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Search Results: 1 - 10 of 229068 matches for " Joseph C. Dickens "
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Field response of Colorado potato beetle to enantiomeric blends of CPB I aggregation pheromone  [PDF]
Thomas P. Kuhar, Erin M. Hitchner, Roger R. Youngman, Kenji Mori, Joseph C. Dickens
Agricultural Sciences (AS) , 2012, DOI: 10.4236/as.2012.37108
Abstract: Colorado potato beetle, Leptinotarsa decemlineata, is attracted to (S)-3,7-dimethyl-2-oxo-oct-6-ene-1,3-diol [(S)-CPB I], a male-produced aggregation pheromone. Pitfall trap studies were conducted to assess the relative attraction of L. decemlineata adults to synthetic mixtures of the (S)- and (R)-enantiomers of the pheromone. Of the following blends that were tested: 97%(S):3%(R), 87%(S):13%(R), 73%(S):27%(R), and 50%(S):50%(R) (racemic blend), only the blend containing 97% of the (S)-enantionmer was attractive in one of the experiments. Our results demonstrate that the behavioral response of the beetle to pheromone-baited pitfall traps is unsubstantial in general, and that enantiomeric blends containing 13% or more of the opposite (R) enantiomer disrupt response to the pheromone. Any future research as well as integrated pest management strategies that incorporate CPB I as an aggregation pheromone should utilize blends containing more than 87% optical purity of the (S)-enantiomer of the pheromone.
Insect Repellents: Modulators of Mosquito Odorant Receptor Activity
Jonathan D. Bohbot,Joseph C. Dickens
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0012138
Abstract: DEET, 2-undecanone (2-U), IR3535 and Picaridin are widely used as insect repellents to prevent interactions between humans and many arthropods including mosquitoes. Their molecular action has only recently been studied, yielding seemingly contradictory theories including odorant-dependent inhibitory and odorant-independent excitatory activities on insect olfactory sensory neurons (OSNs) and odorant receptor proteins (ORs).
Characterization of an Enantioselective Odorant Receptor in the Yellow Fever Mosquito Aedes aegypti
Jonathan D. Bohbot, Joseph C. Dickens
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0007032
Abstract: Enantiomers differ only in the left or right handedness (chirality) of their orientations and exhibit identical chemical and physical properties. In chemical communication systems, enantiomers can be differentially active at the physiological and behavioral levels. Only recently were enantioselective odorant receptors demonstrated in mammals while their existence in insects has remained hypothetical. Using the two-microelectrode voltage clamp of Xenopus oocytes, we show that the yellow fever mosquito, Aedes aegypti, odorant receptor 8 (AaOR8) acts as a chiral selective receptor for the (R)-(—)-enantiomer of 1-octen-3-ol, which in the presence of other kairomones is an attractant used by blood-sucking insects to locate their hosts. In addition to steric constraints, chain length and degree of unsaturation play important roles in this recognition process. This is the first characterization of an enantioselective odorant receptor in insects and the results demonstrate that an OR alone, without helper proteins, can account for chiral specificity exhibited by olfactory sensory neurons (OSNs).
Functional Characterization of the Octenol Receptor Neuron on the Maxillary Palps of the Yellow Fever Mosquito, Aedes aegypti
Alan J. Grant,Joseph C. Dickens
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0021785
Abstract: 1-Octen-3-ol (octenol) is a common attractant released by vertebrates which in combination with carbon dioxide (CO2) attracts hematophagous arthropods including mosquitoes. A receptor neuron contained within basiconic sensilla on the maxillary palps of adult mosquitoes responds selectively to 1-octen-3-ol. Recently, an odorant receptor (AaegOR8) known to occur on the maxillary palps was expressed in a heterologous system and demonstrated to be selectively sensitive to (R)-(?)-1-octen-3-ol, one of two enantiomeric forms. Lesser responses were elicited by stimulation with the (S)-enantiomer and various structural analogs.
Selectivity of odorant receptors in insects
Jonathan D. Bohbot,Joseph C. Dickens
Frontiers in Cellular Neuroscience , 2012, DOI: 10.3389/fncel.2012.00029
Abstract: Insect olfactory receptors (ORs) detect chemicals, shape neuronal physiology, and regulate behavior. Although ORs have been categorized as “generalists” and “specialists” based on their ligand spectrum, both electrophysiological studies and recent pharmacological investigations show that ORs specifically recognize non-pheromonal compounds, and that our understanding of odorant-selectivity mirrors our knowledge of insect chemical ecology. As we are progressively becoming aware that ORs are activated through a variety of mechanisms, the molecular basis of odorant-selectivity and the corollary notion of broad-tuning need to be re-examined from a pharmacological and evolutionary perspective.
Multimodal Stimulation of Colorado Potato Beetle Reveals Modulation of Pheromone Response by Yellow Light
Fernando Otálora-Luna,Joseph C. Dickens
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0020990
Abstract: Orientation of insects to host plants and conspecifics is the result of detection and integration of chemical and physical cues present in the environment. Sensory organs have evolved to be sensitive to important signals, providing neural input for higher order multimodal processing and behavioral output. Here we report experiments to determine decisions made by Colorado potato beetle (CPB), Leptinotarsa decemlineata, in response to isolated stimuli and multimodal combinations of signals on a locomotion compensator. Our results show that in complete darkness and in the absence of other stimuli, pheromonal stimulation increases attraction behavior of CPB as measured in oriented displacement and walking speed. However, orientation to the pheromone is abolished when presented with the alternative stimulation of a low intensity yellow light in a dark environment. The ability of the pheromone to stimulate these diurnal beetles in the dark in the absence of other stimuli is an unexpected but interesting observation. The predominance of the phototactic response over that to pheromone when low intensity lights were offered as choices seems to confirm the diurnal nature of the insect. The biological significance of the response to pheromone in the dark is unclear. The phototactic response will play a key role in elucidating multimodal stimulation in the host-finding process of CPB, and perhaps other insects. Such information might be exploited in the design of applications to attract and trap CPB for survey or control purposes and other insect pests using similar orientation mechanisms.
Neurophysiological and Behavioral Responses of Gypsy Moth Larvae to Insect Repellents: DEET, IR3535, and Picaridin
Jillian L. Sanford, Sharon A. Barski, Christina M. Seen, Joseph C. Dickens, Vonnie D. C. Shields
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0099924
Abstract: The interactions between insect repellents and the olfactory system have been widely studied, however relatively little is known about the effects of repellents on the gustatory system of insects. In this study, we show that the gustatory receptor neuron (GRN) located in the medial styloconic sensilla on the maxillary palps of gypsy moth larvae, and known to be sensitive to feeding deterrents, also responds to the insect repellents DEET, IR3535, and picaridin. These repellents did not elicit responses in the lateral styloconic sensilla. Moreover, behavioral studies demonstrated that each repellent deterred feeding. This is the first study to show perception of insect repellents by the gustatory system of a lepidopteran larva and suggests that detection of a range of bitter or aversive compounds may be a broadly conserved feature among insects.
Chemical Ecology of the Colorado Potato Beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), and Potential for Alternative Control Methods
Ludovic Sablon,Joseph C. Dickens,éric Haubruge,Fran?ois J. Verheggen
Insects , 2013, DOI: 10.3390/insects4010031
Abstract: The Colorado potato beetle (CPB) has been a major insect pest to potato farming for over 150 years and various control methods have been established to reduce its impact on potato fields. Crop rotation and pesticide use are currently the most widely used approaches, although alternative methods are being developed. Here we review the role of various volatile and nonvolatile chemicals involved in behavior changes of CPB that may have potential for their control. First, we describe all volatile and nonvolatile chemicals involved in host plant localization and acceptance by CPB beetles, including glycoalcaloids and host plant volatiles used as kairomones. In the second section, we present the chemical signals used by CPB in intraspecific communication, including sex and aggregation pheromones. Some of these chemicals are used by natural enemies of CPBs to locate their prey and are presented in the third section. The last section of this review is devoted a discussion of the potential of some natural chemicals in biological control of CPB and to approaches that already reached efficient field applications.
Olfactory Cues Are Subordinate to Visual Stimuli in a Neotropical Generalist Weevil
Fernando Otálora-Luna, Stephen L. Lapointe, Joseph C. Dickens
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0053120
Abstract: The tropical root weevil Diaprepes abbreviatus is a major pest of multiple crops in the Caribbean Islands and has become a serious constraint to citrus production in the United States. Recent work has identified host and conspecific volatiles that mediate host- and mate-finding by D. abbreviatus. The interaction of light, color, and odors has not been studied in this species. The responses of male and female D. abbreviatus to narrow bandwidths of visible light emitted by LEDs offered alone and in combination with olfactory stimuli were studied in a specially-designed multiple choice arena combined with a locomotion compensator. Weevils were more attracted to wavelengths close to green and yellow compared with blue or ultraviolet, but preferred red and darkness over green. Additionally, dim green light was preferred over brighter green. Adult weevils were also attracted to the odor of its citrus host + conspecifics. However, the attractiveness of citrus + conspecific odors disappeared in the presence of a green light. Photic stimulation induced males but not females to increase their speed. In the presence of light emitted by LEDs, turning speed decreased and path straightness increased, indicating that weevils tended to walk less tortuously. Diaprepes abbreviatus showed a hierarchy between chemo- and photo-taxis in the series of experiments presented herein, where the presence of the green light abolished upwind anemotaxis elicited by the pheromone + host plant odor. Insight into the strong responses to visual stimuli of chemically stimulated insects may be provided when the amount of information supplied by vision and olfaction is compared, as the information transmission capacity of compound eyes is estimated to be several orders of magnitude higher compared with the olfactory system. Subordination of olfactory responses by photic stimuli should be considered in the design of strategies aimed at management of such insects.
Enriching Stakeholder Theory: Student Identity of Higher Education  [PDF]
Joseph W. C. Lau
American Journal of Industrial and Business Management (AJIBM) , 2014, DOI: 10.4236/ajibm.2014.412082
Abstract: While students commonly assume the identity of being key stakeholders of higher education, the present article explores the possible complications stemmed from such key identity. Stakeholder theory has its strengths attributed by its conceptual breath and versatility; the limits of the theory arise for the same merit. Making reference to the theory with no restrains leads reasonably to the conclusion that the educational institute is unwilling to take measure closely to the long term effect, tangible or intangible, of such approach. Providing multiple perspectives on the identity of students are observed, an enrichment of stakeholder theory catering student identity is necessary.
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