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Biomedical subjects

Gerd Kobal

Publications and source records attributed to Gerd Kobal.

12 recordsLinked to original sources
PubMed2006

Substance and tongue-region specific loss in basic taste-quality identification in elderly adults.

Physiological anorexia, decreased dietary variation, and weight loss associated with poor health are common conditions in the elderly population, with changes in chemosensory perception as important contributing causes. The present study of age-related taste loss aimed to investigate the question whether this loss is generalised and unspecific, or whether it exhibits differences in relation to certain tastants and/or differences in the topographical distribution of age-related loss. Impregnated "taste strips" with four concentrations of each of the tastants sucrose, NaCl, quinine-hydrochloride, and citric acid were applied on the tip, midlateral and posteromedial tongue regions to be identified as either sweet, salty, bitter, or sour by 30 young and 26 elderly adults. The results showed more pronounced age-related loss in identification for citric acid and quinine-hydrochloride than for sucrose and NaCl at both the tip and midlateral regions, but not at the posteromedial region where both age groups performed close to chance level. These findings may have implications for food preferences, and thus, the diets of elderly people.

Aged↗
PubMed2006

A self-administered odor identification test procedure using the "Sniffin' Sticks".

Assessment of smell function in clinical routine is often limited due to a lack of time and/or costs of the personnel administering the test. The aim of the present study was to validate a procedure allowing for self-administered olfactory testing in a clinical setting. Seventy-four healthy subjects (13 male, 61 female) from 18 to 30 years of age (mean 20.3 years) were tested on 2 days (interval 7-21 days, mean 8.7 days) with 16 odors of the "Sniffin' Sticks" identification test kit. On one occasion, the test was administered by an examiner. On another occasion, subjects administered the test to themselves, with the odors being identified after they had been "painted" on a sheet of paper. No significant differences were obtained between the results from both test procedures. With a maximum score of 16, assisted testing yielded a mean score of 13.7 [standard deviation (SD) 1.3] while the self-administered procedure yielded an average score of 13.8 (SD = 1.5) (P = 0.72). The mean difference between the assisted and the self-administered smell test procedures was 0.05 (SD = 1.28). The 95% confidence interval of differences ranged from -2.51 to 2.61. These results suggest that odor identification with the Sniffin' Sticks can also be administered by the subjects themselves.

Adolescent↗
PubMed2006

Electro-olfactograms are present when odorous stimuli have not been perceived.

After chemical stimulation of the human olfactory epithelium it is possible to record a negative response (electro-olfactogram, EOG) which is interpreted as the summated generator potential of olfactory neurons. The aim of the present investigation was to test whether the EOG is present when olfactory stimuli have not been perceived. Stimulation was performed with vanillin and eugenol at supraliminal and subliminal levels. Twelve healthy volunteers participated in the experiments. Stimuli were applied at an interstimulus interval of approximately 60s. Although recordings were successful in 4 of the 12 subjects, for both stimulants EOG could be obtained even when the stimuli had not been perceived by the subjects. EOG recordings in response to supra- and subliminal stimuli exhibited no major differences, except for the onset of the EOG in response to subliminal eugenol-stimuli which were prolonged compared to supraliminal stimulation. All in all, the present data provide a physiological basis for the subliminal influence of odorous stimuli on human behavior.

Adult↗
PubMed2004

Anesthesia affects olfaction and chemosensory event-related potentials.

OBJECTIVE: Olfactory and trigeminal systems interact and contribute to the perception of odorants. This study was aimed at investigating the effect of local anesthesia on olfaction. METHODS: One percent of tetracaine on a cotton swab was applied intranasally at three different locations in 20 volunteers and 4% of lidocaine was applied to the olfactory cleft in a head-down position. Before and after anesthesia, self-assessment, psychometric testing and olfactory event-related potentials [OERPs, using H(2)S and phenyl ethyl alcohol (PEA)], and chemosomatosensory event-related potentials (CSSERPs, using CO(2)) were examined. RESULTS: Anesthesia at all four locations significantly lowered the perceived self-assessment of olfaction, while using the cotton swab only anesthesia in the middle meatus elevated threshold (P = 0.020), lowered discrimination (P = 0.015), and prolonged OERP (PEA, P = 0.008; H(2)S, P = 0.016), as well as CSSERPs latencies (CO(2), P = 0.020). However, complete temporary anosmia was only achieved after applying 4% lidocaine into the olfactory cleft. CONCLUSIONS: Intranasal anesthesia applied with a swab reduced self-assessment of olfaction but was unable to produce anosmia. Psychometric test results were concordant with changes in chemosensory event-related potentials. SIGNIFICANCE: Temporary anosmia is technically difficult to achieve but could be demonstrated for the first time using local anesthesia. Even though anesthesia influences self-assessment, measurable olfactory function can remain unchanged.

Administration, Intranasal↗
PubMed2003

Pain in the trigeminal system: irritation of the nasal mucosa using short- and long-lasting stimuli.

The paper describes methods which allow intranasal irritation using short- and long-lasting painful stimuli in humans. Short-lasting pain is induced by gaseous CO(2), while long-lasting pain is induced by a stream of dry air. Both models have been explored regarding their major determinants, e.g. stimulus duration, stimulus intensity, or repeated stimulation. Short-lasting, non-inflammatory pain stimuli seem to provide specific indicators of A(delta)-fiber function, while responses to long-lasting, inflammatory pain appear to be indicative of C-fiber function. Responses to both types of painful stimuli are modulated by analgesic drugs. As these well-investigated models allow the detailed and precise analysis of modulatory effects on intranasal nociception, they appear to be suited for the investigation of subtle changes of intranasal irritation, e.g. induced by environmental agents.

Analgesics↗
PubMed2003

Test-retest reliability of chemosensory evoked potentials.

This study investigated the test-retest reliability of chemosensory event-related potentials in humans. Olfactory event-related potentials and chemosomatosensory event-related potentials were evaluated in 20 healthy, normosmic subjects. Phenyl ethyl alcohol (PEA, 40% v/v) and H(2)S (4 ppm) served as olfactory stimuli whereas CO(2) (60% v/v) was the chemosomatosensory stimulus. Fifteen stimuli of each compound were applied to each nostril. Identical stimulation sequences were used during three test sessions. Sessions 1 and 2 were separated by a mean of 6.8 days; sessions 2 and 3 by 12.5 days. Electroencephalographic recordings were made from Fz, Cz, Pz, C3, and C4. Amplitudes and latencies of P1, N1, P2, N2, and P3 were measured. Pearson's correlation coefficient was calculated to test the test-retest reliability, and the general linear model examined the differences. Most correlations ranged between 0.4 < r < 0.75. Latencies correlated significantly better (P = 0.008) between sessions than amplitudes, even though with CO(2) stimulus amplitudes correlated significantly better than with PEA (P = 0.006) or H(2)S (P = 0.003). No differences arose between measurements from different nostrils for any stimulus. Chemosensory event-related potentials show good test-retest reliability. Carbon dioxide amplitudes exhibit better signal-to-noise ratios than PEA or H(2)S amplitudes. Chemosensory event-related potentials are a clinically valuable objective and are reproducible.

Administration, Inhalation↗
PubMed2003

Circadian rhythm and desensitization in chemosensory event-related potentials in response to odorous and painful stimuli.

Olfactory (H2S) and trigeminal (CO2) event-related potentials (ERPs) were studied with respect to circadian rhythm and desensitization. ERPs, perceived odor and pain intensity, oral temperature, blood pressure, heart rate, nasal volume, and sleepiness were assessed four times at 04:00, 08:00, 12:00, 16:00, 20:00, and 24:00 hr in five young men. For each of these 24 sessions per participant, H2S and CO2 were each presented in 15 series of five stimuli with a 5-s ISI within and 30-s ISI between series. ERP amplitudes, but not latencies, followed a circadian rhythm (largest at 16:00 and smallest at 04:00) similar to oral temperature and opposite to sleepiness. Amplitudes decreased (most pronounced at 16:00 and 20:00) and latencies increased with repeated stimulation, suggesting desensitization, in accordance with odor and pain intensity. These findings imply that circadian rhythm and desensitization should be considered in chemosensory ERP studies.

Adult↗
PubMed2002

Sensitivity of the negative mucosal potential to the trigeminal target stimulus CO(2).

CO(2) is frequently used in an experimental pain model and in imaging studies investigating the central processing of trigeminal nociceptive information because of its specific trigeminal stimulation properties. The aim of the current study was (1) to investigate the sensitivity of the NMP to small increments of CO(2) stimulus concentrations (3% CO(2), v/v) and (2) to characterize the sensory input of CO(2) by determining NMP, detection and pain thresholds and by registering subjective verbal descriptions. Ten subjects participated in the first experimental sessions investigating NMP responses to stimuli of 62, 65, 68% CO(2) (v/v) (stimulus duration: 1000 ms). Our statistical analysis revealed a dose-dependent increase of the NMP amplitudes and areas under the curves (AUCs) demonstrating the high dynamic resolution of the NMP. Ten subjects participated in the second experimental sessions determining thresholds for NMP, detection and pain (stimulus duration: 1000 ms). MANOVA analysis revealed significantly different thresholds for detection, NMP and subjective pain judgements (mean and S.D. as percentage CO(2) (v/v): detection: 20.6+/-9.6, NMP: 42.6+/-12.5, pain: 50.4+/-12.0). We could demonstrate the existence of a prepain range below subjective pain thresholds with activation of trigeminal nociceptive sensors resulting in the generation of NMPs. The detection threshold of 20.6% CO(2) (v/v) was surprisingly low, i.e. 22% CO(2) (v/v) below the NMP threshold. The involvement of newly discovered alpha-gustducin positive trigeminal chemosensory cells in CO(2) detection is hypothesized.

Adult↗
PubMed1997

Bilateral hyperalgesia to chemical stimulation of the nasal mucosa following unilateral inflammation.

The aim of the present study was to investigate the bilateral sensory changes to chemical noxious stimuli in the trigeminally innervated areas following unilateral nasal inflammation. Twenty healthy volunteers took part in five experiments. Intranasal inflammation was induced by means of a constant flow of cold air (145 ml/s); temperature and humidity of the airstream were varied across experiments. For the non-inflamed (NOI) condition, air temperature was 36 degrees C and its humidity 80%. In the other experiments the airstream's humidity was either 25% or 80% with a constant temperature of 20 degrees C; the airstream was applied to the left or right nostril. In order to produce noxious chemical stimuli, gaseous CO2 was applied to the left nostril (36 stimuli of 200 ms; 65% v/v CO2; interstimulus interval 30 s). Subjects rated the pain intensity of the stimuli by means of a visual analogue scale (VAS). As an indicator for hyperalgesia, the subjective pain ratings to CO2 stimuli increased not only while they were applied at the inflamed site, but also during their application contralaterally to the inflamed side. These results demonstrate the occurrence of bilateral hyperalgesia to noxious chemical stimuli in the nasal mucosa following unilateral inflammation which indicates the involvement of central changes.

Adult↗
PubMed1993

[Computer-assisted teaching in pharmacology]

Computer-assisted teaching has become a valuable alternative to experimental animals in the training of medical students. The available software may be classified as follows: 1.Computerised textbooks, which include text, graphics, animations, videoclips and sound. 2.Programmes prompting the student to make decisions which may be commented by the programme. 3.Interactive simulations of biological processes. 4.Computer-based, interactive engineering of experiments which include the processing of off-line recorded data. Within the last ten years, programmes fitting all of these categories have been developed at the Department of Experimental and Clinical Pharmacology and Toxicology at the University of Erlangen-Nürnberg. Although both, development and maintenance are time-consuming processes, these programs have been introduced most successfully to medical students in pharmacology which, in turn, emphasises the growing importance of computer-based teaching.

Journal Article↗
PubMed1985

Pain-related electrical potentials of the human nasal mucosa elicited by chemical stimulation.

For the first time a non-invasive method was employed to record pain-related electrical potentials from the human respiratory nasal mucosa. Gaseous stimulants at painful concentrations were presented by the newly developed stimulating device. The amplitudes of the potentials were found correlated (a) with concentrations of the stimulants, and (b) with subjective estimations of pain intensity. The local anesthetic tetracaine hydrochloride, and also a systemically administered analgesic drug pentazocine given prior to painful stimulation decreased the amplitude of the negative potentials. The peripheral response was interpreted as a summated receptor potential from chemical nociceptors. It is thought to be analogous to the electro-olfactogram. This non-invasive technique of stimulation and recording offers an objective and quantitative measure related to pain sensations and their inhibition by analgesic drugs.

Adult↗