Perception of illusory contours enhanced in motion

Investigation on illusory contours is important for understanding the mechanisms underlying the object recognition of human visual system. Numerous researches have shown that illusory contours formed in motion and stereopsis are generated by the unmatched features. Here we conduct three psychophysical experiments to test if Kanizsa illusory contours are also caused by unmatched information. Different types of motion (including horizontal translation, radial expanding and shrinking) are utilized in the experiments. The results show that no matter under what kind of motion, when figures or background move separately illusory contours are perceived stronger, and there is no significant difference between the perceived strength in these two types of motion. However, no such enhancement of perceived strength is found when figures and background move together. It is found that the strengthened unmatched features generate the enhancement effect of illusory contour perception in motion. Thus the results suggest that the process of unmatched information in visual system is a critical step in the formation of illusory contours.     

Perception of illusory contours enhanced in motion

Object perception is one of the most important components of visual perception of human beings and mammalian animals. It is a most confusing problem on object perception that how we separate object from background and obtain the picture of the whole object. In many cases one object partly occludes the other one in natural world. When the brightness of the occluding object is the same as or similar to that of the background, though there is no difference between visual stimuli, we can still ret…     

Management affects the pollinator abundance but not the reproductive success of butterfly orchids

Management of semi-natural grasslands should be based on the requirements of plants as well as their pollinators since conditions beneficial for plants are not necessarily beneficial for their pollinators and vice versa. The factors affecting the reproductive success (fruit set) of Platanthera bifolia and Platanthera chlorantha and their pollinators in agricultural landscape and woodlands were studied. In the years 2014–2016, we observed and caught moths during the flowering period of Platanthera species (late June–mid July) in four pure P. bifolia, five pure P. chlorantha and nine mixed populations under management or no management in Estonia. We determined pollinator species richness, pollinator abundance, fruit set and visibility of Platanthera plants in each population. We found that pollinator assemblages of P. bifolia and P. chlorantha did not differ between managed and unmanaged sites. Pollinator abundance had an effect on the fruit set of P. bifolia but not on that of P. chlorantha. Presence or absence of management, visibility of plants and rarefied pollinator species richness did not affect the fruit set of either plant species. Pollinator abundance was significantly higher in unmanaged populations of both plant species but rarefied pollinator species richness was higher only in unmanaged populations of P. chlorantha. Based on our findings the recommendations for management of semi-natural grasslands are to promote larger landscape diversity for the benefit of moth abundance by leaving unmanaged patches in different parts of a grassland in different years and rotational and post-fruiting management for higher reproductive success of orchids.     

Repeated sampling but not sampling hour affects plasma carotenoid levels

Carotenoid pigments have become a central subject of research on animal signaling systems during the past decade. Thus, measurement of plasma carotenoid levels is widespread in the literature. Many plasma biochemical parameters tend to vary with the hour of sampling, which may be an important source of sampling error. However, little is known about this kind of variation for circulating carotenoids. With a sampling protocol that allowed us to separately analyze the effect of sampling hour and repeated blood extraction at the within-individual level, we evaluated the effect of these two parameters on plasma carotenoid concentration in captive red-legged partridges (Alectoris rufa). The hour of sampling did not show a significant influence on carotenoid variability. Nevertheless, carotenoid levels significantly decreased as a result of repeated sampling. In fact, carotenoid variability was positively related to hematocrit values, which also decreased throughout the experiment. Furthermore, the effect was evident from the second sampling event. These results suggest that blood samples for carotenoid analysis may be obtained at random during the daytime with no serious risk of adding variance to data obtained. However, the effect of hemodilution associated with repeated blood extraction should be carefully considered in those studies involving repeated sampling.     

Moderate acidification affects growth but not survival of 6-month-old oysters

Oyster populations periodically exposed to runoff from acid sulfate soils (ASS) are of depressed abundance and have fewer smaller individuals than unaffected populations, despite having similar recruitment levels to unaffected sites during dry periods. We examined how the timing and duration of exposure to ASS runoff influences the growth and survival of successfully settled oysters. We predicted that among 6-month-old oysters, growth and survival would be (1) lower among individuals continuously exposed to ASS-acidified waters than those that are episodically exposed, and (2) most negatively affected during rainfall events, which enhance transport of ASS runoff to estuaries. Six-month-old Sydney rock oysters, Saccostrea glomerata, were deployed at ASS-affected and unaffected sites within each of two south-east Australian estuaries. After 10 weeks, oysters were transplanted within and across sites in an estuary and maintained in situ for another 10 weeks. Oysters that remained for 20 weeks at ASS-affected sites grew at just over half the rate of oysters at reference sites. Oysters transplanted from acidified to reference sites grew more than oysters transplanted from reference to acidified sites or oysters that remained at reference sites. Unexpectedly, overall oyster mortality was low. Greater rainfall, and hence a lower pH, is likely to have accounted for the greater impact of acidification on growth during the second 10 weeks. Where oysters recruit to a 6-month age cohort, they may be able to tolerate subsequent, moderate, acidification events. Reduced growth during acidification periods may be offset by positive growth during intervening dry periods.     

Regulated dimerization of the thyrotropin-releasing hormone receptor affects receptor trafficking but not signaling

To investigate the function of dimerization of the TRH receptor, a controlled dimerization system was developed. A variant FK506 binding protein (FKBP) domain was fused to the receptor C terminus and dimerization induced by incubating cells with dimeric FKBP ligand, AP20187. The TRH receptor-fusion bound hormone and signaled normally. Addition of dimerizer to cells expressing the receptor-FKBP fusion dramatically increased the fraction of receptor running as dimer on SDS-PAGE. AP20187 caused dimerization in a time- and concentration-dependent manner, acting within 1 min. Dimerizer had no effect on TRH receptors lacking the FKBP domain, and its effects were blocked by excess monomeric FKBP ligand. AP20187-induced dimerization did not cause receptor phosphorylation, inositol phosphate production, or ERK1/2 activation, and dimerizer did not alter signaling by TRH. Induced dimerization did, however, alter TRH receptor trafficking. TRH promoted greater receptor internalization in cells treated with AP20187 but not monomeric ligand, based on loss of surface binding sites and immunostaining. Dimerization increased the rate of internalization of TRH receptors and decreased the apparent rate of receptor recycling. AP20187 enhanced the small amount of TRH-induced receptor internalization when the receptor-FKBP fusion protein was expressed in cells lacking beta-arrestins. The results show that controlled dimerization of the TRH receptor potentiates hormone-induced receptor trafficking.     

Leptin perfusion affects insulin secretion but not insulin receptors in rats

The aim of the study was to investigate acute leptin effects on insulin secretion and liver insulin binding in rats in vitro. In the in situ experiments leptin changed the pattern of insulin secretion from the pancreas but did not influence insulin binding in the liver. Perfusion of the pancreas with leptin (1, 10, and 100 nmol/l, respectively) at physiological and supraphysiological levels of glucose (6.66 and 25.0 mmol/l, respectively) did not evoke the inhibition of insulin output observed by the authors previously in the in vivo manners. On the contrary, leptin perfusion resulted in stimulation of insulin secretion. Simultaneously, liver perfusion with leptin for 30 min did not influence specific insulin binding. Analysis of Scatchard's plots indicated no changes in the number of high- and low-affinity insulin receptors and in their affinity to the hormone. Additionally, leptin did not influence general carbohydrate and lipid metabolism of the perfused liver. After the treatment with leptin, the output of glucose, free fatty acids and triglycerides to perfusate and the final contents of glycogen and triglycerides in liver were comparable to values obtained in control animals. The results indicate that some in vitro effects exerted by leptin differ from those observed in vivo.     

Energy restriction but not protein source affects antioxidant capacity in athletes

The primary purpose of this study was to examine the effect of energy restriction on antioxidant capacity in trained athletes. Secondly, our study determined whether dietary protein source influenced the antioxidant response, performance, and immunity. Twenty male cyclists consumed either whey or casein supplement (40 g/day) in addition to their diet for 17 days. All subjects subsequently underwent 4 days of energy restriction using a formula diet (20 kcal/kg) while continuing protein supplementation. Energy restriction caused 2.7 +/- 0.3 kg weight loss, increased lymphocyte total glutathione (tGSH) 37%, red blood cell glutathione peroxidase 48%, plasma cysteine 12%, and decreased whole blood reduced to oxidized GSH (rGSH/GSSG) ratio by 52%. The only immunity factor altered by energy restriction was an increase in stimulated phagocytosis (65%). Acute submaximal exercise reduced blood tGSH but increased glutathione peroxidase. Performance of a high intensity cycle test following 45 min of moderate exercise tended to be reduced by energy restriction (P = 0.06) but was unaffected by protein source. Energy restriction caused a negative nitrogen balance with no difference from dietary protein source. In conclusion, acute energy restriction increased plasma cysteine and several markers of the glutathione antioxidant system in trained athletes. A high cysteine dietary protein source did not influence these responses.     

Calreticulin affects focal contact-dependent but not close contact-dependent cell-substratum adhesion.

We used two cell lines expressing fast (RPEfast) and slow (RPEslow) attachment kinetics to investigate mechanisms of cell-substratum adhesion. We show that the abundance of a cytoskeletal protein, vinculin, is dramatically decreased in RPEfast cells. This coincides with the diminished expression level of an endoplasmic reticulum chaperone, calreticulin. Both protein and mRNA levels for calreticulin and vinculin were decreased in RPEfast cells. After RPEfast cells were transfected with cDNA encoding calreticulin, both the expression of endoplasmic reticulum-resident calreticulin and cytoplasmic vinculin increased. The abundance of other adhesion-related proteins was not affected. RPEfast cells underexpressing calreticulin displayed a dramatic increase in the abundance of total cellular phosphotyrosine suggesting that the effects of calreticulin on cell adhesiveness may involve modulation of the activities of protein tyrosine kinases or phosphatases which may affect the stability of focal contacts. The calreticulin and vinculin underexpressing RPEfast cells lacked extensive focal contacts and adhered weakly but attached fast to the substratum. In contrast, the RPEslow cells that expressed calreticulin and vinculin abundantly developed numerous and prominent focal contacts slowly, but adhered strongly. Thus, while the calreticulin overexpressing RPEslow cells "grip" the substratum with focal contacts, calreticulin underexpressing RPEfast cells use close contacts to "stick" to it.     

Conspecific pilferage but not presence affects Merriam's kangaroo rat cache strategy

We investigated the effects of pilferage on caching behaviorin the Merriam's kangaroo rat by manipulating two factors associatedwith pilferage: the presence of a conspecific, and the opportunityfor pilferage. In one experiment we assessed animals in either"Stealer" or "Victim" roles and measured changes in caching,space use, and behavior after caches were pilfered. Victimsshifted from a majority scatter-hoarding to a majority larder-hoardingstrategy after their caches were pilfered by the Stealer. InExperiment 2, we measured changes after exposure to a conspecificwhen there was no pilferage, with or without prior exposureto pilferage from Experiment 1. Merriam's kangaroo rats werevigilant when a conspecific was present, but did not changecache strategy. Prior exposure did not have any major effecton caching or behavior. Food storage is an economic decisionthat is often made by a solitary forager. Our results suggestthat social competition nonetheless influences such economic decisions, even in a nonsocial forager.     

Food affects the potential reproductive rates of sand goby females but not of males

The interspawning interval of female sand gobies, Pomatoschistusminutus, a batch-spawning fish with paternal care, was significantlyshorter when the fish were fed daily than when they were fedevery fourth day. The incubation time of males was not affectedby feeding, nor was the interbrood interval Males have an equalor higher potential reproductive rate than females. As femalesreproduce more slowly when food is scarce than when it is abundant,and males do not, the difference between the sexes in potentialreproductive rate increases when there is food shortage. Becauseof this difference, both male bias in operational sex ratioand intensity in male-male competition for mates are predictedto increase as food availability decreases. Furthermore, a tradeoffbetween current and future reproduction is demonstrated to operateonly when resources are limited, because the correlation betweenegg number of the first and second clutch was positive amonghigh-food females but negative among low-food females. The numberof eggs per female clutch did, however, not differ between treatmentsin first or second dutch. I conclude that operational sex ratioand sexual selection are expected to vary within and betweensand goby populations in accordance with prey availability     

Inbreeding affects sexual signalling in males but not females of Tenebrio molitor

In many species of animals, individuals advertise their quality with sexual signals to obtain mates. Chemical signals such as volatile pheromones are species specific, and their primary purpose is to influence mate choice by carrying information about the phenotypic and genetic quality of the sender. The deleterious effects of consanguineous mating on individual quality are generally known, whereas the effect of inbreeding on sexual signalling is poorly understood. Here, we tested whether inbreeding reduces the attractiveness of sexual signalling in the mealworm beetle, Tenebrio molitor, by testing the preferences for odours of inbred and outbred (control) individuals of the opposite sex. Females were more attracted to the odours produced by outbred males than the odours produced by inbred males, suggesting that inbreeding reduces the attractiveness of male sexual signalling. However, we did not find any difference between the attractiveness of inbred and outbred female odours, which may indicate that the quality of females is either irrelevant for T. molitor males or quality is not revealed through female odours.     

The novel Drosophila tim(blind) mutation affects behavioral rhythms but not periodic eclosion

Circadian clock function depends on the tightly regulated exclusion or presence of clock proteins within the nucleus. A newly induced long-period timeless mutant, tim(blind), encodes a constitutively hypophosphorylated TIM protein. The mutant protein is not properly degraded by light, and tim(blind) flies show abnormal behavioral responses to light pulses. This is probably caused by impaired nuclear accumulation of TIM(BLIND) protein, which we observed in brain pacemaker neurons and photoreceptor cells of the compound eye. tim(blind) encodes two closely spaced amino acid changes compared to the wild-type TIM protein; one of them is within a putative nuclear export signal of TIM. Under constant conditions, tim(blind) flies exhibit 26-hr free-running locomotor rhythms, which are not correlated with a period lengthening of eclosion rhythms and period-luciferase reporter-gene oscillations. Therefore it seems possible that TIM--in addition to its well-established role as core clock factor--functions as a clock output factor, involved in determining the period length of adult locomotor rhythms.     

The direction of retinal motion facilitates binocular stereopsis.

Visual information from binocular disparity and from relative motion provide information about three-dimensional structure and layout of the world. Although the mechanisms that process these cues have typically been studied independently, there is now a substantial body of evidence that suggests that they interact in the visual pathway. This paper investigates one advantage of such an interaction: whether retinal motion can be used as a matching constraint in the binocular correspondence process. Stimuli that contained identical disparity and motion signals but which differed in their fine-scale correlation were created to establish whether the direction, or the speed, of motion could enhance performance in a psychophysical task in which binocular matching is a limiting factor. The results of these experiments provide clear evidence that different directions of motion, but not different speeds, are processed separately in stereopsis. The results fit well with properties of neurons early in the cortical visual pathway which are thought to be involved in determining local matches between features in the two eyes'' images.     

Whole-stream nitrate addition affects litter decomposition and associated fungi but not invertebrates

We assessed the effect of whole-stream nitrate enrichment on decomposition of three substrates differing in nutrient quality (alder and oak leaves and balsa veneers) and associated fungi and invertebrates. During the 3-month nitrate enrichment of a headwater stream in central Portugal, litter was incubated in the reference site (mean NO₃-N 82 μg l⁻¹) and four enriched sites along the nitrate gradient (214–983 μg NO₃-N l⁻¹). A similar decomposition experiment was also carried out in the same sites at ambient nutrient conditions the following year (33–104 μg NO₃-N l⁻¹). Decomposition rates and sporulation of aquatic hyphomycetes associated with litter were determined in both experiments, whereas N and P content of litter, associated fungal biomass and invertebrates were followed only during the nitrate addition experiment. Nitrate enrichment stimulated decomposition of oak leaves and balsa veneers, fungal biomass accrual on alder leaves and balsa veneers and sporulation of aquatic hyphomycetes on all substrates. Nitrate concentration in stream water showed a strong asymptotic relationship (Michaelis–Menten-type saturation model) with temperature-adjusted decomposition rates and percentage initial litter mass converted into aquatic hyphomycete conidia for all substrates. Fungal communities did not differ significantly among sites but some species showed substrate preferences. Nevertheless, certain species were sensitive to nitrogen concentration in water by increasing or decreasing their sporulation rate accordingly. N and P content of litter and abundances or richness of litter-associated invertebrates were not affected by nitrate addition. It appears that microbial nitrogen demands can be met at relatively low levels of dissolved nitrate, suggesting that even minor increases in nitrogen in streams due to, e.g., anthropogenic eutrophication may lead to significant shifts in microbial dynamics and ecosystem functioning. Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .     

Drought stress affects constitutive but not induced herbivore resistance in apple plants

Plant–herbivore interactions are influenced by chemical plant traits, which can vary depending on the plants’ abiotic and biotic environment. Drought events, which are predicted to become more frequent and prolonged due to climate change, may affect primary and secondary plant metabolites contributing to constitutive resistance. Furthermore, the ability of plants to respond to herbivore attack in terms of induced resistance may be altered under drought conditions. We assessed the effects of drought stress on constitutive and induced apple plant resistance to a generalist insect herbivore by quantifying plant and herbivore responses in concert. Plants were exposed to different drought stress intensities (constitutive resistance) and subsequently to herbivore damage treatments that included different damage durations (induced resistance). As drought stress intensified, plant growth and concentrations of the leaf phenolic phloridzin decreased, whereas leaf glucose concentrations increased. Changes in fructose concentrations and in herbivore feeding preferences indicated a non-monotonic shift in constitutive resistance. Moderately stressed plants showed reduced fructose concentrations and were consumed least, while severely stressed plants were fructose-enriched and consumed most compared to well-watered control plants showing intermediate fructose concentrations and palatability. We found no evidence for effects of drought stress on induced resistance, as herbivore feeding preferences for undamaged over damaged plants were independent of drought intensity. Our results suggest a strong role of primary metabolites for drought-dependent variation in constitutive plant resistance and offer novel experimental insights into the effects of drought stress on induced plant resistance across a gradient of water deprivation.     

Short-term inhibition of the energy metabolism affects motility but not surface properties of sperm cells

Centrifugal countercurrent distribution (CCCD) in aqueous two-phase systems has been proven to be a useful method to study subtle surface properties of spermatozoa. The present work shows that a short-term inhibition of the energy metabolism of sperm cells effected by incubating bovine sperm cells with KCN or ouabain, did not account for changes in the cell surface properties, as assessed either by estimation of the cell viability or by CCCD analysis. However, the short-term inhibition of energy metabolism provoked a clear decrease of cell motility, suggesting that a drop of cellular ATP levels brings about a rapid decrease of motility followed by a very delayed effect on cell surface properties. The relevance of these results on the handling of sperm and on the understanding of the molecular events underlying asthenospermia is discussed.