Octopamine increases the excitability of neurons in the snail feeding system by modulation of inward sodium current but not outward potassium currents

Background: Although octopamine has long been known to have major roles as both transmitter and modulator in arthropods, it has only recently been shown to be functionally important in molluscs, playing a role as a neurotransmitter in the feeding network of the snail Lymnaea stagnalis. The synaptic potentials cannot explain all the effects of octopamine-containing neurons on the feeding network, and here we test the hypothesis that octopamine is also a neuromodulator. Results: The excitability of the B1 and B4 motoneurons in the buccal ganglia to depolarising current clamp pulses is significantly (P << 0.05) increased by (10 mu M) octopamine, whereas the B2 motoneuron becomes significantly less excitable. The ionic currents evoked by voltage steps were recorded using 2-electrode voltage clamp. The outward current of B1, B2 and B4 motoneurons had two components, a transient I-A current and a sustained I-K delayed-rectifier current, but neither was modulated by octopamine in any of these three buccal neurons. The fast inward current was eliminated in sodium - free saline and so is likely to be carried by sodium ions. 10 mu M octopamine enhanced this current by 33 and 45% in the B1 and B4 motoneurons respectively (P << 0.05), but a small reduction was seen in the B2 neuron. A Hodgkin-Huxley style simulation of the B1 motoneuron confirms that a 33% increase in the fast inward current by octopamine increases the excitability markedly. Conclusion: We conclude that octopamine is also a neuromodulator in snails, changing the excitability of the buccal neurons. This is supported by the close relationship from the voltage clamp data, through the quantitative simulation, to the action potential threshold, changing the properties of neurons in a rhythmic network. The increase in inward sodium current provides an explanation for the polycyclic modulation of the feeding system by the octopamine-containing interneurons, making feeding easier to initiate and making the feeding bursts more intense

The ordered K-theory of a full extension

Let A be a C*-algebra with real rank zero which has the stable weak cancellation property. Let I be an ideal of A such that I is stable and satisfies the corona factorization property. We prove that 0->I->A->A/I->0 is a full extension if and only if the extension is stenotic and K-lexicographic. As an immediate application, we extend the classification result for graph C*-algebras obtained by Tomforde and the first named author to the general non-unital case. In combination with recent results by Katsura, Tomforde, West and the first author, our result may also be used to give a purely K-theoretical description of when an essential extension of two simple and stable graph C*-algebras is again a graph C*-algebra.Comment: Version IV: No changes to the text. We only report that Theorem 4.9 is not correct as stated. See arXiv:1505.05951 for more details. Since Theorem 4.9 is an application to the main results of the paper, the main results of this paper are not affected by the error. Version III comments: Some typos and errors corrected. Some references adde

Crystal structure of Schmallenberg orthobunyavirus nucleoprotein-RNA complex reveals a novel RNA sequestration mechanism

Schmallenberg virus (SBV) is a newly emerged orthobunyavirus (family Bunyaviridae) that has caused severe disease in the offspring of farm animals across Europe. Like all orthobunyaviruses, SBV contains a tripartite negative-sense RNA genome that is encapsidated by the viral nucleocapsid (N) protein in the form of a ribonucleoprotein complex (RNP). We recently reported the three-dimensional structure of SBV N that revealed a novel fold. Here we report the crystal structure of the SBV N protein in complex with a 42-nt-long RNA to 2.16 Å resolution. The complex comprises a tetramer of N that encapsidates the RNA as a cross-shape inside the protein ring structure, with each protomer bound to 11 ribonucleotides. Eight bases are bound in the positively charged cleft between the N- and C-terminal domains of N, and three bases are shielded by the extended N-terminal arm. SBV N appears to sequester RNA using a different mechanism compared with the nucleoproteins of other negative-sense RNA viruses. Furthermore, the structure suggests that RNA binding results in conformational changes of some residues in the RNA-binding cleft and the N- and C-terminal arms. Our results provide new insights into the novel mechanism of RNA encapsidation by orthobunyaviruses

Search for associations containing young stars (SACY). V. Is multiplicity universal? Tight multiple systems

Context: Dynamically undisrupted, young populations of stars are crucial to study the role of multiplicity in relation to star formation. Loose nearby associations provide us with a great sample of close ($<$150 pc) Pre-Main Sequence (PMS) stars across the very important age range ($\approx$5-70 Myr) to conduct such research. Aims: We characterize the short period multiplicity fraction of the SACY (Search for Associations Containing Young stars) accounting for any identifiable bias in our techniques and present the role of multiplicity fractions of the SACY sample in the context of star formation. Methods: Using the cross-correlation technique we identified double-lined spectroscopic systems (SB2), in addition to this we computed Radial Velocity (RV) values for our subsample of SACY targets using several epochs of FEROS and UVES data. These values were used to revise the membership of each association then combined with archival data to determine significant RV variations across different data epochs characteristic of multiplicity; single-lined multiple systems (SB1). Results: We identified 7 new multiple systems (SB1s: 5, SB2s: 2). We find no significant difference between the short period multiplicity fraction ($F_\mathrm{m}$) of the SACY sample and that of nearby star forming regions ($\approx$1-2 Myr) and the field ($F_\mathrm{m}\leq$10%) both as a function of age and as a function of primary mass, $M_1$, in the ranges $P$ [1:200 day] and $M_2$ [0.08 $M_{\odot}$-$M_1$]. Conclusions: Our results are consistent with the picture of universal star formation, when compared to the field and nearby star forming regions (SFRs). We comment on the implications of the relationship between increasing multiplicity fraction with primary mass, within the close companion range, in relation to star formation.Comment: 14 pages, 18 figures, published, A&A http://dx.doi.org/10.1051/0004-6361/20142385

Paspalum grass

Originally native to Uruguay and Argentina, Paspalum dilatatum was introduced into the U.S.A. about the middle of the 19th century and is now firmly established and cultivated in the Gulf States where it is known as Dallis erass after A. T. Dallis of La Grange, Georgia. It was introduced into Australia by Baron von Mueller about 1880 and since 1898 its cultivation has steadily increased

Some Problems in Liquidating Personal Holding Companies

Ordinarily, distributions by a personal holding company qualify for the dividends paid deduction only if they are dividends under section 316. However, certain distributions in liquidation may also qualify. These liquidating distributions of a personal holding company are divided into two categories: (1) Distributions to the extent of earnings and profits for the taxable year (computed without regard to capital losses) made in complete liquidation of the corporation occurring within 24 months after the adoption of the plan of liquidation; and (2) distributions in liquidation properly chargeable to earnings and profits accumulated after February 28, 1913

Elephant Grass

Elephant Grass, sometimes known as Napier\u27s Fodder, is a hardy, palatable and nutritious plant which under good conditions will give heavy yields. When once established it will remain as a permanent stand so long as it receives good treatment. It grows well in many parts of Western Australia and up to date appears to be free from attack by pests and diseases. * (Revised from Leaflet No. 600, by H. G. Elliott

Exact solution of a many-fermion system and its associated boson field

Journal ArticleLuttinger's exactly soluble model of a one-dimensional many-fermion system is discussed. We show that he did not solve his model properly because of the paradoxical fact that the density operator commutators [p(p), p(-p')], which always vanish for any finite number of particles, no longer vanish in the field-theoretic limit of a filled Dirac sea. In fact the operators p(p) define a boson field which is ipso facto associated with the Fermi-Dirac field

Theory of paramagnetic impurities in semiconductors

Journal ArticleIn this paper, a model of a paramagnetic impurity in a semiconductor (or of an F' center in an alkali halide) is proposed. It is an exactly soluble form of the quantum-mechanical 3-body problem. Specifically, we deal with 2 interacting particles in any number of dimensions in an attractive external potential, and present the qualitative features of the resulting eigenvalues and eigenfunctions

Incorporating the advantages of clickers and mobile devices to teach economics to non-economists

In the twenty-first century, teaching practitioners in higher education (HE) have found themselves confronted with more challenges to help students engage in learning. Particularly, one of the main problems with the traditional lecture format to teach non-economists economics is that students tend to lack interest in the subject and therefore have a low level of engagement. Student response systems (i.e. “clickers”) have been used in classes for about 20 years and become more popular on many college campuses. Many studies reveal that clicker technology offers great promise in increasing students’ participation and engagement in lectures. Meanwhile, thanks to fast development of mobile technology, personal mobile devices can be integrated with clicker systems into teaching and learning with improved features. The programme we used and found as a very useful interactive teaching tool for learning is called Kahoot!. This paper offers a brief guidance on how to use Kahoot! to encourage active learning and engage non-economics majors in learning economics. Meanwhile, the existing relevant literature with regard to the use of clickers in HE is highlighted. In addition, the effectiveness of using Kahoot! in teaching economics to non-economists is evaluated by a student survey