Abstract: The olfactory organ of tench is functionally divided in a vestibule and a gallery. Experimental observations are presented indicating that an unidirectional watercurrent is created from the vestibule to the gallery via the corridors which are formed by the leaves of the olfactory rosette. The conditions for creating the watercurrents are: oriented and symmetrical beats of cilia situated on the walls of the corridors, and appropriate spacing of the corridors. This principle for water sampling is found in the olfactory organs of trout, carp, roach, catfish, eel, rockling and dogfish. In some other fishes studied the olfactory organs have accessory olfactory sacs and there is no subdivision in vestibule and gallery. In these organs the watercurrents are achieved by a pumping mechanism of the sacs.

Abstract: 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.

Abstract: Carnosine in the chemoreceptor neurons of the olfactory epithelium can be labeled in vivo by intranasal irrigation with either14C-β-alanine or14C-L-histidine. This newly synthesized carnosine (but not the precursor amino acids) is translocated to the olfactory bulb, where the olfactory chemoreceptor axons synapse with the dendrites of mitral cells and other second-order neurons. Labeled carnosine arrives in the bulb several hours after intranasal administration of precursor. Similar arrival time is seen for macromolecules after intranasal administration of [3H]L-fucose, [14C]L-proline, or [14C]L-histidine. Macromolecules labeled with [3H]uridine take much longer to reach the bulb. Carnosine is also labeled after [3H]uridine administration. No labeling of macromolecules is observed after administration of 1-[14C]-β-alanine. Oral administration of the same dose of [14C]-β-alanine gives almost no labeled carnosine in bulb or epithelium. This method has permitted us to estimate that the half-life of labeled carnosine in both the bulb and epithelium is about 20 h. This method provides a means of selectively prelabeling the olfactory chemoreceptor neurons in the olfactory epithelium and their synapses in the olfactory bulb prior to cellular and subcellular separation procedures, and may also enable us to monitor the influences of olfactory stimulation on synthesis and transport of carnosine.

Abstract: The olfactory sensilla on the maxillary palp tip of Locusta migratoria (L.) resemble the surrounding contact chemoreceptors in general morphology. The perforated peg has a thicker wall than is commonly found in olfactory sensilla. The form and position of the sensilla are considered in relation of the olfactory function. The fine structure of the dendrites is discussed in relation to that described in other olfactory sensilla.

Abstract: On the basis of his knowledge of the patterns of evolutionary development of the olfactory system and other forebrain structures, Herrick’ proposed that the olfactory cortex served an activating function for “all cortical activities.” In recent years, without addressing Herrick’s proposal directly, several investigators have provided evidence that is pertinent to it. In an extensive review of this topic, Wenzell concluded that a number of behaviors are altered by a greatly diminished olfactory input and that this effect is not readily explicable in terms of perceptual loss alone. One of the principal themes emerging from this review is the apparent lack of influence on the cognitive or problem-solving aspect of behavior, as compared with the motivational or affective aspect. Regardless of the species being studied, after reducing or removing olfactory input it is typical to find significant changes occurring in such characteristics as reactivity to handling, aggression, and shock-avoidance learning. By contrast, relatively little effect is reported for such tasks as lever pressing with different schedules of food reinforcement or complex visual discriminations reinforced by food. Because so much of this work has been done with rodents, a group of animals for which olfactory signals are of notable importance, it is difficult to determine the degree to which reduced olfactory input represents a loss of specific information rather than a more general effect. For this reason, we have chosen to work exclusively with the pigeon so that the contaminating influence of the cue value of olfaction can be minimized. Although good evidence exists3 that pigeons rely to some extent on olfactory cues for guidance in homing, no other segment of their behavior has as yet been shown to depend directly on odorous information. In addition to this fundamental advantage, the pigeon also presents a distinct anatomical advantage in the ease with which the olfactory nerve fibers can be completely sectioned as compared with the rat, for example, in which such an operation is much more problematic. In a series of reports beginning in 1968,4-6 several types of behavior in the pigeon were shown to be affected by bilateral removal of the olfactory bulbs or bilateral section of the olfactory nerves. No effect on the behaviors in question was observed following the control operation of unilateral removal of a superficial piece of the hyperstriatum dorsale approximately equal in size to that of the olfactory bulbs.

Abstract: Many hypotheses have been developed to account for the process of olfaction (for reviews see MOULTON and BEIDLER, 1967; DAVIES, 1971 and POYNDER, 1974), but at the present time none of them has been verified. The olfactory organ demonstrates very interesting receptor properties. It interacts with a great variety of compounds, called odorants (STAHL, 1973). Appropriate biochemical and biophysical methods including the separation of sensory surfaces should be able to provide important evidence about receptive mechanisms and attempts to use such techniques have begun in recent years (e.g. KONORRING,CH and NORRING, 1969; ASH and SKOGEN, 1970; KOYAMA et al., 1971; KOROLEV and FROLOV, 1973; MENCO et al., 1974; MARGOLIS, 1975). Techniques for separating receptor structures have also been suggested by OTTOSON (1970), but sofar none of these methods has yielded a pure fraction of receptor endings (see DODD, 1974). The present account will deal mainly with the anatomy of the bovine olfactory epithelium emphasizing prospects for isolating receptor moieties. The adjacent nasal respiratory epithelium has also been investigated since, like the olfactory bipolar nervous cells such respiratory cells bear cilia. In the latter case, however, they are motile, rather than sensory, thus enabling a determination of features which are specific for the olfactory cilia and a comparison between two adjacent epithelium types allows such specific characterizations (LUCAS and DOUGLAS, 1934; SLEIGH, 1974). The cow has been used as an experimental animal, since the size of its olfactory organ and the availability of samples seemed most convenient for this work. Some of the studies presented here were carried out on sheep. Indications for behaviour towards odorants in cows have been reviewed by ERNST and PUSHKARSKII (1975). In Chapter 1, the distal processes of both epithelium types are described, using different microscopical methods, including light microscopy, scanning electron microscopy, thin section transmission electron microscopy and thick section high- voltage transmission electron microscopy. This latter method was used in the hope that it would permit olfactory cilia to be followed over their whole lengths. In this chapter some attention will also be devoted to macroscopic observations. Chapter 2 deals with the results of freeze-etch and electron spin resonance studies on both epithelium types. Both techniques allow predictions of some of the molecular properties of the receptive area through investigation of intact tissue in vitro. Chapter 3 deals with a quantitative analysis of the morphological data. Statistical methods are used where it is possible. Several features of the olfactory nerve endings are compared for different nasal areas and for adult as opposed to juvenile animals. Special emphasis is placed on the ciliary processes. Olfactory and respiratory cilia are also compared with each other. Furthermore, estimates for possible receptor concentrations based chiefly on freezeetch results are presented. Such quantitative information is important for biochemical work, since it indicates whether one can consider nerve ending preparations as homogeneous or if one has to take into account that biochemical preparations may contain morphologically different nerve ending types. Furthermore, some ideas about receptor quantities which might be isolated can be obtained. Finally, Chapter 4 deals with attempts to isolate peripheral receptor membranes. The conventional criteria used by others for assessing the purity of the fractions have been shown to be inadequate (DODD, 1974); this prompted us to initiate anatomical studies on the bovine olfactory mucosa, so as to provide ourselves with a more adequate basis for future biochemical studies.

Abstract: • Changes in the olfactory system in five patients with sarcoidosis were studied by clinical and histopathological examination. Every patient studied had hypogeusia and/or hyposmia as measured by psychophysical testing. In two patients who died with this disease, the olfactory bulbs and tracts were involved by granulomatous infiltration. Two other patients showed granulomas and chronic inflammation in nasal biopsy specimens. The fifth patient was studied only clinically. Changes in olfactory and gustatory acuity are rarely searched for in patients with sarcoidosis, but they may be important indicators of major and later irreversible damage to the CNS. If diminished olfaction is established in suspect patients, nasal biopsy and examination of the CNS should be performed to confirm the presence of active sarcoidosis. Appropriate therapy may prevent damage to the patient's sensory capabilities and CNS function.

Abstract: The amount and specificity of binding ofL-carnosine (β-alanyl-L-histidine) by crude soluble and particulate fractions of several tissues were investigated with proton magnetic resonance (1HMR) spectrometry. It was found that the particulate fraction of only nasal olfactory mucosa exhibited a specific binding requiring a particular orientation of the carnosine molecule relative to the binding site. This suggests that whatever role carnosine may play in olfaction is expressed within the nasal olfactory mucosa rather than elsewhere in the olfactory pathway. Possible binding of carnosine to carnosinase was observed in the soluble fractions of nasal olfactory mucosa and kidney. However, the bulk of the carnosine present in the nasal olfactory mucosa in vivo probably is not bound within the cells of this tissue as a complex with soluble protein. These observations are of interest because the nasal olfactory mucosa is the neural tissue that has the highest activities of the enzymes catalyzing the synthesis and degradation of carnosine.

Abstract: Previous experiments from this laboratory using complete hypothalamic deafferentation have demonstrated that the adrenocortical discharge following olfactory stimulation is essentially mediated by neural pathways. In order to identify the neural afferents and the hypothalamic areas involved, this response was studied in rats with anterior (AD) and posterior (PD) partial hypothalamic deafferentations as well as in animals with bilateral lesions in the ventrolateral medial forebrain bundle (VMFB) and the gemini region (GR) in the hypothalamus. While rats with PD had a normal adrenocortical response to odor stimulation, this was completely inhibited in animals with AD and partially reduced in VMFB and GR lesioned rats. These data would indicate that the adrenocortical response following olfactory stimulation is mediated by anterior afferents to the hypothalamus and involves the VMFB and GR.

Abstract: Based upon his electrophysiological work during the early 1950’s, Adrian (1950, 1951, 1953, 1954) has left a legacy concerning the mechanisms which might underlie olfactory discrimination at the level of the olfactory mucosa. One such mechanism involves the selective sensitivity of individual receptor cells to particular odorants or groups of odorants. Any given cell would not be equally sensitive to all odorants, but would instead be maximally excited by some odorants and excited less, or not at all, by others. Thus, each receptor cell would signal the degree to which its particular sensitivity is matched by the molecules of incoming odorants.

Abstract: Histochemical localization of phospholipids in the olfactory epithelium of rainbow trout (Salmo gairdneri), whitefish (Coregonus clupeaformis), Arctic char (Salvelinus alpinus), brook trout (Salvelinus fontinalis), lake trout (Salvelinus namaycush), and black bullhead (Ictalurus melas) was examined. The present results indicate that phospholipids are highly localized in the receptor neurons of all species examined, present not only in the membranes, but also in the cytoplasm. Although the phospholipids of membranes and cytoplasm may not be of the same kind, their localization suggests a role in olfactory function. The Baker acid hematein method shows clear morphological features of the olfactory neurons beyond those obtainable by routine histological methods. The technique may be useful in determining morphological changes and (or) phospholipid alterations caused by a deleterious environment.

Abstract: Olfactory information is transmitted from the olfactory receptors in the nose through several stages of processing in the olfactory bulb and the olfactory regions of the brain. Through recent and ongoing work, we are learning a good deal about the basic anatomy and physiology of these pathways. I shall confine myself to reviewing here some of the areas in which progress has been most rapid and most promising for understanding mechanisms of odor processing.

Abstract: The flow of water through the olfactory organ of fishes is of interest in order to understand the first step in the process of olfaction: the way molecules are brought to transmit information about their nature to the receptor cells in the sensory epithelium of the organ. The olfactory organ of fishes demonstrates the great variability that is found within specialized organs due to the adaptation process in different species to diverse environmental and behavioural conditions. The understanding of the evolution of such a specialized organ may throw some light on the evolution of determinate taxonomic groups. This implies that the influence of the morphological details of the organ on the flow has to be understood. The group selected for the present investigation are the so called Cyprinodonts. Their olfactory organs show evolutionary divergence in several different directions. Two species, Aplocheilus lineatus and Xiphophorus helleri were selected for the first investigations. In addition to measurements in vivo it is the idea to reproduce their olfactory organs as a model at a scale enlarged by a factor of about 200.

Abstract: It is plain why we know so little about the neural processing of odor signals. Beginning at the receptor level there appear to operate a number of different mechanisms for stimulus separation and transduction (Beidler, 1971). But even if there were a single simple process, say an orderly array of specific receptor types or a spatiotemporal map (Davies, 1971), we would need take only one step further centrally before order was chaos once again. From receptor sheet to olfactory bulb there is only the faintest hint of a topographic mapping (Clark, 1951). Then we face the convergence of 26,000 receptor cells, on the average, into a single glomerulus and thence to second order neurons in the bulb, each participating in many glomeruli (Allison and Warwick, 1949). Finally, most every region of the bulb distributes axons to the whole of the olfactory cortex (see Fig.1; White, 1965; Lohman and Mentink, 1969; Price, 1973; Broadwell, 1975; Devor, 1976a). This looks like a structure specifically designed to scramble the message received by single receptors. Nor is there much evidence of specificity in electrophysiological recordings from single cells at receptor, bulbar or cortical levels (e.g. Gesteland, 1971; Mathews, 1972; Haberly, 1969). If we accept the premise that nature is not perverse, then there may well be a mechanism operating here that is different from that of most other sensory systems in which feature extraction and topographic mapping and remapping play such a prominent role.