An alternative model of olfactory quantitative interaction in binary mixtures

The "vectorial model" proposed in 1973 by Berglund et al. certainlyconstitutes an important progress in the field of olfactoryquantitative interaction. An alternative model called "U model",based also upon perceived odorous intensity of a mixture asa function of perceived odorous intensity of the components,is here presented. The "U model" fits the experimental data of Cain and Drexler(1974) and of Cain (1975) slightly better than the "vectorialmodel". ^*Presented at the VIth International Symposium Olfaction andTaste, Gif-sur-Yvette, Paris, France, 15–17th July, 1977.     

An approach to a physico-chemical model of olfactory stimulation in vertebrates by single compounds

During recent years, numerous attempts have been made to correlate both quantitative (Davies &; Taylor, 1959; Engen, 1962; Beck, 1964; Engen, Cain &; Rovee, 1968; Cain, 1969; Dravnieks &; Laffoit, 1970; Laffort, 1969a,b) and qualitative (Davies, 1965; Amoore &; Venstrom, 1965; Döving, 1966a,b; Wright &; Michels, 1964; Leveteau &; MacLeod, 1969) odorous properties of single compounds to their molecular properties. These attempts have been only partially successful.In the present paper we will try to explain the several odorous properties of single compounds on the basis of the non-specific properties of odorants involved in solubility.This model is a first approach, and although it gives statistically highly significant relations, it is not as accurate as those advanced with respect to the physical and sensory dimensions of stimuli in the fields of vision and audition.We will first give the present definitions of the most suitable physicochemical parameters, and then advance quantitative and qualitative models for single compounds. Quantitative odorous properties are: odour threshold, rate of change of odour intensity with odorant concentration in the suprathreshold region, and the somewhat controversial upper odour intensity. Qualitative properties refer to odour character.     

Jacques Le Magnen (1916-2002)

View larger version (162K): [in this window] [in a new window]   Jacques Le Magnen with his wife Régine on July 14, 1976, the eve of ISOT VI, which he organized at Gif-sur-Yvette.   One of the pioneers in research on olfaction and taste, andon the regulation of water and food intake left us on Thursday,May 23, 2002, at the age of 85. Jacques Le Magnen was a discipleof the famous French physiologist Henri Piéron at theCollège de France, and from 1949 till 1989 developedhis own laboratory of sensory     

Application of the U and gamma' models in binary sweet taste mixtures

The U and Gamma' models of sensory interactions, successfully applied in olfaction for several years, are tested here using data from published studies on sweetness. The models are subsequently tested on new data obtained in studies of binary mixtures of four sodium sulfamates. The U model allows for the estimation of a global interaction, whereas the Gamma' model allows for the distinction between that which is due to an intrinsic interaction in the mixture itself and that which may be due to the power function exponents in the mixture. The models give satisfactory predictions for observed phenomena of sweet taste suppression, synergism or pure additivity. Additionally, they appear to be more suitable than other models recently applied in taste, particularly the equiratio model. Application of the models to the sulfamate mixtures, reveals additivity for sodium cyclohexylsulfamate (cyclamate)/potassium cyclohexylsulfamate and sodium cyclohexylsulfamate/sodium exo-2-norbornylsulfamate, respectively; whereas for sodium cyclohexylsulfamate/sodium 3-bromophenylsulfamate, the models revealed a slight hypo addition which is simply due to the dissimilarity values of the power function exponents of the components.     

Implications of power law exponent in synergy and inhibition of olfactory mixtures

An index of olfactory quantitative interaction has been definedby Laffort and Dravnieks (1982). This index is obtained by combiningthe experimental effectiveness of mixtures with the power lawexponent of the components. When its value equals 1, this meansthat the ‘apparent’ inhibitions and synergies canbe expressed only through the power law exponents of the components.This, of course, holds true when a substance is added to itself.Values less than or greater than 1 are interpreted as ‘true’inhibition and synergy respectively. In a slightly modifieddefinition, this index [called (Gamma)] has been applied totwo sets of data, (i) By using an appropriate computer program,theoretical iso-intensity curves for binary mixtures were generatedby given values of this index, the variables being the concentrations.The diversity of curves is comparable to that observed in certainpsychophysical studies (Köster, 1969). (ii) EAG responsesof honey bees to 18 binary mixtures of three reciprocal concentrationseach, have been recorded. Absence of true interaction was observedin two-thirds of cases and the results concerning the last thirdare discussed. These two sets of results illustrate the integrativestrength of the index. The present work was also presentedin a condensed form in French by Laffort et al. (1984).     

Several models of suprathreshold quantitative olfactory interaction in humans applied to binary, ternary and quaternary mixtures

Performances were compared of several mathematical models forprediction of the perceived odour intensities of odorant mixturesfrom the odour intensities and some other related propertiesof the components. The models included Berglund's vectorial,an extension of the U model proposed by Patte and Laffort, aUPL model which utilizes exponents of the psychophysical powerlaw, and some simplified models. Data for the model testingwere obtained from literature and from new experimental measurementsin which the odour intensity of vapours of 28 odorous substancesand their 168 binary, 112 ternary, and 28 duplicated quaternarymixtures were matched vs. 1-butanol. The best performance onthe literature data, which have been obtained by the magnitudeestimation methods, was shown by the U model. The best performanceon the new data obtained by the butanol scale method was bythe simplified vectorial and U models; these used constant valuesof the interaction term cos . ^*Presented in a condensed form at the 3rd Congress of ECRO,Pavia, Italy, and in J. Physiol. (Paris), 1978, 74, 19A.     

Olfactory properties of some gases in hyperbaric atmosphere

The first demonstration of olfactory perception, at hyperbaricatmosphere, for gases inodorous at normal atmosphere, was madeby Laffort (1966, 1968). Nevertheless, two difficulties arosewith this earlier experimentation. First, the pressure was limitedto 5 absolute atmospheres (ATA) on account of the safety ofthe subjects. Secondly, the temperature was not maintained constantand it is well known that the olfactory perception depends onthis parameter (Tucker, 1963; Grundvig et al., 1967; Laffort,1969). The present experiment was carried out in a range of2–23 ATA, at a constant temperature, using methane andkrypton. The dose–response curve was obtained as a wholewith methane and partially with krypton. This work shows theexistence of olfactory sensitivity for these seemingly ‘inodorous’gases. Moreover, planning a QSAR study (quantitative structure–activityrelationships), it is possible to know the olfactory thresholdsof small mol. wt compounds (the human olfactory thresholds ofn-paraffin were known in a range of C₂–C₁₀ until now)(Van Gemert and Nettenbreijer, 1977).