[Breath changes induced by short chemosensory stimuli cannot be intentionally suppressed]. / Atemänderungen durch kurze chemosensorische Reize lassen sich nicht absichtlich unterdrücken.

INTRODUCTION: Breathing changes induced by repeated short olfactory stimuli are used as an objective indicator of the integrity of the olfactory system. Until now, it has not been investigated whether chemosensorically induced changes in inspiratory and expiratory time parameters can be suppressed intentionally. The same applies to breathing changes due to weak CO2 stimuli. METHODOLOGY: 34 healthy adult normosmics were stimulated during relaxed regular nasal breathing using a flow olfactometer with nine differently concentrated H2S and three weak CO2 stimulation pulses. They were instructed to intentionally maintain regular nasal breathing during the stimulation. A significant breathing change was present if the duration of the inspiration (DIN) or the expiration (DEX) of the first stimulatory breath was outside the double standard deviation of the mean of five prestimulatory regular breaths. These could be shortened or extended the DIN or DEX. RESULTS: Despite high motivation, the chemosensorically induced breathing changes could not be suppressed intentionally. Rest breathing reacted to both stimulants by changes in both the inspiratory and the expiratory time parameters. However, it outweighed the expiratory reactions. CO2 evoked more breathing changes than H2S. The frequency of reaction rate of H2S stimuli was not concentration-dependent. Strong H2S stimuli induced more frequent shortening than prolongation of DEX. CONCLUSIONS: Chemosensorically triggered breathing changes cannot be suppressed intentionally. They therefore provide an additional objective tool to check the functionality of nasal chemosensory afferents.

[Hydrogen sulphide stimuli shorten exhalation during sleep as well as in wakefulness]. / Schwefelwasserstoffreize verkürzen im Schlaf- wie im Wachzustand die Ausatmung.

BACKGROUND: In the attentive waking state, pleasant odours often prolong inhalation while unpleasant odours often shorten the exhalation. It should be checked whether this induced breathing pattern is maintained even during sleep. METHODOLOGY: 23 healthy normosmic adults were examined by polysomnography for one night and randomized pulsed either with H2S, phenylethyl alcohol (PEA) or CO2 via a flow olfactometer. The determination of the sleep stages was based on the standard polysomnography curves. From the breathing curves (respiratory nasal pressure breathing, thoracic or abdominal belt breathing) a low-artefact curve was selected and seven breaths were measured from their breathing signal around the trigger impulse. The duration of inspiration (DIN) and the duration of the expiration (DEX) were determined from the six prestimulatory breaths and from breath with the stimulus onset and thus defined a reaction index (RI) indicating whether there is a significant change in shortening or prolonging DIN and/or DEX. These different RI were corrected by the spontaneous baseline RI and analysed according to the type of stimulus and the sleep stages. RESULTS: Reaction indices with reductions of DEX were larger than spontaneous RI and RI for PEA and H2S stimulation. In the case of CO2 irritation, RI with reductions of DIN and DEX were larger than with olfactory stimulation. All RI were equal in their amount between sleep stages. In REM, the difference between olfactory RI with shortened DEX between H2S and PEA stimulation was greatest. CONCLUSION: When stimulated with an unpleasant smell in sleep, the respiratory reaction pattern from the awake state is preserved. RI with shortened DEX can be considered as an imperfect arousal.

[Aerobic exercises during mouth breathing do not change the detection threshold of H2S]. / Aerobe Belastung bei Mundatmung verändert die Wahrnehmungsschwelle für H2S nicht.

BACKGROUND: In a previous study, the detection threshold for H2S during aerobic exercise worsened with forced nasal breathing. The cause remained unclear. It is to be examined how the detection threshold changes with exclusive mouth breathing. MATERIAL AND METHODS: During a resting phase, an aerobic physical load and subsequent recovery phase, different H2S concentrations were applied inspiratory-synchronously intranasal using a flow-olfactometer in a staircase procedure. The missing nasal breathing was objectified online and offline. The reaction times were determined. In parallel, various vital parameters have been measured. RESULTS: The passive detection thresholds for H2S between the load and recovery phases did not differ. In the resting phase, the threshold was highest. The reaction times were not different in the three experimental phases. CONCLUSION: An increased sympathetic tone, resulting from an approximately half-hour aerobic exercise, did not change the passive olfactory threshold for H2S during oral respiration compared to the subsequent recovery period. The high olfactory threshold in the resting phase might be explained by initial adaptation difficulties to the experimental conditions.

[Aerobic exercises worsen the detection threshold of short H2S pulses]. / Aerobe Belastung verschlechtert die Wahrnehmungsschwelle kurzer H2S-Impulse.

BACKGROUND: Whether smelling is reduced during aerobic exercise is described contradictorily in the sparse literature. MATERIAL AND METHODS: To clarify this question, in healthy subjects the passive detection thresholds for short H2S stimuli were determined by means of a flow olfactometer in an inspiration-synchronous manner during nasal breathing in a staircase procedure during a resting phase, a subsequent submaximal load on a bicycle ergometer and a subsequent recovery phase. In parallel, the measurements of heart rate, blood pressure, blood lactate and body temperature were monitored to confirm an aerobic exercise. RESULTS: The participants achieved the highest values for the detection threshold in the load phase. By means of rm-ANOVA and post-hoc tests, a significant difference in the mean values of detection thresholds between the measurements at rest and during cycling as well as between the recovery and load phases was observed. However, the mean values of the detection thresholds between the resting and recovery phases did not differ. CONCLUSION: The worsening of olfactory detection thresholds during acute aerobic physical exercise and their immediate improvement during recovery phase to rest values suggests that the detection threshold is influenced by exercise. The most probable cause for this is a dilution effect caused by additional inflowing neutral ambient air in the case of forced nasal breathing.

[On the assessment of spontaneous respiratory changes in respiration-olfactometry]. / Zur Bewertung spontaner Atemänderungen bei der Respirations-Olfaktometrie.

INTRODUCTION: Alterations of breathing pattern evoked by odors are used to proof the integrity of the olfactory system in the sense of respiratory olfactometry. Spontaneous breathing changes normally cannot be distinguished from evoked changes. It is therefore necessary to repeatedly apply stimuli with a pure odorant during tidal breathing, randomized with neutral air, to detect a majority of olfactory-evoked respiratory changes. METHODS: In 26 adult normosmics, 15 H2S and 15 neutral air stimuli (duration: 2 sec) were randomly applied with an interstimulus interval of at least 1 minute, using a flow olfactometer. Before stimulation, the respiration was not allowed to scatter significantly (variation coefficient of the duration of inspiration (DIN) and expiration (DEX) ≤0.1). A respiratory response was fulfilled when respectively DIN and DEX of the stimulus breath exceeded the double standard deviation of the same parameters in the five preceding respiratory cycles. The number of reactions was normalized to the number of stimuli and to the off-line as regularly calculated respiratory complexes and thus reaction indices were formed. RESULTS: H2S stimuli clearly evoked more respiratory changes than neutral air stimuli. DIN and DEX decreased with olfactory stimulation more frequently than with an application of neutral air. Extensions of DIN and DEX were not different between the two stimulus qualities. CONCLUSIONS: Only the randomized nasal stimulation with an odor and a blank makes the respiration-olfactometry meaningful.

Sex-related differences in the wheel-running activity of mice decline with increasing age.

Laboratory mice of both sexes having free access to running wheels are commonly used to study mechanisms underlying the beneficial effects of physical exercise on health and aging in human. However, comparative wheel-running activity profiles of male and female mice for a long period of time in which increasing age plays an additional role are unknown. Therefore, we permanently recorded the wheel-running activity (i.e., total distance, median velocity, time of breaks) of female and male mice until 9months of age. Our records indicated higher wheel-running distances for females than males which were highest in 2-month-old mice. This was mainly reached by higher running velocities of the females and not by longer running times. However, the sex-related differences declined in parallel to the age-associated reduction in wheel-running activities. Female mice also showed more variances between the weekly running distances than males, which were recorded most often for females being 4-6months old but not older. Additional records of 24-month-old mice of both sexes indicated highly reduced wheel-running activities at old age. Surprisingly, this reduction at old age resulted mainly from lower running velocities and not from shorter running times. Old mice also differed in their course of night activity which peaked later compared to younger mice. In summary, we demonstrated the influence of sex on the age-dependent activity profile of mice which is somewhat contrasting to humans, and this has to be considered when transferring exercise-mediated mechanism from mouse to human.

Microarray-based gene expression profiling suggests adaptation of lung epithelial cells subjected to chronic cyclic strain.

BACKGROUND/AIMS: Mechanical strain of the lung tissue is a physiological process that affects the behavior of lung cells. Since recent evidence also suggests alterations in the expression of certain genes as a consequence of mechanotransduction, our study aimed at the analysis of the gene expression profile in lung epithelial cells subjected to chronic cyclic strain. METHODS: Various human lung epithelial cell lines (A549 as principal adherent cell line and four others) were subjected to cyclic strain (16 % surface distension, 12 min(-1)) in a Strain Cell Culture Device for 24 h. In comparison to static controls, expression analyses were performed by gene microarray and qPCR. RESULTS: Microarray analysis revealed many differences in the gene expression but at moderate levels. Altogether 25 genes were moderately down-regulated (0.86-fold ± 0.06) and 26 genes were up-regulated (1.18-fold ± 0.10) in A549 and the others. Strain-regulated genes often code for transcription factors, such as E2F4 and SRF. qPCR analyses confirmed the up-regulation of both transcription factors and further genes, such as PLAU (urokinase-type plasminogen activator) and S100A4 (S100 protein A4). Moreover, we showed the down-regulations of AGR2 (anterior gradient 2) and LCN2 (lipocalin 2). CONCLUSIONS: We identified many genes of which the expression was moderately altered in lung epithelial cells subjected to chronic cyclic strain. Although many moderate changes in the gene expression profile might affect cellular behavior, it also suggests an effective adaptation of cells to mechanical forces in long-term conditions.

Suprathreshold gustatory stimuli cause biphasic respiratory responses during resting respiration in humans.

OBJECTIVES/HYPOTHESIS: Until now there has been no standardized and internationally accepted method available to objectify taste perception. Such a method would be useful for expert opinions in the assessment of gustatory disorders. The aim of our study was to develop and evaluate an analogous method for the gustatory sense. STUDY DESIGN: Nonrandomized, controlled clinical trial. METHODS: A continuous flow of water was presented to the tongues of 34 healthy adult subjects (15 men, 19 women). In this stream, suprathreshold gustatory stimuli were applied during regular resting respiration. Nasal respiration was measured unilaterally with a differential pressure transducer. RESULTS: No significant differences were measured between the different tastants but were between tastants and blanks. Gustatory-evoked changes in the breathing pattern resulted frequently in a prolongation of the first poststimulatory breath. The second and third breath became frequently shorter. CONCLUSIONS: The observed gustatory-evoked respiratory responses are probably orienting reflex (OR) reactions. The deceleration of the first breath could be related to attention toward any chemosensory input. The acceleration of the second and third breath could reflect the subject's intention to recognize the four taste qualities. The measurement of respiratory OR evoked by gustatory stimuli can be used as a simple, inexpensive, and reliable objectifying clinical tool to prove intact central gustatory processing.

Lactate production upon short-term non-ischemic forearm exercise in mitochondrial disorders and other myopathies.

BACKGROUND: The nonischemic forearm exercise test (NIFET) has been shown to be as effective as the classic ischemic forearm exercise test (IFET) in the diagnosis of patients with McArdle disease. Recently, the lactate increase normalized to the mechanical energy production in NIFET was suggested to have a intermediate sensitivity and satisfactory specifity for the screening of mitochondrial disorders. METHODS: NIFET at 80% maximal contraction force (MCF) was performed in normal controls (n = 41), patients with mitochondrial disorders (n = 15) and other myopathies (diseased controls, n = 20). 26 healthy volunteers also underwent IFET at 80% MCF. The ratio of lactate increase and workload was defined as specific lactate production (mmol x s/N x l). RESULTS: In normal controls there was no significant different lactate increase during NIFET and IFET. The workload performed showed only a weak significant positive correlation with the lactate increase in the NIFET in normal controls (r(2) = 0.20) but not in IFET and NIFET with patients. A moderate negative correlation of specific lactate production and the absolute workload was found in all groups and in both protocols (r(2) = 0.22-0.34). The specific lactate production was highest in patients with other myopathies, intermediate in patients with mitochondrial disorders and lowest in normal controls. NIFET showed a sensitivity of only 20 % and a specifity of 95% for normal controls, but only 75 % for diseased controls. CONCLUSION: The specific lactate production during NIFET is neither sufficiently specific nor sensitive for the diagnosis of mitochondrial disorders. Increased specific lactate production during rest-to-work transition period might be caused by increased acetyl group deficits.