The design of an image bank

Image Banks, which are collections of images with associated data and captions, are a valuable teaching tool for Astronomy courses at the Open University. Until now web pages have been created for each image and its associated information. This paper examines how a database, front-ended by a multimedia authoring tool, can provide a much more flexible and maintainable architecture for producing Image Banks. Accessibility issues are discussed

Human melanopsin forms a pigment maximally sensitive to blue light (λmax ≈ 479 nm) supporting activation of G(q/11) and G(i/o) signalling cascades.

A subset of mammalian retinal ganglion cells expresses an opsin photopigment (melanopsin, Opn4) and is intrinsically photosensitive. The human retina contains melanopsin, but the literature lacks a direct investigation of its spectral sensitivity or G-protein selectivity. Here, we address this deficit by studying physiological responses driven by human melanopsin under heterologous expression in HEK293 cells. Luminescent reporters for common second messenger systems revealed that light induces a high amplitude increase in intracellular calcium and a modest reduction in cAMP in cells expressing human melanopsin, implying that this pigment is able to drive responses via both G(q) and G(i/o) class G-proteins. Melanopsins from mouse and amphioxus had a similar profile of G-protein coupling in HEK293 cells, but chicken Opn4m and Opn4x pigments exhibited some G(s) activity in addition to a strong G(q)(/11) response. An action spectrum for the calcium response in cells expressing human melanopsin had the predicted form for an opsin : vitamin A1 pigment and peaked at 479 nm. The G-protein selectivity and spectral sensitivity of human melanopsin is similar to that previously described for rodents, supporting the utility of such laboratory animals for developing methods of manipulating this system using light or pharmacological agents

Akt1 sequentially phosphorylates p27(kip1 )within a conserved but non-canonical region

BACKGROUND: p27(kip1 )(p27) is a multifunctional protein implicated in regulation of cell cycling, signal transduction, and adhesion. Its activity is controlled in part by Phosphatylinositol-3-Kinase (PI3K)/Akt1 signaling, and disruption of this regulatory connection has been identified in human breast cancers. The serine/threonine protein kinase Akt1 directly phosphorylates p27, so identifying the modified residue(s) is essential for understanding how it regulates p27 function. Various amino acids have been suggested as potential targets, but recent attention has focused on threonine 157 (T157) because it is located in a putative Akt1 consensus site. However, T157 is not evolutionarily conserved between mouse and human. We therefore re-evaluated Akt1 phosphorylation of p27 using purified proteins and in cells. RESULTS: Here we show purified Akt1 phosphorylates human and mouse p27 equally well. Phospho-peptide mapping indicates Akt1 targets multiple sites conserved in both species, while phospho-amino acid analysis identifies the targeted residues as serine rather than threonine. P27 deletion mutants localized these sites to the N-terminus, which contains the major p27 phosphorylation site in cells (serine 10). P27 phosphorylated by Akt1 was detected by a phospho-S10 specific antibody, confirming this serine was targeted. Akt1 failed to phosphorylate p27S10A despite evidence of a second site from mapping experiments. This surprising result suggested S10 phosphorylation might be required for targeting the second site. We tested this idea by replacing S10 with threonine, which as expected led to the appearance of phospho-threonine. Phospho-serine was still present, however, confirming Akt1 sequentially targets multiple serines in this region. We took two approaches in an attempt to explain why different residues were previously implicated. A kinetic analysis revealed a putative Akt1 binding site in the C-terminus, which may explain why mutations in this region affect p27 phosphorylation. Furthermore, commercially available recombinant Akt1 preparations exhibit striking differences in substrate specificity and site selectivity. To confirm S10 is a relevant site, we first showed that full-length wild type Akt1 purified from mammalian cells phosphorylates both human and mouse p27 on S10. Finally, we found that in cultured cells under physiologically relevant conditions such as oxidative stress or growth factor deprivation, endogenous Akt1 causes p27 accumulation by phosphorylating S10. CONCLUSION: Identifying where Akt1 phosphorylates p27 is essential for understanding its functional implications. We found that full-length wild type Akt1 – whether purified, transiently overexpressed in cells, or activated in response to cellular stress – phosphorylates p27 at S10, a noncanonical but evolutionarily conserved site known to regulate p27 activity and stability. Using recombinant Akt1 recapitulating this specificity, we showed modification of p27S10 also leads to phosphorylation of an adjacent serine. These results integrate PI3K/Akt1 signaling in response to stress with p27 regulation through its major phosphorylation site in cells, and thus identify new avenues for understanding p27 deregulation in human cancers

Influence of the rod photoresponse on light adaptation and circadian rhythmicity in the cone ERG

Purpose: In the mammalian retina, rod and cone pathways are fundamentally intertwined, with signals from both converging on cone bipolar cells to reach retinal ganglion cells. Psychophysical and electrophysiological data suggests that, as a consequence, rod signal transduction has a suppressive effect on the activity of cone pathways. It therefore might be assumed that the balance between rod and cone input to cone bipolar cells would be subject to dynamic regulation. There is evidence of light and time-of-day dependent alterations in this parameter. Here we set out to determine the extent to which such changes in rod-cone pathway convergence explain alterations in cone pathway function associated with light adaptation and circadian phase by recording cone electroretinograms (ERGs) in mice deficient in rod phototransduction. Methods: Cone-isolated ERGs elicited by bright flashes superimposed on a rod saturating background light were recorded from wild-type and rod transducin deficient (Gnat1−/−) mice. The process of light adaptation was observed by tracing changes in the ERG waveform over 20 min exposure to the background light in these genotypes, and circadian control by comparing responses at subjective midday and midnight. Results: The cone ERG b-wave exhibited significantly enhanced amplitude and reduced latency (implicit time) in Gnat1−/− mice under all conditions. Light adaptation was associated with a robust increase in b-wave amplitude in Gnat1−/− mice but, in contrast to wild types, almost no change in implicit time. Gnat1−/− mice retained circadian rhythms in the cone ERG with b-wave amplitudes larger and latencies reduced during the subjective day. Conclusions: Rod phototransduction has a strong suppressive effect on the cone ERG. Light adaptation in cone pathways relies in part on reductions in this effect, although mechanisms intrinsic to cone pathways also play an important role. Similarly, while changes in coupling between rod and cone pathways over the course of the day may contribute to circadian regulation of the cone pathway they are not sufficient to explain circadian rhythms in the wild-type cone ERG

Foreign direct investment and spillovers : gradualism may be better

The definitive version is available at www3.interscience.wiley.comThe standard argument says that in the presence of positive spillovers foreign direct investment should be promoted and subsidized. In contrast, this paper claims that the very existence of spillovers may require temporarily restricting FDI. Our argument is based on two features of spillovers: they are limited by the economy's absorptive capacity and they take time to materialize. By letting in capital more gradually, initial investment has the time to create spillovers – and upgrade the economy's absorptive capacity – before further investment occurs. The economy converges to a steady state with a superior technology and a greater capital stockPublicad

Test Facility Simulation Results for Aerospace Loss-of-Lubrication of Spur Gears

Prior to receiving airworthiness certification, extensive testing is required during the development of rotary wing aircraft drive systems. Many of these tests are conducted to demonstrate the drive system's ability to operate at extreme conditions, beyond that called for in the normal to maximum power operating range. One of the most extreme tests is referred to as the loss-of-lubrication or run dry test. During this test, the drive system is expected to last at least 30 min without failure while the primary lubrication system is disabled for predetermined, scripted flight conditions. Failure of this test can lead to a partial redesign of the drive system or the addition of an emergency lubrication system. Either of these solutions can greatly increase the aircraft drive system cost and weight and extend the schedule for obtaining airworthiness certification. Recent work at NASA Glenn Research Center focused on performing tests, in a relevant aerospace environment, to simulate the behavior of spur gears under loss-of-lubrication conditions. Tests were conducted using a test facility that was used in the past for spur gear contact fatigue testing. A loss-oflubrication test is initiated by shutting off the single into mesh lubricating jet. The test proceeds until the gears fail and can no longer deliver the applied torque. The observed failures are typically plastically deformed gear teeth, due to the high tooth temperatures, that are no longer in mesh. The effect of several different variables to gear tooth condition during loss-of-lubrication have been tested such as gear pitch, materials, shrouding, lubrication condition, and emergency supplied mist lubrication in earlier testing at NASA. Recent testing has focused on newer aerospace gear steels and imbedding thermocouples in the shrouding to measure the air-oil temperatures flung off the gear teeth. Along with the instrumented shrouding, an instrumented spur gear was also tested. The instrumented spur gear had five thermocouples installed at different locations on the gear tooth and web. The data from these two types of measurements provided important information as to the thermal environment during the loss-of-lubrication event. This data is necessary to validate on-going modeling efforts

Reproducible and sustained regulation of Gαs signalling using a metazoan opsin as an optogenetic tool

Originally developed to regulate neuronal excitability, optogenetics is increasingly also used to control other cellular processes with unprecedented spatiotemporal resolution. Optogenetic modulation of all major G-protein signalling pathways (Gq, Gi and Gs) has been achieved using variants of mammalian rod opsin. We show here that the light response driven by such rod opsin-based tools dissipates under repeated exposure, consistent with the known bleaching characteristics of this photopigment. We continue to show that replacing rod opsin with a bleach resistant opsin from Carybdea rastonii, the box jellyfish, (JellyOp) overcomes this limitation. Visible light induced high amplitude, reversible, and reproducible increases in cAMP in mammalian cells expressing JellyOp. While single flashes produced a brief cAMP spike, repeated stimulation could sustain elevated levels for 10s of minutes. JellyOp was more photosensitive than currently available optogenetic tools, responding to white light at irradiances ≥1 µW/cm(2). We conclude that JellyOp is a promising new tool for mimicking the activity of Gs-coupled G protein coupled receptors with fine spatiotemporal resolution

Understanding Stock Price Behavior around the Time of Equity Issues

It is well-documented that stock prices rise significantly prior to an equity issue, and fall upon announcement of the issue. We expand on earlier studies by using a large sample which includes OTC firms, by examining the cross-sectional properties of the price rise, and by using accounting data to track the pattern of debt ratios and Tobin's q around the time of equity issues. We consider a number of explanations for our results, and conclude that the data is largely consistent with informational models in which managers are asymmetrically informed about the value of the firm. Surprisingly, debt ratios do not increase prior to equity issues, suggesting that strained debt capacity is not the main reason for equity issues. The behavior of Tobin's q is consistent with equity issues being used to finance new investments.