Modulation of the response of a photosensitive muscle by beta-adrenergic regulation of cyclic AMP levels

The light-induced constriction of the irises of some vertebrates is mediated by photosensitive pupillary sphincter cells, which have rhodopsin molecules in their sarcolemmas. Light-induced isomerization of these rhodopsin molecules leads to the release of Ca2+ from an internal pool, which in turn activate the contractile proteins. A central nervous reflex is therefore not essential for the light responsiveness of these irises, but they do appear to be innervated. The photosensitive iris of the toad receives sympathetic (adrenergic) innervation. Stimulation of sympathetic nerves to the eye or application of adrenergic agonists to the iris cause pupillary dilation due to relaxation of the sphincter muscle. We show here that beta-adrenergic stimulation of toad sphincter cells modulates their photoresponses by elevating the intracellular levels of cyclic AMP. However, cyclic AMP does not appear to be involved in the transduction event but rather alters the availability of Ca2+ for contraction.     

Genomics of cellulosic biofuels

The development of alternatives to fossil fuels as an energy source is an urgent global priority. Cellulosic biomass has the potential to contribute to meeting the demand for liquid fuel, but land-use requirements and process inefficiencies represent hurdles for large-scale deployment of biomass-to-biofuel technologies. Genomic information gathered from across the biosphere, including potential energy crops and microorganisms able to break down biomass, will be vital for improving the prospects of significant cellulosic biofuel production.     

A subset of dopamine neurons signals reward for odour memory in Drosophila

Animals approach stimuli that predict a pleasant outcome. After the paired presentation of an odour and a reward, Drosophila melanogaster can develop a conditioned approach towards that odour. Despite recent advances in understanding the neural circuits for associative memory and appetitive motivation, the cellular mechanisms for reward processing in the fly brain are unknown. Here we show that a group of dopamine neurons in the protocerebral anterior medial (PAM) cluster signals sugar reward by transient activation and inactivation of target neurons in intact behaving flies. These dopamine neurons are selectively required for the reinforcing property of, but not a reflexive response to, the sugar stimulus. In vivo calcium imaging revealed that these neurons are activated by sugar ingestion and the activation is increased on starvation. The output sites of the PAM neurons are mainly localized to the medial lobes of the mushroom bodies (MBs), where appetitive olfactory associative memory is formed. We therefore propose that the PAM cluster neurons endow a positive predictive value to the odour in the MBs. Dopamine in insects is known to mediate aversive reinforcement signals. Our results highlight the cellular specificity underlying the various roles of dopamine and the importance of spatially segregated local circuits within the MBs.     

九华山唐代炼铜炉渣研究

考古调查已认定九华山古铜矿冶遗址年代为唐代。通过对６７个渣样的理论分析和模拟实验，笔者对九华山唐代的冶炼技术进行了复原。九华山有高钙和高铁两种冰钢渣，二者在随机取样时出现的比例约为７．４：１。高钙渣是熔炼脉石含钙的含铜黄铁矿（经焙烧）得到品位约为２５％的冰铜的炉渣，高铁渣是将品位为２５％的冰铜焙烧后熔炼成品位的４０％的冰铜的炉渣。物料平衡计算揭示的冶炼流程显示，含铜约６％的手选矿石要经历两次部分脱硫焙烧、两次鼓风炉熔炼，才能先后炼成品位为３５％和４０％的两种中间产物冰铜。九华山古铜矿冶遗址的研究表明，宋明时期文献《大冶赋》、《菽国杂记》所记载的使用“硫化矿—冰铜—铜”工艺冶炼低品位含铜黄铁矿的技术在唐代就已存在并已成熟。     

表面活性剂对超细氧化铁催化乙苯脱氢反应性能的影响

在Ｆｅ２Ｏ３超细催化剂制备中，采用表面活性剂对超细粒子进行保护．乙苯脱氢反应的实验表明，表面活性剂的种类和用量不仅影响超细催化剂的活性．而且影响其选择性．     

Signalling by the sevenless protein tyrosine kinase is mimicked by Ras1 activation.

Cell-fate specification of R7 photoreceptors in the developing Drosophila eye depends on an inductive signal from neighbouring R8 cells. Mutations in three genes, sevenless (sev), bride-of-sevenless (boss) and seven-in-absentia (sina) cause the R7 precursor to become a non-neural cone cell. The sev gene encodes a receptor protein tyrosine kinase (Sev) localized on the R7 surface, activated by a boss-encoded ligand presented by R8. The sina gene encodes a nuclear factor required in R7. Reduction in the dosage of the Ras1 gene impairs Sev-mediated signalling, suggesting that activation of Ras1 may be an important consequence of Sev activation. We report here that Ras1 activation may account for all of the signalling action of Sev; an activated Ras1Va112 protein rescues the normal R7 precursor from transformation into a cone cell in sev and boss null mutants and induces the formation of supernumerary R7 cells. Similar activation of the Drosophila Ras2 protein does not produce these effects, demonstrating Ras protein specificity.