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At least 433 records · Page 24Linked to original sources
PubMed2004

Olfaction: scent-triggered navigation in honeybees.

The honeybee, Apis mellifera, navigates rapidly and accurately to food sources that are often kilometres away. They achieve this by learning visual cues, such as the location and colour of nectar-bearing flowers, and chemical cues, such as the scent and the taste of the nectar. Here we train bees to visit differently scented sugar feeders placed at specific outdoor locations and find that they can be induced to visit the same locations simply by having the corresponding scent blown into the hive, even when the destinations no longer have the food or carry the scent. A familiar nectar scent can trigger specific memories of a route and therefore expedite navigation to the food source.

Animals↗
PubMed1996

Olfaction in bird dogs during hunting.

The ability to catch scent continuously while running, which may be an essential skill for many animals of prey, requires that ambient air flows inward through the nose also during expiration. In this study on bird dogs, the direction of air flow was detected by measuring the temperature in the air inside the nostril. While resting, nose ventilation was synchronous with lung ventilation. While searching for ground scent, the dog was sniffing at a frequency of up to 200 s-1, a strategy which may create turbulence in the nasal passages and thereby enhance transport of scent molecules to the receptors in the ethmoidal cavity. When the bird dog was searching for game while running with its head high against the wind, it maintained a continuous inward air stream through the nose for up to 40s spanning at least 30 respiratory cycles. We suggest that expiratory gas flowing at high velocity from the trachea to the mouth cavity creates a lower pressure than in the nose thus causing an inward air stream through the nose during expiration by a Bernoulli effect.

Animals↗
PubMed1997

Olfaction in migraine.

Olfactory thresholds for acetone and vanillin and the unpleasantness rating of concentrated acetone were measured in 20 migraine sufferers and 21 controls. The olfactory threshold for vanillin was lower in migraine sufferers than in controls. In addition, patients who reported that odours frequently seemed stronger during attacks of migraine were able to detect acetone at a lower concentration than most other patients. No differences were found between migraine sufferers and controls for ratings of the unpleasantness of concentrated acetone. These findings suggest that hyperacuity to odours persists between episodes of migraine. Sensitivity to odours could contribute to the migraine predisposition.

Acetone↗
PubMedDate not supplied

Change in olfaction after radiotherapy for nasopharyngeal cancer--a prospective study.

PURPOSE: To evaluate the changes in olfactory function in patients with nasopharyngeal carcinoma who have received radiation to the head and neck. MATERIALS AND METHODS: Olfactory function of consecutive patients with nasopharyngeal carcinoma was assessed prospectively before irradiation and serially up to 1 year after radiotherapy by the Sniffin' Sticks (Erlangen, Germany) olfactory function test and by a patient symptom visual analogue scale. RESULTS: Fifty-eight patients were recruited before radiotherapy was commenced. Three patients could not give a reliable response to the Sniffin' Sticks test even in this first assessment, and 7 patients did not return for evaluation after irradiation. Forty-eight patients were available for follow-up assessment. Mean olfactory threshold scores by the Sniffin' Sticks test were found to deteriorate significantly at 12 months when compared with the scores before irradiation (8.3 at 12 months vs 11.5 before irradiation; P =.001). Scores for olfactory discrimination and for identification did not exhibit any significant changes when assessed at 12 months (P >.05 for both). Subjective patient assessment of olfactory function with the visual analogue scale at 12 months did not demonstrate any significant differences when compared with patients' assessment before irradiation (P =.90). An increase in discharge was the only nasal symptom that demonstrated a significant change at 12 months when compared with the assessment before irradiation (P < 001). CONCLUSIONS: Deterioration in olfactory threshold scores was found at 12 months after irradiation and was not noticed by the patients.

Adult↗
PubMed1980

Biochemical studies of olfaction: isolation, characterization, and odorant binding activity of cilia from rainbow trout olfactory rosettes.

The role of cilia in recognition of olfactory stimuli has been controversial. Cilia from the intact olfactory rosettes of the rainbow trout Salmo gairdneri were isolated, characterized biochemically, and examined by electron microscopy. The markers studied are those associated with cilia in other organisms. Dynein arms contain Mg2+-AtPase; this enzyme was enriched in the isolated cilia preparation. Guanine nucleotides are associated with the outer microtubule doublets of cilia but adenine nucleotides are not; a substantial enrichment in guanine, relative to adenine, was found in the cilia preparation. Tubulin, the structural protein component of microtubules, occurs in large amounts in cilia. Disc gel electrophoresis indicated tubulin in the cilia preparation. Electron microscopy confirmed the presence of cilia in the isolated preparation. Rainbow trout have an acute sense of smell and many amino acids are odorants to this species. Functional activity of the cilia preparation relevant to odorant recognition was assessed by using binding of radioactively labeled odorant amino acids. L-Alanine, L-serine, L-threonine, L-lysine, and D-alanine bound to the cilia preparation. This study provides direct biochemical evidence that olfactory cilia bind odorant molecules and supports the hypothesis that odorant recognition sites are integral parts of the cilia.

Amino Acids↗
PubMed1981

Molecular parameters and olfaction in the oriental fruit fly Dacus dorsalis.

The methyl eugenol receptor of the male oriental fruit fly (Dacus dorsalis) has been further characterized by evaluating the role of the linear free energy parameters product operator and sigma in the depolarization of the receptor by 37 substituted 3,4-dimethoxybenzenes. There was a strong positive correlation between the hydrophobic character of the primary substituent and intense odor and a positive correlation between the electron donating property of the primary substituent and intense odor. Maximum odor intensity was also associated with substituents of 3 atomic diameters and was improved by a center of unsaturation. Preference tests suggest that this simple and versatile odor receptor can serve as a model for investigation of molecular interactions between receptors and odorant molecules.

Journal Article↗
PubMed1992

Termination of second messenger signaling in olfaction.

By using isolated rat olfactory cilia and a fast kinetics methodology, it has been demonstrated that odorant-induced second messenger signaling in the millisecond time range is terminated via phosphorylation reactions catalyzed by specific protein kinases. The cyclic adenosine nucleotide pathway is turned off by kinase A activity, whereas the inositol trisphosphate cascade is terminated by kinase C. The data support the concept that desensitization of odorant responses involves phosphorylation of key elements in the transduction cascade.

1-Methyl-3-isobutylxanthine↗
PubMed1997

Emotion, olfaction, and the human amygdala: amygdala activation during aversive olfactory stimulation.

Electrophysiologic and lesion studies of animals increasingly implicate the amygdala in aspects of emotional processing. Yet, the functions of the human amygdala remain poorly understood. To examine the contributions of the amygdala and other limbic and paralimbic regions to emotional processing, we exposed healthy subjects to aversive olfactory stimuli while measuring regional cerebral blood flow (rCBF) with positron emission tomography. Exposure to a highly aversive odorant produced strong rCBF increases in both amygdalae and in the left orbitofrontal cortex. Exposure to less aversive odorants produced rCBF increases in the orbitofrontal cortex but not in the amygdala. Change of rCBF within the left amygdala and the left OFC was highly intercorrelated, indicating a strong functional interaction between these brain regions. Furthermore, the activity within the left amygdala was associated significantly with subjective ratings of perceived aversiveness. These findings provide evidence that the human amygdala participates in the hedonic or emotional processing of olfactory stimuli.

Adult↗
PubMed1997

Olfaction: transient expression of a putative odorant receptor in the avian notochord.

In vertebrates, odors are thought to be detected by a multigene family encoding several hundreds of seven-transmembrane-domain G-protein-coupled receptors found in fish, rat, mouse, dog, and human. Recently, the putative odorant receptor (OR) gene family in the chicken has been characterized. Twelve members have been isolated and subdivided into six subfamilies. Herein, we have further characterized the chicken olfactory receptor subfamily 7 (COR7) composed of two highly related genes (named COR7a and COR7b) which are 98.5% identical. By in situ hybridization experiments, both COR7a and COR7b transcripts were detected in the olfactory epithelium from embryonic day 6 (E6) to the new born stage. Within the olfactory epithelium, the spatial distribution of COR7a and COR7b labeled cells was random. We also observed that every individual positive cell did not coexpress the COR7a and COR7b genes. Interestingly, the COR7b gene was found to be transiently expressed in the notochord from E2 to E6, whereas COR7a or any of the other known members of the COR gene family were not detected in this mesodermal tissue. These data suggest that, in addition to its potential role as an OR in the olfactory system, COR7b may also have a function in the notochord that is essential for the dorsoventral organization of the neural tube and of the somitic mesoderm. We also discuss the possible role(s) of a putative OR present in both the notochord and the sensory olfactory epithelium.

Amino Acid Sequence↗
PubMed2001

Olfaction in the gypsy moth, Lymantria dispar: effect of pH, ionic strength, and reductants on pheromone transport by pheromone-binding proteins.

The pheromone-binding proteins (PBPs) are 16-kDa abundant proteins in specialized olfactory hairs in insects. The mechanism by which the PBPs remove the pheromone from the inner surface of sensory hairs and deliver it to the sensory cell remains unclear. Existing qualitative models postulate that pheromone is released near the dendrite by a decrease in pH or by a reduced form of the PBP. This study focuses on the two PBPs from the gypsy moth and the enantiomers of the pheromone cis-2-methyl-7,8-epoxyoctadecane. The pH dependence of pheromone binding has revealed three ionizations that are important. The type of ligand influences two of these ionizations. We propose that the (-)-enantiomer of the pheromone interacts with one of the ionizable residues on the protein while the (+)-enantiomer does not. Simultaneous variation of pH and KCl concentration in the physiological range or reduction of disulfide bridges does not change the affinity of PBP for pheromone. We propose a revised model of pheromone transport from the inner surface of the sensory hair to the sensory neuron.

Animals↗