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At least 163 records · Page 9Linked to original sources
PubMed2000

The Ras-MAPK pathway is important for olfaction in Caenorhabditis elegans.

The Ras-MAPK (mitogen-activated protein kinase) signal transduction pathway is well known to control cellular proliferation and differentiation in response to extracellular signals, but its other functions are less understood. In Caenorhabditis elegans this pathway regulates several developmental events, such as vulval induction and progression of meiosis, but its function in the nervous system is unknown. Here we report that the Ras-MAPK pathway is involved in olfaction in this organism. Mutational inactivation and hyperactivation of this pathway impairs efficiency of chemotaxis to a set of odorants. Experiments in which let-60 ras was expressed using a heat-shock promoter and a cell-specific promoter show that a normal activity of LET-60 Ras is required in mature olfactory neurons. Application of the odorant isoamylalcohol to wild-type animals leads to the activation of MAP kinase in olfactory neurons within 10 seconds. This induction is dependent on the function of the nucleotide-gated channel TAX-2/TAX-4 and the voltage-activated calcium channel subunit UNC-2. These results suggest a dynamic regulatory role for the Ras-MAPK pathway in perception and transmission of sensory signals in olfactory neurons.

Animals↗
PubMed2003

Dissociated neural representations of intensity and valence in human olfaction.

Affective experience has been described in terms of two primary dimensions: intensity and valence. In the human brain, it is intrinsically difficult to dissociate the neural coding of these affective dimensions for visual and auditory stimuli, but such dissociation is more readily achieved in olfaction, where intensity and valence can be manipulated independently. Using event-related functional magnetic resonance imaging (fMRI), we found amygdala activation to be associated with intensity, and not valence, of odors. Activity in regions of orbitofrontal cortex, in contrast, were associated with valence independent of intensity. These findings show that distinct olfactory regions subserve the analysis of the degree and quality of olfactory stimulation, suggesting that the affective representations of intensity and valence draw upon dissociable neural substrates.

Adult↗
PubMed2004

A psychophysical test of the vibration theory of olfaction.

At present, no satisfactory theory exists to explain how a given molecule results in the perception of a particular smell. One theory is that olfactory sensory neurons detect intramolecular vibrations of the odorous molecule. We used psychophysical methods in humans to test this vibration theory of olfaction and found no evidence to support it.

Adult↗
PubMed1995

Effect of a tracheostomy speaking valve on secretions, arterial oxygenation, and olfaction: a quantitative evaluation.

Tracheostomy speaking valves consist of a one-way valve that closes upon exhalation, causing a redirection of exhaled gas into the upper airway, thus allowing for the primary benefit of speech. The present study was undertaken to test various hypotheses concerning the secondary benefits of speaking valves. We hypothesized that use of a speaking valve will result in a decrease in accumulated secretions, an increase in arterial oxygenation and an improvement in olfactory function. A total of 8 tracheotomized patients met the following inclusion criteria: age > 18; ability to tolerate wearing a speaking valve for at least 3 hours; no unstable medical conditions; no use of thrombolytic agents. While using the speaking valve patients accumulated fewer secretions (74.3 +/- 63.6 vs. 122.8 +/- 44.6 ml/day, p = 0.004, n = 7) and had improved olfactory function (accuracy = 28.4 +/- 5.2 vs 8.1 +/- 2.9%, p = 0.02; and percent correct = 64.2 +/- 2.6 vs 50.0 +/- 3.9%, p = 0.03, n = 6) than when off the speaking valve. No significant differences were found in 24-hour arterial oxygen saturation (pulse oximetry and ABG analysis respectively, n = 7), arterial PO2, pH, PCO2, HCO3, or 24-hour heart rate (n = 7). Thus, the present study found a significant decrease in secretions and improvements in olfaction when tracheotomized patients wore a speaking valve, but no difference in arterial oxygenation.

Adult↗
PubMed1997

A prospective study of olfaction following endoscopic sinus surgery with adjuvant medical treatment.

Few studies on the outcome of endoscopic sinus surgery have assessed the effect of this treatment on the sense of smell. We have collected data prospectively on 115 patients, before and 6 weeks after surgery. All patients had bilateral chronic rhinosinusitis. Visual analogue and a 4-grade, patient-rated symptom score related to olfaction was collected. Patients were also asked after surgery whether their sense of smell was normal, better, a little better, the same, a little worse or worse. Paired phenylethyl methyl ethyl carbinol olfactory detection thresholds were determined for 102 of the patients. All parameters showed a statistically significant improvement (P < 0.001). Acoustic rhinometry was performed pre- and postoperatively in 96 patients. The improvement in all olfactory symptom scores was found to correlate with the increase in nasal volume (Spearman rank correlation: visual analogue score, P < 0.005; 4-grade scale, P = 0.03; 'better, same, worse' scale, P = 0.001).

Chemotherapy, Adjuvant↗
PubMed2001

Extended transbasal approach with preservation of olfaction: ananatomical study.

Many craniofacial approaches to the sphenoethmoidal region, anterior fossa, and central skull base compartment have been described, a number of which involve the mobilization of the frontonasoorbital complex en bloc. Spetzler's modification incorporates osteotomies around the cribriform plate, to preserve olfaction. In this morphological study of three cadavers, photographs were used to show the technique and define its anatomical boundaries and limitations. The study illustrates access to a number of anatomical regions, particularly the exposure of the medial orbit, the cavernous sinus, the clivus, and the vertebrobasilar complex.

Cavernous Sinus↗
PubMed2004

Organization of a primitive memory: olfaction.

I present a tentative, and schematic, picture of the olfaction storage system in early mammalians: (i) how the excitation trains from the olfactory bulb excite selectively N types of cells in the piriform cortex and (ii) how these cells transfer their information to a storage area. Simple size and connectivity requirements impose that each odor is stored in a very small cluster of approximately 3 neurons. This surprising result holds even if the model parameters are strongly altered (e.g., if N = 10(3) rather than 10(2)).

Animals↗
PubMed1978

Biochemical studies of olfaction: binding specificity of radioactively labeled stimuli to an isolated olfactory preparation from rainbow trout (Salmo gairdneri).

The extent of binding of 10 radioactively labeled odorant amino acids to a sedimentable fraction (fraction P2) derived from the olfactory rosettes of the rainbow trout Salmo gairdneri corresponded closely with their reported relative stimulatory effectiveness measured electrophysiologically. L isomers were bound to a greater extent than their respective D isomers. Binding of L-alanine was strongly and irreversibly inhibited by mercurials but was not affected by sulfhydryl-blocking reagents. Binding was saturable and reversible. Scatchard analyses gave evidence of two types of binding sites for most of the amino acids studied. The Kd values of the higher-affinity binding sites were similar among the amino acids, being in the range of 10(-6) M; differences occurred in the relative numbers of sites, n. These results, coupled with those from competition experiments, lead to the postulate that a multiplicity of types of olfactory binding sites exist in the trout: site TSA, which binds L-threonine, L-serine, and L-alanine; site L, which binds L-lysine; and site AB which binds beta-alanine. Tentative assignments are: site V, which binds L-valine; site H, which binds L-histidine; and site AD, which binds D-alanine. Site AD may be a lower affinity site for L-alanine. Binding of olfactory stimulus molecules appears to be an initial discrimination step in olfaction.

Amino Acids↗
PubMed1988

Olfaction by melanophores: what does it mean?

Hypotheses on general olfaction can be divided into two broad groups: those that predict the existence of olfactory-specific olfactory receptor proteins and those that do not. Recently, much attention has been paid to the discovery of an odorant-stimulated adenylate cyclase in purified olfactory cilia. This finding has, for the most part, been accepted as evidence that the former hypotheses are correct. Here we report that frog melanophores, which are nonolfactory in nature, disperse their melanosomes in response to the same types and concentrations of odorants used in the investigations of olfactory cilia and that pigment dispersion is accompanied by rises in intracellular cAMP levels. The effects show that the existence of a cAMP-based second messenger system in olfactory cilia is not in itself proof of the existence of olfactory-specific olfactory receptor proteins. Also they explain the basis of Ottoson's pioneering work of 30 years ago on the electrical responses of frog olfactory epithelium to stimulation with alcohols. The results suggest that there could be two mechanisms that are important for the detection of odorants: one based on specific receptors, the other nonspecific, but both working through activation of cAMP.

Adenylyl Cyclases↗
PubMed1995

Requirement for a phospholipase C in odor response: overlap between olfaction and vision in Drosophila.

A central problem in sensory system biology is the identification of the signal transduction pathways used in different sensory modalities. Genetic analysis of transduction mutants provides a means of studying in vivo the contributions of different pathways. This report shows that odorant response in one olfactory organ of Drosophila melanogaster depends on the norpA phospholipase C (EC 3.1.4.3) gene, providing evidence for use of the inositol 1,4,5-trisphosphate (IP3) signal transduction pathway. Since the norpA gene is also essential to phototransduction, this work demonstrates overlap in the genetic and molecular underpinnings of vision and olfaction. Genetic and molecular data also indicate that some olfactory information flows through a pathway which does not depend on norpA.

Animals↗
PubMed2001

Sex differences in human olfaction: between evidence and enigma.

The sex of individuals plays an important part in determining their olfactory abilities, with females generally being superior to males. The present review examines the way in which sex differences influence sensitivity, identification, familiarity, and recognition of odours. It also examines whether sex differences are more pronounced with some odours than others, and how sex differences are affected by the manner of testing. Two different explanations for the superiority of females over males in olfaction are evaluated.

Female↗
PubMed2002

Implication of SAR of male medfly attractants in insect olfaction.

Medfly (Ceratitis capitata) males are strongly attracted by different compounds, not described as pheromones. The best attractants reported are (+)-alpha-copaene, a sesquiterpene of natural source and (-)-ceralure-B1, a non-natural iodinated cyclohexane ester. Although their origin, atomic composition, chemical and physical properties are rather different, they show similar attraction to medflies. The question of why these compounds, act behaviorally in the same way, has been never addressed in research papers. We show here for the first time that these compounds have quite similar stereochemistry, water accessible surfaces, certain local dipole moments and, to some extent, similar octanol/water partition coefficient (log P). When seven carbons, one oxygen and one iodine belonging to (-)-ceralure-B1 are selectively chosen based on topological homology with (+)-alpha-copaene and are overlaid with nine corresponding carbons of (+)-alpha-copaene, the RMS is 0.367 A. This represents a high degree of steric resemblance. Local dipole moments and charges are similar in those regions where the molecules show topological homologies. Thus, we hypothesize that these two molecules could interact with the same male medfly's odorant receptor(s). The implications of this result in future research in insect olfaction is discussed.

Animals↗
PubMed1998

Data management in olfaction studies.

Problems arising in the collection of data in olfaction studies are discussed in relation with the specific nature of perception and description of odors. Olfactory data depend strongly on individual physiological differences, on measurement methods and on psychological factors. Classifications of odors are necessary to put some order in odor descriptions which are used in structure-odor relationships. Published classifications have been based on empirical, semi-empirical, or statistical approaches. In the last category data may be obtained using semantic descriptions, or profiles, or similarity estimations. Examples of each kind of classification are presented and discussed. The intensity data are most often threshold data. They also present a huge variability which makes it difficult to relate them to physicochemical properties. Data on thresholds and attempts to standardize them are presented and discussed.

Data Interpretation, Statistical↗
PubMed1994

Sulfhydryl-reagent inhibition of olfaction in a moth and effects of exposure to pheromone compounds or a pheromone analogue.

The effects on olfaction of N-ethylmaleimide (NEM), a specific reagent of free sulfhydryl groups, were studied in the moth Mamestra brassicae. The antennae of male M. brassicae bear two types of specialist receptor neurons involved in pheromone communication. One type is tuned to (Z)-11-hexadecenyl acetate (Z11-16:Ac), the main pheromone component; the second type is tuned to (Z)-9-tetradecenyl acetate (Z9-14:Ac), an interspecific inhibitor not produced by the females of this species. Vapours of NEM irreversibly inhibited the electro-antennographic (EAG) responses to Z11-16:Ac and Z9-14:Ac. When Z11-16:Ac was applied before and during NEM treatment, the responses to Z9-14:Ac were preserved and some protection was observed in the responses to Z11-16:Ac. In return, Z9-14:Ac partially prevented the disappearance of responses to Z11-16:Ac but not to Z9-14:Ac. A third compound, hexadecyl acetate (16:Ac), found in the pheromone gland, but not detected by the antennal receptors, did not prevent the inhibition caused by NEM.

Acetates↗
PubMed2005

Smell intensity monitoring using metal oxide semiconductor odor sensors during intravenous olfaction test.

The intravenous olfaction test using prosultiamine (PST) solution is simple to perform and has been used clinically in Japan. We monitored intranasal intensity of smell continuously in real time under various conditions of administration using metal oxide semiconductor odor sensors and established an optimal PST injection procedure. In this study, we found that 1) although there was fluctuation in the pattern of intensity of increase in smell in the PST original solution test, the pattern of increase in intranasal smell intensity could be stabilized by prolonging the injection time to 40 s and 2) dilution of PST with physiological saline was effective in preventing angialgia during intravenous injection. It appears that PST administration is best performed by adding 10 ml of saline to 10 mg (2 ml) of PST and injecting the resulting 12-ml solution (6x dilution) and that the best respiratory cycle for testing is once in every 2 s.

Adult↗
PubMed2006

Cross-modal interactions between olfaction and touch.

We report two experiments designed to investigate the nature of any cross-modal interactions between olfactory and tactile information processing. In Experiment 1, we assessed the influence of olfactory cues on the tactile perception of fabric softness using computer-controlled stimulus presentation. The results showed that participants rated fabric swatches as feeling significantly softer when presented with a lemon odor than when presented with an animal-like odor, demonstrating that olfactory cues can modulate tactile perception. In Experiment 2, we assessed whether this modulatory effect varied as a function of the particular odors being used and/or of the spatial coincidence between the olfactory and tactile stimuli. The results replicated those reported in Experiment 1 thus further supporting the claim that people's rating of tactile stimuli can be modulated by the presence of an odor. Taken together, the results of the two experiments reported here support the existence of a cross-modal interaction between olfaction and touch.

Adolescent↗
PubMed2001

The Caenorhabditis elegans odr-2 gene encodes a novel Ly-6-related protein required for olfaction.

Caenorhabditis elegans odr-2 mutants are defective in the ability to chemotax to odorants that are recognized by the two AWC olfactory neurons. Like many other olfactory mutants, they retain responses to high concentrations of AWC-sensed odors; we show here that these residual responses are caused by the ability of other olfactory neurons (the AWA neurons) to be recruited at high odor concentrations. odr-2 encodes a membrane-associated protein related to the Ly-6 superfamily of GPI-linked signaling proteins and is the founding member of a C. elegans gene family with at least seven other members. Alternative splicing of odr-2 yields three predicted proteins that differ only at the extreme amino terminus. The three isoforms have different promoters, and one isoform may have a unique role in olfaction. An epitope-tagged ODR-2 protein is expressed at high levels in sensory neurons, motor neurons, and interneurons and is enriched in axons. The AWC neurons are superficially normal in their development and structure in odr-2 mutants, but their function is impaired. Our results suggest that ODR-2 may regulate AWC signaling within the neuronal network required for chemotaxis.

Alternative Splicing↗
PubMed1994

Olfaction and gustation in fish: an overview.

Living in an aquatic environment, often devoid of light but rich in dissolved compounds, fish have highly developed chemosensory and chemical signalling systems. The olfactory and gustatory systems comprise the major chemosensory pathways. Despite considerable variations in structural organization of the peripheral olfactory organ throughout fish species, ultrastructural organization of the olfactory sensory epithelium is extremely consistent. The olfactory receptor cell is a bipolar neurone which is directly exposed to the external environment and sends information to the brain by its own axon (cranial nerve I). Four major classes of chemicals have been identified as specific olfactory stimuli and their stimulatory effectiveness characterized: amino acids, sex steroids, bile acids/salts and prostaglandins. Olfactory signals such as those involved in reproduction and feeding may be processed independently through two distinct subsystems: the lateral and medial olfactory systems. The taste buds constitute the structural basis of the gustatory organ. Taste buds may occur not only in the oropharyngeal cavity, but on the whole body surface. Chemical information detected by specialized epithelial cells, gustatory cells, is transmitted to the central nervous system by cranial nerve VII (facial), IX (glossopharyngeal), and X (vagal). Besides diverse sensitivities and specificities for amino acids, fish gustatory receptors detect various organic acids, nucleotides and bile salts. Putative receptors, molecular mechanisms of transduction and the role played by olfaction and gustation in feeding, reproduction, migration and other fish behaviours are discussed.

Animals↗