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At least 703 records · Page 39Linked to original sources
PubMed2006

Evaluation of leaf-derived extracts as an environmentally sustainable source of essential oils by using gas chromatography-mass spectrometry and enantioselective gas chromatography-olfactometry.

In consideration of the world's present environmental situation and the threat of species extinction, investigations concerning alternative sustainable sources of natural substances represent an extremely important issue. In this respect, the present research is focused on the analytical evaluation of Brazilian rosewood (Aniba rosaeodora Ducke) leaves, as an alternative source (with respect to wood) of rosewood essential oil and, as such, of natural linalool, which is extensively used in perfumery. Enantioselective-gas chromatography-olfactometry (Es-GC-O) was used as a tool for the simultaneous stereodifferentiation and olfactive evaluation of the volatile optically active components present in the analyzed samples. In addition to Es-GC-O analyses, direct olfactive analyses were also performed, enabling the evaluation of the global aroma exerted by each sample and the influence of each linalool antipode, as also other minor compounds. The samples were also submitted to gas chromatography-mass spectrometric analysis, thus establishing their chemical profiles. The assessment of enantiopure chiral compounds through Es-GC-O, along with direct olfactive analyses, confirmed that the leaves are a potential substituent for wood in the extraction of Brazilian rosewood essential oil, representing a sustainable nonwood source of natural linalool.

Chromatography, Gas↗
PubMed1998

Sniffing and smelling: separate subsystems in the human olfactory cortex.

The sensation and perception of smell (olfaction) are largely dependent on sniffing, which is an active stage of stimulus transport and therefore an integral component of mammalian olfaction. Electrophysiological data obtained from study of the hedgehog, rat, rabbit, dog and monkey indicate that sniffing (whether or not an odorant is present) induces an oscillation of activity in the olfactory bulb, driving the piriform cortex in the temporal lobe, in other words, the piriform is driven by the olfactory bulb at the frequency of sniffing. Here we use functional magnetic resonance imaging (fMRI) that is dependent on the level of oxygen in the blood to determine whether sniffing can induce activation in the piriform of humans, and whether this activation can be differentiated from activation induced by an odorant. We find that sniffing, whether odorant is present or absent, induces activation primarily in the piriform cortex of the temporal lobe and in the medial and posterior orbito-frontal gyri of the frontal lobe. The source of the sniff-induced activation is the somatosensory stimulation that is induced by air flow through the nostrils. In contrast, a smell, regardless of sniffing, induces activation mainly in the lateral and anterior orbito-frontal gyri of the frontal lobe. The dissociation between regions activated by olfactory exploration (sniffing) and regions activated by olfactory content (smell) shows a distinction in brain organization in terms of human olfaction.

Adult↗
PubMed1995

Analysis of chemical signals by nervous systems.

Intraspecific and interspecific communication and recognition depend on olfaction in widely diverse species of animals. Olfaction, an ancient sensory modality, is based on principles of neural organization and function that appear to be remarkably similar throughout the zoosphere. Thus, the "primitives" of olfactory stimuli that determine the input information of olfaction, the kinds of "molecular images" formed at various levels in the olfactory pathway, and the cellular mechanisms that underlie olfactory information processing are comparable in invertebrates and vertebrates alike. A case in point is the male-specific olfactory subsystem in moths, which is specialized to detect and analyze the qualitative, quantitative, and temporal features of the con-specific females' sex-pheromonal chemical signal. This olfactory subsystem can be viewed, and is here presented, as a model in which common principles of organization and function of olfactory systems in general are exaggerated to serve the requirements of a chemical communication system that is crucial for reproductive success.

Animal Communication↗
PubMedDate not supplied

Prediction of olfactory response based on age, gender and smoking habits.

The measurement of olfaction has been neglected compared with the other senses. Recently, some progress has been made in the search for an instrument to objectively measure olfaction. This article outlines the early test results of a low cost, computer-based olfactometer which uses the frequency content of evoked potentials to quantify a subject's response to an olfactory stimulus. Clinical trials have been undertaken to establish the validity of the olfactometer and several thousand tests have been carried out using patients with olfactory dysfunctions as well as normals for norm referencing. The paper discusses a theoretical model for olfaction based on the age, gender and smoking habits of a subject. The validity of the model is then compared with the experimental data. The correlation between the model and the experimental results is strong.

Aging↗
PubMed1999

Hemispheric lateralization in the processing of odor pleasantness versus odor names.

It is well established that for most people linguistic processing is primarily a left hemisphere activity, whereas recent evidence has shown that basic odor perception is more lateralized to the right hemisphere. Importantly, under certain conditions, emotional responding also shows right hemisphere laterality. Hedonic (pleasantness) assessments constitute basic level emotional responses. Given that olfaction is predominantly ipsilateral in function, it was hypothesized that odor pleasantness evaluations may be accentuated by right nostril perception and that odor naming would be superior with left nostril perception. To test this prediction we presented eight familiar neutral-mildly pleasant odors for subjects to sniff through the left and right nostrils. Subjects smelled each odor twice (once through each nostril) at two different sessions, separated by 1 week. At each session subjects provided pleasantness, arousal and naming responses to each odorant. Results revealed that odors were rated as more pleasant when sniffed through the right nostril and named more correctly when sniffed through the left. No effects for arousal were obtained. These findings are consistent with previously demonstrated neural laterality in the processing of olfaction, emotion and language, and suggest that a local and functional convergence may exist between olfaction and emotional processing.

Adolescent↗
PubMed2002

Potential changes with gamma-band oscillation at the frontal scalp elicited by intravenous olfactory stimulation in humans.

Intravenous olfaction is a unique stimulation method often used in Japan to diagnose olfactory disturbances. Odorant is injected into a vein and transported by blood flow and respiration to the upper air tract. The intravenous olfaction might allow the potential at the frontal scalp to be recorded without contamination from electromyograms, such as those caused by sniffing. We injected Alinamin (thiamine propyldisulphide) into healthy subjects according to a standard protocol for clinical intravenous olfaction testing and we simultaneously recorded potential changes at the frontal scalp. When Alinamin was injected into the right median cubital vein over a 20 s period, the potential changes with gamma-band oscillations were detected 17.6 +/- 6.7 s (mean +/- SD) after the start of the injection. The main frequency component of this gamma-band oscillation is 30-160 Hz. The gamma-band oscillation elicited by intravenous olfactory stimulation (VOP) was similar to the induced wave of the olfactory bulb. Mapping the VOPs on the frontal scalp of a subject with less developed frontal sinuses and the relation between the thickness of the frontal sinuses and VOP amplitude suggest an intracranial source, possibly the olfactory bulb. The gamma-band potential at the frontal scalp is a useful measure of central disturbance.

Adult↗
PubMed2005

Specific expression of olfactory binding protein in the aerial olfactory cavity of adult and developing Xenopus.

Olfactory binding proteins (OBP), commonly associated with aerial olfaction, are found in the olfactory mucus of mammals but have never been identified in fish. It is still not clear whether the presence of OBP in aerial olfactory systems is due to phylogenetic or to functional differences linked to the adaptation of the olfactory system to an aerial environment. To test this alternative, the olfactory system of Xenopus offers a unique opportunity because it includes two olfactory cavities, one of which is thought to be devoted to aquatic olfaction and the other to aerial olfaction. We therefore purified and cloned OBPs in two Xenopus species. Xenopus laevis OBP (XlaeOBP) and Xenopus tropicalis OBP (XtroOBP) exhibit 158 and 160 amino acids, respectively, sharing 89 residues. cRNA probes allowed us to demonstrate that XlaeOBP and XtroOBP are expressed at the level of Bowman's gland specifically in the aerial olfactory cavity, as confirmed using anti-XlaeOBP antiserum. OBP mRNA transcription occurs early during metamorphosis, as early as stage 57. This is the first study to demonstrate that OBPs are exclusively present in the aerial chamber and are only expressed as the tadpole becomes an adult in species which possess both aquatic and aerial olfactory organs.

Aging↗
PubMed2004

Detection of single and mixed VOCs by smell and by sensory irritation.

UNLABELLED: We have measured complete concentration-detection (i.e., psychometric or detectability) functions to study the olfactory and ocular/nasal chemesthetic (a term that includes sensory irritation) impact of VOCs presented singly and in various binary mixtures. Such functions provide considerably more information than that provided by measuring only a "threshold". The outcome for single VOCs confirmed the much higher absolute sensitivity of olfaction compared to chemesthesis, but also demonstrated that the detection of ocular and nasal sensory irritation increases as a function of vapor concentration at a much higher rate than that for the detection of odor. The outcome for the binary mixtures revealed that, for both olfaction and chemesthesis, complete additivity of detection of individual components held at relatively low levels of detectability but broke down at higher levels. The breakdown for odor detection, compared to that for sensory irritation detection, was, first, more extensive, and, second, dependent to a larger extent on the degree of structural and chemical similarity/dissimilarity between the mixed VOCs. PRACTICAL IMPLICATIONS: Concentration-detection functions for the chemesthetic and olfactory detectability of VOCs have shown that, even when nasal pungency and eye irritation begin to be evoked at concentrations orders of magnitude larger than those evoking odor, they sharply increase in detectability to become clearly noticeable. In contrast, odor detectability increases with concentration at a much lower rate. As a result, any fixed reduction (e.g., 10-times) in the concentration of a VOC will reduce detectability of sensory irritation much more dramatically than detectability of odor, within their respective ranges. Concentration-detection functions are particularly informative when employed to probe into the rules of dose- and response-additivity in mixtures. Our results for olfaction, and to a lesser extent for chemesthesis, indicate that additivity of detection of individual VOCs in mixtures is level-dependent: as detectability increases, the degree of additivity decreases. This suggests that a substantial improvement of perceived air quality could follow from control of just the few dominating chemosensory sources.

Adolescent↗
PubMed2006

Changes in juvenile coho salmon electro-olfactogram during and after short-term exposure to current-use pesticides.

For anadromous salmonids, olfaction is a critical sense, enabling return migration. In recent years, several pesticides have been identified that interfere with salmonid olfaction at concentrations in the microg/L range; thus, they may pose a risk to species longevity. In the present study, we investigated the acute effects of five agricultural pesticides on juvenile coho salmon (Oncorhynchus kisutch) olfaction using the electro-olfactogram (EOG), a measure of odorant-evoked field potentials. Electro-olfactogram responses to the odorant L-serine were measured during and following a 30-min exposure of the left olfactory rosette to chlorothalonil, endosulfan, glyphosate acid, iodocarb (IPBC), trifluralin, and 2,4-dichlorophenoxyacetic acid. With the relatively insoluble pesticides endosulfan and trifluralin, decreases in EOG amplitude were only apparent at relatively high concentrations (100 and 300 microg/L, respectively) following 20 min of exposure and were absent for chlorothalonil (1 mg/L). With the water-soluble herbicide glyphosate, significant EOG reductions occurred within 10 min of exposure to 1 mg/L and more rapidly with higher concentrations. Recovery of EOG post-glyphosate exposure was concentration-dependent, and complete recovery was not observed with some concentrations at 60 min postexposure. Dichlorophenoxyacetic acid only affected EOG at high concentration (100 mg/L), where it eliminated EOG within 2 min of exposure. With IPBC, EOG was decreased at 25 min of exposure to 1 microg/L; higher concentrations caused decreases to occur more rapidly. Excluding IPBC and glyphosate, all EOG reductions occurred at concentrations greater than the current Canadian water-quality guidelines and reported 96-h lethality values. Our results show that olfactory neurons can be impaired rapidly by some current-use pesticides, even at exposures in the low-microg/L range.

Animals↗
PubMed1984

The formation of the human paranasal sinuses.

The paranasal sinuses, which formed in mammals as turbinates and air spaces to perform or aid olfaction, eventually came to participate in the formation and maintenance of the entire cranium and to have concomitant functions as well. Evolving through primates to humans, they were influenced by the retraction of the maxillo-facial cranium and the enlargement of the cerebral cranium and thus reached the state unique to humans. The evolutionary phenomena involved in the formation and functions of the paranasal sinuses include adaptation to olfaction, respiration, and cranial formation. These were the phenomena which caused allometric development. Therefore, the paranasal sinuses did not always perform the same functions as they did when they originated, but, influenced by the evolutionary level of each animal and especially by the evolution to apes and humans, the original functions changed to different ones, mostly as instances of preadaptation, according to the evolutionary stage of each paranasal sinus. As the sense of smell ascribed to the mammalian nose began to regress together with the retraction of the jaw (maxilla and mandible), the orbits started to form in primates, and the ethmoturbinate became full of cavities and formed the lateral walls of the nasal cavity. This occurred because the evolution of primates and higher made olfaction non-essential and respiration foremost. When hominization began and the facial cranium distinctly retracted, the maxillary sinus enlarged because of the enlargement of the molars, the change in the dental arch, and the enlargement of the masticatory muscles, and its air-conditioning function became established. The secondary sinuses of the frontal and sphenoid sinuses, which had expanded in mammals, started to regress in response to the new conditions. Especially when the cranium became spherical in the transition from the homo sap. neanderthalensis stage to the homo sap. sap. stage, the transformation of the cerebral cranium forced an increase in the angle between the forehead and the frontal cranial base and a decrease in the angle of the cranial base at the sella turcica. The frontal and sphenoid sinuses then expanded in adjustment to this transformation.

Animals↗
PubMed2002

[Normative data of the Biolfa(R) olfactory test].

OBJECTIVES: To evaluate the feasibility of the Biolfa(R) olfaction test and establish normative values. PATIENTS AND METHODS: The new Biolfa(R) olfaction test includes a quantitative test to measure the olfactory threshold of three substances in a concentration range from 1 to 9 and a semi-quantitative test to assess olfactory "acuteness" for eight substances. Substances used for this test entail non-significant trigeminal stimulation. A population of 28 women and 24 men without olfactory dysfunction were tested. RESULTS: The olfactory threshold obtained with the quantitative test ranged from 5.86 to 9.54 for women, and from 6.4 to 9.6 for men. Analysis of the thresholds identified with the semi-quantitative test enabled establishing normative values for recognition of the eight substances. These values were reported on a diagram to allow partial translation of each subject's olfactory "acuteness". Olfactory threshold and smell identification ability were statistically superior for women. CONCLUSION: The Biolfa(R) olfaction test is the first allowing determination of both the olfactory threshold and quantification of smell identification ability. Normative values were obtained in this study to detect disease states.

Feasibility Studies↗
PubMed1991

Molecular cloning and sequencing of general odorant-binding proteins GOBP1 and GOBP2 from the tobacco hawk moth Manduca sexta: comparisons with other insect OBPs and their signal peptides.

Odorant-binding proteins (OBPs) are small, water-soluble proteins uniquely expressed in olfactory tissue of insects and vertebrates. OBPs are present in the aqueous fluid surrounding olfactory sensory dendrites and are thought to aid in the capture and transport of hydrophobic odorants into and through this fluid. OBPs may represent the initial biochemical recognition step in olfaction, because they transport odorants to the receptor neurons. Insect OBPs are represented by multiple classes: pheromone-binding proteins (PBPs) and general odorant-binding proteins (GOBP1 and GOBP2). PBPs associate with pheromone-sensitive neurons, while GOBPs associate with general odorant-sensitive neurons. Analysis of N-terminal amino acid sequences of 14 insect OBPs isolated from six species indicated that the PBPs were variable and the GOBPs were highly conserved. However, inferred properties of these proteins were based only on partial sequence data. We now report the full-length sequences of a GOBP1 and GOBP2 from the moth Manduca sexta and compare these sequences with those of PBPs from three species, including M. sexta, Antheraea polyphemus, and A. pernyi. We also compare these with a GOBP2 of A. pernyi, previously identified only as a novel OBP. These comparisons fully support our N-terminal analysis. The signal peptide sequences of seven insect OBPs reveal conserved sequences within OBP classes, but not between OBP classes even within the same animal species. This suggests that multiple OBPs may be coexpressed in the same cell type, but differentially processed in a class-specific manner. Properties of the GOBPs suggest that general olfaction is broadly receptive at the periphery. Properties of the PBPs suggest that pheromone olfaction is discriminatory at the periphery, and that the initial biochemical steps in pheromone detection may play an active role in odor perception.

Amino Acid Sequence↗
PubMed1991

[Development of the sense of smell, a review].

The pre- and postnatal development of human olfaction is described. Data from animal experiments a partially reviewed as a base for understanding of the results of olfactory testing of babies and children. In rat fetuses the vomero-nasal-organ is used as detector of molecules in the amnion fluid. The perinatal aeration of the nasal cavity allows the adequate stimulation of the olfactory epithelium. The early postnatal olfaction is a brainstem function; later the olfactory cortical area are used for the discrimination between odorants. There are only a few investigations about the olfactory function in childhood, so that the testing of olfaction for detecting abnormal brain developments is just in the beginning.

Animals↗
PubMedDate not supplied

[Functional properties of chemoreceptor systems].

It is proposed that the majority of organisms with developed sensory chemoreception possesses two distinct systems of chemical sensitivity performing different tasks. The first system (taste) serves for perception of alimentary substances -- metabolites, or dangerous compounds. The second one (olfaction) perceives metabolically neutral substances which serve as pure signals. All other features of these two systems of chemoreception are considered as secondary, resulting from the main task of each system. In particular, the signal function of olfaction demands sufficiently high sensitivity and a large number of individually recognizable stimuli. The physical state of olfactory stimulants (vapours or solutions) is non-essential. Arguments are presented showing the existence of contact chemoreception with pure signal function both invertebrates and in invertebrates which serves as "contact olfaction". Several problems of chemical communication in animals are discussed, in particular, the role of chemoreception systems in the perception of pheromones and also different kinds of sensory analysis involved in the recognition of chemical stimuli.

Animals↗
PubMed2007

Retronasal and orthonasal olfactory ability after laryngectomy.

OBJECTIVE: To characterize orthonasal and retronasal olfactory ability in patients who have had a total laryngectomy (TL). DESIGN: Prospective psychophysical evaluation of orthonasal and retronasal olfactory function. SETTING: Academic center outpatient clinic. PATIENTS: Volunteer sample of 36 subjects who underwent laryngectomy 0.5 to 25.0 years after TL (median, 3.5 years) and 36 age-, sex-, and smoking history-matched controls. MAIN OUTCOME MEASURES: Scores on established psychophysical tests of orthonasal and retronasal olfaction and self-rating scores of smell assessed with a visual analog scale. RESULTS: Assessment of orthonasal olfactory ability yielded a mean composite score of 4.3 (maximum score, 7) for the TL group and 5.3 for the control group (P = .002). Evaluation of retronasal olfactory ability resulted in a mean score of 11.0 (maximum score, 20) for the TL group vs 14.3 for the control group (P<.001). The mean self-rating scores of smell were 2.9 and 6.6 (maximum score, 10) for the TL and control groups, respectively (P<.001). Self-ratings of smell positively correlated with orthonasal (r(S) = 0.42; P<.001) and retronasal (r(S) = 0.50; P<.001) olfactory ability. CONCLUSIONS: Laryngectomy is associated with measurable decreases in olfactory function that are also subjectively perceived. Quantification of decrements in orthonasal and retronasal olfactory function can be used to characterize the severity of hyposmia and to assess the potential for, and efficacy of, olfactory rehabilitation. Although self-assessment with a simple visual analog scale successfully identifies many laryngectomy patients who have objective evidence of olfactory dysfunction, further investigation is necessary to evaluate and compare its validity and reliability with other available survey instruments that purport to measure olfaction.

Aged↗
PubMed2002

Prevalence of olfactory impairment in older adults.

CONTEXT: Older adults represent the fastest-growing segment of the US population, and prevalences of vision and hearing impairment have been extensively evaluated. However, despite the importance of sense of smell for nutrition and safety, the prevalence of olfactory impairment in older US adults has not been studied. OBJECTIVE: To determine the prevalence of olfactory impairment in older adults. DESIGN, SETTING, AND PARTICIPANTS: A total of 2491 Beaver Dam, Wis, residents aged 53 to 97 years participating in the 5-year follow-up examination (1998-2000) for the Epidemiology of Hearing Loss Study, a population-based, cross-sectional study. MAIN OUTCOME MEASURES: Olfactory impairment, assessed by the San Diego Odor Identification Test and self-report. RESULTS: The mean (SD) prevalence of impaired olfaction was 24.5% (1.7%). The prevalence increased with age; 62.5% (95% confidence interval [CI], 57.4%-67.7%) of 80- to 97-year-olds had olfactory impairment. Olfactory impairment was more prevalent among men (adjusted prevalence ratio, 1.92; 95% CI, 1.65-2.19). Current smoking, stroke, epilepsy, and nasal congestion or upper respiratory tract infection were also associated with increased prevalence of olfactory impairment. Self-reported olfactory impairment was low (9.5%) and this measure became less accurate with age. In the oldest group, aged 80 to 97 years, sensitivity of self-report was 12% for women and 18% for men. CONCLUSIONS: This study demonstrates that prevalence of olfactory impairment among older adults is high and increases with age. Self-report significantly underestimated prevalence rates obtained by olfaction testing. Physicians and caregivers should be particularly alert to the potential for olfactory impairment in the elderly population.

Aged↗
PubMed2006

Association of olfactory dysfunction with incidental Lewy bodies.

Olfactory dysfunction is found in early Parkinson's disease (PD) and in asymptomatic relatives of PD patients. Incidental Lewy bodies (ILB), the presence of Lewy bodies in the brains of deceased individuals without a history of PD or dementia during life, are thought to represent a presymptomatic stage of PD. If olfactory dysfunction were associated with the presence of ILB, this would suggest that olfactory deficits may precede clinical PD. The purpose of this study was to determine the association of olfactory dysfunction during late life with ILB in the substantia nigra or locus ceruleus. Olfaction was assessed during the 1991-1994 and 1994-1996 examinations of elderly Japanese-American men participating in the longitudinal Honolulu-Asia Aging Study. Among those who later died and underwent a standardized postmortem examination, brains were examined for Lewy bodies in the substantia nigra and the locus ceruleus with hematoxylin and eosin stain. Lewy bodies in the brains of individuals without clinical PD or dementia were classified as ILB. There were 164 autopsied men without clinical PD or dementia who had olfaction testing during one of the examinations. Seventeen had ILB. The age-adjusted percent of brains with ILB increased from 1.8% in the highest tertile of odor identification to 11.9% in the mid-tertile to 17.4% in the lowest tertile (P = 0.019 in test for trend). Age-adjusted relative odds of ILB for the lowest versus the highest tertile was 11.0 (P = 0.02). Olfactory dysfunction is associated with ILB. If incidental Lewy bodies represent presymptomatic stage of PD, olfactory testing may be a useful screening tool to identify those at high risk for developing PD.

Aged↗
PubMed1998

Trigeminal and olfactory sensitivity: comparison of modalities and methods of measurement.

OBJECTIVE: The principal objective was to chart sensitivity for human nasal irritation by alternative psychophysical methods, namely, a common detection procedure versus a nasal lateralization procedure that required the subject to indicate whether a vapor had stimulated the left or right nostril. This objective relates to the broader issues as to (a) whether subjects with normal olfaction (normosmics) can yield, through novel methodology, an index of sensitivity to nasal irritation comparable with that obtained from subjects without olfaction (anosmics) and (b) whether both types of subjects have similar irritation sensitivity in general. This study sought to gauge interconvertability both between types of subjects and between modes of stimulus presentation for irritative and, where appropriate, olfactory stimulation. METHODS: Static dilution series of four n-aliphatic alcohols, chosen to represent volatile organic compounds (VOCs), provided the source of calibrated olfactory and irritative vapors emitted from their squeezable containers into the nose or eye either by a mechanical device or by hand. Standard psychophysical methodology (forced-choice; ascending strength of stimulation) served to chart detection thresholds for irritation and odor and an analogous procedure served to chart the threshold for localization of stimulation. RESULTS: Within the limits of resolution, detection thresholds and nasal localization thresholds yielded comparable indices of the potency of the VOCs to evoke nasal irritation. The thresholds agreed well with those for detection of eye irritation, though only the eyes proved to be capable of detecting irritation from l-octanol. The method of emitting the stimulus had little material effect on measures of either irritative or olfactory detection. CONCLUSIONS: The threshold for nasal localization offers a suitable way to measure nasal irritation in normosmic persons. Olfactory stimulation does not interfere with the measure since subjects cannot localize on that basis. Anosmic and normosmic persons have comparable sensitivity to nasal and ocular irritation. If anosmic persons have any lower sensitivity, as sometimes claimed, it would seem to have only trivial consequences for estimates of the irritative potency of VOCs.

Adult↗