Odor interaction

FIGURE 50-1 A schematic diagram of the olfactory epithelium. The initial events in odor perception occur in the olfactory epithelium of the nasal cavity. Odorants interact with specific odorant receptors on the lumenal cilia of olfactory sensory neurons. The signals generated by the initial binding events are transmitted along olfactory neuron axons to the olfactory bulb of the brain. 

Garda, J., Holder, M. D., and Yirmiya, R. (1986). Taste and odor interactions in conditioned flavor aversions. Appetite 7,259. 

How are such diverse compounds detected and recognized to elicit the associated behavior Several steps contribute to the odor coding, such as olfactory receptor interactions and processing in mushroom bodies, but also including odor interactions with OBPs. The diversity and heterogeneity of OBPs implicates these proteins in the process of odor discrimination. 

Selzer (1981) found that components of a complex food odor did not activate a single ORN independently from each other. Mixtures of odorants interact when stimulating ORNs to produce less (mixture suppression) or more (synergism) activity then would be expected from a simple competitive binding model. The transduction mechanisms that underlie the difference in temporal firing properties and inhibitory odor responses are likely to cause interactions when such odorants are combined as a single stimulus. 

Lai PC, Singer MS, Crasto CJ. Structural activation pathways from dynamic olfactory receptor-odorant interactions. Chem. Senses 2005 30 781-792. 

That this peripheral interaction of odorivectors is a reality and not Just a postulate resulting from lengthy speculations has been confirmed by statistically significant experimental proof obtained in malodor/"antlmalodor"-interaction studies (l ), and on a more general base, in odor/odor-interactions. These resiolts give implicit proof that specific receptor sites for moleciLLar and active profiles exist. 

Analogous events occur in the nose when many odorants interact with the epithelia therein. The odor component is conveyed via the odorant s interaction with molecular receptors on olfactory sensory neurons (first cranial nerve) in the olfactory epithelium [9] irritation is initiated by interactions with receptors or other mechanisms that stimulate the trigeminal (fifth cranial) nerve [10]. The term chemesthesis has been applied to distinguish this sensory experience from olfaction or, in the oral cavity, taste [11,12]. Importantly, chemesthesis is a bodywide experience. It is only on some portions of the head, e.g., eyes, nose, mouth, and some other facial areas, where information is conveyed by the trigeminal nerve (Fig. 1). 

BC Sun, BP Halpern. Retronasal and orthonasal odorant interactions Masking (abstract). Chem Senses 26 1103, 2001. 

Section 7 8 Both enantiomers of the same substance are identical m most of then-physical properties The most prominent differences are biological ones such as taste and odor m which the substance interacts with a chiral receptor site m a living system Enantiomers also have important conse quences m medicine m which the two enantiomeric forms of a drug can have much different effects on a patient... 

The vomeronasal organ (VNO), located in the nose, is a small chemical sensing stmcture associated with odors and behavioral effects. The vomeronasal system, which is made up of the VNO and a portion of the brain s limbic system, is stmcturaHy independent of the olfactory and nervous terminalis systems in the nose. It may, however, interact with these systems in a manner dependent on prior experience or learning, and therefore be direcdy related to the association of smells and experiences. This independent chemosensory system in the nose may prove to open doors to new learning associated with the sense of smell and human behavior. 

Absorption, metaboHsm, and biological activities of organic compounds are influenced by molecular interactions with asymmetric biomolecules. These interactions, which involve hydrophobic, electrostatic, inductive, dipole—dipole, hydrogen bonding, van der Waals forces, steric hindrance, and inclusion complex formation give rise to enantioselective differentiation (1,2). Within a series of similar stmctures, substantial differences in biological effects, molecular mechanism of action, distribution, or metaboHc events may be observed. Eor example, (R)-carvone [6485-40-1] (1) has the odor of spearrnint whereas (5)-carvone [2244-16-8] (2) has the odor of caraway (3,4). 

The G-proteins are heterotrimers made of three families of subunits, a, P, and y, which can interact specifically with discrete regions on G-protein-coupled receptors. This includes most receptors for neurotransmitters and polypeptide hormones (see Neuroregulators). G-protein-coupled receptors also embrace the odorant receptor family and the rhodopsin-linked visual cascade. 

Bismuth subgaHate [12552-60-2] (basic bismuth gaHate), Dermatol, is a bright yellow powder that can be prepared by the interaction of bismuth nitrate and gaUic acid in an acetic acid medium. It has been employed as a dusting powder in some skin disorders and as an ingredient of suppositories for the treatment of hemorrhoids (183,185). It has been taken orally for many years by colostomy patients in order to control fecal odors, but the dmg may cause serious neurological problems (186). 

Antioxidant additive in the polyethylene resin. While such an additive can prevent oxidation, and thus odor, it also can contribute directly to the odor. If an antioxidant is needed, it must be FRA approved, should have a high melting point, and should be used at a minimum level consistent with the extrusion process. Catalyst residues and antioxidants present in polyethylene sometimes interact to form odorous products. 

The other major class of extracellular LBPs of mammals is the lipocalins (Flower, 1996). These are approximately 20 kDa, P-sheet-rich proteins, performing functions such as the transport of retinol in plasma or milk, the capture of odorants in olfaction, invertebrate coloration, dispersal of pheromones, and solubilizing the lipids in tears (Flower, 1996). The retinol-binding protein (RBP) of human plasma is found in association with a larger protein, transthyretin, the complex being larger than the kidney threshold and thus not excreted, although the RBP itself may dissociate from the complex to interact with cell surface receptors in the delivery of retinol (Papiz et al., 1986 Sundaram et al., 1998). 

Social hymenoptera must contend with other organisms chemically mimicking a semiochemical to gain advantage. Chemical mimicry may result from the organism biosynthesizing the compounds themselves or simply acquiring the chemical odor of the host colony once inside. The many interactions are well reviewed [4,6,128] and include mimicry by hymenoptera of the same or different species, other arthropods, and even orchids. 

Odor discrimination could involve a very large number of different odorant receptors, each specific for one or a small set of odorants. At the other extreme, there could be a relatively small number of different odorant receptors (ORs), each of low specificity and capable of interacting with a wide assortment of different odorous ligands. Individual OSNs could each express only a single OR type or multiple different odorant receptors. 

When it comes to indoor air quality, interaction of people with their gaseous surroundings is the most important factor. In rooms with poor air exchange, the presence of people causes a steady deterioration in air quality. Air quality may be understood here and henceforth as a numeric measurement for the content of unhealthy and odorous components (air comfort). Additionally, building materials... 

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