1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

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21 Slide Ecology and Social ChemicalsCHEMICALS AND ECOLOGY: MULTITROPHIC PREDATORPREY INTERACTIONS MEDIATED BY CHEMISTRYFerrer R.P. 1 , Zimmer R. 1 1 Ecology and Evolutionary Biology,University of California, Los Angeles, CADuring development, sensory systems undergo changes in cellreceptor machinery. Such modifications may alter the way an animalperceives its olfactory environment. Here we investigate a cannibalisticinteraction between two discrete life history stages of the Californianewt (Taricha torosa). The defense compound tetrodotoxin (TTX), inadult newt skin is recognized by conspecific larvae as an avoidancesignal. Yet, antipredator behavior is suppressed when TTX is mixedwith odors from alternative adult prey. In laboratory assays, newt larvaewere exposed to TTX alone, or in binary mixtures with test compoundsisolated from invertebrate prey tissues. The larval escape response toTTX (0.1 µM) was significantly reduced when Arg (0.1 to 0.01 µM)was added. Free-ranging adult newts were exposed to components ofprey tissue extracts in the field. Arg was the most attractive compoundtested, evoking plume-tracking behavior at concentrations as low as 10nM. A comparable array of Arg analogs and TTX/Arg analog mixtureswas tested on adults and larvae, respectively. Adult responses wereeliminated by even slight alterations to Arg, such as the addition of asingle carbon to the side chain or esterification of the α-carboxyl group.In contrast, larval responses to TTX were inhibited by Arg as well as byanalogs with the guanidinium group. Thus, adults were more narrowlytuned than larvae to Arg analogs. These results show that Arg hasopposing effects (inhibitory/stimulatory) on larval/adult newts, andapparently acts on different suites of olfactory receptors for individualsof the two, distinct, life history stages.22 Slide Ecology and Social ChemicalsENANTIOMERIC PHEROMONE BLENDS IN MAMMALS:ASIAN ELEPHANTS AND BARK BEETLES SHARE CHIRALCHEMISTRYGreenwood D. 1 , Rasmussen L. 2 1 School of Biological Sciences,University of Auckland, Auckland, New Zealand; 2 Environmental &Biomolecular Systems (EBS), Oregon Health & Science University,Portland, ORFrontalin (1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane) a bicyclicketal of terpene origin can exist in two chiral or mirror image forms.Our recent finding that both enantiomeric forms of frontalin are presentin the temporal gland secretions of male Asian elephants during musth(Greenwood et al., Nature 438:1097-8, 2005) mirrors that seen in anumber of bark beetle species. Moreover changes in the ratio of the twoforms has implications for chemical signalling in both diverse phyleticgroups as important behavioral consequences are dependent on this. Ourresults suggest that stereochemical control of the enantiomeric ratioimplemented during biosynthesis involving a putative dihydroxylationstep provides modulation of the pheromonal message. This modulationis likely translated into a differential message at the level of pheromonereception based on the inherent chiral selectivity of receptor proteins.Supported by ISAT.23 Slide Ecology and Social ChemicalsBEHAVIORAL EVIDENCE THAT GOLDFISH DISCERNMOSAICS OF PHEROMONAL ODORANTS THAT INCLUDEBOTH SEX HORMONE DERIVATIVES AND BILE ACIDSSorensen P.W. 1 , Fine F. 2 , Murphy C. 2 , Bjerselius R. 2 , Kihslinger R. 31 University of Minnesota, St. Paul, MN; 2 Fisheries, Wildlife, andConservation Biology, University of Minnesota, St. Paul, MN;3 Neurobiology, Physiology and Behavior, University of California,Davis, Davis, CAAlthough behavioral studies have established that many species ofteleost fish employ species-specific pheromonal odors to mediatereproduction, all cues identified to date are common hormonal productsincapable of imparting species-specific information. A possibleexplanation for this phenomenon is that fish discern mixtures or`mosaics´ of odorants which include compounds such as bile acids(taxon-specific steroids released via the fish gut). Here, we tested thispossibility for the goldfish. Examining bile acid release, we found thatwhile most fish release similar suites of bile acids, their ratios differ.Thus, goldfish release mostly cyprinol sulfate (a bile acid specific tominnows), trout release mostly taurocholic acid, and gouramis releasemostly cholic acid (see Thwaits et al., this conference). Examining theolfactory sensitivity and specificity of the goldfish olfactory system toseveral dozen bile acids using EOG recording, we next found thatcyprinol sulfate is especially potent with a detection threshold of 10-11M. Cross-adaptation studies found sensitivity to be highly specific.Finally, we found that behavioral responses of male goldfish to 15 ketoprostaglandinF2a (a pheromonal cue released by female goldfish) wasstrongly suppressed by the addition of bile acids only released by otherspecies. In conclusion, odor mixtures seem important to naturalpheromone function in fish. (NSF 9723798).24 Slide Ecology and Social ChemicalsPHEROMONAL RECOGNITION MEMORY INDUCED BYTRPC2-INDEPENDENT VOMERONASAL SENSINGKelliher K.R. 1 , Spehr M. 1 , Li X. 1 , Zufall F. 1 , Leinders-Zufall T. 11 Anatomy and Neurobiology, University of Maryland at Baltimore,Baltimore, MDOne of the best known examples of olfactory imprinting in adultvertebrates is the selective pregnancy block (or Bruce effect) in themouse, which depends on the formation and maintenance of apheromonal recognition memory by the vomeronasal system. Peptideligands of major histocompatibility complex (MHC) molecules are thefirst identified vomeronasal stimuli that can mediate the Bruce effect,but the molecular mechanisms underlying this effect remain to beexplored. The cation channel gene TRPC2 plays a critical role in thesignal transduction mechanism of vomeronasal sensory neurons (VSNs)and TRPC2 -/- mice constitute an important genetic model forinvestigating the role of the vomeronasal organ (VNO) in mammalianpheromonal sensing. By using mice with a homozygous deficiency inTRPC2, we tested whether TRPC2 is essential for a pheromonalrecognition memory. Surprisingly, the loss of the TRPC2 channel genedoes not significantly influence the establishment of this memory,whereas, surgical lesions of the VNO do. Furthermore, field potentialand single cell patch-clamp recordings show that TRPC2 is dispensablefor the transduction of MHC peptide ligands by sensory neurons in thebasal zone of the VNO. This indicates that a previously unrecognizedTRPC2-independent signal transduction mechanism in the VNOunderlies the formation of this pheromonal recognition memory.Supported by grants from NIH/NIDCD (to K.R.K, F.Z., and T.L.-Z.)and the Emmy Noether Program of the DeutscheForschungsgemeinschaft (to M.S.).6
25 Symposium Impact of Odorant Metabolism on ScentPerceptionODORANT/PHEROMONE METABOLISM IN INSECTSVogt R. 1 1 Biological Sciences, University of South Carolina, Columbia,SCSignal termination plays a critical role in all chemically mediatedbiological processes, and this is no less so in odor detection. Theprocess of insect pheromone degradation has been studied for someyears, at least as far back as Kasang (1971) in Bombyx mori andFerkovich et al., (1973) in Trichoplusia ni. Since then, a few pheromoneand odor degrading enzymes (ODEs) have been identified andcharacterized in detail and the general principal of odor degradation hasbecome well established. One reason to expand efforts studying ODEsis their potential in insect control. If it is true that pheromones and odorsin general are perceived as precise mixtures, then the targeted inhibitionof the ODE for a specific component should alter the blend ratio withina sensillum resulting in misperception of the odor. Of the three proteinclasses with which odors interact (ORs, OBPs and ODEs), ODEs maybe the least specific and thus the more generally targetable protein forbehavioral inhibition. ODEs characterized include extracellular solubleenzymes localized in the compartmentalized fluid that surrounds theolfactory neurons, enzymes associating with the neuron or support cellmembranes, cytosolic enzymes which may serve the dual purpose ofinactivating xenobiotics, and body surface enzymes insuring thatadsorbed odors do not desorb and become false signals. Enzymes maybe sex specific suggesting roles targeting pheromones; others may besex indifferent suggesting broader roles. Individual species may havemultiple but parallel metabolic pathways. The complexity and diversityof odor degrading processes suggests strong evolutionary selectiontowards noise reduction (rapid removal of accumulated odor signal).Support has been gratefully received from NIH, NSF and USDA.26 Symposium Impact of Odorant Metabolism on ScentPerceptionMAMMALIAN NASAL P450 ENZYMES AND ODORANTMETABOLISMDing X. 1 1 Wadsworth Center, NYSDOH, Albany, NYThe role of mammalian nasal biotransformation enzymes, such as thefamily of cytochrome P450 (P450) monooxygenases, in olfactorychemoreception has been a subject of much speculation. Nasalmetabolism may influence the levels of odorants in the olfactoryreceptor environment, activate non-odorants to odorants, convertodorants to non-odorants, or change an odorant to a ligand for adiffering odorant receptor. Earlier studies have concentrated on theidentification and pharmacological characterization of the numerousP450s, as well as other biotransformation enzymes, expressed in theolfactory mucosa. These studies, fueled by findings of tissue-specific,abundant, and relatively early developmental expression of select P450genes, demonstrated the in vitro activity of the olfactory mucosa totransform inhaled chemicals to metabolites that potentially differ fromthe parent compounds in olfactory potency and odor quality. However,in vivo evidence for a chemosensory function of the nasal P450s hasbeen difficult to obtain. Recently, my laboratory has been developingknockout mouse models that can be used to demonstrate the roles ofnasal P450 enzymes in odorant metabolism and odor detection. Thesemice have either a germ-line deletion of one or more P450 genes thatare abundantly expressed in the nose, such as the olfactory mucosaspecificCyp2g1, or a very low expression of the cytochrome P450reductase (CPR), which is required for the function of all microsomalP450 enzymes. The unique features of these mouse models, andpotential confounding factors for application to odorant metabolism andchemosensory studies, will be discussed (Supported in part by NIHgrants DC05487 and ES07462).27 Symposium Impact of Odorant Metabolism on ScentPerceptionODORANT METABOLISM IN THE HUMAN NOSESchilling B. 1 1 Givaudan Schweiz AG - Fragrance Research,Duebendorf, Zurich, SwitzerlandThe initial events taking place in odor recognition have been studiedextensively in recent years primarily at the olfactory receptor andolfactory bulb level. Much less attention has been paid to peri-receptorevents that may influence the responsiveness of receptors to olfactorystimuli. Occurrence of enzymatic reactions in nasal tissue has beendescribed for rodents in connection with xenobiotic metabolism andtoxicity. A human P450 enzyme (CYP2A13) that is predominantlyexpressed in nasal tissue has been characterized, and additionalbiotransformation enzyme genes that are expressed in human olfactoryepithelium have been described (Su et al., 2000; Zhang et al., 2005).Several studies were conducted to address the question whether or notsuch metabolism is changing the odorant quality and if such perireceptorevents are increasing the chemical variability of potentialreceptor ligands in the nose. In-vitro enzymatic studies were used toidentify substrates and inhibitors of nasal P450 enzymes which exhibitbroad substrate specificity. In-vivo studies were designed to monitormetabolite formation in real time by detecting metabolites in exhaled airusing mass spectrometry (APCI-MS). Ultimately, sensory tests usingsubstrates and inhibitors of P450 enzymes showed that enzymaticmetabolism can influence the quality of a provided odorant. The latterstudies also showed that there seems to be variability in the extent ofmetabolism among individuals. The results indicate that in-nosebiotransformation of odorants can modify the quality and quantity ofcompounds reaching the olfactory mucosa, and those events may haveto be taken into consideration when interpreting SAR, SOR and OBimagingresults.28 Symposium Impact of Odorant Metabolism on ScentPerceptionFLAVOR METABOLISM IN THE ORAL CAVITYBuettner A. 1 1 German Research Center for Food Chemistry, Garching,GermanyProlonged retronasal aroma perception, called aftertaste or better"aftersmell," is relevant for food consumption, but also for medical orcosmetic purposes, such as usage of mouthwashes or toothpastes. Also,undesired aftersmell impressions as from cigarettes or onions are part ofthis phenomenon. Various factors influence the dwell time of odorantswithin the oral cavity. This study highlights the influence of odorantadsorption to oral mucosa, and that of odorant degradation by saliva. Itwas shown that odorants can be effectively metabolized, depending onthe odorant concentrations and the food composition. The turn-overrates were highly dependent on the chemical structures of the odorants,with significant differences in metabolization for diverse substanceclasses, e.g. esters, thiols, aldehydes, etc. These results were correlatedwith sensory experiments, as well as with quantitations by means ofSOOM (Spit-Off Odorant Measurement)- and BOSS (Buccal OdorScreening System) techniques [1,2]. Both methodologies monitor tracekey odorant adsorption to oral mucosa and subsequent release under invivo conditions. Using this analytical concept, salivary odorantmetabolization together with adsorption to mucosal tissue were found toplay a decisive role in aftersmell. This work was financed by theDeutsche Forschungsgemeinschaft , the Deutsche Forschungsanstaltfuer Lebensmittelchemie and the Hochschulwissenschaftsprogramm II.I thank Prof. P. Schieberle for his support. 1) Buettner, A., Schieberle,P. (2000) In: Flavor release (Roberts, D.D.; Taylor, A.J.; eds), ACSSymp. Ser. 763, 87-98. 2) Buettner, A., Welle, F. (2004). Flavour Fragr.J. 19, 505-514.7
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