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M M Mozell

Publications and source records attributed to M M Mozell.

At least 37 records · Page 2Linked to original sources
PubMed1987

"Imposed" and "inherent" mucosal activity patterns. Their composite representation of olfactory stimuli.

Both regional differences in mucosal sensitivity and a gas chromatography-like process along the mucosal sheet have been separately proposed in two sets of earlier studies to produce different odorant-dependent activity patterns across the olfactory mucosa. This investigation evaluated, in one study, whether and to what degree these two mechanisms contribute to the generation of these activity patterns. Summated multiunit discharges were simultaneously recorded from lateral (LN) and medial (MN) sites on the bullfrog's olfactory nerve to sample the mucosal activity occurring near the internal and external nares, respectively. Precisely controlled sniffs of four odorants (benzaldehyde, butanol, geraniol, and octane) were drawn through the frog's olfactory sac in both the forward (H1) and reverse (H2) hale directions. By combining the four resulting measurements, LNH1, LNH2, MNH1, and MNH2, in different mathematical expressions, indexes reflecting the relative effects of the chromatographic process, regional sensitivity, and hale direction could be calculated. Most importantly, the chromatographic process and the regional sensitivity differences both contributed significantly to the mucosal activity patterns. However, their relative roles varied markedly among the four odorants, ranging from complete dominance by either one to substantial contributions from each. In general, the more strongly an odorant was sorbed by the mucosa, the greater was the relative effect of the chromatographic process; the weaker the sorption, the greater the relative effect of regional sensitivity. Similarly, the greater an odorant's sorption, the greater was the effect of hale direction. Other stimulus variables (sniff volume, sniff duration, and the number of molecules within the sniff) had marked effects upon the overall size of the response. For strongly sorbed odorants, the effect of increasing volume was positive; for a weakly sorbed odorant, it was negative. The reverse may be true for duration. In contrast, the effect of increasing the number of molecules was uniformly positive for all four odorants. However, there was little evidence that these other stimulus variables had a major influence upon the effects of the chromatographic process and regional sensitivity differences in their generation of mucosal activity patterns.

Acyclic Monoterpenes↗
PubMed1987

Improvement of olfaction in laryngectomized patients with the larynx bypass.

Hyposmia following laryngectomy is an often recognized phenomenon. A larynx bypass device was used to determine whether this olfactory deficit could be reversed simply by restoring nasal airflow. Odorant detection thresholds and confusion matrix identification tests were administered to laryngectomy and normal comparison groups. Data on nasal airflow characteristics with and without the bypass were also analyzed. The results suggested that restoration of nasal airflow completely reversed the hyposmia for trigeminal nerve stimuli. However, the reversal of hyposmia was not complete for those odorants which primarily, if not exclusively, stimulate the olfactory nerve. This suggested that other factors may contribute to laryngectomy-induced hyposmia for olfatory nerve stimuli. Additionally, nasal airflow analysis revealed that confusion matrix identification scores were depedent upon inspiratory sniff flow rates with and without the larynx bypass. It is argued that rehabilitation for the laryngectomee should include efforts to restore and maintain preoperative olfactory acuity.

Adult↗
PubMed1985

Olfactory stimulation variables. Which model best predicts the olfactory nerve response?

Mozell et al. (1984. J. Gen. Physiol. 83:233-267) have examined the traditional manner in which olfactory stimulus-response relationships have been addressed. They developed a model that describes the olfactory nerve response as a function of three factors, viz., the number of odorant molecules (N), the stimulus duration (T), and the stimulus volume (V). In addition, two models derived from this three-variable model were also found to predict the response well. These were the [F, N] model involving flow rate (F = V/T) and, ranking closely behind, the [C, T] model involving concentration (C = N/V). A model involving the delivery rate (D = N/T) and volume was found to predict the response poorly. These models imply very different stimulus-response relationships. The present study was designed to assess the validity of this earlier approach by testing specific predictions drawn from each of the models. Because of the excellence of the [F, N] model, one would predict that the response will not change when F and N are held constant in spite of proportional increases in V and T. Similarly, one would predict from the [C, T] model that the response will be constant when C and T are held constant in spite of proportional increases in N and V. Because of the poor showing of the [D, V] model, one would predict changes in the response even when D and V are held constant while N and T are increased proportionately. It was observed that when F and N were held constant, the response was, in fact, constant. When D and V were held constant, the response increased dramatically. When C and T were held constant, there was a statistically significant, but small, change in the response. These results support the approach taken by Mozell et al. (op. cit.) and highlight the applicability of the [F, N] model to peripheral olfactory processing. The results are discussed in terms of their impact on the traditional manner in which olfactory stimulus-response relationships are conceived.

Animals↗
PubMed1984

A parametric study of the stimulation variables affecting the magnitude of the olfactory nerve response.

The magnitude of olfactory responses can be related to three primary variables [number of odorant molecules (N), sniff volume (V), and sniff duration (T)] and three derived variables [concentration (C = N/V), flow rate (F = V/T), and delivery rate (D = N/T)]. To evaluate the effects of these interdependent variables upon the olfactory response, the summated multiunit discharges were recorded from the olfactory nerves of nine frogs in response to octane presented at two levels (in 2:1 ratio) of each primary variable. This presentation defined eight "sniff" combinations representing three levels of each derived variable. In an ANOVA of the logs of the responses, the effect of each primary variable was highly significant, with no significant interactions. A multiplicative regression model incorporating the effects of the three primary variables represented responses exceedingly well, with positive effects of N and T and a negative effect of V. When, with this model, the effect of each of the derived variables was isolated from the effects of all other variables, the analysis showed a positive effect for C, a near-zero positive effect for D, and a negative effect for F. Placing certain constraints upon the model parameters generates 13 distinct one- and two-variable models (e.g., the [C, T] model requires N and V to have equal but opposite effects). In ranking these reduced models in terms of their ability to predict the neural response, the predictive ability of [F, N] and [C, T] was at least as good as that of the three-variable model.

Analysis of Variance↗
PubMed1981

Olfactory receptor response characteristics: a reevaluation.

The activity of single olfactory receptor cells previously reported was reexamined using Guttman-Lingoes multidimensional scaling, cluster analysis and factor analysis. These analyses were compared and contrasted with similar analyses using another olfactory unit data set and a color vision receptor data set. Questions were raised regarding the interpretation of the results of these analyses for any of the data sets employed.

Animals↗
PubMed1977

Factors influencing the differential sorption of odorant molecules across the olfactory mucosa.

By use of a flow dilution olfactometer, tritium-labeled odorants were presented through the external naris to the bullfrog's intact olfactory sac. After stimulation the animal was frozen in liquid nitrogen. The dorsal surface and eminentia of the olfactory sac were then removed and sawed into sections perpendicular to the long axis of the mucosal surface. Each section was dissolved in a tissue solubilizer and counted in a liquid scintillation system. The amount of radioactivity in each section was used to estimate the number of odorant molecules it sorbed. For tritiated butanol there was a significant decrease in radioactivity from the section containing the external naris to that overhanging the internal naris. The steepness of the gradient was unaffected by a rather large range of stimulus flow rates, volumes, and partial pressures. Only when these parameters were pushed to extreme physical limits did this gradient change significantly. When the stimulus was presented through the internal rather than the external naris, the butanol gradient reversed its direction, decreasing from the internal to external. Unlike butanol, tritiated octane presented through the external naris was rather evenly distributed among the mucosal sections. That is, octane showed no distribution gradient across the mucosa. These results complement previous electrophysiological data that suggested a "chromatographic-like" differential sorption of odorant molecules across the mucosa.

Adsorption↗
PubMed1976

Electrophysiological evidence for a topographical projection of the nasal mucosa onto the olfactory bulb of the frog.

Three olfactory nerve branches respectively subserving either a medial, an intermediate, or a lateral region of the dorsal olfactory receptor sheet of the bullfrog Rana catesbeiana were electrically stimulated with bipolar platinum hook electrodes. Extracellular single unit responses from 93 second-order cells in different regions of the olfactory bulb were recorded with metal-filled glass micropipets. The excitatory responsiveness of each unit to the stimulation of each of the three nerve branches (response profile) was determined. Some units were sensitive to stimulation of each of the three nerve branches, thus suggesting a wide projection from the entire receptor sheet. On the other hand, other units were more selective. Of this latter group, units in the lateral bulb were excited by nerve branches subserving the more lateral regions of the receptor sheet; units in the medial bulb were excited by the nerve branches subserving the more medial regions of the receptor sheet. These data provide electrophysiological evidence for a topographical projection of the olfactory receptor sheet onto the olfactory bulb, and further suggest that the projections onto different bulbar cells vary in degree of localization.

Animals↗
PubMed1970

Evidence for a chromatographic model of olfaction.

The gradient of activity produced along the olfactory mucosa by odorant stimulation was measured by the ratio (the LB/MB ratio) of the summated neural discharges recorded from two branches of the olfactory nerve, a lateral branch (LB) supplying a mucosal region near the internal naris and a medial branch (MB) supplying a region near the external naris. Twenty-four frogs "sniffed" sixteen different odorants, each odorant at four concentrations and two flow rates. Increases in concentration and flow rate produced statistically reliable increases in the ratios; the magnitude of these increases was considerably smaller than the magnitude of the statistically significant changes that could be achieved by shifting the odorants themselves. Even the small change due to concentration depended upon the odorant presented. Thus, even at the highest physiologically possible concentrations and flow rates, the general level of the activity gradient along the mucosa appeared to be determined mainly by the particular odorant used. The relative retention time of each of these 16 different odorants was measured in a gas chromatograph fitted with a Carbowax 20M column. In general, the longer the odorant's retention time the smaller its LB/MB ratio. This suggests that the different mucosal gradients of activity are established for different odorants by a chromatographic process. The data further suggest that the mucosa behaves like a polar chromatographic column.

Air↗
PubMed1966

The spatiotemporal analysis of odorants at the level of the olfactory receptor sheet.

Activity in two separate regions of the frog olfactory mucosa was sampled by simultaneously recording the summated neural discharges from the olfactory nerve branches originating from them. The difference in the activity from these two regions in response to a stimulus was measured by: (a) the ratio of the response amplitude recorded from the lateral nerve branch to that recorded from the medial nerve branch (LB/MB ratio), (b) the latency difference (or time interval) between these two responses. Equal concentrations of four different odorants were drawn into the nose by an artificially produced sniff of known dimensions. At each concentration in every animal the four chemicals were ranked in order of the magnitudes of their LB/MB ratios and again in order of their latency differences. Regardless of their concentration, the same chemicals fell into the same ranks in different animals. In addition, for each chemical the magnitudes of the ratios and latency differences showed only minimal changes with concentration. Thus, spatiotemporal patterns of relative response magnitudes and latency differences across the mucosa differentially represented the odorants. Such a spatiotemporal code, together with physicochemical considerations, suggested that the nose separates vapors in a manner similar to a gas chromatograph. This is further supported by the previously observed reversal of the ratio patterns with reversal of air flow direction through the olfactory sac.

Animals↗
PubMedDate not supplied

Olfactory receptor response characteristics: a factor analysis.

The responses to odor stimulation of 22 single olfactory units in the frog olfactory mucosa were recorded with metal filled micropipettes. Seven purified odorants matched in concentration and a pure air stimulus were administered. The change in firing frequency for each unit to each chemical was evaluated to determine: (1) whether the response patterns developed across all units are different from chemical to chemical and, (2) whether individual units can be grouped in terms of their similarity of their responses to all odorants. The results of a Bartlett Sphericity test suggest that each odorant produces an independent pattern of responses across units. To answer the second question, a factor analysis was employed. It examined the responses of each unit to all chemicals and yielded 7 out of a possible 22 independent factors, suggesting that there are 7 ways by which the units studied look at the odorant stimuli and an air control employed in this study. These analyses were evaluated and discussed in terms of previously published data suggesting receptor site specificity.

Animals↗