838 research outputs found
Coordination of opposing sex-specific and core muscle groups regulates male tail posture during Caenorhabditis elegans male mating behavior
Background
To survive and reproduce, animals must be able to modify their motor behavior in response to changes in the environment. We studied a complex behavior of Caenorhabditis elegans, male mating behavior, which provided a model for understanding motor behaviors at the genetic, molecular as well as circuit level. C. elegans male mating behavior consists of a series of six sub-steps: response to contact, backing, turning, vulva location, spicule insertion, and sperm transfer. The male tail contains most of the sensory structures required for mating, in addition to the copulatory structures, and thus to carry out the steps of mating behavior, the male must keep his tail in contact with the hermaphrodite. However, because the hermaphrodite does not play an active role in mating and continues moving, the male must modify his tail posture to maintain contact. We provide a better understanding of the molecular and neuro-muscular pathways that regulate male tail posture during mating.
Results
Genetic and laser ablation analysis, in conjunction with behavioral assays were used to determine neurotransmitters, receptors, neurons and muscles required for the regulation of male tail posture. We showed that proper male tail posture is maintained by the coordinated activity of opposing muscle groups that curl the tail ventrally and dorsally. Specifically, acetylcholine regulates both ventral and dorsal curling of the male tail, partially through anthelmintic levamisole-sensitive, nicotinic receptor subunits. Male-specific muscles are required for acetylcholine-driven ventral curling of the male tail but dorsal curling requires the dorsal body wall muscles shared by males and hermaphrodites. Gamma-aminobutyric acid activity is required for both dorsal and ventral acetylcholine-induced curling of the male tail and an inhibitory gamma-aminobutyric acid receptor, UNC-49, prevents over-curling of the male tail during mating, suggesting that cross-inhibition of muscle groups helps maintain proper tail posture.
Conclusion
Our results demonstrated that coordination of opposing sex-specific and core muscle groups, through the activity of multiple neurotransmitters, is required for regulation of male tail posture during mating. We have provided a simple model for regulation of male tail posture that provides a foundation for studies of how genes, molecular pathways, and neural circuits contribute to sensory regulation of this motor behavior
Mesoscopic organization reveals the constraints governing C. elegans nervous system
One of the biggest challenges in biology is to understand how activity at the
cellular level of neurons, as a result of their mutual interactions, leads to
the observed behavior of an organism responding to a variety of environmental
stimuli. Investigating the intermediate or mesoscopic level of organization in
the nervous system is a vital step towards understanding how the integration of
micro-level dynamics results in macro-level functioning. In this paper, we have
considered the somatic nervous system of the nematode Caenorhabditis elegans,
for which the entire neuronal connectivity diagram is known. We focus on the
organization of the system into modules, i.e., neuronal groups having
relatively higher connection density compared to that of the overall network.
We show that this mesoscopic feature cannot be explained exclusively in terms
of considerations, such as optimizing for resource constraints (viz., total
wiring cost) and communication efficiency (i.e., network path length).
Comparison with other complex networks designed for efficient transport (of
signals or resources) implies that neuronal networks form a distinct class.
This suggests that the principal function of the network, viz., processing of
sensory information resulting in appropriate motor response, may be playing a
vital role in determining the connection topology. Using modular spectral
analysis, we make explicit the intimate relation between function and structure
in the nervous system. This is further brought out by identifying functionally
critical neurons purely on the basis of patterns of intra- and inter-modular
connections. Our study reveals how the design of the nervous system reflects
several constraints, including its key functional role as a processor of
information.Comment: Published version, Minor modifications, 16 pages, 9 figure
Evaluation of Ammoniated Wheat Straw in Receiving and Growing Diets
Drought conditions in the past have created a shortage of prairie hay and other grass hays that are used as roughage sources for growing beef diets. Ammoniated wheat straw historically has been available for purchase at a lower than prairie hay. Although some research has been conducted using ammoniated wheat straw as a feedstuff for mature cows, little information is available on the use and outcome its inclusion in beef cattle receiving and growing diets. Our objective was to compare the performance outcomes of newly arrived and growing calves fed total mixed rations containing either ammoniated wheat straw, wheat straw, or a traditional blend of prairie hay and alfalfa hay
Left ventricular free wall impeding rupture in post-myocardial infarction period diagnosed by myocardial contrast echocardiography: Case report
BACKGROUND: Left ventricular free wall rupture occurs in up to 10% of the in-hospital deaths following myocardial infarction. It is mainly associated with posterolateral myocardial infarction and its antemortem diagnosis is rarely made. Contrast echocardiography has been increasingly used for the evaluation of myocardial perfusion in patients with acute myocardial infarction, with important prognostic implications. In this case, we reported its use for the detection of a mechanical complication following myocardial infarction. CASE PRESENTATION: A 50-year-old man with acute myocardial infarction in the lateral wall underwent myocardial contrast echocardiography for the evaluation of myocardial perfusion in the third day post-infarction. A perfusion defect was detected in lateral and inferior walls as well as the presence of contrast extrusion from the left ventricular cavity into the myocardium, forming a serpiginous duct extending from the endocardium to the epicardial region of the lateral wall, without communication with the pericardial space. Magnetic resonance imaging confirmed the diagnosis of impending rupture of the left ventricular free wall. While waiting for cardiac surgery, patient presented with cardiogenic shock and died. Anatomopathological findings were consistent with acute myocardial infarction in the lateral wall and a left ventricular free wall rupture at the infarct site. CONCLUSION: This case illustrates the early diagnosis of left ventricular free wall rupture by contrast echocardiography. Due to its ability to be performed at bedside this modality of imaging has the potential to identify this catastrophic condition in patients with acute myocardial infarction and help to treat these patients with emergent surgery
Strangelet search at RHIC
Two position sensitive Shower Maximum Detector (SMDs) for Zero-Degree
Calorimeters (ZDCs) were installed by STAR before run 2004 at both upstream and
downstream from the interaction point along the beam axis where particles with
small rigidity are swept away by strong magnetic field. The ZDC-SMDs provides
information about neutral energy deposition as a function of transverse
position in ZDCs. We report the preliminary results of strangelet search from a
triggered data-set sampling 100 million Au+Au collisions at top RHIC energy.Comment: Strange Quark Matter 2004 conference proceedin
Pion interferometry in Au+Au collisions at = 200 GeV
We present a systematic analysis of two-pion interferometry in Au+Au
collisions at = 200 GeV using the STAR detector at RHIC. We
extract the HBT radii and study their multiplicity, transverse momentum, and
azimuthal angle dependence. The Gaussianess of the correlation function is
studied. Estimates of the geometrical and dynamical structure of the freeze-out
source are extracted by fits with blast wave parameterizations. The expansion
of the source and its relation with the initial energy density distribution is
studied.Comment: 21 pages, 30 figures. As published in Physics Review
Longitudinal double-spin asymmetry for inclusive jet production in p+p collisions at sqrt(s)=200 GeV
We report a new STAR measurement of the longitudinal double-spin asymmetry
A_LL for inclusive jet production at mid-rapidity in polarized p+p collisions
at a center-of-mass energy of sqrt(s) = 200 GeV. The data, which cover jet
transverse momenta 5 < p_T < 30 GeV/c, are substantially more precise than
previous measurements. They provide significant new constraints on the gluon
spin contribution to the nucleon spin through the comparison to predictions
derived from one global fit of polarized deep-inelastic scattering
measurements.Comment: 7 pages, 4 figures + 1 tabl
Multiplicity and Pseudorapidity Distributions of Charged Particles and Photons at Forward Pseudorapidity in Au + Au Collisions at sqrt{s_NN} = 62.4 GeV
We present the centrality dependent measurement of multiplicity and
pseudorapidity distributions of charged particles and photons in Au + Au
collisions at sqrt{s_NN} = 62.4 GeV. The charged particles and photons are
measured in the pseudorapidity region 2.9 < eta < 3.9 and 2.3 < eta < 3.7,
respectively. We have studied the scaling of particle production with the
number of participating nucleons and the number of binary collisions. The
photon and charged particle production in the measured pseudorapidity range has
been shown to be consistent with energy independent limiting fragmentation
behavior. The photons are observed to follow a centrality independent limiting
fragmentation behavior while for the charged particles it is centrality
dependent. We have carried out a comparative study of the pseudorapidity
distributions of positively charged hadrons, negatively charged hadrons,
photons, pions, net protons in nucleus--nucleus collisions and pseudorapidity
distributions from p+p collisions. From these comparisons we conclude that
baryons in the inclusive charged particle distribution are responsible for the
observed centrality dependence of limiting fragmentation. The mesons are found
to follow an energy independent behavior of limiting fragmentation while the
behavior of baryons seems to be energy dependent.Comment: 17 pages and 20 figure
Transverse-momentum dependent modification of dynamic texture in central Au+Au collisions at sqrt(S_NN)=200 GeV
Correlations in the hadron distributions produced in relativistic Au+Au
collisions are studied in the discrete wavelet expansion method. The analysis
is performed in the space of pseudorapidity (|eta| < 1) and azimuth (full 2 pi)
in bins of transverse momentum (p_t) from 0.14 < p_t < 2.1 GeV/c. In peripheral
Au+Au collisions a correlation structure ascribed to mini-jet fragmentation is
observed. It evolves with collision centrality and p_t in a way not seen before
which suggests strong dissipation of minijet fragmentation in the
longitudinally-expanding medium.Comment: 6 pages, 3 figure, accepted as Phys.Rev.C Rapid Communication. This
version fixes journal style issue
Azimuthally sensitive Hanbury Brown-Twiss interferometry in Au+Au collisions at sqrt(s_{NN}) = 200 GeV
We present the results of a systematic study of the shape of the pion
distribution in coordinate space at freeze-out in Au+Au collisions at RHIC
using two-pion Hanbury Brown-Twiss (HBT) interferometry. Oscillations of the
extracted HBT radii vs. emission angle indicate sources elongated perpendicular
to the reaction plane. The results indicate that the pressure and expansion
time of the collision system are not sufficient to completely quench its
initial shape.Comment: 6 pages, 4 figures, published versio
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