Activation of a plant plasma membrane Ca2+ channel by TGalpha1, a heterotrimeric G protein alpha-subunit homologue

Trinucleotide repeats in several human genes have been found to undergo spontaneous variation in repeat numbers in succeeding generations. Expansion of the repeat beyond a certain length causes specific pathological disorders. So far, a naturally occurring triplet repeat instability of transcribed sequences has been reported only from humans. However, the signal peptide encoding region of the receptor tyrosine kinase gene Xmrk from fish of the genus Xiphophorus contains a CTG repeat that differs in length even between closely related individuals. The consequence of this variability is signal peptides with shorter or longer hydrophobic core regions reaching, in some individuals, the critical maximum length for functional protein export or even exceeding it. In one stock, animals that are homozygous for such an allele were extremely rare, indicating that the triplet repeat length variability of the Xmrk gene of Xiphophorus may indeed have an influence on the function of the gene product and, under certain conditions, may affect the fitness of the individual.     

Analysis and design guidance for the lateral stiffness of bellows expansion joints

Thin-walled bellows expansion joints are frequently applied in piping systems for absorbing thermal and mechanical movement. There have been several failures in service due to the lateral buckling of bellows under pressure, the most notable case being the Flixborough disaster in 1974. The problem of bellows squirming, as the phenomenon is more commonly termed, was first investigated by the Dutch engineer J. A. Haringx in 1952. In the intervening years there has been little additional research carried out and consequently there is a paucity of experimental data and practical theories on the subject. The present paper offers guidance to avoid bellows squirming and provides the design engineer with simple procedures for evaluating the stability of a pressurised bellows subject to either small or large lateral displacements. Formulae are also presented in order to determine the strength of bellows supports which limit and control the amount of bellows movement in service.     

Energy Upconversion via Triplet Fusion in Super Yellow PPV Films Doped with Palladium Tetraphenyltetrabenzoporphyrin: a Comprehensive Investigation of Exciton Dynamics

One of the key issues concerning the development of efficient polymer solar cell technology is the lack of viable materials which absorb in the near‐infrared (NIR) region. This could be resolved by up‐converting energy from the NIR into visible using triplet fusion (TF) with an additional layer that is fabricated separately from the solar cell and deposited on top. Theoretically a maximum upconversion (UC) via TF efficiency of 50% could be obtained. Here, it is demonstrated that in a film of commercially available poly(para‐phenylene vinylene) copolymer “super yellow” (SY) doped with 4% palladium(meso‐tetraphenyl‐tetrabenzoporphyrin) (PdTPBP) sensitizer, an UC efficiency of 6% can be achieved. By using femtosecond and nanosecond spectroscopies it is shown that the main UC efficiency loss mechanism is due to triplet quenching in PdTPBP aggregates. The PdTPBP intersystem crossing rate constant is determined to be 1.8 × 10¹¹ s^?1 and the triplet energy transfer rate constant from PdTPBP to SY to be 10⁹ s^?1. Quenching in PdTPBP aggregates can account for a triplet concentration loss in the range of 76‐99%. As such, preventing sensitizer aggregation in NIR‐to‐visible upconverting films is crucial and may lead to substantial increase of UC efficiencies in films.     

Females prefer leading males: relative call timing and sexual selection in katydid choruses

Females of several acoustic insects and anurans have recently been shown to orient preferentially to the leading of two identical male calls presented in close succession. We studied this phenomenon via two-choice phonotaxis trials in the neotropical katydid Neoconocephalus spiza and found that females avoided male calls occurring during an interval beginning immediately after the onset of a leading call. This avoidance occurred whether or not the following call was overlapped by the leader, indicating that the mechanism of preference for leading calls may represent a psychoacoustic precedence effect rather than simple call masking. We also found that females preferred leading calls as long as the amplitude of the following call was not more than 2 dB higher than the leader. Under certain circumstances, preferences for leading calls remained when females were presented with a sequence of four calls. Thus, preferences for leading calls probably influence a male's attractiveness and mating success in complex natural choruses: females are expected to orient towards males producing leading calls regardless of call length (and the probability of overlapping a following call), when the leading call is up to 1.5 times as distant as a follower, and when succeeded by multiple followers. We suggest that female preferences for leading male calls represent sensory biases that originated in contexts unrelated to sexual selection. None the less they currently play an important role in sexual selection and influence individual male signalling behaviour, and thus chorus structure. Copyright 1998 The Association for the Study of Animal Behaviour.     

Two isoforms of glutamate decarboxylase in Arabidopsis are regulated by calcium/calmodulin and differ in organ distribution

The nucleotide sequences of cDNAs encoding two isoforms of Arabidopsis glutamate decarboxylase, designated GAD1 (57.1 kDa) and GAD2 (56.1 kDa) and sharing 82% identical amino acid sequences, were determined. The recombinant proteins bound [35S] calmodulin (CaM) in the presence of calcium, and a region of 30-32 amino acids from the C-terminal of each isoform was sufficient for CaM binding when fused to glutathione S-transferase. Full-length GAD1 and GAD2 were expressed in Sf9 insect cells infected with recombinant baculovirus vectors. Recombinant proteins were partially purified by CaM affinity chromatography and were found to exhibit glutamate decarboxylase activity, which was dependent on the presence of Ca2+/CaM at pH 7.3. Southern hybridizations with GAD gene-specific probes suggest that Arabidopsis possesses one gene related to GAD1 and one to GAD2. Northern hybridization and western blot analysis revealed that GAD1 was expressed only in roots and GAD2 in roots, leaves, inflorescence stems and flowers. Our study provides the first evidence for the occurrence of multiple functional Ca2+/CaM-regulated GAD gene products in a single plant, suggesting that regulation of Arabidopsis GAD activity involves modulation of isoform-specific gene expression and stimulation of the catalytic activity of GAD by calcium signalling via CaM.     

The identification of 2,8-dihydroxyadenine, a new component of urinary stones

Stones passed by a child homozygous for a deficiency of the enzyme adenine phosphoribosyltransferase have been identified by u.v., i.r. and mass spectrometry as 2,8-dihydroxyadenine.     

Conditioned and unconditioned suppression as a function of age in rats.

Examined age differences in a cer paradigm. 72 sprague-dawley albino rats were treated at 15, 22, 35, or 70 days of age in 1 of 3 ways: (a) paired tone-light and shock trials; (b) unpaired tone-light and shock trials; or (c) no treatment at all. Subsequent tests in a suppression of drinking situation show that only the 15-day old ss failed to acquire a cer, as measured by the difference between paired and unpaired groups. Older ss extinguished more quickly than younger ss and also habituated an unconditioned suppression response more quickly. Results are related to thompson's model, and to the literature on the development of learning abilities. (french summary) (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Facile syntheses,crystal structures and magnetic properties of NdBaMnCoO5 and NdBaMnCoO6

NdBaMnCoO₅ has been synthesized using a mass-flow controlled reducing reaction, followed by low (800 °C) temperature oxidation to produce NdBaMnCoO₆. The structures and properties have been analyzed using powder neutron diffraction and magnetic susceptibility measurements. At room temperature both phases are tetragonal with unit cells a_p × a_p × 2a_p (a_p = perovskite subcell length) showing full order of the A-site cations and no order of either B-site cations or charge. Low temperature neutron diffraction shows a fully antiferromagnetic (G-type) structure for NdBaMnCoO₅ (cell √2a_p × √2a_p × 2a_p) and an orthorhombic cell (2a_p × 2a_p × 2a_p) for NdBaMnCoO₆.