autologous T cell clone.
In contrast to the ease of cloning and characterizing, at the molecular level, helper and cytotoxic T cells, suppressor T cells remain an enigma, and their existence as discrete entities is being increasingly challenged. Here we review evidence that CD4+ regulatory clones, capable of expressing both helper and suppressor functions, may account for much of the suppressor function. It is suggested that a single T cell clone, depending on the signals it receives from its environment, may release either helper or suppressor cytokines. Studying such clones under defined conditions (providing suppressor signals), may preclude detection of their helper capacity. Since some therapeutic approaches in various human diseases are based on the manipulation of helper and suppressor functions, the question whether committed suppressor cells exist has important practical implications in medicine