Polarizing optics in a spider eye

Many arthropods including insects and spiders exploit skylight polarization for navigation. One of the four eye pairs of the spider Drassodes cupreus is dedicated to detect skylight polarization. These eyes are equipped with a tapetum that strongly plane-polarizes reflected light. This effectively enhances the polarization-sensitivity of the photoreceptors, improving orientation performance. With a multidisciplinary approach, we demonstrate that D. cupreus exploits reflective elements also present in non-polarizing tapetal eyes of other species such as Agelena labyrinthica. By approximately orthogonal arrangement of two multilayer reflectors consisting of reflecting guanine platelets, the tapetum uses the mechanism of polarization by reflection for polarizing reflected ligh

Adaptation of a distributed controller depending on morphology

In this paper, we investigate the influence of an agent's morphology on its neural controller. Our model consists of a number of identical modules, each of which comprises two half-wheels for movement and a central pattern generator (CPG) as its own neural control. Based on a series of simulation experiments, we conclude that one single type of CPG can adapt well to different types of morphologies, and that there seems to be a suitable or optimal morphology depending on the environmental given

Specialized ommatidia of the polarization-sensitive dorsal rim area in the eye of monarch butterflies have non-functional reflecting tapeta

Many insects exploit sky light polarization for navigation or cruising-course control. The detection of polarized sky light is mediated by the ommatidia of a small specialized part of the compound eye: the dorsal rim area (DRA). We describe the morphology and fine structure of the DRA in monarch butterflies (Danaus plexippus). The DRA consists of approximately 100 ommatidia forming a narrow ribbon along the dorsal eye margin. Each ommatidium contains two types of photoreceptor with mutually orthogonal microvilli orientations occurring in a 2:6 ratio. Within each rhabdomere, the microvilli are well aligned. Rhabdom structure and orientation remain constant at all retinal levels, but the rhabdom profiles, as seen in tangential sections through the DRA, change their orientations in a fan-like fashion from the frontal to the caudal end of the DRA. Whereas these properties (two microvillar orientations per rhabdom, microvillar alignment along rhabdomeres, ommatidial fan array) are typical for insect DRAs in general, we also report and discuss here a novel feature. The ommatidia of monarch butterflies are equipped with reflecting tapeta, which are directly connected to the proximal ends of the rhabdoms. Although tapeta are also present in the DRA, they are separated from the rhabdoms by a space of approximately 55 μm effectively inactivating them. This reduces self-screening effects, keeping polarization sensitivity of all photoreceptors of the DRA ommatidia both high and approximately equa

Photosynthesis and Degree of Polymerization of Fructan during Reproductive Growth of Meadow Fescue at two Temperatures and two Photon Flux Densities

Accumulation of dry weight was measured in plant parts of meadow fescue (Festuca pratensis Huds.) that was grown at 16/11 °C or 26/21 °C and with 20 or 60 nE cm−2 s−1 photosynthetically active radiation. Plants reached anthesis about 3 weeks later at 16/11 °C than at 26/21 °C and had then a higher proportion of dry weight in inflorescences and less in leaf blades. Growth temperature had little effect on CO2 exchange rate (CER) but plants grown at 60 nE cm−2 s−1 had higher CER than those grown at 20 nE cm−2 s−1. The concentration of water-soluble carbohydrates (WSC) at similar growth stages was usually higher at 16/11°C than at 26/21°C. High radiation also led to higher WSC in stem and leaf tissue. Root tissue changed least and WSC did not exceed 10% of dry weight during the experiment. In all tissues, when WSC was high, the fructans were distributed into a group with a high degree of polymerization (DP) and another with a low DP. The low DP group included sucrose, reducing sugars and fructans up to about 20 units long. An apparent threshold concentration of WSC was necessary for synthesis of the high DP fructans. This concentration was near 12% for leaf tissue, about 6% for stem base tissue, and 2.5% for root tissue. The average apparent DP of the high DP fructan group was 43 to 50 for leaf tissue, 31 to 93 for stem base tissue, and 27 to 31 for roots. These characteristics appeared to be mostly tissue dependent with less effect from temperature and radiatio

NGF-mediated transcriptional targets of p53 in PC12 neuronal differentiation

<p>Abstract</p> <p>Background</p> <p>p53 is recognized as a critical regulator of the cell cycle and apoptosis. Mounting evidence also suggests a role for p53 in differentiation of cells including neuronal precursors. We studied the transcriptional role of p53 during nerve growth factor-induced differentiation of the PC12 line into neuron-like cells. We hypothesized that p53 contributed to PC12 differentiation through the regulation of gene targets distinct from its known transcriptional targets for apoptosis or DNA repair.</p> <p>Results</p> <p>Using a genome-wide chromatin immunoprecipitation cloning technique, we identified and validated 14 novel p53-regulated genes following NGF treatment. The data show p53 protein was transcriptionally activated and contributed to NGF-mediated neurite outgrowth during differentiation of PC12 cells. Furthermore, we describe stimulus-specific regulation of a subset of these target genes by p53. The most salient differentiation-relevant target genes included <it>wnt7b </it>involved in dendritic extension and the <it>tfcp2l4/grhl3 </it>grainyhead homolog implicated in ectodermal development. Additional targets included <it>brk</it>, <it>sdk2</it>, <it>sesn3</it>, <it>txnl2</it>, <it>dusp5</it>, <it>pon3</it>, <it>lect1</it>, <it>pkcbpb15 </it>and other genes.</p> <p>Conclusion</p> <p>Within the PC12 neuronal context, putative p53-occupied genomic loci spanned the entire <it>Rattus norvegicus </it>genome upon NGF treatment. We conclude that receptor-mediated p53 transcriptional activity is involved in PC12 differentiation and may suggest a contributory role for p53 in neuronal development.</p

Reciprocal Influences of Drinking Motives on Alcohol Use and Related Consequences: A Full Cross-Lagged Panel Study Among Young Adult Men.

Using a full cross-lagged model, this study investigates the extent to which drinking motives predict alcohol use and related consequences, and vice versa. At baseline and 15 months later, 4575 men (mean age = 19.4 years) in Switzerland completed a questionnaire assessing drinking motives, average weekly consumption, risky single-occasion drinking, and alcohol-related consequences. Results indicated that social and enhancement motives more strongly influenced alcohol use over time than the other way round. Coping motives predicted an increase in alcohol-related consequences, and vice versa. Higher social motives predicted an increase in coping motives while higher coping motives predicted a decrease in enhancement motives. These results suggest that social and enhancement motives amplify each other in early adulthood and predict increases in risky drinking. Structural measures aimed at reducing opportunities to engage in heavy drinking are recommended. Additionally, the detection of young adult men vulnerable to maladaptive coping behaviors appears important for alcohol prevention strategies

Do Individual and Situational Factors Explain the Link Between Predrinking and Heavier Alcohol Consumption? An Event-Level Study of Types of Beverage Consumed and Social Context

Aim: Predrinking (drinking in private settings before going to licensed premises) has been shown to be positively associated with amount of alcohol consumed. The present study assesses whether this association is explained by general drinking patterns or situational factors, including drinking duration, beverage type and drinking companions. Methods: In a sample of 183 young adults from French-speaking Switzerland, data on alcohol consumption, whereabouts and drinking companions were collected using questionnaires sent to participants' cell phones at five time points from 5 p.m. to midnight every Thursday, Friday and Saturday over five consecutive weeks. Means and proportion tests and multilevel models were conducted based on 6650 assessments recorded on 1441 evenings. Results: Over the study period, predrinkers drank more frequently than did non-predrinkers and, among males, predrinkers drank more heavily. Predrinking was related to increased drinking duration and thus total consumption in the evenings. Larger groups of people were reported for predrinking compared with off-premise only drinking situations. Among women, the consumption of straight spirits (i.e. not mixed with soft drinks) while predrinking was associated with higher total evening alcohol consumption. Among men, drinking with exclusively male friends or female friends while predrinking was associated with higher consumption. Conclusion: Heavier drinking on predrinking evenings mainly results from longer drinking duration, with individual and situational factors playing a smaller role. Prevention efforts on reducing the time that young adults spend drinking and harm reduction measures such as restriction of access to on-premise establishments once intoxicated are recommende

A quasi-randomized group trial of a brief alcohol intervention on risky single occasion drinking among secondary school students

Objectives: To show the effectiveness of a brief group alcohol intervention. Aims of the intervention were to reduce the frequency of heavy drinking occasions, maximum number of drinks on an occasion and overall weekly consumption. Methods: A cluster quasi-randomized control trial (intervention n=338; control n=330) among 16- to 18-year-old secondary school students in the Swiss Canton of Zürich. Groups homogeneous for heavy drinking occasions (5+/4+ drinks for men/women) consisted of those having medium risk (3-4) or high risk (5+) occasions in the past 30days. Groups of 8-10 individuals received two 45-min sessions based on motivational interviewing techniques. Results: Borderline significant beneficial effects (p<0.10) on heavy drinking occasions and alcohol volume were found 6months later for the medium-risk group only, but not for the high-risk group. None of the effects remained significant after Bonferroni corrections. Conclusions: Group intervention was ineffective for all at-risk users. The heaviest drinkers may need more intensive treatment. Alternative explanations were iatrogenic effects among the heaviest drinkers, assessment reactivity, or reduction of social desirability bias at follow-up through peer feedbac