175 research outputs found
Mutants on the Small Screen
A recent television series in the UK celebrates the genetic diversity of human lif
The ERK MAP Kinase Cascade Mediates Tail Swelling and a Protective Response to Rectal Infection in C. elegans
AbstractThe nematode Caenorhabditis elegans is proving to be an attractive model organism for investigating innate immune responses to infection [1]. Among the known pathogens of C. elegans is the bacterium Microbacterium nematophilum, which adheres to the nematode rectum and postanal cuticle, inducing swelling of the underlying hypodermal tissue and causing mild constipation [2]. We find that on infection by M. nematophilum, an extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase cascade mediates tail swelling and protects C. elegans from severe constipation, which would otherwise arrest development and cause sterility. Involvement in pathogen defense represents a new role for ERK MAP kinase signaling in this organism
Reflection Positivity and Monotonicity
We prove general reflection positivity results for both scalar fields and
Dirac fields on a Riemannian manifold, and comment on applications to quantum
field theory. As another application, we prove the inequality
between Dirichlet and Neumann covariance operators on a manifold with a
reflection.Comment: 11 page
The gon-1 Gene Is Required for Gonadal Morphogenesis in Caenorhabditis elegans
AbstractIn wild-type Caenorhabditis elegans, the gonad is a complex epithelial tube that consists of long arms composed predominantly of germline tissue as well as somatic structures specialized for particular reproductive functions. In gon-1 mutants, the adult gonad is severely disorganized with essentially no arm extension and no recognizable somatic structure. The developmental defects in gon-1 mutants are limited to the gonad; other cells, tissues, and organs appear to develop normally. Previous work defined the regulatory “leader” cells as crucial for extension of the gonadal arms (J. E. Kimble and J. G. White, 1981, Dev. Biol. 81, 208–219). In gon-1 mutants, the leader cells are specified correctly, but they fail to migrate and gonadal arms are not generated. In addition, gon-1 is required for morphogenesis of the gonadal somatic structures. This second role appears to be independent of that required for leader migration. Parallel studies have shown that gon-1 encodes a secreted metalloprotease (R. Blelloch and J. Kimble, 1999, Nature 399, 586–590). We discuss how a metalloprotease may control two aspects of gonadal morphogenesis
The Monitor project: Rotation of low-mass stars in the open cluster M34
We report on the results of a V and i-band time-series photometric survey of
M34 (NGC 1039) using the Wide Field Camera (WFC) on the Isaac Newton Telescope
(INT), achieving better than 1% precision per data point for 13 <~ i <~ 17.
Candidate cluster members were selected from a V vs V-I colour-magnitude
diagram over 14 < V < 24 (0.12 <~ M/Msun <~ 1.0), finding 714 candidates, of
which we expect ~ 400 to be real cluster members (taking into account
contamination from the field). The mass function was computed, and found to be
consistent with a log-normal distribution in dN/dlogM. Searching for periodic
variable objects in the candidate members gave 105 detections over the mass
range 0.25 < M/Msun < 1.0. The distribution of rotation periods for 0.4 <
M/Msun < 1.0 was found to peak at ~ 7 days, with a tail of fast rotators down
to periods of ~ 0.8 days. For 0.25 < M/Msun < 0.4 we found a peak at short
periods, with a lack of slow rotators (eg. P >~ 5 days, consistent with the
work of other authors (eg. Scholz & Eisloffel 2004) at very low masses. Our
results are interpreted in the context of previous work, finding that we
reproduce the same general features in the rotational period distributions. A
number of rapid rotators were found with velocities ~ a factor of two lower
than in the Pleiades, consistent with models of angular momentum evolution
assuming solid body rotation without needing to invoke core-envelope
decoupling.Comment: 22 pages, 19 figures, 5 tables, MNRAS accepte
trt-1 Is the Caenorhabditis elegans Catalytic Subunit of Telomerase
Mutants of trt-1, the Caenorhabditis elegans telomerase reverse transcriptase, reproduce normally for several generations but eventually become sterile as a consequence of telomere erosion and end-to-end chromosome fusions. Telomere erosion and uncapping do not cause an increase in apoptosis in the germlines of trt-1 mutants. Instead, late-generation trt-1 mutants display chromosome segregation defects that are likely to be the direct cause of sterility. trt-1 functions in the same telomere replication pathway as mrt-2, a component of the Rad9/Rad1/Hus1 (9–1–1) proliferating cell nuclear antigen–like sliding clamp. Thus, the 9–1–1 complex may be required for telomerase to act at chromosome ends in C. elegans. Although telomere erosion limits replicative life span in human somatic cells, neither trt-1 nor telomere shortening affects postmitotic aging in C. elegans. These findings illustrate effects of telomere dysfunction in C. elegans mutants lacking the catalytic subunit of telomerase, trt-1
Detection of the secondary eclipse of WASP-10b in the Ks-band
WASP-10b, a non-inflated hot Jupiter, was discovered around a K-dwarf in a
near circular orbit (). Since its discovery in 2009, different
published parameters for this system have led to a discussion about the size,
density, and eccentricity of this exoplanet. In order to test the hypothesis of
a circular orbit for WASP-10b, we have observed its secondary eclipse in the
Ks-band, where the contribution of planetary light is high enough to be
detected from the ground. Observations were performed with the OMEGA2000
instrument at the 3.5-meter telescope at Calar Alto (Almer\'ia, Spain), in
staring mode during 5.4 continuous hours, with the telescope defocused,
monitoring the target during the expected secondary eclipse. A relative light
curve was generated and corrected from systematic effects, using the Principal
Component Analysis (PCA) technique. The final light curve was fitted using a
transit model to find the eclipse depth and a possible phase shift. The best
model obtained from the Markov Chain Monte Carlo analysis resulted in an
eclipse depth of of and a phase
offset of of . The eclipse phase
offset derived from our modeling has systematic errors that were not taken into
account and should not be considered as evidence of an eccentric orbit. The
offset in phase obtained leads to a value for of .
The derived eccentricity is too small to be of any significance.Comment: 8 pages, 10 figure
- …