40 research outputs found
Neurexin in Embryonic Drosophila Neuromuscular Junctions
Background: Neurexin is a synaptic cell adhesion protein critical for synapse formation and function. Mutations in neurexin and neurexin-interacting proteins have been implicated in several neurological diseases. Previous studies have described Drosophila neurexin mutant phenotypes in third instar larvae and adults. However, the expression and function of Drosophila neurexin early in synapse development, when neurexin function is thought to be most important, has not been described. Methodology/Principal Findings: We use a variety of techniques, including immunohistochemistry, electron microscopy, in situ hybridization, and electrophysiology, to characterize neurexin expression and phenotypes in embryonic Drosophila neuromuscular junctions (NMJs). Our results surprisingly suggest that neurexin in embryos is present both pre and postsynaptically. Presynaptic neurexin promotes presynaptic active zone formation and neurotransmitter release, but along with postsynaptic neurexin, also suppresses formation of ectopic glutamate receptor clusters. Interestingly, we find that loss of neurexin only affects receptors containing the subunit GluRIIA. Conclusions/Significance: Our study extends previous results and provides important detail regarding the role of neurexin in Drosophila glutamate receptor abundance. The possibility that neurexin is present postsynaptically raises new hypotheses regarding neurexin function in synapses, and our results provide new insights into the role of neurexin i
Six‐Month Follow‐up of the Families on Track Intervention Pilot Trial for Children With Fetal Alcohol Spectrum Disorders and Their Families
Spin correlations in Ca3Co2O6: Polarized-neutron diffraction and Monte Carlo study
We present polarized-neutron diffraction measurements of the Ising-type spin-chain compound Ca3Co2O6 above and below the magnetic ordering temperature TN. Below TN, a clear evolution from a pure spin-density wave (SDW) structure to a mixture of SDW and commensurate antiferromagnet (CAFM) structures is observed on cooling. For a rapidly cooled sample, the majority phase at low temperature is the SDW, while if the cooling is performed sufficiently slowly, then the SDW and the CAFM structure coexist between 1.5 and 10 K. Above TN, we use Monte Carlo methods to analyze the magnetic diffuse scattering data. We show that both intrachain and interchain correlations persist above TN, but are essentially decoupled. Intrachain correlations resemble the one-dimensional ferromagnetic Ising model, while interchain correlations resemble the frustrated triangular-lattice antiferromagnet. Using previously published bulk property measurements and our neutron diffraction data, we obtain values of the ferromagnetic and antiferromagnetic exchange interactions and the single-ion anisotropy. © 2014 American Physical Society
Prevention of Secondary Conditions in Fetal Alcohol Spectrum Disorders: Identification of Systems-Level Barriers
Pinch points and Kasteleyn transitions in kagome ice
Complex disordered states - from liquids and glasses to exotic quantum matter
- are ubiquitous in nature. Their key properties include finite entropy,
power-law correlations and emergent organising principles. In spin ice, spin
correlations are determined by an ice rules organising principle that
stabilises a magnetic state with the same zero point entropy as water ice. The
entropy can be manipulated with great precision by a magnetic field: with field
parallel to the trigonal axis one obtains quasi two dimensional kagome ice
which can be mapped onto a dimer model. Here we use a field tilted slightly
away from the trigonal axis to control the dimer statistical weights and
realise the unusual critical behaviour predicted by Kasteleyn. Neutron
scattering on Ho2Ti2O7 reveals pinch point scattering that characterises the
emergent gauge structure of kagome ice; diffuse peaks that shift with field,
signaling the Kasteleyn physics; and an unusual critical point.Comment: 17 pages, 5 figures. Significantly improved version appears in Nature
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