Mechanical obstruction of the olfactory cleft reveals differences between orthonasal and retronasal olfactory functions

Following up on recent observations in patients with nasal polyposis (NP), the present study aimed to investigate whether a mechanical obstruction of the anterior olfactory cleft (OC) would produce differential effects on orthonasal and retronasal olfactory functions. To this end, we studied 33 healthy subjects in a randomized trial. Sponges with high content of saline were either placed in the OC or on the respiratory epithelium, such that this was blinded to both subject and observer. The results indicated that orthonasal (P = 0.04) but not retronasal (P = 0.15) olfactory identification ability was lower when the OC was blocked. This confirms the idea that differences between orthonasal and retronasal olfactory functions, as observed in NP patients, are, at least to some degree, due to mechanical obstruction of the anterior portion of the OC. The present data also suggest that mechanical obstruction is a means to induce reversible hyposmia void of side effects which can be performed in a blinded fashion. This might become a valuable model of hyposmia for future investigations.     

Effect of anatomy on human nasal air flow and odorant transport patterns: implications for olfaction

Recent studies that have compared CT or MRI images of an individual's nasal anatomy and measures of their olfactory sensitivity have found a correlation between specific anatomical areas and performance on olfactory assessments. Using computational fluid dynamics (CFD) techniques, we have developed a method to quickly (相似文献   

MHC-correlated odour preferences in humans and the use of oral contraceptives

Previous studies in animals and humans show that genes in the major histocompatibility complex (MHC) influence individual odours and that females often prefer odour of MHC-dissimilar males, perhaps to increase offspring heterozygosity or reduce inbreeding. Women using oral hormonal contraceptives have been reported to have the opposite preference, raising the possibility that oral contraceptives alter female preference towards MHC similarity, with possible fertility costs. Here we test directly whether contraceptive pill use alters odour preferences using a longitudinal design in which women were tested before and after initiating pill use; a control group of non-users were tested with a comparable interval between test sessions. In contrast to some previous studies, there was no significant difference in ratings between odours of MHC-dissimilar and MHC-similar men among women during the follicular cycle phase. However, single women preferred odours of MHC-similar men, while women in relationships preferred odours of MHC-dissimilar men, a result consistent with studies in other species, suggesting that paired females may seek to improve offspring quality through extra-pair partnerships. Across tests, we found a significant preference shift towards MHC similarity associated with pill use, which was not evident in the control group. If odour plays a role in human mate choice, our results suggest that contraceptive pill use could disrupt disassortative mate preferences.     

The effect of meat consumption on body odor attractiveness

Axillary body odor is individually specific and potentially a rich source of information about its producer. Odor individuality partly results from genetic individuality, but the influence of ecological factors such as eating habits are another main source of odor variability. However, we know very little about how particular dietary components shape our body odor. Here we tested the effect of red meat consumption on body odor attractiveness. We used a balanced within-subject experimental design. Seventeen male odor donors were on "meat" or "nonmeat" diet for 2 weeks wearing axillary pads to collect body odor during the final 24 h of the diet. Fresh odor samples were assessed for their pleasantness, attractiveness, masculinity, and intensity by 30 women not using hormonal contraceptives. We repeated the same procedure a month later with the same odor donors, each on the opposite diet than before. Results of repeated measures analysis of variance showed that the odor of donors when on the nonmeat diet was judged as significantly more attractive, more pleasant, and less intense. This suggests that red meat consumption has a negative impact on perceived body odor hedonicity.     

Retronasal but not oral-cavity-only identification of "purely olfactory" odorants

Identifications of 5 odorants selected to be nontrigeminal stimuli were compared using retronasal and oral-cavity-only (OCO) air-phase presentations, with OCO produced by both exhalation through the mouth and a nose clip that closed the nostrils. Nine identifiers were available on each trial; 1 or 2 were correct for each odorant. Correct retronasal identifications were more common than OCO identifications and exceeded chance across subjects and for each subject; OCO correct identifications did not exceed chance. Retronasal reaction times were briefer than OCO reaction times. Correct retronasal identifications for vanillin, octanoic acid, phenylethyl alcohol, coumarin, and octane were 88%, 73%, 87%, 70%, and 85%, respectively; correct OCO identifications were, respectively, 10%, 12%, 18%, 35%, and 33%. Identifiers selected for retronasally presented odorants differed from those for other retronasally presented odorants, but identifiers for OCO-presented odorants did not differ between odorants. Overall, the retronasal identifications of nontrigeminal odorants both depended upon the odorant that was presented and corresponded to previous reported orthonasal identifications. In contrast, the OCO identifications, characterized by low percentages of correct identifications and an absence of differences between odorants in selected identifiers, suggested that OCO responses to nontrigeminal, purely olfactory odorants lack sufficient sensory information for either correct or differential identification.     

Influences of age and sex on a microencapsulated odor memory test

While the influences of such variables as age and sex are well established for most standardized tests of odor identification and detection, this is not the case for tests of odor memory. In this study, 231 non-smoking men and women, ranging in age from 10 to 68 years, were administered a standardized 12-item match-to-sample microencapsulated odor memory test (OMT). Anosmics were excluded from the study. Each participant was asked to smell a target odorant after its release from a microencapsulated odorant pad and then, after a delay interval of 10, 30 or 60 s, to pick the target from a similarly presented set of four odors, three of which were foils. Backward counting by threes was required during the delay intervals in an effort to minimize semantic rehearsal. Overall OMT scores were higher for women than for men, and decreased, in each sex, as a function of age in a manner similar to the age-related decline observed in tests of odor identification and detection. Performance did not change as a function of delay interval. A significant correlation between the overall OMT test scores and scores on the University of Pennsylvania Smell Identification Test was observed for women, but not for men, in accord with the notion that women may be more likely to employ semantic cues in their strategies to remember odors. The findings are discussed in light of the complexities of the construct of odor memory.     

A simple and reliable method for clinical assessment of odor thresholds

We investigated whether presenting of dilutions of phenyl ethyl alcohol at random succession according to the method of constant stimuli can replace the standard procedure of presenting a various number of dilutions in a staircase paradigm. Forty-six men and 44 women, aged 19-76 years, participated in this study. Phenyl ethyl alcohol was diluted in a ratio of 1:2, starting from 4%. Presentation of the odorant followed a three-alternative, temporal forced-choice paradigm with two blanks in addition to the odorant. Twenty dilutions were administered in a randomized order. Odor threshold was obtained by logistic regression of the correct and incorrect identifications of the probe containing the odorant. Thresholds were also calculated on the basis of the first 16 dilution steps only. Results from these procedures were compared with 'gold-standard' threshold assessment employing a three-alternative, temporal forced-choice staircase paradigm with seven reversals using 16 dilutions of phenyl ethyl alcohol. The method of constant stimuli took a shorter and less variable testing time than the staircase technique. The use of 20 dilution steps provided no better results than the use of 16 steps. The method of constant stimuli exhibited a good test-retest reliability (r = 0.7; P < 0.001) comparable to that of the staircase method and provided unbiased results highly correlated (r = 0.8; P < 0.001) with those of the staircase technique with similar inter-test variability. Applying 16 dilutions (1:2 steps) of phenyl ethyl alcohol at random succession in a three-alternative, temporal forced-choice paradigm is thus a simple and reliable procedure for the reproducible assessment of odor thresholds that may be contemplated as an alternative to the 'gold-standard' staircase method of clinical odor threshold assessment.     

Developing and maintaining a nose-to-brain map of odorant identity

Olfactory sensory neurons (OSNs) in the olfactory epithelium of the nose transduce chemical odorant stimuli into electrical signals. These signals are then sent to the OSNs'' target structure in the brain, the main olfactory bulb (OB), which performs the initial stages of sensory processing in olfaction. The projection of OSNs to the OB is highly organized in a chemospatial map, whereby axon terminals from OSNs expressing the same odorant receptor (OR) coalesce into individual spherical structures known as glomeruli. This nose-to-brain map of odorant identity is built from late embryonic development to early postnatal life, through a complex combination of genetically encoded, OR-dependent and activity-dependent mechanisms. It must then be actively maintained throughout adulthood as OSNs experience turnover due to external insult and ongoing neurogenesis. Our review describes and discusses these two distinct and crucial processes in olfaction, focusing on the known mechanisms that first establish and then maintain chemospatial order in the mammalian OSN-to-OB projection.     

Experimental and numerical determination of odorant solubility in nasal and olfactory mucosa

Odorant deposition in the nasal and olfactory mucosas is dependent on a number of factors including local air/odorant flow distribution patterns, odorant mucosal solubility and odorant diffusive transport in the mucosa. Although many of these factors are difficult to measure, mucosal solubility in the bullfrog mucus has been experimentally determined for a few odorants. In the present study an experimental procedure was combined with computational fluid dynamic (CFD) techniques to further describe some of the factors that govern odorant mucosal deposition. The fraction of odorant absorbed by the nasal mucosa (eta) was experimentally determined for a number of odorants by measuring the concentration drop between odorant 'blown' into one nostril and that exiting the contralateral nostril while the subject performed a velopharyngeal closure. Odorant concentrations were measured with a photoionization detector. Odorants were delivered to the nostrils at flow rates of 3.33 and 10 l/min. The velopharyngeal closure nasal air/odorant flows were then simulated using CFD techniques in a 3-D anatomically accurate human nose modeland the mucosal odorant uptake was numerically calculated. The comparison between the numerical simulations and the experimental results lead to an estimation of the human mucosal odorant solubility and the mucosal effective diffusive transport resistance. The results of the study suggest that the increase in diffusive resistance of the mucosal layer over that of a thin layer of water seemed to be general and non-odorant-specific; however, the mucosa solubility was odorant specific and usually followed the trend that odorants with lower water solubility were more soluble in the mucosa than would be predicted from water solubility alone. The ability of this approach to model odorant movement in the nasal cavity was evaluated by comparison of the model output with known values of odorant mucosa solubility.     

Lack of predator‐odor detection and avoidance by a songbird,the House Wren

ABSTRACT Recent studies suggest that songbirds have a better sense of smell than initially suspected. Work is now focused on determining how birds use their sense of smell to enhance survival and reproduction. One question is whether birds use smell to detect and avoid predators. We examined the reaction of House Wrens (Troglodytes aedon) to the odor of a potential predator in their nests. On two different days of the nestling stage, we placed papers infused with the urine and anal scent gland material of a mustelid (American mink, Neovison vison), a neutral odoriferous substance (cologne, garlic, or vinegar), or water in nest boxes. The proportion of individuals that hesitated to enter nest boxes after first arrival did not differ significantly between treatments on either day. We also found no significant differences on either day in the time it took wrens to first enter nest boxes, time spent in nest boxes after first entry, the propensity to stay in nest boxes and brood young, or latency to return to nest boxes after first exposure to treatments. Our results suggest that House Wrens either did not detect or did not respond to foreign odors in nest cavities, including the odor of a mustelid predator. In a similar study ( Amo et al. 2008 . Functional Ecology 22: 289–293), adult Blue Tits (Cyanistes caeruleus) were less likely to enter nest boxes that contained the odor of a mustelid. One explanation for this difference is that Blue Tits may have a better sense of smell than House Wrens. Alternatively, or additionally, Blue Tits may be inherently (or as result of experience) more prone than House Wrens to avoid unusual odors or, specifically, the odor of mustelid predators in their nests. Additional studies are needed to determine the extent to which songbirds use their sense of smell to detect and avoid nest predators.     

The odour of things: Smell and the cultural elaboration of disgust in Eastern Indonesia

Recent years have witnessed an increasing number of calls for anthropology to devote more attention to non‐visual modes of perception. Frequently, the implicit suggestion of these calls has been that the acknowledgement of different ways of organising the senses could help us escape the supposed malaise of modern ‘ocular‐centrism ‘. This paper explores the sense and symbolism of smell in Buli, a village in eastern Indonesia, to argue that smell is part of an ontology that catches Buli people in a malaise of their own. ‘Bad’ smell attests to an ambiguous moral order that can be traced across myth, ritual and everyday life. Ambiguity is ever‐present because ‘bad’ or disgusting smells destabilise the very conceptual order they also help support. The analysis of smells as they relate to local notions of disgust is therefore suggested as an alternative way to conceptualise the contradictory nature of power.     

Dissecting the molecular mechanism of drosophila odorant receptors through activity modeling and comparative analysis

To gain insight into the molecular mechanism of odorant receptors (ORs) in Drosophila species, we developed a Quantitative Structure Activity Relationship (QSAR) model that predicts experimentally measured electrophysiological activities between 24 D. melanogaster ORs and 108 odorants. Although the model is limited by the tested odorants,analyzing the model allowed dissection of specific topological and chemical properties necessary for an odorant to elicit excitatory or inhibitory receptor response. Linear odorants with five to eight nonhydrogen atoms at the main chain and hydrogen‐bond acceptor and/or hydrogen‐bond donor at its ends were found to stimulate strong excitatory response. A comparative sequence analysis of 90 ORs in 15 orthologous groups identified 15 putative specificity‐determining residues (SDRs) and 15 globally conserved residues that we postulate as functionally key residues. Mapping to a model of secondary structure resulted in 14 out of 30 key residues locating to the transmembrane (TM) domains. Twelve residues, including six SDRs and six conserved residues, are located at the extracellular halves of the TM domains. Combining the evidence from the QSAR modeling and the comparative sequence analysis, we hypothesize that the Drosophila ORs accept odorants into a binding pocket located on the extracellular halves of its TM domains. The QSAR modeling suggests that the binding pocket is around 15 Å in depth and about 6 Å in width. Twelve mainly polar or charged key residues, both SDRs and conserved, are located inthis pocket and postulated to distinguish docked odorants via primarily geometry fitting and hydrogen‐bond interaction. Proteins 2010. © 2009 Wiley‐Liss, Inc.     

The chemistry and biogenesis of the S-containing metabolites of vinyl chloride in rats.

In order to determine whether vinyl chloride yields chloroethylene oxide in vivo, the biogenesis of the various urinary S-containing metabolites in rats has been investigated.N-Acetyl-S-(2-hydroxyethyl)cysteine is a major vinyl chloride metabolite in rats, but according to the method of protective esterification that is used, so either N-acetyl-S-(2-chloroethyl)cysteine or N-acetyl-S-(2-hydroxyethyl)cysteine may be isolated from the body fluids. N-Acetyl-S-vinylcysteine is a second related metabolite. These S-containing vinyl chloride metabolites are not mutagenic in S. typhimurium. Neutral methanol methylates N-acetyl-S-(2-hydroxyethyl)cysteine. N-Acetyl-S-(2-methoxyethyl)cysteine plus N-acetyl-S-vinylcysteine degrade to give the volatile S-(2-methoxyethyl)(prop-1 or 2-enyl)sulphide.Administration of several vinyl chloride metabolites and closely related compounds to rats shows that chloroacetaldehyde and S-(carboxymethyl)cysteine, but not chloroacetic acid, lie on a pathway or pathways connecting vinyl chloride with thiodiglycollic acid. The fact (a) that chloroacetaldehyde affords both thiodiglycollic acid and N-acetyl-S-(2-hydroxyethyl)cysteine in the animal and (b) that S-(carboxymethyl)cysteine has been identified amongst the hydrolytic products from an hepatic extract prepared from vinyl chloride-treated animals is consistent with the formation of chloroacetaldehyde, and with the reaction of chloroethylene oxide or chloroacetaldehyde with glutathione in the presence of a glutathione S-epoxide transferase to give the identified S-containing metabolites.     

Olfactory physiology in the Drosophila antenna and maxillary palp: acj6 Distinguishes two classes of odorant pathways

This article provides characterization of the electrical response to odorants in the Drosophila antenna and provides physiological evidence that a second organ, the maxillary palp, also has olfactory function in Drosophila. The acj6 mutation, previously isolated by virtue of defective olfactory behavior, affects olfactory physiology in the maxillary palp as well as in the antenna. Interestingly, abnormal chemosensory jump 6 (acj6) reduces response in the maxillary palp to all odorants tested except benzaldehyde (odor of almond), as if response to benzaldehyde is mediated through a different type of odorant pathway from the other odorants. In other experiments, different parts of the antenna are shown to differ with respect to odorant sensitivity. Evidence is also provided that antennal response to odorants varies with age, and that odorants differ in their age dependence. © 1992 John Wiley & Sons, Inc.     

Numerical modeling of turbulent and laminar airflow and odorant transport during sniffing in the human and rat nose

Human sniffing behavior usually involves bouts of short, high flow rate inhalation (>300 ml/s through each nostril) with mostly turbulent airflow. This has often been characterized as a factor enabling higher amounts of odorant to deposit onto olfactory mucosa than for laminar airflow and thereby aid in olfactory detection. Using computational fluid dynamics human nasal cavity models, however, we found essentially no difference in predicted olfactory odorant flux (g/cm2 s) for turbulent versus laminar flow for total nasal flow rates between 300 and 1000 ml/s and for odorants of quite different mucosal solubility. This lack of difference was shown to be due to the much higher resistance to lateral odorant mass transport in the mucosal nasal airway wall than in the air phase. The simulation also revealed that the increase in airflow rate during sniffing can increase odorant uptake flux to the nasal/olfactory mucosa but lower the cumulative total uptake in the olfactory region when the inspired air/odorant volume was held fixed, which is consistent with the observation that sniff duration may be more important than sniff strength for optimizing olfactory detection. In contrast, in rats, sniffing involves high-frequency bouts of both inhalation and exhalation with laminar airflow. In rat nose odorant uptake simulations, it was observed that odorant deposition was highly dependent on solubility and correlated with the locations of different types of receptors.     

Comparative studies of social behavior in Callicebus and Saimiri: Behavioral and physiological responses of established pairs to unfamiliar pairs

The influences of cage size and novelty on the behavior of Galago senegalensis braccatus were examined in two captive groups (five adults and one immature per group) having similarly furnished but unequally sized cages. One group experienced expansion, and the other experienced contraction of space. Each group experienced the novelty of a new cage and return to its old cage. Exploration, nonsocial activity, and social sniffing behaviors were most frequent in both groups during the novelty phase independent of cage size. These behaviors remained elevated after return to the original cage. This pattern indicated that novelty, not space, was responsible for these behavioral changes. The increase in social sniffing indicated that group members may use olfactory cues to recognize each other, expecially when the setting is novel. In both groups, frequencies of displacements and chases were highest in the smaller space. Group differences in behavior prior to cage change also influenced a group's response to change.     

Divergence of odorant signals within and between the two European subspecies of the house mouse

The olfactory acuity of mice allows them to discriminate odorsof conspecifics differing by a few genes. This acuity is usedin habituation procedures where investigation of novel odorsby the mouse can be translated into relative difference or similaritybetween the stimuli. This study adapts these behavioral proceduresto address suprapopulation divergence among urinary odors inthe house mouse. Specifically, we investigate geographical patternsof odor divergence within and between 2 subspecies of the housemouse, Mus musculus musculus and Mus musculus domesticus, whichdiverged in allopatry and met secondarily in Europe where theyhybridize. Based on M. m. musculus perception, our study suggeststhat odors of the 2 subspecies differ in both allopatric andcontact zone populations and that divergence is more markedin the latter. Our earlier studies documented mate preferenceand signal divergence between the 2 subspecies. Hence, we considerthe role of the urinary odors as mating signals. We discusshow signal divergence between the 2 subspecies may relate toreproductive character displacement. This study validates theuse of habituation procedures to reconstruct geographical patternsof odorant signal divergence, providing a strong methodologicalplatform to address reproductive character displacement affectingcryptic mating signals in mammals.