Chemical Senses - recent issues

Thu, 15 Oct 2009 00:37:02 PDT

Cover

Thu, 15 Oct 2009 00:37:03 PDT

Editorial Board

Thu, 15 Oct 2009 00:37:03 PDT

Subscriptions

Thu, 15 Oct 2009 00:37:03 PDT

Articles Highlighted

Meyerhof, W. — Thu, 15 Oct 2009 00:37:03 PDT

Rating a New Hedonic Scale: A Commentary on "Derivation and Evaluation of a Labeled Hedonic Scale" by Lim, Wood and Green

Prescott, J. — Thu, 15 Oct 2009 00:37:03 PDT

Derivation and Evaluation of a Labeled Hedonic Scale

Lim, J., Wood, A., Green, B. G. — Thu, 15 Oct 2009 00:37:03 PDT

The objective of this study was to develop a semantically labeled hedonic scale (LHS) that would yield ratio-level data on the magnitude of liking/disliking of sensation equivalent to that produced by magnitude estimation (ME). The LHS was constructed by having 49 subjects who were trained in ME rate the semantic magnitudes of 10 common hedonic descriptors within a broad context of imagined hedonic experiences that included tastes and flavors. The resulting bipolar scale is statistically symmetrical around neutral and has a unique semantic structure. The LHS was evaluated quantitatively by comparing it with ME and the 9-point hedonic scale. The LHS yielded nearly identical ratings to those obtained using ME, which implies that its semantic labels are valid and that it produces ratio-level data equivalent to ME. Analyses of variance conducted on the hedonic ratings from the LHS and the 9-point scale gave similar results, but the LHS showed much greater resistance to ceiling effects and yielded normally distributed data, whereas the 9-point scale did not. These results indicate that the LHS has significant semantic, quantitative, and statistical advantages over the 9-point hedonic scale.

Psychometric Functions for Ternary Odor Mixtures and Their Unmixed Components

Miyazawa, T., Gallagher, M., Preti, G., Wise, P. M. — Thu, 15 Oct 2009 00:37:03 PDT

People are often able to reliably detect a mixture of 2 or more odorants, even if they cannot reliably detect the individual mixture components when presented individually. This phenomenon has been called mixture agonism. However, for some mixtures, agonism among mixture components is greater in barely detectable mixtures than in more easily detectable mixtures (level dependence). Most studies that have used rigorous methods have focused on simple, 2-component (binary) mixtures. The current work takes the next logical step to study detection of 3-component (ternary) mixtures. Psychometric functions were measured for 5 unmixed compounds and for 3 ternary mixtures of these compounds (2 of 5, forced-choice method). Experimenters used air dilution olfactometry to precisely control the duration and concentration of stimuli and used gas chromatography/mass spectrometry to verify vapor-phase concentrations. For 2 of the 3 mixtures, agonism was approximately additive in general agreement with similar work on binary mixtures. A third mixture was no more detectable than the most detectable component, demonstrating a lack of agonism. None of the 3 mixtures showed evidence of level dependence. Agonism may be common in ternary mixtures, but general rules of mixture interaction have yet to emerge. For now, detection of any mixture must be measured empirically.

Plant Terpenes Affect Intensity and Temporal Parameters of Pheromone Detection in a Moth

Party, V., Hanot, C., Said, I., Rochat, D., Renou, M. — Thu, 15 Oct 2009 00:37:03 PDT

In moths, the components of the female pheromone blend are detected in the male antennae by pheromone olfactory receptor neurons (Ph-ORNs) expressing narrowly tuned olfactory receptors. Responses to sex pheromones have generally been thought to be independent from the odorant background. However, interactions between pheromone components and plant volatiles have been reported at behavioral and detection levels. To document the mechanisms of such interactions, we analyzed Ph-ORN responses of Spodoptera littoralis to the main pheromone component, Z9E11-14:Ac, in the presence of 4 monoterpenes. To mimic natural contexts in which plant odors and pheromone emanate from different sources, the 2 stimuli were presented with different temporal patterns and from independent sources. Linalool reversibly reduced the firing response to Z9E11-14:Ac and produced an off effect. Geraniol and geranyl and linalyl acetates reduced the responses to Z9E11-14:Ac with a longer time course. Pulses of linalool over prolonged pheromone stimulation resulted in a discontinuous firing activity. Pulses of pheromone were better separated over a background of linalool, compared with odorless air. The data confirm that plant compounds may modulate the intensity and the temporal coding by Ph-ORNs of pheromone information. This modulation might positively affect mate location at high pheromone density especially nearby a pheromone source.

Prenatal Flavor Exposure Affects Flavor Recognition and Stress-Related Behavior of Piglets

Oostindjer, M., Bolhuis, J. E., van den Brand, H., Kemp, B. — Thu, 15 Oct 2009 00:37:03 PDT

Exposure to flavors in the amniotic fluid and mother's milk derived from the maternal diet has been shown to modulate food preferences and neophobia of young animals of several species. Aim of the experiment was to study the effects of pre- and postnatal flavor exposure on behavior of piglets during (re)exposure to this flavor. Furthermore, we investigated whether varying stress levels, caused by different test settings, affected behavior of animals during (re)exposure. Piglets were exposed to anisic flavor through the maternal diet during late gestation and/or during lactation or never. Piglets that were prenatally exposed to the flavor through the maternal diet behaved differently compared with unexposed pigs during reexposure to the flavor in several tests, suggesting recognition of the flavor. The differences between groups were more pronounced in tests with relatively high stress levels. This suggests that stress levels, caused by the design of the test, can affect the behavior shown in the presence of the flavor. We conclude that prenatal flavor exposure affects behaviors of piglets that are indicative of recognition and that these behaviors are influenced by stress levels during (re)exposure.

Double P2X2/P2X3 Purinergic Receptor Knockout Mice Do Not Taste NaCl or the Artificial Sweetener SC45647

Thu, 15 Oct 2009 00:37:03 PDT

The P2X ionotropic purinergic receptors, P2X2 and P2X3, are essential for transmission of taste information from taste buds to the gustatory nerves. Mice lacking both P2X2 and P2X3 purinergic receptors (P2X2/P2X3^Dbl–/–) exhibit no taste-evoked activity in the chorda tympani and glossopharyngeal nerves when stimulated with taste stimuli from any of the 5 classical taste quality groups (salt, sweet, sour, bitter, and umami) nor do the mice show taste preferences for sweet or umami, or avoidance of bitter substances (Finger et al. 2005. ATP signaling is crucial for communication from taste buds to gustatory nerves. Science. 310[5753]:1495–1499). Here, we compare the ability of P2X2/P2X3^Dbl–/– mice and P2X2/P2X3^Dbl+/+ wild-type (WT) mice to detect NaCl in brief-access tests and conditioned aversion paradigms. Brief-access testing with NaCl revealed that whereas WT mice decrease licking at 300 mM and above, the P2X2/P2X3^Dbl–/– mice do not show any change in lick rates. In conditioned aversion tests, P2X2/P2X3^Dbl–/– mice did not develop a learned aversion to NaCl or the artificial sweetener SC45647, both of which are easily avoided by conditioned WT mice. The inability of P2X2/P2X3^Dbl–/– mice to show avoidance of these taste stimuli was not due to an inability to learn the task because both WT and P2X2/P2X3^Dbl–/– mice learned to avoid a combination of SC45647 and amyl acetate (an odor cue). These data suggest that P2X2/P2X3^Dbl–/– mice are unable to respond to NaCl or SC45647 as taste stimuli, mirroring the lack of gustatory nerve responses to these substances.

Residual Chemosensory Capabilities in Double P2X2/P2X3 Purinergic Receptor Null Mice: Intraoral or Postingestive Detection?

Hallock, R. M., Tatangelo, M., Barrows, J., Finger, T. E. — Thu, 15 Oct 2009 00:37:03 PDT

Mice lacking the purinergic receptors, P2X2 and P2X3 (P2X2/P2X3^Dbl–/–), exhibit essentially no tastant-evoked activity in the chorda tympani and glossopharyngeal nerves and substantial loss of tastant-evoked behavior as measured in long-term intake experiments. To assess whether the residual chemically driven behaviors in these P2X2/P2X3^Dbl–/– mice were attributable to postingestive detection or oropharyngeal detection of the compounds, we used brief access lickometer tests to assess the behavioral capabilities of the P2X2/P2X3^Dbl–/– animals. The P2X2/P2X3^Dbl–/– mice showed avoidance to high levels (10 mM quinine and 10–30 mM denatonium benzoate) of classical "bitter"-tasting stimuli in 24-h, 2-bottle preference tests but minimal avoidance of these substances in the lickometer tests, suggesting that the strong avoidance in the intake tests was largely mediated by post-oral chemosensors. Similarly, increases in consumption of 1 M sucrose by P2X2/P2X3^Dbl–/– mice in long-term intake tests were not mirrored by increases in consumption of sucrose in lickometer tests, suggesting that sucrose detection in these mice is mediated by postingestive consequences. In contrast, in brief access tests, P2X2/P2X3^Dbl–/– mice avoided citric acid and hydrochloric acid at the same concentrations as their wild-type counterparts, indicating that these weak acids activate oropharyngeal chemoreceptors.

Taste Preference and Nerve Response to 5'-Inosine Monophosphate Are Enhanced by Glutathione in Mice

Yamamoto, T., Watanabe, U., Fujimoto, M., Sako, N. — Thu, 15 Oct 2009 00:37:03 PDT

Previous human sensory evaluation studies have shown that glutathione (GSH) enhances deliciousness, accompanied by thickness, mouthfulness, and continuity feeling, which is known as "kokumi" in Japanese, in an umami solution containing monosodium glutamate and 5'-inosine monophosphate (IMP). We conducted behavioral and electrophysiological experiments to explore possible interactions of taste effectiveness between GSH and umami substances in mice. The 2-bottle preference test revealed that the mice preferred GSH at concentrations ranging from 1 to 10 mM. When GSH was added to IMP or a mixture of IMP and monopotassium glutamate (MPG), the mice showed increased preference for these solutions over the individual IMP or the binary mixture of IMP and MPG in both short-term and long-term tests. The addition of GSH to MPG, however, did not increase preference. Neural responses of the chorda tympani and glossopharyngeal nerves to the mixture of IMP and GSH showed synergism, whereas synergism was not observed in the mixture of MPG and GSH in either taste nerve. Another behavioral study with the use of the conditioned taste aversion paradigm showed that aversions to MPG generalized moderately to GSH, but aversions to GSH did not generalize to MPG. The present study suggests that GSH enhances preference for umami solutions containing 5'-ribonucleotide rather than glutamate. On the basis of these results, we discuss possible receptors involved for the action of GSH.

Mexico City Air Pollution Adversely Affects Olfactory Function and Intranasal Trigeminal Sensitivity

Guarneros, M., Hummel, T., Martinez-Gomez, M., Hudson, R. — Thu, 15 Oct 2009 00:37:03 PDT

Surprisingly little is known about the effects of big-city air pollution on olfactory function and even less about its effects on the intranasal trigeminal system, which elicits sensations like burning, stinging, pungent, or fresh and contributes to the overall chemosensory experience. Using the Sniffin’ Sticks olfactory test battery and an established test for intranasal trigeminal perception, we compared the olfactory performance and trigeminal sensitivity of residents of Mexico City, a region with high air pollution, with the performance of a control population from the Mexican state of Tlaxcala, a geographically comparable but less polluted region. We compared the ability of 30 young adults from each location to detect a rose-like odor (2-phenyl ethanol), to discriminate between different odorants, and to identify several other common odorants. The control subjects from Tlaxcala detected 2-phenyl ethanol at significantly lower concentrations than the Mexico City subjects, they could discriminate between odorants significantly better, and they performed significantly better in the test of trigeminal sensitivity. We conclude that Mexico City air pollution impairs olfactory function and intranasal trigeminal sensitivity, even in otherwise healthy young adults.

Articles Highlighted

Meyerhof, W. — Wed, 16 Sep 2009 12:28:37 PDT

Impact of Novel Olfactory Stimuli at Supra and Subthreshold Concentrations on the Perceived Sweetness of Sucrose after Associative Learning

Labbe, D., Martin, N. — Wed, 16 Sep 2009 12:28:37 PDT

The impact of coexposure to a novel olfactory stimulation in combination with sweet taste on the construction of perceptual interaction was studied. The first objective was to explore whether a new flavoring perceived retronasally at a subthreshold concentration could enhance the perceived sweetness after a coexposure with sucrose using an approach encouraging associative learning. After validating the associative learning by showing an increase of the perceived sweetness by the flavoring at a suprathreshold concentration, we showed that the flavoring stimulation did not impact the perceived sweetness when presented at a subthreshold concentration. The second objective was to validate the absence of associative learning when subjects were exposed to the sucrose flavored solution in a context of coexposure akin to sensory profiling training. As expected, we confirmed that coexposure following sensory profiling training did not promote associative learning, probably because this approach encouraged subjects to consider the olfactory and sweet taste combination as a set of distinct qualities. The potential role of neural integration processes in these results was discussed.

Taste Coding after Selective Inhibition by Chlorhexidine

Wang, M.-F., Marks, L. E., Frank, M. E. — Wed, 16 Sep 2009 12:28:37 PDT

Coding of the complex tastes of ionic stimuli in humans was studied by combining taste confusion matrix (TCM) methodology and treatment with chlorhexidine gluconate. The TCM evaluates discrimination of multiple stimuli simultaneously. Chlorhexidine, a bis-biguanide antiseptic, reversibly inhibits salty taste and tastes of a subset of bitter stimuli, including quinine hydrochloride. Identifications of salty (NaCl, "salt"), bitter (quinine·HCl, "quinine"), sweet (sucrose, "sugar"), and sour (citric acid, "acid") prototypes, alone and as components of binary mixtures, were measured under 4 conditions. One was a water-rinse control and the others had the salt and quinine tastes progressively reduced by treatment with 1 mM chlorhexidine, 3 mM chlorhexidine, and ultimately to zero by elimination of NaCl and quinine·HCl. Treatment with chlorhexidine perturbed identification of salt more than quinine; both were thereafter more often confused with "water" and unidentified when mixed with sucrose or citric acid. All pairwise discriminations that depended on the tastes of NaCl and quinine·HCl deteriorated, and although H₂O was mistakenly identified as quinine after chlorhexidine, this may have been a decisional bias. Other confusions reflected "unprompted mixture analysis" and an obscuring of salt taste by a less-inhibited stronger quinine or sugar or acid tastes in mixtures. Partial inhibition of the tastes of NaCl and quinine·HCl by chlorhexidine was considered in the context of multiple receptors for the 2 compounds. Discrimination among prototypic stimuli with varying strengths was consistent with a gustatory system that evaluates a small number of independent tastes.

Seasonal Increase in Olfactory Receptor Neurons of the Japanese Toad, Bufo japonicus, is Paralleled by an Increase in Olfactory Sensitivity to Isoamyl Acetate

Nakazawa, H., Ichikawa, M., Nagai, T. — Wed, 16 Sep 2009 12:28:38 PDT

Japanese toads (Bufo japonicus) migrate to and from breeding sites in the early spring, possibly guided by olfactory cues. We previously showed that the electrical activity of olfactory receptor neurons (ORNs) in the toads was enhanced in the breeding period. We undertook morphological and physiological studies of the olfactory epithelium to determine whether any cellular substrate of the epithelium underlies the enhanced electrical activity of ORNs. The ORNs of the toads were labeled by antiserum to olfactory marker protein (OMP), and the morphology of the labeled cells and their distribution in the epithelium were examined throughout the year. The OMP-positive cells, distributed mainly in the basal and intermediate layers of the epithelium, were most numerous in the early breeding period. Cell proliferation in the epithelium detected by 5-bromo-2'-deoxyuridine labeling was most elevated in this period. The electrical activity of ORNs was examined by recording the electroolfactogram (EOG) in the toads throughout the year. Statistical analysis showed a positive correlation between the density of OMP-positive cells in the epithelium and the amplitude of the EOG responses. A greater number of ORNs in the breeding period possibly aids the toads in migrating to their breeding sites.

Design and Evaluation of New Analogs of the Sweet Protein Brazzein

Walters, D. E., Cragin, T., Jin, Z., Rumbley, J. N., Hellekant, G. — Wed, 16 Sep 2009 12:28:38 PDT

We have previously modeled the interaction of the sweet protein brazzein with the extracellular domains of the sweet taste receptor. Here, we describe the application of that model to the design of 12 new highly potent analogs of brazzein. Eight of the 12 analogs have higher sweetness potency than wild-type brazzein. Results are consistent with our brazzein–receptor interaction model. The model predicts binding of brazzein to the open form of T1R2 in the T1R2–T1R3 heterodimer.

Role of Olfaction in the Conditioned Sucrose Preference of Sweet-Ageusic T1R3 Knockout Mice

Zukerman, S., Touzani, K., Margolskee, R. F., Sclafani, A. — Wed, 16 Sep 2009 12:28:38 PDT

Prior work has shown that sweet taste–deficient T1R3 knockout (KO) mice developed significant sucrose preferences when given long-term sugar versus water tests. The current study investigated the role of olfaction in this experience-conditioned sucrose preference. T1R3 KO and C57BL/6 wild-type (WT) mice were given 24-h sugar versus water tests with ascending concentrations of sucrose (0.5–32%), after which the mice received olfactory bulbectomy (OBx) or sham surgery. When retested with sucrose, the Sham-KO mice preferred all sugar solutions to water, although their intake and preference were less than those of the Sham-WT mice. The OBx-KO mice, in contrast, showed no or weak preferences for dilute sucrose solutions (0.5–8%) although they strongly preferred concentrated sugar solutions (16–32%). OBx-WT mice displayed only a partial reduction in their sucrose preference. Although the OBx mice of both genotypes underconsumed dilute sucrose solutions relative to Sham mice, they overconsumed concentrated sucrose. These results indicate that olfaction plays a critical role in the conditioned preference of T1R3 KO mice for dilute sugar solutions. Further, the fact that OBx-KO mice preferred concentrated sucrose solutions in the absence of normal sweet taste and olfactory sensations underscores the potency of postoral nutritive signals in promoting ingestion.

Expression Patterns of Odorant Receptors and Response Properties of Olfactory Sensory Neurons in Aged Mice

Lee, A. C., Tian, H., Grosmaitre, X., Ma, M. — Wed, 16 Sep 2009 12:28:38 PDT

The sense of smell deteriorates in normal aging, but the underling mechanisms are still elusive. Here we investigated age-related alterations in expression patterns of odorant receptor (OR) genes and functional properties of olfactory sensory neurons (OSNs)—2 critical factors that define the odor detection threshold in the olfactory epithelium. Using in situ hybridization for 9 representative OR genes, we compared the cell densities of each OR in coronal nose sections at different ages (3–27 months). The cell density for different ORs peaked at different time points and a decline was observed for 6 of 9 ORs at advanced ages. Using patch clamp recordings, we then examined the odorant responses of individual OSNs coexpressing a defined OR (MOR23) and green fluorescent protein. The MOR23 neurons recorded from aged animals maintained a similar sensitivity and dynamic range in response to the cognate odorant (lyral) as those from younger mice. The results indicate that although the cell densities of OSNs expressing certain types of ORs decline at advanced ages, individual OSNs can retain their sensitivity. The implications of these findings in age-related olfactory deterioration are discussed.

High Test-Retest Reliability of the Extended Version of the "Sniffin' Sticks" Test

Wed, 16 Sep 2009 12:28:38 PDT

The "Sniffin’ Sticks" test kit is a validated and commonly used tool for assessment of olfactory function in subjects with normal sense of smell and in individuals with smell loss. That test incorporates subtests for odor threshold, discrimination, and identification. To gain higher subtest reproducibility, tests on odor discrimination and odor identification were extended using 32 instead of the usually applied 16 single trials each. In developing the extended Sniffin’ Sticks test, a number of preliminary experiments were performed in 46 healthy, normosmic individuals 1) to evaluate intensity and familiarity of the additionally selected odors, 2) to select distractors for the discrimination and identification test, and 3) to evaluate the test–retest reliability of each subtest. Furthermore, the extended test was applied to 126 patients with olfactory loss and 71 normosmic individuals. Follow-up investigation could be performed in 69 controls within an average interval of 4 days. Results revealed significant differences between patients and healthy subjects. Estimated intensity and familiarity of the newly selected 16 items of the discrimination test did not differ significantly from the 16 standard items. Test–retest reliability was found to be r = 0.80 (odor discrimination), r = 0.88 (odor identification), and r = 0.92 (odor threshold). In conclusion, the extended test kit allows a precise evaluation of olfactory function, especially when different olfactory tasks are assessed using individual subtests. Furthermore, the high test–retest reliability of both the 16 and the 32-item tests allows the evaluation of even relatively small changes of olfactory function over time by means of either test.

Profiles of Volatiles in Male Rat Urine: The Effect of Puberty on the Female Attraction

Osada, K., Kashiwayanagi, M., Izumi, H. — Wed, 16 Sep 2009 12:28:38 PDT

Rat urine contains many volatile constituents that may be used for chemical communication. The levels of certain urinary volatiles are strongly dependent on the sex and endocrine status (e.g., puberty). We performed chemical and behavioral studies to identify the volatiles in adult male rat urine that attract mature females. Our results demonstrated that adult male rats have higher levels of 2-heptanone (2-HP), 4-methylphenol (4-MP), and 4-ethylphenol (4-EP) than prepubescent male rats; furthermore, female rats are more attracted to the odor of adult male rat urine than that of prepubescent males. When prepubescent rat urine was supplemented with 2-HP, 4-MP, and 4-EP to the levels found in adult male urine, the attractiveness of the urine to females was markedly enhanced. Our results suggested that this attraction is due to an increased level of chemosignaling.

Chemical Polymorphism and Chemosensory Recognition between Iberolacerta monticola Lizard Color Morphs

Lopez, P., Moreira, P. L., Martin, J. — Wed, 16 Sep 2009 12:28:38 PDT

In the lizard Iberolacerta monticola, there are 2 discrete color morphs ("blue" vs. "green") that seem to have alternative reproductive strategies. Because scent marking of territories and chemoreception are important in social organization of these lizards, we explored whether there is also chemical polymorphism and chemosensory recognition between color morphs. Analyses by gas chromatography–mass spectrometry showed that adult males of different morphs had similar chemical compounds in femoral gland secretions, but the proportions of some shared chemicals were different; blue morph males had higher proportions of steroids and lower proportions of fatty acids than green males. Differential tongue-flick rates to scents from femoral secretions of males indicated that males were able to detect the scent of any male from a baseline odorless control (water) but did not discriminate between the scent of males of different morphs. In contrast, females detected and discriminated between scents of the 2 male morphs by chemical cues alone. We suggest that differences in males’ chemical signals between morphs and the ability of females of discriminating chemically between male morphs might be required to maintain spatial behavior, social organization, and mate choice decisions and, thus, be important for the maintenance of alternative reproductive strategies and polymorphism in lizards.

Tue, 18 Aug 2009 20:52:19 PDT

Cover

Tue, 18 Aug 2009 20:52:19 PDT

Editorial Board

Tue, 18 Aug 2009 20:52:19 PDT

Subscriptions

Tue, 18 Aug 2009 20:52:19 PDT

Abstracts from the Thirty-first Annual Meeting of the Association for Chemoreception Sciences

Tue, 18 Aug 2009 20:52:20 PDT

Articles Highlighted

Meyerhof, W. — Tue, 18 Aug 2009 20:52:19 PDT

Molecular Tuning of Odorant Receptors and Its Implication for Odor Signal Processing

Reisert, J., Restrepo, D. — Tue, 18 Aug 2009 20:52:19 PDT

The discovery of the odorant receptor (OR) family by Buck and Axel in 1991 provided a quantum jump in our understanding of olfactory function. However, the study of the responsiveness of ORs to odor ligands was challenging due to the difficulties in deorphanizing the receptors. In this manuscript, we review recent findings of OR responsiveness that have come about through improved OR deorphanization methods, site-directed mutagenesis, structural modeling studies, and studies of OR responses in situ in olfactory sensory neurons. Although there has been a major leap in our understanding of receptor–ligand interactions and how these contribute to the input to the olfactory system, an improvement of our understanding of receptor structure and dynamics and interactions with intracellular and extracellular proteins is necessary.

Enhancement of Odorant-Induced Responses in Olfactory Receptor Neurons by Zinc Nanoparticles

Tue, 18 Aug 2009 20:52:19 PDT

Zinc metal nanoparticles in picomolar concentrations strongly enhance odorant responses of olfactory sensory neurons. One- to 2-nm metallic particles contain 40–300 zinc metal atoms, which are not in an ionic state. We exposed rat olfactory epithelium to metal nanoparticles and measured odorant responses by electroolfactogram and whole-cell patch clamp. A small amount of zinc nanoparticles added to an odorant or an extracellular/intracellular particle perfusion strongly increases the odorant response in a dose-dependent manner. Zinc nanoparticles alone produce no odor effects. Copper, gold, or silver nanoparticles do not produce effects similar to those of zinc. If zinc nanoparticles are replaced by Zn⁺² ions in the same concentration range, we observed a reduction of the olfactory receptor neuron odorant response. Based on these observations, we hypothesize that zinc nanoparticles are closely located to the interface between the guanine nucleotide-binding protein and the receptor proteins and are involved in transferring signals in the initial events of olfaction. Our results suggest that zinc metal nanoparticles can be used to enhance and sustain the initial olfactory events.

Discrimination of "Odorless" Mineral Oils Alone and as Diluents by Behaviorally Trained Mice

Gamble, K. R., Smith, D. W. — Tue, 18 Aug 2009 20:52:19 PDT

Odorant diluents are generally chosen because of their odorless qualities, allowing them to dilute a target odorant without otherwise altering its perception. Unpublished observations from our laboratory, however, suggest that mineral oil (MO), a common diluent for oil-based odorants, may possess a distinct odor when used in the behavioral testing of mice. To test this, mice were trained to discriminate between 4 brands of MO, using a commercial, liquid-dilution olfactometer and a 2-odorant discrimination task. The results demonstrate that mice were able to detect MOs and to discriminate between MO pairs obtained from different sources. Additionally, we sought to determine if mice could discriminate different MOs when used as a diluent for suprathreshold levels of cineole. Mice were required to discriminate between bottles containing identical concentrations of cineole diluted in different brands of MO. The results showed that the mice readily discriminated each cineole/MO pairing. These data demonstrate that mice are able to detect and discriminate MOs obtained from different sources, both when presented alone and in mixtures. The results also indicate that MO is not an odorless diluent and should be used with caution in olfactory experiments, as the perception of odors being diluted may be unintentionally altered.

Human Axillary Odor: Are There Side-Related Perceptual Differences?

Ferdenzi, C., Schaal, B., Roberts, S. C. — Tue, 18 Aug 2009 20:52:19 PDT

Most studies on perception of human social odors in axillary sweat do not distinguish between samples from the right and left axillae. However, each axilla might not produce identical odor samples due, for instance, to the increased use of one arm as a result of lateralization. The aim of the present study was to test whether odor samples from the right and left axillae provided by right- and left-handed men were perceived differently by female raters. Participants were 38 males and 49 females, aged 19–35 years. Fresh odor samples (cotton pads worn underarm for 24 h) were evaluated for attractiveness, intensity, and masculinity, with left and right samples being presented as independent stimuli. A side-related difference emerged in left-handers only (no difference in right-handers): The odor from the axilla corresponding to the dominant side (left) was rated more masculine and more intense than the other side (right). This effect was limited to the ratings of a restricted group of females, that is, those who did not take hormone-based contraception and were estimated to be in the fertile phase of their menstrual cycle. In conclusion, future studies using axillary odor samples can consider left and right samples as perceptually equivalent stimuli when the participant samples are representative of the general population, which comprises relatively low proportions of left-handed men and spontaneously ovulating fertile women. The results also provide new evidence of the variation of female sensitivity to biologically relevant stimuli across the menstrual cycle.

Olfactory Nerve Recovery Following Mild and Severe Injury and the Efficacy of Dexamethasone Treatment

Kobayashi, M., Costanzo, R. M. — Tue, 18 Aug 2009 20:52:19 PDT

To investigate factors that influence the degree of neural regeneration and recovery, we studied 2 olfactory nerve injury models. Transection of the olfactory nerves along the surface of the olfactory bulb was performed in OMP-tau-lacZ mice using either a flexible Teflon blade (mild injury) or a stainless steel blade (severe injury). Histological assessment of recovery within the olfactory bulb was made at 5, 14, and 42 days after injury. We used X-gal staining to label the degenerating and regenerating olfactory nerve fibers and immunohistochemical staining to detect the presence of reactive astrocytes and macrophages. Areas of injury-associated tissue were significantly smaller in the mild injury model, and at 42 days, the regenerated nerves had reestablished connections to the glomerular layer of the bulb. With severe injury, there were larger areas of injury-associated tissue, more astrocytes and macrophages, and a decrease in regenerated nerve fibers. When dexamethasone (DXM) was injected after severe injury, there was a significant reduction in injury-associated tissue, better nerve recovery, and fewer astrocytes and macrophages. These results demonstrate that recovery in the olfactory system varies with the severity of injury and that DXM treatment may have therapeutic value by reducing injury-associated tissue and improving recovery outcome.

Histological Properties of the Nasal Cavity and Olfactory Bulb of the Japanese Jungle Crow Corvus macrorhynchos

Tue, 18 Aug 2009 20:52:19 PDT

The nasal cavity and olfactory bulb (OB) of the Japanese jungle crow (Corvus macrorhynchos) were studied using computed tomography (CT) and histochemical staining. The nasal septum divided the nasal cavity in half. The anterior and maxillary conchae were present on both sides of the nasal cavity, but the posterior concha was indistinct. A small OB was present on the ventral surface of the periphery of the cerebrum. The OB–brain ratio—the ratio of the size of the OB to that of the cerebral hemisphere—was 6.13. The olfactory nerve bundles projected independently to the OB, which appeared fused on gross examination. Histochemical analysis confirmed the fusion of all OB layers. Using a neural tracer, we found that the olfactory nerve bundles independently projected to the olfactory nerve layer (ONL) and glomerular layer (GL) of the left and right halves of the fused OB. Only 4 of 21 lectins bound to the ONL and GL. Thus, compared with mammals and other birds, the jungle crow may have a poorly developed olfactory system and an inferior sense of olfaction. However, it has been contended recently that the olfactory abilities of birds cannot be judged from anatomical findings alone. Our results indicate that the olfactory system of the jungle crow is an interesting research model to evaluate the development and functions of vertebrate olfactory systems.

Changes in Sweet Taste Across Pregnancy in Mild Gestational Diabetes Mellitus: Relationship to Endocrine Factors

Belzer, L. M., Smulian, J. C., Lu, S.-E., Tepper, B. J. — Tue, 18 Aug 2009 20:52:19 PDT

Gestational diabetes mellitus (GDM) is glucose intolerance diagnosed during pregnancy. Previous work suggested that women with GDM showed exaggerated preferences for sweet taste, but data were limited to a single time point during pregnancy. This study longitudinally assessed sweet taste changes across pregnancy in women who developed GDM (n = 15) as compared with women with normal glucose tolerance (NGT; n = 93) and nonpregnant controls (n = 19). A second objective was to relate sweet taste changes in GDM to fasting leptin and insulin profiles. Following an overnight fast, subjects evaluated strawberry-flavored milks varying in sucrose and fat content, as well as glucose solutions. Evaluations were made at 3 time points during pregnancy and during early postpartum. At 34–38 weeks gestation, women with GDM gave higher liking ratings to moderately sweetened (5% and 10% sucrose) strawberry milks than women with NGT. These differences were not related to alterations in the perception of the samples. At 24–28 weeks gestation, and in women with GDM only, fasting insulin was correlated with liking of the glucose solutions (R² = 0.63, P = 0.004) and fasting leptin was correlated with sweetness liking of the 10% sucrose milk (R² = 0.42, P = 0.017). These data suggest that women with GDM exhibit higher liking ratings for a sweet fat milk drink late in pregnancy. Also, higher hedonic ratings for sweet taste in GDM may be related to elevated leptin and insulin concentrations at midpregnancy. GDM may increase the desire for sweet taste that could influence dietary management of this disease.

Responses of the Hamster Chorda Tympani Nerve to Sucrose+Acid and Sucrose+Citrate Taste Mixtures

Formaker, B. K., Lin, H., Hettinger, T. P., Frank, M. E. — Tue, 18 Aug 2009 20:52:19 PDT

Studies of taste receptor cells, chorda tympani (CT) neurons, and brainstem neurons show stimulus interactions in the form of inhibition or enhancement of the effectiveness of sucrose when mixed with acids or citrate salts, respectively. To investigate further the effects of acids and the trivalent citrate anion on sucrose responses in hamsters (Mesocricetus auratus), we recorded multifiber CT responses to 100 mM sucrose; a concentration series of HCl, citric acid, acetic acid, sodium citrate (with and without amiloride added), potassium citrate, and all binary combinations of acids and salts with 100 mM sucrose. Compared with response additivity, sucrose responses were increasingly suppressed in acid + sucrose mixtures with increases in titratable acidity, but HCl and citric acid were more effective suppressors than acetic acid. Citrate salts suppressed sucrose responses and baseline CT neural activity to a similar degree. Citrate salts also elicited prolonged, concentration-dependent, water-rinse responses. The specific loss in sucrose effectiveness as a CT stimulus with increasing titratable acidity was confirmed; however, no increase in sucrose effectiveness was found with the addition of citrate. Further study is needed to define the chemical basis for effects of acids and salts in taste mixtures.

Morphometry of Olfactory Lamellae and Olfactory Receptor Neurons During the Life History of Chum Salmon (Oncorhynchus keta)

Kudo, H., Shinto, M., Sakurai, Y., Kaeriyama, M. — Tue, 18 Aug 2009 20:52:20 PDT

It is generally accepted that anadromous Pacific salmon (genus Oncorhynchus) imprint to odorants in their natal streams during their seaward migration and use olfaction to identify these during their homeward migration. Despite the importance of the olfactory organ during olfactory imprinting, the development of this structure is not well understood in Pacific salmon. Olfactory cues from the environment are relayed to the brain by the olfactory receptor neurons (ORNs) in the olfactory organ. Thus, we analyzed morphometric changes in olfactory lamellae of the peripheral olfactory organ and in the quantity of ORNs during life history from alevin to mature in chum salmon (Oncorhynchus keta). The number of lamellae increased markedly during early development, reached 18 lamellae per unilateral peripheral olfactory organ in young salmon with a 200 mm in body size, and maintained this lamellar complement after young period. The number of ORNs per olfactory organ was about 180 000 and 14.2 million cells in fry and mature salmon, respectively. The relationship between the body size (fork length) and number of ORNs therefore revealed an allometric association. Our results represent the first quantitative analysis of the number of ORNs in Pacific salmon and suggest that the number of ORNs is synchronized with the fork length throughout its life history.

Odor Interaction between Bourgeonal and Its Antagonist Undecanal

Brodin, M., Laska, M., Olsson, M. J. — Tue, 18 Aug 2009 20:52:20 PDT

The perceived quality of a binary mixture will, as a rule of thumb, be dominated by the quality of the stronger unmixed component. On the other hand, there are mechanisms that, in theory, suggest that this will not always be true; one example being receptor antagonism. Undecanal has been indicated as an antagonist for bourgeonal-sensitive receptors in the human olfactory epithelium. Therefore, we investigated mixtures of isointense concentrations of bourgeonal and undecanal and, as a control, mixtures of isointense concentrations of bourgeonal and n-butanol. Both mixture types were investigated at 2 levels of concentration. The particular aim was to see if the bourgeonal–undecanal mixtures would exhibit asymmetric odor quality favoring the perception of the antagonist and the control mixture would not. For the control mixture, indeed odor quality tended to be dominated by the strongest component before mixing as would be suggested from previous studies. In line with the hypothesis, the bourgeonal–undecanal mixture was dominated by the antagonist's quality, but only when mixed at higher concentrations, altogether suggesting the effects of a low-affinity receptor antagonism. This is, to our knowledge, the first demonstration of how antagonistic interaction at the level of the receptor can affect the perception of odor mixtures in humans.

List of Abstracts from the Thirty-first Annual Meeting of the Association for Chemoreception Sciences

Tue, 18 Aug 2009 20:52:20 PDT

Chemical Senses - recent issues

Table of Contents

Cover

Editorial Board

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Articles Highlighted

Rating a New Hedonic Scale: A Commentary on "Derivation and Evaluation of a Labeled Hedonic Scale" by Lim, Wood and Green

Derivation and Evaluation of a Labeled Hedonic Scale

Psychometric Functions for Ternary Odor Mixtures and Their Unmixed Components

Plant Terpenes Affect Intensity and Temporal Parameters of Pheromone Detection in a Moth

Prenatal Flavor Exposure Affects Flavor Recognition and Stress-Related Behavior of Piglets

Double P2X2/P2X3 Purinergic Receptor Knockout Mice Do Not Taste NaCl or the Artificial Sweetener SC45647

Residual Chemosensory Capabilities in Double P2X2/P2X3 Purinergic Receptor Null Mice: Intraoral or Postingestive Detection?

Taste Preference and Nerve Response to 5'-Inosine Monophosphate Are Enhanced by Glutathione in Mice

Mexico City Air Pollution Adversely Affects Olfactory Function and Intranasal Trigeminal Sensitivity

Articles Highlighted

Impact of Novel Olfactory Stimuli at Supra and Subthreshold Concentrations on the Perceived Sweetness of Sucrose after Associative Learning

Taste Coding after Selective Inhibition by Chlorhexidine

Seasonal Increase in Olfactory Receptor Neurons of the Japanese Toad, Bufo japonicus, is Paralleled by an Increase in Olfactory Sensitivity to Isoamyl Acetate

Design and Evaluation of New Analogs of the Sweet Protein Brazzein

Role of Olfaction in the Conditioned Sucrose Preference of Sweet-Ageusic T1R3 Knockout Mice

Expression Patterns of Odorant Receptors and Response Properties of Olfactory Sensory Neurons in Aged Mice

High Test-Retest Reliability of the Extended Version of the "Sniffin' Sticks" Test

Profiles of Volatiles in Male Rat Urine: The Effect of Puberty on the Female Attraction

Chemical Polymorphism and Chemosensory Recognition between Iberolacerta monticola Lizard Color Morphs

Contents

Cover

Editorial Board

Subscriptions

Abstracts from the Thirty-first Annual Meeting of the Association for Chemoreception Sciences

Articles Highlighted

Molecular Tuning of Odorant Receptors and Its Implication for Odor Signal Processing

Enhancement of Odorant-Induced Responses in Olfactory Receptor Neurons by Zinc Nanoparticles

Discrimination of "Odorless" Mineral Oils Alone and as Diluents by Behaviorally Trained Mice

Human Axillary Odor: Are There Side-Related Perceptual Differences?

Olfactory Nerve Recovery Following Mild and Severe Injury and the Efficacy of Dexamethasone Treatment

Histological Properties of the Nasal Cavity and Olfactory Bulb of the Japanese Jungle Crow Corvus macrorhynchos

Changes in Sweet Taste Across Pregnancy in Mild Gestational Diabetes Mellitus: Relationship to Endocrine Factors

Responses of the Hamster Chorda Tympani Nerve to Sucrose+Acid and Sucrose+Citrate Taste Mixtures

Morphometry of Olfactory Lamellae and Olfactory Receptor Neurons During the Life History of Chum Salmon (Oncorhynchus keta)

Odor Interaction between Bourgeonal and Its Antagonist Undecanal

List of Abstracts from the Thirty-first Annual Meeting of the Association for Chemoreception Sciences