Effects of nasal-airway volume and body temperature on intranasal chemosensitivity

Size of nostril opening as a measure of intranasal volume

The anatomy of the human intranasal cavity is complex and anatomical variations are known to affect olfactory functions. Measurement of anatomical variations via delineation of intranasal volume is, however, technically complicated as well as time-consuming. It is well documented that size of various body parts tends to correlate within the same individual. Therefore, in the current study, we explored the relationship between intranasal volume and the size of the nares, with the aim of using the area of the nostril opening as a potential predictor of intranasal volume. Structural whole-brain T1-weighted MR images of 69 healthy volunteers (35 women) were obtained using a 1.5 T standard clinical MRI scanner. The intranasal volume, as well as the area of the nostril opening, were delineated. Our results suggest that the intranasal volume is positively correlated with the area of the nostril opening. Intranasal volume did not differ significantly between men and women although men had significant larger nostril openings. However, the correlation between intranasal volume and nostril opening was not influenced by the subject's gender. In conclusion, it is possible to obtain a good estimate of the intranasal volume using measurements of the nares.

Odor thresholds and breathing changes of human volunteers as consequences of sulphur dioxide exposure considering individual factors

Objectives

Though sulfur dioxide (SO₂) is used widely at workplaces, itseffects on humans are not known. Thresholds are reported without reference to gender or age and occupational exposure limits are basedon effects on lung functioning,although localized effects in the upper airways can be expected.This study's aim is to determine thresholds with respect to age and gender and suggests a new approach to risk assessment using breathing reflexes presumably triggered by trigeminal receptors in the upper airways.

Methods

Odor thresholds were determined by the ascending method of limits in groups stratified by age and gender.Subjects rated intensities of different olfactory and trigeminal perceptions at different concentrations of SO₂. During the presentation of the concentrations, breathing movements were measured by respiratory inductive plethysmography.

Results

Neither age nor gender effects were observed for odor threshold. Only ratings of nasal irritation were influenced bygender. A benchmark dose analysis on relative respiratory depth revealed a 10%-deviation from baseline at about 25.27 mg/m³.

Conclusion

The proposed new approach to risk assessment appearsto be sustainable. We discuss whether a 10%-deviation of breathingdepth is relevant.

The influence of ambient temperature and thermal acclimation on hearing in a eurythermal and a stenothermal otophysan fish

Being ectothermic, fish body temperature generally depends on ambient water temperature. Thus, ambient temperature might affect various sensory systems, including hearing, as a result of metabolic and physiological processes. However, the maintenance of sensory functions in a changing environment may be crucial for an animal's survival. Many fish species rely on hearing for acoustic orientation and communication. In order to investigate the influence of temperature on the auditory system, channel catfish Ictalurus punctatus was chosen as a model for a eurytherm species and the tropical catfish Pimelodus pictus as a model for a stenotherm fish. Hearing sensitivity was measured with animals acclimated or unacclimated to different water temperatures. Ambient water temperature significantly influenced hearing thresholds and the shape of auditory evoked potentials, especially at higher frequencies in I. punctatus. Hearing sensitivity of I. punctatus was lowest at 10 degrees C and increased by up to 36 dB between 10 degrees C and 26 degrees C. Significant differences were also revealed between acclimated and unacclimated animals after an increase in water temperature but not a decrease. By contrast, differences in hearing thresholds were smaller in P. pictus, even if a similar temperature difference (8 degrees C) was considered. However, P. pictus showed a similar trend as I. punctatus in exhibiting higher hearing sensitivity at the highest tested temperature, especially at the highest frequency tested. The results therefore suggest that the functional temperature dependence of sensory systems may differ depending upon whether a species is physiologically adapted to tolerate a wide or narrow temperature range.

Olfactory Discrimination and Transient Mood Change in Young Men and Women: Variation by Season, Mood State, and Time of Day

Odor performance varies by clinical state and gender, though little is known about its variation by season or time of day. Many odors, including lavender, induce transient mood changes. This study explored discrimination differences between various lavender oil blends and their effects on transient mood in the morning and evening in depressed and nondepressed adults. We also determined seasonal influences on these measures. A total of 169 subjects, 98 women and 71 men (mean age +/- SD, 19.3 +/- 1.6 y) participated, with different subjects studied at different times of the year. The Beck Depression Inventory (BDI) classified subjects as depressed (score > or =10; N= 57) or nondepressed (score <10; N= 112). In the discrimination test, subjects compared pairs of two different lavender oil blends or a control. Transient change in mood was assessed by the Profile of Mood States (POMS) after each trial of five lavender blends interspersed by three control odors. Tests were conducted in the morning (08:00-10:00 h) and evening (18:00-20:00h). In all subjects, discrimination was significantly better for some odor pairs than for others, thus demonstrating test specificity. Discrimination was better overall in the fall than winter/spring and better in depressed than nondepressed subjects for specific odor pairs. No significant gender or time-of-day differences in discriminability were detected. There were, however, significant group differences in transient mood profiles. Current depressed state affected mood response, with lavender increasing anger in depressed subjects only. In addition, depressed subjects and men, whether or not depressed, exhibited diurnal mood variation, with better mood in the evening; the former group also showed more evening energy. All subjects were more confused in the morning than evening. Season also affected transient mood; winter/spring-tested subjects reported more vigor than fall-tested subjects. In addition, summer-tested subjects showed more tension in the morning, whereas fall-tested subjects showed the opposite pattern in the evening. In all subjects, lavender increased fatigue, tension, confusion, and total mood disturbance, and it decreased vigor. The study showed that both chronobiological (seasonal and time-of-day) and clinical factors modify discrimination and mood response to odors. Brief lavender odor presentation may serve as a nonphotic method for altering mood in young depressed and nondepressed adults particularly during the fall, a time of heightened discriminability.

Nostril dominance: differences in nasal airflow and preferred handedness

Because there appears to be a general propensity among many people to have a consistency in the sidedness of their lateral preferences, the purpose of the present study was to determine if this consistency extends to the airflow through the individual nostrils as well. To test for this, hot wire anemometers measured the airflow in each nostril at 15-minute intervals for 6 continuous hours in 11 right-handed and 9 left-handed adult males. Participants also provided self-reports of which nostril appeared to have the greater airflow. The airflow measurements supported the hypothesis of a handedness by nostril interaction, in that left-handers more often experienced greater airflow in their left nostrils whereas right-handers showed the opposite pattern. Self-reports were not an especially reliable measure of nasal patency. In most subjects the same nostril was not always the more open one. This left/right shifting of the more patent nostril is termed the nasal cycle. This study also provides the first data comparing the nasal cycle patterns of left-handers and right-handers.

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.