Abstract: Through his sense of smell man has long encountered the phenomenon of molecular recognition. As early as first century BC, the Roman poet and philosopher Lucretius wrote (based on Democritus' atomic theory), "Such substances as agreeably titilate the senses are composed of smooth round atoms; those that seem bitter and harsh are more tightly compacted of hooked particles . . . " (Lucretius 55 BC). The last century has brought the realization that similar recognition of atomic or molecular configurations constitutes the basis of all life processes. Probably because olfaction has been a subject of study and speculation long before the advent of modern biochemistry, numerous olfactory theories have been proposed (Davies 1971, Amoore 1982). However, in the eyes of a contemporary molecular biologist, a special theory accounting for the initial steps in olfaction may seem superfluous, as the sensory cells in the nose are not unique in their ability to receive chemical signals selectively. It would be most parsi­ monious to assume that odorant recognition involves membrane protein receptors and transduction components analogous to those which mediate the specific responses to hormones, growth factors, neurotransmitters, and antigens. This notion, which corresponds to the combined Stereo­ chemical/Functional-group theories of olfaction (Amoore 1982, Beets 1971), is validated by many of the studies reviewed here. Olfactory recognition is mediated by a large ensemble' of sensory cells, each conveying a fraction of the information that signifies the nature of the odorant and its concentration. The sensory neurons receive chemical signals at their dendritic membrane and respond by firing action potentials down their axons. The olfactory response is therefore analogous to neurotransmitter reception, and the sensory organ is a simple but

Abstract: The interaction of an odorant with the chemosensitive membrane of olfactory receptor neurons initiates a sequence of molecular and membrane events leading to sensory transduction, impulse initiation, and the transmission of sensory information to the brain. The main steps in this sequence are summarized in Figure 6. Several lines of evidence support the hypothesis that the initial molecular events and subsequent stages of transduction are mediated by odorant receptor sites and associated ion channels located in the membrane of the cilia and apical dendritic knob of the olfactory receptor neuron. Similarly, the membrane events associated with impulse initiation and propagation are mediated by voltage-gated channels located in the initial axonal segment and the axolemma. The ionic and electrical events associated with the proposed sequence have been characterized in general using a variety of experimental techniques. The identification, localization, and sequence of membrane events are consistent with the neurophysiological properties observed in specific regions of the bipolar receptor neuron. The influence of other cells in the primary olfactory pathway such as the sustentacular cells in the olfactory epithelium, the Schwann cells in the olfactory nerve, and the astrocytes in the olfactory nerve layer in the olfactory bulb on the physiological activity of the olfactory receptor neuron is an emerging area of research interests. The general principles derived from the experimental results described in this review provide only a framework that is both incomplete and of necessity somewhat speculative. As noted in the Introduction, the multidisciplinary study of the primary olfactory pathway is undergoing a renaissance of research interest. The application of modern biophysical, cell, and molecular biological techniques to the basic issues of odorant recognition and membrane excitability will clarify the speculations and lead to the establishment of new hypotheses. Three broad areas of research will benefit from such studies. First, the application of biophysical techniques will lead to a detailed characterization of the membrane properties and associated ion conductance mechanisms. Second, the isolation and biochemical characterization of intrinsic membrane and cytosolic proteins associated with odorant recognition, sensory transduction, and the subsequent electrical events will result from the utilization of cell and molecular biological techniques.(ABSTRACT TRUNCATED AT 400 WORDS)

Abstract: Intracerebral cannulas were implanted in both olfactory bulbs of 6 rabbits. A surface electrode-array (8 X 8) was implanted epidurally on the lateral surface of the left bulb. Each rabbit was conditioned to respond to sniffing to an odor paired with cutaneous shock while receiving continuous intrabulbar infusion of either vehicle or propranolol (100 microM at 1 microliter/hr) in vehicle. After two training sessions to the original odor, a response to a new odor was conditioned under the influence of the alternate infusate. Electroencephalographic (EEG) activity was sampled on inspirations before and during odor presentations. During vehicle infusion a transient alteration in the pattern of activity was acquired that occurred during the second and third inspirations following presentation of the reinforced odor. The acquisition did not occur when propranolol was infused. No significant pattern changes occurred with unreinforced odors in either condition. There was no local anesthetic effect of the racemic mixture of propranolol found for any type of electric activity, including antidromic spike activity observed in an independent control group. Intrabulbar norepinephrine injection (100 microM, 10 microL) resulted in an amplitude increase of the bulbar 40-80-Hz EEG and a potentiation of the transient spatial pattern change to a novel odor, when compared with those observed during vehicle infusion. It is concluded that norepinephrine released under centrifugal control may act to prevent or delay habituation that otherwise occurs rapidly to unreinforced odors.

Abstract: The sensory neurons of the olfactory epithelium, as a consequence of their odor detection function, contact both the external environment and the central nervous system. The possibility that substances applied to the epithelium might reach the central nervous system was investigated by the intranasal application of peroxidase-conjugated wheat germ agglutinin (WGA-HRP). WGA-HRP was transported through olfactory receptor axons to the glomerulus of the olfactory bulb. Reaction product was localized electron microscopically to tubulovesicular profiles and dense bodies in sensory axons. Evidence of transneuronal transport was indicated by reaction product localized in dense bodies in dendrites postsynaptic to receptor cell axons. Periglomerular, tufted and mitral cells in the olfactory bulb also were transneuronally labeled. Anterograde transneuronal labeling occurred in the olfactory tubercle, piriform cortex and surrounding the lateral olfactory tract. Retrograde transneuronal label was found in neurons of the basal forebrain with the largest number of perikarya in the lateral nucleus of the horizontal limb of the diagonal band, a major source of cholinergic afferents to the olfactory bulb. These data suggest that substances, specifically those which bind to receptors, are transported from the olfactory receptor neurons in the nasal epithelium to the brain. Thus, the olfactory system may provide a route of entry for exogenous substances to the basal forebrain.

Abstract: An odorant-binding protein (OBP) was isolated from bovine olfactory and respiratory mucosa. We have produced polyclonal antisera to this protein and report its immunohistochemical localization to mucus-secreting glands of the olfactory and respiratory mucosa. Although OBP was originally isolated as a pyrazine binding protein, both rat and bovine OBP also bind the odorants [3H]methyldihydrojasmonate and 3,7-dimethyl-octan-1-ol as well as 2-isobutyl-3-[3H]methoxypyrazine. We detect substantial odorant-binding activity attributable to OBP in secreted rat nasal mucus and tears but not in saliva, suggesting a role for OBP in transporting or concentrating odorants.

Abstract: Male-female courtship interactions inDrosophila melanogaster are mediated in part by chemical cues. A comparison of the courtship behaviors of normal and genetically olfaction-deficient (olfD) flies lends strong support to this hypothesis and leads to the following inferences regarding the importance of chemical interchange during courtship. Virgin females respond to male courtship by slowing and finally stopping their movements, which appears to enhance the probability of copulation; (olfD) females are defective in this stopping response and in their receptivity to mating. Males can be stimulated to court by airborne cues from virgin females which are effective over a distance of ca. 5 mm. By comparison, the chemical courtship-stimulating cues from immature flies have little airborne efficacy; immature males appear to stimulate courtship only by contact chemoreception. The genetic upset or removal from courtship interactions of olfactory, visual, and auditory cues (thus leaving contact chemoreception as the probable major means of male-female interaction) results in virtual behavioral sterility.

Abstract: Twenty-four (12 males, 12 females) healthy, full-term neonates were exposed to an artificial odorant within the first day after birth for approximately 24 hrs to determine if mere exposure would lead to a subsequent preference for that odor In choice tests following the treatment period, female infants displayed preferential orientation to the exposure odor Males, in contrast, displayed no evidence of preference for the exposure odor; rather, they demonstrated a right turning bias regardless of odor location These data suggest that familiarization with an odor shortly after birth is sufficient for female infants to develop preferential responsiveness to that odor

Abstract: The sense of smell involves the stimulation of sensory neurons by odorants to produce depolarization and action potentials. We show that olfactory responses may be mediated by a GTP-binding protein (G protein), a homolog of the visual, hormonal, and brain signal transducing polypeptides. The olfactory G protein is identified in isolated dendritic membranes (olfactory cilia preparations) of chemosensory neurons from three vertebrate species and is shown to mediate the stimulation by odorants of the highly active adenylate cyclase in these membranes. The G protein of olfactory neurons is most similar to Gs, the hormonal stimulatory GTP-binding protein. Its alpha subunit has a molecular weight of about 42,000, and it undergoes ADP-ribosylation catalyzed by cholera toxin that leads to adenylate cyclase activation. The slight difference in molecular weights of the frog olfactory and the liver Gs alpha subunits and the higher sensitivity of olfactory adenylate cyclase to nonhydrolyzable GTP analogs are consistent with the possible existence of different Gs variants. Signal amplification due to the olfactory G protein may be responsible for the unusual acuity of the sense of smell.

Abstract: Ten participants sought to detect four odorants: benzaldehyde, pyridine, and two alcohols, n-butyl and n-amyl alcohol, that smelled similar to each other. These were presented repeatedly on 3 successive days. The sequence of testing during a session made it possible to determine whether experience with one odorant would specifically facilitate the detectability of a similar-smelling odorant and whether any such facilitation would restrict itself to the nostril through which the experience was gained. Neither of these possibilities occurred. Instead, measured sensitivity increased rather uniformly both within and across days. Net gain from beginning to end exceeded an order of magnitude. Averaging across sessions gave a picture of smaller than usual individual differences, under 20 to 1, attributable mainly to general rather than odorant-specific differences in sensitivity. The results indicate that thresholds gathered in customary brief testing will underestimate olfactory sensitivity and overestimate individual differences. Incorporation of a reference odorant into threshold experiments should increase comparability among studies.

Abstract: One: Some General Considerations.- A Quarter of a Century of Studies of Chemical Communication in Vertebrates.- The Tetrapod Epidermis: A System Protoadapted as a Semiochemical Source.- Mammalian Semiochemistry: Issues and Futures, with some Examples from a Study of Chemical Signalling in Cattle.- Motor Patterns Dedicated to Sensory Functions.- Two: Chemistry.- Chemical Control of Feeding in Herbivorous and Carnivorous Fish.- Characteristics of Earthworm Washings Detected by the Vomeronasal System of Snakes.- Chemical and Biological Investigations of Female Mouse Pheromones.- Behavioral Function and Chemistry of Volatiles From Feces and Anal Secretions of House Mice, Mus musculus - A Preliminary Report.- Three: Fishes.- The Evolution of Chemical Alarm Signals in Fishes.- Fish Reproductive Pheromones.- Chemosensory Orientation Mechanisms of Fish.- Release of Spawning Pheromone(s) by Naturally-ovulated and Prostaglandin-injected, Nonovulated Female Goldfish.- The Structural and Functional Relationships Between Olfactory and Reproductive Systems From Birth to Old Age in Fish.- Four: Amphibians.- The Evolution of Salamander Courtship Pheromones.- Pheromonal Markers as Territorial Advertisement By Terrestrial Salamanders.- The Recognition and Use of Chemical Signals By a Nesting Salamander.- Evolution of Chemical Signals as a Premating Isolating Mechanism in a Complex of Terrestrial Salamanders.- Chemical Ecology of Kin Recognition in Anuran Amphibians.- Five: Reptiles.- Pheromones and Reproduction in Garter Snakes.- The Role of Pheromone Trails in the Sociobiology Of Snakes.- Pheromone Mimicry in Garter Snakes.- Initial Den Location by Neonatal Prairie Rattlesnakes: Functions, Causes, and Natural History in Chemical Ecology.- Exploratory Tongue Flicking by Green Iguanas In Laboratory and Field.- Lizard Pheromones: Behavioral Resnonses and Adaptive Significance in Skinks of the Genus Eumeces.- Chemoreception in the Homing and Orientation Behavior of Amphibians and Reptiles, with Special Reference To Sea Turtles.- Six: Birds.- The Ecological and Evolutionary Challenges Of Procellariiform Olfaction.- Chemoreception and the Selection of Green Plants as Nest Fumigants by Starlings.- Seven: Mammals.- Economic Consequences of Scent Marking in Mammalian Territoriality.- Chemical Signals and Kin Recognition in Spiny Mice (Acomys cahirinus).- Genetic Basis for Individual Discriminations: The Major Histocompatibility Complex of the Mouse.- The Suppression of Ovarian Function By Chemosignals.- The Evolutionary Significance of the Olfactory Block to Pregnancy.- Puberty-Influencing Chemosignals in House Mice: Ecological and Evolutionary Considerations.- The Puberty Delaying Pheromone of the House Mouse: Field Data and a New Evolutionary Perspective.- Effects of Genotype, Social Interaction, and Testosterone on Esterases in Male Mouse Urine.- The Mammalian Vomeronasal System: Its Role in Learning and Social Behaviors.- Olfactory Communication Among Rats: Information Concerning Distant Diets.- Alarm Chemosignals in a Meriones unguiculatus: Prey-Predator Interactions.- Avoidance Response of Pocket Gophers (Thomomys talpoides) to Mustelid Anal Gland Compounds.- The Comparative Responses of Mice and Voles To Conspecific and Heterospecific Odors in The Field - A Lesson in Social Behavior.- Morphometric Patterns Among Microtine Rodents. I. Sexual Selection Suggested by Relative Scent Gland Development in Representative Voles (Microtus).- Female-induced Delay of Puberty in Bank Vole and European Pine Vole Females.- Familial Chemosignals Interfere with Reproductive Activation in Female Pine Voles, Microtus pinetorum.- Odor Images: Responses of Beaver to Castoreum Fractions.- Scent-marking in Pikas (Ochotona princeps): Test of a Breeding-facilitation Hypothesis.- Histology and Gross Morphology of the Sexually Dimorphic Sternal Gland in the North American Opossum, Didelphis virginiana Kerr.- Chemical Communication in Gray Short-tailed Opossums (Monodelphis domestica) with Comparisons to other Marsupials and with Reference to Monotremes.- Observations on Chemical Communication and its Glandular Sources in Selected Insectivora.- Plantar Glands in North American Mustelidae.- The Marking Behavior of Male Przewalski's Horses.- Chemical Communication Among Asian Elephants.- Territorial Scent Marking by Two Sympatric Lemur Species.- Chemical Signals in Callitrichid Monkeys - A Comparative Review.- Cross-cultural Studies of Taste and Smell Perception.- Author Index.- Subject And Taxonomic Index.

Abstract: Membranes prepared from the olfactory mucosa of the rat show a high level of adenylate cyclase activity. The activity increases up to 2-fold in the presence of physiologically relevant concentrations of odorants and is inhibited by Ca2+. The level of cyclase activity found is sufficient to explain the speed of olfactory transduction, which occurs on a time scale of tens of milliseconds.

Abstract: The Turkey Vulture (Cathartes aura) is generally thought to rely on olfactory cues to locate carrion. Because vertically rising odorants are dispersed rapidly by wind tur- bulence, we predict that Turkey Vultures should be highly sensitive to these chemicals to detect them at foraging altitudes. Olfactory thresholds to three by-products of animal decomposition (1 x 10 -6 M for buta- noic acid and ethanethiol, and 1 x 10 -5 M for trimethylamine) were determined from heart- rate responses. These relatively high thresholds indicate that these odorants are probably not cues for foraging Turkey Vultures. Odorant thresholds, food habits of Turkey Vultures, and the theoretical properties of odorant dispersion cast some doubt on the general impor- tance of olfaction in food location by this species. Received 23 September 1985, accepted 3 March 1986. THE sensory modality by which Turkey Vul- tures (Cathartes aura) locate carrion has been debated by naturalists for nearly 140 years (see Stager 1964 for review). Most of the controver- sy concerned whether olfaction or vision was the more important sense, although other the- ories included an "occult" sense (Beck 1920), the noise of carrion-eating rodents, or the noise of carrion-eating insects (Taber 1928, Darling- ton 1930) as attracting Turkey Vultures to their prey.

Abstract: Rats are shown to acquire a preference for protein-predictive olfactory cues which depends on a state of mild deficit in protein intake—i.e. a learned protein-specific appetite.

Abstract: The guanine nucleotide-binding stimulatory protein (Gs) couples hormone–receptor interaction to the activation of adenylate cyclase and the generation of cyclic AMP (see ref. 1 for a review). Studies using frog neuroepithelium indicate that the sense of smell is mediated by a Gs–adenylate cyclase system2, and this prompted us to test olfaction in the only known model of Gs deficiency in the animal kingdom, Gs-deficient (type 1a) pseudohypoparathyroidism (PHP), which occurs in humans3–8. Such patients are resistant to the cAMP-mediated actions of several hormones9. (Although Henkin10 has reported disturbances in the sense of smell in six patients with PHP, currently available biochemical measurements such as the cAMP response to parathyroid hormone (PTH) and determination of Gs activity were not reported and olfactory testing was limited.) In the present study, we found that all Gs-deficient patients had impaired olfaction when compared with PHP patients who had normal Gs activity (type 1b PHP, in which patients are resistant only to the action of PTH in the kidney). This is the first evidence of human olfactory impairment which can be related to Gs deficiency and suggests that Gs-deficient PHP patients may be resistant to cAMP-mediated actions in other non-endocrine systems.

Abstract: The olfactory system in vertebrates comprises a highly specialized sensory organ for detection and identification of minute quantities of chemicals in the environment. Experimental studies have documented the role played by olfactory information in social relationships, prey or predator recognition, and the search for food. The demands imposed by the aquatic environment have made the olfactory apparatus of fish a sensory system with many specialized features. At present only a few properties of the fish olfactory organ have been investigated.

Abstract: The recently introduced frog olfactory cilia preparation (Chen and Lancet, 1984; Pace et al., 1985) has been useful for studies of molecular chemosensory mechanisms. Here we describe in detail the properties of this cilia preparation. The "calcium shock" procedure leads to a complete removal of the cilia from the olfactory epithelial surface. Isolated cilia constitute segments of proximal regions with 9 X 2 + 2 microtubular arrangement and a large proportion of membrane vesicles, probably derived from the ciliary distal segments. Polypeptides unique to the olfactory cilia preparation, compared to a control preparation of palate respiratory cilia, are identified by Coomassie brilliant blue staining, silver staining, and radiolabeled lectin overlays, as well as by biosynthetic labeling with 35S-methionine in epithelial explants and protein phosphorylation in isolated cilia. The olfactory cilia preparation contains odorant-sensitive adenylate cyclase, which is absent in control membranes from deciliated epithelium. High activities of tyrosine and serine/threonine protein kinases are also present. The olfactory cilia preparation described should be instrumental in the further elucidation of the biochemistry and molecular biology of vertebrate olfaction.

Abstract: The objective of this research was to determine the acute toxicities of mercury (Hg), copper (Cu), and zinc (Zn) to coho salmon olfaction The authors used a behavioral assay of olfaction based on an avoidance reaction to L-serine in a two-choice Y-trough A second objective was to gain some understanding of the mechanism of metal-induced olfactory inhibition by observing how metals affect the binding of L-serine to its olfactory cell membrane receptor They have also taken the novel approach of addressing olfactory toxicology from the perspective of the odor molecule by considering metal speciation and metal-serpine complexation chemistry on the basis of chemical equilibrium computations

Abstract: Brown trouts, Salmo trutta, were exposed to 109Cd2+ in concentrations of 0.1, 0.5, 1.0 and 10.0 μg/1 in aquarial water during 1 or 2 weeks. The disposition of the 109Cd2+ in the tissues was then examined by whole‐body autoradiography and gamma spec‐trometry. The tissues accumulating the highest levels of 109Cd2+ were the olfactory apparatus, the gills and the trunk kidney. The autoradiography showed that in the olfactory apparatus there was a labelling of the epithelium of the olfactory rosette, the olfactory nerve and the anterior part of the olfactory bulb of the brain. The cadmium is probably taken up in the nerve cells in the olfactory epithelium and transported via axonal transport to the axonal terminations in the olfactory bulb of the brain. The 109Cd2+ in the gills comprised from about 75% to about 40% of the total body burden of the metal, the highest proportions being present at the lowest cadmium concentrations in the water and at the 1 week exposure interval. The 109Cd2+ in the kidney, which w...

Abstract: Disturbances in the sense of smell may be important both clinically and theoretically in Alzheimer's disease. Initial evidence of poor olfactory recognition performance in Alzheimer's and parkinsonian dementias was followed by two reports which corroborated olfactory dysfunction in Alzheimer's disease. The neuroanatomical and neurochemical bases for this disturbance are discussed. Despite an abundance of preclinical and clinical data linking olfaction with acetylcholine, a preliminary study failed to show any effect of scopolamine on olfactory thresholds. Two of the olfaction-Alzheimer's studies found significantly better performance in other demented groups (alcoholics and patients with vascular dementia), suggesting possible utility in the differential diagnostic workup. The effect of aging per se on olfactory performance cannot be assessed without rigorous control for cognitive dysfunction in sampled populations.

Abstract: A series of experiments revealed that humans can use olfaction to discriminate closely related strains of mice, differing genetically only at the major histocompatibility gene complex (H-2). In Experiment 1, subjects were asked to distinguish between the whole-body odors of live mice. In Experiments 2 and 3, the odor source was mouse fecal pellets, and in Experiments 4 and 5, the odor source was mouse urine.

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Abstract: A bioassay based on an olfactory conditioning method simulating the foraging situation in laboratory conditions was coupled with chemical analysis of volatile sunflower blends. Behavioural data obtained from for-agers'responses to volatile fraction point out that honeybees need to use only a limited fraction acting as a “simplified aromatic pattern” of the plant, among hundreds of compounds constituting the whole aroma. This active fraction included 27 polar compounds among which 14 were identified. Extension of such data to crop pollination and plant improvement is discussed.

Abstract: Differential conditioning of the proboscis extension reflex in honeybees is used to assess whether worker honeybees can be trained to discriminate between volatile odors emanating from different kin groups consisting of 2 or 20 workers. These odor source group workers are all reared and maintained under identical environmental conditions. They are the progeny of a queen that has been instrumentally inseminated so that eclosing adult workers can be sorted into colormorph full sister patrilines (workers are half sisters across patrilines). We demonstrate that workers are able to discriminate between the odors from groups of 20 individuals only if the groups represent individuals from different patrilines. However, discrimination occurs between groups of 2 individuals even if groups do not represent different patrilines. A number of environmental control experiments are also conducted. From our results we infer that there is heritable variation in the production of volatile odors by worker honeybees at a level that can be detected by the workers.