The sense of agency is action–effect causality perception based on cross-modal grouping

Sense of agency, the experience of controlling external events through one''s actions, stems from contiguity between action- and effect-related signals. Here we show that human observers link their action- and effect-related signals using a computational principle common to cross-modal sensory grouping. We first report that the detection of a delay between tactile and visual stimuli is enhanced when both stimuli are synchronized with separate auditory stimuli (experiment 1). This occurs because the synchronized auditory stimuli hinder the potential grouping between tactile and visual stimuli. We subsequently demonstrate an analogous effect on observers'' key press as an action and a sensory event. This change is associated with a modulation in sense of agency; namely, sense of agency, as evaluated by apparent compressions of action–effect intervals (intentional binding) or subjective causality ratings, is impaired when both participant''s action and its putative visual effect events are synchronized with auditory tones (experiments 2 and 3). Moreover, a similar role of action–effect grouping in determining sense of agency is demonstrated when the additional signal is presented in the modality identical to an effect event (experiment 4). These results are consistent with the view that sense of agency is the result of general processes of causal perception and that cross-modal grouping plays a central role in these processes.     

Reception and learning of electric fields in bees

Honeybees, like other insects, accumulate electric charge in flight, and when their body parts are moved or rubbed together. We report that bees emit constant and modulated electric fields when flying, landing, walking and during the waggle dance. The electric fields emitted by dancing bees consist of low- and high-frequency components. Both components induce passive antennal movements in stationary bees according to Coulomb''s law. Bees learn both the constant and the modulated electric field components in the context of appetitive proboscis extension response conditioning. Using this paradigm, we identify mechanoreceptors in both joints of the antennae as sensors. Other mechanoreceptors on the bee body are potentially involved but are less sensitive. Using laser vibrometry, we show that the electrically charged flagellum is moved by constant and modulated electric fields and more strongly so if sound and electric fields interact. Recordings from axons of the Johnston organ document its sensitivity to electric field stimuli. Our analyses identify electric fields emanating from the surface charge of bees as stimuli for mechanoreceptors, and as biologically relevant stimuli, which may play a role in social communication.     

When growth models are not universal: evidence from marine invertebrates

The accumulation of body mass, as growth, is fundamental to all organisms. Being able to understand which model(s) best describe this growth trajectory, both empirically and ultimately mechanistically, is an important challenge. A variety of equations have been proposed to describe growth during ontogeny. Recently, the West Brown Enquist (WBE) equation, formulated as part of the metabolic theory of ecology, has been proposed as a universal model of growth. This equation has the advantage of having a biological basis, but its ability to describe invertebrate growth patterns has not been well tested against other, more simple models. In this study, we collected data for 58 species of marine invertebrate from 15 different taxa. The data were fitted to three growth models (power, exponential and WBE), and their abilities were examined using an information theoretic approach. Using Akaike information criteria, we found changes in mass through time to fit an exponential equation form best (in approx. 73% of cases). The WBE model predominantly overestimates body size in early ontogeny and underestimates it in later ontogeny; it was the best fit in approximately 14% of cases. The exponential model described growth well in nine taxa, whereas the WBE described growth well in one of the 15 taxa, the Amphipoda. Although the WBE has the advantage of being developed with an underlying proximate mechanism, it provides a poor fit to the majority of marine invertebrates examined here, including species with determinate and indeterminate growth types. In the original formulation of the WBE model, it was tested almost exclusively against vertebrates, to which it fitted well; the model does not however appear to be universal given its poor ability to describe growth in benthic or pelagic marine invertebrates.     

The reproductive phenology of Delesseria sanguinea and Odonthalia dentata off the Isle of Man

Samples of individual plants of Delesseria sanguinea and Odonthalia dentata were collected from shallow subtidal populations off the south end of the Isle of Man during the reproductive season. Reproductive bladelets were measured and their state of fertility noted. In Delesseria, male bladelets appeared in early September and achieved maximum size in mid October when bladelets of all sizes became fertile; the largest of these dehisced first and all were spent by mid December. Females appeared 3 weeks later; carpogonia were fertilized during October but carpospores were not released until about February when maximum bladelet length was reached. In about half the bladelets carpogonia remained unfertilized and did not grow further and only 40% of successful fertilizations resulted in carpospore release. Tetrasporangial bladelets did not appear until November and tetraspores were released in January and February while bladelets were still growing. Gametophytes and tetrasporophytes existed in about equal numbers. In Odonthalia, all three types of bladelet appeared in early November and fertilization took place in December, but later-developing carpogonia seemed to remain unfertilized in spite of a second wave of production of spermatangia, resulting in a low fertilization success of about 7%. Both carpospores and tetraspores dehisced from January to April. In this species the gametophytes formed about 58% of the population, a proportion expected from equal survival of number of spores per parent.     

The morphology and life history of Mazoyerella gen. nov. (M. arachnoidea (Harvey) comb. nov.)—Rhodophyta,Ceramiaceae—from Southern Australia

Mazoyerella gen. nov., based on Corynospora arachnoidea Harvey from Tasmania, is placed provisionally in the Compsothamnieae tribe of the Ceramiaceae. All plants can produce elongate-ovoid monosporangia which reproduce the same phase. Sporophytes also bear polysporangia and sexual plants are dioecious, bearing either spermatangial heads or subterminal procarps followed by carposporophytes with nearly all gonimoblast cells becoming carposporangia and an involucrum of sterile filaments developing from sterile cells associated with the procarp. The life-history has been followed through successive generations in culture.     

Synthesis and pharmacological investigation of new N-hydroxyalkyl-2-aminophenothiazines exhibiting marked MDR inhibitory effect

Novel N-hydroxyalkyl-2-aminophenothiazines implying a tetrazole moiety at the alkyl chain have been synthesized by hydroboration–oxidation of dienes followed by Buchwald–Hartwig cross-coupling reaction. Also, some sulfoxide and sulfone derivatives have been prepared by selective oxidations. MDR inhibition studies on rat hepatocyte cell culture revealed that some derivatives exhibit marked biological efficacy exceeding that of the standard verapamil (e.g., 3h, 4h, 16). Selected derivatives were subjected to chemical resolution to provide both enantiomers which were shown of similar activity on P-gp interaction measurements. The new compounds exhibited no toxicity.     

The Transport Systems for Selenomethionine/Methionine and Selenocystine/Cystine in Escherichia Coli K-12 Appear to be Cooperative

Dopamine transporters of bovine and rat striata were identified by their specific [³H]cocaine binding and cocaine-sensitive [³H]dopamine ([³H]DA) uptake. Both binding and uptake functions of bovine striatal transporters were potentiated by lectins. Concanavalin A (Con A) increased the velocity but did not change the affinity of the transporter for DA; however, it increased its affinity for cocaine without changing the number of binding sites. This suggests that the DA transporter is a glycoprotein and that Con A action on it produces conformational changes

Inorganic and organic mercury reagents inhibited both [³H]DA uptake and [³H]cocaine binding, though they were all more potent inhibitors of the former, n- Ethylmaleimide inhibited [³H]DA uptake totally but [³H]cocaine binding only partially. Also, n-pyrene maleimide had differential effects on uptake and binding, inhibiting uptake and potentiating binding. [³H]DA uptake was not affected by mercaptoethanol up to 100 mM, whereas [³H]cocaine binding was inhibited by concentrations above 10 mM. On the other hand, both uptake and binding were fairly sensitive to dimercaprol (< 1 mM). The effects of all these sulfhydryl reagents suggest that the DA transporter has one or more thiol group(s) important for both binding and uptake activities. The Ellman reagent and dithiopyridine were effective inhibitors of uptake and binding only at fairly high concentration (>10 mM). Loss of activity after treatment with the dithio reagents may be a result of reduction of a disulfide bond, which may affect the transporter conformation     

Analogs of iso-azepinomycin as potential transition-state analog inhibitors of guanase: Synthesis,biochemical screening,and structure–activity correlations of various selectively substituted imidazo[4,5-e][1,4]diazepines

Guanase is an important enzyme of the purine salvage pathway of nucleic acid metabolism and its inhibition has beneficial implications in viral, bacterial, and cancer therapy. The work described herein is based on a hypothesis that azepinomycin, a heterocyclic natural product and a purported transition state analog inhibitor of guanase, does not represent the true transition state of the enzyme-catalyzed reaction as closely as does iso-azepinomycin, wherein the 6-hydroxy group of azepinomycin has been translocated to the 5-position. Based on this hypothesis, and assuming that iso-azepinomycin would bind to guanase at the same active site as azepinomycin, several analogs of iso-azepinomycin were designed and successfully synthesized in order to gain a preliminary understanding of the hydrophobic and hydrophilic sites surrounding the guanase binding site of the ligand. Specifically, the analogs were designed to explore the hydrophobic pockets, if any, in the vicinity of N1, N3, and N4 nitrogen atoms as well as O⁵ oxygen atom of iso-azepinomycin. Biochemical inhibition studies of these analogs were performed using a mammalian guanase. Our results indicate that (1) increasing the hydrophobicity near O⁵ results in a negative effect, (2) translocating the hydrophobicity from N3 to N1 also results in decreased inhibition, (3) increasing the hydrophobicity near N3 or N4 produces significant enhancement of inhibition, (4) increasing the hydrophobicity at either N3 or N4 with a simultaneous increase in hydrophobicity at O⁵ considerably diminishes any gain in inhibition made by solely enhancing hydrophobicity at N3 or N4, and (5) finally, increasing the hydrophilic character near N3 has also a deleterious effect on inhibition. The most potent compound in the series has a K_i value of 8.0 ± 1.5 μM against rabbit liver guanase.     

果实生态学的概念、研究现状及研究方向

总结了果实生态学的概念及主要研究内容,对国内外的果实生态学研究领域的进展进行了综述,分析了这些研究尚存在的不足之处,并指出了未来研究的科学问题.迄今为止,果实生态学在果实与种子的关系、果实颜色与环境、果实化学成分与环境、群落果实构成式样的地理分布特征、果实及食果动物的协同进化等方面已经取得了若干进展.果实重量谱等物理性状的空间分异格局及机理、果实化学成分的时空变异格局、果实类型的组成式样及大尺度地理分布格局及其机制的探讨、果实传播与食果动物的协同进化等是未来亟待开展的工作.