Search PubMed⌕ Search

Biomedical subjects

K M Dorries

Publications and source records attributed to K M Dorries.

9 recordsLinked to original sources
PubMed2000

Relationships between odor-elicited oscillations in the salamander olfactory epithelium and olfactory bulb.

Oscillations in neuronal population activity, or the synchronous neuronal spiking that underlies them, are thought to play a functional role in sensory processing in the CNS. In the olfactory system, stimulus-induced oscillations are observed both in central processing areas and in the peripheral receptor epithelium. To examine the relationship between these peripheral and central oscillations, we recorded local field potentials simultaneously from the olfactory epithelium and olfactory bulb in tiger salamanders (Ambystoma tigrinum). Stimulus-induced oscillations recorded at these two sites were matched in frequency and slowed concurrently over the time course of the response, suggesting that the oscillations share a common source or are modulated together. Both the power and duration of oscillations increased over a range of amyl acetate concentrations from 2.5 x 10(-2) to 1 x 10(-1) dilution of saturated vapor, but peak frequency was not affected. The frequency of the oscillation did vary with different odorant compounds in both olfactory epithelium and bulb (OE and OB): amyl acetate, ethyl fenchol and d-carvone elicited oscillations of significantly different frequencies, and there was no difference in OE and OB oscillation frequencies. No change in the power or frequency of OE oscillations was observed after sectioning the olfactory nerve, indicating that the OE oscillations have a peripheral source. Finally, application of 1.0 and 10 microM tetrodotoxin to the epithelium blocked OE oscillations in a dose-dependent and reversible manner, suggesting that peripheral olfactory oscillations are related to receptor neuron spiking.

Ambystoma↗
PubMed1999

Characterizing complex chemosensors: information-theoretic analysis of olfactory systems.

The mechanisms that underlie a wine lover's ability to identify a favorite vintage and a dog's ability to track the scent of a lost child are still deep mysteries. Our understanding of these olfactory phenomena is confounded by the difficulty encountered when attempting to identify the parameters that define odor stimuli, by the broad tuning and variability of neurons in the olfactory pathway,and by the distributed nature of olfactory encoding. These issues pertain to both biological systems and to newly developed 'artificial noses' that seek to mimic these natural processes. Information theory, which quantifies explicitly the extent to which the state of one system (for example, the universe of all odors) relates to the state of another (for example, the responses of an odor-sensing device),can serve as a basis for analysing both natural and engineered odor sensors. This analytical approach can be used to explore the problems of defining stimulus dimensions, assessing strategies of neuronal processing, and examining the properties of biological systems that emerge from interactions among their complex components. It can also serve to optimize the design of artificial olfactory devices for a variety of applications, which include process control, medical diagnostics and the detection of explosives.

Animals↗
PubMed1997

Rapid classical conditioning of odor response in a physiological model for olfactory research, the tiger salamander.

In recent years there have been a number of important advances in the understanding of cellular mechanisms related to olfactory function. Hypotheses regarding the complex relationships among odorant structure, physiological activity and behavioral outcome generated by these findings, however, remain largely untested due to a paucity of psychophysical data on stimulus discrimination in the same experimental species. Comparisons between behavioral and physiological responses are essential for elucidating the critical aspects of stimulus coding in sensory systems. We have developed a method for generating psychophysical data in one of the primary model species used in olfactory research, the tiger salamander, Ambystoma tigrinum. These psychophysical experiments are carried out under the same conditions as physiological experiments in our laboratory. Using classical conditioning, individual salamanders are trained over a period of 2-3 h to show skin potential responses to odor and not air. Failure to train using backward pairing demonstrates that the response is not due to sensitization or pseudoconditioning. The conditioned response is mediated by the olfactory pathway, as it is blocked by olfactory nerve section. We show that salamanders detect three odorants that are commonly used stimuli in physiological experiments (butyl alcohol, butyl acetate and amyl acetate), but cannot detect a fourth common experimental odorant, camphor. This method should be a powerful tool for studying olfactory information processing by providing data on discriminability of stimuli used in salamander physiological studies.

Acetates↗
PubMed1997

Sensitivity and behavioral responses to the pheromone androstenone are not mediated by the vomeronasal organ in domestic pigs.

Based largely on results of studies of laboratory rodents, the vomeronasal or accessory olfactory system is believed to function mainly in social communication, mediating the effects of stimuli such as urine or glandular secretions on the behavior or endocrine response of conspecifics. In the domestic pig (Sus scrofa), the steroid androstenone has been identified as a pheromone that facilitates expression of both attraction to the male and a receptive mating stance in estrous females. Though the domestic pig is one of the few vertebrate species in which the identity of a compound that functions as a pheromone is known, the role of the vomeronasal system in domestic pigs has never been investigated. We have examined the role of the vomeronasal organ in mediating the pheromonal effects of androstenone in pigs. In addition, we have examined the structure of the vomeronasal organ at the gross and light-microscopic levels. The vomeronasal organ appears functional, with sensory epithelium lining the medial wall, and has access to stimuli from both the oral and nasal cavities. To determine whether the vomeronasal organ is necessary for androstenone detection or attraction or receptive behavior in female pigs, access to the vomeronasal organ was blocked with surgical cement, and androstenone detection threshold and sexual behavior were measured. Experimental animals did not differ significantly in androstenone sensitivity, measured behaviorally, from untreated controls. Vomeronasal organ-blocked animals also did not differ from untreated controls in either androstenone-mediated receptive standing behavior or attraction to the odor of androstenone. We conclude that in the domestic pig, the vomeronasal organ is not necessary for androstenone detection or androstenone-mediated sexual behavior in estrous females.

Animals↗
PubMed1995

Olfactory sensitivity to the pheromone, androstenone, is sexually dimorphic in the pig.

Sexually dimorphic pheromone pathways have been used successfully to study insect olfactory coding. As one of the few mammalian species with an identified sex pheromone, the domestic pig (Sus scrofa) may be an ideal vertebrate species in which to examine sex differences in olfactory processing of a specific stimulus. In this experiment, androstenone and control odor detection thresholds were measured in adult male, female, and castrated male pigs. In an operant task, pigs were tested with descending concentration series of both androstenone and geraniol. All groups were equally sensitive to geraniol, but there was a sex difference in sensitivity to the odor of androstenone. Female pigs' detection threshold was a dilution fivefold lower than the threshold for intact males. Castrated males did not differ significantly from either males or females. This is the first example of a sexual dimorphism in sensitivity to a mammalian pheromone.

Acyclic Monoterpenes↗
PubMed1989

Changes in sensitivity to the odor of androstenone during adolescence.

While it has been reported that most, if not all, very young children are able to detect the odor of 5 alpha-androst-16-en-3-one (androstenone), approximately 40-50% of human adults cannot detect its odor. The present study focused on changes in sensitivity to androstenone during adolescence, which may account for this discrepancy. Sensitivity to androstenone was determined in 247 subjects aged 6 to 50. There was a significant increase in the number of males anosmic to androstenone between 9-14 and 15-20 years of age, and a significant increase in threshold with age among males able to detect the odor. We infer that a smaller percentage of females than males becomes anosmic to the odor of androstenone during development, and those able to detect it apparently show a decrease in threshold with age. No age-related changes were observed in tests of pyridine or d,l-beta-phenylethylmethylethylcarbinol (PEMEC).

Adolescent↗
PubMed1989

Ability to perceive androstenone can be acquired by ostensibly anosmic people.

Nearly half the adult human population does not perceive an odor when sniffing androstenone (5 alpha-androst-16-en-3-one), a volatile steroid found in human perspiration, boar saliva, some pork products (e.g., bacon), truffles, and celery. This variation in ability to perceive androstenone has a significant heritable component, suggesting that androstenone insensitivity is in part determined genetically. We now report that the ability to perceive androstenone was induced in 10 of 20 initially insensitive subjects who were systematically exposed to androstenone. Since olfactory neurons of the olfactory epithelium undergo periodic replacement from differentiating basal cells, and assuming the induction of sensitivity to be peripheral, we propose that a portion of the apparently anosmic human population does in fact possess olfactory neurons with specific receptors for androstenone. Such neurons may undergo clonal expansion, or selection of lineages with more receptors or receptors of higher affinity, in response to androstenone stimulation, much in the manner of lymphocytes responding to antigenic stimulation, thus raising odor stimulation to the level of conscious perception. As a guide to further study of the genetics and mechanism of variation of androstenone perception, we provisionally envisage three categories of human subjects, the truly anosmic, the inducible, and those subjects who either are constitutionally sensitive or have already experienced incidental induction.

Androstenes↗