Página 3 dos resultados de 1432 itens digitais encontrados em 0.020 segundos

New-issues markets as behavioural barriers to entry : an agent-based model of choices and market structure

Morais, Ulisses Lacerda de
Fonte: FEUC Publicador: FEUC
Tipo: Dissertação de Mestrado
Português
Relevância na Pesquisa
35.88%
The possibility that the existence of New-Issues Markets (NIM) could promote, through a behavioural response of potential entrants, a greater market concentration on economic sectors is the object of the present work. I analyse in what conditions do entrepreneurs choose to abandon their plans of entering some industry in order to invest in securities of companies in that same industry. To engage this matter an agent-based model, named Utility Load, was developed and simulated in NetLogo platform, where the entrepreneurs rely on a hybrid heuristic among Prospect Theory and Random Walk Model of perceptual decision-making to choose between starting a firm, assembling a portfolio or doing neither by postponing their decision. I arrive at the conclusion that a lengthy investment horizon or high bonds’ coupon, by offering greater prospective gains, attracts the vast majority of potential entrants to the NIM, which has a nefarious effect on the sector’s structure by increasing its concentration – measured by the Herfindahl-Hirschman Index. Moreover, the model indicates that a more bounded rationale is welfare increasing whilst allowing firms to continuously issue new debt to the public diminishes welfare. The results narrow the scope of reality to be emulated in experimental works and open the door for future empirical researches on this matter by making them more attainable.; Dissertação de mestrado em Economia (Economia Industrial)...

Overshadowing in conditioned taste aversion or in conditioned emotional response after neonatal ventral hippocampal lesions in rats

MACEDO, Carlos Eduardo; ANGST, Marie-Josee; GOUNOT, Daniel; SANDNER, Guy
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.88%
The neonatal hippocampus lesion thought to model schizophrenia should show the same modifications in behavioural tests as other models, especially pharmacological models. namely decreased latent inhibition, blocking and overshadowing. The present study is set out to evaluate overshadowing in order to complement our previous studies, which had tested latent inhibition. ""Overshadowing"" refers to the decreased conditioning that occurs when the to-be-conditioned stimulus is combined with another stimulus at the conditioning stage. We used the same two Pavlovian conditioning paradigms as in our previous works, namely conditioned taste aversion (CTA) and conditioned emotional response (CER). A sweet taste overshadowed a salty conditioned stimulus, and a tone overshadowed a flashing light. Totally different stimuli were used to counter possible sensory biases. The protocols were validated with two groups of Sprague Dawley rats. The same two protocols were then applied to a cohort of rats whose ventral hippocampus had been destroyed when they were 7 days old. Only rats with extended ventral hippocampus lesions were included. The overall effect of Pavlovian conditioning was attenuated, significantly so in the conditioned emotional response paradigm...

The `club` cell and behavioural and physiological responses to chemical alarm cues in the Nile tilapia

BARRETO, Rodrigo Egydio; BARBOSA JUNIOR, Augusto; GIASSI, Ana Catarina Casari; HOFFMANN, Anette
Fonte: TAYLOR & FRANCIS LTD Publicador: TAYLOR & FRANCIS LTD
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.9%
The alarm response to skin extract has been well documented in fish. In response to skin extract, there is a decline in both locomotion activity and aggressive interactions. Our observation herein of these responses in the cichlid Nile tilapia, Oreochromis niloticus, confirmed the existence of the alarm response in this species. However, so far there has been a paucity of information on the autonomic correlates of this response. In this study, the ventilatory change in response to the chemical alarm cue was evaluated. This parameter was measured 4 min before and 4 min after exposure to 1 mL of either conspecific skin extract or distilled water (extract vehicle). Skin extract induced an increase in the ventilation rate, which suggested an anticipatory adjustment to potentially harmful stimuli. The chemical cue (alarm substance) also interfered with the prioritisation of responses to different environmental stimuli (stimuli filtering); this was suggested by the observation that the Nile tilapia declined to fight after exposure to a cue that indicates a risk of predation. Furthermore, histological analysis of the Nile tilapia skin revealed the presence of putative alarm substance-producing (club) cells.; Universidade de São Paulo - FMRP-USP; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo-FAPESP[2005/04771-5]

Neural Basis of Delta-9-Tetrahydrocannabinol and Cannabidiol: Effects During Response Inhibition

BORGWARDT, Stefan J.; ALLEN, Paul; BHATTACHARYYA, Sagnik; FUSAR-POLI, Paolo; CRIPPA, Jose A.; SEAL, Marc L.; FRACCARO, Valter; ATAKAN, Zerrin; MARTIN-SANTOS, Rocio; O`CARROLL, Colin; RUBIA, Katya; MCGUIRE, Philip K.
Fonte: ELSEVIER SCIENCE INC Publicador: ELSEVIER SCIENCE INC
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.86%
Background: This study examined the effect of Delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) on brain activation during a motor inhibition task. Methods: Functional magnetic resonance imaging and behavioural measures were recorded while 15 healthy volunteers performed a Go/No-Go task following administration of either THC or CBD or placebo in a double-blind, pseudo-randomized, placebo-controlled repeated measures within-subject design. Results: Relative to placebo, THC attenuated activation in the right inferior frontal and the anterior cingulate gyrus. In contrast, CBD deactivated the left temporal cortex and insula. These effects were not related to changes in anxiety, intoxication, sedation, and psychotic symptoms. Conclusions: These data suggest that THC attenuates the engagement of brain regions that mediate response inhibition. CBD modulated function in regions not usually implicated in response inhibition.; Psychiatry Research Trust, United Kingdom; MRC Clinical Research Training Fellowship; Guy`s & St. Thomas Charitable Foundation; New Services and Innovations in Health Care

Dynamics of handling time and functional response by larvae of Chrysomya albiceps (Dipt., Calliphoridae) on different prey species

Faria, L. D. B.; Godoy, W. A. C.; Trinca, L. A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 432-436
Português
Relevância na Pesquisa
35.91%
One way to understand the behavioural patterns exhibited by a predator in response to prey density is to evaluate its functional response. Such evaluation yields information about basic mechanisms of prey-predator dynamics, and is an essential component of prey-predator models. In this paper we analysed experimentally the functional response and the handling time spent by Chrysomya albiceps on different prey species and larval instars of blowflies. The type II functional response was observed when second instar larvae of Chrysomya megacephala and Chrysomya macellaria were consumed. The handling time spent by the predator was significantly different between instars and species. The implications of the functional response and handling time for the interaction dynamics of Brazilian Chrysomyinae species are discussed.

In-situ quasi-static and dynamic behavioural response of steel tubular frames subjected to lateral impact loads

Zeinoddini,M.
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 Português
Relevância na Pesquisa
35.86%
Steel tubular members are widely used as primary and secondary structural framing members in offshore oil and gas platforms. A platform is inherently liable to collisions from ships which can create severe structural damages in the rig. The effect of this damage has been studied by a number of researchers through investigating the impact behaviour isolated tubular members. This is while, the in-situ response of a member located in a structural frame, to lateral impact loads, is not necessarily the same as the response of an individual isolated impacted member. In this paper the behaviour of a chord member forming part of a tubular frame, subjected to impact loads, has been investigated. The tubular frame was tested experimentally by other researchers and reported in the literature. The non-linear numerical models of the frame presented by the authors have been validated against the experimental results. These validated models have been examined under both quasi-static and dynamic impact loads with operational pre-loading applied. It has been found that, in a pre-loaded frame, quasi-static impact loading results in the failure of the impacted member. Interestingly, dynamic modelling of the impact results in the dynamic instability of an adjacent bracing member. It has been noticed that...

Identification of higher brain centres that may encode the cardiorespiratory response to exercise in humans

Thornton, Judith M; Guz, Abe; Murphy, Kevin; Griffith, Alison R; Pedersen, David L; Kardos, Attila; Leff, Alex; Adams, Lewis; Casadei, Barbara; Paterson, David J
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Publicado em 15/06/2001 Português
Relevância na Pesquisa
35.86%
Positron emission tomography (PET) was used to identify the neuroanatomical correlates underlying ‘central command’ during imagination of exercise under hypnosis, in order to uncouple central command from peripheral feedback.Three cognitive conditions were used: condition I, imagination of freewheeling downhill on a bicycle (no change in heart rate, HR, or ventilation, ): condition II, imagination of exercise, cycling uphill (increased HR by 12 % and by 30 % of the actual exercise response): condition III, volitionally driven hyperventilation to match that achieved in condition II (no change in HR).Subtraction methodology created contrast A (II minus I) highlighting cerebral areas involved in the imagination of exercise and contrast B (III minus I) highlighting areas activated in the direct volitional control of breathing (n = 4 for both; 8 scans per subject). End-tidal PCO2 (PET,CO2) was held constant throughout PET scanning.In contrast A, significant activations were seen in the right dorso-lateral prefrontal cortex, supplementary motor areas (SMA), the right premotor area (PMA), superolateral sensorimotor areas, thalamus, and bilaterally in the cerebellum. In contrast B, significant activations were present in the SMA and in lateral sensorimotor cortical areas. The SMA/PMA...

Population response to the risk of vector-borne diseases: lessons learned from socio-behavioural research during large-scale outbreaks

Setbon, M; Raude, J
Fonte: CoAction Publishing Publicador: CoAction Publishing
Tipo: Artigo de Revista Científica
Publicado em 31/07/2009 Português
Relevância na Pesquisa
35.96%
Vector-borne infectious diseases, such as malaria, dengue, chikungunya, and West Nile fevers are increasingly identified as major global human health threats in developing and developed countries. The success or failure of vector control rests mainly on the nature and scale of the behavioural response of exposed populations. Large-scale adoption of recommended protective behaviour represents a critical challenge that cannot be addressed without a better understanding of how individuals perceive and react to the risk of infection. Recently, French overseas territories faced large-scale outbreaks: an epidemic of chikungunya fever in La Re′ union and Mayotte (2005–2006) and four successive outbreaks of dengue fever in one Caribbean island, Martinique (1995–2007). To assess how these populations perceived and responded to the risk, and how the nature and scale of protection affected their clinical status, socio-epidemiological surveys were conducted on each island during the outbreaks. These surveys address three crucial and interconnected questions relevant to the period after persons infected by the virus were identified: which factors shape the risk of acquiring disease? Which socio- demographic characteristics and living conditions induce a higher likelihood of infection? What is the impact of risk perception on protective behaviours adopted against mosquito bites? Grounded on the results of these surveys...

Stimulus detection after interruption of the feedforward response in a backward masking paradigm

Romeo, August; Puig, Maria Sole; Zapata, Laura Pérez; Lopez-Moliner, Joan; Supèr, Hans
Fonte: Springer Netherlands Publicador: Springer Netherlands
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.89%
In backward masking, a target stimulus is rendered invisible by the presentation of a second stimulus, the mask. When the mask is effective, neural responses to the target are suppressed. Nevertheless, weak target responses sometimes may produce a behavioural response. It remains unclear whether the reduced target response is a purely feedforward response or that it includes recurrent activity. Using a feedforward neural network of biological plausible spiking neurons, we tested whether a transient spike burst is sufficient for face categorization. After training the network, the system achieved face/non-face categorization for sets of grayscale images. In a backward masking paradigm, the transient burst response was cut off thereby reducing the feedforward target response. Despite the suppressed feedforward responses stimulus classification remained robust. Thus according to our model data stimulus detection is possible with purely, suppressed feedforward responses.

Nucleus of the solitary tract catecholaminergic neurons modulate the cardiovascular response to psychological stress in rats

Daubert, Daisy L; McCowan, Michael; Erdos, Benedek; Scheuer, Deborah A
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.88%
Catecholaminergic neurons within the central nervous system are an integral part of stress-related neurocircuitry, and the nucleus of the solitary tract (NTS) plays a critical role in cardiovascular regulation. We tested the hypothesis that NTS catecholaminergic neurons attenuate psychological stress-induced increases in blood pressure and promote neuroendocrine activation in response to psychological stress. Anti-dopamine-β-hydroxylase antibody conjugated to the neurotoxin saporin (DSAP) or saline vehicle was microinjected into the NTS to lesion catecholaminergic neurons in male Sprague–Dawley rats, and 17 days later the rats were subjected to 60 min of restraint stress for five consecutive days. DSAP treatment significantly enhanced the integrated increase in mean arterial pressure during restraint on the first (800 ± 128 and 1115 ± 116 mmHg (min) for saline- and DSAP-treated rats) and fifth days (655 ± 116 and 1035 ± 113 mmHg (min) for saline- and DSAP-treated rats; P < 0.01 for overall effect of DSAP treatment) of restraint. In contrast, after 60 min of restraint plasma corticosterone concentration was significantly lower in DSAP-treated compared with saline-treated rats (25.9 ± 7 compared with 46.8 ± 7 μg dl−1 for DSAP- and saline-treated rats; P < 0.05). DSAP treatment also significantly reduced baseline plasma adrenaline concentration (403 ± 69 compared with 73 ± 29 pg ml−1 for saline- and DSAP-treated rats)...

Classification of frequency response areas in the inferior colliculus reveals continua not discrete classes

Palmer, Alan R; Shackleton, Trevor M; Sumner, Christian J; Zobay, Oliver; Rees, Adrian
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.91%
A differential response to sound frequency is a fundamental property of auditory neurons. Frequency analysis in the cochlea gives rise to V-shaped tuning functions in auditory nerve fibres, but by the level of the inferior colliculus (IC), the midbrain nucleus of the auditory pathway, neuronal receptive fields display diverse shapes that reflect the interplay of excitation and inhibition. The origin and nature of these frequency receptive field types is still open to question. One proposed hypothesis is that the frequency response class of any given neuron in the IC is predominantly inherited from one of three major afferent pathways projecting to the IC, giving rise to three distinct receptive field classes. Here, we applied subjective classification, principal component analysis, cluster analysis, and other objective statistical measures, to a large population (2826) of frequency response areas from single neurons recorded in the IC of the anaesthetised guinea pig. Subjectively, we recognised seven frequency response classes (V-shaped, non-monotonic Vs, narrow, closed, tilt down, tilt up and double-peaked), that were represented at all frequencies. We could identify similar classes using our objective classification tools. Importantly...

Reproductive Experience Alters Neural and Behavioural Responses to Acute Oestrogen Receptor α Activation

Byrnes, E. M.; Casey, K.; Carini, L. M.; Bridges, R. S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/2013 Português
Relevância na Pesquisa
35.88%
Reproductive experience (i.e. parturition and lactation) leads to persistent alterations in anxietylike behaviour that are influenced by the oestrous cycle. We recently found that repeated administration of the selective oestrogen receptors (ER)α agonist propyl-pyrazole triol (PPT) results in anxiolytic-like behaviours on the elevated plus maze (EPM) in primiparous (but not nulliparous) female rats. The present study examined the effects of the acute administration of PPT on EPM behaviour in primiparous and aged-matched, nulliparous female rats. In addition, corticosterone secretion, corticotrophin-releasing hormone (CRH) gene expression and expression of the immediate early gene product Fos in the paraventricular nucleus (PVN) and amygdala were measured either after EPM testing or in home cage controls. Acute PPT administration significantly modified EPM behaviour as a function of reproductive experience, with nulliparous females tending toward increased anxiety-like behaviours and primiparous females tending toward decreased anxiety-like behaviours. In home cage controls, PPT increased corticosterone secretion in all females; however, both vehicle- and PPT-treated, primiparous females had reduced corticosterone levels compared to their nulliparous counterparts. Significant effects of PPT on CRH mRNA within the PVN were observed after the administration of PPT but only in primiparous females tested on the EPM. PPT also increased Fos expression within the PVN of EPM-exposed females; however...

Response of seaward-migrating European eel (Anguilla anguilla) to manipulated flow fields

Piper, Adam T.; Manes, Costantino; Siniscalchi, Fabio; Marion, Andrea; Wright, Rosalind M.; Kemp, Paul S.
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
Publicado em 22/07/2015 Português
Relevância na Pesquisa
35.96%
Anthropogenic structures (e.g. weirs and dams) fragment river networks and restrict the movement of migratory fish. Poor understanding of behavioural response to hydrodynamic cues at structures currently limits the development of effective barrier mitigation measures. This study aimed to assess the effect of flow constriction and associated flow patterns on eel behaviour during downstream migration. In a field experiment, we tracked the movements of 40 tagged adult European eels (Anguilla anguilla) through the forebay of a redundant hydropower intake under two manipulated hydrodynamic treatments. Interrogation of fish trajectories in relation to measured and modelled water velocities provided new insights into behaviour, fundamental for developing passage technologies for this endangered species. Eels rarely followed direct routes through the site. Initially, fish aligned with streamlines near the channel banks and approached the intake semi-passively. A switch to more energetically costly avoidance behaviours occurred on encountering constricted flow, prior to physical contact with structures. Under high water velocity gradients, fish then tended to escape rapidly back upstream, whereas exploratory ‘search’ behaviour was common when acceleration was low. This study highlights the importance of hydrodynamics in informing eel behaviour. This offers potential to develop behavioural guidance...

Response Monitoring, Repetitive Behaviour and Anterior Cingulate Abnormalities in Autism Spectrum Disorders (ASD)

Thakkar, Katharine N.; Tuch, David S.; Barton, Jason J.S.; Polli, Frida E.; Joseph, Robert Michael; Hadjikhani, Nouchine; Manoach, Dara S
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.91%
Autism spectrum disorders (ASD) are characterized by inflexible and repetitive behaviour. Response monitoring involves evaluating the consequences of behaviour and making adjustments to optimize outcomes. Deficiencies in this function, and abnormalities in the anterior cingulate cortex (ACC) on which it relies, have been reported as contributing factors to autistic disorders. We investigated whether ACC structure and function during response monitoring were associated with repetitive behaviour in ASD. We compared ACC activation to correct and erroneous antisaccades using rapid presentation event-related functional MRI in 14 control and ten ASD participants. Because response monitoring is the product of coordinated activity in ACC networks, we also examined the microstructural integrity of the white matter (WM) underlying this brain region using diffusion tensor imaging (DTI) measures of fractional anisotropy (FA) in 12 control and 12 adult ASD participants. ACC activation and FA were examined in relation to Autism Diagnostic Interview-Revised ratings of restricted and repetitive behaviour. Relative to controls, ASD participants: (i) made more antisaccade errors and responded more quickly on correct trials; (ii) showed reduced discrimination between error and correct responses in rostral ACC (rACC)...

Développement d’un modèle centré sur l’individu des déplacements du caribou, du loup et de l’orignal, et de leurs interactions, en forêt boréale aménagée

Latombe, Guillaume
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
Relevância na Pesquisa
35.96%
Le caribou forestier est une espèce menacée au Canada, la principale hypothèse au déclin des populations étant l’intensification de la prédation provoquée par les perturbations anthropiques du paysage. Afin de faire face à cette situation, il est nécessaire d’étudier et comprendre l’impact de l’environnement sur les interactions prédateur-proies entre le caribou et le loup, ainsi qu’avec l’orignal, qui est sa principale proie alternative. Pour cela, cette thèse présente la conception d’un modèle centré sur l’individu des déplacements de ces trois espèces en fonction de leur environnement, dont résulteront les interactions prédateur-proies. Afin de permettre l’application de ce modèle sur de longues périodes, et donc pour un environnement changeant, une méthodologie a été développée, qui s’articule atour de deux aspects principaux. Tout d’abord, la notion de niveaux d’émergence est introduite, permettant d’ordonner les comportements observables du système selon leurs interdépendances, afin de choisir comme trait du modèle un com- portement correspondant au domaine d’applicabilité visé. Ordonner les comportements selon leurs niveaux d’émergence permet également d’identifier la redondance entre les patrons...

Caregiving for children with developmental disabilities is associated with a poor antibody response to influenza vaccination

Gallagher, Stephen; Phillips, Anna C; Drayson, Mark T; Carroll, Douglas
Fonte: Lippincott, Williams & Wilins Publicador: Lippincott, Williams & Wilins
Tipo: info:eu-repo/semantics/article; all_ul_research; ul_published_reviewed
Português
Relevância na Pesquisa
35.9%
peer-reviewed; Objective: Older spousal caregivers of dementia patients have been found to show a relatively poor antibody response to medical vaccination. The present case control study compared the antibody responses to vaccination of younger parental caregivers of children with developmental disabilities and parents of typically developing children. Methods: At baseline assessment, 32 parents of children with developmental disabilities and 29 parents of typically developing children completed standard measures of perceived stress and child problem behaviours. They also provided a blood sample and were then vaccinated with the thymus-dependent trivalent influenza vaccine. Further blood samples were taken at 1- and 6-month follow-ups. Results: Relative to parents of typically developing children (mean titre = 458, SD = 155.7 at 1-month and mean titre = 265, SD = 483.0 at 6-month followup) caregivers (mean titre = 219, SD = 528.4 at 1-month and 86, SD = 55.0 at 6- month) mounted a poorer antibody response than controls to the B/Malaysia strain of the vaccine. It was those caregivers reporting more child problem behaviours that tended to show the weakest antibody response. Conclusion: The negative impact of caregiving on antibody response to vaccination would not appear to be restricted to older spousal caregivers...

Parental caregivers of children with developmental disabilities mount a poor antibody response to pneumococcal vaccination.

Gallagher, Stephen; Phillips, Anna C; Drayson, Mark T; Carroll, Douglas
Fonte: Elsevier Publicador: Elsevier
Tipo: info:eu-repo/semantics/article; all_ul_research; ul_published_reviewed
Português
Relevância na Pesquisa
35.89%
peer-reviewed; In older populations, caregiving for a spouse with dementia has been associated with a poor antibody response to vaccination. The present study examined whether younger caregivers, specifically the parents of children with developmental disabilities, would also show a diminished antibody response to vaccination. At baseline assessment, 30 parents of children with developmental disabilities and 29 parents of typically developing children completed standard measures of depression, perceived stress, social support, caregiver burden, and child problem behaviours. They also provided a blood sample and were then vaccinated with a pneumococcal polysaccharide vaccine. Further blood samples were taken at 1- and 6-month follow-ups. Caregivers mounted a poorer antibody response to vaccination than control parents at both follow-ups. This effect withstood adjustment for a number of possible confounders and appeared to be, at least in part, mediated by child problem behaviours. The negative impact of caregiving on antibody response to vaccination is not restricted to older spousal caregivers, but is also evident in younger parents caring for children with developmental disabilities. The behavioural characteristics of the care recipients may be a key consideration in whether or not immunity is compromised in this context.; ACCEPTED; peer-reviewed

Behavioural response of Triatoma infestans (Klug) (Hemiptera: Reduviidae) to quinazolines

Alzogaray, R. A.; Fontán, A.; Camps Díez, Francisco; Masuh, H.; Santo Orihuela, P.; Fernández, Darío; Cork, A.; Zerba, E.
Fonte: Multidisciplinary Digital Publishing Institute Publicador: Multidisciplinary Digital Publishing Institute
Tipo: Artículo Formato: 58933 bytes; application/pdf
Português
Relevância na Pesquisa
35.88%
7 pages, 2 schemes, 3 tables.-- PMID: 18007385 [PubMed].; The behavioural responses of the haematophagous bug Triatoma infestans towards some previously identified components of its faeces: 4-methylquinazoline, 2,4- dimethylquinazoline and their mixtures were evaluated using a video tracking system. Fifth instar nymphs and females but not males were significantly attracted to polyethylene glycol formulations of 4-methyl + 2,4-dimethylquinazoline (50 μg each). Fifth instar nymphs were also attracted to 4-methylquinazoline alone (50 μg) but females were only attracted by the mixture of both methyl quinazolines (50 μg each). Syntheses of both methyl quinazolines were carried out starting from 2-aminoacetophenone by modifying the conditions of reported procedures.; Financial support from the Agencia Nacional de Promoción de Ciencia y Técnica of Argentina, the Consejo Nacional de Investigaciones Científicas y Técnicas of Argentina (CONICET) and the European Communities Programme on Scientific and Technical Cooperation with Developing Countries.; Peer reviewed

The optomotor response and spatial resolution in the visual system of male Xenos vesparum (Strepsiptera).

Pix, Waltraud; Zanker, Johannes; Zeil, Jochen
Fonte: The Company of Biologists Ltd Publicador: The Company of Biologists Ltd
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.91%
The Strepsiptera are an enigmatic group of parasitic insects whose phylogenetic relationships are hotly debated. Male Strepsiptera have very unusual compound eyes, in which each of a small number of ommatidia possesses a retina of at least 60 retinula cells. We analysed the optomotor response of Xenos vesparum males to determine whether spatial resolution in these eyes is limited by the interommatidial angle or by the higher resolution potentially provided by the extended array of retinula cells within each ommatidium. We find that the optomotor response in Strepsiptera has a typical bandpass characteristic in the temporal domain, with a temporal frequency optimum at 1-3 Hz. As a function of spatial wavelength, the optomotor response is zero at grating periods below 12° and reaches its maximum strength at grating periods between 60° and 70°. To identify the combination of interommatidial angles and angular sensitivity functions that would generate such a spatial characteristic, we used motion detection theory to model the spatial tuning function of the strepsipteran optomotor response. We found the best correspondence between the measured response profile and theoretical prediction for an irregular array of sampling distances spaced around 9° (half the estimated interommatidial angle) and an angular sensitivity function of approximately 50°...

Phenotypic plasticity for Drosophila melanogaster (Diptera: Drosophilidae) larval olfactory behaviour in response to whole fruit olfactory stimuli

Lavagnino,Nicolás J.; Fanara,Juan J.
Fonte: Revista de la Sociedad Entomológica Argentina Publicador: Revista de la Sociedad Entomológica Argentina
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2011 Português
Relevância na Pesquisa
35.96%
Drosophila melanogaster Meigen 1830 (Diptera: Drosophilidae) is the quintessential insect model organism. However, with a few exceptions, ecological features of this species have been poorly investigated. In the present work we describe a behavioural assay to quantify olfactory behaviour of D. melanogaster larvae in response to complex olfactory stimuli that are present in the natural environments, i. e.: rotten fruits that act as hosts in nature. Results obtained using this assay reveal that there is intra-population genetic variation and phenotypic plasticity for the character in a natural population from west-central Argentina.