Nasal exposure to airway irritants triggers a mucociliary defence reflex in the rabbit maxillary sinus

Influence of different types of bedding material on the prevalence of pododermatitis in rabbits

Pododermatitis is a disorder with a complex etiology, because potentially determined by various factors such as posture, nutrition and genetics. In the case of presence of pododermal lesions, it is often noticed that rabbits go to eat at the bowl less frequently, but an evident weight loss is not always perceptible. In fact, similarly to poultry, overweight animals seem to be prone to the onset of pododermatitis. An experiment was carried out to test the effect of different types of bedding material (straw vs. wood shavings vs. coarse bark mulch vs. cotton) on the prevalence of pododermatitis in 30 fattening Separator rabbits. Once a week, the four experimental runs were assessed for contamination (macroscopic contamination by faeces/urine/litter) as well as for lesion scoring of the footpad. In addition, the water and ammonia binding behaviour of bedding was tested. The most favourable values as to dry matter, NH₃ (p < .05) and also scoring of the litter were generally observed when cotton was used as bedding material. This is probably due to the high water binding capacity, the faster water release and the structural effects of the material itself (softness). By contrast, the structure of the coarse bark mulch was not suitable for binding liquids (especially urine) and led to increased contamination of the barrels. These results suggest that rabbits with an increased tendency to sore soles should be kept on bedding materials with desirable physical properties (e.g. cotton litter).

Experience in Counting Ciliary Beat Frequency from Vital Cytologic Sampling

From a viable cytologic brush biopsy of the respiratory epithelium you can get an insight into the functional state of the epithelial cell layer, especially of the ciliated cells. We report on our experience of several hundred sampling procedures from the nasal and bronchial mucosa. The technique of the method is described, including the microphotometric apparatus to determine the ciliary beat frequency. We stress the importance of checking the ciliary beat frequency of the 10 most active cells of one preparation to get representative results. Futhermore it is decisive to watch them over a period of 10 seconds, considering the time shift of the ciliary beat frequency. Putting the cell solution into a counting chamber gives the possibility of differentiating viable and dead ciliated cells as well as squamous cells in the sample. These results proved to yield a good picture of the functional state of the sampled respiratory mucosal site.

Intracellular alkalization causes pain sensation through activation of TRPA1 in mice

Vertebrate cells require a very narrow pH range for survival. Cells accordingly possess sensory and defense mechanisms for situations where the pH deviates from the viable range. Although the monitoring of acidic pH by sensory neurons has been attributed to several ion channels, including transient receptor potential vanilloid 1 channel (TRPV1) and acid-sensing ion channels (ASICs), the mechanisms by which these cells detect alkaline pH are not well understood. Here, using Ca2+ imaging and patch-clamp recording, we showed that alkaline pH activated transient receptor potential cation channel, subfamily A, member 1 (TRPA1) and that activation of this ion channel was involved in nociception. In addition, intracellular alkalization activated TRPA1 at the whole-cell level, and single-channel openings were observed in the inside-out configuration, indicating that alkaline pH activated TRPA1 from the inside. Analyses of mutants suggested that the two N-terminal cysteine residues in TRPA1 were involved in activation by intracellular alkalization. Furthermore, intraplantar injection of ammonium chloride into the mouse hind paw caused pain-related behaviors that were not observed in TRPA1-deficient mice. These results suggest that alkaline pH causes pain sensation through activation of TRPA1 and may provide a molecular explanation for some of the human alkaline pH-related sensory disorders whose mechanisms are largely unknown.

Recordings of mucociliary activity in vivo: benefit of fast Fourier transformation of the photoelectric signal

Investigations of mucociliary activity in vivo are based on photoelectric recordings of light reflections from the mucosa. The alterations in light intensity produced by the beating cilia are picked up by a photodetector and converted to photoelectric signals. The optimal processing of these signals is not known, but in vitro recordings have been reported to benefit from fast Fourier transformation (FFT) of the signal. The aim of the investigation was to study the effect of FFT for frequency analysis of photoelectric signals originating from an artificial light source simulating mucociliary activity or from sinus or nasal mucosa in vivo, as compared to a conventional method of calculating mucociliary wave frequency, in which each peak in the signal is interpreted as a beat (old method). In the experiments with the artificial light source, the FFT system was superior to the conventional method by a factor of 50 in detecting weak signals. By using FFT signal processing, frequency could be correctly calculated in experiments with a compound signal. In experiments in the rabbit maxillary sinus, the spontaneous variations were greater when signals were processed by FFT. The correlation between the two methods was excellent: r = .92. The increase in mucociliary activity in response to the ciliary stimulant methacholine at a dosage of 0.5 microgram/kg was greater measured with the FFT than with the old method (55.3% +/- 8.3% versus 43.0% +/- 8.2%, p < .05, N = 8), and only with the FFT system could a significant effect of a threshold dose (0.05 microgram/kg) of methacholine be detected. In the human nose, recordings from aluminum foil placed on the nasal dorsum and from the nasal septa mucosa displayed some similarities in the lower frequency spectrum (< 5 Hz) attributable to artifacts. The predominant cause of these artifacts was the pulse beat, whereas in the frequency spectrum above 5 Hz, results differed for the two sources of reflected light, the mean frequency in seven healthy volunteers being 7.8 +/- 1.6 Hz for the human nasal mucosa. It is concluded that the FFT system has greater sensitivity in detecting photoelectric signals derived from the mucociliary system, and that it is also a useful tool for analyzing the contributions of artifacts to the signal.

Gaseous dynamics of the rabbit maxillary sinus

To better understand the mechanisms underlying maxillary sinus function, the gas composition of the sinus antrum in spontaneously breathing and tracheotomized rabbits (n = 17) was compared. The gas composition of samples (n = 117) obtained from rabbit maxillary sinuses was determined by gas chromatography. Results demonstrated significant differences (P < .005) in sinus gas composition between nasal breathing and tracheotomized animals for oxygen (02) and carbon dioxide (CO2). In tracheotomized animals O2 levels decreased while CO2 levels increased markedly to suprasystemic levels. This unexpected finding may be due to reduced sinus blood flow and the effects of nasal versus tracheal respiration. We conclude that the gaseous dynamics and perhaps the function of the maxillary sinus vary under different respiratory conditions. A better understanding of these processes may lead to earlier diagnosis and the development of improved treatments for sinus disease.

Effects of Halothane on Mucociliary Activity in Vivo

The effect of halothane on mucociliary activity in the rabbit maxillary sinus in vivo was recorded photoelectrically. Administration of halothane (1%, 2% or 4%) into the maxillary sinus induced a temporary acceleration of mucociliary activity. The peak increase (39.1% ± 9.1%, p < 0.05, n = 5) was seen after the 4% concentration. Long-term exposure (60 minutes) of the maxillary sinus to halothane (2%) first induced an increase of 28.4% ± 4.6% ( p < 0.05, n = 6), lasting approximately four minutes, and followed after about 15 minutes by a decrease of mucociliary activity. The maximum decrease during the 60-minute period was 19.6% ± 2.8% ( p < 0.05, n = 6). Mucociliary activity returned to its baseline level approximately 25 minutes after withdrawal of halothane. Halothane delivered to the rabbit through a tracheal cannula at 1.1% for 60 minutes did not impair mucociliary activity in the maxillary sinus. On the contrary, it initially stimulated mucociliary activity, 19.9% ± 2.7% ( p < 0.05, n = 5). There was also an initial increase in respiratory rate from 62 ± 7.3 to 89 ± 12.9 breaths per minute ( p < 0.05), which was noticeable after approximately 10 seconds and lasted 4 to 5 minutes. The dose-dependent increase in mucociliary activity seen after short-term exposure to halothane is probalby due to stimulation of afferent C fibers, because halothane may be considered an airway irritant. The reversible depressant effect seen after 15 minutes of exposure is in accordance with findings in previous studies in vitro. The mechanism by which halothane impairs mucociliary activity is at present not known. However, halothane administered to the lower airways does not impair mucociliary activity in the maxillary sinus, indicating that halothane affects the ciliated epithelium directly and that the state of anesthesia itself has no effect on mucociliary activity.

Method for in vivo measurement of mucociliary activity in the human nose

The aim of the investigation was to develop a method for observing mucociliary activity in the human nose in vivo without possible artifacts introduced by anesthesia or surgical intervention. A probe containing an optical system was constructed for the purpose, mucociliary activity on the nasal septum being photoelectrically analyzed by computer. Challenges with pharmacologic substances were administered with a standardized nebulizer delivering an aerosol heated to 33 degrees C. The baseline mucociliary wave frequency in vivo was 691.7 +/- 93.0 waves per minute (11.5 +/- 1.6 Hz), and the corresponding ciliary beat frequency in vitro was 800.7 +/- 85.4 beats per minute (13.3 +/- 1.4 Hz). The coefficients of variation were 13.4% between individuals and 11.3% +/- 2.1% (range 8.3% to 14.3%) within a subject. The method showed good reproducibility regarding recordings from different spots on the mucosa and on a day-to-day basis. Challenge with the beta 2-agonist terbutaline sulfate produced an increase of mucociliary activity of 40.6% +/- 7.8% (mean +/- SEM), which is consistent with previous results in animal models. This is the first report of a method suitable for in vivo studies of the mucociliary effects of challenge with autonomic agonists and airway irritants in humans.

NK1 receptors mediate the increase in mucociliary activity produced by tachykinins

The mucociliary activity of the rabbit maxillary sinus is increased after exposure to airway irritants such as cigarette smoke and capsaicin. This effect is partly due to a cholinergic reflex but involves an atropine-resistant response probably mediated by the release of tachykinins such as substance P or neurokinin A from sensory nerve endings. The aim of the present investigation was to evaluate the type of tachykinin receptor which mediates this increase in mucociliary activity. The mucociliary activity of the rabbit maxillary sinus was studied photoelectrically in vivo. It was found that a selective NK1 receptor agonist, [Sar9,Met(O2)11]substance P, dose dependently stimulated mucociliary activity, the maximum increase being 43.74 +/- 6.07% at a dose of 1 nmol/kg. A selective NK2 receptor agonist, [Nle10]neurokinin A-(4-10), produced a much weaker response, the maximum increase being 15.23 +/- 3.86% at a dose of 10 nmol/kg, whereas an NK3 receptor agonist, [Pro7]neurokinin B, was without effect. When the effects of the selective agonists were compared with the responses elicited by naturally occurring tachykinins at a dose of 1 pmol/kg, the order of the magnitude of the responses was [Sar9,Met(O2)11]substance P > substance P > neurokinin A. At this dosage the NK2 and NK3 receptor agonists did not have a significant effect. Pretreatment with the endopeptidase inhibitor phosphoramidon did not influence the magnitude of the responses but increased their duration. It is concluded that the NK1 receptor is responsible for the increase in mucociliary activity elicited by tachykinins released from sensory afferents in the upper airways.

Neuropeptide Y in the rabbit maxillary sinus modulates cholinergic acceleration of mucociliary activity

The distribution of neuropeptide Y (NPY)-immunoreactivity was investigated in the rabbit maxillary sinus and adjacent ganglia. A moderate supply of NPY-containing nerve fibers occurred around seromucous glands and a denser supply around small blood vessels. Only a few immunoreactive nerve fibers were seen beneath the epithelium. Double immunostaining showed that vasoactive intestinal peptide (VIP) coexisted with NPY in the nerve fibers surrounding blood vessels and seromucous glands. NPY-containing nerve cell bodies were numerous in the superior cervical ganglion, and moderately numerous in the sphenopalatine ganglion. The finding of NPY-containing neurons in the latter parasympathetic ganglion suggests that NPY may influence the cholinergic regulation of mucociliary activity. The effect of NPY on the mucociliary activity of the maxillary sinus in connection with cholinergic stimulation has therefore been investigated in vivo using a photoelectric technique. At dosages of 2.5 and 5.0 micrograms/kg, the ganglionic stimulant nicotine bitartrate, which increases mucociliary activity by a cholinergic pathway, accelerated mucociliary activity by 28.0 +/- 7.5% and 36.8 +/- 6.2%, respectively. In the same experiment repeated during infusion of NPY (0.1 microgram/kg/min), the increase in mucociliary activity was reduced to 10.8 +/- 2.3% and 28.9 +/- 7.1%, respectively. Infusion of NPY did not affect the stimulating effect on mucociliary activity by bolus injections (0.1 and 0.5 microgram/kg) of the cholinergic agonist, methacholine. It is concluded that NPY-like immunoreactivity is present in nerve fibers in the rabbit maxillary sinus and in neurons in the sympathetic and parasympathetic ganglia that supply the nose and paranasal sinuses. NPY attenuates the effect of nicotine on mucociliary activity, probably via a prejunctional mechanism, and may act as a modulator of cholinergic regulation of the mucociliary system.

The effect of ammonia on the respiratory nasal mucosa of mice. A histological and histochemical study

The effects of prolonged exposure to ammonia vapour on the histological pattern and enzymatic activity of the respiratory nasal mucosa of 75 adult male mice were investigated and compared with a control group. In the exposed animals, the nasal epithelial cells showed patches of squamous metaplasia, dysplasia, and even malignant changes in the nose of 2 animals. As regards the histochemical changes, the apical border of epithelial cells showed increased succinic dehydrogenase activity denoting increased energy production. The acid phosphatase activity was also higher, and this seemed to be a constant feature in metaplastic and neoplastic transformation. The alkaline phosphatase activity was detected only in the basal parts of epithelial and goblet cells, which was attributed to an increased activity of basal cells to form a thicker basement membrane. The periodic acid Schiff's reaction was weak in the cilia due to their partial degeneration. Prolonged exposure to ammonia interfered with the normal physiological mucociliary action resulting in accumulation of particulate matter initiating or promoting a neoplastic process.

Tissue kallikrein stimulates mucociliary activity in the rabbit maxillary sinus

The in vivo effect of tissue kallikrein on the mucociliary activity in the rabbit maxillary sinus was investigated administering the substance (0.1-5 mU/kg) via a. maxillaris and recording the response with a non-invasive photoelectric technique. Tissue kallikrein accelerated mucociliary activity, with a maximum response for the dose 5 mU/kg (33.7 +/- 13.4% from basal levels, n = 5). The effect had a latency of abut 1 min, with a peak within 2-3 min after the beginning of the administration. The response to tissue kallikrein displayed tachyphylaxis with a second dose producing a weaker response. Pretreatment with the protease inhibitor aprotinin (10,000 KIU bolus/kg) inhibited the action of tissue kallikrein. Tissue kallikrein probably stimulates mucociliary activity by producing lysylbradykinin from kininogen. Bradykinin has in an earlier study been shown to stimulate mucociliary activity.

Mucociliary activity and the diving reflex

It has previously been shown that mucociliary activity in the rabbit maxillary sinus is immediately increased after short-term exposure to such airway irritants as cigarette smoke and ammonia vapor. This increase is mediated through the stimulation of capsaicin-sensitive nerve endings. Besides producing the mucociliary effect, these irritants inhibit breathing, a response characteristic of the diving reflex in mammals. Whether an increase in mucociliary activity is part of the diving reflex was investigated by injecting 0.5 mL water into the nasopharynges of anesthetized rabbits. Mucociliary and respiratory responses were compared with the effects of mechanical stimulation (ie, rotating an intranasal catheter until sneezing occurred). Water challenge produced an increase in mucociliary activity of 21.6% +/- 2.4%, a response that began approximately 10 seconds after injection. Mucociliary acceleration was completely blocked by atropine, indicating a cholinergic mechanism, but was unaffected by pretreatment with capsaicin. The respiration rate was inhibited by about 45% after challenge with water. Pretreatment with atropine and capsaicin had no effect on this reduced respiratory rate. Mechanical stimulation of the nasal mucosa accelerated mucociliary activity. This response appeared approximately 4 seconds after stimulation was begun, and occurred simultaneously with the onset of sneezing. The peak increase was 22.0% +/- 2.1%. Sneezing was followed by an increase in the respiration rate of about 40%. Pretreatment with atropine or capsaicin had no effect on respiratory responses, but did inhibit mucociliary acceleration, suggesting that the response is mediated through cholinergic effector neurons after activation of capsaicin-sensitive nerve endings.(ABSTRACT TRUNCATED AT 250 WORDS)