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At least 19 recordsLinked to original sources
PubMed1975

Olfaction in fish.

1. Recent progress in the studies on olfaction in fish, with particular emphasis on electrophysiological and behavioral responses to biological odors and related chemicals, is reviewed. 2. One of the most characteristic features in fish olfaction is that it takes place entirely in the aquatic environment. The carrier of stimulant molecules is not air but water; therefore, chemicals that are detected olfactorily by fish need not be volatile, but must be soluble in water. 3. The olfactory organs of fishes are diversely developed. At one extreme they are well developed (macrosmatic) such as in sharks and eels, and at the other they are poorly developed (microsmatic) such as in pike and stickleback. 4. The nasal cavity is lined with the olfactory epithelium, which is raised from the floor of the organ into a series of lamellae to make a rosette. The arrangement, shape and degree of development of the lamallae in the rosette vary considerably from species to species. 5. It is doubtful whether simple relation exists between the surface area of the olfactory epithelium and sensitivity to odors, since the sensory epithelium is not distributed uniformly over the surface of the olfactory lamellae. 6. The olfactory epithelium of fish, like other vertebrates, consists of three cell types: receptor cells, supporting cells and basal cells. 7. The receptor cell, which is a bipolar primary sensory cell, sends a slender cylindrical dendrite toward the surface of the epithelium and is directly connected with the olfactory bulb by its axon. The dendrite terminates in a minute swelling (olfactory knob) which bears a variable number of cilia. 8. The information from the receptor cell is conveyed into the olfactory bulb, the first relay station, where signals are processed and integrated. The dominant feature of the bulb is the synaptic contact between the primary and secondary olfactory neurones in the form of glomerulus. 9. All the available evidence points to a great acuity of the olfactory sense in many fish species both in the capability and discriminating odorous chemicals. However, much discrepancies exist among data obtained by behavioral and electrophysiological techniques mainly because of the lack of systematic investigations. 10. Electrophysiological studies of olfaction have been hampered by the extremely small size of the olfactory neurones. 11. A slow negative monophasic potential is induced in the olfactory epithelium when stimulated with odorous chemicals (electro-olfactogram, EOG).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Olfaction: the neglected sense.

Although olfactory complaints prompt an estimated 200,000 people each year to seek medical consultation in the U.S., there is a dearth of information available in the nursing literature. Recent research links olfaction to degenerative processes in Alzheimer's disease, Parkinson's disease and human immunodeficiency virus infection. This article reviews anatomy and physiology of the olfactory system, describes alterations in smell function and reviews assessment with the University of Pennsylvania Smell Identification Test and odor detection threshold testing. Nurses can advocate thorough assessment and prompt treatment of associated conditions, and educate the patient and family regarding ways to maximize current functioning when olfaction is impaired.

Humans↗
PubMedDate not supplied

The effects of prenatal alcohol exposure on behavioral and neuroanatomical components of olfaction.

Prenatal alcohol exposure is associated with deficits in odor-associative learning in very young rat pups. One alternative explanation for these findings is that rather than a learning deficit per se, alcohol-exposed pups may display a sensory deficit. The present study was designed to examine the effects of prenatal alcohol exposure on behavioral and neuroanatomical components involved in olfaction. The subjects in this study were pups exposed to 35% ethanol-derived calorie (EDC) liquid diet from gestation days (GD) 6-20. Two control groups were included, a 0% EDC pair-fed and an ad lib lab chow group. In Experiment 1, respiratory response to a novel odor was examined in pups tested at either 3, 4, or 10 days of age. The 35% EDC offspring clearly detected the odor. Furthermore, there was an apparent alcohol-related development delay in respiratory rate as shown by a lower baseline respiratory rate at PN 3 relative to controls which was no longer apparent by PN 4. Experiment 2 examined the volume of two neuroanatomical structures involved in olfaction, the main olfactory bulb (MOB) and the vomeronasal organ (VNO) in 3-day-old pups. Prenatal alcohol exposure was associated with a decreased volume of the MOB although the VNO was unaffected.

Animals↗
PubMed1992

Relative importance of vision and olfaction for detection of estrus by bulls.

The objective of this experiment was to determine the relative importance of olfaction and visual observation of heifer mounting behavior to the detection of estrus by bulls. An observation pen was designed to allow the evaluation of the preference of five sexually experienced bulls under three sets of stimuli. The observation pen was 4 m x 17 m with a smaller enclosure (2 m x 4 m) at each end that housed either a pair of heifers in diestrus (D), a pair of heifers in estrus that were allowed to mount one another (EM), or a pair of heifers in estrus that were separated by an aluminum panel to prevent mounting behavior (E). The preference of bulls was determined between EM heifers compared to D heifers, EM heifers compared to E heifers, and E heifers compared to D heifers. Each bull was individually allowed 5 min inside the observation pen to demonstrate its preference. Preference was defined as the total time that bulls spent within 2.5 m of either pair of heifers. Each bull was subjected to 10 observation periods of each set of stimuli during a 4-mo period. Bulls preferred to be near EM heifers compared with either E or D heifers (P less than .05). However, the bulls demonstrated no preference (P greater than .05) for E heifers compared with D heifers. These data indicate that when physical contact is denied, bulls use visual observation of female homosexual behavior as the primary indicator of estrus and that olfaction alone provides insufficient stimuli for bulls to indicate preference toward heifers in estrus compared with heifers in diestrus.

Animals↗
PubMed1978

Olfaction in health & disease.

The significance of olfaction is frequently overlooked by health professionals. The purpose of this presentation is to briefly review the neurophysiology of olfaction, survey the relevant research, and present specific implications for occupational therapists working in both physical disabilities and psychiatric settings.

Adult↗
PubMed1977

Clinical testing of olfaction reassessed.

Odours in current use for testing olfaction (e.g., peppermint, camphor) cause considerable trigeminal nerve stimulation; this would render them relatively inefficacious in the detection of lesions of the main olfactory pathway. Musks and floral odours are considered to be relatively 'pure' olfactory stimulants, acting virtually exclusively via the first cranial nerve. These odours have been compared with standard odours in a group of patients whose olfactory pathways had been damaged by frontal tumours, surgical operation, head injury, multiple sclerosis and miscellaneous causes. Hyposmia or anosmia was detected more frequently and more reliably by musks and floral odours in all groups of patients; a number of patients had gross deficits of odour description without hyposmia or anosmia. Two-thirds of an unselected group of patients with multiple sclerosis had olfactory abnormalities. A substantial improvement in the rate of detection of organic lesions affecting the olfactory pathway can be achieved by substituting odours such as musk ketone, exaltolide, linalyl acetate and coumarin for those in current use.

Humans↗
PubMed1992

Ultrastructural studies on membrane, cytoskeletal, mucous, and protective compartments in olfaction.

There is a great variety in the morphological appearance of olfactory structures across the metazoan animal kingdom. Despite this variety the receptive structures themselves have a strikingly similar architecture, namely some type of elongated cellular extension that is spanned by a membrane and surrounded by mucus. These cellular extensions can either be modified primary or secondary cilia, or microvilli. There are more similarities between membranes of these extensions than between the cytoskeletal elements immediately underneath the membranes. One might infer that the cytoskeletal elements of the cellular extensions merely serve as a scaffold for the membranes, whereas the similarity in membrane ultrastructure provides morphological evidence supporting the concept that these membranes are responsible for the initial olfactory transduction process. The transduced message is transported to the brain, where it is decoded to initiate the cascade of events resulting in the organisms' appropriate behavioral response to the initial odorous stimulus. The varying appearance of olfactory structures across the animal kingdom is probably produced by evolutionary pressure to adapt the olfactory system to the animal's environment. This review deals with the ultrastructural aspects of these facets of olfaction.

Animals↗
PubMed1977

Taste and olfaction in human obesity.

Earlier studies have shown differences between normal weight and obese humans in responsivity to external and internal stimuli. This study shows that normal weight and obese subjects do not differ in hedonic response to sucrose (taste) and benzaldehyde (odor). However, a perceptual typing of individuals based upon hedonic response is possible for both gustatory and olfactory processes. Ratings of pleasantness for the sweet taste of sucrose appear to generalize to the food-related odor of bitter almonds. The method of magnitude estimation as applied to the study of taste and olfaction in man may reveal relationship between changes in internal state and hedonic behavior.

Adult↗
PubMed1979

A study of olfaction and gustatory senses in sheep after olfactory bulbectomy.

The importance of taste and smell in discrimination of sodium salts was examined in normal and anosmic sheep. To test for anosmia, faeces of pig, calf and sheep were used as noxious odours. Intact sheep, and sheep with one olfactory bulb removed avoided the aversive stimulus whereas following total bulbectomy, the faecal odour was no longer a deterrent. Olfactory bulbectomy did not affect food intake but changes in fluid intake, urinary loss and electrolyte excretion were apparent. In two-choice preference tests, normal sheep showed a marked aversion for 0.48 M NaHCO3 and 0.51 M NaCl when compared to water. Following either unilateral or bilateral olfactory bulbectomy the aversion for sodium salts persisted but was less extreme. This suggests that in the final discrimination of sodium salts the sense of taste is dominant but olfaction or the olfactory bulb may have a minor role.

Animals↗
PubMed1992

Molecular messengers of olfaction.

Our knowledge of olfactory signal transduction has been greatly clarified by several recent advances. Molecular cloning has revealed a large family of putative odorant receptors localized to olfactory epithelium that display a seven-transmembrane-domain motif suggesting an association with G proteins. Very potent and rapid enhancement of both adenylyl cyclase and phosphoinositide turnover has been demonstrated in response to odorants both in isolated olfactory cilia and primary olfactory receptor neuronal cultures. A Ca(2+)-calmodulin-dependent phosphodiesterase has been localized to olfactory cilia. A key role for Ca2+ is evident from many investigations. More recently, odorants have also been shown to affect the levels of cGMP in olfactory receptor neurons. The involvement of multiple second messengers may provide mechanisms for both fine-tuning and desensitization of olfaction.

Animals↗
PubMed1992

Second messenger signalling in olfaction.

The primary reactions of the chemo-electrical signal transduction pathway in olfactory receptor neurons are mediated by two alternative second messengers, cAMP and inositol 1,4,5-trisphosphate. The rapid and transient intracellular signalling is terminated by the action of negative-feedback loops which uncouple the reaction cascades (desensitization). Recent evidence suggests that secondary reactions in olfaction (adaptation) may also be controlled by second messengers.

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↗
PubMed1975

[Significance of olfaction in the feeding behavior of toads (Amphibia, Anura, Bufonidae): studies with the natterjack (Bufo calamita Laur.)].

The influence of olfactory and visual prey stimuli on the feeding behaviour of toads was studied as well as their response to lasting olfactory cues. A further aim was to find simple methods for testing olfactory responsiveness in anurans. Subjects were 8 adult specimens of the European species Bufo calamita (natterjack) kept in captivity one year at least. The results point to the rôle of olfaction in these animals.

Animals↗
PubMed1992

Olfaction in migraineurs.

Many investigators have described olfactory dysfunction among migraineurs. Olfactory stimuli can precipitate migraine, and olfactory hallucinations can occur as auras of migraines or as part of the symptom complex. Despite many reports linking olfactory phenomena and migraine, no evaluations of the olfactory abilities of migraineurs have been documented. To begin such assessments, sixty-seven consecutive migraine patients were given Pyridine odor threshold tests. Twelve of them (18%) scored as hyposmic or anosmic. In comparison, 1% of the general population of the U.S. is hyposmic or anosmic. Aside from possible diagnostic or methodological error, several possibilities may account for our result: migraine may induce olfactory pathology; olfactory pathology may induce migraine, or; a common pathogen may induce both olfactory dysfunction and migraine. The association of migraine with the emotional component of the limbic system has long been recognized, and our results strengthen its association with the olfactory component as well. Headache patients should be tested for olfactory loss and warned of such risks as inability to detect gas leaks and spoiled food.

Humans↗