Papers by John G Hildebrand
Although they arise from lines of evolution that diverged hundreds of millions of years ago, inse... more Although they arise from lines of evolution that diverged hundreds of millions of years ago, insects and vertebrates possess differentiated olfactory systems that exhibit similarities far more striking than their differences [1]. In both groups of animals, olfactory receptor cells (ORCs), which arise and reside in an epithelium and have receptor dendrites exposed to the environment, transduce qualitative, quantitative, and temporal information about chemical stimuli into patterns of action potentials across the population of ORCs. The information encoded in those impulses is transmitted along the axons of the ORCs to the first synaptic way-station of the olfactory system in the brain, the vertebrate olfactory bulb (OB) or the insect antennal lobe (AL).
Frontiers in neuroscience, Sep 26, 2001
Journal of Experimental Biology, 1995
ABSTRACTThe modulatory effects of 5-hydroxytryptamine (5-HT or serotonin) on voltage-gated curren... more ABSTRACTThe modulatory effects of 5-hydroxytryptamine (5-HT or serotonin) on voltage-gated currents in central olfactory neurones of the moth Manduca sexta have been examined in vitro using whole-cell patch-clamp recording techniques. Central olfactory neurones were dissociated from the antennal lobes of animals at stage 5 of the 18 stages of metamorphic adult development. The modulatory actions of 5-HT on voltage-activated ionic currents were examined in a subset of morphologically identifiable antennal lobe neurones maintained for 2 weeks in primary cell culture. 5-HT caused reversible reduction of both a rapidly activating A-type K+ current and a relatively slowly activating K+ current resembling a delayed rectifier-type conductance. 5-HT also reduced the magnitude of voltage-activated Ca2+ influx in these cells. The functional significance of 5-HT-modulation of central neurones is discussed.
Zeitschrift für Naturforschung C, 1979
The first sex pheromone of a Sphinx moth has been isolated from Manduca sexta (Lepidoptera: Sphin... more The first sex pheromone of a Sphinx moth has been isolated from Manduca sexta (Lepidoptera: Sphingidae) with the aid of an electroantennogram assay. It is attractive to males in a field test where its activity might be augmented by a second component in female extracts. Chemical tests and chromatographic properties identify the pheromone as a C16-aldehyde with a pair of conjugated double bonds. (E , Z)-0,12-hexadecadienal, (“bombykal”) was identical with the natural product. The comparison includes chromatography on three different capillary columns and determination of specific activities in the electroantennogram test.
The Journal of Neuroscience, 1990
To facilitate studies of the development and membrane biophysics of cells in the central olfactor... more To facilitate studies of the development and membrane biophysics of cells in the central olfactory pathway of the moth Manduca sexta, we have dissociated neurons and glial cells from the antennal lobes (ALs) and cultivated them in the controlled environment of tissue culture. Cultures produced from cells of the lateral group of AL neurons alone are enriched in local interneurons (LNs), while cultures made from cells of the median and anterior groups of AL neurons contain projection neurons (PNs) but lack LNs. Cultures containing only PNs, but not cultures with both PNs and LNs, require a conditioning factor derived from a conspecific cell line in order to ensure survival. Under these conditions, we identify 5 types of cells in the “PN-only” cultures that are consistently observed and distinguishable on the basis of their morphology and characteristic whole-cell current profiles. In cultures that contain both PNs and LNs, we find 3 additional types of cells with neuronlike appearance...
Handbook of Brain Microcircuits, 2017
Olfactory circuits of all animals face a common challenge of extracting meaningful odor cues from... more Olfactory circuits of all animals face a common challenge of extracting meaningful odor cues from background odors. This chapter summarizes what the authors have learned from their ongoing work toward the goal of understanding how the neural circuits in a moth’s antennal lobe (AL) determine diverse physiological responses that ultimately mediate the animal’s natural behavior. The text describes the different types of cellular elements that participate in the glomerular circuitry, focuses on the functional organization of these elements, and attempts to explain observed physiological responses in the context of behavior using the understood operating principles of the AL circuits. For convenience, the connections from the perspective of the main output neurons of the circuitry, uniglomerular projection neurons (uPNs), are described.
Acta biologica Hungarica, 1992
The antennal lobe (AL) of the sphinx month Manduca sexta is characterized by a typically glomerul... more The antennal lobe (AL) of the sphinx month Manduca sexta is characterized by a typically glomerular neuropil and two principal classes to neurons local interneurons and projection neurons. The somata of these neurons reside in defined neural cell-body groups in the AL, and the neurons exhibit characteristic patterns of innervation of the glomeruli. Evidence gathered to date indicates that individual antennal olfactory receptor-cell axons project to single glomeruli in the ipsilateral AL and make excitatory, apparently cholinergic synapses with neurites of AL neurons (usually local neurons) innervating the target glomeruli. Much has been learned about the physiology of the projection neurons, but only recently have the physiological properties and functions of the local interneurons been examined systematically through the use of intracellular recording and staining methods. Immunocytochemical studies have shown that most of the local interneurons contain GABA as well as one or more ...
Animal Behaviour, 2010
Studies of plantepollinator interactions have often documented species differences in preferences... more Studies of plantepollinator interactions have often documented species differences in preferences for floral advertisements and rewards. However, the contribution of intraspecific variation in behaviours, especially between sexes, remains less understood. We explored resource preference and resource use by male and female Manduca sexta hawkmoths, relative to two important nectar resources in southern Arizona, U.S.A. Manduca sexta is the major pollinator of one of these species (Datura wrightii, Solanaceae). Because females must also seek out D. wrightii as an oviposition resource, females were predicted to feed upon it more than would males, which should be free to choose the best nectar resource. Using naïve laboratory-reared moths in flight arena experiments, we found that both sexes preferred Datura wrightii over Agave palmeri (Agavaceae). Exposure to only one species and an odourless paper control, however, revealed sex-specific differences in foraging behaviour, with females feeding longer from A. palmeri and males feeding longer from D. wrightii, leading us to reject our hypothesis. Differences in feeding preferences directly translated into differences in energy intake. Females gained significantly more energy than did males by feeding from A. palmeri. We also examined whether behavioural preferences of moths in the laboratory translated into foraging behaviour in the field. Pollen load analysis of moths caught in 2004 showed that females carried significantly more A. palmeri pollen than did males, whereas males carried more D. wrightii pollen than did females. Whereas most studies examine pollination associations at the species level, our results highlight the potential importance of between-sex variation in floral visits. The Association for the Study of Animal Behaviour. Published by Elsevier Ltd.
Frontiers in Neuroscience, 2004
Physiological Entomology, 1990
Electroantennograms were recorded from the antennae of adult male and female corn earworms, Helio... more Electroantennograms were recorded from the antennae of adult male and female corn earworms, Heliothis zea (Boddie). A total of seventeen female moth sex pheromone components from several species were tested. Of these, two components elicited significantly greater responses than the other fifteen. These were (2)-11hexadecenal, a conspecific component, and (2)-9-tetradecenal, a component found in the pheromone blend of a sympatric species H. virescens (F.) that inhibits attraction of H.zea males. The results from dose-response and selective adaptation studies indicate that there are separate populations of receptors for these two chemical signals on the antenna of male H.zea. The more sensitive population is selective for (2)-11-hexadecenal, while the less sensitive one responds to (Z)-9tetradecenal. These findings provide a physiological basis by which H.zea males can distinguish the interspecific repellent from the conspecific pheromone blend. It is likely that this discrimination contributes to reproductive isolation between these two species.
Journal of Chemical Ecology, 2004
IEEE Transactions on Biomedical Engineering, 2010
We describe a flexible multisite microelectrode for insect flight biasing using neural stimulatio... more We describe a flexible multisite microelectrode for insect flight biasing using neural stimulation. The electrode is made of two layers of polyimide (PI) with gold sandwiched in between in a split-ring geometry. The split-ring design in conjunction with the flexibility of the PI allows for a simple insertion process and provides good attachment between the electrode and ventral nerve cord of the insect. Stimulation sites are located at the ends of protruding tips that are circularly distributed inside the split-ring structure. These protruding tips penetrate into the connective tissue surrounding the nerve cord. We have been able to insert the electrode into pupae of the giant sphinx moth Manduca sexta as early as seven days before the adult moth emerges, and we are able to use the multisite electrode to deliver electrical stimuli that evoke multidirectional, graded abdominal motions in both pupae and adult moths. Finally, in loosely tethered flight, we have used stimulation through the flexible microelectrodes to alter the abdominal angle, thus causing the flying moth to deviate to the left or right of its intended path.
Nature, 2001
This article focuses on the passage in the 8th epistolary letter in which Abelard focuses on sile... more This article focuses on the passage in the 8th epistolary letter in which Abelard focuses on silence as the essential rule for monastic life, for it reveals that it is not only a theological aspect, but to reflect on silence itself and the strange relation with language relates to us regardless of the era. This text is divided into two moments, the first one contextualizes the problem as well as Abelard´s thoughts and life; in the second one there is a hermeneutical analysis on the passage 259 D-262 A, the third guideline for Abelard´s spiritual direction to Eloise, in which he points out silence as a way to relate to God, at the same time, there is a distinction between the language that comes from the divine to that which comes from one.
The Journal of Neuroscience, 1983
During the metamorphosis of holometabolous insects, the larval nervous system is restructured to ... more During the metamorphosis of holometabolous insects, the larval nervous system is restructured to provide the circuitry needed by the developing adult. Prominent new centers in the brain, the antennal lobes, arise to receive olfactory afferent axons from the developing adult antennae and provide an excellent system in which to study the development of synapses in a central nervous system. We have examined the anatomy and physiology of developing synapses in the antennal lobes of the moth Manduca sexta during the 18 days of metamorphic adult development. On day 5, the neuropil of the newly emerging antennal lobe condenses into distinct glomeruli, in which intercellular junctional complexes have already begun to form. Although some junctions have associated synaptic vesicles, most complexes are desmosome-like until day 9, when the number of synaptic complexes begins to increase. Early synapses are characterized by membrane-associated densities in at least two abutting cellular processes and a small number of synaptic vesicles clustered near the membrane of one process. As adult development proceeds, the membrane-associated densities become denser and more extensive, and the number of synaptic vesicles in the clusters increases. At day 14 synapses appear ultrastructurally mature, and almost all junctions in the neuropil can be identified as synaptic. Not until day 9 do antennal lobe neurons begin to respond postsynaptically when the antennal nerve is stimulated electrically, suggesting that the earliest synapses observed in the electron microscope may not be made by antennal nerve axons. At first the postsynaptic responses are graded and fatigue rapidly. By day 11, the antennal lobe neurons respond with action potentials, but the fatigability does not decline to adult levels until day 13. Filling of antennal lobe neurons with cobalt reveals that the arborizations of both local interneurons and output neurons continue to mature morphologically until about day 13. Previous work (Schweitzer,
Journal of Comparative Physiology A, 1987
Responses of neurons in the antennal lobe (AL) of the moth Manduca sexta to stimulation of the ip... more Responses of neurons in the antennal lobe (AL) of the moth Manduca sexta to stimulation of the ipsilateral antenna by odors consist of excitatory and inhibitory synaptic potentials. Stimulation of primary afferent fibers by electrical shock of the antennal nerve causes a characteristic IPSP-EPSP synaptic response in AL projection neurons. The IPSP in projection neurons reverses below the resting potential, is sensitive to changes in external and internal chloride concentration, and thus is apparently mediated by an increase in chloride conductance. The IPSP is reversibly blocked by 100 microM picrotoxin or bicuculline. Many AL neurons respond to application of GABA with a strong hyperpolarization and an inhibition of spontaneous spiking activity. GABA responses are associated with an increase in neuronal input conductance and a reversal potential below the resting potential. Application of GABA blocks inhibitory synaptic inputs and reduces or blocks excitatory inputs. EPSPs can be protected from depression by application of GABA. Muscimol, a GABA analog that mimics GABA responses at GABAA receptors but not at GABAB receptors in the vertebrate CNS, inhibits many AL neurons in the moth.
Journal of Experimental Biology, 2010
SUMMARY The primary olfactory centres of the sphinx moth Manduca sexta, the antennal lobes, conta... more SUMMARY The primary olfactory centres of the sphinx moth Manduca sexta, the antennal lobes, contain a small number of sexually dimorphic glomeruli: the male-specific macroglomerular complex and the large female glomeruli. These glomeruli play important roles in sex-specific behaviours, such as the location of conspecific females and the selection of appropriate host plants for oviposition. The development of sexually dimorphic glomeruli depends strictly on the ingrowth of sex-specific olfactory receptor cell afferents. In the present study we tested the role of female-specific olfactory receptor cells (ORCs) in mediating female-specific host plant approach behaviour and in determining the response of downstream antennal lobe neurons. We generated male gynandromorphs by excising one imaginal disc from a male larva and replacing it with the antennal imaginal disc from a female donor. Most male gynandromorphs had an apparently normal female antenna and a feminised antennal lobe. These ...
Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology, Jan 11, 2017
The Asian longhorned beetle Anoplophora glabripennis (Motchulsky) is an exotic forest pest that h... more The Asian longhorned beetle Anoplophora glabripennis (Motchulsky) is an exotic forest pest that has repeatedly invaded North America and Europe from Asia, and has the potential to kill millions of trees and cause billions of dollars in damage. Traps baited with an attractive mixture of volatile organic compounds from hosts have been of limited success in monitoring invasion sites. We propose that lures might be improved through studying the olfactory system of adult beetles, especially the gene family of odorant receptors (ORs) and the structure of the antennal lobes of the brain. Here, we report identification of 132 ORs in the genome of A. glabripennis (inclusive of one Orco gene and 11 pseudogenes), some of which are orthologous to known pheromone receptors of other cerambycid beetles. We also identified three ORs that are strongly biased toward expression in the female transcriptome, and a single OR strongly biased toward males. Three-dimensional reconstruction of the antennal l...
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Papers by John G Hildebrand