Biomedical subjects

S L Youngentob

Publications and source records attributed to S L Youngentob.

15 recordsLinked to original sources

PubMed1995

Enhancement of odorant-induced mucosal activity patterns in rats trained on an odorant identification task.

Previous studies have demonstrated that there are intrinsic spatial patterns of odorant sensitivity across the rat olfactory mucosa. The question of how these patterns are determined and whether they are modifiable with experience remains open. Therefore, the present study examined whether the odorant-induced spatial activity patterns which are characteristic of different odorants would be altered by experience. Odorant exposure was achieved as a consequence of training and testing on a five odorant identification task in which rats were trained to differentially report (i.e. identify) the odorants propanol, ehtylacetoacetate, carvone, citral, and propyl acetate. At the completion of testing, each animal was sacrificed and their mucosal activity patterns recorded using optical techniques and a voltage-sensitive dye. Using the dye, di-4-ANEPPS, we monitored the fluorescence changes at 100 contiguous sites with a 10 x 10 photodiode array on the olfactory mucosa of each rat's septum and medial surface of the turbinates in response to the same five odorants. The recorded spatial activity patterns of trained animals were compared to those of age-matched controls. For the trained animals, both mucosal surfaces showed a significant increase in the average response magnitude. Furthermore, for the septal mucosa only, there was a significant increase in the distinctiveness of an odorant's characteristic 'hot spot'.

1-Propanol↗

PubMed1995

Mucosal inherent activity patterns in the rat: evidence from voltage-sensitive dyes.

1. Fluorescence changes in the dye di-4-ANEPPS were monitored on the rat's nasal septum and medial surface of the turbinates in response to odorant stimuli. For each mucosal surface a 6.0 x 6.0-mm area was sampled at 100 contiguous sites with a 10 x 10 photodiode array. The odorants were propyl acetate, 2-propanol, citral, L-carvone and ethylacetoacetate, each presented at a low and high concentration. 2. Like previous work using optical recording techniques and potential-sensitive dyes on the amphibian epithelium, the fluorescence signals elicited by odorant stimuli in the rat preparation were nearly identical in shape, time course, and response characteristics as the electroolfactogram (EOG). As with the EOG, a response could only be recorded in the presence of odorant stimuli (that is, no response was detected when nonodorized, humidified air was presented as the stimulus); the amplitude depended on odorant concentration, and the response was abolished both by ether and Triton X-100. 3. Although the entire expanse of each sampled tissue (i.e., septum and medial surface of the turbinates) responded to stimulation with each odorant, each stimulus induced a distinct spatial pattern of activity that was independent of odorant concentration and consistent from animal to animal. Furthermore, the spatial activity patterns recorded for the septum were mirror images of those recorded from the medial surface of the turbinates. 4. Formal statistical analysis of the loci of maximal activity or "hot spot" indicated highly significant effects of the odorants for both the septum and medial surface of the turbinates. 5. The results of these studies give further support to the hypothesis that odorant quality is encoded by differential spatial activity patterns in the olfactory epithelium that are characteristic of different odorants.

Animals↗

PubMed1994

Retroviral lineage studies of the rat olfactory epithelium.

Replication-incompetent retroviral vectors that encode the heritable marker enzyme, beta-galactosidase, were used to study the lineage relationships of cells in the olfactory epithelium of unmanipulated animals and in the olfactory epithelium as it reconstitutes after lesion. Virally-marked cells are categorized as to type based on their position in the epithelium and on expression of NCAM (limited to neurons) and the carbohydrate moiety recognized by Griffonia lectin (limited to the dark/horizontal basal cells and the microvillar class of supporting cells). Direct injections of the vectors into the olfactory epithelium of otherwise intact animals produce clusters of beta-galactosidase-labeled cells when assessed 6-10 days after infection; these clusters are composed of neurons and NCAM-negative/lectin-negative light/globose basal cells exclusively. In contrast, clusters of virally-marked cells after MeBr-induced lesion of the epithelium frequently contain both neurons and supporting cells, as well as both types of basal cells. Other clusters contain supporting cells and/or Bowman's gland/duct cells. It is likely that the clusters of marked cells are derived from a single founder cell, i.e. the cells are clonal and lineally related, since the clusters are widely dispersed. Furthermore, infusion of mixtures of viruses that can be distinguished on the basis of the type and subcellular localization of the marker enzyme that is expressed produce clusters that are homogenous with respect to enzyme type, providing strong evidence in favor of the notion that the clusters are clonal in nature. Thus, the founders of the clones that contain neurons, supporting cells and basal cells are pluripotent in their capacity for differentiation. It is unlikely that the pluripotent cells are found in Bowman's gland/duct, since we have yet to observe a clone that contains neurons and cells in Bowman's gland/duct. Hence, the pluripotent stem cells are to be found in the basal cell compartment of the epithelium. However, the exact nature of these stem cells remains unknown and a subject for future investigation.

Animals↗

PubMed1991

Successful treatment of phantosmia with preservation of olfaction.

A 26-year-old woman had an 8-year history of phantosmia in her left nostril. The phantosmia could be eliminated by nostril occlusion or cocainization of the olfactory epithelium on the involved side. Because her symptoms and testing suggested a peripheral problem, a full-thickness "plug" of olfactory epithelium from under the cribriform plate (including all the fila olfactoria) was excised. At 5 weeks postoperatively, the phantosmia was completely gone, and her olfactory ability had returned to preoperative levels. Either the removal of abnormal peripheral olfactory neurons from the nose or the interruption of incoming signals to the olfactory bulb eliminated the phantosmia. This form of therapy for phantosmia offers an alternative to more radical procedures such as olfactory bulbectomy and may offer a significant sparing of olfactory ability.

Adult↗

PubMed1991

Determination of carbon dioxide detection thresholds in trained rats.

Concentration-response functions for the detection of CO2 were established for six rats. The animals were tested in a wind tunnel apparatus and trained using standard operant techniques and a discrete trials, go, no-go successive discrimination paradigm. The primary conclusion to be drawn from the performance measurements is that, at least under carefully controlled conditions, rats can detect physiologic concentrations of CO2 (0-4%). Minimum detectable concentrations fell within the range of 0.04-1.7% CO2. The concentration-response function describing the detectability of CO2 for the six rats was divided into an upper and lower limb at a concentration (5%) that was approximately equal to the end expiratory CO2 levels for the rat (4.88%). High levels of performance were observed for concentrations above this point, while those below it (0.02-2.5%) represented the dynamic range of detectability. Based on a 65% performance criterion, the average threshold performance for six rats was 0.52%. Possible interpretations of these data are discussed.

Animals↗

PubMed1991

Odorant identification in rats: an update.

In a previous report, Youngentob et al. (8) described a new and substantially different type of animal psychophysical procedure in which rats were trained to differentially report (i.e., identify) five different odorants. The present study confirms and extends the usefulness of the cross-modal association paradigm as an effective means for developing an extensive nonverbal "vocabulary" with which an animal can communicate multiple changes in sensory stimuli. Given the appropriate nonverbal means of communication, a rat has the channel capacity to differentially report (i.e., identify), at least ten different odorants. The expansion to a ten odorant identification task is discussed with respect to the analytic capabilities of the animal model for the study of olfactory quality perception.

Algorithms↗

PubMed1990

Fish-odor syndrome presenting as dysosmia.

We describe a patient who had perceived an unpleasant odor or taste for at least 20 years. Several other physicians had unsuccessfully treated her for infections, mucus membrane dryness and inflammation, chronic tonsillitis, and psychiatric disorders. Her workup at the State University of New York Health Science Center at Syracuse Olfactory Referral Center included a thorough history, examinations (including endoscopic studies of her nose, pharynx, and lungs), roentgenograms, taste testing, olfactory testing, and selective anesthesia of her chemosensory areas. The perception occurred only during exhalation, and appeared to be binasal. These findings, together with her morning mucus sample having a strong fishlike odor, prompted us to suspect a metabolic problem. Further testing at the Monell-Jefferson Chemosensory Clinical Research Center, Philadelphia, Pa, confirmed that she had trimethylaminuria. It is important to consider this and other treatable conditions when evaluating individuals with olfactory complaints.

Adult↗

PubMed1990

A method for establishing a five odorant identification confusion matrix task in rats.

Using a cross-modal association paradigm, rats were trained to associate a particular tunnel and response location with one of five different odorants (isoamyl acetate, propyl acetate, acetic acid, phenethyl alcohol, and anethole). Each of the five tunnels differed with respect to: 1) the illuminated pattern on the response key; 2) the brightness of the illuminated pattern; and 3) the somesthetic quality of the tunnel floor. Standard operant techniques were used to train trial initiating and sampling behavior at a central odorant presentation point. Following acquisition training, the animals were tested using a standard 5 X 5 confusion matrix design. The results showed for the first time that rats are capable of performing, with a high degree of accuracy, an odorant identification confusion matrix task analogous to humans. Furthermore, using multidimensional scaling techniques, these data represent the first instance in which the perceptual odor space of an animal can be determined. With the animal model in hand, we can begin to examine how, in the presence of neural dysfunction, one odorant may be correctly identified as another.

Animals↗

PubMed1987

Olfactory mucosa/air partitioning of odorants.

The present study evaluates the contribution of the receptor cell compartment to the total mucosal odorant uptake. Using radioactive odorants, partition coefficients for normal bullfrog olfactory mucosa were compared to the partition coefficients from mucosa in which the receptor cells had been removed by cutting one of the olfactory nerves and allowing two weeks for complete degeneration. For the more water-soluble odorants (butanol and isobutyric acid), both sides sorbed the same amount of odorant, suggesting that the mucosal uptake mostly reflects uptake by the water in the mucosa. For the less water soluble odorants (octane and amyl acetate), the uncut side did sorb significantly more odorant than the cut side.

1-Butanol↗

PubMed1987

Airflow patterns in a human nasal model.

Nasal airflow patterns were studied by using xenon 133 gas to image the course taken by air as it flowed through a plastic model of the human nasal cavity. The model was produced from the head of a human cadaver, and was anatomically correct. A needle catheter was used to infuse the radioactive xenon into a continuous flow of room air maintained through the model by a variable vacuum source connected to the nasopharynx. The radioactive gas was infused at one of five release sites in the nostril, and the distribution of the radioactivity was imaged in the sagittal plane with a scintillation camera. The data were organized to show the activity in six contiguous regions of the midnose. For each catheter, release site activity patterns were determined for three flow rates. The results of this experiment showed that both catheter position and flow rate had significant and reproducible effects on the distribution of radioactivity within the model.

Catheterization↗

PubMed1987

A quantitative analysis of sniffing strategies in rats performing odor detection tasks.

The sniffing strategies of rats performing two learned odor detection tasks were monitored with a pneumotachograph and quantitatively analyzed with respect to fifty-two characteristics. The results of this study demonstrated that the rat's sniffing varied for different odorants, different concentrations of the same odorant, and between air and odor trials. The variations resulted from changes in such descriptors as volume, duration, average flow rate, peak flow rate and sniff number. In general, a sniffing pattern began with one or two inspirations followed by alternating inspirations and expirations. Comparison of earlier and later sniffs in a bout demonstrated a growth towards both a maximum inspiratory and expiratory sniff which had the largest duration, volume, average flow rate and peak flow rate. These maximum sniffs occurred at or near the end of a bout. Although analysis of the fifty-two characteristics was quantitatively useful in determining the physiologic values and airflow patterns generated by sniffing, a single univariate response measure incorporating twelve characteristics was the best descriptor of how sniffing patterns varied with odorant stimuli.

Animals↗

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↗

PubMedDate not supplied

Initial mechanisms basic to olfactory perception.

Animal experimentation has proposed three mechanisms at the olfactory mucosa that may underlie olfactory discrimination. First, the olfactory receptor cells appear selectively tuned to different odorants. Second, in a gas chromatographic-like process, the molecules of different odorants appear to be distributed in different sorption patterns across the mucosal surface. Third, different regions of the mucosa appear to have different selective sensitivities. These three mechanisms could complement each other by together generating a greater number of neural discharge patterns to encode the odorants passing over the mucosal surface. In this interplay, the mucosal distribution patterns could differentially limit the receptor cells and mucosal regions to which different odorants have access. The mucosal distribution pattern could thereby affect the odorant analyses made by these other mechanisms as well as contribute its own analysis. The mucosal distribution patterns appear fairly stable in the face of rather wide variations in the pertinent variables characterizing the nasal airflow (namely, odorant concentration, flow rate, volume, and duration). There are, however, limits to these variables beyond which significant shifts in the molecular distributions and neural discharge patterns can be produced. Thus, in humans any naturally occurring or surgically induced alteration in the nasal airflow which appreciably alters these variables may affect olfactory perception. Olfaction in a laryngectomized patient is discussed as an example.

Animals↗

PubMedDate not supplied

Effect of airway resistance on perceived odor intensity.

Because of the wide range of human nasal anatomic configurations, some people sniff odorants against comparatively high resistances. To assess the relationship between sniff resistance and olfaction, ten subjects without nasal pathology or complaint were asked to estimate the perceived magnitude of the odorant, ethyl butyrate, at each of four concentrations and against each of four different resistances. In addition, the airflow profile of the subjects' sniffs was monitored during the performance of the odor task. As expected, perceived intensity increased with concentration, but more noteworthy was the finding that perceived intensity decreased with increasing resistance. Initially, this latter finding, together with the lack of interaction between concentration and resistance, suggested an olfactory analogue to conductive hearing losses. However, the sniffing data suggested that under the conditions of the experiment, the subjects attempted to maintain consistent sniffing behavior across the 16 different treatment combinations of concentration and resistance. These observations, taken together with the finding that subjects could estimate the perceived effort of sniffing, give support to the concept of a perceptual constancy model in olfaction. That is, olfactory magnitude may depend not only on the odorant itself, but also on the perceived effort associated with the sniff.

Airway Resistance↗